Studies of combustion characteristics of biofuels in premixed and non-premixed flames

Currently, there is broad world interest in advancing the characterization, understanding, and use of biofuels, as they constitute an attractive alternative to reduce petroleum dependence. Additionally, biofuels are more environmentally friendly since their use results in lower greenhouse emissions. Biofuels include alcohols, ethers, esters, and other oxygenates produced from a variety of biological non-fossil fuel sources. The purpose of this investigation is to contribute toward the understanding of biofuel burning, and to evaluate the consequences of using these alternative, untested fuels on engine performance and the environment. In this study, the combustion characteristics of low molecular weight biofuels such as dimethyl ether (DME) as well as a saturated (methyl-butanoate) and an unsaturated (methyl-crotonate) C₄ methyl ester were investigated in the counterflow configuration. The experiments were conduced at ambient pressure and elevated temperatures over a wide range of fuel/oxidizer ratios. Fundamental flame properties such as laminar flame speeds and extinction limits were determined using digital particle image velocimetry and laser Doppler velocimetry. A number of recently developed kinetic mechanisms were tested against the experimental data and insight was provided into the controlling physico-chemical processes.