Abstract: Hydrogen energy as a clean fuel has a broad application prospect, but its violent combustion and poor stability is easy to induce safety hazards. Nitrogen doping to regulate the combustion characteristics of the hydrogen flame is a key technology to enhance the safe utilization of hydrogen energy. In this study, the effect of nitrogen doping on the combustion characteristics of hydrogen jet flames was investigated through experiments, and the influence of different nitrogen doping ratios on the temperature field, stable combustion time and morphology of the flame was systematically analyzed. The experimental results show that the maximum flame temperature decreases significantly with the increase of nitrogen doping ratio. The maximum temperature of the pure hydrogen flame in vertical flame reaches 842.8 ℃, which decreases to 726.5 ℃ with 30% of nitrogen doping, with a decrease of 13.8%, and that of the horizontal flame decreases from 859.3 ℃ to 706.0 ℃, with a decrease of 17.8%. When the nitrogen doping volume fraction reached 40%, the gas mixture could not maintain continuous combustion and reached the stability critical value. The stabilized combustion time of the flame was nonlinearly shortened with the doping ratio, and the pure hydrogen flame lasted 15.58 s, which was sharply reduced to 2.61 s with 30% of nitrogen doping. After nitrogen doping, the brightness of the flame was significantly reduced, and the horizontal flame jet showed an elongated jet-like propagation. Nitrogen doping can effectively regulate the core region temperature and combustion intensity of hydrogen flame.

Key words: combustion, flame, nitrogen inertization, jet, hydrogen safety