Combustion phasing and work output modeling for homogeneous charge compression ignition (HCCI) engines

Combustion phasing and work output are the two critical indicators for achieving and maintaining homogeneous combustion for homogeneous charge compression ignition (HCCI) engines. However, the complicated thermodynamic process keeps the combustion phasing model from being explicit. The current models for CA₅₀ (crank angle when 50% fuel consumed) requires information that is hardly available for commercial engines. In this paper, polynomial models for combustion phasing and work output are proposed. The intake conditions, including intake manifold temperature, pressure and burned gas fraction as well as the fuel injection are chose as the four variables by whom the combustion phasing and work output are determined. The impacts of various compression ratios on the two indicators (represented by CA₅₀ and IMEP) were investigated and have been classified into two groups: vertical shift and curve deformation and both can be well modeled and, therefore compensated. The models are validated through high-fidelity simulations.