蒸気タービン長翼用高反動度型超音速タービン翼列の設計法

概要

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The purpose of this paper is development of the design method for high-reaction-type supersonic turbine cascades. First, an allowable design space between the pitch-to-chord ratio and the axial-chord-to-pitch ratio is clarified by formulating three geometrical constraints to accelerate supersonic flow smoothly. Second, when there is no solution in the theoretically allowable design space because of the large pitch-to-chord ratio, methods to reduce shock wave losses are proposed. Increasing the outlet metal angle of the pressure surface by around 10 degrees from the theoretical outlet flow angle reduces the loss caused by the trailing shock wave. The physical mechanism for this is as follows: the increased outlet metal angle increases the outlet flow passage area so that the overexpansion is suppressed downstream from the flow passage. Third, both a cusped leading edge and an upstream pressure surface which has both an angle corresponded to the inflow angle and near-zero curvature can reduce the loss caused by the leading shock wave and satisfy the unique incidence relation. Finally, the aerodynamic performance of supersonic turbine cascades and the design concept are validated by supersonic cascade wind tunnel tests.
2013-03-19