Spectral and Global Radiative Heat Transfer Models for Liquid Propellant Rocket Engines

Wall heat transfer analysis of rocket thrust chambers requires accurate modeling of the convective and radiative heat fluxes generated by the combustion products. While convection is usually considered the main heat transfer mode, radiation may yield an important contribution, especially in the cylindrical part of the combustion chamber and on the injection plate. However, there is a lack of radiation models specifically validated for the high temperatures and pressures typical of rocket engines. In this work, engineering radiation models available in the literature, such as weighted sum of gray gases or gray gas, are compared to line-by-line and narrow-band spectral approaches, revealing errors that may exceed 100% in typical oxygen-hydrogen and oxygen-methane rocket engine conditions. Two new effective and readily usable weighted sum of gray gases models for H2O and H2O-CO2 mixtures are obtained up to 300 bar and 4000 K. Their performance is verified by comparing the computed radiative heat flux with spectral results on subscale and full-scale liquid rocket engines, showing less than 5% error at a fraction of the computational cost.