Experimental Investigation of Flame Stabilization in a Deflected Jet

Citation

Broman, Gunnar Erik (1959) Experimental Investigation of Flame Stabilization in a Deflected Jet. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/J5D1-MX07. https://resolver.caltech.edu/CaltechETD:etd-02022006-105147

Abstract

An experimental investigation has been made of flame stabilization in a two-dimensiona1 deflected jet of propane-air mixture at 70°F and atmospheric pressure. By a 90° deflection of the jet entering a combustion chamber duct through a slot, a recirculation zone is created which serves as a heat source in the flow. The chemical reaction in mixing zone between the fresh mixture in the jet and the hot gas in the recirculation zone supplies heat for the stabilization of a flame in the flow. The influence of the flow parameters on the stability was determined by changing the burner size and geometry. When the geometry was changed by variation of the ratio between slot width and burner height, two types of flow were observed. First, for large ratios, the mixing zone was covered by the flow of fresh mixture along the complete length of the mixing zone. This type of flow with a free mixing zone shows a great deal of similarity with the flow of the bluff body flameholder. The characteristic time introduced for the bluff body flameholder was also found to be a satisfactory correlation parameter for stability of burners of different size and geometry. In the second type of flow found for small slot to height ratios, the mixing zone reached the burner wall before the end of the recirculation zone. By a detailed study of flow, it was shown that the actual residence time in the mixing zone was the primary parameter for stability. Comparisons between burners with small slot to height ratios and the can burner also suggest that the same concept can be applied to the can burners. The results of the present investigation show that the ignition delay concept, on which the characteristic time for the bluff body flameholder is based, can be extended to flame stabilization in a deflected jet.

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