Method for positioning internal leakage of fuel cell stack

Abstract

The invention relates to the technical field of fuel cells, and discloses a fuel cell stack inner leakage positioning method, which can simply and efficiently realize positioning of a single cell with leakage by adopting voltage monitoring. The method comprises the following steps: firstly, determining the type of serial leakage: water cavity-cavity, water cavity-hydrogen cavity or cavity-water cavity-hydrogen cavity; and secondly, the voltage change condition of each single battery is monitored, interference of voltage acquisition time factors is eliminated through multiple times of detection, rapid and accurate positioning of a galvanic pile leakage point is realized, and the detection efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a method for locating internal leakage of a fuel cell stack. Background Art

[0002] A fuel cell stack is a device that converts hydrogen and oxygen into electrical energy through an electrochemical reaction, and is widely used in the fields of transportation and energy. Due to the flammable and explosive characteristics of hydrogen, leakage detection of fuel cell stacks is crucial. Leakage can not only lead to explosions and fires, but also affect battery performance and lifespan. Therefore, timely and accurate leakage detection is crucial for ensuring personnel safety, system stability, and environmental protection.

[0003] For example, a Chinese invention patent with a publication number of CN110504471A discloses a method and device for diagnosing and locating internal air leakage faults in a fuel cell stack. The method includes: supplying hydrogen to the anode of the fuel cell stack, supplying an inert gas in the forward direction to the cathode of the fuel cell stack, and recording the concentration difference potential of each fuel cell single piece of the fuel cell stack through voltage inspection as the first concentration difference potential group; supplying hydrogen to the anode of the fuel cell stack, supplying an inert gas in the reverse direction to the cathode of the fuel cell stack, and recording the concentration difference potential of each fuel cell single piece of the fuel cell stack through voltage inspection as the second concentration difference potential group; comparing the first concentration difference potential group with the second concentration difference potential group, and judging the cause and location of the internal air leakage fault of the fuel cell stack according to the comparison result.

[0004] However, when locating internal leakage of the battery stack according to the comparison result of the concentration difference potential groups, the main reasons for internal leakage that can be judged are: sealing problems of the cathode inlet / outlet manifold of the battery stack, and problems of membrane electrode damage (hydrogen-cavity cross-leakage). It is difficult to judge the cross-leakage between the cooling water cavity and the cavity, the cross-leakage between the cooling water cavity and the hydrogen cavity, and the situation where the cooling water cavity leaks to both the hydrogen cavity and the cavity at the same time; and the potential of the concentration difference potential generated by hydrogen / nitrogen is low and is easily affected by various factors, such as factors like moisture, residual gas, and the surface state of the catalyst layer.

[0005] In view of this, developing a method for more accurate and comprehensive internal leakage location of a fuel cell stack has important value for the production and use of fuel cell stacks. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for locating internal leakage of a fuel cell stack that can quickly determine the leaking single cell, so as to solve one or more technical problems existing in the prior art, and at least provide a beneficial choice or create conditions.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions.

[0008] A method for locating internal leakage in a fuel cell stack, comprising the following steps: Step 1, determining the type of internal leakage in the fuel cell stack, where the type of internal leakage in the fuel cell stack includes cross-leakage between the cooling water chamber and the air chamber, cross-leakage between the cooling water chamber and the hydrogen chamber, and cross-leakage of the cooling water chamber to both the hydrogen chamber and the air chamber simultaneously; Step 2: Locating the leakage point; performing N detections, where N is equal to the number of single cells in the fuel cell stack; in the i-th detection, using the voltage monitoring channel of the i-th single cell as the starting point, and each time the detection is based on the single cell that first shows a voltage change as the potential leakage point; after N detections, counting the single cell with the most times marked as the leakage point, which can be determined as the actual leakage location; 1 ≤ i ≤ N.

[0009] More preferably, the method for determining whether there is cross-leakage between the cooling water chamber and the air chamber is as follows: 1) Purge the air chamber, hydrogen chamber, and cooling water chamber of the fuel cell stack with nitrogen to ensure that there are no other residual gases in the fuel cell stack; 2) Introduce air into the air chamber and hydrogen into the cooling water chamber; 3) Detect the instantaneous voltage of each single cell. If a voltage is detected, it indicates that there is cross-leakage between the cooling water chamber and the air chamber. If no voltage is detected, it indicates that there is no cross-leakage between the cooling water chamber and the air chamber.

[0010] More preferably, the method for determining whether there is cross-leakage between the cooling water chamber and the hydrogen chamber is as follows: 1) Purge the air chamber, hydrogen chamber, and cooling water chamber of the fuel cell with nitrogen to ensure that there are no other residual gases in the fuel cell stack; 2) Introduce air into the hydrogen chamber and hydrogen into the cooling water chamber; 3) Detect the instantaneous voltage of each single cell. If a voltage is detected, it indicates that there is cross-leakage between the cooling water chamber and the hydrogen chamber. If no voltage is detected, it indicates that there is no cross-leakage between the cooling water chamber and the hydrogen chamber.

[0011] More preferably, the method for determining whether there is cross-leakage of the cooling water chamber to both the hydrogen chamber and the air chamber simultaneously is as follows: 1) Purge the air chamber, hydrogen chamber, and cooling water chamber of the fuel cell with nitrogen to ensure that there are no other residual gases in the fuel cell stack; 2) Introduce air into the air chamber, introduce low-concentration hydrogen into the cooling water chamber, and introduce air into the hydrogen chamber; 3) Detect the instantaneous voltage of each single cell. If a voltage is detected, it indicates that there is cross-leakage of the cooling water chamber to both the hydrogen chamber and the air chamber simultaneously. If no voltage is detected, it indicates that there is no cross-leakage of the cooling water chamber to both the hydrogen chamber and the air chamber simultaneously; the hydrogen volume concentration of the low-concentration hydrogen is 5% - 10%.

[0012] More preferably, the low-concentration hydrogen is composed of 5% - 10% hydrogen and 90% - 95% nitrogen by volume percentage.

[0013] More preferably, the fuel cell stack comprises a plurality of single cells packaged and assembled together. Each single cell has a corresponding air chamber, a hydrogen chamber, and a cooling water chamber. The air chambers, hydrogen chambers, and cooling water chambers of different single cells are respectively interconnected, and the cooling water chambers between adjacent single cells are shared.

[0014] On the other hand, the present invention also provides a fuel cell stack internal leakage positioning system, which is used to implement the above-mentioned fuel cell stack internal leakage positioning method. The fuel cell stack internal leakage positioning system includes a voltage monitoring system and a positioning judgment system. The voltage monitoring system is used to read the instantaneous voltage of each single cell, and the positioning judgment system is used to generate an internal leakage positioning result according to the instantaneous voltage monitored by the voltage monitoring system.

[0015] In the present invention, the single cell with internal leakage will first show a voltage change. However, the fuel cell stack contains a large number of single cells. Once gas leakage occurs, it will diffuse from the single cell with internal leakage through the main pipe to other non-leaking single cells, resulting in all single cells being able to detect voltage. And there is a time difference between the voltage monitoring channels of different single cells. Therefore, it is necessary to accurately locate the leaking single cell by repeating the detection process.

[0016] Compared with the method in CN110504471A that uses hydrogen passing through the anode and nitrogen passing through the cathode to locate the leakage according to the concentration difference potential, the present invention uses the reaction potential of hydrogen and oxygen to locate the leakage. The concentration difference potential generated by hydrogen / nitrogen has a low potential and is easily affected by many factors, such as moisture, residual gas, the surface state of the catalyst layer, etc. The potential generated by the reaction of hydrogen / oxygen is much higher than that of hydrogen / nitrogen. Therefore, the monitored potential is more accurate.

[0017] The present invention is based on the principle of electrochemistry, that is, the leaked hydrogen and air react to generate voltage, and the hydrogen leakage is located by monitoring the voltage. Based on the mature voltage detection technology, the positioning accuracy is high. The present invention can accurately and quickly locate the fuel cell leakage without disassembling the stack.

[0018] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of a fuel cell stack in an embodiment of the present invention. Detailed Embodiments

[0020] The following further describes the specific embodiments of the present invention in conjunction with the accompanying drawings of the specification, making the technical solutions and their beneficial effects of the present invention clearer and more definite. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The additional aspects and advantages of the present invention will become apparent in the following description section, or be learned through the practice of the present invention.

[0022] Referring to Figure 1 As shown, a fuel cell stack packs and assembles a plurality of single cells. Each of the single cells has a corresponding air chamber 1, hydrogen chamber 2, and cooling water chamber 3. The air chambers 1, hydrogen chambers 2, and cooling water chambers 3 of different single cells are respectively interconnected. When performing the internal leakage positioning measurement of the fuel cell stack, a fuel cell stack internal leakage positioning system is used to achieve this. The fuel cell stack internal leakage positioning system includes a voltage monitoring system and a positioning judgment system. The voltage monitoring system is used to read the instantaneous voltage of each single cell, and the positioning judgment system is used to generate an internal leakage positioning result based on the instantaneous voltage monitored by the voltage monitoring system.

[0023] The specific internal leakage positioning method is as follows.

[0024] Step 1: Determine whether there is a cross-leakage between the cooling water chamber and the air chamber. 1) Purge the air chamber 1, hydrogen chamber 2, and cooling water chamber 3 of the fuel cell stack with nitrogen to ensure that there are no other residual gases in the fuel cell stack; 2) Introduce air into the air chamber 1 and hydrogen into the cooling water chamber 3; 3) Use the voltage monitoring system to read the instantaneous voltage of each single cell. If a voltage is detected, it indicates that there is a cross-leakage between the cooling water chamber and the air chamber. If no voltage is detected, it indicates that there is no cross-leakage between the cooling water chamber and the air chamber. Among them, helium can also be used instead of nitrogen. In the present invention, the purging of inert gas serves to discharge the impurity gases in the chamber. Relatively speaking, the application cost of nitrogen is lower.

[0025] Step 2: Determine whether there is a cross-leakage between the cooling water chamber and the hydrogen chamber. 1) Purge the air chamber 1, hydrogen chamber 2, and cooling water chamber 3 of the fuel cell with nitrogen to ensure that there are no other residual gases in the fuel cell stack; 2) Introduce air into the hydrogen chamber 2 and hydrogen into the cooling water chamber 3; 3) Use the voltage monitoring system to read the instantaneous voltage of each single cell. If a voltage is detected, it indicates that there is a cross-leakage between the cooling water chamber and the hydrogen chamber. If no voltage is detected, it indicates that there is no cross-leakage between the cooling water chamber and the hydrogen chamber.

[0026] Step 3: Determine whether there is a simultaneous leakage from the cooling water chamber to both the hydrogen chamber and the air chamber. 1) Purge the air chamber 1, hydrogen chamber 2, and cooling water chamber 3 of the fuel cell with nitrogen to ensure that there are no other residual gases in the fuel cell stack; 2) Introduce air into the air chamber, introduce low-concentration hydrogen into the cooling water chamber (the volume concentration of hydrogen is 5% - 10%, and the volume concentration of nitrogen is 90% - 95%), and introduce air into the hydrogen chamber; 3) Use the voltage monitoring system to read the instantaneous voltage of each single cell. If a voltage is detected, it indicates that there is a simultaneous leakage from the cooling water chamber to both the hydrogen chamber and the air chamber. If no voltage is detected, it indicates that there is no such leakage.

[0027] Here, low-concentration hydrogen is selected because: when the hydrogen concentration is high, if there is a simultaneous leakage from the cooling water chamber to both the hydrogen chamber and the air chamber, it will result in a large amount of hydrogen and air existing simultaneously at the anode and cathode of the fuel cell, which will cause damage to the fuel cell and pose an explosion risk. If the hydrogen concentration is too low, it may lead to insufficient monitoring sensitivity and make it difficult to detect some minor leaks.

[0028] Step 4: After determining the leakage type according to Step 1, Step 2, and Step 3, perform leakage point location. The specific operation is as follows: Use the voltage monitoring system to perform N detections, where N is equal to the number of single cells in the fuel cell stack; in the i-th detection, use the voltage monitoring channel of the i-th single cell as the starting point, and each detection can identify the single cell that first shows a voltage change, that is, the potential leakage point; after N detections, use the positioning judgment system to count the single cell with the most times marked as the leakage point, and the actual leakage location can be determined.

[0029] During the detection process, the single cell with internal leakage will first show a voltage change. Since the fuel cell stack contains a large number of single cells, once a gas leak occurs, it will diffuse from the single cell with internal leakage to other non-leaking single cells through the main pipe, resulting in all single cells being able to detect voltage; also, during voltage inspection, the voltage acquisition system monitors the voltage of each single cell in sequence according to the set channels, so there is a time difference between the voltage monitoring channels of different single cells. The present invention accurately locates the leaking single cell by repeating the detection process, with accurate positioning, high efficiency, and strong operability.

[0030] Through the above description of the structure and principle, those skilled in the art should understand that the present invention is not limited to the above specific embodiments. Improvements and substitutions using well-known technologies in the art based on the present invention fall within the protection scope of the present invention. The protection scope of the present invention shall be defined by each claim item and its equivalents. The parts not described in the specific embodiments are all prior art or common general knowledge.

Claims

1. A method for locating internal leakage of a fuel cell stack, characterized in that: The following steps are involved: Step 1, determining the type of internal leakage of the fuel cell stack, wherein the type of internal leakage of the fuel cell stack includes leakage between the cooling water chamber and the air chamber, leakage between the cooling water chamber and the hydrogen chamber, and leakage between the cooling water chamber and the hydrogen chamber and the air chamber at the same time; Step 2: Locate the leak point; perform N tests, where N is equal to the number of cells in the fuel cell stack; in the i-th test, use the voltage monitoring channel of the i-th cell as the starting point for inspection, and use the cell that first shows a voltage change as a potential leak point in each test; after N tests, count the cells that are marked as leak points the most times to determine the actual leak location; 1≤i≤N.

2. A fuel cell stack internal leakage positioning method according to claim 1, characterized in that: The method for determining whether there is leakage between the cooling water cavity and the air cavity is as follows: 1) purge the air cavity, hydrogen cavity and cooling water cavity of the fuel cell stack with inert gas to ensure that there is no other residual gas in the fuel cell stack; 2) introduce air into the air cavity and hydrogen into the cooling water cavity; 3) detect the instantaneous voltage of each single cell. If voltage is detected, it means that there is leakage between the cooling water cavity and the air cavity. If no voltage is detected, it means that there is no leakage between the cooling water cavity and the air cavity.

3. A fuel cell stack internal leakage positioning method according to claim 1, characterized in that: The method for determining whether there is leakage between the cooling water cavity and the hydrogen cavity is as follows: 1) purge the air cavity, hydrogen cavity and cooling water cavity of the fuel cell with an inert gas to ensure that there is no other residual gas in the fuel cell stack; 2) introduce air into the hydrogen cavity and hydrogen into the cooling water cavity; 3) detect the instantaneous voltage of each single cell. If a voltage is detected, it means that there is leakage between the cooling water cavity and the hydrogen cavity. If no voltage is detected, it means that there is no leakage between the cooling water cavity and the hydrogen cavity.

4. A fuel cell stack internal leakage positioning method according to claim 1, characterized in that: The method for judging whether there is leakage from the cooling water cavity to the hydrogen cavity and the air cavity at the same time is as follows: 1) purge the air cavity, hydrogen cavity and cooling water cavity of the fuel cell with an inert gas to ensure that there is no other residual gas in the fuel cell stack; 2) introduce air into the air cavity, introduce low-concentration hydrogen into the cooling water cavity, and introduce air into the hydrogen cavity; 3) detect the instantaneous voltage of each single cell. If voltage is detected, it means that there is leakage from the cooling water cavity to the hydrogen cavity and the air cavity at the same time. If no voltage is detected, it means that there is no leakage from the cooling water cavity to the hydrogen cavity and the air cavity at the same time. The hydrogen volume concentration of the low-concentration hydrogen is 5%-10%.

5. A fuel cell stack internal leakage positioning method according to claim 4, characterized in that: The low-concentration hydrogen consists of 5%-10% hydrogen and 90%-95% inert gas, calculated by volume percentage.

6. A fuel cell stack internal leakage positioning method according to claim 1, characterized in that: The fuel cell stack comprises a plurality of single cells packaged and assembled together, each of the single cells having a corresponding air cavity, a hydrogen cavity and a cooling water cavity, the air cavities, hydrogen cavities and cooling water cavities of different single cells are interconnected, and the cooling water cavities between adjacent single cells are shared.

7. A fuel cell stack internal leakage positioning system, characterized in that: Used to implement a fuel cell stack internal leakage positioning method as described in any one of claims 1 to 6, the fuel cell stack internal leakage positioning system includes a voltage monitoring system and a positioning judgment system, the voltage monitoring system is used to read the instantaneous voltage of each single cell, and the positioning judgment system is used to generate an internal leakage positioning result based on the instantaneous voltage monitored by the voltage monitoring system.

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