Closed-loop combustion phase control for multiple combustion modes by multiple injections in a compression ignition engine fueled by gasoline-diesel mixture

Partially premixed combustion with low octane fuel aims to reduce NOx and soot emission simultaneously without fuel consumption penalty. Cylinder pressure based combustion phase control is an essential technology for partially premixed combustion. A novel closed-loop combustion phase control strategy for multiple combustion modes is proposed in the current study. The combustion modes are classified into three basic categories based on injection patterns and heat release stages: (1) with only one heat release stage; (2) with two separated heat release stages; (3) with two overlapped heat release stages. Crank angle when 50% fuel is consumed (CA50) is chosen as the combustion phase indicator for the first case. Start of combustion (SOC) of each heat release stage is the combustion phase indicator for the second case. Both SOC and CA50 are the combustion phase indicators for the third case. Each combustion phase is closed-loop controlled by a proportional-integral (PI) controller with the timing adjustments of the corresponding injection. The control strategy is verified under different operating conditions in a 1.9 L light duty diesel engine fueled by gasoline-diesel mixture (volumetric 70% gasoline, 30% diesel). The experimental results show that the control strategy is able to control the combustion phase, reduce cylinder to cylinder variations as well as cycle to cycle variations under the operating conditions with exhaust gas circulation (EGR) rates of 10% and 15%.