Experimental and numerical investigation into the effects of spline mid-passage gap on endwall film cooling performance and aerodynamic characteristics

The coolant leakage flowing out from the mid-passage gap has been proved to offer an extra cooling to the endwall surface and was investigated by many scholars. While most studies focused on the straight mid-passage gap. In this paper, different types of spline mid-passage gap were introduced and studied experimentally and numerically, with the mass flow ratio ranged from 0.5% to 1.5%. Pressure sensitive paint technique was adopted to evaluate the film cooling performance, and numerical simulation was carried out to predict the aerodynamic performance. The results showed that compared to straight mid-passage gap, spline mid-passage gap can obviously improve the film cooling performance, and the curvature of the spline mid-passage gap will affect the peak value of the film cooling effectiveness and area of the coolant coverage. Back point case can achieve the maximum value of film cooling effectiveness, while center point case can achieve widest coolant coverage. What’s more, Back point case will also lead to larger aerodynamic loss and center point case can obtain better cooling-aerodynamic performance at a larger mass flow ratio.