Standardized Planck-Mean Absorption Coefficients for High-Temperature Gases

Abstract

Planck-mean absorption coefficients of pure gases are calculated from line-by-line integrations of HITEMP and ExoMol spectra up to 5000 K for use in high-enthalpy radiative heat transfer simulations. The dataset extends beyond conventional combustion products, including high-temperature radicals, nitrogen-bearing species, soot precursors, metal oxides, metal hydrides, and halides: AlF, AlH, AlO, BH, C2, C2H2, CH, CH4, CN, CO, CO2, H2O, HBO, HCN, HF, MgH, MgO, N2O, NO, NO2, OH, SiO, TiH, TiO. New calculations are validated against historical correlations for overlapping species, demonstrating good agreement over their applicable temperature ranges. Strong visible opacities result in large Planck-mean absorption coefficients for many of the considered species, highlighting the need to account for their radiative contribution in extreme environments. A brute-force search over several candidate functional forms is performed to provide a common set of coefficients, establishing a standardized framework that can be easily integrated into production solvers and extended as additional high-temperature line lists become available.