Structure of a Lean Laminar Hydrogen-Air Flame

Numerical simulations of flame structure and laminar burning velocity SL are performed for a lean (12%) hydrogen-air mixture under standard conditions. An analysis of the concentration profiles of intermediate species shows that a change in the kinetic mechanism that controls heat release dynamics occurs with increasing temperature. Thus, heat release in the flame consists of two stages. In the region of maximum temperature gradient, the concentrations of H2O2 and HO2 reach their peak values. The subsequent decrease in H2O2 and HO2 concentrations is accompanied by a concurrent increase in H, O, and OH concentrations. Variation of the rate constants for the reactions responsible for heat release results in changes in both temperature gradient and the value of SL. The value of SL is most sensitive to the reaction in which molecular hydrogen combines with hydroxyl radical to produce water vapor.