The effect of turbulence intensity on full coverage film cooling for a turbine guide vane

This paper investigates the effect of turbulence intensity on the full coverage film cooling effectiveness at mass flow ratio of 5.5% and 12.5%. The investigated turbulence intensities are 2%, 9% and 15%. The experiments adopt an actual three-dimensional twisted vane in a two-passage linear cascade. The Reynolds number of 1.2×10⁵ based on the inlet velocity and the chord length is performed in the experiment. The mainstream and secondary flow use air as a medium (density ratio=1), but have independent air supply. This test vane has two cavities to feed 18 rows of film cooling holes. There are 14 rows of film cooing holes that are arranged in the suction side, the leading edge and the front half of the pressure side. Additionally, the rear half of pressure surface has 4 rows of film cooing holes. The film cooling effectiveness is obtained by using transient liquid crystal measurement technique. Results show that when the mass flow ratio is low, the film cooing effectiveness decreases with the increase of the turbulence intensity. However, the high turbulence intensity is found to improve the film cooing effectiveness at high mass flow ratio. There is a wavy cooling effectiveness distribution on the suction surface only existing at Tu=2% and MFR=12.5%. The high turbulence intensity enhances the mixing of the mainstream and secondary flow, and promotes lateral spreading which causes the secondary flow to more uniformly cover the entire surface.