1、REPORT 1201PERFORNIANCEAREA RATIOAND BOUNDARY-LAYER DATA FROM 12 AND 23 CONICAL DIFFUSERS2.0 AT MACH NUMBERS UP TO CHOKING AND REYNOLDS NUMBERS UPTO 7.5x1o tBy B. H. LITTLE, JR. and STAFFORD W. WILBURSUMMARYFor eachof twoin?.d-boundarv-huierthicknesses,performanceand bownda-luyer Characti-tics- have
2、 been dGirwd fora 12)10-inch-inletdiumeter diuser, a 19,fi14 and inlet pipe lengthsof z inlet diameter and 4% inlet diametem for the 2 l-inchdiitusers produced inlet boundary layers with =0.0017 and0.0095, respectively. The diffusers were connected to con-stant-area tailpipes about 2 diameters in le
3、nh. The in-terior surfaces were made aerodynamically smooth.The arrangement of static-pressure oritkes was similar forall three diffusers. Six equally spaced statipressure ori6ceswere installed around the periphery at the inlet and exit anda row of orifices was placed along a generati of each diilus
4、er.Similar static-pressure oriiices lined the transition sectionjoining the inlet length to the dif?user. All static-pressureorifices were comected to multitube manometers and pres-sures were recorded photographically. Total pressure andtotal temperature were medsured in the plenum chamberupstream o
5、f the inlet bell.The surveys from which mass flow d total-pressure 10Swere determined were made across the stxem at the exit exit-t-42: 84.8t21 I2 29.7! I II Wsl-bldl WI+I ”-” I-+=*II I I I$a) 12 conical diffuser; inlet diameter, 10 inohcs.) 12 conical diffuser; inlet diameter, 21 inohes.(c) 23 cord
6、ed diffuser; inlet diameter, 21 inohesFIGURE I.Arrangement of diffusersin duet systom.COMPUTATIONAL METHODS AND ANALYSISCorrelating parameter,-l%e requirement that the inletduct and difFuser be free of all obstructions upstream of anystation at which transverse pressure surveys were in progressmade
7、it impossible to survey at two stations sinmhneously.In order to compare and combine measurements from dif-ferent tests, the inlet-static-pressure ratio pJHo was used asa correlating parameter for the computation of tlm per-formance coefficients.Inlet flow measurements. Pressure surveys (from whicht
8、he mass flow and mean total pressure were calculated) wwomade at the inlets (measuring position given in table I) ofthe three diffusem. Total pressure is presented only insofaras it is used in computing the change in total pressure throughthe difluser. The mass-flow measurements -were used tocompute
9、 mean inlet Mach numbers and Reynolds numbem,which are plotted as functions of the correlating stotic-pressure ratios in figure 3. The mean inlet Reynolds numberwas obtained by using the mean value of flow density, thoinlet diameter of the diffuser, and the viscosity based onstream static temperatur
10、e; that is,p/uiDiR,=TSince the mean inlet mass flow decreased with increasi however, thereal signiik+mce of 6* and o in these cases is questionable and,consequently, no attempt was made to measure accuratelyreverse-flow velocities.Performance parameters.-hvo parameters, andAp are used to present the
11、 perfommnce data. The co-AptimzAHefficient (referred to as the loss coefficient herein) is the%, ,ratio of total-pressure loss through the diffuser to the meaninlet impact premnre. This parameter is convenient for usein evaluating the total loss in a duchsystem component andis commonly used in the l
12、iterature. It has the advantageof tending to remain constant with change9 in flow rate aslong as the basic flow pattern in a configuration does notProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1016 REPORT 1201NATIONAII ADVISORY COMMJTPE El FOR AERO
13、NAUTICSLo I IqII-L 8*JQ.9 - 21 0.0017/ “ - 10 .0039/ / -.8 / 0 - - 21 ,0095/ / /“ - - 1: a ,A k. 1I. IJ! IA .: “-2 .= 0 A =. .: .7 . ./ “z a75 c- x o9: “(1a75 h: o c1.- .-. - . _ - . a 0.6 0n -1. . b8*i/Dj Diffuser .o ,o 0.CQ39“o 0122 12?,10 in. o - .00170 ,A - .oo95 12,21 in a75.5 An - :J 23;21 in-
14、 = ,0 .1 .2 .3 .4 .5 .6 .7 .8 .9 IMeon inlet Moth number, fliFmurm “; ; “f.1.47 I /8x3.80 /8“= 1.00 -. ,/ /890.604 . ,j6 ,/ “/ (h!0 .2 4 .6 .8 1.0Vebcity rotb, ufl(a) Station 2.(b) Station 6.Frffmm 17.Comparir3on ofsame point at tierent=o.oo95.boundary-layerthmx in theprofflw measured at tho23,21-in
15、oh diffuser forProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-PERFORMANCE AND BOUNDARY-LAYER DATA FROM2. The adverse effects of increasing flow rate (increasing“det Mach rmd Reynolds numbers) upon performanceranged from no effect for the thinnest in
16、let-boundary-layercondition to very strong effeci% for the thickest inlet-boundary-lnyer condition. The severity of the9e effectsalso incressed progressively with increasing difhser angles.3. The existence of n distorted irdet-boundsxy-layer-proiileshpe for the thinner inlet boundary layer of the 12
17、0,10-inchdifiser resulted in some flow sepmation ati nearly W inletMach numbers. This unusual flow pattern obscured theeffects of inlet-bound,ary-layer thiclmess in that diffuser.In the 120,21-inch diffuser, only a small region of separatedflow was observed at the highest inlet Mach number.4. In the
18、 23 ,21-iDCh diffuser, the flow was separated overthe major portion of the diffuser for all Mach numbers andwas so unsteady that reliable transverse pressure surveyscould not be made near the diffuser exit. When the difYusersurface was uniformly roughened by applying O.lO-inch-diameter particles of
19、cork, the flow wcs made steady through-out the flow range investigated. This roughness did notsigniiicdntly affect the performance.5. Observations rut different points around the diffuserperipheries reverded that the separated flow pattern was notsymmetricrd about the center line, and furthermore, t
20、hat theregions of separated flow shifted with time.LANGLEY AERONAUTICAL LABORATORY,NATIONAL ADVISORY COMMIT-TEE FORLANGLEY FIELD, VA., November 16,REFERENCESAERONAUTICS,1964.1. Gibson, A, H.: On the Flow of Water Through Pipes and PassagesHnving Converging or Divergfng Boundaries. Proo. Roy. Sot.(Lo
21、ndon), ser. A, vol. 83, no. 563, March 2, 1910, pp. 366-378.2. Peters, H.: Conversion of Energy in Croa+ectional DivergencesUnder Diffenmt Conditions of Inflow. NACA TM 737, 1934.3. Ifi6ner, Riohard: Versuche fiber Str6mungen in stark erweitertenIGmTlen. Fomch.-Arb. Geb. Ing.-Wes. VDI-Verlag G.m.b.H
22、.(Berlin), Heft 222, 1920, pp. 1-86.4, Vedornikoff, A. N.: An Experimental Investigation of the Flow ofAir in a Flat Broadening Channel. NACA TM 1059, 1944.12 AND 23 CONICALDII?FUSDRSOF AREA R4TI0 2.0 10275. Jones, IL, and Williams, D. H.: The Effeot of SurfaceRoughnessonthe Characteristic of the Ae
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