No abstract

Syngas has the potential to become an alternative fuel for internal combustion engines. In this work, a detailed mechanism containing 1389 species and 5942 reactions was developed to examine the combustion of syngas/gasoline blends. The influence of syngas addition on the ignition delay time (IDT) and laminar flame speed of gasoline fuel was studied. Two influencing factors were considered: the mixing ratio of syngas and the H 2 /CO ratio in syngas. The changes in heat release, free radical concentrations, and emissions were also studied. Syngas can boost the system's reaction activity and promote ignition in the hightemperature area over 1000 K. However, the diluting effect is visible at low temperatures below 1000 K, leading to an IDT lag. The effect of the H 2 /CO ratio on the IDT was not as pronounced as expected. The addition of syngas can inhibit the knock combustion of the engine to a certain extent, but it will also lead to a violent exothermic process and a decrease in the total release of heat. Syngas addition increases the concentration of small molecule radicals and promotes the laminar flame speed. At higher temperatures and pressure levels, the trend of syngas/gasoline laminar flame speed is more dependent on changes in OH radical concentrations. The addition of syngas favors the promotion of complete combustion and the reduction of HC emissions but also results in an additional increase in CO. Combustion at lower temperatures has lower CO and HC emissions.

It is an effective way to introduce syngas fuel into gasoline engine for blending combustion to improve combustion and reduce emissions. In this paper, the combustion and emission characteristics of the direct injection engine under the condition of mixed combustion of syngas were analyzed by a numerical simulation method. The engine ran at 2000 rpm, and the mass fraction of syngas was from 0 to 20%. The results showed that with the increase in the mass ratio of syngas in the dual fuel, the average pressure and temperature in the cylinder increased first and then decreased. The maximum in-cylinder pressure and in-cylinder temperature increased by 27.5 and 2.97%, respectively. The instantaneous heat release rate also showed a law of first increasing and then decreasing, in which the peak value of the instantaneous heat release rate increased by 32.1% at the highest. In addition, with the increase in the ratio of syngas, the emission of nitrogen oxides in the cylinder gradually decreased, with a maximum reduction of 27.4%. The unburned hydrocarbons first decreased and then increased, with a maximum reduction of 7.6%. Meanwhile, the emission of carbon dioxide was negatively correlated with the ratio of syngas in the dual fuel. With the increase in hydrogen ratio in syngas, the carbon monoxide was gradually reduced, with a maximum reduction of 65%. The carbon dioxide increased first and then decreased, with a maximum addition of 4.8%. The ratio of hydrogen and carbon monoxide in syngas had little effect on the emission of unburned hydrocarbons.