High Temperature Microsystems: Recent Advances in Microcombustion

Recent times have seen a growing interest in developing next generation energy systems and devices for building very small engines, power plants, and high temperature microchemical reactors, all running on the combustion of hydrocarbon fuels due to their inherently high energy densities. In particular, much interest lies in creating small-scale fuel reformers to produce hydrogen and/or syngas for fuel cells. Over the past decade, most microscale combustion systems that have been developed employ catalytic and heterogeneous combustion processes. In this paper, discussion towards the development of sub-millimeter or microscale homogeneous combustion systems operating at high temperatures, which can approach adiabatic flame temperatures, to achieve potentially high power densities (∼ 10³ W/cm³) will be presented. Results from previous work are summarized to discuss the role and importance of surfaces in creating and sustaining homogeneous flames in narrow, confined structures with channel dimensions as small as 100 μm. At these length scales, some unusual flame structures and flame dynamics have been observed that vary strongly with changes in boundary conditions. This paper reviews recent experimental and computational data, observations of flame structure and dynamics, and discusses several open questions that remain to be answered.