Lithium ion battery thermal runaway gas-liquid-solid multiphase jet simulation device and method

Abstract

The invention discloses a lithium ion battery thermal runaway gas-liquid-solid multiphase jet simulation device and method, and belongs to the technical field of battery safety testing. The device comprises mixed gas, high-temperature steam and dust sampling pipelines which are arranged in parallel and converged to a nozzle, a closed reaction container provided with an environment regulation and control system, a system for ignition and multi-parameter monitoring and a master control system. According to the method, multi-phase medium parameters and a container environment are set through general control, and the whole process of environment creation, multi-phase jet injection, ignition and data acquisition is automatically completed. According to the invention, the defects of high cost, high risk, poor repeatability and incapability of independently regulating and controlling multiphase components caused by dependence on a real battery in the prior art are overcome, the complex multiphase jet combustion behavior can be safely, accurately and repeatedly simulated, and a key experimental platform is provided for quantitative research on thermal runaway flame characteristics and a prevention and control technology.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion battery safety experimental testing, and particularly relates to a comprehensive simulation device and method for simulating, reproducing and studying the high-speed injection and combustion behavior of a multi-phase mixture of gaseous, liquid and solid phases generated inside a lithium ion battery when thermal runaway occurs in a laboratory environment. BACKGROUND

[0002] As high-energy-density storage devices, lithium ion batteries have been widely used in various electronic devices, electric vehicles and stationary energy storage systems. However, the risk of thermal runaway that may occur under misuse conditions such as overheating, overcharging or mechanical damage has always been a core challenge to the safe development of lithium ion batteries. During the thermal runaway process, intense chain reactions occur inside the battery, producing a large amount of high-temperature flammable gas, volatile electrolyte vapor and active material particles peeled off from the electrodes within a very short time. These gaseous, liquid and solid substances mix to form a multi-phase jet, which is injected at high speed from the rupture of the battery shell. This injection itself is flammable, and the high temperature it carries is sufficient to ignite the surrounding combustible material, which is the key initial fire source and energy carrier that leads to the spread of fire and even explosion of the battery module or even the entire system. Therefore, accurately reproducing and in-depth studying this transient, multi-phase, high-speed injection and combustion physical and chemical process in a controlled experimental environment has indispensable scientific value and engineering significance for revealing the thermal runaway propagation mechanism, assessing the fire hazard, and developing effective early warning and fire extinguishing protection technologies.

[0003] Currently, the mainstream experimental method for studying the thermal runaway injection behavior of batteries still highly depends on direct misuse testing of real battery monomers, such as triggering thermal runaway inside the battery by means of needle puncture, heating or overcharging. Although this method can observe phenomena closest to reality, its inherent limitations are also quite obvious:

[0004] Firstly, each experiment consumes a complete battery, which is costly and time-consuming;

[0005] Secondly, due to slight differences in manufacturing process, initial capacity and aging state of each battery, the triggering conditions, severity and specific composition and total amount of the injection vary inevitably, making the repeatability and comparability of experimental results poor and difficult to accurately quantify;

[0006] More critically, this "black box" type of testing method cannot separate and independently control different phase media in the injection, such as gaseous products (e.g. hydrogen, carbon monoxide), condensed droplets (electrolyte vapor) and solid particles (electrode dust), thus it cannot study the specific influence of each phase component and its proportion change on key combustion parameters such as jet ignition characteristics, flame propagation speed and thermal radiation intensity.

[0007] In addition, some experimental devices aiming at studying the combustion characteristics of the jet have been developed. For example, there is a scheme to trigger the battery by heating and guide the jet of the battery to a combustion tube or container for combustion observation. Such devices separate the triggering and combustion processes to some extent, but they still fundamentally rely on real batteries, and the composition and flow of the jet are uncontrollably determined by the reaction of the battery itself. At the same time, the design of such devices usually focuses on capturing and burning gaseous products, and often lacks effective introduction and quantitative control means for the co-flow transport of a large number of micron or even nanometer solid particles and aerosol droplets that exist simultaneously in real thermal runaway, which significantly affect flame instability and radiation heat transfer.

[0008] Furthermore, the control ability of these devices for the combustion environment is usually limited, for example, it is difficult to accurately and quickly set and maintain a specific low pressure or oxygen-rich / oxygen-deficient atmosphere in the combustion chamber, and the environmental pressure and oxygen concentration are the decisive parameters that affect the combustion mode and intensity.

[0009] In summary, the existing technical system still has a significant technical gap in the problem of "how to build a highly flexible, fully controllable parameter, and safe and repeatable physical simulation platform to replace real batteries and quantitatively reproduce the whole process of thermal runaway multiphase jet". This hinders researchers from conducting systematic and mechanistic in-depth research on the complex phenomenon of battery thermal runaway fire. SUMMARY

[0010] The present application aims to solve the technical problems in the prior art that the cost is high, the risk is great, the repeatability is poor, and the gas, liquid and solid three-phase jet ratio, initial conditions and combustion environment cannot be independently and accurately controlled, thereby it is difficult to quantitatively study the complex multiphase jet combustion characteristics due to the dependence on real batteries for thermal runaway experiments.

[0011] In order to achieve the above purpose, on the one hand, the present application provides a lithium ion battery thermal runaway gas-liquid-solid multiphase jet simulation device, comprising:

[0012] A multiphase sampling system, an environment control system, a monitoring and ignition system, and a total control system;

[0013] The multiphase sampling system is composed of a mixed gas pipeline, a high-temperature steam pipeline and a dust sampling pipeline arranged in parallel, and the outlet ends of the mixed gas pipeline, the high-temperature steam pipeline and the dust sampling pipeline are commonly connected to a nozzle;

[0014] The environment control system comprises a closed reaction container, a vacuum system, an oxygen sensor and a temperature control device connected to the reaction container, and the nozzle penetrates the wall of the reaction container and has a nozzle opening in the internal cavity of the reaction container.

[0015] The monitoring and ignition system comprises an ignition device, a temperature acquisition device and a radiative heat flow meter arranged in the internal cavity of the reaction container.

[0016] The total control system is electrically connected to the multiphase sampling system, the environment control system and the monitoring and ignition system to control the coordinated operation of the systems.

[0017] As an optional implementation, the nozzle is mounted on the wall of the reaction container through a detachable structure and is provided with replaceable nozzle heads with different throat diameters.

[0018] As an optional implementation, the mixed gas pipeline comprises a high-pressure gas cylinder group, a gas premixing tank and a first flow control valve connected in sequence.

[0019] The high-temperature steam pipeline comprises a liquid storage tank, a high-pressure pump, a steam generator and a second flow control valve connected in sequence.

[0020] The dust sampling pipeline comprises a dust storage bin, a powder injector connected to the outlet of the dust storage bin, and a third flow control valve connected to the driving gas inlet of the powder injector.

[0021] The outlet ends of the mixed gas pipeline, the high-temperature steam pipeline and the dust sampling pipeline are connected to the nozzle through a three-way mixer.

[0022] As an optional implementation, the vacuum system comprises a vacuum pump connected to the reaction container through a vacuum pipeline, and a vacuum gauge and a vacuum valve are arranged on the vacuum pipeline.

[0023] The probe of the oxygen sensor extends into the internal cavity of the reaction container.

[0024] The temperature control device is a temperature control jacket wrapped around the outer wall of the reaction container.

[0025] As an optional implementation, the monitoring and ignition system further comprises a high-speed camera arranged outside the reaction container and facing the observation window.

[0026] As an optional implementation, the total control system is an industrial computer, which is connected with the flow control and measurement components of the mixed gas pipeline, the high-temperature steam pipeline and the dust sample pipeline, the vacuum gauge of the vacuum system, the oxygen sensor, the temperature control jacket, the ignition device, the temperature acquisition device, the radiant heat flow meter and the high-speed camera through data lines.

[0027] As an optional implementation, the reaction container is provided with a burst disc sealed explosion vent.

[0028] In another aspect, the application provides a lithium ion battery thermal runaway gas-liquid-solid multiphase jet simulation method using the above device, comprising the following steps:

[0029] S1. Set the medium delivery parameters of the mixed gas pipeline, the high-temperature steam pipeline and the dust sample pipeline, and set the target initial environmental parameters in the reaction container through the total control system;

[0030] S2. Start the environment control system to make the inside of the reaction container reach the preset initial environmental parameters;

[0031] S3. Start the multiphase sample system to make the gas, liquid and solid three-phase medium spray into the inside of the reaction container through the nozzle to form a multiphase jet;

[0032] S4. At a predetermined time after the start of the jet, trigger the ignition device to ignite the multiphase jet;

[0033] S5. Collect data during the combustion process through the monitoring and ignition system.

[0034] As an optional implementation, the medium delivery parameters set in step S1 include:

[0035] The component ratio and total flow of the mixed gas, the temperature of the steam and the flow of the liquid precursor, the dust delivery mode and the carrier gas flow;

[0036] The initial environmental parameters include pressure, temperature and oxygen concentration.

[0037] As an optional implementation, step S2 specifically includes:

[0038] S21. Turn on the vacuum system to vacuum the reaction container;

[0039] S22. Fill the background gas into the vacuumed reaction container, and monitor through the oxygen sensor and the vacuum gauge until the pressure, temperature and oxygen concentration in the reaction container reach the preset initial environmental parameters.

[0040] The application replaces real batteries with programmable controlled analog medium to carry out experiments, eliminates inherent explosion and out-of-control risks in traditional misuse tests, greatly reduces the cost of single experiment, and makes the experiment process highly repeatable. Further, through a parallel multi-phase sampling system, the proportion and flow of gas, vapor and solid dust can be flexibly and accurately adjusted, so that complex jet "formula" under different battery systems or different out-of-control degrees can be reproduced; an integrated environment control system realizes independent and accurate control of key initial conditions such as pressure, temperature and oxygen concentration in the combustion cavity, and provides stable and repeatable boundary conditions for scientific research. At the same time, the application first integrates the simulation of gas phase, liquid phase (vapor) and solid phase (dust) in the same experimental platform, overcomes the shortcomings of the prior art which is limited to single-phase or two-phase research, can more truly reconstruct the intrinsic state of gas-liquid-solid three-phase mixed jet in thermal runaway, and greatly improves the fidelity of simulation.

[0041] The application combines multi-parameter synchronous monitoring system and full-process automatic control, and first provides a reliable and efficient standardized experimental platform for quantitative research on the mapping relationship between key parameters such as ignition delay, flame instability, propagation speed, heat release rate and radiation characteristics of multi-phase jet flame and various control variables. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows.

[0043] Figure 1 It is a front view of the simulation device of the application;

[0044] Figure 2 It is an elevation view of the simulation device of the application;

[0045] Figure 3 It is a side view of the simulation device of the application;

[0046] Figure 4 It is a top view of the simulation device of the application;

[0047] Figure 5 It is a rear view of the simulation device of the application;

[0048] In the diagram: 1. High-pressure gas cylinder group; 2. Gas premixing tank; 3. First mass flow controller; 4. First flow control valve; 5. Three-way mixer; 6. Liquid storage tank; 7. High-pressure pump; 8. Steam generator; 9. Second flow control valve; 10. Dust silo; 11. Powder injector; 12. Second mass flow controller; 13. Third flow control valve; 14. Nozzle; 15. Reaction vessel; 16. Observation window; 17. Temperature control jacket; 18. Vacuum pump; 19. Vacuum gauge; 20. Vacuum valve; 21. Dust filter; 22. Oxygen sensor; 23. Explosion vent; 24. Ignition device; 25. Temperature acquisition device; 26. Temperature acquisition instrument; 27. Radiative heat flow meter; 28. High-speed camera; 29. ​​Main control system. Detailed Implementation

[0049] Example 1:

[0050] Please see Figures 1 to 5 This embodiment provides a multiphase jet simulation device for thermal runaway of lithium-ion batteries, which, in its overall structure, is as follows: Figure 1 As shown, the system includes a multiphase sample introduction system, an environmental control system, a monitoring and ignition system, and a central control system 29. These four systems are organically integrated through physical and electrical connections. The central control system 29 is electrically connected to the multiphase sample introduction system, the environmental control system, and the monitoring and ignition system. It is used to centrally control the operation of the entire simulation device, coordinate the synchronous operation of each component, and collect and process experimental data.

[0051] The multiphase injection system is one of the core components of this device. Its main function is to generate and stably deliver a gas-liquid-solid three-phase mixture simulating the thermal runaway of a lithium-ion battery. Structurally, the multiphase injection system consists of three parallel independent pipelines: a mixed gas pipeline, a high-temperature steam pipeline, and a dust injection pipeline. These three pipelines are responsible for preparing and delivering the gaseous, liquid (vapor), and solid phase simulants, respectively, and ultimately converge downstream to a nozzle 14, through which the fully mixed multiphase medium is ejected at high speed.

[0052] like Figure 1 and Figure 4As shown, the mixed gas pipeline is used to simulate the mixture of flammable and non-flammable gases generated by thermal runaway. This pipeline originates from high-pressure cylinder group 1. Preferably, high-pressure cylinder group 1 includes at least carbon monoxide, hydrogen, methane, and carbon dioxide cylinders to simulate the main components of gases generated in real thermal runaway. Of course, other gases, such as ethylene and ethane, can be added as needed. Each cylinder outlet is equipped with a first pressure reducing valve (not shown) and a high-precision first mass flow controller 3. This first mass flow controller 3 is precisely controlled by the overall control system 29 to precisely control the instantaneous flow rate of each component gas according to a preset ratio. After all component gases are output from their respective first mass flow controllers 3, they are connected to the inlet of a gas premixing tank 2 via high-pressure hoses. The function of the gas premixing tank 2 is to fully premix the gases before they enter the main reaction zone to ensure the uniformity of the ejected gas components. Optionally, the volume of the gas premixing tank 2 is 5L, and its preset working pressure can be 2MPa. After thorough mixing, the mixed gas flows out from the outlet of the gas premixing tank 2 and is connected to a first flow control valve 4 via a pipeline. This first flow control valve 4 acts as a main switch to control the on / off state of the mixed gas pipeline. Subsequently, the gas pipeline is connected to the first inlet of a three-way mixer 5.

[0053] The high-temperature steam pipeline is used to simulate the evaporation of electrolyte solvent during thermal runaway. For example... Figure 1 As shown, the pipeline begins at a liquid storage tank 6 for storing the liquid precursor (deionized water is used as an example in this embodiment, but other simulated solvents can also be used in actual applications). The outlet of the liquid storage tank 6 is connected via a pipeline to a high-pressure pump 7, which can be a high-pressure liquid chromatography pump, as it provides a stable and precise flow rate of small liquids. The outlet of the high-pressure pump 7 is then connected to the inlet of a steam generator 8. The steam generator 8 is the core component for generating high-temperature steam; optionally, its power can be 6kW, its maximum operating pressure can reach 1.5MPa, and it can generate superheated steam up to 450°C, which is sufficient to simulate the high-temperature state of electrolyte vapor. The outlet of the steam generator 8 is connected to a second flow control valve 9 via a high-temperature resistant insulated pipeline (to prevent steam condensation). This second flow control valve 9 is also used for on / off control, and its outlet is subsequently connected to the second inlet of the three-way mixer 5.

[0054] The dust inlet pipeline is used to simulate solid particles such as electrode active materials ejected during thermal runaway. Figure 1 and Figure 3As shown, the pipeline includes a dust hopper 10 for pre-loading solid powders (e.g. cathode material powders, graphite powders, etc.) for simulation purposes. The lower part of the dust hopper 10 is connected to a Venturi-type powder injector 11. The powder injector 11 uses the principle of fluid mechanics to fluidize and stably output the powders in the hopper 10 by high-speed carrier gas. In order to provide the high-speed carrier gas, the driving gas inlet of the powder injector 11 is connected by pipeline to a second mass flow controller 12, which in turn is connected to a high-pressure inert gas source, such as a nitrogen or carbon dioxide cylinder, in the high-pressure cylinder group 1. The second mass flow controller 12 is used to accurately control the flow rate of the carrier gas, thereby indirectly controlling the injection rate of the powders. The outlet of the powder injector 11, i.e. the carrier gas outlet carrying the dust, is connected to a third flow control valve 13 through a dedicated powder delivery pipe. The third flow control valve 13 is responsible for controlling the on-off of the dust flow, and its outlet is connected to the third inlet of the three-way mixer 5.

[0055] The three-way mixer 5 serves as the convergence point of the three pipelines, and its outlet is connected to the final nozzle 14 through a section of high-temperature and high-pressure resistant special alloy pipeline, such as Inconel 625 alloy pipeline. The purpose of choosing Inconel 625 alloy is to withstand the high temperature (from steam) and high pressure that the mixed medium may have, as well as potential corrosion. The nozzle 14 is the final outlet of the multiphase medium, and its installation method is particularly critical. In this embodiment, the nozzle 14 can adopt a quick-release flange structure and is detachably installed on the side wall of the reaction vessel 15 described later. This design not only facilitates installation and maintenance, but more importantly, allows for easy replacement of different specifications of nozzle heads according to experimental needs. In order to ensure that the shape and direction of the jet meet the expectations, the nozzle 14 is set to be axially aligned with the center of the internal cavity of the reaction vessel 15. To support the simulation of different thermal runaway intensities, the device is preferably equipped with a variety of interchangeable nozzles 14 with different throat diameters, including but not limited to three specifications: 2mm throat diameter, 4mm throat diameter, and 6mm throat diameter.

[0056] The environmental control system is used to provide a precisely controllable background environment for the injection and combustion simulation of multiphase jets. The system mainly consists of a reaction vessel 15, a vacuum system, an oxygen sensor 22, and a temperature control device. Figures 1-3 and Figure 5As shown, the reaction vessel 15 is the core component that bears the jet and combustion phenomena. It can be designed as a vertical cylindrical pressure vessel, with an internal size of 600 mm in inner diameter and 800 mm in height. The vessel has good pressure-bearing and temperature-resistant performance, with a design pressure range of -0.1 MPa to 0.5 MPa and a design temperature of up to 450℃. The vessel body is preferably made of 316 stainless steel to ensure its corrosion resistance and high-temperature strength. To facilitate real-time observation of the internal jet and flame morphology, as Figure 1 As shown, a large-size observation window 16 is provided at the front end of the reaction vessel 15. The observation window 16 is preferably a circular quartz glass window with a diameter of 200 mm, which has excellent temperature-resistant performance and can withstand a transient high temperature of up to 800℃.

[0057] To achieve precise control of the internal environment temperature of the reaction vessel 15, the temperature control device is designed as a temperature control jacket 17 wrapped around the outside of the reaction vessel 15. As Figure 2 As shown, the temperature control jacket 17 has integrated silicon rubber heating sheets and cooling water coils inside. Through program control of the total control system 29, both heating and cooling can be achieved. It has a wide temperature control range and can achieve program heating, cooling and high-precision constant temperature control in the range of -20℃ to 200℃, thereby providing a guarantee for simulating thermal runaway under different environmental temperatures. The specific heating structure and principle can refer to existing technologies, which will not be described in detail here.

[0058] To achieve control of the internal pressure and gas atmosphere of the reaction vessel 15, the system also includes a vacuum system. As Figure 1 As shown, the upper side wall of the reaction vessel 15 is connected to a vacuum pump 18 through a vacuum pipeline. The vacuum pump 18 is used to perform vacuumizing operation on the reaction vessel 15 to exclude the original internal air or exhaust gas after combustion. Optionally, the limit vacuum degree of the vacuum pump 18 can be 0.1 Pa, and the pumping speed can be 25 L / s. On the vacuum pipeline, starting from the end close to the reaction vessel 15, a vacuum valve 20, a vacuum gauge 19 and a dust filter 21 are installed in sequence. The vacuum gauge 19 is used to monitor the absolute pressure inside the reaction vessel 15 in real time; the vacuum valve 20 is used to control the on-off of the vacuum pipeline; and the dust filter 21 is crucial, which functions to prevent solid particulate matter generated by injection and combustion from entering and damaging the downstream vacuum pump 18 when exhaust gas is being pumped.

[0059] To achieve precise control of the oxygen concentration inside the reaction vessel 15, as Figure 2As shown, the top of the reaction vessel 15 is also equipped with a wide-range oxygen sensor 22. The probe of the oxygen sensor 22 extends into the internal cavity of the vessel, and can monitor the oxygen concentration in the ambient atmosphere in real time, with a measurement range optionally covering 0.1% to 25%. Thus, the environmental control system constitutes a closed-loop control system: the output signal of the oxygen sensor 22 is fed back to the total control system 29 in real time, and the total control system 29 automatically adjusts the intake state of the vacuum system (e.g. controls the start-stop of the vacuum valve 20 and the vacuum pump 18) or the mixed gas pipeline (e.g. supplements oxygen or nitrogen gas through the first mass flow controller 3) according to the deviation between the feedback signal and the set value, so as to achieve dynamic and accurate control of the oxygen concentration in the vessel.

[0060] In addition, for safety reasons, as shown in Figure 1 and Figure 5 , the reaction vessel 15 is also provided with a vent 23. The vent 23 is normally sealed by a rupture disc, and once the pressure inside the reaction vessel 15 suddenly rises due to abnormal conditions such as intense burning, exceeding the safety threshold, the rupture disc will immediately rupture, achieving rapid pressure relief and protecting the safety of the vessel body and the operator.

[0061] The monitoring and ignition system is responsible for igniting the multi-phase jet and collecting key parameter data during the combustion process. As shown in Figure 1 and Figure 2 , the system mainly includes an ignition device 24, a temperature acquisition device 25 and a radiative heat flow meter 27. The ignition device 24 is preferably a high-frequency high-voltage spark igniter. It is installed by inserting from the bottom of the reaction vessel 15, so that the tip of its ignition electrode can be close to the downstream position on the outlet axis of the nozzle 14, to ensure that it can reliably and timely ignite the combustible mixture ejected from the nozzle 14. Optionally, the single ignition energy of the spark igniter can be 1 J, and its spark frequency can be adjusted within the range of 1 Hz to 10 Hz.

[0062] The temperature acquisition device 25 is used to measure the temperature of the jet flame and the environment. The device preferably includes three S-shaped high-temperature thermocouples, with a maximum use temperature of 1600°C, sufficient to withstand high flame temperatures. The three thermocouples extend into the reaction vessel 15 through different interfaces on the vessel wall and are arranged at key positions: one is located in the jet core area about 50 mm in front of the nozzle 14, for measuring the highest temperature of the flame; one is located at a radial position of 100 mm from the inner wall of the reaction vessel 15, for measuring the radial temperature distribution of the flame plume; the last one is located in the top space of the reaction vessel 15, for monitoring the rise of the background environment temperature. The signal output ends of all thermocouples are connected to a multi-channel temperature acquisition instrument 26, which performs signal amplification, cold end compensation and digitization.

[0063] The radiation heat flow meter 27 is used to measure the heat radiation flux generated by the flame. The heat flow meter is preferably a water-cooled foil heat flow meter to ensure stable operation under strong heat radiation. The range is optionally 0 to 200 kW / m 2 As shown in Figure 2 The radiation heat flow meter 27 is installed on the bottom wall of the reaction vessel 15, with the installation height flush with the axis of the nozzle 14, and its position is preferably 180° opposite to the inlet of the nozzle 14, i.e. installed on the opposite side of the nozzle 14, so that its sensing surface can face the expected flame area, thereby measuring the maximum radiation heat flow.

[0064] In addition, in order to visually record the flame shape and propagation process, the monitoring and ignition system further comprises a high-speed camera 28. As shown in Figure 1 The high-speed camera 28 is arranged outside the reaction vessel 15, with its lens facing the observation window 16 at the front end of the reaction vessel 15. Optionally, a Phantom VEO 710S type high-speed camera 28 can be used, which can be set to a shooting speed of 5000 FPS as needed, to clearly capture the transient development and turbulent details of the flame.

[0065] The overall control system 29 is the "brain" of the entire simulation device. As shown in Figure 1 and Figure 5 The overall control system 29 preferably uses an industrial control computer. The industrial computer is electrically connected and communicates with all the aforementioned components that need to be controlled and monitored through data cables and signal interfaces. The specific connections include:

[0066] Connection with the first mass flow controller 3 and the second mass flow controller 12 (and the high-pressure pump 7) in the multi-phase sampling system to set and control the flow rate;

[0067] Connection with the temperature controller of the temperature-controlled jacket 17, the vacuum gauge 19 and the signal processor of the oxygen sensor 22 in the environment regulation system to set and monitor the environmental parameters;

[0068] Connection with the multi-channel temperature acquisition instrument 26, the radiation heat flow meter 27 and the controller of the electric spark igniter in the monitoring and ignition system to trigger ignition and collect data.

[0069] The overall control system 29 runs dedicated control software, such as software developed based on LabVIEW, through which the operator can centrally set all experimental parameters, one-key control the sequence start and stop of the experiment, and can display all the collected data curves in real time, and automatically store the data to the hard disk.

[0070] In summary, the lithium ion battery thermal runaway gas-liquid-solid multiphase jet simulation device provided in the embodiment has the independent precise control sampling system of the gas, liquid and solid three-phase medium, the environment regulation and control system with controllable pressure-temperature-oxygen concentration three parameters, the monitoring and ignition system with synchronous high-speed acquisition of multiple parameters, and the highly integrated total control system 29 organically integrated into one. The device overcomes the drawbacks of the prior art, such as dependence on real batteries, poor repeatability, and inability to independently regulate parameters, and can highly controllable, safe and reliable and high-precision reproduce the whole process of the multiphase jet of the battery thermal runaway. Using the device, researchers can carry out in-depth research on jet ignition and combustion characteristics in a safe and repeatable manner in a laboratory environment, providing key experimental platform support for understanding thermal runaway mechanisms, assessing fire risks, developing fire prevention strategies and developing thermal management systems.

[0071] Embodiment Two

[0072] The embodiment provides a method for simulating a lithium ion battery thermal runaway multiphase jet flame based on the simulation device of embodiment one. The method uses the high controllability of the device to achieve quantitative research on the thermal runaway jet combustion process. The following will combine an example of simulating the jet combustion of a NCM811 ternary lithium battery thermal runaway to elaborate the specific implementation steps of the method.

[0073] First, the preparation and parameter setting steps before the experiment are performed. The operator first performs a system self-check, closes all valves, turns on the power of the total control system 29 and all peripheral devices, runs the control software, and confirms that all sensors, such as the first mass flow controller 3, the second mass flow controller 12, the temperature acquisition device 25, the vacuum gauge 19, the oxygen sensor 22, etc., are in normal communication and reading.

[0074] Next, the specific experimental load preparation is performed. For example, in order to simulate large-scale jetting, a nozzle 14 with a throat diameter of 6 mm is selected and installed. Then, according to the gas generation characteristics of the target battery (NCM811), the corresponding mixed gas is configured in the high-pressure gas cylinder group 1. For example, based on literature or DMS data, a mixed gas with a volume fraction of 52% hydrogen, 22% carbon monoxide, 16% carbon dioxide and 10% methane can be configured, and it is noted that this ratio can be flexibly adjusted by the total control system 29. At the same time, a predetermined amount of simulated powder is added to the dust bin 10, for example, 50g of dried and processed positive material powder with an average particle size of 12μm. Finally, ensure that there is sufficient liquid precursor in the liquid tank 6.

[0075] Then, all the operating parameters of this experiment are set through the software interface of the total control system 29. These parameter settings are designed to reproduce the conditions of real thermal runaway. For example:

[0076] Sample parameters: Set the total flow rate of the mixed gas line to 25 SLM, and the flow rate of each component is automatically calculated by the software according to the ratio of 52:22:16:10 and is executed by the first mass flow controller 3. Set the temperature of the steam generator 8 of the high-temperature steam line to 280°C (to simulate electrolyte vapor), and set the liquid flow rate of the high-pressure pump 7 to 0.8 mL / min. Set the flow rate of the carrier gas (second mass flow controller 12) of the dust sample line to 8 SLM, and set the powder feeding mode to pulse, with a frequency of 8 Hz and a duty cycle of 50%, to simulate pulse blasting.

[0077] Environmental parameters: Set the target initial environment in the reaction vessel 15. To simulate the state of burning in standard air, the initial absolute pressure can be set to 100 kPa, the environmental temperature to 30°C, and the target oxygen concentration to 21%.

[0078] Ignition and collection parameters: Set the ignition device 24 to automatically trigger 1 s after the start of injection, with a spark frequency of 5 Hz. At the same time, set the sampling rate of each data collection device, such as the high-speed camera 28 to 5000 FPS, the radiative heat flow meter 27 to 100 Hz, and the temperature acquisition instrument 26 to 500 Hz (per channel). Set all collection devices to start pre-recording 2 s before the ignition signal is sent.

[0079] Second step, create the initial environment inside the reaction vessel 15. The operator clicks “Start creating environment” on the software interface of the total control system 29. The system automatically performs the following operations:

[0080] First, close the flow control valves (4, 9, 13) of all sample lines, open the vacuum valve 20, and start the vacuum pump 18. Vacuum the inside of the reaction vessel 15 to a lower pressure value, such as below 1 kPa. Then, close the vacuum valve 20 and the vacuum pump 18, and slowly fill the background gas into the reaction vessel 15 through the program-controlled first mass flow controller 3 (or a dedicated gas filling line). During this process, the total control system 29 monitors the changes in environmental conditions in the reaction vessel 15 in real time through the oxygen sensor 22 and the vacuum gauge 19. When the pressure is stable at 100 kPa and the oxygen concentration is stable at 21%, the environment creation is complete.

[0081] Third step, start the injection of multiphase jet. The operator clicks the "start experiment" button on the software interface of the general control system 29. At this time, the general control system 29 will automatically execute all the injection instructions according to the preset experiment timing. The software sends instructions to open the first mass flow controller 3 and the first flow control valve 4 of the mixed gas pipeline; turn on the heating power of the high-pressure pump 7 and the steam generator 8, and open the second flow control valve 9; open the second mass flow controller 12 and the third flow control valve 13 of the dust carrier gas. The gas, liquid and solid three-phase medium immediately starts from the respective pipelines according to the set flow rate, and then flows into the three-way mixer 5 for preliminary mixing, and then is injected at high speed into the central cavity of the reaction container 15 through the nozzle 14. At the same time, the high-speed camera 28 and other data acquisition equipment start recording according to the preset. From the real-time picture of the high-speed camera 28, a multiphase jet carrying dust particles can be seen forming from the nozzle 14.

[0082] Fourth step, trigger ignition and combustion. After 1 second of injection, the general control system 29 automatically sends a trigger instruction to the electric spark igniter. The ignition device 24 generates a high-frequency electric spark in the core area of the jet, which instantly ignites the injected combustible mixture. Since the nozzle 14 continuously supplies fuel, a stable combustion flame is formed in the reaction container 15.

[0083] Fifth step, data acquisition during the combustion process. During the entire combustion process, all monitoring equipment continues to work. The video recorded by the high-speed camera 28 shows that the jet flame is bright yellow-white, the flame root is close to the nozzle 14, and the shape presents violent turbulence, indicating that the combustion is very sufficient. Through image analysis, the flame length fluctuates between 0.5-1.2m. At the same time, the thermocouple located in the core area of the jet records a peak temperature of up to 1385℃; the thermocouple located at the top of the container shows that the ambient temperature rises by about 120℃ in just 10s; the radiation heat flow meter 27 opposite the flame measures a peak heat flux density of up to 162kW / m 2 .

[0084] Sixth step, experiment ends and data post-processing. When the injection continues for a predetermined time (for example, 10 seconds), the general control system 29 automatically executes the shutdown program to close all flow control valves (4, 9, 13) and flow controllers (3, 12) and high-pressure pump 7, and stops the injection. After the fuel supply is interrupted, the flame is quickly extinguished within 150ms.

[0085] After the experiment, the system automatically starts the vacuum pump 18 again, and the exhaust gas generated by the combustion is pumped to the exhaust treatment device through the dust filter 21. After the reaction container 15 cools down, the operator can safely open and disassemble the nozzle 14, the inside of the reaction container 15 and the smoke dust attachments on the observation window 16, and prepare for the next experiment. All the data collected are saved in the total control system 29 and can be used for subsequent analysis. For example, by processing the video frames of the high-speed camera 28, it can be analyzed that the average propagation speed of the flame in this test is about 18 m / s, and the pulse frequency of the flame is about 12 Hz.

[0086] The simulation method provided by the embodiment successfully reproduces the key characteristics of the multiphase jet flame of the NCM811 battery thermal runaway. The method is not only safe, controllable and repeatable, but also can quantitatively measure and collect a series of key parameters such as flame temperature, thermal radiation characteristics, propagation speed, pulse frequency and the like. These data provide valuable quantitative data support for the fire safety design and thermal spread protection of the battery pack. By changing the parameters set in the first step of the method, such as changing the gas composition, dust type, flow size, or changing the initial pressure, temperature and oxygen concentration in the reaction container 15, researchers can systematically study the influence law of different factors on the risk of thermal runaway jet combustion, so as to realize the in-depth understanding and quantitative characterization of the thermal runaway fire behavior.

[0087] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A gas-liquid-solid multiphase jet simulation device for lithium-ion battery thermal runaway, characterized in that, The device comprises a multiphase injection system, an environment control system, a monitoring and ignition system, and a general control system (29). The multiphase injection system is composed of a mixed gas pipeline, a high-temperature steam pipeline, and a dust injection pipeline arranged in parallel, and the outlet ends of the pipelines are connected to a nozzle (14). The environment control system comprises a sealed reaction container (15), a vacuum system, an oxygen sensor (22), and a temperature control device connected to the reaction container (15), and the nozzle (14) penetrates the wall of the reaction container (15) and its nozzle is located in the internal cavity of the reaction container (15). The monitoring and ignition system comprises an ignition device (24), a temperature acquisition device (25), and a radiation heat flow meter (27) arranged inside the reaction container (15). The general control system (29) is electrically connected to the multiphase injection system, the environment control system, and the monitoring and ignition system for controlling the coordinated operation of each system. The nozzle (14) is detachably mounted on the wall of the reaction container (15) and is equipped with replaceable nozzle heads of different throat diameters.

2. The Li-ion battery thermal runaway gas-liquid-solid multiphase jet simulation device according to claim 1, wherein:

3. The device according to claim 1, wherein: The mixed gas pipeline comprises a high-pressure gas cylinder group (1), a gas premixing tank (2), and a first flow control valve (4) connected in sequence. The high-temperature steam pipeline comprises a liquid storage tank (6), a high-pressure pump (7), a steam generator (8), and a second flow control valve (9) connected in sequence. The dust injection pipeline comprises a dust bin (10), a powder injector (11) connected to the outlet of the dust bin (10), and a third flow control valve (13) connected to the driving gas inlet of the powder injector (11). The outlet ends of the mixed gas pipeline, the high-temperature steam pipeline, and the dust injection pipeline are connected to the nozzle (14) through a three-way mixer (5). The vacuum system comprises a vacuum pump (18) connected to the reaction container (15) through a vacuum pipeline, and a vacuum gauge (19) and a vacuum valve (20) are arranged on the vacuum pipeline.

4. The Li-ion battery thermal runaway gas-liquid-solid multiphase jet simulation device of claim 1, wherein: The probe of the oxygen sensor (22) extends into the internal cavity of the reaction container (15). The temperature control device is a temperature control jacket (17) wrapped around the outer wall of the reaction container (15). The monitoring and ignition system further comprises a high-speed camera (28) arranged outside the reaction container (15) and facing the observation window (16).

5. The Li-ion battery thermal runaway gas-liquid-solid multiphase jet simulation device of claim 1, wherein, The general control system (29) is an industrial computer that is communicatively connected to the flow control and measurement components of the mixed gas pipeline, the high-temperature steam pipeline, and the dust injection pipeline, the vacuum gauge (19) of the vacuum system, the oxygen sensor (22), the temperature control jacket (17), the ignition device (24), the temperature acquisition device (25), the radiation heat flow meter (27), and the high-speed camera (28) through data lines.

6. The Li-ion battery thermal runaway gas-liquid-solid multiphase jet simulation device of claim 1, wherein: ​ 7. The Li-ion battery thermal runaway gas-liquid-solid multiphase jet simulation device of claim 1, wherein: The reaction container (15) is provided with a burst disc sealed burst vent (23).

8. Lithium-ion battery thermal runaway gas-liquid-solid multiphase jet simulation method using the apparatus of any one of claims 1 to 7, characterized in that, The method comprises the following steps: S1. Setting medium delivery parameters of the mixed gas pipeline, high-temperature steam pipeline and dust sample pipeline by the total control system (29), and setting target initial environment parameters in the reaction container (15); S2. Starting the environment control system to make the inside of the reaction container (15) reach the preset initial environment parameters; S3. Starting the multiphase sample system to make the gas, liquid and solid three-phase medium be sprayed to the inside of the reaction container (15) through the nozzle (14) to form a multiphase jet flow; S4. At a predetermined time after the jet flow starts, triggering the ignition device (24) to ignite the multiphase jet flow; S5. Collecting data in the combustion process by the monitoring and ignition system.

9. The Li-ion battery thermal runaway gas-liquid-solid multiphase jet simulation method of claim 8, wherein, The medium delivery parameters set in step S1 include: The component ratio and total flow of the mixed gas, the temperature of the steam and the flow of the liquid precursor, the delivery mode of the dust and the carrier gas flow; The initial environment parameters include: pressure, temperature and oxygen concentration.

10. The Li-ion battery thermal runaway gas-liquid-solid multiphase jet simulation method of claim 8, wherein, Step S2 specifically includes: S21. Turning on the vacuum system to vacuumize the reaction container (15); S22. Filling the background gas into the vacuumized reaction container (15), and monitoring by the oxygen sensor (22) and vacuum gauge (19) until the pressure, temperature and oxygen concentration in the reaction container (15) reach the preset initial environment parameters.

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