NASA-TN-D-4083-1967 Investigation over moving ground plane of a transport airplane model using blowing over flaps for boundary-layer control《使用边界层控制的平息襟翼的运输机模型的移动地平面研究》.pdf

1、-, - I NASA TECHNICAL NOTE cr) 00 0 P n z c - -2 - 4 - E INVESTIGATION OVER MOVING GROUND PLANE OF A TRANSPORT AIRPLANE MODEL USING BLOWING OVER FLAPS FOR BOUNDARY-LAYER CONTROL !- I %L by Raymond D. Vogler LungZey Research Center Ley Station, Hampton, Va. h NATIONAL AERONAUTICS AND SPACE ADMINISTRA

2、TION WASHINGTON, D. C. AUGUST 1967 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM I llllll1111111111 lllll IHI 111ll1111111ll I#I INVESTIGATION OVER MOVING GROUND PLANE OF A TRANSPORT AIRPLANE MODEL USING BLOWING OVER FLAPS FOR

3、BOUNDARY-LAYERCONTROL By Raymond D. Vogler Langley Research Center Langley Station, Hampton, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151 - CFSTI price $3.00 Provided by IHSNot for ResaleN

4、o reproduction or networking permitted without license from IHS-,-,-INVESTIGATION OVER MOVING GROUND PLANE OF A TRANSPORT AIRPLANE MODEL USING BLOWING OVER FLAPS FORBOTJNDARY-LAYERCONTROL By Raymond D. Vogler Langley Research Center SUMMARY An investigation at low speeds over a still and a moving gr

5、ound plane was made to determine the effects of ground proximity on the longitudinal aerodynamic characteristics of a model of a transport airplane. The four-engine model was equipped for blowing over the flaps for boundary-layer control. Compressed air was used to furnish flap blowing as well as to

6、 furnish the thrust for the two inboard engines. in and out of ground effect through an angle-of-attack range, a flap blowing momentum range, and a thrust range. The model was investigated Results show that flap blowing substantially increases (100 percent at a = Oo) the The presence lift coefficien

7、t through the angle-of-attack range in or out of ground effect. of the ground reduces the lift and drag coefficients and reduces the down load on the tail; thereby, more negative tail incidence is required for trim. The lift reduction increases with increase in flap blowing and height reduction to a

8、 maximum of about 20 percent of the out-of-ground-effect lift. The still and the moving ground planes show negligible differ- ence in effect on model forces and moments except for the model very close to the ground and with a large amount of blowing momentum where the more realistic moving ground pl

9、ane shows small increments of increased lift, decreased drag, and positive pitch when compared with the still ground plane. 1 INTRODUCTION The effect of ground proximity on the aerodynamic characteristics of aircraft is of increasing importance for airplanes with high-lift devices such as jet flaps

10、and vertical- lift jet engines. board under the model. tunnel produces a boundary-layer velocity gradient adjacent to the ground board which does not exist in actual flight in still air. The effect of the boundary layer on tunnel data has in the past been neglected, but with jet flaps and jet-lift e

11、ngines, impingement of the The ground in a wind tunnel is usually simulated by a false floor or The simulation is not quite true in that the moving air in the Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-jet on the tunnel ground board would cause

12、boundary-layer separation. Whether the sep- aration has a significant effect on,the model data depends upon the particular model con- figuration (ref. 1). A number of methods have been used in getting model data in which the problem of boundary-layer separation has been avoided or alleviated. Refere

13、nces 2 and 3 report the results of a moving model over a stationary ground plane. Reference 4 reports the use of an image model to simulate a ground midway between the model and the image model. In the present investigation, the ground plane was a belt that moved with approximately the same speed as

14、 the free-stream tunnel air. This setup prevented the buildup of any boundary layer on the ground plane. The purposes of this investigation were (1) to determine the aerodynamic charac- teristics of the model at low speed in the presence of a moving ground plane with the model operating under variou

15、s combinations of thrust and blowing over deflected flaps and (2) to determine any differences between the data obtained with the model over a moving and over a stationary ground plane. SYMBOLS The force and moment data are presented about the stability axes. The units of measure used in this report

16、 are given in the International System of Units (SI). ref. 5.) (See b wing span, centimeters - C mean aerodynamic chord of wing, centimeters CL CD Cm Lift lift coefficient, - gs drag coefficient, Drag qs pitching-moment coefficient about 0.30F7 Pitching moment qsz ACL,ACD,AC, incremental lift, drag,

17、 and pitching-moment coefficients Engine thrust jet engine thrust coefficient, qs inV flap blowing momentum coefficient, - c!, qs 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-h height of model above ground plane, measured to quarter-chord point

18、of Z (model with power off, CY = Oo, and q = 0), centimeters it incidence of horizontal tail with respect to wing chord plane, degrees m mass rate flow from nozzles in wing, kilograms per second q free-stream dynamic pressure, 412 newtons per square meter S wing area, square meters V jet velocity fr

19、om nozzles in wing, based on isentropic expansion from wing- plenum-chamber total pressure to tunnel static pressure, meters per second Q! fuselage angle of attack, degrees (Wing incidence = ao) tail angle of attack for zero lift on the tail, degrees 470 6f flap deflection, degrees E downwash angle,

20、 degrees MODEL AND APPARATUS The model with the vertical tail removed was a 0.068-scale model of a commercial transport airplane. A three-view drawing of the model is shown in figure 1 and photo- graphs of the model over the moving ground plane are shown in figures 2 and 3. The vertical cable shown

21、in the photographs was attached to the model near the moment center and to a counterweight outside the test section. (See fig. 4.) Without the counter- weight, the model weight would have exceeded the load capacity of the balance. The cable passed over pulleys, allowing vertical movement of the coun

22、terweight as the model height changed. The four-engine model had leading-edge slats and plain flaps on the wing and leading-edge slats on the horizontal tail. Boundary-layer control was obtained by blowing over the flaps from nozzles in the wing. High pressure air was brought to the model through tw

23、o tubes having a diameter of 1.90 centimeters. One tube furnished air for blowing over the flaps and the other tube supplied thrust power to the two inboard engines. The two outboard engines were not powered since they were outboard of the deflected flaps. 3 Provided by IHSNot for ResaleNo reproduct

24、ion or networking permitted without license from IHS-,-,-Desired thrust and blowing momentum were maintained by monitoring total pressures in the engine exits and wing plenum chambers. A sketch showing the model, sting support system, and the moving ground plane (belt) in the 17-foot (5.18-meter) te

25、st section of the Langley 300-MPH 7- by 10-foot tun- nel is shown in figure 4. The air lines were securely anchored to the top of the vertical section of the sting. The lines from the model to the anchor point were shielded from the free stream as shown in the photographs (figs. 2 and 3). The telesc

26、oping vertical arm of the sting system provided model vertical movement, and angle of attack was varied by pitching the sting system by moving it along a sector of a vertical circular track. The moving ground plane was obtained by means of a fabric belt between two rollers driven by an electric moto

27、r. The boundary layer on the tunnel floor upstream of the belt was removed with a suction slot just upstream of the belt. Boundary-layer buildup on the moving ground plane could be prevented by making the belt velocity approximately equal to the free-stream velocity. TESTS AND CORRECTIONS Tests were

28、 made with the model at heights from the ground plane of 10 to 69 per- cent of the model span. Landing-wheel touchdown is at a height of 9.4 percent span. The angle of attack ranged from -4O to 160 with the model out of ground effect and from 00 to 8O at the position nearest to the ground plane. Mos

29、t of the data were obtained with the flaps deflected 600 though some were obtained at deflections of 30 and 70. Various combinations of engine thrust and blowing over the flaps were used throughout the range of heights over the ground plane. The jet flap blowing coefficient Cp was varied from 0 to 0

30、.15, and the engine thrust coefficient Cj run at a free-stream dynamic pressure of 412 newtons per square meter. was varied from 0 to 0.32. All tests were Data at all model heights above the ground plane (except at h/b = 0.69, which is considered out of ground effect) were obtained with the ground p

31、lane moving with approxi- mately free-stream velocity. A few tests with the model at various heights and several tests with the model close to the ground plane (h/b = 0.10) were made with the ground plane stationary to determine the effect of the moving ground plane. The height of the model was meas

32、ured with the model at rest at CY = Oo, and this height h is the height of the model above the ground plane measured to the quarter-chord point of the wing mean aerodynamic chord. This height increases with model lift because of the bending of the sting system. since the pivot center of the circular

33、 track supporting the sting system is above and downstream of the mounting point of the model. quarter-chord point of the mean aerodynamic chord to the model span may be obtained The measured height also increases as the angle of attack increases The corrected ratio of the height of the 4 Provided b

34、y IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-from the following equation: (i)corr e ct ed = 0.3582(1 - cos a) + 0.1695 sin a + cos cos a + CD sin The correction to the measured height ratio is generally small but can reach a maximum of 0.03 or 0.04 at high

35、angles of attack near the ground plane. No blockage or jet-boundary corrections to the data have been made. Blockage corrections to the free-stream velocity are negligible in this tunnel for conventional models. Reference 6 indicates that jet-boundary corrections for model heights and wake deflectio

36、n angles encountered in this investigation would be small or negligible for all model heights except the greatest. RESULTS AND DISCUSSION Presentation of Results Basic wind-tunnel data showing the longitudinal aerodynamic characteristics of the Some summarizing plots giving model for various distanc

37、es (heights) from the ground plane and for various power and flap blowing conditions are presented in figures 5 to 14. more detailed effects of the ground plane are presented in figures 15 to 18. A description of the contents of these data figures is presented in the following table: Figure 5 6 7 a

38、9 10 I1 12 13 14 15 16 17 18 Description Effect of ground, power off, no flap blowing . Effect of ground, power off, flap blowing Effect of ground, power on, flap blowing Effect of ground, power on, flap blowing Effect of moving ground plane Effect of thrust, flap blowing Effect of thrust, flap blow

39、ing Effect of thrust, flap blowing Effect of horizontal tail, away from ground plane Effect of horizontal tail, near the ground plane . Incremental coefficients due to ground effect Incremental coefficients produced by moving ground plane . Downwash angles over the horizontal tail Comparison of grou

40、nd-plane effects . h/b 0.10 to 0.69 0.10 to 0.69 0.10 to 0.69 0.10 to 0.69 0.10 to 0.41 0.69 0.69 0.69 0.69 0.12 0.10 to 0.25 1.10 and 0.69 0.10 1.12 and 0.69 6f, leg 30 70 60 60 60 60 60 60 60 60 60 60 60 60 - % 0 0 to 0.15 0 to 0.15 0 to 0.10 0.10 0 to 0.15 0 to 0.10 0 to 0.10 0 to 0.10 0 to 0.10

41、0 to 0.10 0 to 0.10 0 to 0.10 0 to 0.10 0 0 0 to 0.32 0 to 0.32 0.32 0 to 0.32 0 to 0.32 0 to 0.32 0 to 0.32 0 to 0.32 0 and 0.32 0 and 0.32 0 to 0.32 0 to 0.32 -6 -6 Tail off -6 -6 Tail off -6 -10 Range Range -6 -6 -6 - The method of coping with the excessive weight of the model and the air-line at

42、tach- ments to the model resulted in restraints on the model which are not ordinarily present in wind-tunnel testing. the angle-of-attack range for each model height from the ground plane for wind-off These restraints were determined for model configurations through 5 Provided by IHSNot for ResaleNo

43、 reproduction or networking permitted without license from IHS-,-,-conditions and subtracted from the force and moment readings for the wind-on tests. However, these restraints or other factors have produced some scatter in the basic data. Longitudinal Aerodynamic Characteristics Over Moving Ground

44、Plane The effect of the ground plane on the model longitudinal aerodynamic characteris- tics is shown in figures 5 to 8. Only a few runs at various heights were made without thrust or flap blowing at a flap deflection of 300 (fig. 5). At a flap deflection of 70 (fig. 6), data were obtained at all mo

45、del heights through the flap momentum range and at zero thrust. The remainder of the basic data at a flap deflection of 600 included the effects of height, thrust, and blowing momentum. Comparison of figures 6(a) and 8(a) indicates little difference between the out-of-ground effect data for the mode

46、l with a flap deflection of 600 and those for the model with a flap deflection of 700. The 70 flaps are a little more effective in ground effect. In either case, the model usually shows a larger lift coefficient in ground effect than out of ground effect at zero angle of attack. However, the fact th

47、at this condition is reversed when the tail is removed (fig. 7(a) indicates that the increased lift in ground effect at a! = Oo is largely a result of the reduction in down load on the tail as it encounters ground effect. Thus, the change in lift-curve slope at various model heights (figs. 6(a) and

48、8(a) results primarily from the ground effect on the tail. An analysis of the incremental pitching moments resulting from the tail without flap blowing (figs. 7 and 8) indicates that at high angles of attack the down load on the tail out of ground effect becomes an up load as the model moves close t

49、o the ground. The preceding discussion was with reference to the model without flap blowing. With flap blowing, the lift coefficients are substantially increased (about doubled at a! = Oo) in or out of ground effect, and the major effect of the ground on the model is a result of the effects of the ground on the wing rather than on the tail. With the tail off or on (figs. 7 and