Chemical Kinetic Uncertainty Minimization through Laminar Flame Speeds of Mixtures of Air with C1-C4-Hydrocarbons

Performing high-fidelity simulations of complex reacting flows requires that the uncertainties associated with predictions of fundamental flame properties are characterized and minimized. Although the kinetics of C1-C4 hydrocarbon flames have been studied extensively in numerous past investigations, notable uncertainties exist. In the present study, the types of hydrocarbon fuels with the greatest impact on model uncertainty reduction are identified along with the attendant accuracy that is needed in flame measurements to facilitate better reaction model development. The results demonstrated that a reaction model constrained only by laminar flame speeds of methane/air flames reduces notably the uncertainty in the predictions of the laminar flame speeds of C3 and C4 alkanes, because the key chemical pathways of all of these flames are similar to each other. However, the uncertainty in the model predictions for flames of unsaturated C3-C4 hydrocarbons would remain to be significant without considering their laminar flames speeds in the constraining target data set, because the secondary rate controlling reaction steps can be different from those in methane flames. It was also demonstrated that the constraints provided by the laminar flame speeds of C4 unsaturated hydrocarbons fuels could reduce notably the uncertainties in the predictions of laminar flame speeds of C4 alcohol/air mixtures. To obtain an accurate prediction of the laminar flame speed of a particular C4 alcohol/air mixture, the best data to acquire is not necessarily those of that particular mixture. In many cases, a consistent set of experimental flame measurements of key molecular intermediates formed during the pyrolysis and oxidation of the parent fuel are more critical to achieving a better prediction for the flame propagation rates of C4 alcohol flames. Paper # 070RK-0048 Topic: Reaction Kinetics 2