Measurements of laminar premixed methane-air flame thickness at ambient conditions

A new experimental data set for the flame thickness of laminar premixed methane-air flames at ambient conditions is presented. Prior to combustion the temperature and pressure of the premixed mixture were 298 K +/- 5 K and 100 kPa +/- 5 kPa, respectively. The fuel-air equivalence ratio was varied from 0.8 to 1.4 in 0.05 steps. The data were obtained using simultaneous imaging of the visible and Schlieren cones on the central axis of the symmetrical flame front of a non-cooled burner configuration. The data were analysed and the plane obtained from the Schlieren image corrected using a one-dimensional energy balance to obtain the position of the cold surface of the flame and hence allow determination of the flame thickness. The data presented agree within experimental errors with the limited existing published data. For the range of equivalence ratios studied, a second-order equation was fitted and presented for methane-air flames at atmospheric pressure and ambient temperatures.