A skeletal gasoline flame ionization mechanism for combustion timing prediction on HCCI engines

A skeletal mechanism for gasoline flame ionization process prediction on HCCI engines was developed based on a primary reference fuel oxidation mechanism and a C1-C4 hydrocarbon flame ionization mechanism. Since the ion concentrations significantly affect the aroused ion current signals the mechanism is targeted on accurately predicting both the ion production concentrations and other key combustion characteristics. Comparison between the detailed gasoline flame ionization mechanism and experimental results revealed that the predicted maximum hydronium ion concentration and the concentration variation tendency are validated. Also the auto-ignition delay time accurately predicted under HCCI engine conditions. Through coupling with a three-dimensional CFD engine model the skeletal mechanism was applied to predict the important information of in-cylinder ion species. The results show that the ion current phase matched well with the positions where the predicted ion concentration reached its maximum and the ion current amplitudes were well predicted under varying conditions of various equivalence ratios and fuel injection ratios.