Thermo-kinetic Combustion Modeling of an Hcci Engine to Analyze Ignition Timing for Control Applications

Ignition timing in Homogeneous Charge Compression Ignition (HCCI) engines is dominated by thermo-kinetic reactions that are dependant on the charge properties. A single zone thermodynamic model, coupled to a kinetic mechanism, is developed to predict the ignition timing of Primary Reference Fuels (PRFs) in an HCCI engine. The model, consisting of 120 chemical reactions and 58 species, is validated against the experimental data from a single cylinder engine for various operating conditions. The model is able to predict the effects of different charge parameters on the HCCI ignition timing. This model is used to perform a sensitivity analysis of HCCI ignition timing to the variations of engine charge properties in order to examine the relative importance of different charge properties for control applications. The sensitivity analysis is done for these main charge variables: initial temperature, initial pressure, Exhaust Gas Recirculation (EGR) rate, equivalence ratio, and octane number. The simulation results show that the sensitivity of HCCI ignition timing is dependant on the crank angle position of the Start of Combustion (SOC). The highest sensitivity of HCCI ignition timing is always seen to the variation of the charge temperature.