Numerical Study on Mixing Characteristics of Fuel and Air in Hydrogen Micro-mix Burner

Realizing the uniform mixing of hydrogen and air outside the tube of the hydrogen gas turbine can avoid flashback and achieve low NO_x emission. In order to achieve as uniform mixing as possible from the nozzle outlet to combustion, the flow characteristics of the micro-mix nozzle outlet and the influence of the interaction between the fuel-air inflow on the mixing of hydrogen and air were calculated and analyzed by numerical simulation, and the effects of the fuel-air momentum ratio, fuel hole gap ratio, jet height and mixing length on the cold mixing of the micro-mix nozzle were investigated respectively. Results show that the mixing effect is directly impacted by the standard jet depth, the neighboring jet disturbance and the vortex structure of the diffusion section. The suitable standard jet depth is achieved with a momentum ratio R_m in the range of 1.19-1.77, which can lead to more uniform mixing. When the fuel hole gap ratio is 0.54, the interaction of adjacent jets causes a larger gradient in the decrease of the hydrogen concentration in the center of the jet. Increasing the jet height and mixing length can reduce the mixing inhomogeneity, and the development of near-wall vortex pair integrity is beneficial to the mixing improvement.