Exothermic reactions in C2 hydrocarbon flames

Premixed stoichiometric flames of acetylene, ethylene, and ethane with air were studied using a chemical scheme composed of 82 pairs of elementary reactions to demonstrate the dependence of the propagation mechanisms of C2 hydrocarbon flames on the heat release distribution. The general role of heat release distribution through flames was depicted through an analytical treatment of the governing equations with the thermal properties of the gases being constant and the temperature profile given by an appropriate function of the flame position. The results showed that the amount of heat released by chemical reactions at low-temperature regions of a flame is of fundamental importance for its propagation and that the main trigger of exothermic reactions at those zone is hydrogen atoms, which diffuses from the flame front. In the acetylene flame reactions, consuming hydrogen atoms at the low-temperature region yielded all the heat released at this zone. Heat release distribution extended down to low-temperature regions led to large burning velocities although the amount of heat released at each position was small.