Design and Numerical Analysis of a Forepart Rotation Vane for a Variable Nozzle Turbine

The influence of nozzle clearance on the flow field for a variable nozzle turbine, and moreover on the turbine stage performance was numerically investigated. Meanwhile, unsteady calculations were also performed to capture the shock waves which were induced by excessive acceleration of the exhaust gas. Aiming at improving the turbine stage performance and mitigating the shock waves, a forepart rotation vane was proposed and investigated in this work. The results indicated that by using the forepart rotation vane, the stage efficiency is increased by 6% and the shock waves were eliminated successfully at small nozzle openings. Additionally, the intensity of pressure fluctuation that acts on the rotor blades was reduced by mitigation of clearance leakage flow and shock waves, which is beneficial for the reliability of rotor blades.