NASA-TN-D-55-1960 Wind-tunnel investigation of longitudinal aerodynamic characteristics of three propeller-driven VTOL configurations in the transition speed range including effect.pdf

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1、NASA TN D-55 TECHNICAL NOTE 0-55 WIND-TUNNEL INVESTIGATION OF LONGITUDINAL AERODYNAMIC CHARACTERISTICS OF THREE PROPELLER-DRIVEN VTOL CONFIGURATIONS IN THE TRANSITION SPEED RANGE, INCLUDING EFFECTS OF GROUND PROXIMITY By Richard E. Kuhn and William C. Hayes, Jr. Langley Research Center Langley Field

2、, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON Februaq 1960 NASA-ZN-D-55) WlNI;-SEIBEL IFFESZIGATION OF N89-70392 1C VTOL CC A 16UbATIC 3s AB TtE IIliANSITICN SPEEG BABE, 16CZODIliG UACldS EJFECIIS GE GfCUbC FECXIBXTY (hA,CA) 135 p 00102 0195453 Provided by IHSNot for ResaleNo reprod

3、uction or networking permitted without license from IHS-,-,-# . NATIONAL AERONAUTICS AND SPACE ADMINISTRATION TECHNICAL NOTE D-53 WIND-TUNNEL INVESTIGATION OF LONGITUDINAL AERODYNAMIC CHARACTERISTICS OF THREE PROPEI;LER-DRIVEN VTOL CONTIGURATIONS IN THE TRANSITION SPEED RANGE, INCLUDING EFFECTS OF G

4、ROUND PROXIMITY By Richard E. Kuhn and William C. Hayes, Jr . SUMMARY An investigation has been made in the 17-foot test section of the Langley 300-MPH 7- by 10-foot tunnel to determine the longitudinal aero- dynamic characteristics of tilt-wing, deflected-slipstream, and combina- tion tilt-wing-def

5、lected-slipstream VTOL configurations in the transi- tion speed range. The results of this investigation are in general agreement with prior related investigations in that although the tilt-wing configuration requires the least power in hovering, the combination tilt-wing- deflected-slipstream confi

6、guration has relatively low power requirements throughout the transition speed range. In addition, the longitudinal trim problems of the combination configuration can be handled easily by use of a rearward location of the wing pivot and by properly programing the flap deflection angle with wing tilt

7、 angle. The power requirements for the combination configuration in the region of ground effect are only slightly larger than those for the tilt- wing configuration at the lower speeds and are lower than the require- ments for the tilt-wing configuration at speeds above about 30 knots. The power req

8、uirements for the deflected-slipstream configuration are greatly increased in the region of ground effect. The extension of a leading-edge slat had little value except in the case of the deflected- slipstream configuration at high flap deflection. An appendix describing the 17-foot test section of t

9、he Langley 3OO-MFH 7- by 10-foot tunnel in which the model was tested is included. INTRODUCTION . . An investigation of the aerodynamic characteristics of wing-propeller configurations that may be applicable to aircraft designed for vertical Provided by IHSNot for ResaleNo reproduction or networking

10、 permitted without license from IHS-,-,-2 ri take-off and landing (VTOL) or short take-off and landing (STOL) is being conducted at the Langley Research Center of the National Aeronautics and Space Administration. generally indicated that a combination of the tilt-wing and deflected- slipstream conf

11、igurations my have several advantages over a configura- tion employing either tilt wings or deflected slipstream alone. Refer- ence 1, for instance, indicates that the trim problem of the tilt wing can be alleviated by adding a trailing-edge flap, the deflection of which could be programed so that t

12、he diving moment arising from the flap deflection would cancel the thrust-induced nose-up pitching moment during transition flight. In addition, reference 2 indicates that the flap is beneficial in reducing the stall and, therefore, the power requirements in the transition or low-speed range. These

13、factors, plus the thrust recovery factor - that is, the ratio of lift produced to thrust input obtainable with only a moderate amount of slipktream deflection - indi- cate the desirability of further investigation of the combination configuration. The results of this work have Inasmuch as the forego

14、ing observations have been made from results obtained from various models having generally different physical charac- teristics, the present investigation was undertaken to obtain, with one combination tilt-wing-deflected-slipstream configurations. a model, a comparison of the tilt-wing, the deflect

15、ed-slipstream, and the i The effects of ground proximity have, in general, been investigated only for the hovering condition (zero forward speed). Very little data on the effects of ground proximity on the performance in the transition speed range are available. A large part of the present investiga

16、tion has, therefore, been devoted to this problem. The flow in the region of possible horizontal-tail locations was surveyed by measuring the floating angle of freely floating downwash vanes and from total-pressure tubes in the vane leading edges which measured the dynamic pressure of the flow. mode

17、l at zero forward speed have been presented in reference 3. The characteristics of this SYMBOLS When a wing operates in the slipstream of luge-diameter propellers, large forces and moments can be produced at low or zero forward speed. Coefficients based on the free-stream dynamic pressure approach i

18、nfinity and thus become meaningless. Therefore, it seems appropriate to base the present paper, coefficients so based are indicated by the use of the subscript s. The relationship between the propeller thrust and the dynamic pressure in the slipstream is discussed in reference 4. the coefficients on

19、 the dynamic pressure in the propeller slipstream; in J U Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-L 5 1 0 i (. Conventional coefficients based on the free stream can be obtained by dividing by (1 - %,s); for example, CL = therefore, cor- rect

20、ions were not considered necessary. The average total pressure was connected to a strain-gage pressure cell, and the readings thus obtained were also printed on a chart potentiometer. The average dynamic-pressure ratio over the span was then obtained from the relation -=P qt O-P 9s 9s where the stat

21、ic pressure p at the vane was obtained from the tunnel calibration. TESTS AND CORRECTIONS The investigation reported in reference 5 indicated that an increased ratio of tunnel size to model size is necessary for deflected-slipstream or tilt-wing configurations in order to avoid large unknown tunnel-

22、wall effects. As a result, a 17-foot test section was constructed in the large end of the Langley 3OO-MPH 7- by 10-foot tunnel, upstream of the regular test section. The arrangement and calibration of this test section are presented in the appendix to this paper. Corrections to the free-stream veloc

23、ity due to blockage and slip- stream contraction were estimated and found to be negligible. boundary corrections applied to the angle of attack and the longitudinal force were estimated for a square test section by a method similar to that of reference 6. Inasmuch as these corrections depend on the

24、circu- lation about the wing, it was necessary to subtract the direct thrust contribution to lift before applying them. The following relations were used : The jet- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 . where CL,l proportional to the ci

25、rculation and is obtained by subtracting the direct thrust contribution as follows: is the increment of lift coefficient that is approximately i where 8 and - F are the turning angle and thrust recovery factor T obtained at zero forward speed (ref. 3). were found to be small; however, they were appl

26、ied. In general these corrections L 5 1 0 The tests were made at a combination of free-stream dynamic pres- sures and propeller thrusts selected to mainthin a dynamic pressure of approximately 8 lb/sq ft in the slipstream. The tests with propeller off and propeller free (windmilling) were run at a f

27、ree-stream dynamic pressure of 8 lb/sq ft. The thrust of the inboard propeller was held could be maintained on both propellers at zero angle of attack by appro- spanwise variation in flow conditions, the thrust of the outboard pro- peller varied slightly from the initial value at angles of attack ot

28、her than zero. constant throughout the angle-of-attack range. The selected thrust 0 priate adjustment in the propeller blade angles; however, because of the i In order to minimize test time, operating conditions were chosen so that only two blade-angle settings were required. A blade angle of about

29、8 was used at the higher thrust coefficients while a blade angle of about 16O was used for the lower thrust coefficients. The Reynolds number in the slipstream, based on a mean aerodynamic chord of 1.20 feet, was 0.63 x 10 6 . PRESENTATION OF RESULTS The results of the investigation are presented. i

30、n the following order: Figure Propeller alone 6 Wing alone 7 Effect of slat position 8 Basic data: * J Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2H 9 Figure L 5 1 0 h V Effect of thrust coefficient and flap deflection: Out of ground-effect regi

31、on; slat extended: Tilt-wing configuration (flaps retracted) Combination configuration (6f,s = 00; 8f,F = 50) . . Deflected-slipstream configurations ( flap deflection variable ) . Combination configuration (6f s = 00; 6f,F = 50“) . . Deflected-slipstream configurations (flap deflection variable) .

32、Out of ground-effect region; slat retracted: In ground-effect region; slat extended: Tilt-wing configuration (flaps retracted) Combination configuration (6f,s = Oo; gf,F = 50) . . Deflected- slipstream configurations ( flap deflect ion variable) . Single (inboard) propeller operation ( Ff,S = Oo; 6f

33、,F = 50) 9 10 11 to 14 15 16, 17 18 19, 20 21 to 24 25 Comparison figures: Effect of flap deflection at constant thrust Effect of ground proximity 27 to 30 coefficient . 26 Effect of slat 31 Calculated transition characteristics of the hypothetical airplane : Power required in transition: . Hypothet

34、ical airplane drawing 32 Effect of flap deflection 33 Comparison of configurations 34, 35 Effect of ground proximity 36 Effect of slat 37 . . Longitudinal trim . 38, 39 The results of the flow-angularity and dynamic-pressure surveys behind the model (in the vicinity of a horizontal tail) are include

35、d as the last part of figures 9 to 19, 21, 23, and 25. The position of the vane pivot point remains fixed with respect to the model, and the vane height parameter quarter-chord line and the relative wind. other than zero, the wing incidence and the airplane angle of attack must be used in calculatin

36、g the effective horizontal-tail position (z/C) to be used in entering the data figures to determine flow angularity and dynamic pressure. z/F is measured with respect to a plane containing the wing Thus, for angles of attack Provided by IHSNot for ResaleNo reproduction or networking permitted withou

37、t license from IHS-,-,-10 DISCUSSION The discussion of the data is divided into two main parts. The first part is a general discussion in which the more significant results are pointed out. The second part demonstrates the application of the data to the estimation of the performance of a hypothetica

38、l airplane. The three configurations considered are the tilt-wing, the combination tilt-wing-deflected-slipstream, and the deflected-slipstream. The variations of lift and pitching-moment coefficients with longitudinal-force coefficient included in figures 7 to 31 are of par- ticular interest in ass

39、essing the aerodynamic characteristics of a given configuration. Positive values of C climbing flight, whereas negative values of CXjs indicate decelerating or descending flight. A value of zero for Cx,s indicates that drag is exactly balanced by a component of thrust and that a condition of steady

40、level flight exists. The angle of steady climb or descent is indicate accelerating or X? s I . L defined as 7 = tan- cx9 . The pitching-moment coefficient for level flight at a particular thrust coefficient or at any climb or glide angle may be read directly at the appropriate value of The values of

41、 thrust coefficient listed in the figure keys are nominal, and typical variations of the actual values with angle of attack are shown in fig- ures 6(a) and 9( c) . CL, s c CX,. General Discussion The basic data for the propeller alone and for the wing alone are presented in figures 6 and 7, respecti

42、vely. The expected high lift coefficients and large negative pitching moments resulting from the extension of the Fowler flap are shown in figure 7(a). Effect of slat position.- The results of the investigation reported in reference 5 indicated that a leading-edge slat would be effective in delaying

43、 wing stall to higher angles of attack. Therefore, the initial phase of the present investigation was the determination of the effec- tiveness of a 30-percent-chord slat at three different positions with respect to the wing (fig. 3). in general, indicate that the highest position investigated gave t

44、he highest maximum lift coefficients and extended the high lift condition well into the deceleration or approach range of CX, values. However, these results are restricted to a thrust coefficient of 0.90 and large These results are shown in figure 8 and, 9 flap deflection angles (6f,s = 50; 6f,F = r

45、oo). Subsequent tests at fi Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-11 IY L 5 1 0 other flap deflection angles and thrust coefficients indicated that the slat was useful only with the combination of high thrust coefficients and high flap defl

46、ection angles. Comparisons of slat-on and slat-off data presented in figure 31 indicate that at lower flap deflection angles the slat slightly reduced both the lift and the longitudinal force except at the highest angles of attack. tests were in progress, and most of the data presented herein were o

47、btained with the slat extended in the high position. This result was not realized while the Effect of flap deflection.- The basic data showing the effect of thrust coefficient for various flap deflection angles (slat extended) are presented in figures 9 to 14, and a comparison of the effects of flap

48、 deflection at given thrust coefficients is presented in figure 26. The lift coefficients attainable for steady level flight = 0) with the flaps retracted (tilt-wing configuration) and with a thrust coeffi- cient of 0.60 are relatively low because of wing stall (fig. 26(a). In addition, nose-up mome

49、nts (about the wing quarter chord) are encountered as a result of both the low position of the thrust line and the direct propeller pitching moments which are as indicated in figure g(b) and in reference 4. tilt-wing-deflected-slipstream configuration) appreciably increases the lift for steady level flight (C = 0) and also produces a large diving moment (fig. 26(a). both flaps ar