Transition from hydrocarbon fuels to hydrogen-fired industrial burners: Comparative investigation of combustion, entrainment and emission characteristics

The adoption of hydrogen in industrial burners requires a comprehensive understanding of how hydrogen flame behavior differs from conventional hydrocarbon fuels. This study combines experiments and Large Eddy Simulation of multi-jet industrial burners operating with methane, LPG, and hydrogen over thermal inputs of 5-20 kW and nozzle diameters of 2 mm, 4 mm and 6 mm. Hydrogen exhibited shorter flames than methane at 2 mm and 4 mm nozzle diameters, but became the longest flame at 6 mm indicated by 73% increase in mixing surface area. Froude-number-based regime analysis reveals fuel-dependent behavior, with LPG flames exhibiting strong buoyancy effects and methane flames spanning across transition regimes while hydrogen flames remain predominantly momentum-controlled. A generalized non-dimensional correlation is developed that predicts flame length across chemically distinct fuels and operating conditions. The insights from this study provide a practical framework for burner retrofitting and the transition from hydrocarbon fuels to hydrogen-fired industrial systems.