Modeling Approaches for Premixed Charge Compression Ignition Combustion

The Representative Interactive Flamelet (RIF) - model has established itself as a model well suited for capturing conventional non-premixed combustion in diesel engines. There are concerns about applying the concept to model combustion modes characterized by high degrees of premixing, since it is argued that the fast-chemistry assumption, on which the model is based, breaks down. However, the level of premixing at which this occurs is still not well established. In this paper the model is successfully applied to the so-called Premixed Charge Compression Ignition (PCCI) mode of combustion, characterized by relatively early injection timings, high EGR, and cooled intake air. For very advanced injection timings, an alternative modeling approach is developed. This is based on a sequential treatment of the in-cylinder processes, where the injection process and fluid dynamics are modeled using the three-dimensional CFD-code GMTEC and the chemical reactions are treated in a multi-zone chemistry code, developed at GM. The computations are compared to experiments conducted in a single-cylinder heavy-duty diesel engine.