Stand-alone single- and multi-zone modeling of direct injection homogeneous charge compression ignition (DI-HCCI) combustion engines

Abstract

Applying the homogeneous charge compression ignition (HCCI) combustion concept leads to advantages regarding fuel economy and particular emissions. One strategy to prepare an in-cylinder homogeneous charge is the very early direct fuel injection referred to as direct-injection (DI) HCCI combustion. In this study, single- and multi-zone models for DI-HCCI engines are developed; a single-zone approach and a novel hybrid approach sequentially applying single- and multi-zone models. Experimental results are compared with model predictions to validate the main assumption of the modeling approach which considers charge homogeneity after fuel entrainment. Results indicate that for DI-HCCI cases, the assumption of neglecting injection-induced stratification is valid. Both approaches show acceptable results which reveals their capability to adequately well capture DI-HCCI combustion engine performance. However, the single-zone approach, as expected, leads to over-prediction of maximum pressure and delivered power. Furthermore, maximum pressure rise rate as an indicator of smooth engine operation is highly over-estimated and combustion phasing is predicted earlier than the experimental measure. Combustion phasing is estimated by single- and multi-zone approaches with average errors of 0.4 and 0.1 crank angle degrees, respectively. Whereas, the power is estimated with average errors of 10 and 1% for single- and multi-zone approaches, respectively.