Effects of Biofuels on Soot and NO Formation during Gasoline Combustion
Shu Zheng, Yuhong Zhang, Yu Yang, Mingxiao Li, Qiang Lü
Abstract
Cofiring of fossil fuels with renewable biomass-derived fuels is a promising way to reduce CO2 emissions. This work numerically investigated the effects of biofuel addition on soot and NO formation in gasoline laminar diffusion flames. Four gasoline/biofuel mixtures, where the biofuel was the mixture of ethanol (EtOH) and ethyl acetate (EA) in different fractions, were used to investigate how the soot volume fraction (SVF) and NO concentration responded with biofuel addition. The results showed that the peak temperature and peak NO concentration increased by 3.02 and 130%, respectively, when EA was increased from 0 to 75% in the biofuel, while the peak SVF was reduced by 75.4%. The flame was elevated vertically due to the low burning velocity and the long ignition delay time of EA. The reaction C6H5CH3 + H < = > A1 + CH3 to form the incipient ring (A1) was limited by the decreased H radicals, which in turn limited the processes of polycyclic aromatic hydrocarbon (PAH) growth, inception, and surface growth and eventually hindered soot formation. Pathway analysis of NO formation showed that the increasing tendency of NO concentration along with increased EA was a result of the combined influence of the thermal NO pathway and NO reburning cycle pathway, with the former playing a major role.