The fuel films that can be generated during the injection process in gasoline direct injection engines are the most important factor in carbon particle mass and number. They also have an influence on combustion chamber and injector tip deposits. A model experiment was set up to study a liquid film, its evaporation, and combustion with soot generation on a metal plate in realistic engine conditions. The experiment was conducted in a dedicated constant volume vessel. A liquid fuel injection system (with injection pressures up to 100 bar) directs the spray onto a plate with a controlled temperature in the range of 80 °C–200 °C. The resulting liquid film and vaporization process were studied when subjected to interaction with a laminar spherical flame. A blend of four components was used as a gasoline surrogate. The liquid film spreading, thickness, and evaporation rates were initially measured in ambient conditions. Mie scattering and schlieren measurements in the chamber conditions returned a qualitative correlation of the vaporized area with the surface temperature. Fluorescence of the light and heavy fuel components was used to quantify the influence of the vaporization process on soot production. Simultaneous measurements of natural luminosity and KL factor were analyzed to understand the process of soot production. The results showed a critical wall temperature of 120 °C at which the maximum quantity of soot is generated, which can be due to the quantity and composition of fuel film in interaction with the entrainment flows generated during combustion.

Gasoline direct injection engines mainly use multi-hole high-pressure injectors. To respect the current pollutant regulation (particle number and particle mass) and continue to decrease pollutant emissions in the future, it is of outmost importance to identify the various sources of carbon particles. In gasoline direct injection, tip wetting can generate a progressive tip sooting that can be a source of large number of particles especially in hot engine conditions. The different topics related to the tip wetting are investigated here without counterbore after the metering hole in order to have a direct access to the optical visualization. In this article, the different phases of the tip wetting are identified experimentally and phenomenological models are proposed.