Study on the Characteristics of Supersonic Film Cooling under Various Film Parameters

Abstract

During high-speed flight in the atmosphere, aircraft with optical windows endure severe aerodynamic heating challenges. This study focuses on a supersonic optical dome with planar side windows. Numerical simulation methods are employed to investigate the effects of the supersonic film pressure, the film Mach number, and the type of cooling gas on the cooling performance of the film. The results indicate that the introduction of a film can alter the velocity profiles of the flow field. Increase in the the static pressure ratio and the exit Mach number of the film can extend the effective cooling length and enhance the cooling effectiveness. This improvement primarily arises from the increased film thickness above the optical window, which better isolates the window from the mainstream. Additionally, this increase suppresses the growth rate of the mixing layer generated by the interaction between the film and the mainstream, thereby extending the length of the potential-core region. However, the excessively high static pressure ratio and the Mach number can lead to waste of the cooling gas. Under the same static pressure ratio and Mach number, NH₃ exhibits a higher mass flow utilization rate and can be considered in future film cooling designs.