Particle distribution in bi-disperse particle-laden jets

Abstract: Numerical simulations have been conducted for bi-disperse particles in particle-laden, co-flow jets to identify the particle behaviour under various particle-to-gas mass loading ratios. A four-way coupling Euler-Lagrangian approach was employed, with large-eddy simulations for the gas phase and the Lagrangian particle tracking method that includes inter-particle collisions for the particles. Here, the treatment of the Lagrangian particles was similar to a simplified discrete element modelling method, where all particles motions and contact collisions were included without packaged simplification, and the deterministic collision pairs collisions of each particle were detected and computed for each particle. Moreover, the inflow condition to the jet was incorporated within the computational domain, so that the model included a particle-laden flow developed in a long straight pipe of 32 pipe diameters in length was employed as the jet inflow upstream from the nozzle exit., In the bi-disperse particle system, the mass fraction of the small particles was fixed at 5%, and their Stokes number at the jet exit of SkD = 1.4. The corresponding values for the large particles were 95% and SkD = 11.2, respectively. This mass fraction corresponds to a number ratio of 1.3 for small to large particles and results in a bulk mean Stokes number at the jet exit of the bi-disperse particles of SkD = 5.6. At this particle composition ratio, three particle-to-gas mass loading ratios from ?m = 0.2 to 0.8 were considered for simulations. Particle statistics were compared between the bi-disperse particle-laden jets and those that are mono-disperse with corresponding Stokes numbers. Overall, it was found that the radial spread of the large particles decreases while that of the small particles increases in the bi-disperse particle system compared with the mono-disperse system. Also, an increase in the total mass loading amplifies the former effect and weakens the latter. Keywords: bi-disperse particles, particle-laden flows, jet flows, four-way coupling, Stokes number