ABSTRACT

Ammonia is a promising sustainable fuel, however, its low reactivity creates challenges in industrial applications. In this study, ammonia/methane mixtures were considered for premixed and non-premixed counterflow flames. The extinction stretch rate was measured over a wide range of ammonia/methane mixing ratios and compared to 1D numerical results from four different mechanisms. Additionally, for counterflow premixed twin flames, quantitative analysis based on the comparison of experimental and numerical FWHM of OH and NO profiles was performed. Results showed that in premixed flames, all the mechanisms investigated were inadequate for predicting the extinction stretch rate, specifically for lean flames. In non-premixed flames, Okafor’s mechanism was accurately predicting the extinction stretch rate. For the FWHM analysis, the numerical mechanisms overpredicted both OH and NO apparition in the flame, except for Tian’s mechanism which underpredicted OH apparition. GRI Mech 3.0 performed well for small quantities of ammonia but failed to reproduce the pure ammonia case. Okafor’s and UCSD mechanisms gave better predictions of experimental trends, though overestimated both OH and NO apparition. In the FWHM analysis of both OH and NO, the lower R² values in the lean region suggest that the lean region should be the focus for mechanism improvement.

摘要

氨是一种很有前途的可持续燃料，然而，它的低反应性给工业应用带来了挑战。在这项研究中，氨/甲烷混合物被考虑用于预混和非预混逆流火焰。消光拉伸率是在广泛的氨/甲烷混合比范围内测量的，并与来自四种不同机制的一维数值结果进行比较。此外，对于逆流预混双火焰，基于 OH 和 NO 分布的实验和数值 FWHM 的比较进行了定量分析。结果表明，在预混火焰中，所有研究的机制都不足以预测熄灭拉伸率，特别是对于贫火焰。在非预混火焰中，奥卡福的机制准确地预测了熄灭拉伸率。对于 FWHM 分析，数值机制高估了火焰中 OH 和 NO 的出现，除了 Tian 的机制低估了 OH 的出现。GRI Mech 3.0 在处理少量氨时表现良好，但无法重现纯氨情况。Okafor 和 UCSD 机制对实验趋势给出了更好的预测，尽管高估了 OH 和 NO 的出现。在 OH 和 NO 的 FWHM 分析中，较低的贫区域的R ²值表明贫区域应该是机制改进的重点。