Numerical simulation on the effect of tip clearance size on unsteadiness in tip clearance flow

Abstract

Unsteadiness of tip clearance flow with three different tip clearance sizes is numerically investigated in this paper. NASA Rotor 67 is chosen as the computational model. It is found that among all the simulated cases, the unsteadiness exists when the size of the tip clearance is equal to or larger than design tip clearance size. The relative total pressure coefficient contours indicate that region of influence by tip leakage flow augments with the increase of tip clearance size at a fixed mass flow rate. Root Mean Square contours of static pressure distribution in the rotor tip region are provided to illustrate that for design tip clearance (1.1% tip chord) the strongest fluctuating region is located on pressure side of blade near leading edge, while for the larger tip clearance (2.2% tip chord), it is in the region of the interaction between the shock wave and the tip leakage flow.