Development of Laser-induced Breakdown Spectroscopy for Multiple Parameter Measurements in Sooting Flames

该项目的目的是发展激光诱导击穿光谱（LIBS），作为实验测定烟尘火焰中温度和化学成分等多种参数的工具。当LIBS应用于气溶胶，如烟熏火焰时，有许多干扰信号。纳米粒子及其聚集体的存在导致激光通过米氏散射和瑞利散射产生显著的弹性散射。此外，粒子可能会吸收激光辐射，从而被加热到高温，从而导致激光诱导白炽（LII）的发射。此外，可以有荧光信号的燃烧中间体和激光产生的物种。因此，为了使LIBS成为调查煤烟火焰的合适诊断工具，必须开发一种策略，允许从推断中区分LIBS信号。为此，需要将各种实验方法和数据评价方法进行组合和系统测试。实验将比较时间积分信号和时间分辨信号的记录。气溶胶中LIBS的另一个挑战是粒子降低了击穿阈值，即诱导击穿所需的最小激光脉冲能量。因此，粒子对等离子体形成和行为的影响需要被理解和预测，以便开发一种可重复的LIBS技术来熏烟火焰。该项目旨在发展对相关过程的基本理解，这些过程与使用LIBS作为熏烟火焰的分析方法有关。一个预测模型将从系统的实验和理论考虑发展。这将构成建立LIBS的基础，使其成为一种多参数测量烟尘火焰的工具。在这个项目中，将开发一种实验方法和数据评估策略的适当组合。

The aim of the project is to develop laser-induced breakdown spectroscopy (LIBS) as a tool for the experimental determination of multiple parameters such as temperature and chemical composition in sooting flames. When LIBS is applied to aerosols like sooting flames, there are a number of interfering signals. The presence of nanoparticles and their aggregates causes significant elastic scattering of laser light via Mie- and Rayleigh scattering. In addition, the particles may absorb the laser radiation and thus be heated to high temperature, which leads to the emission of laser-induced incandescence (LII). Furthermore, there can be fluorescence signals of combustion intermediates and laser-generated species. Hence, in order to make LIBS a suitable diagnostic tool for the investigation of sooting flames, a strategy must be developed that allows distinguishing the LIBS signal from the inferences. For this purpose, various experimental approaches and data evaluation methods need to be combined and tested systematically. Experimentally, the recording of time-integrated and time-resolved signals will be compared. Another challenge for LIBS in aerosols is that the particles reduce the breakdown threshold, i.e. the minimum laser pulse energy required to induce a breakdown. Therefore, the influence of the particles on the plasma formation and behavior need to be understood and predictable in order to develop a reproducible LIBS technique for sooting flames. This project aims at developing a fundamental understanding of the involved processes that are relevant for using LIBS as an analytical method in sooting flames. A predictive model will be developed from systematic experiments and theoretical considerations. This will form the basis for establishing LIBS as a tool for multiple parameter measurements in sooting flames. Within this project, a suitable combination of an experimental method and a strategy for data evaluation will be developed.