REG NASA-TM-X-1960-1970 Jet effects on the boattail axial force of conical afterbodies at subsonic and transonic speeds.pdf

1、- - - NASA -, , NASA TM X-IT60 1 AXIAL FORCE OF GONICAL AFTFmODIES AT SUBSONIC AND TRANSOM(: SPEEDS by Wii/aam B. Compdon III and Jack F. Runckel Lwngky Research Center Lzngky SstJan, Hamptan, Vrc. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ERRA

2、TA NASA Technical Memorandum X- 1960 JET EFFECTS ON THE BOATTAIL AXIAL FORCE OF CONICAL AFTERBODIES AT SUBSONIC AND TRANSONIC SPEEDS By William B. Compton I11 and Jack F. Runckel February 1970 Page 71, figure l5(b): The CA scale for ,?/dm = 1.0 (top plot) should be shifted so that the zero line will

3、 fall where the .04 line is indicated; that is, the range of the scale should be from -.04 to .16. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-o or sale by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 2

4、2151 1. Report No. NASA TM X-1960 2. Government Accession No. 3. Recipients Catalog No. 4. Title and Subtitle JET EFFECTS ON THE BOATTAIL AXIAL FORCE OF CONICAL AFTERBODIES AT SUBSONIC AND TRANSONIC SPEEDS 7. Author(s) William B. Compton II I and Jack F. Runckel 9. Performing Orgonizotion Name and A

5、ddress NASA Langley Research Center Hampton, Va. 23365 12. Sponsoring Agency Name and Address National Aeronautics and Space Administration Washington, D.C. 20546 5. Report Date February 1970 6. Performing Organization Code 8. Performing Organization Report No L-6730 10. Work Unit No. 720-03-1142-23

6、 11. Contract or Grant No. 13. Type of Report and Period Covered Technical Memorandum 14. Sponsoring Agency Code 15. Supplementary Notes 16. Abstract A parametric investigation has been conducted to determine the jet effects on the boattail axial force of nozzles having truncated conical afterbodies

7、. The boattail axial force for nozzle configurations having boattail angles of 3O, 54 lo0, and 15O and having ratios of boattail length to maximum diameter of 1.0, 0.8, and 0.6 was compared for the jet-off condition and for a wide range of jet pressure ratios. A nozzle con- figuration with a boattai

8、l angle of 7.5O, one with a boattail angle of 20, and one with a circular-arc boattail were tested also. The tests were run at an angle of attack of O0 and through a Mach number range of 0.30 to 1.30. 18. Distribution Statement Unclassified - Unlimited Provided by IHSNot for ResaleNo reproduction or

9、 networking permitted without license from IHS-,-,-JET EFFECTS ON THE BOATTAIL AXLAL FORCE OF CONICAL AFTERBODIES AT SUBSONIC AND TRANSONIC SPEEDS By William B. Compton ID and Jack F. Runckel Langley Research Center SUMMARY A parametric investigation has been conducted to determine the jet effects o

10、n the boattail axial force of nozzles having truncated conical afterbodies. The boattail axial force for nozzle configurations having boattail angles of 3O, 5O, lo0, and 15 and having ratios of boattail length to maximum diameter of 1.0, 0.8, and 0.6 was compared for the jet-off condition and for a

11、wide range of jet pressure ratios. The different nozzle con- figurations represented various positions of three variable-f lap conver gent-divergent nozzles of different lengths. A nozzle configuration with a boattail angle of 7.5O, one with a boattail angle of 20, and one with a circular-arc boatta

12、il were tested also. The tests were run at an angle of attack of O0 and through a Mach number range of 0.30 to 1.30. Reynolds number based on model length was in the range of 8 X 106 to 16 x 106 depending on the Mach number. Results indicate that, in general, boattail axial force continually decline

13、d with increasing jet pressure ratio above an exit-pressure ratio of 1.0. For the same jet exit-pressure ratio, or equal jet pluming, the configurations with the larger boattail angles generally received more favorable jet interference, compared with the jet-off conditions, than those with the small

14、er boattail angles. With the jet operating, short- ening the boattail length at conditions in which the boattail pressures have recovered to greater than free-stream value can cause a decrease in axial force. INTRODUCTION Aircraft which have operational capabilities at subsonic, transonic, and super

15、sonic speeds require variable-geometry exhaust nozzles for which both the internal-expansion ratio and the external boattail angle must change with Mach number and altitude for opti- mum performance (ref. 1). The wide range of external geometric variations that is pos- sible with engines proposed fo

16、r multimission aircraft have made prediction of the nozzle boattail drag difficult. Many of the available prediction methods are based on theoretical or experimental models which do not account for flow exhausting from the boattail base. For supersonic speeds, theoretical calculations of boattail dr

17、ag have been used for Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-axisymmetric boattailed afterbodies with cylindrical forebodies (for example, refs. 2 to 6). Experimental results at supersonic speeds on conical boattails are presented in ref- er

18、ences 4 and ?. In the subsonic and transonic speed range, however, experimental data have been the basic source of information (ref. 8, for example). Recently some progress in theoretical analysis at subsonic speeds has been accomplished by using potential-flow theory and by accounting for compressi

19、bility and viscous effects (ref. 9). This analysis, however, has not been applied to conical boattails with sharp corners and does not include jet interference effects. Unless the jet interference effects on boattail pressures can be predicted, the jet-off pressure drag of conical boattails in exter

20、nal flow is of little value in determining exhaust- nozzle thrust-minus-boattail-drag performance. These effects can be large, particularly at subsonic speeds with the jet operating underexpanded. Examples of jet effects on conical-boattail drag are given in references 10 to 19. One of the few attem

21、pts to provide data for a systematic variation in conical-boattail geometric parameters, with jet inter- ference effects included, is reported in reference 12. This information, however, has limited application for current conical-boattail exhaust nozzles because (1) a sonic jet at the exit of the b

22、oattail was used and (2) models with large bases and generally much larger boattail angles than those proposed for current aircraft engine nozzles were investigated. The present investigation was conducted in the Langley 16-foot transonic tunnel to provide parametric information on the variable-flap

23、-type convergent-divergent nozzle. The primary variables selected were conical-boattail angle and length of the variable external flap. A nacelle model with a 15.24-cm diameter was tested with a series of fixed conical-boattail convergent-divergent nozzles using airflow for jet simulation. Data were

24、 obtained over a wide range of jet pressure ratio in order to operate each fixed nozzle in both overexpanded and underexpanded conditions. The model configurations were investigated at Mach numbers ranging from 0.30 to 1.30 and at an angle of attack of 0. For the Mach number range and the nozzle exp

25、ansion ratios of the configurations of the present investigation, the jet interference effects on boattail axial force should be similar to those for air -breathing turbine engines. Information on a reference nozzle with a circular-arc boattail is given in appendix A. SYMBOLS A area, m2 FA axial-for

26、ce coefficient, - q Am Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-pressure coefficient, pz - p, q length of convergent section of nozzle (see fig. 4), m diameter, m axial force, N axial distance from nozzle throat, positive aft (see fig. 4), m i

27、ntegers boattail length in axial direction (see fig. 4), m length of boattail flap parallel to boattail surface (see fig. 4), m free-stream Mach number local Mach number pressure, N/m2 free-stream dynamic pressure, N/m2 maximum radius of model, m radial distance from center line of model, m spacing

28、between nozzle throat and exit (see fig. 4), m local velocity, m/s velocity at edge of boundary layer, m/s axial distance from boattail corner, positive aft (see fig. 4), m axial distance from nose of model, m radial distance from model surface, m Provided by IHSNot for ResaleNo reproduction or netw

29、orking permitted without license from IHS-,-,-nozzle divergence half-angle (see fig. 4), deg boattail angle, angle between axis of symmetry and generatrix of model afterbody (see fig. 4), deg boundary - layer thickness, m nozzle internal- expansion ratio, Ae/Ath nozzle convergence half-angle (see fi

30、g. 4), deg angular location measured from, and in a plane perpendicular to, axis of symmetry of model, clockwise direction positive when viewed from rear, O0 at top of model (see fig. 4), deg Subscripts: a afterbody av average b base bal balance des design dw divergent wall e exit f friction j jet Z

31、 local m maximum Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-throat boattail free stream APPARATUS AND PROCEDURE Wind Tunnel This investigation was conducted in the Langley 16-foot transonic tunnel, which is a single-return, continuous tunnel wit

32、h an octagonal slotted test section measuring 4.73 meters across the flats. By pumping low-energy air from the plenum which sur- rounds the slotted test section, a Mach number of 1.3 can be attained. For cooling, the tunnel is equipped with an air-exchange tower which continuously exchanges air with

33、 the atmosphere, the result being that the tunnel stagnation pressure is approximately equal to atmospheric pressure. Model General.- The basic model to which the different nozzle configurations tested in this investigation were attached was an air-powered cone-cylinder nacelle with a rounded should

34、er at the junction of the nose and the cylindrical section (see fig. 1). A continuous flow of dry high-pressure air at a total temperature of approximately 270 K to 300 K was used for the jet exhaust. Boundary-layer transition was fixed at 5.08 cm from the nose of the model by a strip of No. 100 gri

35、t approximately 5 mm wide. The model was supported from the tunnel floor by a 5-percent-thick strut swept back with respect to the model and having a leading-edge sweep of 45O. The details of the model including the air introduction and balance arrangements are shown in figure 2 in which the portion

36、 of the model supported by the balance is indi- cated by fine hatching and dots, and in which the path of the air is indicated by arrows. The air is introduced perpendicularly to the model axis into the section of the model sup- ported by the balance through eight sonic nozzles equally spaced radial

37、ly around a center core. The eight radial nozzles are not supported by the balance; therefore, the balance measures the true thrust due to the acceleration of the air rearward. Two flexible metal bellows, arranged so that one is ahead and one is behind their respective points of attach- ment to the

38、fixed portion of the model, seal the forward portion of the air chamber, an arrangement which prevents the pressurizing of the bellows from loading the balance. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The flow-smoothing screens were made of 0

39、.635-mesh 0.0635-cm-diameter wire cloth backed by four support vanes. The total pressure and temperature behind the screens were measured by single pressure and temperature probes to minimize flow distortion. The measurement of average total pressure by using only one probe was found to be acceptabl

40、e by rake surveys which indicated that the total-pressure profile in this region was essentially flat for all the sizes of nozzles used in this investigation. Nozzle configurations.- The different configurations tested in this investigation were intended to simulate various positions of each of thre

41、e variable-flap convergent-divergent nozzles. The corifiguration series was formulated by assuming that a variable-flap convergent-divergent nozzle having a ratio of basic flap length to maximum diameter of 1.0 would have a O0 boattail at a design jet total-pressure ratio of 34. Configuration extern

42、al geometry was varied only aft of axial station 104.14, the location of the theoret- ical hinge point for the nozzle flaps. The selected fixed boattail angles p were 0, 3O, 5O, lo0, and 15 for each of the three nozzles having respective ratios of flap length to maximum nacelle diameter of 1.0, 0.8,

43、 and 0.6. The extent of the boattail geometric variations is indicated graphically in figure 3 in which the symbols represent the config- urations investigated. Three other nozzles, one with a boattail angle of 7.5O, one with a boattail angle of 20, and one with a ratio of boattail length to maximum

44、 diameter of 0.638, are also indicated in the figure. The top portion of the figure shows the variation of the ratio of base diameter to maximum diameter with boattail angle whereas the bottom por- tion represents the variation of boattail fineness ratio /d, with the ratio of base area to maximum ar

45、ea. The corner insert sketch illustrates how the boattail angle varies for a flap hinge point which is located at station 104.14. A sketch of a typical variable-flap nozzle configuration is presented in figure 4 and pertinent geometric parameters are listed for all test configurations along with the

46、 con- figuration numbers. At the theoretical hinge point of the nozzle flaps, all nozzles had a cross-sectional area of 182.4 cm2. The junction of the cylindrical section and the boattail was machined as a sharp corner and was at the same station for all the variable-flap noz- zle configurations. In

47、 keeping with the variable-flap design, the difference between the exit and base diameters was kept small (see fig. 4). The nozzle internal geometry was chosen to represent two types of flight operation, acceleration with maximum augmentation (large throat area) and cruise at unaugmented power (smal

48、l throat area). Nozzles representing augmented-power configurations included those with 3O, 5O, and 10 boattails (see fig. 4). Also, some of the nozzles with 0 boat- tails represented augmented-power configurations. A ratio of throat area to maximum cross- sectional area of about 0.4 5 was maintaine

49、d for these configurations except config- uration 5 for which model geometric constraints altered the design. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The subsonic-cruise nozzles, p = 20, 15O, and 7.5, are represented by configu- rations 6, 12, and 18 to 21. Co