A Modeling Investigation into the Optimal Intake and Exhaust Valve Event Duration and Timing for a Homogenous Charge Compression Ignition Engine

Homogenous Charge Compression Ignition (HCCI) engine operation has been demonstrated using both residual trapping and residual re-induction. A number of production valve train technologies can accomplish either of these HCCI modes of operation. Wide-scale testing of the many valve timing and duration options for an HCCI engine is both time and cost prohibitive, thus a modeling study was pursued to investigate optimal HCCI valve-train designs using the geometry of a conventional gasoline Port-Fuel-Injected (PFI) Spark-Ignition (SI) engine. A commercially available engine simulation program (WAVE), as well as chemical kinetic combustion modeling tools were used to predict the best approaches to achieving combustion across a wide variety of valve event durations and timings. The results of this study are consistent with experimental results reported in the literature: both residual trapping and residual re-induction are possible strategies for HCCI combustion. The best valve timing strategies seem to be either very short intake and exhaust events (trapping), or short intake and long exhaust (re-induction). The effect of inlet air temperature on HCCI combustion with a residual trapping valve strategy was also investigated, and modeling suggests HCCI combustion is feasible even at low inlet air temperatures.