Large-eddy simulation of swirling flows in a pulverized coal combustion furnace with a complex burner

LES (Large-eddy simulation) of swirling cold flows in a pulverized coal combustion furnace is performed and validated by comparing with experiment and RANS (Reynolds-Averaged Navier-Stokes) simulation with the standard k-ε model. Unstructured grids and energy-conserving scheme are employed to obtain robust and accurate solutions at high swirl numbers. The results show that LES is in good agreement with the experiment in terms of the recirculation flow, though RANS overestimates. This is considered due to the capability of prediction of turbulent mixing. The effect of secondary and tertiary swirler angles on the behavior of the recirculation flow are also well predicted by LES. The recirculation flow affects the flame stabilization and combustion efficiency related to the particle residence time in the furnace. It can be said, therefore, that LES is strongly recommended for the accurate prediction of the strong swirling flows in such furnaces.