A Simple Model of Transient Thermal Flame Quenching

A simple analysis of transient thermal flame quenching at a cold wall is presented. A quenching Peclet number is derived and has the form of a sum of a constant and a simple function of adiabatic flame temperature, actual flame temperature, and wall temperature. Typical values of the quenching Peclet number are slightly less than the Peclet number corresponding to the preheating zone thickness. This implies that the values of the quenching Peclet number that have been proposed by other investigators, i.e., 30 to 60, are too high. A comparison of calculated and experimental values for quenching distance was made for a number of fuels. Calculated one wall quenching distances are smaller than experimentally obtained two wall quenching distances by a factor of 0.4 ∼ 0.5. The effect of wall material on flame quenching was examined and found to be of minor importance. The wall temperature does not increase appreciably during the quenching process and may be treated as constant.