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

Abstract

Zero-carbon alternative fuels such as hydrogen and ammonia are gaining popularity. Blending these fuels with hydrocarbons is an intermediate approach to mitigate soot and carbon dioxide production. Recent studies have concentrated their attention to the effects of ammonia and hydrogen on the soot production of hydrocarbon fuels. It is still necessary to completely comprehend how this influence is dependent on the type of fuel and flame configuration. In this work, the effect of hydrogen and ammonia addition on soot production in ethylene laminar inverse diffusion flames (IDF) was numerically examined for the first time. The thermal, chemical, and combined effects of hydrogen and ammonia were assessed by fictitious species. The experimental results from the literature were used to validate the temperature and soot volume fraction profiles. Results indicated that the flame temperature and the production of radicals are promoted chemically by hydrogen addition but inhibited under the thermal effect of ammonia. The principal source of the reduction in OH-represented flame height, soot volume fraction, average diameter, and primary particle number density in the IDF is the thermal effect of additives, and hydrogen addition performs better than ammonia. The major and intermediate species, the aromatic hydrocarbons, and the soot formation or oxidation reaction rates are decreased mainly by the hydrogen and ammonia thermal effect while increased moderately by the chemical effect. Therein, the reduction in soot generation is mainly due to the polycyclic aromatic hydrocarbon condensation rate being slowed down by additives. The inhibition is attributed to the thermal effect of additions, and hydrogen behaves better than ammonia.