Is the liquid penetration in diesel sprays mixing controlled?

Abstract

Computations of spray penetration and vaporization under diesel conditions are performed under different injection and ambient conditions. A two-fluid model which solves Eulerian field equations for the gas and the liquid phases is employed to model vaporizing non-combusting sprays under high injection pressure diesel conditions. As a first step, the locally homogenous flow (LHF) approximation is considered where the two phases have the same velocity at a given spatial location and time. Under this assumption, the mixing controlled vaporization is modeled using thermodynamic equilibrium between the two phases. The liquid-phase penetrantion is compared with constant-volume measurements made under diesel conditions by Siebers at Sandia National Laboratories. The variation of liquid penetration with the injection velocity, ambient temperature, and the ambient density is studied. Comparison with measurements show reasonable agreement of trends with respect to injection velocity and ambient temperature. The trends of variation with ambient density to not show adequate agreement at lower densities. The results suggest that vaporization may be largely controlled by turbulent mixing at higher ambient densities, but non-equilibrium vaporization effects may be important at lower ambient densities. Furthermore, the LHF approximation may not be applicable, in particular, at lower densities where the two phases have significantly different velocities.