research in internal and external aerodynamics for the ... · •conclusion outline 2. research...
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Pratt & Whitney Canada Proprietary Information
Export Classification: [Yes -Technical Data, USML N/A, P-USML N/A, ECL
NLR, ECCN N/A, P-ECCN 9E991]
Research in Internal and External
Aerodynamics for the Next
Generation of Efficient Aircraft
Huu Duc Vo
Associate Professor
Department of Mechanical Engineering
École Polytechnique de Montréal
2017 National Colloquium on Sustainable Aviation at UTIAS
June 21, 2017
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• Research Areas
• Research Approach
• Experimental Facilities
• Internal Aerodynamics Research
• External Aerodynamics Research
• Conclusion
OUTLINE
2
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RESEARCH AREAS
3
I) Internal flows: compressor aerodynamics
II) External flows:
flight control
ROTOR
SHROUD
rotor speed
Tip clearance flow
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RESEARCH APPROACH
4
Analytical • Modeling
Experimental• Validation of concepts• Validation of models/flow physics• Validation of numerical setup
Numerical (CFD)• Preliminary assessment of concepts• Elucidate flow physics
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EXPERIMENTAL FACILITIES
5
Difuser
Max. Power 200 HP
Max. Rotational Speed 21 100 RPM
Max. Mtip, circumferential 0.90
Mass flow ∼ 8 lbm/s
1) Transonic compressor test rig
Utility: Validate concepts in compressor aerodynamics at realistic speeds
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Max. Power 7.7 HP
Max. Rotational Speed 8900 RPM
Max. Mtip, circumferential 0.25
Mass flow ∼1-1.2 lbm/s
2) Low-speed compressor test rigs
Utility: Low-cost validation of concepts
in compressor aerodynamics
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EXPERIMENTAL
EXPERIMENTAL
CFD
CFD
Rotor 1 exit
Stator 1 exit
Rotor 2 exitStator 2 exit
Radial
traverse
Radial-
circumferential
traverse
Detailed flow measurement capability
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Max. Power 200 HP
Max. Speed 91 m/s
3) Closed-Loop Wind Tunnel and Cascade Test Section
Utility: - Low-cost validation of concepts external aerodynamics
- Detailed measurements of blade passage flow in turbomachinery
24 x 24 x96 inch test section
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4) Aerodynamic Plasma Actuation
DBD plasma actuator
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INTERNAL AERODYNAMICS RESEARCH
A) Prediction of Non-Synchronous Vibrations (NSV)
Frequency
Engine speed
Blade resonance from forced response: predictable critical speeds
NSV: non-predictable critical speeds
Excitation frequencies
integer (blade #) multiple
of engine speed
Mode 1
Mode 2
Mode 3
Mode 4
Blade natural
frequencies
NSV can cause
premature blade
failure in aero-engine
compressors and fans
Original hypothesis
to explain NSV
impingement of tip
clearance flow on
adjacent blade
PROBLEM: Resonance of impinging air jets Mach > 0.65 (Ho & Nosseir 1981)
BUT tip clearance flow relative velocity usually < 0.5
Objective: Safe use of lighter aero-engine compressor/fan blades
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NEW impinging jet behavior proposed and proven experimentally
Flexible wall allows for jet resonance well below Mach 0.65
Application to
compressor & fan blade
context
First explanation and
predictive tool for NSV
Validated on transonic compressor rig at P&WC
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B) Delay of Rotating Stall
Objective: Improve aero-engine efficiency/operating envelope
- Sudden loss of power/thrust- Engine damage
rotating stall surgestall/surge line
mass flow
speed-=cst.
running line
cruise operating point
stall margin
maximum effciency point
effciency contours
mass flow
new stall/surge line
Possible new cruise operating point
rotating stall delay strategies
stall margin improvement
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Project 1: Effective and lossless casing treatment
Casing treatment: passive stall margin improvement strategy
(figures from Fujita and Takata, 1984)
Numerical parametric study for slot casing treatment on mixed-flow compressor
Baseline (40% open area ratio) 60% open area ratio 20% open area ratio
Preliminary geometrical design rules for effective lossless
slots casing treatment
stall delay
peak efficency
unchanged
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Project 2: Delay of rotating stall with plasma actuators
Preliminary numerical (CFD) assessment on low-
speed axial compressor
Top View: radial plane at blade tip
LE spillage below
blade tip
incoming
flow
(relative
frame)
Vx
U
∆Vx from
actuation
incoming/tip
clearance flow
flow interface
tip clearance
flow
backflowROTOR
Side View
plasma actuator
dielectric
rotor tip
LE TE
casing
no actuation (spike formation)
with plasma actuation
flow
incoming
flow
x
dir.
∆Vx from
actuation
No Actualtion
(stall point)
With Plasma
Actualtion
stall
delay
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Application to low-speed axial-centrifugal compressor rig
Numerical (CFD) assessment
Configuration 1: Two-stage, actuator on axial stage
Configuration 2: Centrifugal stage only, actuator on impeller
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Installation of plasma actuators
Axial stage Centrifugal stage
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Results
Actuator on axial stage Actuator on centrifugal stage
Successful demonstration of concept for both axial and centrifugal compressors (first)
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Transient operation → diff. thermal exp. → temp. t.c. increase
Operational age → rotor tip rubbing → permanent t.c. increase
Fuel consumption ↑
Operating envelope ↓
C) Desensitization of compressor performance & stall margin
Objective: Prevent degradation in aero-engine performance and
operating envelope with age
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BASELINE BLADE (BASE)
Back Axial Sweep
Forward Axial Sweep
Back Lean
Forward Lean
Aft Chordwise Sweep
Forward Chordwise Sweep
Negative Dihedral
Positive Dihedral
Extensive numerical (CFD) parametric study of geometric design of axial rotor
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Identification of two desensitizing flow features
(1) Reduction of double tip leakage
(2) Increased incoming flow
momentum in tip region
Features to be exploited in blade
geometry and casing treatment designRotation
Base
VH
Explanation of associated flow mechanisms
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Desensitizing blade design strategies
Features to be exploited in blade
geometry and casing treatment designRotation
New desensitizing casing treatment concept
BASE
FFCS
PLS
BASE
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Rotor
Capacitance probe mount
Stator
LE
rake
Rake
at
stator
exit
Aluminum shroud insert
over rotor
Capacitan
ce probe
Rotor Section Stator Section
Experimental validation on real transonic axial compressor stage at Polytechnique
(In progress)
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D) Plasma actuation on aero-engine components
Collaboration with & led by NRC Gas Turbine Laboratory
Project 1: Reduce inlet distortion in non-axial aero-engine intake/inter-turbine duct
Objective: Improve engine performance/operating envelope & reduce turbine length/weight
No actuation
With actuation
ITD test rig at NRC
CFD
Start of (pulsed) actuation cycle
End of (pulsed) actuation cycle
WT test rig at NRC
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Project 2: Reduce compressor blade corner separation
Objective: Improve compressor stage pressure ratio & effciency (reduce # stages )
NRC Cascade WT
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Project 3: Flashback control in lean-premixed dump combustor via plasma actuators
Objective: Improve operability of (low-NOx) lean-premixed dump combustors
No actuation
With actuation
flashback
flashback
NRC atmospheric
combustion rig
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EXTERNAL AERODYNAMICS RESEARCH
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Flight Control with Plasma Actuation
Objective: Eliminate all movable flight control surfaces
Impact: - Reduction of weight and (production/operating) costs
- Increase in range (more fuel volume)
‘Clean’ wing without movable surfacesConventional wing
• Alter lift on wing surfaces• Generate lift on empennages
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A) Wing tip plasma actuation
No actuation With actuation
Lif
t (N
/m)
% span
With actuation
No actuation
Vorticity contours
Test Wing Geometry
CFD Simulations
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Wind Tunnel Test Setup
Concept of wing tip plasma actuation can
generate sufficient lift change for flight
control with sufficient actuator strength
Results
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B) Plasma Gurney Flap (collaboration with & led by Prof .N.W. Mureithi)
Wind Tunnel Tests with PIV
No actuation
With plasma Gurney flap
With physical Gurney flap
Concept of
plasma Gurney
flap can work
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C) Lift reduction with plasma actuation
Measured velocity vectors on suction side with
PIV
U∞ = 12.6 m/s
No actuation
With actuation
Concept of ‘plasma spoiler’ can work
with sufficient actuation strength
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• Research on aerodynamics of aero-engine and aircraft wings to make
future aircraft more fuel efficient, lighter and mechanically simpler
• Preliminary study of concepts
• Emphasis on understanding of flow mechanism, preliminary
numerical assessment/experimental validation of concepts
• Work continuing on further assessment of some of the concepts shown
on more realistic geometries/conditions
CONCLUSION
31
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Thank
You
Question
s?