Numerical Study of the Effect of Tip Clearance and Rotor-Stator Distance on the Performance of an Axial Turbine

The use of unshrouded turbine rotor blades can considerably reduce the weight of an aero engine. However, in an unshrouded high-pressure turbine, the tip leakage flow generates about 30% of the turbine total loss. Another factor which affects the loss in axial-flow turbines, is the axial distance between the rotor and stator. The purpose of the current work is to investigate the impacts of the blade tip clearance and the axial distance between rotor and stator on the performance of a high-pressure axial turbine, by using three-dimensional numerical simulations. Comparing the numerical results to the experimental data shows that the numerical simulations can predict the turbine performance fairly accurately. Results reveal that increasing the tip clearance and the axial distance between the rotor and stator reduce the turbine efficiency. The effects of tip clearance and rotor-stator axial distance on the performance and endwall flow field of the studied turbine stage have been presented and discussed.