Premixed flame heat release-based optimum global single-step chemistry for H$$_2$$, CH$$_4$$, and C$$_3$$H$$_8$$ mixtures with air

Abstract

Despite the significant development of comprehensive detailed chemical kinetics mechanisms for combustion simulation in the past decades, reduced descriptions of the chemical process still enable engineering and direct numerical simulations. This work proposes a new formulation for the heat release rate of laminar premixed flame which extends the classical one-step Arrhenius global kinetics using a kinetically controlled assumption for the scalar governing the final reaction steps. The proposed methodology considers that the heat release rate as a function of temperature is known and obtained via a freely propagating laminar premixed flame model together with various detailed chemical kinetics mechanisms. The resulting formulation involves three free parameters, one of which is the Zel'dovich number, whereas the new ones characterize the final heat release stages. The proposed formulation is characterized for H 2 , CH 4 and C 3 H 8 mixtures with air and compared to several detailed chemical mechanisms, exhibiting errors between 6 % and 15 % for the first of these and smaller than 6 % for the hydrocarbons. The three free parameters are determined for a range of equivalence ratios and seem to be mixture properties. In particular, the Zel'dovich number exhibits a minimum around stoichiometry. The hydrocarbons fuels are also characterized when diluted by CO 2 , which is motivated by its presence in Brazilian pre-salt oil wells. The new free parameters are not influenced by dilution, whereas the Zel'dovich number is found to increase.