1、. .,. ;. ,” : . . / . ., . . :. , 1 ,/ , I . .,./. ,.” I . . _ ,. , . . . / .- , ,_ .I : . . , : I . 1954 . I ._ _ . . L . . . Superintendent : /- , A. of Documents. U. 9. Government Printing Otlh, WIcshington 25, D. C. Yearly enbscription, $10; foreign, $11.25; single cop, priavuies according to si
2、ze - - - - - - - - - Price 16 cents .j. . ., .,. ,. i ,. .I - _ . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-REPORT 1193 THEORETICAL PERFORMANCE CHARACTERISTICS OF SHARP-LIP INLETS AT SUBSONIC SPEEDS By EVAN A. FRADENBURGH and DeMARQUIS D. WYATT
3、 Lewis Flight Propulsion Laboratory Cleveland, Ohio .-_ - I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-National Advisory Committee for Aeronautics Headquarters, 1512 H Street NW., Washington 25, D. C. Created by act of Congress approved March 3,
4、 1915, for the supervision and direction of the scientific study of the problems of flight (U. S. Code, title 50, sec. 151). Its membership wa.s increased from 12 to 15 by act approved March 2, 1929, and to 17 by act approved May 25, 1948. The members are appointed by the President, and serve as suc
5、h without compensation. JEROME C. HUNSAKLR. SC. D., Massachusetts Institute of Technology, Chazrman DETLEV W. BRONR, PH. D., President, Rockefeller Institute for Medical Research, Vice Chazrman JOSEPH P. ADAMS, LL. D., member, Civil Aeronautics Board. ALLEN V. ASTIN. PH. D Director, National Bureau
6、of Standards. PRESTON R. BASSETT, M. A.; President, Sperry Gyroscope Co., Inc. LEONARD CARMICHAEL, PH. D., Secretary. Smithsonian Insti- tution. RALPH S. DAMON. D. Eng., President, Trans World Airlines. Inc. JAMES H. DOOLITTLE, SC. D., Vice President, Shell Oil Co. LLOYD HARRISON, Rear Admiral, Unit
7、ed States Navy, Deputy and Assistant Chief of the Bureau of Aeronautics. RONALD M. HAZEN, B. S., Director of Engineering, Allison Division, Genera.1 Motors Corp. RALPH A. OFSTIE, Vice Admiral, United States Navy, Deputy Chief of Naval Operations (Air). DONALD L. PUTT, Lieut.enant General, United Sta
8、tes Air Force, Deputy Chief of Staff (Development). DONALD A. QUARLES, D. Eng., Assistant Secretary of Defense (Research and Development). ARTHUR E. RAYMOND, SC. D., Vice President-Engineering, Douglas Aircraft Co., Inc. FRANCIS W. REICHELDBRFER, SC. D., Chief, United States Weather Bureau. OSWALD R
9、YAN, LL. D., member, Civil Aeronautics Board. NATHAN F. TWINING, General, United States Air Force, Chief of Staff. HUGH L. DRYDEN, PH. D., Director JOHN F. VICTORY, LL. D., Executive Secretary JOHN W. CROWLIY, JR., B. S., Associate Director for Research EDWARD H. CHAMBERLIN, Executive Offker HENRY J
10、. E. REID, D. Eng., Director, Langley Aeronautical Laboratory, Langley Field, Va. SMITH J. DEFRANCE, D. Eng., Director, Ames Aeronautical Laboratory, Moffett Field, Calif. EDWARD R. SHARP, SC. D., Director, Lewis Flight Propulsion Laboratory, Cleveland Airport, Cleveland, Ohio LANGLEY AERONAUTICAL L
11、ABORATORY AMES AERONAUTICAL LABORATORY LEWIS FLIGHT PROPULSION LABORATORY Langley Field, Va. Moffett Field, Calif. Cleveland Airport, Cleveland, Ohio Conduct, under uniJied control, for all agencies, of scientiJic research on the fundamental problems of flight II Provided by IHSNot for ResaleNo repr
12、oduction or networking permitted without license from IHS-,-,- _-.-.- . . . ? ; . . NACA REPORT mE0RET1cALpERFQRMANcE OFSHARP-LIP lIKW3TSAT ; ByEvanA.Fradenburghand 1954 page 6: Equation (14) sho ; TM0 - ao I I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
13、 IHS-,-,-REPORT 1193 THEORETICAL PERFORMANCE CHARACTERISTICS OF SHARP-LIP INLETS AT SUBSONIC SPEEDS 1 By EVAN A. FRADENRURGH and DEMARQUIS D. WYATT SUMMARY A method is presented for the estimation of the subsonic-jbight- speed characteristics of sharp-lip inlets applicable to supersonic aircraft. Th
14、e analysis, based on a simple momentum balance consideration, permits the computation qf inlet-pressu.re- recovery-mass-$ow relations and addiiive-drag coe$icients for forward velocities from zero to the speed qf sound. Y P t,otol pressure, p l+q iM2ye1 ( The penalties for operation of a sharp-lip i
15、nlet at velocity rotios other than 1.0 may be severe; at lower velocity ratios an additive drag is incurred that is not cancelled by lip suction, while at higher velocity ratios, unavoidable losses in inlet total pressure will result. In particular, at the take-of condition, the total pressure and t
16、he mass flow for a choked inlet are only 79 perceni of the values ideally attainable with a rounded lip. Experimental data obtained at zero speed with a sharp-lip super- sonic inlet model were in substa,ntial agreement with the theoret- ical results. INTRODUCTION P static pressure . P dynamic pressu
17、re, f pV=G pM2 s,s streamlines v velocity momentum parameter, mV+ (p-p0)A=pM2A+ (P-POM Y ratio of specific heats, 1.4 for air P mass density Subscripts : d external downstream station t throat 0 free stream 1 inlet 2 diffuser outlet ANALYSIS Air inlets designed for operation at supersonic speeds gen
18、erally must employ thin, sharp lips if the large drag penalties associated with blunt lips at these speeds are to be avoided. A turbojet-powered supersonic aircraft must take off and accelerate at subsonic Mach numbers, however; therefore, it is of importance to be able to estimate sharp-lip inlet c
19、haracteristics in the low-speed range as well as at supersonic velocities. DETERMINATION OF INLET MOMENTUM PARAMETER This report presents a simple method dcvelopcd at thr NACA Lewis laboratory for estimating the zero-angle-of, attack characteristics of sharp-lip inlets at subsonic flight speeds. Tot
20、al-pressure recoveries and additive-drag coeffi- cients are presented for flight velocities from zero to the speed of sound over the full range of inlet operating conditions. The inviscid-potential-flow pattern into a cylindrical air inlet operating at subsonic free-stream Mach numbers is shown sche
21、matically in figure 1 (a). (The word “cylin- drical” does not necessarily imply a circular cross section in this report.) The stagnation point of the dividing stream- line s occurs inside of the lip for inlet velocity ratios less than 1 .O (corresponding to MI/MOl or A,/A, 1 ), as shown in refcrcnce
22、 1 for the two-dimensional incompressible case. Two important characteristics of this ideal flow may be mentioned: (1) The total pressure is con- stant throughout the flow field, and (2) a finite suction force F exists on the lip as inclicated by the dashed vectors. SYMBOLS The following symbols are
23、 used in this report: A flow area AT area projection on plane normal to inlet axis a local speed of sound a, stagnation speed of sound, a ( l+ W f b external body surface C D Da additive-drag coeEcient, 2 clOA1 DC? additive drag F lip suction force M Mach number, V/a m mass flow, pVA=e m* reference
24、mass flow (eq. (5) 1 Supersedes NSCA TN 3004, “Theoretical Performance Characteristics of Sharp-Lip Inlets at Subsonic Speeds,” by Evan -4. Frndenburgh and DeMnrquis D. Wyatt, 19.53. 323361-55 ,. 1 For extremely thin inlet lips, the actual flow will differ substantially from the ideal case. In parti
25、cular, a zero- thickness lip cannot sustain any suction force, and the flow cannot t,urn the 180 required to stay attached to the wall. The tot.al pressure of the actual flow will not remain con- stant in the regions affected by the resultant separation. As indicated in figure 1 (b), for A,/A,l the
26、external flow will be similar to the ideal, but the internal flow will be sepa- rated with a resultant loss in total pressure. The actual flow phenomena are complex, but one-dimensional approxi- mations to total-pressure recoveries and inlet forces may be determined by a simple momentum balance cons
27、ideration. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 REPORT 1193-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Inlet velocity ratio greater than l.O.-For the actual flow into an inlet for velocity ratios greater than 1.0 (A,/A,l), the inlet con
28、ditions will not be uniform but may be approxi- mated by an equivalent one-dimensional flow of the same mass flow, energy, and momentum parameter. With this assumption of one-dimensional flow, the inlet station may be considered to be at any point within the constant-area section behind the lip. The
29、 conservation of energy require- ment will be satisfied if the total temperature and, conse- quently, the stagnation speed of sound of the flow is held constant. Calculation of the inlet momentum parameter as a funct,ion of mass flow will permit the calculation of all the characteristics of this equ
30、ivalent flow. The momentum parameter of the internal flow at the inlet 1 is equal to the free-stream value plus all forces exerted on the internal flow in a downstream direction. These forces, for velocity ratios greater than 1.0, include the lip suction force F and the integral of the pressure incr
31、ement, along the stagnation streamline up to the stagnation point (all pressure forces are referenced to free-stream static pressure). %=%+F+ (p-pP,)cZA.z L”Z -w / Inlet axis -_- _- Velocity ratio I, (A : P._ ., ,1. ,2,. L ._ . -,j .A. ;-.A,/A, .9 I.0 II:URE 8.-Effect of contraction ratio on sharp-l
32、ip inlet, pcrformauce at critical flow (throat. Mach number, 1.0). incrascd by a contraction for the lower free-stream Mach numbers because of the reduction in inlet Mach number. A mass-flow ratio m/met, where m *L corresponds to isentropic choking at the throat area A, rather than the inlet area Al
33、, is equal to PI/P, for this case. Thus the mass flow for a given minimum flow area A, increases as the ratio of throat area t.o inlet area decreases. The mass-flow ratio based on choking at the inlet area m/m*, however, decreases as At/AI decreases. It may also be seen that an internal contraction
34、carries an additive-drag pena1t.y at the higher free-stream Mach numbers, because the inlet velocity ratio becomes less than 1.0. CONCLUDING REMARKS It has been shown that the subsonic-flight-speed character- istics of sharp-lip air inlets applicable to supersonic aircraft b S 1 AA . I . Station 0 (
35、b) Stotion d _ _ -_- (c) F - b (a) Curved cowl. Velocity ratio greater thau 1.0. (b) Equivalent solid boundary. (c) Cylindrical cowl. Velocity ratio greater than 1.0. (d) Cylindrical cowl. Velocity ratio less thau 1.0. FIGURE !I.-Inlet flow patterns. may br estimated by a simple momentum balance cou
36、sidera- t.ion. Pressure-recovery-mass-flow relations and additive- drag coefficients may be calculated for flight velocities from zero to the speed of souncl,ovcr the full range of inlet operating conditions. The penalties for operation a,t inlet velocity ratios other than 1.0 m.ay be severe; at low
37、er velocity ratios an additive drag is incurred that is not cancelled by lip suction, while at higher velocity ratios, unavoidable losses in inlet total pressure will result. In particular, at zero forward velocity (take-off condition), the total-pressure recovery and the mass-flow ratio for a choke
38、d inlet are only 79 percent of the values ideally attainable with a rounded lip. Experimental data obtained at zero speed with a sharp-lip supersonic inlet model were in substantial agreement with the theoretical results. LEWIS FLIGHT PROPULSION LABORATORY NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
39、 CLETELAND, OHIO, July S?, 1953 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 REPORT 1193-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS APPENDIX EVALUATION OF PRESSURE INTEGRAL ON STAGNATION STREAMLINE FOR INLET VELOCITY RATIOS GREATER THAN 1.0 The
40、 flow into an inlet for velocity ratios greater than 1.0 is represented schematically by figure 9 (a). The stagnation streamline is labeled s and the exterior body surface down- stream of the stagnation point is labeled b. The external flow may be considered independently of the internal flow by rep
41、lacing the stagnation streamline by a solid boundary, as in figure 9 (b), and finding the inviscid-potential-flow solution for the pressure integral of this boundary. It is assumed that the inlet region is connected to the rest of the aircraft by a cylindrical section of sufficient length to make th
42、e flow near the inlet independent of disturbances caused by other components of the aircraft. Thus in figure 9 (b) the solid boundary may be assumed to be extended to infinity in both directions without changing the flow near the inlet. The static pressure at the downstream infinity station cl will
43、be equal to the free-stream static pressure. The total pressure is assumed constant, and thus the Mach number at cl will be equal to the free-stream Mach number: Pd=Po p,=po M,z=M, (AlI When the flow between the solid boundary (s and b) and a streamline s is considered, the mass flow must be equal a
44、t the two stations: aa =mo WI From equations (Al) and (AZ), it is evident that the flow areas at the two stations must be equal: A,=A, 3) The difference in momentum parameter at the two stations is therefore Qjd-o=dMadAd+(pd-po) A,-rpoM;Ao=O (A4) As there is no change in the momentum parameter betwe
45、en the two stations, the combined longitudinal force on s, b, and s must be zero. By selecting a streamline s a sufficient distance from s, the difference between the static pressure on s and the free-stream static pressure may be made to ap- proach zero. Since the longitudinal area projection AA of
46、 this streamline is finite, the longitudinal force on s must be zero. Thus the combined longitudinal force on s and b must also be zero : L45) For a cylindrical cowl (fig. 9 (c), the body surface down- stream of the stagnation point has no longitudinal area projection as long as the stagnation point
47、 of the flow occurs on the external cylindrical portion. Thus for this case, the longitudinal force on s is zero: s s(-po) dA,=o W) The preceding analysis may be extended to the case of inlet velocity ratios less than 1.0. Figure 9 (d) represents this case for a cylindrical cowl. Equation (A.5) indi
48、cates that any pressure force on the streamline s is cancelled by the lip suction force F. It should be noted, however, that this result is dependent on the assumption of constant total pressure for the external flow. If the inlet lip is thin, the external flow will separate at the lip and the total
49、 pressure will not be constant; therefore, the proof does not apply. The pressure force on the streamline s will, in general, be only partially cancelled by lip suction for this case. REFERENCES 1. Coale, Charles W.: Suction Force on the Lip of a Two-Dimensional Idealized Scoop in Non-Viscous Subsonic Flow. Rep. No. SM- 13742, Douglas Aircraf
