Effect of hydrogen blending ratio on combustion characteristics of methane-hydrogen micro-mixing combined flames

Heavy-duty gas turbines are major contributors to greenhouse-gas emissions from large stationary sources. Using H₂/CH₄ blended fuel effectively reduces emissions and mitigates warming. This study employed an annular micro-mixing combined nozzle setup to investigate how hydrogen blending alters the reacting flow field and thereby affects flame structure and combustion stability. We examined the influence of hydrogen blending ratio (X_H2) on H₂/CH₄ micro-mixing flame structure and NO formation. Using OH-PLIF and flue-gas analysis, we simultaneously measured flame structure, centerline temperature, and NO emission for X_H2 of 60∼100%, adiabatic temperatures of 1450∼1700 °C, and equivalence ratios of 0.41∼0.59. Results show that hydrogen blending modifies methane-air flame structure and extends the blow-off limit. At fixed ϕ and airflow, higher X_H2 raises thermal input and stabilizes the flame. At lower X_H2 of 60%, the lift-off height increases. With fixed conditions, higher X_H2 elevates adiabatic temperature and increases NO emission, yet values remained below 10 μL/L (@15% O₂).