Optical diagnostics to characterize the sooting propensity of biofuel-diesel diffusion flames

Alternative renewable biofuels can be promising in the transportation sector as the demand for energy increases while the world oil supplies decrease. The combustion of diesel and biofuel mixtures in a practical system is not only feasible but also favorable due to the lower emissions characteristics. The following thesis investigates and compares the soot emissions property of biofuels by blending 0%, 5%, 10%, 15%, 20%, and 25% by volume of soybean biofuel with Ultra Low Sulfur Diesel. Both classic smoke point measurements and more recently developed laser diagnostics are the main tools utilized to investigate the sooting propensity of biofuel-diesel laminar diffusion wick-fed flames. Following the ASTM D1322 standard, the maximum flame height at the smoke point condition for pure diesel is 18.5mm. As the biofuel concentration increases in the fuel mixture, the maximum flame height at the incipient sooting condition also increases. The maximum flame height observed for 25% mixture of biofuel is 23.5mm, which indicates that fuel mixtures with higher concentrations of biofuels have lower tendency to soot. Laser diagnostics including Laser-Induced Incandescence (LII) and Laser Light Extinction provide both qualitative soot distributions and soot volume fraction information, respectively. The LII signals show the greatest soot concentration zone for pure diesel fuel and the least for B20 blending ratio. Laser Light Extinction calibrations indicate that the maximum soot volume fraction obtained for diesel fuel is 12.26 ppm. While all experimental data are measured from a wick-fed diffusion flame, future works include investigating the emissions and combustion properties of biofuels using a counterflow flame configuration. The basic features, flow field properties, design, and assembly of the counterflow burner are also presented in the thesis.