Experimental investigations on cooling characteristics of different trailing-edge cutback geometries

Abstract

One important method for enhancing the performance of modern engines is to increase the turbine inlet temperature. Due to the high velocity near the throat, the heat transfer to the blade trailing edge is high, particularly on the pressure side near the trailing edge. Therefore, the design methodology for cooling structures becomes critical for the thinner trailing edge compared to other parts of the blade. Trailing-edge cutback is a common cooling structure that guides cold air to form an effective film near the blade pressure side. However, the cutback lip induces strong and unsteady shedding vortexes, which significantly reduce the downstream coolant effectiveness.Previous studies have explored the film cooling performances of cutback structures and the interaction between coolant and mainstream using experimental and numerical methods. Experimental results were obtained using Pressure-Sensitive Paint (PSP) and Particle Image Velocimetry (PIV) in a large-scale wind tunnel, while the Delayed Detached Eddy Simulation (DDES) with the Shear Stress Transport (SST) turbulence model was employed for capturing the unsteady flow field.In this paper, further investigation will be conducted on the lip profiles of the fillet structure to improve the effectiveness of the film coolant. The rounded lip design delays boundary layer separation, thereby reducing the scale and intensity of shedding vortices. This improvement in the effectiveness of the rounded lip nozzle model is observed across all blowing ratios. Furthermore, at low or medium blowing ratios, the rounded lip design significantly reduces momentum exchange, inhibiting the mixing between the mainstream flow and cooling air. This leads to a more pronounced enhancement in cooling effectiveness.