Simulation Research On Key Parameters Of Integrated Battery Fire Extinguishing System

Through mass accident investigations of fire accident,it is found that the vast majority of electric vehicle fires are caused by local fire spread from battery packs.Due to the limitation of existing technology,active safety measures such as battery management system(BMS)are difficult to ensure that battery packs are free from fire threats.Therefore,the introduction of an integrated fire extinguishing system can effectively remedy the technical defects of BMS and solve the difficulty of extinguishing the whole electric vehicle fire from the outside,so as to minimize the damage caused by the battery bag fire,and ensure the safety of consumers' lives and property,which can promote the popularity of electric vehicle.Starting from the experiment about fire characteristics of lithium ion batteries,this paper studies the law before and after fire spread,as well as the sprawl of battery fire.Then,three main units of integrated fire extinguishing system are designed and analyzed based on the law.The key parameters involved in the fire extinguishing unit are numerically simulated and studied.The specific ontents are as follows:Firstly,through the establishment of battery overcharge experiment,overcharging the single 12 Ah lithium-ion battery and 5S1 P battery modules to trigger fire,and the regularity of battery fire process and fire spread between modules in space and time dimension was obtained.Then,based on the research results of battery fire characteristics,an integrated battery pack fire extinguishing system was designed,and the three main units of system: fire detection,control and fire extinguishing are analyzed respectively.Secondly,the lithium-ion battery model of fire dynamics is established and simulated by PyroSim.Compared with the experiment,the simulation results verify and optimize the model.Finally,adding a water mist extinguisher module to the model and simulating the effects of the four parameters: cone angle,flow intensity,initial velocity and droplet diameter on the fire extinguishing,so as to obtaine the optimal parameters combination.Focusing on different layout schemes of water mist sprinklers,three different position of fire initiatial source were designed to simulate the,and the results were weighted.The comprehensive fire extinguishing time of different layout schemes was calculated,and the optimal layout scheme of water mist sprinkler was obtained.The fire characteristics of the lithium-ion battery,design of the main units of integrated fire-extinguishing system,the fire-dynamic model and modeling method of the lithium-ion battery,as well as the optimal parameter combination of water mist and layout scheme of sprinklers,which are obtained from the study are of great significance for the numerical analysis of lithium ion battery fire and the improvement of fire safety of vehicle battery packs.