Strained Propane-Air Flames With Detailed and Reduced Kinetic Schemes

The study of strained flames is of great interest for turbulent combustion modelling. The structure and properties of these flames are usually determined with either very simple but unrealistic one-step or modeled multiple-step kinetics or with large detailed chemical mechanisms. Recent studies initiated by Peters indicate that it may be possible to employ reduced mechanisms and still obtain accurate solutions. It is our objective to evaluate this approach in the context of propane-air flames. The reduced scheme of Peters et al. is first tested. A systematic analysis of the successive steps leading to reduced scheme is conducted. An augmented reduced mechanism which contains new species OH and O and involves additional equilibrium reactions for H₂, O₂, and CO₂is proposed. All the computations are compared with respect to solutions obtained with an initial complex scheme due to Warnatz. The results obtained at atmospheric pressure are generally satisfactory. It is observed that the differences between the augmented reduced mechanism and the complex scheme vary with the parameters such as equivalence ratio and pressure. Our reduced scheme comes closest to the complex scheme for rich conditions while the reduced mechanism of Peters is more appropriate for lean flames. As pressure is increased, the results differ more markedly from the complex scheme. While flame structures are still well predicted, the flame stand off distance is not well retrieved and as a consequence the crititcal extinction value of the strain rate is not very accurate.