Sensitivity analysis of combustion timing and duration of Homogeneous Charge Compression Ignition (HCCI) engines

The goal of this paper is to investigate which factors have a more dominant effect and should be included in a control oriented model that predicts the start of combustion and combustion duration of a Homogeneous Charge Compression Ignition (HCCI) engine. Qualitative and quantitative information on the individual effects of fuel and exhaust gas recirculation (EGR) on the HCCI combustion is provided. Using sensitivity analysis around several operating points obtained from an experimental gasoline HCCI engine, we find that temperature is the dominant factor in determining start of combustion. In determining combustion duration, temperature is not necessarily the dominant effect compared to composition. The influences from the fuel and oxygen compositions, however, either tend to cancel each other or are very limited at all the operating conditions we investigated. Therefore, a model without the composition terms should be adequate for model-based regulation of the combustion timing in an HCCI engine.