Effects of the leading edge injection slot on the film cooling and heat transfer performance of the vane endwall

Abstract

To obtain the high performance, turbines are designed to operate with extremely high inlet temperature. This results in a high level of thermal load to the vane leading edge–endwall junction of the first stage vane. This “hot spot” needs special attention for effective cooling to ensure the safe operation of the gas turbine. In the present study, the effects of the leading edge injection slot on the film cooling and heat transfer of the vane leading edge–endwall junction were numerically investigated. Three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations with shear stress transport (SST) k–ω turbulence model were solved to conduct the numerical simulation based on the validated turbulence model. The numerical results indicate that the film cooling effectiveness of the leading edge–endwall junction is significantly enhanced by introducing the leading edge injection slot. The case with leading edge injection slot obtains larger coolant coverage than that of the case without the injection slot. The case with divergent slot achieves the largest overall film cooling effectiveness in comparison with the nominal and convergent slots for M=0.3 and M=0.5 due to the uniform film cooling coverage. However, all cases share the similar film cooling effectiveness for M=1.0. Moreover, the influence of the leading edge injection slot on the film cooling effectiveness of the downstream endwall surface is gradually reduced with the increase of the injection slot blowing ratio. The local film cooling effectiveness of the suction side leading edge–endwall junction presents a different variation from other regions. Additionally, the heat transfer of the regions near the injection slot is significantly augmented for M=0.3, then the heat transfer is reduced with the increase of the blowing ratio. In general, the divergent has a positive effect on the overall performance of film cooling and heat transfer in terms of the net heat flux reduction (NHFR) near the leading edge.