Bio-butanol Fuel Utilization Technologies: Electrostatic Sprays, Diffusion Flames and Kinetic Modeling 2011-01-0619

Butanol produced from agricultural sources is emerging as a potentially renewable bio-fuel. In this work, three bio-butanol fuel utilization technologies were considered to evaluate its potential: Electrostatic sprays, non-premixed flames and kinetic modeling. Butanol electrospray phenomenology was investigated through high-speed visualization and compared with the corresponding electrosprays of ethanol and heptane. Electrospray structure was probed using Phase Doppler Anemometry and both droplet size and velocity measurements were obtained for sprays of the three fuels under consideration. Particular emphasis was placed on the determination of the dependence of droplet size and velocity on mass flow rate and applied electric field. These results indicated an unstable, and polydisperse electrospray behavior and secondary droplet break-up due to high Weber numbers was investigated. Non-premixed flames were studied in a counter-flow burner configuration. Major combustion species were measured using line Raman imaging and K-type thermocouples were used in order to perform temperature scans across the flame. Also, extinction strain rates were measured as a function of overall stoichiometry. Butanol flames were compared with flames of methane (which is not oxygenated) as well as ethanol which is a currently widely employed bio-fuel and a butanol-methane mixture. Particular emphasis was placed on flames of the same heating value and equivalence ratio. It was shown that butanol flames could sustain higher strain rates at extinction than ethanol flames but significantly smaller than methane flames. Kinetic modeling was performed in a zero-dimensional piston-cylinder assembly and a MATLAB code was used in order to solve the energy conservation and species equations. Pressure and temperature results were computed for stoichiometric conditions as a function of time, along with major and radical species concentrations. Similar results were obtained for ethanol and n-heptane for the purpose of comparison with butanol.