RESEARCH MEMO-RAN DUM

I -._,*i (r -P Ii U G ' C c P 4 c 2 RESEARCH MEMO-RAN DUM PERFORMANCE OF AN ISENTROPIC, ALL-INTERNAL-CONTRACTION, -. AXISYMMETRIC INLET DESIGNED FOR MACH 2.5 By Dvid N. Bowditch nd Bernhrd H. Anderson Lewis Flight Propulsion Lbortory Clevelnd, Ohio._ - -.. - - JSTIONAL ADVISORY COMMITTEE WASHlNGTON Microfiche (MF) 'h@

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS RESEARCH MEMORANDUM PERFORMANCE OF AN ISENTROPIC, ALL-INTERNAL-CONTRACTION, -I c.?i AXISYMMETRIC INLET DESIGNED FOR MACH 2.5W By Dvid N. Bowditch nd Bernhrd H. Anderson SUMMARY An experimentl investigtion of n internl-contrction, xilly symmetric inlet with isentropic compression surfces on both the cowl nd centerbody ws conducted over rnge of Mch numbers from 2. to 2.7 t ngles of ttck from Oo to 6'. The study ws mde to determine the optiinum bleed system, together with method of controlling the inlet. At Mch 2.5, bleeding of bout.3 percent by mens of perfortions hed of the throt llowed 3-percent-lrger running contrction rtio thn could be obtined with no supersonic bleed nd permitted the centerbody to retrct to the design position. The best subsonic bleed system consisted of flush slots locted opposite ech other on the cowl nd -_--t-r~~+~ J O-- ;~-ct&~.r.~~ctyem pf +hp thrnnt. Ry hlppdinp. 13 nercent. with this system, pek recovery of.91ws obtined t Mch 2.5. Cowl sttic pressures hed of these slots ppered to be stisfctory for sensing the norml-shock position. However, the centerbody position would hve to be scheduled with Mch number, ngle of ttck, nd Reynolds number since no pressure signl ws found tht would permit prediction of criticl internl contrction. INTRODUCTION. Externl-compression inlets re cpble of efficient compression t Mch numbers bove 2., but the wve drg ssocited with the externl cowl tends to be high. One pproch to eliminte high cowl wve drg is to use ll-internl-compression-type inlets with low cowl ngles, such s in references 1 nd 2. The problems ssocited with the opertion of internl-compression inlets re numerous. To investigte some of these problems, the test t Ames lbortory of n internl-compression xisymmetric inlet ws extended in the Lewis 1- by 1-foot wind tunnel (refs. 3 nd 4). Of primry " Title, Unclssified

2 interest in this investigtion ws the effect of vrious bleed configurtions on the operting chrcteristics of the inlet, the effect of off-design opertion, nd the evlution of ' control prmeter for optimizing inlet performnce. SYMBOLS A A2 Ain Ath M P P c1p P flow re nnulr cowl-lip flow re inlet cpture re throt re Mch number totl pressure verge totl pressure difference between mximum nd minimum totl pressures t sttion sttic pres sure R cowl rdius t sttion 2 r Re rdil distnce from inlet centerline Reynolds number ngle of ttck Subscripts: free strem 1 cowl lip 2 inlet throt sttion t design centerbody position.i diffuser inlet 4 flow mesuring sttion 14 in. upstrem of choked re

.e e.. e.. e. e e... e.. e. e e. e. ** e.e e NACA. RM E58E16 e * 3 e. e * e. e.. e. e e e** e. APPARATUS AND PROCEWRE The inlet ws investigted in the 1- by 1-foot supersonic wind tunnel t Mch numbers of 1.99, 2.1, 2.2, 2-3, 2.4, 2.5, 2.59, nd 2.69 nd Reynolds numbers per foot of 2.5X16, 1.5X1O6, nd.64~1~. Angle of ttck ws vried frm ' to 6'. The theoreticl contour of the supersonic compression surfces of the inlet ws determined by using xilly symmetric chrcteristics. The flow ws ssumed to be Mch 2.5 in the free strem nd 1.2 t the throt. Previous experimentl tests of similr inlet hd indicted tht throt Mch number s low s 1.2 could not be obtined nd tht considerble boundry-lyer buildup occurred on the compression surfces. The throt re ws incresed to 113.2 percent of the theoreticl re to llow for these conditions. The re increse ws diminished with distnce upstrem of the throt nd becme zero t the spike tip nd cowl lip.. Two inlets differing only in supersonic diffuser length were designed by this method nd will herefter be clled the originl long inlet nd the short inlet. The longer inlet hd bout one third the mximum pressure grdient nd twice the length from cowl lip to throt of the short inlet. After testing the originl long inlet, enlrgement of the throt re n dditionl 2 percent by reducing the centerbody dimeter ws found to be desirble. The long inlet with the 2-percentlrger throt re shll herefter be clled the modified long inlet. A pl?-tf.t.p.>r.rrjew nf t.hp inlet. showin2 the sugersonic comyession surfces nd the optimum subsonic bleed locted in the intermedite section is presented in figure 1. The severl bleed configurtions tested included perforted bleed in the supersonic nd subsonic prts of the dif- fuser, nd flush slots t two loctions in the subsonic diffuser. The configurtions for which dt re presented re shown in figure 2. Figure 2() shows the bsic inlet with no bleed, while figure 2(b) shows the long nd short inlets with the constnt-mch-number section nd supersonic perforted bleed. The subsonic slots nd perfortions were lwys tested in combintion with pproximtely 1 percent bleed through supersonic cowl perfortions to the free strem, s shown in figures 2(c) nd (d). Also shown in figure 2 re the loctions of sttions 1, 2, nd 3 corresponding to the cowl lip, throt, nd diffuser exit. Sttion 4, the mss-flow mesuring sttion, is locted 14 inches hed of the choked exit. The rer prt of the model contined plugs for controlling the min flow s well s spike- nd cowl-bleed flows. The intermedite prt of the model in the region of the throt could be ssembled so tht either bleed slots, perforted bleed, constnt-mch-number section, or some

4 combintions of these could be included. The forwrd cowl-bleed slot, with the supersonic prt of the cowl nd spike removed, is shown in figure 3(), nd the three centerbody constnt-mch-number sections contining the forwrd nd rer slots nd perforted bleed re shown in figure 3(b). The inlet supersonic compression surfces of the cowl nd centerbody ttch to the front of the intermedite section, s shown in figure 1. Both the centerbody tip nd the cowl lip were roughened by grooves to try to induce erly trnsition. The bleed-slot dimensions re given in figure 4. The res of perf orted bleed consist of 1/8-inch-dimeter holes drilled perpendiculr to the inlet centerline. The holes were stggered from row to row (s seen in fig. 3(b)) with.188 inch between hole centers in ech row. The distnce between centerlines of two djcent circumferentil rows ws 3/16 inch. Perforted bleed could be locted nywhere in the region from 1.4 inches hed of the throt to 8. inches downstrem of the throt on the cowl nd 1 inches downstrem of the throt on the centerbody. The internl-flow re for vrious centerbody positions is given in figure 5 for the configurtions of primry interest. The coordintes for the short inlet nd the two long inlets re presented in tble I. These coordintes include the constnt-mch-number section between 1.2 nd 5.2 inches behind the throt. When the constnt-mch-number section ws not in use, the smll step on the centerbody indicted by the coordintes in tble I ws fired. "he inlet pressure recovery nd distortions were mesured t the diffuser exit (sttion 3) with 36 re-weighted totl-pressure tubes (in six rkes) nd six wll sttic-pressure orifices. Distortions were clculted by tking the difference between the mximum nd minimum totl pressures nd dividing by the verge. Sttic orifices were locted on the inner cowl surfce from 1.5 inches downstrem of the cowl lip to downstrem of the throt. The centerbody hd no pressure instrumenttion becuse of the difficulties imposed by the lrge trnsltion of the entire centerbody. The conditions t sttion 2 were mesured by eight totl-pressure tubes in rke nd three sttic-pressure orifices. Throt Mch numbers were clculted from the rtio of the verge totl pressure from the rke to the verge sttic pressure. The rkes t sttions 2 nd 3 nd the cowl orifices cn be seen in figure 1. Min-duct nd bleed-duct mss flows were clculted by using six sttic orifices locted t sttion 4 nd by ssuming isentropic onedimensionl flow between sttions 4 nd the known choked-dischrge re. The bleed-flow recoveries were mesured by two 19-tube re-weighted rkes, locted t sttion 4, in both the centerbody- nd cowl-bleed ducts.

. b m omm : m i m mm mmm mmm m m m m em m NACA RM E58E16 tm -.. 5 m m m. mo 4 Sttic-pressure vritions were obtined from three pressure trnsducers locted hed of the forwrd cowl-bleed slot nd one locted just behind the cowl slot. Signls from these trnsducers nd the exit-plug position were recorded on n opticl oscillogrph, while the plug ws opened from the pek-recovery position nd then closed until the inlet went subcriticl. Plug position nd inlet recovery were correlted so tht plot of pressure signl ginst recovery could be obtined. RESULTS AND DISCUSSION Generl Inlet Performnce The performnce of the short inlet ws poor becuse its centerbody could not be retrcted into the design position without subcriticl opertion up to free-strem Mch number of 2.7. With the inlet strted, mximum obtinble contrction remined pproximtely constnt from Mch 2.4 to 2.7, even though the corresponding llowble isentropic contrction incresed bout 3 percent. Throt-rke mesurements showed lrge low-energy-ir region on the spike, which indictes tht some kind of shock boundry-lyer interction ws lwys encountered t this minimum spike extension. The short inlet ws not investigted further becuse of this strting problem. The pek-pressure-recovery performnce of the long inlet is presented in figure 6. At Mch 2.5 with no bleed (open circles) the centerbody of the originl inlet could be retrcted to only.42 inlet dimezer he ui c& iiesiwl,+jfti~ii -;hilt AI.- "Lb -1-C ALA--" A vmninnil u..----- c+ct,r+ei( I --- I_ The ddition of smll mount of perforted bleed upstrem of the throt (solid circles) llowed the spike to be fully retrcted with the resulting increse in pressure recovery from.79 to.845. The best subsonic bleed configurtion (squres) further incresed the recovery to.91 nd decresed the distortion from.31 to.12. This configurtion obtined similr gins t Mch 2.6, but t Mch 2. it gve lower totl-pressure recovery thn the configurtion with no constnt-mch-number section in spite of the fct tht it hd no bleed. The better performnce is believed due to the better linement of the compression surfces t the mximum contrcted condition when no constnt-mch-number section ws included. Another fctor is tht the bleeds were not locted in the most effective re, the throt, when the centerbody ws extended bout 1.2 inlet dimeters for Mch 2 opertion.. With no subsonic bleed, the use of the constnt-mch-number section gve conflicting results. For exmple, the mximum obtinble recovery t design centerbody position ws incresed 1.5 percent by using the section t Mch 2.6, while it dropped 1 percent t Mch 2.5 (fig. 6). At Mch 2.5, configurtion with no constnt-mch-number section but

6 with two rows of perfortions on the centerbody opposite the forwrd cowl slot ws run to determine the effect of the constnt-mch-number section with good subsonic bleed, nd no mesurble effect ws observed. Bsed on these observtions, the constnt-mch-number section does not seem to pprecibly increse the recovery t Mch 2.5, nd the dditionl extension required by the section decresed the recovery t Mch 2.. Incresing the throt re 2 percent over tht of the originl inlet did not chnge the mximum obtinble contrction rtio (Ac/AT) of bout 2.2 with the inlet strted t Mch 2.5. A contrction rtio of 2.22 ws needed to retrct the spike of the modified inlet to the design position, however, so tht neither inlet could operte under strted conditions with the centerbody fully retrcted. When both long inlets were run in the design position with the ddition of perforted bleed hed of the throt, they both obtined the sme throt recoveries t pek-inlet-recovery conditions. The Mch number clculted t the throt t these conditions ws less for the modified inlet, even though its throt re ws 2 percent lrger. With the norml shock well downstrem, however, the throt Mch number of the modified inlet incresed until it ws higher thn tht of the originl inlet, which ws little ffected by shock position. It therefore ppers tht the terminl shock ffected the flow hed of the throt of the modified inlet in such mnner tht both inlets obtined essentilly the sme throt recovery. All further dt re for the modified long inlet unless otherwise indicted. * I-.. The inlet ws sensitive to centerbody position s shown in figure 6, where t Mch 2.5 n extension of.42 inlet dimeter cused loss of 2. to 3.5 counts in totl-pressure recovery. The corresponding chnge in contrction rtio (Ain/&) from 2.22 to 2.18 chnges the cl- culted recovery only l percent. Figure 7() presents comprison between the theoreticl (isentropic) pressure distribution nd the experimentl pressure distributions for the two points A nd B in figure 6. The design condition (point A) shows smooth inlet pressure distribution nd good greement with the theoreticl prediction. Off-design centerbody position (point B), however, cuses lrge vritions in pressure from the theoreticl curve, s shown in figure 7(). This poor pressurt distribution incresed the cowl boundry-lyer thickness t sttion 2, s illustrted by the totl-pressure profile in figure 7(b). The effect of ngle of ttck on pek pressure recovery is presented in figure 8. At zero ngle of ttck nd free-strem Mch number of 2.5, pressure recovery of 91 percent ws obtined. Incresing the ngle of ttck to 3' cused the recovery to drop to 88.8 per-. cent. The spike position for both these conditions ws the design position for Mch 2.5.

NACA RM E58E16 :.* :.............. 7 A similr trend existed t Mch 2., where pek pressure recovery decresed from 86 percent t zero ngle of ttck to 78.3 percent t 6 ngle of ttck. During the test, it ws observed tht the inlet remined supercriticl t the design contrction rtio (Ain/Ath = 2.22) up to n ngle of ttck of 4.75 t Mch 2.5, fter which the inlet becme subcriticl. The mximum contrction rtio tht could be obtined t 6 ngle of ttck ws 2.175, which corresponds to centerbody extension of.575 inlet dimeter hed of the design position. At Mch 2., n extension of.61 inlet dimeter from the minimum obtinble t = ws required to rech = 6O, s seen in figure 8. The effect of Reynolds number on the mximum obtinble contrction rtio is shown in figure 9. A decrese in Reynolds number from 2.5X1O6 to.64~16 per foot required centerbody extension of.6 inlet dimeter in order to mintin supercriticl flow. This is lrge centerbody trnsltion, but it represents chnge of only 3 percent in the contrction rtio. The Reynolds number chnge is much lrger thn would be encountered on n ctul ircrft during mximum flight speed, but it illustrtes tht it my be necessry to ccount for this effect. When the norml shock is regurgitted, lrge spike trnsltion nd n increse in irflow is required to strt the inlet. The strting contrction rtios (Az/Ath) for one of the configurtions tested re shown in figure 1. The mximum theoreticl contrction rtio bsed on free-sfrenm hhch niimher is shown for commrison. The bility of the inlet to strt with more contrction thn tht predicted by the freestrem Mch number is probbly due to the seprtion on the centerbody, s shown in figure ll(g). This seprtion spilled flow round the inlet cowl lip while the inlet ws unstrted, but disppered just s the inlet strted. Schlieren pictures of the inlet during the strting cycle t Mch 2.5 re given in figure 11. Figure ll() shows the inlet just fter the shock ws lost nd before the bck pressure ws reduced. Under these conditions the inlet obtins norml-shock recovery of bout.5 nd is unstble. The instbility, mes-wed with the spike in the design position just fter the shock ws lost, ws found to be rndom. Two sep.rte mesurements t the cowl-bleed slot indicted mplitudes of 3 nd 6 percent of the free-strem totl pressure. The flow ws intermittently stble, s in figures ll(c), (f), nd (g), nd unstble s shown by the wviness of the shock wves in figures ll(), (b), (d), nd (e) when the centerbody ws extended. The inlet went supercriticl t centerbody extension of 1.337 inlet dimeters, which ws indicted by the disppernce of the seprted flow region on the centerbody between figures ll(g) nd (h). The inlet in the running condition t Mch 2.5 is shown in figure ll(i).

Bleed Performnce Supersonic perforted bleed upstrem of the throt of only bout.3 percent of the cpture mss flow ws required to retrct the spike of the originl long inlet into the design position t Mch 2.5. The bleed thus llowed n increse in the contrction rtio of 3 percent nd therefore ccomplished wht 2-percent increse in throt re could not. Figure 12, which presents the performnce of the bleed systems tested, shows tht n increse bove this minimum mount of supersonic bleed hd little effect on the inlet pressure recovery. Sttic pressures in the throt region indicted tht dditionl supersonic bleed lso bdly distorted the flow. All subsonic slot nd perforted bleed configurtions tht could be retrcted into the design position bled pproximtely 1 percent hed of the throt to the free strem. In ddition to the supersonic bleed performnce, figure 12 lso presents the pek inlet recovery, bleed-flow recovery, nd inlet distortion s function of cowl- nd spike-bleed flow for the subsonic bleed configurtions. The most successful bleed system, consisting of the originl forwrd slots, obtined the highest inlet recovery with reltively low bleed flow. The inlet recovery incresed linerly with cowl-bleed flow from F3/Po =.847 until the cowl bleed choked t P3/Po =.91, s cn be seen by the bleed recovery decresing shrply t.9 bleed flow. The distortion decresed from.23 to.115, while the bleed flow ws incresed over the sme rnge. Enlrging the cowl bleed did not ffect the bleed performnce below bleed-mss-flow rtio of.7, but bove this the performnce dropped below tht of the originl forwrd slot nd never quite reched n inlet recovery of.91 in spite of bleedmss-flow rtios up to.126. However, the bleed recovery ws gretly incresed nd the inlet distortion ws slightly improved by enlrging - the cowl-bleed slot. Moving the slots bck to the rer position incresed the bleed flow required for given pressure recovery. The cowl-bleed recovery improved over tht for the originl forwrd slot, but not s much s with the enlrged forwrd slot. Also, the distortion ws considerbly higher for the rer slots thn for either of the forwrd slots. The forwrd nd rer centerbody slots both produced bout the sne performnce except tbt the slot in the rer position did not choke t s low weight flow. The subsonic perforted bleed produced bout the sme inlet recovery s the forwrd slots up to bleed mss flow of bout.4 nd recovery of.875. Additionl bleed flow improved the distortion but hd little effect on the inlet recovery. The bleed-flow recoveries were poor for this bleed system. The sttic pressure t Mch 2.5 in the vicinity of the forwrd slots is shown in figure 13, where it is plotted s function of inlet recovery.

i3;1uwili.......... NACA RM E58E16 :::' :... 9.......... 2. d Probe D indictes tht the shock trin begins to rech the forwrd slot t n inlet pressure recovery of.83, which is the pek recovery with no subsonic bleed. The shock trin consolidtes on the bleed, s indicted by continued increse in probe D pressure; nd its effects re not felt forwrd of the slot until recovery of.886 is reched, s shown by probes A, B, nd C. At inlet pressure recoveries bove.886, the sttic pressure hed of the slot incresed until the inlet becme subcriticl t recovery of bout.91. The noise indicted in the figure is the mplitude of high-frequency oscilltion observed when the sttic probes begn to indicte the effects of the shock. Inlet Control The control of this inlet presents two problems: the control of the norml or terminl shock, nd the positioning of the centerbody for optimum internl contrction. The norml-shock position cn be controlled by bypss tht will hve to be firly lrge to meet strting nd off-design weight-flow requirements. These requirements re illustrted by the corrected weight flow t sttion 3 incresing 45 percent during strting t Mch 2.5, nd being 31 percent higher t pek-recovery conditions t Mch 2. thn t the sme conditions t Mch 2.5. The sttic pressure hed of the forwrd slot produced potentilly useful bypss-control signl, s seen from figure 13. No control-signl dt were tken t off-design spike positions nd Mch numbers. In the previous discussion of ngle-of-ttck performnce, it ws L'--L bll,v V" --,.-& ILUbLL z - Eo :dth the inle.+. siiprcriticl, the centerbody would hve to be extended hed of the pek-recovery position t zero degrees. This centerbody extension would cuse loss in recovery t = ' of 2 nd 4 counts t Mch 2. nd 2.5, respectively. The centerbody of this inlet therefore must be positioned s function of ngle of ttck to obtin good performnce. Also, to obtin good inlet performnce, the control will hve to ccount for Reynolds number, s cn be seen from the dt presented in figure 9. The centerbody trnsltion required by the chnge in Mch number from 2.5 to 2. is 1.32 inlet dimeters for the long inlet with constnt- Mch-number section, s illustrted in figure 6. To hve essentilly no internl contrction for trnsonic opertion, this configurtion would require n extension of bout 2 inlet dimeters. This extension could be reduced to 1.14 nd 1.56 for Mch 2. nd pproximtely no contrction conditions, respectively, by removing the constnt-mch-number section. This centerbody movement would probbly hve to be scheduled with Mch number, s no internl pressure signls were observed tht would predict the optimum internl contrction.

1 SUMMARY OF RESULTS An ll-internl-contrction isentropic inlet ws tested in the 1- by 1-foot wind tunnel with the following results: 1. At Mch 2.5, the inlet recovery ws incresed from.83 to.91 by bleed of.13 of the inlet mss flow by mens of flush slots just downstrem of the throt. 2. Bleed forwrd of the throt ws very effective in permitting retrction of the spike into the design position. However, incresing the mount of this bleed beyond the minimum required for spike retrction hd little effect on the inlet pressure recovery. 3. Centerbody position would hve to be scheduled with ngle of ttck nd Reynolds number s w ell s flight Mch number in order to void significnt losses in inlet pressure recovery. 4. The sttic pressures in the throt forwrd of the flush slots ppered to be potentilly useful for controlling the inlet norml-shock position t Mch 2.5 nd zero ngle of ttck. Lewis Flight Propulsion Lbortory Ntionl Advisory Committee for Aeronutics Clevelnd, Ohio, My 22, 1958 1. Mossmn, met A., nd Pfyl, Frnk A.: An Experimentl Investigtion t Mch Numbers from 2.1to 3,O of Circulr-Internl-Contrction Inlets with Trnslting Centerbodies. NACA RM A56G6, 1956. 2. Kepler, C. E.: Performnce of Vrible-Geometry Chin Inlet t Mch Numbers from 1.6 to 3.. Res. Dept., Rep, R-955-24, United Aircrft Corp., Oct. 1957. (Contrct NO(s)55-133-c.) 3. Hubbrtt, J. E.: Preliminry Investigtion of Isentropic Internl Contrction Inlets. Rep. LR.12229, Lockheed Aircrft Corp., Sept. 2, 1957. 4. Rozycki, R. C.: Experimentl Investigtion of Isentropic Internl Contrction Inlets t Mch Numbers from 2. to 2.7- Rep. 12565, Lockheed Aircrft Corp., Oct. 1, 1957.

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15 () Forwrd cowl slot with cowl nd centerbody removed. - C-45156 (b) Centerbody constnt-re sections showing bleed s l o t s (forwrd nd rer) nd perfortions. Figure 3. - Representtive prts of bleed configurtions.

16 Flow.25 -In. rdius B Originl cowl (forwrd nd rer) Enlrged forwrd cowl Figure 4. - Slot geometry.

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2 NACA RM E58E16 c 7- I- 8 No subsonic bleed or constnt-mch-number section Optimum subsonic bleed nd constnt-mch-number section Constnt-Mch-number section but no subsonic bleed Perforted subsonic bleed nd constnt-mch-number section 1- Solid symbols indicte bout 1 percent perforted cowl bleed hed of throt A!id B - points used in fig. 7 H- Mch number, TI I 1. 1.4 1.8.4.4.B 2 cc.aterbociy position, inlet dim hed of design position Figure 6. - Over-nll inlet performnce. Reynolds number, 2.5x1G per foot.

I - I - * NACA RM E58E16 21 1. Liner distnce from throt, in. f,-, -1 o-.tl - -.. - ztn+i o-prpss11re distribution..8.6.5.6.7.8.9 1. Throt totl-pressure rtio, P2/Po (b) Throt totl-pressure profile. Figure 7. - Effect of centerbody trnsltion on supersonic performnce of modified long inlet with subsonic perforted bleed. Mch number, 2.5; Reynolds number, 2.5~1~ per foot.

22 NACA RM E58E16 Mo 2.5-2. Angle of ttck, deg Figure 8. - Effect of ngle of ttck on pek pressure recovery (modified long inlet with forwrd enlrged cowl nd originl centerbody slots nd constnt-mch-number section; Re, 2.5X16 per ft). 2.3 2.2 - -- 2.1.c 1.o 1.4 1.8 2.2 2.6 Reynolds number x1-6 Figure 9. - Effect of Reynolds number on mximum obtinble contrction rtio t Mch 2.5 (modified long inlet with forwrd enlrged cowl nd originl centerbody slots nd constnt-mch-number section)

NACA RM E58E16 --- - - m m m m m m m m mmm 23 d. 2. 2.1 2.2 2.3 2.4 2.5 2.6 Free-strem Mch number, I+, Figure 1. - Strting chrcteristics for the originl long inlet with no constnt-mch-number section nd no bleed. Reynolds number, 2.5x16 per foot.

() Subcriticl t design position. () Extension,.778 inlet dimeter. (b) Extension hed of design position,.144 inlet dimeter. (c) Extension,.462 inlet dimeter. (e) Extension,.936 inlet dimeter. (f) Extension, 1.97 inlet dimeters. Y (g) Extension, 1.32 inlet dimeters. L A (h) Minimum extension f o r strting, 1.337 inlet dimeters. (i) Supercriticl t design position. Figure 11. - Sprk schlieren photogrphs of inlet strting t Mch 2.5. Reynolds number, 2.5X16 per foot.

-, 25 h Supersonic perforted bleed Originl forwrd slots Forwrd enlrged cowl nd originl centerbody slots Rer slots Cowl bleed, m/mg () Cowl-bleed performnce for optimum centerbody-bleed flow..4.or Centerbody bleed, m/w (b) Centerbody-bleed perfomnce for optirnun covl-bleed flow. Figure 12. - Performnce of bleed configurtions. Mch number, 2.5; Reynolds number, 2.5x16 per foot.

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