CO2* Chemiluminescence in Premixed Flames

Chemiluminescence from species such as CH*, C2*, OH* and CO2* often are used as a quantitative diagnostic in experimental studies of premixed combustion. This paper reports results from a numerical investigation of CO2* chemiluminescence as a quantitative diagnostic in laminar and turbulent premixed flames. Calculations are carried out using a complex reaction mechanism for methane and propane and a model for CO2* chemiluminescence. Relationships between chemiluminescent intensity and both H-atom concentration and heat release rate are quantified as functions of dilution, equivalence ratio, steady and unsteady strain-rate. These relationships are monotonic, but not unique; they depend on which flame parameter is varied. However, the effect of unsteadiness on the relationship for a strained flame is negligible, and this allows the use of chemiluminescence-based diagnostics for measurement of relative H-atom concentration and relative heat release rates in unsteady laminar and turbulent premixed flames.