Method and system for detecting leakage of fuel cell stack

Abstract

The invention belongs to the technical field of fuel cell detection, and particularly relates to a fuel cell stack leakage detection method and system, and the detection method comprises the following steps: introducing an oxidant gas into a first gas cavity of a fuel cell stack, introducing a reducing agent gas into a second gas cavity of the fuel cell stack, and enabling the fuel cell stack to operate normally; maintaining the gas pressure in the first gas cavity and the second gas cavity, and introducing inert gas into the package of the fuel cell stack, so that the gas pressure in the package is greater than the gas pressure in the first gas cavity and the second gas cavity; and electrical property changes of all the single cells in the fuel cell stack are detected, and leakage detection of the single cells and positioning of the leakage single cells are realized. Compared with the prior art, the method solves the defect that in the prior art, inner leakage or outer leakage of single cells in the fuel cell stack cannot be distinguished. According to the scheme, the leakage of the fuel cell stack is distinguished, and the leaked single cell can be accurately positioned.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell testing technology, specifically relating to a method and system for detecting external leakage in a fuel cell stack. Background Technology

[0002] A fuel cell stack contains two gas chambers and one liquid chamber. When the fuel cell stack fails to maintain its airtightness, it mainly results in two types of leakage: external leakage due to encapsulation failure and internal leakage due to damage to the CCM (Chemical Management Center) or electrode plates. Specifically: internal leakage refers to leakage between the three chambers, such as gas from the hydrogen chamber flowing into the air or water chamber without leaking to the outside of the stack; external leakage occurs when any one of the three chambers leaks to the outside of the stack. If the stack has a shell, then it is leakage from the stack core to the shell. Severe internal leakage can lead to problems such as burn-through and reverse polarity in leaking cells; severe external leakage can cause the hydrogen concentration inside the encapsulation to reach the explosive limit, potentially triggering an explosion or deflagration upon contact with internal sparks, high-temperature components, or electrostatic discharge.

[0003] When testing the airtightness of a fuel cell stack, under normal circumstances, the presence of airtightness issues in individual cells can be observed through natural discharge. The detailed steps are as follows: First, hydrogen and air are introduced into the fuel cell stack to ensure its normal operation. After the voltage stabilizes, the air supply is cut off, while maintaining the hydrogen supply and hydrogen-air pressure difference. If natural discharge is observed, the individual cell with the fastest voltage drop in the fuel cell stack has an airtightness problem. Existing technologies such as the rapid airtightness testing system and method for fuel cell stacks disclosed in CN116565263A and the detection and repair method for bipolar plate leakage in fuel cell stacks disclosed in CN114512694A employ the above-mentioned methods to achieve the airtightness testing of fuel cell stacks.

[0004] However, this method can only locate the poor airtightness of a single cell in the fuel cell stack, but cannot accurately determine whether the leakage of the single cell is external or internal. This is not conducive to the subsequent analysis and judgment of the stack's airtightness leakage and the determination of the repair direction (internal leakage: adjust the plates and membrane electrode; external leakage: adjust the encapsulation). Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for detecting external leakage in a fuel cell stack, thereby addressing at least one of the aforementioned problems and overcoming the limitation of existing technologies that cannot distinguish between internal and external leakage in individual cells within a fuel cell stack. This solution enables the differentiation of external leakage in a fuel cell stack and allows for precise location of leaking individual cells.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The first aspect of this invention discloses a method for detecting external leakage in a fuel cell stack, comprising the following steps:

[0008] Oxidizing gas is introduced into the first gas chamber of the fuel cell stack, and reducing gas is introduced into the second gas chamber of the fuel cell stack to enable the fuel cell stack to operate normally.

[0009] Maintain the gas pressure in the first gas chamber and the second gas chamber, and introduce inert gas into the encapsulation of the fuel cell stack so that the gas pressure in the encapsulation is greater than the gas pressure in the first gas chamber and the second gas chamber.

[0010] It detects changes in the electrical performance of all individual cells within a fuel cell stack, enabling external leakage detection of individual cells and locating leaking cells.

[0011] Preferably, the gas pressure in the second gas chamber is greater than the gas pressure in the first gas chamber.

[0012] Generally speaking, the gas pressure in the second gas chamber should be greater than that in the first gas chamber, and the gas pressure inside the package should be greater than that in the second gas chamber. At the same time, the pressure difference between the gas pressure inside the package and atmospheric pressure should be controlled within a certain threshold (determined according to the configured explosion-proof valve).

[0013] Preferably, the change in electrical performance is a change in voltage; after the inert gas is introduced, the voltage of the single cell with external leakage decreases.

[0014] Preferably, the oxidizing gas is air or oxygen, and the reducing gas is hydrogen.

[0015] The voltage change satisfies the following equation:

[0016]

[0017] In the formula, ΔE is the change in electromotive force of a single cell, ΔE0 is the initial change in electromotive force of a single cell, and T is the temperature. The activity of hydrogen gas. This represents the activity of oxygen in the oxidant gas.

[0018] Preferably, the gas activity 'a' is expressed in terms of pressure:

[0019]

[0020] In the formula, P is the pressure or partial pressure of the gas. 0 This is the standard pressure of the gas, i.e., 1 atm.

[0021] Preferably, the oxidizing gas is air or oxygen, the reducing gas is hydrogen, and the inert gas is helium or argon or other inert gases.

[0022] The second aspect of this invention discloses a detection system for external leakage of a fuel cell stack, used for detecting external leakage of a packaged fuel cell stack, the detection system including a gas supply source and an electrical performance monitoring device;

[0023] The encapsulated fuel cell stack has an encapsulation inlet and an encapsulation outlet on the encapsulation shell, and the encapsulated fuel cell stack has a first gas chamber inlet, a first gas chamber outlet, a second gas chamber inlet, and a second gas chamber outlet on the fuel cell stack.

[0024] The gas supply sources include an oxidant gas source, a reducing agent gas source, and an inert gas source; the oxidant gas source is connected to the inlet of the first gas chamber, the reducing agent gas source is connected to the inlet of the second gas chamber, and the inert gas source is connected to the encapsulation inlet.

[0025] The electrical performance monitoring device is electrically connected to each individual cell in the packaged fuel cell stack.

[0026] The detection system uses any of the detection methods described above to detect external leakage.

[0027] Preferably, the electrical performance monitoring device is a fuel cell voltage monitoring instrument.

[0028] Preferably, the oxidant gas source is air or oxygen, the reducing gas source is hydrogen, and the inert gas source is helium or argon.

[0029] Preferably, the packaged fuel cell stack also has a coolant inlet and a coolant outlet; the detection system further includes a coolant storage container; the coolant storage container is connected to the coolant inlet.

[0030] The working principle of this invention is as follows:

[0031] First, reducing agent gas and oxidizing agent gas are introduced into the fuel cell stack to enable the fuel cell stack to operate normally. Then, inert gas is introduced into the fuel cell stack encapsulation to keep the pressure of the inert gas greater than the pressure of the first gas chamber and the second gas chamber.

[0032] If any single cell leaks, inert gas will enter the first and second gas chambers through the leak, thereby reducing the concentration (partial pressure) of the reducing agent and oxidizing agent gases, and thus reducing electrical performance. The voltage of each single cell can be collected by external monitoring equipment. A single cell with leakage will show a rapid decline in performance in the fuel cell stack.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This solution effectively distinguishes between internal and external leaks in fuel cell stacks through convenient methods, providing a basis for subsequent analysis of leak causes, repair directions, and process / structural improvements. If the test results indicate an external leak, it may be due to insufficient adhesion between the seal and the electrode plate, or excessive stack pressing pressure, leading to an airtight leak. Further investigation can be conducted by examining the stack pressing pressure and the electrode plate adhesion. If the pressing pressure is insufficient, the stack pressing pressure during production can be traced back to see if it was significantly lower than the normal value. If the adhesion to the electrode plate is insufficient, the primer can be further improved to ensure the electrode plate adhesion meets design requirements. If the test results indicate an internal leak, it is sufficient to directly determine whether there is a leak in the corresponding channel's membrane electrode or electrode plate. This detailed distinction between internal and external leaks saves research effort and costs related to fuel cell stack manufacturing processes and structures.

[0035] This solution is easy to implement, can directly utilize existing testing equipment, has low learning and implementation costs, and can be easily promoted and applied. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the detection system.

[0037] In the diagram: 1-Encapsulated fuel cell stack; 11-Encapsulation inlet; 12-Encapsulation outlet; 13-First gas chamber inlet; 14-First gas chamber outlet; 15-Second gas chamber inlet; 16-Second gas chamber outlet; 17-Coolant inlet; 18-Coolant outlet; 21-Oxidant gas source; 22-Reducing agent gas source; 23-Inert gas source; 24-Coolant storage container; 3-Electrical performance monitoring equipment. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] A method for detecting external leakage in a fuel cell stack includes the following steps:

[0041] Oxidizing gas is introduced into the first gas chamber of the fuel cell stack, and reducing gas is introduced into the second gas chamber of the fuel cell stack to enable the fuel cell stack to operate normally.

[0042] Maintain the gas pressure in the first gas chamber and the second gas chamber, and introduce inert gas into the encapsulation of the fuel cell stack so that the gas pressure in the encapsulation is greater than the gas pressure in the first gas chamber and the second gas chamber.

[0043] It detects changes in the electrical performance of all individual cells within a fuel cell stack, enabling external leakage detection of individual cells and locating leaking cells.

[0044] A corresponding detection system for external leakage of fuel cell stacks, such as... Figure 1 As shown, the detection system is used for external leakage detection of the encapsulated fuel cell stack 1. The detection system includes a gas supply source and an electrical performance monitoring device 3.

[0045] The encapsulated fuel cell stack 1 has an encapsulation inlet 11 and an encapsulation outlet 12 on the encapsulation shell. The encapsulated fuel cell stack 1 also has a first gas chamber inlet 13, a first gas chamber outlet 14, a second gas chamber inlet 15, and a second gas chamber outlet 16 on the fuel cell stack.

[0046] The gas supply sources include an oxidant gas source 21, a reducing agent gas source 22, and an inert gas source 23; the oxidant gas source 21 is connected to the inlet 13 of the first gas chamber, the reducing agent gas source 22 is connected to the inlet 15 of the second gas chamber, and the inert gas source 23 is connected to the encapsulation inlet 11.

[0047] The electrical performance monitoring device 3 is electrically connected to each individual cell in the packaged fuel cell stack 1.

[0048] More specifically, in this embodiment:

[0049] This detection system is designed for detecting external leakage in the encapsulated fuel cell stack 1 and can accurately locate the individual cell where the leakage has occurred.

[0050] like Figure 1As shown, the detection system specifically includes a gas supply source, a coolant storage container 24, and an electrical performance monitoring device 3. The gas supply source specifically includes an oxidant gas source 21, a reducing agent gas source 22, and an inert gas source 23. The electrical performance monitoring device 3 specifically adopts a fuel cell voltage monitor (CVM). The encapsulated fuel cell stack 1 consists of an external encapsulation shell and an internally encapsulated fuel cell stack. The encapsulation shell has an encapsulation inlet 11 and an encapsulation outlet 12. The fuel cell stack has a first gas chamber inlet 13, a first gas chamber outlet 14, a second gas chamber inlet 15, a second gas chamber outlet 16, a coolant inlet 17, and a coolant outlet 18. The first gas chamber inlet 13 and the first gas chamber outlet 14 are the inlet and outlet of the first gas chamber (for introducing oxidant gas), respectively. The second gas chamber inlet 15 and the second gas chamber outlet 16 are the inlet and outlet of the second gas chamber (for introducing reducing agent gas), respectively. The coolant inlet 17 and the coolant outlet 18 are the inlet and outlet of the coolant chamber (for introducing coolant), respectively. Oxidant gas source 21 is connected to the first gas chamber inlet 13 via a pipeline; reducing agent gas source 22 is connected to the second gas chamber inlet 15 via a pipeline; inert gas source 23 is connected to the encapsulation inlet 11 via a pipeline; and coolant storage container 24 is connected to the coolant inlet 17 via a pipeline. The CVM maintains electrical connection with each individual cell in the fuel cell stack to acquire changes in the electrical performance (voltage value) of each cell during the detection process.

[0051] When this detection system detects external leakage in a fuel cell stack:

[0052] First, oxidant gas is introduced into the first gas chamber of the fuel cell stack through oxidant gas source 21, and reducing agent gas is introduced into the second gas chamber of the fuel cell stack through reducing agent gas source 22, so that the fuel cell stack can operate normally.

[0053] Maintain the gas pressure in the first gas chamber and the second gas chamber, and introduce inert gas into the encapsulation shell of the fuel cell stack through the inert gas source 23, so that the gas pressure in the encapsulation is greater than the gas pressure in the first gas chamber and the second gas chamber.

[0054] By using CVM to detect changes in the electrical performance (voltage) of all individual cells within the fuel cell stack, external leakage detection of individual cells and location of leaking cells can be achieved.

[0055] The gas pressure in the second gas chamber is greater than that in the first gas chamber. Normally, the gas pressure in the encapsulation (the gas pressure of the inert gas) can be set to be greater than the gas pressure of the oxidant gas in the first gas chamber, and the gas pressure in the encapsulation (the gas pressure of the inert gas) can be set to be greater than the gas pressure of the reducing agent gas in the second gas chamber, and the gas pressure in the second gas chamber is greater than that in the first gas chamber, and the difference between the gas pressure in the encapsulation (the gas pressure of the inert gas) and atmospheric pressure is controlled within a certain range (determined by the explosion-proof valve configured in the fuel cell stack). By controlling the gas pressure in the encapsulation to be greater than that in the second gas chamber and greater than that in the first gas chamber, it is possible to: 1) ensure that the gas pressure in the second gas chamber is greater than that in the first gas chamber, (1) avoid the generation of the hydrogen-air interface, (2) ensure that there is a tail discharge at the cathode, which can prevent hydrogen accumulation and thus protect the fuel cell; 2) ensure that the gas pressure in the encapsulation is greater than that in the first and second gas chambers, so that when there is an external leakage point, the inert gas can enter the first and second gas chambers through the pressure difference, thereby reducing the gas partial pressure and reducing the voltage value of the single cell due to external leakage.

[0056] The following example uses air as the oxidizing gas, hydrogen as the reducing gas, and argon as the inert gas for detailed explanation:

[0057] In this example, the hydrogen fuel cell reaction is as follows:

[0058] 1 mol H2+0.5 mol O2→1 mol H2O

[0059] First, hydrogen and air are introduced into the fuel cell stack to enable normal operation. Then, argon gas is introduced into the fuel cell stack encapsulation, maintaining an argon pressure higher than the pressures in the hydrogen and air chambers. If a single cell leaks, argon gas will enter the gas chamber through the leak point, reducing the concentration (partial pressure) of hydrogen in the hydrogen chamber or oxygen in the air chamber. This alters the gas activity, hindering the hydrogen oxidation (HOR) and oxygen reduction (ORR) reactions and increasing polarization resistance, thereby reducing catalyst performance and changing the theoretical voltage value. This change can be clearly observed in the single-cell voltage collected by CVM, specifically manifested as a rapid decline in the performance of the leaking single cell within the stack.

[0060] Activity is a measure of the effective concentration of a substance in a reaction system; that is, the effective concentration of ions that play a role in a chemical reaction is called activity, denoted by the symbol 'a'. Given a fixed volume, the encapsulated fuel cell stack 1 in this scheme has a definite volume. Therefore, the effective concentrations of hydrogen and air are directly proportional to their pressures. Thus, activity can be expressed in terms of pressure as follows:

[0061]

[0062] In the formula, P is the pressure or partial pressure of the gas. 0 This is the standard pressure of the gas, i.e., 1 atm.

[0063] For a thermodynamic isothermal process, the Gibbs free energy can be expressed as:

[0064] d G =V m ×d P ;

[0065] For an ideal gas, the following equation is satisfied:

[0066] P×V m =RT;

[0067] Therefore, we can obtain:

[0068]

[0069] Integrating the above formula:

[0070]

[0071] Based on the hydrogen fuel cell reaction in this example, the Nernst equation for a hydrogen fuel cell can be obtained:

[0072]

[0073] Among them, liquid water The above formula can then be simplified to:

[0074]

[0075] Assuming a typical oxygen concentration of 21% in the air, the above equation can be rewritten as follows:

[0076] In the formula, R = 8.314 J·K -1 ·mol -1 , T=298.15K (25℃), F=96485mol -1 .

[0077] Let's take the following two states of a fuel cell (concentration reduced by 5%) as an example for calculation:

[0078] The first method: 100% hydrogen concentration and 100% air concentration;

[0079] The second method: 95% hydrogen concentration and 95% air concentration;

[0080] Substituting the two states into the equation and subtracting them, we get:

[0081]

[0082] Based on this, the relationship between gas concentration and theoretical voltage change can be obtained as shown in Table 1 below.

[0083] Table 1 Relationship between gas concentration and theoretical voltage change

[0084]

[0085] This method can accurately locate whether there is external leakage in the fuel cell stack, and precisely pinpoint the location and serial number of the leaking battery.

[0086] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for detecting external leakage in a fuel cell stack, characterized in that, Includes the following steps: Oxidizing gas is introduced into the first gas chamber of the fuel cell stack, and reducing gas is introduced into the second gas chamber of the fuel cell stack to enable the fuel cell stack to operate normally. Maintain the gas pressure in the first gas chamber and the second gas chamber, and introduce inert gas into the encapsulation of the fuel cell stack so that the gas pressure in the encapsulation is greater than the gas pressure in the first gas chamber and the second gas chamber. It detects changes in the electrical performance of all individual cells within a fuel cell stack, enabling external leakage detection of individual cells and locating leaking cells.

2. The method for detecting external leakage of a fuel cell stack according to claim 1, characterized in that, The gas pressure in the second gas chamber is greater than the gas pressure in the first gas chamber.

3. The method for detecting external leakage of a fuel cell stack according to claim 1, characterized in that, The electrical performance change is a voltage change; after the inert gas is introduced, the voltage of the single cell with external leakage decreases.

4. The method for detecting external leakage of a fuel cell stack according to claim 3, characterized in that, The oxidizing gas is air or oxygen, and the reducing gas is hydrogen. The voltage change satisfies the following equation: In the formula, ΔE is the change in electromotive force of a single cell, ΔE0 is the initial change in electromotive force of a single cell, and T is the temperature. The activity of hydrogen gas. This represents the activity of oxygen in the oxidant gas.

5. The method for detecting external leakage of a fuel cell stack according to claim 4, characterized in that, The activity 'a' of a gas is expressed in terms of pressure: In the formula, P is the pressure or partial pressure of the gas. 0 This is the standard pressure of the gas.

6. The method for detecting external leakage of a fuel cell stack according to claim 1, characterized in that, The oxidizing gas is air or oxygen, the reducing gas is hydrogen, and the inert gas is helium or argon.

7. A detection system for external leakage of a fuel cell stack, characterized in that, For external leakage detection of the encapsulated fuel cell stack (1), the detection system includes a gas supply source and an electrical performance monitoring device (3); The encapsulated fuel cell stack (1) has an encapsulation inlet (11) and an encapsulation outlet (12) on the encapsulation shell. The encapsulated fuel cell stack (1) has a first gas chamber inlet (13), a first gas chamber outlet (14), a second gas chamber inlet (15), and a second gas chamber outlet (16) on the fuel cell stack. The gas supply sources include an oxidant gas source (21), a reducing agent gas source (22), and an inert gas source (23); the oxidant gas source (21) is connected to the inlet (13) of the first gas chamber, the reducing agent gas source (22) is connected to the inlet (15) of the second gas chamber, and the inert gas source (23) is connected to the encapsulation inlet (11); The electrical performance monitoring device (3) is electrically connected to each individual cell in the packaged fuel cell stack (1); The detection system uses the detection method described in any one of claims 1-6 to perform external leakage detection.

8. The detection system for external leakage of a fuel cell stack according to claim 7, characterized in that, The electrical performance monitoring device (3) is a fuel cell voltage monitoring instrument.

9. The detection system for external leakage of a fuel cell stack according to claim 7, characterized in that, The oxidant gas source (21) is air or oxygen, the reducing gas source (22) is hydrogen, and the inert gas source (23) is helium or argon.

10. The detection system for external leakage of a fuel cell stack according to claim 7, characterized in that, The encapsulated fuel cell stack (1) is provided with a coolant inlet (17) and a coolant outlet (18); the detection system also includes a coolant storage container (24); the coolant storage container (24) is connected to the coolant inlet (17).

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