SPH simulations of drop impact on heated walls and determination of impact criteria

The outcomes of fuel drop impact on a combustion chamber wall will affect the fuel-air mixture distribution and subsequent combustion performance of an internal combustion engine. In this paper, the process of fuel drop impact on a solid dry surface was simulated, using a numerical method based on smoothed particle hydrodynamics (SPH). This method was first validated using experimental data on the impact regimes of ethanol drops and n-heptane drops on a heated surface. Various impact outcomes: deposition, contact-splash, bounce, and film-splash, were predicted successfully. Then, the impact process of iso-octane drops on a solid surface under engine-relevant conditions was studied. Numerical results show that the splash threshold will decrease as the wall temperature increases. A variety of impact regimes were identified and the impact outcomes in each regime were analyzed. Based on the simulation results, the splashed mass ratio will increase as the kinetic energy of the incident drop and the wall temperature increase. The impact outcomes were found to be similar if the wall temperature is higher than the drop’s Leidenfrost temperature. The effect of wall temperature on the impact outcomes was characterized and incorporated into the model. The proposed drop/wall interaction model, derived from the present SPH study, can be readily implemented for engine spray/wall impingement simulation.