FR3139600A1 - Installation of hydrogen internal combustion engine with hydrogen injection in the exhaust line, and associated control method - Google Patents

Abstract

The present invention relates to a hydrogen internal combustion engine installation. The installation (1) comprises an exhaust line (4) with a selective NOx reduction catalysis means sensitive to hydrogen (10). In addition, the installation comprises a hydrogen capture line (5) present within a casing (20) of the internal combustion engine (2), this hydrogen capture line (5) injecting into the minus a portion of the hydrogen in the exhaust line (4) upstream of the hydrogen-sensitive selective NOx reduction catalysis means (10). Figure 1 to be published

Description

Hydrogen internal combustion engine installation with hydrogen injection into the exhaust line, and associated control method

The present invention relates to the field of pollution control and safety of hydrogen internal combustion engines.

The transport sector, and in particular land transport, is forced, like other sectors, to reduce its _CO2 emissions in order to limit global warming to 2°C by the end of the century. In order to meet this societal challenge, mobility technologies must evolve to aim for _CO2 emissions close to zero. Thus, three main families of technologies are envisaged to achieve this objective, each of which can be more or less adapted to a specific application.

• The all-electric solution: which combines a traction battery and an electric drivetrain. The latter can use one or more electric machines depending on the power required by the application in question. This solution has two major drawbacks: the volume and mass of the batteries are significant, limiting their use to vehicles that do not require high energy requirements; in addition, their recharge time is significant, thus penalizing continuity of service.
• The fuel cell system, which is a chemical converter that creates electricity from a reaction between hydrogen and air. The electricity thus produced is used by an electric drive train similar to that of the all-electric vehicle. The advantages of the fuel cell compared to the battery are in the energy storage density, higher with hydrogen, and the speed of filling the hydrogen storage tank. On the other hand, the fuel cell is an expensive solution due to the use of precious metals. The latter also presents increased complexity in the management of transients.
• To overcome the various drawbacks listed above, a third solution is to use hydrogen as fuel in an internal combustion engine. This approach brings several advantages:

o From a user point of view, this approach allows for certain specific applications such as heavy goods vehicles, construction machinery, maritime or river boats to offer interesting characteristics in terms of autonomy, and especially recharge time, which battery systems cannot offer. Only the fuel cell would be able to ensure an identical level of performance, but at a much higher cost.

o The hydrogen internal combustion engine is based on mature, reliable and cost-optimized technology, allowing the use of existing industrial tools without major modifications, unlike alternative electrical solutions which require disruptive production methods.

o The hydrogen internal combustion engine is virtually insensitive to external conditions, such as extreme cold and hot temperatures, altitude, and the presence of dust in the air. It is also insensitive to vibrations. These advantages make it particularly relevant for applications such as construction or mining machinery.

o The hydrogen internal combustion engine is much less sensitive than the fuel cell to the quality of the hydrogen used. By quality, we mean the degree of purity of the hydrogen, as well as the low presence of contaminants in it, the possible contaminants being listed in the ISO 14687-2 standard. Examples include argon, _CO2 and sulfur compounds. It is therefore possible to use lower quality hydrogen in the hydrogen internal combustion engine, with an advantage in terms of its cost.

Thus, the hydrogen internal combustion engine makes it possible to respond in the short term to the need to reduce _CO2 emissions for different applications. This hydrogen engine can either be designed and manufactured directly from a blank sheet of paper or by converting the petrol, diesel or gas engines currently used in order to accelerate the ecological transition with an immediately ready solution.

While the hydrogen-powered thermal engine has a number of advantages, a specific problem has nevertheless been identified: the presence of residual hydrogen in the crankcase gases. Crankcase gases are gases resulting from the combustion taking place in the combustion chamber which escape in small quantities through the gaps between the pistons and cylinders (particularly the clearances at the ring cut), until they reach the engine crankcase. In state-of-the-art gasoline, diesel, LPG (liquefied petroleum gas) or CNG (natural gas for vehicles) engines, these crankcase gases consist of combustion gases, unburned hydrocarbons and oil vapors. These are usually recycled to the intake in order to avoid a pressure build-up in the engine crankcase, which could damage the seals involved in sealing the lubrication circuit. In hydrogen internal combustion engines, unburned hydrogen replaces unburned hydrocarbons in the composition of the crankcase gases. Since the hydrogen molecule is much smaller than the molecules constituting conventional unburned hydrocarbons, a higher level of leakage has been experimentally observed between the pistons and the cylinders, leading to much higher hydrogen concentrations. Thus, it is possible to reach hydrogen concentration levels in the crankcase gases higher than the lower explosive limit (LEL) which is around 4% vol. Experimental measurements have shown levels of up to 7 to 8% vol. In the presence of oxygen, hydrogen can therefore ignite or even cause a crankcase explosion, creating a risk for people and property in the vicinity. This phenomenon is all the more marked when the engine is below its optimum operating temperature, as the clearances between the pistons, rings and cylinders are greater and thus create higher levels of gas leakage.

Patent application CN114320529A contemplates the recycling of hydrogen from the crankcase of the internal combustion engine to the engine intake. This recycling makes it possible to reduce the hydrogen concentration in the crankcase, and to avoid hydrogen losses.

A second problem with this type of engine is the emission of nitrogen oxides NOx by the internal combustion engine. Due to its inherently high laminar flame speed, hydrogen combustion is conducive to lean mixture combustion, typically between lambdas (defined by the ratio between the actual air-fuel ratio and the stoichiometric air-fuel ratio) of 2 and 3. These very lean mixture combustions allow both an improvement in combustion efficiency and a reduction in nitrogen oxide emissions NOx at source. These NOx emissions, although very low compared to the emissions observed on comparable gasoline or Diesel engines, require the use of a pollution control system adapted to lean mixture combustion: the best-known system consists of using one or more SCR catalysts (for Selective Catalytic Reduction or SCR according to the English acronym), a technique widely used on Diesel vehicles over the last fifteen years. This RCS catalyst selectively reduces NOx to nitrogen through the action of a reducing agent. This reducing agent is generally injected upstream of the RCS catalyst. On commercial diesel engines, this reducing agent can be ammonia or a compound that generates ammonia by decomposition, such as urea, or it can be a hydrocarbon from an oxygenated or non-oxygenated hydrocarbon substance. However, urea, like hydrocarbons, contains carbon in its composition. The decomposition of these reducing agents in the exhaust line will therefore inevitably create CO ₂ , with the consequence of not having a zero carbon emission solution.

Alternatively, dihydrogen, more commonly referred to as hydrogen, is also known to those skilled in the art as an effective reducing agent for SCR catalysis. The use of this reducing agent is therefore particularly relevant if the internal combustion engine partially or completely uses hydrogen as fuel. In addition, it has the advantage of not emitting carbon and CO ₂ when used as a reducing agent for SCR catalysis. Commonly, the SCR catalyst is used in addition to other pollution control systems in the exhaust line: an oxidation catalyst is, very commonly, positioned at the outlet of the combustion chamber of the engine, and upstream of the SCR catalyst. The purpose of this is to oxidize the emissions of unburned fuel and carbon monoxide at the outlet of the combustion chamber, as well as to partially oxidize the nitrogen monoxide into nitrogen dioxide. The objective of this last function is to get as close as possible to a stoichiometric ratio between nitrogen monoxide and nitrogen dioxide at the outlet of the oxidation catalyst, and upstream of the RCS catalyst, because it is known in the literature that an equimolar distribution makes it possible to maximize the efficiency of NOx conversion in the RCS catalyst. Furthermore, a particle emission reduction system is often associated with the oxidation catalyst and RCS catalyst already mentioned. This generally takes the form of a filter with porous walls responsible for continuously filtering particles, including the finest, typically less than 50 nm. This particle filter can be positioned either upstream of the RCS catalyst, or downstream of it, or even be integrated into it in order to simultaneously carry out particle filtration and the NOx reduction reaction. This is then referred to as an RCS filter, or FRCS.

Patent application FR 3013381 (US 2016/0298514) relates to a method for depolluting exhaust gases and a plant using such a method. The technology described uses two selective catalytic reduction catalysts for NOx: one sensitive to ammonia and one sensitive to hydrogen. To obtain hydrogen and ammonia, the method and plant require a decomposition, in particular by electrolysis, of a reducing agent into a gaseous phase of hydrogen and a gaseous phase of ammonia. Thus, this method and plant require a tank of reducing agent and means ensuring this decomposition, which can be complex, energy-intensive, and bulky.

The invention aims to ensure the safety and pollution control of a hydrogen internal combustion engine, while remaining simple, energy-efficient and space-saving. To this end, the present invention relates to a hydrogen internal combustion engine installation. The installation comprises an exhaust line with a hydrogen-sensitive selective NOx reduction catalysis means, which means that hydrogen is used as a NOx reducing agent using an RCS catalysis adapted to this chemical reaction. In addition, the installation comprises a line for capturing hydrogen present in a crankcase of the internal combustion engine, this hydrogen capture line injecting at least part of the hydrogen into the exhaust line upstream of the hydrogen-sensitive selective NOx reduction catalysis means. Thus, the hydrogen level in the crankcase of the engine is reduced, and the NOx at the exhaust line outlet is simultaneously reduced. In addition, this solution allows optimized management of hydrogen, particularly for RCS catalysis.

The invention relates to an internal combustion engine installation using partially or totally hydrogen as fuel, said installation comprising an exhaust line with a hydrogen-sensitive selective NOx reduction catalysis means, and a line for capturing hydrogen present in a crankcase of said internal combustion engine with a de-oiling system. Said hydrogen capture line is connected to said exhaust line upstream of said hydrogen-sensitive selective NOx reduction catalysis means to inject at least part of the captured hydrogen into said exhaust line.

According to one embodiment, said hydrogen capture line is further connected to an intake line of said internal combustion engine, and said hydrogen capture line comprises at least one controlled valve for controlling a flow rate of hydrogen injected into said exhaust line and/or a flow rate of hydrogen recycled into said intake line of said internal combustion engine.

According to one implementation, said housing of said internal combustion engine comprises at least one hydrogen sensor.

Advantageously, said exhaust line comprises at least one NOx probe, preferably a first NOx probe upstream of said hydrogen-sensitive selective NOx reduction catalysis means and a second NOx probe downstream of said hydrogen-sensitive selective NOx reduction catalysis means.

Advantageously, said exhaust line comprises at least one depressurizing member, in particular an orifice plate, a diaphragm plate, a nozzle or a Venturi tube.

According to one aspect, said hydrogen capture line comprises at least one gas pump.

According to one embodiment option, said exhaust line further comprises at least one hydrogen injector upstream of said hydrogen-sensitive selective NOx reduction catalysis means.

According to one embodiment, said exhaust line comprises at least one means of selective NOx reduction catalysis sensitive to ammonia.

Advantageously, said selective NOx reduction catalysis means sensitive to ammonia is arranged downstream of said selective NOx reduction catalysis means sensitive to hydrogen.

According to one aspect, said ammonia-sensitive selective NOx reduction catalysis means is arranged upstream of said hydrogen-sensitive selective NOx reduction catalysis means.

Furthermore, the invention relates to a method for controlling a hydrogen internal combustion engine installation according to one of the preceding characteristics, in which the following steps are implemented:

1. Hydrogen present in said crankcase of said internal combustion engine is captured; and
2. At least a portion of the captured hydrogen is injected into the exhaust line to treat the NOx in association with said hydrogen-sensitive selective NOx reduction catalysis means.

Other characteristics and advantages of the system and method according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the figures appended and described below.

List of figures

There illustrates a hydrogen internal combustion engine installation according to a first embodiment of the invention.

There illustrates a hydrogen internal combustion engine installation according to a second embodiment of the invention.

There illustrates a hydrogen internal combustion engine installation according to a third embodiment of the invention.

There illustrates a hydrogen internal combustion engine installation according to a fourth embodiment of the invention.

There illustrates a hydrogen internal combustion engine installation according to a fifth embodiment of the invention.

In this application, the terms “upstream”, “downstream” are defined in relation to the direction of flow of gases, for example hydrogen, intake gases, or exhaust gases.

The present invention relates to a hydrogen (to denote dihydrogen) internal combustion engine installation. It may be an internal combustion engine directly designed to operate with dihydrogen as fuel, or, alternatively, it may be a gasoline, diesel or gas internal combustion engine operated with dihydrogen as fuel, this approach being known as retrofitting.

By hydrogen internal combustion engine is meant an internal combustion engine that can operate partially or completely with hydrogen as fuel. The amount of hydrogen used as fuel in this context of the invention is between 10% and 100% vol. Preferably, the internal combustion engine can operate mainly with hydrogen as fuel. Preferably, the internal combustion engine can operate solely with hydrogen as fuel (with the exception of impurities).

Typically, a hydrogen internal combustion engine installation includes:

• At least one cylinder within a crankcase, in which a piston moves, the piston and the cylinder delimiting with a cylinder head a combustion chamber,
• An air intake line, with a set of pipes, to supply air to the combustion chamber,
• A fuel injection, direct or indirect, to supply the combustion chamber with fuel, and
• An exhaust line, with a set of pipes, for the evacuation of burnt gases from the combustion chamber to the atmosphere.

According to the invention, the hydrogen internal combustion engine installation comprises an exhaust line with a hydrogen-sensitive NOx nitrogen oxide reduction catalysis means. In other words, the exhaust line comprises a NOx RCS catalyst whose reducing agent is hydrogen, to ensure the post-treatment of the exhaust gases. The RCS post-treatment consists of reducing the nitrogen oxides NO and NO ₂ (commonly called NOx) on a catalytic device whose formulation generally comprises at least one noble metal impregnated on a support. The state-of-the-art supports generally used are alumina Al ₂ O ₃ , cerium oxides CeO ₂ , zirconia ZrO ₂ , tungsten WO ₃ , or titanium TiO ₂ , used alone or in combination, zeolites (ZSM-5, beta, chabazite) and perovskite oxides. Alternatively, formulations using these same supports in combination with non-noble metals such as copper or iron, or with metallic alloys (for example PtNi) or non-metallic, also present interesting performances in terms of activity and selectivity. This catalyst promotes the reduction of NOx to nitrogen, by reaction with the reducing agent. In addition, hydrogen is an excellent NOx reducer and this with temperatures of the order of barely 100 ° C. For example, hydrogen RCS catalysts with a composition based on Pt/SiO ₂ or Pt/TiO ₂ -ZrO ₂ Pd/WO ₃ /ZrO ₂ have shown good activity and selectivity from 90°C. Thus, the NOx rate in the exhaust line is reduced.

In addition, the installation includes a line for capturing residual hydrogen present in the crankcase of the internal combustion engine. In other words, the capture line is designed to evacuate the residual hydrogen in the crankcase. The capture line includes a set of pipes and a de-oiling system for separating the hydrogen from the oil from the crankcase. Such a de-oiling system can in particular be achieved by passive mechanical systems such as baffles, or by more efficient active systems, based for example on oil centrifugation (for example cyclone de-oilers or centrifugal separators), or a combination of passive and active systems. Thus, the safety of the installation is improved by reducing the hydrogen level in the crankcase.

According to the invention, the hydrogen capture line is connected to the exhaust line upstream of the hydrogen-sensitive NOx reduction catalysis means, to inject at least part of the captured hydrogen into the exhaust line. Thus, the hydrogen-sensitive RCS catalyst is supplied with reducing agent taken directly from the crankcase. Thus, the invention makes it possible to simultaneously ensure the safety and depollution of the internal combustion engine. The use of this hydrogen taken from the crankcase makes it possible to reduce NOx emissions without having to use:

- either only hydrogen contained in the vehicle's storage tanks, which would have the effect of reducing its autonomy,

- or only to an additional reducing agent, which would require the use of a dedicated tank reducing the volume available on board the vehicle. In addition, most known reducing agents, for example urea, emit _CO2 emissions when they decompose in the exhaust line.

According to one embodiment of the invention, the hydrogen capture line can be further connected to the intake line of the internal combustion engine. In this way, a portion of the captured hydrogen can be recycled to the intake of the internal combustion engine. Thus, the efficiency of the engine can be improved. For this embodiment, the hydrogen capture line can comprise at least one piloted valve for controlling a flow of hydrogen injected into the exhaust line and/or a flow of hydrogen recycled from the intake of the internal combustion engine. For example, the capture line can comprise two piloted valves, one upstream of the connection to the exhaust line and the other upstream of the connection to the intake line. In this example, the valves can be piloted simultaneously, so that when one of them opens, the second closes. This control mode allows to divert between 0 and 100% of the crankcase gas flow to the exhaust line in order to use the adequate quantity of hydrogen contained in the deoiled crankcase gas as a reducing agent for the RCS catalysis reaction depending on the total quantity of NOx to be treated. Alternatively, the capture line may comprise a single valve, for example a three-way valve, with one inlet and two outlets.

According to one aspect of the invention, the exhaust line may further comprise a hydrogen injector, this hydrogen injector being arranged upstream of the hydrogen-sensitive selective NOx reduction catalysis means. Thus, it is possible to increase the amount of hydrogen in the exhaust line if the amount coming from the capture line is insufficient for effective NOx catalysis. The hydrogen injected by this injector may come from the fuel tank.

According to an implementation of the invention, the crankcase of the internal combustion engine may comprise a hydrogen sensor. Such a sensor makes it possible to measure the hydrogen concentration within the crankcase. This measurement makes it possible both to meet a safety objective by making it possible to monitor that the hydrogen content present in the crankcase gases does not exceed the Lower Explosive Limit (LEL), and also to control the control of the hydrogen internal combustion engine installation. Where appropriate, the opening of at least one valve of the capture line may depend on the quantity of hydrogen within the crankcase. The hydrogen sensor may be positioned in the gas volume of the crankcase, or be installed remotely relative to the latter with gas communication between the crankcase and the sensor via a gas pipe. Alternatively to the hydrogen sensor, the hydrogen concentration within the crankcase may be estimated by logical and/or computer means (for example a computer of the internal combustion engine).

According to one aspect of the invention, the exhaust line may comprise at least one NOx sensor. Thus, the quantity of NOx can be measured within the exhaust line. Alternatively to the NOx sensor, the quantity of NOx within the exhaust line can be estimated by logical and/or computer means (for example a computer of the internal combustion engine). This quantity of NOx can be used in particular for controlling the hydrogen internal combustion engine installation.

Where appropriate, the opening of at least one valve in the capture line may depend on the quantity of NOx to be treated in the exhaust line, or the quantity of hydrogen injected by the injector may depend on the quantity of NOx in the exhaust line and the quantity of hydrogen injected by the capture line. Indeed, the RCS catalysis can be adapted according to the quantity of NOx to be treated by adjusting the quantity of hydrogen injected into the exhaust line. If the quantity of hydrogen contained in the crankcase gases is greater than the quantity required to carry out the NOx reduction reaction, then the corresponding excess portion of the crankcase gases can be recycled to the intake of the heat engine, so that the hydrogen contained therein is burned in the combustion chamber, and produces work. Conversely, if the quantity of hydrogen contained in the crankcase gases is less than the quantity required to carry out the NOx reduction reaction, an additional supply of hydrogen can possibly be carried out additionally in the exhaust line, upstream of the RCS catalyst, for example by using an injector.

According to a variant of this configuration, the exhaust line may comprise a NOx probe upstream of the hydrogen-sensitive selective NOx reduction catalysis means and a NOx probe downstream of the hydrogen-sensitive selective NOX reduction catalysis means. Thus, these measurements make it possible to know the efficiency of the RCS catalyst, and to adjust the quantity of hydrogen injected into the exhaust line.

According to one embodiment of the invention, the exhaust line may comprise a pressure-reducing member, at the junction between the exhaust line and the hydrogen capture line, to locally reduce the pressure within the exhaust line. The pressure-reducing member is a member capable of generating a local pressure reduction. Indeed, the relative pressure prevailing in the exhaust line can reach several hundred millibars (several tens of thousands of Pascals), whereas that encountered in the engine oil sump does not exceed a few tens of millibars (several thousand Pascals). In order to guarantee a sufficient flow rate of the bypassed crankcase gases to the exhaust line (where appropriate, when the controlled valves are in positions favorable to this bypass), it may be useful to create a localized depression at the junction between the exhaust line and the pipe containing the crankcase gases of the hydrogen capture line. The depressogenic organ can notably take the form of an orifice plate, a diaphragm plate, a nozzle or a Venturi tube.

According to one implementation, the hydrogen capture line may comprise at least one gas pump. The gas pump makes it possible to create a positive crankcase gas flow between the crankcase of the internal combustion engine and the exhaust line, i.e. from the crankcase to the exhaust line. The gas pump may be arranged downstream of the de-oiling system, and may operate in suction mode. This configuration makes it possible to avoid creating excess pressure in the crankcase of the internal combustion engine. Alternatively, a pump operating in blowing mode may be used on the capture line, upstream of the crankcase.

According to one option, the exhaust line may include a temperature sensor placed at the inlet of the exhaust line to know at any time the temperature of the exhaust gases circulating in this line. Alternatively, it may be provided to use logical and/or computer means which make it possible to estimate at any time the temperature of the exhaust gases circulating in the line.

According to one embodiment of the invention, the exhaust line may further comprise a selective NOx reduction catalysis means sensitive to ammonia. In other words, the exhaust line comprises a NOx RCS catalyst whose reducing agent is ammonia. In this way, the exhaust line comprises two RCS catalysts: one sensitive to hydrogen and one sensitive to ammonia. This ammonia-sensitive RCS device contains a catalyst. In state-of-the-art industrial applications, the most common RCS catalyst formulations are based on iron- or copper-exchanged zeolites, or based on vanadium oxide V ₂ O ₅ . To introduce gaseous ammonia into the exhaust gas treatment system, it is known to produce it directly in the pipe conveying these gases to the RCS system by vaporizing an aqueous solution of a precursor of this reducing agent such as, for example, urea. Urea, injected at an average exhaust temperature generally of 150 to 400°C, releases ammonia through successive thermolysis and hydrolysis reactions. Other ammonia precursor compounds can be used under similar conditions. An ammonia injector is usually used to introduce the aqueous urea solution into the pipe carrying the exhaust gases to the RCS catalyst, upstream of the latter. A mixer or blender, installed between this injector and the RCS catalyst, can be used to improve the vaporization of the aqueous urea solution spray in the exhaust gas flow. This ammonia can be injected into the exhaust line upstream of the ammonia-sensitive RCS catalyst. Ammonia can be obtained indirectly by decomposition of a precursor injected in liquid form, generally urea in aqueous solution at 32.5% m better known under the trade name "AdBlue ^TM " or "DEF ^TM ".

According to one embodiment, the RCS catalyst using hydrogen as a reducing agent can be mounted upstream of the RCS catalyst using ammonia as a reducing agent. This architecture makes it possible to optimize NOx depollution for low exhaust temperatures, typically below 150 °C, thanks to the hydrogen-sensitive RCS catalyst mounted in a position close to the outlet of the combustion chamber. Indeed, this type of RCS catalyst is particularly suitable for temperatures between 80 and 150 °C.

When the operating conditions of the thermal engine evolve towards higher temperature levels, the hydrogen-sensitive RCS catalyst will gradually become less efficient, unlike the ammonia-sensitive RCS catalyst which will become increasingly efficient. This exhaust line architecture therefore presents an obvious interest, by making it possible to target NOx depollution over a wider exhaust temperature range compared to the use of a single RCS catalyst formulation.

Alternatively, the SCR catalyst using ammonia as a reducing agent can be mounted upstream of the SCR catalyst using hydrogen as a reducing agent. This architecture is particularly advantageous for treating nitrogen oxides when the exhaust gas temperature is high, typically above 150 °C. Since the SCR catalyst using hydrogen as a reducing agent is more suitable for low exhaust temperatures, it is positioned away from the combustion chamber, downstream of the SCR catalyst using ammonia as a reducing agent. Thus, the heat losses incurred by the SCR catalyst using ammonia as a reducing agent and by the intermediate exhaust line between the two SCR catalysts lead to a reduced exhaust gas temperature at the inlet of the hydrogen-sensitive SCR catalyst, the level of which will depend on the intensity of these heat losses. For example, a very distant position of the hydrogen-sensitive RCS catalyst from the ammonia-sensitive RCS catalyst will result in significant heat losses, and therefore reduce the exhaust gas temperature at the hydrogen-sensitive RCS catalyst.

According to one embodiment option, the exhaust line may include other post-treatment devices, such as a particulate filter. Thus, the pollutant emissions from the hydrogen internal combustion engine installation are reduced. Such a particulate filter generally takes the form of a filter with porous walls responsible for continuously filtering particles, including the finest, typically less than 50 nm. This particulate filter may be positioned either upstream of the hydrogen-sensitive RCS catalyst, or downstream thereof, or even be integrated into it in order to simultaneously filter the particles and the NOx reduction reaction. This is then referred to as an RCS filter, or FRCS.

The hydrogen internal combustion engine installation according to the invention is particularly suitable for an on-board application, for example within a vehicle: heavy goods vehicle, ship, construction equipment, hovercraft, etc.

Furthermore, the invention relates to a method for controlling a hydrogen internal combustion engine system. The control method is suitable for a hydrogen internal combustion engine system according to any of the variants or combinations of variants described above. For this method, the following steps are implemented:

1. Hydrogen is captured from the crankcase of the internal combustion engine, using the hydrogen capture line; and
2. At least part of the captured hydrogen is injected into the exhaust line to treat the NOx in association with the hydrogen-sensitive selective reduction catalysis means.

The control method may further comprise at least one of the following steps (in particular depending on the embodiment variant of the internal combustion engine installation):

• The oil and hydrogen are separated from the fluid captured in the capture line, so that only gas is injected into the exhaust line.
• At least part of the captured hydrogen is injected into the intake line, for the recycling of part of the captured hydrogen,
• The hydrogen concentration in the crankcase is measured or estimated, in order to adapt the control to the hydrogen concentration in the crankcase,
• The quantity of NOx in the exhaust line is measured or estimated, in order to adapt the control to the quantity of NOx in the exhaust line, this measurement or estimation can be carried out at several points in the exhaust line, preferably upstream or downstream of each means of selective NOx reduction catalysis,
• The temperature of the exhaust gases is measured or estimated, in order to adapt the control to the quantity of NOx in the exhaust line,
• The amount of hydrogen injected into the exhaust line is controlled, where appropriate based on the estimated or measured hydrogen concentration in the crankcase and/or the estimated or measured amount of NOx in the exhaust line, for efficient operation of the RCS catalyst,
• NOx is treated in the exhaust line with a selective reduction catalysis medium sensitive to ammonia, and ammonia is injected into the exhaust line, for a significant reduction of NOx over a wide temperature range,
• Hydrogen is also injected into the exhaust line to ensure a sufficient quantity of hydrogen for the RCS catalysis.

For example, the control method may implement the following steps:

• If the amount of hydrogen contained in the crankcase gases is greater than the amount required to carry out the NOx reduction reaction, then the corresponding excess portion of the crankcase gases is recycled to the intake of the heat engine, so that the hydrogen contained in them is burned in the combustion chamber, and produces work, and
• Conversely, if the quantity of hydrogen contained in the crankcase gases is less than the quantity required to carry out the NOx reduction reaction, an additional supply of hydrogen may be injected additionally into the exhaust line, upstream of the RCS catalyst, for example using an injector.

Furthermore, for the embodiment for which the installation comprises a hydrogen-sensitive RCS catalyst and an ammonia-sensitive RCS catalyst, the method may comprise the following steps:

• For exhaust gas temperatures below 150°C, NOx from the exhaust line is treated using the hydrogen-sensitive RCS catalyst,
• For exhaust gas temperatures above 150°C, NOx in the exhaust line is treated using the ammonia-sensitive RCS catalyst.

There illustrates, schematically and in a non-limiting manner, a hydrogen internal combustion engine installation according to a first embodiment of the invention. The hydrogen internal combustion engine installation 1 comprises an internal combustion engine 2 with a casing 20. The internal combustion engine 2 is supplied with air by an intake line 3. The exhaust gases of the internal combustion engine 2 are discharged by the exhaust line 4. The hydrogen internal combustion engine 1 comprises a hydrogen supply from a tank (not shown). This hydrogen supply can be direct into the combustion chamber or into the intake line 3. In addition, the internal combustion engine installation 1 comprises a hydrogen capture line 5. The hydrogen capture line 5 captures the hydrogen present in the crankcase 20. The capture line 5 comprises a de-oiling system 6. At the outlet of the de-oiling system 6, the hydrogen is distributed either into the exhaust line 4 or into the intake line 3, respectively by means of valves 7 and 8. The valves 7 and 8 are controlled simultaneously and in opposition (this simultaneous control is represented by the broken line which connects the two valves). The exhaust line 4 comprises a hydrogen-sensitive selective NOx reduction catalysis means 10. The capture line 5 injects hydrogen into the exhaust line 4 at a junction point 9 upstream of the hydrogen-sensitive selective NOx reduction catalysis means 10. In addition, the exhaust line 4 further comprises a hydrogen injector 11. The hydrogen injection 11 can be connected to the hydrogen tank allowing the internal combustion engine to be supplied with hydrogen. The hydrogen internal combustion engine installation 1 further comprises several sensors: a hydrogen sensor 12 placed on the crankcase 20, and two NOx probes arranged on the exhaust line 4. A first NOx probe 13 is provided upstream of the hydrogen-sensitive selective NOx reduction catalysis means 10 in order to determine the quantity of NOx to be treated, and a second NOx probe 14 is provided downstream of the hydrogen-sensitive selective NOx reduction catalysis means 10 in order to determine the NOx conversion efficiency in the SCR catalyst.

There illustrates, schematically and in a non-limiting manner, a hydrogen internal combustion engine installation according to a second embodiment of the invention. The elements identical to the first embodiment of the are not described again. Compared to the first embodiment of the , the exhaust line 4 further comprises a pressure reducing member 15 arranged at the junction point 9 between the collection line 5 and the exhaust line 4.

There illustrates, schematically and in a non-limiting manner, a hydrogen internal combustion engine installation according to a third embodiment of the invention. The elements identical to the second embodiment of the are not described again. Compared to the second embodiment of the , the collection line 5 further comprises a gas pump 16 downstream of the de-oiling system 6 and upstream of the valves 7 and 8.

There illustrates, schematically and in a non-limiting manner, a hydrogen internal combustion engine installation according to a fourth embodiment of the invention. The elements identical to the third embodiment of the are not described again. Compared to the third embodiment of the , the exhaust line 4 further comprises ammonia-sensitive selective NOx reduction catalysis means 17 downstream of the hydrogen-sensitive selective NOx reduction catalysis means 10. For this ammonia-sensitive selective NOx reduction catalysis means 17, the exhaust line 4 comprises an ammonia injector 19 upstream of the ammonia-sensitive selective NOx reduction catalysis means 17. In addition, the exhaust line comprises a third NOx probe 18 downstream of the ammonia-sensitive selective NOx reduction catalysis means 17 intended to calculate the NOx conversion efficiency downstream of the two catalysts.

There illustrates, schematically and in a non-limiting manner, a hydrogen internal combustion engine installation according to a fifth embodiment of the invention. The elements identical to the third embodiment of the are not described again. Compared to the third embodiment of the , the exhaust line 4 further comprises ammonia-sensitive selective NOx reduction catalysis means 17 upstream of the hydrogen-sensitive selective NOx reduction catalysis means 10, and even upstream of the connection point 9 between the capture line 5 and the exhaust line 4. For this ammonia-sensitive selective NOx reduction catalysis means 17, the exhaust line 4 comprises an ammonia injector 19 upstream of the ammonia-sensitive selective NOx reduction catalysis means 17. Furthermore, the exhaust line comprises a third NOx probe 18 downstream of the ammonia-sensitive selective NOx reduction catalysis means 17 intended to determine the NOx conversion efficiency downstream of the two catalysts.

The embodiments of Figures 3 to 5 are illustrated with the depressurizing member, and the gas pump, however, these equipments are optional. Similarly, the embodiments of Figures 1 to 5 are illustrated with the different sensors (hydrogen sensor and NOx probes). However, these sensors are optional and can in particular be replaced by estimates of these quantities.

It goes without saying that the invention is not limited to the embodiments described above as examples; on the contrary, it encompasses all variant embodiments.

Claims (11)

Internal combustion engine installation using partially or totally hydrogen as fuel, said installation comprising an exhaust line (4) with a hydrogen-sensitive selective NOx reduction catalysis means (10), and a hydrogen capture line (5) present within a casing (20) of said internal combustion engine with a de-oiling system (6), characterized in that said hydrogen capture line (5) is connected to said exhaust line (4) upstream of said hydrogen-sensitive selective NOx reduction catalysis means (10) to inject at least part of the captured hydrogen into said exhaust line (4). Hydrogen internal combustion engine installation according to claim 1, wherein said hydrogen capture line (5) is further connected to an intake line of said internal combustion engine (3), and said hydrogen capture line (5) comprises at least one piloted valve (7, 8) for controlling a flow rate of hydrogen injected into said exhaust line (4) and/or a flow rate of hydrogen recycled into said intake line (3) of said internal combustion engine. Hydrogen internal combustion engine installation according to one of the preceding claims, wherein said casing (20) of said internal combustion engine (2) comprises at least one hydrogen sensor (12). Hydrogen internal combustion engine installation according to one of the preceding claims, wherein said exhaust line (4) comprises at least one NOx probe (13, 14), preferably a first NOx probe (13) upstream of said hydrogen-sensitive selective NOx reduction catalysis means (10) and a second NOx probe (14) downstream of said hydrogen-sensitive selective NOx reduction catalysis means (10). Hydrogen internal combustion engine installation according to one of the preceding claims, in which said exhaust line (4) comprises at least one depressurizing member (15), in particular an orifice plate, a diaphragm plate, a nozzle or a Venturi tube. Hydrogen internal combustion engine installation according to one of the preceding claims, in which said hydrogen capture line (5) comprises at least one gas pump (16). Hydrogen internal combustion engine installation according to one of the preceding claims, in which said exhaust line (4) further comprises at least one hydrogen injector (11) upstream of said hydrogen-sensitive selective NOx reduction catalysis means (10). Hydrogen internal combustion engine installation according to one of the preceding claims, in which said exhaust line (4) comprises at least one ammonia-sensitive selective NOx reduction catalysis means (17). A hydrogen internal combustion engine installation according to claim 8, wherein said ammonia-sensitive selective NOx reduction catalysis means (17) is arranged downstream of said hydrogen-sensitive selective NOx reduction catalysis means (10). A hydrogen internal combustion engine installation according to claim 8, wherein said ammonia-sensitive selective NOx reduction catalysis means (17) is arranged upstream of said hydrogen-sensitive selective NOx reduction catalysis means (10). Method for controlling a hydrogen internal combustion engine installation according to one of the preceding claims, in which the following steps are implemented:

1. Hydrogen present in said crankcase (20) of said internal combustion engine (2) is captured; and
2. At least a portion of the captured hydrogen is injected into the exhaust line (4) to treat the NOx in association with said hydrogen-sensitive selective NOx reduction catalysis means (10).