Abstract

Laser-induced incandescence (LII) is an optical technique that is widely used for the in situ measurement of the soot volume fraction in flames. The low intensity of LII signals in low-sooting turbulent flames means that long camera acquisition times are needed to achieve sufficiently high signal-to-noise ratios. The direct application of auto-compensating LII (AC-LII) to infer the soot volume fraction from the measured LII signals can lead to large errors due to the significant decrease in the temperature of the soot particles over the duration of the camera gate. In order to reduce the measurement errors from AC-LII, we propose an improved approach in which the cooling of soot particles during the camera acquisition of LII signals is considered. The proposed methodology is applied to planar AC-LII measurements for the determination of soot volume fraction and primary particle diameter in a low-sooting turbulent flame, with the help of the open source LII software LIISim. This study represents the first application of planar AC-LII to a turbulent flame. A sensitivity analysis is also conducted in order to determine the main factors affecting the uncertainty of the proposed approach.

Copyright © 2021 American Association for Aerosol Research

摘要

激光诱导白炽度 (LII) 是一种光学技术，广泛用于原位测量火焰中的烟尘体积分数。低烟灰湍流火焰中 LII 信号的低强度意味着需要较长的相机采集时间才能实现足够高的信噪比。直接应用自动补偿 LII (AC-LII) 从测得的 LII 信号推断烟尘体积分数会导致很大的误差，因为在相机门的持续时间内烟尘颗粒的温度显着降低。为了减少 AC-LII 的测量误差，我们提出了一种改进的方法，其中考虑了相机采集 LII 信号期间烟尘颗粒的冷却。在开源 LII 软件 LIISim 的帮助下，所提出的方法应用于平面 AC-LII 测量，以确定低烟尘湍流火焰中的烟尘体积分数和初级粒子直径。这项研究代表了平面 AC-LII 在湍流火焰中的首次应用。还进行了敏感性分析，以确定影响所提出方法的不确定性的主要因素。

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