1、!ru.s. DEPARTMENTOF COMMERCENationalTechnicalInformationServiceNACA-TR-920THE I)EVELOPMENT AND APPLICATION OF HIGH-CRITICAL-SPEED INLETSD.D. Baals, et alNational Advisory Committee for AeronauticsWashington, D.C.Provided by IHSNot for ResaleNo reproduction or networking permitted without license fro
2、m IHS-,-,-TI_i|iProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-REPORT No. 920THE DEVELOPMENT AND APPLICATION OF HIGH-CRITICAL-SPEED NOSE INLETSBy DONALD D. BAALS, NORMAN F. SMITH, and JOHN B. WRIGHTSUMMARYAn analysis of the nose-inlet shapes develop
3、ed in previousinvestigations to represent the optimum from the standpoint ofcritical speed has shown that marked similarity exists betweenthe nondimensional profiles of inlets which have widely differ-ent proportions and critical speeds. With the nondimensionalsimilarity of such profiles established
4、, the large differencesin the critical speeds of these nose inlets must be a function oftheir proportions.An investigation was undertaken in the Langley 8-foothigh-speed tunnel to establish the effects of nose-inlet propor-tions on critical 3lach number and to develop a rational methodfor the design
5、 of high-critical-speed nose inlets to meet desiredrequirements. The nondimensional ordinates of the B noseinlet, which were developed in a previous investigation to beoptimum .from the standpoint of critical speed, were extendedand modified slightly to improve the fairing. These ordinates,now desig
6、nated the NACA 1-series, were then applied to agroup of nose inlets involving a systematic variation of pro-portions. Wind-tunnel tests of these nose inlets were madethrough wide ranges of inlet-velocity ratio and angle of attackat .tiach numbers of 0.3 and 0.4. Tests of representativenose inlets we
7、re carried to high speed (a maximum .tlachnumber qf 0.7). Pressure distributions and critical .tIachnumber characteristics are presented for each of the nose inletstested. The results of these tests show that the length ratio(ratio of length to maximum diameter) of the nose inlet is theprimary facto
8、r governing the maximum critical speed. Theeffect of inlet-diameter ratio (ratio of inlet diameter to maxi-mum diameter) on critical speed is, in general, secondary;but this ratio has an important function in governing the extentof the inlet-velocity-ratio range for maximum critical speed.The highes
9、t critical Mach number attained for any of the noseinlets tested was 0.89.The data have been arranged in the form of design charts.from which NACA l-series nose-inlet proportions can beselected for given values of critical ,VIach number and airflowquantity. Examples of nose-inlet selections are pres
10、ented fora typical je_-propulsion installation (critical ,t/lach number of0.83) and for two conventional radial-engine installations(critical ,_Iach number of 0.76).The selection charts and NACA 1-series ordinates areshown to be applicable to the design of cowlings with spinnersand to the design of
11、high-critical-speed fuselage scoops. Thepossibility of application of the NACA 1-series ordinates tothe experimental development of wing inlets is also indicated.INTRODUCTIONMarked increases in airplane speeds have created a demandfor design data on high-critical-speed air inlets suitable foruse wit
12、h jet-propulsion units, gas-turbine propeller units,and conventional engine installations. Previous develop-ment programs on air inlets have produced the NACA Ccowling having a critical Mach number of 0.63 (reference 1)and the B nose inlet having a critical Mach number of 0.84(reference 2). These in
13、lets have widely different propor-tions; the first is short with a large-diameter air inlet; thesecond is of considerably greater length with a small-diameterair inlet. Each nose inlet was developed to represent theoptimum design from the standpoint of critical speed forthe particular proportions in
14、volved.Little information has been available on air inlets havingproportions in the range between these two specific shapes.The research program reported herein was undertaken atthe Langley 8-foot high-speed tunnel to establish the effectsof variations of nose-inlet proportions on the critical Machn
15、umber and to develop a rational method for the design ofnose inlets intermediate to the NACA C cowling and B noseinlets, both in proportions and in design critical Machnumbers. Such data have direct application to the designof high-critical-speed nose inlets and to the development ofscoop-type air i
16、nlets.SYMBOLSa speed of sound, feet per secondV velocity, feet per secondM Mach number (V/a)V1/Vo inlet-velocity ratioa model angle of attack, measured from model centerline, degreesdensity, slugs per cubic footratio of specific heats (for air, 1.40)static pressure, pounds per square footpressure co
17、efficient (_0P)critical pressure coefficient, corresponding to localMach number of 1.0mass flow, slugs per second (pAir)area, square feet ,mass-flow coefficient “_: .dynamic pressure, pounds per square foot (2 pV“)“- “_535pPP*p,mAmqProvided by IHSNot for ResaleNo reproduction or networking permitted
18、 without license from IHS-,-,-536aH0Ddd/DXX/DFYYrKREPORT NO. 920_NATIONAL ADVISORY cOMMITTEE FOR AERONAUTICStotal-pressure loss between free stream and measure-ment station, pounds per square foottotal conical-diffuser angle, degreesmaximum diameter of nose inletinlet diameterinlet-diameter ratiodis
19、tance from entrance, measured along nose-inletcenter linenose-inlet length, measured from inlet to maximum-diameter stationlength ratiomaximum frontal area of nose inlet, corresponding toD, square feetordinate measured perpendicular to reference linemaximum ordinate, measured perpendicular to ref-er
20、ence line at maximum-diameter station (Seetable I.)nose-inlet lip radiusarbitrary factor (See section entitled “Effects ofvariations in basic profile“ and fig. 7.)Subscripts:rain minimumcr critical0 free stream1 nose-inlet entranceDESIGN ANALYSISDRRIVATIONOF BASICNOSl OI_DINATE3The A, B, and C nose
21、inlets presented in reference 2 werederived experimentally in a systematic series of wind-tunneltests to approach the optimum from the standpoint of criticalspeed. A comparison from reference 2 of the nondimensionalprofiles for these nose inlets having different proportions(fig. 1) indicates a simil
22、arity of profile for all three inlets.Marked similarity of profile is noted for the B and C noseinlets; the A nose inlet, however, varies somewhat from thebasic profile of the B and C nose inlets. This variation isbelieved to be due to the limitations encountered in the testsof reference 2, which in
23、volved the fairing of this nose inletof large diameter into the basic streamline body at a given80.66V7 Y.30,vos. _., U_c“ _ -_NAC,4 Ill bo_ill,= _,i fIx.40f/-X _ -.25L 1t1,/0 .20 ,.30 .50 .60 ,70 .80 90=TXFio_az l.-Comp_rfaon d uondmenston_ p_flie$ _d pm_rtio_ of the $r_ high-c_ft_l.speed nose nle_
24、 developed in _s_ _ rderen_ 2,/.O0Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-THE DEVELOPMENT AND APPLICATION OF HIGH-CRITICAL-SPEED NOSE INLETS 537point and with a given slope. These limitations were notserious for the B and C nose inlets, which
25、 have small inletdiameters, and correspondingly greater lengths were avail-able for fairing than for the A nose inlet. A flat pressuredistribution similar to the distributions obtained for theB and C nose inlets was not obtained for the A nose inlet,for which a pressure peak ocnrred at all inlet-vel
26、ocity ratios.Although the difference between the nondimensional B andC nose-inlet ordinates is small, the ordinates of the B noseinlet have been selected for general use because the originalproportions were considered to correspond more nearly tocurrent design applications than those of the C nose i
27、nlet.The nondimensional B nose-inlet ordinates have been appliedto the layout of various nose inlets that differ appreciablyfrom the original nose-inlet proportions in length, inletdiameter, and maximum diameter. In reference 3, in whichthe variation from the original B nose-inlet proportions wascon
28、siderable, the pressure distribution over the resultingnose inlets exhibited the characteristic flat contour with lowvalues of the pressure peak. It was thus indicated that thebasic B nose-inlet profile and the method of nose design couldbe applied to the design of nose inlets having proportionsgrea
29、tly different from those of the original nose-inlet shapetested.Difficulty was experienced, however, in the applicationof the original B nose-inlet ordinates.- The slope of thenose-inlet profile at the station at which the nose fairedonto the streamline body was a finite value that variedwith the no
30、se-inlet proportions assumed. It was evidentthat the nondimensional profile should be extended to apoint at which the slope was zero (maximum-diameterstation). In order to attain this extension, the B nose-inletordinates were considered to include the NACA 111 stream-line body (to which the original
31、 nose inlet was faired)as far back as the maximum-diameter station. The resultingordinates were developed in a nondimensional form andare plotted in figure 2.The fairness of the extended B nose-inlet ordinates couldnot be determined from the measured pressure distributionpresented in reference 1beca
32、use the wing-support interferenceaffected the pressure distribution over the rear part of thenose inlet. Plots of the slope and the rate of change of slopeof the extended B nose-inlet ordinates indicated a slightamount of unfairness in the region where the original Bnose inlet joined the streamline
33、body. On the assumptionthat the curves of slope and rate of change of slope shouldbe fair (these two curves together specify the local radiusof curvature), the two curves were faired and the resultingordinates determined. The faired ordinates, hereinafterdesignated the NACA l-series ordinates, are g
34、iven in table Iand are plotted in figure 2 in comparison with the extendedB nose-inlet ordinates. The two curves are practicallyidentical over the critical forward sect.ion and have onlyminor differences over the rear section. The resultantNACA 1-series ordinates are, therefore, essentially theorigi
35、nal NACA B nose-inlet ordinates with the addition ofa faired extension back to the maximum-diameter station.7C .6C.50V Y40+20.20I0it tit _LAA_.+=.+L.+,+,+-,+, L L_L_ I I I I II I I_L_L _II111 II _1+ t I _.,-+o,-,-,+_,-,.,.,+.y+.,-?,+/lllI I I I I I / lJtI I I I II .-L_ ,_! _J_L_I L_! I_J_I_I_J_L I t
36、 I I I I I+_1,+,(iI I t I I I i I 1/ / I I I I , / I I I I I I 1 tl/ I III1+1 I IIII Ill+, ,:Y I :LLLI_I_+_I.+.,+ ,_ , ,._J_L_L_ I III I lilt111 III I I l I_ ._t_t_/._LA_A_LL_LI_t_ +tl +L_L_ +_i_-I_-/t tit t l tll. t il+i. t llll.: .+-_ I,“_/_t l J L+I / J_LJ+_+_L_L_I_L =-/_ /A/-_t I I I It _L_I_L_L
37、._L_JlIII_.It i _. I.- .,+ JL 1111 III _L_I_L_L_!_+_L_J_LL_._U_LL_L_LU_+I_.L_i._tf. i lit II1 _L_L_L_A_ _ . LLJ_ “_N_J_L_LItI till III /1t I I I I I|1 I I I I I I I I I I I I0 ./0 .20 .30 .40 .50 .60 .70 .80 .90 ,tOO=/XFIO_Z 2.-Compcrlson of the extended B no_-inlet profile of reference 2 with NACA
38、l-serle_ ncee-inlet profile.905385-51-35Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-538 REPORT NO. 920-NATIONAL ._I)VISORY COMMITTEE FOR AERONAUTICSNACA 1-SERIES ORDINATES In figure 3 the NACA C cowling -=0.70; =0.31Ordinates in percent“._Nose ro
39、d us, r “=.JTeference /hey_D-d r2For r=O.O25Y:Y=_._-_ 2.0560.1160._92._.11_. 9594. 7560._.3597.87_._.74_,09_.40_.6560._60._60._1_.09y/Y4L 9443.6645. 3046.8848.4049. 8851.3154.0555, 3756.5657. 9259. I560.3561, 5262. 6763.7964. 8965. 9787.0368.07v/Y9.3312. 7214. 7216. 5718. 3119.9421.4822.9624. 3627.
40、0129.4731.8134. 0336.1338.1540. 09_os_X34.035. O38.037. 038. 039.0_iO.O4LO42. 043,044,045, 047. 048.049, f)50,0-52. 054,056,058,0,v/Y z/X60.0_ 60.070, (_ 62. 071.05 54.09696.074. 75 72. 075. 63 74.076. 48 76.07S.iS_.95 s_o79, 74 84. 0_0,50 86.08L 25 60. 081.99 60.082.69 92.084.10 94.085.45 96.0,_._
41、gS. 0$7. 95 100.0radius: 0.025 YThe NACA C cowling ordinates are presented in reference 1.These cowling ordinates, derived from a systematic seriesof wind-tLlnnel tests, were developed to attain the maxi-mum critical speed for conventional cowling proportions.The cowling pressure distribution approa
42、ches the fiat shapethat is optimum from the standpoint of critical speed.A comparison of the NACA C cowling profile with theNACA 1-series ordinates on a nondimensional basis (fig. 3)shows reasonabIe agreement. Figure 3 also shows thenondimensional profile of an NACA wing-inlet shape thatis discussed
43、 in the section entitled “Wing inlets.“.Y and the original B nose inlet (D=0.38; _.=1.85)aresketched to scale. The great difference in the proportionsof these two nose inlets, which approach the optimum fromthe standpoint of critical speed, is evident. The criticalMach numbers of the NACA C cowling
44、and B nose inlet are,from references 1 and 2, 0.63 and 0.84, respectively. Withthe nondimensional similarity of the profiles of these twonose inlets established (fig. 3), the large variation in criticalspeed must be a function of the nose-inlet proportions. Itis indicated, therefore, that nose inlet
45、s having proportionsintermediate to these two nose inlets and having critical-speed characteristics approaching the optimum can be de-rived from essentially the same nondimensional profile.With the NACA 1-series ordinates as a basic profile, a sys-tematic series of wind-tunnel tests was undertaken t
46、o de-termine the effects of nose-inlet proportions on critical speed.NOSF_INLET DESIGNATIONA designation system for nose inlets has been devised thatincorporates the following basic proportions (see sketch intable I):d inlet diameterD maximum outside diameter of nose inletX length of nose inlet, mea
47、sured from inlet to maximum-diameter stationThe number designation is written in the form 1-40-150.The first number in the designation represents the series; thenumber 1 has been assigned to the present series. Thesecond group of numbers specifies the inlet diameter in per-cent of maximum diameter d
48、/D; the third group of numbersspecifies the nose-inlet length in percent of maximum diameterX/D. The NACA 1-40-i50 nose inlet, therefore, has at-series basic profile with _=0.40 and _= 1.50.APPARATUS AND TESTSMODELSThe nose inlets of the N-ACA 1-series investigated areillustrated in table II. These
49、nose inlets represent a syste-matic variation of inlet-diameter ratio diD from 0.40 to0.70 and of length ratio X/D from 0.30 to 2.00 All nose-inlet models were of 12-inch maximum diameter and wereconstructed of wood. With the exception of the nose inletsof _=2.00, for which the length was 24 inches, the lengthof the detachable nose
