Abstract Measurements of autoignition delay times of NH3 and NH3/H2 mixtures in a rapid compression machine are reported at pressures from 20–75 bar and temperatures in the range 1040–1210 K. The equivalence ratio, using O2/N2/Ar mixtures as oxidizer, varied for pure NH3 from 0.5 to 3.0; NH3/H2 mixtures with H2 fraction between 0 and 10% were examined at equivalence ratios 0.5 and 1.0. In contrast to many hydrocarbon fuels, the results indicate that, for the conditions studied, autoignition of NH3 becomes slower with increasing equivalence ratio. Hydrogen is seen to have a strong ignition-enhancing effect on NH3. The experimental data, which show similar trends to those observed previously by He et al. (2019) [28] , were used to evaluate four NH3 oxidation mechanisms: a new version of the mechanism described by Glarborg et al. (2018) [29] , with an updated rate constant for the formation of hydrazine, NH2 + NH2 (+M) = N2H4 (+M), and the literature mechanisms from Klippenstein et al. (2011) [30] , Mathieu and Petersen (2015) [25] , and Shrestha et al. (2018) [31] . In general, the mechanism from this study has the best performance, yielding satisfactory prediction of ignition delay times both of pure NH3 and NH3/H2 mixtures at high pressures (40–60 bar). Kinetic analysis based on present mechanism indicates that the ignition enhancing effect of H2 on NH3 is closely related to the formation and decomposition of H2O2; even modest hydrogen addition changes the identity of the major reactions from those involving NHx radicals to those that dominate the H2/O2 mechanism. Flux analysis shows that the oxidation path of NH3 is not influenced by H2 addition. We also indicate the methodological importance of using a non-reactive mixture having the same heat capacity as the reactive mixture for determining the non-reactive volume trace for simulation purposes, as well as that of limiting the variation in temperature after compression, by limiting the uncertainty in the experimentally determined quantities that characterize the state of the mixture.

中文翻译：

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高压下 NH3 和 NH3/H2 混合物自燃行为的实验和数值分析

摘要 在 20-75 bar 的压力和 1040-1210 K 的温度范围内，对快速压缩机中 NH3 和 NH3/H2 混合物的自燃延迟时间进行了测量。当量比，使用 O2/N2/Ar 混合物作为氧化剂, 纯 NH3 从 0.5 到 3.0 变化；在 0.5 和 1.0 的当量比下检查了 H2 分数介于 0% 和 10% 之间的 NH3/H2 混合物。与许多碳氢燃料相比，结果表明，对于所研究的条件，NH3 的自燃随着当量比的增加而变慢。氢气被认为对 NH3 具有很强的点火增强作用。实验数据显示出与 He 等人先前观察到的趋势相似的趋势。(2019) [28] 用于评估四种 NH3 氧化机制：Glarborg 等人描述的机制的新版本。(2018) [29] , 使用更新的肼形成速率常数，NH2 + NH2 (+M) = N2H4 (+M)，以及 Klippenstein 等人的文献机制。(2011) [30]、Mathieu 和 Petersen (2015) [25] 以及 Shrestha 等人。(2018) [31]。总的来说，这项研究的机制具有最好的性能，在高压（40-60 巴）下对纯 NH3 和 NH3/H2 混合物的点火延迟时间进行了令人满意的预测。基于现有机理的动力学分析表明，H2对NH3的助燃作用与H2O2的形成和分解密切相关；即使是适度的加氢也会将主要反应的性质从涉及 NHx 自由基的反应改变为主导 H2/O2 机制的反应。通量分析表明NH3 的氧化路径不受H2 添加的影响。