Abstract:

To address the safety risks caused by rapid fire spread and thermal smoke accumulation in confined spaces such as basements and underground warehouses due to lithium-ion electric bicycle fires, this study combines experimental and numerical simulation methods to investigate the temperature field evolution, flame characteristics, and smoke diffusion behavior of lithium-ion electric bicycle combustion under different ambient temperatures, clarifying the effect of temperature on combustion characteristics. The results show that under experimental conditions, the average temperature at the combustion center in the confined space is approximately 600 ℃, with a peak temperature exceeding 920 ℃. Ambient temperature significantly affects the initial stage of lithium-ion electric bicycle combustion. In a 40 ℃ environment, the time for combustion to enter the rapid development phase is shortened by 20 seconds compared to 20 and 0 ℃ environments. The time required for nearby temperatures to reach the ignition point of the lithium-ion electric bicycle is reduced by approximately 25 seconds compared to 20 and 0 ℃ environments. After about 80 seconds, the temperature rise rates converge. At 20 seconds, the flame morphology of lithium-ion electric bicycle combustion differs noticeably across environments: the flame height at 40 ℃ is approximately 1.15 times that at 20 ℃ and 1.32 times that at 0 ℃. Flame morphology converges after about 80 seconds. Within the first 30 seconds, the smoke diffusion velocity and production rate in a 40 ℃ environment are significantly higher than those at 20 and 0 ℃, but smoke concentrations stabilize to similar levels after approximately 50 seconds.

Key words: lithium-ion electric bicycles, confined spaces, ambient temperature, combustion features, numerical simulation