Power Transmission, Distribution And Plants Power Transmission And Distribution

Pressure dependence of NO formation in laminar fuel-rich premixed CH 4/air flames

Authors: van Essen, V.M. Sepman, A.V. Mokhov, A.V. [Laboratory for Fuel and Combustion Science, University of Groningen, Groningen (Netherlands)] Levinsky, H.B. [Laboratory for Fuel and Combustion Science, University of Groningen, Groningen (Netherlands) Gasunie Engineering and Technology, N.V. Nederlandse Gasunie, Groningen (Netherlands)]
 
Abstract: Effects of pressure on NO formation in CH 4/air flames at a fixed equivalence ratio of 1.3 are investigated. The axial profiles of temperature, OH, CH, and NO mole fractions are measured using laser-induced fluorescence and compared with one-dimensional flame calculations. The measured and calculated temperature, CH, and NO profiles in free flames are observed to vary upon increasing the pressure from 40 to 75 Torr, following a scaling law derived for a chemical mechanism containing only second-order reactions. At pressures 300-760 Torr, the measurements and calculations in burner-stabilized flames show increasing flame temperature and NO mole fractions when the mass flux is increased linearly with pressure, while the CH profiles remain unchanged. The observed deviation from the scaling law in the temperature profiles arises from the increasing contribution of three-body reactions to the flame front propagation velocity, leading to a decrease in the degree of burner stabilization. The deviation from the pressure scaling law for the NO mole fractions is due to the temperature dependence of the rate coefficient for the reaction between CH and N 2 and the fact that the temperature profiles themselves do not scale. In contrast, the surprisingly good scaling of the CH mole fractions with pressure indicates the dominant role of two-body reactions participating in the chain of chemical reactions leading to CH formation. The calculations using GRI-Mech 3.0 substantially overpredict (up to 50%) the measured nitric oxide concentrations for all pressures studied. The observed differences in the NO mole fraction may be addressed by improving the CH prediction. (author)
Publication Date: 15 May 2008
Resource Type: Journal Article
Resource Relation: Journal: Combustion and Flame; Journal Volume: 153; Journal Issue: 3; Other Information: Elsevier Ltd. All rights reserved
Country of Publication: United States
Language: English
Keywords relating to this report:
AIR
COMBUSTION PROPERTIES
ERRORS
LAMINAR FLAMES
MASS TRANSFER
METHANE
NITRIC OXIDE
ONE-DIMENSIONAL CALCULATIONS
PRESSURE DEPENDENCE
PRESSURE RANGE KILO PA
SCALING LAWS
STABILIZATION
SYNTHESIS
TEMPERATURE DEPENDENCE
THREE-BODY PROBLEM
TWO-BODY PROBLEM

Subjects:
Related subjects:
LOW-PRESSURE FLAMES