1、NASA CONTRACTORREPORT#/3 - 3 o1h,_7NASA CR-2299o,I,1Ii,j,ZCASE Fi LECOPYPRESSURE RECOVERy PERFORMANCEOF CONICAL DIFFUSERSAT HIGH SUBSONICM_ACH NUMBERSby Francis X. Dolan and Peter _ Runstadler, Jr.Prepared byCREARE INCORPORATEDHanover, N.H. 03755for Lewis Research CenterNATIONAL AERONAUTICSAND SPACE
2、ADMINISTRATION WASHINGTON,D. C. AUGUST 1973iProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No. NASA CR-22994. Title end Subtitle2. Government
3、 Accession No.PRESSURE RECOVERY PERFORMANCE OF CONICALDIFFUSERS AT HIGH SUBSONIC MACH NUMBERS7. Author(s)Francis X. Dolan and Peter W. Runstadler, Jr.g. Performing Organization Name and AddressCreare IncorporatedP.O. Box71Hanover, New Hampshire 03/5512. Sponsoring Agency Name end AddressNational Aer
4、onautics and Space AdministrationWashington, D.C. 205463. Recipients Catalog No.5. Report DateJuly 19736. Performing Organization Coda8. Performing organization Report No.TN-16510. Work Unit No.11. Contract or Grant No.NAS 3-1533113. Type of Report end Period CoveredContractor Report14. Sponsoring A
5、gency Code.=15. Supplementary NotesProject Manager, Jerry R. Wood,R i.e. it was designedto respond to this small a deviation from the set point. Inpractice it was found that Pot could be held within thisspecification by controlling the makeup air supply rate throughthe regulator.The flow rate of air
6、 through the diffuser test section,and therefore the throat Mach number, was set by manuallyadjusting the bypass control valve and the throttle valvesat the outlet of the downstream plenum, while maintaininga fixed Pot“ This combination of controls permitted operationwith diffuser throat stagnation
7、pressures from 54.5 kN/m 2absolute to 218 kN/m 2 absolute and over the full range ofsubsonic diffuser throat Mach numbers from 0.2 to 1.0.Test Section .and Diffuser DesignThe main test section, shown in cross section in Figure 3,consisted of an inlet nozzle, boundary !ayer growth blocks,the diffuser
8、 assembly and a dump plenum. All compcnentsmanufactured for this program were fabricated from aluminum.Inlet nozzle and boundary layer growth blocks. Availableair pumping capacity and inlet stagnation pressure levelsdictated the use of a 1.27 cm diffuser throat diameter.i0Provided by IHSNot for Resa
9、leNo reproduction or networking permitted without license from IHS-,-,- ,4(-l-_“r-,! i I! I;!k I I, _iiI, icT- - l,_,k_y_tTq, I I i-1_/ I iA0mtlIJ,ti4-10,-4I-4; 01.4_ fnf _ I L.i_from the flow meter through the discharge plenuma leak-tight condition was maintained. The maincompressor was brought on
10、line and the desiredthroat total pressure Pot set by means of thepressure control system.While Pot was being controlled, the flow rate wasset to give the desired throat Mach number M t,This was determined by monitoring and adjustingto a predetermined level the static pressure level(for fixed Pot ) j
11、ust upstream of the diffusergeometric throat. Using this approach, it waspossible to set M t, as measured by the traversetube static pressure, very close to the specifiedvalues of 0.2, 0.4, 0.6, 0.8 and 1.0.After the system had reached equilibrium (Pot andTot steady and M t set as desired) all data
12、wererecorded on a standard format. The axial pressureprobe was traversed to determine the minimum pressure.The location and indicated pressure of the traversetube then defined the aerodynamic “throat“ conditions.Following the recording of the data, the operatorchanged the flow rate to achieve a new
13、M t whilemaintaining Pot constant and step 4 was repeateduntil all five M t values had been run. These fivetests constituted a “run“ and the data were reducedas a set.The next step in the testing procedure involvedchanging Pot (to change inlet Reynolds number) andrepeating steps 3, 4 and 5. In all,
14、three Potlevels were used, resulting in 15 data points forpressure recovery for each combination of inletand diffuser geometry. Table IV lists the Reynoldsnumber for each Pot and M t combination.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-o When
15、all tests for the particular geometry werecompleted, the loop was shut down and the geometrychanged. Five different inlet configurations wereused, in combination with twenty diffuser geometries.These various geometry and flow combinations resultedin some 1100 data points, excluding repeat runs.In ad
16、dition, wall static pressure readings were measuredand recorded for each test run. This information wascollected mainly as a check on the operation of the loop andonly in a few cases have pressure profiles been reduced andplotted from the raw data.TABLE IV - DIFFUSER THROAT REYNOLDS NUMBERThroat Tot
17、al Throat Mach Throat ReynoldsPressure Number NumberPot Mt ReD54.5 kN/m 2109 kN/m 2218 kN/m20.2 30,0000.4 57,0000.6 78,0000.8 93,0001.0 101,0000.2 60,0000.4 114,0000.6 156,0000.8 186,0001.0 202,0000.2 120,0000.4 227,0000.6 312,0000.8 371,0001.0 404,00021Provided by IHSNot for ResaleNo reproduction o
18、r networking permitted without license from IHS-,-,-The data needed to determine diffuser pressure recoveryperformance were the barometric pressure, stagnation pressureand temperature in the inlet plenu_ and throat and exit planestatic pressures. To determine throat blockage, the tempera-ture and pr
19、essure at the flow meter inlet and flow meterdifferential were required.Data ReductionThe results of this test program are presented in termsof the measured pressure recovery C for fixed throat MachPnumber M t, blockage B t, and inlet Reynolds number Re D .Static pressure recovery. The static pressu
20、re recoverycoefficient is defined as the increase in measured staticpressure between the throat and exit plane, divided by thetotal dynamic head at the throat.Pe - PtC = (7)P Pot - PtIn this study, Pe was measured on the wall at the exit planeand Pt is measured along the diffuser centerline, and is
21、theminimum pressure recorded in the vicinity of the geometricthroat. Throat total pressure, Pot is measured as the totalpressure in the upstream plenum; i.e. an isentropic coreflow is assumed to exist from the inlet plenum to the throat.Throat Mach number.lated from the measured throat static and to
22、tal pressures,again assuming an isentropic core flow from the inlet tothe throat.The throat Mach number was calcu-k-iPot) kFor all data reported in this study, the diffuser throatlocation is defined as the point of minimum pressure in theregion of the geometric throat, as determined from the tra-ver
23、se pressure probe measurements.(8)22Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Throat blockage. Blockage at the diffuser throat is de-fined in terms of the ratio of the actual mass flow through thediffuser throat to the ideal, one-dimensional fl
24、ow for apassage with the same geometric area, throat stagnationtemperature and pressure and measured throat static pressure.mactualB = 1 - (9)midealThe actual mass flow, mactual is measured with the calibratedflow meter upstream of the test section. The ideal mass flow,mideal is calculated from one-
25、dimensional, isentropic flowconsiderations:mideal = _ Pot AtTotM t(i+_ Mt2)k+l2 (k-l)(i0)Throat Reynolds number.number is defined byThe diffuser throat ReynoldsVDRe Dwhere:V is the throat core velocityD is the diameter of the throatv is the fluid kinematic viscosity at the throatconditions.(ii)The t
26、hroat core velocity is calculated from the previouslydetermined throat Mach number:M tV = 4 kRTot (12)23Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Calculated pressure.recovery coefficient. A second diffuserperformance parameter was also determin
27、ed and given the name“calculated“ pressure recovery C to distinguish it from thepcmeasured performance Cp“Pe - PtC - _ (13)pc Pot - Ptwhere :Pot is a “mass-averaged“ throat stagnation pressure;i.e. the throat stagnation pressure which wouldhave to exist given the measured mass flow (_actual)and thro
28、at static pressure and stagnationtemperature and throat geometric area.The ratio of the calculated to measured pressure recoverycoefficients is very closely given by the expressionCpc = 1C 2p (1-B t)(14)with only a small compressibility factor error. A moredetailed derivation of C is found in Append
29、ix A along withpca graphical relationship among Cp, Cpc, Bt and Mt. All of thedata are reported in terms of the measured pressure recoverycoefficient; however, given the measured blockage values, asimple conversion can be made, if desired.Data ProcessingBecause of the large amount of data generated
30、in thisprogram, a routine procedure was adopted for processing thedata from the “raw“ form all the way through to the plottingof the final performance maps.A digital computer was used in the first stage of thisprocedure to calculate throat Mach number, the actual andideal mass flow rates, throat blockage, the measured andcalculated pressure recovery coefficients and throat Reynolds24Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
