Large-eddy simulation of swirling particle-laden flows in a coaxial-jet combustor

Large-eddy simulation (LES) of particle-laden, swirling flow in a coaxial-jet combustor is performed. A mixture of air and lightly loaded, spherical, glass-particles with a prescribed size-distribution enters the primary jet, while a swirling stream of air flows through the annulus. The incompressible, spatially filtered Navier–Stokes equations are solved on unstructured grids to compute the turbulent gas-phase. A Lagrangian formulation and an efficient particle-tracking scheme on unstructured meshes is developed to compute the dispersed phase. The particles are treated as point sources and influence the gas phase only through momentum-exchange terms. The particle-dispersion characteristics are examined in detail; in particular, the dependence of particle trajectories and residence times upon particle sizes is emphasized. The mean and turbulent quantities for the gas and particle phases are compared to experimental data and good agreement is obtained. The LES results are significantly more accurate than the Reynolds-averaged Navier–Stokes equation (RANS) predictions of the same problem. Insight into the two-phase swirling flows is obtained through the residence-times and particle velocity-diameter correlations.