The method of extinguishing agent application in lithium battery fire extinguishing devices has a decisive impact on fire suppression effectiveness. Its core lies in precisely controlling the coverage, penetration capacity, and action time of the extinguishing agent to achieve rapid cooling, suppress thermal runaway reactions, and prevent reignition. Different application methods, when addressing the complexities of lithium battery fires, require comprehensive consideration of battery structure, fire development stage, and environmental factors to maximize extinguishing efficiency.
Vertical application of extinguishing agents is a common and effective method in lithium battery fire suppression. Since flames typically spread vertically upwards during thermal runaway of lithium batteries, vertical application allows the extinguishing agent to act directly on the core area of the fire source, reducing agent loss due to airflow interference. For example, gaseous extinguishing agents such as perfluorohexanone or heptafluoropropane, when applied vertically, can quickly fill the battery compartment space, creating a total flood coverage, interrupting the combustion chain reaction through both physical endothermic action and chemical inhibition. Vertical application also ensures that the extinguishing agent penetrates the gaps between battery modules, precisely targeting concealed fire points and preventing reignition due to incomplete coverage.
Horizontal spraying of lithium battery fire extinguishing devices is more suitable for localized fires or specific scenarios. When a lithium battery fire is confined to a certain area, horizontal spraying can concentrate the extinguishing agent to form a localized high-concentration area, rapidly reducing temperature and isolating oxygen. For example, a fine water mist fire extinguishing system can form a water film on the battery surface through horizontal spraying, suppressing the fire through cooling and suffocation. The limitation of horizontal spraying is that the agent distribution may be uneven due to gravity, especially in three-dimensional spaces where complete coverage is difficult. Therefore, it needs to be combined with other spraying methods or the nozzle angle adjusted to optimize the effect.
Multi-angle composite spraying is a key strategy to improve fire extinguishing efficiency. Lithium battery fires have three-dimensional diffusion characteristics, and single-direction spraying is insufficient to deal with complex fire scenes. By combining vertical, horizontal, and inclined sprays, a three-dimensional coverage network can be formed, ensuring that the extinguishing agent penetrates to every corner of the battery module. For example, a thermal aerosol lithium battery fire extinguishing device uses multi-angle spraying to rapidly diffuse a mixture of sub-nanometer solid particles and inert gas, forming total flooding protection and effectively blocking the propagation of thermal runaway. This spraying method also reduces agent waste and improves utilization efficiency.
Intermittent spraying achieves efficient cooling and fire suppression through periodic start-stop cycles. In lithium battery fires, continuous spraying can cause the extinguishing agent to rapidly vaporize at high temperatures, creating excessively high local pressure that hinders agent penetration. Intermittent spraying, by controlling the cycle and duty cycle, allows the extinguishing agent to continuously absorb heat during alternating release and pause, while avoiding damage to the battery structure caused by sudden drops in ambient temperature. For example, intermittent spraying of perfluorohexanone can maintain the extinguishing concentration while extending the agent's action time, preventing reignition.
Directional spraying provides precise fire suppression for specific battery components or structures. Lithium battery fire extinguishing devices typically contain multiple cells and connecting components. Directional spraying can concentrate the extinguishing agent to high-risk areas, such as electrolyte leak points or overheated cell surfaces. This spraying method requires the integration of intelligent detection systems, using temperature or gas sensors to locate the fire source, achieving "point-to-point" suppression. Directional spraying also reduces ineffective coverage of unheated areas and minimizes potential interference with the battery management system.
The matching of spray pressure and flow rate directly affects the penetration capability of the extinguishing agent. High-pressure spraying enhances the penetration of extinguishing agents, allowing them to reach deep into cracks and pores within the battery. However, excessive pressure can cause the battery casing to rupture, leading to electrolyte splashing or short circuits. While low-pressure spraying reduces secondary damage, insufficient power may prevent the agent from reaching the fire source. Therefore, the spray pressure needs to be dynamically adjusted based on the battery type and fire stage; for example, high-pressure rapid coverage can be used in the initial stages of a fire, transitioning to low-pressure continuous cooling in later stages.
Optimization of the spraying method requires coordinated design with the characteristics of the extinguishing agent. Different extinguishing agents have significantly different physicochemical properties, necessitating targeted adjustments to spray parameters. For instance, water-based extinguishing agents require high-pressure atomization for rapid vaporization and heat absorption, while gaseous extinguishing agents require controlled release rates to avoid excessive local concentrations that could cause asphyxiation. Newer extinguishing agents, such as microcapsules, also require consideration of the degree of damage to the capsule structure caused by spraying to ensure precise release of the extinguishing medium upon contact with the fire source. Deeply adapting the spraying method to the characteristics of the extinguishing agent can significantly improve the efficiency and safety of extinguishing lithium battery fires.
