共轨和直列泵管嘴系统喷油嘴压力室流动分析

摘要

喷油嘴内部的穴蚀和流动影响着燃油的破碎雾化等喷雾特性.试验得到了泵管嘴系统和电控共轨系统的针阀升程曲线,结果显示共轨系统针阀的开启速度随着轨压的增大而加快,关闭速度几乎不受轨压的影响,并且共轨系统针阀的开启和关闭要慢于泵管嘴系统.依据试验得到的压力和升程曲线,利用软件AVL-Fire对两种供油系统下不同针阀升程进行喷油嘴压力室内部流动计算,分析了空穴在喷油嘴内形成及分布情况.两种供油系统下喷油规律的计算结果与试验结果基本接近.穴蚀发生的部位在两种供油系统下存在不同,针阀开启过程中,共轨系统存在着穴蚀部位从入口的下部到上部的移动,而泵管嘴系统的穴蚀部位只在喷孔入口的上边沿.%Flow characteristics of nozzle significantly influence spray break up and atomization. Needle lift and pressure of nozzle was obtained in common rail (CR) and pump-line-nozzle (PLN) system. Resuits show that the needle of the injector opens more quickly as injection pressure is increased in CR system while closing speed is hardly influenced by injection pressure. The opening and closing speeds of CR system are lower than those of the PLN system. FIRE code was used to calculate the flow characteristics ofthe injector in the two injection systems. Development and distribution of cavitations in the nozzle were analyzed. The calculated flow rate has good agreement with the experimental results. Cavitations of the injector arc different under two injection systems. Cavitation location moves from the bottom to the top of the inlet during needle rising in the CR system. In contrast to this, cavitation location is always at the top of the inlet in the PLN system.