Numerical study of multicomponent fuel spray flame propagation in a spherical closed volume

The flame propagation through a fuel spray-air mixture in a spherical geometry is investigated by means of a one-dimensional, unsteady mathematical model with a hybrid Eulerian-Lagrangian formulation. Finite-difference numerical schemes are employed, with non-uniform grid spacing and adaptive time step. The solution applies to the whole extent of the propagation, giving an accurate description of the ignition and flame propagation towards the wall, until combustion is completed. Multi-component and polydisperse sprays are considered. Emphasis is given to: presence and role of diffusion and premixed flames; the movement of the droplets due to expansion of hot gases and the resulting stratification; 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; fuelrich and fuel-lean zones are present, and both premixed type and diffusion-type flames are observed at the same time.