An Experimental Investigation of Combustion Induced Vortex Breakdown Flashback in a Swirl Stabilized Burner

Abstract

This paper presents an experimental investigation of combustion induced vortex breakdown (CIVB) flashback propensity for flames yielded from Hydrogen (H2) - Carbon Monoxide (CO) fuel blends and actual synthesized gas (syngas) mixtures. A two-fold experimental approach, consisting of a high definition digital imaging system and a high speed PIV system, is employed. The main emphasis was on the effect of concentration of different constituents in fuel mixtures on flashback limit. In addition, the effect of Swirl Number on flashback propensity was discussed. The percentage of H2 in fuel mixtures played the leading role to cause CIVB flashback. For a given air mass flow rate, the mixture containing higher percentage of H2 underwent flashback at much leaner condition than that containing less H2. Flashback map for actual syngas fuel compositions showed distinct behavior due to the presence of various diluents in the mixture. CO had significant dominance over H2 that helped retarding flashback propensity. Of the two major diluents carbon dioxide (CO2) and nitrogen dioxide (NO2), CO2 was more dominant. It appeared that the flashback propensity decreased with an increase in Swirl Number. The analysis of flow field of reacting flames revealed the complex vortex-chemistry interaction leading to vortex breakdown and flashback. Based on the experiential results a parametric model similar to Peclet Number approach was developed employing flame quenching concept. A value of the quench parameter, Cquench was obtained from the correlation of flow Peclet Number and flame Peclet Number, which was observed to be dominated by the fuel composition rather than Swirl Number.