스월, 스퀴시 유동이 연료 성층화에 미치는 영향

Abstract

Lean burn considered to overcome high thermal load and improve fuel economy in heavy duty si engine however, lean burn generally causes unstable engine operation due to combustion instability such as cyclic variation,misfire, or partial buning, to overcome such undesirable phenomena charge statification inside the engine cylinder through fuel injection strategy was utlized and flow field enhancement through intake port and pistion shape was adopted. in this study, the effects of swirl ratio and piston bowl shape on the mixture preparation were investigated. high intensity of squish flow as well as swirl flow was acquired by the enlarged pistion squish area and helical intake port. to obtain two dimensional fuel distribution planar laser induced fluorescence(PLIF) was used. acetone was excited by KrF exciner laser(248nm) and its fluoresoence image was acquied by ICCD camera. fuel injection stategy with respect to the intake process was found to have the key role of the whole stratification process. the intense squish flow was found to be effective to place relatively rich mixture to the vicinity spark plug in the end period of compression process