# Piere Bouger, August Beer, And Laser Reflection Methods

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The light extinction method was developed based on the works of Piere Bouger, August Beer, and Johann Heinrich Lambert (1760). Bouger observed for the first time that the light intensity of a candle decreases when it passes trough a transparent medium and appointed the length and the medium property as the main parameter to explain the light extinction. The correlation of absorbance and light path was proposed by Lambert. Finally, Beer concluded that absorbance is also proportional to the concentration. Nowadays, the laser extinction measurement is a suitable tool to reliably measure the soot concentration. Laser extinction is the light intensity ratio measured before the probe volume and the intensity after. The volume fraction is a function …show more content…
Two diagnostics commonly applied in combustion are the Rayleigh and Mie scattering. When the incident light interacts with molecules and particulate-matter much smaller than the wavelength, Rayleigh scattering is produced. Mie scattering is also an elastic light scattering in case the particles are larger than the incident wavelength of light. Elastic light scattering (ELS) is a powerful technique to characterize nanoparticles. The particle morphology, such as aggregate size, gyration radius, and fractal dimension can be estimated by ELS \cite{Sorensen}. Many researchers have used ELS to determine the soot aggregate morphology in combustion processes \cite{Oltmann2010516, Oh1997937, …show more content…
Therefore, these parameters are also subject of investigation to improve the diagnostics. This thesis entails seven chapters. Chapter \ref{sootformation} briefly describes the background of soot formation, diffusion flame and counterflow flame. Chapter \ref{liigrund} presents the theoretical background of the measurement techniques used. In Chapter \ref{ch:LTT-HAB-Results}, the motivation of the experiment, the description of experimental setup, and experimental procedure are presented. In this chapter, the experiments include flame imaging, laser extinction, and TiRe-LII. The numerical simulation which is extensively described in Chapter \ref{liigrund} is applied to evaluate the experimental results. The prompt LII versus laser fluence is extensively studied. The correlation between prompt LII and soot volume fraction obtained by laser extinction is investigated. The results are discussed in detail at the end of the chapter. Chapter \ref{ch:Inertgas_Results} is dedicated to the investigation of the mitigation of soot inception by adding $N_2$, $Ar$ and $CO_2$ separately to the fuel supply. For this, laser edge extinction and slice method are introduced. Planar elastic light scattering (PELS), TiRe-LII, and two-color laser-induced incandescence

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