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

该项目的目的是开发激光诱导击穿光谱(LIBS)作为一种工具，用于实验确定煤烟火焰中的多个参数，如温度和化学成分。当LIBS应用于像煤烟火焰这样的气溶胶时，会有许多干扰信号。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，颗粒会吸收激光辐射，从而被加热到高温，从而导致激光诱导白炽光(LII)的发射。此外，还可能存在燃烧中间体和激光生成物种的荧光信号。因此，为了使LIBS成为研究煤烟火焰的合适诊断工具，必须开发一种策略来区分LIBS信号和推论。为此，需要将各种实验方法和数据评估方法结合起来，进行系统的测试。在实验上，将对时间积分信号和时间分辨信号的记录进行比较。气溶胶中LIBS的另一个挑战是粒子降低击穿阈值，即诱导击穿所需的最小激光脉冲能量。因此，需要了解和预测粒子对等离子体形成和行为的影响，以便开发一种可重复使用的LIBS技术来烟化火焰。本项目旨在对使用LIBS作为分析方法在灭火方面相关的相关过程有一个基本的了解。预测模型将从系统的实验和理论考虑中开发出来。这将为建立LIBS作为在煤烟火焰中进行多参数测量的工具奠定基础。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.