Abstract. Field measurement of flare emissions in turbulent flare plumes is an important and complex challenge. The simplest approaches necessarily assume that combustion species are spatially and/or temporally correlated in the plume, such that simple species ratios can be used to close a carbon balance to calculate species emission rates (i.e. emission factors) and flare conversion efficiency. This study examines the veracity of this assumption and the associated implications for measurement uncertainty. A novel tunable diode laser absorption spectroscopy (TDLAS) system is used to measure the correlation between H₂O and black carbon (BC) volume fractions in the plumes of a vertical, turbulent, non-premixed, buoyancy-driven lab-scale gas flare. Experiments reveal that instantaneous, path-averaged concentrations of BC and H₂O can vary independently and are not necessarily well-correlated over short time intervals. The scatter in the BC / H₂O ratio along a path through the plume was well beyond that which could be attributed to measurement uncertainty and was asymmetrically distributed about the mean. Consistent with previous field observations, this positive skewness toward higher BC / H₂O ratios implies short, localized, and infrequent bursts of high BC production, that are not well-correlated with H₂O. This demonstrates that the common assumption of fixed species ratios is not universally valid, and measurements based on limited samples, short sampling times, and/or limited spatial coverage of the plume could be subject to potentially large added uncertainty. For BC emission measurements, the positive skewness of the BC / H₂O ratio also suggests that results from small numbers of samples are more likely to be biased low. However, a bootstrap analysis of the results shows how these issues should be easily avoidable with sufficient sample size and provides initial guidance for creating sampling protocols for future field measurements using analogous path-averaged techniques.

中文翻译：

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湍流火炬羽中的物种相关性测量：现场测量的注意事项

摘要。湍流火炬烟流中火炬排放的现场测量是一项重要而复杂的挑战。最简单的方法必须假定燃烧物质在羽流中在空间和/或时间上相关，因此可以使用简单的物质比率来关闭碳平衡以计算物质的排放速率（即排放因子）和火炬转化效率。这项研究检验了该假设的准确性以及对测量不确定度的相关影响。一种新型的可调二极管激光吸收光谱（TDLAS）系统用于测量H ₂之间的相关性垂直，湍流，非预混合，浮力驱动的实验室规模火炬烟羽中的O和黑碳（BC）体积分数。实验表明，瞬时，路径平均的BC和H ₂ O浓度可以独立变化，并且不一定在短时间间隔内具有良好的相关性。沿羽流路径的BC / H ₂ O比值的散布远超出可归因于测量不确定性的散布，并且围绕平均值不对称分布。与以前的实地观察一致，这种向较高的BC / H ₂ O比值的正偏态意味着高BC产生的短暂，局部和偶发，这与H ₂没有很好的相关性O.这表明固定物种比率的普遍假设并非普遍有效，并且基于有限的样本，较短的采样时间和/或有限的羽状空间覆盖范围进行测量可能会带来较大的不确定性。对于BC排放测量，BC / H ₂ O比值的正偏度也表明，少量样品的结果更可能被偏低。但是，对结果进行的自举分析表明，在具有足够的样本量的情况下应如何轻松避免这些问题，并为使用类似路径平均技术为将来的现场测量创建采样协议提供了初步指导。