Abstract:

Asystematic multi-stage mechanismreduction strategy for performing skeletal reductions of gasoline four-component surrogate fuel is presented. The approach includes the directed relation graph with error propagation, peak concentration analysis, linear isomer lumping, principal component analysis, temperature sensitivity analysis and rate of production analysis. The final reduced mechanism comprises 149 species and 414 reactions with embedded cross-reactions, which is suitable for homogeneous charge compression ignition (HCCI) engine application. Comparisons between computational and experimental data including the shock tube and rapid compression machine, indicate that the new reduced mechanism can provide good predictability of the ignition delay over extensive parameter space. Applying the reduced mechanism to the HCCI single zone model also shows satisfactory combustion and emission characteristics of the boosted HCCI combustion. Further heat release analysis demonstrates that R + O₂ are the key reactions controlling the intermediate temperature heat release and under high pressure and low temperature conditions, iso-octane is the most important species resulting in a large portion of heat release. After the addition of 2-pentene, the new four component model displays better predictability than the three component model, especially relative to the firststage ignition delay. Based on these new findings, we can use different composition ratios to arbitrarily control the combustion phasing of HCCI combustion.

Key words: Gasoline surrogate fuel, Multi-stage mechanism reduction, HCCI engine, Intermediate temperature heat release, Chemical kinetic modeling