Flame propagation in metal slurry sprays

Abstract

An analytical and computational study of vaporizing and burning liquid hydrocarbon-metal slurry droplet streams injected into a hot gas is presented. The objective is to investigate the mass and energy interactions between the slurry droplet streams and the gas flow. An idealized configuration consisting of parallel droplet streams is used. The governing gas-phase equations are analytically integrated by using the Green's function approach and a resulting set of first order nonlinear ordinary differential equations is numerically solved. The slurry droplet model includes transient heating and particle drag, a shell-bubble formulation, heating and ignition of the metal agglomerate subsequent to the vaporization of the liquid fuel, and vapor-phase burning of the metal. Results show that, at different combustor locations, interacting and distinct premixed and diffusion type reaction zones are present. For the metal particle to be ignited, at a given metal loading, there exists a minimum inlet gas temperature requirement which depends upon the equivalence ratio. The heating and burning times of the metal agglomerate are found to be much larger in comparison to the liquid fuel vaporization times, and they increase with increasing metal particle size and metal loading of the slurry droplets.