Method for operating an internal combustion engine, system for carrying out the method, and internal combustion engine

Abstract

The invention relates to a method for operating an internal combustion engine (2), wherein the internal combustion engine (2) comprises: at least one combustion chamber (3) in which fuel is at least partially combusted with ambient air; an exhaust passage (6) which is fluidly connected to the outlet side (7b) of the at least one combustion chamber (3), wherein hydrogen is used as fuel for the internal combustion engine (2), wherein the internal combustion engine (2) further has at least one NOx storage catalyst (13), and the exhaust gas discharged from the at least one combustion chamber (3) into the exhaust passage (6) at least partially preferably completely flows through the at least one NOx storage catalyst (13), wherein a lean hydrogen-air mixture is combusted in the at least one combustion chamber (3) in a first operating state, wherein the NOx storage catalyst (13) is regenerated in a second operating state, and in order to easily operate the internal combustion engine with a low-emission system, a rich hydrogen-air mixture is combusted in the at least one combustion chamber (3) in the second operating state.

Description

Field of the Invention

[0001] The present invention relates to a method for operating an internal combustion engine, a system for implementing the method, and an internal combustion engine. Background Art

[0002] It is known that hydrogen-powered internal combustion engines are preferred in terms of emissions. For example, carbon-containing emission products such as soot and carbon monoxide are removed in these internal combustion engines.

[0003] In addition, DE102016107466A1 proposes a selective catalytic reduction for reducing NOx components in the exhaust gas from a hydrogen-powered internal combustion engine. However, the reducing agent must be continuously supplied into the exhaust passage. This requires precise dosing of the reducing agent and has continuous control requirements, where, if a failure occurs, NOx emissions may be released into the atmosphere.

[0004] JP2006057504 discloses a method for operating an internal combustion engine using hydrogen. A NOx storage catalyst is located in the exhaust passage of the internal combustion engine, and the NOx storage catalyst stores nitrogen oxides generated during the combustion process. Fossil fuel is added to the combustion mixture to regenerate the NOx storage catalyst.

[0005] US2004 / 055 281A1 and EP 1 754 874 A1 each disclose a method according to the preamble of claim 1. EP 1 319 813 A2 discloses a method according to the preamble of claim 4.

[0006] Regeneration requires difficult control. In addition, the formation of the combustion mixture involves multiple fuels, which makes the system and combustion complex. Summary of the Invention

[0007] Therefore, the fundamental problem of the present invention is to operate an internal combustion engine as a zero-emission / low-emission system in a simple and robust manner.

[0008] This problem is solved by a method for operating an internal combustion engine according to the present invention.

[0009] According to a first aspect, a method for operating an internal combustion engine is provided, wherein the internal combustion engine includes: at least one combustion chamber in which fuel is at least partially combusted with ambient air; an exhaust passage fluidly connected to an outlet side of the at least one combustion chamber. Hydrogen is used as fuel for the internal combustion engine. The internal combustion engine further has at least one NOx storage catalyst, and the exhaust gas discharged from the at least one combustion chamber into the exhaust passage at least partially, preferably completely, flows through the at least one NOx storage catalyst. In a first operating state, a lean air / hydrogen mixture is combusted in the at least one combustion chamber. In a state where a rich air / hydrogen mixture is combusted in the at least one combustion chamber in a second operating state, the NOx storage catalyst is regenerated in the second operating state.

[0010] According to the first aspect, the internal combustion engine has at least one NOx storage catalyst, and the discharged exhaust gas flows through the at least one NOx storage catalyst. This allows nitrogen oxides (NOx) emissions to be stored in the NOx storage catalyst, which is also referred to as an LNT catalyst. This eliminates the need for continuous supply of a reducing agent.

[0011] The first aspect utilizes the synergistic effect resulting from the fact that hydrogen is used as fuel for the internal combustion engine. An internal combustion engine operated in this way produces only thermal nitrogen oxides as harmful combustion products. Therefore, other devices for exhaust gas aftertreatment can be omitted. Thus, there is available space in the exhaust passage for a properly sized NOx storage catalyst.

[0012] Furthermore, for example, compared to a diesel engine, the combustion temperature of a hydrogen-powered internal combustion engine, such as the processing conditions, results in the formation of low nitrogen oxides. This means that nitrogen oxides can be reliably stored in the NOx catalyst for a long time.

[0013] In addition, in this method, a lean air / hydrogen mixture is combusted in the at least one combustion chamber in the first operating state.

[0014] By combusting a lean mixture, the efficiency of the internal combustion engine can be increased. At the same time, the combustion temperature can be reduced, which further inhibits the formation of nitrogen oxides and thus allows the NOx storage catalyst to store nitrogen oxides for a long time. In this process, the combustion of the lean mixture is preferably operated continuously, thus operating in multiple cycles of the internal combustion engine. The lean air / hydrogen mixture is a super-stoichiometric mixture. Preferably, λ is set to be greater than or equal to 1 and less than or equal to 5; depending on the operating point, particularly preferably λ is greater than or equal to 1.3 and less than or equal to 3.5.

[0015] In addition, in the second operating state, the NOx storage catalyst is regenerated.

[0016] The nitrogen oxides stored in the NOx storage catalyst can be converted into atmospheric nitrogen and released into the atmosphere. The NOx storage catalyst can then absorb nitrogen oxides again. In this way, continuous emissions of harmful emissions can be prevented.

[0017] According to the invention, in a second operating state, a rich air / hydrogen mixture is combusted in at least one combustion chamber.

[0018] In the second operating state, a sub-stoichiometric air / hydrogen mixture can thus be supplied to the combustion chamber. Preferably, a λ greater than or equal to 0.6 and less than or equal to 1.0 is set, particularly preferably greater than or equal to 0.8 and less than or equal to 0.9. On the one hand, the rich air / hydrogen mixture can reduce and preferably completely prevent the formation of nitrogen oxides due to oxygen deficiency, and on the other hand, it can ensure that unburned hydrogen is supplied to the exhaust duct as a reducing agent. This means that the excess hydrogen can be used to regenerate the NOx storage catalyst.

[0019] Due to the low formation of nitrogen oxides and the corresponding long-term storage possibility, the rich mixture can be provided in appropriate situations.

[0020] Preferably, the internal combustion engine further has an exhaust gas recirculation device for returning exhaust gas from the exhaust duct to the combustion chamber.

[0021] This allows the inert components of the combustion products to be recirculated from the exhaust duct into the combustion chamber. These components no longer participate in the combustion and extract exothermic energy from the combustion process. The processing temperature can thus be reduced, which inhibits the formation of more nitrogen oxides. Preferably, the exhaust gas is recirculated as high-pressure exhaust gas, particularly from a position upstream of the turbine in the exhaust duct. This ensures a sufficient recirculation rate.

[0022] According to a further aspect, in the second operating state, the exhaust gas can be recirculated into at least one combustion chamber via the exhaust gas recirculation device.

[0023] Therefore, in the second operating state of regenerating the NOx storage catalyst, the formation of more nitrogen oxides can be reduced and preferably completely prevented, and the regeneration of the storage catalyst can be reliably implemented. Another preferred effect is particularly related to hydrogen, because the less reactive mixture can prevent the tendency of early ignition, i.e., pre-ignition.

[0024] According to an alternative, the second operating state is set during the idling operation of the internal combustion engine.

[0025] In this way, it is possible to prevent the influence of the regeneration operation on the behavior of the device driven by the internal combustion engine. In particular, in a motor vehicle with a hydrogen-powered internal combustion engine, it is possible to prevent the influence on the driving behavior. As described above, therefore, the second operating state can be implemented in appropriate situations such as stopping at a traffic light, especially when, for example, the internal combustion engine is operated without performing the operation predetermined for it by disconnecting it from at least one drive wheel of the vehicle or, in other words, without a load being applied to the internal combustion engine. Since this situation is likely to occur when the internal combustion engine is used in a motor vehicle, the operation of the motor vehicle is not restricted by the necessary regeneration phase of the catalyst. In addition, by throttling the air supply amount during idling, a high exhaust gas recirculation rate can be achieved. This is because, in this state, the exhaust gas back pressure (upstream of the turbine of the possible exhaust gas turbocharger) is greater than the pressure in the intake manifold. Thus, the above-mentioned exhaust gas recirculation effect can be reliably achieved in the regeneration mode.

[0026] According to another alternative, the second operating state is set during the overrun operation of the internal combustion engine. The overrun operation is particularly characterized in that the power generated by the internal combustion engine is less than the drag power applied to the internal combustion engine. In other words, the internal combustion engine can keep rotating from the output side.

[0027] In this case, the operation of the motor vehicle is also not restricted by the necessary regeneration phase of the catalyst, because overrun operation is also likely to occur in the internal combustion engine during a long journey. When the air supply amount is throttled in the idling mode, in the overrun operation, the fuel supply amount can be specifically set to burn a rich mixture. At the same time, the ignition may occur very late, which can stabilize the combustion and thus reduce or preferably prevent the formation of more nitrogen oxides. Preferably, the ignition occurs in the range from a maximum of 40° before top dead center of the crankshaft angle to the opening of the exhaust valve, especially in the following range of the crankshaft angle: from a maximum of 40° before top dead center to a maximum of 360° after, further preferably from a maximum of 20° before top dead center to a maximum of 360° after, and still more preferably from the maximum angle corresponding to top dead center to a maximum of 360° after top dead center.

[0028] The rich mixture and the delayed ignition can increase the exhaust gas enthalpy, thus ensuring a sufficient temperature for catalyst regeneration. The power generated by the internal combustion engine during overrun operation is less than the applied drag power, so the overrun operation can be maintained. The advantage of implementing rich mixture combustion as the regeneration mode during the overrun phase is that the conversion from a lean to a rich mixture range can occur discontinuously and thus does not have to pass through the mixture range where λ is equal to 1. In this range, the formation of nitrogen oxides is usually very high.

[0029] Preferably, the exhaust gas is recirculated at least temporarily during the transition between the first operating state and the second operating state.

[0030] Thus, even when passing through a mixture close to stoichiometry during the conversion process, it is possible to reduce, preferably completely prevent, the formation of nitrogen oxides.

[0031] According to another aspect disclosed herein, which can be provided as an aspect dependent on the first aspect, there is provided a method for operating an internal combustion engine, wherein the internal combustion engine has at least one combustion chamber and an exhaust passage, in at least one combustion chamber, fuel is at least partially combusted with ambient air, and the exhaust passage is fluidly connected to the outlet side of at least one combustion chamber. Hydrogen is used as the fuel of the internal combustion engine, wherein the internal combustion engine further has at least one NOx storage catalyst, and the exhaust gas discharged from at least one combustion chamber into the exhaust passage at least partially preferably completely flows through at least one NOx storage catalyst, wherein in a first operating state, a lean air / hydrogen mixture is combusted in the at least one combustion chamber, wherein in a second operating state, the NOx storage catalyst is regenerated, wherein in the second operating state, a reducing agent for reducing the nitrogen oxides stored in the NOx storage catalyst is supplied into at least one combustion chamber as part of the exhaust gas, or supplied into the exhaust passage downstream of at least one combustion chamber upstream of the NOx storage catalyst, or supplied into the NOx storage catalyst.

[0032] According to this aspect, during the combustion of the lean air / hydrogen mixture, only thermal nitrogen oxides are produced as harmful combustion products. Therefore, other exhaust gas aftertreatment devices can be omitted. Thus, there is available space in the exhaust passage for a NOx storage catalyst of appropriate size.

[0033] Furthermore, for example, compared to a diesel engine, the processing conditions such as combustion temperature of a hydrogen-powered internal combustion engine operating in a lean and / or high exhaust gas recirculation rate result in low nitrogen oxide formation. This means that nitrogen oxides can be reliably stored in the NOx catalyst for a long time.

[0034] The combustion of the lean mixture can increase the efficiency level of the internal combustion engine. At the same time, the combustion temperature can be reduced, thereby further suppressing the formation of nitrogen oxides, so that the NOx storage catalyst can store nitrogen oxides for a long time. In this process, the combustion of the lean mixture is preferably continuously operated, so as to operate in multiple cycles of the internal combustion engine. The lean air / hydrogen mixture is a super-stoichiometric mixture. Preferably, λ is set to be greater than or equal to 1 and less than or equal to 5; depending on the operating point, particularly preferably λ is greater than or equal to 1.3 and less than or equal to 3.5.

[0035] Furthermore, in the second operating state, the NOx storage catalyst is regenerated.

[0036] The nitrogen oxides stored in the NOx storage catalyst can be converted into atmospheric nitrogen and released into the atmosphere. The NOx storage catalyst can then absorb nitrogen oxides again. In this way, continuous emissions of harmful emissions can be prevented.

[0037] Furthermore, according to this aspect, the reducing agent can be supplied directly into the exhaust passage without having to be provided as part of the exhaust gas from the combustion process. Thus, the internal combustion engine can continue to operate in a first operating state in which a lean air / hydrogen mixture is combusted. In particular, the lean air / hydrogen mixture can continue to burn. Thus, the first operating state and the second operating state are not mutually exclusive, but can also coexist. Of course, the direct supply of the reducing agent into the exhaust passage can also take place simultaneously with the combustion of a rich mixture, so that only the second operating state exists.

[0038] However, according to this aspect, it is also possible, particularly in an internal combustion engine in which fuel is directly supplied into the combustion chamber, to provide the reducing agent as part of the exhaust gas. In this case, the reducing agent can be supplied into the combustion chamber and then, after being discharged from the combustion chamber, be supplied into the exhaust passage.

[0039] Preferably, at least a rotational or divergent component is applied to the flow of the supplied reducing agent.

[0040] This can increase the mixing in the exhaust passage, and as the reducing agent flows uniformly through the storage catalyst, the storage catalyst can be reliably regenerated.

[0041] Preferably, the reducing agent is hydrogen, and particularly preferably from the same source as the hydrogen used as fuel. In particular, if the reducing agent is directly injected into the combustion chamber, the same supply device used for supplying hydrogen into the combustion chamber can be used.

[0042] This reduces the system complexity since all components can be adapted to hydrogen. Furthermore, no additional storage means, such as a tank for the reducing agent, is required.

[0043] Preferably, the reducing agent is supplied into the combustion chamber after the combustion process is completed, and more preferably during the exhaust stroke in which the exhaust gas is discharged from the combustion chamber. This ensures that the reducing agent does not burn together with the oxygen in the air contained in the combustion chamber.

[0044] According to another aspect, the setting of the second operating state can be carried out when the saturation of the NOx storage catalyst is greater than 20% or less than 100%, preferably 70 - 90%, particularly preferably 80%. Known methods for determining the saturation can be used.

[0045] This means that the storage catalyst can be used for a large part of its storage capacity. Due to the low NOx formation in the first operating state, supersaturation can be prevented during the switching, so that the switching can be carried out very close to the storage capacity limit.

[0046] According to another aspect, which can be provided as another independent aspect or as an aspect dependent on the above aspects, there is provided a method for operating an internal combustion engine, wherein the internal combustion engine has at least one combustion chamber and an exhaust passage, in which at least one combustion chamber, fuel is at least partially combusted with ambient air, and the exhaust passage is fluidly connected to the outlet side of at least one combustion chamber, wherein hydrogen is used as the fuel of the internal combustion engine. The exhaust passage has a plurality of exhaust passage portions connected in parallel, wherein each of at least two of the plurality of exhaust passage portions has at least one NOx storage catalyst, and at least a part of the exhaust gas discharged from at least one combustion chamber into the exhaust passage at least temporarily flows through at least one NOx storage catalyst, wherein preferably by means of a variable throttle device arranged upstream of at least one NOx storage catalyst, the flow rate through at least one NOx storage catalyst in at least one of the exhaust passage portions is at least temporarily changed.

[0047] Thus, the flow of the exhaust gas can be affected depending on the remaining capacity of at least one NOx storage catalyst. If the NOx storage catalyst in the exhaust passage is close to the capacity limit, the flow rate in this exhaust passage can be reduced, while the NOx storage catalysts connected in parallel can continue to have a large flow through. This also allows the NOx storage catalyst to operate effectively, as in the above aspects.

[0048] The flow rates in the plurality of exhaust passage portions each including at least one NOx storage catalyst are changed independently of each other.

[0049] For this purpose, variable throttle devices are arranged in a plurality of the plurality of exhaust passage portions, which are arranged side by side upstream of at least one NOx storage catalyst, and the variable throttle devices are individually controlled to regulate the amount of exhaust gas in each exhaust passage portion.

[0050] Thus, it is possible to react independently with each NOx storage catalyst connected in parallel.

[0051] Furthermore, in order to regenerate at least one NOx storage catalyst, the flow rate in at least one exhaust passage portion can be reduced, preferably completely inhibited.

[0052] If the internal combustion engine is operated with a lean combustion mixture, for example, nitrogen oxides will continue to flow through at least one exhaust passage portion in which the NOx storage catalyst is close to the capacity limit in the throttle-free state. Thus, during regeneration, the reduction can inhibit the further strong supply of nitrogen oxides in at least one exhaust passage portion.

[0053] A reducing agent for reducing nitrogen oxides stored in a NOx storage catalyst is supplied to at least one of a plurality of exhaust passage portions connected side by side upstream of at least one NOx storage catalyst, particularly preferably to each exhaust passage portion, or to at least one other NOx storage catalyst, and particularly preferably, the supply amount of the reducing agent is controlled individually for each exhaust passage portion.

[0054] This can improve the efficiency of NOx storage and regeneration. The internal combustion engine can continue to operate in the case of a lean combustion mixture. If only a single exhaust passage is provided in this method, a large amount of reducing agent (hydrogen) must be added to compensate for the oxygen present due to lean combustion. Only in this way can regeneration be carried out in an oxygen-deficient situation. On the contrary, through the above aspects, the oxygen supply in at least one corresponding exhaust passage portion can be reduced, for example, by a throttle device, so that even if the internal combustion engine continues to operate with a lean combustion mixture, a smaller amount of hydrogen is required compared to the case where only one exhaust passage portion is provided. Therefore, if the flow rate in the corresponding exhaust passage portion is reduced for regeneration compared to a non-regenerative state, such as a non-throttled state, it is particularly preferred to supply the reducing agent individually to the corresponding exhaust passage portion.

[0055] According to another aspect, at least two exhaust passage portions can be regenerated alternately, at least temporarily.

[0056] For example, when the internal combustion engine is operating at half of its maximum output and two storage catalysts are connected side by side, the highest improvement in efficiency is obtained. This is because in this case, at least for the regeneration of the storage catalyst arranged therein, the throttle device of the exhaust passage portion can be controlled to completely block the exhaust gas supply in this exhaust passage portion, and at least one storage catalyst will be regenerated. In the side-by-side exhaust passage portions, the throttle device is preferably controlled to be completely open. This means that regeneration occurs alternately in the two exhaust passage portions, where regeneration occurs in one exhaust passage portion and does not occur in the other exhaust passage portion. Similarly, compared to a reference state such as a non-regenerative state, changes in the flow rate, particularly a decrease, can occur alternately. Particularly preferably, during the operation of the internal combustion engine, each throttle device is alternately completely opened and closed until half of the maximum output, so that each flow rate is alternately completely suppressed rather than reduced. Preferably, the flow rate is alternately reduced to the rated output minus one divided by the number of side-by-side arranged exhaust passage portions multiplied by the rated output, particularly completely suppressed rather than reduced.

[0057] According to another aspect, at least the storage catalysts connected in parallel, preferably in each case the entire exhaust duct section, can be arranged in such a way that the nitrogen oxides produced in the unthrottled state of all exhaust duct sections at maximum output can be completely stored, so that when the flow rate is not reduced, in particular the sum of all storage catalysts connected in parallel is arranged according to a predetermined space velocity. Preferably, the storage catalysts and the exhaust duct section have the same dimensions.

[0058] However, it is also conceivable to configure at least the storage catalysts connected side by side, preferably the entire corresponding exhaust duct section, so that the flow rate can be completely suppressed at rated power in at least one exhaust duct section. The flow rate can then flow at rated power through the remaining exhaust duct sections in which the flow rate is not reduced and in which the storage catalyst is arranged. This ensures that the nitrogen oxides produced even at rated output are stored in the unreduced storage catalysts of the exhaust duct section. In particular, the sum of the remaining storage catalysts connected side by side can be configured according to a predetermined space velocity. In the case of two exhaust duct sections side by side, each of the exhaust duct sections is preferably configured in such a way that at rated output, the nitrogen oxides produced can be completely stored in at least one storage catalyst in the exhaust duct section in which the flow rate is not reduced. This allows the mapping range in which complete regeneration is feasible to be expanded.

[0059] Furthermore, the problem is solved by a control device which is configured to implement a method according to one of the preceding aspects.

[0060] Such a control device allows the platform on which it is installed to operate as a low-emission system.

[0061] In addition to the control device, the present invention also relates to a program which, when executed on a computer connected to an internal combustion engine, implements the above method. Likewise, the present invention relates to a computer-readable storage medium on which the program is executed.

[0062] The above problem is further solved by a system for implementing the method according to one of the above aspects, wherein the system comprises: an internal combustion engine defined according to one of the above aspects; and a hydrogen storage device connected to the internal combustion engine in a fluid communication manner.

[0063] Such a system constitutes a reliable zero emission / low emission system.

[0064] Preferably, the system further comprises a control device configured to implement the method according to one of the above aspects.

[0065] The above-mentioned effects can be reliably achieved through the interaction of the control device, the internal combustion engine and the storage device.

[0066] Preferably, in the system, the internal combustion engine further has at least one inflow device through which the reducing agent can be supplied to the combustion chamber or the exhaust passage. In the case where a plurality of exhaust passage portions are connected side by side, preferably, at least one inflow device is provided for each exhaust passage portion.

[0067] This allows the reducing agent to be supplied to the exhaust passage in the internal combustion engine via the combustion chamber or bypassing the combustion chamber, such that the mixture does not need to be switched from a lean mixture to a rich mixture.

[0068] Preferably, in the system, the internal combustion engine is further configured to, at least in part, apply a rotational or diverging component to the flow of the reducing agent in the exhaust passage, wherein the internal combustion engine preferably has a turning device or a profile angled with respect to the main flow direction.

[0069] This can improve the mixing of the reducing agent in the exhaust passage, thereby improving the efficiency of the catalyst. The rotational component can be easily applied by the turning device. The flow can be made to diverge along the profile by the angled profile.

[0070] There is further provided an internal combustion engine for the above system, which can particularly have any combination of the structural features of the present disclosure. Description of the Drawings

[0071] The above aspects will now be described in more detail with reference to exemplary embodiments according to the drawings.

[0072] Figure 1 A system capable of implementing the above method is schematically shown.

[0073] Figure 2 A schematic longitudinal sectional view showing a modified example of the exhaust passage of the internal combustion engine according to the present invention is shown.

[0074] Figure 3 A flowchart of a method for regenerating a NOx storage catalyst is shown.

[0075] List of Reference Numerals

[0076] 1 System

[0077] 2 Internal Combustion Engine

[0078] 3 Combustion Chamber

[0079] 5 Intake Manifold

[0080] 6, 106 Exhaust Passage

[0081] 106a, 106b Exhaust Passage Portions

[0082] 7a, 7b Inlet, Outlet

[0083] 8 Throttle Valve

[0084] 9 Injection device

[0085] 10 Spark plug

[0086] 11 Piston

[0087] 12 Crankshaft

[0088] 13, 13a, 13b NOx storage catalyst

[0089] 14 Manifold

[0090] 14a, 14b Manifolds

[0091] 15 Storage device

[0092] 16 Pipeline

[0093] 16a End

[0094] 19a, 19b Inflow device

[0095] 16a1 Outlet

[0096] 17 Control device

[0097] 18a, 18b Throttle device / throttle valve

[0098] 21a, 21b Nitrogen oxide sensors Detailed implementation mode

[0099] System 1 includes an internal combustion engine 2 (engine), which is shown in Figure 1 a longitudinal cross-sectional view along the cylindrical combustion chamber 3 of the internal combustion engine 2. In addition to the combustion chamber 3, the internal combustion engine 2 also has an intake manifold 5 and an exhaust passage 6. The intake manifold 5 and the exhaust passage 6 are respectively connected to the combustion chamber in a fluid communication manner via an inlet 7a and an outlet 7b. The inlet 7a and the outlet 7b are respectively opened and closed via valves.

[0100] As Figure 1 shown, a throttle valve 8 for adjusting the air volume and an injection device 9 for injecting fuel into the intake manifold 5 can be located in the intake manifold 5. At the upper end, the combustion chamber 3 is closed by a cylinder head, and a spark plug 10 is arranged in the cylinder head to ignite the air / fuel mixture entering the combustion chamber through the inlet 7a. At the lower end, the combustion chamber 3 is closed by a piston 11, and the piston 11 is rotatably connected to a crankshaft 12. Preferably, only hydrogen is used as fuel.

[0101] The outlet 7b is located on the opposite side of the inlet 7a with respect to the axis, and the exhaust gas generated by burning the air / fuel mixture flows into the exhaust passage 6 through the outlet 7b.

[0102] The NOx storage catalyst (NSK) 13 is located downstream of the outlet 7b in the exhaust passage 6. The NOx storage catalyst 13 essentially consists of, for example, an alumina substrate coated with CeO2 and Ba(OH)2 or BaCO3. For example, platinum and rhodium or palladium can be used as the active components.

[0103] Upstream of the NOx storage catalyst 13, the exhaust passage has a branch pipe 14. The branch pipe 14a where the NOx storage catalyst 13 is located terminates in the end pipe of the exhaust passage, while the other branch pipe 14b is part of the exhaust gas recirculation device and leads to the intake manifold 5 at a position downstream of the downstream end of the branch pipe. Therefore, the exhaust gas recirculation device recirculates the high-pressure gas. The exhaust gas recirculation device can also include, for example, valves and sensors for monitoring the recirculated exhaust gas. In the branch pipe 14a, preferably upstream of the NOx storage catalyst 13, a turbine for driving the exhaust gas turbocharger can also be provided.

[0104] The system 1 further includes a storage device 15 filled with hydrogen. The storage device 15 is connected to the intake manifold 5 in a fluid communication manner via an injection device 9, where the injection device 9 can inject hydrogen into the intake manifold 5 upstream of the inlet 7a. The injection device 9 is an example of a supply device for supplying fuel. In addition, the storage device 15 is connected to the exhaust passage upstream of the NOx storage catalyst 13 in a fluid communication manner via a pipeline 16. The end 16a (injection device) of the pipeline 16 has a divergent shape in the direction of the outlet 16a1, and thus represents a profile at an angle with respect to the main flow direction of the pipeline 16. The end 16a having the outlet 16a1 is an inflow device for the reducing agent.

[0105] In addition, the system 1 has a control device 17 such as an ECU. The control device 17 receives signals from a plurality of sensors arranged in the system 1 (as shown by the dashed lines), and correspondingly controls the actuators and valves arranged in the system 1 via electrical signals (as shown by the dashed lines).

[0106] The system 1 can be used to implement the above method. When the control device 17 receives a start signal for starting the internal combustion engine 2, the injection device 9 is activated to inject hydrogen fuel into the air in the intake manifold 5 during the intake stroke. The hydrogen / air mixture in the combustion chamber 3 is ignited by the spark plug 10 to provide power to the crankshaft 12. The combustion products enter the exhaust passage 6 as exhaust gas through the outlet 7b. The exhaust gas flows through the NOx storage catalyst 13 there.

[0107] The function of the NOx storage catalyst 13 is as follows. In the normal first operating state of the internal combustion engine 2 (λ > 1, combustion of lean mixture), NO is oxidized to NO2 by the oxygen present in excess on the noble metal of the NOx storage catalyst 13, such as platinum for example, and the NO2 combines with the storage component, preferably a basic storage component, such as Ba(OH)2 or BaCO3, to form nitrites, especially nitrates.

[0108] The internal combustion engine 2 can operate continuously in the first operating state. By burning a lean mixture, the efficiency of the internal combustion engine 2 can be increased. At the same time, the combustion temperature can be reduced, which inhibits the formation of nitrogen oxides, so that the NOx storage catalyst 13 can store nitrogen oxides for a long time. The combustion of the lean mixture is preferably a continuous operation and thus takes place in multiple cycles of the internal combustion engine. Preferably, a λ greater than or equal to 1 and less than or equal to 5 is set; depending on the operating point, a λ greater than or equal to 1.3 and less than or equal to 3.5 is particularly preferred.

[0109] If the control device 17 now receives information that the internal combustion engine 2 is idling, for example because the motor vehicle using the system 1 is stopped at a traffic light, the control device 17 controls the throttle valve 8 so as to reduce the amount of air in the intake manifold 5. At the same time, the control device 17 activates the exhaust gas recirculation device, for example by opening the cut-off valve arranged in the branch pipe 14b and reducing the flow rate of the exhaust gas in the branch pipe 14a. This sets a second operating state during idling, in which a rich air / hydrogen mixture (λ < 1) is burned, because the amount of air is reduced to such an extent that a rich mixture is produced with the same mixture calorific value for the amount of fuel injected by the injection device 9. At the same time, the recirculated exhaust gas is supplied to the mixture. The air supply is preferably set to achieve a sub-stoichiometric mixture with the mixture calorific value required for at least idling power.

[0110] On the one hand, the rich air / hydrogen mixture can reduce and preferably completely prevent the formation of nitrogen oxides due to the complete combustion of oxygen and hydrogen, and on the other hand, it can ensure that the unburned hydrogen is supplied as a reducing agent to the exhaust duct 6. This means that the excess hydrogen can be used to regenerate the NOx storage catalyst 13. The recirculated exhaust gas returns the inert components of the combustion products from the exhaust duct 6 to the combustion chamber 3. These components no longer participate in the combustion process. This means that the treatment temperature can be reduced, thus inhibiting the formation of more nitrogen oxides. This means that the storage catalyst can be reliably regenerated. Therefore, it is also preferred if the exhaust gas is recirculated at least temporarily during the transition between the first operating state and the second operating state.

[0111] Preferably, the second operating state is set by the control device 17 until the NOx storage catalyst 13 is completely regenerated.

[0112] Similar to idling operation, the control device is also able to set a second operating state during the coasting operation of the internal combustion engine 2. For example, if the control device 17 detects the presence of a coasting mode, the control device 17 controls the injection device 9 such that a rich mixture is present according to the supplied air quantity, which can be adjusted by means of the throttle valve 8. In addition, the exhaust gas recirculation is activated in a manner similar to idling operation.

[0113] A prerequisite for coasting operation is that the operator (e.g., the driver) does not demand any torque from the internal combustion engine, i.e., the accelerator pedal is not depressed. To ensure zero torque regardless of the fuel supply, the spark plug 10 is activated at a very late stage.

[0114] Preferably, ignition occurs in a range of up to a maximum of 40° before top dead center of the crankshaft angle up to the opening of the exhaust valve, in particular in the following range of crankshaft angles: up to a maximum of 40° before top dead center to a maximum of 360° thereafter, further preferably up to a maximum of 20° before top dead center to a maximum of 360° thereafter, and still more preferably from the maximum angle corresponding to top dead center to a maximum of 360° after top dead center.

[0115] Preferably, the air supply during coasting operation is reduced, for example by adjusting the throttle valve, compared to the operating mode (driven by the internal combustion engine). This means that only a small amount of hydrogen needs to be supplied in order to form a rich mixture.

[0116] The rich mixture and the retarded ignition can increase the exhaust gas enthalpy, thus ensuring a sufficient temperature for the regeneration of the NOx storage catalyst 13. The power generated by the internal combustion engine during coasting operation corresponding to the calorific value of the rich mixture is less than the drag power applied to the internal combustion engine. The advantage of burning a rich mixture during the coasting phase as a regeneration operation is that the transition from a lean mixture to a rich mixture range can occur discontinuously and thus does not have to pass through the mixture range where λ is equal to 1. In this range, the formation of nitrogen oxides is usually very high. During the transition to idling operation, if the mixture is continuously converted from the excess stoichiometric range to the low stoichiometric range, a mixture range with a high formation of nitrogen oxides may occur in some cases.

[0117] By Figure 3 The above method is summarized. In step S1, the system 1 continuously monitors the saturation state NOx% of the NOx storage catalyst 13, where known methods by measurement and / or modeling of the saturation state can be used, for example. If the control device 17 determines that the saturation state has reached a predetermined limit value Th, for example greater than 20% or less than 100%, preferably 70% - 90%, then in step S2, regeneration is requested, thereby indicating the second operating state.

[0118] In step S3, it is checked whether idling operation LL or coasting operation SB can be expected within a predetermined time interval. For example, route information or navigation data of a vehicle equipped with an internal combustion engine can be used. The predetermined time interval preferably depends on a limit value Th. If idling or coasting operation can be expected within the specified time interval, regeneration is carried out in one of the two states in step S3a. If it is determined that there is no or will be no idling operation or coasting operation, for example, the cut-off valve in line 16 is released and hydrogen from the storage device 15 bypasses the combustion chamber 3 via end 16a and is directly supplied to the exhaust passage 6. In this way, regeneration of the NOx storage catalyst 13 can be ensured even when the appropriate conditions for rich mixture combustion do not occur for a long time. In particular, the NOx storage catalyst 13 can be regenerated under full load VL or TL.

[0119] If necessary, line 16 and end 16a can also be omitted. In this case, for example, when the saturation of the NOx storage catalyst 13 is greater than 20% or less than 100%, preferably 70 - 90%, the control device 17 can issue a warning to the user (driver) of the internal combustion engine 2 indicating the need to switch to idling operation. The limit value is preferably lower than the value when the inflow device is present, so as to provide sufficient time to switch to coasting or idling operation.

[0120] However, it is also possible to program a control device 17 not according to the present invention such that it does not set the combustion of a rich mixture under exhaust gas recirculation during either coasting operation or idling operation. In this case, regeneration in the second operating state can only be carried out via line 16 and end 16a, where the reducing agent is directly supplied into the exhaust passage 6. This means that the internal combustion engine 2 can continue to operate in the first operating state (lean mixture) while the second operating state exists. However, alternatively or additionally, especially if the fuel is directly supplied to the combustion chamber 3 via a supply device in the engine, the reducing agent can also be provided as part of the exhaust gas. In this case, the reducing agent can be supplied into the combustion chamber 3 and then, after being discharged from the combustion chamber 3, be supplied to the exhaust passage 6. The supply into the combustion chamber 3 is preferably carried out after the completion of the combustion process, so especially during the exhaust stroke after the spark plug ignition is completed and the energy of the combustion mixture is not sufficient to burn the supplied reducing agent. In particular, the reducing agent is hydrogen and can be supplied via the same supply device as the hydrogen being burned. In this case, a lean mixture can also be burned.

[0121] Figure 2 A schematic longitudinal sectional view of a modified example of the exhaust passage 106 of the engine is shown.

[0122] As Figure 2As shown, the exhaust passage 106 is different from the above-described exhaust passage 6 in that, for example, it is divided into two exhaust passage portions 106a and 106b, preferably downstream of the branch pipe shown in Figure 1 and the two exhaust passage portions are connected side by side with each other. Each of the exhaust passage portions 106a and 106b has a NOx storage catalyst 13a and 13b, respectively. Upstream of each of the two NOx storage catalysts 13a and 13b are throttle valves (throttling devices) 18a and 18b. Between the throttle valves 18a and 18b and the NOx storage catalysts 13a and 13b, an inflow device 19a or 19b is also provided in each case, through which a reducing agent for regenerating the NOx storage catalysts 13a and 13b can be supplied to the corresponding exhaust passage portions 106a and 106b, bypassing at least one combustion chamber. In other words, each of the exhaust passage portions 106a and 106b includes the inflow devices 19a and 19b upstream of the NOx storage catalysts 13a and 13b. Each of the inflow devices 19a and 19b preferably includes an injector. The injector injects a reducing agent (hydrogen) into the exhaust passage portions 106a and 106b.

[0123] The throttling degree of the throttle valves 18a and 18b is variable. The opening angles of each of the throttle valves 18a and 18b can be set individually, thereby independently of the other throttle valves. Thus, it is possible to change, in particular, individually adjust the exhaust gas volume flowing to each of the exhaust passage portions 106a and 106b. The inflow device (injector) can also be controlled individually so that the reducing agent can be supplied to each of the exhaust passage portions 106a and 106b separately. In particular, the supply amount (mass flow) of the reducing agent is individually controlled.

[0124] The advantage of the above modification is that the engine can be operated at the optimal operating point, and rich combustion does not have to be implemented to avoid oxygen and nitrogen oxide components in the exhaust gas. According to the above modification, the storage and regeneration efficiency of the nitrogen oxide catalyst can be improved. If one of the NOx storage catalysts 13a and 13b in the side-by-side exhaust passage sections (for example, the NOx storage catalyst 13a) approaches its capacity limit, for example, the above-mentioned predetermined limit value Th, the exhaust gas can continue to be stored in the other NOx storage catalyst 13b in the other exhaust passage section 106b through the throttling device 18a of the exhaust passage section where the NOx storage catalyst 13a is located, and the NOx storage catalyst 13a is operated close to its capacity limit, thereby reducing, preferably completely suppressing, the flow rate supplied to the exhaust passage section. This configuration is particularly effective for regeneration. When there is only one storage catalyst, the internal combustion engine must be operated rich to regenerate, or a large amount of reducing agent must be supplied to the exhaust passage alone by bypassing at least one combustion chamber. In the latter method, the internal combustion engine can still be operated lean, but a large amount of reducing agent (hydrogen) must be supplied to compensate for the oxygen generated by lean combustion. Only then can regeneration be performed with exclusion of oxygen. In contrast, the present embodiment allows the throttling device 18a to reduce the oxygen supply in the corresponding exhaust tract section 106a, which means that less hydrogen is required compared to only one exhaust tract section in the first embodiment.

[0125] Preferably, the NOx storage catalysts 13a and 13b and the exhaust passage sections 106a and 106b are of the same size. The NOx storage catalysts 13a and 13b and the exhaust passage sections 106a and 106b connected in parallel are arranged together in such a way that the nitrogen oxides generated at the maximum power can be completely stored in the unthrottled state of all the exhaust passage sections when the flow rate is not reduced. In other words, when the exhaust passage sections 106a and 106b are fully opened, the nitrogen oxides of the entire exhaust gas (possibly minus the exhaust gas recirculation amount) generated at the maximum power can be removed.

[0126] In this case, the highest increase in efficiency is achieved when two storage catalysts are connected side by side, when the internal combustion engine is running at half the maximum power. Therefore, the flow rate is alternately reduced, in particular, completely suppressed, and not reduced at an applied power up to the rated power minus the inverse value of the number of exhaust duct sections arranged side by side (two, inverse: 1 / 2) times the rated power.

[0127] This is because in this case, the throttling device 18a of the exhaust passage portion can be controlled, at least for the regeneration of the NOx storage catalyst 13a disposed therein, so as to completely block the supply of exhaust gas in the exhaust passage portion 106a, where at least one NOx storage catalyst 13a is to be regenerated. At the same time, it is preferable to control the throttling device 18b in the parallel exhaust passage portion 106b to be fully opened. Therefore, the corresponding flow rate is alternately completely suppressed rather than reduced.

[0128] Particularly preferably, when half of the maximum power is applied, during the operation of the internal combustion engine, the respective throttling devices 18a and 18b are alternately fully opened and closed. The control device 17 (ECU) controls the throttle valves 18a and 18b and the inflow devices 19a and 19b.

[0129] However, it is also conceivable to configure at least the storage catalysts arranged in parallel, preferably the entire corresponding exhaust passage portion, such that the flow rate can be completely suppressed in at least one exhaust passage portion at the rated power (maximum power). Then, the flow rate can flow through the remaining exhaust passage portion where the flow rate is not reduced and the storage catalyst is disposed therein at the nominal power. This ensures that the nitrogen oxides generated even at the nominal output are stored in the non-reduced storage catalyst in the exhaust passage portion. In the case of two parallel exhaust passage portions, each of the exhaust passage portions is preferably configured such that at the rated output, the generated nitrogen oxides can be completely stored in at least one storage catalyst in the exhaust passage portion where the flow rate is not reduced. This allows the expansion of the mapping range in which complete regeneration can be performed. Therefore, compared with the case where the catalyst and the exhaust gas section are adjusted together to be able to purge the entire exhaust gas volume in a non-throttled state, the sizes of the catalyst and the exhaust gas section are oversized.

[0130] There are NOx sensors 21a and 21b downstream of the catalyst, which detect the NOx content in the post-treatment exhaust gas, so as to be able to determine the complete saturation or malfunction of the catalyst. For example, if the NOx content is detected downstream of the NOx storage catalyst 13a, the control device 17 can control the throttle valve 18a to be fully closed. At the same time, the other throttle valve 18b is fully opened. Known methods can be used to measure the saturation of the catalyst itself. The saturation can also be modeled.

[0131] At least one NOx sensor can also be arranged upstream of the storage catalyst. This can be done in each of the parallel exhaust passage portions 106a and 106b, preferably in the common exhaust passage 106 upstream of each throttle valve and / or upstream of the shunt. In particular, the output of the at least one NOx sensor can be used to control the parallel exhaust passage portions arranged.

[0132] Accordingly, the exhaust passage section, in particular the throttle valve and the injector, can be controlled based on signals from at least one NOx sensor upstream or downstream of the catalyst. Preferably, the throttle valves 18a and 18b are controlled in such a way that when the regeneration limit value of 80% saturation level is reached in one NOx storage catalyst 13a, the other NOx storage catalyst 13b is at least 20% saturation level away from its regeneration limit value. In this way, it is possible to ensure that when the NOx storage catalyst 13a is regenerated, the other NOx storage catalyst 13b has sufficient capacity for more nitrogen oxides.

[0133] In the modified example, the number of exhaust passage sections is not limited to two. On the contrary, more than two exhaust passage sections can also be provided. In addition, if only one exhaust passage section upstream of the catalyst has a variable throttle device, the preferred effect has been achieved. This is because when the capacity limit is reached, the catalyst of interest can remain free of more nitrogen oxides and can be regenerated independently of other side-by-side catalysts. Preferably, the side-by-side arranged catalysts and / or exhaust passage sections are each adapted to a 1:1 size ratio in terms of their storage volume or cross-sectional area. This allows a significant increase in efficiency.

[0134] The rich combustion mixture can also be burned for regeneration.

[0135] Similarly, in the above embodiment, a plurality of combustion chambers can be provided instead of one combustion chamber.

[0136] As previously mentioned, the type of mixture formation is not important. This can occur inside or outside the combustion chamber.

[0137] Instead of the angled profile in the end 16a of the line 16, a steering device with helical vanes can also be provided, along which the fluid is forced to flow. The main flow direction of the outlet 16a1 can also be inclined with respect to the main flow direction of the exhaust passage or the exhaust passage section. There is no need to provide an angled profile. The inclined arrangement imposes a rotational component on the flow.

[0138] Preferably, the exhaust gas is recirculated upstream of at least one storage catalyst. However, the exhaust gas recirculation can also occur downstream of at least one storage catalyst.

[0139] Unless otherwise specified in this disclosure, "at least" also includes the respective wholes.

[0140] The above system 1 is preferably used in and installed in a motor vehicle. The internal combustion engine 2 is preferably a modified conventional diesel engine, particularly preferably a diesel engine for commercial vehicles such as trucks. The system is also provided with a hydrogen tank as a storage device 15 for fuel, replacing the diesel tank. For the system 1 and the above method, it is therefore preferred to use an internal combustion engine according to the diesel principle including a NOx storage catalyst, which is correspondingly large and thus ensures a long storage time for the hydrogen engine.

[0141] Therefore, another aspect of the present invention relates to a method for converting an existing diesel power system, which can be implemented in a motor vehicle. For example, the fuel storage device is replaced by a hydrogen storage device, and the direct injection device is replaced by a spark plug. It is also conceivable to provide a supply device for supplying hydrogen to the combustion chamber, preferably provided on the cylinder head. If not available, a throttle valve can also be added. In addition, the control device is programmed to implement the above method.

[0142] The present invention also relates to the use of an internal combustion engine used in a diesel power system, which is equipped with at least one storage catalyst, and / or at least one storage catalyst in the system described in the present disclosure and / or the method described in the present system.

Claims

1. A method for operating an internal combustion engine (2), wherein, The internal combustion engine (2) includes: At least one combustion chamber (3) in which fuel is at least partially combusted with ambient air; An exhaust passage (6, 106) fluidly connected to the outlet side (7b) of the at least one combustion chamber (3); wherein hydrogen is used as fuel for the internal combustion engine (2); wherein the exhaust passage has a plurality of exhaust passage portions (106a, 106b) connected side by side with each other, and at least one NOx storage catalyst (13a, 13b) is provided in each of at least two of the plurality of exhaust passage portions (106a, 106b), and at least a part of the exhaust gas discharged from the at least one combustion chamber (3) into the exhaust passage (6) at least temporarily flows through the at least one NOx storage catalyst (13a, 13b); wherein the flow rate of the exhaust gas flowing through the at least one NOx storage catalyst (13a, 13b) in at least one of the exhaust passage portions (106a, 106b) is at least temporarily changed; It is characterized in that the flow rates of the exhaust gas in the plurality of exhaust passage portions (106a, 106b) each including the at least one NOx storage catalyst are independently changed from each other by throttling devices, the throttling degree of the throttling devices is variable, and the throttling devices are respectively arranged upstream of the at least one NOx storage catalyst (13a, 13b) in the plurality of exhaust passage portions (106a, 106b), and a reducing agent for reducing nitrogen oxides stored in the NOx storage catalyst (13a, 13b) is supplied into the plurality of exhaust passage portions (106a, 106b) between the corresponding at least one NOx storage catalyst (13a, 13b) and the variable throttling devices (18a, 18b).

2. The method according to claim 1, wherein, The flow rate in at least one of the exhaust passage portions (106a, 106b) is reduced for the regeneration of the at least one NOx storage catalyst (13a, 13b).

3. The method according to claim 1 or 2, wherein, A reducing agent for reducing nitrogen oxides stored in the NOx storage catalyst (13, 13a, 13b) is at least temporarily supplied into at least one exhaust passage portion (106a, 106b) upstream of the at least one NOx storage catalyst (13a, 13b), or is supplied separately into the at least one NOx storage catalyst (13a, 13b).

4. The method according to claim 1, wherein, At least two of the exhaust passage portions (106a, 106b) are at least temporarily regenerated alternately.

5. A control device (17) configured to carry out the method according to any one of the preceding claims.

6. An internal combustion engine (2), comprising: At least one combustion chamber (3) in which hydrogen is at least partially combusted with ambient air; An exhaust passage (6, 106) fluidly connected to the outlet side (7b) of the at least one combustion chamber (3); Among them, the exhaust passage (106) has a plurality of exhaust passage portions (106a, 106b) connected in parallel with each other, wherein each of at least two of the plurality of exhaust passage portions (106a, 106b) has at least one NOx storage catalyst (13a, 13b), and at least a part of the exhaust gas discharged from the at least one combustion chamber (3) into the exhaust passage (6) at least temporarily flows through the at least one NOx storage catalyst (13a, 13b). Among them, in the plurality of exhaust passage portions (106a, 106b) arranged in parallel with each other upstream of the at least one NOx storage catalyst (13a, 13b), throttle devices (18a, 18b) with variable throttle degrees are respectively arranged. The variable throttle devices can be individually controlled to adjust the amount of exhaust gas in the corresponding exhaust passage portions (106a, 106b), and the plurality of exhaust passage portions (106a, 106b) respectively include inflow devices (19a, 19b) for supplying a reducing agent for reducing nitrogen oxides stored in the NOx storage catalyst (13a, 13b) between the corresponding at least one NOx storage catalyst (13a, 13b) and the variable throttle device (18a, 18b).

7. A system for carrying out the method according to any one of claims 1 to 4, comprising: The internal combustion engine according to claim 6; and The control device (17) according to claim 5.

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