Research on cooling characteristics of annular supersonic film cooling for hypersonic optical domes with different coolants

Abstract

In the hypersonic flight environment, the surface of the spherical optical domes will face high aerodynamic heat, resulting in uneven heating and rupture. Based on a proposed annular supersonic film cooling method, combined with hypersonic shock wave wind tunnel experiment (Ma_∞ = 7.1) and numerical simulation technology, this study investigates the effects of different coolants (Ar, CO₂, He, and N₂) on the annular supersonic film cooling of an optical dome. The results indicate that, under the unit mass flow rate, the cooling efficiency of the different cooling gases follows the order: He > N₂ > Ar > CO₂. Lower molar mass coolants result in higher gas film exit velocities, increased gas film momentum, and greater gas film thickness, thereby enhancing the gas film’s ability to resist the high-temperature mainstream flow. The Higher specific heat at constant pressure and the exit velocity of the gas film led to a reduction in gas film static temperature, consequently improving the gas film’s thermal insulation effectiveness. The maximum difference between the experimental data of cooling efficiency of four types of coolants and the predicted value of the improved $\xi {\left(c_{p,air}/c_{p,c}\right)}^{1/3}$ Goldstein theory is 65.21%. At the same time, the cooling efficiency curves of different coolants also differ significantly from the distribution trend of the improved $\xi {\left(c_{p,air}/c_{p,c}\right)}^{1/3}$ Goldstein theory predicted fitting curve. Furthermore, the improved $\xi {\left(c_{p,air}/c_{p,c}\right)}^{1/3}$ Goldstein theoretical prediction model has poor correlation with experimental data.