NASA NACA-TN-2795-1952 Effects of wing sweep on the upwash at the propeller planes of multiengine airplanes《掠翼对多发动机飞机螺旋桨飞机气流上洗的影响》.pdf

1、.FOR AERONAUTICSTECHNICAL NOTE 2795EFFECTS OFAT THEWING SWEEP ON THE UPWASHPROPELLER PMNES OFMULTIENCHNE AIRPLANESBy Vernon L. RogalloAmes Aeronautical LaboratoryMoffett Field, Calif. -WashingtonSeptember 1952Provided by IHSNot for ResaleNo reproduction or networking permitted without license from I

2、HS-,-,-1P NATIONAL ADVISORY COMMITTEEFOR AERONAUTICS:*EFFECTS!CECHNAL NO= 2795OF WING SWEEP ON TKE UPWASHAT THE PROPELLER PLANES OFMULTIZNGINE AIRPLANESBy Vernon L. Rogslloa71a15d.An analysis has been made to give a qualitativepicture of theeffects of wing sweqp on the upwash at the propeller planes

3、 of muMi-engine airplanes. The method used in this analysis is, in general, thessme as that given in NACA TN 2528,1951,with the necessary extensionsas suggested therein. To provide a basis for judging the effects ofsweep the method was applied to two hypothetical airplanes of the high-speed long-ran

4、ge type, one having an unswept wing and the other a swept-back wing. ticluded as a part of the report are charts which facilitatethe prediction of qwash in the the dis-. ,= tributionswere-determinedby the method”of.referetie2.Wing upwash.- The method of reference 3 f,orcuting wi% d ade from already

5、published wok, topredict upwash”in the chord-plane”reon ahead of a wing; “” =Total Upflow at-PrOpellerDiskSince the oscillatingair load is dfi.ctly depadefit upon total “-”upflow atiglesjA, for a given airplane fli”t condifion (reference4),the magnitude and distribution of the angles provide a ratio

6、nal basisby which to compare the severity of propdl oscilting.afr loadst.“The total upflow angl whereas, with the unsweptwing, the differencewas 10 percent or lessWhen considering the complete airplane,“nacelle-axisinclinationwas found to be a powerful factor in the reduction ;o_fthe over-allupflowa

7、ngles at thepropeller disks (the angles of local flow with respect tthe nacel.le”axisresulting from wing upwash, upwash af bodies, and gea-metric angle of nacelle axis). With the nacelles inclined, it was foundthat-the upflow angles were only slightly greater in magnitud=for theairplane having the s

8、wept wing than for the airplane having the Wswepfitig, indicating that first-order excitationwould be little greater thanin the case of the airplane with the unswept wing. .e asymmetry of theupflow distribution in the case of the airplane having the swept wing wasquite pronounced indicating that the

9、 propellers would be subjected tohigher-order excitations. -Ames Aeronautical LaboratoryNational Advisory Committee for AeronauticsMoffett Field, Calif., July 17, 192:.-,.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.NhCATN 2795 13PREDICTION OFAPP

10、ENDIX AUPWASE OF ARBITRARY WINGSReference 3 indicates that if the symmetrical loading distributionis known, from computations or measurements, the values of the awcoefficients given in reference 3 can be used to find correspondingvalues of the downwash. The same basic equations given in reference 3a

11、re applicable to the computation of upwash, but new values of the amcoefficientsmust be used.The upwash csm be found at specific points in the chord-plane region .between the wing tips and ahead of the wing leading edge. The generalexpression for the upwash is given as(:).,v=LGnn=1where the am coeff

12、icients are obtained from figure 17. The specificstation at which the upwash may be found corresponds to v=1,2,3,4or TV = cos (vTc/8)= 0.924, 0.707, 0.383, and 0, respectively. Forconvenience, the preceding equation is rewritten so that the upwash angleand loading distribution are in terms of unit l

13、ift coefficient. Thus,(*v)T,;2p , O.75; Sea levelQ?0Q* M= 0.90; CL 0.27; 4 000 altitudep -4 - -vry,-80 1 1 1 I 1./ .2 .3 .4 .5 .6Sponwise station, , fraction of semispun figure /3- The distribution of the total upflow angle d the horizontalcenter lines of the propeller disks of the two hypotheticaloirplones with the nacelles inclined.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-