Modeling wall film formation and vaporization of a gasoline surrogate fuel

To simulate the wall film formation and vaporization processes in gasoline direct-injection spark-ignition engines including considerations of the physical properties and vapor-liquid equilibrium of multi-component fuels, spray-wall interaction sub-models were implemented with the 3D-CFD software HINOCA which has been developed for automotive engine cylinder simulations. The models used were the Senda model for spray-wall impingement including splash, deposition, droplet-droplet interactions, and droplet-film interactions; the O'Rourke model for heat transfer and film vaporization; a simple film flow model considering momentum conservation; and Raoult's law for vapor-liquid equilibrium. First, the model validated the calculated results for a single-component fuel (iso-octane) through comparisons with experimental data in terms of wall film area and heat flux between the wall and film. Second, numerical simulations were conducted with a 5-component gasoline surrogate fuel which was designed taking into account the average octane number, aromatic content, and distillation characteristic. The results showed clear differences in the contributions of the 5 components to the wall film, and the possibility that the aromatic content with higher carbon atoms could be a source of soot formation.