Hybrid modeling for switching between SI and HCCI combustion modes

We present a hybrid model for switching between Spark Ignition and Homogeneous Charge Compression Ignition modes of engine operation. The model can serve as a tool for examining the engine transient behaviour and as a platform for optimisation during a mode switch. It is a physical model of the combustion and gas exchange of a 4-cylinder engine based on simple thermodynamic concepts and empirical relations. The in-cylinder charge is assumed to be homogeneous at all times. The model persists between multiple cycles to capture the cyclic coupling that inherently exists in residual-gas diluted Homogeneous Charge Compression Ignition. The different parts of the cycle are modelled by different sets of continuous-time dynamics with appropriate transitions between them. The actuation employed for mode switching on a specific engine setup is incorporated in the model. Part of the actuation occurs on a cyclic basis, part of it is continuous in time and part of it is discrete. The model outputs were compared to experimental results in steady state operation and during mode-switch and reasonably good agreement was found.