Variable guide vanes radial turbine blade surface pressure fluctuation excitation mechanism

A three dimension numerical simulation of the flow field in variable geometry turbine, suffered high cycle fatigue, was performed to research the aerodynamic interaction between the nozzle and rotor, which includes the clearance leakage from the nozzle, wake and the shock wave stood on the surface of the nozzle vane. And then the attention was focused on understanding the special locations affected respectively by three kinds of factors on the surface of the rotor. The results show that the shock wave and clearance leakage are the main reasons for rotor blade surface pressure fluctuation. The shock wave only affects the leading edge of the rotor blades because of the special blade shape. For close condition, the shock wave and the amplitude of the pressure fluctuations on the surface of the rotor is increased compared to that for open condition. In the regions near the tip and hub side on the suction surface of the rotor blade, the size of the pressure fluctuation is increased significantly by the influence of the clearance leakage. This may be one of the main reasons for the high cycle fatigue.