Upstream flame propagation in prevaporizing/premixing continuous combustors was examined. Simplified axisymmetric burners used in this investigation were selected to simulate the same fundamental combustion processes in practical hardware. Straight cylindrical premixing tubes were used to reduce the possibility of upstream flame propagation mechanisms not associated with classical flashback. Combustor pressure oscillations were monitored and indicated that no flashback occurred due to these oscillations. Propane was selected as the test fuel because of its rapid vaporization characteristics.

A characteristic time approach was used to analyze the data because the flashback process can be viewed as a competition between a fluid mechanic time and a chemical reaction time. Use of this technique revealed that stoichiometric contours existed in the premixing tubes of this system at most overall equivalence ratios tested, since the flashback limit was observed to be independent of overall stoichiometry.

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