Hydrodynamic Behavior of Biomass Micro-Particles in Counter-Flow Combustion of Dust Clouds

A mathematical model is investigated in order to predict the effect of hydrodynamic forces, especially thermophoretic forces, on the micro-organic particles in counter-flow combustion in this research work. Hydrodynamic forces change the velocity and concentration of evaporative organic particles moving toward the flame, and they make a particle-free distance above the flame surface. Particle evaporation creates a thrust force that affects the velocity of the particles, which can be ignored compared to the other hydrodynamic forces. Also the temperature difference between the particles and the interaction of the particles on each other are neglected. The distance between the inlet nozzle and the flame surface is divided into four zones in order to investigate the dynamic behavior of the particles in the flame front, and in each case, the dynamic particles equations are written, and the effects of thermophoretic force, weight force, drag force, and buoyant force are analyzed on the particles, and as a result, the velocity and concentration profiles of the particles are obtained in terms of distance from the flame front at different strain rates and with different particle diameters. The particle concentration of above the flame front increases with the balance of these forces, and increasing the particle accumulation above the flame decreases the combustibility of particles in the flame front. Then the length of the particle-free zone is extracted under the influence of different strain rates at different temperatures. As the flame surface approaches, the temperature gradient rises, and the thermophoretic force increases. Accordingly, the heavier particles accumulate closer to the flame surface.