A method and device for detecting gas tightness of a fuel cell stack

Abstract

The present invention relates to the field of fuel cell detection technology, and discloses a fuel cell stack air tightness detection method and device. The present invention uses a flexible expansion airbag to prevent the flow of gas to accurately locate the leakage point of the stack, quickly and accurately find the bipolar plate with cross-leakage inside the stack, and improve the detection efficiency. The flexible expansion airbag used in the detection process can achieve the function of isolating the gas without causing damage to the inside of the stack. The method is simple in principle, easy to implement, and can effectively reduce the detection cost.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell detection technology, and in particular to a fuel cell stack air tightness detection method and device. Background Art

[0002] Fuel cells, such as proton membrane exchange fuel cells (PEMFC, short for Proton Exchange Membrane FuelCell), have the advantages of high power density, high energy conversion efficiency, clean and environmentally friendly, and have broad application prospects in many fields such as aerospace, electricity, and automobiles. They are the focus of research and development.

[0003] Sealing defects are easily caused during the processing and assembly of the fuel cell stack. In order to avoid a series of safety problems caused by sealing defects, the airtightness of the fuel cell stack often needs to be tested before use, including the airtightness of a single cavity, gas cross-talk between cavities, and overall sealing.

[0004] Some existing methods for detecting gas tightness of fuel cell stacks can be found in the following patent documents.

[0005] 1) The invention patent application with publication number CN111129549A and publication date May 8, 2020, entitled "A system and method for rapid detection of fuel cell stack leakage", comprises a fuel cell stack having mutually independent hydrogen chambers, water chambers and air chambers, the hydrogen chamber having mutually connected hydrogen chamber inlet and hydrogen chamber outlet, the water chamber having mutually connected water chamber inlet and water chamber outlet, the air chamber having mutually connected air chamber inlet and air chamber outlet, the hydrogen chamber inlet, the water chamber inlet and the air chamber inlet are respectively connected with inlet valves, and the inlet valves are respectively connected with a nitrogen injection device, the hydrogen chamber outlet, the water chamber outlet and the air chamber outlet are respectively connected with outlet valves, and pressure gauges are respectively provided between the hydrogen chamber outlet and the outlet valve, between the water chamber outlet and the outlet valve, and between the air chamber outlet and the outlet valve. The invention can detect leakage and cross-leakage problems of fuel cells.

[0006] 2) The Chinese invention patent application with publication number CN111982420A and publication date November 24, 2020, entitled A fuel cell stack pressure differential leakage test device, includes a first detection structure connected to a water cavity, a second detection structure connected to an oxidant cavity, and a third detection structure connected to a fuel cavity. The first detection structure, the second detection structure, and the third detection structure all have pressure sensors and flow meters. The first detection structure is used to pass gas into the water cavity, the second detection structure is used to pass gas into the oxidant cavity, and the third detection structure is used to pass gas into the fuel cavity. This invention can effectively detect the leakage and size of each cavity in the bipolar plate.

[0007] 3) CN 114976150 A, published on August 30, 2022, is an invention patent application entitled "A method, device, equipment and medium for detecting leakage of a single cell in a fuel cell stack", the method comprising: purging the hydrogen pipeline and the air pipeline; connecting the hydrogen pipeline and the air pipeline to the stack respectively; introducing hydrogen into the hydrogen pipeline, and introducing nitrogen into the air pipeline; obtaining hydrogen parameters of the hydrogen pipeline and nitrogen parameters of the air pipeline, and obtaining the hydrogen permeation voltage of each single cell in the stack; hydrogen parameters include inlet hydrogen temperature and outlet hydrogen pressure; nitrogen parameters include inlet nitrogen temperature, inlet nitrogen flow rate and outlet nitrogen pressure; for each single cell in the stack, determining the amount of hydrogen leakage based on hydrogen parameters, nitrogen parameters and hydrogen permeation voltage. The invention can accurately calculate the amount of hydrogen leakage of each single cell in the stack and determine whether there is a single cell gas leakage.

[0008] Some of the existing fuel cell stack air tightness detection methods are difficult to confirm the cause and leakage point of the leakage, and some require a voltage monitor (CVM) to be configured for each single cell and combined with complex formula calculations; none of the detection methods are satisfactory. Summary of the invention

[0009] The purpose of the present invention is to provide a fuel cell stack air tightness detection method which is simple in principle, easy to implement, and can locate leakage points quickly and accurately, so as to at least provide a beneficial choice or create conditions for solving one or more technical problems existing in the prior art.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions.

[0011] A method for detecting the air tightness of a fuel cell stack comprises the following steps: 1) detecting cross-leakage between different cavities, when it is determined that a cavity has a leak, using a flexible expansion airbag to selectively block other cavities, introducing a detection gas into the cavity with the leak, and keeping the cavity closed and the air pressure greater than or less than the external air pressure; judging whether the air pressure in the cavity changes; if there is a change in air pressure, it means that there is a cross-leakage between the cavity with the leak and the unblocked cavity; if there is no change in air pressure, it means that there is a cross-leakage between the cavity with the leak and the unblocked cavity; There is no cross-leakage; 2) Cross-leakage bipolar plate detection, after determining the two cavities with cross-leakage in step 1), introduce the test gas into one of the cavities, keep the cavity closed and the air pressure greater than or less than the external air pressure, and use a flexible expansion airbag to block the inlet and outlet of some bipolar plates in the other cavity; determine whether the air pressure of the cavity into which the test gas is introduced changes. If there is a change in air pressure, it means that the bipolar plate not blocked by the expansion airbag has a leak. If there is no change in air pressure, it means that the bipolar plate not blocked by the expansion airbag has no leak. When using a flexible expansion airbag to block the cavity, it is achieved by placing the flexible expansion airbag into the inlet and outlet channels of the cavity to block the inlet and outlet of the corresponding bipolar plate.

[0012] More preferably, the method for detecting whether a single cavity has a leak is to respectively introduce a test gas into the hydrogen cavity, air cavity and cooling water cavity of the fuel cell stack, keep the tested cavity closed and the air pressure greater than or less than the external air pressure, and determine whether the air pressure in the tested cavity has changed; if there is a change in air pressure, it means that the cavity has a leak; if there is no change in air pressure, it means that the cavity has no leak.

[0013] More preferably, in step 2), flexible expansion airbags of different lengths are used to block the inlets and outlets of different bipolar plates, so as to complete the detection of all bipolar plates and find out all bipolar plate leakage points.

[0014] More preferably, the method for detecting air tightness of a fuel cell stack further includes a leakage detection step. When it is determined that a cavity has a leak, the outlet of the cavity is closed and a detection gas is introduced into the cavity. The pressure is kept constant and the flow rate of the detection gas flowing into the cavity is measured. The flow rate is the gas leakage amount of the cavity.

[0015] More preferably, the method for detecting air tightness of a fuel cell stack further includes a small leakage detection step, in which helium is introduced into a single cavity. When the detection instrument detects the presence of helium in other cavities, it indicates that there is a small leakage between the two cavities, and the location of the gas leakage needs to be further determined; helium is introduced into the hydrogen cavity, the air cavity, and the cooling water cavity in turn for detection to determine the small leakage between the cavities.

[0016] More preferably, after confirming the presence of a cavity with a slight leak, further confirm the position of the bipolar plate with the slight leak; use a flexible expansion airbag to block the inlet and outlet of some bipolar plates of the cavity and introduce helium into the cavity, at which time the introduced helium can only pass through the bipolar plates that are not blocked by the flexible expansion airbag; if helium can be detected in another cavity, it means that the bipolar plates that are not blocked by the flexible expansion airbag have a cross-leakage, and if helium cannot be detected in another cavity, there is no cross-leakage problem in the bipolar plates that are not blocked by the flexible expansion airbag.

[0017] More preferably, when performing small leak detection, purging is required before each measurement.

[0018] More preferably, the cavity is sealed by a pipe connected to the cavity and a valve arranged on the pipe, and the air pressure change in the sealed cavity is detected by a barometer.

[0019] As another aspect of the present invention, a fuel cell stack air tightness detection device is also provided, including: a flexible expansion airbag, which is made of a flexible expansion material and the size of which can be changed by passing gas; the flexible expansion airbag is placed in the gas flow channel or cooling water flow channel of the fuel cell stack and is in close contact with the bipolar plate, encapsulating the corresponding inlet and outlet of the bipolar plate; and a pressure gauge for detecting whether there is an air pressure change in the cavity of the closed fuel cell stack.

[0020] The above-mentioned fuel cell stack air tightness detection device also includes a flow meter for measuring the gas flow rate flowing into a certain cavity of the fuel cell stack and using it to characterize the leakage amount; and a helium detector for realizing the detection of tiny leaks.

[0021] Compared with the prior art, the present invention has the following beneficial effects.

[0022] 1) The present invention can accurately locate the leakage point of the battery stack, quickly and accurately find the bipolar plate with cross-leakage inside the battery stack, and improve the detection efficiency.

[0023] 2) The present invention uses a flexible expansion airbag to prevent the flow of gas. The flexible expansion airbag is small in size and can be easily placed inside the fuel cell stack. In addition, due to the material properties of the flexible expansion airbag, it can isolate the gas without causing damage to the inside of the fuel cell stack.

[0024] 3) In the present invention, a flexible expansion airbag is used to locate the leakage point of the battery stack. The method is simple in principle, easy to implement, and reduces the detection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Shown is a schematic structural diagram of a fuel cell stack air tightness detection device provided by the present invention.

[0026] Figure 2 Shown is a schematic structural diagram of a fuel cell stack.

[0027] Figure 3 Shown is a schematic diagram of the side structure of a fuel cell stack.

[0028] Figure 4 Shown is a schematic diagram of hydrogen chamber-cooling water chamber leakage detection.

[0029] Figure 5 The above is a schematic diagram of tiny leak detection.

[0030] Description of Figure Numbers.

[0031] 1: fuel cell stack, 2: flexible expansion airbag, 3: pressure gauge, 4: flow meter, 5: valve.

[0032] 1-1: bipolar plate, 1-2: end plate, 1-3: binding band, 1-4: channel opening. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings.

[0035] Example 1.

[0036] Combination Figure 1 As shown, a fuel cell stack air tightness detection device mainly comprises: a fuel cell stack 1, a flexible expansion airbag 2, a pressure gauge 3 and a flow meter 4; the fuel cell stack 1 comprises a plurality of bipolar plates 1-1 assembled together; the flexible expansion airbag 2 is made of a flexible expansion material, has good ductility, and can be changed in size by passing gas; after the flexible expansion airbag 2 is placed in the flow channel of the fuel cell stack 1, gas can be blown into it to increase its volume, so that the flexible expansion airbag 2 is in close contact with the bipolar plate to prevent gas circulation; the pressure gauge 3 is used to measure the pressure change inside the cavity; the flow meter 4 is used to measure the flow rate of the detection gas flowing into the cavity.

[0037] The flexible expansion material can be selected from various reversible highly elastic polymer materials that are currently known or will be realized in the future and have good air tightness, such as rubber and the like.

[0038] Combination Figure 2 , Figure 3As shown, a proton membrane exchange fuel cell stack is taken as an example to perform gas leakage detection. The proton membrane exchange fuel cell stack includes two end plates 1-2, a plurality of bipolar plates 1-1 and a binding band 1-3 assembled together, each of the bipolar plates 1-1 is arranged side by side, and two of the end plates 1-2 are arranged on both sides of the stack to clamp each of the bipolar plates 1-1, and the binding band 1-3 binds the bipolar plate 1-1 and the end plate 1-2 into one; the hydrogen cavity outlet, cooling water cavity inlet, air cavity outlet, air cavity inlet, cooling water cavity outlet, and hydrogen cavity inlet of each of the bipolar plates 1-1 arranged side by side are respectively connected to the hydrogen cavity outlet channel, cooling water cavity inlet channel, air cavity outlet channel, air cavity inlet channel, cooling water cavity outlet channel, and hydrogen cavity inlet channel, and channel openings 1-4 corresponding to each channel are respectively provided on the two end plates 1-2.

[0039] Figure 3 In the figure, the three channel openings 1-4 located on the upper side of the end plate 1-2 correspond to the hydrogen cavity outlet channel, the cooling water cavity inlet channel, and the air cavity outlet channel from left to right, and the three channel openings 1-4 located on the lower side of the end plate 1-2 correspond to the air cavity inlet channel, the cooling water cavity outlet channel, and the hydrogen cavity inlet channel from left to right.

[0040] In this embodiment, the detection gas is nitrogen. The detection workflow is as follows.

[0041] To detect the leakage of the hydrogen chamber, nitrogen is introduced into the hydrogen chamber inlet channel or the hydrogen chamber outlet channel, and the hydrogen chamber inlet channel and the hydrogen chamber outlet channel are closed through valve 5 to make the hydrogen chamber in a closed state; at this time, the pressure change of the hydrogen chamber is detected by pressure gauge 3. If the data read by pressure gauge 3 changes, it means that there is leakage in the hydrogen chamber, and the specific leakage mode needs to be further detected. Based on the same leakage detection principle, the air tightness of the air chamber and the cooling water chamber are checked in turn.

[0042] In this embodiment, taking the gas leakage in the hydrogen cavity as an example, further detect which cavity has cross-leakage between the hydrogen cavity and the cooling water cavity. Put the flexible expansion airbag 2 into the air cavity inlet channel and the air cavity outlet channel, so that the length of the flexible expansion airbag 2 is equal to or longer than the length of the corresponding channel, and completely block the air cavity inlet and air cavity outlet of each bipolar plate 1-1. Introduce nitrogen into the hydrogen cavity, and close the valve 5 of the hydrogen cavity inlet channel and the hydrogen cavity outlet channel; at this time, if the data read by the pressure gauge 3 changes, it means that there is cross-leakage between the hydrogen cavity and the cooling water cavity. If the data read by the pressure gauge 3 does not change, it means that there is no cross-leakage between the hydrogen cavity and the cooling water cavity.

[0043] Based on the same leakage detection principle, check whether there is leakage between the hydrogen cavity and the air cavity. When checking whether there is leakage between the hydrogen cavity and the air cavity, put the flexible expansion airbag 2 into the cooling water cavity inlet channel and the cooling water cavity outlet channel, and use the flexible expansion airbag 2 to completely block the cooling water cavity inlet and the cooling water cavity outlet of each bipolar plate 1-1. Introduce nitrogen into the hydrogen cavity, and close the valve 5 of the hydrogen cavity inlet channel and the hydrogen cavity outlet channel. At this time, if the data read by the pressure gauge 3 changes, it means that there is leakage between the hydrogen cavity and the air cavity.

[0044] In this embodiment, the hydrogen chamber-cooling water chamber leakage is taken as an example to further detect the bipolar plate with leakage. The flexible expansion airbag 2 is placed in the cooling water chamber inlet channel and the cooling water chamber outlet channel, so that the flexible expansion airbag 2 blocks the cooling water chamber inlet and the cooling water chamber outlet of part of the bipolar plate 1-1. Figure 4 As shown. A test gas is introduced into the hydrogen chamber, and the valves 5 of the hydrogen chamber inlet and outlet channels are closed. If the data read by the pressure gauge 3 changes, it means that there is leakage in the part of the bipolar plate 1-1 that is not blocked by the flexible expansion airbag 2. Otherwise, there is no leakage in the part of the bipolar plate 1-1. The flexible expansion airbags 2 of different lengths are used in turn to block the inlet and outlet, and the detection of all the bipolar plates 1-1 is completed.

[0045] Furthermore, if the leakage of the hydrogen cavity is to be measured, the working process is as follows.

[0046] To detect the leakage of the hydrogen chamber, close one of the hydrogen chamber inlet channel and the hydrogen chamber outlet channel, and introduce nitrogen into the hydrogen chamber through the other, keep the pressure gauge 3 degrees unchanged, and measure the detection gas flow Q flowing into the hydrogen chamber. The flow Q is the gas leakage of the hydrogen chamber.

[0047] It should be noted that the above detection method is not limited to use on the proton membrane exchange fuel cell exemplified above, and any other fuel cell with a similar cavity can use the above detection method to perform airtightness detection.

[0048] Example 2.

[0049] A method for detecting minute leaks in a fuel cell stack, using helium as the detection gas, and the working process is as follows.

[0050] Helium is introduced into the air cavity. At this time, a gas detection instrument (commonly used helium detector in industry) is used to detect the hydrogen cavity and the cooling water cavity. If no helium is detected, it means that there is no leakage from the air cavity to the hydrogen cavity and the cooling water cavity. If helium is detected in the hydrogen cavity or the cooling water cavity, it indicates that there is leakage between the air cavity and the cavity, and the gas leakage location needs to be further confirmed. Based on the same detection principle, helium is introduced into the hydrogen cavity and the cooling water cavity in turn for detection to determine the cavity leakage.

[0051] To ensure the detection effect, after helium is introduced into the air cavity, a certain pressure should be maintained in the air cavity, which is greater than the standard atmospheric pressure.

[0052] After confirming the existence of mutually leaking cavities, further confirm the location of the bipolar plates with leaking inside the stack. In this embodiment, taking the leakage from the air cavity to the cooling water cavity as an example, the location detection of the leaking position is performed.

[0053] like Figure 5 As shown, the flexible expansion airbag 2 is placed in the cooling water cavity inlet channel and cooling water cavity outlet channel to block the cooling water cavity inlet and cooling water cavity outlet of some bipolar plates 1-1; helium is introduced into the air cavity. If helium is not detected in the cooling water cavity at this time, the unblocked bipolar plate does not have the problem of air cavity leaking into the cooling water cavity. If helium is detected, it means that the unblocked bipolar plate has the problem of air cavity leaking into the cooling water cavity. According to the actual situation of the battery stack, flexible expansion airbags 2 of different lengths are used in turn to detect leakage of the battery stack to find the bipolar plate with leakage.

[0054] When performing small leak detection, purging is required before each measurement to avoid interference caused by residual helium.

[0055] In this embodiment, the detection of a small leak refers to a leak with a leakage volume less than 0.1 mL / min. The advantages of using helium for the detection of small leaks are: helium molecules are small in size, have good evasion properties, and helium is chemically inactive and is difficult to react with other substances under normal conditions. According to actual tests by the inventors, the detection effect of small leaks cannot be achieved by using other inert gases or nitrogen.

[0056] Through the description of the above structure and principle, those skilled in the art should understand that the present invention is not limited to the above specific implementations, and improvements and substitutions based on the present invention using the known technology in the art fall within the protection scope of the present invention, and the protection scope of the present invention should be defined by the claims and their equivalents. Parts not described in the specific implementations are prior art or common knowledge.

Claims

1. A method for detecting the air tightness of a fuel cell stack, characterized in that: The following steps are involved: 1) Leakage detection between different cavities: When a cavity is leaking, use a flexible inflatable airbag to block other cavities, introduce detection gas into the cavity with leakage, and keep the cavity closed and the air pressure greater than or less than the external air pressure; determine whether the air pressure in the cavity changes; if there is a change in air pressure, it means that there is leakage between the cavity with leakage and the unblocked cavity; if there is no change in air pressure, it means that there is no leakage between the cavity with leakage and the unblocked cavity; 2) Leakage detection of bipolar plates: after determining the two cavities with leakage in step 1), a detection gas is introduced into one of the cavities, and the cavity is kept closed and the air pressure is greater than or less than the external air pressure. The inlet and outlet of part of the bipolar plates in the other cavity are blocked with a flexible expansion airbag; it is determined whether the air pressure of the cavity into which the detection gas is introduced changes. If there is a pressure change, it indicates that the bipolar plate not blocked by the expansion airbag has leakage; if there is no pressure change, it indicates that the bipolar plate not blocked by the expansion airbag has no leakage; When the cavity is blocked with a flexible expansion airbag, the flexible expansion airbag is placed in the inlet and outlet channels of the cavity to block the inlet and outlet of the corresponding bipolar plate.

2. A fuel cell stack air tightness detection method according to claim 1, characterized in that: The method for detecting whether a single cavity has a leak is to respectively introduce a test gas into the hydrogen cavity, air cavity and cooling water cavity of the fuel cell stack, keep the cavity being tested closed and the air pressure greater than or less than the external air pressure, and determine whether the air pressure in the cavity being tested changes; if there is a change in air pressure, it means that the cavity has a leak; If there is no change in air pressure, it means that there is no leakage in the cavity.

3. A fuel cell stack air tightness detection method according to claim 1, characterized in that: In step 2), flexible expansion airbags of different lengths are used to block the inlets and outlets of different bipolar plates, complete the detection of all bipolar plates, and find out all bipolar plate leakage points.

4. A fuel cell stack air tightness detection method according to claim 1 or 2, characterized in that: The method includes a leakage detection step. When it is determined that a cavity has a leak, the outlet of the cavity is closed and a detection gas is introduced into the cavity. The pressure is kept constant and the flow rate of the detection gas flowing into the cavity is measured. The flow rate is the gas leakage of the cavity.

5. A fuel cell stack air tightness detection method according to claim 1, characterized in that: The method includes a small leak detection step, in which helium is introduced into a single cavity. When the detection instrument detects the presence of helium in other cavities, it indicates that there is a small leak between the two cavities; helium is introduced into the hydrogen cavity, the air cavity, and the cooling water cavity in turn for detection to determine the small leaks between the cavities.

6. A fuel cell stack air tightness detection method according to claim 5, characterized in that: After confirming the cavity with a small leak, further confirm the position of the bipolar plate with a small leak; A flexible expansion air bag is used to block the inlet and outlet of some bipolar plates of the cavity and helium is introduced into the cavity. At this time, the introduced helium can only pass through the bipolar plates that are not blocked by the flexible expansion air bag. If helium can be detected in other cavities, it means that there is leakage in the bipolar plates that are not blocked by the flexible expansion air bag. If helium cannot be detected in other cavities, there is no leakage problem in the bipolar plates that are not blocked by the flexible expansion air bag.

7. A fuel cell stack air tightness detection method according to claim 5, characterized in that: When testing for small leaks, purging is required before each measurement.

8. A fuel cell stack air tightness detection method according to claim 1 or 2, characterized in that: The cavity is sealed by a pipe connected to the cavity and a valve arranged on the pipe, and the air pressure change in the sealed cavity is detected by a barometer.

Images