Gec-alsthom Limited

Brian Robert Haller

David Moreton Hall

Viccars Jeremy Andrews

Robert G Unsworth

Geoffrey L Parker

The invention relates to the design of a fixed-blade assembly in an axial flow steam turbine and is based on the recognition that the design of the interfacing region (fillets) between the radial ends of the blades and the end-blocks to which they are attached or of which they form a part has a significant effect on stage efficiency. The invention recognizes an optimum fillet radius in the range 0.15-0.3 of the throat dimension between the trailing edge of one blade and the suction surface of an adjacent blade, and more particularly 0.20-0.50. The fillet configuration is advantageously applied to a turbine having blades which are of constant cross-section, are curved in the radial (height) direction and are convex from root to tip on its pressure face, the result being a considerable gain in stage efficiency.

Turbine blade

The invention relates to the design of (particularly) a fixed blade in an axial flow steam turbine. A conventional blade is of prismatic form with an aerofoil cross-section and extends radially between annular end blocks. The inventive blade is curved in the radial (height) direction, being convex from root to tip on its pressure face. The setting angle relative to the corresponding prismatic blade is therefore fine at the root and tip and coarse at the blade mid-height. The throat opening is thus reduced at root and tip and increased at mid-height so displacing some mass flow away from both lossy end wall regions. A considerable gain in the stage efficiency results. A further improvement results from providing an optimum corner fillet between the blades and end walls at the root and tip.

A fixed blade assembly for an axial flow turbine, in which each blade (23) is secured between a radially inner ring (21) and a radially outer ring (22). The trailing edge (25) of each blade is straight and leans at an angle .theta. away from a radial line (28) from the turbine axis through the inner end of that edge and in the circumferential direction that the suction side (24) of the blade faces. The blades (23) have this (negative) angle of lean in the range 5 degrees to 12 degrees.

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Warwickshire, United Kingdom

Brian Robert Haller