HYDROGEN ENGINE AND ITS EXHAUST SYSTEM

Abstract

The present invention relates to an engine assembly comprising an internal combustion engine (1) connected to an exhaust line (2), the internal combustion engine being configured to run on hydrogen, characterized in that the exhaust line (2) is equipped with a single pollution control device consisting of a nitrogen oxide trap (2b). Figure 1

Description

Title of the invention: HYDROGEN ENGINE AND ITS EXHAUST LINE

[0001] The present invention relates to the field of internal combustion engines. More particularly, the invention relates to a hydrogen engine and its exhaust system.

[0002] One of the major challenges for the automotive industry is to further reduce the release into the atmosphere of pollutants contained in the exhaust gases emitted by engines. For example, the combustion of diesel fuel by a lean-burn engine generates the emission of carbon monoxide, hydrocarbons, soot particles, and nitrogen oxides, commonly referred to by the acronym NOx.

[0003] Hydrogen-powered internal combustion engines represent an alternative to both fossil fuel engines and all-electric vehicles. Initial experiments involved, for example, using adapted diesel engines with their original emissions control systems, namely: a diesel oxidation catalyst (DOC) and a filter coated with an SCR (Selective Catalytic Reduction) or SCRF (Selective Catalytic Reduction on Filter) impregnation, and an ASC (Ammonia Slip Catalyst), particularly to meet the future requirements of the Euro 7 emissions standard for ammonia. With such an exhaust system, NOx emissions are satisfactorily reduced.However, such an exhaust system remains expensive and complex, particularly due to its nitrogen oxide conversion system (SCR or SCRF) and associated diagnostics.

[0004] A processing system is also known from document CN116641776A exhaust gas from a hydrogen-powered internal combustion engine using a "three-way" catalyst at the end of the exhaust line and a complex bypass system.

[0005] There is therefore a need for a simple and inexpensive system for treating nitrogen oxides from a hydrogen-powered internal combustion engine.

[0006] To achieve this objective, the invention provides an engine assembly comprising an internal combustion engine connected to an exhaust line, the internal combustion engine being configured to run on hydrogen, characterized in that the exhaust line is equipped with a single pollution control device consisting of a nitrogen oxide trap.

[0007] The technical effect is to obtain a compact pollution control system sized precisely as needed when the engine is running on hydrogen.

[0008] Various additional features may be provided, alone or in combination:

[0009] In one embodiment, the nitrogen oxide trap is located near the exhaust outlet of the internal combustion engine.

[0010] In one embodiment, the engine assembly includes hydrogen injection means disposed in the exhaust line upstream of the nitrogen oxide trap and a hydrogen tank fluidly connected to these injection means.

[0011] In one embodiment, the hydrogen tank is fluidly connected to a hydrogen injection system of the internal combustion engine.

[0012] In one embodiment, the engine assembly includes a control unit configured to control the hydrogen injection means so as to introduce an excess of hydrogen into the exhaust line in order to regenerate the nitrogen oxide trap and to control at the same time the operation of the internal combustion engine at a richness of less than 1.

[0013] In one embodiment, the assembly includes a nitrogen oxide sensor disposed in the exhaust line downstream of the nitrogen oxide trap connected to the control unit to provide it with a measurement of nitrogen oxides, this control unit being configured to control the hydrogen injection means so as to introduce an excess of hydrogen into the exhaust line in order to regenerate the nitrogen oxide trap if the measurement of the nitrogen oxide sensor reaches a predefined limit threshold.

[0014] In one embodiment, the internal combustion engine is compression-ignition, with a compression ratio between 12 and 13.

[0015] In one embodiment, the exhaust line is equipped with more than one particulate filter disposed downstream of the nitrogen oxide trap.

[0016] In one embodiment, the particulate filter is located near the exhaust outlet of the internal combustion engine, downstream of the nitrogen oxide trap.

[0017] In one embodiment, the exhaust line is equipped with more than one ammonia removal catalyst disposed downstream of the particulate filter.

[0018] The invention also relates to a vehicle comprising an engine assembly according to one of the variants described above.

[0019] In an embodiment in which the vehicle is equipped with the exhaust line with the ammonia removal catalyst, this ammonia removal catalyst is disposed under a floor of this vehicle.

[0020] The invention also relates to a stationary installation comprising a motor assembly according to one of the variants previously described.

[0021] Other features and advantages will become apparent upon reading the description below of a particular embodiment, not limiting the invention, made with reference to the figures in which:

[0022] [Fig. 1]: This figure represents a first example of an embodiment of an internal combustion engine connected to an exhaust line according to the invention.

[0023] [Fig.2]: This figure represents a second example of an embodiment of a motor with internal combustion connected to an exhaust line according to the invention.

[0024] [Fig.3]: This figure represents a third example of an embodiment of a motor with internal combustion connected to an exhaust line according to the invention.

[0025] [Fig.4]: This figure schematically illustrates the storage and reactions of reduction of nitrogen oxides in a nitrogen oxide trap.

[0026] Figure 1 shows a first embodiment of an engine assembly according to the invention. This engine assembly comprises an internal combustion engine 1 connected to an exhaust line 2.

[0027] The internal combustion engine 1 is configured to operate with hydrogen as fuel. The internal combustion engine 1 may be a spark-ignition or compression-ignition engine. If the internal combustion engine 1 is a compression-ignition engine, the compression ratio is preferably between 12 and 13. The engine assembly of the invention is suitable for equipping a vehicle, for example for its propulsion, or a stationary installation such as a generator set.

[0028] The internal combustion engine 1 is supplied with hydrogen from a hydrogen reservoir 3. The reservoir 3 can be a tank storing hydrogen, for example, in pressurized gaseous form, in liquid form, or in solid form via hydrides. The reservoir 3 is fluidly connected, via a hydrogen supply line 4, to a hydrogen injection system (not shown), this hydrogen being intended to be introduced into the combustion chambers of the internal combustion engine 1.

[0029] In this first embodiment, the exhaust line 2 is equipped with a single pollution control device. According to the invention, this pollution control device consists of a nitrogen oxide trap 2b.

[0030] The exhaust line 2 includes an exhaust manifold 2a fixed to the internal combustion engine 1. By defining upstream and downstream relative to the direction of flow of the exhaust gases in the exhaust line 2, the nitrogen oxide trap 2b is disposed in the exhaust line 2 downstream of the exhaust manifold 2a.

[0031] The exhaust line 2 also includes hydrogen injection means 2d, here also fluidly connected to the hydrogen tank 3 via a hydrogen supply line 5. Thus, the tank 3 is common to all the means hydrogen injection of the engine assembly. The hydrogen injection means 2d are arranged upstream of the nitrogen oxide trap 2b, in other words between the engine outlet and this nitrogen oxide trap 2b.

[0032] The exhaust line 2 is further equipped with a nitrogen oxide sensor 2e. The nitrogen oxide sensor 2e is located in the exhaust line 2 downstream of the nitrogen oxide trap.

[0033] The exhaust manifold 2a and the pollution control device 2b of the exhaust line 2 can be connected to each other by means of exhaust conduits 2f.

[0034] The engine assembly further includes a control unit 6, such as an electronic computer, configured for controlling the internal combustion engine 1. For this purpose, the control unit 6 includes the means for acquiring and processing information by means of software instructions stored in memory, as well as the control means required for controlling the internal combustion engine 1 (injection, combustion, etc.), the means for injecting hydrogen 2d into the exhaust and the nitrogen oxide sensor 2e.

[0035] In operation, the internal combustion engine 1, since it is fueled by hydrogen, emits almost exclusively nitrogen oxides with a small amount of carbon monoxide and unburned hydrocarbons, for example, from the lubricant burning in the combustion chamber. According to the invention, a nitrogen oxide trap 2b is capable of reducing nitrogen oxide emissions and also oxidizing the small amount of carbon monoxide (CO) and unburned hydrocarbon (HC) emissions. This avoids the need for an additional dedicated device such as an oxidation catalyst.

[0036] Indeed, as also illustrated in [Fig. 4], catalytic formulations of nitrogen oxide traps generally contain: • A platinum-based phase, Pt, to oxidize nitrogen oxide, NO, to nitrogen dioxide, NO2, • A nitrogen dioxide storage phase, NO2 in the form of NO3- based on Barium, Ba, or Potassium, K, • A rhodium-based phase, Rh, to selectively reduce nitrogen dioxide, NO2, to nitrogen, N2, • An oxygen exchange phase via a material with oxygen storage capacity, OSC (for the English expression "Oxygen Storage Capacity").

[0037] In a lean mixture, i.e. with a richness R less than 1, nitrogen oxides, NOx, contained in the exhaust gases emitted are stored in the form of NO3. First, the platinum phase, Pt, oxidizes the nitrogen oxides, NO, into nitrogen dioxide, NO2, according to the following reaction:

[0038] NO + ±O2^NO2

[0039] Then the Ba or K storage phase allows the storage of nitrogen dioxide, NO2, in the form of NO3-:

[0040] 2NO2 + “Ba” Ba(NO3) 2

[0041] In a rich state, that is to say with a richness R greater than 1, in other words in excess of hydrogen, this excess hydrogen H2 is used as a reducing agent to reduce nitrogen oxides, NOx, stored as nitrates on the barium, Ba, or potassium, K sites, to restore nitrogen and water according to the following reactions:

[0042] Ba(NO3)2 NOX + “Ba" then NOX + xH2 - N2+ H2O

[0043] In this nitrogen oxide trap 2b, the phase, here platinum, Pt, which allows oxidation The oxides also allow the oxidization of carbon monoxide, CO and unburned hydrocarbons, HC, into CO2 and H2O.

[0044] Thus, the nitrogen oxide trap 2b stores nitrogen dioxide emitted by the engine in the form of nitrates on the adsorption sites of barium, Ba, or potassium, K. Once all the barium or potassium adsorption sites have been used, the nitrogen oxide trap 2b is no longer effective and allows nitrogen oxide emissions to pass through. It must then be regenerated to free up adsorption sites again and convert the nitrogen oxides into nitrogen using the rhodium present in the platinum impregnation.

[0045] When it is necessary to regenerate the nitrogen oxide trap 2b, that is to say when the nitrogen oxide sensor 2e positioned downstream of the nitrogen oxide trap 2b, measures a certain level of nitrogen oxides, for example a predefined Lnox limit threshold, stored in the control unit 6, this control unit 6 which has received the information from the nitrogen oxide sensor 2e activates, via the injection means 2d, the arrival through the conduit 5 of hydrogen upstream of the pollution control system composed of the nitrogen oxide trap 2b.

[0046] The regeneration of the nitrogen oxide trap 2b is independent of the operation of the internal combustion engine 1 thanks to the supply via a conduit 5, which is separate from the hydrogen supply conduit 4 for the internal combustion engine 1. Thus, the internal combustion engine 1 can continue to operate with a lean mixture (air-fuel ratio R < 1), which is favorable for fuel consumption, while the control unit 6 manages an excess of hydrogen at the inlet of the nitrogen oxide trap 2b such that this excess hydrogen reduces the nitrates adsorbed on the barium or potassium sites to a predefined limit threshold LH. The amount of hydrogen to be injected depends on the maximum amount of nitrogen oxides, Lnox, that the nitrogen oxide trap 2b is capable of storing.

[0047] It can thus be predicted that this quantity of hydrogen, which can be translated into a hydrogen injection time varies depending on the age of the nitrogen oxide trap 2b and is stored in the control unit 6. Once this LH limit is reached, the introduction of hydrogen into the exhaust line 2 directly downstream of the internal combustion engine 1 and upstream of the nitrogen oxide trap 2b is stopped until the next need for regeneration of the nitrogen oxide trap 2b.

[0048] For this engine assembly described in [Fig. 1], the nitrogen oxide trap 2b can be positioned near the exhaust outlet of the internal combustion engine, or in a "close-coupled" configuration, according to Anglo-Saxon terminology. This English term refers to a placement near the exhaust manifold 2a of the engine. Such a "close-coupled" position of the nitrogen oxide trap 2b has the advantage of allowing it to reach operating temperature rapidly and become operational very quickly after the engine 1 is started.

[0049] Figure 2 shows a second embodiment of an engine assembly according to the invention. This second embodiment differs from the first embodiment in that a particulate filter 2c is also disposed in the exhaust line 2, downstream of the nitrogen oxide trap 2b; in other words, the NOx trap is the first pollution control device intended to be traversed by the exhaust gases.

[0050] For this engine assembly described in [Fig.2], it is possible to plan to place the nitrogen oxide trap 2b and the particulate filter 2c close to the exhaust outlet of the internal combustion engine, or in "close-coupled" according to Anglo-Saxon terminology.

[0051] Figure 3 shows a third embodiment of an engine assembly according to the invention. This third embodiment differs from the second embodiment in that an ammonia removal catalyst 2g is additionally disposed in the exhaust line 2, downstream of the particulate filter 2c. Such a catalyst is also called by the acronym ASC (for the English expression "Ammonia Slip Catalyst").

[0052] Indeed, the amount of hydrogen introduced upstream of the nitrogen oxide trap 2b during the regeneration phase must be close to the amount required to convert all the stored nitrates (in other words, the LH limit), as the risk is that ammonia will form if the amount of hydrogen introduced is higher. Therefore, to avoid this risk, it may be advisable to add such an ASC downstream of the particulate filter 2c, before the silencer, to eliminate any residual ammonia.

[0053] In the case where the engine assembly described in [Fig.2] is fitted to a motor vehicle, it is possible to relocate the ammonia removal catalyst 2g under the floor of the vehicle, in order to free up space around the internal combustion engine 1.

[0054] The invention is not limited to the embodiments described in Figures 1 to 3. In an alternative not shown, a motor assembly can be provided as described in [Fig. 1]. equipped with an ammonia removal catalyst located downstream of the nitrogen oxide trap. This variant therefore does not include a particulate filter.

[0055] The invention has the advantage of eliminating the need for a nitrogen oxide (NOx) removal system, such as a catalytic reduction catalyst (SCR) or a catalytic reduction catalyst on an SCRF filter, with its additive injection system and additive tank. The invention thus represents a less expensive and simpler solution to control and operate. Thanks to a reduced number of pollution control components, the invention allows for a more compact pollution control system and a weight reduction.

Claims

Claims

1. Engine assembly comprising an internal combustion engine (1) connected to an exhaust line (2), the internal combustion engine being configured to operate on hydrogen, characterized in that the exhaust line (2) is equipped with a single pollution control member consisting of a nitrogen oxide trap (2b).

2. Assembly according to claim 1, characterized in that the nitrogen oxide trap (2b) is arranged near the exhaust outlet of the internal combustion engine (1).

3. Assembly according to claim 1 or claim 2, characterized in that it comprises hydrogen injection means (2d) arranged in the exhaust line (2) upstream of the nitrogen oxide trap (2b) and a hydrogen tank (3) fluidly connected to these injection means (2d).

4. Assembly according to claim 3, characterized in that the hydrogen tank (3) is fluidically connected to a hydrogen injection system of the internal combustion engine (1).

5. Assembly according to claim 3 or 4, characterized in that it comprises a control unit (6) configured to control the hydrogen injection means (2d) so as to introduce into the exhaust line (2) an excess of hydrogen in order to regenerate the nitrogen oxide trap (2b) and to control at the same time the operation of the internal combustion engine (1) at a lower richness.

6. a i. Assembly according to the preceding claim, characterized in that it comprises a nitrogen oxide sensor (2e) arranged in the exhaust line (2) downstream of the nitrogen oxide trap (2b) connected to the control unit (6) to provide it with a measurement of nitrogen oxides, this control unit (6) being configured to control the hydrogen injection means (2d) so as to introduce into the exhaust line (2) an excess of hydrogen in order to regenerate the nitrogen oxide trap (2b) if the measurement of the nitrogen oxide sensor (2e) reaches a predefined limit threshold (LNOx).

7. Vehicle, characterized in that it comprises an engine assembly according to one of the preceding claims.

8. Stationary installation, characterized in that it comprises a motor assembly according to one of claims 1 to 6.

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