Modeling of NO formation in premixed, high-pressure methane flames

The Sandia steady, laminar, one-dimensional, premixed flame code is used to investigate NO formation in a series of lean-premixed CH4/O-2/N-2 laminar flames at pressures of 1-14.6 atm. Two different chemical kinetic mechanism s are evaluated in this study. The first mechanism, originally proposed by Glarborg et al. and then modified by Drake and Blint (GMK-DB), is an older mechanism that has previously been shown to be superior to other early mech anisms when making quantitative predictions of NO concentration in lean, hi gh-pressure laminar flames. The second mechanism is the newer GRI mechanism version 2.11. The modeling results for both mechanisms are compared to las er-induced fluorescence (LIF) measurements of NO concentration in the postf lame region of a series of flat, laminar, lean (0.5 less than or equal to p hi less than or equal to 0.8), premixed flames (N-2/O-2 dilution ratio of 2 .2) stabilized on a water-cooled McKenna burner. The GRI mechanism, despite uniformly underpredicting NO formation in these flames: is shown to produc e better qualitative agreement under these conditions than the GMK-DB mecha nism. The study is then extended to a wider range of equivalence ratios (0. 6 less than or equal to phi less than or equal to 1.6) at an N-2/O-2 diluti on ratio of 3.1. The results demonstrate that the GRI mechanism is not yet suitable for the quantitative prediction of NO concentrations in rich, prem ixed flames. (C) 1999 by The Combustion Institute.