1、REPORT No. 747WIND-TUNNEL TESTS OF FOUR- AND SIX-BLADE SINGLE- AND DUAL-ROTATINGTRACTOR PROPELLERSBy DAVID BIERMANN and EIIWIN P. HAETMANSUMMARYTe8t8 of 10-foot dknwter, four- and six-blade sin-rotating and dual-rotating propeller were conductedin the N.AC the 66 getting corresponds to airplane spee
2、dsgreater than 600 ndeg per hour.% rewh indicate thut dud-rotating propellers werefrom O to 6 percent more eent than single-rotatingones; but, when the propellers operatedin tlu pregenceof amung, the gain um reduced about one-half. Otheradwttageg of dual-rotating propelm were found toinclude greater
3、 power absorption and greater ej?ciency atthe low.J“nDoperating range of high-pitch propeller.INTRODUCTIONTheoretical treatments of propelIer Iosses, such asthose given in references 1 tid 2, have indicated ro-tational losses in the slipstream amounting to severalpercent for highIy loaded propellers
4、 operating at highvalues of T/nD. MiIitary aircraft have now reachedthe stage of speed and power wherein it appears thatduakotating propeIks might be justified on thegrounds of improved efEciency alone ahhough theelimination of the engine torque reaction might be amore important consideration. In vi
5、ew of theseadvantages of dual-rotating propellers over sin.e-rotating ones, the need for full-scale propeIIer tests isobvious, inasmuch as very Iittle information on thesubjeot ia avaiIabIe.A test program was irtstituted for the propellm-research tunnel to. cover the following conditions:Tests of tw
6、o-, tl tests of four-, six-, and eight-blade dual-rotating propellers operating both ss tractors andpushers; tests b determine the effect of a wing inreduci the slipstream”rotational losses.The present report covers the results of the tractortests made with four- and si=blade single-ratating andfour
7、- and six-bIade dual-rotating propellers operatingwith and without a wing in the slipst.ieam.APPARATUS AND METHODSThe tests were made in the NACA propeIIer-researchtunnel.Propellers.-The propelIem, which incorporate theCIark Y section, were approximately 10feet in diameter.They varied sIightIy in di
8、ameter, depending on the hubnsed. The drawing numbers are HwniItrm Standard ,_3155-0 for the right-hand blades and HamiltonStandard 3156+3 for the left-hand black. BIade-form curves are given in figure 1.Driving mechanism.-The propellers were driren bytwo 25-horsepower electric motors arranged in ta
9、n-dem. (See fig. 2.) The front motor was directlyconnected to the front propelIer and the rear motordrove the rear propelIer through chains and a counter- _shaft. The propelIer shafts were Iocked together for$/1./0.09.C.07.C4s. r, stntionrsdhw b,eectkmchord;k,seetkmthkkness;P, Pita a19 !-.-.,.”.”.-.
10、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-320 REPORT No”: 747NATIONAL ADVIaORY COMMITTEE FOR- tiR0NAuHCf3 .-single-rotation operating conditions. The raotoIwwermounted on bearings. concentric with the shaft axis.Each motur frame was restrained
11、from rotating byhdical springs connecting with the supporting frame,which proi Rear mokrJ“ Tbr-que springFIGrItE 2.-FroerAlve mehenkn.ided means of measuring the torque.)Scdsyndevices were used to transmit the motion ofthe motor frames to the test. chamber i.n order thttorque measurementscould be ma
12、de1. i80ffII IFtIIcrrri3.PlmvtewehowlngdhnenslmaldetaflsofWIIJEmd noeelle. Mnensiona k-r Iour-bledepropelleM.7 Inchceend for slx-bkic lwole= 10.11inchesFront end rear nrmlleltneem Iderrtkal.Body.An outline of the streamline body housingthe motors is showmin figure 3. A photograph of thesetup is give
13、n in figuro 4. Teds were.made with andwithout the symmetrical wing in place. The wing waslocated in the midwing position tind set at an angle ofuttack of OO. Both ends of the body were madeidenticaI in order that comparative tractor and pushertests.could be made without altering the body shape.Spinn
14、ers were used for all tests. Both wing and bodywere constructed of wooden forming members coveredwith shcet+duminum skin.Measuring equipment,-The net thrust or drag of thepropeIIm-body combination was measured on a thrustbalance located on the floor of the test chambw. Thetorque of each motor was mm
15、.surcd with thr spring-dynamorneter Selsyn repeating system, TIN a-mometerwas calibratedbefore and after the seriesof Lwttiwas made, Frictiondet,ermination tests were mwkfrequently duringcthe program. The propollty spmdwas rnimsured with an accurate electric taclwmctcr.checked frequently during the
16、investigation. F.achpropeller of the dual combinations was run at tho sameF1OURE4.Test setul). The )hotomh chowsa dwblndcAe-rotetIrrermrekrwith M!In IIlmre.speed. A synclwoscop was used to iridicatc synchro-nism, Control of the relative speeds of the two motwawas obtained with a frequency converter
17、placed in thcline feeding one of the induction ivc motors.Test oonditionstThe tunnel speed ranged from mmJOabout 110 miles per hour. The maximum propdlrrpeed was about 550 rpm, which corrcspomis LO n.oame torque at peak efficiency as for the front proprllrr.,4 plot of the.difference bctwwm the front
18、 and lhc ruryopeller-bIade settings is given in figure L. A typicalplot of the resultsis given in figure 6. The amount thatthe test points scatter gives an indication of the .ccuracy of the results.The four- and the six-blade single-rotating propdlursmre made up with two two-way nnd t.lmw-way huhslm
19、spoctively, mounted in tandem. BCCnUSCof LIICI)()i-tion of the shaft splines when the shtifls were krywlioget,her, equal spacing butwcen front ml rwtr lhtdwiv impossible and Lhcrcforc the front IJude Icd thu:ear by 85,4 and 75.0 for four-blade and six-ldadpropellers,respectively. This mmmgrment rcsu
20、llrd in,dent.icalbIade shank and spiruwr conditions for lJtJh:1)0 single- and dunl-rotalion tesls.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.24y,20 -16 -G. r2 -,08 -.04 - t -0FOUR- AND SIX-BLADE SINGLE- AND DUAL-ROTATING TRACTOE PROPELLEES.4 .8
21、 /2 /6323.48.40.32Cp24./6_082.0 2.4 0 .8VwIB12.IndMduaJpm.wuWllnt curvesforfour-bkdcduaMotatln2IKUPMCISwthuutwlIw.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-FOUR- AND SIX-BLADE SINGLJI- AND DtiBoTANG TRAmoE pROpEE 32ti .-.28.24?0.)6c.12.08.04a11
22、.08.6c.4.20., . .-. . .,/-.,.-”.i-.=-. .J- .,- a-4. . . . . . . . . .-.,.+.d .FfficuE13.Powwchnt mmcsfu fowbhde dtmhrotnlhg propelkmwIchcd WWProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Imwwr No. 747NATIONAL ADVIfJORY cmmrmE E FOR AERONAUTICSLo.8.
23、6n.4.2 .0 .4 .8 1.2 L6 2.(7 2!4 2B 32 36 4.0 4.4 4.8 K2 Qi 60fJnDFIGLTJIE14.EIlMencycurvesfcxsx-blsdeslngkrots.ths propdlrr wlthmltwhit?.;.36.3228.24.20c,.16.12.08,040 .4 .8 12 L6 20 24 J?W .32 = 4B 44 48 52 56 60ljwPIGUUS! 15,-Thrusttident curvssfw sk-hlrde single-rotatlnsUSWIMIIWwllhout wIns.Provi
24、ded by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.FOUR- AND SIX-BLADE SINGLE- AND DUAIAtOTATING TRACJ70Fi PROPELLERSo .4 .8 L2 6 /?01.8/.6f.4/.2c,i.o.a.6.4.20327.4 .8 12 16 2.0 2.4 28 32 .36 4.0 4.4 4.8 5.2 53i$%iD.-.-Provided by IHSNot for ResaleNo reprod
25、uction or networking permitted without license from IHS-,-,-328 REPORT NO, 747NATIONAL ADvIsoRY COIWITTEE F-OR AER0NAuTIc91.0.8.6v.4.20v/rLDFrcurm 17.-EtTicknoycuwcs tm sk-blsde dud-rotating proRollorsrrlthout wing,dmwlngsumpmwd cnrvrs fortlw mrrmpom!hrgSbrv-rotDc z!O 24 2.8 .lFwLUtE 35.-Poww+xwme b
26、ut,at a lfn of 5.0, there was a gain of 5 percent in favorof dutd rotation. The wing improved the efficiency ofthe single-rotating propeller about 2 percent for onlythe high V/n.D range. The wing had no. effect ou thefour-blade dual-propeIler results.The six-blade duaI-rotatin.g propeller w-asfrom 1
27、 h)6 percent m,ore efiient than the single-rotating pro-peller. The wing improved the efficiency of the singhrotating propeller O to 4 percent and also improvedthe efficiency of the dual-rotating propeller O to3 permrlt.These results seem to check theory roughly in thatthe gain due to dual rotation,
28、 witbh the limits of themtW.s, amounts to from O to about 6 percent, depend-ing upon the blade-angIe setting and the disk loading.The presence of the wing resulted in about half as muchimprovement in efEciency as duaI rotaticn.Ln figure X is aka shown the effect of differentnumbem of bIades on effic
29、iency. The rewdts for hetwo- and three-blade prcpellem, whi11:.,:1Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-%FrauRc 4fL-DmI chut m prcq?ellrmW35+ h 31M- namely,ihe dual-propder Ah were interpolated to bringthe 1“/nD for zero thrust in coinciden
30、ce with that forthe single propeller. The results indicate that thefour-blade single and dual propellers absorbed gboutthe same power for the peak-efficiency condition; butthat at lnD values corresponding to the take-off anddiibmg conditions the dual-rotating propeller rtb-sorbed 5 ta 17 percent mor
31、e power than the single-rotating propeiler. The six-blade comparison (fig. 39)shows more pronounced effects, even for the high-speedcondition; the dual propeller absorbed several percentmore power for the high-speed condition and as muchas 30 percent more power for the take-off condition.This rewdt
32、indicates either that the diameter of thedual propeller will be smaller than that of the singleone for eqmd power absorption or that the blade anglesfor the trike-offand climbing conditions wiUbe lower.The relative thrust available for dual-rotating andsingle-rotating propellers operating at equal v
33、alues ofCp is given in figure 40. These curves show a truecomparison of contrdable ptipdfers of equal diameteroperating at all flight speeds but at cmstant torque,engine speed, and altitude and, consequently, show thedirect effect of dual-rotating propellers on the thrustfor the takedf and climbing
34、conditions. Relativethrust curves are given for se-iernl girplane categories,defined by the blade-angle settings for high speed.Thus blade anghs of 30”, 45, 50, 55”, 60”, and 65correspond roughly to speeds of 250, 375, 425, 450, 500,and 52!5miles per hour, respectively, if a tip speed of900 to 1000
35、feet per second is assumed. Inasmuch asthe engine speed and diameter are assumed constnnt,the 1/n i3 is directly proportional to the airspeed.This annlysis indicntes thnt there is a marked gitindue to dual rotation for the take+ff fmd climb of nir-phmes operating at conditions of CP greater than 0.4
36、or for conditions wherein the blade angles for tda+offand climb exceed 30. In terms of airphme categories,the take-off and climbing thrust of airplanes havinghigh speeds at sea level in-excess of tibout 375 miles perhour WOUMbe benefited by dunl-rotating propellers.firplnnes hnving high specclsnt 20
37、,000 feet greater thanthout 460 miIes per hour wonkl hae take-off Nndetingles (nssuming ecunl ptiwer) in exces of 30 andconsaquently would benefit by dual rotation for this .rendition; the benefit would be eren greater for the _ _.dhnbiig condition at 20,000 feet.A sample calculation will illustrate
38、 this point. Givn: “- -High speed of 500 roles per hour at 20,000 feetBfor high speed = 60”V/nD for high speed = 3.6Cp for high speed = 1.118To find relative thrust at reduced speeds:V/nD for climb at 20,000 feet= 3.6 XO.65 = 2.34 - “- Cr. = 1.2 (cIimb at 20,000 ft)CP for sea level = 0.595 (assuming
39、 ccmstim “-”engine power)Cr# the higher these values, the greater the differ-ence in efficiency up to the limiting test blnde nngle of65.2. The mmimum efficiency of a single-rotating pro-peller was increased by insteJ.Iinga wing in the slip-stream. Dual rotation (without wing) yielded a gainof appro
40、ximately twice as much.3. Dual-rotating propellers absorbed onIy slightlymore power at peak efficiency than did single-rotating , ones; but at V values corresponding to the take-offand chmbing conditions the difTerencowas more pro-nounced.4. The take-off and chubii thrusts of dual-rotatingcontrollab
41、le propellers for airphnes in the category of400 miles per hour nnd up were found to exceed thevalues for singIe-rotnting propellers by substantialmmgins.LANmJZY MEMOEUAL AEIZONAUTICAL LABORATORY,hTATIONAL ADVI&BY COMMITTEE FOR AERONAUTICS,LANGLEY FIELD, A., July 1S, 19.REFERENCES1. iveinfg, Fritz:
42、&genIMige i%hraukm ffir ugzeuge. Jahrh _ _ _1937 der deutschen Luftfahrtforschung, R. OIdelihourg(Munich), pp. I 215-1223.2. Lazzarino, Lucio: Study of AwY for High Speed Aero-pkmes. R. A. S. Jour., VOI. XLIV, no. 352, April” 1940,pp. 322-327.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
