Ammonia (NH3) is regarded as an important NOx precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of ammonia, accurate in-situ detection of ammonia in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectral-resolved UV absorption cross sections of ammonia in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of ammonia were determined, and used for a calculation of the absorption cross section of ammonia at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 to 230 nm, where spectral structures of the A1A"2 âX1A'1 transition of ammonia in the umbrella bending mode, v2, were recognized. The absorption cross section was found to decrease at higher temperatures. For example, the absorption cross section peak of the (6, 0) vibrational band of ammonia decreases from ~2Ã10-17 to ~0.5Ã10-17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross section, in-situ nonintrusive quantification of ammonia in different hot gas environments was achieved with a detection limit varying from below 10 ppm to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of ammonia combustion process. The concentrations of NH3 and NO in the post flame zone of NH3-CH4-air premixed flames at different equivalence ratios were measured.

中文翻译：

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EXPRESS：高温下 NH3 的紫外线吸收截面，用于燃烧环境中氨的非侵入式定量检测

氨（NH3）被认为是一种重要的 NOx 前体，也是通过燃烧在能源利用中去除 NOx 的有效还原剂，它最近成为一种有吸引力的非碳替代燃料。为了更好地了解氨的热化学性质，需要在高温环境中准确地原位检测氨。紫外 (UV) 吸收光谱是一种可行的技术。为了实现定量测量，首次通过实验测量了 295 K 至 590 K 不同温度下热气环境中氨的光谱分辨紫外吸收截面。根据实验结果，确定了氨的振动常数，并用于使用 PGOPHER 软件计算 590 K 以上高温下氨的吸收截面。研究的紫外光谱覆盖了 190 到 230 nm 的波长范围，其中氨在伞形弯曲模式 v2 中的 A1A"2 ∷X1A'1 跃迁的光谱结构被识别。发现吸收截面在较高时减小例如，随着温度从 295 K 增加到 1570 K，氨的 (6, 0) 振动带的吸收截面峰从~2×10-17 减小到~0.5×10-17 cm2/分子。使用获得的吸收截面，随着温度从 295 K 增加到 1570 K，检测限从低于 10 ppm 到约 200 ppm 不等，实现了对不同热气环境中氨的原位非侵入式定量。定量测量应用于氨燃烧过程的实验研究. 测量了不同当量比的 NH3-CH4-空气预混火焰的后焰区中 NH3 和 NO 的浓度。