Turbine Blade Tip Leakage Flow Control by Unsteady Periodic Wakes of Upstream Blade Row

An experimental and numerical study of tip leakage flow control in axial turbine was performed by means of unsteady periodic wakes of upstream blade row. The flow field was investigated respectively in linear turbine cascade and turbine rotor. Focus was placed on the analysis of unsteady interaction mechanism between upstream periodic wakes and tip leakage vortices. The influence of the upstream periodic wakes on turbine performance was also discussed. The results indicate that the upstream periodic wakes can effectively reduce the strength of the tip leakage vortices. The loss measurements and computations at the exit of the turbine blade showed a decrease in stagnation pressure loss or entropy rise and an increase in efficiency. It means the engine specific fuel consumption and the exhaust gas temperature margin can be improved as well as increased turbine total efficiency.