The Study Of Lithium-ion Batteries Fire Propagation Characteristics In A Low-pressure Environment

This study is supported by National Science Foundation of China(Grant No.U1633203),the key technology and experiment verification of water mist fire suppression in the civil aircraft cargo compartment.This study focuses on the process of thermal runaway propagation among 18650 lithium-ion batteries,and investigates the characteristics of thermal runaway propagation in a low-pressure environment.The tests were conducted in an aircraft cargo compartment chamber,at Kangding airport with the altitude of 4290 m.The pressure condition of tests was set as 30 kPa and 101 kPa.The type of 18650 lithium-ion batteries which was produced in China was selected as samples in this research.The state of charge of the lithium-ion batteries keeps 100%.The characteristics of thermal runaway propagation among lithium-ion batteries were revealed,through comparing the tests in different ambient pressure environment(101kPa and 30kPa).The main results are as follows.(1)There need a trigger condition for the forming of thermal runaway propagation among lithium-ion batteries,a better sealing property,worse heat dispersion of the environment,and more trigger energy will make the propagation easer.(2)The process of propagation among lithium-ion batteries in 101 kPa always accompany with the spraying fire,explosive fire and other violent fire behaviors.The main behaviors are the process of spraying high temperature materials and inflammable gases under the ambient pressure of 30 kPa.(3)The violent fire behaviors in 101 kPa will rise the danger of high temperature fire to the environment.The inflammable gases without the reaction of combustion in the low-pressure of 30 kPa will rise the risk of the explosion and the hazard of toxicity,such as CO and other toxic gas released from batteries.(4)The characteristics of energy transfer and propagation sequence in the process of thermal runaway propagation among batteries in 101 k Pa and 30 kPa were summarized.The time of propagation becomes shorter under the low-pressure environment of 30 kPa.(5)The high temperature area of flame is the bottom area of flame about 1170? and 760? above the batteries in the pressure of 101 kPa.The scale of high temperature area in the environment under the pressure of 30 kPa is smaller than that under the pressure of 101 kPa.