Effects of low Reynolds number on turbine blade tip leakage flow

The flow field of a small gas turbine cascade was numerically simulated with the preconditioning method at low Reynolds number varying from 4.40×104 to 2.55×105. Both the cases with and without tip clearance were considered in the simulation. The numerical results of the loss caused by the tip clearance agree well with the experimental data and the values predicted by the Denton formula. It is indicated that this loss will not change with the increase of the Reynolds number but the intensity of the passage vortex increases with the decrease of the Reynolds number. The tip leakage flow will weaken with the increase of the passage vortex because of the interaction between the passage vortex and the tip leakage vortex, and the position of the tip leakage vortex is more close to the middle of the passage. In addition, the distributions of the total pressure loss and the flow angle at the exit of the cascade are influenced by the intensity and the position of the tip leakage vortex.