Eulerian–Eulerian multi-fluid methods for pulverized coal flames with nongray radiation

A new Favre averaging method based on gas phase density applied to Eulerian–Eulerian simulations of turbulent multiphase reacting flows is proposed. The new Favre averaging method can reproduce turbulent dispersions of mass, momentum, heat and species of solid phases from their averaged transport equations. A new radiation model that can account for nongray gas–solid mixtures is developed for pulverized coal flames. The new models are validated against a pulverized coal ignition flame. Predictions of velocity, temperature and gas major species are found in good agreement with experiments. Pyrometer measurements of temperature are predicted by a radiation transport calculation. It is found that radiation cooling effects can lead to a 500 K temperature decline in solid phases. Radiation also has indirect influence on CO2 predictions through the slow yet strongly temperature-dependent char reaction rates. The consideration of radiation improves predictions of both temperature and CO2 concentrations. Effects of devolatilization model and number of phases are also discussed.