Model Based Control for Premixed Charge Compression Ignition Diesel Engine

Premixed charge compression ignition (PCCI) combustion is effective to reduce diesel engine harmful exhaust gas and improve fuel consumption. However, PCCI combustion has a problem of low combustion stability compared to diesel diffusive combustion, and there are few examples of application to mass production engines. In addition to engine speed and load, it needs complicated injection control according to environmental conditions such as outside air temperature, pressure, and engine water temperature, and transient changes such as supercharging delay, EGR delay, and intake air temperature delay. Although there is example where the control maps are switched according to the intake condition, it needs huge maps considering all the parameters mentioned above. Thus it requires a significant calibration man-hour. And this may lead to deterioration of reliability such as combustion noise and torque fluctuation. In this study, the physical model is applied to calculate the ignitability in the cylinder cycle by cycle, and the ignition delay is controlled according to the ignitability changing injection pattern, thereby eliminating a huge control maps. And this can improve the calibration reliability by making continuous control according to the ignitability. The target ignition delay is determined according to the ignitability. The lower the ignitability, the longer the target ignition delay, and the higher the ignitability, the shorter the target ignition delay. As a result, it was demonstrated that even if there are environmental changes and transient changes, the same heat release rate can be formed with stability.