To achieve low-emission and high-efficiency in the metallurgy and cement industries, the high-temperature reducing gases generated by hydrogen-oxygen rich premixed combustion can be used for low-carbon and efficient reduction of metallic ores and calcium carbonate. Hydrogen-oxygen rich premixed combustion technology is one of the core methods for this process and provides theoretical support for the development of related burners. In this study, the combustion characteristics of hydrogen-oxygen rich premixed combustion in a combustor with a bluff-body are numerically simulated. The results show that the flammability limits of the hydrogen-oxygen mixture are wide at different Reynolds numbers, and stable operating equivalence ratios range from 1.75, 2.05 and 2.10 at Reynolds numbers of 300, 400 and 500, respectively. The flame remains symmetrically stable before flashback or blow-off occurs, and is C-shaped. The reverse flow of the flow field carries the hydrogen gas to the vicinity of the recirculation zone immediately adjacent to the bluff-body, where it subsequently mixes with the high temperature combustion products and flows out of the burner. However, oxygen is completely consumed near the upstream boundary of the flame front. Further analysis indicates that as the Reynolds number increases, the hydrogen content in the exhaust gas decreases slightly, while the hydrogen content increases almost linearly with the equivalence ratio. By adjusting the flow rate and equivalence ratio, the hydrogen percentage in the reductive gas can be precisely controlled over a wide range. This study offers a new approach to achieving ultra-low CO₂ emissions while efficiently reducing limestone or metallic minerals using green hydrogen.

A miniature double-layer disc-combustor with porous medium and Swiss-roll preheated channel, which can act as a miniature heat source, is proposed in this study, and the lean premixed flame behavior and thermal performance of 60% H₂-40% CH₄-air mixture in the case of various combustion chamber heights in it are investigated by the means of the experiment. The experimental results indicate that the effect of the combustion chamber height on the blow-off limit is insignificant. In the case of a constant combustion chamber height, the blow-off limit enlarges with the decreased Reynolds number, which is induced by a decreased stretch effect of incoming fresh mixture on the flame front. The lean premixed flames present the circle-shape in the case of the majority of operating conditions. At a large Reynolds number, the maximum and mean values of the upper wall temperature profiles of the combustor both increase with the increased equivalence ratio. In addition, they present the similar change rules with the increased Reynolds number at a constant equivalence ratio. At a small Reynolds number, the effects of equivalence ratio on the maximum and mean values of the upper wall temperature profiles are insignificant. The present work provides theoretical bases for the engineering application of lean premixed combustion technology which can realize clean and efficient combustion.