Oscillating transient flame propagation of biochar dust cloud considering thermal losses and particles porosity

Abstract

This research investigates the transient flame propagation and oscillation phenomenon in the flame speed of porous biochar dust cloud. Time-dependent mass, momentum and energy equations are solved in the spherical coordinate. The gas phase reaction includes the chemical reactions, thermodynamic properties, and multi-element transition properties. To account for the porosity effects of particles, the biochar dusts are modeled as spherical particles with unlimited number of pores (semi sphere) on the surface. The particle trajectory is governed by the equation of motion. The thermophoretic, gravitational, buoyancy and drag forces are employed in this model. In the energy equation, the absorption and radiation emissions by particles is considered. The results reveal that the inertia differences between the particles and gas causes a difference in the velocities of these two phases at the flame front—which is more evident at the early stages of flame propagation when there is a significant change in the density of dust particles. Moreover, the oscillation is further intensified by enhancing the oxygen concentration due to a higher reaction rate, and, as a result, higher velocity difference between the two phases.