Spectral emissivity inversion of quartz composite ceramics under hypersonic airflow collision

In this paper, the radiation spectra of quartz composite ceramic thermal protective materials in a pneumatic environment were measured in a plasma arc wind tunnel experiment. Spectral emissivities and material temperature at varying airflow speeds were calculated based on the algorithm of slow variation properties of emissivity. The inversion results show that the spectral emissivity reaches its maximum at a maximum airflow velocity of Mach 10. Emissivity uncertainty caused by the spectral measurement was analyzed. Relative error was determined by comparing real and calculated emissivities from Standard blackbody radiation spectrums at 2298 K in the wavelength range of 420-900 nm and 1573 K for 1200-2400 nm. Results obtained by the algorithm of slow variation properties for emissivity show that the maximum relative error in 420-900 nm is 3.3% and the average relative error is 2.7%; the maximum relative error for 1400-2400 nm is 4.1% and the average relative error is 2.1%. This provides a new method for the study of material emissivity under hypersonic flow collision aerodynamic heating conditions.