Quantitative Measurements of Chemiluminescence in a Laminar Methane-Air Premixed Flame and Comparison to Numerical Methods

Quantitative measurements of chemiluminescence emissions as a result of CH*, OH*, C-2*, and CO2* were conducted in CH4/air premixed flames at different equivalence ratios (theta = 0.7-1.33), and numerical results based on one-dimensional flame simulations were compared to these data. A wavelength-dependent and optical-path-corrected emission calibration method was applied to quantify the emission of each excited species. The numerically simulated emission intensities of OH* and CH* are within the same order of magnitude as the experimental values for the same flame conditions. When self-absorption and cooling water thermosteresis are taken into account, the simulated OH* values are 1.0-1.4 times greater than the experimental results, while the CH* values are approximately 2.3-4.1 times greater. These findings suggest that more work is required to refine the temperature dependence factors for the CH* formation rate coefficients at high temperatures.