Laser-Induced Fluorescence (LIF) is an essential optical diagnostic technique for the high-resolution and low-uncertainty measurement of combustion species concentration in a variety of applications and conditions. Two different calibration techniques are explored in this study to obtain quantitative Nitric Oxide (NO) concentration measurements in flames. The first technique, the most employed in the literature, uses the extrapolation of the fluorescence signal from seeded to nascent NO and is only valid under negligible NO reburn conditions. The second technique uses the optical calibration of the experimental setup to relate it to a modelled LIF signal and can be applied regardless of NO reburn. Both of these techniques are explored under two different assumptions: constant and non-constant interfering LIF signal on the NO absorption spectrum. While the former is most often used in the literature, the latter is necessary when the LIF signal from interfering species cannot be distinguished from the NO-LIF signal, especially in high pressure conditions. Hence, a total of four techniques are presented in this work and are found to be in excellent agreement when performed in different flame conditions. The calibration techniques are applied to three lean, atmospheric, laminar, premixed, methane-air flames to explore their field of applicability. Specifically, the study explores the relevance of the techniques in reburn conditions, which occur mostly in high pressure, rich, highly-seeded, or NH3-containing flames. This study aims to offer the reader a portfolio of calibration techniques to use according to the conditions in which they need to be applied. While this study was carried out measuring NO concentration in a stagnation flame burner, the concepts and equations presented can be transposed to the measurement of other species and to other experimental configurations.

中文翻译：

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使用激光诱导荧光进行定量 NO 测量的校准技术


激光诱导荧光 （LIF） 是一种重要的光学诊断技术，用于在各种应用和条件下对燃烧物质浓度进行高分辨率和低不确定性测量。本研究探讨了两种不同的校准技术，以获得火焰中一氧化氮 （NO） 浓度的定量测量值。第一种技术是文献中最常用的技术，它使用荧光信号从种子到新生 NO 的外推，并且仅在可忽略不计的 NO 再燃烧条件下有效。第二种技术使用实验装置的光学校准将其与建模的 LIF 信号相关联，并且无论是否 NO reburn 都可以应用。这两种技术都是在两个不同的假设下探索的：NO 吸收光谱上的恒定和非恒定干扰 LIF 信号。虽然前者在文献中最常使用，但当来自干扰物质的 LIF 信号无法区分与 NO-LIF 信号时，尤其是在高压条件下，后者是必需的。因此，这项工作中总共提出了四种技术，并且在不同的火焰条件下进行时发现它们非常一致。校准技术应用于三种稀薄、大气、层流、预混合、甲烷-空气火焰，以探索其适用范围。具体来说，该研究探讨了这些技术在再燃烧条件下的相关性，再燃烧条件主要发生在高压、浓烈、高度种子或含有 NH3 的火焰中。本研究旨在为读者提供校准技术组合，以便根据需要应用它们的条件进行使用。 虽然这项研究是在停滞火焰燃烧器中测量 NO 浓度进行的，但所提出的概念和方程可以转移到其他物质和其他实验配置的测量中。