Kerosene-H₂ blending effects on flame properties in a multi-fuel combustor

In this study, the macroscopic properties of kerosene-H₂ blended flames are investigated in a multi-phase, multi-fuel combustor, focusing on the effects of increasing H₂ blending fractions. The non-reacting flow field of the swirl-stabilized combustor is characterized using PIV, and macro-structures in the flow and spray-swirl interactions are analyzed. Kerosene atomizers are tested to estimate variations in spray quality across different fuel blends. The changes in the optical properties of the flames are recorded using broadband chemiluminescence imaging while the changes in the acoustic emissions are recorded using a microphone. Results show that H₂ addition significantly alters the flame topology, transitioning from a lobed flame for pure kerosene to a single contiguous swirling flame for blended or pure H₂ cases. The flame luminosity decreases, with the emission color shifting from bright yellow (pure kerosene case) to dull yellow (multi-fuel cases) to a red-blue hue (pure H₂ case). These changes are attributed to variations in fuel distribution, heat release patterns, combustion mode, flame speed, and soot formation tendencies. The acoustic analysis reveals that a strong tonal behavior is observed under pure fuel conditions (prominent peaks at higher harmonics of 150 Hz) while broadband characteristics are exhibited under blended fuel conditions. The overall acoustic emissions in multi-fuel cases are reduced by ~80% compared to pure H₂ and ~55% compared to pure kerosene. This study highlights the effects of high levels of H₂ blending on flame dynamics and acoustic behavior in a multi-phase, multi-fuel combustor, offering valuable insights for the development of fuel-agnostic combustion systems.