Fuel cell stack airtightness test method and detection device

Abstract

The embodiment of the invention relates to the technical field of air tightness detection, in particular to a fuel cell stack air tightness test method and detection device.The method comprises the steps that a target test cavity of a fuel cell stack is filled with test gas with set pressure through the detection device; filling the same gas with the same pressure into a reference volume cavity in the detection device at the same time, isolating the target test cavity from the reference volume cavity, and monitoring a pressure difference; after the target test cavity and the reference volume cavity do not have pressure fluctuation, determining whether the gas tightness of the fuel cell stack is qualified or not based on the change value of the pressure difference in the preset period, the volume of the target test cavity, the test time and the gas property parameters; according to the embodiment of the invention, the differential pressure comparison system with equal-pressure balance is established and the pressure difference change is monitored, so that accurate, efficient and automatic detection of the air tightness of the fuel cell stack is realized.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of air tightness detection, in particular to a fuel cell stack air tightness testing method and a detection device. BACKGROUND

[0002] As a core component of a fuel cell system, the air tightness of a fuel cell stack is a key performance indicator to ensure the safe, reliable and efficient operation of the system. Poor air tightness can lead to a variety of serious problems: hydrogen leakage can cause safety hazards; cross penetration between reaction gases (hydrogen and air / oxygen) or to the cooling liquid cavity can lead to performance degradation, shortened life and even internal short circuit of the stack; cooling liquid leakage can also cause stack short circuit failure.

[0003] Currently, there are various methods for testing the air tightness of fuel cell stacks in the industry, but each has its limitations: Water detection method (bubble method): immerse the measured cavity in water after pressurizing, and observe whether bubbles are generated. This method is simple to operate, but is highly subjective and low in precision, cannot quantify the volume leakage rate, and water may remain in the stack after testing, posing a pollution risk, making it unsuitable for precision components; Absolute pressure decay method: fill a certain pressure gas into the cavity and monitor the change of its absolute pressure over time. This method can quantify leakage, but the measurement results are easily disturbed by environmental temperature fluctuations and the thermodynamic effects of the test system itself (such as changes in gas temperature after inflation), resulting in long test times, insensitivity to small leaks, and poor repeatability; Traditional differential pressure test method: usually only for independent sealing test of a single cavity (such as hydrogen cavity, air cavity, cooling liquid cavity) of the stack. For cross leakage between different cavities inside the stack, additional and complex test steps and pipe connections are often required, making the test process tedious and inefficient, and difficult to meet the rapid and comprehensive detection needs of the production line; Existing detection equipment: the functions are often single, the degree of automation is not high, the pipe connection is complex, manual intervention is required for test item switching, the test pace is slow, and the processing and interpretation of test data rely on the experience of operators, making it difficult to achieve standardized and traceable quality control.

[0004] Therefore, there is an urgent need in the art for a method and a highly integrated device that can quickly, accurately, comprehensively and automatically complete the detection of the sealing of a fuel cell stack and the cross leakage between cavities, in order to meet the quality detection requirements of modern industrial production. SUMMARY

[0005] To this end, the present application provides a kind of fuel cell stack air tightness test method and detection device, to overcome the problems of low test efficiency, poor precision, insufficient automation and unable to evaluate the comprehensive air tightness of cavity itself and cross leakage once in prior art.

[0006] To achieve the above object, the present application provides a kind of fuel cell stack air tightness test method. It comprises: Step S1, the target test cavity of the fuel cell stack to be tested is connected with the corresponding interface of the detection device, and all external interfaces are sealed; Step S2, the detection device is used to fill the test gas of set pressure into the target test cavity of the fuel cell stack, and the same gas of the same pressure is filled into the reference volume cavity inside the detection device, so that the pressure between the target test cavity and the reference volume cavity reaches equilibrium, wherein the test gas is inert gas; Step S3, after the pressure between the target test cavity and the reference volume cavity reaches equilibrium, the target test cavity and the reference volume cavity are isolated, and the pressure difference is monitored; Step S4, the first absolute pressure value of the target test cavity and the second absolute pressure value of the reference volume cavity are monitored, and whether the target test cavity and the reference volume cavity exist pressure fluctuation is determined based on the first absolute pressure value and the second absolute pressure value; Step S5, after the target test cavity and the reference volume cavity do not exist pressure fluctuation, the change value of the pressure difference in the preset period is recorded, the volume leakage rate is calculated based on the change value of the pressure difference in the preset period, the volume of the target test cavity, the test time and the gas property parameters, and whether the air tightness of the fuel cell stack is qualified is determined based on the volume leakage rate.

[0007] Further, in step S4, whether the target test cavity and the reference volume cavity exist pressure fluctuation is determined based on the first absolute pressure value and the second absolute pressure value, which comprises: Step S41, the data sequence of the first absolute pressure value and the second absolute pressure value in the preset determination period is continuously obtained; Step S42, the change rate of the first absolute pressure value data sequence and the second absolute pressure value data sequence is calculated respectively; Step S43, the change rate of the first absolute pressure value and the change rate of the second absolute pressure value data sequence are compared with the preset threshold value respectively; Step S44, if the change rate of the first absolute pressure value and the change rate of the second absolute pressure value are both less than the preset threshold value, it is determined that the target test cavity and the reference volume cavity do not exist pressure fluctuation.

[0008] Further, in step S5, based on the change value of the pressure difference in the preset period, the volume of the target test cavity, the test time and the gas property parameters, the volume leakage rate is calculated, comprising: In step S511, the initial value and the end value of the pressure difference in the preset period are obtained, and the change value of the pressure difference is calculated; In step S512, the volume of the target test cavity, the test time corresponding to the preset period and the parameters of the test gas are obtained, and the parameters include the gas constant, the average absolute temperature of the gas in the target test cavity during the test process; In step S513, the change value of the pressure difference, the volume of the target test cavity, the test time and the gas constant are substituted into the ideal gas state equation, and the volume leakage rate is calculated.

[0009] Further, in step S5, based on the volume leakage rate, it is determined whether the gas tightness of the fuel cell stack is qualified, comprising: In step S521, the calculated volume leakage rate is compared with the preset volume leakage rate; In step S522, if the volume leakage rate is less than or equal to the preset volume leakage rate, it is determined that the gas tightness of the current target test cavity of the fuel cell stack is qualified; In step S523, if the volume leakage rate is greater than the preset volume leakage rate, it is determined that the gas tightness of the current target test cavity of the fuel cell stack is unqualified.

[0010] Further, in step S5, the preset volume leakage rate is determined based on the type of the target test cavity.

[0011] A gas tightness test device applied to the fuel cell stack gas tightness test method, comprising a host computer, a differential pressure sensor, a gas supply device, a connecting pipe and a plurality of electric valves, wherein, The gas supply end of the gas supply device is connected to the target test cavity of the fuel cell stack through the electric valve and the connecting pipe; The two ends of the differential pressure sensor are respectively connected to the target test cavity of the fuel cell stack and a reference volume cavity through the electric valve, for monitoring the pressure difference between the two; The host computer is connected to the differential pressure sensor, the gas supply device and each electric valve, for controlling the output of the test gas by the gas supply device, controlling the opening and closing of each electric valve, receiving and processing the signal of the differential pressure sensor and calculating the volume leakage rate of the target test cavity.

[0012] Further, a calibrated reference volume chamber is included, which is in communication with the gas supply end of the gas supply device and one end of the differential pressure sensor through electrically operated valves, and is used as a reference for differential pressure comparison with the target test chamber during testing.

[0013] Further, the host computer is configured to automatically switch and execute at least two test modes by controlling the combined action of the electrically operated valves; in the first test mode, the gas supply device simultaneously charges the target test chamber and the reference volume chamber to a set pressure and balances, then isolates the two and monitors the pressure difference, to test the target test chamber's own sealing; in the second test mode, the gas supply device charges the first target chamber, while the second target chamber is in communication with the reference volume chamber and charged to the same pressure, then isolates the first target chamber and the combination of the second target chamber and the reference volume chamber, and monitors the pressure difference, to test the cross leakage between the first target chamber and the second target chamber.

[0014] Further, the host computer is further configured to control the electrically operated valves to sequentially execute at least two of the following test items: hydrogen chamber self-sealing test, air chamber self-sealing test, cooling liquid chamber self-sealing test, cross leakage test between hydrogen chamber and air chamber, and cross leakage test between hydrogen chamber and cooling liquid chamber.

[0015] Further, the host computer further includes a human-computer interaction unit for inputting test parameters, setting qualified thresholds, displaying real-time test data and curves, and generating and outputting test object information, test time, and volume leakage rate calculation results.

[0016] Compared with the prior art, the present application has the beneficial effect that, by actively monitoring and confirming the stability of the test system (target cavity and reference cavity) before formal leak testing, the present application effectively identifies and eliminates pressure change interference caused by non-leakage factors. These interferences can include residual gas temperature changes after inflation (thermal relaxation), slow fluctuations in ambient temperature, electronic noise or slight vibrations of the sensor itself, etc. Only after confirming the stability of the system, the pressure difference is recorded for leak calculation, improving the accuracy of the final result and the repeatability of the test; by setting a "preset threshold" based on the system characteristics as the judgment standard, the method has certain self-adaptability to environmental changes. In different test environments (such as day and night temperature difference, different laboratories) or using slightly different equipment, as long as the system inherent noise and thermal inertia are within the coverage of the preset threshold, the method can reliably identify the true stable state, avoid test failure or result misjudgment due to slight changes in environmental conditions, and improve the universality and reliability of industrial application of the method.

[0017] Further, by substituting the change value of the pressure difference, the target cavity volume, the test time, the gas constant and the average absolute temperature into the calculation formula derived based on the ideal gas state equation, the specific volume leakage rate value is calculated through a rigorous physical model (ideal gas state equation). This makes the evaluation of the leakage degree highly accurate and objective and comparable, providing direct and quantitative data support for product quality classification and process improvement. The calculation formula integrates all key influencing factors: ΔP directly reflects the pressure imbalance caused by leakage; V ensures that the result is independent of the cavity size and can be used for different models of the battery; the introduction of T and R corrects the influence of temperature changes and gas types, making the calculation result closer to the real physical leakage rate. This ensures that the test results after parameter correction are highly consistent and comparable under different times, different environments, and even using different test gases (such as nitrogen, helium), meeting the requirements of modern quality systems for data traceability.

[0018] Further, the present application can instantly complete the qualification determination without manual intervention to select or input the threshold value after completing the volume leakage rate calculation of one cavity in the automatic test sequence, and the upper computer can automatically match and apply different threshold values. This can complete the complex multi-criteria determination work by the machine at high speed and accurately, significantly shortens the decision-making time of the entire test, and is a key link to support the full-automatic and fast-paced production line detection. The preset value is stored in the software, so that the qualification standard is no longer a hardware solidification, but a flexible configurable parameter. When the product design is updated, the process is improved, or the customer standard changes, the hardware equipment does not need to be changed, and only the preset value database in the upper computer needs to be updated under the authority management, so that the test system can adapt to the new requirements. This greatly prolongs the life cycle of the detection device, reduces the upgrading cost, and can quickly respond to diversified customer needs.

[0019] Further, the present application realizes the leap from simple "leakage detection" to "reliable quality determination" by introducing an abnormal source analysis and intelligent re-determination decision mechanism based on double absolute pressure monitoring. It effectively solves the biggest problem in high-precision differential pressure detection, that is, how to distinguish between real leakage and environmental equipment interference. This mechanism can significantly reduce false positives caused by transient instability of the test system or environmental disturbance, improve production pass rate, and reduce quality cost. At the same time, it gives the detection device preliminary self-diagnosis and fault tolerance capability, improves the intelligent level and overall reliability of the automatic test line, makes the detection result more authoritative, and lays a foundation for the quality inspection application of unmanned and black light factory. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the working flow chart of the fuel cell stack airtightness test method provided by the embodiment of the present application; Figure 2 is a connection schematic diagram of the airtightness detection device provided by the embodiment of the present application for detecting the fuel cell stack; Figure 3 is a structure schematic diagram of the airtightness detection device provided by the embodiment of the present application; Among them, 1, detection device; 2, fuel cell stack; 3, connecting pipe; 4, hydrogen outlet; 5, air outlet; 6, cooling liquid outlet; 7, hydrogen inlet; 8, air inlet; 9, cooling liquid inlet; 10, differential pressure sensor; 11, electric valve; 12, upper computer; 13, gas supply device. DETAILED DESCRIPTION

[0021] In order to make the purpose and advantages of the present application more clear and explicit, the present application will be further described below in combination with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the present application.

[0022] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art will appreciate that the embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0023] Please refer to Figure 1 shown, Figure 1 is a work flow chart of a fuel cell stack airtightness test method provided by the embodiments of the present application.

[0024] To achieve the above object, the present application provides a fuel cell stack airtightness test method. The method comprises the following steps. Step S1, connecting a target test cavity of a fuel cell stack to be tested to a corresponding interface of a detection device, and sealing all external interfaces; Step S2, filling a test gas with a set pressure into the target test cavity of the fuel cell stack through the detection device, and filling the same gas with the same pressure into a reference volume cavity inside the detection device, so that the pressure between the target test cavity and the reference volume cavity reaches equilibrium, wherein the test gas is an inert gas; Step S3, after the pressure between the target test cavity and the reference volume cavity reaches equilibrium, isolating the target test cavity and the reference volume cavity, and monitoring the pressure difference; Step S4, monitoring a first absolute pressure value of the target test cavity and a second absolute pressure value of the reference volume cavity, and determining whether there is a pressure fluctuation between the target test cavity and the reference volume cavity based on the first absolute pressure value and the second absolute pressure value; Step S5, after there is no pressure fluctuation between the target test cavity and the reference volume cavity, recording the change value of the pressure difference in a preset period, calculating the volume leakage rate based on the change value of the pressure difference in the preset period, the volume of the target test cavity, the test time and the gas property parameters, and determining whether the airtightness of the fuel cell stack is qualified based on the volume leakage rate.

[0025] In the embodiment of the present application, the target test cavity includes but is not limited to a hydrogen cavity, an air cavity and a coolant cavity; the hydrogen inlet / outlet, the air inlet / outlet and the coolant inlet / outlet of the fuel cell stack to be tested are respectively connected to the corresponding quick interfaces of the detection device through connecting pipes, and the unused interfaces are plugged using sealing plugs to ensure the sealing of all external interfaces; the host computer of the detection device starts the test program to control the gas supply device to simultaneously fill dry nitrogen into the hydrogen cavity (i.e. the target test cavity) of the stack and the reference volume cavity inside the device until the pressures of the two reach the preset value (e.g. 150 kPa) and are balanced. After the pressure is stabilized, the host computer (12) controls the corresponding electric valve to close to isolate the gas path between the hydrogen cavity and the reference volume cavity, and then continuously monitors the pressure difference between the two cavities through a high-precision differential pressure sensor.

[0026] Specifically, in step S4, it is determined whether the target test cavity and the reference volume cavity have pressure fluctuations based on the first absolute pressure value and the second absolute pressure value, including: Step S41, continuously obtaining a data sequence of the first absolute pressure value and the second absolute pressure value within a preset determination period; Step S42, calculating the change rates of the data sequence of the first absolute pressure value and the data sequence of the second absolute pressure value respectively; Step S43, comparing the change rates of the first absolute pressure value and the data sequence of the second absolute pressure value with a preset threshold value respectively; Step S44, if the change rates of the first absolute pressure value and the second absolute pressure value are both less than the preset threshold value, it is determined that the target test cavity and the reference volume cavity do not have pressure fluctuations.

[0027] In this embodiment of the invention, after isolating the gas path in step S3, the host computer continuously reads data from the absolute pressure sensor connected to the hydrogen chamber (for acquiring the first absolute pressure value) and the absolute pressure sensor connected to the reference volume chamber (for acquiring the second absolute pressure value). Within a preset 30-second determination period, the host computer continuously collects the two pressure values ​​at a frequency of once per second, forming two sequences containing 30 data points each. Subsequently, the host computer applies linear regression to each sequence or calculates the average rate of change between adjacent points to obtain the rate of change of the first absolute pressure value (e.g., 0.2 Pa / s) and the rate of change of the second absolute pressure value (e.g., 0.3 Pa / s). The host computer compares these two rates of change with a preset threshold (e.g., 0.5 Pa / s). Since both rates of change (0.2 Pa / s and 0.3 Pa / s) are less than the preset threshold (0.5 Pa / s), the system determines that there are no significant pressure fluctuations in either the hydrogen chamber or the reference volume chamber, the system state is stable, and the formal volume leakage rate test phase can begin. The preset threshold is determined through a combination of experimental calibration and experience, based on the inherent noise of the test system, the sensitivity to environmental temperature changes, and the desired test accuracy. The determination method is as follows: Under ideal, leak-free, and sealed conditions, the complete test procedure is executed multiple times. The rate of change of the pressure value during the stable phase is recorded and statistically analyzed. This statistical value (e.g., the mean plus three times the standard deviation) is taken as the preset threshold to ensure that the judgment logic effectively filters out environmental interference without being overly lenient and leading to misjudgment.

[0028] This invention effectively identifies and eliminates pressure variation interference caused by non-leakage factors by actively monitoring and confirming the stability of the test system (target cavity and reference cavity) before formal leakage testing. These interferences may include residual gas temperature changes after inflation (thermal relaxation), slow fluctuations in ambient temperature, electronic noise from the sensor itself, or minor vibrations. Only after confirming system stability is pressure difference recorded for leakage calculation, improving the accuracy of the final results and the repeatability of the test. By setting a "preset threshold" based on system characteristic calibration as a judgment criterion, the method possesses a certain degree of adaptability to environmental changes. In different test environments (such as day-night temperature differences, different laboratories) or when using slightly different equipment, as long as the system's inherent noise and thermal inertia are within the coverage range of the preset threshold, the method can reliably identify the true stable state, avoiding test failures or misjudgments due to slight changes in environmental conditions, thus improving the method's universality and reliability for industrial applications.

[0029] Specifically, in step S5, based on the change in pressure difference within the preset period, the volume of the target test chamber, the test time, and gas property parameters, the volume leakage rate is calculated, including: Step S511: Obtain the initial and final values ​​of the pressure difference within the preset period, and calculate the change in pressure difference; Step S512: Obtain the volume of the target test chamber, the test time corresponding to the preset cycle, and the parameters of the test gas, including the gas constant and the average absolute temperature of the gas in the target test chamber during the test. Step S513: Substitute the change in pressure difference, the volume of the target test chamber, the test time, and the gas constant into the ideal gas law to calculate the volume leakage rate.

[0030] In this embodiment of the invention, the pressure difference change is as follows: within a preset period of 30 seconds (t), the pressure difference between the target cavity (hydrogen cavity) and the reference cavity, measured by the differential pressure sensor, changes from an initial value of 0 Pa to an ending value of -5 Pa. Therefore, the pressure difference change ΔP = -5 Pa; the target cavity volume is known to be V = 0.8 L = 0.0008 m³. 3 Test gas parameters: The test gas is nitrogen, with a gas constant R = 296.8 J / (kg × K). During the test, the average absolute temperature of the gas in the hydrogen chamber was measured by a temperature sensor to be approximately 298 K (about 25°C). Volume leakage rate calculation: The above parameters were substituted into the volume leakage rate calculation formula derived based on the ideal gas law (e.g., volume leakage rate Q = (ΔP × V) / (Pref × t), where ΔP is the change in pressure difference (Pa) within the preset period, and V is the volume of the target test chamber (m³). 3 Pref is the average absolute pressure (Pa) during the test, which can usually be the initial equilibrium pressure or atmospheric pressure, and t is the test time (s) corresponding to the preset cycle, which needs to be adjusted according to the specific defined volume leakage rate dimension.

[0031] This invention calculates the specific volumetric leakage rate by substituting the pressure difference change, target cavity volume, test time, gas constant, and mean absolute temperature into a calculation formula derived from the ideal gas law. This is achieved through a rigorous physical model (ideal gas law). This makes the assessment of leakage highly accurate and objectively comparable, providing direct, quantitative data support for product quality grading and process improvement. The calculation formula integrates all key influencing factors: ΔP directly reflects the pressure imbalance caused by leakage; V ensures the result is independent of cavity size and can be used with different fuel cell stack models; the introduction of T and R corrects for the effects of temperature changes and gas type, making the calculation result closer to the actual physical leakage rate. This ensures high consistency and comparability of test results across different times, environments, and even when using different test gases (such as nitrogen and helium) after parameter correction, meeting the data traceability requirements of modern quality systems.

[0032] Specifically, in step S5, determining whether the gas tightness of the fuel cell stack is qualified based on the volume leakage rate includes: Step S521: Compare the calculated volumetric leakage rate with the preset volumetric leakage rate; Step S522: If the volume leakage rate is less than or equal to the preset volume leakage rate, then the airtightness of the current target test chamber of the fuel cell stack is determined to be qualified. Step S523: If the volume leakage rate is greater than the preset volume leakage rate, then the airtightness of the current target test chamber of the fuel cell stack is determined to be unqualified.

[0033] Specifically, in step S5, the preset volumetric leakage rate is determined based on the type of the target test chamber.

[0034] In this embodiment of the invention, the detection device (host computer) has pre-stored preset volume leakage rates for different types of cavities: for the hydrogen cavity, the preset volume leakage rate is 5.0×10-6Pa×m3 / s; for the air cavity, the preset volume leakage rate is 2.0×10-5Pa×m3 / s; and for the coolant cavity, the preset volume leakage rate is 2.0×10-5Pa×m3 / s.

[0035] In this invention, after calculating the volumetric leakage rate of a cavity in an automated testing sequence, the pass / fail determination can be completed instantly without manual intervention to select or input thresholds. The host computer automatically matches and applies different thresholds. This allows the complex multi-standard determination work to be completed by the machine at high speed and accuracy, significantly shortening the overall testing decision time. It is a key link supporting fully automated, high-speed production line testing. Preset values ​​are stored in the software, making the pass / fail standards no longer fixed in hardware but flexibly configurable parameters. When product design is updated, processes are improved, or customer standards change, there is no need to modify the hardware. Only the preset value database in the host computer needs to be updated under access control to adapt the testing system to the new requirements. This greatly extends the life cycle of the testing device, reduces the cost of upgrades, and enables rapid response to diverse customer needs.

[0036] Specifically, when it is determined that the air tightness of the current target test chamber of the fuel cell stack is unqualified, a second air tightness test is determined based on the abnormal fluctuation type of the first and second absolute pressure values. When the abnormal fluctuations of the first and second absolute pressure values ​​are synchronous abnormal fluctuations, it is determined that a second airtightness test is required. When the abnormal fluctuation type of the first and second absolute pressure values ​​is unilateral abnormal fluctuation, it is determined that no secondary airtightness test is required.

[0037] In this embodiment of the invention, the host computer retrieves the first absolute pressure value data sequence and the second absolute pressure value data sequence recorded within the preset judgment period in step S4, analyzes their change patterns, and identifies the type of abnormal fluctuation. The types of abnormal fluctuations mainly include: synchronous abnormal fluctuations: the rate of change of both the first and second absolute pressure values ​​is greater than a preset threshold, and their trends show a high positive correlation (e.g., simultaneously rising or simultaneously falling); determining that the current test environment or the state of the detection device itself is abnormal (e.g., drastic changes in ambient temperature, unstable test gas source pressure, unidentified leaks in the reference volume chamber, or strong interference with the data acquisition system). In this case, the initial test result of non-compliance has low reliability and may not be caused by actual product leakage. Therefore, the system automatically determines that "a secondary airtightness test needs to be initiated." Simultaneously, the system records this abnormal event and can issue an "environmental interference warning" or "system self-check suggestion" through the human-machine interface. Unilateral abnormal fluctuation: Only the rate of change of the first absolute pressure value or only the rate of change of the second absolute pressure value is greater than the preset threshold; or both are greater than the threshold, but the trends of change are opposite or there is no significant correlation. The system determines that the benchmark of the test system is basically stable, the "unqualified" conclusion of the initial test has high credibility, and determines that "no secondary airtightness test is required", and can directly output the final unqualified report.

[0038] This invention achieves a leap from simple "leak detection" to "reliable quality assessment" by introducing an anomaly root cause analysis and intelligent re-judgment decision-making mechanism based on dual absolute pressure monitoring. It effectively solves the biggest challenge in high-precision differential pressure testing: how to distinguish between actual product leaks and environmental interference. This mechanism significantly reduces false failures caused by transient instability in the testing system or environmental disturbances, improving production first-pass yield and reducing quality costs. Simultaneously, it endows the testing device with preliminary self-diagnostic and fault-tolerant capabilities, enhances the intelligence level and overall reliability of automated testing lines, makes test results more authoritative, and lays the foundation for quality inspection applications in unmanned, lights-out factories.

[0039] Specifically, when it is determined that a secondary airtightness test is required, the test parameters for the secondary airtightness test are adjusted based on the comparison between the absolute value of the difference between the volumetric leakage rate calculated in the initial test and the preset volumetric leakage rate, and the preset difference value. This includes: If the absolute value of the difference is greater than or equal to the preset difference, the differential pressure monitoring cycle is increased. If the absolute value of the difference is less than the preset difference, an inflation test is performed using a different set pressure than the initial test.

[0040] In this embodiment of the invention, the preset difference is the average of the absolute values ​​of the differences between the volumetric leakage rate and the preset volumetric leakage rate when several target test chambers of the same type fail the airtightness test. When the absolute value of the difference is greater than or equal to the preset difference, it indicates that the leakage degree of the tested chamber has reached or exceeded the typical non-compliance level of this type of product, and the leakage is relatively significant. In this case, the initial non-compliance conclusion is highly likely to be due to defects in the product itself. The main purpose of conducting secondary testing is to confirm the severity and consistency of the leakage under more stringent conditions and to provide more accurate data for quality analysis. Therefore, the system chooses to increase the differential pressure monitoring cycle (e.g., from the standard 30 seconds to 60 seconds, 90 seconds, or longer, increasing the monitoring time by 2 or 3 times). Extending the monitoring time allows for a longer data sequence, which helps filter out random noise and improves the accuracy and confidence of the calculated average leakage rate QQ. Observing whether the pressure difference change remains linear over a longer period helps determine whether the leak is a stable micropore leak or if other nonlinear factors exist (such as the initial stage of trace infiltration). In cases of significantly exceeding the limit, a confirmation result based on longer and more stable data is more authoritative and better supports subsequent repair or scrapping decisions. When the absolute value of the difference is less than the preset difference, it indicates that the leakage of the tested cavity is slight, just exceeding the pass line, and is in a critical unqualified state. Such situations are most susceptible to misjudgment due to slight fluctuations in test conditions (such as slight deviations in inflation pressure or slight temperature inhomogeneity). The core objective of secondary testing is to verify whether the leak actually exists and to eliminate the influence of test condition specificity. Therefore, the system selects a different set pressure for inflation testing than the initial test (for example, the initial test pressure is P1, and the secondary test pressure is changed to P2, and P2 ≠ P1; typically, P2 can be selected as 80% or 120% of P1). The reason for adopting this strategy is that for real physical leaks (such as orifices of fixed size), the volumetric leakage rate is positively correlated with the test pressure within a certain pressure range (the higher the pressure, the greater the leakage). If two tests at different pressures both show unacceptable results, and the calculated leakage rate roughly matches the proportional relationship of pressure changes, then it can be strongly confirmed that there is a real leak in the product. Some systematic errors (such as very slight internal leakage in valves or zero drift in sensors) may be insensitive to pressure or exhibit a different pressure correlation than real leaks. By changing the pressure for testing, it is possible to effectively distinguish between product leakage and inherent equipment errors; for fuel cell stacks at the boundary of sealing performance, the performance may differ under different pressures. This test can help determine the robustness of its sealing performance.

[0041] Please see Figures 2-3 As shown, Figure 2 This is a schematic diagram of the airtightness testing device provided in this application for testing a fuel cell stack. Figure 3This is a schematic diagram of the airtightness testing device provided in the embodiments of this application.

[0042] Specifically, an airtightness testing device 1 applied to the aforementioned fuel cell stack airtightness testing method includes a host computer 12, a differential pressure sensor 10, a gas supply device 13, a connecting pipe 3, and several electric valves 11, wherein... The gas supply end of the gas supply device is connected to the target test chamber interface of the fuel cell stack 2 via an electric valve and the connecting pipe. The differential pressure sensor is connected at both ends to the target test chamber of the fuel cell stack and a reference volume chamber via electric valves, respectively, to monitor the pressure difference between the two. The host computer is connected to the differential pressure sensor, the gas supply device, and each of the electric valves, and is used to control the gas supply device to output test gas, control the opening and closing of each of the electric valves, receive and process the signal from the differential pressure sensor, and calculate the volume leakage rate of the target test chamber.

[0043] In this embodiment of the invention, the target test chamber includes a hydrogen chamber, an air chamber, and a coolant chamber. The hydrogen chamber includes a hydrogen outlet 4 and a hydrogen inlet 7; the air chamber includes an air outlet 5 and an air inlet 8; and the coolant chamber includes a coolant outlet 6 and a coolant inlet 9.

[0044] Specifically, it also includes a calibrated reference volume chamber, which is connected to the gas supply end of the gas supply device and one end of the differential pressure sensor via electric valves, and is used to form a differential pressure comparison benchmark with the target test chamber during the test.

[0045] Specifically, the host computer is configured to automatically switch and execute at least two test modes by controlling the combined actions of the electric valves. In the first test mode, the gas supply device simultaneously inflates the target test chamber and the reference volume chamber to a set pressure and balances them, then isolates them and monitors their pressure difference to test the sealing performance of the target test chamber itself. In the second test mode, the gas supply device inflates the first target chamber, while simultaneously connecting the second target chamber and the reference volume chamber and inflating them to the same pressure, then isolates the first target chamber from the assembly consisting of the second target chamber and the reference volume chamber, and monitors their pressure difference to test the cross-leakage between the first target chamber and the second target chamber.

[0046] Specifically, the host computer is further configured to control the electric valve to sequentially perform at least two of the following test items: hydrogen chamber self-sealing test, air chamber self-sealing test, coolant chamber self-sealing test, cross-leakage test between hydrogen chamber and air chamber, and cross-leakage test between hydrogen chamber and coolant chamber.

[0047] Specifically, the host computer also includes a human-computer interaction unit, which is used to input test parameters, set qualified thresholds, display real-time test data and curves, and generate and output test object information, test time, and volume leakage rate calculation results.

[0048] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method for testing the airtightness of a fuel cell stack, characterized in that, include: Step S1: Connect the target test chamber of the fuel cell stack under test to the corresponding interface of the testing device, and seal all external interfaces. Step S2: Test gas at a set pressure is introduced into the target test chamber of the fuel cell stack through the detection device, and the same gas at the same pressure is introduced into the reference volume chamber inside the detection device, so that the pressure between the target test chamber and the reference volume chamber is balanced. The test gas is an inert gas. Step S3: After the pressure between the target test chamber and the reference volume chamber reaches equilibrium, the target test chamber and the reference volume chamber are isolated, and the pressure difference is monitored. Step S4: Monitor the first absolute pressure value of the target test chamber and the second absolute pressure value of the reference volume chamber, and determine whether there is pressure fluctuation in the target test chamber and the reference volume chamber based on the first absolute pressure value and the second absolute pressure value; Step S5: After there is no pressure fluctuation in the target test chamber and the reference volume chamber, record the change value of the pressure difference within a preset period. Based on the change value of the pressure difference within the preset period, the volume of the target test chamber, the test time, and the gas property parameters, calculate the volume leakage rate, and determine whether the airtightness of the fuel cell stack is qualified based on the volume leakage rate.

2. The fuel cell stack airtightness testing method according to claim 1, characterized in that, In step S4, determining whether there are pressure fluctuations in the target test chamber and the reference volume chamber based on the first absolute pressure value and the second absolute pressure value includes: Step S41: Continuously acquire the data sequence of the first absolute pressure value and the second absolute pressure value within a preset determination time period; Step S42: Calculate the rate of change of the first absolute pressure value data sequence and the second absolute pressure value data sequence, respectively; Step S43: Compare the rate of change of the first absolute pressure value and the rate of change of the second absolute pressure value data sequence with preset thresholds respectively; Step S44: If the rate of change of the first absolute pressure value and the rate of change of the second absolute pressure value are both less than the preset threshold, then it is determined that there is no pressure fluctuation in the target test chamber and the reference volume chamber.

3. The fuel cell stack airtightness testing method according to claim 1, characterized in that, In step S5, based on the pressure difference change within the preset period, the volume of the target test chamber, the test time, and the gas property parameters, the volume leakage rate is calculated, including: Step S511: Obtain the initial and final values ​​of the pressure difference within the preset period, and calculate the change in pressure difference; Step S512: Obtain the volume of the target test chamber, the test time corresponding to the preset cycle, and the parameters of the test gas, including the gas constant and the average absolute temperature of the gas in the target test chamber during the test. Step S513: Substitute the change in pressure difference, the volume of the target test chamber, the test time, and the gas constant into the ideal gas law to calculate the volume leakage rate.

4. The fuel cell stack airtightness testing method according to claim 1, characterized in that, In step S5, determining whether the gas tightness of the fuel cell stack is qualified based on the volume leakage rate includes: Step S521: Compare the calculated volumetric leakage rate with the preset volumetric leakage rate; Step S522: If the volume leakage rate is less than or equal to the preset volume leakage rate, then the airtightness of the current target test chamber of the fuel cell stack is determined to be qualified. Step S523: If the volume leakage rate is greater than the preset volume leakage rate, then the airtightness of the current target test chamber of the fuel cell stack is determined to be unqualified.

5. The fuel cell stack airtightness testing method according to claim 4, characterized in that, In step S5, the preset volumetric leakage rate is determined based on the type of the target test chamber.

6. A gas tightness testing apparatus for use in the gas tightness testing method for fuel cell stacks according to any one of claims 1-5, characterized in that, It includes a host computer, differential pressure sensor, gas supply device, connecting pipes, and several electric valves, among which, The gas supply device is connected to the target test chamber interface of the fuel cell stack via an electric valve and the connecting pipe. The differential pressure sensor is connected at both ends to the target test chamber of the fuel cell stack and a reference volume chamber via electric valves, respectively, to monitor the pressure difference between the two. The host computer is connected to the differential pressure sensor, the gas supply device, and each of the electric valves, and is used to control the gas supply device to output test gas, control the opening and closing of each of the electric valves, receive and process the signal from the differential pressure sensor, and calculate the volume leakage rate of the target test chamber.

7. The airtightness testing device according to claim 6, characterized in that, It also includes a calibrated reference volume chamber, which is connected to the gas supply end of the gas supply device and one end of the differential pressure sensor via electric valves, and is used to form a differential pressure comparison benchmark with the target test chamber during the test.

8. The airtightness testing device according to claim 6, characterized in that, The host computer is configured to automatically switch and execute at least two test modes by controlling the combined actions of the electric valves. In the first test mode, the gas supply device simultaneously inflates the target test chamber and the reference volume chamber to a set pressure and balances them. Then, the two are isolated and their pressure difference is monitored to test the sealing performance of the target test chamber itself. In the second test mode, the gas supply device inflates the first target chamber and simultaneously connects the second target chamber and the reference volume chamber and inflates them to the same pressure. Then, the first target chamber is isolated from the combination formed by the second target chamber and the reference volume chamber, and their pressure difference is monitored to test the cross-leakage between the first target chamber and the second target chamber.

9. The airtightness testing device according to claim 6, characterized in that, The host computer is further configured to control the electric valve to sequentially perform at least two of the following test items: hydrogen chamber self-sealing test, air chamber self-sealing test, coolant chamber self-sealing test, cross-leakage test between hydrogen chamber and air chamber, and cross-leakage test between hydrogen chamber and coolant chamber.

10. The airtightness testing device according to claim 6, characterized in that, The host computer also includes a human-computer interaction unit, which is used to input test parameters, set qualified thresholds, display real-time test data and curves, and generate and output test object information, test time, and volume leakage rate calculation results.

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