A proton exchange membrane fuel cell single cell multi-stress condition test tool

Abstract

The application discloses a kind of proton exchange membrane fuel cell single cell multi-stress condition test tooling. Including the polar plate with multichannel serpentine flow field, semiconductor refrigerating sheet, flexible film thermocouple, flexible film pressure sensor and electromagnet. Semiconductor refrigerating sheet is pasted to the two sides of cell, and temperature control is realized in two directions by switching polarity;Flexible film thermocouple is coupled therebetween, for in-situ temperature measurement;Flexible film pressure sensor and electromagnet are correspondingly arranged, and pressure is controlled and monitored in real time by adjusting electromagnet current. The application realizes the coordinated accurate regulation and control of temperature, pressure and flow field, solves the problem of temperature control lag and pressure unevenness in traditional test, and significantly improves the test reliability and data quality.

Description

Technical Field

[0001] This invention relates to the field of fuel cell testing technology, specifically to an integrated, high-precision testing device for testing the performance of a single cell in a proton exchange membrane fuel cell, and in particular to a dedicated testing fixture capable of actively, rapidly, and precisely controlling the operating temperature and assembly pressure of a single cell. Background Technology

[0002] In the research and development and performance evaluation of proton exchange membrane fuel cells (PEMFCs), single-cell testing is fundamental for analyzing key materials (such as membrane electrodes), optimizing operating parameters, and validating flow field designs. A precise, reliable, and controllable testing environment is crucial for obtaining accurate and repeatable experimental data. Currently, conventional single-cell testing devices or fixtures have significant limitations in controlling key environmental variables.

[0003] In terms of temperature control, mainstream methods rely on external circulating water baths or heating plates to indirectly regulate battery temperature by heating or cooling the plates. This approach suffers from high thermal inertia, slow response speed, and poor temperature field uniformity, making it difficult to achieve rapid heating and cooling or accurately simulate transient operating conditions. Regarding assembly pressure control, mechanical bolt fastening is commonly used. This method results in uneven pressure distribution and cannot monitor and adjust pressure continuously and in real-time during testing, leading to unstable contact resistance and affecting battery performance and test consistency. Furthermore, traditional testing fixtures often use external or inserted sensors for temperature and pressure measurement, which cannot accurately reflect the true physical state at the interface of the battery's active areas.

[0004] Therefore, there is an urgent need to develop a specialized chemical apparatus that can integrate in-situ sensing and achieve rapid and active coordinated control of temperature and pressure, in order to improve the accuracy, efficiency and scientific rigor of PEMFC single-cell testing. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing proton exchange membrane fuel cell single cell test fixtures, such as uneven mass transfer in the flow field, low temperature control accuracy, and poor pressure regulation effect. It provides a highly adaptable test fixture that can optimize mass transfer in the flow field, achieve high-precision control of single cell temperature within ±1℃, and flexible and precise adjustment of pressure, thereby improving the accuracy and reliability of single cell performance test data.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] The proton exchange membrane fuel cell single cell multi-stress condition test fixture of the present invention adopts a stacked integrated structure. The components stacked from top to bottom are: upper electromagnet (1), upper flexible thin film pressure sensor (2), upper semiconductor cooler (TEC, 3), single cell with multi-channel serpentine flow field (4), lower semiconductor cooler (TEC, 5), lower flexible thin film pressure sensor (6), and lower electromagnet (7). The components of each layer are tightly attached, and the interface between the semiconductor cooler (3, 5) and the flow field plate of the single cell (4) is coated with thermally conductive silicone grease to achieve low thermal resistance heat transfer.

[0008] Its features are:

[0009] The flow field structure of the single cell (4) is a multi-channel serpentine flow field, specifically: at least two independent serpentine flow channels are arranged in parallel on the surface of the flow field plate, and the inlet ends of each flow channel are connected to the same inlet chamber and the outlet ends are connected to the same outlet chamber; through the multi-channel parallel structure, the effective contact area between the reaction gas and the electrode is increased, and the gas mass transfer uniformity in the flow channel is improved, and the concentration polarization inside the single cell is reduced.

[0010] The temperature control system is equipped with flexible thin-film thermocouples for each of the semiconductor coolers (3, 5). These flexible thin-film thermocouples are attached to the contact interface between the semiconductor cooler and the single cell (4) to collect the operating temperature signal of the single cell in real time. The temperature control adopts a PID closed-loop control algorithm, using the temperature signal collected by the flexible thin-film thermocouple as feedback to adjust the magnitude and direction of the operating current of the semiconductor cooler in real time.

[0011] When the feedback temperature is lower than the target temperature, the current direction is adjusted to put the semiconductor cooler into heating mode, and the heating power is controlled by matching the current magnitude.

[0012] When the feedback temperature is higher than the target temperature, the current direction is adjusted to put the semiconductor cooler into cooling mode, and the cooling power is controlled by matching the current magnitude.

[0013] Through the above closed-loop control, high-precision regulation of the single battery operating temperature within ±1℃ is achieved.

[0014] Pressure control system: The flexible thin film pressure sensors (2, 6) respectively collect real-time pressure signals from the upper and lower sides of the single battery (4);

[0015] Pressure control is achieved by adjusting the positive and negative polarities of the electromagnets (1, 7), thereby changing the magnitude of the magnetic attraction / repulsion force between the two electromagnets:

[0016] When it is necessary to increase the pressure, the polarity is adjusted so that the two electromagnets are magnetically attracted, and the pressure on the single cell is increased through the magnetic attraction force.

[0017] When it is necessary to reduce the pressure, the polarity is adjusted so that the two electromagnets are in a repulsive state, and the pressure on the single cell is reduced through the repulsive force.

[0018] By using the pressure signal from a flexible thin-film pressure sensor as feedback, flexible and precise control of the working pressure of a single battery can be achieved. Beneficial effects

[0019] The temperature control system based on semiconductor cooler, flexible thin film thermocouple and PID closed loop control achieves high-precision temperature control of ±1℃ and can quickly switch between heating / cooling modes to meet the testing needs of single battery under multiple temperature conditions.

[0020] The pressure control mechanism, which combines a flexible thin-film pressure sensor with an electromagnet, enables rapid, flexible, and precise pressure adjustment, and is easy to operate with minimal response lag. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a test flowchart of a multi-stress condition test fixture for a proton exchange membrane fuel cell single cell provided in an embodiment of the present invention.

[0023] Figure 2 This is an exploded view of a multi-stress condition testing fixture for a single proton exchange membrane fuel cell provided in an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram of a multi-stress condition testing fixture for a single proton exchange membrane fuel cell provided in an embodiment of the present invention. Detailed Implementation

[0025] The following detailed description of the multi-stress condition testing fixture for a single proton exchange membrane fuel cell according to the present invention, with reference to specific embodiments, is provided. These embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0026] The core of this invention is to provide a proton exchange membrane fuel cell single-cell test fixture with high-precision temperature and pressure control and uniform mass transfer capability. Through the coordinated operation of a stacked precision positioning structure, a multi-channel serpentine flow field design, a PID closed-loop temperature control system, and an electromagnetic flexible pressure control mechanism, it achieves accurate simulation testing of a single cell under multiple operating conditions. Its specific implementation structure and working process are as follows:

[0027] I. Overall Structure and Assembly of Tooling

[0028] The test fixture described in this embodiment adopts a coaxial stacked integrated structure. It is stacked in sequence from top to bottom in the order of "upper electromagnet (1) - upper flexible film pressure sensor (2) - upper semiconductor cooler (3) - single battery (4) - lower semiconductor cooler (5) - lower flexible film pressure sensor (6) - lower electromagnet (7)". The central axes of each component coincide, and the mating surfaces of adjacent components remain flat and smooth.

[0029] During assembly, the contact surfaces of adjacent components must be kept clean and free of impurities. Specifically, a uniform layer of thermal grease must be applied to the contact interfaces between the upper thermoelectric cooler (3), the lower thermoelectric cooler (5), and the flow field plate of the single cell (4). A scraper is used to apply the grease in the same direction, with the thickness controlled between 0.05mm and 0.1mm. After application, microscopic observation confirms the absence of bubbles and localized accumulation, ensuring low thermal resistance and efficient heat transfer at the contact interface. In this embodiment, the thermal grease used has a thermal conductivity of 3.2 W / (m·K), which effectively reduces the thermal resistance between the thermoelectric cooler and the single cell, ensuring efficient temperature control response.

[0030] II. Specific Configuration of Each Core Component

[0031] 1. Single cell and multi-channel serpentine flow field

[0032] In this embodiment, the single cell (4) to be tested is a proton exchange membrane fuel cell single cell. The surfaces of its anode plate and cathode plate are processed with multi-channel serpentine flow fields, which are the core mass transfer structures. The specific parameters are as follows: The flow field contains no less than two parallel independent serpentine channels. The cross-sectional shape of each channel is rectangular, the channel width is 1.0 mm, the channel depth is 0.8 mm, and the distance between two adjacent channels (i.e., the channel ridge width) is 1.2 mm. The inlet ends of each serpentine channel are all connected to the same inlet gas collection chamber, and the outlet ends are all connected to the same outlet gas collection chamber. The cross-sectional dimensions of the inlet gas collection chamber and the outlet gas collection chamber are 10 mm × 8 mm, and their cross-sectional area is 4 times that of a single serpentine channel. This can achieve uniform distribution and convergence of the reaction gas, significantly improve the mass transfer uniformity of the gas in the channel, reduce the concentration polarization inside the single cell, and ensure the consistency of the electrochemical reaction.

[0033] 2. Temperature control system components

[0034] The core components of the temperature control system are the upper semiconductor cooler (3), the lower semiconductor cooler (5), the flexible thin-film thermocouple, and the PID closed-loop temperature control module. Among them, the semiconductor coolers (3 and 5) adopt a multi-stage semiconductor cooling chip integrated structure, with a rated operating voltage of 24V and a rated operating current range of 0.5A to 5A. Their cold side faces the flow field plate of the single cell (4), and their hot side faces the pressure sensor (2 and 6). In order to improve the heat dissipation efficiency of the hot side of the semiconductor cooler, aluminum heat dissipation fins are attached to the hot side of both semiconductor coolers. The heat dissipation fins and the hot side of the semiconductor cooler are also coated with the above-mentioned thermal grease to ensure smooth heat dissipation.

[0035] The flexible thin-film thermocouple is a K-type thermocouple with a polyimide substrate and a thickness of 0.1 mm. Its sensing end is attached to the contact interface between the cold surface of the semiconductor cooler (3, 5) and the flow field plate of the single cell (4), and the sensing end is in direct contact with the surface of the flow field plate. It is used to collect the temperature signal during the operation of the single cell in real time, and the collection frequency is not less than 10 Hz. The signal output end of the flexible thin-film thermocouple is connected to the signal input end of the PID closed-loop temperature control module through a shielded wire to ensure stable temperature signal transmission and avoid interference.

[0036] The PID closed-loop temperature control module uses an STM32F103 microcontroller as the core control unit, integrating signal conditioning circuit, D / A conversion circuit and constant current drive circuit, which can realize the acquisition and processing of temperature signals and the precise adjustment of the operating current of the semiconductor cooler.

[0037] 3. Pressure control system components

[0038] The core components of the pressure control system are an upper flexible thin-film pressure sensor (2), a lower flexible thin-film pressure sensor (6), an upper electromagnet (1), a lower electromagnet (7), and an electromagnetic pressure control module. Among them, the flexible thin-film pressure sensors (2 and 6) are both piezoelectric thin-film sensors with a thickness of 0.3 mm and an effective sensing surface area of ​​50 mm × 50 mm. The overlap with the hot surface area of ​​the semiconductor cooler is 98%, the pressure detection range is 0.01 MPa to 0.5 MPa, and the detection accuracy is ±0.001 MPa. The upper flexible thin-film pressure sensor (2) is sandwiched between the hot surface of the upper electromagnet (1) and the upper semiconductor cooler (3), and the lower flexible thin-film pressure sensor (6) is sandwiched between the hot surface of the lower electromagnet (7) and the lower semiconductor cooler (5). The sensing surfaces of the sensors are fully in contact with the end face of the electromagnet and the hot surface of the semiconductor cooler, respectively, to ensure the accuracy of pressure signal acquisition.

[0039] Both the upper electromagnet (1) and the lower electromagnet (7) adopt a composite structure in which an electromagnetic coil is wrapped around a permanent magnet. The permanent magnet is made of neodymium iron boron material, and the electromagnetic coil is made of enameled copper wire with 250 turns and a coil resistance of 10Ω. The current range is 0.2A~2A. The opposite surfaces of the two electromagnets are the working surfaces of the magnetic poles, and their areas are matched with the sensing surface area of ​​the pressure sensor. The coil leads of the electromagnets are connected to the output end of the electromagnetic pressure control module, and the polarity and current magnitude are adjusted by the control module.

[0040] The electromagnetic pressure control module also uses the STM32F103 microcontroller as its core, integrating an H-bridge drive circuit and a pressure signal conditioning circuit. It can receive pressure feedback signals from the flexible thin-film pressure sensor and adjust the polarity and current of the electromagnet according to control commands.

[0041] III. Tooling Working Process

[0042] 1. Temperature control process

[0043] First, the target operating temperature of the single battery (e.g., 80°C) is set through the human-machine interface (such as a touch screen) of the PID closed-loop temperature control module. After the module is started, the flexible thin-film thermocouple collects the operating temperature signal of the single battery (4) in real time and converts the signal into a voltage signal and transmits it to the temperature control module. The signal conditioning circuit filters and amplifies the voltage signal and then converts it into a digital temperature value through the A / D conversion circuit. The microcontroller compares the digital temperature value with the set target temperature value to obtain the temperature deviation value.

[0044] When the temperature deviation is negative (i.e., the feedback temperature is lower than the target temperature), the microcontroller outputs a control signal through a PID algorithm to control the constant current drive circuit to switch the direction of the operating current of the semiconductor cooler (3, 5), so that the semiconductor cooler enters the heating mode, and adjusts the current according to the size of the temperature deviation (the larger the deviation, the larger the current) to increase the heating power; when the temperature deviation is positive (i.e., the feedback temperature is higher than the target temperature), the microcontroller controls the constant current drive circuit to switch the direction of the current, so that the semiconductor cooler enters the cooling mode, and adjusts the current according to the size of the deviation to control the cooling power; through the above PID closed-loop regulation, the operating temperature of the single battery is stabilized within the target temperature ±1℃ range, achieving high-precision temperature control.

[0045] 2. Pressure control process

[0046] The target working pressure of a single battery (e.g., 0.2 MPa) is set through the human-machine interface of the electromagnetic pressure control module. After the module is started, the upper and lower flexible thin film pressure sensors (2, 6) collect the pressure signals on the upper and lower sides of the single battery in real time and convert the pressure signals into voltage signals and transmit them to the pressure control module. After the signal conditioning circuit processes the voltage signal, it obtains the digital pressure value through A / D conversion. The microcontroller compares the digital pressure value with the target pressure value to obtain the pressure deviation value.

[0047] When the pressure deviation is positive (i.e., the feedback pressure is lower than the target pressure), the microcontroller adjusts the polarity of the upper electromagnet (1) and the lower electromagnet (7) through the H-bridge drive circuit, so that the opposite surfaces of the two electromagnets are in a "opposite poles facing each other" state, generating a magnetic attraction force. At the same time, the current flowing into the coil is adjusted according to the pressure deviation (the larger the deviation, the larger the current, and the stronger the magnetic attraction force), so that the pressure on the single battery gradually increases until the feedback pressure is consistent with the target pressure. When the pressure deviation is negative (i.e., the feedback pressure is higher than the target pressure), the microcontroller adjusts the polarity of the two electromagnets, so that the opposite surfaces are in a "like poles facing each other" state, generating a repulsive force. At the same time, the current is adjusted to control the intensity of the repulsive force, so that the pressure on the single battery gradually decreases until the target pressure is reached. During the entire adjustment process, the pressure control accuracy can reach 0.01MPa, and the adjustment response time does not exceed 0.5s, realizing flexible and precise pressure control.

[0048] 3. Testing process

[0049] Once the temperature control system and pressure control system have both reached a stable state (i.e., the temperature and pressure of the single cell are stable at the target values), the anode and cathode of the single cell (4) are connected to the load module of the fuel cell test system, respectively. Hydrogen is introduced into the anode of the single cell and air (or oxygen) is introduced into the cathode. The hydrogen and air are evenly distributed to each serpentine flow channel through the air inlet manifold of the single cell, and fully contact the electrodes to undergo an electrochemical reaction. The test system collects the voltage, current and other performance parameters of the single cell in real time to complete the performance test of the single cell under the temperature and pressure conditions. If it is necessary to test the performance under different conditions, it is only necessary to adjust the target temperature and target pressure through the corresponding control module, and the test can be carried out after the system stabilizes.

[0050] Through the above specific embodiments, those skilled in the art can fully reproduce and implement the present invention. Using this platform, the operator can apply precise and programmable mechanical and thermal boundary conditions to a single battery and simultaneously collect multi-physical field data such as voltage, current, temperature, and pressure, thereby systematically revealing the impact of assembly pressure, operating temperature, and their dynamic interaction on the output performance, hydrothermal management, and lifespan degradation of PEMFC.

Claims

1. A multi-stress condition testing fixture for a single proton exchange membrane fuel cell, characterized in that, The integrated structure, including coaxially stacked layers, consists of the following from top to bottom: Upper electromagnet (1), upper flexible thin film pressure sensor (2), upper semiconductor cooler (3), single cell with multi-channel serpentine flow field (4), lower semiconductor cooler (5), lower flexible thin film pressure sensor (6), lower electromagnet (7). Each layer of components is tightly fitted together, and the hot surfaces of the upper semiconductor cooler (3) and the lower semiconductor cooler (5) are respectively fitted to the corresponding upper flexible thin film pressure sensor (2) and lower flexible thin film pressure sensor (6), while the cold surfaces are respectively in contact with the upper and lower flow field plates of the single cell (4). The test fixture is equipped with a PID closed-loop temperature control module and an electromagnetic pressure control module, which are respectively connected to the same microcontroller. The upper semiconductor cooler (3) and the lower semiconductor cooler (5) are both coupled with flexible thin-film thermocouples. The flexible thin-film thermocouples are attached to the contact interface between the upper semiconductor cooler (3), the lower semiconductor cooler (5) and the single battery (4) to collect the working temperature signal of the single battery (4) in real time. The PID closed-loop temperature control module uses the temperature signal of the flexible thin-film thermocouple as feedback to adjust the magnitude and direction of the working current of the upper semiconductor cooler (3) and the lower semiconductor cooler (5) respectively, so as to realize high-precision bidirectional control of the working temperature of the single battery (4). The upper flexible film pressure sensor (2) and the lower flexible film pressure sensor (6) are used to collect real-time pressure signals on both sides of the single battery (4). The electromagnetic pressure control module uses the pressure signals from the flexible film pressure sensors (2, 6) as feedback quantities, and adjusts the positive and negative polarities and current magnitude of the upper electromagnet (1) and the lower electromagnet (7) through the H-bridge drive circuit to change the magnetic attraction or repulsion between the two electromagnets, thereby realizing closed-loop control of the working pressure of the single battery (4).

2. The multi-stress condition testing fixture for a single proton exchange membrane fuel cell according to claim 1, characterized in that, The flexible thin-film thermocouple is a K-type thermocouple with a polyimide substrate and a thickness of 0.1 mm. Its sensing end is attached to the contact interface between the cold surface of the upper semiconductor cooler (3) and the lower semiconductor cooler (5) and the flow field plate of the single cell (4), and is in direct contact with the surface of the flow field plate. The sampling frequency is not less than 10 Hz.

3. The multi-stress condition testing fixture for a single proton exchange membrane fuel cell according to claim 1, characterized in that, The microcontroller of the PID closed-loop control module is an STM32F103. The PID closed-loop control module adjusts the direction and magnitude of the operating current of the upper semiconductor cooler (3) and the lower semiconductor cooler (5) according to the temperature signal fed back by the flexible thin-film thermocouple: When the feedback temperatures of the upper semiconductor cooler (3) and the lower semiconductor cooler (5) are both lower than the target temperature, the current direction is adjusted so that both enter the heating mode, and the current is adjusted according to the temperature deviation. When the feedback temperatures of both the upper semiconductor cooler (3) and the lower semiconductor cooler (5) are higher than the target temperature, the current direction is adjusted so that both enter the cooling mode, and the current is adjusted according to the temperature deviation.

4. The multi-stress condition testing fixture for a single proton exchange membrane fuel cell according to claim 1, characterized in that, The pressure control module uses the pressure signals collected by the upper flexible film pressure sensor (2) and the lower flexible film pressure sensor (6) as feedback quantities. It adjusts the positive and negative polarities and current magnitude of the upper electromagnet (1) and the lower electromagnet (7) through the H-bridge drive circuit, so that the pressure control accuracy of the single battery (4) reaches ±0.01MPa and the control response time does not exceed 0.5s.

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