MILD COMBUSTION IN DUST CLOUD OF MICRO ORGANIC PARTICLES

Abstract

This paper presents the effect of mass recirculation on the structure of steady state flame propagation in a uniform cloud of volatile organic particles. Based on large Zeldovich number or high reaction rate of combustion, asymptotic analysis is used. This one-dimensional laminar flame structure is divided into three zones. The first zone is a preheat zone in which the rate of chemical reaction is small, and evaporation plays a significant role in temperature and mass distribution. The second zone is a reaction zone in which convection and vaporization rates of particles are small. The third zone is a convection zone in which diffusive terms in the conservation equations are negligible. In this model, it is assumed that particles vaporize to yield a gaseous fuel; also, a massive exhaust gas recirculates to the preheat zone where it mixes with primary particles and gases either to dilute the combustion air and to generate relatively low flame temperature. At last, the flame characteristics for different equivalence ratios of the solid mixture are studied by considering the effects of radiation and mass recirculation. Radiations from reaction zone to the mixture of particles and gases existed in the preheat zone increase flame temperature and burning velocity. As the hot exhaust gases are recirculated to the inlet combustion air, the combustion air is diluted; thus, flame temperature and consequently NO_x emission are decreased.

DOI: http://dx.doi.org/10.5755/j01.mech.19.4.5042