Numerical Simulation Of Thermal Runaway And Fire Resistance Of Lithium Battery To Fire Impingement

The safety of lithium batteries has become a new focus of global research.The operating temperature of the lithium battery is too narrow,which will cause thermal runaway under various conditions,and will cause battery fire and explosion.This shortcoming will cause certain safety hazards to electronic products equipped with lithium batteries.For lithium-ion battery pack under fire conditions of thermal runaway problem,this paper proposes a two-way coupling conjugate heat transfer model,can be used in the numerical study of lithium battery in a fire under the condition of external temperature changes as well as the spread of thermal runaway in lithium battery pack.Large eddy simulation(LES)was used to simulate the fire in the external fluid calculation region,and a three-dimensional governing equation was established for the solid calculation region of the lithium battery pack.The solid calculation region was divided into six parts,namely,one solid calculation region of the composite shell of the lithium battery and five solid calculation regions of the battery core.The reliability of the conjugate heat transfer model used in this paper is verified by the fire experiment of propane burner with lithium battery pack.In the paper,the surface temperature distribution,surface heat flux and thermal runaway propagation of lithium battery pack under fire condition were studied numerically by using the numerical model.The results show that the change of surface temperature of lithium battery pack can better reflect the state of thermal runaway of each lithium battery.The change of heat flux on the outer surface of lithium battery pack is closely related to the temperature difference between lithium battery pack and external fire environment.The thermal runaway propagation of lithium battery pack under fire condition has remarkable characteristics.Finally,according to the international general standards for the fire resistance of lithium battery,a numerical study on the fire resistance of lithium battery is carried out on foam aluminum refractory materials.The effects of refractory materials with different thicknesses on the temperature of the lithium battery shell,the temperature of the lithium battery cell and the surface heat flux of each interface are studied.The thickness of the refractory layer that meets the safety criteria is obtained,and the surface heat flux of the material will be affected by the thickness of the refractory material.The results of the numerical study provide a guiding significance for the fire resistance experiment of lithium battery.