Numerical investigation on the effect of tip clearance on a turbine stage flow-field and aerodynamic performance

Three-dimensional numerical method was adopted to study the flow field and aerodynamic performance of a high pressure turbine stage of a turbo-shaft engine. The flow characteristics and aerodynamic parameters were compared under uniform and non-uniform tip clearance. The influence of tip leakage flow and the flow-field changes on dynamic performance of gas turbine with different gap forms was also discussed. The results show that the high-loss region closed to the tip gradually incorporates with the high-lose region of the upper passage vortex increased with the tip clearance. The new large scale separation structure leads to increased losses and the total efficiency reduces by 5% when the clearance height is 1.2 mm. Increasing the tip clearances near the leading edge has less adverse effect on loss than that of near the trailing edge. Reducing the tip clearance to 0.3 mm near the trailing edge can effectively improve the total efficiency about 1%. As a result, controlling the tip clearance in different regions of blade tip can effectively control the leakage flow rate and reduces blockage in the gap for improving the total performance in the gas turbine.