Investigation of turbine tip flow control technology based on the Tesla valve principle at different Mach numbers

The tip leakage phenomenon in axial-flow turbines is one of the key factors restricting the improvement of turbine efficiency. Among the current control methods for tip leakage, reducing the tip leakage flow rate is considered an effective way to reduce leakage loss. Based on this principle, this study innovatively adopts a special structure (Tesla valve) to effectively control the tip leakage flow (tip leakage/tip leakage flow is the fluid flow that leaks through the clearance between the tip of the rotor and the casing). Due to the unique structural design of Tesla valves, when fluid flows backward through them, the valves can significantly reduce the flow rate. This characteristic precisely meets the requirement for reducing leakage loss. Therefore, an innovative blade tip design, namely the Tesla-valve blade tip, is presented. By investigating Tesla valves with different arrangement orientations, the effectiveness of this novel tip structure is verified under various Mach numbers. Furthermore, this research has clarified the operational principle underlying this structure for controlling tip leakage flow. On the one hand, this control effect originates from the blocking structures designed based on Tesla valves, which prevent fluid from entering their interiors, thereby blocking the leakage flow and reducing its flow rate. During this process, complex recirculating vortices are generated within Tesla valves. On the other hand, these vortices create additional resistance to the flow inside the clearance.