Numerical Study on Combustion of a Novel Micromix Multi-Nozzles for Kerosene/Hydrogen Fuels

Abstract Hydrogen combustion is emerging as one of the most promising options for future commercial aircraft propulsion. Transition from fossil fuels to hydrogen is expected to take time, and drop-in technologies, such as blending hydrogen with hydrocarbon fuels for combustion, are of significant importance for meeting decarbonization goals in the short term. Liquid kerosene and gaseous hydrogen have significant differences in physical and combustion characteristics. It is a significant challenge to achieve stable combustion of both kerosene and hydrogen simultaneously. A new micro-mixed coaxial nozzle for kerosene/hydrogen fuels was proposed. The kerosene spray flame is stabilized by a micro swirler, while hydrogen is mixed in a circular microchannel surrounding the swirler and coaxially arranged with the central axis of the spray nozzle. The numerical simulation including a skeletal reaction kinetics model with 54 species and 269 reactions was conducted and validated through comparisons with experimental data. The impact of hydrogen injection parameters, hydrogen blending ratio, swirling intensity, and nozzle distance on the combustion characteristics of the kerosene/hydrogen mixture were investigated. It is shown that the uniformity of hydrogen circumferential distribution in the annular mixing channel results in either individual multi-beam flames or a complete annular flame. Increasing the swirl number reduces the axial lengths of both the hydrogen and kerosene flames, resulting in more compact flame branches. NO emissions are minimized when the hydrogen blending ratio falls within the range of 10%–20%. The merged flame mode and free flame mode are observed for the adjacent hydrogen flames in different nozzle distances. It provides guidance for the design of low-carbon multi-fuel nozzle in gas turbine combustor.