Study on the effect of main stream turbulence for the film cooling effectiveness of a circular and a fan-shaped film cooling hole

Abstract

The reliability of turbine blades and vanes of ultra-high temperature gas turbines is achieved with turbine blade cooling technologies. Among the many cooling methods, film cooling is used for turbine blades and vanes that withstand ultra-high temperatures. Therefore many papers have been published aiming at the improvement of film cooling effectiveness by optimization of film cooling hole geometries. Although the turbulence intensity of the main stream generated in the gas turbine combustor is very high and it can be presumed to lower the film cooling effectiveness on the turbine vane and blade surface, there are few papers that investigate the effect of the mainstream turbulence on the film cooling quantitatively. For this reason, the influence of the turbulence intensity of the mainstream on the film cooling effectiveness of circular and fan-shaped film cooling holes was investigated by measuring the three-dimensional turbulent mixing field of the mainstream and the film cooling air by quantitative measurement methods such as PIV and LIF. As a result, it was revealed that when the mainstream turbulence is high the counter-rotating vortex pair is weakened, the film cooling air spreads in the span-wise direction and the average film cooling effectiveness decreases about 10%.