Abstract:

A two-dimensional diffusion model was developed using the computational fluid dynamics software Fluent across various longitudinal wind speeds to examine the impact of longitudinal ventilation in underground tunnels on the dispersion of thermal runaway gases from lithium-ion batteries. The findings demonstrate that the diffusion of thermal runaway gas on the upwind side of the gas inlet is restricted by longitudinal ventilation, while it is enhanced on the downwind side. At a wind speed of 3 m/s, the time it takes for thermal runaway gas to diffuse to the exit boundary in about 40% that when there is no wind. Moreover, increasing wind speed within the computational domain results in a larger diffusion area under the same diffusion time. The expansion of the explosion area generally exhibits an increasing-then-decreasing trend as diffusion time advances. In the wind speed range of 0.25-3 m/s, the maximum explosion area grows proportionally with wind speed, forming an exponential relationship. Notably, the maximum hazardous area reaches a minimum of 6.79 m² at a wind speed of 0.75 m/s. Considering the maximum explosion range, wind speeds between 0.5 and 0.75 m/s appear optimal for diluting and diffusing thermal runaway gas in the tunnel.

Key words: longitudinal ventilation, lithium-ion battery, thermal runaway gas, gas diffusion, longitudinal wind velocity, tunnel, explosion area