Development of combustion diagnostics: LII for soot measurement and WMS for gas-phase analysis

Laser-Induced Incandescence (LII) has recently emerged as an attractive alternative technique for soot volume fraction measurements with higher spatial and temporal resolution than the traditional light extinction technique. The rapid laser heating of soot particles is also thought to cause morphological changes to the soot particles. Thus, a detailed analysis was required to determine the influence of excitation fluence levels on accurate interpretation of the resulting LII. A series of double-pulsed LII experiments were performed over a wide range of excitation fluence levels wherein two identical laser pulses heated the same soot particles in a laminar diffusion flame. The resulting intensity profiles from both pulses were compared to an independent measurement of soot volume fraction to determine the most appropriate fluence levels.; The use of LII as a measurement of soot volume fraction requires accurate calibration of the LII intensities. There are inherent flaws in the traditional methods of calibration of LII signals. Therefore, a calibration and correction technique that requires only a simultaneous single line-of-sight light extinction measurement has been developed. This novel technique can be applied to transient axisymmetric flames for which full-field light extinction calibration cannot be performed. This technique has been applied for calibration and correction in a laminar ethene diffusion flame.; Simultaneous 2-dimensional LII and LIF (laser-induced fluorescence) measurements were performed in laminar diffusion flames using selective gating, incident laser intensity, and detection spectrum. The spatially defined regions of various-sized PAH molecules and carbonaceous soot has improved the understanding of soot formation in diffusion flames. This analysis helped identify the region soot precursor particle formation. Subsequent thermophoretic sampling and TEM analysis was performed to confirm the existence of these particles.; Historically, measurements of the burning rate and flame diameter have served a useful purpose in testing the early theoretical predictions of droplet combustion. However, the advent of refined droplet combustion models required a more sophisticated experimental measurements to validate these models and/or guide their further development. To this end, a wavelength modulation spectrometer was used to measure water concentration and temperature in microgravity methanol flames. Measurements were compared to model predictions of the Princeton CRFM model. These experiments represent the first spatially-resolved temperature and major species measurements for droplet combustion under microgravity conditions.