Method and apparatus for controlling drain of fuel cell system in off state

Abstract

The invention relates to a method for controlling drainage of a fuel cell system in a shutdown state. The method comprises the following steps: determining that the system is shut down in an operation process; determining whether the shutdown is an emergency shutdown caused by a fault or a potential fault of the system; when it is determined that the shutdown is emergency shutdown, a drain valve arranged at the downstream of a gas-liquid separator in the system is controlled, so that the drain valve is opened at a delay time after the emergency shutdown occurs, and the drain valve is closed again after the drain valve is opened for a duration time; the opportunity at which the drain valve delays opening and closing is determined based on the time elapsed from the occurrence of an emergency shutdown until the separated anode medium in the gas-liquid separator reaches a final steady state or based on a parameter of the gas-liquid separator related to the efficiency of draining the liquid water. The invention further relates to related control equipment and computer program products, liquid water in the gas-liquid separator is discharged as much as possible under the emergency shutdown condition, the time and energy consumption required by cold start are reduced, and the cold start performance and low-temperature robustness of the fuel cell system are improved.

Description

Technical Field

[0001] This invention generally relates to the technical field of fuel cell systems, and more specifically to a method and apparatus for controlling anode drainage of a fuel cell system during shutdown. This invention also relates to related computer program products. Background Technology

[0002] Fuel cells, as a clean energy source that can reduce greenhouse gas emissions, are widely used in electric vehicles. They typically use hydrogen as the fuel gas and oxygen or air as the oxidizing gas, converting chemical energy into electrical energy through an electrochemical reaction. During actual operation, the electrochemical reaction occurring inside the fuel cell stack produces water. Some of this water permeates from the cathode to the anode and, after being discharged, recirculates back into the anode, causing a "flooding" phenomenon (i.e., accumulated liquid water hinders the supply of hydrogen to the membrane electrode assembly). This results in reverse voltage (negative voltage) in the fuel cell stack. Carbon corrosion during reverse voltage can lead to catalyst shedding and even physical failure of the membrane, such as perforation.

[0003] To avoid the aforementioned issues, a gas-liquid separator and a drain valve are typically installed in the anode circuit at the anode outlet of the fuel cell stack. The drain valve is periodically opened based on the system's operating power or output current to periodically discharge the separated accumulated water / liquid. On the other hand, during normal shutdown of existing fuel cell systems, excess water inside the fuel cell is typically removed by purging the anode and / or cathode sides. However, when a fuel cell malfunctions (e.g., low cell voltage, high coolant temperature, excessive DC / DC converter deviation, air compressor failure, etc.), an emergency shutdown is required, which may prevent timely and effective purging, leading to excessive water accumulation after separation by the gas-liquid separator. During the next cold start of the fuel cell system, the large amount of accumulated water severely impacts the duration of the cold start, especially when the ambient temperature is below the freezing point of the water, causing it to freeze. In practice, achieving a cold start, whether using resistance heating elements to defrost or heating the cooling water, consumes excessive energy and time, thus affecting the performance of the fuel cell system. Since the water accumulation generated during normal shutdown can be controlled by purging, how to efficiently reduce the volume of water generated in the fuel cell system during emergency shutdown is an urgent technical problem to be solved in order to optimize cold start performance.

[0004] It should be noted that the "Background Art" paragraph is only used to help understand the content of this invention. Therefore, the content disclosed in the "Background Art" paragraph may include some prior art that is not known to those skilled in the art. The content disclosed in the "Background Art" paragraph does not mean that the content or the problems to be solved by one or more embodiments of this invention were known or understood by those skilled in the art before this application was filed. Summary of the Invention

[0005] The purpose of this invention is to provide an improved method and apparatus for controlling drainage of a fuel cell system during shutdown. This method can discharge as much liquid water collected by the gas-liquid separator in the anode circuit as possible during an emergency shutdown of the fuel cell system, thereby reducing the time and energy required for the next cold start and improving the performance of the entire fuel cell system.

[0006] According to one aspect of the present invention, a method for controlling drainage of a fuel cell system in a shutdown state is provided, the fuel cell system comprising: a stack, an anode circuit, a gas-liquid separator, and a drain valve;

[0007] The fuel cell stack has an anode inlet and an anode outlet;

[0008] The anode circuit receives the reacted anode medium from the anode outlet and transmits it to the gas-liquid separator for gas-liquid separation. A portion of the separated gas and the anode gas supply from the hydrogen source are provided to the anode inlet via the anode circuit.

[0009] The drain valve is installed in the tail drain line downstream of the gas-liquid separator to discharge the liquid water separated in the gas-liquid separator to the external environment when it is open.

[0010] The method includes the following steps:

[0011] It was determined that the fuel cell system experienced a shutdown during operation;

[0012] Determine whether the shutdown is an emergency shutdown caused by a fault or potential fault in the fuel cell system;

[0013] When the shutdown is determined to be an emergency shutdown, the drain valve is controlled to open after a delay following the occurrence of the emergency shutdown, and then closed again after a certain duration of opening. The timing of opening and closing the drain valve is determined based on the time elapsed from the occurrence of the emergency shutdown to the anode medium in the gas-liquid separator reaching its final steady state, or based on parameters of the gas-liquid separator related to the efficiency of discharging liquid water.

[0014] According to another aspect of the present invention, there is provided an apparatus for controlling drainage of a fuel cell system in a shutdown state, which is used to perform the method according to the above-described invention, the apparatus comprising:

[0015] A data acquisition unit is used to acquire parameters related to environmental conditions for draining the gas-liquid separator installed in the anode circuit of a fuel cell system; and

[0016] The control unit, which is communicatively connected to the data acquisition unit, is capable of receiving parameters from the data acquisition unit and controlling the delayed opening and closing of the drain valve based on the parameters in the event of an emergency shutdown of the fuel cell system.

[0017] According to another aspect of the present invention, a computer program product is provided, wherein executable instructions are stored, which, when executed by a processor, are capable of implementing the method described above.

[0018] Further features and advantages of the present invention are described in detail in specific embodiments and are the subject of the appended dependent claims. Attached Figure Description

[0019] The above and other aspects of the invention will now be understood and appreciated more thoroughly in conjunction with the accompanying drawings. It should be understood that the drawings are provided for illustrative purposes only and depict only typical or exemplary embodiments. These drawings are provided to facilitate an understanding of the concepts disclosed herein and should not be construed as limiting the breadth, scope, or applicability of these concepts. Wherein:

[0020] Figure 1 This is a simplified schematic diagram of the fuel cell stack anode and a portion of the anode circuit, showing the gas-liquid separator and its downstream tailpipeline.

[0021] Figure 2 This diagram illustrates the different stages of a gas-liquid separator during an emergency shutdown of a fuel cell system, from the moment of emergency shutdown until the liquid water at the anode reaches its final steady state.

[0022] Figure 3 This is a flowchart of a method for controlling drainage of a fuel cell system in a shutdown state according to an exemplary embodiment of the present invention.

[0023] Figure 4 The timing diagrams showing the opening and closing of the drain valve and exhaust valve during the transition from normal operation to emergency shutdown of the fuel cell system are shown, as well as the curves showing the changes in the current generated by the fuel cell stack and the concentration of hydrogen in the exhaust gas.

[0024] Figure 5 To and Figure 1A schematic block diagram of a device for controlling drainage of a fuel cell system, according to an exemplary embodiment of the present invention, which combines the stack anode and a portion of the anode circuit of a fuel cell system. Detailed Implementation

[0025] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the use of ordinal numbers such as "first," "second," etc., in the specification, claims, and drawings of the present invention is for distinguishing similar objects and is not necessarily for describing a specific order or sequence. Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Furthermore, techniques and devices known to one of ordinary skill in the art may not be discussed in detail, but where appropriate, such techniques and devices should be considered part of the specification. In this document, the term "upstream" refers to a portion of piping / loop that the reaction medium and / or product passes through earlier than the reference component during system operation; while the term "downstream" refers to a portion of piping / loop that the reaction medium and / or product passes through later than the reference component during system operation.

[0027] Figure 1 This is a simplified schematic diagram of the fuel cell stack anode and a portion of the anode circuit. As shown, the stack anode 10 has an anode inlet 101 and an anode outlet 102. It should be noted that... Figure 1The locations of the anode inlet 101 and anode outlet 102 are illustrative and not restrictive. It is understood that the anode inlet and outlet can be flexibly configured at the anode end of the fuel cell stack according to actual needs. As shown in the figure, the anode circuit includes an anode gas supply line 201, an anode exhaust line 202, and a circulation line 203. The anode gas supply line 201 supplies hydrogen from a hydrogen source (not shown) sequentially through an anode shut-off valve 21, a hydrogen injector 22, and an ejector 23 to the anode inlet 101. The anode exhaust line 202 transports the anode medium, after reaction and discharged from the anode outlet 102, to a downstream gas-liquid separator 24. During operation of the fuel cell system, the anode medium generally comprises residual hydrogen after the reaction, a small amount of nitrogen from the air, saturated gas consisting of water vapor produced by the reaction, and a portion of liquid water generated at the fuel cell stack cathode and permeated back through the proton exchange membrane. After receiving the anode medium, the gas-liquid separator 24 performs gas-liquid separation. The separated gas is discharged from the first upper outlet of the gas-liquid separator 24 and partially circulated to the anode gas supply line 201 (especially the ejector 23 installed therein) via the circulation line 203 under the action of the hydrogen circulation pump 25 for the circulation supply of anode gas. In addition to the separated gas participating in the anode gas supply, some of the excess gas obtained after gas-liquid separation in the anode medium is discharged to the external environment from the second upper outlet of the gas-liquid separator via the gas tail discharge line 2041; and the liquid water collected after gas-liquid separation in the anode medium is discharged to the external environment from the lower outlet of the gas-liquid separator via the liquid tail discharge line 2042. As shown in the figure, corresponding exhaust valves 26 and drain valves 27 are respectively installed in the gas tail discharge line 2041 and the liquid tail discharge line 2042, and the gas tail discharge line 2041 and the liquid tail discharge line 2042 can be collectively referred to as the tail discharge line 204. In practice, the exhaust valve 26 and the drain valve are controlled by the control unit so that when the nitrogen content in the gaseous product obtained after gas-liquid separation is too high, the exhaust valve 26 is opened to exhaust gas to the external environment through the tailpipe 204; and when the liquid water content collected after gas-liquid separation is too high, the drain valve 27 is opened to drain water to the external environment through the tailpipe 204.

[0028] In practical applications of fuel cell systems, it has been observed that water generated through electrochemical reactions occurs within the fuel cell stack. This water, in the form of water vapor and liquid water, is discharged to the outside of the fuel cell stack along with unconsumed anode gas and then enters the anode circuit. If the liquid water condensed from water vapor in the anode circuit is not properly drained using a drain valve, it can cause flooding of the fuel cell stack or waste of hydrogen. This not only degrades the power generation performance of the fuel cell stack but may also pose safety hazards. As described in the background section, although excessive water inside the fuel cell can be removed by purging during normal shutdown, in cases of component failure or potential faults discovered through pre-diagnosis based on operational data, emergency shutdowns are required, making timely and effective purging impossible. This results in excessive water accumulation after separation by the gas-liquid separator.

[0029] Figure 2 This diagram illustrates the different stages of a gas-liquid separator during an emergency shutdown of a fuel cell system, from the instant of the emergency shutdown until the anode medium reaches its final steady state. From left to right, these stages correspond to Stage I (0 seconds after the emergency shutdown), Stage II (1 second after the emergency shutdown), Stage III (2 seconds after the emergency shutdown), and Stage IV (3 seconds after the emergency shutdown). In Stage I, due to the rotary separation design of the gas-liquid separator, an inverted conical cavity 30 is formed in the middle of the separator, and the separated liquid water occupies the space inside the separator except for the cavity 30. As shown in the diagram, the height difference h1 between the lower apex of the inverted conical cavity 30 (i.e., the lowest liquid level of the collected liquid water in the gas-liquid separator) and the lower drain port of the gas-liquid separator is at its minimum, and the top surface of the inverted conical cavity 30 (i.e., the liquid level of the separated liquid water around the cavity) is at a relatively high level. As time progresses, combined with... Figure 2 As can be seen from left to right, the lower apex of the inverted conical cavity 30 gradually rises while the top surface gradually descends, until, as shown in stage IV, they reach the same height. At this point, the liquid water separated by the gas-liquid separator reaches its final steady state. For a 132 kW fuel cell system, in the event of an emergency shutdown, approximately 70 g of liquid water will accumulate in the gas-liquid separator.

[0030] In practice, when encountering such an emergency shutdown, the control unit is usually used to simultaneously send signals to the system (including...). Figure 1The anode circuit (which also includes the cathode circuit, not shown in the figure) sends control commands to various components to stop the current operation, such as stopping the hydrogen supply to the anode side and the air supply to the cathode side, shutting down various pumps and valves in the system, etc. In this situation, it will be impossible to purge the anode and / or cathode sides of the fuel cell to remove excess water from inside the fuel cell. As described in the background section, the large amount of accumulated water not only significantly increases the duration of the next cold start, but also consumes excessive energy if the ambient temperature is below the freezing point of the water, leading to freezing. To efficiently reduce the volume of water generated in the fuel cell system during emergency shutdowns, this invention proposes a method for controlling the drainage of the fuel cell system by delaying the opening and closing of the drain valve.

[0031] Reference Figure 3This document illustrates a flowchart of a method for controlling drainage of a fuel cell system in a shutdown state according to an exemplary embodiment of the present invention. First, at S10, it is determined that a shutdown has occurred during operation of the fuel cell system. Next, at S11, it is determined whether the shutdown is an emergency shutdown. In this invention, an "emergency shutdown" refers to a shutdown operation performed due to other special circumstances (such as component failure of the fuel cell system or detection of abnormal operating data, i.e., potential faults, for safety protection purposes) other than shutdowns performed during normal operation of the fuel cell system. It should be noted that the aforementioned abnormal data includes not only deviations between the actual operating data of the fuel cell system itself and normal operating data, but also abnormalities in the operating data of electrical components powered by the fuel cell system. In practice, regardless of the situation, an emergency shutdown operation needs to be performed on the fuel cell system to protect both the fuel cell system itself and the electrical components powered by the fuel cell system from damage. Next, if the result at step S11 is "No," meaning the shutdown operation is not an emergency shutdown, then proceed to step S12, where the drain valve downstream of the gas-liquid separator is kept closed as in a normal shutdown operation. Since the anode and / or cathode sides of the fuel cell are purged, the amount of liquid water separated in the gas-liquid separator is limited, so no additional drainage operation is required at this stage. Conversely, if the result at step S11 is "Yes," meaning the fuel cell system is performing an emergency shutdown due to component failure and / or detected abnormal operating data, then proceed to step S14 to perform the following operation: control the drain valve to open after a delay following the emergency shutdown, and close it again after a certain duration of opening. In an optional embodiment, if the result at step S11 is "Yes," an additional step S13 (shown in a dashed box in the figure) may be included, which uses a temperature sensor located in or near the gas-liquid separator to measure the current ambient temperature and determine whether the current ambient temperature is below the freezing point of water (normally zero degrees Celsius). If the result at S13 is "No", meaning that even if there is a lot of liquid water collected in the gas-liquid separator, there is no risk of it freezing, then proceed to step S12 to keep the drain valve closed; otherwise, if the result at S13 is "Yes", then proceed to step S14, delay for a period of time to open the drain valve to perform the drainage operation and then close the drain valve.

[0032] When it is determined that the opening of the downstream drain valve of the gas-liquid separator needs to be delayed to perform a drainage operation, the timing of the delayed opening and the timing of its subsequent closure need to be rationally planned (in other words, the time elapsed from the emergency shutdown to the delayed opening of the drain valve and the duration from the delayed opening to the subsequent closure of the drain valve need to be rationally selected) to maximize drainage efficiency. Higher drainage efficiency means less liquid water remaining in the gas-liquid separator collection section, less time and energy required for the next cold start, thereby improving the overall efficiency of the fuel cell system. In practice, it has been found that in the event of an emergency shutdown, opening the drain valve immediately and keeping it open for as long as possible does not significantly improve drainage efficiency. In fact, the drainage efficiency is related to the gas pressure in the anode medium received by the gas-liquid separator and the height difference between the lowest liquid water level obtained from the separation and the lower drain port of the gas-liquid separator.

[0033] Return again Figure 2The following description of the gas-liquid separator's states at different stages during an emergency shutdown (from the moment of shutdown to the final steady state) illustrates the timing for delaying the opening and closing of the drain valve. Regarding the influencing factor of gas pressure inside the gas-liquid separator, at the moment of emergency shutdown (corresponding to stage I in the diagram), the gas pressure inside the separator is at its highest point (typically 1.5–2.5 bara) because the separator continues to receive the anolyte discharged from the anode outlet. It should be noted that gas pressure and ambient pressure referred to in this article are absolute pressures. On the other hand, during an emergency shutdown, both the hydrogen supply to the anode side and the air supply to the cathode side are stopped. The hydrogen and air already supplied to the fuel cell stack will continue to react and consume themselves for a short period, causing the gas pressure in the anolyte discharged through the anode exhaust line to drop rapidly within a short time until the gas pressure inside the gas-liquid separator reaches its lowest point (typically 0.7–1 bara) at the final steady state (corresponding to stage IV in the diagram). In other words, if the drain valve is delayed and maintained for a considerable period of time (e.g., close to the final steady state of the gas-liquid separator), a negative pressure will be generated inside the gas-liquid separator at the transition point when the gas pressure inside the gas-liquid separator drops to the ambient pressure (usually 1 bara). This will make it easier for some of the previously discharged liquid water to be drawn back into the gas-liquid separator, thus negatively affecting the drainage efficiency of the entire system. On the other hand, although theoretically, opening the drain valve when the gas pressure inside the gas-liquid separator is relatively high is beneficial for discharging the collected liquid water to the external environment, as mentioned earlier, in the initial stage of an emergency shutdown, the height difference h1 between the lower apex of the inverted conical cavity occupied by gas and the drain port at the bottom of the gas-liquid separator is at its minimum due to the rotary separation design. If the drain valve is opened immediately at this time, only a small volume of liquid water near the center of the drain port (see the cylindrical volume approximately h1 above the lower drain port in the figure) can be easily discharged, while the liquid water around the higher level of the inverted conical cavity cannot be discharged, thus reducing drainage efficiency to some extent. Therefore, the above two factors should be considered to reasonably select the timing of delaying the opening of the drain valve, that is, on the one hand, ensuring that the gas pressure inside the gas-liquid separator is at a higher level than the ambient pressure, and on the other hand, ensuring that the height difference between the lower apex of the inverted conical cavity and the drain port at the bottom of the gas-liquid separator exceeds a certain height threshold, so that the amount of liquid water discharged can be significantly increased when the drain valve is opened. In other words, the timing of opening and closing the drain valve should be determined based on parameters related to the efficiency of the gas-liquid separator in discharging liquid water. In this invention, these parameters include the gas pressure in the anode medium received by the gas-liquid separator and the height difference between the lowest level of the separated liquid water and the lower drain port of the gas-liquid separator.

[0034] Figure 3 The diagram also illustrates the sub-steps included in step S14 (i.e., controlling the drain valve to open after a delay following the emergency shutdown and then closing it again after a certain duration) in the event of an emergency shutdown. Specifically, in sub-step S141, the gas pressure in the anode medium received by the gas-liquid separator is measured using a pressure sensor located at the upstream inlet of the gas-liquid separator in the anode circuit, and / or the height difference between the lowest liquid level in the gas-liquid separator and the lower drain port is measured using a level sensor located in the gas-liquid separator. The drain valve is controlled to open when the gas pressure drops from its maximum value at the start of the emergency shutdown to a pressure threshold higher than ambient pressure (e.g., 1.5 bara) and / or when the height difference rises from its minimum value at the start of the emergency shutdown to exceed a height threshold. Next, in sub-step S142, the drain valve is controlled to close when the gas pressure continues to drop to the ambient pressure. It should be noted that, since using a liquid level sensor requires a relatively high cost, and on the other hand, experiments have shown that the pressure and height thresholds suitable for efficient drainage are generally reached at roughly the same time after an emergency shutdown, the timing of opening and closing the drain valve can also be selected by measuring the gas pressure in the anode medium entering the gas-liquid separator.

[0035] In addition to determining the timing of the drain valve's opening and closing based on parameters related to the efficiency of the gas-liquid separator in discharging liquid water, the experiment also revealed a correlation between the delayed opening and closing of the drain valve and the time elapsed from an emergency shutdown to the anode medium within the gas-liquid separator reaching its final steady state. (Refer to...) Figure 4 The figure specifically illustrates the timing diagram of controlling the opening and closing of the drain valve and exhaust valve during the transition of the fuel cell system from normal operation to emergency shutdown. It also shows the curves illustrating the changes in the fuel cell stack current and the exhaust hydrogen concentration. As shown in the figure, the vertical dashed line divides the fuel cell system's operating state into normal operation (On on the left) and emergency shutdown (Off on the right); correspondingly, the stack current SC changes from the rated current, for example, 527A, during normal operation to 0A during emergency shutdown. Furthermore, Figure 4Also shown is a timing diagram of the opening and closing of the drain valve (DV) and the purge valve (PV) in the form of a square wave, where a high level indicates that the corresponding valve is open and a low level indicates that the corresponding valve is closed. As can be seen from the figure, during the normal operation stage, the drain valve and the purge valve are alternately opened to discharge the excess liquid water and gas products obtained by separation in the gas-liquid separator through the aforementioned tail discharge pipeline respectively. For the drain valve, the duration of the last closing of the drain valve before an emergency shutdown occurs is t0, and the length of this time determines the amount of liquid water finally accumulated in the gas-liquid separator without opening the drain valve again. Further, as can be seen from the figure, different from the traditional operation of closing all components (including the drain valve and the purge valve) in the case of an emergency shutdown, according to the concept of the present invention, the drain valve is delayed to be opened and closed once after an emergency shutdown to discharge as much liquid water accumulated in the gas-liquid separator as possible. Among them, the delay time before the drain valve is ready to open (that is, the time elapsed from the emergency shutdown to the delayed opening of the drain valve) is t1, and the duration after the drain valve is delayed to open is t2. Combining the description of the states of the gas-liquid separator in different stages in the case of the aforementioned emergency shutdown, the delay time t1 should be selected such that the gas pressure in the gas-liquid separator is significantly higher than the ambient pressure, and at the same time, the lower vertex of the inverted conical cavity formed in the gas-liquid separator rises to a height difference from the drain port exceeding a height threshold, so as to ensure that the liquid water can be efficiently discharged. On the other hand, the duration t2 after the drain valve is delayed to open is selected such that the gas pressure in the gas-liquid separator is still higher than the ambient pressure after being reduced. Taking Figure 2 the four stages I to IV shown as an example, the total elapsed time is about 3 seconds (s), and the preferred durations of t1 and t2 are such that 0 < t1 < 1 s and t1 + t2 < 2 s. In other words, the drain valve opens at a moment between stage I and stage II shown in Figure 2 the figure and closes before reaching stage III to complete the drainage in the case of an emergency shutdown. The test results show that for the fuel cell system with a power of 132 kW mentioned above, in the case of not adopting the control method of the present invention (that is, the drain valve is no longer opened), about 70 g of liquid water finally remains in the gas-liquid separator when an emergency shutdown occurs; while by using the operation of delaying the opening of the drain valve according to the present invention, at least an additional 20 g of liquid water can be effectively discharged from the gas-liquid separator, so that as much liquid water collected by the gas-liquid separator in the anode circuit can be discharged as possible in the case of an emergency shutdown of the fuel cell system, reducing the time and energy consumption required for the next cold start, thereby improving the cold start performance and robustness of the entire fuel cell system.

[0036] The above selection of the timing for the delayed opening and subsequent closing of the drain valve is based on experimental research on a fuel cell system with a power of 132 kW. For fuel cell systems with other powers and rotary gas-liquid separators of different specifications, the inventors also found that the time suitable for delaying the opening of the drain valve and the duration after the drain valve is delayed to open are related to the time elapsed from the start of emergency shutdown until the accumulated liquid water in the gas-liquid separator reaches the final steady state, but generally maintain approximately the same proportional relationship as in the above embodiments. That is to say, assuming that the time elapsed from the start of emergency shutdown until the accumulated liquid water in the gas-liquid separator reaches the final steady state is T, the delay time t1 before the drain valve is ready to open and the duration t2 after the delayed opening are preferably selected such that 0 < t1 < T / 3 and t1 + t2 < 2T / 3. It can be understood that the specific range of the above time T is related to the gas flow rate entering the gas-liquid separator and the radius of the rotating plane of the gas-liquid separator. Further, the above gas flow rate increases or decreases synchronously with the power of the fuel cell system, and the radius of the rotating plane of the gas-liquid separator is related to the design specifications of the gas-liquid separator. Generally speaking, for gas-liquid separators of the same specification, the higher the power of the fuel cell system, the higher the gas flow rate entering the gas-liquid separator, and the greater the time T required to reach the final steady state; for fuel cell systems of the same power, the larger the rotating radius of the gas-liquid separator, the smaller the time T required to reach the final steady state.

[0037] In addition to selecting the duration t2 after the drain valve is delayed to open in the above manner, in a further optional embodiment of the present invention, a secondary emergency shutdown mechanism for closing the drain valve by monitoring the concentration of the tail gas hydrogen is introduced. As shown in Figure 1 Although in the case where the drain valve is open, the liquid water is discharged to the external environment through the liquid tail discharge pipeline in the tail discharge pipeline, in practice, some of the separated gas in the gas-liquid separator will also be discharged together with the liquid water through the drain pipeline. In addition, Figure 1 the tail discharge pipeline in the anode circuit in Figure 4At the bottom, curves showing the changes in exhaust hydrogen concentration (EHC) monitored with the drain valve and exhaust valve open are displayed. The first of two adjacent peaks represents the exhaust hydrogen concentration when the exhaust valve is open, and the second represents the exhaust hydrogen concentration when the drain valve is open. Accordingly, in an emergency shutdown, since the exhaust valve remains closed, only the exhaust hydrogen concentration caused by the delayed opening of the drain valve can be monitored. In practice, this exhaust hydrogen concentration should not be too high. Therefore, a concentration threshold (e.g., 2%) is set for the exhaust hydrogen concentration. When the hydrogen concentration sensor at the end of the exhaust line detects that the exhaust hydrogen concentration reaches the above concentration threshold, the drain valve is closed. It should be noted that this concentration threshold is not the maximum allowable exhaust hydrogen concentration to be emitted into the environment according to industry standards, but slightly lower. This is because, according to… Figure 1 As shown in the simplified diagram, when the drain valve is open, there is a certain delay from the time the gas-liquid separator discharges the gas until the hydrogen concentration in the tailpipe is detected at the end of the tailpipe. The magnitude of this delay depends on the design of the tailpipe and the discharge rate, and is typically on the order of 0.3 to 0.5 seconds. Setting the concentration threshold slightly below the maximum permissible tailpipe hydrogen concentration can effectively compensate for the impact of this delay.

[0038] To implement the aforementioned method of delaying the opening of the drain valve in an emergency shutdown to control drainage of the fuel cell system, the present invention also proposes a corresponding device. For example... Figure 5As shown in the schematic block diagram, the device 40 includes a data acquisition unit 401 and a control unit 402 communicatively connected thereto. It is understood that the device can be implemented either as part of a fuel cell system or separately from it. The data acquisition unit 401 is used to acquire parameters related to environmental conditions for dredging a gas-liquid separator located in the anode circuit of the fuel cell system. The data acquisition unit 401 includes multiple sensors or is communicatively connected to multiple sensors (as shown by dashed lines in the schematic diagram). The sensors include, but are not limited to, a pressure sensor PS, a temperature sensor TS, a liquid level sensor LLS, and a hydrogen concentration sensor HCS. The pressure sensor PS is installed in the anode exhaust line of the anode circuit at the upstream inlet of the gas-liquid separator to measure the gas pressure in the anode medium entering the gas-liquid separator. The temperature sensor TS measures the ambient temperature of the gas-liquid separator. The liquid level sensor LLS is installed in the gas-liquid separator to measure the height difference between the lowest point of the cavity occupied by gas (i.e., the lowest liquid level of the separated liquid water) and the drain port of the gas-liquid separator. The hydrogen concentration sensor HCS is installed in the tailpipe line of the anode circuit downstream of the gas-liquid separator to measure the concentration of tailpipe hydrogen in the anode medium discharged to the external environment. The data acquisition unit 401 acquires the parameters measured by the above sensors and sends them to the control unit 402. Based on the parameters, the control unit 402 controls the delayed opening and closing of the drain valve installed in the tailpipe line in the event of an emergency shutdown to discharge some of the liquid water accumulated in the gas-liquid separator. Specifically, in the event of an emergency shutdown, when the gas pressure measured by the pressure sensor PS drops from its maximum value (e.g., 1.5–2.5 bara) at the start of the emergency shutdown to a pressure threshold (e.g., 1.5 bara) higher than the ambient pressure and / or when the height difference measured by the level sensor LLS rises from its minimum value at the start of the emergency shutdown to exceed a height threshold, the control unit 402 sends a control signal to open the drain valve; and when the gas pressure measured by the pressure sensor PS continues to drop to the ambient pressure or when the exhaust hydrogen concentration measured by the hydrogen concentration sensor HCS reaches a concentration threshold, the control unit 402 sends a control signal to close the drain valve. Those skilled in the art will understand that the device provided in this embodiment for controlling the drainage of a fuel cell system in a shutdown state can execute the method provided in any of the foregoing embodiments for controlling the drainage of a fuel cell system in a shutdown state, possessing the corresponding functional modules and beneficial effects for executing the method. Various steps and technical details for executing the above methods can be stored in software form in the corresponding functional modules, or implemented by a combination of software and hardware. The technical details described in the embodiments of the method or device for controlling the drainage of the fuel cell system described above can be combined accordingly.

[0039] The present invention also relates to a computer program product storing executable instructions that, when executed by a processor, can implement the control method described above in the specification.

[0040] It is understood that processors can be implemented using electronic hardware, computer software, or any combination thereof. Whether these processors are implemented as hardware or software will depend on the specific application and the overall design constraints imposed on the system. As an example, the processor, any portion of the processor, or any combination of processors provided in this invention can be implemented as a microprocessor, microcontroller, digital signal processor (DSP), field-programmable gate array (FPGA), programmable logic device (PLD), state machine, gate logic, discrete hardware circuitry, and other suitable processing units configured to perform the various functions described in this disclosure. The functionality of the processor, any portion of the processor, or any combination of processors provided in this invention can be implemented as software executed by a microprocessor, microcontroller, DSP, or other suitable platform.

[0041] It is understood that software should be broadly considered as representing instructions, instruction sets, code, code segments, program code, programs, subroutines, software modules, applications, software applications, software packages, routines, subroutines, objects, running threads, procedures, functions, etc. Software may reside on a computer-readable medium. Computer-readable media may include, for example, memory, which may be, for example, magnetic storage devices (e.g., hard disks, floppy disks, magnetic stripes), optical disks, smart cards, flash memory devices, random access memory (RAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, or removable disks. Although memory is shown as separate from the processor in several aspects set forth in this disclosure, memory may also reside within the processor (e.g., in caches or registers).

[0042] The preferred embodiments of a method and apparatus for controlling drainage of a fuel cell system in a shutdown state have been described in detail above with reference to the accompanying drawings. Modifications and additions to the technology and structure, as well as recombinations of features in the various embodiments, should be considered within the scope of this invention by those skilled in the art without departing from the scope and spirit of this disclosure as set forth in the following claims. Therefore, such modifications and additions conceivable under the teachings of this invention should be considered part of this disclosure. The scope of this disclosure is defined by the following appended claims and includes equivalent technologies known at the filing date of this disclosure and equivalent technologies not yet foreseen.

Claims

1. A method of controlling drainage of a fuel cell system in a shutdown condition, the fuel cell system comprising: fuel cell stack, anode circuit, gas-liquid separator, and drain valve; The fuel cell stack has an anode inlet and an anode outlet; The anode circuit receives the reacted anode medium from the anode outlet and transmits it to the gas-liquid separator for gas-liquid separation. A portion of the separated gas and the anode gas supply from the hydrogen source are provided to the anode inlet via the anode circuit. The drain valve is installed in the tail drain line downstream of the gas-liquid separator to discharge the liquid water separated in the gas-liquid separator to the external environment when it is open. The method includes the following steps: It was determined that the fuel cell system experienced a shutdown during operation; Determine whether the shutdown is an emergency shutdown caused by a fault or potential fault in the fuel cell system; When the shutdown is determined to be an emergency shutdown, the drain valve is controlled to open after a delay following the occurrence of the emergency shutdown, and then closed again after a certain duration of opening. The timing of opening and closing the drain valve is determined based on the time elapsed from the occurrence of the emergency shutdown to the anode medium in the gas-liquid separator reaching its final steady state, or based on parameters of the gas-liquid separator related to the efficiency of discharging liquid water.

2. The method according to claim 1, wherein, The delay time and the duration are selected such that the delay time is less than one-third of the time elapsed from the occurrence of an emergency shutdown to the time elapsed for the anode medium in the gas-liquid separator to reach its final steady state, and the sum of the delay time and the duration is less than two-thirds of the time elapsed from the occurrence of an emergency shutdown to the time elapsed for the anode medium in the gas-liquid separator to reach its final steady state.

3. The method according to claim 1, wherein, The parameters include the gas pressure in the anode medium received by the gas-liquid separator and the height difference between the lowest liquid level of the separated liquid water and the lower drain port of the gas-liquid separator.

4. The method according to claim 3, wherein, When the gas pressure drops from its maximum value at the start of the emergency shutdown to a pressure threshold higher than the ambient pressure and / or when the height difference rises from its minimum value at the start of the emergency shutdown to exceed a height threshold, the drain valve is controlled to open; and when the gas pressure continues to drop to the ambient pressure, the drain valve is controlled to close.

5. The method according to claim 4, wherein, The pressure threshold is 1.5 bara and the ambient pressure is 1 bara.

6. The method according to any one of claims 1 to 5, wherein, When it is determined that the shutdown is an emergency shutdown, the following steps are also included: Measure the ambient temperature of the gas-liquid separator and determine whether the measured ambient temperature is lower than the freezing point of liquid water; When it is determined that the ambient temperature is lower than the freezing point of the liquid water, the drain valve is controlled to open after a delay following an emergency shutdown, and then closed again after a certain duration; otherwise, the drain valve remains closed.

7. The method according to any one of claims 3 to 5, wherein, The parameters also include the concentration of hydrogen gas in the tail gas pipeline caused by the opening of the drain valve. When the concentration of hydrogen gas in the tail gas exceeds a concentration threshold, the drain valve is controlled to close.

8. An apparatus (40) for controlling drainage of a fuel cell system in a shutdown state, for performing the method according to any one of claims 1 to 7, said apparatus (40) comprising: A data acquisition unit (401) is used to acquire parameters related to the environmental conditions for draining the gas-liquid separator (24) installed in the anode circuit of the fuel cell system; and a control unit (402) communicatively connected to the data acquisition unit (401) is capable of receiving parameters from the data acquisition unit (401) and controlling the delayed opening and closing of the drain valve (27) based on the parameters in the event of an emergency shutdown of the fuel cell system.

9. The device according to claim 8, wherein, The data acquisition unit (401) includes or is communicatively connected to a sensor, the sensor including: A pressure sensor (PS), located at the upstream inlet of the gas-liquid separator (24) in the anode circuit, is used to measure the gas pressure in the anode medium entering the gas-liquid separator (24); and One or more of the following: A liquid level sensor (LLS) is installed in the gas-liquid separator (24) to measure the height difference between the lowest liquid level of the separated liquid water and the lower drain port; A hydrogen concentration sensor (HCS), installed in the tailpipe line (204) downstream of the gas-liquid separator (24), is used to measure the concentration of tailpipe hydrogen in the anode medium discharged to the external environment; and Temperature sensor (TS) is used to measure the ambient temperature of the gas-liquid separator (24).

10. A computer program product storing executable instructions that, when executed by a processor, can perform the method according to any one of claims 1 to 7.

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