Experimental study of flame chemiluminescence for premixed methane based binary fuel flames

The growing requirements in using natural gas with varying compositions, biogas, syngas, and hydrogen enriched natural gas have increased the need for fuel composition and equivalence ratio sensing methods for modern gas turbine combustors. Chemiluminescence has been suggested as a promising heat release rate and equivalence ratio indicator in methane premixed flames. However, its ability in flames fuelled by the complex composition of fuels is less understood. Therefore, the main object of the present study is assessing the chemiluminescence based equivalence ratio and fuel composition sensors in binary mixtures fuelled premixed flames. The CH₄ + C₃H₈, CH₄ + CO₂, and CH₄ + H₂ fuel mixtures are selected since they are typical compositions for the interested fuel applications. A thorough analysis of chemiluminescence characteristics including spectrum, flame patterns, chemiluminescent intensities, and intensity ratios was conducted by the measurements in a counterflow burner. The results conclude that the OH*/CH(A) chemiluminescent intensity ratio with proper removal of background emission is competent for indicating fuel composition and equivalence ratio for the examined fuel mixtures. The intensity ratio between CO₂* and OH*, CH(A), and C₂* can be used to monitor the proportion of C₃H₈, H_2, and CO₂ respectively in the methane-based fuel mixtures.