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Contra‐rotating turbines offer reduced size, weight, and cooling requirements, compared to conventional co‐rotating machinery. In spite of the associated mechanical complexity, their aero‐thermal performance is superior to conventional turbines, not only due to the elimination of stator blade rows, but also because lower turning airfoils can be implemented as a result. The purpose of this paper is to present a methodology to determine the optimum velocity triangles of the turbine, together with a two‐dimensional design and optimization tool to minimize the blade unsteady force using radial basis function network, coupled to a genetic algorithm. The proposed design methodology is illustrated with the aerodynamic design of a contra‐rotating two‐axis turbine, which is able to deliver the power necessary to drive the LOX and LH2 pumps of an improved expander rocket engine.

This paper presents a methodology to determine the optimum velocity triangles of the turbine, together with a two dimensional design and optimization tool to minimize the blade unsteady force using radial basis function network, coupled to a genetic algorithm. The proposed design methodology is illustrated with the aerodynamic design of a contra‐rotating two‐axis turbine, which is able to deliver the power necessary to drive the LOX and LH2 pumps of an expander rocket engine, namely the Japanese LE‐5B.

The airfoil optimizer allows reductions in the downstream pressure distortion of 40 per cent. Consequently, the unsteady forces in the downstream blade row are minimized.

This paper presents to turbomachinery designers in liquid propulsion a novel tool to enhance the aerodynamic performance while reducing the unsteady forces on the blades.