A new energy vehicle battery pack internal fire extinguishing method

Abstract

This invention specifically relates to a fire extinguishing method for the internal structure of a new energy vehicle battery pack, belonging to the field of new energy vehicle safety technology. The method includes: opening an electronically controlled valve based on a trigger signal, causing the extinguishing agent in the pressure vessel to flow along a U-shaped extinguishing pipeline and spray after breaking through the sealing membrane on the nozzle. In this invention, a three-in-one composite sensor integrating temperature, smoke, and air pressure is deployed one-to-one around the explosion-proof valve of each battery cell, changing the traditional lagging mode of area-level monitoring. The sensor uses high thermal conductivity silicone to directly adhere to the surface of the battery cell, ensuring that high-temperature gas, smoke particles, and pressure fluctuations escaping from the explosion-proof valve in the early stages of thermal runaway can be instantly captured. Combined with a three-level threshold tiered early warning system and multi-feature fusion judgment logic, the system can accurately identify a fire in the very early stage, before the battery cell diaphragm breaks down and open flames have formed.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle safety technology, and in particular to a method for extinguishing fires inside a new energy vehicle battery pack. Background Technology

[0002] Currently, the main technical bottleneck in thermal runaway protection of new energy vehicle power battery packs is the lag in detection. Existing solutions mostly employ module-level or regional-level sensor deployment, meaning a single sensor needs to monitor the status of multiple cells simultaneously. However, the high-temperature fumes in the early stages of thermal runaway initially escape from the narrow area of ​​the cell's explosion-proof valve and need to spread throughout the entire module before being detected by the regional sensors. This process results in a detection blind spot of tens of seconds or even longer, and by the time the system triggers an alarm, the optimal time for fire suppression has often passed.

[0003] In addition, existing technologies mostly rely on a single temperature parameter for judgment, which is easily affected by temperature fluctuations or electromagnetic interference inside the battery pack, resulting in a high false alarm rate; while smoke sensors can capture early signals, single smoke monitoring cannot distinguish between electrolyte leakage and normal exhaust, which also poses a risk of false triggering.

[0004] At the fire suppression execution level, the existing piping system design has significant flaws. The traditional single-end input straight pipe configuration results in significant pressure loss along the pipe, with the flow rate at the far end of the nozzle being much lower than that at the near end. This easily leads to an imbalance where the extinguishing agent supply is insufficient in the fire area while excessive spraying occurs in surrounding areas, making it difficult to achieve uniform coverage of the entire battery pack. At the same time, the nozzle structure mostly adopts a normally open design, which is prone to clogging due to long-term exposure to dust and condensate in the battery pack environment. Although a few solutions using electrically controlled valves can solve the clogging problem, they increase the system complexity, and the reliability of the valve control circuit is difficult to guarantee under the high temperature environment of thermal runaway.

[0005] Therefore, a fire extinguishing method for the internal battery pack of new energy vehicles is proposed to address the aforementioned problems. Summary of the Invention

[0006] The purpose of this invention is to provide a fire extinguishing method for the inside of a new energy vehicle battery pack in order to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for extinguishing fires inside a battery pack of a new energy vehicle, comprising: Step 1: Deploy a three-in-one composite sensor around the explosion-proof valve of each cell in the battery pack to monitor the cell's temperature, smoke concentration, and air pressure change rate in real time, and set three threshold levels. Step 2: When the monitored parameters exceed the threshold, the fire situation is confirmed by multi-feature fusion, and a trigger signal is generated; Step 3: Open the electronic control valve according to the trigger signal to allow the extinguishing agent in the pressure vessel to flow along the U-shaped extinguishing pipeline and spray after breaking through the sealing membrane on the nozzle. Step 4: The extinguishing agent is symmetrically distributed in the U-shaped pipeline to achieve pressure balance and uniform flow rate at each nozzle; Step 5: The extinguishing agent is sprayed in a directional atomization from the nozzle, covering the area of ​​the battery cell explosion-proof valve, and extinguishing the fire through cooling, suffocation and chemical suppression.

[0008] Preferably, the three-in-one composite sensor in step one is encapsulated in a high-temperature resistant ceramic package and bonded to the surface of the battery cell using high thermal conductivity silicone.

[0009] Preferably, the three threshold levels in step one include a temperature threshold, a smoke concentration threshold, and a pressure change rate threshold, wherein the temperature warning level is 80℃, the level two warning level is 100℃, and the level three triggering level is 120℃; the smoke concentration triggering threshold is 0.5 mg / L. The trigger threshold for the rate of change of air pressure is ≥50Pa / s.

[0010] Preferably, the multi-feature fusion judgment in step two includes: when a single sensor exceeds the limit, increasing the sampling frequency for monitoring; if the limit continues to be exceeded, triggering an early warning; when two or more sensors exceed the limit simultaneously, directly determining it as a fire and initiating the fire extinguishing process.

[0011] Preferably, step two also includes a redundancy design: when the BMS fails, an independent trigger module receives sensor signals and directly drives the electronically controlled valve. The independent trigger module is powered by a built-in supercapacitor to ensure that the valve can still be opened when the vehicle is powered off.

[0012] Preferably, the electrically controlled valve in step three is a two-position two-way direct-acting solenoid valve; the pressure vessel is pre-pressurized to 1.2~1.8MPa, and the extinguishing agent is perfluorohexanone or heptafluoropropane.

[0013] Preferably, the sealing film on the nozzle in step three is made of polyimide, which ruptures under the pressure of the extinguishing agent or high temperature, exposing all nozzles simultaneously within 10-20 ms.

[0014] Preferably, the U-shaped fire extinguishing pipeline in step four has a symmetrical configuration, with the input end located in the middle of the transverse section, the difference in flow channel length between the farthest and nearest nozzles meeting the preset requirements, and the inlet pressure of each nozzle being stable at 1.0~1.2MPa.

[0015] Preferably, the nozzle diameter in step five is set according to the type of extinguishing agent: 1.0~1.2mm for perfluorohexanone and 0.8~1.0mm for heptafluoropropane; the spray direction is angled downwards at 30~45°, pointing towards the center of the battery cell explosion-proof valve; under the spray pressure, the droplet size achieves rapid vaporization and heat absorption, forming an inert gas isolation layer.

[0016] Preferably, in step five, after the extinguishing agent extinguishes the fire, a slight positive pressure of 0.12~0.15MPa is maintained in the U-shaped pipeline to prevent backflow. The BMS monitors the status of the battery cells, and the system is manually reset after the temperature drops below 80℃ and the smoke concentration returns to zero.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention changes the traditional lagging mode of regional monitoring by deploying integrated temperature, smoke, and air pressure sensors one-to-one around the explosion-proof valve of each battery cell; the sensors are made of high thermal conductivity silicone directly attached to the surface of the battery cell to ensure that high-temperature gas, smoke particles, and air pressure fluctuations escaping from the explosion-proof valve in the early stage of thermal runaway can be captured instantly; combined with a three-level threshold tiered early warning and multi-feature fusion judgment logic, the system can accurately identify the fire in the very early stage when the battery cell diaphragm breaks down and no open flame has formed.

[0018] 2. This invention, by adopting a U-shaped symmetrical pipeline configuration and an inner wall electrolytic polishing process, enables the extinguishing agent to flow bidirectionally within the pipeline, and the inlet pressure of each nozzle is stabilized at 1.0~1.2MPa, eliminating the extinguishing blind zone caused by insufficient flow at the far end in traditional straight pipe schemes; the nozzles are sealed with polyimide hot-melt sealing films, which not only prevent daily dust blockage, but also can automatically rupture at ≥120℃ or ≥0.3MPa pressure without the need for additional drive. Attached Figure Description

[0019] Further details, features, and advantages of this application are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which: Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0020] Several embodiments of this application will now be described in more detail with reference to the accompanying drawings to enable those skilled in the art to implement this application. This application may be embodied in many different forms and for various purposes and should not be limited to the embodiments set forth herein. These embodiments are provided to make this application thorough and complete, and to fully convey the scope of this application to those skilled in the art. The embodiments described do not limit this application.

[0021] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It will be further understood that terms such as those defined in commonly used dictionaries shall be interpreted as having a meaning consistent with their meaning in the relevant field and / or the context of this specification, and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0022] Example 1

[0023] Its specific implementation method is combined with the appendix Figure 1 Please provide a detailed explanation.

[0024] Appendix Figure 1 The flowchart of a fire extinguishing method for the inside of a new energy vehicle battery pack provided in this embodiment of the invention shows the complete steps from deploying a three-in-one composite sensor around the explosion-proof valve of each cell in the battery pack to the directional atomization spraying of the fire extinguishing agent from the nozzle.

[0025] In this embodiment, it includes: Step 1: System Initialization and Comprehensive Perception Deployment The battery pack fire suppression system maintains a low-power standby mode while the vehicle is in motion, charging, or stationary. Its core objective is to accurately detect the initial characteristics of thermal runaway in the battery cells, buying time for subsequent fire suppression actions, while ensuring the system itself suffers no abnormal damage and remains stable in its long-term operation. This step clarifies the specific technical details of sensor deployment, monitoring parameters, actuator status, and communication mechanisms to ensure the reliability and feasibility of the sensing system.

[0026] Sensor deployment and packaging requirements The "cell-level precision monitoring" solution is adopted, and the following deployment standards are applicable to the square, cylindrical and pouch cells commonly used in new energy vehicles: In the critical area of ​​5~10mm around the explosion-proof valve on the top of each cell (this area is where smoke and high-temperature gas first escape in the early stage of thermal runaway, which can minimize the detection lag), a three-in-one composite sensor (integrating temperature, smoke and air pressure detection functions, the sensor model can be selected from the MSP430 series integrated sensor, which is suitable for automotive-grade working environment) is deployed one-to-one. The sensor uses a high-temperature resistant ceramic package (withstanding temperatures ≥150℃, long-term operating temperature -40℃~+125℃, meeting the requirements of extreme working environments of the battery pack). It is directly bonded to the surface of the battery cell using high thermal conductivity silicone (thermal conductivity ≥2.0W / (m·K), model TC-5021). A 0.5~1mm thick layer of thermally conductive adhesive is applied to the bonding surface to ensure no air bubbles remain and eliminate detection blind spots. The sensor pins are packaged with high-temperature resistant waterproof terminals, and the connection with the wires is wrapped with heat shrink tubing to prevent condensation and electrolyte leakage from the battery pack from corroding the pins. This ensures that the temperature rise, smoke generation, and pressure fluctuations in the early stages of thermal runaway can be quickly conducted to the sensor detection end, with a signal transmission delay ≤10ms, avoiding signal delays that could lead to missed opportunities for fire suppression.

[0027] Monitoring parameters and grading threshold settings: Based on the thermal runaway evolution patterns of mainstream ternary lithium batteries (NCM811, NCM622) and lithium iron phosphate batteries (the initial thermal runaway temperature of ternary lithium batteries is approximately 120℃, and that of lithium iron phosphate batteries is approximately 150℃; this solution takes both battery types into account, and the threshold settings are adapted to mainstream battery cells), a three-level monitoring threshold is set to achieve a stepped response of "early warning-confirmation-triggering". The basis for setting each threshold and the specific implementation standards are as follows: Temperature monitoring: Focusing on the surface temperature of the battery cell, a PT1000 platinum resistance temperature sensing element is used (measurement accuracy ±0.5℃, measurement range -50℃~+200℃). The first-level warning threshold is 80℃ (the normal operating temperature of the battery cell is 25~45℃, and 80℃ is the critical value for abnormal heating of the battery cell, at which point the electrolyte inside the battery cell begins to decompose slightly), the second-level warning threshold is 100℃ (a precursor to thermal runaway, the battery cell diaphragm begins to shrink, the internal resistance increases, and the heating rate accelerates), and the third-level trigger threshold is 120℃ (thermal runaway begins, the battery cell diaphragm breaks down, the positive and negative electrodes are short-circuited, and a large amount of high-temperature gas and smoke begins to be generated). Smoke concentration monitoring: Utilizing the optical scattering detection principle, the detection wavelength is set to 650nm (this wavelength offers the highest sensitivity for detecting smoke particles (0.1~10μm in diameter) generated during electrolyte decomposition). A trigger threshold of 0.5mg / L is set for the visible smoke (mainly composed of carbonate decomposition products) generated in the initial stage of electrolyte decomposition. This threshold has been verified through multiple tests and can detect smoke before it spreads to the entire battery pack, avoiding detection delays caused by smoke diffusion, with a detection response time of ≤50ms. Pressure change rate monitoring: A miniature piezoresistive pressure sensor (measurement range 0~100kPa, accuracy ±1kPa) is used to track the rate of increase in internal air pressure of the battery pack. The trigger threshold is set to ≥50Pa / s. This threshold corresponds to the typical air pressure characteristics of high-temperature gas ejection after the explosion-proof valve is opened (the opening pressure of the explosion-proof valve is usually 100~300kPa, and the instantaneous air pressure rise rate after opening can reach 50~100Pa / s). It can accurately identify thermal runaway escalation signals and avoid misjudging them as normal air pressure fluctuations in the battery pack (the air pressure fluctuation rate of the battery pack during normal driving is ≤10Pa / s).

[0028] Execution component standby status: Electrically controlled valve: A two-position, two-way direct-acting solenoid valve (model VZ5120 series, suitable for automotive environments) is selected. It is normally closed, with the valve core return spring preload set to 50~80N to ensure no leakage in the normally closed state. The solenoid coil has a rated voltage of 24V (suitable for the vehicle's low-voltage power supply system). When there is no current input, the valve core remains closed by the spring preload, ensuring no leakage in daily use. Simultaneously, the coil response time is ≤50ms, providing a rapid response capability. The valve body inlet and outlet are threaded (thread specification M12×1.5) for easy installation and maintenance. U-shaped fire extinguishing pipeline: Made of 304 stainless steel (wall thickness 1.5~2mm, inner diameter 10~12mm), it can withstand high pressure and high temperature corrosion, and the internal air pressure is maintained at normal atmospheric pressure (the air pressure is the same as the external atmospheric pressure, about 101kPa); the nozzles are sealed with a heat-melting sealing film, and the sealing film material is polyimide (melting point ≤120℃, rupture pressure ≤0.3MPa, thickness 0.1~0.2mm). This material has both high temperature resistance and easy rupture characteristics, which can prevent blockage caused by daily vibration, air pressure fluctuation and dust entering the pipeline, and can automatically rupture in the early stage of thermal runaway as the temperature rises (≥120℃) or pressure impact (≥0.3MPa), without the need for additional drive; the nozzle spacing is matched with the battery cell layout, and the spacing between adjacent nozzles is ≤50mm to ensure no coverage blind spots; Extinguishing agent pressure vessel: A seamless carbon steel cylinder (5-10L capacity, design pressure 3.0MPa, working pressure 1.2-1.8MPa) is used, conforming to GB / T5099 standard requirements, and can safely store high-pressure extinguishing agents; it internally stores perfluorohexanone (model FK-5-1-12) or heptafluoropropane (model HFC-227ea) extinguishing agents, which are interchangeable. Perfluorohexanone is suitable for enclosed spaces in battery packs, offering high extinguishing efficiency and leaving no residue, while heptafluoropropane is suitable for low-temperature environments (it can still release normally at -40℃); the container valve is a pilot-operated valve (opening pressure 1.2MPa), in the closed state. The valve interface is connected to the high-pressure hose using a quick-connect fitting to ensure sealing performance. A pressure monitoring gauge is installed at the bottom of the container to display the internal pressure in real time, facilitating daily maintenance.

[0029] System communication mechanism

[0030] All sensors establish real-time communication with the Battery Management System (BMS) via the CAN 2.0B bus, with a communication baud rate set to 500kbps (adapting to automotive-grade communication speeds to ensure stable data transmission). The data refresh frequency is ≥10Hz, meaning sensor data is refreshed every 100ms, ensuring that temperature, smoke, and air pressure data collected by the sensors can be transmitted to the BMS within 100ms. The BMS has a built-in data processing module that performs real-time filtering on the received sensor data (using a Kalman filter algorithm with a filtering coefficient of 0.1~0.3) to eliminate abnormal data caused by electromagnetic interference, enabling rapid identification and preliminary judgment of abnormal signals and providing accurate data support for subsequent triggering decisions. At the same time, the BMS establishes bidirectional communication with the Vehicle Control Unit (VCU) and can report the system's standby status in real time, facilitating collaborative monitoring of the entire vehicle system.

[0031] Step 2: Thermal runaway detection and signal triggering: When a battery cell experiences thermal runaway, and the characteristic parameters captured by the sensor exceed the set threshold, the system immediately switches from standby mode to rapid judgment and triggering mode. The core is to avoid false alarms through multi-parameter fusion judgment, while linking the whole vehicle system to achieve safety protection and ensure the timeliness and accuracy of fire extinguishing actions.

[0032] Multi-feature fusion judgment logic A "double confirmation" mechanism is adopted to reduce the probability of false alarms (such as electromagnetic interference to the temperature sensor, false triggering of the smoke sensor, etc.). The judgment logic time is ≤100ms (including signal filtering, debouncing, and logic operation). The specific judgment process and parameter settings are as follows: Single sensor exceeding limit: If only one sensor parameter exceeds the threshold (e.g., temperature ≥120℃, but smoke concentration <0.5mg / L), the limit is exceeded. If the air pressure change rate is <50Pa / s, the system will automatically increase the sampling frequency of the sensors in that area to 100Hz (refreshing data every 10ms) and continuously monitor for 300ms to determine if it is a transient anomaly. If the parameters return to normal within 300ms, it is determined to be a false trigger and the system returns to standby mode. If the parameters continue to exceed the limit, a level 2 warning will be triggered, and the BMS will be notified to strengthen the monitoring of that area. Exceeding limits for dual or more sensors: If two or more sensors simultaneously exceed the threshold (e.g., temperature ≥ 120℃ + smoke concentration ≥ 0.5mg / L). Or, a temperature ≥120℃ + a pressure change rate ≥50Pa / s, or a smoke concentration ≥0.5mg / L. If the air pressure change rate is ≥50Pa / s, it is directly judged as "fire confirmed" and the subsequent fire extinguishing process is immediately initiated. This judgment logic has been verified by multiple tests and the false alarm rate is ≤0.1%, which can effectively avoid false triggering caused by the failure of a single sensor.

[0033] Signal transmission and execution triggering Signal path: After the BMS confirms the fire, the signal is transmitted via a hard wire (1.5m). The system uses a shielded cable (with strong electromagnetic interference resistance) or CAN bus to send a 24V pulse trigger signal to the electronically controlled valve driver. The trigger signal lasts for ≥500ms (tested to ensure the valve core is fully open, preventing incomplete valve operation due to signal interruption). After receiving the signal, the driver outputs a current ≥2A to drive the solenoid coil to engage, allowing the valve core to open against the spring preload. After opening, the driver sends a "valve open" signal back to the BMS to ensure the BMS monitors the valve status in real time. Vehicle-wide linkage: The BMS synchronously reports the "battery pack fire alarm" status to the vehicle controller (VCU). The reporting signal uses a dual transmission method of hard wire + CAN bus to ensure that the signal is not lost. After receiving the fire alarm signal, the VCU immediately triggers the high-voltage safety protection, disconnecting the high-voltage relays (including the positive main relay, negative main relay and pre-charge relay) within 50ms, stopping the vehicle's charging and discharging operation, and disconnecting the high-voltage connection between the battery pack and other components of the vehicle to prevent high-voltage circuit short circuits from aggravating the fire. In addition, the VCU synchronously triggers the vehicle alarm system, turns on the in-vehicle alarm lights and buzzers, and sends fire alarm information to the vehicle terminal to remind the driver and maintenance personnel to deal with the situation in a timely manner.

[0034] Redundant design (fault tolerance mechanism) To prevent the fire suppression process from being interrupted due to the failure of core components, a dual redundancy design is implemented to ensure that the fire suppression process can still be initiated normally in extreme situations such as BMS failure or low-voltage power failure of the entire vehicle. The specific redundancy design is as follows: Control redundancy: When the BMS fails (e.g., BMS power supply failure, data processing module failure), the sensor is directly connected to the independent trigger module via hardwire (the independent trigger module uses an STM32F103 series microcontroller, operating voltage 12~24V). Without the need for BMS relay, the independent trigger module can directly receive the sensor over-limit signals. When two or more sensors are detected to be over-limit, it immediately outputs a 24V pulse signal to drive the electronically controlled valve to open. The independent trigger module and BMS are designed in parallel, which can monitor the BMS operating status in real time. When the BMS failure is detected, it automatically switches to independent control mode. Power supply redundancy: The independent trigger module has a built-in supercapacitor (capacity 1000F, working voltage 24V). The supercapacitor is normally charged by the vehicle's low-voltage power supply. After being fully charged, it can maintain the independent trigger module and the electronic control valve to work normally for ≥5 seconds. Even if the vehicle's low-voltage power supply is cut off (such as a collision causing the low-voltage line to break), it can still maintain the electronic control valve open for ≥5 seconds to ensure that the extinguishing agent can be released normally, complete the initial fire extinguishing action, and buy time for subsequent rescue.

[0035] Step 3: Pipeline opening and extinguishing agent release: Upon receiving a trigger signal, the electrically controlled valve rapidly opens, utilizing the pre-pressurized potential energy of the pressure vessel to propel the extinguishing agent along the pipeline, breaking through the nozzle seal and achieving rapid flow of the extinguishing medium. The core principle is to ensure both valve response speed and pipeline flow efficiency, guaranteeing the extinguishing agent reaches the fire area in the shortest possible time. This step clarifies the specific technical details and parameter basis for valve action, extinguishing agent flow, and nozzle seal rupture, ensuring the feasibility and stability of the fluid activation process.

[0036] Details of the operation of the electronically controlled valve Response speed: The response time of the solenoid valve from receiving the trigger signal to the valve core being fully opened is ≤50ms (this response time has been tested and can meet the requirements for rapid fire extinguishing in the early stage of thermal runaway, preventing the spread of fire); the test conditions for response time are: ambient temperature 25℃, voltage 24V±1V, current ≥2A, and the test method uses an oscilloscope to monitor the valve core action signal to ensure the accuracy of the test data; Structural parameters: Valve diameter ≥ 6mm, precisely matched with the inner diameter of the fire extinguishing pipeline (10~12mm); valve inlet / outlet cross-sectional area ratio ≥ 0.8 to pipeline cross-sectional area to avoid throttling effect when fluid passes through and ensure fire extinguishing agent flow rate; valve core is made of stainless steel (304 stainless steel) with surface hardening treatment (hardness HRC≥50) to improve wear resistance and extend service life. Material and Sealing: The valve body is made of stainless steel (304 stainless steel), which can withstand high pressure and corrosion from fire extinguishing agents; it has a built-in fluororubber sealing ring (model O-ring, specification Φ6×1.5), which can withstand a temperature range of -40℃ to +150℃ and can resist corrosion from perfluorohexanone and heptafluoropropane fire extinguishing agents, ensuring that there is no leakage when the valve is closed and no resistance when it is opened; when installing the sealing ring, apply special lubricant (model PFPE, compatible with fluororubber) to reduce frictional resistance when the valve core moves and improve response speed.

[0037] Initial flow characteristics of extinguishing agent Pressure-driven: The pre-pressure potential energy of 1.2~1.8MPa in the pressure vessel is applied to the pipeline inlet instantaneously after the valve is opened, forming an instantaneous driving force; the pre-pressure setting is based on ensuring that the extinguishing agent can quickly fill the pipeline and break through the sealing membrane, while avoiding excessive pressure that could cause pipeline rupture. 1.2~1.8MPa is the optimal pressure range verified by multiple tests, which can balance flow velocity and pipeline safety. Flow path: The extinguishing agent is drawn from the pressure vessel through a high-pressure hose (made of polytetrafluoroethylene, pressure resistance ≥3MPa, length ≤300mm, inner diameter 8~10mm) and quickly enters the inlet end of the U-shaped pipeline. The high-pressure hose is wrapped with stainless steel braided mesh to enhance its pressure resistance while also providing a certain degree of flexibility for easy installation in the complex space inside the battery pack. Both ends of the hose are connected with compression fittings, and the fittings are sealed with copper gaskets to ensure no leakage and reduce pressure loss along the hose (pressure loss along the hose ≤0.1MPa). Flow control: The initial flow rate is determined by the total flow area of ​​the nozzle, which is calculated based on the battery enclosure volume (a total flow area of ​​≥10m² corresponds to a battery enclosure volume of 10L). Taking perfluorohexanone as an example, the peak flow rate at the pipeline inlet is designed to be 20~30g / s. This flow rate can ensure that the extinguishing agent fills the entire U-shaped pipeline within 1~2s and quickly reaches each nozzle, laying the foundation for subsequent uniform spraying. The flow rate is tested using a mass flow meter with a test accuracy of ±0.1g / s.

[0038] Mechanism of nozzle sealing membrane rupture

[0039] After the extinguishing agent enters the U-shaped pipeline, the internal pressure of the pipeline rapidly rises to ≥0.5MPa, far exceeding the rupture pressure of the heat-fused sealing membrane (≤0.3MPa). Simultaneously, the high temperature (≥120℃) generated by thermal runaway causes the sealing membrane to melt and rupture rapidly. The rupture sequence of the sealing membrane is as follows: the sealing membrane of the nozzles near the fire area ruptures first, followed by the synchronous rupture of the sealing membranes of other nozzles under pressure. All nozzles can be exposed simultaneously within 10~20ms, completing the spray preparation and ensuring that the extinguishing agent can be sprayed synchronously, avoiding localized fire extinguishing delays. The rupture pressure and melting point of the sealing membrane have been batch tested, with a batch pass rate of ≥99.5%, ensuring that the sealing membrane of each nozzle can rupture under the set conditions. In addition, the connection between the sealing membrane and the nozzle uses a hot-press bonding process, with a bonding strength of ≥5N / cm, preventing the sealing membrane from falling off due to daily vibration.

[0040] Step 4: Uniform flow distribution and pressure equalization: After the extinguishing agent enters the U-shaped pipeline, the pipeline configuration is optimized, the inner wall is treated, and the fluid dynamics simulation design is used to achieve consistent pressure and uniform flow across all nozzles, ensuring that the extinguishing medium can cover all battery cell areas and avoid incomplete local extinguishing.

[0041] U-shaped symmetrical flow splitting principle (core design) The system adopts a U-shaped symmetrical pipeline configuration, with the inlet located in the middle of the transverse section of the U. After entering the pipeline, the extinguishing agent flows bidirectionally along the two longitudinal sections. Compared with the traditional single-end inlet straight pipe, this significantly shortens the flow path length difference and optimizes pressure distribution. Specific design details and parameter basis are as follows: Flow channel length control: The transverse section length of the U-shaped pipe is set according to the battery pack width (consistent with the battery pack width, usually 800~1200mm), and the longitudinal section length is set according to the battery pack height (usually 200~300mm); the flow channel length difference between the farthest nozzle (U-shaped end) and the nearest nozzle (near the input end) is ≤300mm. This length difference is optimized by CFD simulation to ensure that the difference in friction pressure loss is ≤5% (friction pressure loss is calculated using the Darcy-Weisbach formula, λ=0.02~0.03). Pressure range assurance: Optimization was achieved through CFD (Computational Fluid Dynamics) simulation using ANSYS Fluent. The simulation boundary conditions were set as follows: inlet pressure 1.2~1.8MPa, outlet pressure 0.1MPa, ambient temperature 25℃, and extinguishing agent density 1.6g / cm³. (Perfluorohexanone); Simulation results show that the inlet pressure of each nozzle is stable at 1.0~1.2MPa (pressure vessel output pressure is 1.2~1.8MPa, and after deducting pipeline friction loss, the minimum pressure is not lower than 1.0MPa). This pressure range can ensure that the extinguishing agent achieves efficient atomization and provides a pressure basis for uniform spraying. The simulation results were verified by physical testing, and the pressure deviation was ≤0.05MPa, which meets the design requirements.

[0042] Pipeline inner wall and interface optimization Internal wall treatment: The inner wall of the pipeline is treated with electrolytic polishing, with polishing parameters of current density 10~15A / d. Polishing time is 10-15 minutes. The polishing fluid is a mixture of phosphoric acid and sulfuric acid (volume ratio 3:1). After polishing, the surface roughness Ra is ≤0.4μm, which minimizes the frictional resistance along the flow of the extinguishing agent and reduces pressure loss. After polishing, the inner wall is passivated to form an oxide protective film, which enhances the corrosion resistance of the pipeline and extends its service life. Elbow Design: All pipe elbows adopt a large radius of curvature (R≥30mm), with a radius of curvature to pipe inner diameter ratio ≥3, to avoid local eddies when fluid flows through the elbow and prevent sudden pressure drops (local pressure loss ≤0.03MPa); the elbows are cold-bent using a pipe bending machine, resulting in no wrinkles or deformation after forming, ensuring a smooth flow path and not affecting fluid flow; Branch interface: If branch pipelines are required (for large battery packs with more than 100 cells), a Y-type tee structure is adopted, with the included angle of the tee being 90°. The inner diameter of the two branch pipelines is consistent with the inner diameter of the main pipeline (10~12mm). The tee adopts a streamlined design to reduce the resistance during fluid diversion, ensuring that the deviation of the diversion uniformity is ≤3%, and avoiding insufficient flow in a certain branch. The connection between the branch interface and the main pipeline and branch pipelines adopts a welding process, and the welding method is argon arc welding. The weld is flat, without pores or cracks, to ensure sealing performance.

[0043] Traffic allocation effect verification Taking 30 nozzles (15 on each side of the U-shaped pipeline) as an example, with nozzle diameters of 1.0~1.2mm (compatible with perfluorohexanone), the uniform flow distribution was ensured through CFD simulation and physical testing. The CFD simulation used ANSYS Fluent software, and the simulation model was established at a 1:1 scale with the actual pipeline dimensions. Simulation results showed that the flow rate of the furthest nozzle was 95%~105% of the flow rate of the nearest nozzle, achieving "equal flow spray." Physical testing used a mass flow meter to measure the flow rate of each nozzle under the following conditions: inlet pressure 1.2MPa, ambient temperature 25℃. The test results were consistent with the simulation results, with a flow rate deviation ≤5%, ensuring that all battery cell areas receive a uniform supply of extinguishing agent and preventing extinguishing failure in localized areas due to insufficient flow. The test data can serve as a basis for verifying the feasibility of the solution, ensuring that it can be reproduced by those skilled in the art.

[0044] Step 5: Precise spraying and fire suppression coverage: After the extinguishing agent is sprayed from each nozzle, it achieves directional and atomized spraying through nozzle parameter design. Combined with the triple mechanism of cooling, asphyxiation and chemical inhibition, it quickly suppresses thermal runaway, covers all critical areas of the battery cell, and prevents reignition, thus completing the entire fire extinguishing process.

[0045] Nozzle design parameters (directional precision spraying) Orifice matching: The orifice size is optimized according to the type of extinguishing agent. Perfluorohexanone is suitable for an orifice size of 1.0~1.2mm (tolerance ±0.05mm), and heptafluoropropane is suitable for an orifice size of 0.8~1.0mm (tolerance ±0.05mm). The orifice size is set based on ensuring that the atomized particle size meets the design requirements while ensuring sufficient flow rate. The orifice size is processed by laser drilling with a drilling accuracy of ±0.01mm to ensure that the orifice size of each nozzle is consistent and to avoid flow rate deviation. Spray direction: The nozzle is angled downwards at 30~45° (angle with the pipeline axis, tolerance ±2°), precisely pointing towards the center of the battery cell explosion-proof valve (deviation ≤5mm), directly hitting the core area of ​​thermal runaway (the explosion-proof valve is the main channel for high-temperature gas and flame jets, and this direction ensures that the extinguishing agent acts directly on the source of the fire); the installation angle of the nozzle is positioned by a special clamp, and the angle is tested after installation. It can only be put into use after passing the test. Coverage: The spray angle is designed with a 120° cone angle (tolerance ±5°), which can fully cover the explosion-proof valve and the surrounding 50mm area, eliminating blind spots in fire extinguishing; the coverage area of ​​a single nozzle is ≥2000m². The coverage area of ​​adjacent nozzles overlaps by ≥10% to ensure that the explosion-proof valve area of ​​all battery cells can be covered by the extinguishing agent; the coverage range is verified by spray test, using a high-speed camera to capture the spray pattern and measure the coverage area and overlap rate to ensure that it meets the design requirements.

[0046] Atomization effect and thermal suppression effect At a spray pressure of 1.0~1.2MPa, the extinguishing agent achieves efficient atomization. The atomization effect directly affects the extinguishing efficiency. The specific atomization parameters, test methods, and thermal suppression effects are as follows: Rapid vaporization and heat absorption: After the droplets come into contact with the flame and the high-temperature battery cell surface, they rapidly vaporize, absorbing a large amount of heat (latent heat of vaporization of perfluorohexanone ≈ 88 kJ / kg, latent heat of vaporization of heptafluoropropane ≈ 171 kJ / kg), quickly reducing the battery cell temperature to below the thermal runaway critical point (≤120℃ for ternary lithium batteries, ≤150℃ for lithium iron phosphate batteries), thus blocking the spread of thermal runaway; the vaporization rate has been tested, and at 120℃, the vaporization time of perfluorohexanone droplets is ≤0.5s, which can quickly achieve a cooling effect; Three-dimensional coverage: The mist droplets rise with the high-temperature airflow and fill the space between the top of the battery cell and the top cover of the battery pack (this space is the area where thermal runaway gas accumulates), forming a three-dimensional coverage layer with a coverage thickness of ≥50mm, avoiding local areas that are not covered by the extinguishing agent; the three-dimensional coverage effect is verified by smoke simulation test. After releasing smoke inside the battery pack and spraying the extinguishing agent, the smoke clearance time is ≤5s, indicating uniform coverage; Inert isolation: The density of the vaporized extinguishing agent is greater than that of air (perfluorohexanone vapor density ≈ 6.5 kg / m³). Heptafluoropropane vapor density ≈ 3.0 kg / m³ The gas settles and covers the surface of the battery cell, forming an inert gas isolation layer with a thickness of ≥10mm. This layer can effectively isolate the oxygen supply (when the oxygen concentration drops below 12%, combustion cannot be sustained), thus suffocating the flame. The oxygen concentration is tested using an oxygen sensor with a test accuracy of ±0.1%, ensuring accurate test data.

[0047] Triple fire extinguishing mechanism works synergistically Cooling mechanism: By absorbing heat through droplet vaporization, the temperature of the battery cell and its surrounding environment is reduced, thereby suppressing thermal runaway reaction from the source (thermal runaway reaction is an exothermic reaction, and the temperature reduction can slow down the reaction rate until it stops); the cooling effect has been tested and found that in a high temperature environment of 150℃, after spraying the fire extinguishing agent, the surface temperature of the battery cell can be reduced to below 80℃ within 30 seconds, which meets the cooling requirements; Asphyxiation mechanism: Inert vapor isolates oxygen, cutting off the necessary conditions for combustion (combustion requires oxygen, combustibles, and ignition source), and quickly extinguishes open flames; Tests have verified that in a sealed battery pack (10L volume), after injecting 500g of perfluorohexanone, the oxygen concentration can drop to below 12% within 10s, and the open flame can be extinguished within 15s. Chemical inhibition mechanism: Perfluorohexanone and heptafluoropropane decompose in a high-temperature flame environment (≥500℃) to produce active free radicals (such as CF3· and CF2·). These free radicals can combine with active free radicals in the combustion reaction (such as H· and OH·), interrupt the combustion chain reaction, further enhance the fire extinguishing effect, and prevent reignition. The chemical inhibition effect has been verified by experiments, with a reignition rate of ≤0.5% after fire extinguishing, ensuring thorough fire extinguishing.

[0048] Continuous fire suppression and reignition control Release duration: The pressure vessel continuously releases extinguishing agent until the internal pressure reaches equilibrium with the external pressure (approximately 101 kPa). The designed release time is ≥30 seconds. The release time is set based on ensuring sufficient extinguishing agent to suppress thermal runaway and completely extinguish the fire, while avoiding waste of extinguishing agent. Testing showed that for a 5L pressure vessel with a pre-pressurization of 1.2 MPa, the release time is approximately 35 seconds, meeting the design requirements. The release time can be adjusted by changing the pressure vessel volume and pre-pressurization pressure. Anti-backflow design: After fire extinguishing, the residual pressure in the U-shaped pipeline maintains a slight positive pressure (0.12~0.15MPa) in the nozzle. This slight positive pressure prevents outside air from being drawn back into the battery pack, thus avoiding reignition (backflow of air would bring in oxygen, causing the extinguished fire to reignite). The slight positive pressure is maintained by a one-way valve at the end of the pipeline. The one-way valve opens at a pressure of 0.12MPa, ensuring that it automatically closes when the pressure in the pipeline falls below this value, preventing backflow. System Reset: The BMS continuously monitors the battery pack status at a frequency ≥10Hz. When the cell temperature drops below 80℃ and the smoke concentration reaches zero (<0.1mg / L), the system resets. When the pressure change rate is ≤10Pa / s, the electronic control valve can be closed by manual reset (the manual reset button is located outside the battery pack for easy operation), or the valve can be kept open until professional maintenance personnel have completed the inspection and confirmed that there is no risk of reignition before resetting. After manual reset, the system returns to standby mode and can be put back into use.

[0049] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

[0050] It should be noted that, in this document, the use of relational terms such as "first" and "second" is merely for distinguishing one entity or operation from another, and does not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0051] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0052] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0053] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0054] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0055] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0057] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for extinguishing fires inside a battery pack of a new energy vehicle, characterized in that, include: Step 1: Deploy a three-in-one composite sensor around the explosion-proof valve of each cell in the battery pack to monitor the cell's temperature, smoke concentration, and air pressure change rate in real time, and set three threshold levels. Step 2: When the monitored parameters exceed the threshold, the fire situation is confirmed by multi-feature fusion, and a trigger signal is generated; Step 3: Open the electronic control valve according to the trigger signal to allow the extinguishing agent in the pressure vessel to flow along the U-shaped extinguishing pipeline and spray after breaking through the sealing membrane on the nozzle. Step 4: The extinguishing agent is symmetrically distributed in the U-shaped pipeline to achieve pressure balance and uniform flow rate at each nozzle; Step 5: The extinguishing agent is sprayed in a directional atomization from the nozzle, covering the area of ​​the battery cell explosion-proof valve, and extinguishing the fire through cooling, suffocation and chemical suppression.

2. The fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, The three-in-one composite sensor described in step one uses a high-temperature resistant ceramic package and is attached to the surface of the battery cell using high thermal conductivity silicone.

3. The fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, The three threshold levels mentioned in step one include a temperature threshold, a smoke concentration threshold, and a pressure change rate threshold. The temperature warning level is 80℃ for level one, 100℃ for level two, and 120℃ for level three. The smoke concentration trigger threshold is 0.5 mg / L. The trigger threshold for the rate of change of air pressure is ≥50Pa / s.

4. A fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, The multi-feature fusion judgment in step two includes: when a single sensor exceeds the limit, the sampling frequency is increased for monitoring; if the limit continues to be exceeded, an early warning is triggered; when two or more sensors exceed the limit at the same time, it is directly determined as a fire and the fire extinguishing process is initiated.

5. A fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, Step two also includes a redundancy design: when the BMS fails, an independent trigger module receives sensor signals and directly drives the electronically controlled valve. The independent trigger module is powered by a built-in supercapacitor to ensure that the valve can still be opened when the vehicle is powered off.

6. A fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, The electrically controlled valve mentioned in step three is a two-position two-way direct-acting solenoid valve; the pressure vessel is pre-pressurized to 1.2~1.8MPa, and the extinguishing agent is perfluorohexanone or heptafluoropropane.

7. A fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, The sealing membrane on the nozzles mentioned in step three is made of polyimide. It ruptures under the pressure of the extinguishing agent or high temperature, exposing all nozzles simultaneously within 10~20ms.

8. A fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, The U-shaped fire extinguishing pipeline described in step four has a symmetrical configuration, with the input end located in the middle of the transverse section. The difference in flow channel length between the farthest and nearest nozzles meets the preset requirements, and the inlet pressure of each nozzle is stable at 1.0~1.2MPa.

9. A fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, The nozzle diameter in step five is set according to the type of extinguishing agent: 1.0~1.2mm for perfluorohexanone and 0.8~1.0mm for heptafluoropropane; the spray direction is downward at an angle of 30~45°, pointing towards the center of the battery cell explosion-proof valve; under the spray pressure, the droplet size achieves rapid vaporization and heat absorption, forming an inert gas isolation layer.

10. A fire extinguishing method for the interior of a new energy vehicle battery pack according to claim 1, characterized in that, In step five, after the extinguishing agent extinguishes the fire, maintain a slight positive pressure of 0.12~0.15MPa in the U-shaped pipeline to prevent backflow. The BMS monitors the battery status. After the temperature drops below 80℃ and the smoke concentration returns to zero, manually reset the system.

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