1、NASA Technical Paper 2005 April 1982 NASA Effects of Axisymmetric and Normal An Jet Plumes and Solid Plume on Cylindrical Afterbody Pressure Distributions at Mach Numbers From 1.65 to 2.50 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY
2、KAFB, NM NASA Technical Paper 2005 1982 National Aeronautics and Space Administration Scientific and Technical information Branch Effects of Axisymmetric and Normal Air Jet Plumes and Solid Plume on Cylindrical Afterbody Pressure Distributions at Mach Numbers From 1.65 to 2.50 Peter F. Cove11 Langle
3、y Research Center Hampton, Virginia 111 111 1111111111111111111111111111111 I II I I 11111111 I“II II I I I 1. I I II 111111111II1111 I 111111 I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SUMMARY An experimental wind-tunnel investigation has bee
4、n conducted to determine simu- lated rocket plume interference effects due to various plume simulation devices. Afterbody pressure distributions and base pressures were measured on a strut-mounted ogive-cylinder afterbody model. A series of axisymmetric air nozzles, a solid plume, and a normal air j
5、et nozzle were tested on the model at Mach numbers from 1.65 to 2.50, a Reynolds number per meter of 6.56 x lo6, and an angle of attack of Oo . The axisymmetric nozzles, which varied in exit lip Mach number from 1.7 to 2.7, were designed to produce a selected underexpanded plume shape for conditions
6、 of no exter- nal flow. The solid plume matched this plume shape. The normal air jet nozzle con- sisted of two circumferential rows of orifices which discharged perpendicular to the longitudinal axis and downstream of the model base. The solid plume induces greater afterbody disturbances and base pr
7、essures than those induced by the axisymmetric nozzle plumes at the selected underexpanded con- ditions, and the differences increase with Mach number. The plume-induced afterbody disturbance distance and base pressure for each axisymmetric air nozzle can be cor- related with the induced effects of
8、the other air nozzles by matching a thrust coef- ficient parameter which is based on nozzle lip conditions. At constant base pres- sures, the normal air jet plume and solid plume induce afterbody disturbance dis- tances that agree to within about 1/10 body diameter with those induced by the axi- sym
9、metric plumes, except at plateau base pressures associated with high thrust levels. INTRODUCTION The interaction of a rocket exhaust plume with the flow over a missile can affect performance, stability, and control characteristics. This interaction arises because the exhaust plume produced by a rock
10、et nozzle operating at underexpanded conditions interferes with the external flow such that the afterbody flow field and base pressures are affected. Previous investigations have been conducted by using air and gas-powered axisymmetric nozzle plumes, normal air jets which exhaust per- pendicular to
11、the body longitudinal axis, and solid plumes to simulate an axisymmet- ric rocket exhaust plume (refs. 1 to 7). The solid plume and normal air jet plume simulators are usually employed on sting-mounted force models where the axisymmetric nozzle is not practical. Efforts to correlate the interference
12、 effects of these simulation methods with each other or with flight or rocket sled data (refs. 8 and 91, particularly at supersonic speeds, have been limited (ref. 10). Reference 11 contains comparisons made between several plume simulation devices at transonic speeds. The purpose of this investigat
13、ion was to measure and correlate the afterbody interference effects induced by various axisymmetric air jet plumes, normal air jet plumes, and a solid plume at supersonic free-stream Mach numbers. Four axisymmetric nozzles with different exit lip Mach numbers and exit angles were designed according
14、to the method of reference 12 to produce congruent exhaust plume geometries over the initial expansion region at one selected underexpanded nozzle operating condition. The effects of the external flow on the air plume boundary were not considered in the analysis. A solid plume simulator with the sam
15、e geometry as the selected under- -. *d Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-expanded design air plume was tested for comparison with the air plumes. The axi- symmetric air nozzles were operated over a range OE jet pressure ratios so that
16、noz- zle operating parameters could be determined which correlate the plume-induced effects or the diEferent nozzles. The normal jet plume simulator nozzle was designed to produce a variable disk-shaped air plume downstream of the model base. The normal jet plume-induced effects were compared and co
17、rrelated with those induced by the axisymmetric plumes. In this investigation, the afterbody pressure distributions and base pressures were measured on a strut-mounted ogive-cylinder body. Tests were run at free-stream Mach numbers of 1.65, 2.00, and 2.50 with angles of attack and sideslip maintaine
18、d at Oo. SYMBOLS A cP CT D M M.8. P Pt,j r X Y cf 2 area, cm pressure coefficient, P - P, qa, Thrust thrust coefficient, - q-% body diameter, cm Mach number model station static pressure, Pa jet total pressure, Pa dynamic pressure, Pa radial distance from model center line, cm distance measured upst
19、ream Erom base, cm ratio of specific heats, 1.4 or air disturbance distance, cm Subscripts: b base e exit R 1 ip nj normal jet r radial 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I t P) throat free-stream conditions MODEL AND APPARATUS The tes
20、t model consisted of an ogive-cylinder body mounted on a strut which supplied high pressure air to the model plenum. (See fig. 1.) Interchangeable afterbody-nozzle sections contained 10 surface static-pressure orifices and a base pressure manifold located opposite the strut. (See fig. 2.) A photogra
21、ph of the model installed in the wind tunnel is shown as figure 3. The strut was inclined 60 from the vertical in order to locate the model near the center of the test section. The four axisymmetric air nozzles were designed to produce a selected geometri- cally congruent exhaust plume shape over th
22、e initial expansion region. The analysis used in the design is the method proposed in reference 12 which uses an improved method of characteristics to determine the initial expansion angle and radius of curvature of the plume. This circular arc approximation is shown in reference 12 to match the plu
23、me geometry as predicted by the method of characteristics solution over about 1 nozzle exit radius from the base plane. The effects of the free-stream flow are not considered. Nozzle design is accomplished by selecting an exit lip Mach number and external ambient pressure and varying the nozzle lip
24、angle and exit pres- sure to achieve the design plume geometry. With the lip angle established, the noz- zle throat is designed to produce the selected exit lip Mach number. For the wind- tunnel tests, the ratio of jet total pressure to base pressure was selected as the nozzle operating parameter ra
25、ther than the conventional jet pressure ratio since the plume expansion is initially influenced by the local base conditions. Figure 4 shows the nozzle geometries, and their coordinates are given in table I. The solid plume simulator, which matches the selected underexpanded air plume geometry, is s
26、hown in figure 5. Also shown is the normal jet nozzle, which consists of 2 circumferential rows of 12 orifices each, located 0.66 body diameter downstream of the base, and discharges normal to the lonyitudinal axis of the model. DATA REDUCTION The thrust coefficient for the axisymmetric air nozzles
27、is computed by using the following one-dimensional isentropic equation: 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The conditions at the exit, Me and per were determined from the nozzle area ratio and one-dimensional isentropic relationships.
28、(thrust coefficient based on lip conditions) is cT,R The correlation parameter computed by using the following thrust coefficient equation. Note that the exit Mach number is replaced by the lip Mach number and the exit pres- sure is replaced by the lip pressure. The lip Mach number is obtained from
29、the analysis in reference 12 and is utilized in the one-dimensional isentropic relation- ship for determining the lip pressure. The radial thrust for the normal jet plume simulator is defined as the sum of the magnitudes of the thrusts of each radially exhausting orifice, and the radial thrust coeff
30、icient is computed as follows: - 0.5283. e t, j where - TEST CONDITIONS The tests were conducted in the Langley Unitary Plan Wind Tunnel at Mach numbers of 1.65, 2.00, and 2.50; a Reynolds number per meter of 6.56 x lo6: and stagnation temperature of 325 K. A detailed description and calibration of
31、this facility is presented in reference 13. The tunnel dew point and model air jet dew point were maintained sufficiently low to insure negligible condensation effects in the test section and model nozzles. Tests were conducted for jet pressure ratios up to 615 which produced ratios of jet total pre
32、ssure to base pressure of up to 275. Model plenum stagnation temperature varied between 300 K and 311 K. Model angle of attack and angle of sideslip were maintained at 00. FZSULTS AND DISCUSSION A comparison of the afterbody pressure distributions for the four axisymmetric air nozzles at the selecte
33、d underexpanded plume design conditions and for the solid plume is shown in figure 6. Table I1 contains a listing of the nozzle operating parameters for these plume design conditions. The solid plume induces higher after- body pressures which also extend further upstream than do those induced by the
34、 design air plumes. The difference in the maximum afterbody pressure increases as the free- stream Mach number increases. Base pressures for these same conditions are shown in figure 7, and as the free-stream Mach number increases, the solid plume induces base pressures much higher than do the air p
35、lumes. The differences between the solid and 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-air plume results as indicated in figures 6 and 7 show that the external free-stream flow significantly alters the effective geometry of the air plumes out
36、side the base region. The afterbody pressure distributions for the four axisymmetric air nozzles operating over a range of underexpanded conditions are presented in figure 8. The afterbody pressures increase and the disturbed flow region moves upstream of the base as the thrust coefficient increases
37、. The plateau afterbody pressures increase with free-stream Mach number. Schlieren photographs (fig. 9) indicate a separated flow region on the afterbody associated with the disturbed flow region noted in the pressure distributions. Although the actual occurrence of boundary-layer separation was not
38、 determined during this test, previous investigations have noted that separation occurs slightly down- stream of the pressure rise (ref. 14). Analysis of jet-off afterbody pressure dis- tributions show that the shocks which appear to cross the afterbody at produce negligible interference effects. Mm
39、 = 1.65 In order to quantitatively define the afterbody disturbance effects, a distur- bance distance 0 was defined as the distance from the base of the model to the point where the plume-induced pressure rise intersects the jet-off pressure distri- bution. The results in figure 10 indicate a nearly
40、 linear variation of the distur- bance distance with the nozzle thrust coefficient for the four axisymmetric air noz- zles. Note that the typical disturbance distance uncertainty due to pressure distri- bution curve fairing corresponds to the distance between the static-pressure orifices on the afte
41、rbody. The variation of base pressure coefficient with thrust coefficient is shown in figure 11. The base pressures correlate as a function of thrust coef- which resembles the nozzle thrust coefficient but is ficient. The parameter computed with nozzle lip con itions, was found to reduce the data sc
42、atter, particu- as larly for the disturbance distance results. (See figs. 12 and 13.) With C the correlation parameter, figure 14 summarizes the interference characteristics induced by all four air nozzles. At constant CT, the disturbance distance and the base pressure coefficient decreases as free-
43、stream Mach number increases. CT,g T,R Presented in figure 15 are the afterbody pressure distributions for the normal air jet model. As the radial thrust coefficient increases, the afterbody pressures increase to a plateau value, and the pressure increases extend further upstream. The results in fig
44、ure 16 show that the variation of the disturbance distance with the radial thrust coefficient is nearly linear and insensitive to free-stream Mach number change. For values of a/D greater than 0.2, the uncertainty band increases because of the greater pressure orifice spacing. The variation of base
45、pressure coefficient with radial thrust coefficient (fig. 17) does change with free-stream Mach number at a constant radial thrust coefficient. Schlieren photographs of the normal air jet plume are shown in figure 18. A comparison of the interference effects induced by the normal air jet and the axi
46、symmetric air plumes is shown in figure 19. By matching the base pressure, the afterbody disturbance distance induced by the normal jet matches that of the axi- symmetric plume within approximately 1/10 body diameter for conditions well below the plateau base pressures. The base pressure has been sh
47、own to correlate afterbody disturbance effects between axisymmetric and normal jet plumes at transonic speeds (ref. 11). At the plateau base pressures, which correspond to high thrust levels, the disturbance distance varies greatly, and the differences between the normal and axisymmetric jet plume e
48、ffects are much larger. Also shown in figure 19 are the 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-results for the solid plume which, with the base pressure as the correlation param- eter, induces disturbance distances that nearly match those
49、induced by the axisymmet- ric air plumes. In order to utilize the solid plume or the normal jet to simulate plume disturbances, it is necessary to have data on the induced base pressures for the axisymmetric nozzle that is being simulated. CONCLUSIONS A wind-tunnel investigation has been conducted to determine the simulated rocket plume interference effects on a strut-mounted ogive-cylin
