1、c Opy 51RM E54113RESEARCH MEMORANDUM “-EXPERIMENTAL INVESTIGATION OF DRAG OF AFTERBODIESWITH EXITING JET AT HIGH SUBSONIC MACH NUMBERSBy Reino J. Sal.miLewis Flight Propulsion LaboratoryIan., Ohio since”with seiated flowthe afterbodymy not experience the full pressure rise. The conventionwske blocka
2、ge correctionwas h the present case calculated to be smallrelative to the corrections applied and was”-notincluded.RESULTS AND DISCUSSIONAfterbodies without JetEffect of boattailing on pressure dra.”- The effects of boattail-ing on the externalpressure drag coefficient of the conical afterbodiesare
3、showrinfigure 6 for the jet-off case (equivalentsolid body). Thebase pressure coefficients-areassumed to apply over the entire base,and the tunnel-interferencecorrectionsapplied were for the full”presQ-sure rise( = 0). Figure 6(a) shows that, with a constant boattailsre of 5.630, increasingthe boatt
4、ail length by”reducing the base sizeresulted in a large kg” reduction for base%o-body dismeter ratios be-”tween 1.0 and 07. Similar results were obtaed in free-flight testsreported in refereiice1.” Figure 6(b) kdicates that,with a base-to-body dismeter ratio of 0.525, the optimum boattail angle at t
5、rsmsonicspeeds is about.lO”. This is somewhat higher than the optimum boattailangle,forthisspeed-range reported in reference 1. The drag.coefficientfor zero boattail angle in fie 6(b) was obtained”byassum3ngthe ssmebase pressme coefficient as S measured for the-model With a base-to=.body diameter ra
6、tio of 1.0.-,.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-“k l?ACA.sureRM E541.13 7Effect of base bleed. - The effects of base bleed on the base pres-coefficient and on the drag coefficient are shown in figure 7. Si.g-nificant reductions inthe pr
7、esswe but, for large base anniz the pressures were decreased. On a small baseannulus the Jet may deflect the free-stream flow outward and thus decel-erate the flow in the region of the base and ,ticreasethe base pressure.For a large base the jet bounda can ret to sn axial.direction beforemeettig the
8、 external flow; and, thus, the deflection of the free strby the jet is small, and the jet aspimuting effect on t= sedead-airregion reduces the base pressure.9 The integratedpressure drag coefficients are presented-in figure9 as a function of the jet pressure ratio. The variations h the dragcoefficie
9、ntwith jet pressure ratio are as would be expectedafter9Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 N therefore,eweriencedem adverse pressure gradient and may have been separated or near seyara-tion as it approached the base. The separation-tyy
10、eboundary-layer pro-file has low velocity orlow shear at the yall comparedwith a fullydeveloped flat-pLiteprofile.(as experiencedwith the nacelle at thepoint of forced separation);and, hence, the flow is less ableto as-pirate the base pressure to low,values. ,is may in part explain whythe presmwes o
11、ver the secondary-shroudfkps remmed high. Ccmpari.sonof the short-shroud ejector configuration is in this case difficult,be-cause the pressures in the large annular bseregion were not obtained. The drag coefficientsof the “iwacelle-“anthe fuselage-type after-bodies are compared in figure U5.on the”b
12、as”isof equal primary-nozzle -areas. It is significantthat the dfag of the fuselage-typeafterbodiesis considerablyless than that of the”na.celle-typeafterbadies, eventhough the resulting fuselagebody diameter is about 50 percent greater.In order to determinewhether the ag of a-body can be reducedby
13、in-creasingthe.body dismeter to obtain”theWnefits of boattailing, the vforebody and friction drag would have to”be considered.a71Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-9Effect of secondary flow. - In the subsonic cruising range of jet.pressu
14、re ratios, the external pressure drag coefficient was relativelylittle affectedly secondary-airflows of about 7 percent of the prhag(fig. 16). When the afterburner cooling passage forms a base annul.usthat is not closed for the cruise conditions, the secondary flow willincrease the static pressure i
15、n the plane of the annulus. Eowever, ifthe secondary air is taken in from the free stream solely for this pur-pose, a net increase in drag will result because of the momentum lossof the secondaryymThe resultsair, as discussed in reference 3, for example.SUMMK3YOF RESULTSof the investigationof the ex
16、ternal pressure drag ofvarious conical afterbody configurationsat high subsonic Mach nuniberscan be summarized as follows:y3 1. The afterbody pressure drag of a blunt-based body of revolutionwas considerably reduced by decreasing the base-to-bdy diameter ratiofrcm 1.0 to 0.7 witha 5.6 boattail. With
17、 a base-to-body diameter ratioof 0.525, tiimum pressure drag was obtained with a boattail angle of. approximately 10.2. When a convergentnozzle having a diameterO.375 that of the.bqdy discharged a jet from the base, boattailtig was again very effec-tive in reducing the afterbody drag. With no boatta
18、il the effect of thejet and stresm was to aspirate the large annular base to a very lowpres-sure. The jet effects were generally favorable for small base annuli.The incorporationof a boattail conibinedthe favorable effects of re-ductig the base annulus and of convergingthe flow before separation,whi
19、ch increased the afterbody and base pressures.3. m sted ejector installationswith a closed secondary shroud,the pressure drag of the high-angle shroud flaps could be very large innacelle-te installationswith no boattail upstream of the flaps. Ina fuselage-type installationwith am appreciableboattail
20、 ahead of theflaps, te dboattall angle, 5.63.I Free-dream Mach numbex%H o0 0.90.8CJo 4 8Wattail angle, , deg(bct of boattallan-e; /II_,. .Figure 6. - Effect of boattailing on afterbody pressure drag of blunt-base bodies.P-1Provided by IHSNot for ResaleNo reproduction or networking permitted without
21、license from IHS-,-,-.NACA RM E54113.12.08.040-.04-.08-.12.,.Inn,2/m%/Dn %,1 CD,2 %,2,neto 1.11 0.043 0.0321 0.087 0.28u.064 .051 : .193 .178.104 .27.208 .15Flagged symbols indicate jet-offSubscripts 1 and 2 refer to pointscm curves-lb .9 1.0 1.1 1.2Nozzle pressure ratio, Hn/PoFigure 7. - Effect of
22、base bleed on basepressureat Mach 0.9.coefficient.-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM E54113 19*.1cclm o-. 4.2.1J40-.1.4.3.2.10-. 1.-. 2rt1 , I I , I 1 I, ,t I I14 6 8 10 12Model station, in.(a) Constant boattall angle, 5.63.Figu
23、re 8. - Effect of jet on pressure distribution over ccnical afterbodiesat Mach 0.9.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.I ,Nozde prmmme ratio,%./P.8Jet-off2.197.061t -wB - 5.s30-.=4 6 6 10 12I Nozzle %ej,ye ,.s,.,$ Jut -off2.197,55 YF(IIi
24、II40)9 . 9:3.+-I I4 6 .9 10 12 4 6 e 10 12KOdel atationr In.(“0)Ccmstmt hmae dlemctnr ratio, =, 0.525.FW8 6. - Concludrd. Hrcct of Jot cm PMBmn dhtributian over ecmicalaftcrtodi” at 21ub 0.9,I1, ,# # ,. Q* , *f, ,/1. :, ,., ,hl, .11 i “ .,11. , Z!.lsProvided by IHSNot for ResaleNo reproduction or ne
25、tworking permitted without license from IHS-,-,-NACA RM E54113 21.36.32.28.24.08.040-.04Nozzle pressure ratio, q/P.(a) F.ree-stream Mach number, 0.8. (b) Free-stream Mach number, 0.9.Figure 9. - Effect or jet on drag of conical afterbodies. Boattail angle,” S.63.Provided by IHSNot for ResaleNo repro
26、duction or networking permitted without license from IHS-,-,-22.08.040.-. . NICA RM E541131 I I Boattail angle,I I I I I$, dego 5.63Db/Dn, 1.40.,.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-(a) -E-B-*Chti=, 0.6.11 1EE/o 2kszle passuro90/ _ _45/ -
27、/ -30/4 eratio, HJPo(b) Free-streamkcb mdmr, 0.8.no Oecolxls.ry flwj AJ&l 0.J!2Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-24.NAC.ARME54113-.14-.18# -.26t?&-.30-034Secondary-nozzle Nozzle pressureflap angle,e, c%:dego 30 Jet-off45 Jet-off 90 Jet-
28、off30v 4.4045b3.8890 3.94.2 .4 .6 .8 1.0Radius ratio, r/rmxFigure 12. - Pressure distribution over flaps ofnacelle-type ejector confim.arations.Fr-etreamMach number, 0.9.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MCA RME54113 25.Long shroud, fla
29、ps closed (B)- Long shroud, open (A).-Short shroud (C)-m-rI I I. OJ I I I I I(a) Free-stream Mach number, 0.6.04 Iw .0(b) Free-stream Mach number, O.8.08 f.04 “o 4 6 8Nozle pressure ratto, /P.(c) Free-stream Mach mmber, 0.9.Figure 13. - Effect of jet on external pressure dragof fuselage-type ejector
30、 configurations. No second-ary flow.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-26 mcA Ill!E54113.,o&o-.08-.16 a75nu /.ec: -.24 02t+ R Long Bhroud,0uIah: -.32m:m-.40-.48- - - _”.BI E10.0 10.5 “11.6 11.5 12.0Model statl. I J tb , I Iw 1-II7 II i t
31、Ol”Gye a101 !o 3.95II 3.43, , I 1 110.0 10.5 11.0 11,5 12.0 -,on, in.-.iR:-(a) Jet-off (b) Primary flow only.Figure 14. - Pressure distributions over fuselage-type-ejector afterbody configurations.Free-stream Maah number, 0.9. .Provided by IHSNot for ResaleNo reproduction or networking permitted wit
32、hout license from IHS-,-,-NACA RME54113 27.12.08.040Long shroud, flaps closedFlap angle, e, 90Flap angle, 13,45Flap angle, 9, 30DmxjDpID1.76Bq 2.542 4 6 8Nozzle pressure ratio, H.#oFigure 15. - Comparison of external pressure drag ofvarious ejector configurationswith equal primary-jet diameters. Fre
33、e-stream Mach number, 0.90Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NK!ARME 5411301 Secondary-to-primarymass-flow ratio.24.20. x/.16 d.12. a.08”.04” +o 2 4 6 8 10Nozzle pressure ratio, /POFigure 16. - Effect of secondary flow on external.afterbody pres-sure drag at free-stream Mach number of 0.9.NACA-Lmgley- 11-29-64-326Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
