Thermal NO/sub x/ in stretched laminar opposed-flow diffusion flames with CO/H/sub 2//N/sub 2/ fuel

Journal Article · Mon May 01 04:00:00 EDT 1989 · Combust. Flame; (United States)

DOI:https://doi.org/10.1016/0010-2180(89)90064-3· OSTI ID:6235786

Drake, M C; Blint, R J

Effect of flame stretch (variations in velocity and concentration gradients) on thermal NO/sub x/ formation has been studied in laminar opposed-flow diffusion flames. Chemistry-transport model calculations agree (within 150 K for peak flame temperature and within 3 ppm for peak thermal nitric oxide concentrations) with previous experiment in CO/H/sub 2//N/sub 2/ laminar opposed-flow diffusion flames at three different velocity gradients (..cap alpha.. = 70, 180, and 330 s/sup -1/). Corrections were required to account for the finite spatial resolution of the probe sampling measurements. Additional model calculations were obtained over a wider range of stretch (..cap alpha.. = 0.1-5000 s/sup -1/). Calculated NO/sub x/ concentrations decreased dramatically as flame stretch was increased (with peak NO/sub x/ values of 2300, 1100, 280, 20, and less than or equal to1 ppm obtained for flames with ..cap alpha.. = 0.1, 1, 10, 100, and greater than or equal to500 s/sup -1/, respectively). This decrease was caused by declines in both the reaction time in high temperature flame zones (proportional to ..cap alpha../sup -1/) and in the net NO/sub x/ formation rates. Net NO/sub x/ formation rates are affected by flame stretch due to changes in peak flame temperature, superequilibrium O atom concentrations, NO destruction reactions, and N/sub 2/O formation reactions. Most of the NO/sub x/ in flames at low stretch is formed by the Zeldovich mechanism, while the N/sub 2/O pathway dominates NO/sub x/ formation in flames at very high stretch where the peak flame temperatures are low. Reactions involving the formation and destruction of NO/sub 2/ occur in lean flame zones, but the amount of NO/sub 2/ formed is small. Both experiments and calculations show that a very effective way to reduce thermal NO/sub x/ formation in the forward stagnation regions of laminar opposed-flow diffusion flames (and possibly in turbulent diffusion flames as well) is to increase flame stretch.

• Research Organization: Physical Chemistry Dept., General Motors Research Labs., Warren, MI (US)
• OSTI ID: 6235786
• Journal Information: Combust. Flame; (United States), Journal Name: Combust. Flame; (United States) Vol. 76:2; ISSN CBFMA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
CALCULATION METHODS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
COMBUSTION KINETICS
DATA
DIFFUSION
ELEMENTS
EXPERIMENTAL DATA
FLAMES
FLOW MODELS
FLUID FLOW
FUELS
HYDROGEN
INFORMATION
KINETICS
LAMINAR FLOW
MATHEMATICAL MODELS
NITRIC OXIDE
NITROGEN
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN
OXYGEN COMPOUNDS
REACTION KINETICS
RESOLUTION
SAMPLING
SPATIAL RESOLUTION
TURBULENT FLOW
VARIATIONS