Theoretical and experimental studies on mesoscale flame propagation and extinction

Mesoscale flame propagation and extinction of premixed flames in channels were studied theoretically and experimentally. The wall flame interaction led to multiple flame regimes and extinction limits. With the decrease in channel width or equivalence ratio, there existed two distinct flame regimes, a fast flame regime, and a slow flame regime. The existence of the new flame regime and its extended flammability limit rendered the classical quenching diameter inapplicable. The dependence of flame speed on channel width and equivalence ratio was non-linear and was strongly affected by the flow rate and Nusselt number. By appropriately choosing the wall thermal properties and heat capacity, a flame in a mesoscale channel could propagate faster than the adiabatic flame. Numerical simulation with detailed chemistry and an experimental study using propaneair flames successfully demonstrated the existence of the multiple flame regimes and the non-linear dependence of the flame speed on equivalence ratio. This non-linear dependence was strongly affected by flow speed, Nusselt number, and wall heat conductivity. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).