Momentum exchange process under non-evaporating spray of hole nozzle in direct injection SI engines

Abstract

Direct fuel injection spray is used to improve thermal efficiency and environmental performance in SI engines. A mixture is formed through momentum exchange between fuel droplets and ambient gas, along with mixing accompanied by droplets evaporation and diffusion. Both the droplets development derived from the liquid fuel atomization and the entrainment ambient air predominate the mixture formation process. The purpose of this study is to elucidate the momentum exchange characteristics of the spray formed by a single-hole injector for direct injection gasoline engines. To clarify the momentum exchange characteristics of spray droplets, the spray was visualized by optical experiments and the spray development process was analyzed. The parameters are injection pressure and ambient density. A comparison of experimental results and a model analysis of a single droplet movement was conducted, and different of deceleration characteristics were evaluated. In the case of the fuel spray, the induced ambient air by the spray tip droplets decreases the relative velocity between the spray droplets and the spray internal flow. A model for predicting the temporal variation of the spray tip penetration from the different of momentum exchange characteristics between the spray and the droplet was proposed.

Keywords

• heat engines
• si engines
• spray
• mixture formation
• momentum exchange
• drag force