1、FOR AERONAUTICSTECHNICAL NOTE 3904INVESTIGATION OF THE EFFECTIVENESS OFBOUNDARY-LAYER CONTROL BY B ILXNDNG OVER A COMBINATIONOF SLJDING AND PLAIN FLAPS IN DEFLECTING A PROPELLERSLIPSTREAM DOWNWARD FORVERTICAL TAKE-OFFBy Kenneth P. Spreermnn and Richard E. KuhnLangley Aeronautical LaboratoryLangley F
2、ield, Va.WashingtonDecember 1956.-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NMNATIONAL ADVISORY COMMITJXEIlllllllllllllllilllllllliilllFOR AERONAUTICS00b7L24TECHNICAL NOTE 3904INVESTIGATIONOF THE EFFEC3?IVEM3SSOFBOUNDARY-LAYE
3、R CONTROL BY BLOWING OVER A COMBINATIONOF SLIDING AND PLAIN FLAPS IN DEFLECTING A PROPEILERSLIPSTREAM lXXNWARD FORVERTICAL TAKE-OFFBy Kenneth P. Spreemsmn and Richard E. Kuhn.STJMMARY.An investigation of the .effectiveness of blowing a jet of air overthe flaps of a wing equipped with a n-percent-cho
4、rd sliding flap and a.2-percent-chordplain flap in deflecting a propeller slipstream down-ward for vertical tske-off has been conducted in a static-thrustfacility at the Iangley Aeronautical Laboratory. The effects of aleading-edge slat, ground proximity, end plate, and propeller positionwere also i
5、nvestigated.The results of the investigation indicated that boundary-ler controlis em effective means of maintaining attached flow to flap deflectionshigher than those which could otherwise be used to provide increases inresultant force and turning engles. Whether it wold be more economicalto use a
6、part of the available power for boundary-lsyer control than toapply all of the power to the propellers would appear to depend stronglyon the system employed and, for a particular installation should bedetermined from a detailed analysis. With flap deflections at which theflow is not separated and at
7、 blowing rates above those necessary tomaintain attached flow, the only gains in resultant force and turningangle are those due to the direct thrust of the blowing system.lJITROIXJCTIONThe Langley 7- by 10-Foot Tunnels Branch is conducting an investi-gation of various wing-flap configurations in an
8、effort to developk relatively simple arrangements capable of deflecting the propeller slip-stream downward for vertical take-off. The capabilities of a few of theconfigurations investigated are reported in references 1 to k. In these.Provided by IHSNot for ResaleNo reproduction or networking permitt
9、ed without license from IHS-,-,-2 NACATN 3904investigationsthe tendency of the slipstreamto separate from the uppersurface of the wing has limited the turning angles obtained and may beresponsible for some of the losses in resultant force. The investi-gation discussed herein was undertaken In order
10、to study the effective-ness of boundary-layer control (blowing air over the flap) as a means ofmaintaining attached flow to higher flap deflectionsthan could other-wise be used. This procedure would increase the downward deflection ofa propeller slipstream.The sliding-flap configurationof reference
11、4 was constructedanda nozzle capable of exhausting a jet of air over the flap was incorpo-rated. Data for this model without boundsry-layer controlby blowingover the flap sre presented in reference 4. Much of the data of thereference paper have been reproduced herein to provide direct comparisonsbet
12、ween data tithout boundary-layer control and the data from thisinvestigationwith the use of boundsry-lqer control.The investigationwas conducted in a static-thrustfacility at theLangley Aeronautical Laboratory anda 50-percent-chordsliding flap and. COD?FICIENTSemployed a model wing equied witha 25-p
13、ercent-chordplain flap.AND SYMBOLSThe positive sense of forces, moments, and angles used in thispaper areindicated in figure 1. Moments me referred to 0.25 of themean aerodynamic chord.b/2 span ofsemispanwing, 2.0 ft% wing chord; 1.5 ftc slat chord, 0.30cWD propeller diameter, 2.0 fth height of wing
14、 trailing edge above ground, f%x longitudinalposition of propeller e.headof wing leadingedge, ftz vertical position of propeller axis relative to wing chordplane, f% (positive downwind)%,1 deflection of forward or sliding flap, degf,2 deflection of rear or plain flap, degProvided by IHSNot for Resal
15、eNo reproduction or networking permitted without license from IHS-,-,-NACA TN.5*.LFxMFTe.qrl%“%PQnPnvP“v“3904slat deflection,chord plsme)lift, lbdeg (positiveupward with respect to winglongitudinal force, lbpitching moment, ft-lbresultant force, lbpropeller thrust, 15 lbturning angle, inclination of
16、 resultant-forcevector fromt-t wis, tan-l L/fi degQnpnVnmomentum coefficient,q“sQnflow coefficient, V“s -P”pressure coefficient,!L”()Pn*:vn 3power in blowing system, ft-lb/sec2p“ f x.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NAC!ATN 3904.Propel
17、ler:Diameter, ft . . . . . . . Nacelle diameter, ft . . . .Airfoil section . . . . . . .Solidity . . . . . . . . . .The forw=d flap, which ishinged forward of the flap nesrchord station (fig. 2(a). The5. . . . . . . . . . . . . . . 2.0. . . . . . . . . . . . . . . 0.33. . . . . . . . . . . . . . . C
18、lark Y. . . . . . . . . . . . . . . 0.07referred to as a sliding flap, wasthe lower wing surface at the 35-percent-slidin.g-rampradius was 15 percent ofthe wing chord and was made tangent to the upper surface of the wing.The rear flap, a plain flap, was made by sawing off the rear 25 percentof the w
19、ing and reattaching it with a piano hinge at the 75-percent-chord station. Wtth the flap deflected, the gap at the hinge line wasfilled sad faired with modeling clay. An end plate made of l/16-inchsheet metal was installed at the wing tip (fig. 2(b).The leading-edge slat was rolled from l/16-inch sh
20、eet steel to a% contour that correspondedto the upper surface of the wing from theleading edge to the 30-percent-chord station. For these tests the uppersurface of the wing was not modified, although modification would benecesssry in a practical application in order to retract the slat;however, it i
21、s believed that this differencewould have only a smalleffect on the results. The slat positions tested are shown in figure 4.Tests were made with the propeller in two positions; one was atx/D = 0.41, z/D = O and the other was at x/D = 0.167, z/D = 0.167.For these tests, the propeller was mounted ind
22、ependentlyas shownin figures 2(a) and 3. The thrust axis was always parallel to the wingchord plane. The propeller was driven by a variable-frequencyelectricmotor at about 5,500 rpm, which gave a tip Mach number of approxi-mately 0.52. The motor was mounted inside sm alumimm-alloy nacelle bymesms of
23、 strain-gagebeams in such a way that the propeller thrust andtorque could be measured. The total lift, longitudinal force, andpitching moment of the model were measured on a strain-gagebalance atthe root of the wing.The ground was simulatedby a sheet of pood as shown in figures 1and 3. All tests wit
24、h the ground board were conductedwith an angle of20 between the ground board and thrust axis of the propeller.The full-span blowing nozzle (approximate chordtise shape shown infig. 2(a) was adjustable by means of jackscrews for gap openingsof 0.M6, O.O, and 0.016 inch. The flow coefficient,pressure
25、coef-ficient, and ratio of power in the blowing system to power in the slip-stream plotted against momentum coefficient for the three nozzle gaps.employed in this investigationare presented in figure 5. The mass flowthrough the nozzle was measured by means of a standard sharp-edge-orificeflowmeter.
26、Air was supplied by a 90-pound-per-square-inchl/2-inch lineProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACATN 3904The investigationwas conducted in a static-thrustfacility at theLangley.AeronauticalLaboratory. KU data presented were obtained atze
27、ro forward velocity with a thrust of 15 pounds from the propeller.Inasmuch as the tests were conductedunder static conditions in a largeroom, none of the correctionsthat are normally applicableto wind-tunnel tests were employed.RESULTS AND DISCUSSIONThe data are presented in the fies as follows:Figu
28、resEffect of flap deflections . . .Effect of ground proximity -End plate off, slat off . . . .End plate on, slat off . . . .End plate on, slat on . . . .Effect of slat position and angleEffect of proyeller location -Endplateoff . . . . . . . .Endplateon . . . . . . . .Effect of nozzle gap . . . . .
29、.Analysis figures . . . . . . . . . . . . . . . . . . . . . 6tog. . . . . . . . . . . . . . . 10. . . . . . . . .0 . . 11a71 . . . . . . . . . . . . . K?. . . . . . . . . . . . . . 13. . .,. . . . . . . . . . . 14. . . . . . . . . . . . . . 15a71 . . . . . . . . . . . . . 16. . . . . . . . . . . . .
30、 . 17 to 21Effect of Flap IkfleetionFrom figures 6 to 9 it is seen that without boundary-layer controlthe resultsnt-forcevector is rotated Uww-d progressivelywith flapdeflectionsup to 600. With only the sliding flap deflected and withoutboundary-layer control,the flap is stQled above a deflection of
31、 approxi-mately 500 (fig. 6(c). With boundsry-layer control, achieved by blowingover the flap, the turning angles we greatly increased at the higherflap deflections. It Is of significsmceto note that large increases inturning angles are induced at very low QmDkhtum coefficientsfor the highflap defle
32、ctions. Evidently these large increases in turning angles arethe result of reattaching the slipstreamto a stalled flap. For example(see fig. 6(c), there is little or no gain in turning angles at 200and 40 flap deflection;however, at 70 and 80, with only a smallquantity of air from the nozzle, the tu
33、rning angles are increased 150tO 250.n.J-.Similar results are obtainedwith combined flap deflectionswhenlarge sliding-flap deflections sre employed (figs. 8 and 9); however, ifthe sliding flap is deflected only 50 (fig. 7) in combinationwith the. . .Provided by IHSNot for ResaleNo reproduction or ne
34、tworking permitted without license from IHS-,-,-lUK!ATN 3904 7.plain flap deflected up to ho, fairly large turning angles are obtainedwithoutboundsry-layer control, and large increases in turning angle due.to boundary-layer control were not experienced. These facts indicatethat the flow over this co
35、nfigurationwas not badly separatedwithoutboundary-layer control.Although the turning angles were increasedwith flap deflectionsand blowing, the ratio of resultant forces noticeably decreased. Thesereductions in resultant force with increases in turning sagles would beof considerable importance in co
36、nsidering a compromise between flapsetting, quantity.of blowing, and thrust available for practical use.Boundary-layer control caused increases in the diving moments forall flap configurations. These increased moments probably resulted fromthe direct thrust of the boundary-layer air being applied do
37、wnward inback of the center of gravity and from the reattachment of the flow ofair to the flaps which increases the flap effectiveness. An idea of the power required in the blowing system can be obtainedfrompsrt (e) of figures 6 to 9. The ratio Ps represents the ratioof air horsepower in the blowing
38、 system to the air horsepower in the. slipstream. Most of the gains in turning angle are made at relativelylow power ratios. If the-blowing ah were obtained from an engine-drivencompressor system, the brake-horsepower ratios would be higher than thevalues shown because the efficiency of the blowing
39、system, includingduct losses, would probablybe less than the static-thmst efficiencyof the propeller.Effects of Proxtity to GroundThe effects of height above the ground are shown in figure 10 forvarious quantities of air blowing over a conibinationflap deflectionof af, =50 and 5f,2 =kOO. tiasmuch as
40、 this flap setting wasconsidered to be one of the better compromise arrangements (Q = 58to 70, F/T = O. to 0.92, fig. 7), it was selected for most of theremainder of the investigation. Large reductions in turning angles andin resultant force were incurred nem the ground without boundary-layercontrol
41、. Application of boundary-layer control, however, only slightlyreduced the adverse effects of the ground below a value of h/D ofapproxtite 0.583.The addition of an end plate (fig. 11) had little effect on thecharacteristicsof the model except that in the position closest to theground the resultant f
42、orce was greatly increased. The overall.detri-mental gound effects were considerably offset by the addition of aleading-edge slat (fig. 12). In figure 13 it is indicated that theleading-edge slat reduced the diving moments to approximately one-haProvided by IHSNot for ResaleNo reproduction or networ
43、king permitted without license from IHS-,-,-8 NACA TN 3904of those of the basic flap configurationof figure 10, and it is alsoindicated in figure 13 that when the slat was being used for control,the control effectivenessbetween slat ahgles (5s) of 20 and 30 wasincreasedby the use of boundary-layer c
44、ontrol. References 3 and 4contain a more comprehensiveanalysis of the leading-edge slat as acontrol device without boundary-layer control.Effects of Thrust Axis Position and Change in Nozzle GapFigures 14 and 15 show the characteristicsof the model with thethrust axis lowered 16.7 percent of the pro
45、peller diameter below thewing chord plane and with the propeller closer to the model .leadingedge. By comparingthe configurationsin figures 14 and 15 with theconfigurationsin figures 10 and 11, it is noted that when the thrustaxis is lowered and the propeller is clo”ser-to the model leading edge,the
46、 diving moments were greatly reduced (from approximately -0.15 and-0.24 to O and -0.05). BY comparingfigures 1.2and 15, it is notedthat the lowering of the thrust axis was more effective than the use of *the leading-edge slat in reducing the diviz moments in this investigation.In figures l.1and 15 i
47、t is shown that aproximately15 to 20 increasesin 13 are evidencedby lowering the th however, from previous investigations(refs. 5 and 6) it *S s,hownthat, within the range of x/D and z/Demployed in this investigation,the longitudinalposition of the pro-peller had little effect on M/!JDand e.forChang
48、es in nozzle gap (fig. 16) had negligible effect on the resultsthese-flap deflections. ANALYSISA brief analysis of the increases in resultant force and turningangle due to boundary-layer control is presented in figures 17 to 21.The experimental data, in general, indicate chatthe action of theblowing
49、 air is primarily to reattach the slipstreamto the wing, andthis action thus gives large increases in resultant force and turningangle at low momentum coefficients;butonce the flow is attached”,theonly increases in resultant force achieved with increasedblowing ratesare due to the direct thrust effects ofthe blowing air. In order tocheck the va
