Effect of geometric characteristics of the nozzle on the flame sizes and temperature distribution of cryogenic hydrogen jet flames

Hydrogen energy has attracted much attention as clean energy. However, there are risks of fires or explosions in the process of storage and transportation of cryogenic hydrogen due to the hydrogen accidental release. The effect of nozzle geometric feature on flame sizes of cryogenic hydrogen jet flames is still unknown. Hence, in this work, experiments are conducted with different nozzle diameters (1.0-2.0 mm) and nozzle aspect ratios (1-16) under release temperatures of 140-300 K at 0.3 MPa to investigate the flame sizes and temperature distribution of turbulent non-premixed cryogenic hydrogen jet flames. It is found that the flame length and width increase with the increase of nozzle diameter and decrease of release temperature. However, the flame length decreases but the flame width increases with the increase of the aspect ratio of the release nozzle. An empirical formula considering the nozzle geometric characteristics is proposed to predict the cryogenic hydrogen jet flame length and width. In addition, the larger the nozzle diameter, the higher the flame temperature at centerline. However, there is little effect of aspect ratio on the temperature distribution of cryogenic hydrogen flame. Finally, the empirical formula for temperature distribution of cryogenic hydrogen jet flame is proposed. A three-stage distribution is presented and the relevant coefficients are obtained. The results can be a reference for assessing the risk of cryogenic hydrogen jet flames, and can be used as a guidance for the standardization of cryogenic hydrogen storage safety.