Study On Mechanism And Airworthiness Of Water Mist Suppressing Thermal Runaway Of Airborne Lithium Battery

Lithium batteries are easy to cause thermal runaway due to their inherent susceptibility to threats to flight safety.At present,more Halon 1301 extinguishing agents are not capable of effectively controlling the thermal runaway process of lithium batteries.Water mist extinguishing technology is considered as a popular alternative for halon because of its high efficiency,low cost,and environmental friendliness.Therefore,in conjunction with the characteristics of thermal runaway of lithium batteries and fine water mist suppression mechanism,targeted research can ensure lithium batteries.Safety and economy in the air transportation process.In this paper,through the thermal runaway experiment of lithium-ion batteries,the thermal runaway process is qualitatively and quantitatively analyzed,and Fluent is used to perform computational fluid dynamics simulation studies to correct the thermal runaway heat release rate of lithium-ion batteries.Based on this,the lithium-ion battery heat is established.Out of control simulation model.On this basis,the quantitative study of the phase characteristics in the process of thermal runaway of lithium-ion batteries is carried out,and the thermal runaway index is used to quantitatively characterize the thermal runaway state of lithium-ion batteries,and the critical energy for controlling the thermal runaway of lithium-ion batteries is obtained by combining the energy balance equations.In this way,the thermal runaway prevention and control strategy for lithium ion batteries is proposed.Subsequently,the water mist was used to simulate the thermal runaway process of the lithium-ion battery,and the critical water volume,droplet size,cone angle and spray intensity of the water mist were determined to suppress the thermal runaway of the lithium ion battery.Finally,combined with the airworthiness requirements of the airborne fire extinguishing system,the experimental study on the suppression of the thermal runaway of the lithium ion battery under different conditions was conducted to obtain the suppression effectiveness of the water mist under different conditions.The research results show that there are two important nodes in the thermal runaway of single-cell Li-ion batteries,namely,the initial explosion and the explosion.The two nodes divide the thermal runaway process into three phases: stability,criticality,and loss of control.The essence of thermal runaway of lithium-ion batteries is the accidental generation,accumulation and propagation of energy.The main body of the propagation process is heat conduction,and the proportion of energy occupied by heat radiation and heat convection is low.Lithium-ion battery thermal runaway index can quantitatively characterize the thermalrunaway state of lithium-ion batteries,and control the spread of thermal runaway of lithium-ion batteries by adding additional heat losses.The critical stage for the suppression of the thermal runaway of the lithium ion battery by the water mist was simulated.The critical water quantity required was 87.6 ml and the droplet size was 112 μm.Under this condition,the optimum mist cone angle of the fine water mist was 60°.The best spray strength is15L/min · m2.Finally,through airworthiness experiments,it was found that the battery arrangement,ambient temperature,and pressure changes have a certain effect on the ability to inhibit water mist.It is necessary to adjust the parameters of the water mist according to the environmental conditions during the flight and the battery arrangement.In this study,the water mist system was used to suppress the domino effect caused by thermal runaway and propagation of lithium-ion batteries.Based on the deep analysis of the characteristics of the thermal runaway and propagation of lithium-ion batteries,a theoretical and experimental analysis was made based on the mechanism of fine water mist suppression.Fully verify the effectiveness and applicability of the water mist system for thermal runaway inhibition of lithium-ion batteries,and conduct research in conjunction with the theoretical system for airworthiness of China’s civil aviation to provide basic theoretical guidance for the verification criteria of water mist airworthiness,and for lithium at the same time Ion battery safety transportation management provides decision support.