H2/NH3 Addition Effects on Flame Characteristics and Soot Formation in Ethylene Inverse Diffusion Flame

Zero-carbon alternative fuels such as hydrogen and ammoniaaregaining popularity. Blending these fuels with hydrocarbons is an intermediateapproach to mitigate soot and carbon dioxide production. Recent studieshave concentrated their attention to the effects of ammonia and hydrogenon the soot production of hydrocarbon fuels. It is still necessaryto completely comprehend how this influence is dependent on the typeof fuel and flame configuration. In this work, the effect of hydrogenand ammonia addition on soot production in ethylene laminar inversediffusion flames (IDF) was numerically examined for the first time.The thermal, chemical, and combined effects of hydrogen and ammoniawere assessed by fictitious species. The experimental results fromthe literature were used to validate the temperature and soot volumefraction profiles. Results indicated that the flame temperature andthe production of radicals are promoted chemically by hydrogen additionbut inhibited under the thermal effect of ammonia. The principal sourceof the reduction in OH-represented flame height, soot volume fraction,average diameter, and primary particle number density in the IDF isthe thermal effect of additives, and hydrogen addition performs betterthan ammonia. The major and intermediate species, the aromatic hydrocarbons,and the soot formation or oxidation reaction rates are decreased mainlyby the hydrogen and ammonia thermal effect while increased moderatelyby the chemical effect. Therein, the reduction in soot generationis mainly due to the polycyclic aromatic hydrocarbon condensationrate being slowed down by additives. The inhibition is attributedto the thermal effect of additions, and hydrogen behaves better thanammonia.