Abstract
This work investigates surface impingement of mono-dispersed trains of hydrocarbon fuels using computational simulations. The three-dimensional simulations include ethanol and diesel drop impingement onto initially dry and wetted stainless steel substrates. The high-speed micron-sized diesel drop size and impact velocity are representative of fuel injection conditions in internal combustion engines (ICEs). The drop trains serve as a simplified representation of fuel spray. The impingement frequency at which drop trains transition from depositing to splashing was identified. Furthermore, effects of impingement frequency on splashed mass were quantified. Additionally, the effects of a pre-existing film on splashing dynamics were investigated at various film thicknesses, where the temporal evolution of splashed mass was obtained. Secondary droplet characterization was performed on simulation results using a robust algorithm that scrutinizes the volume fraction and velocity fields. This analysis provides insights into the stages of secondary droplet formation. Instantaneous and time-averaged distributions of secondary droplet size, velocity magnitude and trajectory angle are reported. The splashed mass ratio and secondary droplet characterization results were compared to commonly used spray-wall interaction (SWI) sub-models, which are heavily relied upon in a Lagrangian-Eulerian (LE) fuel injection modeling frame-work. The comparison reveals the SWI sub-models suffer from significant inaccuracy under engine-relevant conditions. Finally, a new SWI sub-model is proposed for diesel fuel injection based on the simulation results. The model provides correlations for splashed mass ratio and secondary droplet size and velocity as a function of a nondimensional velocity. To the best of the author’s knowledge, the proposed model is the first SWI sub-model based on engine-relevant drop impingements, which is expected to improve the accuracy of LE combustion simulations.