Influence of swirl intensity and hydrogen nozzles on the combustion performance of pure-hydrogen combustor

The influence of swirl intensity and hydrogen nozzle configuration on the combustion performance of a pure-hydrogen combustor was investigated. A dual-swirler design with hydrogen injection at the venturi exit was adopted. Through combined numerical and experimental analysis, the effects of inner swirl presence, outer swirl number (ranging from 0.9 to 1.5), and hydrogen orifice number (12 and 15) on mixing, flame structure, and NOx emissions were systematically examined. Results indicated that increasing the outer swirl number from 0.9 to 1.5 reduced the mixing distance from 45 mm to 15 mm and lowered NOx emissions by approximately 10 r/min at a constant equivalence ratio. While the inner swirl promoted flame stability, an inner axial-flow design dispersed the central high-temperature zone, decreasing its volume by about 30% and further suppressing NOx formation. Increasing the number of hydrogen orifices from 12 to 15 improved upstream circumferential fuel distribution, reduced local peak temperatures, and shortened flame length without altering the overall mixing rate, thereby reducing NOx emissions. The combustor also exhibited effective thermoacoustic suppression, with pressure oscillations maintained below 20 Pa, ensuring stable operation across all tested conditions. This work provides a viable design strategy for high-efficiency, low-emission pure-hydrogen combustion systems, supporting the development of clean energy technologies and carbon-neutrality objectives.