Real-time start of a combustion detection algorithm using initial heat release for direct injection diesel engines

Abstract

The start of combustion (SOC) in a compression ignition engine may not be consistent due to the engine operating conditions of each engine cycle. This is true even if fuel is injected at a consistent time. Variable factors include humidity, temperature, fuel quality, exhaust gas recirculation (EGR) rate, and boost pressure. These variations in SOC cause an increase in harmful emissions as well as deterioration of engine performance; therefore, SOC has to be detected and controlled. In this study, we present a simplified heat release (HR) equation to detect SOC for real-time closed-loop combustion control in a compression ignition engine. The proposed method extracts SOC using an initial heat release (IHR) equation that is a modified heat release equation. The detected SOC using IHR reveals a close correlation with one percent of heat release at various engine operating conditions such as main injection timing, injected fuel quantity, fuel-rail pressure, and EGR rate changes. In addition, the SOC detected from the proposed method shows great potential for real-time applications as it reduces of the amount of cylinder pressure data by 50.2% and computational load by 55.2%. Finally, SOC was well controlled in real-time with the estimated SOC despite engine operating condition changes.