Hydrogen fuel has significant importance in mitigating global climate change and protecting the environment by achieving zero carbon emission in aviation engines, aerospace propulsion engines, and ground gas turbines. However, the application of hydrogen combustion technology still faces many challenges. Hydrogen combustion in traditional burners poses a risk of flashback and high nitrogen oxide (NO_x) emission. Thus, it requires exploration of new combustion technologies and pollution control measures to satisfy the urgent need of hydrogen energy. Micromix combustion technology implements hundreds of microchannels combined with micro-injection of hydrogen to rapidly mix air and hydrogen to form small-scale flames. The residence time of N₂ in the high-temperature zone is shortened to the level of milliseconds, significantly reducing the production of nitrogen oxide. This paper reviews the application history of hydrogen in gas turbine engines and the progress of hydrogen combustion simulation and experimental studies, summarizes the hydrogen characteristics, NO_x generation mechanism, micromix combustion principle, premixed combustion, diffusion combustion and dome structure characteristics, and discusses the influence of critical parameters of micromix combustors on aerothermodynamic process, NO_x generation and control measures, providing theoretical and empirical bases for the engineering design of hydrogen combustion chambers. Finally, the future development of hydrogen combustion technology is prospected.

Hydrogen is one of the fuels with the most potential to achieve zero carbon emission of aero-engines. In this paper, a micromix diffusive combustion structure based on the honeycomb bluff body is proposed. The micro bluff body is built in the honeycomb to disturb the mainstream air and enhance its mixing with hydrogen. The flow and combustion characteristics of the standard scheme without hydrogen injection, the cold field, and the hot field are simulated using the k-ω Shear Stress Transfer (SST) turbulence model and the diffusion flame method in Flamelet Generated Manifold (FGM). The aerothermal process of the micromixing unit is analyzed. The optimal design process of the honeycomb bluff body element is established based on Genetic aggregation approximate model. The design variables are angle and height of the bluff body whereas the minimum NO_x emission is the optimization objective. The influences of the parameters on NO_x emission and the optimal scheme are obtained. Results show that reverse rotating vortex pairs and three-dimensional jet vortices are formed in the cross section when hydrogen is injected into the high-speed mainstream air, the turbulent disturbance and hydrogen and air mixing are significantly enhanced, the hydrogen jet vortex is considerably affected by the working conditions and structure parameters, and the height of the bluff body is the sensitive parameter affecting the formation of NO_x. Under the intake condition of 2 030 kPa and 818 K, the NO_x emission of the optimal case is lower than 5×10^-6 under the 15% O₂ content condition.