advanced trailing edge blowing concepts for fan noise control: experimental validation · 2020. 9....
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Advanced Trailing Edge Blowing Concepts for Fan Noise Control:
Experimental Validation
Christopher W. Halasz
Master of Science
in
Mechanical Engineering
Ricardo Burdisso, Chair
Wing Ng
Marty Johnson
20 June 2005
Blacksburg, VA
Keywords: Fan Noise Reduction, Interaction Noise, Turbofan Engine
Copyright 2005, Christopher W. Halasz
Thesis submitted to the faculty of the
Virginia Polytechnic Institute and State
University in partial fulfillment of the
requirements for the degree of
Advanced Trailing Edge Blowing Concepts for Fan Noise Control:
Experimental Validation
Christopher W. Halasz
(ABSTRACT)
This thesis documents trailing edge blowing research performed to reduce rotor / stator
interaction noise in turbofan engines. The existing technique of filling every velocity deficit
requires a large amount of air and is therefore impractical. The purpose of this research is to
investigate new blowing configurations in order to achieve noise reduction with lesser amounts
of air. Using the new configurations air is not injected into every fan blade, but is instead varied
circumferentially. For example, blowing air may be applied to alternating fan blades. This type
of blowing configuration both reduces the amount of air used and changes the spectral shape of
the tonal interaction noise. The original tones at the blade passing frequency and its harmonics
are reduced and new tones are introduced between them. This change in the tonal spectral shape
increases the performance of acoustic liners used in conjunction with trailing edge blowing. This
thesis presents numerical predictions performed to estimate the sound power reductions due to
these concepts, as well as experimental results taken on the ANCF rig at NASA Glenn for
validation purposes. The results show that the new concepts are successful in increasing the
efficiency of trailing edge blowing.
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Acknowledgements:
First I would like to thank my advisor Ricardo Burdisso for all of his advice and support
throughout this research. Many thanks are also extended to Wing Ng and Marty Johnson for
making this work possible as my committee members.
I am thankful to all the members of the Vibration and Acoustics Laboratory (VAL). Especially
David Arntz, whose initial work in this area paved the way for my own, and Diego de la Riva for
all of his help and teaching.
I would like to acknowledge the work of Daniel Sutliff and the staff at NASA Glenn's AAPL
facility for conducting the experimental testing. I am grateful to NASA for providing funding for
this research under STTR Contract NAS3-03077.
Finally, I thank Matt Langford and the staff at Techsburg, Inc. for their contributions.
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Table of Contents
Chapter 1 : Introduction .................................................................................................................. 1
1.1: Aircraft Noise Problem........................................................................................................ 1
1.2: Characterization and Measurement of Aircraft Noise ......................................................... 2
1.3: Aircraft Noise Sources......................................................................................................... 4
1.4: Rotor / Stator Interaction Noise ........................................................................................... 5
1.5: Trailing Edge Blowing and Previous Work......................................................................... 6
1.6: Thesis Objectives and Organization .................................................................................... 8
Chapter 2 : Advanced Trailing Edge Blowing Concept ................................................................. 9
Chapter 3 : Experimental Setup .................................................................................................... 14
3.1: ANCF Rig .......................................................................................................................... 14
3.2: TEB Fan Blades ................................................................................................................. 16
3.3: In-Duct Velocity Instrumentation and Data Reduction ..................................................... 17
3.4: In-Duct Acoustic Instrumentation and Data Reduction..................................................... 20
3.5: Far-field Acoustic Instrumentation and Data Reduction ................................................... 25
3.6: Experimental Test Configurations ..................................................................................... 27
3.6.1: First Test Entry ........................................................................................................... 27
3.6.2: Second Test Entry....................................................................................................... 29
Chapter 4 : Experimental Results ................................................................................................. 31
4.1: Hotwire Results (First Test Entry)..................................................................................... 31
4.2: Rotating Rake Results (First Test Entry)........................................................................... 35
4.2.1 Rake Results - No TEB Configuration ........................................................................ 35
4.2.2 Rake Results - Full TEB Configuration....................................................................... 37
4.2.3 Rake Results - ATEB 1x1 Configuration .................................................................... 39
4.2.4 Rake Results - ATEB 2x2 Configuration .................................................................... 41
4.3 Far-Field Results (First Test Entry) .................................................................................... 45
4.3.1: Configurations using 0 Vanes..................................................................................... 45
4.3.2: Configurations using the Inlet Duct and 14 Vanes ..................................................... 46
4.3.3: Configurations using the Aft Duct and 14 Vanes ....................................................... 51
4.3.4: Configurations using the Inlet Duct and 28 Vanes ..................................................... 55
4.3.5: Configurations using the Aft Duct and 28 Vanes ....................................................... 58
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4.4 Hotwire Results (Second Test Entry) ................................................................................. 61
4.5 Far-Field Results (Second Test Entry)................................................................................ 64
4.5.1: Configurations using the Inlet Duct (Second Test Entry)........................................... 64
4.5.2: Configurations using the Aft Duct (Second Test Entry)............................................. 66
Chapter 5 : Acoustic Liner Performance with ATEB................................................................... 69
5.1: Numerical Codes................................................................................................................ 69
5.1.1: "V072" Rotor Wake / Stator Interaction Code ........................................................... 69
5.1.2: Eversman Finite Element Radiation Code.................................................................. 70
5.2: Proof of Concept - Acoustic Liner Performance ............................................................... 72
5.2.1: Liner Performance - Configurations with Inlet Duct and 14 Vanes........................... 73
5.2.2: Liner Performance - Configurations with Inlet Duct and 28 Vanes........................... 76
Chapter 6 : Conclusions ................................................................................................................ 80
References..................................................................................................................................... 82
Appendix A: Rake Data (First Test Entry) ................................................................................... 85
Appendix B: First Test Entry Far-Field Results ......................................................................... 113
Appendix C: Second Test Entry Far-Field Results..................................................................... 119
Appendix D: Initial Numerical Predictions ................................................................................ 123
Appendix E: Validation of Eversman Code Accuracy ............................................................... 128
Vita.............................................................................................................................................. 129
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List of Figures
Figure 1.1: Noise Level Certifications............................................................................................ 2
Figure 1.2: EPNL Measurement Locations. ................................................................................... 4
Figure 1.3: Turbofan Engine Noise Sources................................................................................... 5
Figure 1.4: Fan Blades and Wakes. ................................................................................................ 6
Figure 2.1: Fan, Wakes, and Interaction Noise with No TEB. ....................................................... 9
Figure 2.2: Fan, Wakes, and Interaction Noise with Full TEB..................................................... 10
Figure 2.3: Fan, Wakes, and Interaction Noise with ATEB 1x1. ................................................. 11
Figure 2.4: Interaction Spectra (a) without ATEB and (b) with ATEB, in comparison with liner
attenuation curves. ........................................................................................................................ 13
Figure 3.1: (a) Photograph and (b) Cross-Sectional Diagram of ANCF Rig................................ 15
Figure 3.2: Predicted (a) Inlet and (b) Aft Liner Impedances....................................................... 16
Figure 3.3: Fan Blades used in (a) Test Entry I and (b) Test Entry II. ......................................... 17
Figure 3.4: Velocity Triangle and Notation.................................................................................. 18
Figure 3.5: Upwash Velocity Definition....................................................................................... 19
Figure 3.6: ANCF Aft Duct with Rotating Rake Microphone Array. .......................................... 20
Figure 3.7: Far-Field Microphone Array Geometry. .................................................................... 26
Figure 3.8: Photograph of ANCF and Far-Field Microphone Arrays. ......................................... 26
Figure 4.1: Upwash Velocity Contours for (a) No TEB, (b) Full TEB 1.1%, (c) Full TEB 1.5%,
(d) Full TEB 1.8%, and (e) ATEB 1x1 0.9%................................................................................ 34
Figure 4.2: Rake Data for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall] at (a) 1xBPF, (b)
2xBPF, (c) 3xBPF......................................................................................................................... 36
Figure 4.3: Rake Data for [Inlet Duct, 14 Vanes, Full TEB 1.5%,Hardwall] at (a)
1xBPF,(b)2xBPF,(c) 3xBPF. ........................................................................................................ 38
Figure 4.4: Rake Data for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall] at (a) 0.5xBPF, (b)
1xBPF, (c) 1.5xBPF, (d) 2xBPF, (e) 2.5xBPF, and (f) 3xBPF..................................................... 40
Figure 4.5: Rake Data for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall] at (a) 0.25xBPF,
(b) 0.5xBPF, (c) 0.75xBPF, (d) 1xBPF, (e) 1.25xBPF, and (f) 1.5xBPF..................................... 43
Figure 4.6: Rake Data for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall] at (a) 1.75xBPF,
(b) 2xBPF, (c) 2.25xBPF, (d) 2.5xBPF, (e) 2.75xBPF, and (f) 3xBPF........................................ 44
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Figure 4.7: 0-Vane Sound Power Spectra for (a) [Inlet Duct, 0 Vanes, No TEB 0%, Hardwall]
and (b) [Aft Duct, 0 Vanes, No TEB 0%, Hardwall] (dB ref. 10-12 W/m2). ................................. 46
Figure 4.8: Power Spectrum for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall]. ....................... 47
Figure 4.9: Power vs. Blowing Rate for the Configurations [Inlet Duct, 14 Vanes].................... 48
Figure 4.10: Power Spectra for (a) [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall], (b) [Inlet
Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall], and (c) [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%,
Hardwall]. ..................................................................................................................................... 50
Figure 4.11: Original and New Tones' Power for (a) [Inlet Duct, 14 Vanes, ATEB 1x1,
Hardwall] and (b) [Inlet Duct, 14 Vanes, ATEB 2x2, Hardwall]................................................. 51
Figure 4.12: Power Spectrum for [Aft Duct, 14 Vanes, No TEB 0%, Hardwall]. ....................... 52
Figure 4.13: Power vs. Blowing Rate for the Configurations [Aft Duct, 14 Vanes].................... 52
Figure 4.14: Power Spectra for (a) [Aft Duct, 14 Vanes, Full TEB 1.5%, Hardwall], (b) [Aft
Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall], and (c) [Aft Duct, 14 Vanes, ATEB 2x2 0.9%,
Hardwall]. ..................................................................................................................................... 54
Figure 4.15: Original and New Tones' Power for (a) [Aft Duct, 14 Vanes, ATEB 1x1, Hardwall]
and (b) [Aft Duct, 14 Vanes, ATEB 2x2, Hardwall]. ................................................................... 55
Figure 4.16: [Inlet Duct, 28 Vanes, No TEB 0%, Hardwall]........................................................ 55
Figure 4.17: Power vs. Blowing Rate for the Configurations [Inlet Duct, 28 Vanes].................. 56
Figure 4.18: Power Spectra for (a) [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall] and (b)
[Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]. .................................................................... 57
Figure 4.19: Original and New Tones' Power for (a) [Inlet Duct, 28 Vanes, ATEB 1x1,
Hardwall] and (b) [Inlet Duct, 28 Vanes, ATEB 2x2, Hardwall]................................................. 58
Figure 4.20: Power Spectrum for [Aft Duct, 28 Vanes, No TEB 0%, Hardwall]. ....................... 59
Figure 4.21: Power vs. Blowing Rate for the Configurations [Aft Duct, 28 Vanes].................... 59
Figure 4.22: Power Spectra for (a) [Aft Duct, 28 Vanes, ATEB 1x1 0.8%, Hardwall] and (b) [Aft
Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]............................................................................... 60
Figure 4.23: Original and New Tones' Power for (a) [Aft Duct, 28 Vanes, ATEB 1x1, Hardwall]
and (b) [Aft Duct, 28 Vanes, ATEB 2x2, Hardwall]. ................................................................... 61
Figure 4.24: Upwash Velocities for (a) No TEB, (b) Full TEB 0.65%, and (c) Full TEB 0.65%
Partial Span ................................................................................................................................... 63
Figure 4.25: Power Spectrum for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall, (2nd Entry)].. 64
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Figure 4.26: Power vs. Blowing Rate for the Configurations [Inlet Duct, 14 Vanes, (2nd Entry)].
....................................................................................................................................................... 65
Figure 4.27: Power Spectra for (a) [Inlet Duct, 14 Vanes, Full TEB 0.65%, Hardwall, (2nd
Entry)] and (b) [Inlet Duct, 14 Vanes, ATEB 1x1 0.43%, Hardwall, (2nd Entry)]...................... 66
Figure 4.28: Power Spectrum for [Aft Duct, 14 Vanes, No TEB 0%, Hardwall, (2nd Entry)].... 67
Figure 4.29: Power vs Blowing Rate for the Configurations [Aft Duct, 14 Vanes,(2nd Entry)]. 67
Figure 4.30: Power Spectra for (a) [Aft Duct, 14 Vanes, Full TEB 0.65%, Hardwall, (2nd Entry)]
and (b) [Aft Duct, 14 Vanes, ATEB 1x1 0.43%, Hardwall, (2nd Entry)]. ................................... 68
Figure 5.1: Eversman Code (a) Inlet Mesh and (b) Aft Mesh. ..................................................... 71
Figure 5.2: Procedure for Predicting Optimum Liner Attenuations ............................................. 73
Figure 5.3: [Inlet Duct, 14 Vanes] Liner Reductions for (a) No TEB, (b) Full TEB, (c) ATEB
1x1, (d) ATEB 2x2. ...................................................................................................................... 75
Figure 5.4: [Inlet Duct, 14 Vanes] Sound Power Reductions from Wake-Filling and from Liner
Attenuation.................................................................................................................................... 76
Figure 5.5: [Inlet Duct, 28 Vanes] Liner Attenuations for (a) No TEB, (b) ATEB 1x1, and (c)
ATEB 2x2. .................................................................................................................................... 77
Figure 5.6: [Inlet Duct, 28 Vanes] Sound Power Reductions from Wake-Filling and from Liner
Attenuation.................................................................................................................................... 78
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List of Tables
Table 3.1: Predicted Circumferential Modes for No TEB / Full TEB Configurations................. 22
Table 3.2: Predicted Circumferential Modes for ATEB 1x1 Configurations............................... 22
Table 3.3: Predicted Circumferential Modes for ATEB 2x2 Configurations............................... 23
Table 3.4: Propagating Interaction Modes for Configurations with No TEB / Full TEB. ........... 24
Table 3.5: Propagating Interaction Modes for Configurations with ATEB 1x1........................... 24
Table 3.6: Propagating Interaction Modes for Configurations with ATEB 2x2........................... 25
Table 3.7: Rake Data Test Matrix (1st Entry)............................................................................... 28
Table 3.8: Far-Field Data Test Matrix (1st Entry)........................................................................ 29
Table 3.9: Far-Field Data Test Matrix (2nd Entry)....................................................................... 30
1
Chapter 1 : Introduction
This section introduces the problem of aircraft noise and the measures being taken to
address it. First a statement of the problem is given, followed by a description of how aircraft
noise is quantified and measured. The different types of aircraft noise sources are discussed.
Rotor / stator interaction noise of turbofan engines, the noise generation mechanism targeted by
this research, is explained. The traditional method of reducing interaction noise, called "trailing
edge blowing" (TEB), is outlined and previous work is cited.
1.1: Aircraft Noise Problem
Aircraft noise is a problem because it disturbs the normal activities of nearby
communities. In the United States about 6,000,000 people on 900,000 acres of land are subjected
to aircraft noise. The general quality of life is degraded as conversation, relaxation, and sleep are
made more difficult. Lawsuits are filed for both decreased property values and punitive damages.
Airport proprietors are forced to buy up residential properties nearby and contribute to the
soundproofing of public buildings like schools. In response to public opposition to noise airports
have imposed restrictions on operations. Examples include night time operating restrictions,
exclusion of certain aircraft, a limited number of aircraft operations, and setting noise preferred
runways. Such measures have an effect on commerce, transportation, and air navigation [1].
Old and noisy aircraft are being replaced by newer and quieter models, but at the same
time the volume of air traffic is increasing. In order to control the amount of noise, local and
federal regulations are imposed and made ever stricter. The next step of these regulations, called
"Stage 4," is to take effect in the year 2006. Figure 1.1 illustrates the downward trend in
allowable noise levels. New technology is required to meet stricter standards and provide
aircraft to meet the replacement and growth requirements of the industry [2].
2
Figure 1.1: Noise Level Certifications.
1.2: Characterization and Measurement of Aircraft Noise
The definition of “aircraft noise” as it is used in this thesis must first be made clear. The
term is used in its capacity describing “community noise,” or more exactly the noise reaching the
ground near airports. This contrasts with its other meaning of “cabin noise,” or the noise
reaching passengers within the aircraft. This thesis and research deal with the issue of aircraft
noise as it relates to communities, not passengers.
When discussing noise it is necessary to have a system of units with which to quantify
measured levels. Noise is, of course, measured as a perturbation of air pressure and is expressed
logarithmically as decibels. However, the measured values in dB do not always give the best
representation of noise as it is experienced by humans. Weighted scales such as dBA are widely
used, but other measures exist specifically to describe aircraft noise. One such measure
quantifies the “annoyance” of each individual flyover. Human response to a single flyover is best
represented in terms of the “Effective Perceived Noise Level” (EPNL) which is used for FAA
certification. The EPNL is a weighting scale that is applied to the measured sound pressure levels
in dB. It considers the frequency content that is audible to humans and emphasizes any pure
tones or “screeches” present in the sound. Furthermore, the EPNL integrates the weighted noise
levels over the flyover time of a passing aircraft. The sensitivity of the unit is such that people
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can detect differences of about 5 dB, and differences of 10 dB are described as “twice as loud” or
“half as loud” as the original level.
When considering a person's reaction to multiple flyovers a measure of the cumulative
noise “dose” is needed. This measure is the “Noise Exposure Forecast” (NEF). The NEF at a
point near an airport is calculated by summing the noise energy reaching that point over a 24
hour time period with a penalty applied to nighttime flights. In addition to quantifying the noise
levels for an existing situation the NEF is used to characterize hypothetical scenarios in which a
prediction of a community’s reaction to a proposed change in noise levels is needed. For
example, the number of complaints about a new airport may be predicted by first predicting the
NEF that would result from the facility’s construction. This would require knowledge of the
number and type of each aircraft operating at the airport, their flight paths, and their power
settings.
Next a standardized procedure for taking noise measurements is required. The NEF can
be measured or predicted at any location of interest. The EPNL, however, must be measured at
three specific locations for certification. These locations are called “Sideline,” “Community,”
and “Approach.” The sideline noise is measured 450 m to the side of the runway. The
community noise is measured on takeoff 6500 m down the runway. The approach noise is
measured 2000 m in front of the runway. Figure 1.2 illustrates these locations. The time signals
measured at these locations are called “Perceived Noise Levels with Tonal Weighting” (PNLT),
and are integrated over time to calculate the EPNL. The FAA imposes a maximum allowable
EPNL for each of the three measurement points. The maximum EPNL for a given aircraft is a
function of its weight and number of engines, with larger planes being allowed to make more
noise [3].
4
Figure 1.2: EPNL Measurement Locations.
1.3: Aircraft Noise Sources
The broadest classifications of aircraft noise are those of airframe and engine noise.
Airframe noise is the non-propulsive noise of an aircraft in flight. Landing gear, flaps, and slats
all contribute to airframe noise and are most used on takeoff and approach when an aircraft is
near the ground. Unsteady flow from wing and tail trailing edge, turbulent flow through or
around flaps and slats, flow past landing gear and other undercarriage elements, fuselage and
wing turbulent boundary layers, and panel vibrations all contribute to airframe noise. Airframe
noise is most significant during approach when the engine noise is low.
Engine noise has been reduced significantly in the past 50 years, first with the transition
from turbojet to turbofan engines and then with evolutionary improvements to turbofan
technology. Switching from the turbojet's small, high-velocity exhaust to the turbofan's large,
low-velocity exhaust drastically reduced the broadband jet noise (roaring, rumbling sound) of
modern aircraft. This noise reduction is achieved because jet noise is an eighth power function of
jet exhaust velocity. With jet noise no longer so dominant the other sources of engine noise have
become significant and noise reduction strategies are needed for all of them.
5
In addition to jet noise, the noise sources of a turbofan engine are the fan, compressor,
turbine, and combustor. The combustor produces what is called "core noise" which is a
combination of the combustion noise itself and the passing of hot combustion products through
the turbine and exhaust. The core noise level is a function of temperature, pressure, and the
geometry of the flow path. It is broadband and low frequency in nature. The fan, compressor, and
turbine produce "turbomachine noise" that is a function of pressure change, tip speed, flow rate,
turbulence, and wakes. It has both broadband and tonal contents. Figure 1.3 shows the noise
sources of a turbofan engine and their relative contributions at the inlet and exhaust [4].
Figure 1.3: Turbofan Engine Noise Sources.
1.4: Rotor / Stator Interaction Noise
One of the tonal contents of the fan noise is due to "rotor / stator interaction." The fan
blades of a turbofan engine introduce wakes or velocity deficits due to viscous effects (losses)
into the working fluid. These rotating wake deficits propagate downstream where they are cut by
stator vanes. The unsteady surface pressure on the vanes is coupled to duct acoustic modes that
are excited to produce tonal noise at the blade passing frequency (BPF) and its harmonics
(2xBPF, 3xBPF, etc.) [5]. Figure 1.4 shows a blade row and associated wakes. The fluid velocity
becomes unsteady after passing the fan blades.
6
Figure 1.4: Fan Blades and Wakes.
1.5: Trailing Edge Blowing and Previous Work
Flow control, also referred to as wake management or trailing edge blowing, has proven
to be effective at reducing fan noise by suppressing the unsteady rotor / stator interaction. The
interaction is suppressed by reducing the wakes due to viscous boundary layer effects. This is
accomplished either by removing (suction) low momentum fluid to decrease boundary layer
thickness or by adding (blowing) high momentum fluid to energize low momentum zones (fill
wake deficits). The first tests conducted to validate the use of flow control were performed on
flat plates [6-8]. These tests were important in showing the feasibility of flow control geometries
in affecting steady and unsteady aspects of wakes with their decay and mixing rates, but are not
applicable to modern engines.
The first application of flow control for the reduction of fan noise by Waitz [9] evaluated
the use of mass addition and removal in order to decrease unsteady stator loading and therefore
rotor / stator interaction in a 2D setting. The two flow control concepts studied were boundary
layer suction and trailing edge blowing, which were investigated using numerical and
experimental techniques. Numerically manipulating Gaussian wakes showed that decreasing
wake depth reduced unsteady stator loading harmonics and therefore acoustic tones. Simulation
concluded that wide, shallow wakes are desired for flow control. Experimental results concluded
7
that trailing edge blowing was a better flow control mechanism than boundary layer suction.
Trailing edge blowing used less mass flow and passage area to produce better interaction
reductions than those achieved with boundary layer suction. The study was taken another step
forward to test different air injection configurations [10]. The conclusion was that many small
jets aimed at the wake centerline was the best trailing edge blowing design.
A later experiment by Brookfield [11] was performed in a rotating fan stage, taking flow
and acoustic measurements. This test used less than 2% of the fan through-flow mass as trailing
edge blowing air in tip-weighted and midspan-weighted blowing distributions. The results
showed that time-mean relative Mach profiles were smoothed such that 85% reductions in wake
harmonic amplitudes were achieved.
A similar technique of stator trailing edge blowing was used on a 3D test rig to reduce
fan noise produced by rotors passing through wakes shed by upstream stators [12, 13]. Velocity
contours showed good results, giving more pitch-wise uniformity with blowing than without.
Extensive trailing edge blowing work has been performed at the NASA Glenn Research
Center using the Advanced Noise Control Fan rig (ANCF). An experimental proof-of-concept
test by Sutliff [14] was performed to demonstrate reduction of rotor / stator interaction noise
through trailing edge blowing. The blade-to-vane spacing used was one chord. The first three
blade passing frequencies were found to be reduced in power by 5.4 dB, 10.6 dB, and 12.4 dB,
respectively. These reductions were achieved at trailing edge blowing rates of 1.6% to 1.8% of
the total mass flow rate through the fan. In a turbofan engine these percentages would be
multiplied by the bypass ratio to calculate the percentage air bled off the compressor, leading to
an impractical air requirement. Two-component flow velocity and stator vane unsteady surface
pressures were also measured to illustrate the physics behind noise reduction. The effects of
trailing edge blowing on broadband fan noise are also documenter by Sutliff [15].
8
1.6: Thesis Objectives and Organization
Previous studies have demonstrated trailing edge blowing as an effective flow control
mechanism for the reduction of rotor / stator interaction noise. However, the trailing edge
blowing air must be bled from a compressor stage downstream. Bleeding enough air off of the
compressor to fill all of the wake deficits reduces the performance of the engine and makes
commercial application of TEB impractical.
The goal of this research is to experimentally validate a new way of applying TEB. The
new concept, called "advanced trailing edge blowing" (ATEB), addresses the problem of
excessive air requirements. The validation is performed by first presenting the results of
experimental testing. This describes the behavior of ATEB under hardwall conditions. Then
numerical codes are used to predict the performance of ATEB when used in combination with
acoustic liners.
The new TEB concept is described in Chapter 2 of this thesis. The experimental setup is
described in Chapter 3. The results of two experimental test entries using two different types of
fan blades are given in Chapter 4. Chapter 5 explains the computer codes used to predict liner
performances, and presents the results of using ATEB in combination with optimized acoustic
liners. Conclusions are drawn in Chapter 6, and lists of experimental data are given in the
Appendices.
9
Chapter 2 : Advanced Trailing Edge Blowing Concept
As discussed in Chapter 1, the root cause of rotor / stator interaction noise is unsteadiness
in the fluid reaching the stator vanes. These unsteady wake deficits are caused by losses incurred
along fan blade surfaces. If no interaction noise control is attempted, every fan blade produces a
wake and these wakes produce interaction noise tones at the blade passing frequency and
harmonics. This baseline configuration is illustrated in Figure 2.1. A fan with 16 blades is shown
(3 blades have been removed for ease of visualization). The blue surface downstream of the
blades represents fluid velocity; there is a ripple downstream of every blade trailing edge
representing the wake due to that blade. The stators (not shown) would be further downstream.
The spectrum shows the interaction noise produced in this situation. Interaction tones are
produced at the blade passing frequency and harmonics (1xBPF, 2xBPF, 3xBPF, etc.)
Figure 2.1: Fan, Wakes, and Interaction Noise with No TEB.
The conventional application of trailing edge blowing requires a large amount of air
because every wake deficit is filled. This configuration of TEB applied to every blade is shown
in Figure 2.2, which shows the same fan as Figure 2.1 except that the wakes are greatly reduced.
With only small amounts of unsteadiness present in the velocity profile only small amounts of
interaction noise are produced. The interaction tones are smaller than they were in the baseline
configuration of Figure 2.2, and would be eliminated completely if the wakes were perfectly
filled. Any remaining interaction noise is, however, present at the same frequencies and modes
as it was with no blowing; only the magnitudes are reduced.
Wakes
10
Figure 2.2: Fan, Wakes, and Interaction Noise with Full TEB.
Advanced trailing edge blowing differs from conventional (full / every blade) trailing
edge blowing because it does not attempt to fill every wake profile. This partial-blowing
configuration results in an immediate savings of air.
Instead of injecting air on every blade to fill every wake deficit, the application of air is
varied circumferentially to selectively fill wakes. This selective wake filling can be done in any
number of different ways, but numerical predictions have identified two configurations in
particular that are used in this research. The two configurations were chosen because they were
predicted to give the best and the worst noise reductions, respectively. The first configuration
predicted to give the most noise reduction is called "ATEB 1x1" and consists of injecting air into
alternating fan blades. The second configuration predicted to give the worst noise reduction is
called "ATEB 2x2" and consists of injecting air into alternating, adjacent fan blades. That is, air
is injected into two adjacent blades, skipped on the next two, applied on the next two, etc. Both
of these advanced layouts use air on exactly half of the fan blades present, and therefore
theoretically should use half as much air as conventional TEB.
The ATEB 1x1 layout serves as an example in Figure 2.3. For this explanation, it is
assumed that TEB perfectly fills any wake that it is applied to. Therefore, applying the ATEB
All Wakes
Filled
11
1x1 configurations is, acoustically speaking, equivalent to halving the number of fan blades. The
shape on the interaction noise is changed accordingly. In this case (ATEB 1x1), the acoustic
blade passing frequency is reduced to half of the physical blade passing frequency. The
harmonics are therefore spaced more closely together. This behavior is demonstrated in Figure
2.3, which shows the effects of applying the ATEB 1x1 layout. The illustration of the fan shows
how alternating wakes are filled. The spectrum shows a reduction in the original tones' power
and the introduction of new tones at new interaction frequencies.
New interaction modes are present at the new interaction frequencies, but the modal
structure at the "original" frequencies (1xBPF, 2xBPF, etc) is not changed by the application of
ATEB. Interaction modes are neither added nor removed at these frequencies, as shown in
section 3.4. This has two implications. The first is that any tone that is cut off with no TEB or
full TEB remains cut off when ATEB is applied. For example, fans are often designed to cut off
the 1xBPF tone. This tone will remain cut off when ATEB is applied. The second implication is
that ATEB should always decrease the original tones' power levels. This is because the modal
structure is held constant at the original frequencies while there are less wakes present to drive
noise generation.
Figure 2.3: Fan, Wakes, and Interaction Noise with ATEB 1x1.
Some Wakes
Filled
12
All of the ATEB layouts are by definition partial-blowing layouts, and as such they do
not achieve as much source-level noise reduction as conventional TEB on every blade. Some of
the velocity deficits are still present and therefore still produce some interaction noise. This
remaining noise is managed with acoustic liners. Acoustic liners used in turbofan engines
typically have high resistances, and are most effective at attenuating broadband noise. The liner
can be tuned to a specific tone at a specific engine power setting by designing the proper liner
cavity depth and having a low resistance. However, the liner becomes less effective for the other
tones and power settings. Thus, the liner is designed to be effective over a broad frequency band
by increasing the liner resistance. Rotor / stator interaction noise is tonal in nature, and the
interaction noise resulting from a fan with no TEB or full TEB has tones only at the BPF and
harmonics. Liner performance on conventional interaction noise is poor because the noise is
strongly tonal in nature but the liners are designed to attenuate broadband noise. When ATEB is
used the spectral shape of the interaction noise is changed. The sound energy is split into more
tones spread out over more frequencies. In addition the distribution of power over radial modes
may be changed even within a particular frequency. The noise from a fan with ATEB is more
"like" broadband noise. Therefore acoustic liner performance is expected to be improved. This
change in liner performance is validated in Chapter 5. Figure 2.4 shows how interaction noise
behaves more like broadband noise when ATEB is used. A standard rotor produces interaction
noise only at the BPF and harmonics, but an ATEB configured rotor produces more interaction
tones. The ATEB interaction spectrum is a better fit for a high resistance liner's attenuation
curve.
13
Figure 2.4: Interaction Spectra (a) without ATEB and (b) with ATEB, in comparison with liner attenuation
curves.
To summarize the concept, advanced trailing edge blowing leaves some of the wake
deficits unfilled in order to use less air. Because some of the deficits are left unfilled, less source-
level noise reduction is achieved with ATEB than is achieved with TEB. A second effect of
ATEB is to modify the spectral shape of the tonal interaction noise. The modified spectrum
allows acoustic liners to perform better, making up for the lesser amount of source-level
reduction. The end result is that similar overall noise reduction levels are achieved while using
less air. This hypothesis is investigated and demonstrated in this thesis.
14
Chapter 3 : Experimental Setup
This chapter describes how the experimental portion of the research was performed. It
describes the experimental fan and specialized blades used. The instrumentation to acquire
acoustic as well as flow data is described. Finally, a description of the test configurations
obtained is given. This material is presented so that the experimental results discussed in Chapter
4 can be understood.
3.1: ANCF Rig
The experimental portion of this research was performed in the Aero-Acoustic Propulsion
Laboratory at NASA Glenn Research Center. This facility provides a dome 130 feet in diameter
and 65 feet high with anechoically treated walls. This is the testing environment for the
"Advanced Noise Control Fan" (ANCF) [16]. The ANCF is a test bed specifically designed to
test fan noise reduction concepts and is equipped with far-field and in-duct instrumentation. It is
a 4-foot ducted fan with 16 blades driven by a 125 hp electric motor (at 1800 rpm for these
experiments). The inlet and aft mach numbers were 0.11 and 0.16, respectively. The rig also
includes a row of stator vanes whose number and location can be changed. Either 0, 14, or 28
vanes were used in these experiments. The axial spacing between the rotors and stators was one
half of a blade chord for the configurations discussed here. (A blade chord is about 5"). Inlet and
aft ducts are attached to the fan as 48 inch diameter spool pieces. The centerbody of the rig is 18
inches in diameter at the rotors and stators, widening to 24 inches in diameter at the aft duct exit.
Figure 3.1 shows a photograph of the ANCF in part (a) and a cross-sectional diagram in part (b).
15
Figure 3.1: (a) Photograph and (b) Cross-Sectional Diagram of ANCF Rig.
Acoustic liners were used on the rig in some configurations, called "softwall." The liners
were used to record data points which were later used to validate numerical predictions of liner
performance. They were not designed to directly demonstrate the performance of ATEB.
The liners were placed on the inlet nacelle as well as on the aft nacelle and aft
centerbody. When in use for softwall configurations, the liners were exposed to the flow through
the duct. When not in use, they were covered with a layer of tape to restore the hardwall
condition. The liners were removed from the rig during a second test entry, i.e. only hardwall
condition tested.
All of the liners used were linear, single degree of freedom liners. They were produced
by Goodrich as contributions to a previous project using the ANCF. The liners are 16 inches long
in the axial direction and are made of a wire mesh bonded to a perforated plate. They are
constructed in two identical halves such that they can be placed in the ducts to provide a nearly
seamless liner without discontinuities. The inlet liner has a normalized resistance of 1.7 pc and a
core depth of 0.85 inches, where pc is the free-field acoustic impedance in air. The aft liners have
normalized resistances of 1.0 pc and core depths of 1.0 inches. Figure 3.2 shows predicted inlet
and aft normalized impedances.
16
Figure 3.2: Predicted (a) Inlet and (b) Aft Liner Impedances.
3.2: TEB Fan Blades
Two test entries were performed on the ANCF during the course of this research. The
first was conducted from August to September 2004 and the second in March 2005. Two
different sets of fan blades were used for these two test entries. Both had internal flow passages
to direct air supplied at the hub into the working fluid.
The first type of blade is designed to inject air through a long slot in the trailing edge.
This results in a blunt trailing edge that causes vortex shedding if the blade is used with no
blowing air. For cases in which TEB was not desired these slots were sealed with an insert (plug)
that restored the blades' usual sharp trailing edge. A photograph of this type of blade is seen in
Figure 3.3A.
The blades used in the second test entry have the same external geometry as the first set,
with the difference being found in the method of TEB air injection. These fan blades use discrete
jets on the suction and pressure surfaces of the blade to inject the air. A photograph of these
blades can be seen in Figure 3.3B. The second set of blades was designed by Techsburg to
17
achieve wake-filling with less air, leading to more efficient noise reduction. This design is
discussed in a recent publication by Langford [17].
In a real engine the source of the blowing air would be a compressor bleed. In this rig the
source was an external, positive displacement blower. The mass flow rate was calculated by
measuring the temperature and pressure of the air supplied by the blower. The amount of air used
is expressed as a percentage of the total mass flow rate through the rig. (The total mass flow rate
is 125 lbm/s when the rig is operated at 1800 rpm.)
Figure 3.3: Fan Blades used in (a) Test Entry I and (b) Test Entry II.
3.3: In-Duct Velocity Instrumentation and Data Reduction
One of the three data types taken on the ANCF was in-duct fluid velocity. This data was
taken to examine the wake deficits responsible for interaction noise. The data can be used to tell
whether or not an application of TEB was successful in eliminating velocity deficits and
unsteadiness. The data can also be used as an input to one of the computer codes discussed in
Chapter 5.
A two component (axial and tangential) hotwire probe was used transduce axial velocity
and tangential flow angle at the stator vanes' axial location. For the experiments in the first test
entry, data were recorded at 80 tangential locations spanning two blade widths or 45 degrees, and
18
15 radial locations ranging from 10 to 23.5 inches from the centerline in increments of 1 inch.
(The hub radius of the blades is 9 inches and the tip radius of the blades is 24 inches.) For the
second test entry hotwire experiments, data were taken at 40 tangential locations spanning one
blade width or 22.5 degrees. The one blade width was sufficient because no ATEB layouts were
used and all wakes were theoretically the same. The full span measurements in the second test
entry used the same radial locations as those in the first test entry. Some measurements were
taken at a greater resolution over a smaller portion of the blade span. These measurements were
taken at radial locations ranging from 18 to 20 inches from the centerline in increments of 0.1
inch.
The velocity profile in the axial and tangential directions can be completely specified by
the axial velocity, tangential flow angle, radial location, and tangential blade speed. (The radial
velocity of the fluid is assumed to be zero.) A velocity triangle is shown below in Figure 3.4,
where "U" is the tangential blade velocity, "C" is the absolute velocity, "Cz" is the axial absolute
velocity, "W" is the relative velocity between the fluid and the rotor, and "a" is the tangential
angle between the axial direction and the absolute flow. The direction of vector W is set by the
direction fluid leaves the rotors. The direction of vector C is the direction required to enter the
stators.
Figure 3.4: Velocity Triangle and Notation.
19
A useful way to describe the wake profiles is with "upwash velocities." The upwash
velocity is the component of the absolute velocity perpendicular to the stator vane surface.
Fluctuations in this component are responsible for noise generation. Figure 3.5 shows the
upwash velocity using two velocity triangles. One triangle represents the freestream velocity,
with no losses caused by the fan blades. The other triangle represents the velocity in a wake.
Losses incurred along the fan blade surface reduce the relative velocity in the wake. This causes
the absolute velocity to change as well, because the blade speed is constant and the triangle must
be closed. Therefore the absolute velocity vector and its upwash component fluctuate between
the freestream and wake conditions. For on-design operation the freestream absolute velocity is
parallel to the stator vanes (to enter without separation) and the upwash velocity is equivalent to
the velocity component perpendicular to the direction of mean flow. The upwash velocity is
calculated at each radius as
Upwash Velocity = Cz*sin(amean-a) (3.1)
where amean is the average tangential flow angle at that radius.
Figure 3.5: Upwash Velocity Definition.
20
3.4: In-Duct Acoustic Instrumentation and Data Reduction
The in-duct microphone instrumentation consists of rotating-rake microphone arrays at
both the inlet and aft ducts. The inlet rotating rake is located between the last hardwall spool
piece and the duct lip. The aft rake is located just at the duct opening. Figure 3.6 shows a
photograph of the aft duct of the rig with the rake array installed. This data was taken to describe
the modal structure inside the rig. It was also used as an input to numerical codes used to make
predictions in Chapter 5.
The rake array rotates at 1% of the speed of the fan while measurements are being taken,
positioning the microphones at different spatial locations in the duct. When post-processed these
data describe modal behavior, giving complex pressures and powers for each mode measured.
The post-processing decomposition was run at multiples of 0.25xBPF from 0.25xBPF to 3xBPF.
The multiples of 0.25xBPF correspond to the expected interaction tones using the ATEB 2x2
configuration. Measured circumferential modes range from -14 to +14 and measured radial
modes range from 0 to 5.
Figure 3.6: ANCF Aft Duct with Rotating Rake Microphone Array.
21
The circumferential interaction modes "m" present in the rig are calculated using the
number of blades "B", the number of vanes "V", the BPF harmonic "N", and the set of integers
k=[0, +-1, +-2, …] using
m = (N*B) + (k*V) (3.2)
For configurations with no TEB or Full TEB, the use of this equation is straightforward
and gives the predicted circumferential interaction modes shown in Table 3.1. This table lists the
circumferential interaction modes "m" for the first three BPFs, for configurations with 14 and 28
vanes. The modes (-14 < m < 14) are of special interest because they lie within the
experimentally measured range. For ATEB 1x1 configurations, the number of blades must be
halved (because some are made acoustically "invisible" by the application of TEB) and the
number of blade passing frequencies under consideration must be doubled to examine the same
frequency range. These predictions are shown in Table 3.2. For ATEB 2x2 configurations, the
number of blades is quartered and the number of blade passing frequencies is quadrupled. These
predictions are shown in Table 3.3.
It is important to note that the circumferential interaction modes at the 1xBPF, 2xBPF,
and 3xBPF are unchanged by the application of ATEB. No interaction modes are added or
removed at these frequencies. This is demonstrated in the sample calculations below. First the
circumferential interaction modes for the 1xBPF of a configuration with 14 Vanes and no TEB
are calculated as
m = (1*16) + ([-2,-1,0,1,2])*14) = [-12,2,16,30,44] (3.3)
where N=1 to denote the 1xBPF tone, B=16 to denote 16 blades present, k=[-2,-1,0,1,2] to
consider five different interaction modes, and V=14 to denote 14 vanes present. Next the
circumferential interation modes for the 1xBPF of a configuration with 14 vanes and ATEB 1x1
are calculated as
m = (2*8) + ([-2,-1,0,1,2]*14) = [-12,2,16,30,44] (3.4)
22
where N=2 to denote the 1xBPF tone. (Every other fan blade is made acousically invisible by
ATEB, halving the effective acoustic blade passing frequency. Therefore the harmonic must be
doubled to examine the frequency corresponding to the no TEB 1xBPF.) The variable B=8
denotes 8 wakes. There are 16 blades present, but only the 8 of them allowed to produce wakes
are acoustically relevant. The variables k and V remain unchanged from the no TEB calculation.
When ATEB 1x1 is applied the variable N is doubled while the variable B is halved, and
therefore the same interaction modes are predicted as were predicted without ATEB.
Table 3.1: Predicted Circumferential Modes for No TEB / Full TEB Configurations.
Table 3.2: Predicted Circumferential Modes for ATEB 1x1 Configurations.
1xBPF 2xBPF 3xBPF 1xBPF 2xBPF 3xBPF-54 -38 -22 -124 -108 -92-40 -24 -8 -96 -80 -64-26 -10 6 -68 -52 -36-12 4 20 -40 -24 -8
2 18 34 -12 4 2016 32 48 16 32 48
No TEB & Full TEB - 14 Vanes No TEB & Full TEB - 28 Vanes
0.5xBPF 1xBPF 1.5xBPF 2xBPF 2.5xBPF 3xBPF-62 -54 -46 -38 -30 -22-48 -40 -32 -24 -16 -8-34 -26 -18 -10 -2 6-20 -12 -4 4 12 20
-6 2 10 18 26 348 16 24 32 40 48
22 30 38 46 54 62
0.5xBPF 1xBPF 1.5xBPF 2xBPF 2.5xBPF 3xBPF-76 -68 -60 -52 -44 -36-48 -40 -32 -24 -16 -8-20 -12 -4 4 12 20
8 16 24 32 40 4836 44 52 60 68 76
ATEB 1x1 - 14 Vanes
ATEB 1x1 - 28 Vanes
23
Table 3.3: Predicted Circumferential Modes for ATEB 2x2 Configurations.
Within each of these circumferential modes are radial modes that may or may not
propagate out of the duct. To determine whether or not a mode will propagate, it is necessary to
compute the mode axial wavenumber [18]. To this end, the free-field acoustic wave number is
given by
k0 = (2*pi*f) / c (3.5)
where f is frequency in Hz and c is the speed of sound in m/s. The flow Mach number "M" and
the mode eigenvalue "kmn" are also required, where "m" is the circumferential mode number and
"n" is the radial mode number. The eigenvalues used were calculated for the hardwall condition
[18]. A mode will propagate if the condition
ko > kmn * sqrt(1-M2) (3.6)
0.25xBPF 0.5xBPF 0.75xBPF 1xBPF 1.25xBPF 1.5xBPF-38 -34 -30 -26 -22 -18-24 -20 -16 -12 -8 -4-10 -6 -2 2 6 10
4 8 12 16 20 2418 22 26 30 34 38
1.75xBPF 2xBPF 2.25xBPF 2.5xBPF 2.75xBPF 3xBPF-42 -38 -34 -30 -26 -22-28 -24 -20 -16 -12 -8-14 -10 -6 -2 2 6
0 4 8 12 16 2014 18 22 26 30 3428 32 36 40 44 48
0.25xBPF 0.5xBPF 0.75xBPF 1xBPF 1.25xBPF 1.5xBPF-52 -48 -44 -40 -36 -32-24 -20 -16 -12 -8 -4
4 8 12 16 20 2432 36 40 44 48 52
1.75xBPF 2xBPF 2.25xBPF 2.5xBPF 2.75xBPF 3xBPF-56 -52 -48 -44 -40 -38-28 -24 -20 -16 -12 -8
0 4 8 12 16 2028 32 36 40 44 48
ATEB 2x2 - 14 Vanes
ATEB 2x2 - 28 Vanes
24
is met.
The propagating interaction modes are therefore first a function of which circumferential
interaction modes exist in the duct, and then of which radial modes propagate out of the duct.
These calculations were performed to identify the propagating interaction modes in the ANCF.
The circumferential modes within the bounds (-14 < m <14) are taken from Tables 3.1 through
3.3. The propagating radial modes within each of these circumferential modes are identified
using the condition of Equation 3.4. Tables 3.4 through 3.6 list the propagating interaction modes
for no TEB / full TEB, ATEB 1x1, and ATEB 2x2 configurations, respectively.
Table 3.4: Propagating Interaction Modes for Configurations with No TEB / Full TEB.
Table 3.5: Propagating Interaction Modes for Configurations with ATEB 1x1.
1xBPF 2xBPF 3xBPF 1xBPF 2xBPF 3xBPF(2,0) (4,0) (-8,0) (none) (4,0) (-8,0)
(4,1) (-8,1) (4,1) (-8,1)(6,0)(6,1)(6,2)
No TEB & Full TEB - 14 Vanes No TEB & Full TEB - 28 Vanes
0.5xBPF 1xBPF 1.5xBPF 2xBPF 2.5xBPF 3xBPF(none) (2,0) (-4,0) (4,0) (-2,0) (-8,0)
(4,1) (-2,1) (-8,1)(-2,2) (6,0)(-2,3) (6,1)
(6,2)
0.5xBPF 1xBPF 1.5xBPF 2xBPF 2.5xBPF 3xBPF(none) (none) (-4,0) (4,0) (none) (-8,0)
(4,1) (-8,1)
ATEB 1x1 - 14 Vanes
ATEB 1x1 - 28 Vanes
25
Table 3.6: Propagating Interaction Modes for Configurations with ATEB 2x2.
3.5: Far-field Acoustic Instrumentation and Data Reduction
The far-field instrumentation of the ANCF consists of 30 microphones arranged around
the rig. One array of 15 microphones is centered on the inlet duct and another array of 15
microphones is centered on the aft duct. The inlet microphones are placed 10 feet away from the
center of the inlet duct opening, from 0 degrees in-line with the duct axis to 90 degrees to the
side. The aft microphones are placed 12 feet away from the center of the aft duct opening and are
arranged from 90 degrees to 160 degrees with respect to the duct axis as shown in Figure 3.7.
Figure 3.8 shows a photograph of the rig with the far-field microphone arrays deployed.
0.25xBPF 0.5xBPF 0.75xBPF 1xBPF 1.25xBPF 1.5xBPF(none) (none) (-2,0) (2,0) (none) (-4,0)
1.75xBPF 2xBPF 2.25xBPF 2.5xBPF 2.75xBPF 3xBPF(0,0) (4,0) (-6,0) (-2,0) (2,0) (-8,0)(0,1) (4,1) (-6,1) (-2,1) (2,1) (-8,1)(0,2) (8,0) (-2,2) (2,2) (6,0)
(-2,3) (2,3) (6,1)(6,2)
0.25xBPF 0.5xBPF 0.75xBPF 1xBPF 1.25xBPF 1.5xBPF(none) (none) (none) (none) (none) (-4,0)
1.75xBPF 2xBPF 2.25xBPF 2.5xBPF 2.75xBPF 3xBPF(0,0) (4,0) (8,0) (none) (-12,0) (-8,0)(0,1) (4,1) (-8,1)(0,2)
ATEB 2x2 - 14 Vanes
ATEB 2x2 - 28 Vanes
26
Figure 3.7: Far-Field Microphone Array Geometry.
Figure 3.8: Photograph of ANCF and Far-Field Microphone Arrays.
The time history measurements of each microphone were used to calculate sound
pressure level spectra. Then the pressure spectra were used to calculate power spectra. To this
end, first each pressure level in decibels was converted into pressure mean-square-value in Pa2.
Then each msv pressure was used to calculate intensity by dividing by pc (characteristic acoustic
impedance). Each intensity was then integrated with area to give sound power.
The interaction tones from these power spectra were used in the far-field data analysis.
Configurations using no TEB or full TEB have interaction tones at multiples of 1xBPF, or 480
27
Hz. On the other hand, configurations using ATEB 1x1 have interaction tones at multiples of
0.5xBPF (240 Hz) and configurations using ATEB 2x2 have interaction tones at multiples of
0.25xBPF (120 Hz).
Using these two steps (conversion from to power spectra and then selecting relevant
tones) the far-field data are reduced to the form used in Chapter 4. Extensive comparisons are
made to describe the performance of different TEB configurations.
3.6: Experimental Test Configurations
As mentioned above, the experiments were performed in two test entries separated by
several months. Results from these test entries are presented in Chapter 4. This section lists and
describes the configurations run.
3.6.1: First Test Entry
The configurations in the first test entry can be described in terms of five parameters. The
first parameter specifies which duct of the ANCF is being used, either the inlet or the aft. The
second parameter specifies how many stator vanes are used, either 0, 14, or 28. The third
parameter specifies the application of TEB, if any. The possible choices for this parameter are no
TEB, full TEB, ATEB 1x1, and ATEB 2x2. The fourth parameter specifies the amount of air
used for wake-filling. The fifth parameter specifies the duct wall condition, either hardwall or
softwall. The softwall condition indicates that the liner was installed in the duct. For example,
[Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall] denotes a configuration using the inlet duct of
the ANCF, 14 stator vanes, the ATEB 1x1 alternating blowing layout, 0.9% of the mass flow
through the rig, and no liner.
In this test entry, hotwire data were collected for five configurations. One baseline
configuration was run with no TEB (0% air). Three more configurations were run with full TEB
using mass flow rates of 1.1%, 1.5%, and 1.8%. The last configuration was run with the ATEB
28
1x1 layout using 0.9% air. Note that the duct, vanes, and liner parameters are not applicable to
the hotwire data type.
Rotating rake and far-field data were collected for many configurations as shown in
Tables 3.7 and 3.8, respectively. Each row of the table lists one or more configurations. If one
blowing rate is listed in a row, that row defines one configuration with the five parameters
discussed above. If a row lists multiple blowing rates, it describes multiple configurations that
have the same duct, number of vanes, TEB layout, and liner condition, but different blowing
rates.
Table 3.7: Rake Data Test Matrix (1st Entry).
Duct # Vanes Layout Liner Blowing Rates (%)Inlet 0 No TEB Hardwall 0Inlet 14 No TEB Hardwall 0Inlet 14 No TEB Softwall 0Inlet 14 ATEB 1x1 Hardwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Inlet 14 ATEB 1x1 Softwall 0.9Inlet 14 ATEB 2x2 Hardwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Inlet 14 ATEB 2x2 Softwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Inlet 14 Full TEB Hardwall 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8Inlet 28 No TEB Hardwall 0Inlet 28 No TEB Softwall 0Inlet 28 ATEB 1x1 Hardwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Inlet 28 ATEB 1x1 Softwall 0.9Inlet 28 ATEB 2x2 Hardwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Inlet 28 ATEB 2x2 Softwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Aft 0 No TEB Hardwall 0Aft 14 No TEB Hardwall 0Aft 14 No TEB Softwall 0Aft 14 ATEB 1x1 Hardwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Aft 14 ATEB 1x1 Softwall 0.9Aft 14 ATEB 2x2 Hardwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Aft 14 ATEB 2x2 Softwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Aft 14 Full TEB Hardwall 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8Aft 28 No TEB Hardwall 0Aft 28 No TEB Softwall 0Aft 28 ATEB 2x2 Hardwall 0, 0.55, 0.7, 0.8, 0.9, 1.0Aft 28 ATEB 2x2 Softwall 0, 0.55, 0.7, 0.8, 0.9, 1.0
29
Table 3.8: Far-Field Data Test Matrix (1st Entry).
Duct # Vanes Layout Liner Blowing Rates (%)Inlet 0 No TEB Hardwall 0Inlet 0 Full TEB Hardwall 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8Inlet 14 No TEB Hardwall 0Inlet 14 No TEB Softwall 0Inlet 14 ATEB 1x1 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Inlet 14 ATEB 1x1 Softwall 0.9Inlet 14 ATEB 2x2 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Inlet 14 ATEB 2x2 Softwall 0.55, 0.7, 0.8, 0.9, 1.0Inlet 14 Full TEB Hardwall 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8Inlet 28 No TEB Hardwall 0Inlet 28 No TEB Softwall 0Inlet 28 ATEB 1x1 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Inlet 28 ATEB 1x1 Softwall 0.9Inlet 28 ATEB 2x2 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Inlet 28 ATEB 2x2 Softwall 0.55, 0.7, 0.8, 0.9, 1.0Aft 0 No TEB Hardwall 0Aft 0 Full TEB Hardwall 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8Aft 14 No TEB Hardwall 0Aft 14 No TEB Softwall 0Aft 14 ATEB 1x1 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Aft 14 ATEB 1x1 Softwall 0.9Aft 14 ATEB 2x2 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Aft 14 ATEB 2x2 Softwall 0.55, 0.7, 0.8, 0.9, 1.0Aft 14 Full TEB Hardwall 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8Aft 28 No TEB Hardwall 0Aft 28 No TEB Softwall 0Aft 28 ATEB 1x1 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Aft 28 ATEB 1x1 Softwall 0.9Aft 28 ATEB 2x2 Hardwall 0.55, 0.7, 0.8, 0.9, 1.0Aft 28 ATEB 2x2 Softwall 0.55, 0.7, 0.8, 0.9, 1.0
3.6.2: Second Test Entry
Hotwire velocity data were taken for a total of six configurations in the second test entry.
The first was a baseline configuration of no blowing. The second was a full TEB configuration at
the optimum blowing rate of 0.65%. The third used the same layout as the second; however, the
data were taken in greater resolution over a smaller portion of the blade span. The last three of
the configurations tested used a blade-to-vane spacing of one rotor chord; to remain focused on
the ATEB concept these results are not presented in this thesis (all experiments presented used a
spacing of one half of a rotor chord).
30
Far-field data were collected for many configurations as shown in Table 3.9, but the
number of vanes was always 14 and the liner conditions was always hardwall. The ATEB 2x2
layout was not used because of its inferior performance in the first test entry.
Rake data were collected for the second test entry, but are not presented in this thesis
because they lead to the same conclusions as the data from the first test entry. Similar behavior
was seen in both test entries, as shown in a discussion of the far-field data results in Chapter 4.
Therefore the second entry rake data are not needed for this discussion of the ATEB concept.
Table 3.9: Far-Field Data Test Matrix (2nd Entry).
Duct # Vanes Layout Liner Blowing Rates (%)Inlet 14 No TEB Hardwall 0Inlet 14 No TEB Hardwall 0Inlet 14 ATEB 1x1 Hardwall 0.36, 0.41, 0.43, 0.46, 0.48, 0.53, 0.56
Inlet 14 Full TEB Hardwall0.40, 0.50, 0.59, 0.67, 0.74, 0.85, 0.93, 0.96, 0.99, 1.03, 1.08
Inlet 14 Full TEB Hardwall 0.57, 0.75, 0.86, 0.87, 0.96, 1.01Aft 14 No TEB Hardwall 0Aft 14 No TEB Hardwall 0Aft 14 ATEB 1x1 Hardwall 0.36, 0.41, 0.43, 0.46, 0.48, 0.53, 0.56
Aft 14 Full TEB Hardwall0.40, 0.50, 0.59, 0.67, 0.74, 0.85, 0.93, 0.96, 0.99, 1.03, 1.08
Aft 14 Full TEB Hardwall 0.57, 0.75, 0.86, 0.87, 0.96, 1.01
31
Chapter 4 : Experimental Results
This chapter presents results from the hardwall experiments performed on the ANCF.
Hotwire results are given first, to show how wake deficits were filled by the application of TEB.
Rake data are shown next, to show how ATEB affected the modal structure in the rig. Far-field
data are shown last, to examine the source-level reductions achieved with TEB and ATEB.
4.1: Hotwire Results (First Test Entry)
This section discusses the wake profiles measured by hotwire probe in the first test entry.
The examination is performed to assess how effectively wake-filling was achieved by each
configuration measured.
The hotwire results are presented as upwash velocity contours in Figure 4.1. The units of
upwash velocity are ft/s. A negative value indicates a wake deficit and a positive value indicates
a wake surplus (over-blowing). The ideal value is 0 ft/s, representing no disturbance. Positive or
negative values lead to noise generation. Each contour describes a profile spanning two blade
widths, or 45 tangential degrees (360 degrees divided by 16 blades equals 22.5 degrees per
blade). The profiles extend from a radial location of 10" to 23.5". (The locations of the hub at 9
inches and the tip at 24 inches are shown with arrows on the figure.) The direction of rotation is
from the left to the right as indicated in the plots. The right side of each wake is the pressure side
and the left side is the suction side.
Part (a) of the figure shows an upwash velocity contour for the configuration of no TEB.
No wake-filling is attempted, and therefore two distinct wakes are seen in the contour. The
wakes are 5 degrees wide and exhibit 10 degrees of sweep from hub to tip. The upwash
velocities in the wakes are about -30 ft/s, and are 0 ft/s in the freestream between wakes. Upwash
velocities in addition of those of the wake itself are seen near the tip of the blade. To the left of
each wake is a region of positive upwash velocity and to the right of each wake is a region of
negative upwash velocity. These velocities are generated by counter-rotating vortices. The
vortices are likely synchronized with the rotational speed of the fan, otherwise the averaging
technique employed to record the hotwire data would eliminate the signal. The ANCF includes
rub strips to ensure a tight tip clearance, therefore the vortices are not likely due to leakage from
32
the pressure to the suction side of the blade. The presence of these vortices is significant because
their respective upwash velocities act as noise sources in the same way as the wakes themselves.
A destructive interference effect may occur because the vortices alternate between positive and
negative upwash velocities in the tangential direction. This is analogous to noise sources out of
phase with one another.
Part (b) shows an upwash velocity contour for the first of the three full TEB
configurations. This configuration uses 1.1% of the mass flow through the rig as blowing air.
The contour plot shows that this configuration was not successful in filling the wake deficits. The
wakes are still present and appear mostly unchanged from the no TEB configuration. Only a
small amount of wake-filling is apparent near the hub, with upwash velocities near -20 ft/s. The
conclusion is that 1.1% air is not enough to achieve effective wake-filling. The tip vortices are
still present, and similar behavior is also seen at the blade hub. Regions of positive upwash
velocity are seen between the wakes at the hub. Tip and hub vortices are seen in all remaining
parts of Figure 4.1.
Part (c) shows an upwash velocity contour for the second of the three full TEB
configurations. This configuration uses 1.5% of the mass flow through the rig as blowing air.
The contour plot clearly shows that upwash velocities have been reduced. The wakes are still
visible, but upwash velocities are now -5 ft/s near the blade tip and -10 ft/s near the blade hub.
The conclusion is that 1.5% air is an appropriate amount to achieve wake-filling, and that
interaction noise should be reduced with this configuration.
Part (d) shows an upwash velocity contour for the third and last full TEB configuration
using 1.8% of the mass flow through the rig as blowing air. Upwash velocities are only -5 ft/s
near the blade hub, but have risen to +15 ft/s near the blade tip. This means that too much air was
injected. The wake deficit became a wake surplus, i.e. over-blowing occurred. The magnitude of
the upwash velocity drives interaction noise, so a wake surplus is a noise generation mechanism
just like a wake deficit. The conclusion is that 1.8% air is excessive and that over-blowing occurs
with an associated increase in noise.
33
Part (e) shows an upwash velocity contour for the ATEB 1x1 configuration using 0.9%
air. It is clear that this air was applied to the left wake, which has been filled with slight over-
blowing. The right wake is unaffected. It is interesting to note that 1.8% air spread over 16 wakes
did not give the same results as 0.9% air spread over 8 wakes. In the former case, severe over-
blowing occurs. In the latter, only minor over-blowing is seen. This means that the optimum
blowing rate for ATEB 1x1 is not necessarily exactly half of the optimum rate for full TEB.
Taken together, the five parts of Figure 4.1 shows how wake-filling is achieved using
different amounts of air. Too little air leaves the wakes unfilled, while too much air causes
counterproductive over-blowing. Using 0.9% air to fill 8 wakes or 1.5% air to fill 16 wakes are
both shown to be effective solutions. In later sections, far-field data is used to show that these are
often the optimum blowing rates for ATEB and TEB, respectively.
34
Figure 4.1: Upwash Velocity Contours for (a) No TEB, (b) Full TEB 1.1%, (c) Full TEB 1.5%, (d) Full TEB
1.8%, and (e) ATEB 1x1 0.9%.
35
4.2: Rotating Rake Results (First Test Entry)
This section presents results for the in-duct rake data measured in the first test entry. This
study is performed because the rake data contains modal information and it is important to show
how ATEB spreads out interaction noise into more modes than conventional TEB. Chapter 3
presented a list of theoretical interaction modes while this section presents experimental
measurements. In addition to its presentation here, rake data is also used in Chapter 5 as an input
to computer codes predicting liner performance.
Not all of the rake data collected in the test entry are presented in this thesis. First, sound
power levels are presented but complex pressures are not. Second, only configurations using no
blowing or optimum blowing rates are presented. Third, only the interaction frequencies relevant
to each configurations are examined. For example, the 1.25xBPF tone is examined for ATEB
2x2 configurations but not for no TEB configurations. The main body of the thesis discusses and
plots data for configurations with the inlet duct and 14 vanes. Appendix A tabulates sound power
levels for these configurations, and also for those with 28 vanes or the aft duct.
4.2.1 Rake Results - No TEB Configuration
From Table 3.4, the only propagating interaction mode for [Inlet Duct, 14 Vanes, No
TEB 0%, Hardwall] at the 1xBPF is (2,0). At the 2xBPF they are the (4,0) and (4,1) modes. At
the 3xBPF they are the (-8,0), (-8,1), (6,0), (6,1), and (6,2) modes. Figure 4.2 (corresponding
with tables A.1 through A.3) shows the modes actually measured in the ANCF rig. Part (a) of
this figure shows the (2,0) mode to be dominant; this agrees with theory because the (2,0) mode
is the only propagating interaction mode at this frequency. Likewise in part (b) the (4,0) mode is
dominant followed by the (4,1) mode - these are also the predicted modes at 2xBPF. At 3xBPF,
part (c) show the (6,0) mode to be dominant followed by the (6,1) mode. These are two of the
predicted modes at this frequency; the (-8,0), (-8,1), and (6,2) modes are either not excited or do
not have enough power to differentiate them from the other, non-interaction modes measured.
These results show agreement between theory and measured results. The dominant modes
measured in the rig are all predicted interaction modes.
36
Figure 4.2: Rake Data for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall] at (a) 1xBPF, (b) 2xBPF, (c) 3xBPF.
37
4.2.2 Rake Results - Full TEB Configuration
Figure 4.3 (corresponding with tables A.4 through A.6) shows the measured modal data
for the configuration [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall]. The predicted modes are
the same as for the no TEB configuration described above. Part (a) of the figure shows that the
predicted (2,0) mode is still dominant at the 1xBPF. At the 2xBPF, part (b) shows that the
predicted (4,0) and (4,1) modes are still dominant as well. However, with full TEB the (4,1)
mode has more power than the (4,0). According to part (c) all power levels are low at 3xBPF, but
the predicted (6,0), (6,1), and (6,2) modes are the dominant modes present. The (-8,0) and (-8,1)
modes have power levels less than 60 dB and do not contribute a significant amount of power to
this configuration.
These results are very similar to the results for no TEB. Power levels are lower but the
predicted modes still dominate. Even though the same interaction modes are present as in the no
blowing case, the distribution of power into radial modes can be different. This change is
important because it can affect the performance of liners.
38
Figure 4.3: Rake Data for [Inlet Duct, 14 Vanes, Full TEB 1.5%,Hardwall] at (a) 1xBPF,(b)2xBPF,(c) 3xBPF.
39
4.2.3 Rake Results - ATEB 1x1 Configuration
When the ATEB 1x1 configuration is applied, new interaction modes are produced. Table
3.5 shows how the original modal structure at 1xBPF, 2xBPF, and 3xBPF remain unchanged
while new modes are added at other frequencies. When 14 vanes are used, propagating
interaction modes are added at the 1.5xBPF and 2.5xBPF tones. The (-4,0) mode is added at
1.5xBPF and the (-2,0), (-2,1), (-2,2), and (-2,3) modes are added at 2.5xBPF.
Figure 4.4 (corresponding to tables A.7 through A.12) shows the modes measured for the
configuration [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]. No propagating interaction
modes are predicted at 0.5xBPF, and correspondingly part (a) of the figure shows only a few
low-power modes at this frequency. The predicted mode at 1xBPF is (2,0) just as it was in the
previous configurations, and part (b) shows this mode to be dominant. A new interaction mode (-
4,0) is predicted at 1.5xBPF, and part (c) shows this to be the second most dominant mode
measured; the (-3,0) mode is 0.6 dB louder but is not an interaction mode. The presence of this
mode is not clear. At 2xBPF the predicted modes are still (4,0) and (4,1), and these modes are
dominant as shown in part (d). The other new modes due to ATEB 1x1 are predicted at 2.5xBPF
and part (e) illustrates their presence. They would be the dominant 4 modes if not for the (11,0)
mode, which is the most dominant but not a predicted interaction mode. The predicted modes at
3xBPF are unchanged from the previous configurations, and part (f) shows the (6,0) and (6,1)
modes to be dominant.
The modal structure at the original three BPF tones remained unchanged by the
implementation of the ATEB 1x1 blowing layout. The predicted interaction modes are dominant
at these frequencies. The new modes due to ATEB 1x1 were measured and showed a strong
presence, but were not the dominant modes at their respective frequencies. At 1.5xBPF and
2.5xBPF the dominant modes were not predicted interaction modes. The reason for the presence
of dominant non-interaction modes is not clear.
40
Figure 4.4: Rake Data for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall] at (a) 0.5xBPF, (b) 1xBPF, (c)
1.5xBPF, (d) 2xBPF, (e) 2.5xBPF, and (f) 3xBPF.
41
4.2.4 Rake Results - ATEB 2x2 Configuration
The ATEB 2x2 configuration leads to new propagating interaction modes at the new
tones. In this case, the new tones take place at 0.25xBPF, 0.5xBPF, 0.75xBPF, and so forth.
However, there are propagating modes at only some of these tones as shown in Table 3.6. The (-
2,0) mode is present at 0.75xBPF; modes (0,0), (0,1), and (0,2) are introduced at 1.75xBPF;
modes (-6,0), (-6,1), and (8,0) are introduced at 2.25xBPF; and modes (2,0), (2,1), (2,2), and
(2,3) are added at 2.75xBPF. The modal structure measured for the configuration [Inlet Duct, 14
Vanes, ATEB 2x2 0.9%, Hardwall] is shown in Figures 4.5 and 4.6.
Figure 4.5 (corresponding to tables A.13 through A.18) shows the measured modal
structure for frequencies up to 1.5xBPF. No propagating interaction modes are predicted at
0.25xBPF, 0.5xBPF, or 1.25xBPF. Parts (a), (b), and (e) of the figure show non-interaction
modes at these frequencies that are small in power compared to the measured interaction modes
of other frequencies. Part (c) shows the dominant mode at 0.75xBPF to be (-2,0), which is the
predicted interaction mode. The predicted mode at 1xBPF is (2,0), and part (d) shows that this
mode is dominant just as it was in all previous configurations. The predicted mode at 1.5xBPF is
(-4,0) and this is the dominant mode present according to part (f).
Figure 4.6 (corresponding to tables A.19 through A.24) shows the measured powers for
modes contained in frequencies from 1.75xBPF to 3xBPF. Part (a) shows the modes at
1.75xBPF. The predicted modes at this frequency are (0,0), (0,1), and (0,2). These are the three
most powerful modes measured. The predicted modes at 2xBPF are (4,0) and (4,1) as they were
in all previous configurations discussed; part (b) shows them to be the two most powerful modes
present. Three new modes are predicted at 2.25xBPF, these are the (-6,0), (-6,1), and (8,0)
modes. Part (c) shows that these are the three most powerful modes measured. As with the
ATEB 1x1 configuration, the modes predicted at 2.5xBPF are (-2,0), (-2,1), (-2,2), and (-2,3).
These are seen in part (d), although the (-2,1) mode shares dominance with the (11,0) mode
which is not an interaction mode. More new modes are predicted at 2.75xBPF, these being the
(2,0), (2,1), (2,2), and (2,3) modes. The (2,0) mode is dominant. Finally, the predicted modes at
3xBPF are again (-8,0), (-8,1), (6,0), (6,1), and (6,2). These are all seen in part (f), with (6,0)
being dominant.
42
As with the ATEB 1x1 data examined in the previous section, the ATEB 2x2 data also
shows that the modal structure at the original, integer multiples of the BPF is unchanged. The
dominant modes at these frequencies are predicted interaction modes. The interaction modes at
the new tones (0.25xBPF, 0.5xBPF, etc.) are also seen in the rake data. The predicted interaction
modes are not always dominant at these new frequencies.
Results for configurations using the aft duct or 28 vanes are found in Appendix A. All of
the configurations with the inlet duct and 28 vanes exhibit the predicted interaction modes, but
they are not always the dominant modes. Especially at the 3xBPF, unexpected modes are found
in the rake data. Considering those configurations with the aft duct and 14 vanes, the no TEB and
full TEB cases behave as expected. The ATEB 1x1 case, again, shows unexpected modes at
3xBPF. The ATEB 2x2 case shows a strongly dominant unexpected mode at 3xBPF, mode (-
12,0). This is an interaction mode for 28 vanes, but data for all other frequencies agrees with the
14 vane predictions. Finally, the configurations with the aft duct and 28 vanes behave as
expected except for the power found at the 1xBPF which should be cut off.
43
Figure 4.5: Rake Data for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall] at (a) 0.25xBPF, (b) 0.5xBPF, (c)
0.75xBPF, (d) 1xBPF, (e) 1.25xBPF, and (f) 1.5xBPF.
44
Figure 4.6: Rake Data for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall] at (a) 1.75xBPF, (b) 2xBPF, (c)
2.25xBPF, (d) 2.5xBPF, (e) 2.75xBPF, and (f) 3xBPF.
45
4.3 Far-Field Results (First Test Entry)
This section presents hardwall results using far-field data from the first test entry. These
results are important because they describe the source-level noise reductions obtained by TEB
and ATEB. The most relevant results are presented here. First a baseline (no blowing)
configuration is shown, and then the optimum blowing rates are found. The configurations using
the optimum blowing rates are described in more detail. For completeness, the sound power
spectra of all configurations can be found in Appendix B.
4.3.1: Configurations using 0 Vanes
The best that TEB can accomplish is to completely eliminate interaction noise; it cannot
eliminate the tonal noise due to the rotor alone. Thus, the minimum possible sound level can be
quantified by examining configurations with zero stator vanes, i.e. there is no interaction noise
and this represents a lower limit for the configurations with blowing.
Sound power spectra for the configurations [Inlet Duct, 0 Vanes, No TEB 0%, Hardwall]
and [Aft Duct, 0 Vanes, No TEB, Hardwall] are shown in Figure 4.7 parts (a) and (b),
respectively. For the inlet duct, the total tonal power is 94.8 dB and for the aft duct the total tonal
power is 98.4 dB. These values are theoretically the lowest that can be achieved by TEB (not
counting the effects of acoustic liners).
46
Figure 4.7: 0-Vane Sound Power Spectra for (a) [Inlet Duct, 0 Vanes, No TEB 0%, Hardwall] and (b) [Aft
Duct, 0 Vanes, No TEB 0%, Hardwall] (dB ref. 10-12 W/m2).
4.3.2: Configurations using the Inlet Duct and 14 Vanes
This thesis breaks the remainder of the far-field data into four groups so that meaningful
comparisons can be made. First the group of configurations using the inlet duct and 14 stator
vanes is considered. The baseline case for this group is [Inlet Duct, 14 Vanes, No TEB 0%,
Hardwall]. Figure 4.8 shows a power spectrum for this configuration. The 1xBPF tone is
dominant and each subsequent BPF tone contributes less power until the 8xBPF tone contributes
an insignificant amount (down 30 dB). The total tonal power is 109.2 dB. Therefore, a 14.4 dB
reduction would occur if interaction noise were completely eliminated.
47
Figure 4.8: Power Spectrum for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall].
The configurations using TEB and ATEB are now discussed. The blowing rate is an
important parameter for such configurations; too little air will not give much noise reduction and
too much air will result in counterproductive over-blowing. It is therefore necessary to identify
the best blowing rates to use with TEB, ATEB 1x1, and ATEB 2x2. The optimum blowing rate
is defined as the blowing rate resulting in the lowest total tonal sound power. The optimum rates
are found by calculating the total tonal powers of configurations with different blowing rates and
comparing them. This is shown in Figure 4.9, which shows sound powers for the TEB, ATEB
1x1, and ATEB 2x2 configurations as functions of the blowing rate. The TEB powers are shown
in blue. At 0% blowing the power is the baseline level of 109.2 dB. As the blowing rate is
increased power falls until a clearly defined optimum rate of 1.5% is reached. The power at this
optimum rate is 101.6 dB (a 7.6 dB reduction). At greater blowing rates the power rises again
due to over-blowing. The ATEB 1x1 powers are shown in green. The optimum blowing rate
using ATEB 1x1 is 0.9%, which results in a power of 104.5 dB (a 4.7 dB reduction). The ATEB
2x2 powers are shown in red, and the optimum blowing rate is also 0.9%, which results in a
power of 106.2 dB (a 3.0 dB reduction). It is interesting to note that the optimum blowing rate
for the ATEB concept seems to be less sensitive than the optimum for the conventional full TEB.
For example, the ATEB 2x2 blowing rate can be reduced to 0.7% and still gives a noise
reduction of 2.7 dB which is virtually the same as the reduction for the 0.9% case.
The important conclusions drawn from this figure is that the ATEB optimum blowing
rate is less than the TEB optimum blowing rate. Advanced TEB uses 60% (or less) as much air
48
as conventional TEB. In return, ATEB gives a lesser amount of source-level noise reduction. It is
also interesting to note that ATEB 1x1 gives more reduction than ATEB 2x2.
100
102
104
106
108
110
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
Blowing Rate (%)
So
un
d P
ow
er (
dB
)
ATEB 1x1 Hardwall ATEB 2x2 Hardwall Full TEB Hardwall
Figure 4.9: Power vs. Blowing Rate for the Configurations [Inlet Duct, 14 Vanes].
Now that the optimum blowing rates have been identified, the sound power spectra for
the TEB configuration using 1.5% air, the ATEB 1x1 configuration using 0.9% air, and the
ATEB 2x2 configuration using 0.9% air are considered. These spectra are shown in Figure 4.10.
Part (a) shows the configuration [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall]. Compared to
the no-blowing case, the 1xBPF, 2xBPF, and 3xBPF tones are reduced by 7.0, 7.8, and 11.6 dB,
respectively. Further reductions of 9.8, 6.1, and 1.7 dB, respectively, would be needed to reduce
these tones to the rotor-alone levels. The arrows shown on the figure at each tone note the change
from the no-blowing case. The cross-bars show the minimum rotor-alone levels. Part (b) shows
the configuration [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]. Compared to the no-
blowing case, the 1xBPF, 2xBPF, and 3xBPF tones are reduced by 3.5, 7.7, and 8.4 dB,
respectively. Further reductions of 13.3, 6.2, and 4.9 dB, respectively, would be needed to reduce
these tones to the rotor-alone levels. New tones appear at multiples of 0.5xBPF. Part (c) shows
the configuration [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]. Compared to the no-
blowing case, the 1xBPF, 2xBPF, and 3xBPF tones are reduced by 1.6, 9.7, and 11.5 dB,
49
respectively. Further reductions of 15.2, 4.2, and 1.8 dB, respectively, would be needed to reduce
these tones to the rotor-alone levels. New tones appear at multiples of 0.25xBPF.
It is also interesting to note that the TEB and ATEB configurations give similar
reductions at the 2xBPF and 3xBPF harmonics. It is only the 1xBPF that is less strongly affected
by ATEB. For example the TEB, ATEB 1x1, and ATEB 2x2 reductions of the 1xBPF are 7.0,
3.5, and 1.6 dB, respectively; TEB gives at least 3.5 dB more reduction at this tone. However,
the reductions at the 2xBPF are 7.8, 7.7, and 9.7 dB, respectively; ATEB gives a similar or even
greater amount of reduction.
50
Figure 4.10: Power Spectra for (a) [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall], (b) [Inlet Duct, 14
Vanes, ATEB 1x1 0.9%, Hardwall], and (c) [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall].
Another important conclusion drawn from this figure is that the original tones at 1xBPF,
2xBPF, etc. are reduced by ATEB, while new tones are introduced between them. The power
contribution of the new tones is important to the performance of ATEB and is examined in more
detail below. The overall sound power reduction is a tradeoff between the reduced power of the
original tones and the increased power of the new tones. If the new tones are large relative to the
51
original tones, overall sound power reduction is low. These effects can be seen in Figure 4.11.
The new tones are small compared to the original tones for these configurations. The new tones'
power is at least 6 dB less than the original tones' power at all blowing rates measured, and
therefore the total power is close to the original tones' power. The new tones do not limit ATEB
performance for these configurations.
Figure 4.11: Original and New Tones' Power for (a) [Inlet Duct, 14 Vanes, ATEB 1x1, Hardwall] and (b)
[Inlet Duct, 14 Vanes, ATEB 2x2, Hardwall].
4.3.3: Configurations using the Aft Duct and 14 Vanes
This section performs a similar study on the aft duct of the rig. Figure 4.12 shows the
baseline configuration of [Aft Duct, 14 Vanes, No TEB 0%, Hardwall]. The 1xBPF tone is no
longer dominant as in the inlet. In the aft duct, the 3xBPF tone is the dominant tone. The total
tonal power is 112.1 dB. If TEB could perfectly eliminate all interaction noise, a 13.7 dB
reduction would bring the level to the rotor-alone level of 98.4 dB.
52
Figure 4.12: Power Spectrum for [Aft Duct, 14 Vanes, No TEB 0%, Hardwall].
The approach described in the previous section is again used to find the optimum blowing
rate for the TEB, ATEB 1x1, and ATEB 2x2 configurations. The results are shown in Figure
4.13. The results are similar to those for the inlet duct. The optimum rate for TEB is 1.5% and
results in an overall power reduction of 7.8 dB. The optimum rates for ATEB 1x1 and ATEB
2x2 are both 0.9% and result in power reductions of 5.8 and 3.4 dB, respectively.
102
104
106
108
110
112
114
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
Blowing Rate (%)
So
un
d P
ow
er (
dB
)
ATEB 1x1 Hardwall ATEB 2x2 Hardwall Full TEB Hardwall
Figure 4.13: Power vs. Blowing Rate for the Configurations [Aft Duct, 14 Vanes].
53
Figure 4.14 shows power spectra for the optimum blowing rate configurations [Aft Duct,
14 Vanes, Full TEB 1.5%, Hardwall], [Aft Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall], and
[Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall] in parts (a), (b), and (c), respectively. In all
three parts of this figure the 2xBPF and 3xBPF tones are reduced. However, the 1xBPF tones are
increased by 1.5, 0.5, and 0.2 dB, respectively. These results are surprising because TEB and
ATEB are predicted to reduce the tones at integer multiples of the BPF. No new modes are
introduced at these frequencies and the number of noise-producing wakes is reduced. The modal
rake data provides more details with which to investigate this behavior.
The only propagating interaction mode with 14 vanes at 1xBPF is the mode (2,0) as
shown in Table 3.4. Compared to the no blowing levels, the full TEB, ATEB 1x1, and ATEB
2x2 levels of this mode are reduced by 0.7, 0.5, and 1.9 dB, respectively. (The relevant rake data
are shown in Appendix A tables A.25, A.28, A.32, and A.40.) Therefore the interaction sound
power at 1xBPF is actually decreased according to the rake data. The increased levels seen here
are not due to interaction noise. In fact, the rake data show that the total tonal power levels are
reduced by 0.5, 0.8, and 1.8 dB for full TEB, ATEB 1x1, and ATEB 2x2, respectively. The rake
and far-field data do not agree, and the rake data make more physical sense because the 1xBPF
level should be reduced by TEB and ATEB.
It is also interesting to note that the 0.75xBPF tone is dominant in the ATEB 2x2
configuration of part (c). This is due to the mode (-2,0) being introduced at this frequency by the
implementation of ATEB 2x2, as shown in Table 3.6 and Table A.39.
Even though the 1xBPF tone is increased in power and the new tones dominate the
ATEB 2x2 spectrum, overall power levels are still decreased. This reduction in total tonal power
is due to the large reduction of the originally dominant 3xBPF tone.
54
Figure 4.14: Power Spectra for (a) [Aft Duct, 14 Vanes, Full TEB 1.5%, Hardwall], (b) [Aft Duct, 14 Vanes,
ATEB 1x1 0.9%, Hardwall], and (c) [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall].
The power due to the original and new tones can be seen in Figure 4.15. The new tones'
power is significant for these configurations, as noted above. At a blowing rate of 1.0%, the new
tones' power is greater than the original tones'. At a 1.0% blowing rate the original tones' power
rises due to over-blowing and the new tones dominate, preventing this from being the optimum
rate.
55
Figure 4.15: Original and New Tones' Power for (a) [Aft Duct, 14 Vanes, ATEB 1x1, Hardwall] and (b) [Aft
Duct, 14 Vanes, ATEB 2x2, Hardwall].
4.3.4: Configurations using the Inlet Duct and 28 Vanes
This section discusses the configurations using the inlet duct and 28 stator vanes. When
28 vanes are used the 1xBPF is cut off, i.e. all modes are cut-off and can’t propagate. Figure 4.16
shows the baseline configuration [Inlet Duct, 28 Vanes, No TEB 0%, Hardwall]. The 1xBPF is
no longer dominant because it is cut off. The 2xBPF is dominant instead and the total tonal
power is 101.6 dB.
Figure 4.16: [Inlet Duct, 28 Vanes, No TEB 0%, Hardwall].
56
The approach described in the previous sections is used again to find the optimum
blowing rate for the TEB, ATEB 1x1, and ATEB 2x2 configurations. The results are shown in
Figure 4.17. (There are no experimental data for the full TEB layout with 28 vanes.) The ATEB
1x1 layout has its optimum blowing rate at 0.9% resulting in a reduction of 2.1 dB. The ATEB
2x2 configurations performed especially poorly, with all of the blowing rates actually increasing
the sound power. The lowest of these powers is achieved at a blowing rate of 0.8%, which
increases the power by 0.8 dB. The reason for the power increase is discussed below.
98
100
102
104
106
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Blowing Rate (%)
So
un
d P
ow
er (
dB
)
ATEB 1x1 Hardwall ATEB 2x2 Hardwall
Figure 4.17: Power vs. Blowing Rate for the Configurations [Inlet Duct, 28 Vanes].
Figure 4.18 shows power spectra for the optimum rate configurations [Inlet Duct, 28
Vanes, ATEB 1x1 0.9%, Hardwall] and [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall] in
parts (a) and (b), respectively. Part (a) shows that the 1xBPF power level is increased by 0.9 dB,
while the 2xBPF and 3xBPF levels are reduced by 4.8 and 2.1 dB, respectively.
It is surprising to see the power of the 1xBPF tone increase when ATEB 1x1 is
implemented. According to Table 3.5 there are no propagating interaction modes at this
frequency when using 28 vanes. Checking the rake data of Appendix A reveals that no single
57
mode is strongly dominant at the 1xBPF frequency. According to tables A.49 and A.53, the total
tonal power at this frequency decreases by 2.4 dB when ATEB 1x1 is applied. This is also
surprising because the power of the 1xBPF is expected to be unaffected by ATEB because it
contains no interaction modes; this also disagrees with the far-field data.
The power of the 1xBPF tone rises 4.3 dB when ATEB 2x2 is applied, as shown in part
(b) of Figure 4.18. Calculating the change in power level with tables A.49 and A.61 of Appendix
A, applying ATEB 2x2 causes a 1.3 dB decrease in the total tonal power. Therefore the rake and
far-field power change disagrees by 5.6 dB in this case, a serious discrepancy. It seems likely
that some noise source is measured in the far-field but not in the duct. In addition to the unusual
behavior of the 1xBPF tone, the 3xBPF tone also increases when it is expected to decrease. The
cut on interaction modes are the modes (-8,0) and (-8,1) according to Table 3.4. Using the in-
duct rake data of tables A.51 and A.69 in Appendix A, the interaction power and the total tonal
power are reduced by 9.0 and 6.6 dB, respectively, when ATEB 2x2 is applied.
Figure 4.18: Power Spectra for (a) [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall] and (b) [Inlet Duct, 28
Vanes, ATEB 2x2 0.8%, Hardwall].
58
The power due to the original and new tones can be seen in Figure 4.19. For the ATEB
1x1 configurations, the new tones' power is small at the lesser blowing rates and nearly equal to
the original tones' power at the highest blowing rate of 1.0%. For the ATEB 2x2 configurations,
the new tones' power is about the same as the original tones' at all of the blowing rates. This
explains the poor performance of ATEB 2x2 according to the far-field data; the new tones
contribute too much power for effective overall noise reduction to occur.
Figure 4.19: Original and New Tones' Power for (a) [Inlet Duct, 28 Vanes, ATEB 1x1, Hardwall] and (b)
[Inlet Duct, 28 Vanes, ATEB 2x2, Hardwall].
4.3.5: Configurations using the Aft Duct and 28 Vanes
This section discusses configurations using the aft duct of the rig and 28 vanes. Figure
4.20shows the baseline configuration [Aft Duct, 28 Vanes, No TEB 0%, Hardwall]. The 3xBPF
tone is dominant and the total power is 107.7 dB.
59
Figure 4.20: Power Spectrum for [Aft Duct, 28 Vanes, No TEB 0%, Hardwall].
The optimum blowing rates are found using the same method as in the above sections,
and shown in Figure 4.21. The optimum blowing rate is 0.8% for both configurations, with
ATEB 1x1 and ATEB 2x2 giving power reductions of 3.4 and 2.0 dB, respectively.
104
104.5
105
105.5
106
106.5
107
107.5
108
108.5
109
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Blowing Rate (%)
So
un
d P
ow
er (
dB
)
ATEB 1x1 Hardwall ATEB 2x2 Hardwall
Figure 4.21: Power vs. Blowing Rate for the Configurations [Aft Duct, 28 Vanes].
The power spectra for [Aft Duct, 28 Vanes, ATEB 1x1 0.8%, Hardwall] and [Aft Duct,
28 Vanes, ATEB 2x2 0.8%, Hardwall] are shown in Figure 4.22 parts (a) and (b). Part (a) shows
the spectrum for ATEB 1x1. Compared to the no-blowing case, the 1xBPF, 2xBPF, and 3xBPF
60
tones are reduced by 4.6, 8.6, and 3.5 dB, respectively. Part (b) shows the spectrum for ATEB
2x2. Compared to the no-blowing case, the 1xBPF, 2xBPF, and 3xBPF tones are reduced by 3.4,
7.2, and 4.4 dB, respectively.
The 1xBPF levels for these configurations are actually lower than the rotor-alone levels.
The rotor-alone level is 95.0 dB, while with 28 vanes the No TEB, ATEB 1x1, and ATEB 2x2
levels are 98.3, 93.7, and 94.9 dB, respectively. As previously mentioned no interaction modes
are cut on at the 1xBPF when 28 vanes are used.
Figure 4.22: Power Spectra for (a) [Aft Duct, 28 Vanes, ATEB 1x1 0.8%, Hardwall] and (b) [Aft Duct, 28
Vanes, ATEB 2x2 0.8%, Hardwall].
The power due to the original and new tones can be seen in Figure 4.23. For the ATEB
1x1 configurations, the new tones' power is small at the lesser blowing rates and greater than the
original tones' power at the high blowing rates. For the ATEB 2x2 configurations, the new tones'
61
power is about the same as the original tones' at all of the blowing rates measured. This explains
why ATEB 1x1 gives more overall power reduction than ATEB 2x2; the later configuration's
performance is more limited by the new tones.
Figure 4.23: Original and New Tones' Power for (a) [Aft Duct, 28 Vanes, ATEB 1x1, Hardwall] and (b) [Aft
Duct, 28 Vanes, ATEB 2x2, Hardwall].
4.4 Hotwire Results (Second Test Entry)
Hotwire data were also taken in the second test entry. These data are presented here to aid
in the understanding of the sound power reductions shown in section 4.5, and to show
similarities and differences compared to the wakes of the first test entry.
Part (a) of Figure 4.24 shows an upwash velocity contour plot for the no blowing
configuration. The velocity deficit due to the blade is clearly visible, with upwash velocities in
the wake reaching -30 ft/s. Counter-rotating vortices are again seen at the tip, as in the first test
entry. This wake is more tip-weighted than the wakes of the first test entry.
The configuration using full TEB and 0.65% air is shown in part (b). The wake has been
reduced from its no blowing state of part (a), but is still present with upwash velocities reaching
25 ft/s. It is surprising that the 0.65% blowing rate was the optimum rate, because it appears that
62
more air could better fill in this wake deficit. Tip vortices are visible, and disturbances are also
seen between the wakes at the hub. Two small regions of positive upwash velocity are seen at
radii of approximately 13 and 23 inches, possibly due to localized over-blowing.
Part (c) presents data taken from the same full TEB configuration as part (b), but in
greater resolution over a smaller portion of the blade span. The wake seen in this plot is very
discontinuous. In the wake centerline, regions of wake-filling alternate with regions of velocity
deficit in the radial direction. In addition, small regions of over-blowing are offset from the wake
by a few degrees.
The fan blades used in the second test entry inject air through discrete jets, and these
results show the effects of each jet. The air supplied by the jets has not mixed with the rest of the
wake by the time the wake reaches the stator vanes. The discussion of the far-field results in
section 4.5 shows that noise reduction is achieved regardless of the discontinuous wake-filling
seen here. The wake is partially filled, which is expected to reduce noise. In addition, the
adjacent regions of under- and over-blowing may be responsible for destructive interference
effects similar to those hypothesized for the counter-rotating tip vortices.
63
Figure 4.24: Upwash Velocities for (a) No TEB, (b) Full TEB 0.65%, and (c) Full TEB 0.65% Partial Span
64
4.5 Far-Field Results (Second Test Entry)
This section presents far-field results from the second test entry. Compared to the first
test entry, a different method of air injection is used. The method of injection causes the amount
of air required to be reduced, which is the main difference between the first and second test
entries. However, the ATEB concept is independent of the wake-filling method and the same
conclusions are reached as in the first test entry. These results are therefore presented for the
sake of completeness.
The results in this section are presented in a similar form as for the first entry discussed in
section 4.3. However, they are described in less detail because of the results' similarity. The
sound power spectra discussed are listed in Appendix C. This appendix also lists results for
configurations not discussed in the main body of the thesis.
4.5.1: Configurations using the Inlet Duct (Second Test Entry)
The configurations using the inlet duct and 14 vanes are discussed in this section. Figure
4.25 shows the baseline configuration [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall, (2nd
Entry)]. The 1xBPF is dominant and the total tonal power is 110.0 dB.
Figure 4.25: Power Spectrum for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall, (2nd Entry)].
The optimum rate using TEB was 0.65% and resulted in a 5.6 dB power reduction. The
optimum rate using ATEB 1x1 was 0.43% and resulted in a 4.2 dB reduction. This is shown in
65
Figure 4.26. It is important to note that the ATEB optimum rate is less well defined in the second
test entry than it was in the first test entry. This is because the sound power versus blowing rate
trend line does not form a smooth curve identifying the optimum rate in a "valley." The
experimental apparatus had difficulty in supplying large amounts of air to the ATEB configured
blades. The mass flow rate is set by controlling the blowing air pressure. At maximum system
pressure the mass flow rate was still small because the second entry fan blades have smaller air
passages than the first entry blades.
Figure 4.26: Power vs. Blowing Rate for the Configurations [Inlet Duct, 14 Vanes, (2nd Entry)].
With the optimum rates identified, the power spectra for [Inlet Duct, 14 Vanes, Full TEB
0.65%, Hardwall, (2nd Entry)] and [Inlet Duct, 14 Vanes, ATEB 1x1 0.43%, Hardwall, (2nd
Entry)] are shown in Figure 4.27. Part (a) shows the full TEB configuration using 0.65% air.
Compared to the no-blowing levels the 1xBPF, 2xBPF, and 3xBPF levels are reduced 3.8, 7.4,
and 12.9 dB, respectively. Part (b) shows the ATEB 1x1 configuration using 0.43% air.
Compared to the no-blowing levels the 1xBPF, 2xBPF, and 3xBPF levels are reduced 3.1, 4.5,
and 6.5 dB, respectively. As in the first test entry, the ATEB configuration gives less source-
level reduction while using less air.
66
Figure 4.27: Power Spectra for (a) [Inlet Duct, 14 Vanes, Full TEB 0.65%, Hardwall, (2nd Entry)] and (b)
[Inlet Duct, 14 Vanes, ATEB 1x1 0.43%, Hardwall, (2nd Entry)].
4.5.2: Configurations using the Aft Duct (Second Test Entry)
This section describes configurations in the second test entry using the aft duct of the rig.
Figure 4.28 shows the baseline configuration [Aft Duct, 14 Vanes, No TEB 0%, Hardwall, (2nd
Entry)]. The 3xBPF is dominant and the total tonal power level is 114.8 dB.
67
Figure 4.28: Power Spectrum for [Aft Duct, 14 Vanes, No TEB 0%, Hardwall, (2nd Entry)].
Figure 4.29 shows how the optimum rate using TEB was 0.65% (resulting in a 7.0 dB
power reduction) and the optimum rate using ATEB 1x1 rate was 0.43% (resulting in a 3.5 dB
power reduction). These are the same optimum rates found at the inlet duct.
106
107
108
109
110
111
112
113
114
115
116
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90
Blowing Rate (%)
So
un
d P
ow
er (
dB
)
Full TEB Hardwall ATEB 1x1 Hardwall
Figure 4.29: Power vs Blowing Rate for the Configurations [Aft Duct, 14 Vanes,(2nd Entry)].
With the optimum rates identified, the power spectra for [Inlet Duct, 14 Vanes, Full TEB
0.65%, Hardwall, (2nd Entry)] and [Inlet Duct, 14 Vanes, ATEB 1x1 0.43%, Hardwall, (2nd
Entry)] are shown in Figure 4.30. Part (a) shows the full TEB configuration using 0.65% air.
68
Compared to the no-blowing levels the 1xBPF, 2xBPF, and 3xBPF levels are reduced 0.6, 10.7,
and 2.0 dB, respectively. Part (b) shows the ATEB 1x1 configuration using 0.43% air. Compared
to the no-blowing levels the 1xBPF, 2xBPF, and 3xBPF levels are reduced 1.9, 6.9, and 5.0 dB,
respectively.
Figure 4.30: Power Spectra for (a) [Aft Duct, 14 Vanes, Full TEB 0.65%, Hardwall, (2nd Entry)] and (b) [Aft
Duct, 14 Vanes, ATEB 1x1 0.43%, Hardwall, (2nd Entry)].
69
Chapter 5 : Acoustic Liner Performance with ATEB
Prior to the experimental effort, numerical codes were used to predict the performance of
ATEB. In addition, after the experiments were conducted a combination of experimental data
and numerical codes was used to predict the performance of ATEB when combined with
optimized acoustic liners. These predictions were needed because only two liners were tested
experimentally; one type in the inlet duct and one type in the aft duct. These liners were not
optimized for use with an ATEB spectrum and therefore can not demonstrate the potential of the
concept. Predictions were needed to find optimum liners and their attenuations for each
configuration. The codes used are described in this chapter so that the results can be understood.
5.1: Numerical Codes
Two computer codes can be used to model the ATEB concept. The codes and how they
were used are described in the following subsections.
5.1.1: "V072" Rotor Wake / Stator Interaction Code
The "V072" Rotor / Stator interaction code was used to make the initial predictions found
in Appendix D, but was not used in the liner performance modeling of section 5.2. This is
because experimental modal data, once available, was used instead. The measured rake data are
assumed to be more accurate than predictions made with the V072 code. The program is
discussed here to describe the modeling process in its entirety.
The V072 code is a program that predicts the rotor / stator interaction noise produced in
an infinite annular duct of constant cross section [19]. There are two parts to the program. The
first part calculates the wake deficits due to losses on fan blade surfaces. The second part then
calculates the acoustic response when these wakes reach the stator vanes.
In its original version, the V072 program requires the user to supply the geometry and
operating conditions of the turbomachine for which predictions are to be made. Given this
information the program outputs the in-duct acoustic mode complex amplitudes and sound
70
powers produced by the interaction of the rotor wakes and the stator vanes. This information is
provided for each acoustic mode propagating both upstream and downstream of the fan and each
tone component.
The V072 code has been modified from its original version so that it can be used with
ATEB layouts [20]. The original program did not have the means to use an ATEB profile; the
wake of every blade must be the same. In order to bypass this restriction the program was
modified to allow the input of an arbitrary wake profile. For example, the ATEB 1x1 layout
consists of TEB applied to alternating blades. To run this layout in V072 a wake profile spanning
two fan blades (one with TEB and one without) is constructed and entered into the program.
Since the program considers this to be the wake resulting from one blade, the variable specifying
the number of blades is halved. As far as the code is concerned, 16 single-blade wakes are
equivalent to 8 double-blade wakes. In this way any arbitrary wake profile can be produced and
input to the code. The program also outputs its internally generated wake profile; modifying this
profile and then inputting it back into the code is often a useful technique.
5.1.2: Eversman Finite Element Radiation Code
Once the modal amplitudes at the stator vanes are calculated by the V072 code or are
measured experimentally, they can then used as the inputs to the Eversman code [22]. The
Eversman code calculates how sound propagates out of the duct into the far-field and predicts the
effects of acoustic liners.
The far-field radiation calculation requires that a finite element mesh be produced for the
inlet and aft ducts. This mesh is generated by the Eversman program provided it is supplied with
the required duct geometry. Figure 5.1 parts (a) and (b) show the meshes used for the inlet and
aft ducts, respectively. If acoustic liners are used, their locations are described in terms of the
elements of these meshes and their impedances are described as a function of frequency.
The Eversman code is run once for each propagating circumferential mode in the duct.
All radial modes associated with a particular circumferential mode are analyzed during the same
71
run. The outputs from the code are the acoustic pressures at each element in the inlet and aft
meshes. These pressures are then used to calculate sound powers in a similar manner to that of
the far-field data discussed in section 3.5.
Figure 5.1: Eversman Code (a) Inlet Mesh and (b) Aft Mesh.
72
5.2: Proof of Concept - Acoustic Liner Performance
This section presents the procedure for and results of predicting liner performance.
Optimum liners and their attenuations are found. These predictions validate the hypothesis that
ATEB configurations increase liner performance.
The only liners previously discussed (in section 3.1) have been the liners physically
installed in the ANCF inlet and aft ducts. These liners were not designed for use with ATEB, and
therefore do not demonstrate the full potential of the concept. They are used only to validate the
accuracy of the Eversman code in Appendix E.
Figure 5.2 outlines the process used to predict optimized liner performance. The process
begins with experimentally measured in-duct modal data for hardwall (no liner) configurations.
This data is input to the Eversman code and run with no liner present to calculate a hardwall
power. Then the code is supplied with a liner impedance and run again to calculate a softwall
power. The predicted attenuation due to the modeled liner is the difference in power between the
hardwall and softwall cases. This is repeated using a 43 study to find the optimum liner for each
configuration. The liners were assumed to be single degree-of-freedom linear liners with
normalized resistances ranging from 0.5 pc to 2.6 pc. Tuned frequencies ranged from 500 Hz to
4300 Hz. The liner normalized impedance were calculated using
Z = R- I * cot(k * d) (5.1)
where R is resistance, d is core depth, and k is wavenumber. This study was performed for no
TEB configurations, ATEB 1x1 configurations using 0.9% air, ATEB 2x2 configurations using
0.9% air, and full TEB configurations using 1.5% air. These rates are the optimum rates found
using the far-field results in sections 4.3.2 and 4.3.4.
73
Figure 5.2: Procedure for Predicting Optimum Liner Attenuations
5.2.1: Liner Performance - Configurations with Inlet Duct and 14 Vanes
In this section, acoustic liner performance for configurations using the inlet duct and 14
vanes is modeled. Modal data from the configurations [Inlet Duct, 14 Vanes, No TEB 0%,
Hardwall], [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall], [Inlet Duct, 14 Vanes, ATEB 1x1
0.9%, Hardwall], and [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall] are used as inputs to
the Eversman code. These data are represented in Figures 4.2 through 4.6, but the complex
pressures directly input to the code are not listed in this thesis due to the volume of data and
difficulty in concise presentation.
Results for these configurations are shown in Figure 5.3. Liner attenuation is shown as a
function of resistance and tuned frequency. Tuned frequency is itself a function of core depth,
and specifies the frequency at which the imaginary component of the liner impedance is equal to
zero, i.e. the resonant frequency.
74
Part (a) shows the liner attenuation when no TEB is used. The maximum attenuation is
6.5 dB for a liner normalized resistance of approximately 1.0 pc and tuned frequency near 900
Hz. When full TEB using 1.5% air is used, Part (b) shows the maximum attenuation to be 8.5
dB. Liner normalized resistance is lower, near 0.7 pc, and tuned frequency is approximately 900
Hz.
Parts (c) and (d) show liner attenuations for the ATEB 1x1 and ATEB 2x2
configurations, respectively. ATEB 1x1 gives a maximum attenuation of 9.8 dB and ATEB 2x2
gives a maximum attenuation of 10.3 dB. Both configurations achieve optimum performance
near normalized resistances of 0.8 pc, whereas the tuned frequency for ATEB 1x1 is near 900Hz
and the tuned frequency for ATEB 2x2 is near 800 Hz.
Comparing these four optimized liner attenuations demonstrates how liner performance is
increased when ATEB is used. The ATEB 1x1 configuration increases liner performance by 3.3
dB relative to the no TEB configuration and 1.3 dB relative to the full TEB configuration. The
ATEB 2x2 configuration increases liner performance by 3.8 dB relative to the no TEB
configuration and 1.8 dB relative to the full TEB configuration. In addition, liner performance is
less sensitive to changes in liner parameters when ATEB is used. High attenuations are achieved
over a greater section of the design space.
75
Figure 5.3: [Inlet Duct, 14 Vanes] Liner Reductions for (a) No TEB, (b) Full TEB, (c) ATEB 1x1, (d) ATEB
2x2.
The overall sound power reduction achieved with the ATEB concept is due to both the
source-level reduction of wake-filling and the attenuation of liners. Figure 5.4 presents these
results in a format such that it is easy to visualize the two types of reduction. All values in this
figure are results of running the Eversman code with rake data inputs. The "wake-filling"
reductions represent the difference in power between a hardwall configuration with no blowing
and a hardwall configuration with blowing. The "liner" reductions represent the difference in
power between a hardwall and a softwall configuration. Optimized liner results from Figure 5.3
are used.
76
The "liner alone" configuration provides only 6.5 dB liner attenuation. The full TEB
layout provides the most wake-filling reduction (8.9 dB) and 8.5 dB liner attenuation for a total
power reduction of 17.4 dB. On the other hand, the ATEB 1x1 and 2x2 layouts provide less
wake-filling reduction (4.3 dB and 2.7 dB, respectively) but more reduction from the liner (9.8
dB and 10.3 dB, respectively.) The ATEB configurations give less total reduction (14.1 and 13.0
dB) as compared to that of full TEB (17.4 dB) but at a cost of using only 60% as much air.
0
4.32.7
8.96.5
9.810.3
8.5
0
2
4
6
8
10
12
14
16
18
20
Liner Only ATEB 1-1 ATEB 2-2 TEB
Po
wer
Red
uct
ion
(d
B)
Wake-Filling Reduction Liner Reduction
6.5
14.113.0
17.4
Figure 5.4: [Inlet Duct, 14 Vanes] Sound Power Reductions from Wake-Filling and from Liner Attenuation.
5.2.2: Liner Performance - Configurations with Inlet Duct and 28 Vanes
The same study was performed for configurations using the inlet duct and 28 vanes. The
only difference is that no experimental in-duct modal data is available for the full TEB
configuration. The configurations used as inputs to the code were [Inlet Duct, 28 Vanes, No TEB
0%, Hardwall], [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall], and [Inlet Duct, 28 Vanes,
ATEB 2x2 0.9%, Hardwall].
0.9% Air 1.5% Air
77
The results of Figure 5.5 show how ATEB increased liner performance relative to the
configuration with no TEB. Part (a) shows the optimized liner reduction with no TEB to be 5.5
dB. This occurs near a normalized resistance of 2.0 pc and a tuned frequency of 1400 Hz. The
best reducing achieved when using ATEB 1x1 is shown by part (b) to be 6.7 dB. The normalized
resistance is near 1.4 pc and the tuned frequency is lower, near 900 Hz. An even greater
optimized liner performance of 7.6 dB is achieved when applying ATEB 2x2, as shown in part
(c). For this configuration the normalized resistance is approximately 1.2 pc and the tuned
frequency is 1000 Hz.
Figure 5.5: [Inlet Duct, 28 Vanes] Liner Attenuations for (a) No TEB, (b) ATEB 1x1, and (c) ATEB 2x2.
78
Wake-filling and liner reductions are shown together in Figure 5.6. The liner alone gives
5.5 dB power reduction. The ATEB 1x1 configuration gives 2.3 dB reduction from wake-filling
and 6.7 dB reduction from the liner for a total reduction of 9.0 dB. The ATEB 2x2 configuration
raises sound power by 0.6 dB due to wake filling and then reduces it by 7.6 dB with the liner for
a total reduction of 7.0 dB.
0
2.3
-0.6
5.5
6.7
7.6
-2
0
2
4
6
8
10
Liner Only ATEB 1-1 ATEB 2-2 TEB
Po
wer
Red
uct
ion
(d
B)
Wake-Filling Liner
5.5
9.0
7.0
(No Data)
Figure 5.6: [Inlet Duct, 28 Vanes] Sound Power Reductions from Wake-Filling and from Liner Attenuation.
This same method was used to attempt a study of the aft duct, but the author has little
confidence in the results. First, the liner performance was not a function of liner properties; all
liners in the parametric study returned attenuations within 0.2 dB of one another. Second, when
the liner on the ANCF was modeled to compare measured and predicted results the values
strongly disagreed. The author interprets these results as a failure to properly treat the modal data
or Eversman code, and not as evidence against the ATEB concept. The concept is expected to
apply to the aft duct for the same reason it applies to the inlet duct - the spreading of sound
power over a greater number of frequencies and modes makes liners more effective. Using the
79
aft duct and 14 vanes the liner attenuations with no TEB, full TEB, ATEB 1x1, and ATEB 2x2
were 1.9 dB, 3.7 dB, 4.7 dB, and 9.1 dB, respectively. Using the aft duct and 28 vanes the liner
attenuations with no TEB and ATEB 2x2 were 1.5 dB and 4.7 dB, respectively.
80
Chapter 6 : Conclusions
Trailing edge blowing (TEB) is a proven technique for reducing rotor / stator interaction
noise, but is made impractical by the amount of air required. A new implementation of TEB was
experimentally validated in this research. The concept "advanced trailing edge blowing" (ATEB)
applies selective wake-filling to achieve noise reduction with less air used. This is possible
because the modified spectral shape of interaction noise from advanced blowing layouts makes
acoustic liners more effective. The interaction noise is spread over more frequencies and modes,
behaving more like broadband noise and better matching liners' attenuation curves. This
compensates for decreased source-level reduction due to leaving some wakes unfilled.
Experiments were performed on the ANCF rig at NASA Glenn Research Center.
Microphone arrays were used in the far-field and in the rig ducts to measure sound pressure
levels. A hotwire probe was used to measure the velocity profile in the duct. Hardwall
configurations using no blowing, TEB, and ATEB were run to compare their noise reduction
capabilities. As expected the conventional TEB configurations gave more noise reduction than
the advanced configurations, but also used more air. Conventional TEB gave an average sound
power reduction of 7.7 dB while using 1.5% of the mass through the rig, and ATEB gave an
average sound power reduction of 3.0 dB while using 0.9% of the mass through the rig.
The performance of ATEB blowing used in combination with acoustic liners was
investigated using experimental data and numerical codes. Experimental data taken by in-duct
microphone arrays described the modal structure of noise inside the rig. This data was used with
the Eversman radiation code to find optimized liners for each blowing layout and their respective
attenuations. It was found that the ATEB configurations had the highest liner attenuations (i.e.
liner performance was increased). The liner attenuations using ATEB were an average of 2.6 dB
higher than the attenuations using no TEB and an average of 1.6 dB greater than the attenuations
using conventional TEB.
The work performed has validated the hypothesis that advanced trailing edge blowing
increases liner performance and can achieve noise reductions comparable to those of
conventional TEB while using less air. The total tonal sound power reduction predicted with
81
TEB and a liner was 17.4 dB and required 1.5% of the mass flow through the rig. A total
reduction of 14.1 dB was predicted for ATEB and a liner, using only 0.9% air. Advanced
blowing layout make TEB more practical, using only 60% as much air.
The ATEB concept has been demonstrated by this research but issues remain unexplained
and ideas remain unexplored, providing the potential for future work. First, ATEB could be
tested on a high-speed rig or on a real engine. Second, different blowing layouts could be
investigated. For example, using a layout in which air is injected randomly rather than in a
pattern could produce interaction noise spread out over even more tones. This could further
increase acoustic liner performance. With increased liner performance the blowing rate could be
lowered while still providing similar overall noise reductions. Third, the potential for noise
reduction through destructive interference effects could be considered. Regions of positive and
negative upwash velocities may act as out-of-phase noise sources.
82
References
[1] The Federal Aviation Administration, Office of Environment and Energy,
http://www.faa.gov/programs/en/impact/1976ANAP.
[2] Huff, D., "Technology Development for Aircraft Noise Alleviation," Presented to Hiller
Aviation Museum, NASA Glenn Research Center, Cleveland Ohio, December 2000.
[3] Lord, W., "Aircraft Noise Source Reduction Technology," Airport Noise Symposium,
Palm Springs California, March 2004.
[4] Rushwald, I. , "Continuing Work on Aircraft Noise Reduction," Aircraft Noise
Symposium, San Diego California, February 2002.
[5] Brookfield, J.M., Waitz, I.A., “Trailing Edge Blowing for Reduction of Turbomachinery
Fan Noise,” Journal of Propulsion and Power, Vol. 16, No. 1, pp. 57-64, 2000.
[6] Naumann, R.G., “Control of Wake from a Simulated Blade by Trailing Edge Blowing,”
Master’s Thesis, Lehigh University, Bethlehem, PA, 1992.
[7] Park, W.J., Cimbala, J.M., “The Effect of Jet Injection Geometry on Two-Dimensional
Momentumless Wakes,” Journal of Fluid Mechanics, Vol. 224, pp. 29-47, 1991.
[8] Corcoran, T.E., “Control of Wake from a Simulated Blade by Trailing Edge Blowing,”
Master’s Thesis, Lehigh University, Bethlehem, PA, 1992.
[9] Waitz, I.A., Brookfield, J.M., Sell, J., Hayden, B.J., “Preliminary Assessment of Wake
Management Strategies for Reduction of Turbomachinery Fan Noise,” Journal of
Propulsion and Power, Vol. 12, No.5, pp. 958-66, 1996.
83
[10] Sell, J., “Cascade Testing to Assess the Effectiveness of Mass Addition/Removal Wake
Management Strategies for Reduction of Rotor-Stator Interaction Noise,” Master’s
Thesis, MIT, Cambridge, MA, 1997.
[11] Brookfield, J.M., Waitz, I.A., Sell, J., “Wake Decay: Effect of Freestream Swirl,” Journal
of Propulsion and Power, Vol. 14, No.2, pp. 215-224, 1998.
[12] Leitch, T.A., Saunders, C.A., Ng, W.F., “Reduction of Unsteady Stator-Rotor Interaction
using Trailing Edge Blowing,” AIAA Paper 99-1952, 1999.
[13] Rao, N.M., Feng, J., Burdisso, R.A., Ng, W.F., “Active Flow control to Reduce Fan
Blade Vibration and Noise,” AIAA Paper 99-1806, 1999.
[14] Sutliff, D., Tweedt, D., Fite, E., and Envia, E., "Low-Speed Fan Noise Reduction with
Trailing Edge Blowing", NASA Glenn Research Center, NASA/TM 2002-
211559,Cleveland, Ohio, May 2002.
[15] Sutliff, D., "Broadband Noise Reduction of a Low-Speed Fan with Trailing Edge
Blowing", NASA Glenn Research Center, AIAA-2005-3028, Cleveland, OH, May 2005.
[16] Heidelberg, L.J., Hall, D.G., Bridges, J.E., and Nallasamy, M., "A Unique Ducted Fan
Test Bed for Active Noise Control and Aeroacoustics Research," NASA TM-107213,
AIAA 96-1740. May 1996.
[17] Langford, M., Minton, C., and Ng, W., "Fan Flow Control for Noise Reduction Part 2:
Investigation of Wake-FillingTechniques", AIAA-2005-3026. Techsburg, Inc.,
Blacksburg, VA, May 2005.
[19] Morse, P. and Ingard, K. Theoretical Acoustics. Princeton: Princeton University Press,
1986. pp. 492-522.
84
[19] Topol, D.A. and Matthews, D.C., "Rotor Wake / Stator Interaction Noise Prediction
Code, Technical and User's Manual," NASA Contract No. NAS3-25952 Report, April
1993.
[20] Arntz, D., Unpublished report "Advanced Trailing Edge Blowing Investigation",
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, July 2003.
[21] Eversman, W., and Danada, R.L., "Ducted Fan Acoustic Radiation Including the Effects
of Non-Uniform Mean Flow and Acoustic Treatment," AIAA-93-4424, October 1993.
85
Appendix A: Rake Data (First Test Entry)
This appendix presents tabulated sound power levels for cut-on modes measured with the
rotating rake arrays.
Table A.1: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall] 1xBPF
Table A.2: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall] 2xBPF
Table A.3: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, No TEB 0%, Hardwall] 3xBPF
86
Table A.4: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall] 1xBPF
Table A.5: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall] 2xBPF
Table A.6: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, Full TEB 1.5%, Hardwall] 3xBPF
87
Table A.7: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
0.5xBPF
Table A.8: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
1xBPF
Table A.9: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
1.5xBPF
88
Table A.10: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
2xBPF
Table A.11: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
2.5xBPF
Table A.12: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
3xBPF
89
Table A.13: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
0.25xBPF
Table A.14: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
0.5xBPF
Table A.15: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
0.75xBPF
90
Table A.16: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1xBPF
Table A.17: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1.25xBPF
Table A.18: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1.5xBPF
91
Table A.19: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1.75xBPF
Table A.20: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2xBPF
Table A.21: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2.25xBPF
92
Table A.22: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2.5xBPF
Table A.23: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2.75xBPF
Table A.24: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
3xBPF
93
Table A.25: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, No TEB 0%, Hardwall] 1xBPF
Table A.26: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, No TEB 0%, Hardwall] 2xBPF
Table A.27: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, No TEB 0%, Hardwall] 3xBPF
94
Table A.28: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, Full TEB 1.5%, Hardwall] 1xBPF
Table A.29: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, Full TEB 1.5%, Hardwall] 2xBPF
Table A.30: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, Full TEB 1.5%, Hardwall] 3xBPF
95
Table A.31: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
0.5xBPF
Table A.32: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
1xBPF
Table A.33: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
1.5xBPF
96
Table A.34: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
2xBPF
Table A.35: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
2.5xBPF
Table A.36: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
3xBPF
97
Table A.37: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
0.25xBPF
Table A.38: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
0.5xBPF
Table A.39: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
0.75xBPF
98
Table A.40: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1xBPF
Table A.41: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1.25xBPF
Table A.42: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1.5xBPF
99
Table A.43: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
1.75xBPF
Table A. 441: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2xBPF
Table A.45: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2.25xBPF
100
Table A.46: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2.5xBPF
Table A.47: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
2.75xBPF
Table A.48: Rake Data Modal Sound Powers (dB) for [Aft Duct, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
3xBPF
101
Table A.49: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, No TEB 0%, Hardwall] 1xBPF
Table A.50: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, No TEB 0%, Hardwall] 2xBPF
Table A.51: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, No TEB 0%, Hardwall] 3xBPF
102
Table A.52: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
0.5xBPF
Table A.53: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
1xBPF
Table A.54: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
1.5xBPF
103
Table A.55: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
2xBPF
Table A.56: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
2.5xBPF
Table A.57: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
3xBPF
104
Table A.58: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
0.25xBPF
Table A.59: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
0.5xBPF
Table A.60: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
0.75xBPF
105
Table A.61: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1xBPF
Table A.62: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1.25xBPF
Table A.63: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1.5xBPF
106
Table A.64: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1.75xBPF
Table A.65: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
2xBPF
Table A.66: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall] 2
2.25xBPF
107
Table A.67: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
2.5xBPF
Table A.68: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
2.75xBPF
Table A.69: Rake Data Modal Sound Powers (dB) for [Inlet Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
3xBPF
108
Table A.70: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, No TEB 0%, Hardwall] 1xBPF
Table A.71: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, No TEB 0%, Hardwall] 2xBPF
Table A.72: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, No TEB 0%, Hardwall] 3xBPF
109
Table A.73: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
0.25xBPF
Table A.74: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
0.5xBPF
Table A.75: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
0.75xBPF
110
Table A.76: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1xBPF
Table A.77: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1.25xBPF
Table A.78: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1.5xBPF
111
Table A.79: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
1.75xBPF
Table A.80: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
2xBPF
Table A.81: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
2.25xBPF
112
Table A.82: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
2.5xBPF
Table A.83: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
2.75xBPF
Table A.84: Rake Data Modal Sound Powers (dB) for [Aft Duct, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
3xBPF
113
Appendix B: First Test Entry Far-Field Results
This appendix lists all sound power level results for far-field experiments in the first test
entry. Shown in the tables below are the sound power spectra for each configuration. The power
of each interaction frequency is given along with the total power.
Table B.1: Sound Power at Each Interaction Frequency, Configurations using Inlet Duct and No TEB / Full
TEB.
Table B.2: Sound Power at Each Interaction Frequency, Configurations using Aft Duct and No TEB / Full
TEB.
Configuration 1 2 3 4 5 6 7 8 Total[Inlet, 0 Vanes, No TEB, Hardwall] 89.9 89.3 87.6 86.5 80.5 75.6 71.3 72.9 94.8[Inlet, 0 Vanes, Full TEB 1.1%, Hardwall] 90.6 93.3 89.4 95.7 90.1 75.3 72.0 79.4 99.6[Inlet, 0 Vanes, Full TEB 1.2%, Hardwall] 86.5 94.7 86.9 95.9 91.4 80.3 81.8 75.4 99.8[Inlet, 0 Vanes, Full TEB 1.3%, Hardwall] 89.5 91.2 90.4 96.3 93.3 78.1 80.8 73.7 100.0[Inlet, 0 Vanes, Full TEB 1.4%, Hardwall] 88.7 92.5 88.7 95.9 92.0 76.7 75.7 76.0 99.5[Inlet, 0 Vanes, Full TEB 1.5%, Hardwall] 85.9 90.9 92.2 95.4 89.8 78.5 77.4 71.9 98.9[Inlet, 0 Vanes, Full TEB 1.6%, Hardwall] 90.6 90.8 87.1 94.0 90.2 76.5 73.6 76.1 98.2[Inlet, 0 Vanes, Full TEB 1.7%, Hardwall] 89.3 92.4 87.6 94.1 89.5 76.2 73.3 79.1 98.3[Inlet, 0 Vanes, Full TEB 1.8%, Hardwall] 91.0 93.3 87.4 96.1 93.2 75.1 80.5 71.6 100.1[Inlet, 14 Vanes, No TEB, Hardwall] 106.7 103.2 100.9 92.3 88.7 81.0 79.1 75.9 109.2[Inlet, 14 Vanes, Full TEB 1.1%, Hardwall] 102.2 101.2 98.5 91.6 87.6 84.4 76.6 76.5 105.9[Inlet, 14 Vanes, Full TEB 1.2%, Hardwall] 101.2 99.8 97.1 90.5 87.4 84.1 76.3 76.9 104.8[Inlet, 14 Vanes, Full TEB 1.3%, Hardwall] 100.3 98.8 95.0 89.5 86.0 81.5 75.2 73.8 103.6[Inlet, 14 Vanes, Full TEB 1.4%, Hardwall] 99.7 96.5 91.9 89.1 84.2 79.0 73.2 73.0 102.2[Inlet, 14 Vanes, Full TEB 1.5%, Hardwall] 99.7 95.4 89.3 85.8 82.4 76.4 72.6 73.0 101.6[Inlet, 14 Vanes, Full TEB 1.6%, Hardwall] 101.9 95.1 90.9 85.4 79.8 73.6 74.8 70.2 103.1[Inlet, 14 Vanes, Full TEB 1.7%, Hardwall] 103.8 95.1 89.7 90.2 84.6 78.4 77.4 72.5 104.8[Inlet, 14 Vanes, Full TEB 1.8%, Hardwall] 104.7 97.2 93.5 90.5 87.7 79.3 79.4 73.7 105.9[Inlet, 14 Vanes, No TEB, Softwall] 106.6 99.1 92.3 89.4 81.8 76.0 77.2 66.1 107.5[Inlet, 28 Vanes, No TEB, Hardwall] 91.9 97.4 91.4 96.2 90.0 86.8 81.0 80.2 101.6[Inlet, 28 Vanes, No TEB, Softwall] 91.6 92.1 83.5 92.9 85.2 85.3 78.5 72.9 97.8
Blade Passing Frequency
Configuration 1 2 3 4 5 6 7 8 Total[Aft, 0 Vanes, No TEB, Hardwall] 95.0 88.4 93.4 86.8 79.5 81.7 77.4 76.0 98.4[Aft, 0 Vanes, Full TEB 1.1%, Hardwall] 86.4 85.8 91.8 88.0 82.9 81.1 74.6 69.6 95.2[Aft, 0 Vanes, Full TEB 1.2%, Hardwall] 85.3 84.6 90.6 85.3 83.4 82.9 77.3 73.2 94.2[Aft, 0 Vanes, Full TEB 1.3%, Hardwall] 85.0 82.3 92.2 88.1 80.2 83.8 74.8 73.3 95.1[Aft, 0 Vanes, Full TEB 1.4%, Hardwall] 86.2 83.9 91.9 88.5 82.1 82.9 73.5 73.7 95.2[Aft, 0 Vanes, Full TEB 1.5%, Hardwall] 85.0 80.5 90.7 85.2 82.3 83.5 75.9 71.7 93.8[Aft, 0 Vanes, Full TEB 1.6%, Hardwall] 86.6 84.2 92.0 87.5 83.9 81.8 74.3 74.6 95.2[Aft, 0 Vanes, Full TEB 1.7%, Hardwall] 86.3 83.4 91.2 87.7 83.1 81.7 76.2 74.3 94.7[Aft, 0 Vanes, Full TEB 1.8%, Hardwall] 86.4 84.7 92.3 87.8 79.6 82.9 75.9 72.3 95.3[Aft, 14 Vanes, No TEB, Hardwall] 101.4 104.1 110.6 97.4 91.3 89.2 88.4 80.9 112.1[Aft, 14 Vanes, Full TEB 1.1%, Hardwall] 104.5 103.6 107.4 96.6 95.3 88.0 84.5 76.4 110.6[Aft, 14 Vanes, Full TEB 1.2%, Hardwall] 103.9 102.6 105.6 95.6 94.1 87.1 84.3 76.7 109.3[Aft, 14 Vanes, Full TEB 1.3%, Hardwall] 103.8 100.9 103.3 94.4 92.9 85.4 83.1 72.6 108.0[Aft, 14 Vanes, Full TEB 1.4%, Hardwall] 103.7 98.0 98.6 92.3 90.5 82.1 80.6 72.8 106.0[Aft, 14 Vanes, Full TEB 1.5%, Hardwall] 102.9 95.1 94.4 89.7 87.5 81.9 78.2 68.6 104.3[Aft, 14 Vanes, Full TEB 1.6%, Hardwall] 103.3 92.1 95.8 85.2 81.9 82.9 73.3 69.5 104.4[Aft, 14 Vanes, Full TEB 1.7%, Hardwall] 101.3 95.6 102.3 90.3 87.3 87.6 80.3 75.8 105.6[Aft, 14 Vanes, Full TEB 1.8%, Hardwall] 99.7 100.3 106.9 93.1 89.8 90.0 82.3 78.1 108.7[Aft, 14 Vanes, No TEB, Softwall] 100.8 101.0 103.2 93.1 87.1 81.6 77.8 73.3 106.8[Aft, 28 Vanes, No TEB, Hardwall] 98.3 101.4 104.2 97.9 94.0 93.7 89.5 86.0 107.7[Aft, 28 Vanes, No TEB, Softwall] 94.2 95.8 96.4 95.4 88.0 85.6 78.9 81.2 101.9
Blade Passing Frequency
114
Table B.3: Sound Power at Each Interaction Frequency, Configurations using Inlet Duct and ATEB 1x1.
Table B.4: Sound Power at Each Interaction Frequency, Configurations using Aft Duct and ATEB 1x1.
Configuration 0.5 1 1.5 2 2.5 3 3.5 44.5 5 5.5 6 6.5 7 7.5 8 Total
72.4 105.2 82.6 100.5 87.7 99.6 80.8 88.381.1 86.5 80.8 82.8 78.1 74.8 70.4 69.1 107.570.5 104.7 80.4 98.7 86.4 96.4 80.6 86.480.3 85.0 79.4 80.9 77.0 74.7 67.7 68.7 106.371.2 103.5 80.7 97.1 84.6 94.1 79.8 86.378.6 83.5 78.8 80.5 75.7 74.2 65.9 68.7 105.074.5 103.2 83.1 95.5 83.7 92.5 81.8 87.883.2 80.9 80.2 80.0 77.0 73.7 67.6 69.6 104.576.8 104.1 90.2 92.8 87.4 86.9 86.4 87.686.7 80.7 83.4 80.1 79.6 74.1 69.2 67.8 105.076.2 102.1 83.7 91.4 79.5 85.0 79.1 83.678.9 80.0 74.1 76.3 72.4 74.7 67.6 73.8 102.778.7 93.4 89.1 98.6 85.9 93.2 79.5 94.887.4 88.0 85.8 87.8 82.8 81.9 73.9 73.7 102.679.6 92.5 88.8 96.5 83.3 93.2 81.0 92.684.9 88.6 83.9 86.3 80.4 80.0 72.6 71.9 101.279.6 93.2 90.5 94.6 82.7 90.9 79.2 90.984.5 86.7 82.8 84.2 78.3 77.5 70.0 73.1 100.179.6 92.8 91.1 92.6 83.8 89.3 81.0 89.388.3 86.3 83.8 82.2 78.7 76.6 69.8 73.6 99.580.9 92.2 94.5 92.4 85.4 88.4 82.2 89.590.9 85.9 86.1 82.2 80.3 75.9 72.8 73.5 100.380.8 92.9 90.0 87.9 81.5 82.3 77.6 86.176.9 83.2 81.2 79.9 73.8 73.3 68.0 71.2 97.0
[Inlet, 28 Vanes, ATEB 1x1 0.8%, Hardwall]
[Inlet, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
[Inlet, 28 Vanes, ATEB 1x1 1.0%, Hardwall]
[Inlet, 28 Vanes, ATEB 1x1 0.9%, Softwall]
[Inlet, 14 Vanes, ATEB 1x1 1.0%, Hardwall]
[Inlet, 14 Vanes, ATEB 1x1 0.9%, Softwall]
[Inlet, 28 Vanes, ATEB 1x1 0.55%, Hardwall]
[Inlet, 28 Vanes, ATEB 1x1 0.7%, Hardwall]
[Inlet, 14 Vanes, ATEB 1x1 0.55%, Hardwall]
[Inlet, 14 Vanes, ATEB 1x1 0.7%, Hardwall]
[Inlet, 14 Vanes, ATEB 1x1 0.8%, Hardwall]
[Inlet, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
Blade Passing Frequency
Configuration 0.5 1 1.5 2 2.5 3 3.5 44.5 5 5.5 6 6.5 7 7.5 8 Total
78.8 103.6 88.4 104.1 85.7 109.0 94.4 96.491.5 92.6 84.3 86.7 83.9 77.8 78.5 76.5 111.579.5 102.9 86.1 101.4 88.7 105.8 91.6 93.889.6 91.0 83.1 85.5 83.0 77.4 76.6 72.4 109.080.5 103.3 93.5 98.5 86.6 102.9 90.3 92.389.2 88.2 82.2 84.3 81.0 76.4 74.5 72.5 107.582.8 101.9 98.9 95.6 86.9 99.9 91.1 91.891.6 85.8 83.2 83.3 81.8 78.0 76.4 74.6 106.384.8 100.5 102.7 90.1 91.2 98.2 92.8 90.894.9 85.0 86.9 82.7 84.2 81.4 80.5 75.5 106.783.5 101.9 95.2 91.2 83.4 91.4 77.1 88.478.4 78.1 76.8 77.6 74.8 73.0 74.3 72.1 103.683.6 94.3 89.1 97.6 88.2 104.0 89.5 94.894.7 89.4 89.5 91.4 84.0 81.2 84.0 83.3 106.682.5 93.7 87.4 95.3 89.6 102.6 87.8 91.492.1 87.1 87.7 89.5 79.7 80.5 81.3 80.1 105.081.0 93.7 96.6 92.8 89.2 100.7 87.7 91.192.8 84.6 86.3 87.6 78.7 80.1 79.2 76.3 104.379.1 93.9 102.4 92.8 90.1 99.3 89.5 92.795.3 83.5 87.7 88.0 81.6 81.0 79.8 76.4 106.080.3 94.5 105.5 93.1 93.0 97.5 92.1 93.698.2 84.4 90.0 88.9 84.9 83.2 81.3 76.8 107.984.8 92.0 100.0 87.2 78.0 92.0 81.4 88.286.0 77.5 78.2 78.3 73.8 74.3 71.0 71.8 101.9
[Aft, 28 Vanes, ATEB 1x1 0.8%, Hardwall]
[Aft, 28 Vanes, ATEB 1x1 0.9%, Hardwall]
[Aft, 28 Vanes, ATEB 1x1 1.0%, Hardwall]
[Aft, 28 Vanes, ATEB 1x1 0.9%, Softwall]
[Aft, 14 Vanes, ATEB 1x1 1.0%, Hardwall]
[Aft, 14 Vanes, ATEB 1x1 0.9%, Softwall]
[Aft, 28 Vanes, ATEB 1x1 0.55%, Hardwall]
[Aft, 28 Vanes, ATEB 1x1 0.7%, Hardwall]
[Aft, 14 Vanes, ATEB 1x1 0.55%, Hardwall]
[Aft, 14 Vanes, ATEB 1x1 0.7%, Hardwall]
[Aft, 14 Vanes, ATEB 1x1 0.8%, Hardwall]
[Aft, 14 Vanes, ATEB 1x1 0.9%, Hardwall]
Blade Passing Frequency
115
Table B.5: Sound Power at Each Interaction Frequency, Configurations using Inlet Duct and ATEB 2x2.
Configuration 0.25 0.5 0.75 1 1.25 1.5 1.75 22.25 2.5 2.75 3 3.25 3.5 3.75 44.25 4.5 4.75 5 5.25 5.5 5.75 66.25 6.5 6.75 7 7.25 7.5 7.75 8 Total
82.7 67.4 91.7 105.6 76.5 79.9 89.6 101.088.5 71.6 88.5 98.6 91.1 75.7 85.8 88.383.6 74.6 82.2 86.9 79.7 70.6 80.4 78.178.1 68.5 76.5 74.8 73.8 64.3 71.7 69.8 108.182.6 70.1 92.9 104.7 73.6 79.0 88.9 97.885.3 73.7 87.4 94.0 87.1 73.2 83.9 88.681.7 75.5 80.0 87.0 77.0 70.0 79.4 76.775.5 67.1 75.3 76.5 71.7 63.3 68.5 71.0 106.579.1 72.0 92.8 104.7 75.6 81.1 89.0 96.485.2 73.2 86.2 93.1 83.8 75.4 81.9 87.978.9 75.9 79.7 85.4 75.2 70.7 78.7 77.973.7 67.0 73.7 78.0 70.3 62.1 65.7 71.4 106.283.9 70.6 93.5 105.1 79.3 81.8 88.9 93.589.0 76.0 85.6 89.4 85.7 71.7 80.3 88.779.7 74.5 77.2 85.8 76.6 70.0 78.6 79.374.1 66.3 74.1 78.3 70.7 62.9 63.5 73.3 106.283.9 71.8 95.6 106.0 82.6 78.1 90.5 94.391.0 71.3 87.0 89.8 90.2 74.5 84.1 88.682.5 74.3 77.6 85.6 79.9 73.1 80.0 82.175.3 69.4 75.5 79.4 71.6 62.8 65.4 74.6 107.381.7 63.8 90.3 104.3 73.7 76.8 84.1 95.979.8 66.3 86.4 88.4 85.4 70.5 78.9 86.578.4 70.1 73.8 80.3 80.1 63.3 74.9 74.172.3 63.8 72.2 72.0 67.6 57.4 66.6 63.5 105.481.8 69.0 90.8 103.5 75.1 75.4 84.0 92.078.4 67.9 84.8 86.8 81.1 69.0 77.6 84.675.9 71.1 73.5 79.9 77.1 64.8 73.6 72.869.9 62.3 70.1 73.9 66.8 58.7 64.3 62.1 104.481.9 67.2 90.3 103.2 76.9 77.5 84.6 89.778.2 69.5 83.1 85.4 77.4 69.8 75.5 84.772.1 70.9 71.8 80.5 73.6 64.8 71.0 75.269.0 61.9 69.1 73.8 65.2 57.5 63.4 66.9 104.081.4 68.0 90.7 103.4 78.5 77.8 85.5 88.679.4 70.3 82.1 84.6 78.5 69.2 77.1 84.774.2 70.8 70.8 78.3 73.6 65.7 71.7 75.168.7 62.8 69.2 74.0 65.2 59.0 61.6 66.3 104.184.8 72.7 93.3 104.2 81.7 74.8 88.2 95.782.4 73.7 84.5 89.9 84.8 71.2 81.8 85.779.1 68.8 74.5 79.9 76.6 67.5 74.4 79.071.3 67.0 71.5 74.9 67.9 59.7 64.3 67.6 105.6
[Inlet, 14 Vanes, ATEB 2x2 0.9%, Softwall]
[Inlet, 14 Vanes, ATEB 2x2 1.0%, Softwall]
[Inlet, 14 Vanes, ATEB 2x2 1.0%, Hardwall]
[Inlet, 14 Vanes, ATEB 2x2 0.55%, Softwall]
[Inlet, 14 Vanes, ATEB 2x2 0.7%, Softwall]
[Inlet, 14 Vanes, ATEB 2x2 0.8%, Softwall]
[Inlet, 14 Vanes, ATEB 2x2 0.55%, Hardwall]
[Inlet, 14 Vanes, ATEB 2x2 0.7%, Hardwall]
[Inlet, 14 Vanes, ATEB 2x2 0.8%, Hardwall]
[Inlet, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
Blade Passing Frequency
116
Table B. 5: Sound Power at Each Interaction Frequency, Configurations using Inlet Duct and ATEB 2x2
(Continued).
Configuration 0.25 0.5 0.75 1 1.25 1.5 1.75 22.25 2.5 2.75 3 3.25 3.5 3.75 44.25 4.5 4.75 5 5.25 5.5 5.75 66.25 6.5 6.75 7 7.25 7.5 7.75 8 Total
81.6 69.0 82.4 95.3 76.8 75.8 90.5 95.497.9 74.1 84.8 92.8 88.1 77.1 87.9 93.489.1 78.5 91.5 84.9 80.8 74.8 82.0 83.881.2 71.8 79.7 75.9 82.3 71.3 71.7 72.2 103.879.5 69.1 80.5 96.2 77.4 78.1 90.0 94.396.4 73.3 85.5 92.7 86.1 76.2 88.6 92.986.7 78.2 90.1 87.2 79.2 74.5 81.3 81.779.2 71.4 76.7 76.1 80.4 70.3 70.3 72.8 103.279.6 67.3 79.6 96.2 80.6 81.2 90.0 93.495.2 73.9 83.6 91.8 84.9 77.4 86.9 92.083.7 77.3 87.8 86.3 76.5 75.5 79.5 81.077.8 69.9 74.1 76.3 79.1 69.1 66.7 75.8 102.481.0 70.1 76.7 95.8 81.9 84.8 90.5 93.497.7 71.7 81.8 91.4 85.1 76.6 85.3 92.884.0 73.3 86.3 86.0 74.3 74.8 78.1 81.877.7 70.6 73.8 76.5 79.1 68.4 67.6 77.5 102.982.0 67.8 73.6 95.7 83.3 86.1 92.7 97.5
101.7 77.2 85.4 91.0 86.7 78.4 87.8 94.787.2 75.2 84.3 87.7 75.0 74.8 79.6 83.178.2 71.0 75.2 77.5 78.5 70.1 68.9 77.0 105.480.2 69.5 83.2 93.0 69.4 71.3 85.5 92.387.4 71.6 74.5 83.7 82.4 74.5 83.9 90.287.6 70.3 75.3 78.3 81.3 72.2 80.4 80.478.4 73.0 71.3 75.5 78.7 70.5 69.7 69.8 99.080.4 67.6 82.3 92.5 69.7 72.3 85.1 90.885.7 71.2 75.6 83.7 80.7 73.8 81.8 88.883.9 70.2 75.3 80.1 78.6 72.3 78.2 78.075.7 72.1 70.2 76.1 77.2 67.4 67.0 64.5 97.980.5 70.9 81.1 92.8 72.8 75.1 86.0 91.283.3 71.7 75.1 83.6 78.8 73.3 80.7 87.581.6 70.0 72.6 81.5 76.7 72.2 76.6 77.773.7 70.8 68.8 72.9 76.2 65.8 63.7 66.5 97.679.9 68.7 80.1 92.8 76.8 79.0 87.5 93.285.7 71.9 76.0 84.9 79.4 74.2 78.8 86.781.0 67.8 71.9 81.6 75.0 71.7 76.0 75.873.6 68.7 67.4 74.0 74.9 65.4 60.4 69.2 98.379.2 68.0 78.7 93.3 78.7 80.9 90.1 97.388.8 71.5 76.4 86.1 80.6 74.9 81.3 87.983.0 67.6 70.7 83.9 74.9 71.2 78.0 78.376.1 66.1 68.1 74.2 74.8 66.4 63.1 71.7 100.7
[Inlet, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 0.9%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 1.0%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 0.9%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 1.0%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 0.55%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 0.7%, Hardwall]
Blade Passing Frequency
[Inlet, 28 Vanes, ATEB 2x2 0.55%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 0.7%, Hardwall]
[Inlet, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
117
Table B.6: Sound Power at Each Interaction Frequency, Configurations using Aft Duct and ATEB 2x2.
Configuration 0.25 0.5 0.75 1 1.25 1.5 1.75 22.25 2.5 2.75 3 3.25 3.5 3.75 44.25 4.5 4.75 5 5.25 5.5 5.75 66.25 6.5 6.75 7 7.25 7.5 7.75 8 Total
78.9 69.9 90.8 104.1 80.2 86.2 92.0 102.491.4 81.1 95.3 108.4 91.0 79.7 90.3 95.489.0 80.6 91.6 93.2 83.2 76.3 85.5 84.386.0 72.7 81.1 81.2 80.0 71.1 78.9 74.4 111.280.1 74.6 96.8 103.9 77.6 85.4 89.7 100.191.2 81.2 92.9 105.2 89.3 80.6 88.8 93.886.2 81.6 89.3 90.6 80.0 77.6 83.3 84.083.8 74.5 78.4 82.2 78.5 71.6 76.7 72.2 109.379.1 74.6 99.3 103.6 78.2 87.8 88.1 98.593.9 84.0 91.6 103.8 90.4 81.6 87.1 93.482.7 82.3 87.2 89.1 77.3 77.7 82.1 85.182.8 75.5 76.1 83.0 76.6 72.5 74.2 75.7 108.781.4 72.4 103.0 101.6 79.7 87.6 89.8 97.396.5 80.4 92.3 102.6 92.4 79.5 87.0 94.485.0 81.1 86.5 88.8 77.0 78.2 80.8 87.283.0 74.2 74.1 84.0 76.1 72.1 72.1 76.9 108.783.5 74.8 106.5 100.6 82.5 89.6 94.1 99.399.3 81.3 96.0 105.5 95.7 81.9 90.6 95.488.7 82.0 89.6 90.9 81.1 77.6 84.0 88.983.9 74.9 77.1 86.1 80.3 71.9 74.4 79.7 111.279.2 74.7 90.2 103.1 79.4 84.7 89.0 99.080.4 76.0 79.0 101.2 85.1 73.2 84.1 93.578.3 71.0 81.7 83.4 74.3 70.0 77.6 80.881.6 69.1 76.8 74.6 76.5 64.8 72.3 69.6 106.875.9 77.0 95.3 102.8 77.6 83.5 86.1 96.580.4 76.6 79.0 98.4 83.1 73.0 82.7 91.674.4 71.6 80.6 81.4 73.3 69.3 75.8 81.579.4 68.8 75.6 77.2 75.1 67.9 70.5 69.0 105.773.5 75.4 98.6 102.1 78.0 85.6 85.5 94.384.5 77.8 76.2 96.1 83.5 74.0 81.1 91.575.2 72.3 77.7 81.1 71.5 68.4 73.7 81.678.0 68.6 72.7 74.6 73.2 67.3 67.0 71.3 105.377.0 76.5 101.9 100.8 80.1 85.2 87.9 92.985.5 76.5 76.5 95.4 84.0 68.6 82.7 90.678.7 70.1 76.9 80.8 74.6 69.6 72.3 83.076.6 66.9 68.7 73.7 73.3 66.9 65.4 70.1 105.680.1 77.3 106.0 100.0 84.2 86.8 93.0 94.289.1 76.0 81.4 99.1 87.0 70.9 87.2 91.481.9 72.5 78.2 83.2 78.1 68.5 76.7 84.878.3 68.5 70.9 73.2 74.1 68.9 70.8 73.6 108.3
[Aft, 14 Vanes, ATEB 2x2 1.0%, Softwall]
[Aft, 14 Vanes, ATEB 2x2 0.55%, Hardwall]
[Aft, 14 Vanes, ATEB 2x2 0.7%, Hardwall]
[Aft, 14 Vanes, ATEB 2x2 0.8%, Hardwall]
[Aft, 14 Vanes, ATEB 2x2 0.9%, Hardwall]
[Aft, 14 Vanes, ATEB 2x2 1.0%, Hardwall]
[Aft, 14 Vanes, ATEB 2x2 0.55%, Softwall]
[Aft, 14 Vanes, ATEB 2x2 0.7%, Softwall]
[Aft, 14 Vanes, ATEB 2x2 0.8%, Softwall]
[Aft, 14 Vanes, ATEB 2x2 0.9%, Softwall]
Blade Passing Frequency
118
Table B.6: Sound Power at Each Interaction Frequency, Configurations using Aft Duct and ATEB 2x2
(Continued).
Configuration 0.25 0.5 0.75 1 1.25 1.5 1.75 22.25 2.5 2.75 3 3.25 3.5 3.75 44.25 4.5 4.75 5 5.25 5.5 5.75 66.25 6.5 6.75 7 7.25 7.5 7.75 8 Total
78.7 74.1 85.2 93.7 76.5 90.3 92.4 98.692.5 73.9 97.4 101.6 92.2 84.2 98.3 92.394.8 83.1 90.9 90.8 82.2 76.5 89.6 89.787.3 78.2 85.4 78.9 88.1 74.2 82.4 78.1 107.479.4 72.7 84.6 93.7 76.7 88.3 91.8 96.990.7 74.8 96.5 100.7 90.2 85.1 96.5 91.691.4 85.8 90.1 88.1 81.3 78.3 88.7 90.085.3 79.2 83.4 80.8 86.6 74.2 81.4 78.4 106.279.9 73.0 84.9 94.9 77.8 92.2 93.2 94.291.1 74.9 95.5 99.8 89.8 84.4 95.1 91.988.7 85.7 87.9 88.2 80.0 79.0 85.4 89.383.4 78.9 80.4 84.1 84.6 74.9 79.5 79.6 105.579.5 72.8 84.3 96.6 77.0 91.4 95.6 93.393.1 73.2 95.7 99.3 91.4 84.6 95.8 93.689.3 86.2 87.7 90.9 81.1 77.0 82.8 89.384.5 79.5 81.0 86.8 84.5 73.2 77.8 80.7 106.077.7 71.4 83.2 97.9 78.9 92.1 99.2 92.497.6 75.5 98.7 100.9 92.8 82.7 97.7 96.593.5 86.4 88.9 93.3 82.8 79.1 83.0 91.487.9 79.9 83.6 89.4 85.0 73.0 77.8 84.1 108.279.5 75.2 86.9 87.6 72.3 87.9 90.2 92.379.9 67.6 79.3 93.7 85.5 77.2 94.0 90.085.6 73.4 86.3 87.5 76.2 67.6 80.5 85.187.7 73.8 77.5 75.7 87.0 69.5 77.6 75.5 101.579.9 75.5 86.7 86.3 72.1 85.9 89.0 89.179.4 67.9 78.5 92.8 83.4 77.2 92.0 86.282.8 75.9 84.4 86.9 74.0 66.1 77.9 83.885.9 70.6 77.4 74.6 85.9 69.0 76.7 71.5 99.981.4 75.8 87.6 87.9 72.4 89.4 90.9 87.480.0 67.5 77.1 91.5 83.2 76.1 90.6 86.281.4 76.2 81.8 86.9 72.2 65.8 75.9 84.184.8 67.9 73.8 73.9 84.9 69.9 75.3 72.5 99.780.7 74.6 87.3 90.0 73.1 88.4 93.5 86.183.1 67.7 75.6 90.7 85.9 75.8 90.7 86.084.5 77.2 79.9 87.1 71.7 67.1 72.9 84.284.2 68.2 72.2 75.0 83.9 70.7 74.2 78.1 100.180.2 74.0 86.5 91.2 74.7 88.6 96.8 86.186.8 66.6 78.5 89.9 87.6 73.5 91.9 84.288.1 76.7 79.1 88.4 75.0 65.5 76.7 86.385.0 69.4 72.0 77.2 83.7 70.0 75.3 80.3 101.6
[Aft, 28 Vanes, ATEB 2x2 0.9%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 1.0%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 1.0%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 0.55%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 0.7%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 0.55%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 0.7%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 0.8%, Hardwall]
[Aft, 28 Vanes, ATEB 2x2 0.9%, Hardwall]
Blade Passing Frequency
119
Appendix C: Second Test Entry Far-Field Results
This appendix lists sound powers for the second test entry. Configurations discussed in
the main body of the paper correspond to Tables C.1 and C.2.
Additional configurations are described in Tables C.3 through C.5. These configurations
were not required for the discussion of the ATEB concept, but are listed for completeness. One
set of configurations uses a blade-to-vane spacing of 1 chord instead of the 1/2 chord spacing
used in all of the other configurations. One set applies blowing air only to the suction side of the
blades. Four sets apply blowing to only part of the blade span. The blades for this test entry use
13 discrete jets on each side of the blade, and these jets can be opened or closed to control the
radial application of air. The pair of jets nearest the hub are called jets #1 and the pair of jets
nearest the tip are called jets #13. The configurations labeled "Tip Blowing" use only jets 10, 11,
12, and 13; this is done for both TEB and ATEB 1x1. The configurations labeled "Alternating
Jets" use only jets 2, 4, 6, 8, 10, and 12. The configurations labeled "Alternating Spans" use only
jets 1, 2, 3, 10, 11, and 12.
120
Table C.1: Sound Power at Each Interaction Frequency, Configurations using No TEB and Full TEB.
Table C.2: Sound Power at Each Interaction Frequency, Configurations using ATEB 1x1.
Configuration 1 2 3 4 5 6 7 8 Total[Inlet Duct, No TEB] 106.6 104.0 100.6 95.6 91.5 81.7 76.4 75.4 109.4[Inlet Duct, Full TEB 0%] 106.5 105.2 102.0 96.0 90.1 83.3 79.8 77.7 110.0[Inlet Duct, Full TEB 0.31%] 106.3 104.9 100.7 95.0 91.2 81.9 79.0 73.3 109.5[Inlet Duct, Full TEB 0.39%] 105.2 103.6 99.9 93.5 89.4 79.7 77.8 72.7 108.4[Inlet Duct, Full TEB 0.45%] 104.6 102.1 98.6 91.0 87.9 77.3 78.6 72.6 107.3[Inlet Duct, Full TEB 0.52%] 103.1 99.7 95.6 89.5 86.8 78.7 77.1 71.5 105.5[Inlet Duct, Full TEB 0.57%] 102.9 97.3 89.1 90.0 87.4 79.4 76.3 70.2 104.4[Inlet Duct, Full TEB 0.65%] 102.7 97.8 89.1 90.4 87.5 80.1 75.6 70.3 104.4[Inlet Duct, Full TEB 0.72%] 103.3 99.9 94.5 92.2 88.1 81.2 76.2 71.9 105.6[Inlet Duct, Full TEB 0.74%] 104.0 101.9 95.6 92.0 88.6 81.4 75.5 72.1 106.7[Inlet Duct, Full TEB 0.76%] 104.7 103.9 98.5 93.3 89.2 81.1 77.7 74.0 108.1[Inlet Duct, Full TEB 0.79%] 106.1 105.5 100.4 94.9 89.9 82.5 78.6 73.1 109.6[Inlet Duct, Full TEB 0.83%] 106.9 106.8 101.2 94.6 90.3 81.3 77.4 72.4 110.6[Aft Duct, No TEB] 106.6 105.4 112.9 102.8 98.5 90.8 88.6 77.0 114.8[Aft Duct, Full TEB 0%] 106.7 106.2 113.6 102.6 96.8 92.0 88.8 83.6 115.3[Aft Duct, Full TEB 0.31%] 104.5 105.5 112.4 101.4 96.5 91.9 87.1 76.8 114.1[Aft Duct, Full TEB 0.39%] 103.8 104.3 111.2 99.5 96.4 90.4 85.2 74.7 112.9[Aft Duct, Full TEB 0.45%] 102.8 102.2 109.8 96.2 96.0 89.6 85.8 76.4 111.5[Aft Duct, Full TEB 0.52%] 103.8 97.9 107.5 92.7 93.3 88.3 85.7 74.9 109.6[Aft Duct, Full TEB 0.57%] 104.9 91.7 104.2 93.3 92.3 89.2 86.4 73.4 108.0[Aft Duct, Full TEB 0.65%] 106.0 94.7 100.9 94.5 91.9 88.8 86.2 72.5 107.8[Aft Duct, Full TEB 0.72%] 107.0 99.4 102.7 95.4 93.9 89.5 87.2 74.5 109.3[Aft Duct, Full TEB 0.74%] 107.7 103.1 106.1 96.1 93.5 89.8 87.8 74.2 111.0[Aft Duct, Full TEB 0.76%] 108.5 104.7 108.3 97.3 94.2 90.2 88.0 78.1 112.5[Aft Duct, Full TEB 0.79%] 109.3 106.3 110.4 98.1 94.2 91.6 88.2 77.7 113.9[Aft Duct, Full TEB 0.83%] 109.8 107.8 111.9 99.5 93.9 91.0 87.5 77.8 115.1
Blade Passing Frequency
Configuration 0.5 1 1.5 2 2.5 3 3.5 44.5 5 5.5 6 6.5 7 7.5 8 Total62.1 107.1 69.1 104.7 73.6 101.0 69.3 97.168.3 89.0 67.9 83.1 63.1 78.2 61.7 76.6 110.068.0 106.7 84.8 104.0 79.0 100.3 79.9 95.774.9 89.2 74.6 82.1 69.7 78.5 64.2 73.9 109.472.5 106.0 89.7 103.5 84.4 99.9 83.2 94.779.2 88.3 76.7 80.3 72.0 77.3 66.9 75.3 108.973.9 105.0 92.4 102.4 88.4 98.5 86.1 93.881.8 88.0 79.3 80.8 73.6 78.0 67.9 74.3 107.975.5 104.4 94.1 101.2 89.9 96.6 87.8 93.183.1 87.5 80.4 80.9 74.1 76.2 68.0 71.5 107.275.0 103.0 95.6 99.6 91.3 94.6 90.1 93.584.5 87.9 81.3 80.3 73.9 76.2 67.6 75.1 106.277.3 103.4 94.9 100.7 90.8 95.5 88.8 93.183.7 88.1 80.8 80.6 73.6 77.5 68.1 73.1 106.677.1 102.3 96.1 99.6 91.6 93.6 89.9 93.484.1 88.1 81.6 81.0 73.2 75.2 67.5 74.3 105.870.3 105.5 81.6 105.7 77.0 113.6 80.5 102.775.7 97.6 73.4 92.3 73.1 88.1 66.1 77.3 115.277.6 104.0 90.3 104.8 84.9 112.5 81.5 101.485.9 96.9 79.9 91.5 79.2 87.0 72.2 76.8 114.180.2 104.0 93.8 104.2 90.0 112.0 84.8 100.088.3 96.9 80.9 90.7 82.2 86.8 74.4 74.9 113.680.8 104.1 95.5 102.7 93.3 111.2 88.0 98.489.3 95.2 82.4 90.2 82.5 86.3 74.8 75.1 112.982.2 104.0 97.1 101.3 95.2 110.1 89.6 98.090.5 95.0 83.6 90.3 83.5 86.2 75.5 76.4 112.183.0 104.6 100.5 98.1 97.2 108.4 91.2 98.292.7 95.5 84.8 91.1 82.3 87.1 74.9 75.2 111.483.8 104.4 98.7 99.5 96.0 109.1 91.0 98.291.5 95.3 83.9 90.4 82.9 87.4 75.4 78.0 111.684.5 104.7 101.9 98.5 97.7 107.9 92.2 98.193.3 95.1 84.7 90.8 82.2 87.8 74.9 75.9 111.3
[Aft Duct, ATEB 1x1 0.41%]
[Aft Duct, ATEB 1x1 0.43%]
[Aft Duct, ATEB 1x1 0.32%]
[Aft Duct, ATEB 1x1 0.33%]
[Aft Duct, ATEB 1x1 0.35%]
[Aft Duct, ATEB 1x1 0.37%]
[Inlet Duct, ATEB 1x1 0.41%]
[Inlet Duct, ATEB 1x1 0.43%]
[Aft Duct, ATEB 1x1 0%]
[Aft Duct, ATEB 1x1 0.28%]
[Inlet Duct, ATEB 1x1 0.32%]
[Inlet Duct, ATEB 1x1 0.33%]
[Inlet Duct, ATEB 1x1 0.35%]
[Inlet Duct, ATEB 1x1 0.37%]
Blade Passing Frequency
[Inlet Duct, ATEB 1x1 0%]
[Inlet Duct, ATEB 1x1 0.28%]
121
Table C.3: Sound Power at Each Interaction Frequency, Additional Configurations using Inlet Duct, Full
TEB.
Configuration 1 2 3 4 5 6 7 8 Total[Inlet Duct, Full TEB 0%, Vanes at 1 Chord] 110.3 107.0 100.5 91.0 87.8 80.3 76.4 71.6 112.3[Inlet Duct, Full TEB 0.44%, Vanes at 1 Chord] 106.9 104.5 98.3 87.1 86.4 79.8 77.6 69.8 109.3[Inlet Duct, Full TEB 0.58%, Vanes at 1 Chord] 102.4 101.2 95.5 86.5 84.2 79.3 76.9 71.7 105.4[Inlet Duct, Full TEB 0.66%, Vanes at 1 Chord] 93.8 94.8 89.3 90.3 86.2 79.0 77.7 72.2 99.0[Inlet Duct, Full TEB 0.67%, Vanes at 1 Chord] 96.0 97.4 92.8 89.0 85.7 79.8 76.0 71.8 101.0[Inlet Duct, Full TEB 0.74%, Vanes at 1 Chord] 93.6 94.0 88.7 91.0 86.9 79.6 76.9 71.7 98.7[Inlet Duct, Full TEB 0.78%, Vanes at 1 Chord] 97.8 96.9 91.3 90.5 85.6 79.2 75.1 70.9 101.4[Inlet Duct, Full TEB 0%, Suction Side Blowing Only] 106.5 105.1 100.9 96.1 90.1 83.1 78.0 74.3 109.8[Inlet Duct, Full TEB 0.31%, Suction Side Blowing Only] 106.6 104.9 100.8 96.0 90.9 81.6 79.2 73.1 109.7[Inlet Duct, Full TEB 0.31%, Suction Side Blowing Only] 106.2 104.3 99.3 95.0 90.5 81.8 78.1 72.0 109.1[Inlet Duct, Full TEB 0.32%, Suction Side Blowing Only] 105.4 103.6 99.4 93.5 89.3 80.2 77.2 73.2 108.4[Inlet Duct, Full TEB 0.38%, Suction Side Blowing Only] 104.8 103.0 98.5 91.8 87.0 78.0 76.1 71.0 107.7[Inlet Duct, Full TEB 0.41%, Suction Side Blowing Only] 103.9 101.9 97.0 88.3 84.9 78.6 74.1 71.6 106.6[Inlet Duct, Full TEB 0%, Tip Blowing] 106.8 104.5 101.2 95.9 91.1 81.6 76.2 73.3 109.8[Inlet Duct, Full TEB 0.24%, Tip Blowing] 106.6 102.8 100.5 95.4 90.8 79.5 76.0 76.5 109.1[Inlet Duct, Full TEB 0.32%, Tip Blowing] 105.7 96.9 94.9 94.4 91.5 79.0 75.5 76.1 106.9[Inlet Duct, Full TEB 0.33%, Tip Blowing] 106.1 101.0 98.8 95.2 91.4 80.0 75.6 75.8 108.2[Inlet Duct, Full TEB 0.41%, Tip Blowing] 105.2 95.9 93.5 94.6 92.0 79.9 75.6 75.2 106.4[Inlet Duct, Full TEB 0.42%, Tip Blowing] 104.9 98.2 93.4 95.8 92.1 82.1 76.7 76.0 106.5[Inlet Duct, Full TEB 0.42%, Tip Blowing] 105.0 97.6 92.1 94.7 92.4 80.0 75.4 76.4 106.4[Inlet Duct, Full TEB 0%, Alternating Jets] 106.1 104.5 100.7 95.6 90.4 81.2 78.5 76.4 109.3[Inlet Duct, Full TEB 0.29%, Alternating Jets] 105.2 103.6 99.8 94.9 88.9 80.4 75.9 75.8 108.4[Inlet Duct, Full TEB 0.35%, Alternating Jets] 103.8 102.7 98.7 92.6 89.1 79.7 77.5 76.5 107.2[Inlet Duct, Full TEB 0.39%, Alternating Jets] 102.2 99.7 93.1 93.9 89.5 80.2 77.6 72.0 105.0[Inlet Duct, Full TEB 0.39%, Alternating Jets] 102.2 100.5 94.2 93.3 88.9 79.6 76.2 75.7 105.3[Inlet Duct, Full TEB 0.44%, Alternating Jets] 101.0 99.3 91.4 93.2 89.5 79.7 77.7 76.7 104.1[Inlet Duct, Full TEB 0.44%, Alternating Jets] 100.4 99.1 90.7 93.1 89.3 80.4 76.1 74.1 103.7[Inlet Duct, Full TEB 0.45%, Alternating Jets] 100.0 99.7 92.4 93.4 89.9 80.0 75.7 75.7 103.9[Inlet Duct, Full TEB 0%, Alternating Spans] 106.9 105.6 102.5 95.9 91.4 82.7 76.8 74.7 110.4[Inlet Duct, Full TEB 0.33%, Alternating Spans] 103.8 98.9 96.0 93.3 88.1 81.6 75.9 72.9 105.9[Inlet Duct, Full TEB 0.36%, Alternating Spans] 103.2 97.9 95.3 93.7 88.1 82.8 75.0 74.3 105.3[Inlet Duct, Full TEB 0.42%, Alternating Spans] 102.5 97.0 95.8 94.1 89.2 81.8 75.0 74.3 104.8[Inlet Duct, Full TEB 0.42%, Alternating Spans] 101.6 97.0 95.6 94.3 88.5 80.8 72.6 76.1 104.2
Blade Passing Frequency
122
Table C.4: Sound Power at Each Interaction Frequency, Additional Configurations using Aft Duct, Full TEB.
Table C.5: Sound Power at Each Interaction Frequency, Configurations using ATEB 1x1.
Configuration 1 2 3 4 5 6 7 8 Total[Aft Duct, Full TEB 0%, Vanes at 1 Chord] 99.3 109.6 109.4 92.7 87.9 83.1 76.7 73.7 112.8[Aft Duct, Full TEB 0.44%, Vanes at 1 Chord] 99.9 107.8 106.9 90.7 85.4 80.2 78.0 75.7 110.8[Aft Duct, Full TEB 0.58%, Vanes at 1 Chord] 99.0 104.4 104.1 87.7 83.6 80.1 76.7 73.7 107.9[Aft Duct, Full TEB 0.66%, Vanes at 1 Chord] 100.6 98.4 101.0 90.3 87.0 82.6 78.5 72.2 105.2[Aft Duct, Full TEB 0.67%, Vanes at 1 Chord] 99.7 100.1 101.4 89.5 85.2 80.0 76.9 71.8 105.4[Aft Duct, Full TEB 0.74%, Vanes at 1 Chord] 99.8 100.2 102.1 89.9 86.6 80.1 76.8 73.3 105.8[Aft Duct, Full TEB 0.78%, Vanes at 1 Chord] 100.6 103.6 104.4 92.7 86.9 82.6 77.7 71.9 108.1[Aft Duct, Full TEB 0%, Suction Side Blowing Only] 106.4 105.7 113.1 101.9 95.9 91.1 86.9 76.6 114.9[Aft Duct, Full TEB 0.31%, Suction Side Blowing Only] 105.1 105.0 112.4 101.4 97.2 91.7 87.6 76.8 114.1[Aft Duct, Full TEB 0.31%, Suction Side Blowing Only] 104.1 104.3 111.9 100.5 96.2 90.3 86.1 75.8 113.5[Aft Duct, Full TEB 0.32%, Suction Side Blowing Only] 104.0 103.8 111.3 99.1 95.5 88.5 84.4 75.8 112.9[Aft Duct, Full TEB 0.38%, Suction Side Blowing Only] 103.7 102.4 110.5 97.2 94.0 87.2 83.6 75.9 112.1[Aft Duct, Full TEB 0.41%, Suction Side Blowing Only] 103.8 101.1 109.5 93.9 94.4 86.0 81.9 74.8 111.2[Aft Duct, Full TEB 0%, Tip Blowing] 106.3 105.6 113.3 102.9 98.0 90.8 87.7 81.1 115.1[Aft Duct, Full TEB 0.24%, Tip Blowing] 105.9 104.6 111.8 101.9 97.6 90.4 87.4 78.5 113.9[Aft Duct, Full TEB 0.32%, Tip Blowing] 104.2 99.7 106.6 100.9 96.8 89.1 86.2 77.6 110.0[Aft Duct, Full TEB 0.33%, Tip Blowing] 104.9 102.6 109.8 101.1 96.7 90.0 86.8 78.5 112.1[Aft Duct, Full TEB 0.41%, Tip Blowing] 103.9 97.3 102.6 100.8 97.1 89.7 86.0 78.1 108.2[Aft Duct, Full TEB 0.42%, Tip Blowing] 103.3 96.5 99.9 100.4 97.2 90.3 85.5 77.7 107.3[Aft Duct, Full TEB 0.42%, Tip Blowing] 103.5 96.7 101.3 100.5 97.8 90.5 86.8 80.1 107.7[Aft Duct, Full TEB 0%, Alternating Jets] 106.3 105.1 112.6 102.7 96.7 90.7 88.5 80.1 114.5[Aft Duct, Full TEB 0.29%, Alternating Jets] 105.9 104.4 111.5 101.7 96.6 89.8 86.3 79.6 113.6[Aft Duct, Full TEB 0.35%, Alternating Jets] 105.2 102.0 110.1 99.2 94.0 88.3 87.2 78.2 112.1[Aft Duct, Full TEB 0.39%, Alternating Jets] 105.0 96.8 107.1 97.9 94.5 89.4 87.9 76.1 109.9[Aft Duct, Full TEB 0.39%, Alternating Jets] 105.2 98.3 107.8 97.8 95.0 89.0 87.1 78.2 110.5[Aft Duct, Full TEB 0.44%, Alternating Jets] 105.5 96.0 105.8 98.1 95.0 89.5 88.3 77.9 109.5[Aft Duct, Full TEB 0.44%, Alternating Jets] 105.6 96.2 105.6 97.6 95.1 90.0 88.1 76.9 109.4[Aft Duct, Full TEB 0.45%, Alternating Jets] 105.9 98.0 105.5 97.6 95.5 89.9 87.5 75.5 109.6[Aft Duct, Full TEB 0%, Alternating Spans] 105.6 105.9 113.4 102.1 96.2 90.6 87.7 78.6 115.0[Aft Duct, Full TEB 0.33%, Alternating Spans] 104.7 100.8 108.3 98.4 94.6 90.3 86.0 76.4 110.8[Aft Duct, Full TEB 0.36%, Alternating Spans] 105.0 99.5 107.4 99.0 94.4 91.2 86.9 76.4 110.4[Aft Duct, Full TEB 0.42%, Alternating Spans] 105.3 99.4 106.2 98.9 94.2 91.0 86.5 78.1 109.8[Aft Duct, Full TEB 0.42%, Alternating Spans] 105.8 99.7 105.7 98.6 94.7 90.8 85.8 77.3 109.8
Blade Passing Frequency
Configuration 0.5 1 1.5 2 2.5 3 3.5 44.5 5 5.5 6 6.5 7 7.5 8 Total66.9 106.4 71.3 104.2 71.4 100.7 70.8 94.867.1 91.3 62.6 79.8 63.4 78.8 61.6 75.2 109.371.7 105.9 77.5 102.5 80.0 99.1 80.8 95.576.5 91.4 68.1 80.4 65.2 79.2 62.7 75.5 108.571.3 105.8 77.8 101.7 81.1 98.3 82.2 94.9
76.705 91.256 67.523 80.667 65.06 79.122 64.192 74.419 108.176.2 106.3 80.2 105.3 75.6 112.9 80.0 103.077.1 97.2 68.9 89.9 72.4 88.7 67.1 77.3 114.877.1 105.5 90.5 103.5 88.1 111.3 82.7 102.783.9 97.0 76.7 90.3 76.4 88.9 69.8 80.1 113.478.3 105.2 93.7 102.7 89.6 110.8 83.4 102.484.7 97.2 76.0 90.6 75.8 88.5 70.6 80.6 113.0
[Aft Duct, ATEB 1x1 0%, Tip Blowing]
[Aft Duct, ATEB 1x1 0.21%, Tip Blowing]
[Aft Duct, ATEB 1x1 0.27%, Tip Blowing]
Blade Passing Frequency
[Inlet Duct, ATEB 1x1 0%, Tip Blowing]
[Inlet Duct, ATEB 1x1 0.21%, Tip Blowing]
[Inlet Duct, ATEB 1x1 0.27%, Tip Blowing]
123
Appendix D: Initial Numerical Predictions
This appendix presents the results of running the V072 and Eversman codes to predict
ATEB performance in the absence of any experimental data. This is done to show the initial
conclusions used to justify experimental testing. These predictions model the liner used on the
ANCF. Work was performed to examine the results of optimized liners, but presenting this
would be redundant to the more rigorous treatment of Chapter 5.
Predictions using V072-Generated Wake Profiles
This first set of predictions was performed using wake profiles generated internally by
the V072 program. Any fan blade without TEB was assumed to produce the wake calculated by
V072. Any blade with TEB was assumed to produce no wake at all (this means that conventional
TEB on every blade could not be modeled using this technique). Velocity profiles for the ATEB
layouts were formed by combining wake profiles and profiles representing only freestream
velocities. This is explained in Figure D.1, which shows normalized relative velocities. Part (a)
of the figure shows the internally calculated wake spanning 22.5 tangential degrees (one blade
width). Part (b) shows the ATEB 1x1 profile spanning 45 degrees (two blade widths); there is
one wake profile covering 22.5 degrees and one "freestream" profile covering the other 22.5
degrees. Part (c) shows the ATEB 2x2 profile covering 90 degrees (four blade widths); two wake
profiles and two freestream profiles are placed side by side.
124
Figure D.1: V072 Wake Profiles (at Blade Hub).
When (A)TEB is used in combination with acoustic liners, there are two sources of noise
reduction; the source-level reduction of wake-filling and also the reduction due to the liner. The
wake-filling reduction is defined as the difference in power between a hardwall configuration
with no blowing and a hardwall configuration with blowing. The liner reduction is defined as the
change in power when a liner is added to any configuration. Using this convention the results are
shown in Figure D.2. The green "liner only" bars represent liner reductions when ATEB is not
used. When ATEB is used some noise reduction is achieved by wake-filling, represented by the
blue bars. Liner performance changes when ATEB is used, with performance being increased in
seven of the eight configurations tested. The liner modeled was the liner physically present on
the ANCF; it is not optimized for this application. Optimized liner results are given in Chapter 5
of the main body of the thesis.
125
Figure D.2: Wake-Filling and Liner Reductions for (a) Inlet Duct with 14 Vanes, (b) Aft Duct with 14 Vanes,
(c) Inlet Duct with 28 Vanes, (d) Aft Duct with 28 Vanes.
Predictions using CFD-Generated Wake Profiles
Another set of predictions was run using CFD-generated wakes rather than V072-
generated wakes. The benefit of doing this was that partially filled wakes could be used to
represent blades with TEB. This means that full TEB as well as ATEB configurations could be
run. The wake profiles were provided by Techsburg, Inc and are shown in Figure D.3. Part (a)
shows a wake from a blade with no TEB and part (b) shows the wake from a blade with TEB. It
is clear how TEB partially fills the wake deficit. ATEB profiles were formed by placing these
two profiles side by side.
126
Figure D.3: CFD-Generated Wake Profiles for (a) No Blowing and (b) TEB.
The same format of presenting the results is used in Figure D.4, showing reductions from
wake-filling and from liner attenuation. Liner performance is lowest with no TEB (liner alone).
Liner performance increases when ATEB 1x1 or ATEB 2x2 is used. In these predictions, liner
performance is best with full TEB. This appears contrary to the ATEB concept, but happens here
only because the modeled liner has not been optimized for use with any given configuration. The
127
liner optimization study of Chapter 5 shows that liner performance is in fact best when ATEB is
used.
Figure D.4: Wake-Filling and Liner Reductions for (a) Inlet Duct with 14 Vanes, (b) Aft Duct with 14 Vanes,
(c) Inlet Duct with 28 Vanes, (d) Aft Duct with 28 Vanes.
128
Appendix E: Validation of Eversman Code Accuracy
The one liner used in the ANCF experiments was used to verify the predictions of liner
performance made by the Eversman code. To do this, experimentally measured hardwall in-duct
modal pressures were used as inputs to the Eversman Code. The code was first run with no
acoustic liner present to give a theoretical hardwall far-field power. The code was then supplied
with the impedance of the liner physically installed on the ANCF and run again to give a
theoretical softwall far-field power. The difference between these two predictions is the
theoretical liner attenuation. This is compared to the experimentally measured liner attenuation.
This comparison was made for 6 configurations, those of [Inlet Duct, 14 Vanes, No TEB 0%],
[Inlet Duct, 14 Vanes, ATEB 1x1 0.9%], [Inlet Duct, 14 Vanes, ATEB 2x2 0.9%], [Inlet Duct,
28 Vanes, No TEB 0%], [Inlet Duct, 28 Vanes, ATEB 1x1 0.9%], and [Inlet Duct, 28 Vanes,
ATEB 2x2 0.9%] (No softwall full TEB experimental data is available.) The predicted
attenuations were an average of 0.7 dB greater than the measured attenuations. Predicted
attenuations were either equal to or greater than measured attenuations, with the [Inlet Duct, 14
Vanes, No TEB 0%] configuration having the greatest theoretical-to-measured difference of 1.2
dB. The [Inlet Duct, 28 Vanes, ATEB 2x2 0.9%]configuration had the smallest difference of 0.0
dB. Figure E.1 shows predicted and measured liner attenuations for these 6 cases.
0
1
2
3
4
5
6
[14 V, NoTEB]
[14 V, ATEB1x1, 0.9%]
[14 V, ATEB2x2, 0.9%]
[28 V, NoTEB]
[28 V, ATEB1x1, 0.9%]
[28 V, ATEB2x2, 0.9%]
Lin
er R
edu
ctio
n (
dB
)
Experimental Farfield Theoretical Farfield
Figure E.1: Measured and Predicted Liner Reductions
129
Vita
Christopher Halasz was born on June 20, 1981 in the suburbs of New Jersey. Upon
completion of high school he entered the College of Engineering at Virginia Tech in 1999. He
then entered the department of Mechanical Engineering in 2000, and as a senior began
performing undergraduate research in the field of acoustics. This led to the opportunity to pursue
a graduate degree in the same area, and immediately after graduating with a B.S. degree he
began his graduate studies as a research assistant in the Vibration and Acoustics Laboratory.