Modeling Thermophoresis Phenomena in Non-Premixed Counterflow Combustion of Particles

In this paper, an analytical model is presented to investigate flame structure that contains uniformly distributed volatile fuel particles in an oxidizing gas mixture. A non-premixed counterflow combustion is considered assuming a thin region of reaction where lycopodium particles are assumed as the solid fuel. Also, effective forces including thermophoretic, vaporization process and particles radius variations have been studied in this configuration. As the thermophoresis effect severely increases by approaching the flame front, it reaches a specific value that balances the gravity, drag and buoyancy forces applied on the particle. One dimensional flame propagation in organic cloud of fuel particles is analyzed in which flame structure is divided into pre-heat, vaporization, post-vaporization and post-flame zones. It is assumed that particles as fuel and air as oxidizer move toward stagnation plane from two nozzles in the counterflow configuration. Particles initially vaporize in order to release a specific chemical gas which then enters the oxidation reaction process. For this purpose, conservation equations with specific boundary conditions are solved in each zone. The results show that both burning velocity and flame temperature increase with a rise in volume fraction and a reduction in particles diameter.