Electric vehicle fires in ro-ro ships and influence of ventilation based on numerical simulation

To explore the influence laws of different ventilation schemes on lithium-ion battery vehicle fires in ro-ro spaces, based on the temperature data and gas products from full-scale fire experiments, the equivalent material of lithium-ion battery vehicles was designed, the combustion equation of the equivalent material was derived, and an equivalent model of lithium-ion battery vehicle fires was constructed and verified. A partial area of the single deck on a car carrier ship was intercepted. With the position, height, and number of ventilation openings as variables, multi-vehicle fire simulations were conducted. The variation laws of fire heat release rate and temperature under different ventilation schemes were mainly analyzed, and the influence mode of ventilation on the heat distribution in the cabin was discussed. The analysis results indicate that the fire can be divided into three stages according to the heat release rate: the initial stage, the rapid development stage, and the intense combustion stage. In the initial stage of the fire, the main way for the fire to expand is to ignite surrounding combustibles, and the expansion of the fire area is the main factor leading to the increase in the heat release rate. In the rapid development stage of the fire, most vehicles have been ignited, and the deepening of the combustion degree of the ignited vehicles is the main factor causing the rise in the heat release rate. By comparing the fire development trends under different ventilation methods, it is found that ventilation has a dual effect on fire development: Ship ventilation can restrict the rate of combustion spread, but at the same time, it provides oxygen to the fire, resulting in more intense combustion. In the initial stage of the fire, ventilation restricts the diffusion of heat, prolongs the ignition time of surrounding combustibles, and inhibits the expansion of the fire. However, in the rapid development stage of the fire, ventilation provides more sufficient oxygen for combustion, thus promoting the development of the fire. Among various ventilation schemes, the lower ventilation and the ventilation directly facing the fire site carry the greatest risks. This paper can provide theoretical support for the ventilation design and fire prevention and control of car carrier ships.