Homogeneous Microcombustion Studies: Progress and Observations

Mark A. Shannon James W. Bayne Professor of Mechanical Engineering Department of Mechanical Science and Engineering University of Illinois at Urbana-Champagne Urbana IL, 61801-2906 ABSTRACT:In the past few years, there has been an intense interest in building very small engines, power plants, and high temperature microchemical reactors, all running on the combustion of hydrocarbon fuels (due to their high inherent energy densities). While most systems employ catalytic and heterogeneous combustion processes, we wished to create and study high-temperature flames confined within burners with the smallest gap below 1 mm in length. The problem we immediately confronted is that flames either could not be created within narrow confined structures, or quenched quickly, similar to that which occurs in flame arrestors. We hypothesized that if we could have hot enough walls with low enough radical recombination probabilities, we could create and sustain homogeneous combustion in burners with sub-millimeter gaps. Therefore, we investigated a number of different wall materials and burner configurations, and found that flames of hydrogen, methane, propane, butane, and acetylene mixed with oxygen can be sustained in cavities as small as 100 microns, provided that the walls are sufficiently "quenchless." In addition, we have observed unusual flame structures at this scale, and flame dynamics that strongly vary with changes in temperature profiles. Homogeneously burning hydrocarbons in air at this scale has proved to be more difficult, requiring even higher wall temperatures and better thermal management. In this talk, I will present the experiments that we have conducted towards developing microcombustion-based systems, some of the observations I find interesting, what we now know is happening within the structures, and the many open questions that remain to be answered (hopefully!) by many of the excellent researchers working in combustion studies throughout the U.S. and world.

Location: Stauffer Science Lecture Hall, Rm 102

Audiences: Everyone Is Invited

Contact: April Mundy