1、RESEARCH MEMORANDUM * EFFECTS OF SOMI3 RIMARY VARIABLES OF RECTANGULAR 7 VORTEX GENETORS ON THE STATIC-PRESSURE. RISE THROUGH A SHORT DIFFUSER By E. Floyd Valentine and Raymond B. Cairoll Langley Aeronautical Laboratory Langley Field, Va. CLASSiFICATtON CANCELLED t,.-.- Date-/ll-/+!y _“_“ “_ “ “ - .
2、 -21 y-$2.uction,.blowing, aqd the uae of vortex generators. Vortex generators had been shown in reference 6 to be effective . in reducing the power reQuirement of a large wind tunnel. Reference 7 gives thk results obtained in a short annular diffuser with vortex generators. me short diffuser of ref
3、erLo, sp-to-inle+boun-l - - X . - C dl 0, and Which for these teswve = 7.3 and - = 0 0065 was taken as an anchor 6“ 6*1 dl point-. .-The geperal grocedure .was to provide for separate variation of c - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N
4、ACA RM 5213 - 5- each parameter tp include the value in the basic arrangement plus two values higher and two values lower than the value for the basic arrange- ment. As in reference 8, variation of spacing was accomplished by varying the nm mentioned n the variation of spacing, corresponding values
5、of span and chord .were obtained and are tabulated in table I. By the use of a fixed nmiber of airfoils of 1-inch span with the 5 chords already required, it was possible to vary the asp-ect ratio while maintaining the other pmameters constant. It was similarly possible to vary independently the ang
6、le of attack, the span-to-inlet-boundary-1-r thiclmess ratio, the inlet-boundary-layer thickness, and the longitudind location eth changes in spaswise length but no additional chords. Instrumentation. - Static-pressure measurements were wall static pressures measured at six radially distributed posi
7、tions at stations 1, 6, and 7 of figure 1. A single line of flush static orificesextended upstream of the diffuser inlet. Static-pressure measurements at these points and the readings from a total-pressure tGbe in the lt stations 6 and 7. This Survey device may be seen in place at station 6 in the p
8、hotograph of figure 2. I diffuser performance data of this investigation. All pressures were % Basis of comparison of vortex-generator arrangements.- In this work, as in reference 8, a quick method of evaA+ting each of a number of vortex- generator arrangements was required. Ream- for the adoption o
9、f the following procedure are detailed in reference 8. Arithmetic averages of the pressures frpn the cirqserentially distributed static-pressure orifices at station 6 and at station 7 were used for the diffuser and for the diffuser-tail-pipe exit pressure, respectively. For aninlet static pressure,
10、use was made of a tap at least 3 chords upstream of the vortex generators .in order to be out of the local pressure field of the - vortex generators and also mt affected by separation areas in the dif- fuser. These two static-pressure values were used with the upstream total-pressure. reading to com
11、pute values of Ap/qcl. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 RESULTS AND DISCUSSION NACA RM 52813 Diffuser With No Vortex Generators b 0bservation.of-mazro;meter board fluctuatTons and tufts described in reference 8 indicated that with th
12、e bare diffuser the flow fluctuated betmen two fairly definite patterns which were referred to as state .a and state b. It appeared. to be a defini.te alternation between two can- ditions rather than a simple rotation of the separated regfons about the Biffuser center line. In the present bvestigati
13、on this alternation was not so definite Hth .the bare diffuser and it was considered that one curve could be considered representative. WFth some of the- vortex- generator arrangements, however, there was an alternation between two definite.conditicrm-.and the results ofthe two are prasented as stat
14、e a and state b in the figures. Pressure rise through the diffuser and through the diffuser plus %ail;pi+ in tezini of inlet dynamic presaure is shown in figure 3 for two Wet-velocity values as a function of SZ/dl. These are cross plots of values picked from plots of the pres- sure rise nLeasUred at
15、 several. vdues of the flow rate. The values of 6*1 were obtained from surveys maae in .the inlet with the exception of- - that for the shortest length Met. duct.whfch ps obtained by a straight- line extrapolation of a logarfithmic plot of 6 l/dl against an inlet- pipe length. . -T$is was done becau
16、se the single measured value of S*l/dl for the shorteat length waa so inconsistent with the other values as to indicate that it-mrst have been influenced by some. local surface con-, dition which would prevent it from being representative of the entire inlet flow. . . . - . . - . . .- . “. - .I r. -
17、 .“ -. d - . . . . “ - .“ . * . The pressure-rise ratio through the diffuser (fig. 3) is seen to decrease as the inlet-buundw-1-r thickness increases far both inlet- velocity values. The pressure-rise ratio was lower dt the higher inlee veloci%y. The .same is true in the case oflthe pressure rise th
18、rough the diffuser plus tailpipe .except that the diminution with increase of Wet- boundary-layer thickness is not so great and there is considerably less difference between the high- a$ Tow-speed values of pressure-rise-ratio. Points ,representing the no-vortex-generator values of reference 8 are g
19、iven which are. seen not to fall exactly on these curves. The reasons for this would include different boundary-layer pr6file because of the cork transition strip upstream of the inlet pipe, reassembly of the entire setup with new joints, and the fact that throughout the present investigation the In
20、let- pipe just upstrean.of the transition sect-ion had its surface smoothness impaired by the large number of holes drilled for attaching the vortex generators. When not In use -the holes were taped on the outside and filled flush Iwith the inaer surface with glazing corn- - pound. It is considered
21、that the results with vortex geerators w0.uI.d not be affecked by these stirface conditions in their immediate vicinity. -. .- - “ - - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-7 Effects of Selectabie Vortex-Generator Varihfckness?of 0.0063 of
22、the wet afimeter. The fluctuation between two flow regimes is- elimiimted for the high-speed condition and at both speeds the circumferential variation is virtually elfminated. The boundary-layer profiles at the diffuser exik usudly could not be measured without vortex generators because .of .flow f
23、luctuation. Eow- ever, xLth the better vortex-generator arrangements they could be mearmred and did not require representation by an a and b case. ExEunples are For the thickest inlet-boundary-layer displacement $hickness, an approxi- mate curve for no vortex generators could be included. The result
24、s with the vortex generators are each similar in that they indicate the velocity gradient near the wall. has been increased by the vortex generators end a region of negative velocity gradient is observed. - given in figures 15 Klevatt, Paul L.: InVestigation of High-Subsonic Performance Characterist
25、ics of a 12O =-Inch Conical Diffuser, rzlcluding the Effects of Change in Lnlet-mdary-Layer Thickness. NACA RM LgHlO, 1950. 2. Little, B. H., Jr., and Wilbur, Stafford W. : High-Subsonic Performance Characteristics and Ibundary-Leyer Investigations of a 12 lO-lnch . Inlet-Diameter Conical Diffuser.
26、NACA RM L5OC02a, 1-950. 3. Copp, Martin R.: Effects of Inlet Wall Contour on the Pressure Recovery of a IOo 10-Inch-Inlet-Diameter Conical Diffuser. NACA RM L5Ulla, 1951. 4. Perah, Jerome: The Effect of the Inlet hkch Number and Inlet-Boundary- Layer Thickness on the Performance of a 23O Conical-Dif
27、fuser - Tail- Pipe Combination. NACA RM LgIUO, 1950. 5. Persh, Jerome: The Effect of Surface Roughness on the Performance of a 23O. Conical Diffuser at Subsonic Mach Numbers. NACA FM L5lKO9, 1951 6. Taylor, H. D.: Application of Vortex Generator ing Principle to Diffusers. Concluding Report. Air For
28、ce Contract W33-038 ac-21825, U.A.C. Rep. R-15064-5, United Aircraft Corp. Res. Dept., Dec. 31, 1948. 7. Wood, Charles C.: Preliminary Investigation of the Effects of Rec- tangular Vortex Generators on the PerformEince of a Short 1.9:l Straight-Wall Annular Diffuser. NACA RM L51G-09, 1951. 8. Valent
29、ine, E. Floyd, and Carroll, Ftaymond B.: Effects- of Several Arrangements of Rectangular Vortex Generators on the Static-Pressure Rise through a Short 2:l Diffuser. NACA RM LWL04, 195r. I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-dl .90 .8 5 p1
30、 HO .7 5 .7 0 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA RM 5213 - 27 .8 .6 ,4 .2 0 60 120 180 200 300 360 Circumferential looatfon, degrees v Figure 14. - Effect of selected vortex-generator arrangement on circum- ferential static-preseure
31、 variation at the diffuser exit (t = 2.09; b -= 7.3; 2 = 0.327; a = 150; 3 = 0.006. 6*1 C dl. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Normal distence from surface, inches 1.0 08 .6 .A 02 0 2 4 6 Normal distance from surface, inohes (a) - = 7.
32、3; a = 17.30; - = * 0.0065. b E*l dl Figure 15. - Diffuser-exit boundary-layer su%veG (: = 2-.09; = 0.327). _I_ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-c WA RM L52B13 . .I 0 2 4 6 8 Normal distance from surface, inches 2 4 6 8 Normal distance from surfaoe, inches (b) - = 4.6; a = 15; - - *I 0.0103. d “1 dl Figure 15.- Continued. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
