Exchange factor model for radiative heat transfer analysis in rocketengines

Abstract

Numerical models based on the discrete exchange factor (DEF) and the zonal methods for radiative analysis of rocket engines containing a gray radiatively participating medium have been developed. These models implement a new technique for calculating the direct exchange factors to account for possible blockage by the nozzle throat. Given the gas and surface temperature distributions, engine geometry, and radiative properties, the models compute the wall radiative heat fluxes at different axial positions. The results of sample calculations for a typical rocket engine (engine 700 at NASA), which uses RP-1 (a kerosene-type propellant), are presented for a wide range of surface and gas properties. It is found that heat transfer by radiation can reach up to 50% of that due to convection. The maximum radiative heat flux is at the inner side of the engine, where the gas temperature is the highest. Although the results of both models are in excellent agreement, the computation time of the DEF method is found to be much smaller. Dimensionless radiative heat fluxes were calculated via a nonhomogeneous medium model using the DEF method.