Investigation of soot inception limits and chemiluminescence characteristics of laminar coflow diffusion flames in C/O ratio space

•Soot inception limits and its difference in coflow flames are interpreted in C/O ratio space.•Effects of Zst on soot inception are studied using kinetics analysis in C/O ratio space.•The position of chemiluminescence in C/O ratio space and the effect of Zst on it are evaluated.•Considering the low-emission combustion technology, oxy-combustion.