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.

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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.

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