The effects of burner stabilization on Fenimore NO formation in low-pressure, fuel-rich premixed CH4/O2/N2 flames

Vincent van Essen , Alexey Sepman, A. V. Mokhov, H. B. Levinsky*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

16 Citations (Scopus)

Abstract

We investigate the effects of varying the degree of burner stabilization on Fenimore NO formation in fuel-rich low-pressure flat CH4/O-2/N-2 flames. Towards this end, axial profiles of flame temperature and OH, NO and CH mole fractions are measured using laser-induced fluorescence (LIF). The experiments are performed at equivalence ratios between 1.3 and 1.5. The flame temperature is seen to decrease by 200-300 K, with a concomitant decrease in OH mole fraction, upon reducing the total flow rate from 5 to 3 L/min, thus increasing stabilization. At equivalence ratios between 1.3 and 1.5, this decrease in flow rate lowers the maximum CH mole fraction by a factor of 2, and the NO mole fraction by similar to 40% in all flames studied. Integrating the reaction rate for CH + N-2 to estimate Fenimore NO formation, using the rate coefficient in GRI-Mech 3.0, and the measured temperatures and CH profiles show very good agreement with the measured NO mole fraction for phi = 1.3 and 1.4, supporting the current choice for this rate. This agreement also shows that the increase in residence time caused by increased stabilization is an important factor in the ultimate impact of the changes in CH mole fraction on NO formation. The results at phi = 1.5 suggest that substantial quantities of fixed nitrogen species, e.g., HCN, are only slowly oxidized in the post-flame zone under these conditions, leading to a significant discrepancy between the measured NO mole fraction and that obtained by integrating over the CH profile. Detailed calculations using GRI-Mech 3.0 predict the experimental results at phi = 1.3 nearly quantitatively, but show increasing differences with the measurements for both CH and NO profiles with increasing equivalence ratio. (C) 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Original languageEnglish
Pages (from-to)329-337
Number of pages9
JournalProceedings of the Combustion Institute
Volume31
Issue number1
DOIs
Publication statusPublished - Jan-2007

Keywords

  • low-pressure flames
  • laser-induced fluorescence
  • NOx formation
  • LASER-INDUCED FLUORESCENCE
  • UPSTREAM HEAT-LOSS
  • PROMPT-NO
  • CH
  • ABSORPTION
  • LIF
  • RADICALS
  • SURFACE
  • GAS

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