Application of CFD to Partial Admission Stages of Steam Turbine

This paper deals with an application of Computational Fluid Dynamics, CFD, to partial admission stages in a steam turbine. Calculation of partial admission stages requires unsteady analysis and full circle modeling. Therefore quasi-3 dimensional analysis on the mean radius is conducted to reduce computational load. First, an experiment of air turbine which has one stage is carried out. This result shows a good agreement with the result of CFD analysis which has the same condition as the experiment, and applying the Q-3D method to partial admission stage analysis is validated. Using this method, 2 stage analysis of partial admission are conducted. The influence of circumferential position of admitted arc on stage efficiency is discussed. The efficiency difference is related to the windage loss which is caused by pressure distribution in the circumferential direction. It was found that there is an optimum circumferential position of admitted arc from the point of view of turbine efficiency.