Modeling of the overall equivalence ratio effects on combustion process and unregulated emissions of an SIDI methanol engine

A non-uniform spray-line distribution nozzle was used to form a stratified charge distribution of methanol-air mixture in-cylinder. Computational fluid dynamics were employed to simulate the methanol chemical kinetics reaction mechanism. The effects of an overall methanol-air equivalence ratio on the mixture distribution of the in-cylinder, cylinder pressure, heat release rate, cylinder temperature, and unregulated formaldehyde and unburned methanol emissions of a stratified charge spark ignition direct injection methanol engines were investigated. The simulation agrees well with experimental results. The maximum cylinder pressure, maximum heat release rate, and maximum cylinder temperature, for an overall equivalence ratio of 0.67, are 65%, 172% and 51% higher than for 0.33, respectively. Formaldehyde and unburned methanol emissions for an overall equivalence ratio of 0.67 are 97% and 95% lower than for 0.33, respectively. Formaldehyde and unburned methanol are mainly from the region close to the cylinder wall. Larger cylinder temperatures produce faster oxidation and hence generate lower concentrations of formaldehyde and unburned methanol, and vice versa. When the maximum cylinder temperature exceeds 1500 K, formaldehyde and unburned methanol emissions are approximately 30 and 300 ppm, respectively.