Influence of Coolant Density on Turbine Platform Film Cooling With Stator–Rotor Purge Flow and Compound Angle Holes

Abstract

A detailed parametric study of filmcooling effectiveness was carried out on a turbine blade platform. The platform was cooled by purge flow from a simulated stator–rotor seal combined with discrete hole filmcooling. The cylindrical holes and laidback fanshaped holes were accessed in terms of filmcooling effectiveness. This paper focuses on the effect of coolanttomainstream density ratio on platform filmcooling (DR = 1 to 2). Other fundamental parameters were also examined in this study—a fixed purge flow of 0.5%, three discretehole filmcooling blowing ratios between 1.0 and 2.0, and two freestream turbulence intensities of 4.2% and 10.5%. Experiments were done in a fiveblade linear cascade with inlet and exit Mach number of 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 750,000 and was based on the exit velocity and chord length of the blade. The measurement technique adopted was the conductionfree pressure sensitive paint (PSP) technique. Results indicated that with the same density ratio, shaped holes present higher filmcooling effectiveness and wider film coverage than the cylindrical holes, particularly at higher blowing ratios. The optimum blowing ratio of 1.5 exists for the cylindrical holes, whereas the effectiveness for the shaped holes increases with an increase of blowing ratio. Results also indicate that the platform filmcooling effectiveness increases with density ratio but decreases with turbulence intensity.