Improved fillet stresses in steam turbine blade

Abstract

The large variety of turbo-machinery blade root geometries used in industry prompted the question if an optimum geometry could be found. The present paper outlines the improved fillet stresses in a steam turbine blade and a special attention is made on SCF of the blade root (T-root) which fails and to guarantee for safe and reliable operation under all possible service conditions. An optimum blade root was defined, as a root with practical geometry, which when loaded returns the minimum fillet stress concentration factor. Finite element analysis is used to determine the fillet stresses and Peterson’s stress concentration factor chart is effectively utilised to modify the blade root. The root is modified due to the difficulty in manufacturing the butting surface of the tang which grips the blade to the disk crowns having small contact area.