Natural parameterizations of flame structure and heat release in lean premixed /air combustion

In reduced-order modeling of premixed combustion, a major concern is whether chemistry submodels capture flame characteristics over a broad range of mixture stoichiometries and reactant temperatures. In order to adapt to local temperature level and stoichiometry, models require a suitable parameterization. Post-processing of a large database of adiabatic laminar flame simulations reveals that characteristic temperatures within premixed flames can be collapsed to self-similar structures throughout the lean and ultra-lean premixed regime. The collapse depends on the parameterization, where adiabatic flame temperatures T ad and stoichiometry Φ are identified as natural primary and secondary parameters, respectively. Furthermore, parameterizations of chemical source terms are superior to parameterizations of species profiles, as they allow for a differentiation of chemical processes from transport processes. A comparison of flame characteristics at low and high T ad illustrates that reaction pathways and resulting contributions to the heat release by individual reactions shift according to the temperature level, whereas flames with comparable T ad have similar flame structures that are almost independent of initial temperatures and stoichiometries.