Particle image velocimetry(PIV),thermocouples and flue gas analyzer are used to study swirling coal combustion and NO formation under different secondary-air ratios.Eulerian-Lagrangian large-eddy simulation(LES)using the Smagorinsky-Lilly sub-grid scale stress model,presumed-PDF fast chemistry and eddy-break-up(EBU)gas combustion models,particle devolatilization and particle combustion models,are simultaneously used to simulate swirling coal combustion.Statistical LES results are validated by measurement results.Instantaneous LES results show that the coherent structures for swirling coal combustion are stronger than those for swirling gas combustion.Particles are shown to concentrate along the periphery of the coherent structures.Combustion flame is located in the high vorticity and high particle concentration zones.Measurement shows that secondary-air ratios have little effect on final NO formation at the exit of the combustor. Particle image velocimetry (PIV), thermocouples and flue gas analyzers are used to study swirling coal combustion and NO formation under different secondary-air ratios. Eulerian-Lagrangian large-eddy simulation (LES) using the Smagorinsky-Lilly sub-grid scale stress model , presumed-PDF fast chemistry and eddy-break-up (EBU) gas combustion models, particle devolatilization and particle combustion models, are simultaneously used to simulate swirling coal combustion. Statistical LES results are validated by measurement results. transient LES results show that the coherent structures for swirling coal combustion are stronger than those for swirling gas combustion. Particles are shown along the periphery of the coherent structures. Combustion flame is located in the high vorticity and high particle concentration zones. little effect on final NO formation at the exit of the combustor.