Experimental and numerical investigation of loss in turbine cascade with low Reynolds number

Low Reynolds number of turbine at high-altitude results in the notable drop of efficiency of turbine. Refs. 3, 4 and 5 gave experimental results of the aerodynamic performance of low-pressure turbine blade at low Reynolds number, but they did not give technical details. Our aim is to provide technical details, reveal the aerodynamic performance of low-pressure turbine blades at low Reynolds number, and also analyze theoretically the cause of the notable drop of turbine efficiency at low Reynolds number. In the investigation, experiments and numerical simulations have been performed to study the behavior of low-pressure turbine blade at several Reynolds numbers. The airfoil is the mid-span section of the low-pressure turbine rotor blade of a turbofan. The Reynolds number, based on the cascade outlet velocity and blade chord, was varied from 180000 to 10000. A finite volume scheme, based on the Jameson cell-centered method for solving the Reynolds averaged Navier-Stokes equations, was used. The experiment was conducted on the low-speed linear cascade tunnel at Northwestern Polytechnical University. Both the calculated and experimental results indicate increased cascade losses as the Reynolds number is reduced to the values associated with aircraft cruise conditions. And they also indicate that, when the Reynolds number is around 40000, the cascade losses begin to increase notably with decreasing Reynolds number. The calculated results indicate that the main cause of increased cascade losses is the flow separation on the suction side of turbine blade. Overall, the calculated aerodynamic and performance results exhibit fair agreement with experimental data.