Investigation of the ignition and flame propagation characteristics in a swirl-stabilized hydrogen-enriched premixed combustor

Swirl-stabilized premixed combustion is widely used in gas turbines, but the influence of hydrogen blending on the ignition process remains insufficiently understood. This study investigates the effects of hydrogen addition on flame kernel propagation and the timescales of ignition in a swirl-stabilized combustor. Hydrogen blending ratios (0%–50%) and varying inlet flow rates, with a focus on 30% hydrogen blending, are examined. High-speed photography and flame chemiluminescence technique are employed to capture flame kernel motion, while numerical simulations provide the flow field. An ignition load factor is proposed to model the ignition process, accounting for both hydrogen ratio and flow rate. A novel method for calculating flame kernel trajectories is introduced, designed for large time-step analysis, offering a single characteristic trajectory. Results indicate that hydrogen blending alters the flow field and fuel-air mixing uniformity. It enables the flame kernel to traverse the shear layer without following the flow, increasing its radial penetration depth. Moreover, the flame kernel's movement remains largely confined to the recirculation zone in most conditions, underscoring the significant influence of the cold flow field. The ignition process is categorized into four stages: initial ignition, flame development, residence, and recovery, and the duration of the stages is sensitive to mixing uniformity. Hydrogen blending reduces ignition delay slightly, but when the ratio exceeds 20%, delay time increases. This study provides essential data for the application of hydrogen-blended fuels in gas turbines.