Methods for managing emissions from hydrogen vehicles
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- PHINIA DELPHI LUXEMBOURG SARL
- Filing Date
- 2024-05-23
- Publication Date
- 2026-06-05
Smart Images
Figure 2026518383000001_ABST
Abstract
Description
Technical Field
[0001]
[0001] The present invention relates to a method for emission control of a hydrogen vehicle and an emission control system for a hydrogen vehicle.
Background Art
[0002]
[0002] As the demand for reducing CO2 emissions from on-road vehicles increases, alternatives to conventional internal combustion engines such as diesel or gasoline engines have been developed. In addition to electric vehicles powered by a battery, typically a lithium-ion battery, vehicles powered by hydrogen are a promising option. These vehicles are classified into two main categories. The first category is hydrogen fuel cell electric (H2FCE) vehicles, which also have an electric drive motor but are powered by a fuel cell that converts the energy of the chemical reaction between hydrogen and oxygen into electrical energy. The other category is hydrogen internal combustion engine (H2ICE) vehicles. In H2ICE, hydrogen (H2) is used as fuel and burned with oxygen, and the reaction product is water.
[0003]
[0003] Hydrogen fuel is stored in one or more hydrogen fuel tanks, which are connected to the engine or fuel cell by a fuel supply system that 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 any unused hydrogen may remain in the fuel supply system itself. In particular, hydrogen in the fuel supply system is typically under a pressure considerably higher than atmospheric pressure (e.g., between 2 and 4 MPa (20 to 40 bar) in the case of a fuel rail), so over time, hydrogen may leak out. If the leak is not controlled, hydrogen, or rather a hydrogen-air mixture, can accumulate in the engine and other parts of the vehicle, creating an explosion hazard, especially when restarting the vehicle. It should also be noted that hydrogen is considered a greenhouse gas, and therefore uncontrolled releases should be avoided. [Overview of the Initiative] [Problems that the invention aims to solve]
[0004]
[0004] Therefore, an object of the present invention is to minimize the amount of hydrogen emitted uncontrolled from hydrogen vehicles. [Means for solving the problem]
[0005]
[0005] This problem is solved by the method described in claim 1 and the system described in claim 15.
[0006] This invention provides a method for managing emissions from hydrogen vehicles. The term "hydrogen vehicle" refers to any vehicle that uses hydrogen as an energy source and is considered synonymous with "hydrogen-powered vehicle." Generally, this refers to road vehicles such as passenger cars, trucks, or motorcycles. However, the fuel recovery system of this invention may also be used for other vehicles, such as ships. Hereinafter, the terms "fuel," "hydrogen fuel," and "hydrogen" are synonymous. This method achieves emissions management, that is, emissions from a vehicle are managed or controlled. In detail, this relates to hydrogen emissions. Some aspects of this method are implemented by physical or "hardware" components, while others may be implemented by software. Some aspects of this method (particularly the control aspect) are considered to be implementable by external components of the hydrogen vehicle, but it is preferable that they be fully implemented using components incorporated into the vehicle. The control functions of this method may be performed by a control device of the hydrogen vehicle. Such a control device can control various functions and receive sensor signals.
[0006]
[0007] This vehicle is equipped with 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, and the fuel supply system is equipped with a purgeable portion. The fuel storage tank, which may be equipped with one or more fuel tanks, stores hydrogen fuel in a high-pressure gaseous form or in a liquid form. The power source is a device from which hydrogen fuel is converted, usually using oxygen, to release energy, which can be used to power various functions of the vehicle, in particular to drive the vehicle. Generally, 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 is sometimes also called a "fuel supply device." This explicitly includes the possibility that at least one component may be interposed between the fuel supply system and the fuel storage tank, and / or between the fuel supply system and the power source. In other words, this connection may be indirect. However, the fuel supply system is at least part of this connection. While the vehicle is in operation, the fuel supply system also fluidly connects the fuel storage tank and the power source, thereby allowing the power source to operate. "Operating state" refers to a state in which the power source is operating, hydrogen fuel is consumed, energy is generated, and as a result the vehicle is moving, or at least ready to move. In vehicles with an internal combustion engine, this is usually the same as the "engine on" state. However, the connection between the fuel tank and the engine may also be present in the "key on, engine off" state. This may also apply to vehicles, for example, those with a fuel cell power source. The fuel supply system may include at least one pipe for guiding hydrogen fuel and at least one valve, in particular a shut-off valve, for controlling the connection to the fuel tank. The fuel supply system may include a purgeable portion, which includes the possibility that the purgeable portion constitutes the entire fuel supply system. As the name suggests, this portion can be purged, as described below.
[0007]
[0008] In one step of this method, the purgeable portion is disconnected from the fuel tank, so that the power source is disconnected from the fuel tank, and the hydrogen fuel remains in the purgeable portion. This disconnection refers to a fluid disconnection, but the physical connection remains. Generally, a shut-off valve is closed to prevent (significant) fluid exchange between the fuel tank and the purgeable portion. As a result, the power source is disconnected from the fuel tank. In other words, disconnecting the purgeable portion of the fuel supply system disconnects the connection between the fuel tank and the power source. However, even after being disconnected from the fuel tank, the purgeable portion still contains hydrogen fuel. This hydrogen fuel is initially under high pressure, for example, above 2 MPa (20 bar) (a), where (a) is the absolute pressure. Different portions of the purgeable portion may have different pressures. The purgeable portion may remain connected to the power source while disconnected from the fuel tank. Alternatively, the purgeable portion may also be disconnected from the power source.
[0008]
[0009] Another step in this method involves a purging operation. The minimum objective of the purging operation described below is to prevent hydrogen emissions that could lead to the formation of a flammable air-fuel mixture inside or outside the vehicle. Optional objectives include reducing hydrogen emissions and improving energy use. The purging operation involves the following three steps, although these steps are not necessarily performed in the order listed below. In particular, there may be time overlaps between the steps.
[0009]
[0010] In one step of the purging operation, hydrogen fuel is discharged from the purgable section, reducing the pressure in the purgable section to a target pressure. In this step, the amount of hydrogen in the fuel supply system decreases, which occurs simultaneously with the pressure drop. The goal is to reduce the pressure to a predetermined target pressure, or possibly even lower. The target pressure is typically not greater than 0.5 MPa (5 bar)(a), and can be, for example, 0.2 MPa (2 bar)(a) or 0.15 MPa (1.5 bar)(a) or less. The target pressure can preferably be chosen so that any potential hydrogen leakage from the purgable section does not lead to the formation of a flammable gas mixture. It is also preferable that at least 50%, at least 70%, at least 90%, or at least 95% of the hydrogen fuel initially contained in the purgable section is discharged. A smaller amount of hydrogen in the purgable section means less hydrogen that can leak uncontrolled into the atmosphere. After transfer, any potential leaks from the purgable section will not (or are unlikely to) produce a flammable mixture. While the hydrogen fuel is discharged or transferred from the purgable section, it is not released directly into the atmosphere. Rather, it is retained within the vehicle for another step in the purging operation.
[0010]
[0011] In another step of the purging operation, vent gas is generated in the vehicle using hydrogen fuel discharged from the purgable section, such that the vent gas has a hydrogen concentration below a threshold concentration. Here and below, “hydrogen concentration” is used synonymously with “hydrogen fuel concentration” or “H2 concentration” and refers to the concentration of elemental hydrogen gas (H2). The vent gas is a gas mixture. The vent gas may contain a non-negligible concentration of hydrogen fuel, but below a predetermined threshold concentration. The threshold concentration can be set so that the vent gas can be considered safe (i.e., non-flammable). This is usually ensured by a threshold concentration of 4% or less. Under these circumstances, the vent gas does not exhibit a flammable mixture, even with a high oxygen content. In most embodiments, the oxygen concentration of the vent gas is similar to or lower than that of air (i.e., about 21%). In some embodiments, all of the hydrogen fuel discharged from the purgable section is used to generate the vent gas, but it is also possible to use only a portion of the discharged hydrogen fuel. At least 80% of the discharged hydrogen fuel. Alternatively, it is preferable that at least 90% is used for the vent gas. It should be noted that all the hydrogen used to generate the vent gas is present in the vent gas, but not in elemental form, i.e., in the form of H2 gas, but may exist as some compounds, particularly water (H2O).
[0011]
[0012] In yet another purging step, the vent gas is released at least partially into the atmosphere. It can also be said that the vent gas is released into the atmosphere surrounding the vehicle. While it is preferable that the vent gas be released while the vehicle is outdoors, this can also be done while the vehicle is inside a building, such as an underground parking garage. In this respect, the interior of a building can also be considered part of the "atmosphere." Since the vent gas has a hydrogen concentration below the threshold concentration, its release can be considered safe by certain safety standards. In particular, it can prevent the formation of flammable mixtures outside the vehicle. In some embodiments, the entire amount of vent gas can be released into the atmosphere, while in other embodiments, only a portion is released.
[0012]
[0013] In any case, the method of the present invention reduces the risk of fire or explosion that may arise from hydrogen fuel remaining in the purgable portion of a fuel supply system. When the pressure in the purgable portion is reduced to the target pressure, any hydrogen leakage from the purgable portion will not lead to a flammable mixture. Furthermore, such leakage will release only a small amount of hydrogen into the atmosphere. By generating and releasing the vent gas described above, the method produces only emissions that can be considered safe from a fire hazard standpoint. In the specific embodiments discussed below, the hydrogen content of the emissions is also minimized with environmental considerations in mind.
[0013]
[0014] The vehicle may be an H2FCE vehicle, and the power source may be a fuel cell. In this 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 electric drive motor and other electrically operated systems of the vehicle. In another preferred embodiment, the power source of the vehicle is a hydrogen internal combustion engine, and the fuel supply system comprises at least one of a fuel rail assembly and a hydrogen adjustment module. A hydrogen internal combustion engine (H2ICE) is used to burn hydrogen with oxygen, and the reaction product is water. Since air rather than pure oxygen is used, it will be understood that its combustion may produce small amounts of other products. Generally, an H2ICE has at least one cylinder with an intake valve, the cylinder communicating with an intake duct via the intake valve. A movable piston is located inside the cylinder, and the piston may be connected to a crankshaft. Each cylinder may have an injector for directly injecting hydrogen fuel into the cylinder. Here and below, “intake duct” refers to any duct through which air passes when the engine and / or at least one cylinder of the engine takes in air. Therefore, this term explicitly includes the intake manifold. Typically, the cylinder also has an exhaust valve that communicates with the exhaust duct (this term explicitly includes the exhaust manifold). Hydrogen fuel can be injected directly into each cylinder. It can also be injected into the intake duct (i.e., upstream of the intake valve), which constitutes indirect injection (e.g., port fuel injection). A combination of both is also possible. Each injector can be connected to a fuel rail or fuel rail assembly, from which it receives hydrogen fuel. The fuel rail may be part of the purgable section, or it may represent the entire purgable section. Typically, the fuel rail is not connected directly to the fuel tank, but via a hydrogen regulation module (HRM) that can perform several functions.The HRM may include a pressure regulator to reduce the hydrogen fuel pressure from, for example, about 5 MPa (50 bar) (a) in the fuel tank to between 2 and 4 MPa (20 to 40 bar) (a) suitable for the operation of the fuel rail and injector. The HRM may also include a filter to remove foreign particles or droplets from the hydrogen fuel. Other elements of the HRM may include a heat exchanger or other heating or cooling device to regulate the fuel temperature. A purgable portion may include at least part of the HRM. In other embodiments, the purgable portion (e.g., fuel rail) may be connected directly to the fuel storage tank without a specific HRM.
[0014]
[0015] There are various options for generating vent gas. One option is to utilize the engine to convert the hydrogen fuel being discharged from the purgable section. In this embodiment, in the first purge mode, the vent gas is generated by transferring the hydrogen fuel at least indirectly from the purgable section to the engine and burning it with oxygen inside the engine. The terms “first,” “second,” and “third purge mode” used here and below are used solely to distinguish between different modes and do not imply any order or priority. Furthermore, embodiments of this method may include a second (third) purge mode without including the first (and second) purge modes. In the first purge mode, the hydrogen fuel is injected directly into the engine (i.e., at least one cylinder) and / or into the intake duct. The hydrogen fuel is burned with oxygen to produce water. The resulting gas mixture contains a fairly small or negligible amount of hydrogen fuel. This vent gas can then be released into the atmosphere through the vehicle’s exhaust duct. It will be understood that the vent gas may contain a large amount of moisture resulting from combustion. Normally, this moisture remains gaseous until released into the atmosphere, but it may also form aerosols in the vent gas or 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 can be used for the first purge mode. In this context, it may be relevant that some injectors used during normal operation require a specific minimum pressure to open. During the first purge mode, the pressure in the purging portion drops towards the target pressure and may become too low for the normal injectors; therefore, a dedicated injector or valve is required for the purge operation. In the first purge mode, the engine runs at idle while disconnected from the fuel reservoir. Therefore, engine operation is typically limited to a few seconds. The first purge mode can be sustained until the target pressure is reached or the hydrogen fuel supplied to the engine becomes insufficient to maintain stable combustion in the engine.If the latter occurs before the target pressure is reached, a different purge mode can be entered after the first purge mode.
[0015]
[0016] In the first purge mode, it is preferable that the engine be operated in a low-efficiency mode, at least temporarily, to increase hydrogen consumption. Such a low-efficiency mode can include various measures. For example, the ignition timing may be retarded considerably relative to top dead center (TDC). Depending on the engine, this can be done up to the limit of stability, which may be between 50° and 60° after TDC. Another possible measure is to slightly increase the speed, for example, to a speed about 50% above the normal idling speed. It is also possible to use the throttle to lower the lambda value, for example, from the typical idling value of between 2.5 and 3.0 to between 1.5 and 2.0, to enrich the fuel-air mixture and maintain good stability. Yet another option is to maximize any auxiliary loads, if possible. The low-efficiency mode may be maintained throughout the entire purge operation. Alternatively, the normal-efficiency mode may be used in the final stage of the purge operation, which may be beneficial when the pressure in the fuel supply system is dropping and approaching the target pressure.
[0016]
[0017] In one preferred embodiment, the method is - A step of receiving a request to stop the vehicle while the engine is running, - A step of cutting off the purging portion from the fuel storage tank, - A step of performing a purge operation in the first purge mode while the engine is running, - When the purging operation is complete, the engine is stopped. This includes the following. In this embodiment, it can be said that the inevitable engine shutdown when the vehicle is stopped is delayed until the purge operation is complete. The request to stop the vehicle can also be called a “key off” request or “ignition off” request, meaning an “engine off” request. In this context, a key off request typically indicates that the driver wants to end the drive, or at least interrupt it for a long period of time. Therefore, it is reasonable to remove most of the hydrogen fuel from the purgeable portion to minimize the risk of leakage. Since the engine is running (i.e., driving) when the request is received, the purge operation of the first purge mode can be performed immediately. Most of the hydrogen fuel in the purgeable portion is converted to water, thereby significantly reducing hydrogen fuel emissions. Also, the energy generated by the engine during the purge operation can be stored in the vehicle's battery and made available when the vehicle is restarted.
[0017]
[0018] In another embodiment, in a second purge mode, vent gas is produced by mixing hydrogen fuel with an oxygen-containing gas and reacting it with oxygen outside the engine to produce water. Here and below, the term “mixing” refers to passive mixing as well as active mixing. Thus, it can be said that hydrogen fuel is mixed with an oxygen-containing gas. Furthermore, this mixing does not need to produce a homogeneous mixture, although a homogeneous mixture is generally advantageous for the reaction. This embodiment does not use an engine to convert the hydrogen fuel and can therefore be used when the engine is stopped (i.e., stationary). However, the second purge mode can also be used while the engine is running and, optionally, can even be used simultaneously with the first purge mode. The second purge mode also relies on a chemical reaction of hydrogen fuel with oxygen to produce water. Thus, the hydrogen content in the gas mixture can be significantly reduced to a negligible amount. The oxygen-containing gas is usually air, but depending on the particular embodiment, it can have a somewhat different composition. For example, it can include exhaust gas from an engine with a lower oxygen content than air. The gas mixture produced by mixing hydrogen fuel with an oxygen-containing gas preferably has a hydrogen concentration of at least 2%. Depending on the embodiment, it may be beneficial to have a hydrogen concentration of up to 10% or up to 30%.
[0018]
[0019] According to a preferred embodiment, the hydrogen fuel is reacted with oxygen in the presence of a catalyst. This catalyst, also called an oxidation catalyst, enables or promotes the water production reaction between hydrogen and oxygen. This catalyst can be, for example, a platinum-based catalyst. Generally, the catalyst requires an activation temperature (typically around 100°C), which may be higher than the ambient temperature. Below this activation temperature, the catalyst is ineffective. Also, a minimum concentration of a particular hydrogen, for example, 2%, is required for effective operation. On the other hand, it should not exceed a specific maximum concentration, for example, 10%, because exceeding this can lead to a temperature at which the reaction can damage the catalyst. The catalyst temperature may depend on the vehicle's operating time (and other operating conditions). If the vehicle is only operated for a short time, the temperature may be insufficient. In such cases, the catalyst can be heated with a dedicated electric heater.
[0019]
[0020] In particular, hydrogen fuel can be reacted with oxygen in an exhaust duct equipped with a catalyst. In this context, the term “exhaust duct” refers to any container connected to an engine that receives exhaust gases during normal engine operation. Thus, in addition to components that transfer exhaust gases from the engine to the atmosphere, the exhaust duct can also be an EGR (exhaust gas recirculation) duct. The catalyst may be provided as a lining for the exhaust duct (or a part thereof). After the engine has been running for some time, it can be expected that the exhaust duct will be above the catalyst's activation temperature. This condition will likely persist for some time after the engine has stopped. It is advantageous that “waste heat” from the exhaust gases can be used to heat the exhaust duct and provide the catalyst with the necessary temperature. In this embodiment, the mixing of hydrogen fuel with oxygen-containing gases may occur inside the exhaust duct, but may also occur, at least in part, outside the exhaust duct (i.e., upstream), for example, inside the engine or in the intake duct.
[0020]
[0021] According to one embodiment, the method includes the steps of receiving a request to stop the engine before the purgable portion is disconnected from the fuel tank, and, if it is determined that the catalyst temperature is below the activation temperature, keeping the engine running until the activation temperature is reached. The request to stop the engine may also be called an “engine off” request. This request may be issued by the driver of the vehicle or by a start-stop system that stops the engine, for example, when it is idling for a few seconds. Regardless of the source of the request, the engine is not automatically stopped, and the catalyst temperature is measured and compared to the activation temperature described above. It should be noted that the “activation temperature” referred to in this embodiment may differ from the “actual” activation temperature of each catalyst. For example, the activation temperature used for comparison may be chosen to be higher in order to ensure that the catalyst is fully activated. The catalyst temperature is measured, which may refer to a direct measurement of the catalyst temperature. Alternatively, the temperature of the exhaust duct or any other component that is thermally related to the catalyst may be measured. It is even possible to omit temperature measurements altogether, and if the vehicle has been running for a certain period of time, the catalyst temperature can be assumed to be higher than the activation temperature. If the catalyst temperature is determined to be lower than the activation temperature, the engine continues to operate until it reaches the activation temperature. If the catalyst temperature is initially determined to be higher than (or equal to) the activation temperature, the engine can be stopped without delay. This embodiment ensures that a purge operation by a second purge mode can be performed if necessary.
[0021]
[0022] As an alternative to catalytic conversion, hydrogen fuel can be reacted with oxygen by combustion outside the engine. The main reaction product of combustion is water, but several by-products may also be produced. Combustion takes place 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 may be preferable to burn the hydrogen fuel only gradually. While the catalytic reaction described above usually requires relatively low hydrogen concentrations, combustion can be carried out at higher concentrations, e.g., between 8% and 30%. It will be understood that the respective lower and upper limits also depend on the oxygen concentration. The values shown here apply when the hydrogen fuel is mixed with air or a gas mixture having a similar oxygen concentration.
[0022]
[0023] The first and second purging modes described above effectively reduce the amount of hydrogen fuel released into the atmosphere. While this is preferable, it may be necessary and permissible to release hydrogen fuel as part of the vent gas while keeping the hydrogen concentration within a safe range. In one embodiment, in a third purging mode, the vent gas is produced by mixing hydrogen fuel with a diluent gas, preferably air, such that the hydrogen concentration of 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. Generally, the diluent gas can be any gas having a hydrogen concentration considerably lower than the threshold concentration. The diluent gas is preferably air, which is introduced into the vehicle and mixed with the hydrogen fuel. However, its composition may differ from that of air, for example, because its oxygen content is reduced by the combustion process inside the hydrogen vehicle. This mixing occurs in a mixing vessel, and the diluent gas, specifically air, can be introduced into this vessel by actively generating a gas flow. The gas flow, preferably an air flow, can be generated by various means. This can be generated by the engine, but 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.
[0023]
[0024] There are various options for the mixing vessel in which the hydrogen fuel is mixed with the diluent gas. One option is to mix it in the engine's intake duct. Another option is the exhaust duct. In these cases, if the exhaust duct is equipped with the aforementioned oxidation catalyst, at least a partial reaction between the hydrogen fuel and oxygen in the diluent gas is possible, provided the catalyst temperature facilitates such a reaction. In this case, the second and third purge modes are not clearly distinguished. Another option is a dedicated mixing vessel, i.e., a container inside the vehicle used solely for generating vent gas through mixing. Partially relying on the mixing vessel, the transfer of the hydrogen fuel can be controlled by a dedicated purge valve or an injector also used during normal engine operation. The latter may be possible if the engine system is compatible with indirect injection, i.e., if the hydrogen fuel from the purgable portion is injected into the intake duct. In this case, each injector can also be used in the third purge mode, and the intake duct can function as a mixing vessel. However, some injectors can only open at pressures above a certain minimum pressure, which are available while the engine is running and the purgable portion is connected to the fuel tank, but not throughout the entire purging operation. In this case, this transfer needs to be controlled by a dedicated purge valve that does not require a specific minimum pressure.
[0024]
[0025] In one embodiment, the method includes receiving a request to stop the vehicle while the engine is stopped, and performing a purge operation in a third purge mode when the catalyst temperature of the catalyst is lower than the operating temperature, or performing a purge operation in a second purge mode otherwise. The request to stop the vehicle, also referred to as a "key-off" request or an "ignition-off" request, is received while the engine is stopped. The first purge mode requires engine restart, which is not desirable if a key-off request has already been received. Thus, the purge operation can be performed in either the second purge mode or the third purge mode. The second purge mode is selected when the catalyst has already reached the activation temperature and thus the catalyst can be used to promote the hydrogen-oxygen reaction. The third purge mode is used when the catalyst is lower than the activation temperature (which is rare when the engine has been operated for a non-negligible period).
[0025]
[0026] In one embodiment, after disconnecting the purgeable portion from the fuel storage tank, when the power source is stopped, the pressure of the purgeable portion is monitored, and when the pressure drop of the purgeable portion exceeds an allowable threshold, a purge operation is performed. In a situation where the purgeable portion is disconnected from the fuel storage tank and the power source (e.g., the engine) is stopped, the pressure of the purgeable portion, which is normally connected to the power source, should remain substantially constant if there is no significant leak. However, if hydrogen fuel is leaking from the purgeable portion, the pressure of the purgeable portion will decrease over time. An allowable threshold can be defined considering minor allowable leaks, measurement errors, etc. When the pressure drop exceeds the allowable threshold (for example, it may be between 0.05 MPa (0.5 bar) and 0.2 MPa (2.0 bar)), this is interpreted as a significant leak and a purge operation is performed. It should be noted that the temperature variation of the purgeable portion may need to be considered in the calculation of the pressure drop. When the power source is stopped, it can be expected that the actual pressure of the purgeable portion will decrease after a while due to the temperature drop. Therefore, when the pressure drop is determined, the temperature-corrected pressure should be calculated.
[0026]
[0027] The present invention further provides an emission management system for a hydrogen vehicle, the vehicle comprising a fuel supply system for supplying hydrogen fuel from a fuel storage tank to a power source of the vehicle when the vehicle is in an operating state, the fuel supply system comprising a purgeable portion, and the emission management system comprising: - a step of disconnecting the purgeable portion from the fuel storage tank such that the power source is disconnected from the fuel storage tank, with hydrogen fuel remaining within the purgeable portion; - a step of performing a purge operation; and being configured to perform at least: - a step of discharging hydrogen fuel from the purgeable portion to reduce the pressure of the purgeable portion to a target pressure; - a step of generating within the vehicle, using the hydrogen fuel discharged from the purgeable portion, vent gas having a hydrogen concentration lower than a threshold concentration; - a step of at least partially discharging the vent gas into the atmosphere. and at least including.
[0027]
[0028] All of these terms have been described above with respect to the method of the present invention and will not be described again. Preferred embodiments of the emission management system of the present invention correspond to preferred embodiments of the method of the present invention.
[0028]
[0029] Next, preferred embodiments of the present invention will be described by way of example only with reference to the accompanying drawings.
Brief Description of the Drawings
[0029] [Figure 1] It is a schematic diagram of components of a hydrogen vehicle having an emission management system according to a first embodiment of the present invention. [Figure 2] It is a schematic diagram of components of a hydrogen vehicle having an emission management system according to a second embodiment of the present invention. [Figure 3]This is a schematic diagram of the components of a hydrogen vehicle having an emissions management system according to a third embodiment of the present invention. [Figure 4] This is a flowchart showing the emission control method according to the present invention. [Modes for carrying out the invention]
[0030]
[0030] Figure 1 is a schematic diagram of some elements of a hydrogen vehicle, more specifically an H2ICE vehicle, having a first embodiment of the emission control system 20 of the present invention. The vehicle is equipped with a hydrogen internal combustion engine 6, which is shown in a highly simplified form with only a single cylinder 7 shown. The engine 6 is connected to an intake duct 8 (which usually includes an intake manifold) and an exhaust duct 9 (which usually includes an exhaust manifold). Each cylinder 7 is equipped with an injector 10 to inject hydrogen fuel directly into the cylinder head, while the end 27 of a purge line 25 is equipped to inject hydrogen fuel into the intake duct 8, which constitutes indirect injection into the engine 6. The end 27 can be a nozzle, a controllable injector, or simply the end of a pipe. The engine 6 represents the power source of the vehicle, in which hydrogen burns with oxygen to convert chemical energy into mechanical energy. This mechanical energy is used to drive the vehicle and can also be converted into electrical energy through a generator (not shown).
[0031]
[0031] The hydrogen fuel required to supply the engine 6 is stored in a fuel storage tank 1, which comprises at least one high-pressure fuel tank. The pressure inside the fuel storage tank 1 may be several tens of MPa (hundreds of bar)(a), for example up to 70 MPa (700 bar)(a). The fuel storage tank 1 is connected to the engine 6 via a fuel supply system 2, which comprises a hydrogen regulating module (HRM) 3 and a fuel rail assembly or fuel rail 5, which are shown only schematically. The fuel storage tank 1 typically includes a regulating valve configured to supply hydrogen fuel to the fuel supply system 2 at a pressure of about 5 MPa (50 bar)(a). The HRM 2 may comprise various elements such as a pressure regulator that reduces the pressure of the hydrogen fuel from, for example, about 5 MPa (50 bar)(a) to between 2 and 4 MPa (20 to 40 bar)(a), a filter for removing foreign particles or droplets from the hydrogen fuel, and a heating or cooling device for regulating the temperature of the hydrogen fuel. In this embodiment, the fuel rail 5 represents the purgeable portion 4 of the fuel supply system 2, but in other embodiments, the purgeable portion 4 may consist only of a portion of the fuel rail 5 and / or comprise at least a portion of the HRM 3. The fuel rail 5 is connected to the injector 10 via the injector line 11, but it may also be connected directly to the injector 10 instead. The fuel rail 5 is connected to the HRM 3 upstream of it. The HRM 3 comprises a shut-off valve 16 that can disconnect the purgeable portion 4 (i.e., the fuel rail 5) and the engine 6 from the fuel storage tank 1.
[0032]
[0032] While the vehicle is in operation, hydrogen fuel is supplied to the injector 10 and the shut-off valve 16 is open. When the vehicle enters a non-operating state with the engine 6 stopped, the shut-off valve 16 is closed so that the fuel rail 5 is isolated from the fuel storage tank 1. However, a considerable amount of hydrogen fuel is still present in the purged portion 4, i.e., the fuel rail 5, and is still at a considerable pressure, typically higher than 1 MPa (10 bar)(a), for example, between 2 and 4 MPa (20 and 40 bar)(a).
[0033]
[0033] The function of the emissions control system 20 is to mitigate the risk of explosion resulting from hydrogen fuel leaking from the purgable section 4 into the engine 6, into other parts of the vehicle, or into the atmosphere 50 around the vehicle. In the embodiment shown in Figure 1, the emissions control system 20 includes a control device 21 that controls a purge valve 26 of a purge line 25. The purge line 25 connects the purgable section 4 to an intake duct 8. A pressure sensor 12 is positioned to measure the pressure in the purgable section 4 and transmits the measurement to the control device 21.
[0034]
[0034] While the vehicle is in operation, the control device 21 keeps the purge valve 26 closed. If there is a request to stop the vehicle, the shut-off valve 16 is closed, thereby separating the purgable portion 4 from the fuel storage tank 1. The control device 21 can control the shut-off valve 16 itself or at least receive a signal indicating a request to stop the vehicle. Before the engine 6 is stopped, a purge operation is performed in this case according to a first purge mode. In this first purge mode, after the purgable portion 4 is separated from the fuel storage tank 1, the hydrogen fuel present in the purgable portion 4 reacts in the engine. Thus, the engine 6 is kept in operation until at least a large portion of the hydrogen fuel is consumed. The purge operation is performed until the pressure in the purgable portion 4 reaches a target pressure, for example, 0.15 MPa (1.5 bar) (a). In the illustrated embodiment, the injector 10 requires a certain minimum pressure to open and therefore cannot be used to inject hydrogen fuel throughout the entire purge operation. On the other hand, the purge valve 26 can be opened even at low pressure. Therefore, the control device 21 can use the purge line 25 throughout the entire purge operation, or use the injector line 11 and injector 10 while the pressure is sufficiently high.
[0035]
[0035] During the purge operation, the engine can be operated in a low-efficiency mode, at least temporarily, to increase hydrogen consumption. Such a low-efficiency mode can include various measures. For example, the ignition timing may be retarded considerably with respect to top dead center (TDC), for example, to a stable limit, which may be between 50° and 60° after TDC. Another possible measure is to slightly increase the speed, for example, to a speed about 50% above the normal idling speed. It is also possible to use the throttle to lower the lambda value, for example, from between 2.5 and 3.0, which is the typical idling value, to between 1.5 and 2.0, to enrich the fuel-air mixture and maintain good stability. These measures can be controlled by a control device 21 that monitors the pressure in the purgable section 4 and terminates the purge operation when the target pressure is reached. In the final stage of the purge operation, as the pressure in the purgable section 4 drops and approaches the target pressure, the engine 6 may operate in a normal efficiency mode. The operation of the engine 6 corresponds to the reaction of hydrogen fuel with oxygen to produce water. The resulting gas mixture exhibits a vent gas with a negligible hydrogen concentration. More specifically, the hydrogen concentration is far lower than, for example, a 4% threshold concentration. Gas mixtures with lower hydrogen concentrations cannot form a flammable mixture outside the vehicle. Therefore, the vent gas can be released into the atmosphere without any problems. Furthermore, since the vent gas contains only a very small amount of hydrogen fuel, it is considered to pose no environmental problems.
[0036]
[0036] Figure 2 shows a second embodiment of the exhaust management system 20 of the present invention. Many of the components are the same as those of the first embodiment and will therefore not be described again. In this embodiment, the purge line 25 comprises three branch pipes 25.1 to 25.3, which are connected by a first directional valve 29. An orifice 28 is also located in the purge line 25 between the purge valve 26 and the first directional valve 29. The air supply line 30 is connected to the intake duct 8, but can instead be connected to the crankcase of the engine 6 or directly to the atmosphere 50. The air supply line 30 comprises a pump 31 (which may be a crankcase ventilation pump) and an air supply valve 32. The air supply line 30 further comprises three branch pipes 30.1 to 30.3, which are connected by a second directional valve 33. The first branch pipes 25.1, 30.1 of the air supply line 30 and the purge line 25 are connected to an exhaust duct 9, which in this case includes a first catalyst 14, more specifically an oxidation catalyst which may be platinum-based. The second branch pipes 25.2, 30.2 are connected to a combustion chamber 22 where a spark plug 23 is located. Alternatively, a glow plug may be used. The combustion chamber 22 is in communication with the atmosphere 50. The third branch pipes 25.3, 30.3 are connected to a catalyst chamber 35 which also includes a second catalyst 34 which can be heated by an electric heater 37. The catalysts 14, 34 are located in different positions but may be of the same type, for example, both may be platinum-based catalysts.
[0037]
[0037] In this embodiment, when the engine 6 is stopped and the purgable section 4 is separated from the fuel storage tank 1 by closing the shut-off valve 16, the control device 21 can monitor the pressure of the purgable section 4 using the pressure sensor 12. The control device 21 can also monitor the temperature of the purgable section 4 using the temperature sensor 13 in order to perform temperature correction on the pressure measurement at that time. If the pressure drop (after temperature correction) exceeds a predetermined allowable threshold (e.g., 0.1 MPa (1 bar)), this is interpreted as excessive leakage from the purgable section 4, and therefore the control device 21 starts a purge operation according to the second purge mode. In this example, there are three options for the purge operation that can be performed depending on the settings of the directional valves 29 and 33. Although these three options are shown here for illustrative purposes, it is more realistic that only one option is available, i.e., that the purge line 25 and the air supply line 30 each have only a single branch pipe.
[0038]
[0038] Figure 2 shows the purge line 25 and air supply line 30 connected to the first branch pipes 25.1 and 30.1, respectively. Thus, when the purge valve 26 and air supply valve 32 are opened, hydrogen fuel and air are transferred to the exhaust duct 9, where they mix and pass through the first catalyst 14. As can be confirmed by another temperature sensor 15, if the catalytic temperature of the first catalyst 14 has reached at least the activation temperature (e.g., 100°C), the hydrogen fuel and oxygen are converted to water by catalytic action. The vent gas resulting from this reaction has a hydrogen concentration considerably lower than the 4% threshold concentration and can be discharged into the atmosphere 50. Different settings of the directional valves 29 and 33 can be used to operate the second branch pipes 25.2 and 30.2 so 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 opened, hydrogen fuel and air enter the combustion chamber 22, where they form a mixture which is ignited by the spark plug 23, thereby forming water. The resulting gas mixture is a vent gas with a low hydrogen concentration that is also safe to release into the atmosphere 50. Further settings of the directional valves 29 and 33 can operate third branch pipes 25.3 and 30.3 so that the purge line 25 and air supply line 30 are connected to the catalyst chamber 35. The reaction in the second catalyst 34 corresponds to the reaction in catalyst 14. Since catalyst 34 is electrically heated, it can be assumed that it always has at least an active temperature. In this case as well, a vent gas with a hydrogen concentration well below the threshold concentration is formed and can be released into the atmosphere 50.
[0039]
[0039] Figure 3 shows a third embodiment of the emission control system 20 of the present invention. Many of the components are the same as those of the first and second embodiments and will therefore not be described again. In this embodiment, the purge line 25 and the air supply line 30 do not branch and are connected to the mixing vessel 24. Again, the control device 21 can initiate a purge operation according to a third purge mode, in this case depending on the pressure drop in the purgable section 4. When the purge valve 26 and the supply valve 32 are opened, the hydrogen fuel and air form a mixture in the mixing vessel 24, and this mixture becomes the vent gas. The air flow rate through the air supply line 30 and the hydrogen flow rate through the purge valve 25 are adjusted relative to each other so that the vent gas has a hydrogen concentration below a threshold concentration. Thus, the vent gas can be released into the atmosphere 50. Instead of using a dedicated mixing vessel 24, mixing can also be performed in the intake duct 8 or exhaust duct 9.
[0040]
[0040] For clarity, the embodiments shown in Figures 1 to 3 are shown separately so that each emission control system 20 is adapted to only a single purge mode. However, the features of these three embodiments can be combined, depending on the situation, into a single system 20 adapted to all three purge modes. The operation of such an emission control system 20 will now be described with reference to Figure 4, which is a flowchart of the emission control method of the present invention.
[0041]
[0041] In the first step 100, the engine 6 of the automobile is started. In step 110, it is checked whether the engine is stalled. If not, in step 120, it is checked whether there is a key-off request (corresponding to the automobile being stopped, such as at the end of a drive). If not, in step 130, it is checked whether there is an engine-off request. Such a request may be issued by the driver or the start-stop system. If there is no such request, the method returns to 110. If there is an engine-off request, in 140, it is checked whether the (first) catalyst 14 is active, i.e., whether the catalyst temperature is higher than the activation temperature. If not, the engine 6 is kept running in 150 and the method returns to 110. After some time, the catalyst 14 reaches the activation temperature and the method stops the engine 6 in step 160 (corresponding to "engine off"), thereby disconnecting the purged portion 5 from the fuel storage tank 1 in step 170.
[0042]
[0042] In step 180, it is checked whether the pressure drop in the purgable portion 4 is excessive, i.e., whether it exceeds the acceptable threshold. If not, in step 190, it is checked whether there is a key-off request corresponding to the driver ending the drive. If not, in step 200, it is checked whether there is an engine-on request. In this case as well, such a request may be issued by the driver or the start-stop system. If so, the method returns to step 100 and the engine 6 is started. Otherwise, it returns to step 180. If the acceptable threshold is exceeded or there is a key-off request, a purge operation is performed. Since the engine 6 is unavailable, only the second or third purge mode is possible at this time. In step 210, it is checked again whether the catalyst 14 is active. If so, in step 220, a purge operation is performed using the second purge mode, and then in step 240, it is checked whether the pressure in the purgable portion 4 is below the target pressure. If so, in step 250 the vehicle is stopped (corresponding to "key off") and the method ends. If the pressure is still higher than the target pressure, the process returns to 210. If catalyst 14 is not in an active state, a purge operation using a third purge mode is performed at 230 before the pressure is confirmed at 240. Depending on the confirmation result, the process returns to 210, or the vehicle is stopped at 250 and the process ends.
[0043]
[0043] If it is found that the engine 6 is stalled in step 110, the method immediately jumps to step 170 and continues as already described. If it is found that a key-off request has been received in step 120, the purgable portion 4 is disconnected in step 260, a purge operation is performed in the first purge mode in step 270, and then the engine is stopped in step 280. After that, the pressure is checked in step 240, and the method ends after the vehicle is stopped in step 250. However, if the target pressure has not been reached, the method cannot re-enter the first purge mode because the engine has already stopped. Therefore, the state in step 210 can be continued and the purge can be completed in either the second purge mode or the third purge mode. Explanation of the symbols 1 Fuel storage tank 2. Fuel supply system 3 HRM 4. Purgeable parts 5 Fuel rails 6 engines 7 cylinders 8. Intake duct 9. Exhaust duct 10 Injectors 11 Injector lines 12 Pressure Sensor 13, 15 Temperature sensor 14, 34 Catalyst 16 Shut-off valve 20 Exhaust Management System 21 Control device 22 Combustion chamber 23 Spark plugs 25 Purge Line 25.1~25.3 Branch pipe 26 Purge valve 27 Terminal part 28 Orifice 29, 33 Directional valves 30 Air supply line 30.1~30.3 Branch pipe 31 pumps 32 Air supply valve 35 Catalyst chamber 37 Electric heater 50 Atmosphere
Claims
1. A method for managing emissions from a hydrogen vehicle, wherein the vehicle is equipped with a fuel supply system (2) for supplying hydrogen fuel from a fuel storage tank (1) to the vehicle's power source (6) when the vehicle is in operation, and the fuel supply system (2) is equipped with a purgeable portion (4), Steps (170, 260) include disconnecting the purgeable portion (4) of the fuel supply system (2) from the fuel storage tank (1) so that the power source (6) is disconnected from the fuel storage tank (1), wherein hydrogen fuel remains in the purgeable portion (4), Steps to perform the purging operation (220, 230, 270) The purging operation includes at least the following: The steps include: discharging hydrogen fuel from the purgable portion (4) to reduce the pressure in the purgable portion (4) to a target pressure; The steps include: generating vent gas inside the vehicle using hydrogen fuel discharged from the purgable portion (4) such that the vent gas has a hydrogen concentration lower than a threshold concentration; The vent gas is released at least partially into the atmosphere (50) and A method that includes at least the following.
2. The method according to claim 1, A method wherein the power source (6) of the automobile is a hydrogen internal combustion engine, and the fuel supply system (2) comprises at least one of a fuel rail assembly (5) and a hydrogen adjustment module (3).
3. A method according to claim 1 or 2, A method comprising, in a first purge mode, transferring hydrogen fuel at least indirectly from the purgable portion (4) to the engine (6), and generating the vent gas by combustion with oxygen inside the engine (6).
4. A method according to any one of claims 1 to 3, A method in which, in the first purge mode, the engine (6) is operated in a low-efficiency mode at least temporarily to increase hydrogen consumption.
5. The method according to any one of claims 1 to 4, The steps include receiving a request to stop the vehicle while the engine (6) is running, The steps include: cutting the purging portion (4) from the fuel storage tank (1) (260), While the engine (6) maintains an operating state, the purge operation (270) is performed in the first purge mode, When the purging operation is completed, the engine (6) is stopped (step 280) Methods that include...
6. A method according to any one of claims 1 to 5, In a second purge mode, the vent gas is generated by mixing hydrogen fuel with an oxygen-containing gas and reacting it with oxygen outside the engine (6) to produce water.
7. A method according to any one of claims 1 to 6, A method for reacting hydrogen fuel with oxygen in the presence of catalysts (14, 34).
8. A method according to any one of claims 1 to 7, A method in which the hydrogen fuel is reacted with oxygen in an exhaust duct (9) equipped with the catalysts (14, 34).
9. The method according to any one of claims 1 to 8, Before the step (170, 260) in which the purged portion (4) is cut off from the fuel storage tank (1), The steps include receiving a request to stop the engine (6), If it is determined that the catalyst temperature of the catalyst (14, 34) is lower than the activation temperature, the engine (6) is kept in operation until the activation temperature is reached. Methods that include...
10. A method according to any one of claims 1 to 9, A method in which the hydrogen fuel is reacted with oxygen by combustion outside the engine (6).
11. A method according to any one of claims 1 to 10, A method wherein, in a third purging mode, the vent gas is produced by mixing hydrogen fuel with a diluent gas, preferably air, such that the hydrogen concentration of the resulting mixture is lower than the threshold concentration.
12. A method according to any one of claims 1 to 11, A method wherein the hydrogen is mixed with the diluent gas in the intake duct (8) of the engine (6), the exhaust duct (9) of the engine (6), or in a dedicated mixing container (24).
13. A method according to any one of claims 1 to 12, The steps include receiving a request to stop the vehicle while the engine (6) is stopped, If the catalyst temperature of the catalyst (14, 34) is lower than the operating temperature, the purge operation is performed in the third purge mode (230); otherwise, the purge operation is performed in the second purge mode (220). Methods that include...
14. A method according to any one of claims 1 to 13, A method comprising the step of disconnecting the purgable portion (4) from the fuel storage tank (1) (170, 260), after which the power source (6) is stopped, the pressure of the purgable portion (4) is monitored, and if the pressure drop of the purgable portion (4) exceeds an allowable threshold, the purging operation is performed (220, 230).
15. A hydrogen vehicle emission control system (20), wherein the vehicle includes a fuel supply system (2) for supplying hydrogen fuel from a fuel storage tank (1) to the vehicle's power source (6) when the vehicle is in operation, and the fuel supply system (2) includes a purgeable portion (4), Steps (170, 260) include cutting the purgeable portion (4) from the fuel storage tank (1) so that the power source (6) is cut off from the fuel storage tank (1), wherein hydrogen fuel remains in the purgeable portion (4), Steps to perform the purging operation (220, 230, 270) It is configured to perform at least the following, and the purging operation is The steps include: discharging hydrogen fuel from the purgable portion (4) to reduce the pressure in the purgable portion (4) to a target pressure; The steps include: generating vent gas inside the vehicle using hydrogen fuel discharged from the purgable portion (4) such that the vent gas has a hydrogen concentration lower than a threshold concentration; The vent gas is released at least partially into the atmosphere (50) and A system (20) including at least the following.