Numerical simulation investigation on a hydrogen micromix combustor

In order to curb the carbon and NOx emissions of the aeroengine and ground gas turbines, a multi-injector combustor dome configuration was proposed. To explore the micromix non-premix combustion mechanism and the impacts of the critical parameters on the combustor performance, the k-ω SST (shear stress transfer) turbulence model, FGM (flamelet generated manifold) diffusion flamelet method and 9 species-26 steps reactions were adopted for the numerical simulation. Sensitivity analysis was performed with regard to the momentum flux ratio, equivalence ration, air-gate height and hydrogen-gate height. The influencing factors of mixing characteristics, flame structure, temperature distribution and NOx emission were explored. Meanwhile, the NOx emission between the conventional kerosene combustor and the hydrogen micromix was evaluated. Results showed that lower momentum flux ratio was beneficial for enhancing the mixing and reducing the flame length, resulting in 169.6% NOx reduction. There existed a critical value of the air gate height which brought about the highest NOx up to 5×10⁻⁶ under the 15% O₂ content condition. As H₂ gate height increased from 3 mm to 11 mm, NOx fell by 75.9%. Compared with the conventional kerosene combustor, NOx emission dramatically dropped by 85.7%, using the optimal combination of critical parameters.