Influences of inlet air pressure, air temperature and secondary air swirl on penetration histories of pulverized coal particles in a tubular combustor

A numerical model has been developed to predict the penetration histories of poly-dispersed pulverized coal particles undergoing the process of devolatilization and subsequent combustion into a turbulent swirling flow of air in a typical tubular combustor. The computation scheme is based on the typical stochastic separated flow model of the gas-particle flow within the combustor. A k–ɛ model with wall function treatment for near wall region has been adopted for the solution of conservation equations in gas phase on a Eulerian frame. The initial size parameters of coal particles are specified by a suitable pdf size distribution. The combustion chemistry has been considered by the typical ‘conserved scalar mixture fraction approach’. The information of pulverized coal particles are generated by the solution of conservation equations of discrete coal particles on a Lagrangian scheme. The temperature and mass histories of coal particles along their trajectories in the combustor have been evaluated at different values of inlet pressure and temperature of air and secondary air swirl. It has been recognized that penetration of particles in the combustor is reduced with pressure and secondary air swirl. While the coarser particles exhibit a relatively larger mass depletion in a situation of air flow without swirl, the finer particles exhibit the same in a flow with swirl.