Experimental and Numerical Study on the Effects of N<sub>2</sub> and NH<sub>3</sub> in NH<sub>3</sub>/Syngas/Air Laminar Premixed Flame
Lijuan Wen, Qifeng Zhu, Jingwei Zeng, Haoxin Deng, Guoyan Chen, Xiaoping Wen, Qizheng Hao
Abstract
Blending syngas with ammonia (NH 3 ) effectively overcomes the high minimum ignition energy and low laminar burning velocity ( S L ) of NH 3, facilitating the realistic application of NH 3 as a fuel for gas turbines. Thus, the present study combines experiments and numerical simulations to investigate the impacts of diluent N 2 (0–60%) and NH 3 (25–50%) on NH 3 /syngas/air flames. The analysis suggests that increasing N 2 and NH 3 content, respectively, results in a decrease in the S L of the mixture. At Φ = 1.0, as the N 2 content increases from 0 to 60%, the S L of the mixture decreases from 80.1 to 28.3 cm/s. The S L decreases from 80.1 to 36.4 cm/s as the NH 3 content increases from 25 to 50%. The increase in N 2 content decreases the maximum mole fractions of H, OH, and O radicals, and the net reaction rates of chain reactions also decrease. The net reaction rate of H + O 2 = O + OH at Z N2 = 60% decreases by 85.8% compared to 0.018 (mol/cm 3 s) at Z N2 = 0% at Φ = 1.0. As NH 3 content increases, the impact of chain reactions associated with the NH 3 reaction mechanism on the combustion process becomes more pronounced. With the increase in NH 3 content, the ratio of chemical effect to physical effect initially increases and then decreases, reaching a maximum value of 25.4% around Z NH3 = 30%. This value is much less than 1, indicating an overall inhibitory effect. The analysis of reaction pathways and NO emissions suggests that the presence of N 2 reduces NH 3 consumption, which in turn reduces NO generation. The increase in NH 3 content promotes the conversion of N 2 O to N 2, simultaneously reducing NO emissions.