1、NASA Technical Paper 1786 Low-Speed Aerodynamic Characteristics of a WPercent-Thick Medium- Speed Airfoil Designed for General Aviation Applications Robert J. McGhee and William D. Beasley Langley Research Center Ha nzpto 11, Virgiuia NASA National Aeronautics and Space Administration Scientific and
2、 Technical Information Branch 1980 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SUMMARY An investigation was conducted in the Langley Low-Turbulence Pressure Tunnel to determine the low-speed two-dimensional aerodynamic characteristics of a 17-per
3、cent-thick medium-speed airfoil designed for general aviation appli- cations. The results are compared with data for the 17-percent-thick low-speed airfoil and the 13-percent-thick medium-speed airfoil. Theoretical predictions of the drag-rise characteristics for the medium-speed airfoil are also pr
4、ovided. The tests were conducted over a Mach number range from 0.10 to 0.32, a chord Reynolds number range from 2.0 x lo6 to 12.0 x lo6, and an angle-of-attack range from about -8O to 20. The results of the investigation indicate that maximum section lift coef- ficients at a Mach number of 0.15 incr
5、eased from about 1.6 to 2.0 as the Reynolds number increased from about 2.0 x lo6 to 12.0 x lo6. teristics were of the trailing-edge type and were docile at all Reynolds num- bers. The application of a roughness strip near the leading edge of the airfoil decreased the maximum section lift coefficien
6、t as much as 0.04 over the test Reynolds number range. Increasing the Mach number from 0.10 to 0.32 at a constant Reynolds number of 6.0 x lo6 decreased the maximum section lift coef- ficient about 0.03. The magnitude of the quarter-chord pitching-moment coeffi- cient was decreased about 25 percent,
7、 and the drag coefficient decreased at all lift coefficients (fixed transition) for the 17-percent-thick medium-speed air- foil compared with the 17-percent-thick low-speed airfoil. The predominant effects of increasing airfoil thickness from 13 percent to 17 percent for the medium-speed airfoils we
8、re to decrease the maximum section lift coefficient and to increase the drag coefficient at all lift coefficients (fixed transition). Stall charac- INTRODUCTION Research on advanced-aerodynamics-technology airfoils for general aviation applications has received considerable attention over the last s
9、everal years at the Langley Research Center. An initial family of low-speed airfoils was devel- oped; this research is summarized in reference 1. Recently, the general avia- tion industry indicated a requirement for airfoils which provide higher cruise Mach numbers than the low-speed airfoils and wh
10、ich still retain good high-lift low-speed characteristics. These medium-speed airfoils have been designed to fill the gap between the low-speed airfoils and the supercritical airfoils for application on light general aviation aircraft. Reference 2 reports the results of a 13-percent-thick medium-spe
11、ed airfoil designed for a lift coefficient of 0.30 and a Mach number of 0.72. The present investigation was conducted to determine the low-speed aerody- namic characteristics of a 17-percent-thick medium-speed airfoil designed for a lift coefficient of 0.30, a Reynolds number of 14.0 x lo6, and a Ma
12、ch number of 0.68. This airfoil is designated as MS(1)-0317. In addition, the results are compared with data for the 17-percent-thick low-speed airfoil (LS (1) -041 7) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-and the 13-percent-thick medium-sp
13、eed airfoil (MS (1 ) -031 3) . Theoretical pre- dictions of the drag-rise characteristics for the medium-speed airfoil are also provided. The investigation was performed in the Langley Low-Turbulence Pressure Tunnel over a Mach number range from 0.10 to 0.32. The Reynolds number, based on the airfoi
14、l chord, varied from about 2.0 x lo6 to 12.0 x lo6, and the geometric angle of attack varied from about -8O to 20. SYMBOLS Values are given in both SI and U.S. Customary Units. The measurements and calculations were made in U.S. Customary Units. cP C CC Cd c: Cl Cm Cn h M P R X 2 Pk - pa7 qa7 pressu
15、re coefficient, airfoil chord, cm (in. 1 section chord-force coefficient, section profile-drag coefficient, c: d(2) Wake point-drag coefficient section lift coefficient, section pitching-moment coefficient about quarter-chord point, cn cos O! - cc sin ci -($ Cp(: - 0.25) d(z) + ($ Cp d(:) section no
16、rmal-force coefficient, - cP d(:) vertical distance in wake profile, cm (in.) free-stream Mach number static pressure, Pa ( lb/ft2) dynamic pressure, Pa ( lb/ft2) Reynolds number based on free-stream conditions and airfoil chord airfoil abscissa, cm (in.) Provided by IHSNot for ResaleNo reproduction
17、 or networking permitted without license from IHS-,-,-“ z airfoil ordinate, cm (in.) ZC Zt mean thickness, cm (in.) a geometric angle of attack, deg mean camber line ordinate, cm (in.) Subscripts : II local point on airfoil max maximum W free-stream conditions Abbreviations: LS (1 1 low-speed, first
18、 series MS(1) medium-speed, first series AIRFOIL DESIGNATION A sketch of the section shape for the 17-percent-thick medium-speed airfoil is shown in figure 1. The airfoil is designated in the form MS(1)-0317. MS(1) indicates medium speed (first series). foil design lift coefficient in tenths (0.30),
19、 and the last two digits designate the airfoil maximum thickness in percent chord (17). The next two digits designate the air- AIRFOIL DEVELOPMENT The intention of medium-speed airfoil development was to combine the best features of low-speed and supercritical airfoil technology; this airfoil devel-
20、 opment is discussed in detail in reference 2. The design objective of the medium-speed airfoils was to increase the cruise Mach number of the low-speed airfoils while retaining their good high-lift, low-speed characteristics. This 17-percent-thick medium-speed airfoil was designed for a lift coeffi
21、cient of 0.30, a Reynolds number of 14.0 x lo6, and a Mach number of 0.68. The airfoil shape was changed iteratively until the design pressure distribution was obtained. (See fig. 2.) The computer program of reference 3 was used to pre- dict the results of various airfoil modifications. The design p
22、ressure distributions for the 13-percent and 17-percent medium- speed airfoils are compared in figure 2. Note that for the 17-percent-thick airfoil, which has higher induced velocities, the start of the aft upper-surface pressure recovery is located at about 0.50 compared with about 0.60 for the 13-
23、percent airfoil. This is required in order to keep the aft pressure gradient gradual enough to avoid separation for the thicker airfoil. The thickness dis- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-tribution and camber line for the 17-percent m
24、edium-speed airfoil are shown in figure 3, and the airfoil design coordinates are presented in table I. MODEL, APPARATUS, AND PROCEDURe Model The airfoil model was constructed with a metal core around which plastic fill and two thin layers of fiberglass were used to form the contour of the air- foil
25、. The model had a chord of 61 cm (24 in.) and a span of 91 cm (36 in.) and was equipped with both upper- and lower-surface orifices located 5 cm (2 in.) off the midspan. The airfoil surface was sanded in the chordwise direction with No. 400 dry silicon carbide paper to provide a smooth aerodynamic f
26、inish. The model contour accuracy was generally within kO.10 mm (0.004 in.). Wind Tunnel The Langley Low-Turbulence Pressure Tunnel (ref. 4) is a closed-throat, single-return tunnel which can be operated at stagnation pressures from 1.0 to 10.0 atm (1 atm = 101.3 kPa) with tunnel-empty test-section
27、Mach numbers up to 0.42 and 0.22, respectively. The maximum Reynolds number is about 49.0 x 106 per meter (15.0 x lo6 per foot) at a free-stream Mach number of about 0.22. The tunnel test section is 91 cm (3 ft) wide and 229 cm (7.5 ft) high. Hydraulically actuated circular plates provided positioni
28、ng and attachment for the two-dimensional model. The plates are 102 cm (40 in.) in diameter, rotate with the airfoil, and are flush with the tunnel wall. The airfoil ends were attached to rectangular model-attachment plates (fig. 41, and the airfoil was mounted so that the center of rotation for the
29、 circular plates was at 0.25 on the model reference line. The air gaps in the tunnel walls between the rect- angular plates and the circular plates were sealed with metal seals. Wake Survey Rake A fixed wake survey rake (fig. 5) at the model midspan was mounted from the tunnel sidewall and located 1
30、 chord length behind the trailing edge of the airfoil. The wake rake used 0.15-cm (0.06-in.) diameter total-pressure tubes and 0.32-cm (0.125-in.) diameter static-pressure tubes. The total-pressure tubes were flattened to 0.10 cm (0.04 in.) for 0.61 cm (0.24 in.) from the tip of the tube. Each stati
31、c-pressure tube had four flush orifices drilled 90 apart; these orifices were located 8 tube diameters from the tip of the tube and in the plane of measurement for the total-pressure tubes. Instrumentation Measurements of the static pressures on the airfoil surfaces and the wake- rake pressures were
32、 made by an automatic pressure-scanning system using variable- capacitance precision transducers. Basic tunnel pressures were measured with 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I precision quartz manometers. digital shaft encoder operate
33、d by a pinion gear and rack attached to the cir- cular model-attachment plates. system and recorded on magnetic tape. Angle of attack was measured with a calibrated Data were obtained by a high-speed acquisition TESTS AND METHODS The airfoil was tested at free-stream Mach numbers from 0.10 to 0.32 o
34、ver an angle-of-attack range from about -8O to 20. airfoil chord was varied from about 2.0 x lo6 to 12.0 x 106. tested both in the smooth condition (natural transition) and with roughness located on both upper and lower surfaces at 0.075. The roughness was sized for each Reynolds number according to
35、 the technique described in reference 5. The roughness was sparsely distributed and consisted of granular-type strips 0.13 cm (0.05 in.) wide which were attached to the surfaces with clear lacquer. Reynolds number based on the The airfoil was The static-pressure measurements at the airfoil surface w
36、ere reduced to standard pressure coefficients and machine integrated to obtain section normal- force and chord-force coefficients as well as section pitching-moment coeffi- cients about the quarter-chord point. Section profile-drag coefficients were computed from the wake-rake total and static press
37、ures by the method reported in reference 6. An estimate of the standard low-speed wind-tunnel boundary corrections (ref. 7) amounted to a maximum of about 2 percent of the measured coefficients; these corrections have not been applied to the data. An estimate of the dis- placement of the effective c
38、enter of a total-pressure tube in a velocity gra- dient on the values of Cd showed these effects to be negligible (ref. 6). PRESENTATION OF RESULTS The test conditions are summarized in table 11. The results of this investigation have been reduced to coefficient form and are presented in the followi
39、ng figures: Figure Section characteristics for MS(1)-0317 airfoil . 6, 7 Effect of roughness on section characteristics . 8 Effect of Reynolds number on section characteristics; modelsmooth; M=0.15 . 9 Effect of Reynolds number on section characteristics; roughness on; M = 0.15 . 10 Effect of Mach n
40、umber on section characteristics; Comparison of section characteristics for LS(1)-0417 Comparison of section characteristics for MS(1)-0313 roughness on; R = 6.0 x lo6 . 11 and MS(1)-0317 airfoils; roughness on; M = 0.15 . 12 and MS(1)-0317 airfoils; roughness on; M = 0.15 . 13 5 Provided by IHSNot
41、for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figure Effect of angle of attack and Reynolds number on chordwise pressure distributions for MS (1) -031 7 airfoil; roughness on; M = 0.15 . distributions for MS(1)-0317 airfoil; roughness on; R = 6.0 x lo6 . Comparison o
42、f chordwise pressure distributions for LS(1)-0417 and MS(1)-0317 airfoils; roughness on; M = 0.15; R = 4.0 x lo6 . MS (1 ) -031 3 and MS (1 1-031 7 airfoils; roughness on; Variation of maximum lift coefficient with Reynolds number for LS(1)-0417 and MS(1)-0317 airfoils; M=0.15 Variation of maximum l
43、ift coefficient with Reynolds number for MS(1)-0313 and MS(1)-0317 airfoils; M=0.15 number for MS (1 ) -031 3 and MS (1 ) -031 7 airfoils; roughness on; R = 6.0 x 106 Variation of drag coefficient with Reynolds number for MS (1)-0317 airfoil; M = 0.15; c2 = 0.30 . Calculated drag-rise characteristic
44、s for medium-speed airfoils; R = 14.0 x lo6; c2 = 0.30 . Effect of Mach number on chordwise pressure Camparison of chordwise pressure distributions for I M = 0.15; R = 4.0 x IO6 . Variation of maximum lift coefficient with Mach . 14 . 15 . 16 . 17 . 18 . 19 . 20 . 21 . 22 DISCUSSION OF RESULTS Secti
45、on Characteristics Lift.- Figure 9(a) shows that the lift-curve slope for the 17-percent , medium-speed airfoil in a smooth condition (natural boundary-layer transi- tion) varied from about 0.11 to 0.12 per degree for the Reynolds numbers investigated (M = 0.15). The angle of attack for zero lift co
46、efficient was about -3O. Maximum lift coefficients increased from about 1.60 to 2.0 as the Reynolds number was increased from 2.0 x lo6 to 12.0 x lo6. effect of Reynolds number on maximum lift coefficient occurred for Reynolds numbers below 6.0 x lo6. The stall characteristics of the airfoil are of
47、the trailing-edge type, as shown by the lift data of figure 9(a) and the pressure data of figure 14. The nature of the stall is docile for all Reynolds numbers tested. The largest The addition of a narrow roughness strip at 0.075 (fig. 8) resulted in the expected decambering effect because of the in
48、crease in boundary-layer thick- ness. The lift coefficient at c1 = Oo decreased about 0.04 at the lower Reynolds numbers, but only small changes occurred at the higher Reynolds numbers. The roughness strip decreased the 0.04 for the test Reynolds number range (fig. 19). c2,max performance of the air
49、foil as much as Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The effects of Mach number on the airfoil lift characteristics at a Reynolds number of 6.0 x 706 with roughness located at 0.075 are shown in fig- ure ll(a). Increasing the Mach number from 0.10 to 0.32 resulted in the expected Prandtl-Glauert increase in lift-curve slop
