Effect of Coolant Inlet Conditions on Supersonic Film Cooling

The influence of the coolant gas inlet height and Mach number on supersonic film cooling were analyzed numerically while keeping the mainstream inlet conditions and coolant mass flow rate unchanged for a given coolant gas. The results indicate that, for the same coolant gas without a shock wave or with a weak shock wave, the supersonic film cooling mainly depends on the coolant gas flow rate and has little relationship to the coolant inlet height or the Mach number. For the cases with a strong shock wave, reducing the coolant inlet height (i.e., increasing the Mach number) improved the supersonic film cooling. The main reason is that the coolant gas velocity increases when the coolant inlet height is reduced for a given coolant mass flow rate, which increases the coolant flow momentum, and so the coolant gas more effectively resists the interference of the shock wave. The results also show that helium is more easily affected by the coolant inlet conditions than methane or nitrogen when the inlet Mach number is the same for the same inlet height.