Model-Based Assessment of Two Variable CAM Timing Strategies for HCCI Engines: Recompression vs. Rebreathing

The paper discusses the development and application of a single-cylinder HCCI engine model within the framework of a 1-D engine simulation software (GT-Power^®). The HCCI combustion model includes a predictive burn model based on the in-cylinder conditions, along with methods to estimate in-cylinder NOx production and ringing intensity. The validation of the model was done by comparing simulation results with available experimental data, highlighting the comparison between two different HCCI variable cam timing strategies (recompression and rebreathing). A comparative study of the two valve strategies was carried out with the validated model and the entire operational range of the strategies was compared and analyzed for the constraints that limit further load extension. Recompression was found to be more efficient than rebreathing in the low load operating region. However, the rebreathing strategy was found to span a wider operational range compared to recompression at all speeds.