电控单体泵燃油喷射系统预喷射试验研究

Experimental Study on Pilot Injection for Electronic Unit Pump Fuel Injection System

设计了电控单体泵预喷射时序控制算法,开发了基于MPC563微控制器的控制器数字系统,考虑预喷射量和主预喷间隔的要求、单体泵凸轮供油段长度限制等因素,在单体泵试验台上进行了预喷射探索试验。试验表明:预喷射会在高压油管内形成压力波动并影响主喷射;压力波动循环间变动小;随着转速升高压力波动逐渐减小;在转速低于1 200r/min时压力波动较大,主喷射针阀开启不稳定,循环油量波动大,不能进行预喷射;在转速高于1 800r/min时,由于主喷射所占曲轴转角较大,预喷射可调整范围较小,不适合进行预喷射;在1 200～1 800r/min时的重型柴油机常用转速区和排放测试区,针阀开启稳定,循环油量变动小,可以实现良好的预喷射。

The algorithm of pilot injection sequential control for electronic unit pump was designed and the controller digital system was developed based on MPC563. The experiment was carried out on a test bench considering both requirements of pilot injection quantity and main pilot injection interval and cam profile limitation. The result shows that the pilot injection causes the pressure fluctuation in the high-pressure fuel pipe and influences the main injection. The variation between pressure fluctuation cycles is small. The pressure fluctuation decreases gradually with the increase of speed. When the speed is lower than 1 200 r/ min, the pressure fluctuation is greater, the opening of main injection needle valve is not stable, the fuel fluctuation per cycle is greater and the pilot injection cannot be carried out. When the speed is higher than 1 800 r/min, the pilot injection is not suitable to be carried out because of the narrow adjustment range of pilot injection that was caused by the occupying larger crank angle of main injection. When the speed is between 1 200 r/min and 1 800 r/min, which is the working and emission measurement range of heavy duty diesel engine, the opening of needle valve is stable, the fuel fluctuation per cycle is little and so the good pilot injection can be realized.