Exhaust and in Situ Measurements of Nitric Oxide in Laminar Partially Premixed C2H6−Air Flames:  Effect of Premixing Level at Constant Burner Tube Flow Rate

• Published in: Energy & fuels 1996-09, Vol.10 (5), p.1060-1066
• Main Authors: Kim, Tae Kwon, Alder, B. J, Reisel, J. R, Laurendeau, N. M
• Format: Article
• Language: English
• Subjects: Air pollution caused by fuel industries; Applied sciences; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Metering. Control
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef960020f

NO formation in laminar partially premixed ethane−air flames is investigated as a function of the amount of air introduced into the central fuel tube of an annular coflow burner. The NO x emission index at the exhaust is determined by chemiluminescent detection while the local NO number density is measured by laser-saturated fluorescence. The measurements are taken in flames with an overall equivalence ratio of 0.9, burner-tube equivalence ratios (φ B) varying from 1.1 to 6.7, and a fixed burner-tube flow rate of 0.9 L(STP)/min. Local NO number densities are measured as a function of both radial position and height above the burner. Despite the increase in fuel flow rate with rising φ B, an intermediate dual-flame pattern is identified which minimizes the NO x emission index. NO production is found to occur primarily between an inner premixed and an outer nonpremixed flame front, which constitutes the dual-flame structure. These results suggest that the optimum burner-tube equivalence ratio occurs due to a compromise between prompt and thermal formation of NO in the predominantly premixed and nonpremixed flame regions, respectively.