Optical Diagnostics Applied to Quantitative Characterization of Coflow Laminar Diffusion Flames in Microgravity and Normal Gravity

摘要

Building on the work previously done in our laboratory, this dissertation extends the use of well-established optical techniques and introduces newly developed ones for the quantification of coflow laminar diffusion flame physical and chemical properties, as well as for the characterization of reactive and non-reactive flows.;Single-photon and two-photon laser-induced fluorescence was used to quantify and map the two-dimensional distributions of nitric oxide and carbon monoxide concentrations in steady and time-varying nitrogen-diluted methane flames.;The signal-to-noise ratio of flame temperature and soot volume fraction results was improved with the adaptation and use of high dynamic range imaging. This new approach was successfully applied to normal gravity and microgravity coflow diffusion flames and allowed for a more complete use of partially saturated images that populate microgravity image databases. The use of high dynamic range and time-resolved averaging was investigated and successfully extended to the measurements of reactive and non-reactive unsteady flows using Rayleigh scattering, with the aim of increasing the result's signal-to-noise ratio.;As part of an ongoing research on microgravity flames and a collaboration with NASA, a consumer camera was used for the quantitative evaluation of CH* concentration in normal and microgravity coflow flames and, thanks to complementing numerical results. CH* chemiluminescence was related to flame heat release rate.;Nitrogen-diluted methane flames were investigated as a function of ambient pressure and fuel dilution, and the results compared with numerical predictions, as a way to validate computational models applied to highly diluted and heavily sooty flames.;Demosaicing algorithms were implemented for the improvement of image spatial resolution and measurement accuracy. and their application tested for the analysis of the Advanced Combustion via Microgravity Experiments (ACME) campaign's images. The flight and ground units of the ACME coflow burners were fully characterized in normal gravity, and the ACME imaging system was calibrated to be used for quantitative imaging experiments.