1998 Volume 41 Issue 4 Pages 1042-1049
Advansed High-Pressure(HP) / Intermediate-Pressure(IP) and Low-Pressure(LP)stages, with three-dimensionally-optimized flow patterns, have been developed in order to further improve steam tubine efficiency. The HP / IP advanced flow pattern stages were designed to provide optimized mass flow distributions and reduced secondary flow losses for short- and medium-height passages. Two new types of stage were numerically and experimentally investigated, and shown to have an efficiency gain of 1-2% over the conventional stage. Applying this concept to the LP section, an advanced flow pattern last-stage nozzle and moving blades have been designed to reduce the secondary losses in the root and tip of the nozzle, and prevent flow separation along the tip wall. The effectiveness of the new stage was verified in a low-pressure test turbine and by numerical calculations.