Study On ULD Integrated Fire Extinguishing System For Lithium Battery During Air Transportation

In recent years, the emerging safety problems of lithium batteries during air transportation aroused widely concern from the civil aviation industry and the whole world, due to the frequent air accidents involving lithium battery fire. Airborne halon fire extinguishing system cannot suppress the fire caused by lithium batteries effectively. Besides, UN and ICAO issued relevant requirements to restrict halon extinguishing agent. Therefore, it becomes top priority that developing effective fire extinguishing technology and designing reasonable fire extinguishing system, in order to ensure the safety of lithium batteries during air transportation.The relevant experiments are launched through the independent built burning and explosion experimental platform. The burning phenomenon of lithium-ion battery and its corresponding mechanism are discussed. Combining with there aspects of fire extinguishing, dectecting and explosion protecting, the units of fire extinguishing system are divided. The water mist and the combustible gas detector are determined to be the fire extinguishing agent and detector in the integrated fire extinguishing system, respectively. And the fire extinguishing unit and detecting unit are integrated into unit load device. Then the simulation model of fire extinguishing system is established via the visual modeling software – Pyro Sim. The influence of extinguishment efficiency against parameters and placement of water mist are analyzed. The parameters and placement scheme of water mist that apply to such system are determined. Eventually, the ULD integrated fire extinguishing system for lithium battery during air transportation is completely formed, after designing system integration scheme.The results show that the combustion and explosion process of lithium-ion battery can be divided into two key stages – initial blast stage and secondary combustion stage. Its fire risk is proportional to the rated capacity and state of charge. The extinguishing efficiency of the water mist is increased with the decrease of the droplets diameter and the increase of the spray speed, intensity and angle. On the premise of ensuring extinguishing efficiency and reducing economic cost, the optimum solution of such system may install a single nozzle with the spraying direction of vertically downward, 100μm droplets diameter, 30m/s spray speed, 2L/min spray intensity and 60°spray angle. And combustible gas detector can provide the most rapid response for the fire of lithium-ion batteries.This study integrated the fire extinguishing system into a ULD, so that it could detect and extinguish a lithium-ion batteries fire rapidly. This may prevent the fire spreading in the aircraft cargo compartment. It can provide continuous protection for lithium-ion batteries without any changes in the existing aircraft fire extinguishing system. With the advantage of low cost, high reliability and easy accessibility, such system can be widely used in cargo compartment of civil aviation aircraft, in order to resolve the safety problem of lithium batteries during air transportation effectively. The results of this study can not only provide theoretical and technical support for the design and implementation of aircraft ULD integrated fire extinguishing system, but also provide technical guidance and decision support for air transport of dangerous goods, especially the lithium-ion batteries.