Laminar Burning Velocity of Methane/Air Mixtures and Flame Propagation Speed Close to the Chamber Wall

Abstract

Experimental studies on the laminar burning velocity (LBV) and the flame propagation speed close to the wall of premixed methane-air flames at a pressure of 1 bar and ambient temperature, for poor and rich mixtures, have been conducted and analyzed. The methane-air mixture LBV and flame propagation speed are studied in a constant volume combustion chamber with acrylic windows using the shadowgraph technique and a high-speed camera. The recorded images are analyzed using a Matlab script and both the system and the Matlab code have been validated against literature data. The results are in quite good agreement with available literature for LBV that shows its decreasing with pressure increase. For the flame propagation speed little literature has been found for validation but using a different set-up. The results show that the flame propagation speed decreases almost linearly except close to the wall where some oscillations are present, due to a combination of multiple phenomena such as compression and heating of the unburned mixture, a combination of radiative heat loss to the wall, flame curvature and flame stretch.