Experimental Study on OH*, CH*, and CO(2)* Chemiluminescence Diagnosis of CH(4)/O(2) Diffusion Flame with CO(2)-Diluted Fuel

[Image: see text] OH* and CH* chemiluminescence in hydrocarbon flames are often applied to characterize flame structure, equivalence ratio, strain rate, heat release rate, etc. In this study, chemiluminescence images of OH*, CH*, and CO(2)* in the CH(4)/O(2) diffusion flame were obtained using a CCD camera imaging system. The effect of CO(2) dilution on the flame structure, strain rate, and other flame characteristics of CH(4)/O(2) diffusion flame was discussed. The results show that CO(2) dilution greatly affects flame morphology and chemiluminescence intensity. There are quantitative functions between the chemiluminescence peak intensity of OH* and CH* and the CO(2) dilution level. The CO(2)* average intensity in the flame zone is better suited to characterize the dilution level than the CO(2)* peak intensity. Moreover, the strain rate of CO(2)-diluted laminar flame is defined. It is found that there is a linear relationship between the thickness of the OH* reaction zone and the square root of the strain rate.