Research Progress on Unsteady Flow Mechanism and Control Strategies of High-Lift Low Pressure Turbine

The turbulence issue in high-lift low pressure turbines is one of the most important factors for the aero-engine performance. For understanding the physical mechanisms of turbulence flow in high-lift low pressure turbines, and mastering flow control strategy, research on the unsteady flow in high-lift low pressure turbine blade is necessary to get the aerodynamic design methodology of low pressure turbine considering unsteady flow characteristics. Based on the large amount of research for high lift low pressure turbine from domestic and foreign researchers, together with the efforts current authors had been done, this paper systematically introduces the evolution process of boundary layer behaviors, the unsteady characteristic change of endwall secondary flow, the loss mechanism and the control strategies of low pressure turbines under periodically unsteady incoming flow conditions. To optimize blade-loading distribution can decrease profile losses and secondary losses to some extent. Upstream wakes can induce the transition of blade suction side boundary layer to decrease profile losses and also contribute to suppress the development of endwall secondary flow, but the effect of wake is double-edged at different Reynolds numbers. The effective flow control strategies are necessary to suppress flow separation for high/ultra-high lift low pressure turbine, especially at low Reynolds number.