345 翼端間隙を有する亜音速タービン性能に及ぼす圧縮性の影響(S36-2 自然の流体エネルギー利用技術(2),S36 自然の流体エネルギー利用技術)  [in Japanese] 345 Compressibility Effects on the performance of subsonic turbines with tip clearance  [in Japanese]

Compressibility effects on the performance of subsonic turbines with tip clearance are investigated theoretically. Flow model of rotating turbine blades with a constant pitch in a duct is employed, which is expressed in helical coordinates. The vortex surfaces of the blade and its wakes are represented by the solutions of Laplace's equation. The equations are solved analytically using Lommel functions for the particular solution and modified Bessel functions for the general solution. With appropriate boundary conditions of tip clearance, the governing equations are solved. The parameter, by which the effects of tip clearance for compressible flow may be estimated, is obtained. The analytical solutions indicate that the increase of Mach number reduces the performance of the turbine with any tip clearances.