Quantitative Measurement of OH and CH Chemiluminescence in Jet Diffusion Flames

• Published in: ACS omega Vol. 5; no. 26; pp. 15922 - 15930
• Main Authors: Liu, Yao, Tan, Jianguo, Wan, Minggang, Zhang, Lang, Yao, Xiao
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07.07.2020
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.0c01093

Quantitative measurement of chemiluminescence is a challenging work that limits the development of combustion diagnostics based on chemiluminescence. Here, we present a feasible method to obtain effective quantitative chemiluminescence data with an integrating sphere uniform light source. Spatial distribution images of OH* and CH* radiation from methane laminar diffusion flames were acquired using intensified charge-coupled device (CCD) cameras coupled with multiple lenses and narrow-band-pass filters. After the process of eliminating background emissions by three filters and the Abel inverse transformation, the chemiluminescence intensity was converted to a radiating rate based on the uniform light source. The simulated distributions of OH* and CH* agree well with the experimental results. It has also been found that the distribution of OH* is more extensive and closer to the flame front than that of CH*, demonstrating that OH* is more representative of the flame structure. Based on the change in the reaction rate of different formation reactions, OH* distributions can be divided into three regions: intense section near the nozzle, transition section in the middle of the flame, and secondary section downstream the flame, whereas CH* only exists in the first two regions. In addition, as the velocity ratio of methane and co-flowing air increases, the main reactions become more intense, while the secondary reaction of OH* becomes weaker.