1、7NASA TECHNICAL NOTE NASA TN D-7429MEASURED PRESSURE DISTRIBUTIONS ONLARGE-ANGLE CONES IN HYPERSONIC FLOWSOF TETRAFLUOROMETHANE, AIR, AND HELIUMby Robert A. Jones and James L. HuntLangley Research CenterHampton, Va. 236651JAN 7 - 1974AERONUTROM LIBRARYNATIONAL AERONAUTICS AND SPACE ADMINISTRATION WA
2、SHINGTON, D. C. DECEMBER 1973Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No.NASA TN D-74292. Government Accession No.4. Title and SubtitleMEASURED PRESSURE DISTRIBUTIONS ON LARGE -ANGLECONES IN HYPERSONIC FLOWS OF TETRAFLUORO-METHANE, A
3、IR, AND HELIUM7. Author(s)Robert A. Jones and James L. Hunt9. Performing Organization Name and AddressNASA Langley Research CenterHampton, Va. 2366512. Sponsoring Agency Name and AddressNational Aeronautics and Space AdministrationWashington, D.C. 205463. Recipients Catalog No.5. Report DateDecember
4、 19736. Performing Organization Code8. Performing Organization Report No.L-883410. Work Unit No.502-37-01-1011. Contract or Grant No.13. Type of Report and Period CoveredTechnical Note14. Sponsoring Agency Code15. Supplementary Notes16. AbstractAn experimental study of surface pressure distributions
5、 on a family of blunt andsharp large angle cones was made in hypersonic flows of helium, air, and tetrafluoro-methane. The effective isentropic exponents of these flows were 1.67, 1.40, and 1.12.Thus, the effect of large shock density ratios such as might be encountered during plane-tary entry becau
6、se of “real-gas“ effects could be studied by comparing results intetrafluoromethane with those in air and helium. It was found that shock density ratiohad a large effect on both shock shape and pressure distribution. The differences inpressure distribution indicate that for atmospheric flight at hig
7、h speed where “real-gas“effects produce large shock density ratios, large-angle cone vehicles can be expected toexperience different trim angles of attack, drag coefficient, and lift-drag ratios than thosefor ground tests in air wind tunnels. Comparison-of the data with several theories indicatedtha
8、t (1) for sharp cones having attached shock waves, the sharp-cone solutions provide agood prediction of pressure, and (2) for both sharp and blunt cones having subsonic flowover the forebody, the semiempirlcal, sin-deficiency method of Love gave the best pre-diction of pressure distribution.17. Key
9、Words (Suggested by Author(s)Real -gas effectsPressure distributionsHigh -drag configurations19. Security Oassif. (of this report)Unclassified18. Distribution StatementUnclassified - Unlimited20. Security Classif. (of this page) 21. No.Unclassifiedof Pages 22. Price*,Q Domestic, $3.5t5 Foreign, $6.0
10、0For sale by the National Technical Information Service, Springfield, Virginia 22151Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MEASURED PRESSURE DISTRIBUTIONSON LARGE-ANGLE CONES IN HYPERSONIC FLOWS OFTETRAFLUOROMETHANE, AIR, AND HELIUMBy Robert
11、 A. Jones and James L. HuntLangley Research CenterSUMMARYAn experimental study of surface pressure distributions on a family of blunt andsharp large angle cones was made in hypersonic flows of helium, air, and tetrafluoro-methane. The effective isentropic exponents of these flows were 1.67, 1.40, an
12、d 1.12.Thus, the effect of large shock density ratios such as might be encountered during plane-tary entry because of “real-gas“ effects could be studied by comparing results in tetra-fluoromethane with those in air and helium. It was found that shock density ratio had alarge effect on both shock sh
13、ape and pressure distribution. The differences in pressuredistribution indicate that for atmospheric flight at high speed where “real-gas“ effectsproduce large shock density ratios, large-angle cone vehicles can be expected to experi-ence different trim angles of attack, drag coefficient, and lift-d
14、rag ratios than those forground tests in air wind tunnels. Comparison of the data with several theories indicatedthat (1) for sharp cones having attached Shockwaves, the sharp-cone solutions provide agood prediction of pressure, and (2) for both sharp and blunt cones having subsonicflow over the for
15、ebody, the semiempirical, sin-deficiency method of Love gave thebest prediction of pressure distribution.INTRODUCTIONThe use of aerodynamic drag and/or lift as a means for deceleration of a vehicleentering the rarefied atmosphere of Mars requires the use of a high-drag entry configu-ration. At the p
16、resent time, cones having total cone angles as high as 140 and practicallyno afterbody are being considered. At supersonic and hypersonic speeds, the aerodynamiccharacteristics, including the surface pressure distribution, shock shape, drag, stability,and lift-drag ratio, of such configurations are
17、determined almost exclusively by the fore-body flow field. Several previous investigations (refs. 1 to 3) have shown that for hyper-sonic speeds (free-stream Mach numbers greater than 4), these characteristics primarilydepend on the shock density ratio, which, in turn, is dependent on the vehicle sp
18、eed, andProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-atmospheric composition, pressure, and temperature. Variations in aerodynamic char-acteristics due to these parameters are the result of real-gas effects, such as dissociationor excitation of hi
19、gher degrees of freedom of the gas. There is no direct dependence onMach number. Therefore, the aerodynamic characteristics on blunt vehicles at hyper-sonic speed can be simulated by matching the shock density ratio. Flight density ratioscan be duplicated by using an ideal gas flow having a suitable
20、 isentropic exponent (refs. 2and 4). For Mars entry simulation, isentropic exponent values in the range from 1.09to 1.3 are required.The purpose of this paper is to provide measured surface pressure data for severallarge-angle cones at three values of the isentropic exponent: 1.12, 1.4, and 1.67. Th
21、esedata were obtained in the pilot CF4 facility at the Langley Research Center, the LangleyMach 8 variable-density hypersonic tunnel, and the Langley 22-inch helium tunnel. Alarge amount of similar data taken in air at various Mach numbers is given in refer-ences 5 to 12.SYMBOLSValues are given in b
22、oth SI and U.S. Customary Units. The measurements andcalculations were made in U.S. Customary Units.CD drag coefficientM free-stream Mach numberoop local surface pressurep free-stream stagnation pressurep_ stagnation pressure behind normal shockR, base radiusRn nose radiusROO free-stream Reynolds nu
23、mber based on diameterProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-surface distancesurface distance to maximum body diameterT stagnation temperatureu 0.16 shows the same strongdependence on y and about the same pressure level as the sharp 100 cone
24、 data. Thepressure-ratio values for helium and air both decrease for S/Smax greater than 0.6, butthe CF data show an increasing pressure in this region. At angles of attack, the pres-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-sure level on the c
25、onical portion indicates much the same trend as for the sharp cone.Newtonian theory and the method of reference 19 are the only methods of those consideredherein which are applicable for the 100 blunt cone, and the method of reference 19 wasonly applicable to the windward ray at angles of attack whe
26、re the equivalent blunt conewas entirely subsonic. In all cases, the method of reference 19 gave better agreementwith the data. In the vicinity of the spherical nose (-0.16 0) HOCDoobC13cuito0)SOrtooooObD14Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-
27、,-,-lOOr80 30060 200O)4020100I I I I L_ I1.04 1.08 1.12 1.16 1.20 1.24 1.28 1.32Figure 2.- Variation of y with altitude for 15 flight-path entry into-mean MarsCatmosphere. V0 = 4.57 km/sec (15 000 ft/sec).15Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS
28、-,-,-ooo1 f-ro?r i- fO3.TZ l-i “ooSPf-l73co.|H8ICOoo16Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-0= 140jLj Rn/Rb = -25-a = 10(b) Blunt cone; Rn/Rb = 0.25.L-73-8007Figure 12.- Schlieren photographs of 100 cone in helium. M = 20.3; P2/Pj = 3-97-25
29、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a =0 a =0Bp KSQa = 5a = 10(a) Sharp cone; 7 = 0.25.a = 10(b) Blunt cone; Rn/Rb = 0.25.L-73-8008Figure 13.- Schlieren photographs of 120 cone in helium. M = 20.3; p /p = 3.97.26Provided by IHSNot for Res
30、aleNo reproduction or networking permitted without license from IHS-,-,-a =0 = 0a = 5 a = 5a = 10 a = 10(a) Sharp cone; Rn/Rb = 0.25. (b) Blunt cone; R = 0.25.L-73-8009Figure 14.- Schlieren photographs of 140 cone in helium. M = 20.3; P/P-, = 3.97.27Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-OOIaiaaCQOOOra*-(!-,aaOucuQ.rtJ=raOOra28Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
