Method for controlling operation of hydrogen combustion engine system of vehicle

Abstract

The invention relates to a method for controlling operation of a hydrogen combustion engine system (10) of a vehicle (1). A hydrogen combustion engine system (10) includes a hydrogen combustion engine (15, 15 ') and an exhaust aftertreatment system (EATS) (20) configured to reduce emissions in engine exhaust. The EATS (20) includes a selective catalytic reduction (SCR) catalyst (40) and an ammonia escape catalyst (ASC) (50) disposed downstream of the SCR catalyst (40). The method comprises: identifying (S10) a regeneration time window for performing regeneration of the ASC (50); in response to identifying the regeneration time window, the hydrogen combustion engine (15, 15 ') is operated in an H2 exhaust excess mode defined by an amount of unburned H2 in the engine exhaust being at least 1.5 mol%, and the ASC (50) is regenerated by using the unburned H2 in the engine exhaust and reaching a regeneration temperature of at least 500 DEG C.

Description

Technical Field

[0001] The invention relates to a method for controlling the operation of a hydrogen combustion engine system of a vehicle, the hydrogen combustion engine system comprising a hydrogen combustion engine and an exhaust gas aftertreatment system EATS, the EATS being configured to reduce emissions of the engine exhaust. The invention further relates to a hydrogen combustion engine system of a vehicle and a vehicle comprising such an engine system, as well as a computer program and a computer readable medium carrying the computer program.

[0002] The present invention is applicable to vehicles, in particular heavy vehicles, such as trucks, for example. However, although the present invention will be described primarily with respect to trucks, the hydrogen combustion engine system is also applicable to other types of vehicles, such as buses, passenger cars, industrial construction machines, wheel loaders, etc. Background Art

[0003] The demand for internal combustion engines has been growing steadily over the years, and engines are constantly being developed to meet the various demands of the market. Reducing exhaust gas, improving engine efficiency (i.e. reducing fuel consumption) and reducing the noise level of the engine are some of the criteria that are important aspects when selecting a vehicle engine. Moreover, in the field of trucks, there are applicable legal directives that have determined, for example, the maximum amount of exhaust gas pollution allowed. Furthermore, reducing the overall cost of the vehicle is important, and since the engine accounts for a relatively large part of the total cost, it is expected that the cost of the engine components will also be reduced.

[0004] In order to meet the described needs, various engine concepts have been developed over the years, in which conventional engine cylinders have been combined with, for example, a pre-compression stage and / or an expansion stage. Other engine concepts relate to the fuel used and burned in the combustion engine. For example, gasoline and diesel can be replaced with more environmentally friendly fuels, for example biofuels, such as ethanol. In some cases, when changing the fuel, the combustion engine needs to be adjusted to operate optimally on the new fuel. Recently, clean combustion engines (such as, for example, near zero emission combustion engines) have become increasingly popular. For example, by changing the fuel to hydrogen or a hydrogen-based fuel, the combustion of hydrogen with oxygen only produces water as a by-product (in theory).

[0005] However, while the engine is adapted to operate on the new fuel, NOx is often formed during the high temperature combustion process, thus requiring cleaning of the engine exhaust. Therefore, there is a need in the industry for an engine system that includes a suitable exhaust aftertreatment system EATS to treat the emissions from a hydrogen combustion engine. In addition, certain emission reduction components of the EATS require regular maintenance or regeneration to improve their performance over time. Summary of the invention

[0006] It is an object of the present invention to at least partially alleviate the disadvantages discussed above with respect to known exhaust gas aftertreatment systems EATS and to provide an improved system.

[0007] According to a first aspect of the present invention, there is provided a method for controlling the operation of a hydrogen combustion engine system of a vehicle, the hydrogen combustion engine system comprising a hydrogen combustion engine and an exhaust gas aftertreatment system EATS configured to reduce emissions in the engine exhaust, the EATS comprising a selective catalytic reduction SCR catalyst and an ammonia slip catalyst ASC arranged downstream of the SCR catalyst. The method comprises:

[0008] - identifying a regeneration time window for performing regeneration of the ASC, the regeneration time window being defined at least by the temperature of the EATS being above a predetermined lower limit and the temperature of the SCR catalyst being below a predetermined upper limit; and

[0009] In response to identifying the regeneration time window, operating the hydrogen combustion engine in a H2 exhaust excess mode, the mode being defined by an amount of unburned H2 in the engine exhaust being at least 1.5 mol%, and regenerating the ASC using the unburned H2 in the engine exhaust to achieve a regeneration temperature of at least 500°C.

[0010] Thus, the ASC can be regenerated in an efficient manner. An efficient method for regenerating an ASC is provided by identifying a regeneration time window for performing regeneration of the ASC, and then operating a hydrogen combustion engine in an H2 exhaust excess mode and using unburned H2 in the engine exhaust to regenerate the ASC in response to the regeneration time window. During regeneration of the ASC, H2 is combusted in the ASC, resulting in an increase in temperature, thereby achieving regeneration of the ASC. During regeneration, particulates and / or pollutants (such as, for example, sulfur-containing pollutants) are burned off in the ASC.

[0011] It should be understood that the regeneration time window is a predefined regeneration time window. According to at least one example embodiment, the identified regeneration time window belongs to a set of predefined regeneration time windows in which regeneration of the ASC is to be performed. By defining a predefined regeneration window or the set of predefined regeneration time windows, the time window for regenerating the ASC at least ensures that the prevailing temperature in the EATS is suitable for performing the method, at least by the temperature of the EATS being above a predetermined lower limit and the temperature of the SCR catalyst being below a predetermined upper limit. That is, the regeneration time window at least ensures that the prevailing temperature in the EATS is suitable for delivering unburned H2 to the ASC and that the initial temperature for regenerating the ASC is appropriate. The regeneration time window should be understood as a time period that at least meets the following temperature criteria: the temperature of the EATS is above a predetermined lower limit; and the temperature of the SCR catalyst is below a predetermined upper limit. In other words, during a time period in which the temperature of the EATS is above a predetermined lower limit and the temperature of the SCR catalyst is below a predetermined upper limit, regeneration of the ASC is performed by operating the hydrogen combustion engine in an H2 exhaust excess mode and regenerating the ASC using unburned H2 in the engine exhaust.

[0012] According to at least one example embodiment, the method comprises the step of determining the temperature of the ASC during regeneration.The temperature may be measured (eg by a temperature sensor) or may be modelled (calculated, using a thermal model of the ASC or EATS).

[0013] According to at least one example embodiment, the regeneration temperature of the ASC is defined as the average temperature across the ASC. For example, the average temperature of the ASC is based on the temperature at the ASC inlet and the temperature at the ASC outlet. As a further alternative, the regeneration temperature of the ASC is defined as the temperature at the ASC inlet, or the temperature of the inlet portion of the ASC.

[0014] According to at least one example embodiment, the method comprises the following steps:

[0015] - determining the temperature of the EATS by at least determining the temperature of the SCR catalyst; and in response to determining that the temperature of the EATS is above a predetermined lower limit and the temperature of the SCR catalyst is below a predetermined upper limit, identifying that a regeneration time window exists.

[0016] According to at least one example embodiment, the temperature of the EATS is defined as the average temperature on the EATS. For example, the average temperature of the EATS is based on the temperature at the exhaust inlet (i.e., the EATS inlet) and the temperature at the EATS outlet. As a further alternative, the temperature of the EATS is defined as the temperature at the exhaust inlet, or the temperature of the inlet portion of the EATS, such as, for example, the temperature upstream of the SCR catalyst. As a further alternative, the temperature of the EATS is defined as the temperature of the SCR catalyst. For the latter, the regeneration time window is defined at least by the temperature of the SCR catalyst being above a predetermined lower limit and the temperature of the SCR catalyst being below a predetermined upper limit.

[0017] According to at least one example embodiment, the predefined upper limit is set to a temperature at which unburned H2 does not burn in the SCR catalyst. According to at least one example embodiment, the predefined upper limit is set to a value between 300°C and 400°C, for example, to 350°C.

[0018] For example, it is believed that when H2 is burned in the ASC during regeneration, each 1 mol% of H2 will therefore result in a temperature increase in the ASC of about 80°C. If the temperature of the SCR catalyst is 380°C, this means that the temperature in the ASC during regeneration will be about 500°C. By adapting the amount of unburned H2 in the engine exhaust within predetermined upper and lower limits, a temperature in the ASC of at least 500°C can be achieved during regeneration.

[0019] According to at least one example embodiment, the predefined lower limit is set to a temperature that can keep the H2 concentration at a moderate level and avoid the ignition of the H2 flame, which would otherwise be a risk when the H2 concentration is too high. According to at least one example embodiment, the predefined lower limit is set to a value between 200°C and 250°C, for example, to 200°C.

[0020] According to at least one example embodiment, the H2 exhaust excess mode includes operating the hydrogen combustion engine by injecting H2 into engine cylinders during an exhaust stroke.

[0021] As a result, H2 is less likely to combust in the engine cylinder, and an amount of unburned H2 in the engine exhaust of at least 1.5 mol% can be more easily achieved. Therefore, H2 is injected into the engine cylinder during the exhaust stroke of the piston in the engine cylinder, resulting in the injected H2 being transported out of the engine cylinder (along with other gases) during the exhaust stroke.

[0022] According to at least one example embodiment, the H2 exhaust excess mode includes operating the hydrogen combustion engine by injecting H2 downstream of an exhaust valve of at least one of the engine cylinders in the hydrogen combustion engine.

[0023] Thus, the injection of H2 can be performed external to the engine cylinders and therefore less dependent on the operating cycle of the engine cylinders, and directly into the engine exhaust to achieve an amount of unburned H2 in the engine exhaust of at least 1.5 mol%. Furthermore, by injecting H2 downstream of the exhaust valve of at least one of the engine cylinders in a hydrogen combustion engine, the H2 is less likely to be combusted by hot surfaces inside the hydrogen combustion engine.

[0024] According to at least one example embodiment, the H 2 exhaust excess mode is included in a combustion mode of the hydrogen combustion engine.

[0025] A combustion mode is a mode in which an engine cylinder of a hydrogen combustion engine performs at least one combustion during an operating cycle. For example, in a four-stroke cycle of a hydrogen combustion engine, four different piston strokes may be defined within the engine cylinder to complete one operating cycle: intake, compression, power (combustion), and exhaust. In such an example, the piston completes two full strokes within the engine cylinder to complete one operating cycle. A hydrogen combustion engine may include one of a plurality of engine cylinders configured to operate in the same manner. For example, each of the engine cylinders may be configured to operate according to the previously mentioned four-stroke cycle.

[0026] According to at least one example embodiment, said step of injecting H2 into the engine cylinders during the exhaust stroke is performed during said combustion mode of the hydrogen combustion engine.

[0027] Thus, H2 is injected into the engine cylinder after combustion (compared to the same operating cycle) and can therefore be passed to the engine exhaust without combustion, at least up to the amount of unburned H2 as defined above. For example, H2 is injected into the engine cylinder after the exhaust valve opens, such as, for example, at least 10 crankshaft angle degrees after the exhaust valve opens. According to at least one example embodiment, H2 is injected into the engine cylinder between 90 crankshaft angle degrees before TDC and TDC or between 130 crankshaft angle degrees before TDC and 60 crankshaft angle degrees. The exhaust stroke is typically the exhaust stroke in the above-mentioned four-stroke cycle in the combustion mode of a hydrogen combustion engine.

[0028] According to at least one example embodiment, the H2 exhaust excess mode includes operating the hydrogen combustion engine to achieve a target lambda by injecting H2 during a compression stroke in an engine cylinder.

[0029] Thereby, combustion of H2 in the engine cylinder is achieved.

[0030] Therefore, and according to at least one example embodiment, during one operating cycle (e.g., the aforementioned four-stroke cycle), H2 may be injected into the engine cylinder at least twice, namely a primary H2 injection during the compression stroke, and a secondary H2 injection during the exhaust stroke. In a normal operating mode of a hydrogen combustion engine (such as a default combustion mode), only the primary H2 injection is used, because an excess of H2 is not required in the engine exhaust. In the normal combustion mode, the amount of H2 in the engine exhaust is typically between 0.02 mol% and 0.15 mol%. Therefore, the H2 exhaust excess mode can be distinguished from the default combustion mode by the secondary H2 injection, and thus can be referred to as the H2 secondary injection mode.

[0031] Target lambda refers to a target air-fuel equivalence ratio and may be determined by the ratio of the actual air-fuel ratio (mass of air to fuel) of a given mixture to the stoichiometric air-fuel ratio. According to at least one example embodiment, the target lambda is higher than 1, such as, for example, between 1.5 and 3. Thus, NOx in the engine exhaust may be kept low.

[0032] According to at least one example embodiment, the hydrogen combustion engine includes a fuel injector for each engine cylinder for injecting H2 into the engine cylinder. According to at least one example embodiment, the fuel injector is used for both the primary H2 injection and the secondary H2 injection as described above. In other words, the method may include performing a primary H2 injection into the engine cylinder by the fuel injector during the compression stroke (to achieve a target lambda), and performing a secondary H2 injection into the engine cylinder by the fuel injector during the exhaust stroke. As an alternative embodiment, the fuel injector is a primary fuel injector configured to perform a primary H2 injection, wherein the hydrogen combustion engine further includes a secondary fuel injector configured to perform a secondary H2 injection. In other words, the method may include performing a primary H2 injection into the engine cylinder by the primary fuel injector during the compression stroke (to achieve a target lambda), and performing a secondary H2 injection into the engine cylinder by the secondary fuel injector during the exhaust stroke. For example, the secondary fuel injector may be arranged to inject H2 closer to the exhaust valve in the engine cylinder than the primary fuel injector.

[0033] As mentioned previously, H2 can be injected into the exhaust valve downstream of at least one of the engine cylinders in the hydrogen combustion engine. Therefore, and according to at least one example embodiment, the secondary fuel injector can be arranged in the downstream of the exhaust valve of the engine cylinder in the hydrogen combustion engine. That is to say, the secondary H2 injection can be performed outside the engine cylinder and directly injected into the engine exhaust to achieve an amount of unburned H2 in the engine exhaust of at least 1.5 mol%. The secondary fuel injector can, for example, be arranged somewhere between the exhaust valve downstream of at least one of the engine cylinders and the inlet upstream to EATS, such as at the engine outlet or at the exhaust passage downstream of the exhaust valve. Therefore, the secondary H2 injection can be achieved by injecting H2 into the engine exhaust somewhere between the exhaust valve downstream of at least one of the engine cylinders and the inlet upstream to EATS.

[0034] According to at least one example embodiment, a hydrogen combustion engine system includes an H2 storage tank including H2 fuel (typically pressurized H2). For example, both the primary fuel injector and the secondary fuel injector are configured to supply H2 from the H2 storage tank. That is, both the primary fuel injector and the secondary fuel injector are configured to supply H2 fuel from the same H2 storage tank. For example, the method may include performing a primary H2 injection into an engine cylinder (to achieve a target lambda) by a primary fuel injector during a compression stroke using H2 fuel from the H2 storage tank, and performing a secondary H2 injection by a secondary fuel injector using H2 fuel from the (same) H2 storage tank to bring the amount of unburned H2 in the engine exhaust to at least 1.5 mol%. Therefore, the unburned H2 in the engine exhaust originates from the H2 storage tank and is not burned in the hydrogen combustion engine.

[0035] According to at least one example embodiment, the H2 exhaust excess mode includes operating the hydrogen combustion engine by injecting water during an intake stroke in an engine cylinder.

[0036] This may be particularly advantageous when the target lambda is relatively low, such as between lambda 1.5 and 2, to reduce NOx in the engine exhaust.

[0037] According to at least one example embodiment, in response to receiving a command to reduce the target lambda to a predefined level (e.g., below 1.8), when the target lambda is above the predefined level, before reducing the lambda to the predefined level, H2 is injected into the engine cylinder during the exhaust stroke of at least two operating cycles of the engine cylinder (e.g., a four-stroke cycle as described above). Thus, before the operation of the hydrogen combustion engine reaches the predefined level of the target lambda, unburned H2 in the engine exhaust can be provided to the ASC. In other words, before the predefined level of the target lambda is reached, the EATS is ready.

[0038] According to at least one example embodiment, the H2 exhaust excess mode is defined by the amount of unburned H2 being at most 4 mol %. Thus, the H2 exhaust excess mode may be defined by the amount of unburned H2 being between 1.5 mol % and 4 mol %.

[0039] It should be noted that the expression “the amount of unburned H2 is at least X mol%” refers to the molar fraction of H2 in the exhaust gas (i.e., the molar percentage of H2 in the exhaust gas), and can be simply referred to as “the amount of H2 is at least X mol%”.

[0040] According to at least one example embodiment, the H 2 exhaust excess mode is included in a non-combustion mode of the hydrogen combustion engine.

[0041] Thus, the hydrogen combustion engine can be operated without the previously mentioned main H2 injection. In order to achieve an amount of unburned H2 of at least 1.5 mol%, injection of H2 can be performed in the engine cylinder during the exhaust stroke, as previously mentioned, or injection of H2 can be performed downstream of the exhaust valve of at least one of the engine cylinders in the hydrogen combustion engine, as previously mentioned. Preferably, such H2 injection is performed using a secondary fuel injector.

[0042] According to at least one example embodiment, the regeneration time window is further defined at least by an amount of NOx and / or NH3 downstream of the ASC being above a respective predetermined emission threshold.

[0043] By defining a predefined regeneration window or a set of predefined regeneration time windows, further at least NOx and / or NH3 downstream of the ASC is above a corresponding predetermined emission threshold, the time window for regenerating the ASC at least ensures that the prevailing temperature in the EATS and the prevailing amount of NOx and / or NH3 downstream of the ASC are suitable for performing the method. That is, the regeneration time window at least ensures that the prevailing temperature in the EATS is suitable for delivering unburned H2 to the ASC and that the initial temperature for regenerating the ASC is suitable, while also ensuring that the regeneration of the ASC is triggered based on the amount of NOx and / or NH3 downstream of the ASC. In other words, regeneration of the ASC is performed by operating the hydrogen combustion engine in an H2 exhaust excess mode and regenerating the ASC using unburned H2 in the engine exhaust gas during a time period when the temperature of the EATS is above a predetermined lower limit and the temperature of the SCR catalyst is below a predetermined upper limit and the amount of NOx and / or NH3 downstream of the ASC is above a corresponding predetermined emission threshold. The predetermined emission threshold for NOx may be referred to as a predetermined NOx emission threshold, and the predetermined emission threshold for NH3 may be referred to as a predetermined NH3 emission threshold. The amount of NOx and NH3 can be a mole fraction, or based on weight, such as a weight-to-volume (W / V) concentration. In addition, the amount of NOx and NH3 can be determined per driving distance, or per unit operating time, or per weight of energy (g / kWh).

[0044] According to at least one example embodiment, the method comprises the following steps:

[0045] - determining an amount of NOx and / or NH3 downstream of the ASC and, in response to determining that at least one of the amounts of NOx and NH3 is above a respective predetermined emission threshold, identifying that a regeneration time window exists.

[0046] According to at least one example embodiment, the regeneration time window is further defined by the absence of engine braking of the hydrogen combustion engine.

[0047] Engine braking may result in excessive temperatures in the engine cylinders and / or engine exhaust, so it will be more difficult to achieve the above defined amount of unburned H2 in the engine exhaust.

[0048] According to at least one example embodiment, the regeneration time window is further defined at least by the time elapsed since the last regeneration of the ASC being above a predetermined time period threshold.

[0049] Thus, the regeneration time window may be adapted based on estimated or anticipated degradation or fouling of the catalyst coating in the ASC. For example, in response to the accumulation of fouling on the catalyst coating over time, the ASC may desire to regenerate regardless of NOx or NH3 downstream of the ASC.

[0050] According to at least one example embodiment, the method further comprises:

[0051] - Pre-filling the SCR catalyst with ammonia before operating the hydrogen combustion engine in H2 excess combustion mode.

[0052] In this way, injection of reducing agent during regeneration of the ASC can be avoided.

[0053] According to at least one example embodiment, the method further comprises:

[0054] - delivering the unburned H2 from an engine outlet of the hydrogen combustion engine to the ASC such that the mole fraction of H2 in the exhaust gas reaching the ASC is at least 80% of the mole fraction of H2 at the engine outlet.

[0055] Therefore, most of the unburned H2 from the engine outlet can be received by the ASC. For example, at least most of the unburned H2 from the engine outlet is received by the ASC. The unburned H2 is usually delivered from the engine outlet to the ASC by the exhaust gas in the EATS. By making the temperature of the SCR catalyst lower than a predetermined upper limit EATS (e.g., lower than 350°C), most of the unburned H2 is prevented from burning. In addition, the temperature of any internal wall structure in the EATS from the engine outlet to the ASC is preferably lower than a predetermined wall structure temperature, for example, lower than 600°C.

[0056] It should be noted that the engine outlet and the exhaust inlet (or EATS inlet) constitute the interface between the hydrogen combustion engine and the EATS. Typically, the engine exhaust at the engine outlet continues as exhaust to the exhaust inlet downstream in the EATS. According to at least one example embodiment, the exhaust inlet defines an interface between the hydrogen combustion engine and the EATS. Therefore, the exhaust inlet is the most upstream portion of the EATS and is therefore the end point of the EATS. Correspondingly, the engine outlet is the most downstream portion of the hydrogen combustion engine. The EATS typically includes a fluid path for the exhaust gas received from the engine outlet of the hydrogen combustion engine, which extends from the exhaust inlet of the EATS to the outlet.

[0057] According to at least one example embodiment, the ASC is a monolith catalyst comprising an oxidation catalyst and a metal-zeolite coating. The oxidation catalyst is configured to convert ammonia into NOx, and the metal-zeolite is configured to convert NOx into N2. The oxidation catalyst may be, for example, Pd, Pt or Rh, and the metal-zeolite may be, for example, Cu-zeo or Fe-zeo. The metal-zeolite may be arranged on top of the oxidation catalyst, for example. The use of metal-zeolites to convert NOx into N2 is typically promoted by the presence of ammonia in the exhaust gas. The oxidation catalyst and / or the metal-zeolite may be applied to the monolith by a corresponding powder coating. According to at least one example embodiment, the monolith may be a flow-through monolith or a wall-flow monolith. The monolith of the ASC may be referred to as a monolith substrate, and may be, for example, a ceramic monolith.

[0058] Therefore, during (normal) operation of the EATS, the ASC is configured to reduce emissions by ammonia oxidation and NOx conversion. In use, ammonia enters the ASC with the exhaust gas and is at least partially oxidized to NO (or NOx). Thus, the oxidized NO and the ammonia that has not yet been oxidized inside the ASC generate N2 by a catalytic conversion reaction using a metal-zeolite (i.e. following the usual SCR reaction scheme).

[0059] According to at least one example embodiment, the coating of the oxidation catalyst increases along the ASC from the ASC inlet to the ASC outlet. Since the temperature of the ASC during regeneration can become particularly high at the ASC inlet, it can be beneficial to use a relatively thin coating of the oxidation catalyst at the ASC inlet, where the coating gradually thickens toward the ASC outlet.

[0060] According to at least one example embodiment, the method further comprises:

[0061] - in response to a requested torque or brake power of the hydrogen combustion engine exceeding a corresponding predetermined threshold, terminating operation of the hydrogen combustion engine in the H2 exhaust excess mode.

[0062] Torque or engine braking exceeding a predetermined threshold may result in excessive temperatures in the engine cylinders and / or engine exhaust, making it more difficult to achieve the above defined amount of unburned H 2 in the engine exhaust.

[0063] According to at least one example embodiment, the method further comprises:

[0064] - In response to not identifying a regeneration time window, preventing the hydrogen burning engine from operating in an H2 exhaust excess mode.

[0065] Thus, use of unburned H2 in the engine exhaust to regenerate the ASC is avoided. For example, the method may include identifying a non-regeneration time window to avoid ASC regeneration, the non-regeneration time window being defined by at least a temperature of the EATS being below a predetermined lower limit and / or a temperature of the SCR catalyst being above a predetermined upper limit.

[0066] According to a second aspect of the present invention, a hydrogen combustion engine system for a vehicle is provided. The hydrogen combustion engine system comprises a hydrogen combustion engine and an exhaust gas aftertreatment system EATS configured to reduce emissions in the engine exhaust, the EATS comprising a selective catalytic reduction SCR catalyst and an ammonia slip catalyst ASC arranged downstream of the SCR catalyst, wherein the hydrogen combustion engine system comprises a control unit, the control unit being configured as follows:

[0067] - identifying a regeneration time window for performing regeneration of the ASC, the regeneration time window being defined at least by the temperature of the EATS being above a predetermined lower limit and the temperature of the SCR catalyst being below a predetermined upper limit;

[0068] In response to identifying the regeneration time window, commanding the hydrogen combustion engine to operate in a H2 exhaust excess mode, the mode being defined by an amount of unburned H2 in the engine exhaust being at least 1.5 mol%, for regenerating the ASC using the unburned H2 in the engine exhaust by reaching a regeneration temperature of at least 500°C.

[0069] The effects and features of the second aspect of the invention are largely similar to those described above in conjunction with the first aspect of the invention. The embodiments mentioned with respect to the first aspect of the invention are largely compatible with the second aspect of the invention, some of which are illustrated below.

[0070] According to at least one example embodiment, the control unit is configured to cause the hydrogen combustion engine system to perform the steps of the method of the first aspect of the invention. According to at least one example embodiment, the control unit is configured to perform regeneration of the ASC by using unburned H2 in the engine exhaust to reach a regeneration temperature of at least 500°C. For example, the control unit includes instructions for performing said regeneration of the ASC.

[0071] According to at least one example embodiment, a hydrogen combustion engine is configured to operate via an Otto cycle.

[0072] According to at least one example embodiment, a hydrogen combustion engine is an internal combustion engine configured to burn hydrogen in one or more engine cylinders of the engine. The engine cylinders referred to throughout the application text may be referred to as combustion cylinders. It should be understood that when the configuration or operation of an engine cylinder is mentioned in the application text, the configuration or operation refers to at least one of the engine cylinders of the hydrogen combustion engine, or all engine cylinders.

[0073] For example, a hydrogen combustion engine is configured to operate with a four-stroke combustion in the engine cylinders. Typically, a hydrogen combustion engine is configured to operate with a lambda between 1.5 and 3.

[0074] For example, a hydrogen combustion engine system includes a delivery conduit defining a fluid path for delivering exhaust gas from an exhaust inlet of the EATS to an outlet of the EATS. Thus, unburned H2 from the engine exhaust can be delivered to the ASC and used there to regenerate the ASC by bringing the regeneration temperature to at least 500° C. According to at least one example embodiment, the EATS is free of any oxidation catalyst arranged downstream of the exhaust inlet of the EATS and upstream of the ASC. Thus, typically, the delivery conduit defining the fluid path is free of any oxidation catalyst.

[0075] As a result, unburned H2 from the engine exhaust can more easily reach the ASC without being burned.

[0076] According to a third aspect of the present invention, there is provided a vehicle comprising a hydrogen combustion engine system according to the second aspect of the present invention.

[0077] According to a fourth aspect of the invention there is provided a computer program comprising program code means comprising instructions for causing the hydrogen combustion engine system of the second aspect of the invention to perform the steps of the method of the first aspect of the invention when said program is run on a computer.

[0078] According to a fifth aspect of the present invention, there is provided a computer readable medium carrying a computer program including program code means, the program code means including instructions for causing the hydrogen combustion engine system of the second aspect of the present invention to execute the steps of the method of the first aspect of the present invention when the computer program is run on a computer.

[0079] The effects and features of the third to fifth aspects of the present invention are largely similar to those described above in conjunction with the first and second aspects of the present invention. The embodiments mentioned with respect to the first and second aspects of the present invention are largely compatible with the third to fifth aspects of the present invention.

[0080] It should be understood that the SCR catalyst and the ASC form different abatement modules in the EATS. For example, each abatement module may include a container or tank that houses abatement components such as various catalysts and substrates.

[0081] According to at least one example embodiment applicable to any one of the first to fifth aspects of the present invention, the EATS further comprises at least one particle filter. The particle filter may be arranged between the SCR catalyst and the ASC, or downstream of the ASC. According to at least one example embodiment, the particle filter is integrated with the SCR catalyst (ie, contained in the same container or tank) and arranged upstream of the SCR catalyst.

[0082] According to at least one exemplary embodiment applicable to any one of the first to fifth aspects of the present invention, the EATS further comprises:

[0083] - an injector configured to inject a reducing agent for providing ammonia to the SCR catalyst, wherein the injector is arranged upstream of the SCR catalyst and downstream of the exhaust gas inlet.

[0084] Therefore, during normal operation of the EATS (typically not when regenerating the ASC), the reductant is injected upstream of the SCR catalyst. Therefore, the exhaust gas flow through the EATS delivers the injected reductant to the SCR catalyst. The injector can be arranged at any position between the exhaust gas inlet and the SCR catalyst. The reductant used by the injector can be at least one of the following: anhydrous ammonia, aqueous ammonia, urea, aqueous urea and diesel exhaust fluid. According to at least one example embodiment, the reductant is urea or liquid urea. As previously mentioned, the ASC is configured to dispose of excess ammonia that is not used in the SCR catalyst.

[0085] According to at least one exemplary embodiment applicable to any one of the first to fifth aspects of the present invention, the SCR catalyst is a metal-zeolite SCR catalyst, such as Cu-zeo or Fe-zeo. As an alternative, the SCR catalyst may include a vanadium-based coating. Therefore, the SCR catalyst is configured to convert nitrogen oxides NOx into diatomic nitrogen N and water with the help of the SCR catalyst coating (i.e., metal-zeolite or vanadium-based coating). During EATS operation, the injected reductant (or resulting ammonia) reacts on the SCR catalyst coating. The SCR catalyst coating can be applied to the substrate of the SCR catalyst by a coating layer, i.e., applied to the substrate by an aqueous slurry, dried and calcined. Thus, it is beneficial to apply the SCR catalyst coating in the substrate. As an alternative, the SCR catalyst coating can be applied by a powder coating. The substrate of the SCR catalyst can be a monolith, such as a ceramic monolith.

[0086] According to at least one example embodiment applicable to any one of the first to fifth aspects of the present invention, the hydrogen combustion engine system further includes various sensors located at various positions in the EATS known to those skilled in the art. For example, NH3 and / or NOx sensors may be located at the exhaust inlet and / or outlet of the EATS, or near the inlet and / or outlet. In addition, a temperature sensor and / or a pressure sensor may be located before and / or after any one of the emission reduction modules (such as SCR catalysts and ASC). In addition, the hydrogen combustion engine system may include one or more sensors for measuring the amount of H2 in the hydrogen combustion engine system. For example, an H2 sensor may be arranged at the engine outlet for measuring the amount of H2 in the engine exhaust. Additionally or alternatively, an H2 sensor may be arranged upstream of the ASC for measuring the amount of H2 in the exhaust gas entering the ASC. The hydrogen combustion engine system may further include a controller configured to control, for example, the introduction of a reductant into the fluid path of the exhaust gas.

[0087] Further advantages and features of the present disclosure are disclosed and discussed in the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Embodiments of the invention cited as examples will be described in more detail below with reference to the accompanying drawings. In the drawings:

[0089] Figure 1 is a schematic side view of a vehicle including a hydrogen combustion engine system and an exhaust aftertreatment system of the hydrogen combustion engine system according to an example embodiment of the present invention,

[0090] Figure 2 is a schematic diagram of a hydrogen combustion engine system of a vehicle and an exhaust gas aftertreatment system of the hydrogen combustion engine system according to an exemplary embodiment of the present invention;

[0091] Figure 3A is a schematic diagram of at least a portion of a hydrogen combustion engine according to an exemplary embodiment of the present invention;

[0092] Figure 3B is a schematic diagram of at least a portion of a hydrogen combustion engine according to yet another exemplary embodiment of the present invention; and

[0093] Figure 4 is a flow chart illustrating the steps of a method according to an example embodiment of the present invention. DETAILED DESCRIPTION

[0094] refer to Figure 1, a vehicle 1 is shown, here embodied as a heavy truck 1, for which a hydrogen combustion engine system 10 of the type disclosed in the present disclosure is advantageous. However, the hydrogen combustion engine system 10 may also be implemented in other types of vehicles, such as in buses, light trucks, passenger cars, marine applications, etc. Figure 1 The hydrogen combustion engine system 10 of the vehicle 1 includes a hydrogen combustion engine 15 and an exhaust aftertreatment system EATS 20, which is configured to reduce the emission of engine exhaust from the hydrogen combustion engine 15. However, according to at least one example embodiment, the vehicle can be a hybrid vehicle further including an electric motor or a fuel cell 16 (optional). The hydrogen combustion engine 15 is powered by a hydrogen fuel (also referred to as H2 fuel) generally included in a fuel tank (also referred to as an H2 storage tank), and any electric motor is generally powered by electricity supplied from at least one energy storage device or conversion device (e.g., a battery (not shown) or a fuel cell), while any fuel cell is generally powered by hydrogen fuel, such as hydrogen fuel from the fuel tank. The hydrogen combustion engine 15 is preferably configured to operate by an Otto cycle or another four-stroke cycle. The operation of the hydrogen combustion engine system 10 can be controlled, for example, by a control unit 18.

[0095] exist Figure 1 In the embodiment, the EATS 20 includes an exhaust inlet (such as Figure 2 The plurality of emission reduction modules 30 are configured to reduce the emission of the engine exhaust. The plurality of emission reduction modules 30 include at least a first emission reduction module 40, which is a selective catalytic reduction SCR catalyst 40, and a second emission reduction module 50, which is an ammonia slip catalyst ASC. Figure 1 In the embodiment, the SCR catalyst 40 is arranged upstream of the ASC 50. The SCR catalyst 40 is configured to convert nitrogen oxides (also referred to as NOx) into diatomic nitrogen N2 and water with the help of the SCR catalyst coating, while the ASC 50 is configured to reduce emissions through ammonia oxidation and NOx conversion, as will be referred to in Figure 2 EATS 20 typically includes further components (such as, for example, piping) and may include additional abatement components ( Figure 1 not shown).

[0096] exist Figure 2 In more detail, Figure 1 The hydrogen combustion engine system 10 includes a hydrogen combustion engine 15 and an exhaust aftertreatment system EATS 20, which is configured to reduce the emissions of the engine exhaust, as shown in FIG. Figure 1 Brief Description. The engine exhaust gas entering the EATS is hereinafter referred to as exhaust gas.

[0097] The EATS 20 includes an exhaust inlet 22 for receiving engine exhaust from an engine outlet 17 of a hydrogen combustion engine 15; an EATS outlet 24 for discharging at least partially cleaned exhaust from the EATS 20; and a fluid path 26 for conveying exhaust from the exhaust inlet 22 to the EATS outlet 24. The EATS outlet 24 may, for example, be connected to or include an exhaust tail pipe of the vehicle 1. The EATS 20 further includes a plurality of emission reduction modules 30 arranged downstream of the exhaust inlet 22. The emission reduction modules 30 are configured to reduce emissions of the engine exhaust along the fluid path 26. Figure 2 In the embodiment of the present invention, the plurality of emission reduction modules 30 are composed of the first emission reduction module as the selective catalytic reduction SCR catalyst 40 mentioned above and the second emission reduction module as the ammonia slip catalyst ASC 50 mentioned above. The ASC 50 is arranged downstream of the SCR catalyst 40. In addition, in Figure 2 In the embodiment of FIG. 5 , an optional third emission reduction module 60 , here a particulate filter, is arranged between the SCR catalyst 40 and the ASC 50 .

[0098] The SCR catalyst 40 preferably includes an SCR catalyst coating, which is a metal-zeolite SCR catalyst, such as Cu-zeo or Fe-zeo. As an alternative, the SCR catalyst coating is a vanadium-based coating. The SCR catalyst 40 is designed to convert nitrogen oxides NOx into diatomic nitrogen N and water with the help of the SCR catalyst coating. The SCR catalyst 40 generally includes a substrate, such as a monolith, on which the SCR catalyst coating is arranged.

[0099] The ASC 50 preferably includes an oxidation catalyst and a metal-zeolite. That is, the ASC 50 preferably includes a first ASC coating as an oxidation catalyst and includes a second ASC coating as a metal-zeolite (i.e., having an SCR catalyst function). The ASC 50 is designed to convert ammonia into NOx with the help of the oxidation catalyst and to convert NOx into N2 with the help of the metal-zeolite. The ASC 50 generally includes a substrate, such as a monolith, on which the first and second ASC coatings are arranged.

[0100] The particulate filter 60 is configured to remove particulates, such as particulate emissions or soot, from the exhaust. Figure 2 In the embodiment of the present invention, the particulate filter 60 is arranged between the SCR catalyst 40 and the ASC 50, but according to an alternative exemplary embodiment, the particulate filter 60 may be arranged upstream of the SCR catalyst 40. In such an embodiment, particulate emissions (such as, for example, sulfur-containing emissions) are filtered from the exhaust gas upstream of the SCR catalyst 40, thereby reducing damage to the SCR catalyst coating arranged downstream.

[0101] In addition, in order to provide ammonia to the SCR catalyst 40 and the ASC 50, the EATS 20 includes an injector 34, which is configured to inject a reductant into the fluid path 26 upstream of the SCR catalyst 40 and downstream of the exhaust gas inlet 22. The reductant may be, for example, urea. Therefore, the injector 34 may be configured to inject urea. During operation of the EATS 20, the injected reductant (or generated ammonia) is delivered to the SCR catalyst 40 through the exhaust gas and reacts on the SCR catalyst coating. The reductant or ammonia that does not react and passes through the SCR catalyst 40 is disposed in the ASC 50, as described above.

[0102] Figure 2 The EATS 20 of the hydrogen combustion engine system 10 is generally operated in the following manner: the engine exhaust or exhaust gas (to be cleaned) from the hydrogen combustion engine 15 leaves the engine outlet 17 and enters the EATS 20 via the exhaust inlet 22, and encounters the SCR catalyst 40. Upstream of the SCR catalyst 40 and downstream of the exhaust inlet 22, the reductant is injected via the injector 34. The injected reductant is therefore mixed with the exhaust gas. Typically, the reductant is evaporated and hydrolyzed into ammonia (heated by a heater or by the exhaust gas). In the SCR catalyst 40, the NOx in the exhaust gas is catalytically reduced using ammonia and an SCR catalyst coating. Thereafter, the exhaust gas passes through a particle filter 60 (optional). Thereafter, at least part of the cleaned exhaust gas encounters the ASC 50. In the ASC 50, emissions are further reduced by ammonia oxidation and NOx conversion, and thereafter the exhaust gas is discharged from the EATS 20 via the EATS outlet 24.

[0103] Likewise Figure 2 As shown, the EATS 20 may include means for providing determination / measurement of various parameters, such as, for example, providing determination / measurement of the temperature of the SCR catalyst 40 and / or the ASC 50 via temperature sensors 33, 35. In addition, the amount of NOx may be determined / measured at the EATS outlet 24 via a NOx sensor 37, for example, a mole fraction of NOx, or a weight of NOx per distance traveled, a weight per unit of operating time, or a weight per energy (g / kWh). The NOx sensor may alternatively or additionally be configured to determine / measure a corresponding amount of NH3. Figure 2In the embodiment of the present invention, the first temperature sensor 33 is arranged to directly measure the temperature of the SCR catalyst 40, and the second temperature sensor 35 is arranged to directly measure the temperature of the ASC 50. However, it is noted that the temperature of the SCR catalyst 40 can be determined by estimation using at least one temperature sensor arranged upstream and / or downstream of the SCR catalyst 40, and / or the temperature of the ASC 50 can be determined by estimation using at least one temperature sensor arranged upstream and / or downstream of the ASC 50 (e.g., a temperature sensor arranged at the EATS outlet 24). In addition, the third temperature sensor 36a is configured to measure the temperature at the EATS outlet 24, and the fourth temperature sensor 36b is configured to measure the temperature at the exhaust inlet 22. Thus, the temperature of the EATS 20 can be determined by an average value using the third and fourth temperature sensors 36a, 36b, and / or the temperature of the EATS 20 at the exhaust inlet 22 can be determined using the fourth temperature sensor, and / or the temperature of the EATS 20 at the EATS outlet 24 can be determined using the third temperature sensor 36a.

[0104] In addition, the hydrogen combustion engine system 10 may include one or more sensors for measuring the amount of H 2 in the hydrogen combustion engine system 10. For example, Figure 2 As shown in the exemplary embodiment of FIG. 1 , a first H2 sensor 39a is arranged at the engine outlet 17 for measuring the amount of H2 in the engine exhaust, and a second H2 sensor 39b is arranged upstream of the ASC 50 for measuring the amount of H2 in the exhaust entering the ASC 50. The operation of the hydrogen combustion engine system 10 may be controlled by the control unit 18 as previously described.

[0105] Now refer to Figure 3A An example embodiment of the configuration of the hydrogen combustion engine 15 and its operation is described in greater detail. Figure 3A An engine cylinder (or combustion cylinder) 310 of the hydrogen combustion engine 15 housing a piston 312 is schematically shown. Typically, the hydrogen combustion engine 15 includes a plurality of such engine cylinders and corresponding pistons. In more detail, the piston 312 is configured to reciprocate within the engine cylinder 310, wherein a combustion chamber 314 is included in the engine cylinder 310 above the piston 312. The hydrogen combustion engine 15 further includes a spark plug 309 arranged in the combustion chamber 314. The piston 312 may be a double-acting piston, wherein the engine cylinder 310 is a combustion cylinder, and the hydrogen combustion engine 15 further includes a compressor cylinder (not shown).

[0106] The hydrogen combustion engine 15 comprises an air intake passage 315, which is arranged downstream of an air chamber, for example, in fluid connection with a compressor (not shown). Air or compressed air is supplied to the combustion chamber 314 via the intake passage 315 and is regulated by an intake valve 316. In addition, the hydrogen combustion engine 15 comprises an exhaust passage 317 regulated by an exhaust valve 318.

[0107] like Figure 3A As can be seen, the hydrogen combustion engine 15 includes an injection system 420, which includes a fuel injector 403, which is configured to supply H2 (usually as a gaseous fuel) to the combustion chamber 314. The fuel injector 403 is fluidly connected to at least one H2 storage tank 405, which includes pressurized H2 fuel or hydrogen-based gas (or a fuel that can be easily adapted to form hydrogen). The injection system 420 can further include a water inlet device 404, which is configured to supply a water-based fluid medium 404a to the combustion chamber 314.

[0108] The hydrogen combustion engine 15 can be operated according to the Otto cycle or another four-stroke combustion mode. Therefore, the four-stroke cycle of the hydrogen combustion engine includes four different piston strokes within the engine cylinder 310 to complete an operating cycle: when the piston 312 reciprocates away from TDC, air is taken in or compressed via the air intake passage 315 and the intake valve 316, compressed when the piston 312 reciprocates toward TDC, power or combustion is generated when the H2 fuel is burned using the spark plug 309, and exhaust gas discharged by the engine leaves the combustion chamber 314 via the exhaust passage 317 and the exhaust valve 318.

[0109] Now refer to Figure 4 A method for controlling the operation of a hydrogen combustion engine system of a vehicle is described in a flowchart of FIG. 1 , which schematically illustrates the steps of such a method. Figure 1 and Figure 2 The hydrogen combustion engine system 10, and Figure 3A The hydrogen combustion engine 15 is shown. Therefore, the hydrogen combustion engine system 10 applicable to the method includes at least a selective catalytic reduction SCR catalyst 40 and an ammonia slip catalyst ASC 50 arranged downstream of the SCR catalyst 40. Figure 4 The method described by the flowchart of FIG. 5 may be performed, for example, in response to a desire to regenerate the ASC 50 .

[0110] In step S10 (eg, as a first step S10), a regeneration time window is identified for performing regeneration of the ASC 50. The regeneration time window is defined at least by the temperature of the EATS 20 being higher than a predetermined lower limit and the temperature of the SCR catalyst 40 being lower than a predetermined upper limit.

[0111] The temperature of the EATS 20 may be determined by an average temperature over the EATS 20, or as a temperature at the exhaust gas inlet 22, or as a temperature at the EATS outlet 24, or as a temperature of the SCR catalyst 40. Such temperature measurement may be achieved by one or more of the previously mentioned temperature sensors 33, 35, 36a, 36b. Step S10 may be performed after step S5, in which the determined temperature of the EATS 20 is compared with a predetermined lower limit, and the determined temperature of the SCR catalyst 40 is compared with a predetermined upper limit. For example, the predetermined lower limit may be a threshold value set between 200°C and 250°C, such as a threshold value set at 200°C, and the predetermined upper limit may be a threshold value set between 300°C and 400°C, such as a threshold value set at 350°C.

[0112] The regeneration time window may be further defined at least by the amount of NOx and / or NH3 downstream of the ASC 50 being above a respective predetermined emission threshold. The NOx and / or NH3 downstream of the ASC 50 may be determined by the previously mentioned NOx sensor 37. Thus, step S5 may include the following sub-steps: determining the amount of NOx and / or NH3 downstream of the ASC 50; and comparing the determined amount of NOx and / or NH3 with a predetermined emission threshold for NOx and a predetermined emission threshold for NH3.

[0113] The regeneration time window may additionally or alternatively be further defined by the absence of engine braking of the hydrogen combustion engine. Thus, step S5 may comprise a sub-step of determining whether engine braking of the hydrogen combustion engine 15 is present.

[0114] In step S20, performed in response to identifying the regeneration time window S10, the hydrogen combustion engine 15 is operated in a H2 exhaust excess mode. The H2 exhaust excess mode is defined by the amount of unburned H2 in the engine exhaust being at least 1.5 mol%.

[0115] In step S21, the hydrogen combustion engine 15 is operated by injecting H2 into the engine cylinder 310 during the exhaust stroke of the piston. Typically, the H2 exhaust excess mode is included in the combustion mode of the hydrogen combustion engine, such as the four-stroke combustion mode described previously, wherein the exhaust stroke is the exhaust stroke of the four-stroke cycle described previously. However, it should be noted that the H2 exhaust excess mode can alternatively be included in the non-combustion mode of the hydrogen combustion engine 15. For the combustion mode, H2 is injected into the engine cylinder 310 after combustion, and can therefore be delivered to the engine exhaust via the exhaust passage 317 without being burned, at least to the excess of unburned H2 as defined above. For example, after the exhaust valve 318 opens, such as, for example, at least 10 degrees of crankshaft angle after the exhaust valve 318 opens, H2 is injected into the engine cylinder 310 and the combustion chamber 314. Additionally or alternatively, H2 is injected into the engine cylinder 310 and the combustion chamber 314 between 90 degrees of crankshaft angle before TDC and TDC.

[0116] In step S22, the hydrogen combustion engine 15 is operated to achieve a target lambda by injecting H2 into the engine cylinder 310 during the compression stroke of the piston. Thus, combustion of H2 in the engine cylinder 310 and the combustion chamber 314 is achieved. The target lambda is typically higher than 1, such as, for example, between 1.5 and 3. It should be noted that the order of steps S21 and S22 can be reversed, and / or looped.

[0117] As apparent from steps S21 and S22 , H2 may be injected into the engine cylinder 310 at least twice during one operating cycle (eg, the aforementioned four-stroke cycle), namely, a primary H2 injection during the compression stroke in step S22 , and a secondary H2 injection during the exhaust stroke in step S21 .

[0118] like Figure 3A As shown, the same fuel injector 403 can be used for both the primary H2 injection and the secondary H2 injection. In other words, both steps S21 and S22 can be implemented by the fuel injector 403.

[0119] Figure 3B A further alternative is shown. Figure 3B is with Figure 3A The same engine cylinder 310 and piston 312 are schematically shown and therefore the same reference numerals are used to indicate the same or corresponding features. Figure 3B The hydrogen combustion engine 15', Figure 3A The fuel injector 403 also shown in FIG. 1 is a primary fuel injector 403 configured to perform primary H2 injection. In addition, the hydrogen combustion engine 15′ includes a secondary fuel injector 406 configured to perform secondary H2 injection. Figure 3BAs shown, the secondary fuel injector 406 can be arranged downstream of the exhaust valve 318 of the engine cylinder 310. Therefore, the secondary H2 injection can be performed outside the engine cylinder 310, (and therefore less dependent on the operating cycle of the engine cylinder), and directly injected into the exhaust passage 317 to achieve an amount of unburned H2 in the engine exhaust of at least 1.5 mol%. Returning briefly to Figure 4 This is exemplified by step S23, which is performed as an alternative to at least step S21, wherein step S23 comprises operating the hydrogen combustion engine by injecting H2 downstream of the exhaust valve 318 of at least one of the engine cylinders 310 in the hydrogen combustion engine 15. Figure 3B As shown, the secondary fuel injector 406 may alternatively be located at the engine outlet 17, as indicated by the dashed box 406. The engine outlet 17 is, for example, a common outlet for a plurality of engine cylinders before the engine exhaust is diverted to the EATS 20. Other locations for the secondary fuel injector 406 are contemplated, for example, somewhere between downstream of the exhaust valve 318 of at least one of the engine cylinders 310 and upstream of the exhaust inlet 22 (e.g., Figure 2 as shown). Figure 3B In a further alternative embodiment not disclosed in , the secondary fuel injector is arranged and configured to inject a secondary injection of H2 into the engine cylinder 310.

[0120] Preferably, both the primary fuel injector 403 and the secondary fuel injector 406 are configured to be supplied with H 2 from an H 2 storage tank 405 .

[0121] Back to Figure 4 In step S24, the hydrogen combustion engine 15 is operated by injecting water during the intake stroke in the engine cylinder 310. This is typically achieved by the water inlet arrangement 404 mentioned previously.

[0122] like Figure 4 As shown, steps S21, S22, S23 and S24 may be sub-steps of step S20, in which the hydrogen combustion engine is operated in the H2 exhaust excess mode. That is, steps S21, S22, S23 and S24 may be performed during operation of the hydrogen combustion engine 15 in the H2 exhaust excess mode.

[0123] In step S26, unburned H2 is delivered from the engine outlet 17 of the hydrogen combustion engine 15 to the ASC 50. The delivery is preferably performed so that the mole fraction of H2 in the exhaust gas reaching the ASC 50 is at least 80% of the mole fraction of H2 at the engine outlet 17.

[0124] In step S30, unburned H2 in the engine exhaust is used to regenerate the ASC 50. During the regeneration of the ASC 50, H2 is burned in the ASC 50, resulting in a temperature increase, thereby achieving regeneration of the ASC 50. The regeneration temperature is at least 500°C. That is, the temperature of the ASC during regeneration is at least 500°C.

[0125] In step S40, the operation of the hydrogen combustion engine 15 in the H2 exhaust excess mode is terminated. This is performed, for example, in response to the requested torque or brake power of the hydrogen combustion engine 15 exceeding the corresponding threshold value. It can be additionally or alternatively determined that one or more of the previously mentioned criteria for operating the hydrogen combustion engine 15 in the H2 exhaust excess mode is no longer met, thereby terminating the operation of the hydrogen combustion engine 15 in the H2 exhaust excess mode S40. As a further alternative, in response to the regeneration of the ASC 50 being completed, the operation of the hydrogen combustion engine 15 in the H2 exhaust excess mode is terminated.

[0126] Likewise Figure 4 As shown, in step S15 executed in response to not identifying the regeneration time window from step S5, the hydrogen combustion engine 15 is prevented from operating in the H2 exhaust excess mode. Thus, the use of unburned H2 in the engine exhaust to regenerate the ASC 50 is avoided or prohibited. For example, the method may include a step S12 of identifying a non-regeneration time window to avoid ASC regeneration, the non-regeneration time window being defined by at least the temperature of the EATS 20 being lower than a predetermined lower limit and / or the temperature of the SCR catalyst 40 being higher than a predetermined upper limit. The hydrogen combustion engine 15 may be operated in a default (or normal) combustion mode, rather than operating the hydrogen combustion engine 15 in the H2 exhaust excess mode. Therefore, an example of preventing the hydrogen combustion engine 15 from operating in the H2 exhaust excess mode in step S15 is to operate the hydrogen combustion engine 15 in the default (or normal) combustion mode. During this default combustion mode, only the previous main H2 injection is used, and the secondary H2 injection is not used. The default combustion mode in S15 generally corresponds to a four-stroke cycle.

[0127] It should be noted that the SCR catalyst 40 , the ASC 50 , and the particulate filter 60 may be housed in separate containers or tanks.

[0128] It should be understood that the present invention is not limited to the embodiments described above and shown in the accompanying drawings; rather, those skilled in the art will recognize that many changes and modifications may be made within the scope of the appended claims. For example, the EATS may be used to clean the exhaust of engines other than hydrogen combustion engines, such as in a dual fuel engine system (one of the engines is a hydrogen combustion engine). For example, the EATS of the present invention may be used to clean exhaust, such as by converting NOx emissions from exhaust gas of an internal combustion engine based on H2 (hydrogen) or a mixture of H2 and natural gas.

[0129] Additionally, variations to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed inventive concept, by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A method for controlling the operation of a hydrogen combustion engine system (10) of a vehicle (1), the hydrogen combustion engine system (10) comprising a hydrogen combustion engine (15, 15') and an exhaust gas aftertreatment system EATS (20) configured to reduce emissions in the engine exhaust gas, the EATS (20) comprising a selective catalytic reduction (SCR) catalyst (40) and an ammonia slip catalyst (ASC) (50) arranged downstream of the SCR catalyst (40), wherein the method comprises: - identifying (S10) a regeneration time window for performing regeneration of the ASC (50), the regeneration time window being defined at least by the temperature of the EATS (20) being above a predetermined lower limit and the temperature of the SCR catalyst (40) being below a predetermined upper limit; and In response to identifying the regeneration time window, operating the hydrogen combustion engine (15, 15') in a H2 exhaust excess mode, the mode being defined by an amount of unburned H2 in the engine exhaust being at least 1.5 mol%, and regenerating the ASC (50) by reaching a regeneration temperature of at least 500°C using the unburned H2 in the engine exhaust.

2. The method of claim 1, wherein the H2 exhaust excess mode comprises operating (S21) the hydrogen combustion engine (15) by injecting H2 into engine cylinders (310) during an exhaust stroke.

3. The method of claim 1, wherein the H2 exhaust excess mode comprises operating (S23) the hydrogen combustion engine (15') by injecting H2 downstream of an exhaust valve (318) of at least one of the engine cylinders (310) in the hydrogen combustion engine (15').

4. The method according to any of the preceding claims, wherein the H2 exhaust excess mode is included in a combustion mode of the hydrogen combustion engine (15, 15').

5. The method according to any one of claims 1-3, wherein the H2 exhaust excess mode is included in a non-combustion mode of the hydrogen combustion engine (15, 15').

6. The method according to any of the preceding claims, wherein the regeneration time window is further defined at least by the amount of NOx and / or NH3 downstream of the ASC (50) being above a respective predetermined emission threshold.

7. The method according to any of the preceding claims, wherein the regeneration time window is further defined by the absence of engine braking of the hydrogen combustion engine (15, 15').

8. The method according to any one of the preceding claims, further comprising: - delivering (S26) the unburned H2 from the engine outlet (17) of the hydrogen combustion engine (15, 15') to the ASC (50) such that the mole fraction of H2 in the exhaust gas reaching the ASC (50) is at least 80% of the mole fraction of H2 at the engine outlet (17).

9. The method according to any one of the preceding claims, further comprising: - In response to the requested torque or brake power of the hydrogen combustion engine (15, 15') exceeding a corresponding predetermined threshold, terminating (S40) the operation of the hydrogen combustion engine (15, 15') in the H2 exhaust excess mode.

10. A hydrogen combustion engine system (10) for a vehicle (1), the hydrogen combustion engine system (10) comprising a hydrogen combustion engine (15, 15') and an exhaust gas aftertreatment system EATS (20) configured to reduce emissions in the engine exhaust, the EATS (20) comprising a selective catalytic reduction (SCR) catalyst (40) and an ammonia slip catalyst (ASC) (50) arranged downstream of the SCR catalyst (40), wherein the hydrogen combustion engine system comprises a control unit (18), the control unit being configured to: - identifying a regeneration time window for performing regeneration of the ASC (50), the regeneration time window being defined at least by the temperature of the EATS (20) being above a predetermined lower limit and the temperature of the SCR catalyst (40) being below a predetermined upper limit; In response to identifying the regeneration time window, the hydrogen combustion engine (15, 15') is commanded to operate in a H2 exhaust excess mode, the mode being defined by an amount of unburned H2 in the engine exhaust being at least 1.5 mol%, for regenerating the ASC (50) using the unburned H2 in the engine exhaust by reaching a regeneration temperature of at least 500°C.

11. The hydrogen combustion engine system (10) of claim 10, wherein the EATS (20) is free of any oxidation catalyst disposed downstream of the exhaust inlet (22) of the EATS (20) and upstream of the ASC (50).

12. A vehicle (1) comprising a hydrogen combustion engine system (10) according to any one of claims 10-11.

13. A computer program comprising program code means comprising instructions for causing a hydrogen combustion engine system according to any one of claims 10-11 to perform the steps of a method according to any one of claims 1-9 when the program is run on a computer.

14. A computer-readable medium carrying a computer program, the computer program comprising program code means, the program code means comprising instructions for causing a hydrogen combustion engine system according to any one of claims 10-11 to execute the steps of a method according to any one of claims 1-9 when the computer program is run on a computer.

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