Theoretical and experimental investigation on diesel HCCI combustion with external mixture formation

Homogeneous Charge Compression Ignition (HCCI) is a concept for achieving ultra-low NOx and particulate matter emissions at part-load operations. HCCI combustion can be obtained on conventional diesel engines by premixing the charge in the intake manifold with a dedicated fuel atomiser. The paper describes experimental and modelling activities oriented to understanding and controlling diesel HCCI combustion with external mixture formation. Results obtained on different engines showed that stable diesel HCCI combustion could be achieved over a range of operating conditions, and confirmed its benefits in terms of NOx and soot reduction. The theoretical activity is focused on HCCI combustion modelling for control by means of a mean-value model of a complete engine system, which imbeds a thermodynamic combustion calculation. The satisfactory agreement with experimental data as well as the low computation time indicate the model suitable for HCCI engines control and diagnostics.