Modeling wall impaction of diesel sprays

Abstract

A model for diesel spray wall impaction is presented, which is assessed against experiments for a number of test cases, including normal or angled injection to a wall into a quiescent space or a cross-flowing gas at various gas pressures. New relationships are given for the velocities of the droplets rebounding from the wall. These relationships take into account the wall roughness and the possible break-up of the droplets during their impingement. The impingement model was incorporated in a spray model based on the stochastic particle technique (Dukowicz 1980) and accounts for the phenomena of droplet injection, break-up, collision and coalescence, turbulent dispersion, and evaporation. The spray model was incorporated in a recently developed three-dimensional (3-D) computational fluid dynamics (CFD) code that simulates the unsteady compressible flow of the gas in internal combustion engines by solving the full Navier-Stokes equations. It was found that the motion of the surrounding gas caused by the spray injection plays a minor role on the predicted results. The latter concern the wall spray radius and the wall spray height. The validity of the spray model is demonstrated through extensive comparisons with experiments over a wide range of gas conditions.