Temperature and soot formation in a natural gas diffusion flame

摘要

Study presents temperature and soot formation profile within a natural gas diffusion flame under the equivalence ratios of 0.35, 0.90, 1.70 and 2.56. An in-house combustion Test-Rig designed for diffusion flame studies was used for temperature distribution and gravimetric soot mass. The soot was samples with an isokinetic probe insert, from this; a fairly accurate value of the soot number density and volume fraction was computed. There was sharp increases in the line-of-sight flame temperature within the centerline with peak values occurring at some distances of 6, 12, 12 and 9 cm from the burner rim, corresponding to 0.35, 0.90, 1.70 and 2.56 equivalence ratios respectively, after which it decreases gradually. A clear marked reduction was observed in temperature values as the condition of fuel mixture changes from lean to heavy rich. This reduced temperature that was most evident of flame equivalence ratio of 2.56 has been traced to be as a result of high sooty condition imposed by this fuel rich mixture. This condition of soot laden, enhances high rate of heat losses through adverse radiative heat transfer, thereby decreases flame temperature and combustion efficiencies of the parent user device. It was also observed that the gravimetric soot mass profile is much regular in behaviour for the lean mixture flames as it increases with increase in measured temperature values. Contrarily, for a richer mixture of 2.56, it increases with decrease in temperature.