This paper describes experimental observations of flame dynamics within an alumina non-premixed combustor with a sub-millimetre (0.75 mm) minimum size. These flame dynamics occur within a total combustor volume of 130 mm and are imaged through a sapphire window. The confined flames are surveyed using visual still-frames, high-speed flame imaging, measurement of external wall temperatures, and recordings of acoustic emissions from the combustor. The observed flame dynamics are characterised by an oscillating edge-flame that is anchored at the combustor inlet and is accompanied by ignition/extinction events leading to the eventual formation of a stable edge-flame and distinct cellular structures along the reaction channel. This paper investigates the unstable and unsteady flame dynamics within the non-premixed sub-millimetre combustors from ignition to the formation of stable flame structures.
Keywords: alumina Al2O3, microcombustion, edge flame, non-premixed combustors, flame cells, methane, instability, transient, flame structure, non-stabilised flames, combustion, flame dynamics, sub-millimetre combustors