1、NASA Contractor Report 3176NASA-CR-3176A Method for Predicting the NoiseLevels of Coannular Jets WithInverted Velocity Profiles-_ ,_,) _ , ,James W. Russell _OR RE; EI.,LNC_lNOT l“O BI_ TAKEN i.i_o_l ll_lS g_O;*|CONTRACT NAS 1-13 5O0OCTOBER 1979q!,3Provided by IHSNot for ResaleNo reproduction or net
2、working permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA Contractor Report 3176A Method for Predicting the NoiseLevels of Coannular Jets WithInverted Velocity ProfilesJames w. RussellKentron International, I
3、nc.Hampton, VirginiaPrepared forLangley Research Centerunder Contract NAS1-13500IXl/XNationalAeronauticsand Space AdministrationScientific and TechnicalInformation Branch1979Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for Resal
4、eNo reproduction or networking permitted without license from IHS-,-,-TABLEOFCONTENTSSUMMARY 1INTRODUCTION . 2LIST OFSYMBOLS. . 3DESCRIPTIONOF DATA BASE . 6PREDICTIONPROCEDURE. 8Equivalent Jet . 9Acoustic Power 10Directivity and Overall Mean Square Pressure IISpectralDistribution 12DATACOMPARISONS 1
5、3StaticCaseData 14WindTunnelCaseData . 16CONCLUSIONS 18REFERENCES 20TABLES 21FIGURES 44APPENDIXA TypicalStaticCaseSpectralDistributions 79APPENDIXB TypicalWindTunnelCaseSpectralDistributions. . . 128iiiProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
6、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SUMMARYThis report presents a method for predicting the noise characteristicsof a coannular jet exhaust nozzle with an inverted velocity profile. Themethod equates the coannular jet to a single stream e
7、quivalent jet with thesame mass flow, energy, and thrust as the coannular jet. The acoustic charac-teristics of the coannular jet are then related to the acoustic characterls-tics of the single jet. The method presented in this report also includesforward flight effects by incorporating a forward ve
8、locity exponent, a Doppleramplification factor, and a Strouhal frequency shift.A comparison of the prediction method with the model test data shows that(1) for the static cases the spectral correlations were generally greater than90 percent and the spectral sound pressure level standard deviations w
9、ere gen-erally less than 4 dB in the aft arc direction. (2) For the static cases, thepredicted overall sound pressure levels were generally within 4 dB of themeasured values. (3)_This method predicts the acoustic characteristics ofcoannular nozzles without centerbodies better than coannular nozzles
10、withcenterbodies located in the primary stream exhaust where the flow must eitheroverexpand or neck down. (4) For the forward flight cases, the method under-predicts the jet noise by approximately 3 dB in the forward arc, and overpre-dicts the jet noise by approximately 2 dB in the aft arc. (5) For
11、the lowvelocity forward fligh_ cases the spectral correlation coefficients were greaterthan 90 percent and the standard deviations of the spectral sound pressurelevels were generally less than 4 dB. (6) For both the static and wind tunnelcases the spectral correlations, sound pressure level deviatio
12、ns, and overallsound pressure level differences between measured and predicted values werenot affected by changes in equivalent jet velocity.= It is recommendedthat (I)theforwardflight effecton jet noisebereevaluatedusingadditionaldata to determinewhetherthe Doppleramplifi-cation factorexponentshoul
13、dbe greaterthanunity,and that (2)additionaldata be obtainedat higherjet exhausttemperaturesand velocitiesto reduceextrapolationerrors incurredin evaluatingnoiselevelsof variablecycleengines.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INTRODUCTION
14、In recent years, advanced engine designs which employ coannular jetexhausts have been studied for application to supersonic transport configur-ations. These engines are efficient at both supersonic and subsonic flightspeeds. The coannular jet exhaust flow scheme has been shown to significantlyreduce
15、 the engine jet exhaust noise levels during takeoff and landingoperations.The prediction method presented herein was developed from threeextensive sets of coannular jet noise model test data sponsored by NASALewis Research Center (refs. I, 2, and 3). These data have been correlatedby S. P. Pao of NA
16、SALangley Research Center (ref. 4), which provides thebasis for the prediction method.Because the coannular jet contains twice as many flow parameters asthe single jet, the prediction scheme is more complex than the SAE singlejet prediction method (ref. 5). The noise emitted from a coannular jetcont
17、ains two major components: the premerged noise produced by the secondaryflow stream and the noise produced by the portion of the jet plume Where:the two streams have merged. In the forward direction angles, the premergednoise is predominant. However, in the aft arc, there are two distinct peaksto th
18、e jet noise spectral distribution. The low frequency peak is associatedwith the plume noise of the merged jet, and the high frequency peak is asso-ciated with the premerged noise of the secondary or outer flow stream.The method presented herein equates the coannular jet to a single streamfequivalent
19、 jet which has the same mass flow, energy flow, and thrust as thecoannular jet. The acoustical power of the coannular jet is then derived bycomputing the power of the single jet and applying a coannular jet noisebenefit function. From the acoustic power, the overall sound pressure levelin a given di
20、rection is defined. Then the spectrum is defined which iscomposed of the premerged and postmerged jet noise components. The predictionmethod also includes forward flight effects by incorporating a forwardvelocity exponent and a Doppler amplification factor. Also, the frequencyis shifted in proportio
21、n to the relative velocity, which is the difference2Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-between the nozzle exit velocity and the forward flight velocity.The following constraints should be applied to the method presenteddue to the limited
22、 data base. The outer to inner stream nozzle exit arearatio should not be less than 0.4 or greater than 2.5. The outer to innerstream velocity ratio should not be less than 1.0. The equivalent jet velo-city should be greater than 0.85 times the local ambient speed of sound. Thetest data upon which t
23、his method is based have a range of equivalent jetvelocities from just below the ambient speed of sound to 2.5 times the localambient speed of sound. This prediction method is designed for obtainingfree field unattenuated source noise levels. It should be noted that coannu-lar jet area ratio and rad
24、ius ratio are not included explicitly due to thelimitations of the data base.LIST OFSYMBOLS2Ae equivalent fully expanded jet area, mA1 nozzle exit plane area of primary stream, m2A2 nozzle exit plane area of secondary stream, m2c ambient speed of sound, m/sD(e) directivity functionDe equivalent jet
25、diameter, mDh hydraulic diameter of secondary stream, mdB decibelf one-third octave band frequency, HzG(e,_) normalized spectral distribution in one-thirdoctave bandH secondary stream annular exit height, mme total mass flow of the equivalent jet, kg/sProvided by IHSNot for ResaleNo reproduction or
26、networking permitted without license from IHS-,-,-ml mass flow of the primary stream, kg/sm2 mass flow of the secondary stream, kg/sn number of one-third octave band frequenciesOAPWL. overall sound power level, re: 10-12 WOASPL(e) predicted overall sound pressure level,re: 2 x 10-5 N/m2OASPLm(e) mea
27、sured overall sound pressure level,re: 2 x 10-5 N/m2_2(e) predicted overall mean square pressure, N2/m4p2(e,f) one-third octave band predicted mean squarepressure, N2/m4pm2(e) measured overall mean square pressure, N2/m4pm2(e,f) one-third octave band measured mean squarepressure, N2/m4p_ ambient atm
28、ospheric pressure, N/m2P(Ve/C ) power deviation factor, WPISA international standard atmospheric pressure,N/m2Q(Ve/C ,V2/V I) power reduction factor, Wr radial distance between source and observer, mR spectral mean square pressure correlationcoefficientS1 peak Strouhal. number of the first spectralc
29、omponentS2 peak Strouhal number of the second spectralcomponentProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SD spectral sound pressure level standard deviation,dBSPL(e,f) predicted one-third octave band sound pressurelevel, re: 2 x 10-5 N/m2SPLm(e
30、,f ) measured one-third octave band sound pressurelevel, re: 2 x 10-5 N/m2Te total temperature of the equivalent single jet, KTIS A international standard atmospheric temperature, KT1 total temperature of the primary stream, KT2 total temperature of the secondary stream, KT ambient air temperature,
31、KVa forward velocity of the jet nozzle, m/sVe fully expanded jet velocity of the equivalentjet, m/sV1 fully expanded jet velocity of the primary stream,m/sV2 fully expanded jet velocity of the secondarystream, m/s_“ magnitude of peak mean square pressure of secondspectral component relative to first
32、 spectralcomponent, N2/m4Ye ratio of specific heats for the equivalent jetY1 ratio of specific heats for the primary streamY2 ratio of specitic heats for the Secondary stream6 directivity angle from the inlet axis, deg.5Provided by IHSNot for ResaleNo reproduction or networking permitted without lic
33、ense from IHS-,-,-H total sound power, Wp_ ambient air density, kg/m3Pe density of equivalent jet, kg/m3_I normalized Strouhal number for the first spectralcomponent_2 normalized Strouhal number for the second spectralcomponent directivity angle from flight path, deg.densityexponentDESCRIPTIONOF DAT
34、ABASEThe inverted flow profile coannular jet data base was obtained from modelscale experimental work (refs. I, 2, and 3). The static tests of references1 and 2 consist of 98 separate test conditions with three different nozzleconfigurations. The first two configurations shown in figures 1 and 2 (mo
35、dels2 and 3) have area ratios of 0.75 and 1.2 respectively. The third configur-ation (model 4) has a centerbody within the core flow stream which extendspast the core flow nozzle exit plane. The area ratio for model 4 of figure3 is 0.647. The wind tunnel tests of reference 3 consist of 92 separatete
36、st conditions with two different nozzle configurations which have invertedflow profiles. The wind tunnel nozzle configurations (models 7 and 8) havearea ratios of 0.75 and 1.2 respectively, and are shown in figures 4 and 5.In all models the core flow exit plane was offset from the secondary flowexit
37、 plane.The acoustic data covered thirty one-third octave bands. All the testswere conducted in outdoor facilities using a polar array of microphones. Thetable below lists the frequency range, directivity range, and microphone dis-tance for each of the test models.6Provided by IHSNot for ResaleNo rep
38、roduction or networking permitted without license from IHS-,-,-Forward Frequency Rangeof DistancetoModel Velocity Range DirectivityAngle Microphone2 O 0.I-80KHz 60 - 165degrees 4.57 m3 O 0.I-80KHz 60 - 165degrees 4.57 m4 0 0.05-40KHz 30 - 160degrees 12.2m7 30-130m/s O.l-80KHz 70 - 150degrees 3.05 m8
39、 30-130m/s O.OI-80KHz 70 - 150degrees 3.05mThe acousticdata were correctedto removeatmosphericattenuationeffectsin accordancewith ARP 866 (ref.6). Sphericaldivergenceeffectswere includedto correctthe data base to a radiusof 45.7m (150ft). In the case of model4, thedata were also correctedfor groundr
40、eflectionand attenuationeffectsusingthemethodof reference2. The forwardflightdata of models 7 and 8of reference3 alreadyhave been correctedfor the effectsof the wind tunnelflow shear layeron the directivityand intensity. In addition,Dopplerfre-quency shiftswere incorporatedinto the data to accountfo
41、r the relativemotioneffect betweenthe sourceand the observer. This effectis includedin the predictionbut is not presentin thewind tunnel.For all casesused in thedevelopmentof this predictionmethod,thesecondarystreamflow velocitywas greaterthan the primarystreamflowvelocity. The tablebelowliststheran
42、geof temperaturesand velocitiesofeach flow streamfor each of the models.VelocityRange,m/s TemperatureRange, KModel Primary Secondary Primary Secondary2 294 - 624 310 - 872 381 - I098 380 - I1333 298 - 441 319 - 859 389 - 810 702 - 10894 291 - 609 295 - 847 286 - 814 392 - 10977 284 - 306 303 - 683 3
43、70- 410 390 - 6698 297 - 307 430 - 638 339 - 407 396 - 710Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The applicabilityof the predictionmethod presentedhereinis limitedto the velocityrangeand temperaturerangeof themodel testdata base. Themaximums
44、econdaryflow velocitywas 872m/s for the staticcasesand 683m/sfor thewind tunnelcases,which is less than the 975m/s for the secondaryflow velocityof a variblecycleenginefor an SSTdesign. Similarly,themaximumsecondaryflow totaltemperatureof thedata was I133 K for thestaticcasesand 710 K for thewind tu
45、nelcases,whichare considerablylessthan the variablecycle enginesecondaryflow temperaturesof 1750 K.PREDICTIONPROCEDUREThe noise predictionmethod presentedin this report is basedon deter-mining the noisecharacteristicsof a singleequivalentjet,which has thesame totalmass flow, energyflow,and thrustas
46、the coannularjet. First,theoverallacousticpowerlevelof the coannularjetmust be defined. Itwas found thatfor the staticcase (noforwardvelocity),that the acousticpowerof the coannularjet is sometimesas much as 4.0 dB lowerthan theover-all sound powerlevelof the singleequivalentjet. The powerof the sin
47、gleequivalentjet for the staticcase is determinedusingthe currentSAEpredictionmethod (ref.5). A jet noisebenefitfunctionis employedtoobtainthe powerlevelof the coannularjet. For thecasewith forwardvel-ocity,a procedureby Hoch (ref.7) is employed. This procedureemploysapowerfunctionto accountfor chan
48、gesin source strengthand soundconvection.Also a Doppleramplificationfactoris used. Both theDopplerfactorandthepowerfunctionvarywith directivityangle. The overallsound pressurelevelin a givendirectionat a givenradius is computedfrom the overallsoundpower levelusinga directivityindexwhich is independent of forwardflightvelocity. Finally,the one-thirdoctave bandsoundpressurelevelis computedby a two componentmethod. The firstComponentis associatedwith the secondarystreamof the premergedjet. The secondcomponenti
