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Abstract
Two ignition criteria. Scmenov-Frank-Kamenetski (SFK) and van't Hoff. are examined for homogeneous-heterogeneous reactions using the parameter continuation technique and bifurcation analysis. The model and parameters are based on the propane oxidation in air with simplified kinetics for stagnation-point flow.
The disagreement between the two criteria for the homogeneous ignition is significant when no heterogeneous reaction occurs. However, when a platinum catalyzed heterogeneous reaction on the stagnation surface occurs along with the homogeneous reaction, the predictions of the homogeneous ignition for the two criteria match well. although the van't Hoff condition predicts too large a composition region for the homogeneous ignition. It is shown that for both situations there always exists a maximum activation energy of homogeneous reaction, above which there will be no ignition for either criterion.
It is demonstrated that the SFK criterion is generally more accurate and that bifurcation analysis is a powerful tool for determining and understanding the qualitatively different behavior of combustion such as ignition and extinction. Key 'Words: Ignition criterion, Bifurcation analysis, Stagnation flow
