Hydrogen leakage detection system and method for constant volume dilution of hydrogen fuel vehicle

Abstract

This invention belongs to the field of hydrogen leak detection technology for hydrogen fuel cell vehicles. It discloses a system for detecting hydrogen leaks in hydrogen fuel cell vehicles using a gas bag for constant-volume dilution. The system includes an insulated chamber for constructing a sealed space, connected to an intake fan, a sunlight simulation system, an regulating airbag, a constant-volume dilution channel, an inflatable sealing ring, and a gate. The constant-volume dilution channel is connected to an exhaust valve, a collection gas bag, a flow control pump, a Venturi flow meter, and an exhaust fan. This invention draws a mixture of leaked hydrogen and air from the sealed space into the constant-volume dilution channel at a constant flow rate using the exhaust fan. This ensures that the hydrogen concentration in the gas sample collected in the gas bag is equal to the average hydrogen concentration in all the gas flowing through the Venturi flow meter. Furthermore, the hydrogen concentration in the collection gas bag is measured by continuous integration of real gas, eliminating approximation errors. This detection system and method have high measurement accuracy and good repeatability, making them suitable for detecting hydrogen leaks in hydrogen fuel cell vehicles.

Description

Technical Field

[0001] This invention relates to the field of hydrogen leak detection technology for hydrogen fuel cell vehicles, specifically to a system and method for detecting hydrogen leaks in a constant-volume diluted hydrogen fuel cell vehicle using a gas bag. Background Technology

[0002] Hydrogen, due to its high combustion efficiency and pollution-free byproducts, is considered one of the three major new energy sources, along with solar and nuclear energy. As a new energy source, hydrogen is widely used in aviation, power, and automotive industries. Hydrogen fuel cell vehicles store hydrogen in storage devices at pressures of 35 MPa or 70 MPa. Because hydrogen molecules are small, low in density, and have strong diffusion capabilities, as well as strong permeation and hydrogen quenching effects, leaks are highly likely. Furthermore, hydrogen is flammable and explosive. Therefore, under the combined effect of high-pressure storage, hydrogen leakage has become a major safety hazard for hydrogen fuel cell vehicles. To avoid this hazard, current safety technical standards for hydrogen fuel cell vehicles propose a hydrogen leakage test procedure in a confined space based on hydrogen sensor concentration detection. This involves placing a hydrogen fuel cell vehicle filled to its nominal pressure in a confined space at an ambient temperature of 25°C for 12 hours, then sealing the confined space for a hydrogen leakage test. If the concentration detected by any one of the seven hydrogen sensors evenly distributed at the top of the confined space exceeds 1% by volume, the vehicle fails the hydrogen leakage test. However, existing methods are based on concentration detection, which has two main drawbacks:

[0003] 1) After a leak occurs, there is a hydrogen concentration gradient in the vertical direction. When the interval between the leak and the reading of the hydrogen sensor is short, the leaked hydrogen does not have enough time to diffuse to the vicinity of the hydrogen sensor at the top under the static and stable conditions in the confined space, leading to an underestimation of the leak concentration and safety risks.

[0004] 2) For the same amount of hydrogen leakage, even under the condition that the leaked hydrogen has fully diffused, the concentration detected by the hydrogen sensor will be affected by external conditions such as the size of the detection space, the specific environment of the detection space, and the size of the vehicle: it will increase as the size of the enclosed space decreases and the size of the vehicle increases; if there are complex structures blocking the hydrogen sensor near its installation location, it may also cause local hydrogen accumulation and higher readings. These factors all increase the uncertainty of the detection method and reduce its repeatability. Summary of the Invention

[0005] This invention aims to provide a system and method for detecting hydrogen leaks in hydrogen fuel cell vehicles using a gas bag. Driven by an exhaust fan, a mixture of leaked hydrogen and air from a sealed space is drawn out through a constant-volume dilution channel. The flow rate is controlled at a constant value by the critical Venturi tube inside a Venturi flowmeter. Gas is continuously drawn from the constant-volume dilution channel at a constant flow rate and injected into a collection gas bag until all gas in the sealed space is exhausted. Finally, a hydrogen concentration analyzer is used to repeatedly read the hydrogen concentration in the collection gas bag and calculate the average value. The product of the average concentration, the flow rate in the constant-volume dilution channel, the sampling time, and the hydrogen density corrected to the test conditions gives the hydrogen leak mass. This addresses the problems of existing technologies that detect hydrogen leaks in hydrogen fuel cell vehicles based on concentration, leading to underestimation of leak concentration and safety risks, uncertainty in detection results, and poor repeatability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A system for detecting hydrogen leaks in a constant-volume dilution hydrogen fuel cell vehicle using an airbag includes an insulated chamber for constructing a sealed space. The insulated chamber is connected to an intake fan, a sunlight simulation system, and a regulating airbag. The intake fan has a filter, and an intake valve controls the gas entering the sealed space. The sunlight simulation system is located at the top of the sealed space to simulate sunlight conditions when the vehicle is parked outdoors. The regulating airbag adjusts its volume within the sealed space to maintain stable pressure. The insulated chamber is also connected to a constant-volume dilution channel, one end of which is located inside the sealed space, and the other end is connected to an exhaust fan to remove the leaked hydrogen and air mixture from the sealed space. The constant-volume dilution channel is connected to an exhaust valve and a Venturi flow meter. The Venturi flow meter is used to control the gas discharge from the sealed space. It is located between the exhaust valve and the exhaust fan. The Venturi flow meter corrects the gas flow rate passing through its interior based on detected atmospheric pressure and temperature, and outputs the corrected real-time gas flow rate at a frequency of 1Hz. A gas collection bag is also connected between the exhaust valve and the Venturi flow meter in the constant-volume dilution channel. A flow control pump is connected between the gas collection bag and the constant-volume dilution channel. In sampling mode, the flow control pump delivers gas from the constant-volume dilution channel to the gas collection bag at a constant flow rate. In venting mode, the flow control pump reverses to discharge the gas from the gas collection bag to the atmosphere. After venting, the pressure inside the gas collection bag is lower than atmospheric pressure. The gas collection bag is connected to a hydrogen concentration analyzer to determine the integral of hydrogen gas inside. The insulated chamber is also rotatably connected to a gate that opens or closes the sealed space.

[0008] Furthermore, the insulated chamber is also connected to an inflatable sealing ring for sealing the gaps at which vehicles enter and exit the gate; when a vehicle needs to enter or exit, the inflatable sealing ring is not inflated to facilitate the opening and closing of the gate; when a vehicle enters the enclosed space and completes internal purging, the inflatable sealing ring is inflated to prevent gas from leaking from the enclosed space to the external environment.

[0009] Furthermore, the insulated chamber includes a temperature control and a heat exchanger. The interior of the insulated chamber has a heat exchange pipe with water as the working fluid, so that the temperature of the main body of the insulated chamber and the sealed space is controlled within the permissible error range of the test temperature. The interior of the insulated chamber is made of polished aluminum or stainless steel plate to reduce the adsorption of hydrogen on the surface of the sealed space.

[0010] Furthermore, the filtration device is a HEPA high-efficiency particulate filter cartridge to remove particulate matter from the purge air and prevent particulate matter from accumulating at the air inlet valve.

[0011] Furthermore, the regulating airbag is made of Teflon material, and its inflation tube is connected to an air pump. When the air pressure in the sealed space increases due to temperature rise, the air pump draws air out of the regulating airbag to reduce its volume. When the air pressure in the sealed space decreases due to temperature drop, the air pump inflates the regulating airbag to increase its volume, thereby maintaining stable air pressure in the sealed space.

[0012] Furthermore, the Venturi flow meter is a critical Venturi tube or an array of multiple critical Venturi tubes arranged circumferentially; under the suction action of the exhaust fan, the gas in the sealed space flows through the throat of the critical Venturi tube at the local sound speed; since the cross-sectional area at the throat is fixed, the gas flow rate in the critical Venturi tube and the constant volume dilution channel is basically constant, only fluctuating slightly with atmospheric pressure and temperature, and the influence of this fluctuation is corrected and compensated when reading the flow meter results after the test.

[0013] Furthermore, the gas collection bag is made of Teflon material, and the same gas supply pipe is used for filling and emptying, with the airflow direction controlled by the flow control pump.

[0014] The method for detecting hydrogen leaks using the above-described gas bag detection system for hydrogen leaks in a volumetric diluted hydrogen fuel cell vehicle includes the following steps:

[0015] S1. Open the gate, the vehicle enters the sealed space constructed by the insulated compartment, and then close the gate;

[0016] S2. Open the air intake valve and turn on the air intake fan with the filter device to purge the air in the sealed space. After purging, turn off the air intake fan and air intake valve, and inflate the inflatable sealing ring to make it expand and fill the gap between the gate and the insulated chamber to prevent the gas in the sealed space from leaking to the outside environment.

[0017] S3. Start the heat exchanger and sunlight simulation system inside the insulated chamber to adjust the temperature in the sealed space to within the allowable error range of the test temperature; start the air pump to adjust the volume of the regulating airbag and adjust the pressure in the sealed space to the standard atmospheric pressure.

[0018] S4. After the vehicle has been stationary in a confined space for more than 12 hours, the leakage test will begin.

[0019] S5. Start the flow control pump to empty the gas in the collection bag;

[0020] S6. After the leakage test period is over, open the exhaust valve, start the exhaust fan, and then open the inlet valve to exhaust the gas in the sealed space. At the same time as starting the exhaust fan, start the flow control pump to extract a small amount of sample from the constant volume dilution channel at a constant flow rate and continuously deliver it to the gas collection bag.

[0021] S7. Record the total volume of gas flowing through the Venturi flow meter in the constant volume dilution channel. When the total gas volume exceeds the internal volume of the sealed space, turn off the exhaust fan and flow control pump.

[0022] S8. Calibrate the hydrogen concentration analyzer and read the hydrogen concentration of the gas sample collected in the gas bag;

[0023] S9. Based on the temperature and pressure within the constant-volume dilution channel, after correcting the total gas volume flowing through the Venturi flowmeter to standard conditions, calculate its product with the integral number of hydrogen gas in the collection bag and the hydrogen density under standard conditions to obtain the hydrogen leakage mass; the calculation formula is:

[0024] m leak =10 3 ×ρ H2 ×V mix ×c H2

[0025] In the formula, m leak Let g be the mass of hydrogen leaked into the confined space, and ρ be the mass of hydrogen leaked into the confined space. H2 To correct the hydrogen density (kg / m³) to the test temperature conditions. 3 V mix The gas velocity (m) flowing through the Venturi flow meter 3 / s,c H2 The integral number of hydrogen gas in the constant volume dilution channel detected by the hydrogen concentration analyzer is 10. -6 .

[0026] The principles and beneficial effects of the technical solution are as follows:

[0027] This invention involves drawing a mixture of leaked hydrogen and air from a sealed space into a constant-volume dilution channel via an exhaust fan. Since both the gas flow rate within the dilution channel and the gas flow rate entering the collection bag are constant, the hydrogen concentration in the gas sample within the collection bag is equal to the average hydrogen concentration in all the gas flowing through the Venturi flowmeter. The total volume of gas flowing through the Venturi flowmeter can be measured using the flowmeter itself. This method ensures a near-constant gas flow rate through the Venturi flowmeter, and the hydrogen concentration in the collection bag is measured by continuous integration of real gas, eliminating approximation errors. Therefore, this detection system and method exhibit high measurement accuracy and good repeatability. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the present invention, which involves placing a vehicle within a hydrogen leak detection system for a constant-volume diluted hydrogen fuel cell vehicle to measure hydrogen leaks.

[0029] The names of the corresponding labels in the attached diagram are:

[0030] 1. Intake fan; 2. Intake valve; 3. Insulated chamber; 4. Inflatable sealing ring; 5. Exhaust fan; 6. Hydrogen concentration analyzer; 7. Gate; 8. Sunlight simulation system; 9. Venturi flow meter; 10. Gas collection bag; 11. Flow control pump; 12. Exhaust valve; 13. Volumetric dilution channel; 14. Regulating airbag; 15. Vehicle. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0032] like Figure 1As shown, the hydrogen leak detection system for a constant-volume diluted hydrogen fuel cell vehicle using a gas bag includes an insulated chamber 3 for constructing a sealed space. The insulated chamber 3 includes temperature control and a heat exchanger. The interior of the insulated chamber 3 has heat exchange pipes using water as the working fluid, ensuring that the temperature of the insulated chamber 3 and the sealed space is controlled within the permissible error range of the test temperature. The interior of the insulated chamber 3 is made of polished aluminum or stainless steel to reduce hydrogen adsorption on the surfaces within the sealed space. The insulated chamber 3 is connected to an intake fan 1, a sunlight simulation system 8, and a regulating airbag 14. The intake fan 1 is located on the left side wall of the sealed space and includes a filter. An intake valve 2 controls the gas entering the sealed space and connects the intake fan 1 to the insulated chamber 3. The HEPA high-efficiency particulate filter element removes particulate matter from the purge air and prevents particulate matter from accumulating at the intake valve 2. The sunlight simulation system 8 and the regulating airbag 14 are both located at the top of the enclosed space. The sunlight simulation system 8 simulates the sunlight conditions when the vehicle 15 is parked outdoors. The regulating airbag 14 is made of Teflon material, and its inflation tube is connected to an air pump. When the air pressure in the enclosed space increases due to temperature rise, the air pump draws air from the outside of the regulating airbag 14 to reduce its volume; when the air pressure in the enclosed space decreases due to temperature drop, the air pump inflates the inside of the regulating airbag 14 to increase its volume, thus maintaining a stable air pressure in the enclosed space. The insulated chamber 3 is also connected to a volumetric dilution channel 13, the upper end of which is located at the top of the enclosed space. Inside the space, an exhaust fan 5 is connected to the lower end of the constant volume dilution channel 13. The exhaust fan 5 is used to remove the leaked hydrogen and air mixture from the sealed space. An exhaust valve 12 and a Venturi flow meter 9 are connected to the constant volume dilution channel 13. The exhaust valve 12 controls the gas discharge from the sealed space. The Venturi flow meter 9 is located between the exhaust valve 12 and the exhaust fan 5. The Venturi flow meter 9 is an array composed of multiple critical Venturi tubes arranged circumferentially. Under the suction of the exhaust fan 5, the gas in the sealed space flows through the throat of the critical Venturi tubes at the local sound speed. Since the cross-sectional area at this throat is fixed, the gas flow rate in the critical Venturi tubes and the constant volume dilution channel 13 is basically constant, fluctuating only slightly with atmospheric pressure and temperature. Based on the detected atmospheric pressure and temperature, the gas flow rate passing through its inner side is corrected, and the corrected real-time gas flow rate is output at a frequency of 1Hz; the constant volume dilution channel 13 is also connected to a gas collection bag 10 between the exhaust valve 12 and the Venturi flow meter 9. The gas collection bag 10 is connected to the constant volume dilution channel 13 by a flow control pump 11. The gas collection bag 10 is made of Teflon material. The same gas supply pipe is used for filling and emptying. The airflow direction is controlled by the flow control pump 11; in the sampling state, the flow control pump 11 delivers gas from the constant volume dilution channel 13 to the gas collection bag 10 at a constant flow rate. In the emptying state, the flow control pump 11 reverses to discharge the gas in the gas collection bag 10 to the atmosphere. After emptying, the pressure in the gas collection bag 10 is lower than the atmospheric pressure;The gas collection bag 10 is connected to a hydrogen concentration analyzer 6, which determines the integral of hydrogen gas inside the bag. A gate 7, for opening or closing the sealed space, is rotatably connected to the right side of the insulated chamber 3. The insulated chamber 3 is also connected to an inflatable sealing ring 4 for sealing the gap at the gate 7 when the vehicle 15 enters or exits. When the vehicle 15 needs to enter or exit, the inflatable sealing ring 4 is not inflated to facilitate the opening and closing of the gate 7. After the vehicle 15 enters the sealed space and completes internal purging, the inflatable sealing ring 4 is inflated to prevent gas leakage from the sealed space to the external environment.

[0033] The method for detecting hydrogen leaks using the above-described gas bag detection system for hydrogen leaks in a volumetric diluted hydrogen fuel cell vehicle includes the following steps:

[0034] S1. Open gate 7, and vehicle 15 enters the sealed space constructed by the insulated compartment 3, and then close gate 7;

[0035] S2. Open the air inlet valve 2 and turn on the air inlet fan 1 with the filter device to purge the air in the sealed space. After purging, close the air inlet fan 1 and air inlet valve 2, and inflate the inflatable sealing ring 4 to make it expand and fill the gap between the gate 7 and the insulation chamber 3 to prevent the gas in the sealed space from leaking to the outside environment.

[0036] S3. Start the heat exchanger and sunlight simulation system 8 inside the heat-insulating chamber 3 to adjust the temperature in the sealed space to the allowable error range of the test temperature; start the air pump to adjust the volume of the regulating airbag 14 and adjust the pressure in the sealed space to the standard atmospheric pressure.

[0037] S4. Vehicle 15 is left to stand in a confined space for more than 12 hours before the leakage test begins;

[0038] S5. Start the flow control pump 11 to empty the gas in the gas collection bag 10;

[0039] S6. After the leakage test period expires, open the exhaust valve 12, start the exhaust fan 5, and then open the inlet valve 2 to exhaust the gas in the sealed space. At the same time as starting the exhaust fan 5, start the flow control pump 11 to extract a small amount of sample from the constant volume dilution channel 13 at a constant flow rate and continuously transport it to the gas collection bag 10.

[0040] S7. Record the total volume of gas flowing through the Venturi flow meter 9 in the constant volume dilution channel 13. When the total gas volume exceeds the internal volume of the sealed space, shut off the exhaust fan 5 and the flow control pump 11.

[0041] S8. Calibrate the hydrogen concentration analyzer 6 and read the hydrogen concentration of the gas sample in the gas collection bag 10;

[0042] S9. Based on the temperature and pressure within the constant-volume dilution channel, after correcting the total gas volume flowing through the Venturi flowmeter to standard conditions, calculate its product with the integral number of hydrogen gas in the collection bag and the hydrogen density under standard conditions to obtain the hydrogen leakage mass; the calculation formula is:

[0043] m leak =10 3 ×ρ H2 ×V mix ×c H2

[0044] In the formula, m leak Let g be the mass of hydrogen leaked into the confined space, and ρ be the mass of hydrogen leaked into the confined space. H2 To correct the hydrogen density (kg / m³) to the test temperature conditions. 3 V mix The gas velocity (m) flowing through the Venturi flow meter 3 / s,c H2 The integral number of hydrogen gas in the constant volume dilution channel detected by the hydrogen concentration analyzer is 10. -6 .

[0045] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A system for detecting hydrogen leaks in a constant-volume diluted hydrogen fuel cell vehicle using a gas bag, characterized in that: The system includes an insulated chamber for constructing a sealed space, connected to an intake fan, a sunlight simulation system, and a regulating airbag. The intake fan is equipped with a filter, and an intake valve connects the intake fan to the insulated chamber to control the gas entering the sealed space. The sunlight simulation system is located at the top of the sealed space to simulate sunlight conditions when a vehicle is parked outdoors. The regulating airbag adjusts its volume within the sealed space to maintain stable air pressure. The insulated chamber is also connected to a constant-volume dilution channel, one end of which is located inside the sealed space, and the other end is connected to an exhaust fan to remove any leaked hydrogen and air mixture from the sealed space. The constant-volume dilution channel is connected to an exhaust valve and a Venturi flow meter; the exhaust valve controls the gas discharge from the sealed space. The enclosed space is described above. A Venturi flow meter is located between the exhaust valve and the exhaust fan. The Venturi flow meter corrects the gas flow rate passing through its interior based on detected atmospheric pressure and temperature, and outputs the corrected real-time gas flow rate at a frequency of 1Hz. A gas collection bag is also connected between the exhaust valve and the Venturi flow meter in the constant-volume dilution channel. A flow control pump is connected between the gas collection bag and the constant-volume dilution channel. In sampling mode, the flow control pump delivers gas from the constant-volume dilution channel to the gas collection bag at a constant flow rate. In venting mode, the flow control pump reverses to vent the gas from the gas collection bag to the atmosphere. After venting, the pressure inside the gas collection bag is lower than atmospheric pressure. A hydrogen concentration analyzer is connected to the gas collection bag to determine the integral of hydrogen gas inside. The insulated chamber is also rotatably connected to a gate that opens or closes the enclosed space.

2. The system for detecting hydrogen leaks in a volume-diluted hydrogen fuel cell vehicle using a gas bag according to claim 1, characterized in that: The insulated chamber is also connected to an inflatable sealing ring for sealing the gaps at which vehicles enter and exit the gate. When a vehicle needs to enter or exit, the inflatable sealing ring is not inflated to facilitate the opening and closing of the gate. After the vehicle enters the enclosed space and completes internal purging, the inflatable sealing ring is inflated to prevent gas from leaking into the external environment.

3. The system for detecting hydrogen leaks in a volume-diluted hydrogen fuel cell vehicle using a gas bag according to claim 2, characterized in that: The insulated chamber includes a temperature control unit and a heat exchanger. The interior of the insulated chamber has heat exchange pipes using water as the working fluid, so that the temperature of the insulated chamber body and the sealed space is controlled within the permissible error range of the test temperature. The interior of the insulated chamber is made of polished aluminum or stainless steel plates to reduce the adsorption of hydrogen on the surface of the sealed space.

4. The system for detecting hydrogen leaks in a volume-diluted hydrogen fuel cell vehicle using a gas bag according to claim 3, characterized in that: The filtration device is a HEPA high-efficiency particulate filter cartridge to remove particulate matter from the purge air and prevent particulate matter from accumulating at the air inlet valve.

5. The system for detecting hydrogen leaks in a constant-volume diluted hydrogen fuel cell vehicle using a gas bag according to claim 4, characterized in that: The regulating airbag is made of Teflon material, and its inflation tube is connected to an air pump. When the air pressure in the sealed space increases due to the rise in temperature, the air pump draws air out of the regulating airbag to reduce its volume. When the air pressure in the sealed space decreases due to the drop in temperature, the air pump inflates the regulating airbag to increase its volume, so as to maintain the air pressure in the sealed space is stable.

6. The system for detecting hydrogen leaks in a volume-diluted hydrogen fuel cell vehicle using a gas bag according to claim 5, characterized in that: The Venturi flow meter is a critical Venturi tube or an array of multiple critical Venturi tubes arranged circumferentially. Under the suction of the exhaust fan, the gas in the sealed space flows through the throat of the critical Venturi tube at the local sound speed. Since the cross-sectional area at the throat is fixed, the gas flow rate in the critical Venturi tube and the constant volume dilution channel is basically constant, fluctuating only slightly with atmospheric pressure and temperature. Moreover, the influence of this fluctuation is corrected and compensated when reading the flow meter results after the test.

7. The system for detecting hydrogen leaks in a volume-diluted hydrogen fuel cell vehicle using a gas bag according to claim 6, characterized in that: The gas collection bag is made of Teflon material, and the same gas supply pipe is used for filling and emptying. The airflow direction is controlled by the flow control pump.

8. The method for detecting hydrogen leaks using the gas bag detection system for volumetric dilution hydrogen fuel cell vehicles as described in claim 7, characterized in that, Includes the following steps: S1. Open the gate, the vehicle enters the sealed space constructed by the insulated compartment, and then close the gate; S2. Open the air intake valve and turn on the air intake fan with the filter device to purge the air in the sealed space. After purging, turn off the air intake fan and air intake valve, and inflate the inflatable sealing ring to make it expand and fill the gap between the gate and the insulated chamber to prevent the gas in the sealed space from leaking to the outside environment. S3. Start the heat exchanger and sunlight simulation system inside the insulated chamber to adjust the temperature in the sealed space to within the allowable error range of the test temperature; start the air pump to adjust the volume of the regulating airbag and adjust the pressure in the sealed space to the standard atmospheric pressure. S4. After the vehicle has been stationary in a confined space for more than 12 hours, the leakage test will begin. S5. Start the flow control pump to empty the gas in the collection bag; S6. After the leakage test period is over, open the exhaust valve, start the exhaust fan, and then open the inlet valve to exhaust the gas in the sealed space. At the same time as starting the exhaust fan, start the flow control pump to extract a small amount of sample from the constant volume dilution channel at a constant flow rate and continuously deliver it to the gas collection bag. S7. Record the total volume of gas flowing through the Venturi flow meter in the constant volume dilution channel. When the total gas volume exceeds the internal volume of the sealed space, turn off the exhaust fan and flow control pump. S8. Calibrate the hydrogen concentration analyzer and read the hydrogen concentration of the gas sample collected in the gas bag; S9. Based on the temperature and pressure within the constant-volume dilution channel, after correcting the total gas volume flowing through the Venturi flowmeter to standard conditions, calculate its product with the integral number of hydrogen gas in the collection bag and the hydrogen density under standard conditions to obtain the hydrogen leakage mass; the calculation formula is: m leak = 10 3 x p H2 x V mix x c H2 In the formula, m leak Let g be the mass of hydrogen leaked into the confined space, and ρ be the mass of hydrogen leaked into the confined space. H2 To correct the hydrogen density (kg / m³) to the test temperature conditions. 3 V mix The gas velocity (m) flowing through the Venturi flow meter 3 / s,c H2 The integral number of hydrogen gas in the constant volume dilution channel detected by the hydrogen concentration analyzer is 10. -6 .

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