부산대학교 도서관

In direct injection spark ignition (DISI) engines, strict control of pollutant emissions at cold start is required to comply with new emission regulations. To clarify the effect of the impingement distance between the nozzle and the wall on the film formation process under low temperature conditions and the relationship between heat transfer and evaporation characteristics of the fuel film in an actual engine, total internal reflection laser induced fluorescence (TIR-LIF) method was applied to visualize the fuel film formation process. The parameters are 14mm, 28mm, 42mm, and 57 mm in wall impingement distance and the wall surface temperatures are 253 K and 293 K. As a result, the wall impingement distance increases, the momentum of the spray droplets just before impingement on the wall is smaller and it follows the gas flow in the spray more easily, resulting in a decrease in the amount of fuel adhesion on the wall. At a wall impingement distance of 14 mm, the amount of dispersion from the fuel film increases due to the large momentum of the spray droplets. In DISI engines, the fuel film easily residual in the intake process due to the reduction of heat transfer from gas to liquid and increase in heat require for evaporation of the fuel film at the earlier injection timing.