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Automatic fire suppression system for vehicles, electric vehicle
1. Cause of battery fire analysis
At present, the industry has encountered a thorny problem in the development and research of lithium batteries-the more energy stored in the battery, the more unstable the battery and even fire.
“The New York Times” once stated that the fire of lithium batteries is caused by its chemical composition, because the small volume of the battery contains all the ingredients that can cause a fire: carbon, oxygen and a flammable liquid-lithium salt Class electrolyte. When the battery is charged, the lithium ions in the cathode move to the anode; during the battery use, the lithium ions return to the cathode to provide energy. In the fully charged state, the cathode, which has lost most of its ions, is very unstable. As the heat accumulates, the battery will be “thermally out of control” as scientists call it. The main reasons are:
a. Electrolyte vaporization caused by high temperature during improper charging;
b. The thermal runaway of the use or rapid release of energy causes the electrolyte to burn or directly causes the battery material to burn and explode, or the air and lithium undergo a violent oxidation reaction after the battery shell is broken and explode. Short circuits, overcharging, and water stains caused by battery design defects and raw material defects.
2. Automatic fire suppression system for vehicles introduce
① Vehicle automatic fire Extinguisher system design
Design case: Bailujia New Energy 6.5-meter long bus with 5 battery compartments, so the protection area to be designed is 5 protection areas, and each protection area is equipped with an automatic fire extinguishing device (model QRR0.03GW/SHS- AR2), 5 devices in 5 protected areas are connected to the module on the driver’s operating panel through the main bearing harness.
When a fire risk occurs in any protection zone, the temperature is detected by the fire detection needle with a set temperature threshold. When the temperature rises to the set value (generally set to 130°C), a fire alarm signal is output and the driver operates the panel The module sends out audible and visual alarm signals. When the driver judges that a fire is in danger, he can manually start the fire extinguishing device through the module button to extinguish the fire.
If unattended or unable to manually start the fire extinguishing device, when the temperature continues to rise to ±175°C, the fire temperature detection harness will automatically (passively) start the fire extinguishing device to achieve fire extinguishing in the protected area.
② Principles of aerosol fire extinguishing
Hot aerosol fire extinguishing gas generator is a solid chemical mixture composed of oxidant, reducing agent, combustion rate control agent and binder. After being activated by heat (electricity), the reaction product is cooled and forms agglomerates in a sol state.
Under the action of heat, the vaporized metal ions and cations in the fire extinguishing gas can have an affinity reaction with the active groups in the combustion, repeatedly consume a large amount of active groups, reduce combustion free radicals, and efficiently absorb and neutralize the combustion in the flame Free radicals, so as to achieve chemical suppression of fire extinguishing effect. The aerosol formed by the solid particles wrapped in the fire extinguishing gas can be suspended for a long time and spread to all corners to effectively extinguish the fire in a fully submerged manner.
③ Start way
Thermal (passive) self-starting
When there is a fire risk in the protected space, when the detection temperature reaches 175 (±10℃) at any point on the temperature-sensitive detection harness arranged in the protected space, the temperature-sensitive fire detection harness will give an activation signal, and the fire extinguishing device will immediately start and release hot aerosol Fire extinguishing gas to extinguish the fire in the protected area. The feedback output function and feedback module (acousto-optic alarm) can be configured to realize the start-up feedback signal output after the fire extinguishing device is started.
Electric (active) manual start
When a fire is judged artificially, the fire extinguishing device (active) is given an electric start signal through a manual button, and the fire extinguishing device is immediately activated and releases hot aerosol fire extinguishing gas to extinguish the fire in the protected area. The feedback output function and feedback module (acousto-optic alarm) can be configured to realize the start-up feedback signal output after the fire extinguishing device is started.
Automatic fire suppression system for vehicles
3. Electric vehicles fire protection system video
4. Product comparison and advantages
In the document “GB7258-2012 Safety Technical Conditions for Motor Vehicle Operation” promulgated and implemented by the state on September 1, 2012, “Section 12.9.3 all special school buses and other passenger cars with rear engines shall be equipped with Engine compartment fire suppression systems.” According to national compulsory According to the requirements of national standards, currently the automatic fire suppression system for vehicles are mainly divided into two categories: dry powder automatic fire extinguishing devices and mini hot aerosol automatic fire extinguishing devices.
① Dry powder type automatic fire extinguishing device
a. Storage pressure hanging dry powder fire extinguishing device
Nitrogen is used as the driving medium for extinguishing agent delivery. The standard (at 20°C) storage pressure is 1.2MPa. The fire extinguishing device is composed of superfine dry powder fire extinguishing agent storage container, thermal wire, nozzle, pressure gauge, hook and other components.
Features: Long extinguishing time and low price. Due to the uniform distribution of the released ultra-fine dry powder, the effective fire extinguishing components of the fire extinguishing agent have poor orientation and are not suitable for local submerged fire extinguishing methods. In addition, because it is a pressure vessel, it is prone to air leakage and ineffectiveness. Secondly, after the fire extinguishing is started, the extinguishing agent deposits in the protected area and needs to be cleaned in time. In addition, the operating environment temperature range is -10～50℃, which is not suitable for my country’s northeast, northwest and other regions, and has regional limitations.
b. Non-storage pressure hanging dry powder fire extinguishing device
Gas is used as the driving medium for the delivery of ultra-fine dry powder fire extinguishing agent. The fire extinguishing device is composed of a shell, a dry powder fire extinguishing agent storage container, a solid agent reaction chamber, a heat-sensitive wire, an initiator, a hook and other components.
Features: In order to achieve a long delivery distance for the release of ultra-fine dry powder and good release directionality, gas is used to deliver the fire extinguishing agent in the form of blasting and accompanied by explosion sound, which has certain safety hazards. There have been accidents caused by debris after the explosion of the fire extinguishing device. . In addition, considering that the dry powder is agglomerated, the fire extinguishing agent driving medium is prone to leakage and failure, so the service life is short, and the general replacement cycle is 3 years.
② Mini aerosol automatic fire suppression system
“Hengshen” mini aerosol automatic fire suppression system for vehicles is a new type of fire extinguishing product designed and launched by Huashen Academician Workstation according to the special needs of the current automobile transportation industry and the environmental characteristics of smaller protected areas. Hot aerosol is a suspension system of liquid or solid particles in the air. Such as fog, smoke, haze, light fog (haze), dust and smog, etc., are all atmospheric aerosols caused by natural or man-made causes.
In addition to the gas component, the hot aerosol fire extinguishing gas has a small amount of solid particles. The solid particles are mainly metal oxides, carbonates or bicarbonates, and the particle size is less than 1 micron; the gas is mainly nitrogen, with a small amount Carbon dioxide gas and water vapor, so the hot aerosol fire extinguishing agent does not destroy the ozone layer, hardly produces the greenhouse effect, and does not pollute the environment.
③ Comprehensive comparison
1. The dry powder fire extinguishing device generally has the characteristics of good fire extinguishing and low cost, so it has been widely used at present. However, the water repellent effect of dry powder fire extinguishing agent is poor, and the powdery agent is easy to absorb moisture. After a certain period of time, agglomeration will generally occur, which will directly cause the discontinuity of powder spraying when the fire is started, which will seriously affect the fire extinguishing efficiency.
After the re-dry powder fire extinguishing device is started, the amount of powder precipitated is large, which is polluting and corrosive, making the protection area difficult to clean and easily causing damage to fine equipment.
2. The storage form of the fire extinguishing agent in the mini hot aerosol fire extinguishing device is a solid agent, which has the characteristics of being less affected by the environment and stable physical and chemical properties of the fire extinguishing agent. At the same time, the fire extinguishing gas produced by the release is basically free of dust, and the fire extinguishing gas still does not exist under high temperature and high humidity. Conductive and corrosive, will not cause any damage to electrical equipment.
At the same time, the gas is non-toxic and harmless and will not cause damage to the environment. It is currently the first new green environmental protection fire extinguishing agent, automatic fire suppression system for vehicles.
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