Numerical simulation study on two-phase flow of thermal runaway evolution and jet fire of 18650 lithium-ion battery under thermal abuse

The influence of particles on the external jet flame generated by 18650 lithium-ion batteries during thermal runaway is considered. A model that employed multi-component Navier-Stokes equations to consider gas-phase flow, and used the Lagrangian method to consider solid particles, was applied to describe the mixing characteristics of the jet flames and particles generated by battery combustion. The related combustion process, with and without particles, was compared and analyzed, and the flow lines outside the battery were obtained. Moreover, the effect of particles on the concentration of combustion components and the elevation of flame height are discussed. The results show that particles reduce the generation of external vortices outside the battery, making the external airflow more stable. The particles reduce the rate of concentration decrease outside the core, leading to an increase in the overall flame height. In the early stage of battery combustion, the flame has not yet stabilized, and the total flame height with the particles is on average 1–2 times higher than that without them. This article demonstrates that particles have a significant impact on the jet flame characteristics and dynamic behavior during thermal runaway process of batteries, providing a reference for the safety evaluation of actual batteries.