Stability of rich laminar hydrogen-air flames in a model with detailed transport and kinetic mechanisms

The diffusive-thermal stability of rich hydrogen-air combustion waves under ambient and elevated pressures is investigated numerically. The model includes the detailed transport and detailed kinetic mechanism of hydrogen oxidation. Three different kinetic mechanisms are employed: truncated GRI3.0, Warnatz and San-Diego. The critical conditions for the onset of pulsating instabilities are found in the equivalence ratio vs pressure parameter plane in each case. It is demonstrated that the boundaries of stability differ significantly depending on the specific kinetic mechanism. This suggests that finding the critical parameters for the onset diffusive-thermal instabilities experimentally offers a new way for the verification of kinetic mechanisms. A sensitivity analysis is undertaken and allows to identify the five key elementary reactions which are shown to be the same for both stationary and non-stationary flames thus implying that a successful reduction of the reaction kinetics is possible for non-stationary combustion regimes.