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 mm 3 ) 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