航空エンジン用高負荷低圧タービン翼面上剥離境界層に与える主流乱れの効果に関する研究

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This paper deals with experimental and numerical investigation on the interaction between inlet freestream turbulence and boundary layers with separation bubble under Ultra-High Lift condition for low-pressure turbine airfoils. The solidity of the cascade can be reduced by increasing the airfoil pitch by at least 25%, while maintaining the throat in the blade-to-blade passage. Reynolds number examined is 57,000, based on chord length and averaged exit velocity. Freestream turbulence intensity is 0.80% (no gird condition) and 2.1% (with grid condition). Hot-wire probe measurements of the boundary layer on the suction surface for LP turbines rotor are carried out to obtain time-averaged and time resolved characteristics of the boundary layers under the influence of the freestream turbulence. The turbulence grid constituting of wires is installed upstream of the cascade. Numerical analysis based on high resolution Large Eddy Simulation is also executed to enhance the understanding on the flow field around the Ultra-High Lift turbine airfoils. Emphasis is placed on the relationship of inherent instability of the shear layer of the separation bubble and the freesteam turbulence. Standard Smagorinsky model is employed for sub grid scale modeling.
2010-03-20