Session: 04-17 Hydrogen Emissions II

Submission Number: 179460

Effect of Nozzle Structure on Combustion Characteristics of Hydrogen Combined Micro-Mixing Flames 

In stationary power-generation installations, combustion hardware is a principal source of regulated pollutants and greenhouse gas emissions. Lean-premixed combustion of methane- hydrogen blends can reduce CO₂ and NO_x but is susceptible to thermoacoustic instability. Increasing the hydrogen fraction modifies the internal flow field and reshapes the flame topology; the associated changes in vortex dynamics alter heat and mass-transfer processes and the local OH radical population, thereby modulating heat-release-rate (HRR) fluctuations and global stability. These effects narrow the operability window and increase susceptibility to flashback and lean blowout (LBO). To address these issues, this work introduces a nozzle architecture and combustion organization tailored for methane-hydrogen blends that promotes rapid air-fuel micro-mixing at short residence times, suppresses hot spots, and thereby limits thermal NO_x formation.

In this work, an annular micro-mixing combined nozzles architecture is employed. Each nozzle comprises two main components: a fuel and an air pipes, both culminating in an annular outlet. The high-temperature air is introduced into the air distribution chamber by two opposing pipelines.  The burner incorporates seven micro-mixing nozzles; for each nozzle, the characteristic diameter is 4.95 mm and the outer diameter is 5.50~5.89 mm. Across the nozzle variants, six radial orifices of 1 mm diameter are positioned at axial offsets of 5.0, 7.5, or 10.0 mm from the exit, where fuel and air intermix. Two outlet-edge geometries are considered: chamfered and sharp-edged. Based on the experimental measurements and complementary numerical simulations, we interrogate the flow-field characteristics, flame structure, and pollutant emissions under these nozzle configurations.

In the current research, the adiabatic flame temperature was fixed at 1450 °C and the hydrogen blending ratio in the fuel was varied from 50% to 100%. With the nozzle characteristic diameter and the tube center distance held constant, we examined the combustion characteristics of annular micro-mixing combined nozzles as functions of outlet diameter, outlet-edge geometry, and axial mixing distance. The investigation encompasses the flame structure,  distribution characteristics of the OH radical, flow-field characteristics in the reaction zone, and pollutant emissions of methane-hydrogen micro-mixing combined flames. The numerical model for methane-hydrogen micro-mixing combined flames was validated against the experimental dataset. Integrating experimental and numerical results, we present a comprehensive assessment of how the micro-mixing nozzle structure governs the combustion characteristics of methane-hydrogen flames.

Presenting Author: Qiming Hu Harbin Institute of Technology

Presenting Author Biography: Hu Qiming is a Ph.D. candidate in Power Engineering at Harbin Institute of Technology (HIT). His doctoral research focuses on the fundamental combustion characteristics and flame stability of methane-hydrogen blended fuel in micro-mixing combustors. His work aims to deepen the understanding of hydrogen-enriched combustion dynamics and contribute to the development of high-efficiency, low-emission gas turbine and industrial burner technologies.

Authors:

Qiming Hu Harbin Institute of Technology
Penghua Qiu Harbin Institute of Technology
Siye Liu Harbin Institute of Technology
Lei He Shanghai XuanYuan Power Technology Co., Ltd.
Yijun Zhao Harbin Institute of Technology
Xiaopei Liu Shanghai XuanYuan Power Technology Co., Ltd.
Li Liu Harbin Institute of Technology
Linyao Zhang Harbin Institute of Technology
Chang Xing Harbin Institute of Technology