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The process of tip wetting at the spray injection end

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.