A mixed numerical-experimental analysis for the development of a partially stratified Compressed Natural Gas Engine.

In modern DI Diesel engines with high pressure injection systems, the impingement of the spray on the piston head frequently occurs. Being the mixture preparation a crucial aspect for the correct operation of the engine, as it greatly influences and alters the combustion process, numerical modeling of the spraywall interaction becomes essential. Three different spray-wall interaction models have been tested and integrated into a modified version of the KIVA-3V. All the models conserve mass, momentum and energy of the impinging droplet and have a different behaviour if the surface is wet or dry. The paper focuses on the main features of the single models, investigating the different criteria used to define the splash occurrence, the ratio of the splashed mass to the incident mass and the splashed droplet size. Comparisons with experimental data are presented. The effects of the initial injection velocity and the spray cone angle are also investigated.