Characterization of Mixture Formation in a Direct Injected Spark Ignition Engine
We have performed simulations and experiments to characterize the mixture formation in spray-guided direct injected spark ignition (DISI) gasoline engines and to help to understand features of the combustion process, which are characteristic for this engine concept. The 3-D computations are based on the KIVA 3 code, in which basic submodels of spray processes have been systematically modified at ETH during the last years. In this study, the break-up model for the hollow-cone spray typical for DISI engines has been validated through an extended comparison with both shadowgraphs and Mie-scattering results in a high-pressure-high-temperature, constant volume combustion cell at ambient conditions relevant for DISI operation, with and without significant droplet evaporation. Computational results in a single-cylinder research engine have been then obtained at a given engine speed for varying load (fuel mass per stroke), swirl and fuel injection pressure.