Integrated Ejector Pump Flow Control for Low-Pressure Turbine

The operation of the low-pressure turbine at cruise conditions produces a Reynolds number significantly below takeoff conditions leading to laminar separation over the blades; consequently, the efficiency of the LP turbine at cruise is significantly below that at takeoff for both military and commercial engines. In the Phase I SBIR Techsburg demonstrated the capability of an innovative flow control technique designed to improve the LP turbine performance leading to a reduction in costs. Flow control was achieved with ejector pumps machined into the blade surface to provide a simple and efficient way of producing blowing and suction. High-pressure supply air from the compressor is injected into the flow as a high momentum jet providing a boundary layer that is resistant to separation, while low momentum fluid in the boundary layer is removed with suction upstream and combined with the supply air to enhance the jet. CFD and experimental data predicted a 72% increase in loss coefficient for a single blade row. Techsburg is proposing a comprehensive Phase II project to perform an in-depth computational optimization, detailed low-speed testing and high-speed cascade testing. The computational effort will focus on optimizing the flow control variables and blade shape for an LP turbine blade to eliminate separation and design a more highly loaded blade. The low-speed testing will validate the CFD work on the most promising blade candidates and subsonic cascade tests at engine Mach conditions will be performed to verify the results in a more realistic test environment.