REG NACA-TN-2528-1951 A method for predicting the upwash angles induced at the propeller plane of a combination of bodies with an upswept wing.pdf

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1、09 /, ,IiNATIONAL ADVISORYFOR AERONAUTICS A METHOD FOR PREDICTING THE UPWASH ANGLES INDUCEDAT THE PROPELLER PLANE OF A COMBINATION OFBODIES WITH AN UNSWEPT WINGBy Paul F. YaggyAmes Aeronautical LaboratoryMoffett Field, Calif.WashingtonOctober 1951.- .- .- . -,. . . . . . . .Provided by IHSNot for Re

2、saleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARYKAFB.NM.lmllMiMllillllilllll10L547i?NAKCONAL ADVISORY COMMITTEE FOR AERONAUTICSTECHNICALNom 2528A MEI!EODFOR J?REDICTINGTHE UPWASH ANGLES INDUCEDAT THE PROPELLER PLANE OF A COMBINATION OFBODIES WITH AN UNSWEPT WINGB

3、y Paul F. YaggyA method has been developedat the horizontal center line ofSUMMARYfor predicting the upwashthe propeller disk of theangles inducedtwin-engineairplane consideredin NACA TN 2192, 1950. The method treats each com-ponent separatelyand includes approximationsfor the interferenceeffects of

4、the other components. Lifting-line theory was used to deter-mine the wing-inducedupwash angles. The theory used for the nacelle isan extension of the airship theory of NACA TM 574, 1930. The fuselage-inducedupwash angles were determinedby means of a solution for thetransverseflow about an infiniteel

5、liptic cylinder.The boundary conditionsof the airship theory used to predict theupwash angles due to the nacelle of the airplane were not strictlysatisfied. Therefore,a comparisonwas made of predicted and measuredupwash angles for an isolatednacelle which approximated in shape thatof the airplane of

6、 NACA TN 2192. The comparison of the computedvaluesof upwash angle tith the measured values showed satisfactoryagreement.Comparison of the computed and measured total upwash angles showedthat the method satisfactorilyaccounted for the upwash angles inducedby the airplane. Although the method was dev

7、eloped for a specificair-plane, the method should be applicable to similar alPplanes; the condi-tions of similari -aredefined in the report.Modifications to the method are suggestedwhich, it is believed,would make it applicable to certain dissimilar airplanes.INTRODUCTIONIt has been shown in investi

8、gationsof first-order vibratorystresses in propellers (references1 and 2) that, for subcriticalspeeds,the oscillatingaerodynamicloadings which excited these stresses couldu-. .- . . _ -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NACA TN 2528be

9、predicted by steady-statepropeller theory if the flow field wereknown. It is apparent from the data of reference 1 that, of the flow-field parsmeters, the upwash angles measured along the horizontal centerline of the propeller disk had the largest effect on the oscillatingaerodynamicloading. It was

10、shown in reference 1 that the upwash esmeasured along this center line were in excess of the computedwing-induced upwash angles, andthe variation had a considerablydifferentshape. The differenceswere such as to indicate that they were due tothe nacelle,primsrily, and to the fuselage to a lesser degr

11、ee. Thedevelopmentand application of a method for predicting the upwash anglesfor the airplane consideredin reference 1 was the purpose of theinvestigationreported herein.In order to avoid the complicationsof an exact theoreticalmethod,an approximatemethod was developedwhereby available theory for e

12、achcomponent of the combinationwas used with certain simple approximationsto account for interferenceeffects. Since the nacelle did not confomnto the restrictions of the theory, it was necessaryto obtain data suit-able for determiningthe applicabilityof the theory to the nacelletested. !l%egeneral a

13、pplicabilityof the method is discussed.NOTATIONnacelIleinlet area, at station ONacelle inlet mass-flow ratio (:;:)distance along any radial line from the longitudinal.axis of abodyradius of a body at any point x on the longitudinalaxisfree-stresmvelocityaverage velocity at the nacelle inlet .increme

14、ntaltransverse-flowvelocityvelocity at a point in a transverseplane normal to a radial lineextending from a body axis through the pointcross velocity (W = V. sin a)longitudinaldistance from any doublet element on the body longitu-dinal axis to a transverseplane containing the point at whichthe upwas

15、h angle is to be computed,positive aft from the doubletelement. . . . -.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN 2528geometric anglefree streamangle of attack3.of attack of the thrust axis with respect to theof the longitudinalaxis of a

16、 body with respect tothe local air-stream directionangle of upwash measured from the free-stream direction in a planeparallel to the model vertical plane of symmetrytan- :momentper unit lengthmass density of air inmBss density of air atpotential functionangularposition aboutof a doublet elementtheth

17、ethefree streamnacelle inlet body aiS,from the upper vertical.position asThe symbolsr, R, Vo, V, W,x, a, C,measured counterclockwiseseen from the front13andfl are further definedin figure 1.SubscriptsLE leading-end of a bodyTE trailing end of a bodyMODEL AND APPARATUSThe nacelle tested had approxima

18、telythe same shape as the nacelleof the airplane (fig.2) and was formed by adding a suitable afterbodyto the engine cowling of the port nacelle of the airplane. Two modifi-cations to this basic nacelle were also made. One was the addition ofa conicalnose fairing to the basic nacelle; the other, the

19、addition ofa conical spinner. Drawings of the basic and modified nacelles weshown in figure 3. Photographs of each of the three nacelles mounted”in the Ames - by 80-foot wind tunnel are shown in figure 4.For all three nacelles, the surveyplane was located 8 inchesahead of the basic nacelle leading e

20、dge. The instrumentation,themethod of surveying,and the location of the survey plane were thesame as described in reference 1. -. . = .- - -z _ . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4 NACA TN 2528TESTS AND REmTsMeasurements of the upwash

21、angle along the horizontal center lineof the propeller disk were made for each of the three nacelles. Thesurveys extended 70.5 inches from the nacelle axis. Data were obtainedthroughout an angleqf-attack range of O0 to 16 at a tunnel speed ofapproxhately lhO miles per hour. The inlet mass-flow ratio

22、 for thenacelle with conical spinnerwas 0.7 and for the basic nacelle was 0.2.The test data for the nacelles are presented in figure 5. Correc-tions to the data for tunnel-wall effects were negligible.METHODThe following theories and procedures were used in calculatingtheupwash angles induced at the

23、 horizontal center line of the propellerdisk by the various componentsof the airplane. The total upwash anglewas then calculatedby summation of the results obtained for eachcomponent.Wing-InducedUpwash AnglesLifting-linetheory was used to determine the wing-induced upwashangles. The span load distri

24、butionwas approximatedby a system ofhorseshoe vortices. The upwash angle was then calculatedfor each vor-tex by the equations given by Glauert in reference 3. A summationofthese angles gave the total upwash angle inducedby the wing.!lEespsm load distributionwas taken to be that for the wing alone.Th

25、is was justified since computation-showed the large differencesbetweenwing-alone and wing-nacelle-fuselagespan loadings to result innegli-gible changes in upwash. Similar agreement was noted for another wing-fuselage-nacellecombination in which the wing had a greatly differentplan form.I?acelle-Indu

26、cedUpwash AnglesThe theory used for the nacelle was that of reference 4, extendedto obtain an expression for the upwash angles inducedby a body at anangle of attack. The expressionfor the upwash angle in the horizontalplane of syrmnetryis derived in the appendix and is as follows:Provided by IHSNot

27、for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN 2528.r.a Jem“2 R2sin edeemThis expression is for closedbodies of revolution. The basicnacelle of the airplane deviated from the boundary condition in thatthere was flow through the nacelle. Therefore,the applicabil

28、ityofthe theory for calculatingthe upwash angle for this nacellewas deter-mined by a comparisonof computed and measured angles of upwash. Thetheorywas further evaluatedby comparisonof computed and measuredvalues of upwash angle for the nacelle with the conical fairing, or withthe conical spinner. Th

29、e former case conformed to the boundary condi-tions of the theory. In computing the upwash angles for the nacelJ.eswith inlets, the surfacewas consideredto continue across the opening.The measured nacelle upwash angles indicated that the thrust axis, whichwas chosen as the reference axis, was tilted

30、 down 2 with respect tothe nacelle longitudinalaxis. This was taken into account when com-puting upwash angles for a given geometric angle of attack. Comparisonsof experimentand theory are presented in figure 6 and satisfactoryagreement is shown.Since the nacelle, when in combinationwith the wing, w

31、as in theupwash field of the wing, it was assumsd that it was at an effectiveangle of attack. This effective angle was taken to be the sum of thegeometric angle of attack and the w5ng-induced upwash angle on thecenter Iine of the nacelle at the propeller plane. Therefore, theupwash WaS computedIn de

32、terminingconsideredto be anfor the nacelle at the effective angle of-attack.Fuselage-InducedUpwash Anglesthe fuselage-inducedupwash angles the fuselage wasinfinite elliptic cylinder. This approach isreasonablebecause the fuselage extended well forward of the propelJerplane and the area of the cross

33、sections,which were approximatelyelliptic in shape, varied only slightly in the vicinity of the yropelJerplane. Further, since the upwash angle contributionof the fuselage wasrelatively small, any error introducedby this procedure would not besignificant.The upwash angles due to an inclined infinite

34、 elliptic cylinderwere determinedfrom values of incrementaltransverse-flowvelocityabout such a cylinder. The expressionused for the upwash angle is:-.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6Values of the ratio AVi/11 can beIt shouldbe noted

35、a difference inpresent report correspondsexactlyNACATN 2528found in figure 7 of reference 5.notation exists wherein W of theto V. of reference .The reasoning regarding the effective angle of attack of the fuse-lage, when tn combinationwith the w3ng, followed that used for thenacelle. Thus, the fusel

36、agewas assumed to be at an effective angle ofattack which was taken to be the geometric angle of attack plus thewing-induced upwash angle on the fuselage center line at the propellerplane. The geometric angle of attack was measured with respect to theslope of the mean-thiclmessline of the fuselage a

37、t the plane of thepropeller. For an angle of atta I :,EEla1 120I 29.0 I/44 26.5/68 22.4192 16.42/7 /.2dimensions are in inches.(a) Basic nacelle.13Geometric characteristics of the three nucelles.,. .-. . - - .- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from

38、 IHS-,-,-14 NACA TN 2528.All dimensions are in inches.p-a.o 2/z o 1- +8.0et59.6_ Survey disk.b) Nacelle with conical fatring.-t-(c) Nacelle with conical spinner.Figure 3.- Concluded. . . . - -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 25

39、28 15. - II(a) Basic Iiixell.e.Tigure 4.- Ths nacelles mounted in the Ames “ -4 _10 20 30 40 50 60 70Percent semispan (a) Predicfed for each component2s16 u oQ*IO Measured2 /2 - PredictedF k/ :8 r0 EKE -0 ,.4=W=-00 10 20 30 40 50 60 70.Percent semispan(b) Measured and predicted for complete airplaneFigure Z - Variation of the angle of upwash at the hor-izontal center line of the survey disk of the airplaneof reference 1. a = 100 .- .-.NACA-IanC -1041-81- 10M. ._ .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-