Study of the chemical kinetic mechanism and aldehyde emissions in methanol/diesel dual-fuel combustion

Abstract

To investigate the combustion characteristics of diesel/methanol in the engine cylinder, this study developed a chemical kinetics model for the diesel/methanol (DM) dual-fuel mechanism, comprising 288 reactions and 101 species. The simplified DM mechanism was optimized by adjusting the rate parameters of key reactions, combined with a sensitivity evaluation system for ignition delay time (IDT) and laminar flame speed (LFS). The model's predictions for IDT, LFS, and the concentrations of key species were verified experimentally using a zero-dimensional model. The effects of methanol substitution rate, and altitude on the formation of aldehyde pollutants were systematically analyzed. The results show that the DM mechanism can accurately predict the IDT, LFS, and the formation of key species for a single fuel within the temperature range of 318 K–2000 K, equivalence ratio range of 0.5–2.0, and pressure range of 0.1 MPa–2 MPa. Compared with existing mechanisms, the DM mechanism significantly improves prediction accuracy for these parameters, with R² values greater than 0.96 and RMSE values below 0.05, demonstrating higher accuracy and consistency. Furthermore, increasing the methanol substitution rate significantly reduces CH₂O emissions, while altitude lead to a marked increase in CH₂O and CH₃CHO emissions. Therefore, the proposed DM mechanism shows strong applicability and generalization capability in combustion characteristic prediction and pollutant emission control.