1、“ i r I =. 5 CONFIDENTIAL COPY R;M L54G23 .1 c “ “ . * .- i i “-. RESEARCH MEMORANDUM EFFECTS OF DIFFUSER AND CENTER-BODY LENGTH ON PERFORMANCE OF ANNULAR DIFFUSERS WITH CONSTANT-DLAMETER OUTER WALLS AND WITH VORTEX-GENERATOR FLOW CONTROLS By Charles C. Wood and James T. Higginbotham NATIONAL ADVISO
2、RY COMMITTEE FOR AERONAUTICS WASHINGTON September 14,1954 . CQNFIDENTIAL Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Y NACA RM L54G21 By Charles C. Wood ezld J.es T. Higgir-botham Date. obtained Fr 8 program to determine the performance imsroveEe
3、nts attzinable through the use of boundary-layer controls in e,nnul=r affusers epplice3le to turbojet afterburners are summarized for five diffusers tested with end withoat vortex-generator controls. The elfects on per- formce of both the diffuser length an6 the center-body length are enpha- sized.
4、The di-?users mied in length from abrupt dump to a length corresponding to a equivalent cone m-gle of 15O. All diffusers had a constat outer-body dimeter of 21 inches, a retFo of outer-body diameter to center-body di mean inlet Mach nufbers up to aboct 0 . and both exial flow and x) .6O of vhirling
5、flow. The diffuser of reference 7 was tested under the same conditions for axial flow only. diaTeter of duct mass flow static pressure . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM: L5kG21 3 I Jr2 pusr e L 1 P weighteO static pressure, im
6、pact pressure, H - p a_C - mean impact pressure, B - p - r rCi static-pressure coefficient based on weighted static pressures, P - Pi Cci Bi - El. loss coefficient, bow-dary-layer boundary-layer boundary-layer %i thickne s s Oisplacener-t thickness, s,“ (1 - ;)dY - 6“ e bo-adary-layer shape pazamete
7、r P mass density , X wMrl agle, measured with respect to the difzuser center line r z wefghted whirl angle , 1 /fr2 J p-dr re loceted at the end of each center bo the correspondh thus, the lesgth of each dizfuser plus its tailpipe is equd to the length of any other diffaser plus its tailpipe (Q/d2 +
8、 therefore, the differences in shape of the initial sectiom ol diffusers 1, 2, and 3 are believed to be unimsortant. Furtherxore, the Soundary-layer theory given in refer- ence 9 shows thzt for short diffusers of the type discussed herein the boundmy-layer growtr, characteristics in e. diffuser of g
9、iven length tend -Lo become kdependent of diffuser shape but Secorce grincipally a function of area ratio. Therefore, it is believed that the differences in center- body shages sizovn in figure 2 are of secondary ixsorta-n-ce and that any variations in serformance are due primarily to differences in
10、 diffuser or center-Sody length. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Vortex Generators - Dzta are compwed herein ?or only the vortex-generator wrangements - which produced the best performance or which illustrate certain inportant, phenom
11、ena. Arrangenents 1 md 2 (see table I were used with axial flow, mci errvlgemnts 3 aad 4 with rotatiozal flow. ArrLngexent 1 was a counterrotating arrangement (adjacent generators set at angles 01“ opposite sense). krengezent 2 included arrengerrent 1 in addition to a second row of counterrotating g
12、enerators located downstream from the first .zt approxi mtely the observed separation point witn no control. In mrmgetnent 3 (see fig. 3), the purpose of the lerge-span generators attached to the outer wall was to straighten the flow; wherees, the szra11-spzn generators attached to the inner shell w
13、ere intended to control seperation. Arrange- ment wrargenent 3 reEoved all the whirl from the flow; whereas, arrangement 4 did not. Thus arrmgement 3 pem-i-lted the formtion of extensive separated-flow regions acijacent -Lo the center body becmse the flow vas epproxinztely ais1 in this region. Tine
14、favorzble ef3ect on diffuser perforrm-ce of a whirling flow ne= the center body hs been noted previously for the abrupt- expansion diffuser reported Ln reference 3. This effect alscj is believed to be responsible for the differences betveen arrangements 3 end 4 ta the benzvior of the static-pressure
15、-rise coefficient (fig. 14(b) with chLnge in center-boay lev this is generally true even when controls are .;sed. Tne radial static-p-essure gradients, which mrangements 3 and k largely eliminate this gradient for all except difhser 5. Red-Action in diffuser le-?g-Lk; poduced unfavorable chmges in t
16、ne velmity distribution at the diffuser exit stations for botn control end no control. Ax the tailsise station, the change in velocity distribution with center-So however, gereral conclusions are not %validated. The diffuser- exit data of figure l7( a) hdicate increasing distortion of tine velocity
17、distribution with progressive shortening of the diffuser. With PO con- trol, each diffuser had a regfon of no positive axial flow ne- the duct center line. Vortex generators elimlnated tzis region for diffuser 1 but did not appreciably improve the distributions for diffusers 2 and 3. The velocity di
18、stribxtions at the fixed teflpipe statioc for all center-b5dy lengths except nLiber 5 ere zpproximately tl?e sane with 110 control. Each has a smll regioc of no axial flow near the dxt center line. Control inproves the velocity distributions and eliminates the regions of no exial flow. The cxrves in
19、diczte that the longer center bodies proaxe somewhat better distribztions. This trend is acceGtmted by %he lass-flow-discregancy data. The rixing accomplisked in Yne tail- pipe section prohces agprecieble improvemen-cs in the velocity distrib-c%ions. Longitudinal static-pressure distributions.- Long
20、itudinal veriations of static pressure along the imer and outer walls are presented in fig- ure 18 for all configuratiors wit3 and without control. A coxparison or figures 11 (axial flow) ad 18 will skow that the lmge radial pres- sure gradients set LIP by the whirling xotion influenced the lor-gitu
21、dinal gradients ts a high degree, especially on the inner wall. This effect prohibits correlatlon of the curves relative to ?low se2aration in a manner similar to tr-e ucial-flow correlation. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-c CONCLUSI
22、ONS The following conclusion the exit velocity distribution becmie progressively less cniforn with diffuser shortening with or vithout vortex generators. 6. Vortex generators improved significcrttly the static-pressure- rise coefficient of the longer diffusers and the velocity distribxtion at the fi
23、xed tailgine stztion for all center bodies teste6 except the a3rupt-expansion case. - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-7. The combination of -e 31 diffxser and tailpipe produced slightly less static-press-xe rise zhan the l5O diffuser
24、for both no control ananguI.ar, untwisted airfoil7 :hoxd., in. 3 3 2 3 3 3 Location upstream (+) or downstream (-) from cylinder- diffuser junction, in. +I ox +4 (4 Wall Inner Inner Inner Outer Inner Inner aGenera-l;ore for all diffusers except diffuser 5 were located at +1. bDiffuser 2 had 20 vorte
25、x generators located at -7 inches; diffuser 3 had 211. mrtex generators located at -4 inches Dif Puser 12345 xxxxx I xx I xxx xx X Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ru N Figure 1 - Schematic diagram of diffuser 2. All d.imensions are in
26、 inches. I . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-“ Coordina.tes for diffuser 2 Coordinates for diffuser 3 I a aL 0 .I .2 .3 3 -5 .6 .7 .8 Distance from the cylinder diffuser junction,d2 Figure 2. - Schematic view and area-distribution cur
27、ve of each of the five diffusers investigated A“ dimensions are in inches. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-t Figure 3.- Diffuser 1 with vortex generators on both Lhe inner and outer walls (vortex-generator arrangement 3). I Provided b
28、y IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- “ -.l I I -1. h1.e I; angle of whirl 0 oo 20.6 0 3. 2 3 0 1. 2 3 - . Distance from the outer wall, in. Figure 4.- Radial variations of total pressure, static pressure, and whirl angle at the diffuser inlet for l
29、am inlet-whirl angles. Pi/Zj.* = 0.93. - 1 2 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3.6 32 2.8 c A .- - 2.4 * - - 0 2.0 L t e, 3 0 E 2 I .6 v- $ 1.2 c 0 co t .- a .8 .4 0 I . - IDiffuser inner wall 1 .5 .6 .7 .% .9 1.0, 1.0, Ratio of local
30、 velocity to peak velocity,u/U 1.00 I .o, Figure 5.- Velocity profiles at four equally spaced sectlons around the diffuser inlet station. 0; pressure ratio, Pihr - Figure 6.- Variation of loss coefficient and static-pressure coefficient at the diffuser exit and tailpipe stations with inlet pressure
31、ra.l;io for each of the five diffusers without vortex generabors. % = 0. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-28 - NACA RM L54G21 Cenfer- body length, (b) Measurements to fixed tailgipe ststion; varia3le center-3ody length. Figure 7.- Vari
32、ations of the static-pressure end loss coefficients with difIZser mi! center-body length. = Oo; ci/Hi = 0.94. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1 Dif fuaer number 54 3 2 -1 0 I I I I I I I I I 1 0 c .1 .2 93 . IC .5 .6 .7 .8 99 1 .o 1 .l Center-body length, 2 d2 Figure 8.- Effects of center-body 1engLh on the apparent errors in mass flow be-Lween-the inlet station and survey sLa.i;ions located downstream. Xi = 0; &/Hi = 0.95. I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
