Zhu Denghao, Ruwe Lena, Schmitt Steffen, Shu Bo, Kohse-Höinghaus Katharina, Lucassen Arnas
Department of Physical Chemistry, Physikalisch-Technische Bundesanstalt (PTB), 38116 Braunschweig, Germany.
Department of Fundamentals of Explosion Protection, Physikalisch-Technische Bundesanstalt (PTB), 38116 Braunschweig, Germany.
J Phys Chem A. 2023 Mar 16;127(10):2351-2366. doi: 10.1021/acs.jpca.2c07784. Epub 2023 Mar 6.
Ammonia (NH) is a promising fuel, because it is carbon-free and easier to store and transport than hydrogen (H). However, an ignition enhancer such as H might be needed for technical applications, because of the rather poor ignition properties of NH. The combustion of pure NH and H has been explored widely. However, for mixtures of both gases, mostly only global parameters such as ignition delay times or flame speeds were reported. Studies with extensive experimental species profiles are scarce. Therefore, we experimentally investigated the interactions in the oxidation of different NH/H mixtures in the temperature range of 750-1173 K at 0.97 bar in a plug-flow reactor (PFR), as well as in the temperature range of 1615-2358 K with an average pressure of 3.16 bar in a shock tube. In the PFR, temperature-dependent mole fraction profiles of the main species were obtained via electron ionization molecular-beam mass spectrometry (EI-MBMS). Additionally, for the first time, tunable diode laser absorption spectroscopy (TDLAS) with a scanned-wavelength method was adapted to the PFR for the quantification of nitric oxide (NO). In the shock tube, time-resolved NO profiles were also measured by TDLAS using a fixed-wavelength approach. The experimental results both in PFR and shock tube reveal the reactivity enhancement by H on ammonia oxidation. The extensive sets of results were compared with predictions by four NH-related reaction mechanisms. None of the mechanisms can well predict all experimental results, but the Stagni et al. [ , , 696-711] and Zhu et al. [ , , 115389] mechanisms perform best for the PFR and shock tube conditions, respectively. Exploratory kinetic analysis was conducted to identify the effect of H addition on ammonia oxidation and NO formation, as well as sensitive reactions in different temperature regimes. The results presented in this study can provide valuable information for further model development and highlight relevant properties of H-assisted NH combustion.
氨（NH₃）是一种很有前景的燃料，因为它不含碳，且比氢气（H₂）更易于储存和运输。然而，由于NH₃的点火性能相当差，技术应用中可能需要诸如H₂这样的点火增强剂。纯NH₃和H₂的燃烧已得到广泛研究。然而，对于这两种气体的混合物，大多仅报道了诸如点火延迟时间或火焰速度等全局参数。具有广泛实验物种分布的研究很少。因此，我们在活塞流反应器（PFR）中于0.97巴压力下、750 - 1173 K温度范围内，以及在激波管中于平均压力3.16巴、1615 - 2358 K温度范围内，对不同NH₃/H₂混合物的氧化相互作用进行了实验研究。在PFR中，通过电子电离分子束质谱法（EI - MBMS）获得了主要物种随温度变化的摩尔分数分布。此外，首次将扫描波长法的可调谐二极管激光吸收光谱（TDLAS）应用于PFR以定量一氧化氮（NO）。在激波管中，也使用固定波长方法通过TDLAS测量了时间分辨的NO分布。PFR和激波管中的实验结果均揭示了H₂对氨氧化的反应性增强作用。将大量实验结果与四种与NH₃相关的反应机理的预测结果进行了比较。没有一种机理能够很好地预测所有实验结果，但Stagni等人[ , , 696 - 711]和Zhu等人[ , , 115389]的机理分别在PFR和激波管条件下表现最佳。进行了探索性动力学分析，以确定添加H₂对氨氧化和NO形成的影响，以及不同温度区域中的敏感反应。本研究给出的结果可为进一步的模型开发提供有价值的信息，并突出H₂辅助NH₃燃烧的相关特性。
