Experimental investigation of the isothermal flow field in an air staged multiswirl 100% hydrogen burner

Abstract Hydrogen is a promising fuel for decarbonizing energy production and aeronautical propulsion. Even though hydrogen is a zero-carbon fuel, its unique physical and chemical properties pose significant challenges for use in conventional combustion systems, particularly due to potential issues with combustion stability and increased NOx emissions. This study investigates a 100% H 2 double coaxial swirl burner, adapted from a prior CH 4 / H 2 burner design. The burner features two concentric, co-rotating swirling jets, with a fast H 2 premixing stage positioned just before the nozzle outlet to mitigate flashback risks. We present a preliminary analysis of the isothermal flow generated by two injector geometries, using Stereo PIV to capture detailed flow dynamics. In addition to examining the time-averaged flow field, we apply Proper Orthogonal Decomposition (POD) to identify coherent structures within the flow. Results show that the two geometries produce distinct flow field configurations and varying intensities of reverse flow in the near-injection region (within 1–2 diameters downstream). Although similar patterns emerge further downstream, subtle differences in flow structure remain.