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NASA Technical Memorandum 109152

Wind-Tunnel Blockage and ActuationSystems Test of a Two-DimensionalScramjet Inlet Unstart Model atMach 6

Scott D. HollandLangley Research Center, Hampton, Virginia

November 1994

National Aeronautics andSpace AdministrationLangley Research CenterHampton, Virginia 23681-0001

1

Summary

The present study examines the wind-tunnel blockage andactuation systems effectiveness in starting and forcibly unstarting atwo-dimensional scramjet inlet in the NASA Langley 20-Inch Mach6 Tunnel. The intent of the overall test program is to study (bothexperimentally and computationally) the dynamics of the inletunstart; however, prior to the design and fabrication of anexpensive, instrumented wind-tunnel model, it was deemednecessary first to examine potential wind-tunnel blockage issuesrelated to model sizing and to examine the adequacy of the actuationsystems in accomplishing the start and unstart. The model isequipped with both a moveable cowl and aft plug. Following theinjection of the model into the freestream, the cowl is raised andlowered to allow the inlet to start. The plug located in the exit planeis then rapidly driven forward to decrease the exit area and force theinlet to unstart. Schlieren windows in the inlet sidewalls allowlimited optical access to the internal shock structure and permit theidentification of model start and unstart. For this blockage test, avideo camera was incorporated into the schlieren system to recordthe schlieren of the entire start/unstart sequence on VHS video tape.The framing rate and shutter speed of the camera were too slow tofully capture the dynamics of the unstart but did prove sufficient toidentify start/unstart. A chronology of each actuation sequence isprovided in tabular form along with still frames from the schlierenvideo. A pitot probe monitored the freestream conditionsthroughout the start/unstart process to determine if there was ablockage effect due to the model start or unstart. Because thepurpose of this report is to make the phase I (blockage and actuationsystems) data rapidly available to the community, the data ispresented largely without analysis of the internal shock interactionsor the unstart process. This series of tests indicated that the modelwas appropriately sized for this facility and identified operabilitylimits required first to allow the inlet to start and second to force theunstart.

Symbols

ae inlet exit area, sq. in.at throat area, 5.16 sq.in.M∞ freestream Mach numberp∞ freestream static pressure, psiapt,1 tunnel stagnation pressure, psiapt,2 freestream pitot pressure, psiaRe∞ unit freestream Reynolds number,

ft-1T∞ freestream static temperature, °RTt,1 tunnel stagnation temperature, °Rx,y,z axial, lateral, and vertical Cartesian

coordinates (respectively) , inch

Conventions

The model is injected into the tunneloriented inverted with respect to flight, i.e.the cowl is shown in the top of the images.Up and down shall be defined with respectto the model such that cowl up indicates theconfiguration with maximum throat area,and cowl down indicated the configurationwith minimum throat area. Therefore, thecowl is moved upward to aid in inletstarting.

2

Introduction

The present work examines the wind-tunnel blockage and actuation systemseffectiveness in starting and forciblyunstarting a two-dimensional scramjet inletin the NASA Langley 20-Inch Mach 6Tunnel. The intent of the overall testprogram is to study the dynamics of theinlet unstart via both computational andexperimental techniques. This work wasinitiated in conjunction with a CFD effort atNorth Carolina State University, whereintime-accurate calculations of a back-pressure induced inlet unstart were made.CFD was used in the preliminary design ofthe 2-D scramjet inlet configuration.Because of the complexity and high speedwith which the unstart takes place (on theorder of 15ms, based on preliminary CFDresults), a blockage model has beendesigned and fabricated (prior to the designof an expensive instrumented wind-tunnelmodel) first to address wind-tunnelblockage issues related to modelsize/interference and second to examine theadequacy of the actuation systems inaccomplishing the start and unstart. Afollow-on phase is planned (fundingpermitting), in which the dynamics of theunstart will be investigated; this secondphase will make use of high-speedschlieren movie cameras and high-frequency instrumentation.

The model is equipped with both amoveable cowl and aft plug. Following theinjection of the model into the freestream,the cowl is raised and lowered to allow theinlet to start. The plug (located in the exitplane) is then rapidly driven forward todecrease the exit area and force the inlet tounstart. Schlieren windows in the inletsidewalls allow limited optical access to theinternal shock structure and permit theidentification of model start and unstart.For this blockage test, a video camera wasincorporated into the schlieren system torecord the schlieren of the entirestart/unstart sequence on VHS video tape.(Copies of the video may be obtainedseparately as Video Supplement L-0194-41

to NASA TM 109152.) The framing rateand shutter speed of the camera were tooslow to fully capture the dynamics of theunstart but did prove sufficient to identifystart/unstart. Frames from the video tapeare included in this report as still imagesalong with tables which provide theactuation sequence for each run. A pitotprobe monitored the freestream conditionsthroughout the start/unstart process todetermine if there was a blockage effect dueto the model start or unstart.

Because this report documents the firstphase of the overall test program (namely,blockage and actuation systems tests), thediscussion is limited to these topics; hence,no analysis is presented with respect to theorigin or nature of the unstart phenomenain this report. In particular, the followingquestions related to the wind-tunnelblockage and actuation systems areaddressed as the primary focus.

1. For a given freestream Reynoldsnumber and plug configuration, will theinlet start through any combination ofsurface movement?

2. If the inlet can be started, is the throwon the aft plug sufficient to force theunstart?

3. If the inlet can be started and unstarted,will the inlet restart by simply retractingthe plug (i.e., is the inlet self-starting)?

4. If the inlet can be started and unstarted,will the inlet restart by cycling the cowlafter the plug is moved aft?

5. Will the inlet (configured with the plugaft and the cowl down) start solely dueto model injection (i.e., will the modelpulse start)?

6. Does the tunnel unstart or exhibit partialblockage effects (change in freestreamconditions) as a result of modelinjection, model start, or model unstart?

3

Experimental Techniques

Model Description

A dimensioned sketch of the inlet modelis shown in Figure 1. The geometryconsists of a 15° ramp (8.85 inches long by7.00 inches wide), a circular arc sector(4.623 inch radius), a 10° expansion (2.15inches long), a constant area section (1.5inches long), and a 20° expansion (0.687inch long). The cowl leading edge islocated 7.511 inches aft of the ramp leadingedge. The minimum throat height is0.7373 inch, yielding a minimum throatarea (at) of 5.16 sq.in. Both the cowl andthe aft plug are actuated during the runusing air cylinders supplied by 150 psisupply air lines. Following model injectioninto the freestream, the cowl is cycled toallow the inlet to start. At its maximumtravel, the cowl rotates upward by almost6° to increase the minimum throat height to1.442 inches. After the cowl has beenreturned to its initial position and the inlethas started, the aft plug is driven forwardto force the inlet to unstart.

The wedge-shaped plug has a 20° half-angle, a maximum thickness of 1.182inches, and spans the entire 7.0 inch exitwidth. The plug is equipped with aremovable shim (0.5 inch thick), whichpermits initial plug leading-edge positions14.5 in and 15.0 in downstream of theramp leading edge; the forward throw ofthe plug is one inch. Without the shim, theratio of exit to throat area ae/at is 1.33 and0.86 for the plug aft and forward,respectively; with the shim, 1.10 and 0.63,respectively.

The model is fabricated of 15-5PH,H1025 stainless steel. Two sets ofschlieren-quality BK-7 glass installed in theinlet sidewalls provide optical access to thethroat and plug regions.

Description of Wind TunnelFacility

The facility used for the present studywas the 20-Inch Mach 6 Tunnel, located atthe NASA Langley Research Center. Adescription of the tunnel and tunnelperformance characteristics can be found inRef. 1, of which the following is asummary. Figure 2 presents a schematic ofthe facility. Dry air is supplied from a 600psia, 42000 ft3 reservoir and heated to amaximum of approximately 1000°R. Theair passes through a dryer and 5 micronfilter before entering the settling chamber,which contains a perforated conical baffleand internal screens. The flow is expandedthrough a fixed-geometry, two-dimensionalcontoured nozzle (0.399 in x 20 in throat)into a 20.5 in x 20 in test section. Thenozzle length from the center of the testsection window to the throat is 7.45 ft.The model is supported on an injectionsystem which inserts the model into theflow from below. Due to the run time ofthis facility (up to 15 minutes for certainconditions), it is possible to have multiplemodel injections per run, either at the samerun conditions (for repeatability) or atdifferent run conditions.

Test Conditions and Test Matrix

Nominal test conditions for the presenttest were chosen to provide as large a rangeof Reynolds numbers as possible and tocoincide with conditions for whichprevious facility calibrations had beenperformed. Tests were performed at Mach6 for nominal reservoir pressures of 30,125, 250, and 475 psia at a nominalreservoir temperature of 910˚R,corresponding to nominal freestream unitReynolds numbers of 0.5, 2.1, 3.9, and7.1 million/ft, respectively. Pitot pressureat the test section was measured for eachrun to serve as an indicator of tunnelblockage. Representative flow conditions(see Ref. 2) are presented in Table 1.

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Table 1: Flow Conditions

pt,1(psia)

Tt,1(°R)

p∞(psia)

T∞(°R)

q∞(psia)

M∞ Re∞million/ft

Test Core(in)

31 866 0.0249 113.1 0.580 5.77 0.638 13x12122 911 0.0830 113.5 2.041 5.93 2.175 13x13241 933 0.1544 114.4 3.874 5.99 4.045 14x14485 932 0.2895 111.7 7.437 6.06 7.959 14x16

Table 2: Test Matrix/Run Log

RunNumber

InjectionNumber

pt,1(psia)

Re∞(million/ft)

PlugConfiguration

1 1 30 0.5 with shim2 100 1.8 with shim3 100 1.8 with shim

2 1 100 1.8 without shim2 100 1.8 without shim3 250 3.6 without shim4 250 3.6 without shim

3 1 30 0.5 without shim2 30 0.5 without shim3 30 0.5 without shim4 125 2.1 without shim5 125 2.1 without shim6 250 3.9 without shim7 250 3.9 without shim8 475 7.1 without shim9 475 7.1 without shim

4 1 30 0.5 with shim2 30 0.5 with shim3 125 2.2 with shim4 125 2.2 with shim5 250 3.9 with shim

5 1 475 7.1 with shim

The test matrix was constructed to test ateach chosen flow condition both with andwithout the plug shim and to allow forrepeat runs. Table 2 presents the testmatrix. (Note again that due to the longrun times of the facility, multiple injectionsare possible within one run, hence the needfor both run and injection number in the

table.) Because the facility shares vacuumspheres and air supply with other facilities,often the order in which the runs are madeis determined by a combination of factors(including the desired test condition andvacuum sphere availability and pressure) inorder to enhance facility productivity.

5

Table 3: Summary of Inlet Starting Behavior

ReynoldsNumber

PlugConfiguration

Starts Self-starts Pulse-starts

0.5 million/ft without shim no no yeswith shim no no --

2 million/ft without shim yes no nowith shim no no no

3.9 million/ft without shim yes no nowith shim yes yes --

7.1 million/ft without shim yes yes yeswith shim no* -- no

* Only one run was obtained at this condition, and due to plug actuation problems, this result is in question,i.e., the failure of the model to start is believed to be due to a malfunction of the plug actuation system.

Results

A chronology of each model injectionsequence is presented in tabular format inthe appendix. Because of the degradationin quality during the frame-grabbingprocess, the still images taken from thevideo did not reproduce well. Thus only aselected sampling of these still frames ispresented, and the reader is referred to thevideo supplement. (Flow is from right toleft, and the inlet is oriented with the cowlon top.) The video possesses higherquality images which provide a better viewof the shock structure for started andunstarted configurations along with at leasta sense of the flow dynamics, of whichonly brief notations are made in the tables.In the video, the plug motion is obviousbecause the plug is visible in the aftwindow. The cowl motion, however, isnot as obvious because the cowl is hiddenby the inlet sidewall. The end of the cowlactuator arm, however, becomes visibleabove the top of the inlet sidewalls betweenthe windows when the cowl is up. (SeeFigure 1b.)

Table 3 presents a summary of the inletstarting behavior for each Reynoldsnumber and plug configuration. Termsused in the table are defined as follows.Starting was identified as the establishment

of an oblique shock structure inside theinlet, as observed in the video. Also, whenthe inlet started, the shock on the outboardside of the cowl (visible above the inlet)was attached and steady. The internal flowfield additionally appeared steady. Self-starting indicates that the inlet will startwithout a change in throat area. This isdetermined by unstarting the inlet by theforward plug motion and observingwhether the inlet restarts when the plug isreturned to its aft position. Self-starting isa significant feature in an inlet designbecause it indicates that variable geometryis not necessary to restart the inlet. Pulse-starting indicates that the inlet would startwhen injected (with the cowl down) intothe tunnel without actuation of any surface,i.e., the inlet starts due to the ram effect ofthe freestream as the model is thrust intothe flow. Pulse-starting may be significantin situations where the inlet is shrouded fora portion of the flight trajectory, becauseshroud separation may effectively pulse-start an inlet in flight. Pulse-starting is alsosignificant for these tests because itdetermines whether the added expense of acowl actuation system is required for thePhase II of this study (the instrumentedmodel to be designed pending the results ofthis blockage and actuation systems test).

6

The ability of the inlet to start at Mach 6in any configuration appears to besignificantly Reynolds number dependent.At Re=0.5 million/ft, the inlet would notstart for any configuration during anysequence of plug/cowl actuation, save onepulse-start when injected with the cowldown. (This pulse start could not besubsequently repeated, and the cause isunclear.)

At Re≈2 million/ft, the inlet startingbehavior is dependent upon plugconfiguration. Despite the fact that for theplug in the aft position, the ratio of exit tothroat area remained greater than unity withthe shim (ae/at=1.10), the inlet would notstart, whereas for the plug configuredwithout the shim (ae/at=1.33), the inletwould start. For this configuration, theinlet would start only by cycling the cowlup and then down, and then once unstartedby the plug, the inlet would not restart(self-start) when the plug was retracted.

At Re=3.4 million/ft, inlet starting wasno longer governed by the plugconfiguration and the inlet would startwhen the cowl was cycled up and thendown. The inlet would not pulse-start, yetfor one injection (Run 4, Injection 5 ---Table A.21), the inlet would repeatablyrestart (self-start) when the plug wasretracted. Oddly, this occurred for the plugconfigured with the shim and not for theplug configured without the shim. This isa nonintuitive result; unfortunately, as ablockage model, the model was notinstrumented, and no data on, for example,wall surface temperature or back pressurewas available for a conjecture to be putforth as to the cause.

At Re=7.1 million/ft, the inlet reliablystarted and restarted (self-started) for plugforward and aft movement, respectively,for the plug configured without the shim.The inlet also pulse-started at this Reynoldsnumber. Sample frames from started andunstarted inlet configurations are presentedin Figures 3 and 4, respectively, forRe=7.1 million/ft with the plug configuredwithout the shim. Despite the poorreproducibility of the image, the difference

between start and unstart is clear. Inaddition to the lack of a clearly-definedoblique shock structure inside the unstartedinlet of Figure 4, the external influence ofthe unstart is significant (due primarily tospillage around the cowl). The largeexternal influence, however, was not largeenough to unstart the tunnel or partiallyblock the facility, as inferred from a pitotprobe located below the inlet whichmonitored freestream conditions. Figure 5shows (on a relatively fine scale) themeasured pitot pressure throughout Run3/Injection 8 (Re=7.1 million/ft), overlaidwith the actuation signals to indicate theposition of the plug and cowl. Figures 6-9show similar results for each of the otherReynolds numbers at which the model wastested, including configurations with andwithout the plug shim. The plots illustratethat the inlet start and unstart process didnot induce partial blockage effects on thefacility (as inferred from pitotmeasurements), and hence that the modelwas appropriately sized for the facility.

Although the primary purpose of thisphase of the study is satisfied by thedetermination of the absence of blockageeffects, some comments regarding the flowfield structure are appropriate. Frame byframe advancement of the video illustratesthat when the inlet is not started, the flowfield is fully three-dimensional andunsteady. The multiple curved shockimages external to the cowl suggest arippled shock with intermittent spillageacross the span of the inlet. When the inletstarts, the flow field appears to becomenominally two-dimensional, with crisp,singular images of the steady attachedoblique shocks, both internal and externalto the inlet.

Preliminary computational work(performed by Rusty Benson at NCSU inMay 1993) suggests that the mechanism forthe unstart is a separation which movesforward of the throat. Similar Mach 3results have been presented in Ref. 3 for aback-pressure induced unstart. (See, forexample, Figure 5.28 of Ref. 3.) Figure10 is a still frame from the schlieren video

7

at unstart. Results from the previouslynoted computational work indicate that theshock interacting with the cowl shock inthe forward window may emanate from aseparation on the forebody plane upstreamof the throat. If the unstart is indeedseparation driven, then increased Reynoldsnumber appears to minimize the size andextent of the separation, which may allowthe inlet to restart when the plug is returnedto its aft position.

Concluding Remarks

The present work examined the wind-tunnel blockage and actuation systemseffectiveness in a generic two-dimensionalscramjet inlet as a first phase in a testprogram designed to study the dynamics ofinlet unstart. An inexpensive,uninstrumented wind-tunnel model wastested in the NASA Langley 20-Inch Mach6 Tunnel to examine the wind-tunnelblockage issues related to model sizing andto examine the adequacy of the actuationsystems in accomplishing the start andunstart. The model was equipped withboth a moveable cowl and aft plug.Following model injection, the cowl wasraised and lowered to allow the inlet tostart. The plug (located in the exit plane)was then rapidly driven forward todecrease the exit area and force the inlet tounstart. Schlieren windows in the inletsidewalls allowed limited optical access tothe internal shock structure and permittedidentification of model start and unstart.For this blockage test, a video camera wasincorporated into the schlieren system torecord the schlieren of the entirestart/unstart sequence on VHS video tape(available separately as Video SupplementL-0194-41 to NASA TM 109152). Theframing rate and shutter speed of thecamera were too slow to fully capture thedynamics of the unstart but did provesufficient to identify start/unstart. A pitotprobe was placed beneath the inlet to

identify any influence of the start/unstartprocess on the local freestream conditions.

The conclusions from this study may besummarized as follows.

1. The ability of the inlet to start at Mach 6appears to be significantly Reynoldsnumber dependent. At Re=0.5million/ft, the inlet would not start foreither the plug configured with orwithout the shim; however, inletstarting steadily improved withincreasing Reynolds number.

2. The one inch throw of the aft plug(which reduced the ratio of exit tothroat area from 1.33 to 0.86 for theplug configured without the shim andfrom 1.10 to 0.63 for the plugconfigured with the shim) wassufficient to force the inlet to unstart.

3. Self-starting was observed only at thehighes t Reynolds numbers .Preliminary computational findingssuggest that the mechanism for theunstart is a separation which movesforward of the throat. If the unstart isindeed separation driven, thenincreased Reynolds number appears tominimize the size and extent of theseparation, which may allow the inlet torestart when the plug is returned to itsaft position.

4. For configurations which were not self-starting, cycling the cowl up and downafter the plug is moved aft wasgenerally sufficient to restart the inlet,i.e. no additional mechanism such asbleed was necessary to restart the inlet.

5. Pulse-starting (the ability of the inlet tostart due to model injection withoutvariable geometry on the cowl) wasobserved for only two configurations;thus, the cowl actuation system remainsa requirement for future testing.

6. The tunnel remained started during eachsequence of model injection, model

8

start, and model unstart and, based onmeasured freestream pitot pressures,exhibited no partial blockage effects(change in freestream conditions) as aresult of the sequences.

In summary, this series of tests indicatedthat the model was appropriately sized forthis facility and identified operability limitsrequired first to allow the inlet to start andsecond to force the unstart.

NASA Langley Research CenterHampton, VA 23681-0001August 29, 1994

References

1. Miller, C. G., III: Langley HypersonicAerodynamic/AerothermodynamicTesting Capabilities - Present andFuture. AIAA 16th AerodynamicGround Testing Conference, June 18-20, 1990, Seattle, WA, AIAA-90-1376.

2. Miller, C. G. and Smith, F. M.:Langley Hypersonic Facilities Complex- Description and Application. AIAA14th Aerodynamic Testing Conference,March 5-7, 1986, West Palm Beach,FL, AIAA-86-0741-CP.

3. Benson, Rusty A.: Development of aTime-Accurate Algorithm Coupled witha Dynamic Solution-Adaptive GridAlgorithm with Applications to GenericInlet/Diffuser Configurations. Ph.D.Dissertation, North Carolina StateUniversity, 1994.

9

17.50015.187

8.850R4.623

10.047

10.84912.999

14.500

2.09

47.511

Cowl Actuation Arm

(a) Dimensioned Sketch (All dimensions in inches)

(b) Sketch of Cowl Actuation Arm With Cowl Raised and Lowered

Figure 1: Two-Dimensional Inlet Model

10

Variablesecond

minimum

Settling Chamber

20 x 20 inchtest section

Schlierenwindows

Annularair ejector

Toatmosphere

To vacuumspheresArc

sector

Modelinjection/retractionsystem

ScreensPerforated

cone

Modelsupportpedestal

Flow

Figure 2: Schematic of 20-Inch Mach 6 Tunnel

11

Figure 3: Still Frame from Schlieren Video of Started Inlet in Run 3, Injection 8 Re∞=7.1 million/ft, pt,1=475 psi, Plug Configuration: without Shim Inlet Configuration: Cowl Down, Plug Aft.

12

Figure 4: Still Frame from Schlieren Video of Unstarted Inlet in Run 3, Injection 8 Re∞=7.1 million/ft, pt,1=475 psi, Plug Configuration: without Shim Inlet Configuration: Cowl Down, Plug Forward.

13

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Figure 5. Effect of Cowl and Plug Position on Freestream Pitot Pressure. Re=7.1 million/ft, Plug configured without shim (Run 3, Injection 8)

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Figure 9. Effect of Cowl and Plug Position on Freestream Pitot Pressure. Re=3.9 million/ft, Plug configured with shim (Run 4, Injection 5)

18

Figure 10: Still Frame from Schlieren Video of Unstarted Inlet in Run 4, Injection 1 Re∞=0.5 million/ft, pt,1=30 psi, Plug Configuration: with Shim Inlet Configuration: Cowl Down, Plug Forward.

19

Appendix A: Inlet Actuation Chronologies

A chronology of the cowl and plug actuation sequences for each model injection is providedin Tables A.1-A.22 to accompany the video supplement. In the video, flow is from right to left.The plug motion is obvious because the plug is visible in the aft window; however, the cowl ishidden from view by the inlet sidewall. The cowl actuator arm (located in the sidewall betweenthe schlieren windows) is visible above the top of the inlet sidewalls between the windowswhen the cowl is up. (See figure 1b.)

Table A.1: Chronology of Run 1, Injection 1pt,1= 30 psi, Re∞= 0.5 million/ft

Plug configured with shim(Pre-run configuration: Cowl up, Plug aft)

Actuation Sequence Comments on Inlet Flow Response

inject model

cowl down appears to be nominally steady but nodistinct internal shock structure; external

spillage evidentplug forward internal structure never establishes;

internal and external flow unsteadiness;beating

retract model


Plug configured with shim(Pre-run configuration: Cowl up, Plug forward)


inject model

cowl down does not start; higher frequencyunsteadiness than 30 psi run

retract model

20




inject model

cowl down external disturbance diminishes whencowl is put down; either steadier or

frequency of unsteadiness ispredominantly faster than video framing

rateplug forward high frequency beating

retract model


Plug configured without shim(Pre-run configuration: Cowl up, Plug aft)


inject model

cowl down does not start

plug forward beating

plug aft not started

cowl up Character of flow oscillates. At times alarger external disturbance, at others, itis as if the inlet is trying to start with the

cowl upcowl down inlet starts

plug forward unstarts, unsteady beating

plug aft does not restart

retract model

21


Plug configured without shim(Pre-run configuration: Cowl down, Plug aft)


inject model inlet does not start due solely toinjection process

cowl up external shock unsteadiness

cowl down does not start, still unsteady but externaldisturbance smaller (less spillage),

external shocks more inclinedretract model




inject model large external disturbance upon injection

cowl down inlet starts

plug forward unstarts; very unsteady; high frequencybeating

plug aft does not restart, yet much more stable(not "beating")

retract model

22




inject model inlet does not start due solely toinjection process

plug forward unsteadiness increases

plug aft unsteadiness decreases

cowl up large external disturbance


plug forward inlet unstarts; unsteady

plug aft flow steadier but not started

cowl up large external disturbance


retract model

23




inject model (zoomed schlieren installed for this andall subsequent runs)

cowl down

cowl up slight increase in external unsteadiness

cowl down steadier, but not started

plug forward slight increase in external unsteadiness

plug aft does not start

cowl up


plug forward slight increase in external unsteadiness


retract model

24




inject model inlet pulse started (i.e., started uponinjection with the cowl down)

cowl up

cowl down unstarted; external shock above cowl iscurved

cowl up unsteady

cowl down unstarted, yet steadier

retract model




inject model inlet does not start upon injection withthe cowl down

cowl up unsteadiness increases

cowl down does not started

plug forward


retract model

25




inject model

cowl down very unsteady flow; not started

plug forward does not significantly worsen the flowcharacteristics

plug aft does not significantly improve the flowcharacteristics

cowl up external flow disturbance evident


plug forward unstarts; unsteady; large externalinteraction


cowl up unsteadiness increases

cowl down does not restart

cowl up


retract model

26




inject model inlet does not start upon injection withthe cowl down

cowl up


plug forward inlet unstarts

plug aft inlet does not restart

cowl up

cowl down inlet does not restart

cowl up


cowl up



plug aft inlet does not restart

cowl up unsteady (beating)

retract model

27




inject model




cowl up




cowl up


retract model

28




inject model does not start solely due to injection ofmodel

cowl up


plug forward very unsteady; large external influence


cowl up

cow down inlet starts

retract model

29




inject model


plug forward unstarts; large external influence

plug aft inlet restarts

cowl up inlet unstarts

cowl down inlet restarts



cowl up



plug aft (plug movement sluggish); inlet doesnot restart

cowl up

cowl down cowl sluggish; does not restart

retract model

30




inject model inlet pulse starts due to model injection


plug aft (aft plug movement very slow)

cowl up cowl actuated up before plug was fullyretracted

cowl down inlet does not start

cowl up

cowl down (cowl moves very slowly); inlet doesnot start

retract model

31




inject model

cowl down external influence decreased, but inlethas not started

cowl up


plug forward low frequency beating

plug aft not started but steadier

cowl up


retract model


Plug configured with shim(Pre-run configuration: Cowl down, Plug aft)


inject model inlet does not pulse start due to modelinjection

cowl up


cowl up

retract model

32




inject model


cowl up


plug forward large unsteady forward influence, butnot quite like beating previously noted.

(Beating = when the entire flowstructure moves in/out together. This

was more ragged.)plug aft inlet does not start

cowl up


retract model

33




inject model inlet does not pulse start

cowl up flow unsteadiness increases

cowl down flow is steadier but not started

cowl up flow unsteadiness increases

cowl down flow is steadier but not started

retract model

34




inject model






cowl up unstarts; plug appears to droop due todownload when cowl is raised


plug forward (plug motion very slow)

plug aft (plug motion very slow); inlet does notrestart

retract model

35




NOTE: Plug actuation rod broke during aprevious run. Rod was replaced prior

to this runinject model inlet does not pulse start; large external

influence is notedcowl up


cowl up (plug droops); inlet does not start

retract model

36

Video supplement L-0194-41 is available for purchase.

This video (11 minutes, color, VHS) shows the schlieren video of the external flow field and aportion of the internal flow field for each model injection sequence, as documented in thisreport.

To obtain the video, fill out the mail-in card below and return it to:

ATTN USER SERVICESNASA CENTER FOR AEROSPACE INFORMATIONP.O. BOX 8757BALTIMORE, MD 21240-0757

Cut here ----------------------------------------------------------------------------

Please send ___ copies of video supplement L-0194-41 to NASA TM 109152.

Attn:Name

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