Abstract
Oxy-fuel combustion of methane in small scales was handled to investigate micro counterflow diffusion flames. We observed methane-oxygen diffusion flames in counterflow burners where the burner distance was less than 1 mm, and obtained the flame thickness and flame diameter as functions of the burner distance, inner diameter and gas flow rate. When burners with large inner diameter were used, counterflow diffusion flames were observed in small burner distance, and the flame thickness and flame diameter were large under the same conditions of burner distance and gas flow rate. The flame thickness and flame diameter decreased as the burner distance became smaller, and they increased as the gas flow rate became larger. Moreover, the flame stretch rate had a great influence on the flame thickness. As the flame stretch rate became larger, the flame thickness decreased monotonously, which depended on the inner diameter and gas flow rate. To scrutinize the dependence of flame thickness on the flame stretch rate, we normalized the flame thickness by the inner diameter and the average velocity of methane. We confirmed that the normalized flame thickness depended only on the flame stretch rate.
