Emission management method for hydrogen-fueled vehicle

Abstract

The invention relates to an emission management method for a hydrogen-fueled vehicle comprising a fuel supply system (2) for supplying hydrogen fuel from a fuel reservoir (1) to a power source (6) of the vehicle when the vehicle is in an operating state. In order to minimize uncontrolled hydrogen emissions from hydrogen-fueled vehicles, the invention provides that the fuel supply system (2) comprises a cleanable part (4) and that the method comprises at least the following steps: disconnecting (170, 260) the cleanable part (4) from the fuel reservoir (1) such that the power source (6) is disconnected from the fuel reservoir (1) wherein hydrogen fuel remains in the cleanable part (4); and performing (220, 230, 270) a purge operation comprising at least: discharging hydrogen fuel from the purgeable portion (4) to reduce the pressure in the purgeable portion (4) to a target pressure; generating a bleed gas inside the vehicle using the hydrogen fuel discharged from the purgeable portion (4) such that the bleed gas has a hydrogen concentration below a threshold concentration; and releasing the bleed gas at least partially into the atmosphere (50).

Description

Technical Field

[0001] This invention relates to an emission management method for hydrogen fuel cell vehicles and an emission management system for hydrogen fuel cell vehicles. Background Technology

[0002] With the increasing need to reduce CO2 emissions from road vehicles, alternatives to traditional internal combustion engines such as diesel or gasoline engines have been developed. In addition to electric vehicles powered by batteries (primarily lithium-ion batteries), hydrogen-powered vehicles are a promising option. These vehicles fall into two main categories. The first is hydrogen fuel cell electric (H2FCE) vehicles, which also have a traction motor but are powered by a fuel cell, in which the energy from the chemical reaction of hydrogen and oxygen is converted into electrical energy. The other category is hydrogen fuel cell internal combustion engine (H2ICE) vehicles. In H2ICE, hydrogen (H2) is used as fuel and burned with oxygen, with water as the reaction product.

[0003] Hydrogen fuel is stored in one or more hydrogen fuel tanks connected to the engine or fuel cell via a fuel supply system, which typically includes multiple pipes, manifolds, and valves. In the case of H2ICE vehicles, the fuel supply system may include a fuel rail. These components must be filled with hydrogen when the vehicle is running. When the vehicle is parked, the fuel supply system is disconnected from the fuel tanks, but unused hydrogen may remain within the fuel supply system itself. Over time, hydrogen may leak out, especially since the hydrogen within the fuel supply system typically has a pressure significantly higher than atmospheric pressure (e.g., between 20 and 40 bar in the case of a fuel rail). If the leak is uncontrolled, hydrogen—or more precisely, a hydrogen-air mixture—can accumulate in volumes and cavities within the engine and other vehicle components, posing an explosion risk, particularly when the vehicle is restarted. Furthermore, it should be remembered that hydrogen is considered a greenhouse gas, and therefore uncontrolled releases should be avoided.

[0004] Technical issues

[0005] Therefore, one object of the present invention is to minimize uncontrolled hydrogen emissions from hydrogen fuel cell vehicles.

[0006] This problem is solved by the method of claim 1 and the system of claim 15. Summary of the Invention

[0007] This invention provides an emission management method for hydrogen fuel cell vehicles. The term "hydrogen fuel cell vehicle" refers to any vehicle that uses hydrogen as an energy source and is considered synonymous with "hydrogen-powered vehicle." Typically, this refers to road vehicles such as passenger cars, trucks, or motorcycles. However, it is conceivable to employ the fuel recovery system of this invention in other modes of transportation, such as ships. Herein and below, the terms "fuel," "hydrogen fuel," and "hydrogen" are synonymous. This method achieves emission management, i.e., managing or controlling emissions from the vehicle. Specifically, this relates to hydrogen emissions. While some aspects of the method are implemented by physical or "hardware" components, others can be implemented in software. While some aspects of the method (particularly the control aspects) are conceivable to be implemented by components external to the hydrogen fuel cell vehicle, preferably, the method is performed entirely by using vehicle-integrated components. The control functions of the method can be performed by a control device of the hydrogen fuel cell vehicle. Such a control device can control various functions and can receive sensor signals.

[0008] The vehicle includes a fuel supply system for supplying hydrogen fuel from a fuel storage tank to the vehicle's power source when the vehicle is in operation, wherein the fuel supply system includes a purifiable portion. In a fuel storage tank that may include one or more fuel canisters, the hydrogen fuel is stored either in a gaseous or liquid form under high pressure. A power source is a device in which hydrogen fuel is typically converted with oxygen to release energy, which can then be used to power various functions of the vehicle, particularly for driving the vehicle. Typically, the reaction product of the power source is water. The fuel storage tank and the power source are physically connected via a fuel supply system, which may also be referred to as a "fuel supply device." This explicitly includes the possibility that at least one component can be inserted between the fuel supply system and the fuel storage tank and / or between the fuel supply system and the power source. In other words, the connection can be indirect. However, the fuel supply system is at least part of the connection. During vehicle operation, the fuel supply system also establishes a fluid connection between the fuel storage tank and the power source, thereby enabling the operation of the power source. "Operating state" is a state in which the power source is operated, hydrogen fuel is consumed, and energy is generated, causing the vehicle to move or at least be ready to move. In vehicles with internal combustion engines, this is typically equivalent to the "engine on" state. However, the connection between the fuel reservoir and the engine can also be established in the "key on, engine off" state. This is also possible, for example, for vehicles where the power source is a fuel cell. The fuel supply system may include at least one conduit for guiding hydrogen fuel, and at least one valve, particularly a shut-off valve for controlling the connection to the fuel reservoir. The fuel supply system includes a purgeable section, which includes the possibility that the purgeable section constitutes the entire fuel supply system. As the name suggests, this section can be purged, as described below.

[0009] In one step of this method, the purgeable section is disconnected from the fuel tank, thereby disconnecting the power source from the fuel tank, where the hydrogen fuel remains in the purgeable section. Disconnection means the fluid flow is interrupted, while the physical connection remains. Typically, a shut-off valve is closed to prevent any (significant) fluid exchange between the fuel tank and the purgeable section. This, in turn, disconnects the power source from the fuel tank. In other words, disconnecting the purgeable section of the fuel supply system severs the connection between the fuel tank and the power source. However, although the purgeable section is disconnected from the fuel tank, it still contains hydrogen fuel. This hydrogen fuel is initially at a high pressure, for example, exceeding 20 bar(a), where “(a)” indicates absolute pressure. The pressure can vary in different sections of the purgeable section. When the purgeable section is disconnected from the fuel tank, it can remain connected to the power source. Alternatively, it can be disconnected from the power source.

[0010] In another step of the method, a purge operation is performed. The minimum objective of the purge operation, as explained below, is to prevent any hydrogen emissions that could lead to the formation of a combustible air-fuel mixture inside or outside the vehicle. Optional objectives include reducing hydrogen emissions and improving energy use. The purge operation comprises three steps, which are not necessarily performed in the order described below. In particular, there may be time overlap between the steps.

[0011] One step in the purification operation specifies that hydrogen fuel is discharged from the purgeable section to reduce the pressure in the purgeable section to a target pressure. In this step, the amount of hydrogen in the fuel supply system is reduced, consistent with the pressure reduction. The goal is to reduce the pressure to a predetermined target pressure, or even lower. The target pressure is typically no greater than 5 bar(a) and can be, for example, 2 bar(a), 1.5 bar(a), or less. Preferably, the target pressure can be selected such that any possible hydrogen leakage from the purgeable section will not lead to the formation of a combustible gas mixture. Furthermore, preferably, at least 50%, at least 70%, at least 90%, or at least 95% of the hydrogen fuel initially contained in the purgeable section is discharged. The reduced amount of hydrogen in the purgeable section means that less hydrogen can escape into the atmosphere uncontrollably. After the transfer, any potential leakage from the purgeable section cannot (or is unlikely) lead to a combustible mixture. The hydrogen fuel is discharged or transferred from the purgeable section but not directly released into the atmosphere. Instead, it is retained inside the vehicle for another step in the purification operation.

[0012] In another step of the purification operation, vent gas is generated inside the vehicle using hydrogen fuel discharged from the purifiable section, such that the vent gas has a hydrogen concentration below a threshold concentration. Herein and below, “hydrogen concentration” is used synonymously with “hydrogen fuel concentration” or “H2 concentration” and refers to the concentration of non-compound hydrogen (H2). Vent gas is a gas mixture. It may include a non-negligible concentration of hydrogen fuel, however, this concentration is below a predetermined threshold concentration. The threshold concentration can be defined as such that the vent gas can be considered safe, i.e., non-flammable. This is typically ensured by a threshold concentration of 4% or less. In these cases, even if the oxygen content is high, the vent gas does not represent a flammable mixture. In most embodiments, the oxygen concentration of the vent gas is similar to that of air (i.e., about 21%) or lower. In some embodiments, all hydrogen fuel discharged from the purifiable section is used to generate the vent gas, while only a portion of the discharged hydrogen fuel may be used. Preferably, at least 80% or at least 90% of the discharged hydrogen fuel is used for the vent gas. It should be noted that although all the hydrogen used to produce the vent gas is present in the vent gas, it may not exist in a non-compound form, that is, not in the form of H2 gas, but as part of a compound, especially water (H2O).

[0013] In another step of the purification process, the vent gas is at least partially released into the atmosphere. This can also be described as releasing the vent gas into the atmosphere surrounding the vehicle. While it is preferred to release the vent gas when the vehicle is outdoors, this can also be done when the vehicle is inside a building (such as an underground parking garage). In this respect, the interior of the building is also considered part of the "atmosphere." Because the vent gas has a hydrogen concentration below a threshold concentration, its release can be considered safe according to a certain safety standard. In particular, the formation of a flammable mixture outside the vehicle can be prevented. In some embodiments, the entire amount of vent gas may be released into the atmosphere, while in other embodiments, only a portion is released.

[0014] Regardless of the method, the present invention mitigates the potential fire or explosion risks that may originate from hydrogen fuel remaining in the purgeable section of the fuel supply system. Once the pressure in the purgeable section has been reduced to the target pressure, any possible hydrogen leakage from the purgeable section will not result in a flammable mixture. Furthermore, such leakage will release only a small amount of hydrogen into the atmosphere. By generating and releasing the aforementioned vented gas, the method produces only emissions that can be considered safe in terms of fire hazard. In some embodiments discussed below, the hydrogen content of the emissions is also minimized with environmental considerations in mind.

[0015] The vehicle can be an H2FCE vehicle, and the power source can be a fuel cell. In such a fuel cell, hydrogen and oxygen react to produce water, and chemical energy is directly converted into electrical energy. This can be used to power the vehicle's drive motor and other electrically operated systems. Another preferred embodiment specifies that the vehicle's power source is a hydrogen fuel cell internal combustion engine, and the fuel supply system includes at least one of a fuel rail assembly and a hydrogen conditioning module. The hydrogen fuel cell internal combustion engine (H2ICE) is used to burn hydrogen with oxygen, with water as the reaction product. It should be understood that, due to the use of air instead of pure oxygen, combustion may produce small amounts of other products. Typically, an H2ICE has at least one cylinder with an intake valve, through which the cylinder is connected to an intake manifold. A movable piston is disposed in the cylinder, which may in turn be connected to a crankshaft. Each cylinder may have an injector for directly injecting hydrogen fuel into the cylinder. Here and below, "intake manifold" refers to any conduit through which the engine and / or at least one cylinder of the engine receives air. Therefore, the term explicitly includes an intake manifold. Typically, a cylinder also has an exhaust valve through which it connects to an exhaust manifold (the term explicitly includes an exhaust pipe). Hydrogen fuel can be injected directly into the corresponding cylinder. It can also be injected into the intake manifold (i.e., upstream of the intake valve), corresponding to indirect injection (e.g., in-line fuel injection). These two possibilities can be combined. Each injector can be connected to a fuel rail or fuel rail assembly from which it receives hydrogen fuel. The fuel rail can be part of a purgeable section, or it can represent the entire purgeable section. Typically, the fuel rail is not directly connected to the fuel tank, but rather via a hydrogen conditioning module (HRM) that performs several functions. It can include a pressure regulator that reduces the pressure of the hydrogen fuel, for example, from about 50 bar(a) at the fuel tank to 20 to 40 bar(a), which is sufficient for the operation of the fuel rail and injectors. The HRM can also include a filter to remove foreign particles or droplets from the hydrogen fuel. Other components of the HRM can include a heat exchanger or other heating or cooling device for regulating fuel temperature. The purgeable section may include at least a portion of the HRM. In other embodiments, the purgeable section (e.g., the fuel rail) may be directly connected to the fuel reservoir without a specific HRM.

[0016] There are several options regarding how the exhaust gases are generated. One option utilizes an engine to convert hydrogen fuel emitted from the purgeable section. This embodiment specifies that, in a first purge mode, the exhaust gases are generated by transferring hydrogen fuel from the purgeable section at least indirectly to the engine and burning the hydrogen fuel with oxygen inside the engine. The terms “first,” “second,” and “third purge mode” used herein and hereinafter are used only to distinguish the various modes and do not imply any order or preference. Furthermore, embodiments of the method may include a second (third) purge mode without including the first (and second) purge modes. In the first purge mode, hydrogen fuel is injected directly into the engine (i.e., at least one cylinder) and / or intake manifold. The combustion of the hydrogen fuel with oxygen produces water. The resulting gas mixture contains a significantly reduced or even negligible amount of hydrogen fuel. This exhaust gas can then be released into the atmosphere through the vehicle's exhaust pipe. It should be understood that the exhaust gas may contain an increased amount of water produced by combustion. Typically, this water remains gaseous before it is released into the atmosphere, but it can also form an aerosol in the exhaust gas, or it can condense on surfaces inside the vehicle. The first purge mode can use the same injectors used during normal engine operation. However, at least one dedicated injector may be available for the first purge mode. In this case, it may be relevant that some injectors used during normal operation require a certain minimum pressure to open. During the first purge mode, the pressure in the purgeable section drops towards the target pressure and may become too low for a normal injector, thus requiring a dedicated injector or valve for purge operation. In the first purge mode, the engine runs at idle while it is disconnected from the fuel tank. Therefore, engine operation is typically limited to a few seconds. The first purge mode can be maintained until either the target pressure has been reached or until the hydrogen fuel supplied to the engine becomes insufficient to maintain stable combustion in the engine. If the latter occurs before the target pressure has been reached, a different purge mode can be entered after the first purge mode.

[0017] Preferably, in the first purge mode, the engine operates at least temporarily in a low-efficiency mode to increase hydrogen consumption. This low-efficiency mode can include various measures. For example, spark timing can be significantly delayed relative to top dead center (TDC). Depending on the engine, this can be done until a stability limit, which may be, for example, between 50° and 60° after TDC. Another possibility is to use a small speed acceleration, for example, about 50% higher than normal idle speed. Moreover, while using the throttle to reduce the λ value, for example, from a typical idle value between 2.5 and 3.0 to between 1.5 and 2.0, the fuel-air mixture can be enriched to maintain good stability. If possible, another option is to maximize any accessory loads. The low-efficiency mode can be maintained throughout the purge operation. Alternatively, a normal efficiency mode can be used during the final stage of the purge operation, which may be beneficial when the pressure in the fuel supply system drops and approaches the target pressure.

[0018] In a preferred embodiment, the method includes the following steps: Receive a request to deactivate the vehicle while the engine is running; Disconnect the cleanable portion from the fuel storage unit; The purification operation is performed in the first purification mode while the engine is kept running; and The engine is shut down once the purification operation is complete.

[0019] In this embodiment, engine shutdown (which is unavoidable when the vehicle is off) is delayed until the purification operation is complete. The request to shut down the vehicle can also be referred to as a "key off" request or an "ignition off" request, and essentially an "engine off" request. In this context, a key off request typically indicates that the driver wants to end the trip, or at least pause the trip for a longer period. Therefore, it makes sense to remove a significant amount of hydrogen fuel from the purification section to minimize any risk of leakage. When the engine is started (i.e., running) upon receiving the request, the purification operation can be performed immediately in the first purification mode. The majority of the hydrogen fuel in the purification section can be converted into water, thereby significantly reducing hydrogen emissions. Furthermore, the energy generated by the engine during the purification operation can be stored in the vehicle's battery and will be available when the vehicle restarts.

[0020] Another embodiment specifies that, in a second purification mode, vent gas is generated by mixing hydrogen fuel with oxygen-containing gas and allowing the hydrogen fuel to react with oxygen outside the engine to produce water. Here and below, the term "mixing" does not imply the need for active mixing, but rather passive mixing. Therefore, it can be said that hydrogen fuel is mixed with oxygen-containing gas. Furthermore, the mixing does not necessarily produce a homogeneous mixture, although this is generally beneficial for the reaction. This embodiment does not use an engine to convert the hydrogen fuel, and therefore can be used when the engine is off (i.e., stopped). However, the second purification mode can also be used when the engine is running, optionally even simultaneously with the first purification mode. The second purification mode also relies on the chemical reaction of hydrogen fuel with oxygen to produce water. Therefore, the hydrogen content in the gas mixture can be significantly reduced, even to a negligible amount. The oxygen-containing gas is typically air, but according to a specific embodiment, the oxygen-containing gas can have a slightly different composition. For example, it can include exhaust gas from the engine, which has a lower oxygen content than air. Preferably, the gas mixture produced by mixing hydrogen fuel with oxygen-containing gas has a hydrogen concentration of at least 2%. According to embodiments, the gas mixture may advantageously have a hydrogen concentration of up to 10% or up to 30%.

[0021] According to a preferred embodiment, hydrogen fuel reacts with oxygen in the presence of a catalyst. The catalyst (also referred to as an oxidation catalyst) enables or enhances the water-producing reaction between hydrogen and oxygen. The catalyst can be, for example, a platinum-based catalyst. Typically, the catalyst requires an activation temperature above ambient temperature (typically around 100°C). Below this activation temperature, the catalyst is ineffective. Furthermore, effective operation requires a certain minimum hydrogen concentration, for example, 2%. On the other hand, a certain maximum concentration should not be exceeded, for example, 10%, because otherwise the reaction may lead to temperatures that could damage the catalyst. The catalyst temperature can depend on the vehicle's operating time (and other operating conditions). If the vehicle has only been running for a short time, the temperature may be insufficient. In this case, the catalyst can be heated using a dedicated electric heater.

[0022] Specifically, hydrogen fuel can react with oxygen in an exhaust manifold containing a catalyst. In this document, the term "exhaust manifold" refers to any container connected to the engine and receiving exhaust gas during normal engine operation. Therefore, it can be an EGR (Exhaust Gas Recirculation) manifold in addition to components that transfer exhaust gas from the engine to the atmosphere. The catalyst can be provided as a liner for the exhaust manifold (or a portion thereof). When the engine has been running for some time, it can be expected that the exhaust manifold has exceeded the catalyst's activation temperature. This is also true for a period of time after the engine has stopped. Advantageously, "waste heat" from the exhaust gas (exhaust gas heating the exhaust manifold) can be used to provide the necessary temperature for the catalyst. In this embodiment, the mixing of hydrogen fuel with the oxygen-containing gas can occur inside the exhaust manifold, but it can also occur at least partially outside the exhaust manifold (i.e., upstream), for example, in the engine or even in the intake manifold.

[0023] According to one embodiment, the method includes, before disconnecting the purifiable portion from the fuel reservoir: receiving a request to shut down the engine; and if the catalyst temperature is determined to be below the activation temperature, keeping the engine running until the activation temperature has been reached. The request to shut down the engine may also be referred to as an "engine shutdown" request. This request may be initiated by the vehicle's driver, or it may be initiated by a start-stop system that shuts down the engine after it has been idling for, for example, a few seconds. Regardless of the source of the request, the engine does not automatically shut down, but the catalyst temperature is determined and compared to the aforementioned activation temperature. It should be noted that the "activation temperature" mentioned in this embodiment may differ from the "actual" activation temperature of the corresponding catalyst. For example, the activation temperature used for comparison may be chosen to be higher to ensure that the catalyst is fully activated. Determining the catalyst temperature may refer to a direct measurement of the catalyst temperature. Alternatively, the temperature of the exhaust pipe or any other component related to catalyst heat may be measured. It is even possible that no temperature measurement is performed at all, and the catalyst temperature may be considered above the activation temperature if the vehicle has been running for a certain amount of time. If the catalyst temperature is determined to be below the activation temperature, the engine remains running until the activation temperature has been reached. If the catalyst temperature is initially determined to be above (or equal to) the activation temperature, the engine can be shut down without delay. This embodiment ensures that, if necessary, a purification operation can be performed according to the second purification mode.

[0024] As an alternative to catalytic conversion, hydrogen fuel can react with oxygen through combustion outside the engine. The main reaction product of combustion will be water, although some byproducts may also be produced. Combustion occurs outside the engine and is therefore independent of engine operation. The gas mixture containing hydrogen fuel and oxygen can be ignited, for example, by a glow plug or spark plug. To avoid explosive combustion, it is preferable to burn the hydrogen fuel only gradually. While the aforementioned catalytic reaction typically requires a relatively low hydrogen concentration, combustion can occur at higher concentrations, such as between 8% and 30%. It should be understood that the corresponding lower and upper limits also depend on the oxygen concentration. The values ​​given here apply if the hydrogen fuel is mixed with air or a gas mixture with a similar oxygen concentration.

[0025] The first and second purification modes described above effectively reduce the amount of hydrogen fuel released into the atmosphere. While this is preferred, it may be necessary and acceptable to release hydrogen fuel as part of the vent gas while maintaining the hydrogen concentration within a safe range. One embodiment specifies that in a third purification mode, the vent gas is generated by mixing hydrogen fuel and a diluent gas (preferably air) such that the hydrogen concentration in the resulting mixture is below a threshold concentration. In other words, the vent gas is simply a mixture of hydrogen fuel and a diluent gas. Thus, the hydrogen fuel is simply diluted to a concentration below the threshold concentration. Typically, the diluent gas can be any gas with a hydrogen concentration significantly below the threshold concentration. Preferably, the diluent gas is air, which is introduced into the vehicle to mix with the hydrogen fuel. However, the composition of the diluent gas may differ from air, for example, because its oxygen content has been reduced through the combustion process inside the hydrogen fuel cell vehicle. Mixing takes place in a mixing container, into which the diluent gas (particularly air) can be introduced by actively generating an airflow. The airflow (preferably an air stream) can be generated in various ways. It can be generated by an engine; however, this results in harmful noise and energy consumption. Alternatively, an electric system, such as an electric turbocharger or electric compressor, can be used. Another option is to use a separate pump, such as a crankcase ventilation pump.

[0026] Regarding the mixing container (in which hydrogen fuel is mixed with dilution gases), various options exist. One option is mixing within the engine's intake manifold. Another option is mixing within the exhaust manifold. In these cases, if the exhaust manifold includes the aforementioned oxidation catalyst, at least a partial reaction between the hydrogen fuel and oxygen in the dilution gases may occur, provided the catalyst temperature supports such a reaction. In this case, the second and third purge modes cannot be clearly distinguished. Another option is a dedicated mixing container, i.e., a container inside the vehicle used solely for generating vent gases through mixing. Depending in part on the mixing container, the transfer of hydrogen fuel can be controlled either through a dedicated purge valve or through injectors also used during normal engine operation. The latter is possible if the engine system is adapted for indirect injection, i.e., if hydrogen fuel from the purgeable section is injected into the intake manifold. In this case, the corresponding injector can also be used in the third purge mode, and the intake manifold can be used as the mixing container. However, some injectors may only open above a certain minimum pressure, which is available when the engine is running and the purgeable section is connected to the fuel reservoir, but not available throughout the purge operation. In this case, the transfer needs to be controlled by a dedicated purge valve that does not require a specific minimum pressure.

[0027] In one embodiment, the method includes: receiving a request to deactivate the vehicle when the engine is deactivated; and performing a purge operation in a third purge mode if the catalyst temperature is below the activation temperature, otherwise performing a purge operation in a second purge mode. Receiving a request to deactivate the vehicle when the engine is deactivated may be referred to as a "key off" request or an "ignition off" request. The first purge mode would require restarting the engine, which is undesirable if a key off request has already been received. Therefore, the purge operation can be performed in either the second or third purge mode. The second purge mode is selected if the catalyst has reached its activation temperature and is therefore available to support the hydrogen-oxygen reaction. The third purge mode is used if the catalyst is below its activation temperature (which rarely occurs if the engine has been running for a non-negligible period).

[0028] One embodiment specifies that after disconnecting the purgeable section from the fuel reservoir, if the power source is shut down, the pressure in the purgeable section is monitored, and if the pressure drop in the purgeable section exceeds a tolerance threshold, a purge operation is performed. With the purgeable section disconnected from the fuel reservoir and the power source (e.g., engine) shut down, the pressure in the purgeable section, which is still connected to the power source, should generally remain more or less constant in the absence of significant leakage. However, if hydrogen fuel leaks from the purgeable section, the pressure in the purgeable section will decrease over time. A tolerance threshold can be defined that takes into account minor, acceptable leaks, measurement errors, etc. If the pressure drop exceeds the tolerance threshold (which can be, for example, between 0.5 bar and 2.0 bar), this is interpreted as a significant leak, and a purge operation is performed. It should be noted that calculating the pressure drop may require taking into account temperature changes in the purgeable section. When the power source is shut down, the actual pressure in the purgeable section can be expected to decrease over time due to the temperature drop. Therefore, when determining the pressure drop, a temperature-corrected pressure should be calculated.

[0029] The present invention also provides an emission management system for a hydrogen fuel cell vehicle, the hydrogen fuel cell vehicle including a fuel supply system for supplying hydrogen fuel from a fuel storage tank to the vehicle's power source when the vehicle is in operation, the fuel supply system including a cleanable portion, wherein the emission management system is configured to perform at least the following steps: The cleanable portion is disconnected from the fuel storage tank, thereby disconnecting the power source from the fuel storage tank, wherein the hydrogen fuel remains in the cleanable portion; and Perform purification operations. The purification operation includes at least: Hydrogen fuel is discharged from the purgeable section to reduce the pressure in the purgeable section to a target pressure; Hydrogen fuel discharged from the purgeable portion is used to generate vent gas inside the vehicle, such that the vent gas has a hydrogen concentration below a threshold concentration; and The vented gas is at least partially released into the atmosphere.

[0030] All these terms have been explained above with respect to the method of the present invention, and therefore will not be explained again. The preferred embodiment of the emission management system of the present invention corresponds to the preferred embodiment of the method of the present invention. Attached Figure Description

[0031] Preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of components of a hydrogen fuel cell vehicle having an emission management system according to a first embodiment of the present invention; Figure 2 This is a schematic diagram of components of a hydrogen fuel cell vehicle having an emission management system according to a second embodiment of the present invention; Figure 3 This is a schematic diagram of components of a hydrogen fuel cell vehicle having an emission management system according to a third embodiment of the present invention; and Figure 4 This is a flowchart illustrating the emission management method according to the present invention. Detailed Implementation

[0032] Figure 1 A schematic diagram of some components of a hydrogen fuel cell vehicle (more specifically, an H2ICE vehicle) having a first embodiment of the emission management system 20 of the present invention is shown. The vehicle includes a hydrogen fuel cell internal combustion engine 6, shown in a highly simplified form with only a single cylinder 7 visible. The engine 6 is connected to an intake manifold 8 (typically including an intake manifold) and an exhaust manifold 9 (typically including an exhaust manifold). For each cylinder 7, an injector 10 is arranged to inject hydrogen fuel directly into the cylinder head, while an end piece 27 of a purging line 25 is arranged to inject hydrogen fuel into the intake manifold 8, corresponding to indirect injection into the engine 6. The end piece 27 may be a nozzle, a controlled injector, or may simply be the end of a pipe. The engine 6 represents the vehicle's power source, in which hydrogen is burned with oxygen to convert chemical energy into mechanical energy. The mechanical energy is used to drive the vehicle and can also be converted into electrical energy by a generator (not shown).

[0033] The hydrogen fuel required to supply the engine 6 is stored in a fuel reservoir 1, which includes at least one high-pressure fuel tank. Inside the fuel reservoir 1, the pressure can be several hundred bar(a), for example, up to 700 bar(a). The fuel reservoir 1 is connected to the engine 6 via a fuel supply system 2, which includes a hydrogen regulation module (HRM) 3 and a fuel rail assembly or fuel rail 5, which are shown schematically only. The fuel reservoir 1 typically includes a regulating valve configured to deliver hydrogen fuel to the fuel supply system 2 at a pressure of approximately 50 bar(a). The HRM 2 may include various components such as a pressure regulator to reduce the pressure of the hydrogen fuel, for example, from approximately 50 bar(a) to between 20 and 40 bar(a), a filter to remove foreign particles or droplets from the hydrogen fuel, heating or cooling devices for regulating the temperature of the hydrogen fuel, etc. In this embodiment, the fuel rail 5 represents a purgeable section 4 of the fuel supply system 2, while in other embodiments, the purgeable section 4 may be only a portion of the fuel rail 5 and / or may also include at least a portion of the HRM 3. Fuel rail 5 is connected to injector 10 via injector line 11, but can alternatively be directly connected to injector 10. Fuel rail 5 is connected to HRM 3 on its upstream side. HRM 3 includes shut-off valve 16, through which purge section 4 (i.e., fuel rail 5) and engine 6 can be disconnected from fuel reservoir 1.

[0034] When the vehicle is in operation, hydrogen fuel is supplied to injector 10 and shut-off valve 16 is open. When the vehicle enters a non-operational state with engine 6 off, shut-off valve 16 closes, isolating fuel rail 5 from fuel reservoir 1. However, a considerable amount of hydrogen fuel remains in the purgeable section 4, i.e., fuel rail 5, and remains at a considerable pressure, typically above 10 bar(a), for example between 20 and 40 bar(a).

[0035] The function of the emission management system 20 is to mitigate the risk of explosion originating from hydrogen fuel leaking from the cleanable section 4 into the engine 6, other parts of the vehicle, or the atmosphere 50 surrounding the vehicle. Figure 1 In the illustrated embodiment, the emission management system 20 includes a control device 21 that controls a purge valve 26 in a purge line 25. The purge line 25 connects the purgeable section 4 to the intake duct 8. A pressure sensor 12 is arranged to measure the pressure in the purgeable section 4 and transmit the measured value to the control device 21.

[0036] When the vehicle is in operation, control device 21 keeps purge valve 26 closed. In the event of a request to shut down the vehicle, shut-off valve 16 closes, thereby separating the purgeable section 4 from the fuel reservoir 1. Control device 21 can control shut-off valve 16 itself, or can at least receive a signal indicating a request to shut down the vehicle. A purge operation is performed before engine 6 is shut down, in this case according to a first purge mode. This first purge mode specifies that after the purgeable section 4 has been separated from the fuel reservoir 1, the hydrogen fuel residing in the purgeable section 4 reacts in the engine. Therefore, engine 6 remains running until at least a major portion of the hydrogen fuel has been consumed. The purge operation is performed until the pressure in the purgeable section 4 has reached, for example, a target pressure of 1.5 bar(a). In the illustrated embodiment, injector 10 requires a certain minimum pressure to open, therefore it cannot be used to inject hydrogen fuel throughout the entire purge operation. On the other hand, purge valve 26 can open even at low pressures. Therefore, control device 21 can use purge line 25 throughout the purge operation, or it can use injector line 11 and injector 10 when the pressure is sufficiently high.

[0037] During the purification operation, the engine can operate at least temporarily in a low-efficiency mode to increase hydrogen consumption. This low-efficiency mode can include various measures. For example, spark timing can be significantly delayed relative to top dead center (TDC), for example, until a stability limit, which can be between 50° and 60° after TDC. Another possibility is to use a small speed acceleration, for example, about 50% higher than normal idle speed. Furthermore, while using the throttle to reduce the λ value, for example, from a typical idle value between 2.5 and 3.0 to between 1.5 and 2.0, the fuel-air mixture can be enriched to maintain good stability. These measures can be controlled by a control device 21 that monitors the pressure in the purifiable section 4 and terminates the purification operation when the target pressure has been reached. During the final stage of the purification operation, when the pressure in the purifiable section 4 drops and approaches the target pressure, the engine 6 can operate in normal efficiency mode. The operation of the engine 6 corresponds to the reaction of hydrogen fuel with oxygen (which produces water). The resulting gas mixture represents a vent gas with a negligible hydrogen concentration. Specifically, the hydrogen concentration is well below the threshold concentration of, for example, 4%. Any gas mixture with a low hydrogen concentration cannot form a combustible mixture outside the vehicle. Therefore, it is safe to release the vent gas into the atmosphere. Furthermore, since the vent gas contains only a small amount of hydrogen fuel, it can be considered environmentally harmless.

[0038] Figure 2A second embodiment of the emission management system 20 of the present invention is shown. Many components are the same as in the first embodiment and will not be explained further. In this embodiment, the purge line 25 includes three branches 25.1-25.3, which are connected via a first directional valve 29. Furthermore, an orifice 28 is provided in the purge line 25, located between the purge valve 26 and the first directional valve 29. The air supply line 30 is connected to the intake manifold 8, but may alternatively be connected to the crankcase of the engine 6 or directly to the atmosphere 50. It includes a pump 31 (which may be a crankcase ventilation pump) and an air supply valve 32. It also includes three branches 30.1-30.3, which are connected via a second directional valve 33. The first branch 30.1 of the air supply line 30 and the first branch 25.1 of the purge line 25 are connected to the exhaust manifold 9, in which case the exhaust manifold 9 includes a first catalyst 14, specifically a platinum-based oxidation catalyst. Second branches 25.2 and 30.2 connect to combustion chamber 22, in which spark plug 23 is disposed. Alternatively, glow plugs may be used. Combustion chamber 22 is in communication with atmosphere 50. Third branches 25.3 and 30.3 connect to catalyst chamber 35, which also includes a second catalyst 34 that can be heated by electric heater 37. Although catalysts 14 and 34 are disposed in different locations, they can be of the same type; for example, both can be platinum-based catalysts.

[0039] In this embodiment, when the engine 6 has been deactivated and the purgeable section 4 has been disconnected from the fuel reservoir 1 via the shut-off valve 16, the control unit 21 can use the pressure sensor 12 to monitor the pressure in the purgeable section 4. Furthermore, it can use the temperature sensor 13 to monitor the temperature in the purgeable section 4 so that temperature correction can be applied to the current pressure measurement. If the pressure drop (after temperature correction) exceeds a predetermined tolerance threshold (e.g., 1 bar), this is interpreted as excessive leakage from the purgeable section 4, and therefore the control unit 21 initiates a purge operation according to a second purge mode. In this example, there are three options for how the purge operation is performed, depending on the settings of the directional valves 29, 23. While these three options are shown here for illustrative purposes, it is more realistic that only one option is available, i.e., the purge line 25 and the air supply line 30 will each consist of only a single branch.

[0040] Figure 2The purge line 25 and air supply line 30 are shown connected to their respective first branches 25.1 and 30.1. Thus, when the purge valve 26 and air supply valve 32 are open, hydrogen fuel and air are delivered to the exhaust pipe 9, where they mix and pass through the first catalyst 14. If the catalyst temperature of the first catalyst 14 has reached at least the activation temperature (e.g., 100°C), as can be verified via another temperature sensor 15, the hydrogen fuel and oxygen are catalytically converted into water. The vent gas resulting from this reaction has a hydrogen concentration significantly below the threshold concentration of 4% and can be discharged into the atmosphere 50. Second branches 25.2 and 30.2 can be activated by different settings of directional valves 29 and 33, such that the purge line 25 and air supply line 30 are connected to the combustion chamber 22. When the purge valve 26 and air supply valve 32 are open, hydrogen fuel and air enter the combustion chamber 22, where they form a mixture, which can be ignited by the spark plug 23, thereby forming water. The resulting gas mixture is also a vent gas with a low hydrogen concentration, which is safe for release into atmosphere 50. Through another arrangement of directional valves 29 and 33, third branches 25.3 and 30.3 can be activated, connecting the purge line 25 and the air supply line 30 to the catalyst chamber 35. The reaction on the second catalyst 34 corresponds to the reaction on catalyst 14. Since catalyst 34 is electrically heated, it can always be assumed that it has at least an activation temperature. Similarly, a vent gas is formed with a hydrogen concentration well below the threshold concentration and can be released into atmosphere 50.

[0041] Figure 3 A third embodiment of the emission management system 20 of the present invention is shown. Many components are the same as in the first and second embodiments, and therefore will not be explained further. In this embodiment, the purification line 25 and the air supply line 30 are non-branched and connected to the mixing container 24. Similarly, the control device 21 can initiate the purification operation based on the pressure drop in the purifiable section 4, in this case according to the third purification mode. When the purification valve 26 and the supply valve 32 are open, hydrogen fuel and air form a mixture in the mixing container 24, which represents the vent gas. The air flow through the air supply line 30 and the hydrogen flow through the purification valve 25 are mutually regulated so that the vent gas has a hydrogen concentration below a threshold concentration. Thus, the vent gas can be released to the atmosphere 50. As an alternative to using a dedicated mixing container 24, mixing can also be carried out in the outlet pipe 9.

[0042] For clarity, Figures 1 to 3 The embodiments shown are presented separately, such that each emission management system 20 is suitable for only a single purification mode. However, features of these three embodiments can be combined in a single system 20, which, depending on the situation, is suitable for all three purification modes. Reference will now be made to... Figure 4Explain the operation of this emission management system 20. Figure 4 This is a flowchart of the emission management method of the present invention.

[0043] In the first step, at 100, the vehicle's engine 6 is started. At 110, it is checked whether the engine has been turned off. If not, at 120, it is checked whether there is a key-off request, corresponding to, for example, the vehicle being deactivated at the end of a trip. If not, at 130, it is checked whether there is an engine-off request. This request can be initiated by the driver or by the start-stop system. If there is no such request, the method returns to step 110. If there is an engine-off request, at 140, it is checked whether the (first) catalyst 14 is active, i.e., whether the catalyst temperature is above the activation temperature. If not, at 150, the engine 6 is kept running, and the method returns to 110. After a period of time, the catalyst 14 will reach its activation temperature, and the method can continue in step 160 by deactivating the engine 6 (corresponding to "engine off"), and in step 170, the purgeable section 5 is disconnected from the fuel reservoir 1.

[0044] In step 180, it is checked whether the pressure drop in the purgeable section 4 is too large, i.e., whether the pressure drop exceeds the tolerance threshold. If not, at 190, it is checked whether there is a key-off request corresponding to the driver ending the trip. If not, at 200, it is checked whether there is an engine-start request. This request can also be initiated by the driver or by the start-stop system. If yes, the method returns to step 100, where the engine 6 is started. If not, it returns to step 180. If the tolerance threshold is exceeded, or if a key-off request exists, a purge operation is performed. Since the engine 6 is unavailable, only the second or third purge mode is possible at this point. At 210, it is checked again whether the catalyst 14 is active. If yes, a purge operation according to the second purge mode is performed at 220, after which at 240 it is checked whether the pressure in the purgeable section 4 is equal to or lower than the target pressure. If yes, the vehicle is deactivated (corresponding to "key-off") at step 250, and the method ends. If the pressure is still higher than the target pressure, the method returns to 210. If catalyst 14 is not active, a purification operation according to the third purification mode is performed at 230 before checking the pressure at 240. Based on the check result, the method either returns to 210 or deactivates the vehicle at 250, and the method ends.

[0045] If engine 6 is found to be off at step 110, the method immediately jumps to step 170 and continues as already described. If a key-off request has been received at step 120, the purifiable part 4 is disconnected at 260 before performing the purification operation according to the first purification mode at 270, and then the engine is deactivated at 280. Afterwards, the pressure is checked at 240, and the vehicle can be deactivated at 250 before the method ends. However, if the target pressure has not been reached, the method cannot re-enter the first purification mode because the engine has been deactivated. Therefore, it continues to step 210 and can complete the purification in either the second or third purification mode.

[0046] Legend of figure labels: 1. Fuel storage container 2. Fuel Supply System 3 HRM 4 Washable parts 5 fuel rails 6 engines 7 cylinders 8. Intake pipe 9. Exhaust pipe 10 Injectors 11. Injector piping 12 Pressure Sensors Temperature sensors 13 and 15 14,34 catalysts 16. Shut-off valve 20 Emission Management System 21 Control device 22 Combustion Chamber 23 Spark plugs 25. Purification Piping Branches 25.1-25.3 26 Purification valve 27 end pieces 28 orifices 29, 33 Directional valves 30 Air supply duct Branches 30.1-30.3 31 pumps 32 Gas supply valve 35 Catalyst Chamber 37 Electric heater 50 atmospheres

Claims

1. An emission management method for a hydrogen fuel cell vehicle, the hydrogen fuel cell vehicle including a fuel supply system (2) for supplying hydrogen fuel from a fuel storage tank (1) to a power source (6) of the vehicle when the vehicle is in operation, the fuel supply system (2) including a purifying portion (4), wherein, The method includes at least the following steps: Disconnect the cleanable portion (4) of the fuel supply system (2) from the fuel storage tank (1) (170, 260), thereby disconnecting the power source (6) from the fuel storage tank (1), wherein the hydrogen fuel is retained in the cleanable portion (4); and Perform purification operations (220, 230, 270). The purification operation includes at least: Hydrogen fuel is discharged from the cleanable section (4) to reduce the pressure in the cleanable section (4) to the target pressure; Hydrogen fuel discharged from the purifiable section (4) is used to generate vent gas inside the vehicle, such that the vent gas has a hydrogen concentration below a threshold concentration; and The vented gas is at least partially released into the atmosphere (50).

2. The method according to claim 1, wherein, The vehicle’s power source (6) is a hydrogen fuel cell internal combustion engine, and the fuel supply system (2) includes at least one of a fuel rail assembly (5) and a hydrogen regulation module (3).

3. The method according to any one of the preceding claims, wherein, In the first purification mode, the vent gas is generated by transferring hydrogen fuel at least indirectly from the purifiable part (4) to the engine (6) and burning the hydrogen fuel with oxygen inside the engine (6).

4. The method according to any one of the preceding claims, wherein, In the first purification mode, the engine (6) operates at least temporarily in an inefficient mode to increase hydrogen consumption.

5. The method according to any one of the preceding claims, the method comprising: A request to deactivate the vehicle is received when the engine (6) is in the start state; Disconnect the cleanable part (4) from the fuel storage unit (1) (260); The purification operation (270) is performed in the first purification mode while the engine (6) is kept running; and When the purification operation is completed, the engine (6) is deactivated (280).

6. The method according to any one of the preceding claims, wherein, In the second purification mode, the vent gas is generated by mixing hydrogen fuel with oxygen-containing gas and reacting the hydrogen fuel with oxygen outside the engine (6) to produce water.

7. The method according to any one of the preceding claims, wherein, Hydrogen fuel reacts with oxygen in the presence of catalysts (14, 34).

8. The method according to any one of the preceding claims, wherein, The hydrogen fuel reacts with oxygen in an exhaust pipe (9) containing the catalysts (14, 34).

9. The method according to any one of the preceding claims, the method comprising, prior to disconnecting the purifiable portion (4) from the fuel reservoir (1) (170, 260): Receive a request to deactivate the engine (6); and If the catalyst temperature of the catalyst (14, 34) is determined to be below the activation temperature, the engine (6) is kept in the start state until the activation temperature has been reached.

10. The method according to any one of the preceding claims, wherein, The hydrogen fuel reacts with oxygen through combustion outside the engine (6).

11. The method according to any one of the preceding claims, wherein, In the third purification mode, the vent gas is generated by mixing hydrogen fuel and a dilution gas, such that the hydrogen concentration in the resulting mixture is below the threshold concentration, and the dilution gas is preferably air.

12. The method according to any one of the preceding claims, wherein, The hydrogen gas is mixed with the dilution gas in the intake pipe (8) of the engine (6), the exhaust pipe (9) of the engine (6), or a dedicated mixing container (24).

13. The method according to any one of the preceding claims, the method comprising: When the engine (6) is deactivated, a request to deactivate the vehicle is received; and If the catalyst temperature of the catalysts (14, 34) is lower than the activation temperature, the purification operation (230) is performed in the third purification mode; otherwise, the purification operation (220) is performed in the second purification mode.

14. The method according to any one of the preceding claims, wherein, After disconnecting the purifiable section (4) from the fuel reservoir (1) (170, 260), if the power source (6) is deactivated, the pressure in the purifiable section (4) is monitored, and if the pressure drop in the purifiable section (4) exceeds the tolerance threshold, the purification operation is performed (220, 230).

15. An emission management system (20) for a hydrogen fuel cell vehicle, the hydrogen fuel cell vehicle including a fuel supply system (2) for supplying hydrogen fuel from a fuel storage tank (1) to a power source (6) of the vehicle when the vehicle is in operation, the fuel supply system (2) including a purifying section (4), wherein, The system (20) is configured to perform at least the following steps: Disconnect the cleanable portion (4) from the fuel storage unit (1) (170, 260), thereby disconnecting the power source (6) from the fuel storage unit (1), wherein the hydrogen fuel is retained in the cleanable portion (4); and Perform purification operations (220, 230, 270). The purification operation includes at least: Hydrogen fuel is discharged from the cleanable section (4) to reduce the pressure in the cleanable section (4) to the target pressure; Hydrogen fuel discharged from the purifiable section (4) is used to generate vent gas inside the vehicle, such that the vent gas has a hydrogen concentration below a threshold concentration; and The vented gas is at least partially released into the atmosphere (50).

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