The Computational Singular Perturbation/Perfectly Stirred Reactor Approach in Reduced Chemistry of Premixed Ethanol Combustion

Ethanol is a bio-fuel widely used in engines as a fuel or fuel additive. It is, in particular, attractive because it can be easily produced in high quality from renewable resources. Its properties are of interest in many fields, such as gas turbines applications as well as fuel cells. In the past decades, research in chemistry and engineering has put a lot of effort into a better understanding of its gas-phase chemical kinetic properties during combustion processes. This work describes a methodology to define an optimal expression of the reaction progress variable in the context of tabulated chemistry in laminar premixed combustion. The choice of the reaction progress variable is based on the investigation of the wide range of consumption rates of the species involved in the reaction. Two methods are used: the computational singular perturbation method and a sensitivity analysis of the time scales evaluated with a perfectly stirred reactor. The thermochemical databases computed with these techniques are compared in the cases of a freely propagating flame and a Bunsen flame, in the laminar premixed regime and under stoichiometric conditions. The influence of the chemical kinetics on the laminar flame speed is estimated from the results of the freely propagating flame. The case where the differences in the performance between the databases become more pronounced is the Bunsen flame, where some databases lead to a premature ignition prediction of the flame.