Numerical Study of Partial Admission Stages in Steam Turbine

(Efficiency Improvement by Optimizing Admission Arc Position)

Abstract

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