NASA Technical Paper 1531

Dynamic ResponSe: of a Mach 2.5

Axisymmetric Inlet _d Turbojet

/'_ ,#_,i,.I_.. _ _ Engine With a P.._r,.t Valve

Controlled Inlet-S_bility Bypass

System When Subjected to Internal

and External "" _ _ " .........

I lll.ll_.J YI¢ Jk Iil 11 _,_ 1 li,, I I 1L i._

o

Bobby _r. Sander_

CASE _

_C 0 pF.flL E i

JANUARY i980

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NASA Technical Paper 1531

Dynamic Response of a Mach 2.5

Axisymmetric Inlet and Turbojet

Engine With a Poppet-ValveControlled Inlet-Stability Bypass

System When Subjected to Internal

and External Airflow Transients

Bobby W. Sanders

Lewis Research Center

Cleveland, Ohio

NI A

National Aeronautics

and Space Administration

Scientific and Technical

Information Office

1980

CONTENTS

SUMMARY .......................................

INTROD UC TION ....................................

APPARATUS AND PROCEDURE ...........................

General Description .................................

Inlet Model ......................................

Stability Bypass Entrance and Bleed Region Configuration .............

Pressure-Activated Poppet Valves .........................

Engine Description ..................................

Upstream Airflow Variation Device .........................

Instrumentation ...................................

RESULTS AND DISCUSSION ..............................

Basic Inlet Stability Data ..............................

Propulsion System Response to Internal Airflow Disturbances ...........

Reductions in overboard-bypass-door area ....................

Reductions in power lever angle ..........................

Reductions in primary-nozzle area ........................

Propulsion System Response to External Airflow Disturbances ..........

Steady-State Stability-Bypass-Bleed Performance .................

SUMMARY OF RESULTS ...............................

APPENDIXES

A - ENGINE AND POPPET-VALVE AIRFLOWS ..................

B - SYMBOLS ....................................

REFERENCES .....................................

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SUMMARY

The throat of a Mach 2.5, mixed-compression inlet with 40-percent internal

supersonic-area contraction was fitted with a stability bypass system that was designed

to provide a large, stable airflow range. With this bypass system the inlet can operate

near the optimum performance condition without being susceptible to inlet unstart as a

result of small variations in inlet airflow. In previous research programs with the inlet

attached to a coldpipe, pressure-activated poppet-valve control of the stability bypass

airflow resulted in very large stable margins. As a further evaluation of this control

system, the inlet was tested on a turbojet engine. Inlet-stability bypass performance

was determined for several transient airflow disturbances, both internal and external.

Internal airflow was varied by transient pulses in overboard-bypass-door area, power

lever angle, and primary nozzle area. Propulsion system response to a compressor

stall was also determined, External airflow was varied by means of a flat gust plate

located upstream of the inlet. For reference, data were also included for a conventional

fixed exit controlling the stability bypass bleed airflow.

At a free-stream Mach number of 2.5 the poppet-valve-controlled stability bypass

system can provide greater inlet stability than a conventional bleed systc.m. The addition of the stability bypass system to the inlet did not adversely affect the en,_tine performance. Limited unstarted-inlet bleed performance data are presented.

INTRODUCTION

At flight speeds above Mach 2.0 an inlet with a mixture of internal and external

compression allows optimum performance by supplying the engine with high-pressure

airflow while maintaining minimum drag. In mixed-compression inlets, maintaininz theterminal shock at the inlet throat gives the highest pressure recovery and least distortion at the engine entrance. However, mixed-compression inlets have an undesirable

airflow characteristic known as "unstart," which may occur when the terminal shock is

placed too near the inlet throat. A slight transient reduction in airflow can cause the

terminal shock to move forward of the throat, where it is unstable and is abruptly expelled ahead of the inlet cowling. This shock expulsion, or unstart, rapidly reduces

mass flow and pressure recovery and greatly increases drag. Inlet buzz, compressor

stall, or combustor blowout may also occur. Obviously, an inlet unstart is extremely

undesirable because of its effects not only on the propulsion system itsell', but also on
the aircraft's aerodynamicqualities. If an unstart doesoccur, complex mechanical

variations of the inlet geometry are required to reestablish the designoperating conditions. An engine relight sequencewill also be necessary if blowoutoccurs.

Both external airflow disturbances (suchas atmospheric turbulence) and internal

airflow disturbances (suchas reducedengineairflow demand)can causethe inlet to unstart. For an internal disturbance the inlet should provide a margin in corrected airflow

below the optimum without incurring unstart. This margin is defined as the stable airflow operating range. Conventional mixed-compression inlets can be designed to have a

limited stable range that is provided by the ability of the performance bleed system to

increase its airflow as the terminal shock moves upstream into the throat bleed region.

With fixed bleed exit areas, this limited stable range may not be adequate to absorb

many airflow transients encountered by a typical supersonic propulsion system. A larger

stable airflow range is currently provided for these inlets by operating them supercritically, with a r_sultant loss in their performance. Since any loss in inlet performance is reflected directly as a loss in propulsion-system thrust and efficiency, supercritical operation should be avoided.

The necessary system stability can be provided without compromising steady-state

performance (i. e., pressure recovery and distortion) by redesigning the inlet. The

throat bleed system can be replaced with an inlet-stability bypass system capable of removing large amounts of airflow (ref. 1). (The nomenclature for the throat airflowremoval system has been changed since ref. 1 was published from throat-bypass system

to inlet-stability bypass system. ) This system prevents unstarts by removing airflow

from the inlet throat to compensate for reduced diffuser-exit airflow demand. As shown

in reference 1, inlet-stability bypass airflow can be greatly increased without removing

prohibitive amounts of airflow during normal operation if the stability bypass exit area

can be controlled to maintain a relatively constant pressure in the bypass plenum. This

stability bypass exit area control can be provided by pressure-activated valves (such as

the poppet valve in ref. 2) at the bypass exit. The valves respond to small pressure increases in the bleed plenum induced by upstream movement of the terminal shock.

References 3 to 6 show that the poppet valves of reference 2 can operate automatically

to provide large, stable airflow margins for the inlet. The effectiveness of several

stability bleed systems (e. g., distributed porous; distributed educated slot; and forwardslanted slot) is discussed in references 1, 3, and 6 to 10.

During the initial research on inlet-stability bypass bleed concepts and bypass

airflow-control valves, the inlet was attached to a coldpipe, choked-exit-plug system.

This test configuration allows the various concepts to be evaluated. However, the final

merit of a concept can only be judged by integrating it into a complete propulsion system.

Therefore, an inlet incorporating a stability bypass system and attached to a J85-GE-13

turbojet engine was tested in the Lewis 10- by 10-Foot Supersonic Wind Tunnel to evalu-
ate its performance, both steadystate anddynamic. The inlet was a Mach2.5, mixedcompression type with 40percent of the supersonic-area contraction occurring internally.

During the investigation, datawere obtainedfor two types of stability bypassexits:

a small, conventionalfixed exit (downstreamof a small or large bypass plenum); and

self-activated poppetvalves. Both steady-state and transient datawere recorded.

Internal airflow disturbances were obtainedby reducing overboard-bypass-door area,

power lever angle, or primary-nozzle area. External airflow was varied by changing

the angle of attack of a large flat gust plate upstream of the inlet. A control system was

used for fast inlet restart and engine relight when the inlet unstarted. Limited steadystate bleed performance data were obtained at a free-stream Mach number of 2.5 with

the inlet unstarted.

U.S. customary units were used in designing the test model and recording and computing the experimental data. These units were converted to the International System of

Units (SI) for this report.

APPARATUS AND PROCEDURE

General Description

An NASA-designed supersonic inlet on a General Electric model J85-GE-13 turbojet

engine was tested in the Lewis 10- by 10-Foot Supersonic Wind Tunnel at the following

nominal free-stream conditions: Mach number 2.5; total pressure, 9.4 N/cm2; total

temperature, 302 K; Reynolds number, 4.3×106 (based on the cowl-lip diameter); and

specific-heat ratio, 1.4. The engine operated from windmill to 90-percent corrected

speed. When data were being taken with the engine running, the tunnel was operating on

its propulsion cycle. In this cycle, the airflow downstream of the test section is vented

to the atmosphere rather than recirculated as in the aerodynamic cycle. Figure 1 shows

the engine and inlet, with nacelle, installed in the wind tunnel.

Inlet Model

A Mach 2.5, axisymmetric, mixed-compression inlet with 40 percent of the design

supersonic-area contraction occurring internally was used in this investigation. The

inlet was attached to a cylindrical nacelle 0. 635 meter in diameter in which a J85-GE-13

engine or a coldpipe, choked-exit-plug assembly could be installed. For this study, only

the engine was used. At the design Mach number, sizing the inlet to match the J85-GE13's airflow requirements resulted in a 47.32-centimeter inlet capture diameter. The

inlet was started by translating the centerbody. A flight version of this inlet with 40-
percent internal contraction would require a collapsing centerbodyfor starting andoffdesignoperation (ref. 4).

Somebasic inlet designdetails are presentedin figure 2. Local theoretical airflow

conditions on the cowl andcenterbody, inlet contours, anddiffuser-area variation are

shownfor the inlet design Machnumber and spike position. A computer program (ref.

11)that incorporated the methodof characteristics was usedto design the supersonic

diffuser. A two-cone surface with half-angles of 10° and 18.5° provided the initial

supersonic compression. The internal oblique shock from the cowl lip was canceled at

its impingement point onthe centerbodyby turning the surface. The remaining supersonic compressionwas isentropic to obtain an averagetheoretical supersonic throat

Machnumber of 1.30 with an inviscid recovery of 0. 9855. At the design centerbody

position, the geometric throat was at an x/R c of 3.26. (SeeappendixB for definition

of symbols.) Downstreamof the geometric throat, the inlet included a throat region

with 1° equivalent conical expansionanda main subsonicdiffuser with anoverboard bypass system. The dfffuser-centerbody boundary layer was controlled by vortex generators that were located in the diffuser at an axial distance ratio of 3. 965 (fig. 3). Details

of the vortex generator design are shownin figure 4. The overall inlet length at design -

(conetip to compressor face) was 7.88 cowl-lip radii. Internal surface coordinates of

the inlet in terms of the cowl-lip radius are presentedin table I. The inlet designcharacteristics are discussed more completely in reference 12.

Bleed regions were located in the throat onthe inlet cowl and centerbodysurfaces.

The forward-cowl bleedflow (notusedduring this part of the program) was dumpeddirectly overboard, as shownin figure 5. Stability bypassflow (usedto give the inlet a

large stable range) was removedthrough the stability bypassentrance, onthe cowl side

of the throat. It was thendirected through the cowling to the pressure-activated poppet

valves andonto the stability bypass coldpipes (figs. 3 and 5). Centerbodybleed flow

was ducted through hollow support struts to the centerbodybleed coldpipes (fig. 3).

Each stability bypass andcenterbodybleed coldpipe houseda choked-plugassembly.

Whenthe choked-plugassemblieswere controlling the stability bypass flow by forming a chokedexit at the downstreamend of the pipes, the pressure-activated poppet

valves in the bypassflow circuit (fig. 3)were set wide openso as not to interfere with

the rear chokepoint. Whenthe pressure-activated poppetvalves were controlling the

stability bypass flow, the choked-plugassemblies were set wide openandthe chokepoint

movedforward to place the effective minimum exit area at the valve station.

The subsonicportion of the inlet diffuser incorporated two remotely controlled bypass systems: a fast-acting overboard bypass, anda slow-acting ejector bypassfor engine andnozzle cooling airflow. For this investigation the ejector bypasswas closed.

Engine cooling airflow was suppliedfrom anexternal source. Cascadeswere installed

in theentrance to the overboard bypasscavity during a previous test program to eliminate resonance(ref. 13).

4
As shownin the figures, a bulky cowl was usedon the test model so that major

changescould easily be madeto the inlet-stability bypass system andassociatedducting

during the wind tunnel tests. It was not representative of flight hardware. Figure 6

shows how an inlet-stability bypass system can be packaged within the low-externalcowl-drag profile essential for supersonic flight.

Stability Bypass Entrance and Bleed Region Configuration

L

The stability bypass configuration used in this test program (fig. 7) was the same

as configuration NF of reference 1. As figure 7 shows, all the bleed regions were composed of rows of normal holes arranged in a concentrated, staggered pattern to provide

uniform circumferential bleeding of the boundary layer. The distributed, porous hole

pattern of 0. 3175-centimeter-diameter holes on 0. 4763-centimeter centers gave a nominal porosity of 40 percent. Fifteen rows of bleed holes were used as the stability bypass

entrance. Reference 1 indicates that this stability bypass system can provide an inlet

stability margin of 28.4 percent from a high-performance-match operating condition if

constant pressure is maintained in the stability bypass plenum to inlet unstart. The

available forward- and aft-cowl bleeds were sealed; the centerbody bleed provided a

performance bleed mass-flow ratio of about 0.025 at the inlet-engine match condition.

Pressure-Activated Poppet Valves

The stability bypass flow was controlled by 16 pressure-activated poppet valves located circumferentially within the inlet cowl at the exit of the small stability bypass

plenum (figs. 8 and 9). Valves installed in the inlet cowl are shown in figure 8(a) and

details of valve mechanical design, in figure 8(b). The poppet valve is essentially a

floating piston with a trapped volume at a preset internal pressure on one side of the

piston. This piston is activated by differential pressure. The valve chamber pressure

was controlled during the test by connecting the valve to an external air supply. (In

flight, suitable valve chamber pressure could be supplied by a probe and a pressure regulator could be used if necessary. The poppet-valve system and its variations are described in a United States patent (ref. 2).) The valve chamber pressure was set to just

close it during normal inlet operation, that is, with the inlet operating at a high pressure

recovery and with the terminal shock at the downstream edge of the stability bypass entrance. Under these conditions, if an airflow disturbance caused the terminal shock to

move upstream over the stability bypass entrance, the pressure in the bypass plenum

would exceed the internal valve pressure and thus cause the valve to open and bypass

flow to occur. Valve control of the stability bypass flow resulted in an effective bypass
plenumvolume of about0.01 to 0.02 cubic meter, smaller thanthe bleed plenumvolume

of 0.40 cubic meter for the choked-plugsystem, which was almost equalto the mainduct volume of 0.42 cubic meter.

The poppetvalve was simply designedsolely to demonstratethe feasibility of

constant-pressure control in a stability bypassplenum. The designallowed the poppet

valve to openfully whenthe pressure onthe valve face (stability bypass total pressure

Psb) was increased about 20percent. The actual valve performance, as determined on

a benchtest standand reported in reference 5, is shownin figure 8(c) in nondimensional

form. The reference pressure Psb,ref was the lowest supplypressure that causedthe

airflow to just chokeat the valve attachmentbulkheadopening. The reference mass flow

mpv_ref was the theoretical airflow through the bulkheadopeningat this reference pressure (flow coefficient of 1.0). The valve was indeedquite sensitive to pressure until the

airflow chokedat the valve attachmentopening. This chokepoint was reachedwith a 25-

percent increase in the pressure at which the valve beganto open.

In flight, manyperturbations of the inlet shock into the throat region wouldprobably

be quite rapid. To absorb such perturbations, the poppet valve had to be fast acting.

For the research programs reported in references 3 and 5, a movable valve-head assembly was therefore designed to minimize weight (fig. 8(b}). For the design valve-head

weight of 0.20 kilogram, the valve natural frequency was estimated at about 12 hertz at

the pressure levels encountered during the test.

A feasibility study of self-acting, inlet-stability bleed valves - including vortex

valves, sliding louver valves, and poppet valves - for the NASA YF-12 supersonic research airplane is reported in reference 14. The results of this study show that only

poppet valves provide the flow capacity and dynamic response required for a good stability bypass system. A bench test evaluation of the poppet valves for the YF-12 is reported in reference 15. Basically, the valve design was the same as for the poppet

valves used in this study.

Steady-state operation of the poppet valves installed in this inlet-stability bypass

system has been successful (refs. 3 to 5). However, with some of the stability bypass

entrance configurations of reference 5 the valves oscillated when operating partly open.

(In some of these configurations the valves did not oscillate when they were moving in

response to a transient, including transients with periods of about 20 seconds. In flight,

the valves would probably never be open in a steady-state situation but would be moving

in response to a transient and would thus not oscillate. ) Because the 16 valves oscillated

in unison at a frequency of 44 hertz, it was concluded that the valve and bleed-plenum

system was acting like a second-order dynamic system, since it was operating well beyond the valve natural frequency of 12 hertz. Adding a linear potentiometer to measure

valve position during the bench test eliminated the oscillations except at very high pressures. (Thus, ref. 5 concluded that a small amount of properly applied friction might

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eliminate the oscillation. )

Poppet-valve oscillation was not observedduring the present investigation.

EngineDescription

A sketch of the engineinstalled with the other test hardware is presentedin figure

10. The General Electric J85-13 is an afterburning turbojet with a high thrust-weight

ratio. The engine has an eight-stage, axial-flow compressor coupledto a two-stage

turbine. It has controlled compressor interstage bleed, variable inlet guidevanes, a

throughflow annular combustor, and an afterburner (not usedin this test) with a variablearea primary exhaustnozzle. The engineinlet diameter is 40.8 centimeters.

The compressor variable geometry consists of interstage bleedvalves on stages 3

to 5 andinlet guidevanes. The guidevanes and valves are linked together and, on the

standard engine, are controlled by the main fuel control as a function of the enginecorrected speed. During this investigation the compressor variable geometry andpower

lever anglewere controlled either by a computer or manually. The primary-nozzle

area, which is normally controlled by the afterburner fuel control, was also controlled

either by a computer or manually for this test.

The inlet performance for an enginestall condition was assessedby stalling the

compressor by slowly closing the primary-nozzle area while maintaining a constant

speed. Sothat the turbine temperature limit would not beexceededduring this procedure, a reduced-area, first-stage turbine stator was installed. Then, at any point on

the compressor map, the turbine was matchedto the compressor at a lower turbineinlet temperature.

Upstream Airflow Variation Device

A flat gust plate was usedto vary the inlet, local, free-stream airflow (figs. 10and

11). With the inlet and the flat gust plate both at 0 ° angle of attack (fig. ll(a)), the local

conditions at the inlet were not changed from the free-stream conditions. Increasing the

plate angle of attack decreased the local Mach number and increased the inlet angle of

attack (fig. ll(b)).

Instrumentation

Static-pressure distributions were measured along the top centerlines of the cowl

and centerbody at the axial locations given in table II. Subsonic diffuser and bleed pres-
sure instrumentation is shownin figures 12and 13. Stability-bypass-bleed total pressure was measuredby two total-pressure rakes just downstreamof the openbleedat an

x/R c of 4. 051. Pressures from theserakes were averagedto determine the stabilitybypass-bleedrecovery. Centerbodyand overboard-bypass-plenumpressures were measured by single tubes (fig. 13).

Overall inlet total-pressure recovery anddistortion were determined from six, 10-

tube total-pressure rakes (fig. 12)at the diffuser exit (inlet station 2). Eachrake consisted of six equal-area-weightedtubes, with additional tubesat the extreme equal-areaweighted tubes in positions corresponding to an 18-tube area-weighted rake. The

compressor-face instrumentation and a calibration curve were used to determine engine

airflow, as described in appendixA. Two piezoelectric transducers (]:)8andD9) were

located at the compressor face (fig. 12). (Dynamicinstrumentation locations are given

in table KI. ).

The compressor discharge pressure was measured by 16 steady-state, totalpressure probes mounted in four rakes as shown in figure 14. One probe (D10) measured both steady-state and transient pressures: A piezoelectric transducer was flush

mounted to the inside of the tube 15.2 centimeters downstream of the probe entrance,

and the tube was extended to the steady-state recording system so that the tube operated

like an infinite line.

One dynamic total-pressure probe and eight dynamic static-pressure taps were

placed along the inlet duct as shown in figures 12 and 15. Outputs of the strain-gage

absolute-pressure transducers in the cowl-lip static-pressure tap (S1) and the throat

total-pressure probe ($2) were used in ratio form (S1/$2) to sense inlet unstart. The

additional absolute pressure transducer ($3) was used to indicate the terminal shock

position for computer control (fig. 16 and ref. 16). The remaining six piezoelectric

transducers (D1 to D6) were flush mounted on the surface.

Turbine discharge temperature T 5 was measured by eight thermocouples that were

installed by the engine manufacturer and wired in parallel to give an average reading.

The engine speed was measured by a magnetic pickup that sensed the tooth passage of a

rotating gear attached to the customer-power takeoff shaft from the engine gearbox.

Combustion flame was sensed by a photodiode. The positions of the inlet centerbody, the

overboard bypass doors, and the pressure-activated poppet valves were determined from

potentiometer measurements.
RESULTSANDDISCUSSION

Basic Inlet Stability Data

The steady-state performance of the inlet configuration that was usedin this test

program has beenreported in reference 1. Althoughthe developmentof an effective

stability bypass entrance configuration andthe required bypass-plenumexit configurat2onis described in references 1 to 5, a few of the basic performance plots are presentedandbriefly discussed in this report.

Steady-stateperformance of the inlet configuration is shownin figure 17. Stability

bypassperformance is shownin figure 17(a), where the bypasstotal-pressure recovery

is given as a function of the bypassmass-flow ratio. The dashedcurves represent the

performance envelopeof the distributed, porous, stability bypass configuration, which

was the sameas configuration NF of reference 1. Thesecurves represent the minimum

(supercritical) and maximum (minimum stable) mass flows that were obtainedfor a series of fixed bleed exits onthe stability bypass system. Data for onefixed exit are

shown(circular symbols). Thesedatawere generatedby reducing the inlet diffuserexit airflow from supercritical (minimum stability bypass airflow) and causingthe termial shock to moveupstream until unstart occurred. Bypass airflow was maximum just

before inlet unstart. This modeof operation gaveloci (dashedcurves) of supercritical

and minimum stable bypass airflows. The bypassperformance with the poppetvalves as

a exit control, also shownin figure 17(a), was obtainedin a similar manner.

Inlet performance is presentedin figure 17(b)by a standard plot of total-pressure

recovery as a function of mass flow. Inlet recovery as a function of diffuser-exit airflow is shownin figure 17(c). In references 1 and5 an airflow index was used to devellope a stability index envelopefor a stability bypass system. However, since specific

bypass-exit-area controls havebeenselectedfor this study (fixed exit or poppetvalve),

the data in figure 17(c)better indicate the stability effectiveness of eachexit control.

Inlet stability could be assessedby the changein diffuser-exit corrected airflow between

the operating condition andthe point just before the inlet unstarted. Since aninletenginematch recovery of 0.90 was selectedfor this investigation, this recovery will be

used to illustrate the steady-state stability. The percentagechangein corrected airflow

from this operating point to the minimum stable condition is the stability index. Therefore, for thesedata, stability indices were 5.0 and25.6 for the fixed-exit andpoppetvalve controls, respectively. The superiority of the poppet-valve control is quite evident from figure 17.

The ability of the inlet with stability bypass systems to absorb internal airflow transients is illustrated in figure 18. Thesedatawere for the inlet with a chokeplate at the

compressor-face station to simulate anengine-installed configuration. The smallest

transient-stability indices (capability of absorbingtransients in diffuser airflow) were
obtainedfor a small bypass-plenumvolume andsmall exit area. This small plenum

volume was the sameplenumvolume usedwith the poppetvalves. Basically, the smallplenumdata represent the capability of a conventionalinlet to absorb aninternal airflow

transient. The changein transient-stability index betweenthe small- andlarge-plenum

data indicates the improved transient-absorbing capability of a stability bypass system

connectedto a small fixed exit through a large plenum. The large-plenum andstability

bypass system could absorb very large transients, for example, above35percent of the

enginecorrected airflow for a transient pulsefrequency 1/T of 20 seconds -1. At lower

pulse frequencies the capability of the large plenum was rather limited and approached

the capability of the small plenum at 1/7 of 1 second -1. The poppet-valve-controlled

system had a large transient-stability index, or capability of absorbing very large transients in diffuser airflow, at all pulse frequencies. It could absorb at least 30 percent

of the diffuser-exit airflow at all test frequencies (fig. 18).

Propulsion System Response to Internal Airflow Disturbances

Transient airflow disturbance data are presented in two parts: inlet response and

engine response. Part (a) of each figure shows the inlet response, which includes inlet

throat pressures (transducers D1 to D5), diffuser static pressure (D6), stability-bypassplenum pressure (DT), overboard-bypass area Aby, and inlet centerbody position Xcb.

Part (b) of each figure shows the engine response, which includes engine speed N, cornbuster flame sensor, combustor spark source, turbine-exit temperature T5, power

lever angle PLA, primary-nozzle area A8, compressor pressures (]:)8, D9, and

P3/P2)_ and the inlet unstart ratio S1/$2. An increase in any of these parameters is

indicated when the trace moves toward the top of the figure.

Reductions in overboard-bypass-door area. - The inlet and engine response to a

single sine-wave pulse reduction in overboard-bypass-door area is presented in figure

19 for a small-fixed-exit bleed configuration. The initial match conditions were an inlet

recovery of 0. 907 and a corrected engine speed of 84.8 percent. At this match inlet recovery, the terminal shock was just downstream of the stability-bypass-bleed region, at

about the same inlet station as the inlet throat transducer D5 (fig. 15). Any reduction in

the airflow demand in the subsonic diffuser would cause the terminal shock to move upstream from this match location toward inlet unstart. The forward movement of the

terminal shock would cause the local static pressure on the inlet throat surface to increase since the airflow downstream of the terminal shock is subsonic. In figure 19,

the reduction in overboard bypass airflow is indicated by the reduction in bypass area

Aby. The increase in static pressure is evident from the trace for transducer D4 in

figure 19. Higher bleed-region surface pressure resulting from the terminal shock

10
movementalso increases bleed-plenumpressure, as reflected by the trace for transducer DT. For a small-fixed-exit-area bleed configuration as in figure 19, a small reduction in subsonicdiffuser airflow moves the terminal shockupstream andinfluences

all the throat pressure transducers. Becausetransducer D1 was just upstream of the

open, porousbleed region, any large pressure rise on this transducer would indicate

that the terminal shockwas upstream of the bleed in anunstableregion and that the inlet

would unstart. The trace for transducer D1 in figure 19(a)showsa slight pressure rise

as a result of the bypass transient. Therefore, the terminal shockwas near the unstart

condition. The trace for transducer D7 indicates anincrease in plenumpressure recovery of 0. 195(0. 195 P/P0 per line times 1.0 line). This increase in pressure was

equalto the increase in steady-state pressure recovery from supercritical to minimum

stable conditions in figure 17. The inlet would unstart if a slightly larger reduction in

diffuser airflow was experienced. During this transient, engineoperation was not significantly affected (fig. 19(b)).

Figure 20 showshow the inlet with the poppet-valve exit control on the stability bypass respondedfor the same-amplitude overboard-bypass disturbance as the fixed-exit

control (fig. 19). The traces for transducers D1 to D5 of thesetwo figures showhow

well the stability bypass and poppetvalves retarded the upstream movementof the terminal shock. Transducers D1 to D3for the small-fixed-exit system of figure 19show

pressure increases that are not evidentfor the poppet-valve system of figure 20. Since

the poppetvalves are a nearly constantpressure control, only a small rise in plenum

pressure (D7)would openthe poppetvalves slightly and allow stability bypass airflow to

exhaustoverboard to compensatefor the reduced subsonicdiffuser airflow.

Each control - small, fixed exit area andpoppetvalves - respondedto a larger

amplitude overboard-bypass-area reduction, as shownin figures 21and 22 The larger

overboard-bypass-area reduction caused the inlet with the small-fixed-exit bleed system

to unstart (fig. 21). This unstart is evident in the figure as the first sudden drop in the

inlet pressures. Again, the terminal shock was initially at transducer D5. The upstream movement of the terminal shock is indicat¢-d by the increase from the initial

match pressure levels for transducers D5 to D1.

The inlet unstart of figure 21 resulted in an engine stall and combustor blowout.

The hammershock from the stall shows up in most of the pressure traces of figure 21 as

a sharp pressure increase just after the initial unstart pressure drop. The combustor

blowout on inlet unstart shows up as the change in the combustor flame sensor trace

(fig. 21(b)) from a fluctuating signal to a steady-state signal. The large drop in

compressor-face total pressure (D9) m_d the lag in the compressor discharge pressure

because of the large combustor volume show up as a significant initial rise in the compressor pressure ratio CPR (fig. 21(b)) immediately after inlet unstart. The hammershock pressure rise at the compressor face shows up as a sharp drop in CPR followed

by an increase when the effects of the hammershock have disappeared.

11
Whenthe unstart sensor sensedinlet unstart (fig. 21(b)), the propulsion system control performed a set of predetermined procedures: The control beganinlet restart by

extendingthe inlet centerbody, at the maximum rate, to a position just beyondthe minimum required extensionfor restart. The point of inlet restart is quite evidentfrom the

return of the unstart sensor trace to its level before unstart. Correlating this trace with

the centerbodytranslation trace (fig. 21(a))indicates that the inlet did restart just before

the maximum extensionwas reached. After inlet restart, the control retracted the

centerbody, at the maximum rate, to the initial designposition. The control also began

firing the combustor spark plug at abouttwo sparks per second. The traces for the

spark andflame sensor (fig. 21(b))show that the combustorrelighted on the second

spark at about0.4 secondafter inlet unstart. During this cycle the power lever angle

andexhaustnozzle area were not varied. Uponunstart, the commandsignal to the

overboard-bypass doors, which hadbeena scheduled, single sine-wave pulse, was

switched to the outputof a control loop. This output varied the bypassto maintain a

predetermined inlet duct pressure during the restart cycle. The reduction in engine

speedand turbine-inlet temperature as a result of engine stall and combustor blowout

canbe seenin figure 21(b).

Whenthe reduction in inlet overboard-bypass-door area that causedthe inlet unstart

of figure 21was duplicatedfor the inlet with poppetvalves, the inlet did not unstart (fig.

22(a)). As in figure 20the poppetvalves openedto allow the airflow to exit overboard

to compensatefor the reduction in diffuser-airflow requirement. Becauseonly the downstream edgeof the bleed region (transducer D4) had a significant pressure rise, the poppet valves obviously allowed the disturbance to be absorbedwithout excessiveterminal

shockmovement. Poppet-valve data in which the overboard-bypassdoor area was varied

from the match condition to a closedposition are presentedin figure 22(b). For these

datathe doors were commandedto move in a sine-wave pulse toward the closedposition.

The flat on the Aby trace in the center of the pulse disturbance indicates that the doors

were completely closed. Thesedata are like thosein figure 22(a). The inlet could not be

forced to unstart by reducing overboard bypassairflow for the poppet-valve configuration

becausebypassairflow was insufficient.

Inlet unstart data resulting from a slow manualreduction in overboard-bypass-door

area for large- and small-plenum configurations with small-fixed-exit-area bleed controls are shownin figures 23 to 25. Thesedatashowvery little effect of plenumsize on

the responseof the inlet and engineduring the unstart-restart cycle. Thedata traces

show that the propulsion system canbe restarted-relighted rapidly (less than 1.5 sec).

Reductions in power lever angle. - The inlet and engine responded to power-leverangle reductions as shown in figures 26 to 31. The poppet-valve control responded to

single sine-wave pulse reductions in the power lever angle as shown in figures 26 and 27.

Although the flame sensor trace in each figure shows a large change, blowout did not

occur. Reducing power lever angle decreased fuel flow, which in turn decreased engine

12
speed. Lower engine speedrequired less diffuser airflow. Therefore, the terminal

shockmovedupstream in the inlet to compensatefor this airflow reduction, as shownby

the trace for transducer D4. Thenthe poppetvalves openedto retard the shockmovement.

Althoughthe power-lever-angle reduction of figure 27was twice that of figure 26,

the responsein the inlet was about the same. Again, as in the overboard-bypass-area

reduction data, the inlet could not be unstarted by reducing subsonicdiffuser airflow

through a decrease in power lever angle. Evenwhenthe engine speedwas reducedto

idle, the poppet-valve-controlled inlet did not unstart.

Steady-state stability bypassdatafor engine speedsfrom match speedto idle are

shownin figure 28. The mass-flow ratios for the poppet-valve stability bypass sytem

were determined by subtraction (appendixA). The ratios obtainedwere adjustedslightly

to put the inlet-engine match condition on the supercritical bleed characteristic, as it

shouldbe. As shownby the tailed symbol, engineidle was obtainedwell within the minimum stable limit of the stability bypass system. The valve characteristic varied between the curve from reference 5 and the datafor this test program becauseof initial

valve plenum pressure. For this test program the valve plenumpressure was adjusted

to be about0.01 in pressure recovery abovethe match stability-bypass-plenum pressure.

Therefore, fairing the data in figure 28indicates that a slight increase in stability plenum recovery of about0.01 was required before the poppetvalves started to open. This

slight valve plenum overpressure was used to eliminate valve reaction to extremely

small airflow variations and to thus eliminate the valve instability problem of reference

5. Also, extending the poppet-valve data of figure 28 shows that the reduced capacity for

airflow removal because of the slight overpressure would be about 0.01 in mass-flow

ratio. This is a relatively small amount when the large capacity of the poppet-valve system is considered.

Similar data for the fixed-exit bleed configuration are presented in figure 29. The

stability-bypass-airflow characteristic obtained by varying the power lever angle was

the same as that for the fixed exit (fig. 17(a)) obtained during an earlier coldpipe investigation. Unlike the results for the poppet valves in figure 28, figure 29 shows that reducing power lever angle and consequently diffuser airflow for the fixed-exit configuration did result in an inlet minimum stable condition (solid symbol). Any additional reduction in power lever angle from the inlet minimum stable position would cause an inlet

unstart. Response data for an inlet unstart caused by further reducing power lever angle

are presented in figure 30. The traces just before unstart represent the steady-state

performance at the minimum stable condition. The inlet unstart caused compressor

stall and combustor blowout.

Data for the fixed-exit controlled bleed system when it was subjected to the same

disturbance as the poppet-valve-controlled bleed system of figure 26 are presented in

figure 31. This pulse reduction in power lever angle caused the inlet with the fixed13
exit-controlled system to unstart. The inlet unstart causedcompressor stall and combustor blowout. The inlet was restarted in about 0.2 second, andthe enginewas relighted about 0.3 secondlater. Comparing these data with the data of figure 26, which

had a similar amplitude disturbance for the poppet-valve control, and with the data of

figure 27, which had a larger amplitude disturbance, again indicates the advantage of a

poppet-valve bleed control in a supersonic inlet: The poppet-valve-controlled bleed system absorbed the transient with the least variation from normal system operation. The

fixed-exit-controlled inlet experienced inlet unstart, which caused engine stall and combustor blowout.

Reductions in primary-nozzle area. - The response of the propulsion system with

poppet-valve-controlled stability bleed to a pulse reduction in primary-nozzle area and

consequently a reduction in required diffuser airflow is presented in figure 32. The results are like those for the overboard-bypass-area and power-lever-angle reductions.

The poppet valves opened to absorb the reduction in diffuser airflow requirement and

thus prevent inlet unstart.

The response of the propulsion system with poppet-valve-controlled stability bleed

to a compressor stall is shown in figure 33. The compressor was stalled by slowly

closing the primary-nozzle area manually to backpressure the engine while manually

varying the power lever angle to maintain a constant engine corrected speed of 90.1 percent. Compressor stall also was attempted at the nominal, test, match engine speed of

just over 87 percent, but the turbine-inlet temperature limit was reached before the engine stalled. Steady-state compressor performance for these two engine speeds is shown

in figure 34. In figure 33(b) the primary-nozzle-area trace A 8 appears to indicate a

constant nozzle area before compressor stall because of the very slow manual closing of

the exhaust nozzle. Stall hammershock shows up as the large initial pressure spike on

all pressure transducer traces in figure 33(a). In figure 33(b) blowout occurred at the

same time that the compressor pressure ratio indicated a stall. The inlet unstart sensor

indicated an inlet unstart about 0.01 second later. After stall a command (scram) to

completely open the nozzle and to chop the fuel flow was given by the control system.

Engine relight was not attempted. The poppet valves opened in response to the pressure

rise in the stability bypass plenum but did not have the capacity to absorb the airflow

transient associated with an engine stall. After stall and the resulting inlet unstart, the

poppet valves closed and remained closed until the inlet was restarted and the centerbody

was being retracted to the design position. During centerbody retraction after inlet restart, the poppet valves opened briefly in response to a pressure rise in the stabilitybypass-bleed region, as indicated by the traces for transducers D2 to D4.

Compressor stall affects a system with fixed-exit-area inlet bleed control as shown

in figure 35. Steady-state compressor performance is presented in figure 36. The compressor was stalled at the same engine speed and by the same procedure as for the

poppet-valve controlled system of figure 33. Upon stall the combustor blew out, the

14
inlet unstarted, and the system was scrammed to a safe condition. However, the pressure transients were muchgreater for the fixed-exit-area-controlled system thanfor the

poppet-valve-controlled system: The hammershock initially causeda larger pressure

rise, the drop in pressure just after unstart was greater, andthe pressure variation for

the throat transducers was larger.

Propulsion System Response to External Airflow Disturbances

The propulsion system responded to disturbances in external airflow as shown in

figures 37 to 44. External airflow variations that reduce inlet free-stream Mach number

and/or increase angle of attack can induce inlet unstart. For some supersonic inlets,

local overcompression of the airflow upstream of the throat region to a subsonic condition causes unstart. When the inlet is operating at an angle of attack, this overcompression (choking) occurs on the leeward side of the inlet. Reference 1 indicates that local

overcompression can be delayed to larger angles of attack by locating bleed forward in

the supersonic diffuser in the overcompression region and by removing airflow in a large

axial region on the cowl with additional bleed airflow removal. Reference 17 indicates

that reducing inlet free-stream Mach number produces an overcompression on the inlet

surface like that obtained near unstart angle-of-attack operation. The overcompression

again appears forward of the throat and circumferentially encompasses the entire inlet

flow field.

External airflow was varied by pulsing (single sine wave) the flat-gust-plate angle of

attack (fig. 11) upstream of the inlet. Increasing the plate angle of attack from 0 ° lowered the local Mach number and increased the local airflow angle into the inlet - for a

combination of changes in external airflow. For a change in Mach number only, the propulsion system would have to be cycled through the same angle of attack as the plate.

For this test the inlet diffuser dynamic pressure instrumentation was on the side

(_ = 90 °) of the inlet. Therefore, increasing the flat-gust-plate angle, which caused a

local downflow into the inlet, resulted in the dynamic-pressure instrumentation being

between the windward (_ = 0 °) and the leeward (q_ = 180 °) sides of the inlet. The inlet

throat transducers do show a local pressure increase because the disturbance was

largely due to Mach number reduction, but they do not show the maximum pressure rise

in the inlet since the combination of Mach number and angle of attack would produce the

maximum change on the leeward side. The poppet valve in this region of high local

pressure was not instrumented, and hence the individual valve response in each circumferentiaI region is not known because valve operation differs due to the asymmetry in the

flow field. The overall response of the inlet and engine system was obtained, however,

and these data indicate some significant results.

15
The poppet-valve-controlled andfixed-exit-area-controlled systems respondedto an

identical external disturbance as presentedin figures 37(a)and 38, respectively. Even

thoughtransducers D1 to D5were onthe side of the inlet, the traces indicate that the

disturbance increased local surface pressure. This pressure increase resulted from

Machnumber variation and may bedecreased slightly on the side of the inlet by the

angle-of-attack operation. Althoughfor thesedata the engineignition was initiated before the external disturbance, engineignition was not required for the conditions of figures 37(a) and38 since the inlet did not unstart and causecombustorblowout.

For a larger flat-gust-plate angle the fixed-exit-area control allows an inlet unstart

(fig. 39), but the poppet-valve control does not (fig. 37(b)). The poppet-valve trace of

figure 37(b) shows little or no response to the disturbance although the poppet valves on

the leeward (high pressure) side of the inlet must have opened and relieved some of the

overcompression that caused the fixed-exit-area-controlled system (fig. 39) to unstart.

Data that are presented in figures 39 and 21 show an inlet unstart resulting from an internal airflow disturbance had more severe pressure variations than an unstart resulting

from an external airflow disturbance. As shown by the combustor flame sensor trace of

figure 39(b), the engine did not blow out when the inlet unstarted. The available data

also indicate that the compressor did not stall: The traces show no evidence of a stall

hammershock pressure rise. The hammershock influence on the pressure transducers,

compressor pressure ratio, and inlet unstart sensor and the very large drop in the diffuser pressures (D6, D8, and D9) associated with a stall in figure 21 are not present in

figure 39.

An additional increase in the flat-gust-plate angle (to 1.4 °) caused an inlet unstart

for the poppet-valve-controlled system, as shown in figure 40. The instrumented poppet

valve opened on unstart and then closed until it opened and closed when retracting the

centerbody after inlet restart. Figure 40(b) shows that compressor stall and combustor

blowout did occur as a result of inlet unstart. Compare these traces with those of figure 39. In figure 40 the hammershock and the very large diffuser pressure drop just

after unstart that are associated with stall are evident. Because relight occurred 0.1

second after blowout, engine operation was affected for only a very short time. In figure 41, another inlet unstart from an external disturbance (created by manually varying

the flat-gust-plate angle) for the poppet-valve-controlled system did not stall the engine

or blow out the combustor. Similar data for the large-plenum, small-fixed-exit bleed

configuration show _at for one case (fig. 42) stall and blowout did not occur but for the

other case (fig. 43) they did. Relight was not attempted in this case. For inlet-engine

systems with poppet-valve controls and large-plenum, small-fixed-exit-area controls,

inlet unstart from an external disturbance (the flat gust plate) caused stall and blowout

for about half of the test points (figs. 38 to 43). For an inlet-engine system with truely

conventional, small-plenum, small-fixed-exit-area controls (fig. 44), inlet unstart from

an external disturbance always caused stall and blowout. After blowout, engine relight

16
was more difficult with this control configuration thanwith the other two. In the first

attempt, engine relight occurred 4.2 secondsafter combustor blowout. But, whenthe

conditionswere duplicatedand the enginedid not relight after 6 seconds, the attempt was

canceled.

The poppet-valve control configuration that was usedfor this investigation was

basically designedto provide the inlet with a large, stable airflow range for internal airflow disturbances. Consequently,the inlet bleedwas in the throat region andnot necessarily where it would provide the greatest tolerance to external (e.g., angleof attack)

disturbances. Nevertheless, the poppet-valve exit control did provide more tolerance to

external disturbances (e.g., 16percent in angleof attack) thana more conventional

_ixed-exit-area bleed system. For greater tolerance to angle-of-attack disturbances,

forward-cowl bleed (fig. 7) shouldalso be used. Reference1 has shownthat forwardcowl bleedcapability would increase steady-state, unstart angleof attack from 4.46° to

7.6 ° if a constant pressure was maintained in the bleed plenum. An additional poppetvalve exit control would be needed for the angle-of-attack system. These valves would

shut off the forward-cowl bleed until angle-of-attack or free-stream Mach number

changes caused the local pressure increase that would activate them.

Steady-State Stability-Bypass-Bleed Performance

Most researchers have concentrated on investigations that define bleed systems for

acceptable, on-design, started-inlet performance. Therefore, very little information on

unstarted-inlet bleed performance has been published. Attempts to minimize the number

of unstarts have resulted in accepting less than optimum performance (supercritical

operation) and in research evaluations of such concepts as the stability bypass system.

Because, under certain conditions, unstarts will still occur, the performance and capabilities of bleed systems with the inlet in an unstarted condition should be a part of all

inlet performance studies.

Started- and unstarted-inlet bleed performance are shown in figures 45 to 47. Cowl

surface pressure distributions for selected data from figure 45 are presented in figure

48. The unstarted-iniet data from figure 45 represent the inlet buzz limits for several

centerbody positions. Attempting to operate beyond the unstarted bleed limit curve for

a given centerbody position resulted in inlet buzz. These curves show that, when the

inlet was in an unstarted condition, the stability-bypass-bleed system was capable of removing large amounts of airflow before the inlet buzz limit was reached. Design centerbody position data (0_ of 25.27 °) indicate that the unstarted buzz limit was between the

started-inlet supercritical and minimum stable bleed curves. The unstarted-inlet bleed

capacity before buzz increased when the centerbody was translated upstream toward the

the restart centerbody position (0t of 22.63°). For this investigation the inlet throat

17
area was increased by upstream centerbody translation. However, similar trends in

unstarted-inlet bleed performance would probably be obtained for inlet configurations in

which the centerbody was collapsed to effect inlet restart.

In an unstarted condition the inlet may operate in a stable mode at any point below

the bleed characteristic curve for a given centerbody position. The specific operating

condition below the bleed characteristic curve was a function of the overboard-bypassarea variation as shown in figure 46. For these data the engine was windmilling and the

diffuser airflow demand was varied by the overboard bypass doors. At diffuser-exit

airflows larger than that represented by an overboard-bypass-area ratio of 0. 1886, the

bleed airflow could vary from zero to any value along the bleed characteristic curve for

the specific bypass-area ratio. The specific stability-bleed airflow rate would be determined by the bleed-plenum exit area. However, any overboard-bypass-area ratio reduction below 0. 1886 required some bleed airflow to maintain an operating condition

below the buzz limit curve. For example, if the overboard-bypass-area ratio was reduced from 0.1886 to 0. 1696, a minimum of about 0.0273 stability-bypass-bleed, massflow ratio was required to prevent buzz. Further reducing the overboard-bypass-area

ratio to 0. 1358 required a mass-flow ratio of about 0. 145 to prevent buzz.

In a sense, the stability system can perform the same basic function during an unstarted condition that it was designed to provide with the inlet started. When the inlet

was started, the stability bypass system allowed the diffuser airflow to vary over a large

range without inducing an inlet unstart. When the inlet was unstarted, as shown in figure 46, proper control on the stability bypass system could also compensate for a large

variation in diffuser airflow before inlet buzz was obtained. Unstarted-inlet bleed characteristics for various overboard bypass areas at the extended centerbody positions have

trends like those in figure 46 for the design centerbody position. At the extended positions the overboard bypass could be reduced even more than at design because of the

large stability bleed capacity before buzz, as shown in figure 45. For example, the

overboard-bypass-area ratio could be reduced to 0. 066 at maximum bleed for a 8_ of

23.28 ° (fig. 45). The stability-bypass-bleed mass-flow ratio at this condition was 0. 221.

Extending the centerbody affects started-inlet, stability bypass performance at the

inlet design Mach number of 2.5, as shown in figure 47. At the off-design centerbody

positions only the minimum stable bleed characteristic curves are presented. These

data indicate that the bleed capability increased slightly for a small extension of the

centerbody, to a 0_ of 24.30 °. Further extending the centerbody toward the inlet restart position reduced the bleed capacity at the larger bleed flow rates below that for the

design centerbody position. However, in general, the minimum stable stability-bleed

capability at the extended centerbody positions was about the same as the capability at

design.

The capability of the large inlet stability-bleed airflows during inlet unstart could be

combined with modern computer inlet control to improve system control during the

18
unstart-restart cycle. During this cycle the present research computer inlet control

retains a closed-loop pressure control on the bypass doors in an attempt to avoid buzz

and to maintain acceptable compressor-face pressure recovery without high distortion.

This control can often command large variations in bypass door area over short time

periods. Since overboard bypass doors usually react rather slowly (particularly on

flight hardware), a compromise is necessary for an optimum inlet control. However,

proper integration of a controlled stability bypass system with the computer inlet controis may require that the bypass doors operate over only a small area range during

most of the unstart. The bypass doors would thus make only minor airflow adjustments,

and the stability bypass system would handle most of the airflow.

The combined system might operate in the following manner: During started-inlet

operation the stability bypass system would provide the inlet with a large stability margin. The stability valves would open in response to diffuser airflow changes. But, if an

airflow disturbance exceeded the poppet-valve airflow tolerance, an inlet unstart would

occur. The poppet valves would begin to close when the inlet unstarted because of the

sudden, extreme pulse decrease in cowl surface pressure. This pressure pulse would

be very short (0.05 sec for the inlet configuration of this investigation); then the local

pressure would increase enough to activate the poppet valves if the subsonic diffuser airflow were controlled at a proper level. To set this level, the bypass-door exit area

would be kept as close to match as possible but large enough to maintain the unstartedinlet operation within the stability-bypass-bleed buzz limit characteristic (fig. 45).

Current control systems could provide such bypass airflow control since only small

variations in bypass door area would be required. When the centerbody is extended to

almost the inlet restart position, the stability bypass system can handle more airflow.

Therefore, the bypass door area could be reduced as the centerbody is extended (fig. 45).

The door area should not be less than the match area because this area would be required upon restart. Since the bypass doors would be at or near the match area at restart, they would not demand large airflows and would not contribute to supercritical

operation.

Several factors would contribute to reducing stability-bypass-bleed airflow at inlet

restart and thus result in less supercritical operation. At the point of restart when the

local conditions would shift from subsonic to supersonic, the bleed airflow would be reduced rather suddenly because of the sharp reduction in flow coefficient. The poppetvalve bleed control would also close because of a drop in local surface pressure and consequently plenum pressure. During centerbody retraction and settling out of the inlet to

normal conditions, any small variation that might cause the terminal shock to move upstream would cause the stability bypass system to function and prevent reoccurrence of

inlet unstart.

19
SUMMARY OF RESULTS

The throat of a Mach 2.5, mixed-compression inlet with 40-percent internal

supersonic-area contraction was fitted with a inlet-stability bypass system designed to

provide the inlet with a large, stable airflow range. This system allows the inlet to be

operated near the optimum performance condition without being susceptible to inlet unstart as a result of small variations in inlet airflow. Previous research programs with

the inlet on a coldpipe have shown that pressure-activated poppet-valve control of the

stability bypass airflow results in very large, stable airflow margins for the inlet. For

further evaluation of the inlet and stability system, the inlet was tested on a turbojet engine. Inlet and engine responses were determined for several transient airflow disturbances, both external and internal. For reference, data were obtained with a conventional fixed exit controlling the bypass airflow. Limited unstarted-inlet bleed performance data were also obtained. The test was conducted in the Lewis 10- by 10-Foot

Supersonic Wind Tunnel at a Mach number of 2.5 with the following results:

1. The poppet-valve-controlled inlet-stability bypass system had no adverse effects

on the performance of the inlet or engine.

2. The inlet with a poppet-valve stability bypass exit control retarded the upstream

movement of the terminal shock. It thus prevented unstart for internal airflow disturbances that had caused unstart for the inlet configuration with conventional, fixed, performance-bleed exits.

3. With the inlet operating at a high performance condition for an inlet-engine match,

the poppet-valve stability bypass control prevented the inlet from unstarting for all

downstream disturbances except an engine stall. For example, the poppet-valve stability bypass system could absorb the reduction in subsonic diffuser airflow caused by reducing the engine speed from the match condition to idle.

4. During an inlet unstart after an engine stall, the pressure fluctuations in the inlet

with poppet-valve stability bypass exit control were not as severe as for the small-fixedexit-area control.

5. The poppet-valve exit control prevented inlet unstart for external airflow disturbances 16 percent larger than that which caused inlet unstart for the fixed-exit control

configuration.

6. When the poppet-valve-controlled inlet unstarted as a result of an external airflow disturbance, the longest time required for the inlet restart - engine relight sequence was 1.5 seconds. In general, this time was dictated by engine relight since inlet

restart required about 0.2 second.

7. Some of the inlet unstarts that resulted from external airflow disturbances did

not cause the engine to stall and the combustor to blow out. In the one inlet unstart for

the poppet-valve-controlled system in which stall and blowout did occur, the engine was

relighted in less than 0.1 second and the inlet was restarted about 0.15 second later.

20
8. Whenthe inlet was in anunstarted condition, the stability bypass system could

remove large amountsof airflow before inlet buzzoccurred. For example, at the design

centerbodyposition, the stability-bypass-bleed, unstarted buzz limit was betweenthe

started supercritical andminimum stable bypass characteristic curves.

9. Extending the centerbody with the inlet unstarted increased the airflow removal

capability of the stability bypass system before the inlet buzz limit was reached.

Lewis Research Center,

National Aeronautics and Space Administration,

Cleveland, Ohio, July 26, 1978,

505 -04.

21
APPENDIX A

ENGINE AND POPPET-VALVE AIRFLOWS

Engine corrected airflow and stability bypass mass flow were determined by the

following procedures.

Engine Airflow

It is very difficult to measure engine airflow either in a wind tunnel or in flight.

Therefore, the engine is usually extensively calibrated in a static test facility before,

and perhaps after, the propulsion test program. But a different approach to obtaining

the engine airflow was used in this investigation.

During the coldpipe investigation of this inlet (ref. 1) the airflow calculated from

compressor-face instrumentation was compared with the airflow measured by the

choked-exit plug system. From this calibration the compressor-face-calculated airflow

can be corrected during an engine test to accurately represent engine airflow. The

compressor-face-calculated airflow Wcorr ' cf and the choked-exit-plug-measured airflow Wcorr ' cep are compared in figure 49.

Compressor-face airflow was calculated by the following equation:

Wcorr, cf =

,o=\_A_7o) t7-7o

Pcf

P0

where A i is the inlet capture area of 0. 1757 m2; Pcf/P0 is the compressor-face,

total-pressure recovery (also P2/P0); (A*/A) 0 is the area ratio for the free-stream

Mach number; and mcf/m 0 was determined from

A*

mcf _ PcfAcf <2_) cf

m0 PoAi A(_-)0

where Acf is the annulus flow area at the compressor-face rake station of 0. 1177 m 2

and where

22
A_) = f(Mcf)

cf

(The compressor-face Mach number Mcf was determined from the average static and

total pressures at the rake station. )

As shown in figure 49, the calculated compressor-face corrected airflow was larger

than the actual corrected airflow as determined by the choked plug. Therefore, during

the engine test program, the engine corrected airflow (Wcorr ' 2 or Wcorr ' cep) was obtained by applying the calibration curve in figure 49 to measured compressor-face airflows Wcorr ' cf" If engine mass-flow m2/m 0 is required, the corrected airflow equation and the value for Wcorr ' 2 are used to obtain the correct value.

Stability Bypass Poppet Valve Airflows

The stability bypass mass-flow ratio was determined by subtraction, as follows:

msb_mi m 2 mby mc b

m 0 m 0 m 0 m 0 m 0

where mi/m 0 is the capture mass-flow ratio (1.0 for the inlet cruise Mach number),

m2/m 0 was determined from the calibration curves for the engine-face rake station,

and mby/m 0 and mcb/m 0 were measured values of overboard bypass and centerbody

mass flows.

23
APPENDIX B

A

A c

A 8

CO

CPR

DI

f

tt

h

M

m

m 0

m/m 0

N

N*

N/N*,/g 2

P

Ap

P

PLA

R c

r

SI

SI t

SYMBOLS

flow area, m 2

cowl-lip capture area, 0. 1757 m 2

2

primary-nozzle area, m

converging-vortex generator pair

compressor pressure ratio, P3/P2

diverging-vortex generator pair

-1 pulse frequency, l/r, see

annulus or rake height at local diffuser station, em

distance from inlet surface, cm

Mach number

mass flow, kg/sec

free-stream mass flow based on Ac, kg/sec

mass-flow ratio

engine speed, rpm

rated engine speed, 16 500 rpm

corrected engine speed

total pressure, N/m 2

fluctuating component of local pressure

static.pressure, N/m 2

power lever angle (throttle), deg

inlet cowl-lip radius, 23.66 cm

radius, em

stability index, (1 Wcorr_ min s_ 2)x 100 Wcorr, op, 2

transient stability index, (1 - Wc°rr_t_ min s_2)X

Wcorr, op, 2

100

24
T

W

Wcorr

x

Xcb

x/R e

OL

5

0

O_

T

Subs c ripts:

av

b

bp

by

cb

cf

cep

e

fp

max

min

min s

op

pv

pvi

total temperature, K

weight flow rate, kg/sec

corrected airflow, W,¢"_/5, kg/sec

axial station, cm

centerbody position measured from

axial distance ratio, inlet radii

angle of attack, deg

P/(10, 13×10 4 N/m 2)

T/288.2 K

cowl-lip position parameter, tan-l

transient pulse width, sec

circumferential position, deg

M 0 = 2.5 design cone tip position, cm

average

bleed

bleed plenum

overboard bypass

inlet centerbody

compressor face

choked exit plug

exhaust

flat plate

local

maximum

minimum

minimum stable inlet operating point

inlet operating point

poppet valve

poppet valve internal

25
ref

sb

t

uns

0

2

3

5

8

reference

stability bypass

transient

unstart

free -stream

compressor-face station

compressor discharge station

turbine-exit station

exhaust station (primary nozzle)

26
REFERENCES

1. Sanders, BobbyW. ; and Mitchell, GlennA. : Throat-Bypass Bleed Systemsfor Increasing the StableAirflow Rangeof a Mach 2.50 Axisymmetric Inlet with 40-

Percent Internal Contraction. NASATM X-2779, 1973.

2. Mitchell, GlennA. ; andSanders,BobbyW. : Airflow Control Systemfor Supersonic

Inlets. U.S. Patent 3,799,475, Mar. 1974.

3. Sanders, BobbyW. ; and Mitchell, Glenn A. : Increasing the Stable Operating Range

of a Mach 2.5 Inlet. AIAA Paper 70-686, June 1970.

4. Bowditch, David N. ; et al. : Supersonic Cruise Inlets. Aircraft Propulsion. NASA

SP-259, 1971, pp. 283-312.

5. Mitchell, Glenn A. ; and Sanders, Bobby W. : Pressure-Activated Stability-BypassControl Valves to Increase the Stable Airflow Range of a Mach 2.5 Inlet with 40-

Percent Internal Contraction. NASA TM X-2972, 1974.

6. Mitchell, Glenn A. ; and Sanders, Bobby W. : Poppet Valve Control of a Throat

Stability Bypass to Increase the Stable Airflow Range of a Mach 2.5 Inlet with 60-

Percent Internal Contraction. NASA TM X-3297, 1975.

7. Shaw, Robert J. ; Mitchell, Glenn A. ; and Sanders, Bobby W. : Forward-Slanted

Slot Throat Stability Bypass to Increase the Stable Airflow Range of a Mach 2.5

Inlet with 60-Percent Internal Contraction. NASA TM X-2973, 1974.

8. Shaw, Robert J. ; Mitchell, Glenn A. ; and Sanders, Bobby W. : Distributed Porous

Throat Stability Bypass to Increase the Stable Airflow Range of a Mach 2.5 Inlet

with 60-Percent Internal Contraction. NASA TM X-2974, 1974.

9. Shaw, Robert J. ; Mitchell, Glenn A. ; and Sanders, Bobby W. : Distributed Educated

Throat Stability Bypass to Increase the Stable Airflow Range of a Mach 2.5 Inlet

with 60-Percent Internal Contraction. NASA TM X-2975, 1974.

10. Mitchell, Glenn A. ; Sanders, Bobby W. ; and Shaw, Robert J. : Throat StabilityBypass Systems to Increase the Stable Airflow Range of a Mach 2.5 Inlet with 60-

Percent Internal Contraction. NASA TM X-2976, 1974.

11. Anderson, Bernhard H. : Design of Supersonic Inlets by a Computer Program Incorporating the Method of Characteristics. NASA TN D-4960, 1969.

12. Wasserbauer, Joseph F. ; and Choby, David A. : Performance of a Bicone Inlet Designed for Mach 2.5 with Internal Distributed Compression and 40-Percent Internal

Contraction. NASA TM X-2416, 1972.

27
13. Coltrin, Robert E. ; and Calogeras, JamesE. : SupersonicWind TunnelInvestigation of Inlet-Engine Compatibility. AIAA Paper 69-487, June 1969.

14. Blausey, G. C. ; Coleman, D. M. ; andHarp, D. S.: Feasibility Studyof Inlet Shock

Stability Systemof YF-12. (Sp-1964,LockheadAircraft Corp.) NASACR-134594,

1972.

15. Dustin, Miles O.; and Neiner, GeorgeH. : Evaluation by StepResponseTests of

Prototype Relief Valves Designedfor YF-12 Inlet Stability Bleed System. NASA

TM X-3262, 1975.

16. Cole, Gary L. ; Neiner, GeorgeH. ; andCrosby, Michael J. : An Automatic Restart

Control System for an Axisymmetric Mixed-Compression Inlet. NASA TN D-5590,

1969.

17. Choby, David A. : Tolerance of Mach 2.50 Axisymmetric Mixed-Compression Inlets

to Upstream Flow Variations. NASA TM X-2433, 1972.

18. McLafferty, George M. ; and Ranard, E. : Pressure Losses and Flow Coefficients of

Slanted Perforations Discharging from Within a Simulated Supersonic Inlet.

R-0920-1, United Aircraft Corp., 1958.

19. Syberg, J. ; and Hickcox, T. E. : Design of a Bleed System for a Mach 3.5 Inlet.

NASA CR-2187, 1973.

28
(a) Centerbody

Axial distance Inlet cowl-lip

from center- radius ratio,

body tip, r/B c

x/R e

0 0

10 ° Conical section

1. 0323 0. 1820

18.5 ° Conical section

2. 800

2.85O

2. 900

2. 950

3. 000

3•,050

3.•100

3. 150

3. 200

3. 250

3. 300

3. 350

3. 400

3. 450

3. 500

3. 550

3. 600

3. 650

3. 700

3. 750

3. 800

3. 850

3. 900

3. 950

4. 000

4• 050

4. 100

4. 150

4.2OO

4. 250

4. 300

4. 350

4. 400

4. 450

4. 500

4. 550

4. 600

4.65O

4. 700

2.7620 0.7608

.7696

.7794

.7874

.7937

.7986

.8025

.8045

.8043

• 8030

• 8015

.8000

.7982

.7964

.7944

•7925

.7906

.7886

.7862

.7834

.7798

.7757

.7711

.7655

.7590

.7513

.7426

.7330

.7230

.7133

.7036

.6924

.6810

•6692

.6577

.6455

,6330

.6205

.6085

.5960

Axial distance

from centerbody tip,

x/R e

4,750

4,800

4.850

4.900

4.950

5.000

5.050

5.100

5.150

5.200

5.250

5.300

5.350

5.400

5.450

5.500

5.550

5.600

5.650

5.700

5.750

5.800

5.850

5.900

5.950

6.000

6.050

6.100

6.150

6.200

6.250

6.300

6.350

6.400

6.450

6.500

6.550

6.600

6.650

6.700

6.750

6.800

6.850

6.900

6.950

7.000

TABLE I. - INLET COORDINATES

Inlet cowl-lip

radius ratio,

r/R e

0.5825

.5700

.5573

.5448

.5320

.5195

.5075

.4983

.4895

.4805

.4715

.4622

.4534

.4444

.4352

.4264

.4175

•4085

.3995

.3900

.3815

.3732

.3650

,3566

.3488

,3412

.3339

.3266

.3196

.3130

,3068

,2985

.2910

•2845

:2780

.2716

.2655

•2597

.2545

.2501

•2464

.2430

.2410

.2400

.2396

.2394

Cylinder

7•8858 0.2394

Axial distance

from centerbody lip,

x/R e

2.117

2. 150

2.200

2.250

2.300

2.350

2.400

2.450

2.500

2.550

2.600

2.650

2.700

2.750

2. 800

2. 850

2. 900

2.950

3.000

3.050

3. 100

3. 150

3.200

3.250

3.300

3.350

3.400

3.450

3.500

3.550

3.600

3.650

3,700

3.750

3.800

3.850

3•900

3.950

4.000

4.050

4, i00

4.150

4.200

4.250

4. 300

4.350

4.400

4.450

4.500

4.550

(b) Cowl

Inlet cowl-lip

radius ratio,

r/R c

1.0000

1.0028

1.0070

l•011l

1•0154

1•0193

1.0228

1•0261

1.0290

1•0317

1.0340

1•0360

1.0373

1.0382

1. 0386

1. 0386

1. 0381

1. 0370

1.0356

1.0337

1.0320

1.0304

1•0290

1.0275

1.0262

1.0251

1.0239

1.0227

1.0215

1.0204

1•0192

1.0176

1•0160

1.0144

1.0124

1.0100

1•0071

1•0037

1.0000

.9955

.9908

.9858

.9808

,9756

,9702

.9659

,9595

.9538

.9481

.9426

Axialdistance

from centerbody tip,

x/R c

4. 600

4. 650

4. 700

4. 750

4. 800

4. 850

4. 900

4. 950

5. 000

5. 050

5. 100

5. 150

5. 200

5. 250

5. 300

5. 350

5. 400

5. 450

5. 500

5. 550

5,600

5.650

5. 700

Inlet-cowl lip

radius ratio,

r/B c

O. 9374

• 9324

• 9276

• 9232

• 9191

.9153

.9120

• 9087

• 9050

.9044

.9049

.9058

• 9071

• 9086

• 9102

• 9118

.9132

• 9145

• 9157

• 9166

• 9173

• 9177

• 9179

Cylinder

6.1747 0.9179

Bypass gap

6.7847 0.8868

6.800 .8865

6.850 .8855

6.900 .8846

6.950 .8837

7.000 .8823

7.050 .8805

7.100 .8785

7.150 .8760

7.2OO .8734

7.250 .8707

7.300 •8677

7.350 .8654

7.400 .8639

7.450 ,8631

7,500 .8627

7.550 .8623

7.600 .8621

Cylinder

7.8858 0.8621

29
TABLE If. - COWL AND CENTERBODY STATICPRESSURE TAP LOCATIONS

[Top centerline. ]

(a) Cowl (b) Centerbody

Axial distance

from centerbody tip,

x/R e

2. 684

2. 807

2.859

2. 894

2. 930

2. 964

2. 999

3. 038

3. 066

3. 101

3. 136

3. 170

3. 205

3.24O

3. 275

3. 310

3. 345

Axial distance

from centerbody tip,

x/R e

3. 380

3. 434

3. 489

3. 564

3.639

3. 714

3.95O

4. 192

4.519

4. 847

5. 202

5.529

6. 119

6. 742

7.311

Axial distance

from centerbody tip,

x/R c

2. 308

2. 670

2.751

2. 802

2.834

2. 858

2.893

2. 963

3. 030

3. 102

3. 140

3. 173

3. 210

3.247

3. 285

3. 317

3. 353

Axial distance

from centerbody tip,

x/R e

3. 389

3. 441

3. 489

3. 543

3. 586

3. 629

3. 671

3. 714

3. 795

3. 875

3.95I

4. 192

4. 519

4. 847

5. 202

7.311

3O
Probe

D1

D2

D3

D4

D5

D6

D7

TABLE HI. - DYNAMIC INSTRUMENTATION LOCATIONS

Description Reference Comments

figure

Cowl static pressure 15 Inlet dynamics

I

!

Stability -bypass -plenum

total pressure

D8 Compressor-face static

pressure

D9 Compressor-face total

pressure

D10 Compressor-exit total

pressure

$1 Cowl static pressure

$2 Inlet throat total pressure

$3 Terminal shock position

sensor

'r

13

15

12

12

14

15

15

15

I'

Used to obtain compressor

pressure ratio

(Inlet unstart sensor

pickups)

Analog computer

31
¢;-70-2762

Figure I. - Bottomviewof model installedin 10- bylO-Foot SupersonicWind

Tunnel.

32
L

o

1,2--

.8--_

==

i

._o"

ro

_a3 ,.-:

E

O

_ _9

I

2-- I.

l- Ip_Ip°l_'-I ...............

o 5- -_

(a-i}Cowl sudace conditions.

2

F Mo2.__,/5 = ,,-Mav = 1.

/ ,' Pav/Po = 0.9855

I_-- 18.50 ..._.... _ -

0 ",t'"

la-21Inlet contours.

31--

....... M_

21--- L ........... .._

1-- P_IP0 )-''""_'" ............

=_::L t l I l • -,,T----Y]

i 2 3 4 5 6 7 8

Axial distance.XlRc, inletradii

(a-3)Centerbody surfaceconditions.

(a)Inletdimensions and airflowconditions. Free-streamMach number,

M o. 2.5.

i

.7_-{- Translating portion I I Compressor-face station--,j fi

51_' \_ _ono!cent.erbody J ......

• I \, '_,_ / _ort strut influence - [

\ ", ," .,//j" ' ' l

I \-_./...,_/-

4l _I I l J J

"2 3 4 5 6 l 8

Diffuser station, xIR c

(b) Diffuser area variation.

Figure 2. - Aerodynamic details. Cowl-lip position parameter, Bi,, 2.5.27°.

Cowl-lip position

parameter,

e_

25.21

24. 90

23.47

21.86

33
Fast-acting

overboard bypass q

Inlet station: 0 1 _

2

Axial distance ratio, _ r Stability bypass pipe

XlRc, inlet radii: 0 L032 2.117 3.779 3.965 5.202 _ 7.295 / (2pipes, @=90°and180 °)

t _ I // w

Large stability bypass plenum_ _ _ Stability bypass n,,or_.,_,-a-

...... _ - _i _ airflow r ....... Pressure-acuvaleo poppetvalves-, _ _ , * * bypass-entrance

"" \ -- " I/ a Small stablhty bypass plenum _ __ _ _'_"_ i 11 S du t-vane cascade

I -- r,._-- "_t._-__.] _l /I _'_----_ (sealed)

T o I _ _il I- _i tl J85-OE-13 '

RC766 c_ _'_Sta_ turbojet engine

t_ L Cent.erbed. y _--.r--.-_, , ,,

Vortex generat°rsZ _ _ Centerbody

bleed airflow

Centerbody strut / _ ,

discharge louvers-' _,.._.. ., , I

CD-11410-01 _x

LCenterbody bleed

pipe (2 pipes,

_o= 60° and 300°)

Figure 3. - Inlet details. (Pipes for ducting bleed airflow are not shown in true circumferential posilions. I

34
i- Upper-side

/ surface coordinates /

v0.0254 rad // from NACA0012airfoil |

,W____2_ k

'

_LFlat lower surface -T

O.1524

z/1⁄2

_Chord, 2.522 --

_///////////////////_

,m Diffuser-exit total-

// \ pressure rakes

, ow,

,,/--,,, ...- y \

-. _ \ / ///

"DI_ _"_I " ""'--Fenterline of

" centerbody

/"

Diverging /

pair (DI) -/

LConverging

l pair (CO)

_/////////_

Flow

support struts

Figure 4. - Vortex generator design. (Dimensionsare in cm.)

Overboardbypassflow -..

\

/

Forward-cowl

bleed flow_,,

\

"-- Chamber for housing

pressure-activated valves

_'_-Small stability

"'-= Forward-cowl bypassplenum

bleedregion

",1_Stability bypassflow

I

L Valve attachment

bulkhead

Stability bypass

entrance _.

"'_'_ Large stability bypassplenum

CD-11411-OI

Figure 5. - Sketch of inlet cowl showing cowl bleedand bypassducting.

35
Stability bypassplenum_

Stability bypass entrance-, _

\

r- Pressure-activated

/ poppet valves

CD-I1412-01

Figure 6. - Possible arrangement of flight inlet incorporating a poppet-valve-controlled inlet-stability bypass

system.

Cowl bleed configuration

Forwardcowl

bleed

t'l_@

Stability bypass bleed Aft-

(configuration NF, ref. 1) cowl

bleed

(1011000410000000000000000 @@

o Bleed hole row open

• Bleed hole row closed

• Alternate holes in row open

e Every third hole in row open

distance ratio,

Axial inlet radii: 3.013 3.397

x/Rc,

Geometric 3.260 _

] thr_t .... I _,-,_ v..-.-H..

COWl _

centerbody _.. Mid-centerbody Aft centerbody

. .,-Vortex generators

rv

Axi

x/R o inlet radii: 2.779 2.988 3. 180 CD-11413-01

Centerbody bleed configuration

_ Mi/b_yblee__ le_

Figure 7. - Sketch of model showing cowl, distributed, porous, stability-bypass-bleed system and centerbody performance-bleed system.

36
C-69-415Z

(a) Poppet-valve installation. {Several valve positions shown.)

r-3.09g rad

Valve attach- l_,,,. A _ r Rolling

mentbulkhead_ I _l _ r3 492 tad 1/ diaphragm

I I _ \_ /J_ /,#-Linear / T_ili_ t -V_---_-_;_ _i

Valve J i _""__ _I--_ / I

_lo,ed) / II I -F_ / /

/ 3.048rad II _L3. o_r_] / ,

t _1__ stroke -L__

ball bushings

e"1 _ Valve internal

//pressure tap (one

"|per quadrant, four

l ltotall

Valve

open

Stabilibj

bypass airflow "_

Valve seat-"17___

/

LValve bypass

holes (four per valve,

M holes, I. 031 diam}

{b) Poppet-valve details.

- --_-_ Internal

pressure

line

{Dimensions are in era. )

Figure 8. - Poppet valve.

3"/
,- Valve

.," atiachment ,-Valve chamber

._ DulKhead /'

I -....

Simulated, _s II Poppet valve To

Supply flow-_.-- stability bypass P m ' l[ (internal _ exhauster

total pressure, sb_ pv ]I pressure, p.,;) _ --

J _ e IJ

Schematic of bench test

1.4

._t.2

E

1.0

_. .8(

.6

__ O Flow choked at valve opening

I __I ..... I I

.2 .4 .6 ,8 ]Io.

Valve mass-flow ratio, mpv/mpv ' ref

(c) Poppet-valve performance. Initial-stability bypass total

pressure, Psb, ]" i Nlcm ; reference pressure, Psb ref,

3. 9 Nlcm2; exhaust pressure, Pe, 1177 to I. 01 Nlcm '2.

Figure 8. - Concluded.

38
.. _////_ _,

(a-l) Small stability-bypass-plenum volume.

cA rValve attachment

// bulkhead opening

64 Holes

L"'"_,.";__Valve-'_ypass holes __ /-Valve

x. _" attachment

_udu _tduuuy "\ _ bulkhead

7/_///////////__;'.',;;;,._'_.'_/_

Section A-A

(a-2) Valve bulkhead hole locations for bypassing a mass flow ratio of approximately O.OZ

I,a) Poppet valve closed.

g

(b)Poppetvalve open; largestabiIily-bypass-plenumvolume.

iFicjure 9. - Small and large stability-bypass-plenum volumes,

39
r-Cooling airflow from

/ external source

Translating /

centerbody q _ Stability _ _- Stall diaphragm

II _\\bleed region / //

1 _ _ ....... I ............................ ;........................ .I>'-I

\, _ _ / r._ I

_J._-I /- Choked plug for

/ / '\ C'_I_ stability bypass

• / '\

/ Sixteen poppet / "- Fast-acting

/ valves arouna / nwrhnard

circw

circumference -' by;'assdoors

Figure lO. - Sketch of propulsion system and flat gust plate (bottomview).

I

%= o°--_ ---......

--.... Mfp 2. 5 ""

M 0 - 2.5 "---... I I

(a) Inlet operating at uniform design conditions: Free-stream Mach number, _ = 2. 50;

angle of attack, a = 0°.

M0 = E 5 _\ _ \_

_\M[ = Mfp f Z5 j_ /

(b) Inlet operating at off-design conditions: Local Mach number, M[ _ 2. 5; local angle

of attack, _ _ 0°.

Figure 11. - Typical installation of Mach 2. 5 inlet with flat plate, where local inlet Mach

number is a function of flat-plate angle.

40
Hollow centerbody

Dynamic total- supportstrut -I

pressure tube D9 -. 0o // "-._ 332.5o ] _= 27.5o /

Probe Stru_''-, _-_'_ /"

centerl_e /""-_ 5 - ,'_ _/

Static-pressure tap __ _ °. ,- v .,,_/

Total-pressurepro e : /

Dynamic pressure [ "_"_ _.f'_ 1

147.5o _- Dynamic staticpressuretap 08 Downstreamview

5o

Ratio of distance

from inlet surface

to rake height,

_0. 982

I o_,_. 907

I "-._.829

I ,--,699

I . _. 552

H = 14.732cm

T'" _ .378

I /. _.m6

I h o _.151

. --. 047

Figure 12. - Subsonic diffuser pressure instrumentation, showing typicalexit rake and

rake position at inlet station 2.

41
Stability bypass Valve facestation L ,

total-pressure (axial distance / t

rakes at circu.m- ratio, x/R , 4. 051 //"

ferentlal positions inlet radii_

of go° and 2700_ -_.-_ .

.7/_.___ total-pressure tube

/ I

Dynamicpressure tap ../

before overboard-bypass/" Axial distance L Centerbody-base

cavity ID6, r# at 320%j ratio, xfi_., total-pressure tube

5. 888 inle_ radii

Figure 13. - Bleedand bypasspressure instrumentation.

• Dynamic and steady-statetotalpressure probe D]O

o Steady-statetotal-pressure probe

Figure 14. - Compressordischarge pressure

instrumentation (downstream view).

42
Dynamic stability-bypassplenum total-pressure Valve

probe D7 (_p_ 12401-.,. attachment

" 1 Dynamic total-pressure \... bu khead_, _.-_"--

probe 52 for inlet "_. \\

unstart sensor_, _

Dynamic pressure

pries through iniet

throat (circumfer- _

ential position, 900): 51 ' D1 D2 D3 D4 05 $3

Axial distance _ cm: 63.5 70.49 72.54 75.00 77:49 79:97 _'_55 92..27

from center- ,_

bodytip Lx/R c 2.684 2.981 3.066 3.170 3.275 3.380 3.489 3.90

Figure 1.5.- Inlet-throat-region dynamic pressure instrumentation.

Flat gust plat_-_----_Supersoni c inlet _T

IJ se

petition |

_di_toLl

i Centerbody

position

actuator I

Analog computer

-Engine and nozzle

Igniter

and power

lever angle

Figure 16. - Block diagram of propulsion system control.

I Primarynozzle

actuator

43
Stability bypass

exit control

0 Fixedexit "_From ref. 5

D Poppetvalvesj

_._ Valve instability

_ _ performance envelopeidistributed, porous

configuration NF, ref. 1)

///`>

\\\ /////

\ /

\ /

\

.05 .10 .15 .20

Stability bypassmass-flow ratio, msblmo

(a)Stability bypassperformance.

•45

\%\\

(b)Inlet performance.

L

_" 14 16 18

Corrected airflow, Wcorr ' 2

{c) Corrected airflow.

F_gure17, - Steady-stateperformance of inlet configuration aSdetermined from previous coldpipe studies with fixed and poppetvalve stability bYl)assexitcontro]s. Free-stream Bach number, MO. 2.5.

44
5O

4O

E

3O

.E

_z,

"_ 2O

1o

{::

,D

u,)

Time

Stability bypass Stability bypass- Total-pressure Stability bypass

exit control plenum volume, recovery, total-pressure

m_ P21P0 recovery,

PsbfP0

-- [] Poppetvalves Small, O.0184 O.895 O.313

0 Fixedexit Large, O.402 .897 .320

I I I 1

10 2O 3O 40

Transient pulse frequency, I/T, sec"I

Figure 18. - Unstart limits of inlet configurationwith severaldifferent stability bypassexit

controls when subjected _otransient internal airflow disturbances. Free-stream Mach

number, M0, 2.5.

45
,n,etthroatstot, cpressoro __[_ '

(0.195 P/Po per line): __ ._ 2

.... _ .... :2: . 2__2:_2_.__£_1___

.... 4----------

D2 __ -:

D4 . -! -_' ......

_ 7-2 __-I-:2 L£

D5 .......

Diffuser static pressure, DO --.--

{0.195 P/Po per line)

Stability-bypass-plenum total -

pressure, D7 {0.195 pIP0 ...... _.;._

per line) ..... _-- 4 ............

Poppet-valveposition(open)

Overboard-bypass-doorarea

variation, Aby{37.9cm2

per line_

Centerbodytranslation, Xcb

(1.82 cm per line)

.... J___.{

----!-.- *

-_+-- +

i

I

......... J._

I

|

..... Im--

--J ........ I

i

__ J -]

.J ........ i _ _J

.... 1___ J

i--

,m

!--

L_

r_d

i

.... i

Ll

._._ __

.... 2:T

li££

L_

I ....

i

.... ! .

I

.... ! ____

i

Time {0.1 sec per line)

(a)Inlet response.

Figure19. - Transient reduction in overboardbypassarea with small, fixedexit as stability-bypass-bleedcontrol

and large stability bypassplenum - for transient overboardbypassflowarea Aby t of 43.4 squarecentimeters.

Free-stream Mach number, MO. 2. _ transient pulsefrequency, 1/T, 2 seconds'l; correctedengine speed,

N/N* _r_, 0.848, total-pressure recovery, P2/Po, 0.907; mass-flowratio, m2/mO. 0.844; primary-nozzlearea,

A8. O.0677square meter.

46
Engine mechanical speed

variation, N (1090rpm

per line)

Combustor flamesensor

Combustorspark source

Turbine exittemperature,

T5 (108o C per line)

Power lever angle, PLA

(14.3o per line)

Primary-nozzle area, A8

(41.1 cm2 per line)

Compressor-facestaticwes- __

sure, D8 i0,195 PlPoper

line)

Compressor-face total pressure. I)g (0.I95 P/Po per

line)

Compressorpressure ratio,

CPR (1.08 P3/P2 per line)

Inlet unstart sensor

Time (0.1 sec per line)_

(b)Engine response.

Figure 19. - Concluded.

4?
Inlet throat staticpressure

(0.195 lYPo per line):.

D1

D2

£_ ___ I _ l t I . _L t t

I

D3

D4

D5

Diffuser staticpressure, D6

(0.195 lYP0 per line)

Stability-bypass-plenum total

pressure,D7 (0.105P/Po

perline)

Poppetvalve position (O.564

cm perline)

Overboard-bypass-door area

variation, Aby(37.9 cm2

per line)

Centerbodytranslation. Xcb

i]. 82cm per line)

=

I| t

Time (0.1 sec per line)_

(a)Inletresponse.

Figure 20. - Transient reduction in overboardbypassareawith poppetvalves as the stability-bypass-bleedcontrol - for

transient, overboardbypassflow area Abv t of 43.4 squarecentimeters. Fre_stream Mach number, M0. 2.5;,

transient pulsefrequency, I/T, 2 seconds'l; correctedengine speed,NIN_ _/0, O.853;total-pressure recovery,

P2/P0. 0.90_ massflowratio, m2/m0. 0.848;. primary-nozzlearea, A8, 0.0647 squaremeter.

4B
Engine mechanical speed

variation, N (1090rpm

per line)

Combustor flame sensor

.....:--I ....TT--: i- f T :

_ _L..... _ll .... b-

-- --F

Combustor spark source . ]

Turbine exittemperature, - ....... +....... -- [- _-......... _f :___

T5 (I0_ Cper line,

Power lower angle. PLA ===================================

,]4.3°per line) .... _-":{_ 'iI__............... LE---_f'Z_ _ _ J " -'i ...... F---

Primary-¢ozzle area, A8 ---_ ! j_ - ......... _T: f-! - :_--__--

(41.1 cm_ per line) _: " --_== ........................

Compressor-Nce static pres ........

sure, D8(0.195 P/Po per --- _' .___:__----[:_-[::.[_:_ ql--: -_: i __.:_j__ ...... .___7

..... :: : _ ]:: .._::J:_:__ " " " ::T_L -

line, --- -i----J ............ -_- t--_--- _ .... -----------_

Compressor-facetotalpres- _:X_:I;__L:_-L:]. _ L--_ L L; .... .1 L

sure, D9(0.195 P/P0 per ....... " tr ...... "-" _:-_'=:-"=" :'_...... if-" :":__]f _"_ ....

line) ...]__ H __L___ ; ._.;_____ _._--L-,-L-_..____ _____._. _. - ........ ................... ....... +__

--4--_ -- _-L_--L__ _-L,--L- I . I I I J __1__ ___L__

Compressorpressure ratio, ___+ .... _._-_- :-._-- ___.___J_..... ___ ..... [ L_ L___I _ __

CPR (].08 P3/P2 per line) ............................................................. . ,,,_.... .: 4 ......

-- _ _L_ J_ L_L_J., :i L l __" _ j :

l,.J ']l L |----l--] !..... l-- *-

Inletunstarf sensor _--L_ __J_ --I "! l : J I -_" :_---

Time (0.I secper line)

(b)Engine response.

Figure 20. - Concluded.

49
Inlet throat static pressure

(0.195 P/Po per line):

D1

D2

D3

D4

D5

Diffuser staticpressure, D6

(0.195 P/Po per line)

Stability-bypass-plenum to_l

pressure, D7 (0.195 _P0

per line)

Poppet-valveposition _penl

Overboard-bypass-door area

variation, Aby(37.9 cm2

per line)

Centerbodytranslation. Xcb

0.82 cmper line)

. / shockmovement

Time (0.I sec per line)_

(a) Inlet response.

Figure 21. - Transient reduction in overboardbypassareawith small, fixed exit as stability-bypass-bleed control and large

stability bypassplenum - for transient overboard bypassflow area Aby t of 75.9 square centimeters. Free-stream

Mach number, M0, 2.5;, transient pulse frequency, I/'r, 2 seconds-l;'corrected engine speed, N/N* _/-0, 0. 848, totalpressure recovery. P2/P0, 0. 907; mass-flow ratio, m2/m0' 0.844, prlmary-nozzle area, A& 0.0647square meter.

5O
Engine mechanical speed

variation, N (1090rpm

per line)

Combustorflame sensor

Combustor spark source

Turbine exit temperature.

T5 (108° C per line)

Power lever angle, PLA

d4.3° per line)

Primary-nozzle area, A8

(41.1cmz per line)

Compressor-facestaticpressure, D8 (0.195 lYP0 per

line)

Compressor-facetotal pressure, D9 (0.105 lYP0 per

line)

Compressor pressure ratio,

CPR (1.08 P_P2 per line)

Inlet unstart sensor

Time _0.1secper Iine)_

(b)Engineresponse.

Figure21. - Concluded.

51
Inlet throat staticpressure

(0,195 P/Po per line):

D1

D2

D3

D4

D5

Diffuser staticpressure, D6

i0.195 P/Po per line)

Stability-bypess-plenu m totaI

pressure, D7 i0.195 P/Po

per line)

Poppet-valveposition tO.564

cmper line)

Overboard-bypass-doorarea

variation, Aby(37.9 cm2

perline) -

Centerbodytranslation, Xcb

(1.82 cm perline)

i I I ; :

Time (0.1 sec per line)_

(a)Transientoverboard bypassflow area, Aby' t, 81.3 square centimeters.

Figure 22. - Transient reduction in overboard bypassareawith poppetvalves as stability-bypass-bleed controL Freestream Mach number. M0' 2. _, transient pulsefrequency, ll'r, 2 seconds-]; corrected engine speed,NfN

0. 853; total-pressure recovery, P2/% 0. gO_ mass-flow ratio, m2/m0, 0. 848;,primary-nozzle area, A8, 0, 0647

square meter.

52
Inlet throat staticpressure

(0.195 lYP0 perline):

D!

r i .3___: --i l ]_L___L___L_IL L.....L --..__

.... ! I

I l _i_=.__ ___ L_J___ ___j !

D2 l I i I L 1 I i . i

'___L. L....

___

-_-_---3r--- ! +_.i--L- l __l__L _=_- , JL LL_L__L__ L __

--t-4 4-+ -

,I I [ --

±

.... I.__I_LL__ ._

=_---d-,-_---t--_f+=fi - ! _ k M _ _---_--I---_ ....... _---

....... 4---. 4-. -.-_-_.L_21, _'- g-- -L--_- _2__j.I_L_[_ _- - i +.... ' ...... I --

..... _---;--_--- _---_ I-_ i._ !_. I. I _+.__I ..... I __[_

+ + t + i + ti / 1 + / _ t

-----! _" -_---'1 - -_--l- - _-- ....... 7 .... -f-- ..... __+_+.+__ _ _+_._+____ _ t +__+:[__+<fi--++_+ [__

-- ' .... - + - +-- L _ ._ +.L ..... L _

_++_, + ....+

' 1 l, I I l_.J___........ Ii,ii.... 1 1 _ +i

i .I ! I _ __2II__L__I -1 I_

.....l....L.+I__.J !. + .1++._l++L-...._j--!- +....!....j j.

Time (0.1 sec per Iine)--

(b)Transient overboard bypassflowarea, Aby' t, 86.7 squarecentimeters.

Figure 22. - Concluded.

Diffuser static pressure, D6

(0.195P/Po per line)

Stability-bypass-plenum total

pressure, D7 (0.195 P/Po

per line)

Poppet-valveposition(0.564

cmper line)

Overboard-bypass-doorarea

variation, Aby (37.9 cm2

per line)

Centerbodytranslation, Xcb

(1.82 cmper line)

53
Inlet throat staticpressure

(0.195 PCPoper line):

D]

D2

D3

D4

D5

Diffuser staticpressure, D6

(O.lg5 I_Po per line)

Stability-bypass-plenum total

pressure, D7(0.195 PlPo

per line)

Poppet-valveposition (open)

Overboard-bypass-door area

variation, Aby (37.g cm2

per line)

Centerbodytranslation, Xcb

(1.82 cmper line)

Time (0.1 sec per line)_

(a) Inlet response.

Figure 23. - Slow, manual reduction in overboardbypassarea to inlet unstart with small, fixed exit as stability-bypassbleedcontrol and large stabilitybypassplenum. Free-streamMach number. MO, 2._ correctedengine speed,

NIN° V_. O.848;.total-pressure recovery, P2/Po. 0.907; mass-flow ratio, m2/mo, 0.844; prlmary-nozzle area, A8,

O.064"/square meter.

54
I_ LL--LL£

 ng,°e i i ,..... ' '----I

variation, N (1090rpm ,li.___ .1 ] __ ,'___I__ L.__J__- _ I_ _I ]_ _ ff_,,_

..... L F_ " r..... :___. _- _=_'=_ '

f

Turbine llOSoexit C per tmperature,Ts line) _[._,!i_ _ ...... ..... +..... _ [-_--I I -[---- ---J --'---'*"'

Power lever angle, PI.,4 __.I - ]_ ............. -L__

114._ per line) __: ---: :=<: -.-=_ .m._._.-_:=-_=_=.,J_..==-_+.._-. ___=_.__i__._.:_ :-.....

! _ _ _ Ti"T ! 1-_- --J'- --

t41"Icm_perline) -- -- ____:_.__L ______.._::__V. _W_L

' I 1

Compressor-facestaticpres- _-_, J , ........ _-[_-- n_.____--2 4'

sure, D8(0.195 P/Po per ,,,,,,,.i, _ ._L..... "_* ---=---_ ..... +--

line) -- _ _ i - =:;--- ---+'--_]--i- ......

Compressor-face total pres- i_,mikm_- _L-L_ -'_'_._-_=:-_-'_"_:i-'-?_"-=:_\-_t:;-"t'-z: -i-.

sure, Dg (o.Ig5 P/Po per ....... ..........._ ....] ......x_ _--__

_-- I ]

line) , - ---]----p -? I "- " l t -

Compressorpressure ratio, _-----_----+ .L--l+-i ...... ---_C _ L ] _i__

CPR(I'' P_P2 perline)_ __-_-----, _---__._--____.._ _ ,,

Inlet unstart sensor i ; _ - - y . -_ , _

" 'i _ _ .... t I I ! . ' I

.... _ - L ' t .

i'fl " .I i _ ! : _ _. I I ]l [ t ±-'

Time (O.Isecperline)_

(blEngineresponse.

Figure 23. - Concluded.

55
Inlet throat staticpressure

(0.195 P/Po per line)

ZZ ....... =.......... I ...... 7 ........

Z S 7£_

..... ,7_:_TTU.... !-t ....

- --I--_ ..... " _________' _ ..... " .... I --1- i -_ i ......... T _-_--1 _ ""

lime {0.1se_perIine)_

{a}InleIresponse.

FigureZ4.- Slow.manualreductioninoverboardbypassareatoinletunstartwithsmall,fixedexitasstabilitybypass-bleedcontroland smallstability bypassplenum-forcorrectedenginespeedN/N*_ of0.82Zand

primary-nozzlearea A8 of0.06?4squaremeter.Free-streamMach number,M0, 2.5;total-pressure recovery,P2/P0, 0.907; mass-flow ratio, mL_mO. O.836.

Diffuser static pressure, D6

(0.195 IEP0 per line)

Stability-bypass-plenu m total

pressure, 07 (0.195 P/Po

per line)

Poppet-valveposition (closed)

Overboard-bypass-doorarea

variation, Aby {37.9 cm2

per line)

Centerbodytranslation, Xcb

{1.82 cm per line)

56
Enginemechanicalspeed

variation, N (1090rpm

per line)

Combustor flame sensor

Combustorspark source

Turbine exittemperature,

T5 (108o C per line)

Powerlever angle, PLA

(14.3° per line)

Primary-nozzle area, A8

(41.1 cm2 per line)

Compressor-facestaticpressure, D8 (0.]95 P/Po per

line)

Compressor-facetotal pressure, D9 (0.195 P/Po per

line)

Compressorpressureratio,

CPR (I.08 P3/P2 perline)

Inlet unstart sensor

I 1 ' ' F _ -i i !

Zt CC _--- } " 'J 'I

_ __,---,jF_hk_ , ,! !

_ L__L_Li__L__

I I i ,,

_-d--_rc---tJ ] ! ;_T-I--

----_ _-....

. , ,-£7F- _L __J.---- !

-- ..............i tl____J__L t i _-i ....

_I_ --_ _- -- : -I---_ -_ _ _--

_ 1__ __ L 1_ j L .L_J/ T--

Time (0.] sec per line)-----,-

(b) Engine response.

Figure 24. - Concluded.

57
Inlet throat staticpressure

(0.195 _Po perline):.

D1

D2

D3

D4

Overboard-bypass-door area =

variation, boy (37.9 cm2

per line) ,I I "

Centerbody translation, Xcb __

(1.82 cmper line) _'- "i _ --_

Time(0.1 sec per line)_

(a) Inlet response.

Figure 2.5. - Slow. manual reduction in overboard bypassarea to inlet unstart with small, fixed exitas stability-bypassbleedcontroland small stability bypassplenum - for corrected engine speed NIN° vrB of O.844 andprimary-nozzle

area A8 of 0,0727 square meter. Free-stream Mach number. MO, 2.5;, total-pressure recovery. P2/Po, 0.904;,massflow ratio, m2/mO, 0.836.

58
Engine mechanicalspeed

variation, N 11090rpm

per line)

Combustorflame sensor

Combustorsparksource

Turbine exittemperature,

T5 (108o C per line)

Powerlever angle, PLA

(14.3° per line)

Primary-nozzle area, A8

(41.1 cm2 per line)

Compressor-face static pressure, D8(0.195 P/Po per

line)

Compressor-face total pressure, D9(0.195 P/P0 per

line)

Compressorpressure ratio,

CPR (1.08 P_P2 per line)

Inlet unstart sensor

r I ] ] [ ] [ ] L L.__L _k L ]__

___$____,I-E__L]:LZL_-_ -L_L. L- L. _

-- I I t I i A / t _I I t

i . L _I_ _---t ......... L ......

I.-< 1---I.....7-: ....

--- l I 1 I L L / i z .

- L [ 7 _''*--- r _--7_--_ ......t-f I -- ] I - -

: ' f I ,_ i t i _-- -_---F- t I 1 _-- , 'i I, _ _/_[__!__-7,_

_ ! .... __

1 - I i-:-,L-_U4 --;I: - 7__; '_ -' i:-::P:" _=_-]---_---4 -

_f ! ___J___J___J_L __L--! -i--_ J _ _ .1_

--: --T-_-_---_. _--_-W-t---_ = ........ • ..... _:-

ttl .I " J : I _ _. i "+ _-- I t 7_ ] --/ I .L 1

- t I I t [ - ]_< ---_]-_ -_--- '_- -

' I 1 '1 f i i i _: ! . I I ii L---

;-=:"-:_-<'r:?: ?"-_-:i :<:_ - ....--'__i ....... r -t -:T...... , :"r, .....

- - _ :.- :" t<. °, t il t ',r'---- _ i / _ I

Time i0.1 sec per Iine)_

(bt Engineresponse.

Figure25. - Concluded.

59
Inlet throat staticpressure

(0.195 lYP0 per line):.

D1

D3

D4

Poppet-valveposition (0.%4

cmper line)

t

+-" I +. +,I 1 • + : ' +' '

t+,!,+I -: Overtx)ard-bypass-doorarea _ + , k... t; I _ +_ + _,, 1 .... i : _ .,. l . I

variation, Abv(37.Ycm2 _-+- _- _- q-- .- "T .... _ '_...... _ .... "_ ']

per line} -- l;. ] " _ _ 't _ I ' I [ { . : _-_ J 'J t ti

t I _ -" i" ! " ' + '

Centerbodytranslation,Xcb ! I ! ] ! i I ' . I I l t _' _ ] :

(]. 82 cmper linel

Time (0.1 secper line)--

(a) Inlet response.

Figure26. - Transient 10o reduction In powerleveranglewith poppetvalvesas stability-bypass-breedcontrol. Freestream Mach number, MO. 2. 5;,transient pulsefrequency, lIT, ! second']; correctedengine speed,NIN" l/e, 0,872;

total-pressure recovery, ]_2/P0, 0. 905;,mass-flow ratio, m2/mO. 0. 877; primary-nozzle area, A8, 0.0536square meter.

6O
Enginemechanical speed

variation, N (1090rpm

per line)

Combustorflame sensor

Combustorspark source

Turbine exittemperatu re.

T5 (108o Cper line)

Powerlever angle, PLA

(14.:_ per line)

Primary-nozzle area, A8

(41.1cm2 per line)

Compressor-face staticpressure. D8(0.195 IWP0 per

line)

Compressor-face total pressure, D9 (0.195pIP0 per

line)

Compressorpressure ratio,

CPR (1.08 P3/P2 per line)

Inlet unstart sensor

-_ ....... T---T--...... ; - "T-----T +--1---i--ri" _-T--T --_-+__

' 1 i , _ ! _ : i 1 I ; - : [ " I • 1-- t _ J _t_=-_

• ] - '- ........ -+- _ A " ' [ , S _ - -- ...... :'-=:

_ _ ............... _ i _ = ..... iii& J. i i I I [ -r" I "'_

+ _ ; _+--M- _ '_ ---a L + ,;( _!;,

--_---- ' + 1 ' ' -- +j ] • i '-, ' f *

--_ , i ' i F -

-q-- .... , .,---._

• __ $ ', I I, ,+

_ _ ....... + ; _,,_.

__ -. ---- _ ......... ___

!* L

E_ :

i

+

i :

i

Time (0.1secperline)--

(b)Engineresponse.

Figure26.- Concluded.

61
Inlet throat static pressure I i ', i ',

(0.195 _Po per line): : i

D1

....... J___l ..... !

__L__L____....L__l .....L__l_J.....J.....J....J...::4:-_:==----

I t i 1 t ,"_

Diffuser staticpressure, D6 I - ] _ --J---L-=-

{0.195 I_PO per line) J I" 1 i _ i i

pressure' lYPOper line) D' (0"195 -- -"t_---__'_ _--__-:"" --L_-_-_ _- Z :_-____;_- __._.-iL- -

i i

Poppet-valveposition -2- ._.;_ 71_-- -_---

(0.564cm per line) ,.'-i,..'_ :.,....

Overboard-bypass-doorarea _- -- I

variation, _v (37. 9 cruz ...... !

......... . , 2£ ......

perline)" _::L"-_--L"'f--Y::''':....I- 'i " "I i' _ I

(1.82 cm per line, _"_. :_1:_,__2: -. _........

Time IO.1 sec perline)--

(a) Inlet response.

Figure 27. - Transient 200 reduction in power lever anglewith poppetvalvesasstability-bypass-bleed control. Freestream Mach number, Me 2. _ transient pu se frequency, lIT, 1 second-_;correctedengine speed,NIN q'O,

0.871; total-pressure recovery, P2/PO, O.gO_,mass-flow ratio, m21mO. 0.877; primary-nozzlearea, A8. 0.0636

square meter.

62
Enginemechanical speed

variation, N (1090 rpm

per line)

Combustorflame sensor

Combustorspark source

Turbine exittemperature,

T5 (1080C per line)

Power leverangle, PLA

(14.3o per line)

Primary-nozzle area, A8

(41.1 cm_ per line)

Compressor-face static pressure, D8 (0.195 I_P0 per

line)

Compressor-facetotal pressure, I)9 (0.195 P/Po per

linel

Compressorpressure ratio,

CPR (1.08 P3/P2 perline)

Inlet unstart sensor

_±L_L__._J

Time (0.1 sec per line)_

(b)Engine response.

Figure27. - Concluded.

63
.6--

.5

.4

(3-

'_ .3

..9,o

J_

.2

.1

\\

r Inlet minimum-

""""_"-----........................ ,/' stable operation

\

\

\

\

,-Supercritical

\_ ,," bleed airflow

\

\

\

\

_Engine idle

\

\

\

Power-lever-angle variation

-- -- -- Performance envelope {distributed, porous configuration NF. ref. 1)

.... Poppet-valve performance curve {configuration I. ref. 5 - same as

configuration NF of ref. 1)

I I t i I I

.04 .08 .12 .16 .20 .24

Stability bypass mass-flow ratio, msblm 0

F!;Jre 28. - Stability-bypass-bleed performance with poppet-valve exit control for a reduction in power lever angle from match to engine

idle. Free-stream Mach number. M 0 2.5.

64
=-i \

\

,--Inlet minimum-

,' stable condition

/

,-Inlet minimum-

/ stable operation

Power-lever-angle variation

-- -- -- Performance envelope (distributed. porous

configuration NF, ref. 1)

\

\

\

\

\ _ Supercritical

bleed airflow

\

\

1 I ...... / I t J

.04 .08 .]2 .16 .20 .24

Stability bypass mass-flow ratio, msb/m 0

Figure 29. - Stability-bypass-bleed performance with small, fixed exit area for a reduction in power lever angle to inlet unstart. Freestream Mach number, M O. 2.5.

65
Inlet throat staticpressure

(0.195 #Po per line):

DI

D2

D3

D4

D5

Diffuser staticpressure. D6

(0.195 P/Po per line)

Stability-bypass-plenum total -

pressure, D7 (0.195 P/Po

per line)

Poppet-valveposition (open)

I

I

L J___ _

I;

/ i ', ' } / __L 4- __

Overb°ard-bypess-d°°r ar-ea 1--_ 1 J } ' -l---:. ._ L___.

variation (37 9cmz -- I 1. ] t- ' I---_ .....

per line)' Aby " '_ i : _ , - _.c__, _-

Cenferl_dytranslation, xcb __]_ J ___--___ __i_-. - _ ........ L.__ _ _'

(1.82cm per line, .______ ...... ,__ ,_r" : ,, _ ___d_:____ ,__=_____

L::i--1 :C4

Time(0.1 sec per line)_

(a) Inlet response.

Figure 30. - Slow, manual reduction in powerlever angle to inlet unstart from inlet minimum stable condition, with small,

fixed exitas stability-bypass-bleed control and large stability bypassplenum. Free-stream Mach number, MO 2. _ stability bypasstotal-pressure recovery, P_hlPn, 0.507; stability bypassmass-flow ratio, msb/mn. 0,032; corrected engine

speed,N/N* !/'0, 0.8403;,total-pressureYeco'very, P2JP0,0.938; mass-flow ratio, m2/mO 0.d_02;primary-nozzle area,

A8, O,0645square meter.

66
Enginemechanical speed

variation. N i]090 rpm

per line)

Combustorflame sensor

Combustor spark source

Turbine exittemperature,

T5 (108o C per line)

Power lever angle, PLA

114.3° per line)

Primary-rkozzle area. A8

(41.1 cm= perline)

Compressor-face static pressure. D8(0.195 PIP0 per

line)

Compressor-face total pressure, D9 (0.195 lYP0 per

line)

Compressor pressure ratio,

CPR (1.08 P_P2 per line)

Inlet unstart sensor

Time iO.1 sec perline)_

(b) Engine response.

Figure 30, - Concluded.

67
Inlet throat static pressure

(0.195 lYP0 per line):.

D]

D2

D3

D4

D5

Diffuser static pressure, DO

_0.195 P/P0 per line)

Stability-bypass-plenum total

pressure, D7 10.195 P_Po

per line)

Poppet-valve position (open]

Overboard-bypass-door area

variation, Aby (37. 9 cm 2

per line)

Cenierbody translation, Xcb

(1.8_ cm per line)

i

I

Time 10.1 sec per line)_

(a) Inlet response.

Figure 31. - Transient 10o reduction in power lever angle with small, fixed exit as stability-bypass-bleed control and large

stability bypass plenum. Free-stream Mach number, M 0, 2. _ transient pulse frequency, lIT, 1 seeond-1; corrected

engine speed, NIN" V"B, 0.872; total-pressure recovery, P2/P0, 0, 901; mass-flow ratio, m2/m 0, 0. 904; primary-nozzle

area, A8, 0.0635 square meter.

68
Engine mechanical speed

variation, N (1090rpm

per line)

Combustor flame sensor

Combustor sparksource

Turbin e exit temperatu re,

T5 (108o C per line)

Powerlever angle, PLA

(14.3o per line)

Primary-nozzle area, A8

(41.1 cm( per line)

Compressor-face static pressure, D8 10.195 P/Po per

line)

compressor-facetotal pressure. D9 (0.195 P/Po per

line)

Compressor pressure ratio,

CPR i]..08 P3/P2 per line)

Inlet unstart sensor

_ l __3__L _L___

Time tO.1 sec per line)_

(b} Engine response.

Figure 3t. - Concluded.

69
Inlet throat staticpressure

(0.195 P/Po perline):

D!

D2

D3

D4

D5

Diffuser static pressure, D6

{0.195 P/Po per line)

Stability-bypass-plenumtotal

pressure, D7 i0.195 ptP0

per line)

Poppet-valve position(0.554

cm per line)

Overboard-bypass-doorarea

variation, Aby 137.gcm 2

per line)

Centerbodytranslation, Xcb

(1.82 cm per line)

__..I_ .....

_---F--! ; 1 ' I l • _ :, 1 :[ - iJ ..... I'," ill i1

= !_ :...._ l _:L_7:-2--.. : ! " --! L:LT W t,:_RV_

Time(0.1 sec per line)_

la) Inlet response.

Figure 32. - Transient reduction in primary-nozzle areawith poppetvalves as stability-bypass-bleed control. Freestream Bach number, M0, 2. 5;, transient primary-nozzlearea, AS.t, 129square centimeters; transient pulse

frequency, ],It, 1 second-I; corrected engine speed.N/N* Y"0,0.8/'4;, total-pressure recovery, P2/P0, 0. 903;,

mass-flow ratio, m2/mly 0.879;, primary-nozzle area, A8, 0.0637square meter.

7O
Engine mechanical speed

variation, N tlOgOrpm

per line)

Combustor flame sensor

Combustor spark source

Turbine exittemperature.

T5 {10_° C per line)

Powerlever angle. PLA

i14,3o per line)

Prlmary-r_ozzle area, A8

(41.1 cm_ per line)

Compressor-facestaticpressure, D8 (0.195 ptP0 per

line)

Compressor-facetotal pressure, D9 t0.195 P/Po per

Fine)

Compressor pressure ratio,

CPR (1.08 P3tP2 per line)

inlet unstart sensor

;_ L ]'!. - _ ._ , I! ii :- - 7 r "!

• i

Time (0.1 sec per Iine)_

_) Engine response.

Figure _. - Concluded.

71
Inlet throat static pressure

(0.195 P/Po per line):

D1

D2

D3

D4

D5

Diffuser static pressure, D6

(0.195 #Po per line)

Siability-bypass-plen um total

pressure,D1 (0.]95P(Po

per line)

Poppet-valveposition (0.564

cm per line)

Overboard-bypass-doorarea

variation, Aby (37.9 cm2

per line)

. J

I

Centerbodytranslation, Xcb ..... _: . .

(1.82 cm per line)

Time (0.1 sec per line)

(a} Inlet response.

Figure 33. - Compressor stall induced by stow, manual reduction in primary-nozzle area. with poppetvalvesas stabilitybypass-bleedcontrol. Free-stream Math number, M0,2.5;, corrected engine speed,N/N° V"e. 0.901; total-pressure

recovery, P2/P0, 0.901; mass-flow ratio, m2/m0. 0.8_6; primary-nozzle area, AS, 0.0553square meter.

72
Engine mechanical speed

variation, N (1090 rpm

per line)

Combustorflamesensor

Combustor sparksource

Turbine exit temperature,

T5 t108° C per line)

r -L , , . f. ,, . _. r_, :]. ,,_ --- -J-_--.,------'---L-------.... -"4--,,_--.

[.' :- f ] _ 1 , _ t t t i , , ,

" i i ' I r t i

_ i : i : ! + +-.

" ', 4 _- _ i !- _ i " ' "--,_ _

;'-"' =t ! --LI : .....

hi, .LI1 i ld _lllli_t'- .,. ' ! * _ ..

,' I r- . ]-_L

Powerlever angle, PLA

(14.3o per line)

Primary-nozzle area, A8

t41.1 cm2 per line)

Compressor-face static pressure, D8 (0.195 P/Po per

line)

Compressor-face total pressure, D? (0.195 P/Po per

line)

Compressor pressure ratio,

CPR 11.08 P_IP2 per line)

Inlet unstart sensor

(b) Engine response.

Figure 33. - Concluded.

73
(3-

E

=

tL

Bo

¢D

Nominal

Corrected engine undistorted

speed, in_

(NfN* _-8)x}00,

percen|

O 87.7

-- O gO.I

/_- Maximu m, steady-state

_l_#ompressor performance

-- q)

I I I I

14 15 16 17 18

Correded airflow, Wcorr, kglsec

Figure 34. - Compressor performance with poppet valves as stability-bypass-bleed control.

Free-stream Mach number, M O, 2. 5.

74
Inlet throat static pressure

(0.195 P/P0 per line):

D1

D2

D3

D4

D5

Diffuser static pressure, D6

(0.195 P/Po per line}

Stability-bypass-plenum total

pressure, D7 {0.195 PlPo

per line)

Poppet-valve position (open)

I ...................

......... T-_ I .............................

Overboar d-bypa ss-cloor area

variation, Aby {37.9 cm 2

per line)

Centerbody translation, Xcb

(1.82 cm per line)

I 1. I _

Time {0.1 sec per line)_

la) Inlet response.

Figure 35. - Compressor stall induced by slow, manual reduction in primary-nozzle area, with small, fixed exit as

stability-bypass-bleed control and large stability bypass plenum. Free-stream Mach number, M0. 2. _ corrected

engine speed, NIN" ,,/8, 0.896; total-pressure recovery, P2/Po, 0.904; mass-flow ratio, m2JmO, 0,891; primarynozzle area, A8. 0.0544 square meter.

75
Engine mechanical speed

variation, N(1090 rpm

per line)

_°

t

f

Combustor flame sensor

Combustor spark source

- • I "

Turbin e exit temperature,

T5 t108° C per line)

Powerlever angle, PLA

(14.30 per line)

Prlmary-r_ozzle area, A8

141.i cm" per line)

÷

Compressor-facestatic pres- .----.- _. _- --_ ! ._. -- = _-:_....... -- :..:=- _ . _,-_ -: _-:- -. . :.:-_

sure, D8 (0.195 PlPn per ....... _-_-:---_-_

line) v _ .... j___ __: ___ ,. _ _._ :

Compressor-face total pres- -- __| ,---"'---"-'--C-- _

sure _,. ,n ln5 ./p -^r _.,._,_,,_u,..,J,_,_,_.,_._.._,.._ j _. _--. _,_.,,_.__

line) " =_'_......... ! "" ...... _ _-l_,mR,_.__m,_. , . ; , ,

Compressor pressure ratio, "-'c"'--_ _;::_'_--"-_-_'"_-_-i - _ i i_' -,I_F_-- _,_

CPR (1.08 P3/P2 per line)"__ ! ! _,._-_.., ......... ,_'-_:...j i..... [ _i___! _-_

! I '- _,l i ' -

Inlet unstart sensor _' i _ _ I_'_ i , £ , ,_

i i i-i _'L _...._ , _ i i _ ! I i i

Time tO.l sec per line)_

(b) Engine response.

Figure 35. - Concluded.

76
E"

o7

Nominal /

Corrected engine undistorted- ./

speed,

iNIN_ _}xlO0, in

percent

-- 0 87.2

0 89.8

/.,./_ [3 []

0 0 __ _ '_ 0 []

0 0 0 _Maximum steady-stale

0 compressor performance

-- 0

0

] 1 1 J

14 15 16 17 18

Corrected airflow, Wcorr, kglsec

Figure 36. - Compressor performance with small, fixed exit as stability-bypass-bleed conlrol

and large stability bypassplenum. Free-stream Mach number, MO, 2.5.

'7'7
Inlet throat static pressure

(0.195 P/Po per line):

D1

D2

D3

D4

D5

Diffuser staticpressure, DO

(0.195 P/Po per line)

----i--'--'-_---_--- /i'--_ - _-----_ .....- ......._ ........................... :

-¢----.-L-----'_- -- L ................ _.................

i _; ................ J

i

J ! _ _ ' I , t.

-f

....... --._ -- _-.:=-_-Tj .... L--_-- ----__:

q

-- -- "7 r .... _-

i

Stability-bypass-plenumtotal

pressure, D7 (0.195 P/Po

per line)

Poppet-valveposition (0.554

cm perline)

Gust-plateangle, afp

Overboard-bypassdoor area

variation, Aby (37.9 cm2

per line)

Centerbodytranslation, Xcb

(1.82 cmper line)

Time (0.1 sec per line)_

(a)Transient flat gust-plate angle, afp,t, 1.0°.

Figure37. - External airflow transients induced by flat gust plate, with poppetvalvesas stability-bypass-bleedcontrol.

Free-streamMach number, MO, 2. _, transient pulse frequency, l/'r, 10seconds'l; correctedengine speed,

N/N° 1/'0, 0.873;,total-pressure recovery, P2/P0, 0.(X)I; mass-flow ratio, m2/mO, 0.903;, primary-nozzle area, A8,

0.0639 square meter.

78
Inlet throat static pressure

10.195 P/Po perline):

DI

D2

D3

D4

D5

Diffuser staticpressure. D6

10.195 lgP0 perline)

Stability-bypass-plen um total

pressure. D1 (0.195P_Po

per line)

Poppet-valveposition (0.564

cm per line)

Gust-plate angle, afp

Overboard-bypass-door area

variation, Aby t37.9 cm2

per line)

Centerbodytranslation, Xcb

(1.82 cm per line)

I

Time (0.1 sec per line)

_) Transient flat gust-plate angle, afp, t, 1.2°.

Figure 37. - Concluded.

/

"/9
Inlet throat staticpressure

(0.195 IEP0 per line}

D1

::- :_:_..:I...'" I i ........ __ ___J -

" :-I": } ;.::. _I • ____L_ __

. ! _- Ii  ̧ J._:

='=-' ]l: 'L-. I ....

• t

• ,_, , j __'- ......

D2 !

D4 ,

D5 ..,;, ..._ L I ....

...._................... - L.... -:/N2..2-_I.7T_,=._C_

Diffuser static pressure, 06

10.195 P/Po per line)

Stability-bypass-plenum total

pressure. D? tO.lg5 PIP0

per line)

Poppet-valveposition (open)

Gust-plate angle, afp

Overboard-bypass-doorarea

variation, Aby (3Z.g cmz

per line)

Centerbodytranslation, Xcb

_1.8'2cm per line)

T_me(0.1 sec per line)_

Ca)Inlet response.

Ficjure 38. - External airflow transient induced by flat gust plate, with small, fixed exit as stability-bypass-bleed control

and large stability bypassplenum - transien| flat-gust plateangle, g'n b 1.0.o Free-streamMach number, Mn. 2.5;,

transient pulse frequency, lit, 10 seconds ; corrected engine speec'i,N/N V"0, 0. 871; total-pressure recovery,

P2/Po, 0._3;, mass-flow ratio, m2_mO. 0.g_. primary-nozzle area, A& 0.063g square meter.

8O
Engine mechanical speed

variation, N (1090rpm

per line)

C , t ! !| J " ;

, : i i I

Combustor flame sensor --i_--]--_-L--_-- .. I ! i--[__. _T_,_,F-'. ---i- ---

' , -- r 2

Turbine exit temperature. _ i___"C_2._. ________2_ ............. , .... 2-. ..... i._-_.___...... _ :

$5 (108° C per line' _-_...... JZ-_Z;_-_--_ t___ ....................... __, . _-_-_--L-"_-'- ' _r _-1 ........ i ':_'-:_...... _'_ _ -

/ -- _ _ T-- --i--= l I i J : ; '_r T

Powerlever angle, PLA J _L '. S-:-:t_.l I I .1_ i l i t_ I _-_

(14.3°per line) _J, f_C__.2__:__L_L 'C ' !:_ i - i'-":

,, ! r

Primary-nozzlearea, A8 .__j ..... .=_;_.... i-d ! __.!__t._ ': .---_----F- ,_ -

(41.1 cm2 per line) .........................................................

i _ i.... I t I 1 L I ! '

compressor-face static pres- . ] , t : i ,, _ _

sure, D8 (0.195 P/Po per _ _ _ -- , _, ,,,r,t,, t , i

,ine) , _:t.....

Compressor-facetotal pres- , , , j ! I !- _i----,_ = ]_ ] i T--_-"-[ -

sure, D9 (0.195 P/Po per .....T-.,.i_.-__.,_,J..._._-,_,_.t_l -l_ t---_ .......

Compressor pressure ratio, _ _ _ ___ _ _[__1"_ _ , ;

CPR (1.08 P_/P2 per line) ............. _L.

Time (0.1 secper line)_

_))Engine response.

Figure 38. - Concluded.

81
Inlet throat static pressure

(0.195 P/Po per line):

DI

D2

:____ Z--:-____---L_L: .......... ..... ._: ..............

D3

D4 __

D5

Diffuser static pressure, D6

(0.195P/Po per line) i

Stabilibj-bypass-plenum total

pressure, D7 (0.195 P/Po

per line)

Poppet-valveposition fopen)

Flat-gust-plateangle, afp

_____ [. .....

Overboard-bypass-doorarea

variation, (37.gcm2 -........

Centerbodytranslation,xcb i_T -_ ' J | /----l"_-t.___ 3L_._____. {1.82cm per line) _ .l J .i]!._._l J ;."%

Time(0.l secper Iine)_

(a) Inlet response.

Figure 39. - External airflowtransient induced by flat gust plate, with small, fixed exit as stability-bypass-bleed control

and arge stabilityypabss plenum - transient flat-gust-plateangle., afn,,."t I. 20 Free-streamMach number, Mn, 2.

transient pulsefrequency, ]H, 10seconds-]; correctedenginespeed',NIN vr8, 0. 871; total-pressurerecovery,

PL;,/P0,0.903;,mass-flow ratio, m2/m0, 0.90;. primary-nozzle area, A8, 0.0639square meter.

82
Engine mechanical speed

variation, N (lOgOrpm

per line)

(b)Engine response,

Figure 39. -Concluded.

83
Inlet throat static pressure i_ --]---]--}_--_---;

(0.195 P/Po per line): _--_-_-i]--_ i--t-'_7_ ....

-V.....

D2 /-- __-L- >__.L_ .

i

I

D4 _-_=:J

1 :...... 1....7.-7-

Diffuser staticpressure D6-_----_ I, I I I-_T ..... _-+---] _--1-I-_

(0.195 IYP0 per line) _A L |__ f*--_--t _--4, ]_ ! |

- .....

Stability-bypass-plenum ._ ....... .._7 _ L.__

total pressure, DI (0.195 . " - -]_ -t

P/P0 per line) _ -......... i-" _%_ _ -, -- ---_ .....

Poppet-valveposition -__7--_i_.i-}i___-_ __{i_ ..... -..... . 2 ___ ....... .- . _-_E_. --_

(0.564cm per line) I_( I 7 - [--LT_ _l_ _L_L__J_ __I_-;]_17L-___.-I---_

Fat ust ateane o° _-4--i- L _ _L. _j_ T-! ._,_\_,7:-7._1.7_._-i-I_ _i

area variation. Ab, (37.9 ..... i..... ...... [ .....__--L.............. g"__ ! _L t g--

cm2 per line) " =--_" _'_ -Z--3 ....... ] .7l -_ :_'---:'_l_i

Centerbodytranslation, - _-- .... _-t-:_>--_-._.] --t_ 7_--__-___

Xcbd.82cm per line, .... [..... L......... L.._.[__.__[.-.... _-._-_-S_:7-_,.-?_. L .._

Time(0.I sec per line)_

(a) Inlet response.

Figure 40. - External airflow transient induced by fiat gust plate, with poppetvalves as stability-bypass-bleed-control -

transient flat-gust-plate angle, OlDt i. 4°. Free-stream IVlachnumber, MO, 2. 5;, transient pulse frequency, I/'r,

i0 seconds-l; corrected engine s_ecl, N/N* 1,fe,0.873;, total-pressure recovery, P2/P0, 0.901; mass-flow ratio,

m2/m0, 0. 90_ primary-nozzle area, A8, 0.0639square meter.

....... # -I--

._ ______+ _1

84
Engine mechanicalspeed

variation, N i1090rpm

per line)

Combustorflame sensor

Combustor spark source

Turbine exittemperature,

T5 (10_ C per line)

Power lever angle, PLA

(14.3o per line)

Primary-nozzle area, A8

(41.1 cm" perline)

Compressor-face static pressure, DStO.195 P/Po per

line)

Compressor-face total pressure, D9 (0.195 P/Po per

line)

Compressor pressure ratio,

CPR(1.08P_/P2 per line)

Inlet unstart sensor

I

Time (0.1 sec per line)--

(b)Engine response.

Figure 40. - Concluded.

85
Inlet throat staticpressure .--

{0.195 P/Po per line):

DI

D2

D3

D4

D5

Diffuserstaticpressure. D6

10.195 P/Po per line)

Stability-bypass-plenum

total pressure. D7(0.195

P/Po per line)

Poppet-valveposition

(0.564cm per line)

Flat-gust-plateangle, (Ifp

Overboard-b,

variation. Aby (37.9cm2 __

per line)

Centerbody translation,

(1.8'2cm per line)

.... , i i _ ........... __________ _

I_ 4-4

_ ..L.__¢__

Time {0.Isecper linel--

(a) Inlet response.

Figure 41. - Slow. manual change in flat-gust-plate angle of attack to inlet unstart, with _ppet valves as stabilitybypass-bleedcontrol. Free-stream Mach number. M0, 2.5. corrected engine speed,NIN _r_, 0. 873;.totalpressure recovery, P2_P0, 0 901; mass-f ow ratio, m_m0, 0.913; primary-nozzlearea, A8, 0.0805 square meter.

86
Engine mechanical speed

variation. N (1090rpm

per line)

Combustor flame sensor

Combustor spark source

Turbine exit temperature,

T5 q108° C per line)

Powerlever angle, PLA

(14.3° per line)

Primary-n,,ozzlearea, A8

(41.1 cm" per line)

Compressor-facestatic pressure. D8i0.195 P/P0 per

line)

Compressor-face total pressure, D9 (0.195 P/P0 per

line)

Compressor pressure ratio,

CPR (1.08 P3/P2 per line)

Inlet unstart sensor

I

i, .... -] ......... ,_............ _;.-

i '

'-_ _.:-"_-..I"_-L __Zl l-,.]!.iL-_--._.. _ i ;,_[ r'! t -I ,i '

_- . ' _ I _d_ I I 1

Time {0.] secper line)-

(b)Engine response.

Figure41. - Concluded.

8'7
Inlet throat stahc pressure _,,?,_CL_-u_.,.+FI._ - _:_,_I_+:_._-_!_P 7t ,. _i' LI. i ,I--_=F _-F_ ] _:

i0.195 pIP0 per line): _L_I_'T'_-_-_-..F_,.: _-- I..-:+_ :_] lu. i 'I" ii I _ " , • ' _ -

o1:-_"!q_:;.:_: ! _J± T-I ..i A _ I I i

_kL-±_l i _ i _I I .... -T---

_;i_: li J :' ',, i! i k '_._i _h-L..._.i,._I _ i I I l i -

L_'+_+y_' I t_f.t+ i ! ' .7 ', ; -_-_ . , ,_---.- -_<' +':'+ _' _ .++U I i i_'_': _ '-_--

-_._.!:,i t ::.: [ i i + I I _--_----

D3

":_ _ _,, _ , , , _----- , I _ _ ,

,. I .i -t....I I t, • __+._ + ', !___t_+_i____

.... " - +-+-+ , " + '_. ' , , , -, r

• " " " } t I

.+,+ +- J.+,.+.+ ,+I _t I,, ., .... " -

_+:t J+',+._,_+:.'.4-,,._ +,.:"L' +--_j' , i" :L_ l_ l'+. l:_i -'-I-'--P'--

D5_.':-i+_b+,++F_:':_+ "I : _ t'-. f'...' -i_"_+ I' i " ,- '_r '_ "- +:i+',+m++.,+.++1 .l •-::E- +-,_'_+, _1",{ ! +:i. I + . + ,_-l-

_,_PL_f'I._..+_._I+-+":L _ ' 3k_ _ ;!.+'.I +.+J_::_f:-I" I :I I i I I [

Diffuserstaticpressure. D6

i0.195 P/P0 per line)

Stability-bypass-plenu m

total pressure, D7 tO. 195

P/P0 per line} ........ _- ..... -'--'--'_ ---- -------- - - - _;

Poppet-valve position Iopen) .............. _ ---

Flat-gust-plateangle. C(fp _-,,, , , ,, ._._e_--._---+-_+_;-_---.-:.+_-,_<_e-:--+- _-_-.--.-:-_

Overboard-bypass-door area : --

variation. Ab,, 137.Qcm 2 - - ' _

Centerbo_ translation, Xcb _+ ++:_'--- -----_- _ - _______

(1. 82 cm per line) +__ _'.... i ............ _ ' "_

Time tO.] sec per line)--

ta) Inlet response.

Figure 42. - Slow, manual change in flat-gust-plate angle of attack to inlet unstart with small, fixed exit as stabilitybypass-bleed control and large stability bypass plenum. Free-stream Mach number, M o, 2. _ corrected engine

speed, NIN _ I/'8, 0.872; total-pressure recovery, P2/P0, 0.901; mass-flow ratio, m2/m0, 0.901; primary-nozzle

area, A8, 0.0656 square meter.

88
Engine mechanical speed

variation, N (I090 rpm

per line)

Combustor flame sensor

Ib) Engine response.

Figure 42. - Concluded.

89
Inlet throat static pressure

[0,195 lYPo per line):

D1

Diffuser static pressure, D6

(0.195 P/Po per line)

Stability-bypass-plenum total

pressure, D7 i0.195 PlPo

per line)

Poppet-valve position (open)

Flat-gust-plate angle, _fp

Overboard-bypass-doorarea

variation, Abv (37,9 cm2

per line) "

Centerbodytranslation, Xcb

(1.82 cm per line)

Time i0.1 secper line)-----

ta) Inlet response.

Figure 4_. - Compressor stall and combustor blowout caused by slow, manualchange in flat-gust-plate angle of attack to

inlet unstart, with small, fixed exit as stability-bypass-bleed control and large stability bypassplenum. Free-stream

Mach number. MO. 2.5;, corrected engine speed,N/N=V% 0.87]; total-pressure recovery, P2/Po, 0.905 mass-flow

ratio, m2/mO, O.904_primary-nozzlearea, A8, O.064_squaremeter.

9O
Engine mechanicalspeed

variation, N (1090rpm

perline)

Combustorflame sensor

........................................... T---

; .; ; -- '- - I. =.: - -;--J'-

p il

Combustorspark source

Turbine exit temperature,

T5 (1080C per line)

Powerlever angle, PLA

(14.3o per line)

Prlmary-rl,ozzlearea, A8

(41.1 cm" per line)

.... ,...... ! . .- ,,,.j ..... :____ ].._.j_,._j .... i :__.,_ .... =_..... j .... i ..... J..... : .... : .... J ..... : ....

- " [ .......... r .... i r . q. . ,, r- i ; - -

Compressor-facestatic pres- _,: I .i - ' '

sure,line) D8 (0.195 P/Po per ." _ "-. ..... ,.... ;-_-: __ ..... "..... :-- -_ ...... :'_

Compressor-face total pres- - ........ .,..., ....... _....... _r.t&;,. _,.._ ...................

sure, D9 (0.195 P/Po per i _ ! i : _ I,-_-._L_,.. ..... . _ " ;-

line) .' : . m t_,f= _ _ _'-.-_--_ :---.--_-- ' _

; ' ] . " ! ! .... LI i , ' , i ,

Compressorpressure ratio, _...._.._. : ' i _ _'__. L:._: . _1 ' " i --- ....

CPR (1.08 P3/P2 per line) __.,__ ........ .!

_ _ ] l [I -'t. t ,I f i i l l i __ ....

_It...L _ i ; i i ' I t ! ....

Inlet unstart sensor _ _ Z 1 _ I 7 _L,_. ! f"_i ! ; _-- .;'--------- .-_--

t,, _ _ '_1-"-_,_ i. i .......... _______

' 1 i + _ U i ' _ , :

Time (0.1 sec per line)--

_o)Engine response.

Figure 43. - Concluded.

91
Inlet throat staticpressure

(0.195 PlPo per line):.

D1 _=-

D2

}- ....

D3

D4

m

J

D5 .......... t±

Diffuser static pressure, D6 -- - --_

(0.195 PlPo per line)

Stability-bypass-plenum total ..............

pressure. D;' (0.195 P/Po ""_"

per line) ........

Poppet-wlve position_dosed)---I2:il ?_ 2_i

Flat-gust-plateangle, Ofp ,m,,_._-----_mm,,

Overboard-bypass-door area ___

variation, Aby(37.9 cm2 ........................

per line)

Centerbodytranslation. Xcb __.____j

11.82cm per line)

...... _" c'_ ' '__..__ _:

_L_....t.........I.....

Time (0.1 sec per line)_

ta)Inlet response.

Figure 44. - Slow, manual change in flat-gust-plate angle of attack to inlet unstart, with small, fixed exit as

stability-bypass-bleed control and small stability bypassplenum. Free-stream Mach number, M0. 2. 5;,

corrected engine speed,N/N" vrB, 0.873;,total-pressure recovery, P2/P0, 0,gO0; mass-flow ratio, m2/m0,

0. 910;.primary-nozzle area, A8, 0.08]2 square meter.

92
Engine mechanical speed

variation, N (]000 rpm

per line)

Combustor flame sensor

: L i

.... __2 7__-_1__C_- __I_LC.__ + _ I t t:_i t - "_i'_--+

]

Combustorsparksource

Turbine exit temperature,

T5 _108° C per line)

Power lever angle, PLA

114.3° per line)

Primary-nozzle area, A8

t41.1 cm2 per line)

Compressor-face static pressure, D8 tO.]g5 P/Po per

line)

Compressor-face total pressure, D9 t0.195 PfPo per

line)

Compressor pressure ratio,

CPR I].08 P3/P2 per line)

Inlet unstart sensor

I

V--P --_----_................... _ - -

.............. _ ....... _ .... ' F --

_.-_-__ ,____..... __L_ ,,

i L_._

TimetO.1 sec per Iine)_

_D)Engine response.

Figure 44. - Concluded.

93
.6

Inlet condition

C_ Started. supercritical

0 Started. match

C) Started. minimum stable

0 Unstarted

[]

0

A

,,3

Cowl-lip position

parameter,

et

25.27

24.30

23.28

22.82

22.63

------ Started-inlet stability bypassperformance envelope

_ .2-- \

\

\

\

.1

1 I I I I I

.04 .08 .12 .16 .20 .24

Stability bypassmass-flow ratio, msb/m0

Figure 45. - Inlet-stability bypasssystem performance for Started- and unstarted-inlet conditions. Free-stream Mach number, MO,2. 5.

94
Ratioof

overboardbypassarea

to inlet area.

Aby/Ai

0 0.1358

[] .16%

.1886

A •2124

-4 .2151

,'1 •2419

Conditions for_iled data points

Total-pressure Stability bypass Stability bypass

ratio, total-pressure mass-flow ratio.

P2/P0 ratio, msblmO

Psb/Po

O.721 0.453 0•0273

. 744 • 390 . 0257

.753 • 321 •0196

• 733 .292 .0189

L

,=-

+_

.1

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\\\\ \\ 'x_

\ \ \

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-\'_\ \ \ \

\ \ \

\ \\ \ \\

\ \ \ \\

\ \ \ \\

\ \ \ \\

\ \\

Inlet buzz

region

\

\

I I I t

.04 .08 ,12 .16

Stability bypassmass-flow ratio, msblmo

Figure 46. - Effect of varying over_ard--bypass area on stability bypassperformance of an unstarted inlet with centerbody at design position. Free-stream Mach number, MO, 2.4 cowllip position parameter. B_,,25.27.

95
/

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_IEEE

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£b

==

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2,

r;

_o

g

g

O

i

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g

96
.8

.7

o3

g-

.6

E

@

.5

r_

Inlet condition Cowl-lip Total-pressure Stability Stability

position ratio, bypasstotal- bypass

parameter, P2/P0 pressure mass-flow

e£ ratio, ratio,

PsblP0 msbfm0

£b Started, supercritical 25,27 0. 849 0, 301 0.0194

O Started, match | .902 .304 .0199

OO Started, Unstartedminimum stable 1 .943 .507 .0329 .725 .449 .0296

[] { 24.30 .743 .496 .0328

© 1 23.28 .772 .536 .0353 A 22,82 .778 .550 .0363

Q 22.63 .833 .585 .0388

.4--

.3 --

.2

2.6

/

I

//

IJ % _. \ /

I

j,-

1 I I

2.8 3.0 3.2 3.4 3.6 3.8

Axial distance from centerbody cone tip, xlRc, inlet radii

Figure 48. - Cowl surface static-pressure distributions for started- and unstarted-intet conditions. Free-stream Math

number, M0. 2.5.

I

4.0

97
E

8

o 0

_g

g,

12 14 16 18 20

Catcu_ated compressor-face corrected airflow, Wcorr.¢ f, kgfsec

Figure 49. - Compressor-Nee corrected airflow calibration.

I

22

98

1. Report No. 2. Government Accession No. 3, Recipient's Catalog No,

NASA TP-1531

4. Title and Subtitle DYNAMIC RESPONSE OF A MACH 2.5 AXISYMMETRIC INLET AND TURBOJET ENGINE WITH A POPPETVALVE-CONTROLLED INLET-STABILITY BYPASS SYSTEM

WHEN SUBJECTED TO INTERNAL AND EXTERNAL AIRFLOW

TRANSIENTS

7, Author(s)

Bobby W. Sanders

9. Performing Organization Name and Address

12.

15.

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135

Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546

Supplementary Notes

5. Report Date

January I980

6. Performing Organization Code

8. Performing Organization Report No

E-9467

_0. Work Urdt N'_.

505-04

11. Contract or Grant No,

13. Type of Report and=Period Covered

Technical Paper

14. Sponsoring Agency Code

16. Abstract

The throat of a Mach 2.5 inlet that was attached to a turbojet engine was fitted with a poppetvalve-controlled stability bypass system that was designed to provide a large, stable airflow

range. Propulsion system response and stability bypass performance were determined for

several transient airflow disturbances, both internal and external. Internal airflow disturbances

included reductions in overboard bypass airflow, power lever angle, and primary-nozzle area

as well as compressor stall. For reference, data are also included for a conventional, fixedexit bleed system. The poppet valves greatly increased inlet sfabiHty and had no adverse effects

on propulsion system performance. Limited unstarted-inlet bleed performance data are presented.

17. K"ey Words (Suggested by Autbor(s}J

Air intakes; Supersonic cruise inlets; Shock

stability; Inlet bleed; Turbojet engine; Stability bypass

18. Distribution Statement

Unclassified - unlimited

STAR Category 07

19. Security Classif. (of this report} 20. Security Classif. (of this page)

Unclassified Unclassified

" Forsale by theNationalTechnical InformationService,Springfield,Virginia 22161

21, No. of Pages

100

22. Price"

A05

NASA-Langley, 1980