A decoupled model of detailed fluid mechanics followed by detailed chemical kinetics for prediction of iso-octane HCCI combustion

We have developed a methodology for predicting combustion and emissions in a Homogeneous Charge Compression Ignition (HCCI) Engine. The methodology judiciously uses a fluid mechanics code followed by a chemical kinetics code to achieve great reduction in the computational requirements; to a level that can be handled with current computers. In previous papers, our sequential, multi-zone methodology has been applied to HCCI combustion of short-chain hydrocarbons (natural gas and propane). Applying the same procedure to long-chain hydrocarbons (iso-octane) results in unacceptably long computational time. In this paper, we show how the computational time can be made acceptable by developing a segregated solver. This reduces the run time of a ten-zone problem by an order of magnitude and thus makes it much more practical to make combustion studies of long-chain hydrocarbons. This sequential, multi-zone methodology is here applied to analyze recent experimental results for combustion of iso-octane in an HCCI engine. The numerical results agree well with the experimental results for all the combustion parameters, and the model also makes reasonable predictions for hydrocarbon and carbon monoxide emissions. The paper also includes a sensitivity analysis on how the resolution of the grid used in the fluid mechanics code affects the results of the HCCI combustion analysis.