Investigation On Gas Turbine Film Cooling Effectiveness And Aerodynamic Loss

Gas turbine plays an important role in aerospace power and electricity industry. Increasing the turbine inlet temperature is an important way to improve the thermal efficiency of gas turbine. Limited to the development of heat-resisting material, advanced cooling technology is extremely demanded to increase the turbine inlet temperature. Film cooling is widely used to decrease metal temperature of turbine vanes or blades. However, the mixing of the coolant and hot gas results in the loss of total pressure and kinetic energy, which leads to the decrease of the effective work of turbine. In the study of different film cooling configurations, the film cooling effectiveness is not the only factor, mixing loss of different film cooling configurations should also be considered.In the study of low-speed flat plate film cooling, we compared the film cooling effectiveness of four different cooling configurations through numerical simulation methods. The results indicated that fan-shaped hole provides the best cooling effectiveness among the four different cooling configurations under the same blowing ratio. Yaw angle could imcrease the film cooling effectiveness. Double-jet film cooling hole could improve film cooling effectiveness even at a high blowing ratio. The cooling effectiveness far downstream the double-jet film cooling hole is close to that of fan-shaped hole. Aerodynamic losses are studied through experiment and numerical simulation. It is found that the aerodynamic losses of different film cooling configuraions increase with the increase of blowing ratio. Aerodynamic loss coefficients of the four film cooling configurations stay close when the blowing ratio is low. Compared to the experimental results, the wall normal diffusion of aerodynamic loss in the near wall area of numerical results is insufficient, and the total pressure of coolant inlet is over-predicted. Although there are discrepancies between the value of numerical results and expereimental results, the variation tendencies with varying blowing ratio are consistent. Therefore, the numerical simulation results have a certain reference value.The influence of mainstream Mach number on film cooling effectiveness and aerodynamic losses are investigated through numerical simulation method. The results show that the increase of mainstream Mach number leads to a increase of film cooling effectiveness and a decrease of aerodynamic loss coeffient. This is because the thcikness of boundary layer is reduced with the increase of mainstream Mach number. Therefore the coolant jet is closer to the wall surface to provide a better cooling performance, the loss in near wall area mainly caused by boundary layer is also reduced. The aerodynamic loss genereated in the film cooling hole is the main source of total aerodynamic loss at a high blowing ratio, which means reducing the loss in film cooling hole is an important way to reduce the aerodynamic loss of film cooling.