The influence of radiative-convective heat transfer on ignition of the drops of coal-water fuel

Abstract

Simulation results are presented for thermal treatment and ignition of coal-water fuel drops under conditions of radiative-convective heating. The data demonstrate reasonbble compliance between theory and experiment for the integral parameter of ignition process — the delay time of ignition. The radiative component of heat transfer is significant for parameters and conditions of ignition. The increase in the fuel particle size makes this influence bigger. Prognostic potential was evaluated for differnet models of radiative heat tarnsfer. The delay time of ignition obtained from radiative heat transfer model “grey wall” is in good agreement with experimental data. Meanwhile, the method based on radiation diffusion approximation gives the simulation data for delay time much higher than experimental data. It is confirmed that while the process of inflammation of a coal-water particle, the key impotance belongs not to fuel-oxidizer reactions, but rather to a chain of heat treatment events, such as radiative-convective heating, water evaporation, and thermal decomposition of fuel.