Effect of longitudinal ventilation on thermal runaway characteristics of LiFePO4 batteries in a tunnel
摘要
The increasing prevalence of tunnels, coupled with the widespread use of lithium-ion batteries, raises significant concerns regarding the risk of thermal runaway incidents. This study investigates the effects of ventilation velocity on the thermal runaway characteristics of LFP batteries in tunnel environments. Based on observed flame combustion behaviors, the thermal runaway process is divided into four stages: heating and the safety valve rupture, jet fire ejection, steady combustion, and smoldering. The time interval between voltage dropped and thermal runaway onset decreased significantly with increasing ventilation velocity, shortening from 49.4 s at 0 m s−1 to 36.4 s at 2 m s−1. Tunnel ventilation suppressed thermal runaway while tilting the flame rightward. Compared with no-ventilated case, the maximum flame height decreased from 334.93 mm to 139.66 mm at a ventilation velocity of 2.0 m s−1, representing a 58.3% reduction. And the tangent of flame inclination is proportional to the ratio of longitudinal ventilation velocity to flame characteristic rising rate. Additionally, tunnel ventilation cooling reduces the maximum ceiling temperature from 333.2 °C at 0 m s−1 to 143.1 °C at 2 m s−1. However, the mass loss initially rises before declining due to competing combustion-supporting and cooling effects of ventilation. The findings provide a critical foundation for understanding LFP battery thermal runaway in tunnels and support the development of safety-optimized ventilation strategies.