Unsteady, Spherically-Symmetric Flame Propagation Through Multicomponent Fuel Spray Clouds

Abstract

The flame propagation through a fuel spray-air mixture in a spherical geometry is investigated by means of a one-dimensional unsteady analysis with a hybrid Eulerian-Lagrangian formulation. Finite-difference numerical schemes have been employed, with nonuniform grid spacing and an adaptive time step. Multicomponent sprays are considered. Emphasis is given to: the presence and role of diffusion and premixed flames; the movement of the droplets due to the expansion of hot gases and the resulting stratifica-tion; the effect of rapid vaporization of more volatile components; and the influence of the droplet size on droplet time history in a spray flame. More volatile fuels produce faster flame propagation. Nonuniform vapor fuel composition is generated due to the different volatilities of the components of the liquid fuel spray. Increasing the droplet size causes strong local deviation from the initially uniform equivalence ratio, due to the relative motion of the two phases. Flames generally have complex premixed and diffusion structures. Emphasis is given to flames propagating through unconfined domains.