Fuel cell airtightness detection system

Abstract

The utility model provides a fuel cell airtightness detection system. The fuel cell airtightness detection system comprises a gas storage tank, a detection pipeline, a pressure reduction pipeline connected between the gas storage tank and the detection pipeline, and a control pipeline used for controlling the pressure reduction pipeline and the detection pipeline, each pressure reduction branch is connected with the detection pipeline after reducing the pressure of the gas storage tank for at least two times, and the pressures on the n pressure reduction branches are different. According to the utility model, the pressure reduction pipeline is arranged between the gas storage tank and the detection pipeline, the pressure reduction pipeline comprises the n pressure reduction branches, and the pressures on the pressure reduction branches are different, so that during detection, the arranged pressure reduction branch can be selected according to the requirements, and the required pressure is provided to realize detection.

Description

Technical Field

[0001] The utility model relates to the technical field of hydrogen energy fuel cell detection, in particular to a fuel cell airtightness detection system. Background Art

[0002] Air tightness and insulation are two major safety indicators of hydrogen fuel cells. During the production of hydrogen fuel cells, air tightness testing is required. The air tightness test mainly includes hydrogen flow channel air tightness test and overall air tightness test.

[0003] When conducting the hydrogen flow channel air tightness test, the airtight pressure test pressure is set to match the working pressure of the hydrogen side of the fuel cell. The test process is: first close the hydrogen outlet, keep other inlets and outlets unobstructed, and pass helium-nitrogen mixed gas (helium concentration is not less than 10%) from the hydrogen inlet to stabilize the pressure to the set pressure. After the pressure stabilizes to the set pressure, close the hydrogen inlet, maintain the pressure for 10 minutes, and record the pressure drop value.

[0004] When conducting the overall air tightness test, close the hydrogen outlet, air outlet and coolant outlet, and introduce helium-nitrogen mixed gas (helium concentration not less than 10%) from the hydrogen inlet, air inlet and coolant inlet to stabilize the pressure to the normal working pressure. Then close the main air inlet, maintain the pressure for 10 minutes, and record the pressure drop value.

[0005] Existing detection systems, such as a fuel cell comprehensive airtightness detection system disclosed in patent announcement number CN220583702U, are designed with a first inlet branch pipe, a second inlet branch pipe, and a third inlet branch pipe connected to the inlet ends of the hydrogen chamber, the air chamber, and the water chamber, respectively, and a first outlet branch pipe, a second outlet branch pipe, and a third outlet branch pipe connected to the outlet ends of the hydrogen chamber, the air chamber, and the water chamber, respectively. However, airtightness detection requires different pressures, such as 0.05 MPa, 0.1 MPa, 0.15 MPa, and 0.2 MPa, etc., and the existing detection system cannot realize the detection of multiple pressure values. Utility Model Content

[0006] The utility model aims to provide a fuel cell airtightness detection system, which can realize the demand detection of multiple pressure values.

[0007] The technical solution of the utility model is: a fuel cell airtightness detection system, including a gas storage tank, a detection pipeline, a pressure reducing pipeline connected between the gas storage tank and the detection pipeline, and a control pipeline for controlling the pressure reducing pipeline and the detection pipeline, the pressure reducing pipeline includes n parallel pressure reducing branches, n≥2, each pressure reducing branch reduces the pressure of the gas storage tank at least twice and then is connected to the detection pipeline, and the pressures on the n pressure reducing branches are different.

[0008] In the above scheme, a pressure reducing pipeline is set between the gas storage tank and the detection pipeline, and the pressure reducing pipeline includes n pressure reducing branches, and the pressure on each pressure reducing branch is different. Therefore, during detection, the pressure reducing branch set can be selected as needed to provide the required pressure to realize detection.

[0009] Preferably, a first pressure reducing valve is connected between the gas storage tank and the pressure reducing pipeline, the first pressure reducing valve is connected to a diverter block, and is diverted into n pressure reducing branches through the diverter block.

[0010] Preferably, n=3, the first pressure reducing branch is connected with a third pressure reducing valve and a third air-controlled valve, the second pressure reducing branch is connected with a fourth pressure reducing valve and a fourth air-controlled valve, the third pressure reducing branch is connected with a fifth pressure reducing valve and a fifth air-controlled valve, the third air-controlled valve, the fourth air-controlled valve and the fifth air-controlled valve are connected to form a connecting pipeline, the connecting pipeline is connected to the detection pipeline, an external leakage flow meter is connected to the connecting pipeline, and the seventh air-controlled valve and the eighth air-controlled valve are connected between the connecting pipeline and the detection pipeline.

[0011] Preferably, the connecting pipeline is also connected to a sixth air-controlled valve, and the sixth air-controlled valve is connected to the atmosphere through a muffler.

[0012] Preferably, the fuel cell air tightness detection system also includes an inflation pipeline connected in parallel with the pressure reducing pipeline, the inflation pipeline is connected with a proportional valve and a second air control valve, the second air control valve is arranged close to the detection pipeline, and the second air control valve is electrically connected to the control pipeline.

[0013] Preferably, a pressure transmitter is connected between the pressure reducing pipeline and the detection pipeline.

[0014] Preferably, the detection pipeline includes a first branch for connecting to the hydrogen chamber of the fuel cell stack, a second branch for connecting to the water chamber of the fuel cell stack, a third branch for connecting to the oxygen chamber of the fuel cell stack, and a reserved branch, and the first branch, the second branch, the third branch and the reserved branch are connected in parallel.

[0015] Preferably, the first branch is connected with a ninth air-controlled valve, a fifteenth air-controlled valve, a twelfth air-controlled valve and a first filter in sequence, the second branch is connected with a tenth air-controlled valve, a sixteenth air-controlled valve, a thirteenth air-controlled valve and a second filter in sequence, the third branch is connected with an eleventh air-controlled valve, a seventeenth air-controlled valve, a fourteenth air-controlled valve and a third filter in sequence, and the reserved branch is connected with the first air-controlled valve.

[0016] Preferably, a series leakage flow meter is connected in parallel to the first branch, the second branch and the third branch, and the series leakage flow meter is connected to the atmosphere.

[0017] Preferably, a plurality of solenoid valves are connected to the detection pipeline, and a second pressure reducing valve is connected to a side of the detection pipeline close to the gas storage tank.

[0018] Compared with the related art, the beneficial effects of the utility model are:

[0019] 1. A pressure reducing pipeline is set between the gas storage tank and the detection pipeline, and the pressure reducing pipeline includes n pressure reducing branches, and the pressure on each pressure reducing branch is different. Therefore, during the detection, the pressure reducing branch set can be selected according to the needs to provide the required pressure to realize the detection;

[0020] 2. All air-controlled valves are controlled by solenoid valves, which have higher stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The schematic diagram of the fuel cell air tightness detection system provided by the utility model;

[0022] Figure 2 This is a structural schematic diagram of a fuel cell air tightness detection system provided by the utility model.

[0023] In the attached drawings: 1, triple joint; 2, gas storage tank; 3, fourth filter; 4, first fixed plate; 5, first pressure reducing valve; 6, diverter block; 7, first three-way joint; 8, second three-way joint; 9, proportional valve; 10, second pressure reducing valve; 11, third pressure reducing valve; 12, fourth pressure reducing valve; 13, fifth pressure reducing valve; 14, external leakage flow meter; 15, string leakage flow meter; 16, first filter; 17, second filter; 18, third filter; 19, second fixed plate; 20, busbar; 21, solenoid valve; 22, blind plate; 23, wiring trough; 24, first gas control valve; 25, second gas control valve; 26, third gas control valve; 27, fourth gas control valve; 28, fifth Air-controlled valve; 29, the sixth air-controlled valve; 30, the seventh air-controlled valve; 31, the eighth air-controlled valve; 32, the pressure transmitter; 33, the ninth air-controlled valve; 34, the tenth air-controlled valve; 35, the eleventh air-controlled valve; 36, the twelfth air-controlled valve; 37, the thirteenth air-controlled valve; 38, the fourteenth air-controlled valve; 39, the fifteenth air-controlled valve; 40, the sixteenth air-controlled valve; 41, the seventeenth air-controlled valve; 42, the air circuit block; 43, the first branch; 44, the second branch; 45, the third branch; 46, the pressure-reducing pipeline; 47, the detection pipeline; 48, the control pipeline; 49, the pressure-reducing branch; 50, the charging pipeline; 51, the silencer; 52, the reserved branch; 53, the air source; 54, the air purifier. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict. For the convenience of description, if the words "upper", "lower", "left" and "right" appear in the following text, they only indicate that the upper, lower, left and right directions are consistent with the drawings themselves, and do not limit the structure.

[0025] Embodiment 1

[0026] like Figure 1 As shown, a fuel cell air tightness detection system provided in this embodiment includes a gas storage tank 2, a detection pipeline 47, a pressure reducing pipeline 46, a control pipeline 48 for controlling the pressure reducing pipeline 46 and the detection pipeline 47, and an inflation pipeline 50 connected in parallel with the pressure reducing pipeline 46.

[0027] The front end of the gas storage tank 2 is connected to the gas source 53 through the air cleaner 54. The rear end of the gas storage tank 2 is connected to the fourth filter 3 and the first joint of the second three-way joint 8. The second joint of the second three-way joint 8 is connected to the detection pipeline 47, and the third joint of the second three-way joint 8 is connected to the first joint of the first three-way joint 7. The second joint of the first three-way joint 7 is connected to the charging pipeline 50, and the third joint of the first three-way joint 7 is connected to the pressure reducing pipeline 46 through the first pressure reducing valve 5 and the diverter block 6.

[0028] The pressure reducing pipeline 46 is divided into three pressure reducing branches 49 by the diverter block 6, wherein the first pressure reducing branch 49 is connected with the third pressure reducing valve 11 and the third air control valve 26, the second pressure reducing branch 49 is connected with the fourth pressure reducing valve 12 and the fourth air control valve 27, and the third pressure reducing branch 49 is connected with the fifth pressure reducing valve 13 and the fifth air control valve 28. The third air control valve 26, the fourth air control valve 27 and the fifth air control valve 28 are connected to form a connecting pipeline. The connecting pipeline is connected to the detection pipeline 47. An external leakage flow meter 14 is connected to the connecting pipeline, and at the same time, the seventh air control valve 30 and the eighth air control valve 31 are connected between the connecting pipeline and the detection pipeline 47. The sixth air control valve 29 is also connected to the connecting pipeline, and the sixth air control valve 29 is connected to the atmosphere through a muffler 51.

[0029] The output pressure of the gas storage tank 2 is P0, which is reduced to P1 after one decompression by the first decompression valve 5. The three decompression branches 49 are selected according to the working pressure of the fuel cell stack during detection. The required pressure values ​​are set in advance on the third decompression valve 11, the fourth decompression valve 12 and the fifth decompression valve 13. On the first decompression branch 49, P1 is reduced to P2 through the third decompression valve 11, on the second decompression branch 49, P1 is reduced to P3 through the fourth decompression valve 12, and on the third decompression branch 49, P1 is reduced to P4 through the fifth decompression valve 13.

[0030] The charging pipeline 50 is connected with a proportional valve 9 and a second gas control valve 25, the second gas control valve 25 is arranged close to the detection pipeline 47, and the second gas control valve 25 is electrically connected to the control pipeline 48. The proportional valve 9 slowly inflates the entire detection pipeline 47 according to the signal. The charging pipeline 50 directly provides the P0 pressure of the gas storage tank 2 to the detection pipeline 47.

[0031] A pressure transmitter 32 is connected between the pressure reducing pipeline 46 and the detection pipeline 47. The detection pipeline 47 includes a first branch 43 for connecting to the hydrogen chamber of the fuel cell stack, a second branch 44 for connecting to the water chamber of the fuel cell stack, a third branch 45 for connecting to the oxygen chamber of the fuel cell stack, and a reserved branch 52. The first branch 43, the second branch 44, the third branch 45 and the reserved branch 52 are connected in parallel. The first branch 43 is used for hydrogen chamber leakage detection, the second branch 44 is used for water chamber leakage detection, and the third branch 45 is used for oxygen chamber leakage detection. A series leakage flowmeter 15 is connected in parallel to the first branch 43, the second branch 44 and the third branch 45, and the series leakage flowmeter 15 is connected to the atmosphere.

[0032] The first branch 43 is connected in sequence with the ninth air-controlled valve 33, the fifteenth air-controlled valve 39, the twelfth air-controlled valve 36 and the first filter 16, the second branch 44 is connected in sequence with the tenth air-controlled valve 34, the sixteenth air-controlled valve 40, the thirteenth air-controlled valve 37 and the second filter 17, the third branch 45 is connected in sequence with the eleventh air-controlled valve 35, the seventeenth air-controlled valve 41, the fourteenth air-controlled valve 38 and the third filter 18, and the reserved branch 52 is connected with the first air-controlled valve 24.

[0033] The detection pipeline 47 is connected to a plurality of solenoid valves 21, and a second pressure reducing valve 10 is connected to the side of the detection pipeline 47 close to the gas storage tank 2. The second pressure reducing valve 10 is used to reduce the pressure P0 of the gas storage tank 2 to P5. The number of solenoid valves 21 corresponds to the number of gas control valves, and all gas control valves are controlled by the solenoid valves 21.

[0034] The plurality of solenoid valves 21 are mounted on the second fixing plate 19 , and blind plates 22 are mounted at holes on the second fixing plate 19 where no solenoid valves 21 are mounted.

[0035] Leakage detection mainly includes flow method and pressure difference method. Among them, the pressure difference method is mainly for hydrogen cavity leakage, water cavity leakage and oxygen cavity leakage. For example, the hydrogen cavity leakage test method is:

[0036] According to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second gas-controlled valve 25 or the third gas-controlled valve 26 or the fourth gas-controlled valve 27 or the fifth gas-controlled valve 28 to open, and open the eighth gas-controlled valve 31 and the ninth gas-controlled valve 33 on the first branch 43 to inflate the hydrogen chamber of the fuel cell stack. After the value of the pressure transmitter 32 stabilizes, close the eighth gas-controlled valve 31, check the value of the pressure transmitter 32 after maintaining the pressure for 10 minutes, and judge whether the hydrogen chamber is leaking according to the change in the value. The fifteenth gas-controlled valve 39 is an exhaust valve, which is opened to exhaust gas only after the detection is completed.

[0037] Water cavity leakage test method: According to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second air-controlled valve 25 or the third air-controlled valve 26 or the fourth air-controlled valve 27 or the fifth air-controlled valve 28 to open, and open the eighth air-controlled valve 31 and the tenth air-controlled valve 34 on the second branch 44 to inflate the water cavity of the battery stack. After the value of the pressure transmitter 32 stabilizes, close the eighth air-controlled valve 31, check the value of the pressure transmitter 32 after maintaining the pressure for 10 minutes, and judge whether the water cavity is leaking by the change in the value. The sixteenth air-controlled valve 40 is an exhaust valve, which is opened to exhaust gas only after the test is completed.

[0038] Oxygen chamber leakage test method: According to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second gas-controlled valve 25 or the third gas-controlled valve 26 or the fourth gas-controlled valve 27 or the fifth gas-controlled valve 28 to open, and open the eighth gas-controlled valve 31 and the eleventh gas-controlled valve 35 on the third branch 45 to inflate the oxygen chamber of the stack. After the value of the pressure transmitter 32 stabilizes, close the eighth gas-controlled valve 31, check the value of the pressure transmitter 32 after maintaining the pressure for 10 minutes, and judge whether the oxygen chamber is leaking by the change in the value. The seventeenth gas-controlled valve 41 is an exhaust valve, which is opened to exhaust gas only after the test is completed.

[0039] Flow method: This method is used to detect hydrogen chamber leakage, water chamber leakage, oxygen chamber leakage, three-chamber total leakage, hydrogen chamber and oxygen chamber leakage, hydrogen chamber and water chamber leakage, oxygen chamber and water chamber leakage, etc.

[0040] The hydrogen chamber leakage test method is as follows: according to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second gas control valve 25 or the third gas control valve 26 or the fourth gas control valve 27 or the fifth gas control valve 28 to open, and open the eighth gas control valve 31 and the ninth gas control valve 33 on the first branch 43 to inflate the hydrogen chamber of the fuel cell stack. After a certain inflation and pressure holding time, determine whether the hydrogen chamber is leaking according to the leakage flowmeter 14.

[0041] The water cavity leakage test method is: according to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second gas control valve 25 or the third gas control valve 26 or the fourth gas control valve 27 or the fifth gas control valve 28 to open, and open the eighth gas control valve 31 and the tenth gas control valve 34 on the second branch 44 to inflate the water cavity of the battery stack. After a certain inflation and pressure holding time, the leakage flow meter 14 is used to determine whether the water cavity is leaking.

[0042] The oxygen chamber leakage test method is as follows: according to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second gas control valve 25 or the third gas control valve 26 or the fourth gas control valve 27 or the fifth gas control valve 28 to open, and open the eighth gas control valve 31 and the eleventh gas control valve 35 on the third branch 45 to inflate the oxygen chamber of the stack. After a certain inflation and pressure holding time, determine whether the oxygen chamber is leaking according to the external leakage flowmeter 14.

[0043] The cross-leakage test method of the hydrogen chamber and the oxygen chamber is: according to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second gas control valve 25 or the third gas control valve 26 or the fourth gas control valve 27 or the fifth gas control valve 28 to open, and open the eighth gas control valve 31, the ninth gas control valve 33 and the fourteenth gas control valve 38, and observe the cross-leakage flowmeter 15 to determine whether the hydrogen chamber and the oxygen chamber are leaking.

[0044] Hydrogen chamber and water chamber leakage test method: according to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second air control valve 25 or the third air control valve 26 or the fourth air control valve 27 or the fifth air control valve 28 to open, and open the eighth air control valve 31, the ninth air control valve 33 and the thirteenth air control valve 37, and observe the leakage flowmeter 15 to determine whether the hydrogen chamber and the water chamber are leaking.

[0045] Oxygen chamber and water chamber leakage test method: according to the required pressure, select the appropriate pressure reducing branch 49, that is, select the corresponding second air control valve 25 or the third air control valve 26 or the fourth air control valve 27 or the fifth air control valve 28 to open, and open the eighth air control valve 31, the eleventh air control valve 35 and the thirteenth air control valve 37, and observe the leakage flowmeter 15 to determine whether the oxygen chamber and the water chamber are leaking.

[0046] Embodiment 2

[0047] like Figure 2 As shown, a fuel cell air tightness detection system provided in this embodiment includes a triple joint 1, a gas storage tank 2, a fourth filter 3, a second three-way joint 8 and a first fixed plate 4. The first fixed plate 4 is equipped with a first three-way joint 7, a first pressure reducing valve 5, a diverter block 6, a proportional valve 9, a second pressure reducing valve 10, a third pressure reducing valve 11, a fourth pressure reducing valve 12, a fifth pressure reducing valve 13, a second fixed plate 19, a gas circuit block 42, an external leakage flowmeter 14, a cross leakage flowmeter 15, a first filter 16, a second filter 17 and a third filter 18.

[0048] The second fixing plate 19 is provided with a bus bar 20, and the bus bar 20 is provided with multiple holes, and the holes are used to install electromagnetic valves 21, and the electromagnetic valves 21 correspond to the air control valves one by one. Blind plates 22 are installed on the redundant holes.

[0049] The gas circuit block 42 is provided with a gas circuit inside, and the first gas control valve 24, the second gas control valve 25, the third gas control valve 26, the fourth gas control valve 27, the fifth gas control valve 28, the sixth gas control valve 29, the seventh gas control valve 30, the eighth gas control valve 31, the pressure transmitter 32, the ninth gas control valve 33, the tenth gas control valve 34, the eleventh gas control valve 35, the twelfth gas control valve 36, the thirteenth gas control valve 37, the fourteenth gas control valve 38, the fifteenth gas control valve 39, the sixteenth gas control valve 40 and the seventeenth gas control valve 41 are installed on the upper surface. The gas circuit is used to connect the pressure transmitter 32 and the above-mentioned gas control valves. The gas circuit block 42 is provided with six joints, namely A, B, C, D, E, and F. The joints A, B, C, D, E, and F are connected to the corresponding gas control valves through the gas circuit inside the gas circuit block 42. A wiring groove 23 is provided on the side of the gas circuit block 42.

[0050] The factory gas source 53 is connected to the gas tank 2 through the triplet 1, and then connected to the fourth filter 3 through the gas tank 2. It is connected to the first three-way joint 7 and the second pressure reducing valve 10 respectively through the second three-way joint 8. The second pressure reducing valve 10 is connected to the bus 20, and all the gas-controlled valves are controlled by the solenoid valve 21. Two air pipes are separated from the other end of the first three-way joint 7 to connect the first pressure reducing valve 5 and the proportional valve 9 respectively. The first pressure reducing valve 5 is connected to the diverter block 6 through an air pipe, and three air pipes are separated from the diverter block 6 to connect the third pressure reducing valve 11, the fourth pressure reducing valve 12 and the fifth pressure reducing valve 13. The proportional valve 9 is connected to the second gas-controlled valve 25. The first pressure reducing valve 5, the third pressure reducing valve 11, the fourth pressure reducing valve 12 and the fifth pressure reducing valve 13 are manually pressure-regulated. For example, if the pressure P0 of the gas storage tank 2 is 0.7 MPa, the first pressure reducing valve 5 sets the pressure P1 to 0.35 MPa, the third pressure reducing valve 11 sets the pressure P2 to 0.05 MPa, the fourth pressure reducing valve 12 sets the pressure P3 to 0.1 MPa, and the fifth pressure reducing valve 13 sets the pressure P4 to 0.25 MPa.

[0051] The third pressure reducing valve 11 is connected to the third air control valve 26, the fourth pressure reducing valve 12 is connected to the fourth air control valve 27, and the fifth pressure reducing valve 13 is connected to the fifth air control valve 28. The corresponding air control valve is selected according to the self-determined intake pressure. The function of the proportional valve 9 is to slowly inflate the entire detection circuit according to the signal.

[0052] The left side of the external leakage flowmeter 14 is connected to the connector A of the gas circuit block 42, and the right side of the external leakage flowmeter 14 is connected to the connector B of the gas circuit block 42. The left side of the string leakage flowmeter 15 is connected to the connector F of the gas circuit block 42, and the string leakage flowmeter 15 is directly connected to the atmosphere through a muffler. The left side of the first filter 16 is connected to the connector C of the gas circuit block 42, and the right side of the first filter 16 is connected to the hydrogen chamber of the battery stack. The left side of the second filter 17 is connected to the connector D of the gas circuit block 42, and the right side of the second filter 17 is connected to the water chamber of the battery stack. The left side of the third filter 18 is connected to the connector E of the gas circuit block 42, and the right side of the third filter 18 is connected to the oxygen chamber of the battery stack. All the solenoid valves 21 are individually connected to all the gas control valves from top to bottom (one-to-one connection), and the entire detection system is controlled through a touch screen or a PC.

[0053] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A fuel cell air tightness detection system, comprising a gas storage tank (2) and a detection pipeline (47), It is characterized in that It also includes a pressure reducing pipeline (46) connected between the gas storage tank (2) and the detection pipeline (47), and a control pipeline (48) for controlling the pressure reducing pipeline (46) and the detection pipeline (47), wherein the pressure reducing pipeline (46) includes n parallel pressure reducing branches (49), where n is greater than or equal to 2, and each pressure reducing branch (49) is connected to the detection pipeline (47) after reducing the pressure of the gas storage tank (2) at least twice, and the pressures on the n pressure reducing branches (49) are different.

2. The fuel cell gas tightness detection system according to claim 1, It is characterized in that A first pressure reducing valve (5) is connected between the gas storage tank (2) and the pressure reducing pipeline (46); the first pressure reducing valve (5) is connected to a flow dividing block (6) and is divided into n pressure reducing branches (49) via the flow dividing block (6).

3. The fuel cell gas tightness detection system according to claim 1, It is characterized in that n=3, the first pressure reducing branch (49) is connected to a third pressure reducing valve (11) and a third air control valve (26), the second pressure reducing branch (49) is connected to a fourth pressure reducing valve (12) and a fourth air control valve (27), the third pressure reducing branch (49) is connected to a fifth pressure reducing valve (13) and a fifth air control valve (28), the third air control valve (26), the fourth air control valve (27) and the fifth air control valve (28) are connected to form a connecting pipeline, the connecting pipeline is connected to a detection pipeline (47), an external leakage flow meter (14) is connected to the connecting pipeline, and a seventh air control valve (30) and an eighth air control valve (31) are connected between the connecting pipeline and the detection pipeline (47).

4. The fuel cell gas tightness detection system according to claim 3, It is characterized in that The connecting pipeline is also connected to a sixth air control valve (29), and the sixth air control valve (29) is connected to the atmosphere via a muffler (51).

5. The fuel cell gas tightness detection system according to claim 1, It is characterized in that It also includes an air charging pipeline (50) connected in parallel with the pressure reducing pipeline (46), the air charging pipeline (50) being connected to a proportional valve (9) and a second air control valve (25), the second air control valve (25) being arranged close to the detection pipeline (47), and the second air control valve (25) being electrically connected to the control pipeline (48).

6. The fuel cell gas tightness detection system according to claim 1, It is characterized in that A pressure transmitter (32) is connected between the pressure reducing pipeline (46) and the detection pipeline (47).

7. The fuel cell gas tightness detection system according to any one of claims 1 to 6, It is characterized in that The detection pipeline (47) comprises a first branch (43) for connecting to a hydrogen chamber of a fuel cell stack, a second branch (44) for connecting to a water chamber of a fuel cell stack, a third branch (45) for connecting to an oxygen chamber of a fuel cell stack, and a reserved branch (52); the first branch (43), the second branch (44), the third branch (45), and the reserved branch (52) are connected in parallel.

8. The fuel cell gas tightness detection system according to claim 7, It is characterized in that The first branch (43) is connected in sequence to a ninth air-controlled valve (33), a fifteenth air-controlled valve (39), a twelfth air-controlled valve (36) and a first filter (16); the second branch (44) is connected in sequence to a tenth air-controlled valve (34), a sixteenth air-controlled valve (40), a thirteenth air-controlled valve (37) and a second filter (17); the third branch (45) is connected in sequence to an eleventh air-controlled valve (35), a seventeenth air-controlled valve (41), a fourteenth air-controlled valve (38) and a third filter (18); and the reserved branch (52) is connected to the first air-controlled valve (24).

9. The fuel cell gas tightness detection system according to claim 7, It is characterized in that A series leakage flow meter (15) is connected in parallel to the first branch (43), the second branch (44) and the third branch (45), and the series leakage flow meter (15) is in communication with the atmosphere.

10. The fuel cell gas tightness detection system according to any one of claims 1 to 6, It is characterized in that The detection pipeline (47) is connected to a plurality of solenoid valves (21), and a second pressure reducing valve (10) is connected to a side of the detection pipeline (47) close to the gas storage tank (2).

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