Film Cooling and Heat Transfer Performance of a Fully-Cooled Turbine Vane at Varied Density Ratios and Mass Flow Ratios

There have been a number of previous studies of the geometric parameters and aerodynamic parameters of the film holes on the film cooling effectiveness, but no previous studies of the full coverage film cooling effectiveness on the vane surface under different density ratios. This paper investigates the effect of density ratio on the full coverage film cooling effectiveness and heat transfer coefficient. The three mass flow ratios are 5.5%, 8.4% and 11%, the turbulence intensity is 15%, and the mainstream Reynolds number based on the inlet velocity and the chord length is 120000. The experiment selects air as the mainstream, and secondary flow has two density ratios 1.0 (air-to-mainstream) and 1.5 (carbon dioxide-to-mainstream). A real three-dimensional vane is scaled 1.41 times based on a similarity analysis. This test vane has two cavities to feed 18 rows of cylindrical holes. The front cavity has 14 rows of film holes that are arranged in the suction side (1~3), the leading edge (4~11) and the first half of the pressure side (12~14). The rear cavity has 4 rows of film holes that are arranged in the second half of pressure side(15~18). Relative experiment data is obtained by using transient liquid crystal measurement technology.

Results show that the film cooling effectiveness of the leading edge and pressure side increases with the increase of density ratio. at high mass flow ratios. However, the film cooling effectiveness decreases with increasing the density ratio on the downstream region of suction side. In addition, on the bottom of vane surface, the effect of the density ratio is less significant compared to the complex passage vortex effect. The heat transfer coefficient of leading edge is less affected by the density ratio. On the pressure side and the downstream region of suction side, when increasing the density ratio, the heat transfer coefficient increases at MFR=5.5%, but its distribution shows the opposite trend at MFR=8.4% and 11%.