Numerical study of the effect of flow/mixture stratification on the combustion of a dual swirl oxymethane flames for gas turbine model

In the current work, a numerical works for oxymethane (CH₄/CO₂/O₂) partially premixed flames were conducted to investigate the complex interactions between different flame features and operational factors by exploring a premixed oxymethane flame within a dual annular counter-rotating swirl (DACRS). The numerical model is validated against experimental temperature along the burner axis. The effect of equivalence ratio, oxygen fractions, and flow/flame interactions on the temperature distribution and flame structure were studied. The burner is divided internally into two annular tubes. The secondary gas stream is routed via the gap between the inner and outer tubes, while the primary gas stream is contained within the inner (pilot) tube. The velocity ratio of 3.0 is consistently maintained by the primary and secondary streams. The secondary stream's velocity is fixed at 1.667 m/s, while the primary stream's velocity is set at 5 m/s. Using this configuration, the relationships between flow and flame dynamics are investigated for a variety of equivalency ratios between different combinations of primary and secondary oxygen fractions (primary being 25%, and secondary being 39%). While the secondary equivalency ratio (φ_s) fluctuates, the primary equivalency ratio (φ_p) stays constant at 0.9. The results show that equivalence ratio changes have a significant impact on flame shape, reactivity, stability, and burner operability, whereas oxygen fraction changes have a significant impact on flame dynamics, recirculation zone formation, and temperature distribution.