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）作为实验测定多个参数的工具，如温度和化学成分在烟灰火焰。当LIBS应用于气溶胶，如烟灰火焰，有一些干扰信号。纳米颗粒及其聚集体的存在通过米氏散射和瑞利散射引起激光的显著弹性散射。此外，颗粒可以吸收激光辐射，从而被加热到高温，这导致激光诱导白炽（LII）的发射。此外，可能存在燃烧中间体和激光生成物质的荧光信号。因此，为了使LIBS一个合适的诊断工具，调查的炭黑火焰，必须制定一项战略，允许区分LIBS信号的推论。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，将比较时间积分和时间分辨信号的记录。LIBS在气溶胶中的另一个挑战是颗粒降低击穿阈值，即诱导击穿所需的最小激光脉冲能量。因此，颗粒对等离子体的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技术用于烟灰火焰。该项目旨在对使用LIBS作为炭黑火焰分析方法的相关过程进行基本了解。预测模型将从系统的实验和理论的考虑。这将成为建立LIBS作为一种工具，在炭黑火焰多参数测量的基础。在这个项目中，将开发一种实验方法和数据评价战略的适当结合。

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.