A backward photon Monte Carlo solver to understand radiative heat transfer under optically-thick conditions*

A backward photon Monte Carlo radiation solver that can account for the spectral effects of gases, soot and droplets is developed in this study, based on the principle of reciprocity. Particularly suitable for the optically thick environments that are commonly encountered in high-pressure diesel engines and gas turbine combustors, the solver can provide the radiative heat source terms within a localized area in a computationally efficient manner. A hierarchy of test cases are constructed, with increasing complexity in the participative media, to systematically verify and validate the solver. A forward Monte Carlo solver is employed to provide the benchmark conditions for comparison. The solver is then applied to a model gas turbine combustor, to investigate the heat transfer pattern on the wall, through frozen field analysis. Parametric studies on the directional and spectral dependency of the radiative heat transfer are performed to provide further details to facilitate the comparison with experiments.