Patent ID: 8221065

Claim:
A steam turbine blade, comprising: a blade airfoil which by a longitudinal extent of the blade airfoil extends from a root-side end to a tip-side end, the blade airfoil having a blade airfoil leading edge and a blade airfoil trailing edge, wherein at one corresponding position of the longitudinal extent, a chord length (s o , s 1 , s m ) is defined from the blade airfoil leading edge to the blade airfoil trailing edge, the blade airfoil including at a root-side end position, a root-side chord length (s o ), at a tip-side end position, a tip-side chord length (s 1 ), and in a middle position of the longitudinal extent, a chord length (s m ), the chord length (s m ) being shorter than the root-side chord length (s o ) and shorter than the tip-side chord length (s 1 ), wherein directions of local camber lines of blade profiles at the blade trailing edge at each position of the blade airfoil, measured in the direction of the longitudinal extent of the blade airfoil, deviate from each other by at most 5°, and a profile curvature in the middle position is greater than in the tip-side end position or root-side end position, such that a Zweifel parameter is set to be substantially 0.9 at the middle position and substantially 0.7 at at least one of the tip-side end position and the root-side end position.