ガソリン直噴エンジン用インジェクタの弁挙動がノズル内部の燃料流れに与える影響

抄録

The formation of deposits on a fuel injector tip is considered a cause of particulate matter (PM) generation. Because wetting by fuel generates the deposits, reducing that adheres to the injector tip is important. In particular, coarse droplets of fuel are generated during the valve opening and closing and cause tip wetting. In this study, we have therefore investigated the effects of valve motion, especially closing and off-axis valve motion, on fuel flow in the injector nozzle by numerical simulations. The results are summarized as follows. (1) The calculated results show that low speed fuel was sprayed during valve closing. (2) Off-axis valve motion decreases the amount of fuel spray in the hole located in the opposite direction to the off-axis valve motion at the valve seating. This is caused by fuel flowing toward the off-axis valve motion in the sac volume. (3) The averaged fuel velocity at the hole outlet located in the off-axis direction with off-axis valve motion is larger than that without off-axis valve motion. During valve bouncing, the averaged fuel velocity at the hole outlet shows little differences in the presence or absence of off-axis valve motion, which indicates that off-axis valve motion for closing barely affects the fuel velocity after the valve seating.