Turbine blade airfoil, turbine blade and turbine blade cascade for axial-flow turbine

Abstract

A turbine blade for an axial-flow turbine includes an intrados generating a positive pressure, and an extrados generating a negative pressure, wherein the intrados and the extrados are provided between a leading edge and a trailing edge. An inflection point is provided between a concave portion on an upstream side and a convex portion on a downstream side in a region extending from a position of 80% on the intrados to a rear throat, and the length of a normal line drawn downwards from the intrados of one of the turbine blades to an extrados of the other turbine blade has at least one maximum value in a region extending from a front throat of the one turbine blade to a rear throat. Thus, it is possible to disperse a shock wave generated from the intrados at the trailing edge to prevent the generation of a strong shock wave, thereby reducing the pressure loss caused by the shock wave. In addition, a speed-reducing area can be formed on the extrados generating the negative pressure to promote the transition from a laminar flow boundary layer to a turbulent flow boundary layer, thereby preventing the separation of the boundary layer caused by the interference with a shock wave to reduce the pressure loss.

Dependencies are inferred from the claim text.