Numerical investigation of gas-particle flow in the primary air pipe of a low NOx swirl burner – The DEM-CFD method

• Gas-particle flow in primary air pipe (PAP) of the burner was simulated by DEM-CFD method.
• Effect of the PAP structure on particle dispersion in and out of PAP was analyzed.
• Effect of Stokes number on particle collision and dispersion was evaluated.

The gas-particle flow in the primary air pipe (PAP) of a low NOx swirl burner was investigated using the computational fluid dynamics (CFD) coupled with the discrete element method (DEM). The mathematical models were validated using the measured values obtained at the outlet of the primary pipe through a phase Doppler anemometer (PDA) system. Particles of different Stokes numbers in the primary air pipe (PAP) were investigated, and the effects of the structure of the primary air pipe and the particle–particle interaction on particle dispersion were analyzed. The results indicate that particles under the combined effects of the Venturi pipe and the spindle body are concentrated into a narrow band area and that the PAP structure can more efficiently concentrate particles with large Stokes numbers. The formed fuel rich/lean jet persists for a long distance out of the burner, thereby favoring of air-staged combustion and NOx reduction. The particle collision frequency and its fluctuation range increase as the particle Stokes number increases. The collisions among particles result in an increase of the spanwise dispersion of particles. Experimental results indicate that the models that take particle–particle collision into consideration are more able to predict particle concentration.

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