Experimental study of impact of swirl number as well as oxygen and carbon dioxide content in natural gas combustion air on flame flashback and blow-off

Abstract

In this paper, experiments involving the combustion of natural gas in a quartz tube using a burner with three swirl generators were conducted to determine ranges of stable combustion limited by flame flashback and blow-off. The swirl generators with a tangential supply of substrates were described using the geometric swirl numbers: 0.69, 1.16, and 1.35. Effects on combustion atmospheres such as air, air enriched with up to 25 vol. % of oxygen, and oxygen-enriched air with addition of 15 vol. % of CO2 per stable combustion range were tested. The findings of the experiments proved that enriching air with oxygen leads to an expansion of the stable combustion range because the curve of flame blow-off progresses quicker than that of flashback. In terms of flame flashback, the burner with swirl generator Sg = 1.35 turned out to be the most favorable for the combustion atmospheres under consideration. The highest resistance of the flame against flashback was recorded for air. Addition of CO2 to oxygen-enriched air improved the flashback limits. The most favorable stable combustion range was calculated for the atmosphere of air enriched with up to 25 vol. % of oxygen when Sg = 1.35 and that of air when Sg = 0.69. The smallest stable combustion range, which was 26% smaller than the best result, was recorded for the mixture of oxygen-enriched air and 15 vol. % of CO2 when Sg = 0.69.