Investigation of detailed flow in a variable turbine nozzle

The detailed flow behavior of the nozzle channel of a variable turbine is presented in this paper. The numerical model of a variable nozzle turbine was developed by using computational fluid dynamics method, and validated by the measured performance data of the turbine. Two opening positions of the nozzle vane, as well as two inlet conditions of the nozzle representing different vane loadings, were investigated to evaluate the clearance flow behaviors. It is shown that the channel shock waves are produced at proper conditions, such as small opening and large inlet pressure, which has significant impact on the end wall clearance leakage flow. When the leakage flows through the end wall clearance from the pressure side to the suction side encountering by the main stream, and the leakage vortex is formed. It is found that this leakage vortex gradually enhanced from the trailing edge to the middle edge.