ChBE Seminar Series: Christopher Cadou
Tuesday, October 13, 2009
11:00 a.m.-12:15 p.m.
Room 2110, Chemical and Nuclear Engineering Bldg.
Professor Sheryl Ehrman
Miniaturizing Combustion-Based Heat Engines: Challenges and Opportunities
Presented by Christopher Cadou
Associate Professor, Department of Aerospace Engineering
University of Maryland
Man's ability to exploit the advantages of ever smaller electronic devices and machines is increasingly limited by his ability to power them. Liquid hydrocarbon fuels are an attractive means of storing energy in miniature systems because of their high energy densities compared to alternate means like batteries. However, constructing practical (i.e., efficient) heat engines for converting this stored chemical potential energy to useful work becomes increasingly difficult as the size of the system is reduced. One reason is that losses scale with surface to volume ratio which increases as the size of the system is reduced. Another is that flames stabilized in small passages (i.e., passages with dimensions of the order or smaller than the freely propagating flame thickness) behave differently than conventional-scale flames because of strong thermal coupling between the reacting gas and the combustor structure. This talk will summarize recent research aimed at answering two questions that are important for miniaturizing combustion-based heat engines: 1) What is different about micro-scale vs. conventional-scale combustion? 2) What is the minimum size of a "practical" combustion device? These questions will be answered using first-principles analyses of flames stabilized in channels, numerical simulations, and experiments.