1、NASA Technical Memorandum 78709. i|BASA-T_I-78709) NASA LOW-AND MEDIUM-SPEED.aIRFOIL _EVELOP_ENT (NASA) 19 p CSCL 01CHC A02/li_ A01G3/03gnclas33612NASA Low- and Medium-SpeedAirfoil DevelopmentRobert J. McGhee, William D. Beasley,and Richard T. WhitcombLangley Research CenterHampton, VirginiaNIL IXNa
2、tional Aeronauticsand Space AdministrationScientific and TechnicalInformation Office1979REPRODUCED BYU.S. DEPARTMENT OF COMMERCENATIONALTECHNICALINFORMATION SERVICESPRINGFIELD, VA 22161Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNo
3、t for ResaleNo reproduction or networking permitted without license from IHS-,-,-U.S. DEPARTMENT OF COMMERCENational Technical Information ServiceN80=21294NASA LOW- AND MEDICUM-SPEED AIRFOIL DEVELOPMENTLANGLEY RESEARCH CENTERHAMPTON, VA1979ilProvided by IHSNot for ResaleNo reproduction or networking
4、 permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No. _ 2. Government Accession No.1NASA TM-787094. Title and SubtitleNASA LOW- AND MEDIUM-SPEED AIRFOIL DEVELOPMENT7. Author(s)Robert J. McGhee, William
5、D. Beasley,and Richard T. Whitcomb9. PerformingO_anizationNameand Addre=NASA Langley Research CenterHampton, VA 2366512. Sponsoring Agency Name and Addr_sNational Aeronautics and Space AdministrationWashington, DC 205463. Recipients Catalog No.5. Report DateMarch 19796. Performing Organization Code8
6、. Performing Organization Report No.L-1226410. Work Unit No.505-O6-33-1011. Contract or Grant No.13. Type of Report and Period CoveredTechnical Memorandum14. Sponsoring Agency Code15. _pplementary NotesThis paper was presented at the NASA Conference on Advanced Technology AirfoilResearch held at Lan
7、gley Research Center on March 7-9, 1978, and is publishedin NASA CP-2046.16. AbstractThe status of NASA low- and medium-speed airfoil research, which was initiatedin 1972 with the development of the GA(W)-I airfoil and which has now emergedas a family of _irfoils, is discussed. Effects of airfoil th
8、ickness-chordratios varying from 9 percent to 21 percent on the section characteristics fora design lift coefficient of 0.40 are presented for the initial low-speed fam-ily of airfoils. Also, modifications to the 17-percent low-speed airfoil toreduce the pitching-moment coefficient and to the 21-per
9、cent low-speed airfoilto increase the lift-drag ratio are discussed. Representative wind-tunnelresults are shown for two new medium-speed airfoils with thickness ratios of13 percent and 17 percent and design-lift coefficients of 0.30. These newairfoils were developed to increase the cruise Mach numb
10、er of the low-speedairfoils while retaining good high-lift, low-speed characteristics. Applica-tions of NASA-developed airfoils to general aviation aircraft are summarized.17. Key Words(Suggested by Author(s)Low-speed airfoilsMedium-speed airfoilsThickness effectsReynolds number effectsMach number e
11、ffects19. Security _a_if.(ofthisreport)Unclassified20. Security Clasit. tot tins _ge)Unclassified 21. No. of Pages1622. FhiceNASA-Langley, 1979ORIGINAL PAGE ISOF POOR QUALITYProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for Resal
12、eNo reproduction or networking permitted without license from IHS-,-,-SUMMARYThe status of NASA low- and medium-speed airfoil research, which wasinitiated in 1972 with the development of the GA(W)- airfoil and which has nowemerged as a family of airfoils, is discussed. Effects of airfoil thickness-c
13、hord ratios varying from 9 percent to 21 percent on the section characteristicsfor a design lift coefficient of 0.40 are presented for the initial low-speedfamily of airfoils. Also, modifications to the 17-percent low-speed airfoil toreduce the pitching-moment coefficient and to the 2-percent low-sp
14、eed airfoilto increase the lift-drag ratio are discussed. Representative wind-tunnelresults are shown for two new medium-speed airfoils with thickness ratios of13 percent and 7 percent and design lift coefficients of 0.30. These new air-foils were developed to increase the cruise Mach number of the
15、low-speed air-foils while retaining good high-lift, low-speed characteristics. Applicationsof NASA-developed airfoils to general aviation aircraft are summarized.INTRODUCTIONResearch on advanced technology airfoils for low-speed general aviationapplications has received considerable attention at Lan
16、gley since the develop-ment of the GA(W)- airfoil in 972. This airfoil was analytically developedusing the subsonic viscous computer code of reference which provided a low-cost analysis of the airfoil performance. References 2 and 3 report theexperimental results for this airfoil and others derived
17、from it, and refer-ences 4 to 6 report flap and control-surface results for several of theseairfoils. Flight test results for the GA(W)-2 airfoil are reported inreference 7.This research effort was initially generated to develop advanced airfoilsfor low-speed applications. Emphasis was placed on des
18、igning airfoils withlargely turbulent boundary layers which had the following performance require-ments: low cruise drag, high climb lift-drag ratios, high maximum lift, andpredictable, docile stall behavior. However, in 1976 the need developed forairfoils with higher cruise Mach numbers than the lo
19、w-speed airfoils provided,while retaining good high-lift, low-speed characteristics. Thus, two medium-speed airfoils were developed. These medium-speed airfoils are intended tofill the gap between the low-speed airfoils and the supercritical airfoilsfor application on light executive-type aircraft.
20、In this paper the statusof low- and medium-speed airfoil research is discussed and the applicationsof NASA-developed airfoils to general aviation aircraft are summarized.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-CpcCdczCmZ/dMRtxSYMBOLSpressure
21、coefficientairfoil chordsection drag coefficientsection lift coefficientsection quarter-chord pitching-moment coefficientsection lift-drag ratioMach numberReynolds numberairfoil thicknessairfoil abscissaangle of attackSubscripts:d designmax maximumSEP separationT transitionAIRFOIL DESIGNATIONSketche
22、s of the section shapes and airfoil designations for the low-and medium-speed airfoils are shown in figure I. The airfoils are desig-nated in the form LS(1)- or MS()-xxxx. LS(1) indicates low speed (firstseries) and MS(l) indicates medium speed (first series); the next two digitsdesignate the airfoi
23、l design lift coefficient in tenths, and the last two digitsare the airfoil thickness in percent chord. Thus, the GA(W)-I airfoil becomesLS(1)-0417 and the GA(W)-2 airfoil becomes LS(I)-0413.LOW-SPEED AIRFOILSInitial FamilyThis initial family of low-speed airfoils was obtained by linearlyscaling the
24、 mean thickness distribution of the 17-percent airfoil (LS(I)-0417).Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Thus, all four airfoils have the same camber distribution and the design liftcoefficient is 0.40. The effects of varying thickness-cho
25、rd ratio from 9 to21 percent on maximum lift coefficient and lift-drag ratio are shown in fig-ure 2 for a Reynolds number of 4 06 with transition fixed near the leadingedge of the airfoils. The maximum lift coefficient increases with thicknessratio up to a thickness ratio of about 13 percent; furthe
26、r increase in thicknessratio results in a decrease in maximum lift coefficient. For the 13-percentairfoil a value of maximum lift coefficient of about 1.9 is indicated. Thelift-drag ratio decreases almost linearly with increasing thickness ratio overthe entire thickness-ratio range at the design lif
27、t coefficient of 0.40. Thisdecrease in lift-drag ratio is essentially a result of increased skin-frictiondrag because of the higher induced velocities for the thicker airfoils. How-ever, at a typical climb lift coefficient of .0, this linear variation is indi-cated only up to a thickness ratio of ab
28、out 7 percent. The large decrease inlift-drag ratio for the 21-percent airfoil is indicative of excessive turbulentboundary-layer separation. This effect has been reduced by redesign of the air-foil and is discussed later.The scale effects on maximum lift coefficient for the low-speed airfoilsfor Re
29、ynolds numbers from about 2 x 06 to 9 x 06 are shown in figure 3.Increases in Reynolds number have a favorable effect on maximum lift coeffi-cient for all thickness ratios shown. The increment in maximum lift coeffi-cient with Reynolds number generally increases with increasing thickness ratio;howev
30、er, note the differences in variation with Reynolds number. Applicationof a roughness strip just sufficient to trip the boundary layer resulted inonly small effects on maximum lift coefficient for the 9- and 3-percent air-foils; however, large decreases occurred for the thicker airfoils.Comparison o
31、f the maximum lift coefficients for this low-speed familywith the older NACA airfoils is shown in figure 4 at a Reynolds number of6 x 06 for the airfoils smooth. The comparison is made with the airfoilssmooth because of the excessive roughness employed on the NACA airfoils. Thelargest value of CZ,ma
32、x, 1.75, for the NACA airfoils was obtained for theforward-camber 230 airfoil series for a thickness ratio of 2 percent, whichis probably the optimum thickness ratio. By contrast a value of CZ,ma xgreater than 2 is shown for the NASA low-speed series for a thickness ratioof 3 percent. Large improvem
33、ents in CZ,ma x performance for thickness ratiosvarying from 9 percent to 21 percent are shown for the NASA low-speed airfoilscompared with the older NACA airfoils.Refinements21-percent-thick airfoil.- As previously discussed, the 21-percentairfoil displayed significantly lower values of lift-drag r
34、atio compared tothe thinner airfoils of the family because of turbulent boundary-layer sepa-ration at typical climb lift coefficients. Therefore, this thick airfoil hasbeen reshaped to substantially decrease the upper-surface adverse pressuregradient and reduce the amount of separation on the airfoi
35、l. The changes inairfoil contour and pressure distribution are illustrated in figure 5. Atheoretical analysis code with improved turbulent boundary-layer separationpredictions (ref. 8) was used for the redesign of the airfoil. Note that theProvided by IHSNot for ResaleNo reproduction or networking p
36、ermitted without license from IHS-,-,-start of the upper-surface pressure recovery was moved forward about 0.30c forthe modified airfoil. At a lift coefficient of 0.40 the theory indicates adecrease in the extent of upper-surface separation of about 0.05c for themodified airfoil. Comparisonof calcul
37、ated and experimental pressure dataindicate good agreement between experiment and theory for the modified airfoil.The experimental results were obtained in the Langley low-turbulence pressuretunneI.Figure 6 compares lift-drag-ratio performance for the two airfoils forReynolds numbers from 2 x 06 to
38、9 06 . At the design lift coefficient of0.40 some improvement in lift-drag ratio is shown for the modified airfoil ata Reynolds number of 2 x 06 even though there was no serious problem at thislift coefficient. However, at a typical climb lift coefficient of .0 largeincreases in lift-drag ratio are
39、shown at all Reynolds numbers for the refinedairfoil. The wind-tunnel results also indicated that the pitching-moment coef-ficient at design lift was reduced for the modified airfoil.7-percent-thick airfoil.- Based on the significant increase in lift-drag ratio obtained for the redesigned 2-percent
40、airfoil at typical climblift coefficients, a redesign of the 7-percent airfoil was initiated. Theobjective of the redesign was twofold; to reduce thepitching-moment coeffi-cient by increasing the forward loading and increase the climb lift-drag ratioby decreasing the aft upper-surface pressure gradi
41、ent. The changes in airfoilcontour and pressure distribution are illustrated in figure 7. A reduction inpitching-moment coefficient of about 28 percent is indicated by the theoreticalcalculations. Note that prior to the start of the aft upper-surface pressurerecovery for the modified airfoil a flat
42、pressure distribution or reduced pres-sure gradient region extends for about 0.20c. This reduced pressure gradientregion with the “corner“ located at x/c = 0.60 is considered to be an impor-tant feature of the airfoil design. Research reported in reference 9 for amodified 13-percent airfoil clearly
43、indicated that this reduced pressure gra-dient region retards the rapid forward movement of upper-surface separationat the onset of stall and promotes docile stall behavior for airfoils whichstall from the trailing edge. The chordwise location of the corner is deter-mined by the aft pressure gradien
44、t which must be gradual enough to avoid sepa-ration at climb lift coefficients (c_ = .0). Thus, the chordwise location ofthe corner is dependent on airfoil thickness ratio and design lift coefficient.The chordwise extent of the reduced pressure gradient region must be determinedfrom experimental tes
45、ts, since we are concerned with stall behavior. The theo-retical separation points and pressure distributions for both 7-percent air-foils are shown in figure 8 at a climb lift coefficient of .0. A reduction inthe extent of separation of about 0.05c is indicated for the modified airfoil.Based on the
46、se theoretical predictions some improvement in lift-drag ratio atcz = 1.0 would also be expected.MEDIUM-SPEED AIRFOILSDevelopmentThe design objective of the medium-speed airfoils was to increase thecruise Mach number of the low-speed airfoils but retain the good high-lift,Provided by IHSNot for Resa
47、leNo reproduction or networking permitted without license from IHS-,-,-low-speed characteristics. Such new airfoils are intended to fill the gapbetween the low-speed airfoils and supercritical airfoils for application onlight executive-type aircraft. Two medium-speed airfoils having thickness-chord
48、ratios of 13 and 17 percent have been developed. The airfoils weredesigned for a lift coefficient of 0.30 and a Reynolds number of 14 x 106 ,and the design Mach numbers for the 13 and 17 percent airfoils were 0.72and 0.68, respectively. The 3-percent medium-speed airfoil was obtained byreshaping the 13-percent low-speed airfoil as indicated in figure 9. Thecalculated pressure distribution shows that increasing the Mach number to 0.72for the low-speed airfoil results in a region of high induced velocities nearthe midchord on the upper surface of the airfoil. Further inc
