Thermokinetic modeling of the HCCI cycle: Predicting the ignition timing

Homogeneous Charge Compression Ignition (HCCI) engines have the potential for both improved fuel efficiency and emissions over standard gasoline and diesel internal combustion engines. Before the HCCI cycle can be widely implemented, it is necessary to understand the autoignition process such that it can be suitably controlled. In this investigation, a thermokinetic model of the HCCI cycle was developed and validated against theoretical and experimental results and found to be capable of predicting the ignition timing in a real HCCI engine. This thermokinetic model was then used to vary the equivalence ratio, EGR rate, initial mixture temperature and pressure, and engine speed independently so that their respective effects on the ignition timing could be understood. A dimensional analysis was used to form a correlation describing the relationship between the engine parameters and the ignition timing. This correlation was used to predict the required conditions for a given ignition timing to within 10%.