A GLOBAL REACTION MODEL FOR OH* CHEMILUMINESCENCE APPLIED TO A LAMINAR FLAT-FLAME BURNER
Combustion diagnostics in practical devices are difficult due to the harsh environment encountered. Many optical diagnostics are attractive for combustion diagnostics applications due to their high temperature compatibility. Chemiluminescence measurements may allow combustion monitoring at a level of detail traditionally thought impossible. Among chemiluminescence species observed in flames, OH* chemiluminescence is attractive due to its relatively strong emission at lean equivalent ratios. In order to help in the interpretation of OH* chemiluminescence measurements, an accurate OH* chemiluminescence model must be developed. Current models rely on the modeling of the complete formation kinetics based on a reaction between CH and molecular oxygen introduced by Krishnamahari and Broida (1961 J. Chem. Phys., 34, 1709-1711). Recent studies as well as the current study are not ableto match experimental results using the customary OH* model. The present study employs a model reaction between formyl radicals and atomic oxygen to stimulate the complicated detailed formation kinetics of OH* chemiluminescence. Experiments were performed on a ceramic flat-flame burner. The flat-flame environment allowed a one-dimensional model to be developed to study the measured variation of global OH* chemiluminescence emission intensity with flow rate and equivalence ratio. The model also allows interesting insights into the burner characteristics, including how the heat transfer processes active within the burner allow the flame position to shift closer to the burner surface for increases in flow rate (in the range of burner flow rates studied). In terms of OH* chemiluminescence, the results show that the proposed global reaction model for OH* chemiluminescence is successful in matching the experimental observations for the flat-flame laminar combustion environment studied. The success of the introducedOH* chemiluminescence model brings with it the possibility of OH* chemiluminescence modeling in more complicated combustion environments because it is no longer necessary to model the scarce intermediate CH to obtain an estimate of OH* chemiluminescence. Further study will be required to determine the rate factor to be used in the introduced model of OH* chemiluminescence more precisely and to determine the exact nature of the relationship between the introduced chemiluminescence model and the actual OH* chemiluminescence kinetics.
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Document Type: Research Article
Affiliations: Reacting Flows Laboratory, Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
Publication date: October 1, 2003