H₂ impact on combustion kinetics, soot formation, and NOx emission of hydrocarbon fuel flames

Soot and carbon dioxide released from internal combustion engines became the key issues when using fossil fuels. The use of zero-carbon fuel, hydrogen, with hydrocarbon fuels can play an important role in reducing the exhaust effect on the environment and mitigating the reliance on nonrenewable energy resources. A numerical approach was executed to elucidate the H₂ impact on combustion kinetics, soot formation, and NOx emission of hydrocarbon fuel under premixed and diffusion flame conditions. The results showed that hydrogen deteriorated the formations of particle number density, the volume fraction of soot, carbon monoxide, carbon dioxide and polycyclic aromatic hydrocarbons thru the reduction of small chain hydrocarbons at both premixed and diffusion flame conditions. The soot volume fraction and soot particle number density formation were prevailing in the air region of the combustion chamber at diffusion flame conditions. NO₃ produced from fuel-related species such as C–H–O and air-related species such as N–O. H₂ reduced the peak molar fraction of small chain HC including C–H–O related species, resulting in a reduction in NO₃ emissions. C₃H₃ species dominantly participated to reduce the CO₂ and NO₃ emissions, while C₂H₂ and C₅H₄CH₂ were the main species to control the soot precursors formation in both HC fuel flames. Besides, NH₃ emission was limited by C₂H₂ in DS flames.