Numerical and experimental investigation of the correlation between inlet flow rates, temperature, and NO_x emissions in pure hydrogen combustion

Many industrial burners currently in use have been designed for fossil fuels and have not been tested with hydrogen. The successful utilization of hydrogen fuel in industrial applications demands the optimization of operating conditions. Optimizing the inlet flow rate is important particularly for industrial burners to ensure safe and efficient operation over a long period. This study investigates the effects of inlet flow rate on temperature distribution and NO_x emissions in a multi-purpose pure hydrogen-fueled industrial burner through numerical simulations and experiments. The numerical simulations, employing the realizable k-ε turbulence model and the eddy dissipation concept for turbulence and combustion modeling, are validated against experimental data, achieving a mean absolute percentage error of approximately 5 % for temperature and less than 2 % for NO_x emissions at 4 % O₂. The results demonstrated that increasing the inlet flow rate enhances reaction intensity and heat release, subsequently increasing combustion temperatures and promoting NO_x formation. However, with a substantial increase in the inlet flow rate, the rate of temperature growth diminishes, and NO_x emissions reach a plateau. This suggests that the burner is approaching maximum capacity, with the combustion process becoming limited by the burner's ability to efficiently mix and react the fuel and oxidizer. Finally, an optimal inlet flow rate of 50.4 LPM for hydrogen in the fuel inlet and 200 LPM for air in the oxidizer inlet, balancing temperature and NO_x emissions, was identified through the weighted sum performance indicator proposed in this work. This study provides critical insights into pure hydrogen burner performance, advancing previous efforts by offering quantitative data essential for improving burner efficiency and reducing harmful emissions in carbon-free combustion.