Closed-loop control of start of combustion using difference pressure management

Abstract

A great deal of attention is being paid to the common-rail direct injection (CRDI) diesel engine as a promising technology for enhancing engine performance and satisfying stringent emission regulations. In a conventional CRDI diesel engine, the start of combustion (SOC) is controlled in an open-loop manner by adjusting the start of energizing (SOE) of an injector. The open-loop SOC control cannot compensate for unexpected variations in the injection delay and ignition delay resulting from cycle-by-cycle variation, cylinder-to-cylinder variation, production variation, and ageing. In this study, cylinder pressure was investigated as a means for controlling the SOC of a CRDI diesel engine. Various pressure variables were compared for the purpose of detecting the SOC of a CRDI diesel engine. The crank angle position at which the difference pressure becomes 10 bar (CADP10) was selected as the pressure variable for the detection of the SOC. The control performance was evaluated with engine-dynamometer experiments in steady and transient operating conditions. The experimental results showed that difference pressure managing can be effectively used for real-time detection of the SOC. Furthermore, the SOC detection technique enables the fuel control strategy to be transformed from an open-loop scheme to a closed-loop scheme.