Hazard analysis on tunnel hydrogen jet fire based on CFD simulation of temperature field and concentration field

In order to research the fire characteristic of hydrogen jet fire in tunnels under different conditions, computational fluid dynamics (CFD) simulations of the hydrogen jet fire from a hydrogen transport vehicle inside a tunnel were carried out. Several new different factors, such as hydrogen leakage rate, leakage area, longitudinal ventilation, transverse ventilation, the volume of the tunnel and the leakage location, were considered to analyze the influence on the temperature and diffusion of hydrogen inside the tunnel during the jet fire. Results indicate that the temperature rise-rate and hydrogen diffusion rate in the tunnel increased with an increase in the hydrogen release rate. However, the excessive leak rate could inhibit further diffusion of hydrogen in the tunnel. Hydrogen diffusion rate decreased as the cross-sectional area of tunnel increased. Longitudinal ventilation can effectively reduce the overall temperature inside the tunnel but will lower the high-temperature layer in the tunnel below the safe height. In addition, compared with an open space, the hazards of the hydrogen jet fire inside a tunnel lie in not only high temperature but also the accumulation of hydrogen, which may pose a secondary disaster inside the tunnel. In order to control the hazard and avoid the secondary disaster after the hydrogen jet fire happened, adequate longitudinal and transverse ventilation is necessary inside the tunnel.