LOW TIP MACH NUMBER STALL CHARACTERISTICS AND HIGH TIP MACH NUMBER COMPRESSIBILITY EFFECTS ON A HELICOPTER ROTOR HAVING AN NACA 0009 TIP AIRFOIL SECTION

摘要

An Investigation has been conducted on the Langley helicopter test tower to determine experimentally the low tip Mach number stall and high tip Mach number drag divergence characteristics of a helicopter rotor having an NACA 0009 tip airfoil section, which tapered to an NACA 0017 root airfoil section and had -5.4° of twist. Data are presented for blade tip Mach numbers Mt of 0.28 to 0.72 with corresponding values of tip Reynolds number of 1.65 x 10 to 4.29 x 10. Comparisons are made of the present rotor with unpublished data on a similar rotor but having NACA 0015 tip airfoil sections. At low tip Mach numbers, the blade maximum mean lift coefficient for the blade having the 9-percent-thicK tip airfoil section was about 0.16 less than that obtained with the blade having the 15-percent-thick tip airfoil section. At the highest tip Mach number of 0.72, the blade mean lift coefficient for drag divergence was about 0.U2 for the blades having 9-percent-thick tip airfoil sections as compared with 0.22 for similar blades having 15-percent-thick tip airfoil sections.