It is now recognized that chemical kinetic effects are indispensable to predictive analysis of complex combustion flows. Detailed models aimed at representing the underpinning chemical transformations have turned out to be rather too large for realistic implementation in computational combustion. In some cases, such models exhibit significant deviations in predictions of the properties of homogeneous reactors, posing a significant challenge to identification of sources of error, given the high degrees of freedom of typical models. Despite the complexity of the models, kinetically controlled combustion phenomena such as ignition, can be captured reasonably well by means of characteristic time scales that are representative of the relaxation of non-equilibrium chemical reactors toward new chemical equilibrium states.
This talk focuses on fuel ignition (oxidative) and pyrolysis (non-oxidative) kinetics with emphasis on their global time scales as a means of capturing the effects of various thermodynamic parameters on the dynamics of homogeneous reactors. The approach is extended to the extraction of such time scales from detailed kinetic models in a manner that sheds light on the controlling elementary kinetics as well as similarity and differences among various fuels. The focus of the current research is on biofuels (furans) in their pure form or blended with conventional fossil fuels. The competition between oxidative and pyrolysis kinetics in high-temperature combustion events is examined and used to suggest minimum modeling requirements for compact chemical kinetic models aimed at reducing the complexity of chemical kinetic models for practical transportation fuels. The shock tube experimental technique and mid infra-red laser absorption diagnostics are employed in the experimental characterizations.