定容燃焼装置内に模擬した二段噴射ディーゼル燃焼に及ぼす噴孔径および噴射圧力の影響

Abstract

This study aims to clarify the process of PCCI-based diesel combustion with two-stage injection. For this purpose, the effects of fuel injection conditions (injection pressure and nozzle-orifice diameter) on heat release rate and NOx formation process for various fuel amounts of pilot injection and various injection intervals between pilot and main injections were investigated using a constant-volume vessel under an ambient condition, which provides PCCI-based combustion with longer ignition delay compared with diesel condition. The results show that, in the case of small pilot-injection quantity and short injection interval, high injection pressure makes over-lean mixture of pilot injection and long ignition delay of main-injection fuel. In the case of large pilot-injection quantity, longer injection interval shifts the combustion from the mixing-controlled mode to premixed mode with reduction of NOx mass.