A numerical approach to elucidate the combustion and emission characteristics of n-dodecane under hydrogen enrichment

Abstract

Soot and CO2 emission are the major challenges when using fossil fuels in internal combustion engines. To mitigate the exhaust effect on the environment and reduce the dependency on fossil fuels, it is a better idea to utilize zero-carbon fuel, H2, with hydrocarbon fuels. A numerical approach was executed to elucidate the combustion and emission characteristics of n-dodecane under hydrogen enrichment. It was found that H and OH made a huge contribution to the formation of benzene to pyrene aromatic rings, while C2H2, C3H3 and C5H4CH2 linear hydrocarbons produced the first benzene aromatic rings of PAH (polycyclic aromatic hydrocarbons). The trend of peak molar fraction of benzene and pyrene was observed correlated to that of small and linear HC (hydrocarbons) at various H2 ratios. Hydrogen mitigated the production of acetylene, C3H3, C5H4CH2, C2H3, ethylene and C3H2, and later these species impeded the formation of benzene and pyrene. Besides, the diminution in the production rate of CH3O and CH2O species indicated a reduction in CO2 emission when adding H2. H2O and CO2 encouraged NH3 and NO2 production, respectively. H2 mitigated the production of peak soot mass concentration and soot particle number density, whereas gravity impact only reduced the peak soot particle number density in the flame.