Effects of suction surface near tip coolant injection on the aerodynamics of tip leakage flow in a high-pressure turbine cascade

Abstract

The current study explores the possibility of using the coolant injected from the near tip suction side of a turbine blade to reduce the tip leakage loss. Each case studied has a cooling hole injecting a coolant stream. To model the mixing of the coolant at different axial locations, each of four cases is investigated with a cooling hole located at 10% blade axial chord [Formula: see text], 20% [Formula: see text], 30% [Formula: see text] or 40% [Formula: see text] from the leading edge. In computational fluid dynamics simulation, the exit area of the cooling hole is defined with mass flow inlet boundary condition to simulate a coolant injection. It is found that the tip leakage loss of the case with a cooling hole located at 10% [Formula: see text] is the lowest and is 3.2% lower than that of the uncooled baseline case. The tip leakage loss increases as the cooling hole located further downstream. For the case with cooling hole at 40% [Formula: see text], the loss is 1.5% higher than the uncooled baseline case. The effect of the blowing ratio on the tip leakage loss is also investigated. For the case with the cooling hole located at 10% [Formula: see text], the tip leakage loss first decreases and then increases as the blowing ratio increases. When the tip leakage loss of one case is less than that of baseline case, it is found that mixing of the coolant and the low-energy fluid in the tip leakage vortex core reduces the stagnation pressure difference between mainstream and the fluid within the vortex core, and thus reducing the mixing loss within the blade passage.