The effect of carbon dioxide diluted on combustion characteristic with a tubular flame burner

In this study, the effect of carbon dioxide diluted (30%~60% in fuel volume) on the combustion characteristics with a tubular flame burner have been systematically investigated, including the flame appearances, the stable flame regions and the axial temperature distributions of the burned gases. For a point of practical view, the exhaust emissions of NOx and CO at the burner exit have also been examined. The main results obtained are as follow: (1) The tubular flame can be successfully obtained for a wide range in the equivalence ratio and the flow rate of the combustible mixture. However, for α ≥ 0.6, the rich flammability limits are slightly lower than that of α = 0.3. (2) Detailed measurements of the burned gas temperature at the central axis against the various equivalence ratio show that the burned gas temperature is decreased with increasing CO2 content in the fuel. (3) More detailed measurements on the exhaust emission show that the value of NOx is reduced approximately to a half value of α = 0.3 with increasing CO2 content to 60%. Thus, the tubular flame burner has the potential for achieving a stable biogas combustion as well as reducing NOx emission.