Abstract
This paper investigates the effect of equivalence ratio on pollutant formation characteristics of CH(4)O/H(2)/NH(3) ternary fuel combustion and analyzes the pollutant formation mechanisms of CO, CO(2), and NO(X) at the molecular level. It was found that lowering the equivalence ratio accelerates the decomposition of CH(4)O, H(2), and NH(3) in general. The fastest rate of consumption of each fuel was found at φ = 0.33, while the rates of CH(4)O and NH(3) decomposition were similar for the φ = 0.66 and φ = 0.4. CO shows an inverted U-shaped trend with time, and peaks at φ = 0.5. The rate and amount of CO(2) formation are inversely proportional to the equivalence ratio. The effect of equivalence ratio on CO(2) is obvious when φ > 0.5. NO(2) is the main component of NO(X). When φ < 0.66, NO(X) shows a continuous increasing trend, while when φ ≥ 0.66, NO(X) shows an increasing and then stabilizing trend. Reaction path analysis showed that intermediates such as CH(3) and CH(4) were added to the CH(4)O to CH(2)O conversion stage as the equivalence ratio decreased with φ ≥ 0.5. New pathways, CH(4)O→CH(3)→CH(2)O and CH(4)O→CH(3)→CH(4)→CH(2)O, were added. At φ ≤ 0.5, new intermediates CHO(2) and CH(2)O(2) were added to the CH(2)O to CO(2) conversion stage, and new pathways are added: CH(2)O→CO→CHO(2)→CO(2), CH(2)O→CO→CO(2), CH(2)O→CHO→CO→CHO(2)→CO(2), and CH(2)O→CH(2)O(2)→CO(2). The reduction in the number of radical reactions required for the conversion of NH(3) to NO from five to two directly contributes to the large amount of NO(X) formation. Equivalent ratios from 1 to 0.33 corresponded to 12%, 21.4%, 34%, 46.95%, and 48.86% of NO(2) remaining, respectively. This is due to the fact that as the equivalence ratio decreases, more O(2) collides to form OH and some of the O(2) is directly involved in the reaction forming NO(2).