Intrinsic low-dimensional manifolds of strained and unstrained flames

The intrinsic low-dimensional manifolds of strained and unstrained premixed CH4-air flames are analysed. We show that in typical flame applications only a small domain of the state space is accessed. This is found by simple one-dimensional flame computations using different strain rates. Secondly, in the different flame regions a different number of time scales is rate limiting. This means that in different regions there exist different numbers of relaxed modes corresponding to equilibration processes (species in quasi-steady states, reactions in partial equilibrium). It is shown that even in critical zones of the flame, such as the pre-heating zone, a considerable number of time scales can be decoupled from the equation system, guaranteeing an accurate description of the flame front by automatically simplified kinetics.

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