Influence of Layout Performance on Combustion Characteristics of the Combined Micromixing Flames at Different Dilution Ratios

Micromixing (MM) combustion technology represents a highly promising approach for achieving low-emission performance in gas turbine applications. As for six types of syngas with N2 dilution ratios (Ω) ranging from 0% to 50%, the experimental and numerical studies are carried out at different tube center distance (TCD) of 1.25, 1.5, 1.75, 2, 2.25, and 2.5D (D represents the nozzle exit diameter, D = 10 mm). The in-depth discussions around the flowfield characteristics, flame structure and pollutant emissions are conducted. The results indicate that the numerical models show a good performance in flame structure and axial temperature distribution prediction. Syngas with lower Ω (Ω < 20%) sustains stable combustion under high flow rates; however, the associated NO emission exceeds regulatory standards. In contrast, higher Ω levels (Ω > 40%) result in diminished flame stability but achieve significant NOx reduction. Consequently, this study recommends a dilution ratio between 20% and 40% when implementing fuel-side dilution strategies to balance combustion stability and effective NOx emissions control. With the increasing TCD, the mutual influence and interaction between the adjacent flames gradually worsen, the flame height and high-temperature zone area significantly decrease, and NO emission rapidly drops. When TCD is higher than 2.25 D, the combustion efficiency across all dilution conditions falls markedly below 99%. The recommended TCD range in this study is set between 1.5 D and 2 D.