Measurements of soot/black carbon emissions via optical observations of atmospheric plume transmittance require a correction to account for bias in perceived plume brightness due to inscatter of ambient light. The ability to accurately correct for inscattering is hampered, however, by the potential for multiple scattering (MS) within the plume, which cannot be directly considered without detailed knowledge of the turbulent plume's structure. MS is thus oft-ignored within such measurement techniques, resulting in an inherent upward bias in calculated emissions. In this work, Monte Carlo “ray tracing” (MCRT) analyses for realistic lines-of-sight through large-eddy simulated, soot-laden atmospheric plumes of gas flares were used as case study data for analysis of MS effects. Through a reverse MCRT procedure, a remarkably simple yet accurate model was derived that relates the quantity of inscattered light under MS conditions to an estimate assuming single-scattering. Case study data from previous field measurements of gas flares using the sky-LOSA technique demonstrate that neglecting MS effects can bias reported soot emission rates by up to and exceeding one-quarter of typical measurement uncertainties. Coupling this model with an additional procedure to correct for minor model biases allows the complex influence of multiple scattering to be directly and accurately considered in optical measurements of soot emissions.

通过光学观察大气羽流透射率来测量烟灰/黑碳排放量需要进行校正，以解决由于环境光的散射而导致感知到的羽流亮度出现偏差的问题。但是，由于羽流内部可能发生多次散射（MS），因此妨碍了准确校正散射的能力，如果不详细了解湍流羽流的结构，就无法直接考虑这种散射。因此，在这样的测量技术中，MS常常被忽略，导致计算的排放量固有的向上偏差。在这项工作中，蒙特卡罗“射线追踪”（MCRT）分析通过大涡流模拟的，充满烟尘的瓦斯火炬烟气，获得了真实的视线，用作分析MS效果的案例研究数据。通过反向MCRT程序，推导了一个非常简单但准确的模型，该模型将MS条件下的散射光量与假设单散射的估计值相关联。以前使用sky-LOSA技术进行的火炬现场测量的案例研究数据表明，忽略MS效应可以使所报告的烟尘排放速率偏离典型测量不确定度的四分之一甚至四分之一以上。将此模型与其他程序耦合以校正较小的模型偏差，可以在烟尘排放的光学测量中直接准确地考虑多重散射的复杂影响。以前使用sky-LOSA技术进行的火炬现场测量的案例研究数据表明，忽略MS效应可以使所报告的烟尘排放速率偏离典型测量不确定度的四分之一甚至四分之一以上。将此模型与其他程序耦合以校正较小的模型偏差，可以在烟尘排放的光学测量中直接且准确地考虑多重散射的复杂影响。以前使用sky-LOSA技术进行的火炬现场测量的案例研究数据表明，忽略MS效应可以使所报告的烟尘排放速率偏离典型测量不确定度的四分之一以上。将此模型与其他程序耦合以校正较小的模型偏差，可以在烟尘排放的光学测量中直接准确地考虑多重散射的复杂影响。