Flame dynamics and structure within sub-millimeter combustors

Non-premixed methane-oxygen flame dynamics and structures confined within an alumina combustor are described. Non-stabilized, transient flame dynamics and phenomena leading to the formation of a stable edge-like flame and distinct cellular structures that take place within combustor channels of dimensions 35 mm long, 5 mm wide, and 0.75 mm high (combustor volume ∼ 130 mm3) are discussed. These confined flames are surveyed by measuring the external wall temperatures, high-speed and still-frame visual flame imaging, recordings of emitted acoustics from the combustor, and capturing visible, CH*, and OH* chemiluminescence through a sapphire window. The observed dynamic flame structure is an oscillating edge-like flame accompanied by ignition-extinction events that precede the formation of a stable edge-like flame and flame cells in the reaction channel. The cellular flame structures in all cases exhibit a confined tribrachial structure with a folded or extinguished rich branch while the lean branch survives. © 2007 American Institute of Chemical Engineers AIChE J, 2007