METHOD FOR DETECTING LEAKS IN A COMPRESSED GAS SUPPLY SYSTEM

Abstract

The present invention relates to a method for detecting leaks in a compressed gas supply system (1), the method comprising a first leak-testing phase of the pipeline (8) including at least one leak test based on a controlled vacuum in a section (5, 6) of the pipeline (8), a leak test based on monitoring the variation of a gas parameter when the sections (5, 6) of the pipeline upstream and downstream of a shut-off element (V3a, V4) have a pressure difference, and if the first diagnostic phase is successful, a second leak-testing phase of the pipeline (8) consisting of activating at least one leak test when said sections (5, 6) have the same pressure value. Figure 1.

Description

Title of the invention: METHOD FOR DETECTING LEAKS IN A COMPRESSED GAS SUPPLY SYSTEM

[0001] The field of the invention relates to a method for detecting leaks in a compressed gas supply system, in particular for a fuel cell.

[0002] In the automotive industry, energy storage systems are currently undergoing significant development to reduce greenhouse gas emissions. Some manufacturers are proposing to equip their vehicles with a fuel cell (FC) system to power the engine. A FC is powered by a fuel system in which hydrogen is stored in tanks as a highly compressed gas. The fuel is then delivered through a pipeline to the FC.

[0003] Fuel cell hydrogen supply systems must comply with stringent safety standards regarding the risk of leaks in order to prevent the accumulation of this gas in a space such as the vehicle's passenger compartment or garage. Current regulations stipulate that the volume of gas in the confined air of this space must not exceed 4% of the volume. Manufacturers have therefore equipped the supply systems with safety valves and developed leak detection systems to prevent the risk of leaks.

[0004] The prior art document US-A1-2023228381 describes a valve for a fuel supply system comprising a temperature sensor and a pressure sensor integrated into a section of piping for detecting gas temperature and pressure in a state where gas is present at the closed safety valve. More specifically, the leak diagnosis consists of closing the valve and performing a leak test based on the detected values.

[0005] Typically, mechanical safety devices for fuel supply systems include a valve positioned on the tank at the inlet of a pipeline, commonly referred to by the English term "On Tank Valve" or OTV, which acts as a first barrier preventing the tank from emptying completely in the event of a leak downstream of the pipeline. In addition, the safety devices include another valve downstream, acting as a second barrier upstream of a pressure regulator, whose function is to prevent the pipeline between the OTV and the fuel pump from emptying completely.

[0006] Leak tests include an internal leak test, that is, a test of the valves' tightness when they are closed, a position in which the gas flow should normally be completely stopped. The tests also include an external leak test to check for leaks in the pipe that generate an outlet. of gas to the external environment. These tests are based on pressure or hydrogen quantity checks in the pipeline, using temperature and pressure measurements in the areas being monitored. This data is compared to thresholds within a predetermined time period following the test's initiation. These tests are generally triggered at least once per driving phase when the vehicle is brought to a stop.

[0007] A known problem is that there are exceptional scenarios that can cause the diagnosis to fail. Depending on the number and / or size of the leaks and their location, the detection of internal and external leaks may fail. Indeed, simulations have revealed cases where an internal leak can compensate for a downstream external leak, resulting in the monitored parameter not exceeding the alert threshold within the associated time frame.

[0008] There is therefore a need to address the aforementioned problems.

[0009] One objective of the invention is to improve the leak diagnosis strategy of a highly compressed gas supply system. Another objective is to enhance existing leak tests.

[0010] More specifically, the invention relates to a method for detecting leaks in a compressed gas supply system adapted to supply a fuel cell, said system comprising at least one tank for highly compressed gas, at least one gas flow stop element disposed downstream of the tank in a pipe.

[0011] According to the invention, a first leak diagnosis phase of the pipe comprises at least:

[0012] - a leak test based on a controlled depression in a sector of the conduct downstream of said stopping element and consisting of detecting the attainment of a predetermined depression threshold in said sector,

[0013] - a leak test based on monitoring the variation of a parameter of the gas relative to a maximum variation threshold when the upstream and downstream sections of the pipeline have a pressure difference,

[0014] - and if the first diagnostic phase is successful, a second phase of pipeline leak diagnosis consisting of commanding the said pipeline sectors upstream and downstream of said shut-off element to the same pressure value and activating at least one leak test based on monitoring the variation of said gas parameter when said sectors have the same pressure value.

[0015] The method according to the invention may include the following additional features, alone or in combination:

[0016] - The first diagnostic phase comprises the following successive sub-steps:

[0017] - a) the closure of a first stop element disposed between the tank and a first the pipe sector in such a way as to generate a controlled vacuum in the first sector and the execution of a first leak test of the first stop element based on the controlled vacuum in the first sector,

[0018] - b) the closure of a second stop element disposed between the first sector and a second sector of the pipe in such a way as to generate a controlled vacuum in the second sector and the execution of a second leak test of the second stop element based on the controlled vacuum in the second sector,

[0019] - c) the execution of a third and fourth leak test based on a monitoring of the variation in quantity of gas in the first sector and in the second sector respectively of the pipeline in relation to a specific maximum variation threshold, the third and fourth leak tests being carried out when the tank, the first sector and the second sector have a pressure difference with respect to each other.

[0020] - The second diagnostic phase comprises:

[0021] - d) the control of the second stop element so as to bring the second sector at the same pressure value as the first sector,

[0022] - e) the activation of a fifth and a sixth leak test comprising the monitoring of the variation in quantity of gas in the first sector and in the second sector respectively in relation to the specific maximum variation threshold.

[0023] - The second diagnostic phase further comprises the following sub-steps:

[0024] - f) the simultaneous control of the first and second stop elements so to bring the first and second sectors to the same pressure value as the reservoir,

[0025] - g) the activation of a seventh and an eighth leak test comprising the monitoring of the variation in quantity of gas in the first sector and the second sector respectively in relation to the specific maximum variation threshold.

[0026] - Monitoring the variation in the quantity of gas involves measuring the pressure and the temperature in the monitored sector section of the pipeline, the calculation of a quantity of gas from the measured pressure and temperature and the volume of the monitored sector.

[0027] - Each leak test based on a controlled depression includes the measurement of the gas pressure downstream of the shut-off element for a period following the start of the depression, and the detection of a leak if the predetermined depression threshold is not reached within said period.

[0028] A compressed gas supply system adapted to power a fuel cell is also provided, said system comprising at least one tank for of highly compressed gas and at least one gas flow stop element disposed downstream of the tank in a pipe, the system includes a control unit configured to implement the leak detection method according to any of the preceding embodiments.

[0029] An electrified vehicle comprising such a power supply system is also planned.

[0030] A control unit comprising specifically configured to implement the leak detection process according to any of the preceding embodiments.

[0031] A computer program is provided comprising instructions which, when the program is executed by a control unit, lead the latter to implement the leak detection method according to any one of the preceding embodiments.

[0032] A computer-readable recording medium is provided comprising instructions which, when executed by a computer, cause the computer to implement the leakage process according to any of the preceding embodiments.

[0033] The invention enhances the reliability of leak testing for hydrogen fuel systems. In particular, it improves hydrogen leak testing into the external environment. Consequently, the method improves vehicle safety and diagnostics to comply with applicable standards.

[0034] Other features and advantages of the present invention will become more apparent upon reading the following detailed description, which includes embodiments of the invention given by way of non-limiting examples and illustrated by the accompanying drawings, in which:

[0035] [Fig.1] schematically represents an embodiment of the compressed gas supply system according to the invention for a fuel cell.

[0036] [Fig.2] represents a block diagram describing an embodiment of the leak detection method according to the invention.

[0037] [Fig.3] represents a time sequence of the leak detection method according to the invention illustrating the control of valves and parameters of the supply system.

[0038] The invention relates to a compressed gas supply system for a consumer and a leak detection method for such a system. The system and the detection method are applicable to a hydrogen-powered fuel cell. Furthermore, the invention is applicable to electrified vehicles equipped with an energy storage system adapted to deliver electrical energy. An electrified vehicle comprises an electric drive machine and electronics. power, with fully or partially electric motorization, preferably motor vehicles, but not only such as aircraft, trucks, tractors, ships.

[0039] Figure 1 schematically represents an embodiment of a compressed gas supply system 1 for a fuel cell 7. The supply system and the fuel cell are installed in an electrified vehicle. The system 1 comprises several highly compressed gas tanks 2a, 2b, and 2c, which store the gas at a pressure of up to approximately 700 bar. A line 8 is fluidly connected to each tank 2a, 2b, and 2c via gas flow shut-off elements V3a, V3b, and V3c, respectively. The line 8 connects each highly compressed gas tank to the fuel cell 7. The shut-off elements V3a, V3b, and V3c are connected at their outlets to a first section 5 of the line 8, which functions as a hydrogen collection network adapted for refueling the hydrogen tanks via a connection 9.The V3a, V3b and V3c shut-off elements are OTV type solenoid valves connected to a tank fitting.

[0040] The first sector 5 of the conduit 8 is adapted for the circulation of high-pressure gas. The supply system 1 further includes a measuring device Cl for a characteristic gas parameter comprising a pressure sensor and a temperature sensor adapted for measuring the pressure and temperature of the gas specifically in the first sector 5. Optionally, it may include a pressure sensor only.

[0041] Another shut-off element V4 is disposed in the pipe 8 downstream of the first sector 5 and upstream of a second sector 6 of the pipe 8. The second sector 6 of the pipe 8 is adapted for the circulation of high-pressure gas. The supply system 1 further includes a measuring device C2 for a characteristic gas parameter, comprising a pressure sensor and a temperature sensor adapted for measuring the pressure and temperature of the gas specifically in the second sector 6. Optionally, it may include a pressure sensor only.

[0042] The second sector 6 of the conduit 8 is fluidly connected to the inlet of a pressure regulator 10 whose function is to reduce the pressure of the hydrogen coming from the tanks to a pressure suitable for the fuel cell 7. In addition, it maintains a constant pressure even when the power demand varies, by adjusting the gas flow according to the needs of the cell.

[0043] A third section 11 of the line 8 connected to the outlet of the pressure regulator 10 is adapted for the circulation of low-pressure gas. A measuring device C3 for a characteristic gas parameter, comprising a pressure sensor and a temperature sensor, is arranged for measuring the pressure and temperature of the gas specifically in the third section 11. Optionally, it may include a pressure sensor only. Another V5 shut-off element is located at the outlet of the third sector before the hydrogen supply to the fuel cell 7.

[0044] Each stop element V3a, V3b and V3c, V4 and V5 can be a controlled solenoid valve, or any suitable safety device to control the opening and closing of the gas flow through the pipe 8. Although the invention finds application for highly compressed gas systems in electromobility applications, i.e. between 30 and 700 bar, the detection method is also suitable for systems that can store gas at higher values ​​and in stationary applications.

[0045] A control unit 12 is configured to drive each stop element V3a, V3b, V3c, V4 and V5 to the open position, closed position or an intermediate position and to measure in real time a parameter value of each measuring device Cl, C2 and C3. The control unit 12 can measure a pressure and temperature value and determine one or more parameters HP1, HP2 and HP3 characteristic of each sector 5, 6 and 11 respectively as a function of the measured parameters.

[0046] In particular, it is configured to determine a pressure value and quantity of hydrogen in a pipe, a mass expressed in grams for example, from the pressure, temperature, and volume of the pipe section delimited by the shut-off elements in the closed position. The quantity improves diagnosis in the event of gas temperature variations resulting from external conditions or system temperatures, including heat emitted by the heat pump.

[0047] Furthermore, the control unit 12 is configured to perform the leak detection method according to the invention. It is equipped with an integrated circuit computer and electronic memories, the computer and the memories being configured to perform the leak detection method according to the invention. However, this is not mandatory. Indeed, the computer could be external to the control unit 12, while still being coupled to it. In this latter case, it could itself be arranged as a dedicated computer including, for example, a dedicated program. Consequently, the control unit, according to the invention, can be implemented in the form of software modules, electronic circuits, or hardware, or a combination of electronic circuits and software modules.

[0048] Figures [Fig. 2] and [Fig. 3] together describe the execution of the process according to the invention. A first diagnostic phase is implemented by the control unit of steps E0 to E9.

[0049] During step E0, the control unit detects that the vehicle has been stopped ("Key Off") by the user after use and, consequently, drives the vehicle into the closed position. Tank shut-off elements. The fuel cell is still operating and consuming hydrogen supplied by the feed system. The hydrogen pressures HPR, HP1 and HP2 are illustrated for tanks 2a, 2b and 2c, the first sector 5 and the second sector 6 respectively by the first graph, the position of the shut-off elements V3a, V3b and V3c is illustrated by the second curve, the position of the shut-off element V4 by the third curve and the hydrogen flow rate QH2 in the line 8, expressed in grams per second by the fourth curve.

[0050] At a step El, the control unit activates a first leak test of a tank shut-off element aimed at detecting a significant internal leak likely to be caused by the presence of particles obstructing complete closure, by a fault in an actuator, or by any failure of the power system and fuel cell preventing the achievement of the desired vacuum.

[0051] More specifically, the first leak test is based on monitoring the HP1 pressure of the hydrogen and consists of generating a controlled vacuum in the sections of the pipeline downstream of the tank shut-off elements. The controlled vacuum is generated by the flow from a compressor in the hydrogen supply line to trigger the fuel cell reaction. The QH2 curve illustrates this hydrogen flow rate. HP1 and HP2 pressure measurements are taken over a predetermined test duration in at least one of said sections 5 and 6. From the moment the valves V3a, V3b, and V3c are closed, the HP1 and HP2 curves show that the pressure values ​​decrease as expected.

[0052] At a step E2, the control unit checks whether the pipeline pressure reaches a predetermined vacuum threshold at the end of a predetermined duration or time delay triggered at time E0. For example, the vacuum threshold is calibrated to an API pressure deviation of 50 bar below the initial pressure for a predetermined test duration. The threshold and duration are calibrated values ​​dependent on the pipeline dimensions and the expected hydrogen consumption rate by the fuel cell.

[0053] If the threshold is not reached before the end of the expected time, this result indicates the presence of a significant leak at one of the V3a, V3b, or V3c shut-off elements, and, more generally, any failure of the fuel system and fuel cell preventing the desired vacuum from being achieved. A diagnostic alert DTC1 is activated, and the control unit terminates the first diagnostic phase.

[0054] If the threshold is reached before the end of the expected time period, this result indicates that the supply system is capable of achieving the desired pressure reduction target within the duration of the test.

[0055] In this latter case, the control unit then drives the V4 stop element to a closed position at step E3 to continue the first diagnostic phase DIAG1 with additional tests. It should also be noted that from this point onward, the fuel cell begins a shutdown sequence which is completed when the hydrogen consumption rate is zero.

[0056] At a step E4, the control unit activates a second leak test, this time of the stop element V4, aimed at detecting a significant leak.

[0057] More specifically, this second test is similar to the first test El in that it involves generating a controlled vacuum in the line. It differs in the calibration of the vacuum threshold AP2 and, optionally, the test duration. As illustrated in [Fig. 3], the value of the deviation AP2 to be detected and the predetermined test duration are lower compared to test El because, in this example, the fuel cell supply line compressor is in a gradual shutdown sequence.

[0058] However, this is not mandatory as they may be equal to or greater depending on the operating mode of the fuel cell.

[0059] During this test, pressure measurements are taken over the predetermined duration of the test in the pipe section downstream of the stop element V4. From the moment of closure of the stop element V4, the pressure value HP1 remains constant and the value HP2 decreases due to the consumption of hydrogen by the fuel cell in this downstream section.

[0060] At a step E5, the control unit checks whether the pressure HP2 at the level of the second sector 6 reaches the predetermined depression threshold for this test at the end of the predetermined duration or time delay triggered at time E3.

[0061] If the threshold is not reached before the end of the expected time, this result indicates the presence of an internal leak in element V4, and, more generally, any failure of the fuel system and fuel cell preventing the desired vacuum from being achieved. A DTC2 diagnostic alert is activated, and the control unit terminates the first phase of leak testing.

[0062] If the threshold is reached before the end of the expected time, this result indicates that the supply system is capable of achieving the desired pressure reduction target within the test duration. The diagnostic phase continues with additional tests aimed at detecting small leaks or micro-leaks that are difficult to detect.

[0063] Then, in step E6 of the process, the control unit triggers a leak test of the line 8 based on monitoring a gas parameter specifically for sector 6, using temperature and pressure data delivered by the measuring device located in that sector. This test aims to detect an internal leak of the element The test involves monitoring the variation in the gas quantity relative to a maximum variation threshold when sections 5 and 6 of the pipeline have a pressure difference. This difference allows for the generation of hydrogen flow through the V4 shut-off element if it were affected by a leak.

[0064] More specifically, the test consists of measuring the change in the quantity of hydrogen specifically in this sector between two instants over a predetermined test period. As is known to those skilled in the art, the control unit performs a calculation of the quantity of hydrogen based on the pressure, temperature, and known pipe volume data for this sector. This calculation allows for a more precise assessment of the hydrogen quantity compared to the E4 test, which is based solely on pressure. It takes into account temperature variations that may occur in the fuel system, the fuel cell, and the vehicle during the diagnostic process. Consequently, the E6 test makes it possible to detect leaks caused by small orifices.

[0065] The quantity value is calculated at least between two instants. The difference in values ​​between the two instants is compared to a maximum permissible external leakage threshold for the time between said two instants. If this value is lower than this threshold, it indicates that this sector 6 of the pipe is not sealed and that hydrogen is escaping to the outside. Consequently, the control unit activates a DTC5 diagnostic alert indicating an external leak and terminates the diagnostic at this stage.

[0066] Furthermore, the difference in quantity values ​​between two times is compared to a maximum permissible internal leakage threshold. If this value exceeds the threshold, it indicates that the V4 stop element is not leak-tight. Consequently, the control unit activates a DTC6 diagnostic alert signaling an internal leak and terminating the first leak-tightness diagnostic phase.

[0067] The values ​​of the internal and external leakage thresholds are determined based on a maximum permissible leakage rate for the duration of the test, the pressure, and the temperature at the time test E6 is initiated. In particular, the external leakage threshold is derived from the applicable standards for hydrogen storage systems. If these thresholds are not exceeded, then, at step E7, the control unit terminates test E6 and continues the diagnostic procedure.

[0068] Furthermore, when the control unit detects the closure of the stop element V4 in step E3, it triggers, in parallel with step E4, a leak test of the pipe 8 in step E8. This test is based on monitoring the variation of the hydrogen quantity relative to a maximum variation threshold specifically for sector 5, using temperature and pressure data provided by the measuring device located in that sector. This test aims to detect an internal leak in one of the Stop elements V3a, V3b and V3c, V4 and an external leak in this sector 5 of the pipeline. Note that sector 5 of pipeline 8 has an API pressure difference with the reservoir and an AP2 pressure difference with the second sector 6.

[0069] More specifically, the E8 test consists of measuring the change in the quantity of hydrogen between two instants over a predetermined test period, identical to the E6 test, except that it is performed on section 5 of the pipe 8. This calculation allows for a more precise assessment of the quantity of hydrogen compared to the E4 test, which is based solely on pressure. It takes into account temperature variations, among other factors. Consequently, the E6 test makes it possible to detect leaks caused by small orifices.

[0070] The hydrogen quantity value is calculated at least between two time points, and the difference between the values ​​between the two time points is compared to a maximum external leakage threshold permitted for the given duration and specific to that sector 5. If this value is lower than this threshold, it indicates that this sector is not leak-tight. Consequently, the control unit activates a DTC3 external leakage diagnostic alert and terminates the first phase of leak-tightness testing.

[0071] Furthermore, the difference in quantity values ​​is compared to a maximum permissible internal leakage threshold. If this value exceeds the threshold, it indicates that the tank shut-off elements are not leak-proof. Consequently, the control unit activates a DTC4 internal leak diagnostic alert and terminates the first diagnostic phase at this stage.

[0072] The values ​​of the internal and external leakage thresholds are determined based on a maximum allowable flow rate for the duration of the test, the pressure and the temperature at the time the E8 test is triggered. If these thresholds are not exceeded, then at step E9, the control unit terminates the E8 test and continues the diagnostic procedure.

[0073] If tests E6 and E8 do not detect any alerts, a second diagnostic phase, DIAG2, is planned to confirm the tightness of the pipeline and the shut-off elements. Indeed, simulations have shown that the simultaneous presence of an internal leak and an external leak on a pipeline can potentially cause the detection strategy to fail due to the compensation that can occur between hydrogen inlets and outlets.

[0074] The control unit therefore initiates the second phase DIAG2 and at step E10 drives the stop element V4 into the open position so as to bring the pressure HP2 of sector 6 of the pipe to the same pressure HP1 as sector 5. When the pressures between the two sectors are equal, the control unit drives, at step Eli, the stop element V4 into the closed position.

[0075] This temporary opening phase also has the advantage of cleaning the gas passage of the stop element V4 due to the gas velocity generated by the pressure difference between sectors 5 and 6 at its opening. If an obstruction by particles is present and has not been detected, then the opening of the V4 stop element could address this problem.

[0076] Next, in step E12 of the process, the control unit again performs a leak test on the pipeline based on monitoring the quantity of hydrogen specifically for sector 5 using temperature and pressure data delivered by the measuring device located in that sector. This test is identical to test E8. The difference at this stage of the diagnostic process is that both sectors 5 and 6 are at the same pressure value, which minimizes the internal air flow factor through the shut-off element V4 at the start of the test. If an internal leak were present, its impact on the test would be minimal, and even negligible at the beginning of the test. This therefore makes the test more robust for detecting external leaks.

[0077] More specifically, test E12 consists of measuring between two instants the variation of the quantity of hydrogen during a predetermined test duration, identical to tests E6 and E8, and comparing the difference in quantity values ​​between two instants with respect to the external leakage threshold and the internal leakage threshold, specific to this sector 5.

[0078] If the difference is less than the external leakage threshold, this indicates that this area is not sealed. Therefore, the control unit activates a DTC7 external leakage diagnostic alert and terminates the second diagnostic phase, DIAG2.

[0079] If the difference exceeds the internal leakage threshold, this indicates that the tank shut-off elements are not leak-proof. Consequently, the control unit activates a diagnostic alert DTC8 and terminates the second diagnostic phase, DIAG2. If these thresholds are not exceeded, the control unit terminates the test and continues the diagnostic procedure.

[0080] In parallel, following the detection of the closure of the stop element V4, the control unit again performs a leak test of the pipe E13 based on monitoring the quantity of hydrogen specifically for sector 6 using temperature and pressure data delivered by the measuring device located in that sector. This test is identical to test E6.

[0081] More specifically, test E13 consists of measuring the variation in the quantity of hydrogen between two instants over a predetermined test period, identical to tests E6 and E8, and comparing the difference in value between two instants with respect to the external leak threshold specific to sector 6. Since sectors 5 and 6 are at the same pressure, this minimizes the potential leakage factor from the shut-off element V4. This step allows the test to be more specifically focused on an external leak in the pipe and to detect the presence of a smaller orifice.

[0082] If the difference is less than the external threshold, this indicates that this sector is not sealed. Therefore, the control unit activates a DTC9 external leakage diagnostic alert and terminates the second diagnostic phase, DIAG2.

[0083] The second phase DIAG2 includes additional tests aimed at ruling out the possibility that a leak on sector 5 at the outlet of the tanks could have escaped diagnosis, in particular in the case where a hydrogen leak to the outside would have been compensated by a leak from the tank shut-off elements.

[0084] To this end, at steps E14 and E15, the control unit actuates the opening of the V3a, V3b, and V3c tank shut-off elements and the V4 shut-off element located between sectors 5 and 6 of the pipeline 8. As illustrated in [Fig. 3], the opening is actuated until the pressure in the two sectors reaches the pressure in the tanks. When the control unit detects that the HP2, HP1, and HPR pressures are equal, it actuates the closing of the shut-off elements at steps E16 and E17.

[0085] The same advantage is produced as for steps E10 and El 1 because it allows the walls of the duct of the stop elements to be cleaned due to the high-speed flow of hydrogen.

[0086] Next, the control unit performs the same tests in steps E18 and E19, for sectors 5 and 6 of the pipeline respectively, as in steps E6, E8, E12, and E13. These tests involve measuring the change in the quantity of hydrogen between two instants over a predetermined test period and comparing the difference in quantity values ​​between two instants to the external leakage threshold for the respective sectors. At this diagnostic stage, identically to tests E12 and E13, the internal leakage factor through the stop elements V3a, V3b, V3c, and V4 is minimized at the beginning of the test.

[0087] For test El8, if the difference in the amount of hydrogen for sector 5 is less than the external leakage threshold, this indicates that this sector is not sealed. Consequently, the control unit activates a DTC10 external leakage diagnostic alert and terminates the second diagnostic phase, DIAG2.

[0088] For test E19, if the difference in the amount of hydrogen in sector 6 is less than the external leakage threshold, this indicates that this sector is not sealed. Consequently, the control unit activates a DTC10 external leakage diagnostic alert and terminates the second diagnostic phase, DIAG2.

[0089] If these thresholds are not exceeded, then the control unit terminates the diagnostic procedure at steps E20 and E21 respectively. The procedure ends without a warning message and will be repeated at the next vehicle shutdown.

[0090] Variations of the leak detection method are considered. If the measuring devices do not include a temperature sensor, then tests E6, E8, E12, E13, E18, and E19 are carried out by calculating pressure variations and by comparison. deviations from pressure thresholds associated with maximum permitted leakage rates, for external and internal leaks specific to each sector.

[0091] The invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different variant embodiments of the invention by combining, for example, the different features above taken alone or in combination, without departing from the scope of the invention.

Claims

Demands

1. A method for detecting leaks in a compressed gas supply system adapted to power a fuel cell, said system comprising at least one reservoir (2a) for highly compressed gas, at least one gas flow shut-off element (V3a, V4) disposed downstream of the reservoir (2A) in a pipe (8), the method being characterized in that it comprises a first leak diagnosis phase (DIAG1) of the pipe (8) comprising at least: - a leak test (El, E4) based on a controlled depression in a section of the pipe downstream of said stop element and consisting of detecting the attainment of a predetermined depression threshold in said section, - a leak test (E6, E8) based on monitoring the variation of a gas parameter from a maximum variation threshold when the pipe sectors upstream and downstream of said element have a pressure difference (API, AP2), - and if the first diagnostic phase (DIAG1) is successful, a second leak diagnostic phase (DIAG2) of the pipe (8) consisting of commanding said pipe sectors upstream and downstream of said shut-off element to the same pressure value and activating at least one leak test (E12, E13, E18, E19) based on monitoring the variation of said gas parameter when said sectors have the same pressure value.

2. A method according to claim 1 wherein the first diagnostic phase (DIAG1) comprises the following successive substeps: a) closing a first shut-off element (V3a) disposed between the reservoir (2a) and a first section (5) of the pipe (8) so as to generate a controlled vacuum in the first section (5) and performing a first leak test (E1) of the first shut-off element (V3a) based on the controlled vacuum in the first section (5), b) closing a second shut-off element (V4) disposed between the first section (5) and a second section (6) of the pipe (8) so as to generate a controlled vacuum in the second section (5) and performing a second leak test (E4) of the second stop element (V4) based on controlled depression in the second sector (6), c) the execution of a third and fourth leak test (E6, E8) based on monitoring the variation of quantity of gas in the first sector (5) and in the second sector (6) respectively of the line (8) with respect to a specific maximum variation threshold, the third and fourth leak test being executed when the tank, the first sector and the second sectors have a pressure deviation (API, AP2) from each other.

3. A method according to claim 2, wherein the second diagnostic phase (DIAG2) comprises: d) the control of the second shut-off element (V4) so ​​as to bring the second sector (6) to the same pressure value as the first sector (5), e) the activation of a fifth and a sixth leak test (E12, E13) comprising monitoring the variation of quantity of gas in the first sector (5) and in the second sector (6) respectively with respect to the specific maximum variation threshold.

4. A method according to claim 3, wherein the second diagnostic phase (DIAG2) further comprises the following substeps: f) the simultaneous control of the first and second shut-off elements (V3a, V3b, V3c, V4) so ​​as to bring the first sector (5) and the second sector (6) to the same pressure value as the tank (2a, 2b, 2c), g) the activation of a seventh and an eighth leak test (E18, E19) comprising monitoring the variation of the quantity of gas in the first and second sectors (5, 6) respectively with respect to the specific maximum variation threshold.

5. A method according to any one of claims 2 to 4 wherein the monitoring of the variation in quantity of gas comprises: - measuring the pressure and temperature in the monitored sector section of the pipeline (8), - calculating a quantity of gas from the measured pressure and temperature and the volume of the monitored sector.

6. A method according to any one of claims 1 to 5, wherein each leak test (E1, E4) based on a controlled depression comprises:

7.

8.

9.

10. - the measurement of the gas pressure downstream of the shut-off element (V3a, V3b, V3c, V4) for a period following the start of the depression, - and the detection (DTC1, DTC2) of a leak in case the predetermined depression threshold is not reached within said duration. Compressed gas supply system (1) adapted to supply a fuel cell (7), said system comprising at least one tank (2a) for highly compressed gas and at least one gas flow stop element (V3a, V3b, V3c, V4) disposed downstream of the tank (2a) in a conduit (8), the system being characterized in that it comprises a control unit (12) configured to implement the leak detection method according to any one of claims 1 to 6. Electrified vehicle comprising a power supply system (1) according to claim 7. Control unit (12) comprising means specifically configured to implement the leak detection method according to any one of claims 1 to 6. Computer program comprising instructions which, when the program is executed by a control unit, cause the latter to implement the leak detection method according to any one of claims 1 to 6.

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