FR3146952A1 - Internal combustion engine installation using hydrogen as fuel with crankcase scavenging line - Google Patents

Abstract

The present invention relates to an internal combustion engine installation using hydrogen partially or totally as fuel. The installation comprises an air intake line (6), a hydrogen capture line (29) present in the crankcase (29) connected to the intake line (6), and a scavenging line (29) of the crankcase (20) by air at atmospheric pressure. For this invention, the capture line (29) comprises a hydrogen concentration sensor (9) at the outlet of a de-oiling system (8). Figure 1 to be published

Description

Internal combustion engine installation using hydrogen as fuel with crankcase scavenging line

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

• La solution tout électrique : qui associe batterie de traction et chaine cinématique électrique. Cette dernière peut faire appel à une ou plusieurs machines électriques suivant les puissances demandées par l’application concernée. Cette solution présente deux inconvénients majeurs : le volume et la masse des batteries sont conséquents, limitant leur utilisation aux véhicules ne nécessitant pas de fortes exigences énergétiques, de plus, leur temps de recharge est important, pénalisant ainsi la continuité de service.
• Le système de pile à combustible, qui est un convertisseur chimique créant de l’électricité à partir d’une réaction entre l’hydrogène et l’air. L’électricité ainsi produite est utilisée par une chaine cinématique électrique similaire à celle du véhicule tout électrique. Les avantages de la pile à combustible par rapport à la batterie se situent au niveau de la densité énergétique de stockage, plus élevée avec l’hydrogène, et de la rapidité de remplissage du réservoir de stockage d’hydrogène. En revanche, la pile à combustible est une solution coûteuse du fait de l’utilisation de métaux précieux. Cette dernière présente également une complexité accrue dans la gestion des transitoires. En outre, cette technologie est moins avantageuse en termes de durabilité et en termes de disponibilité à grande échelle.
• Pour pallier les différents inconvénients listés ci-dessus, une troisième solution consiste à utiliser l’hydrogène en tant que carburant dans un moteur à combustion interne. Cette approche apporte plusieurs avantages :
  • D’un point de vue de l’utilisateur, cette approche permet pour certaines applications spécifiques comme les poids lourds, les engins de chantier, les bateaux maritimes ou fluviaux d’offrir des caractéristiques intéressantes en termes d’autonomie, et surtout de temps de recharge, que les systèmes à batterie ne peuvent pas proposer. Seule, la pile à combustible serait à même d’assurer un niveau de prestation identique, mais avec un coût bien plus élevé.
  • Le moteur à combustion interne d’hydrogène repose sur une technologie mature, fiable et optimisée en termes de coûts, permettant d’utiliser l’outil industriel existant sans grosse modification contrairement aux solutions électriques alternatives qui requirent des moyens de production en rupture. En effet, cette technologie permet de bénéficier d’infrastructures de production déjà existantes, sans dépendre de matériaux rares.
  • Le moteur à combustion interne d’hydrogène est quasiment insensible aux conditions extérieures, comme les températures extrêmes, froides et chaudes, l’altitude, et la présence de poussières dans l’air. Il est également insensible aux vibrations. Ces avantages le rendent particulièrement pertinent sur des applications de type engins de chantier ou engins miniers.
  • Le moteur à combustion interne d’hydrogène est beaucoup moins sensible que la pile à combustible à la qualité de l’hydrogène utilisée. Par qualité, on entend ici le degré de pureté de l’hydrogène, ainsi que la faible présence de contaminants dans celui-ci, les contaminants possibles étant listés dans la norme ISO 14687-2. On peut citer par exemple l’argon, le CO₂et les composés soufrés. Il est donc possible d’utiliser un hydrogène de moindre qualité dans le moteur à combustion interne d’hydrogène, avec un avantage sur le coût de celui-ci.

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 concerned. 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 density of storage, 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. In addition, this technology is less advantageous in terms of sustainability and in terms of large-scale availability.
• 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:
  • 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.
  • The hydrogen internal combustion engine is based on a mature, reliable and cost-optimized technology, allowing the use of existing industrial tools without major modifications, unlike alternative electrical solutions that require disruptive production methods. Indeed, this technology allows the use of already existing production infrastructures, without depending on rare materials.
  • 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.
  • 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.

Although 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 from the combustion chamber that 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 gasoline, diesel, LPG or CNG engines, these crankcase gases consist of combustion gases, unburned hydrocarbons and oil vapors. These are usually reinjected into 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 and to comply with pollution standards, for which it is not possible to discharge these effluents directly into the atmosphere. 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 approximately 4% by volume. Experimental measurements have shown contents of up to 7 to 8% by volume. 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.

In a standard Petrol, Diesel, LPG (liquefied petroleum gas) or CNG (natural gas for vehicles) engine, after passing through an oil separator (also called a de-oiling system), the crankcase gases are reinjected into the intake, either after the butterfly valve for a naturally aspirated engine, or at the compressor inlet or both at the compressor inlet and after the butterfly valve for a supercharged engine. In this standard system, the crankcase gases (called "blow-by" gases) naturally flow from the crankcase to the intake, the pressure at the crankcase being higher than that at the intake. Of course, there may not be excessive overpressure at the crankcase, but if the concentration of blow-by gases is not diluted, it can exceed the flammability limit in the case of an engine running on hydrogen.

The patent application bearing the filing number FR22/09249 concerns the capture of hydrogen in the crankcase and its reinjection into the exhaust line, so as to enable selective Nox reduction catalysis. Thus, this method makes it possible to reduce the pollutant emissions of such an internal combustion engine while limiting the quantity of hydrogen present in the crankcase. However, this method does not improve the performance of the internal combustion engine, and requires a specific exhaust line.

The objective of the system described in patent application JP2021-127704 is to reduce the hydrogen content in the crankcase to prevent the ignition of hydrogen contained in the crankcase gases for a hydrogen-powered engine. For this system, the crankcase is swept either with burnt gases from the exhaust or with filtered air from outside by means of a pump or fan. The use of such a pump or fan increases the costs of the system, as well as the complexity of installation. In addition, the gases are discharged to the outside and not readmitted to the intake, but recent studies have shown that hydrogen released into the atmosphere has a significant indirect impact on the greenhouse effect. In addition, a hydrogen sensor is provided in the crankcase. However, in this part of the crankcase, the oil present is brought to high temperatures of around 90 or even 110°C with blow-by gases from the combustion which are quite hot, which imposes very severe conditions on the hydrogen sensor (presence of oil and high temperature).

The system described in patent application US6606982 allows the scavenging of a crankcase of a hydrogen engine. This system uses two non-return valves: one at the inlet and one at the outlet of the oil sump. This system does not implement control of the hydrogen concentration in the blow-by gases, and does not implement control of the air flow rate passing into the lower engine crankcase. This patent does indeed propose an air scavenging of the oil sump for an engine running on hydrogen but with a specific system. In particular, if there is an air sweep in the crankcase that takes place, it will be low at full load because the throttle will be open to its maximum, and in this case the pressure difference will be very low between the inlet and the outlet of the oil sump, which will have the consequence of lowering the air sweep, whereas it is at these points that there is the greatest need to sweep the oil sump to remain below the flammability limit. In addition, the configuration illustrated by the of this patent application is not recommended. The oil separator never manages to remove all the oil present in the blow-by gases, oil vapors could rise upstream of the filter and therefore soak the filters, which would result in reducing the permeability of the filters. In addition, impurities could pollute the oil because there is no mention of filtering upstream of the venturi system, the impurities can therefore rise up to the oil separator during operation or when the engine is stopped.

The system of patent application US5603290 describes a sweep of the oil sump by air via a pump but with a low sweep rate. The purpose of this system is not to remain below the LEL limit in the lower engine crankcase, but to prevent the rise of oil vapor in the combustion chamber. To do this, it is proposed to put the lower engine crankcase at a certain level of depression (5 inches of Hg = 170 mbar of pressure = 17000 Pa) so as to reduce the rise of oil through the segmentation towards the combustion chamber of an engine running on hydrogen. The rise of oil through the segmentation being a priori the source of the pre-ignition phenomenon of the air-hydrogen mixture in the combustion chamber. In this patent, there is no provision for measuring the hydrogen concentration, in order to carry out adequate control.

The system described in patent application CN114320529 also concerns crankcase scavenging. To do this, the system uses a hydrogen sensor. In this system, it is the air compressed by the supercharging that sweeps the crankcase (by opening the solenoid valve that connects the intake manifold to the crankcase). The hydrogen in the crankcase will then pass through the separator and be readmitted to the intake, so the gases in the intake plenum used to sweep the crankcase will always contain hydrogen. In this system, it is possible to lower the hydrogen content of the crankcase but not reduce it to zero. In such a system, the crankcase is overpressurized compared to atmospheric pressure in supercharged mode. There is therefore a risk of hydrogen and other oil degradation compounds leaking through the crankcase seals into the atmosphere with their wear over time. Such a system is not suitable for an engine with indirect hydrogen injection, because by injecting hydrogen into the intake plenum or even afterwards into the intake ducts before the valves, given that in supercharged mode, the plenum is under overpressure compared to the crankcase, air highly charged with hydrogen enters the crankcase. In such a system, the hydrogen sensor is housed in the crankcase, which implies the use of an expensive sensor capable of withstanding the oil temperature in particular, and which requires a complex installation of such a sensor. The hydrogen concentration in the crankcase is not necessarily homogeneous (hydrogen entry point through the segments and air entry point through their tubing), especially since they close and open the solenoid valve intermittently. This arrangement does not allow the engine control to take into account the precise quantity of hydrogen readmitted to the intake, nor to readjust the quantity of hydrogen to be injected into the engine to monitor the target richness (improvement of richness control).

The invention aims to ensure the safety of a hydrogen internal combustion engine, while increasing the engine's performance, in a simple and inexpensive manner. To this end, the present invention relates to an internal combustion engine installation partially or completely using hydrogen as fuel. The installation comprises an air intake line, a line for capturing hydrogen present in the crankcase connected to the intake line, and a line for scavenging the crankcase with air at atmospheric pressure. For this invention, the capture line comprises a hydrogen concentration sensor at the outlet of a de-oiling system. Thus, the hydrogen captured in the crankcase is reintroduced to the intake, which makes it possible to increase the performance of the internal combustion engine. Such a system does not require a pump or fan for scavenging the crankcase, so this installation is simple and inexpensive. In addition, the installation of a hydrogen concentration sensor at the outlet of a de-oiling system allows the use of an inexpensive hydrogen concentration sensor that is easy to implement on a pipeline.

Furthermore, the invention relates to a method for controlling such an installation.

The invention relates to an internal combustion engine installation partially or totally using hydrogen as fuel, said installation comprising an air intake line, a line for capturing hydrogen present within a casing of said internal combustion engine, said capture line comprising a de-oiling system and being connected to said intake line upstream of the internal combustion engine. The air intake line comprises a duct for scavenging said casing with air at atmospheric pressure from said intake line, and in that said capture line comprises a hydrogen concentration sensor at the outlet of said de-oiling system.

According to one embodiment, said intake line comprises a valve, in particular a butterfly valve, controlled as a function of said measured hydrogen concentration.

According to one implementation, said sweep line and/or said intake line comprises a pilot-operated valve for controlling an air flow at atmospheric pressure in said sweep line.

According to one aspect, said intake line comprises a compressor, in particular a compressor of a turbocharger, and said capture line is connected to said intake line upstream and/or downstream of said compressor.

Advantageously, said intake line comprises a hydrogen injector.

According to one configuration, said sweep line comprises a non-return valve.

According to one embodiment, said sweep line comprises a flow meter.

Advantageously, said intake line comprises means for measuring the air flow.

According to one implementation, said collection line comprises a non-return valve.

1. On mesure la concentration en hydrogène dans ladite ligne de captage au moyen dudit capteur de concentration en hydrogène ; et
2. On injecte de l’air à la pression atmosphérique dans ledit carter du moteur à combustion interne pour balayer ledit carter, en fonction de la mesure en concentration d’hydrogène dans ladite ligne de captage.

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

1. The hydrogen concentration in said collection line is measured by means of said hydrogen concentration sensor; and
2. Air at atmospheric pressure is injected into said crankcase of the internal combustion engine to sweep said crankcase, depending on the measurement of hydrogen concentration in said capture line.

According to one embodiment, the wear of at least one segment of a piston of said internal combustion engine is further diagnosed as a function of said hydrogen concentration measured by said hydrogen concentration sensor.

Other characteristics and advantages of the system 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 an installation of an internal combustion engine according to a first embodiment of the invention.

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

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

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

In the present application, the terms “upstream” and “downstream” are defined in relation to the direction of flow of the gases, for example hydrogen, intake gases, or exhaust gases. Similarly, the terms “inlet” and “outlet” are defined in relation to the direction of flow of the gases, and mean that the two components are successive in relation to the direction of flow of the gases (there are no devices between the components). For example, if component A is at the inlet of component B, this means that the gas flows successively in component A and then in component B, without an intermediate component.

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 can be between 10% and 100% by volume. 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).

• Au moins un cylindre au sein d’un carter, dans lequel se déplace un piston, le piston et le cylindre délimitant avec une culasse une chambre de combustion, le carter étant fermé dans sa partie inférieure (dans la position d’utilisation du moteur à combustion interne) d’une partie de carter appelée « carter bas moteur», servant notamment à la récupération de l’huile de lubrification,
• Une ligne d’admission d’air, avec un ensemble de conduites, pour alimenter la chambre de combustion en air,
• Une injection de carburant, directe ou indirecte, pour alimenter la chambre de combustion en carburant, et
• Une ligne d’échappement, avec un ensemble de conduites, pour l’évacuation des gaz brulés depuis la chambre de combustion vers l’atmosphère.

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, the crankcase being closed in its lower part (in the position of use of the internal combustion engine) by a crankcase part called "lower engine crankcase", used in particular for the recovery of lubricating oil,
• 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.

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, in particular in the lower engine 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 carried out 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. The oil separated from the hydrogen can be reinjected, for example by gravity, by means of a pipe into the lower engine crankcase. Thus, the safety of the installation is improved by reducing the hydrogen level in the crankcase, in particular in the lower engine crankcase.

According to the invention, the capture line is connected to the intake line upstream of the internal combustion engine. Thus, the hydrogen captured in the crankcase is reinjected into the cylinder of the internal combustion engine, which makes it possible to reduce the quantity of fuel to be injected into the cylinder. In this way, the energy performance of the internal combustion engine is improved, and the pollutant emissions are reduced.

In addition, the intake line comprises a line for sweeping the crankcase with air at atmospheric pressure or slightly lower. In other words, the intake line comprises a bypass of air at atmospheric pressure or slightly lower (therefore uncompressed) through the crankcase. This bypass ensures sweeping of the crankcase, and allows the hydrogen capture line to capture residual hydrogen within the crankcase and dilute the residual gas from the crankcase with air at atmospheric pressure. This air pressure makes it possible to avoid a risk of hydrogen leakage, compared to an air pressure that would be compressed. Preferably, the bypass of the intake line can be provided downstream of an air filter arranged on the intake line, and preferably the bypass can be arranged at the outlet of an air filter arranged on the intake line. Advantageously, the connection between the capture line and the intake line can be arranged downstream of the bypass forming the scavenging line. Thus, the captured hydrogen is injected into the intake line after the air has been sampled for scavenging. As a result, the gas for scavenging comprises only air. In the remainder of the description, the intake line pipe that does not belong to the scavenging line is called the main intake line pipe.

According to the invention, the capture line comprises a hydrogen concentration sensor at the outlet of a de-oiling system. Thus, the residual gas in the capture line can be measured. This embodiment makes it possible to use a simple and inexpensive sensor: in fact, it does not need to withstand the temperature present in the crankcase (due to its position and due to the dilution by air at atmospheric pressure), it is not subjected to the oil that could be captured, and it can be a sensor of simple design to install on a pipe. This measurement of the quantity of residual gas makes it possible in particular to control the internal combustion engine installation, in particular the different flow rates, for example the air flow rate for sweeping the crankcase. In addition, this configuration coupled with an estimation of the flow rate leaving the lower engine crankcase makes it possible to go back to the mass flow rate of hydrogen recirculated to the intake. Furthermore, this configuration allows for precise and reliable measurement of the hydrogen concentration. Indeed, in the prior art, the sensor performs the measurement directly in the lower engine crankcase. However, the hydrogen concentration can be highly heterogeneous in the lower engine crankcase, in particular due to the fresh air entering, and the gas puffs coming from the segmentation of the different cylinders, which makes the estimation of the quantity of recirculated hydrogen imprecise and unreliable.

According to one embodiment of the invention, the intake line may comprise at least one piloted valve, in particular a butterfly valve. Thus, it is possible to control the air flow in the intake line. Advantageously, the valve may be piloted according to measurements from different sensors on the intake line (including the scavenging line), the exhaust line, and the capture line. In particular, the valve may be piloted according to the measurement of the hydrogen concentration in the capture line. For example, a piloted valve may be arranged upstream of the connection between the capture line and the intake line, in particular to control the air flow in the intake manifold of the internal combustion engine.

According to one implementation of the invention, the main line and/or the scavenging line of the intake line may comprise a controlled valve, in particular a butterfly valve, for controlling an air flow rate in the scavenging line. Thus, it is possible to provide a sufficient quantity of air for scavenging the crankcase, in particular the lower engine crankcase, which allows efficient capture of the hydrogen present in this portion of the crankcase. In particular, the valve may be controlled based on the measurement of the hydrogen concentration in the capture line. In this way, the crankcase can be scavenged only in the case of a high hydrogen concentration in the capture line. According to one exemplary embodiment, the intake line may comprise a three-way valve (in particular a three-way solenoid valve) at the connection between the intake line and the scavenging line for controlling this air flow rate. This configuration allows simplified control with a single valve. Alternatively, the flush line may include a pilot-operated valve, and the main intake line may include a pilot-operated valve downstream of the connection between the intake line and the flush line. This configuration allows for simpler valves to be used.

According to one aspect of the invention, the internal combustion engine may be non-supercharged, in which case it may be referred to as a naturally aspirated engine. In this case, the intake line does not include a compressor.

Alternatively, the internal combustion engine may be supercharged. In this case, the intake line comprises a compressor, for example a compressor of a turbocharger. For this configuration, the capture line may be connected to the intake line upstream of the compressor and/or downstream of the compressor. These embodiments allow a design adapted according to the air pressures implemented within the installation. Preferably, in the case of a supercharged engine, the capture line may comprise two branches, one allowing a connection upstream of the compressor, and one allowing a connection downstream of the compressor.

According to one configuration of the invention, the fuel injection may be direct. In this case, a hydrogen injector may be provided directly in the cylinder of the internal combustion engine. Alternatively, the fuel injection may be indirect. In this case, a hydrogen injector may be provided in the intake line. For example, the hydrogen injector may be provided between the connection of the capture line and the intake line and the intake manifold of the internal combustion engine.

According to one embodiment of the invention, the scavenging line may comprise a flow meter, for measuring the air flow rate for scavenging. This measurement may be used for controlling the internal combustion engine, in particular, where appropriate, for controlling the at least one valve for adjusting the air flow rate in the scavenging line. Alternatively, the scavenging line may comprise a pressure difference sensor measuring the pressure drop across the terminals of the optionally controlled valve.

According to one embodiment, the scavenging line may comprise a non-return valve, to prevent the residual gases and the oil present in the crankcase from entering the scavenging line and then into the intake line. Preferably, the non-return valve may be arranged on the scavenging line at the inlet of the crankcase. Thus, any components (valve, flow meter, etc.) of the scavenging line are not crossed by the residual gases and the oil present in the crankcase.

According to one implementation of the invention, the intake line, in particular the main pipe of the intake line, may comprise a flow meter, for measuring the air flow in the intake line. This measurement may be used for controlling the internal combustion engine, in particular for controlling the richness of the mixture within the cylinder of the internal combustion engine. Alternatively, the main pipe of the intake line may comprise a pressure difference sensor measuring the pressure drop across the terminals of the possible controlled valve. A calibration carried out beforehand may make it possible to determine a transfer function between the flow rate and the measured pressure drop, in particular with the pressure and temperature information of the fresh gases. The total flow rate drawn in by the internal combustion engine may be estimated from the engine displacement, the speed, the pressure and the temperature in the intake plenum, the richness of the air/fuel mixture and the injection phasing, the impact of the injection phasing on the filling being done by calibration.

Advantageously, the installation can include a flow meter (or pressure difference sensor) in the sweep line, and a flow meter (or pressure difference sensor) in the main line of the intake line. These two measurements make it possible to determine the flow rate of residual gases passing through the segmentation. Indeed, the following formula can be written:

with the mass flow rate of diluted residual gases leaving the de-oiling system, the total mass flow rate sucked in by the internal combustion engine, and the mass flow rate of air passing through the main intake line.

This information makes it possible to monitor the wear rate of the segmentation over time and to warn the driver in the event of pronounced wear or a failure of the segmentation which may be linked in particular to spontaneous self-ignition of the air-hydrogen mixture before ignition by the spark plug (pre-ignition phenomenon) or partial self-ignition of the charge after ignition of the charge by the spark plug (knocking).

According to one aspect of the invention, the capture line may include a non-return valve, to prevent intake air from entering the capture line, particularly when the intake line includes a compressor.

According to one embodiment of the invention, the installation may comprise different sensors for carrying out measurements at different points, so as to carry out suitable control of the installation. In particular, the installation may comprise pressure and/or temperature sensors for the gases used. According to a non-limiting example, a pressure and/or temperature sensor may be arranged at the inlet of the intake manifold and downstream of the connection of the capture line, for measuring the pressure and/or the temperature of the fuel mixture entering the intake manifold.

Advantageously, neither the sweep line nor the collection line may include a pump or fan. Indeed, the pressures and flow rates implemented ensure the circulation of gases within the installation. This configuration simplifies the design of the internal combustion engine installation, and avoids energy consumption for sweeping and recycling of residual gases.

• Lorsque le moteur à combustion interne fonctionne à des niveaux de charges faibles à moyennes, avec l’éventuelle vanne de la ligne d’admission (vanne papillon) partiellement fermée, c’est-à-dire avec une pression plénum inférieure à la pression atmosphérique, les gaz résiduels du carter sont aspirés dans la ligne de captage, qui relie la sortie du système de déshuilage au plénum d’admission (le plénum d’admission étant le volume compris entre le papillon des gaz et les soupapes d’admission),
• De plus, pour un moteur suralimenté, lorsque le moteur à combustion interne fonctionne sur des niveaux de charge élevés avec activation du compresseur d’air, la pression du plénum d’admission devient supérieure à la pression atmosphérique. Dans ce mode de fonctionnement, l’éventuel clapet anti-retour de la ligne de captage se ferme, et les gaz résiduels du carter dilués sont aspirés dans la branche de la ligne de captage, qui relie le système de déshuilage à l’entrée du compresseur d’air.

According to a non-limiting example, the installation can be implemented by means of at least one of the following phases:

• When the internal combustion engine is operating at low to medium load levels, with the possible intake line valve (butterfly valve) partially closed, i.e. with a plenum pressure lower than atmospheric pressure, the residual crankcase gases are sucked into the collection line, which connects the outlet of the de-oiling system to the intake plenum (the intake plenum being the volume between the throttle valve and the intake valves),
• In addition, for a supercharged engine, when the internal combustion engine is operating at high load levels with the air compressor activated, the intake plenum pressure becomes higher than atmospheric pressure. In this operating mode, the possible check valve of the capture line closes, and the diluted residual crankcase gases are sucked into the branch of the capture line, which connects the de-oiling system to the air compressor inlet.

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. However, the invention is also suitable for a stationary application.

1. On mesure la concentration en hydrogène dans la ligne de captage au moyen du capteur de concentration en hydrogène ; et
2. On injecte de l’air à la pression atmosphérique dans le carter du moteur à combustion interne pour balayer le carter, en fonction de la mesure en concentration d’hydrogène dans ladite ligne de captage.

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. The hydrogen concentration in the collection line is measured using the hydrogen concentration sensor; and
2. Air at atmospheric pressure is injected into the crankcase of the internal combustion engine to flush the crankcase, depending on the hydrogen concentration measurement in said capture line.

The method according to the invention makes it possible to dilute the hydrogen present in the crankcase of the internal combustion engine, and allows the hydrogen to be scavenged. Thus, the hydrogen can be captured in the capture line, then can be reintroduced (recycled) as fuel in the intake line. Preferably, air can be injected for scavenging when the concentration in the capture line is higher than a predefined threshold. In addition, if necessary, the air flow rate in the scavenging line can be controlled according to the measured concentration. For example, if the value measured by the hydrogen concentration sensor approaches the limit that has been predefined, namely LEL – X, (therefore approximately 4% - X for hydrogen), the method modifies the opening of any controlled valves so as to increase the air flow rate scavenging the lower engine crankcase. It should be remembered that X in % is the safety margin set in relation to the LEL of hydrogen. X can vary from 0 to about 4%. In addition to a need for a safety margin, the calibration of the X value in % can be linked to the desire to adjust the air flow to remain in the optimum operating flow zone of the deoiling system, while remaining below the LEL in the engine crankcase.

According to one embodiment of the invention, the method may further comprise a step of diagnosing the wear of at least one segment of a piston of the internal combustion engine based in particular on the measurement of hydrogen concentration by the hydrogen concentration sensor. For example, if the hydrogen value measured by the sensor exceeds the LEL value for more than Y seconds, Y possibly being a predefined calibratable parameter, the engine control may provide information about a system fault, in particular via a message on the on-board computer, and may also trigger the engine to stop.

According to one aspect of the invention, at a (predefined) frequency that is configurable, the control method can perform a test to close the possible controlled valve of the scavenging line. If the hydrogen value remains low while the possible controlled valve of the scavenging line is closed, this means that there is a fault in measuring the hydrogen concentration or a fault on the possible valve or the possible non-return valve. Such a fault can be reported via the on-board computer.

According to an implementation of the invention, control strategies can also be launched when the engine is stopped. The purpose of these strategies is to help comply with the standards on hydrogen emissions or other pollutants from the vehicle when parked and coming from the engine crankcase (oil vapor, by-product resulting from oil degradation by combustion). When the engine is stopped, the possible valve of the scavenging pipe can open completely so as to maximize the scavenging air flow and minimize the presence of hydrogen and other polluting components in the engine crankcase. In a second step, the possible controlled valves of the main pipe and the scavenging pipe close completely so as to prevent the escape of hydrogen and other residual pollutants, even still present in minute traces in the engine crankcase, to the atmosphere via the engine air inlet duct.

According to one aspect, the control method may further comprise a step of determining the mass flow rate of hydrogen to be injected, then a step of injecting this determined flow rate of hydrogen directly or indirectly into the cylinder of the internal combustion engine. For this embodiment, the mass flow rate of hydrogen recirculated to the intake may be determined from the measurement of the hydrogen concentration in the capture line, and from any flow rate or pressure difference measurements. Then, a flow rate of hydrogen to be injected may be determined using the following formula:

with the mass flow rate of hydrogen to be injected, a mass flow rate instruction deduced from the operating point of the internal combustion engine (in particular speed, torque), and the mass flow rate of recirculated hydrogen from the measurement of hydrogen concentration in the capture line.

This control aims to reduce the quantities to be injected and therefore avoids excess richness leading to the production of nitrogen oxide. Indeed, although the combustion of hydrogen does not produce _CO2 , its combustion at high temperature generates the formation of nitrogen oxide, a pollutant regulated in the exhaust of thermal propulsion vehicles. The higher the richness of the air and hydrogen mixture, the more the formation of nitrogen oxide increases. The typical target richness to remain at acceptable nitrogen oxide emission levels to pass the standards without excessive exhaust post-treatment device is of the order of 0.4. The device also improves engine efficiency by limiting the quantity of hydrogen injected to just what is necessary.

• On peut séparer l’huile et l’hydrogène du fluide capté dans la ligne de captage, de manière à injecter seulement du gaz dans la ligne d’admission.
• On peut mesurer ou on estimer la température des gaz d’admission, pour adapter la commande du moteur à combustion interne, et
• On peut comprimer l’air dans la ligne d’admission pour réaliser une suralimentation du moteur à combustion interne.

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 can be separated from the fluid captured in the capture line, so that only gas is injected into the intake line.
• The temperature of the intake gases can be measured or estimated, to adapt the control of the internal combustion engine, and
• Air can be compressed in the intake line to achieve supercharging of the internal combustion engine.

There illustrates, schematically and in a non-limiting manner, an internal combustion engine installation according to a first embodiment. This embodiment relates to a direct injection supercharged internal combustion engine installation using partially or totally hydrogen as fuel. The installation comprises an internal combustion engine with at least one cylinder 21, in which a piston 28 slides. The piston 28 actuates a connecting rod - crank - crankshaft system 23, arranged in a crankcase 20 (in this case a lower engine crankcase), in which oil 24 is located. The piston 28 and the cylinder head of the engine limit a combustion chamber, which comprises at least one intake valve 15, at least one exhaust valve 27, and a possible spark plug. For the embodiment of the with direct injection, the combustion chamber also includes a hydrogen injector 25. The piston 28 includes several segments 22, the sealing of which with the cylinder 21 may be imperfect and allow hydrogen to pass into the lower engine crankcase 20.

The intake valve 15 is connected to an intake line 6. The intake line 6 comprises successively from the air inlet 19 to the intake valve 15 the following components: an air filter 1, a pilot valve 2, a flow meter 16, a compressor 13, a pilot valve 14, a pressure and/or temperature sensor 18.

The exhaust valve 27 is connected to an exhaust line 26. This exhaust line may comprise a turbine (not shown), in particular a turbocharger, and an exhaust gas post-treatment system (not shown), for example a means of selective NOx reduction catalysis.

The intake line 6 comprises a scavenging line 4, which is a branch of the intake line at the outlet of the air filter 1, and which conducts air at atmospheric pressure into the lower engine crankcase 20. The scavenging line 4 comprises a pilot valve 3, a flow meter 17 and a non-return valve 5 at the inlet of the crankcase 20.

The installation further comprises a capture line 29, for capturing the residual gases in the crankcase 20 and for recycling the residual gases in the intake line 6. At the outlet of the crankcase, the capture line 29 comprises a de-oiling system 8 for separating the oil from the residual gases. The oil being reintroduced into the crankcase 20 by means of the pipe 7 and the gases being introduced into the pipes of the collection line 29. The collection line 29 is equipped, at the outlet of the de-oiling system 8, with a hydrogen concentration sensor 9. For the illustrated embodiment, the collection line 29 separates into two branches 11 and 12. The branch 11 is connected to the intake line downstream of the compressor 13 and the piloted valve 14. The branch 11 comprises a non-return valve 10. The branch 12 is connected to the intake line upstream of the compressor 13.

There illustrates, schematically and in a non-limiting manner, an internal combustion engine installation according to a second embodiment. This embodiment relates to an indirect injection supercharged internal combustion engine installation using partially or totally hydrogen as fuel. The elements identical to the are not re-detailed. For this second embodiment, the hydrogen injector 25 is arranged in the intake line 6 upstream of the intake valve 15, and downstream of the connection between the capture line 29 and the intake line 6.

There illustrates, schematically and in a non-limiting manner, an internal combustion engine installation according to a third embodiment. This embodiment concerns an atmospheric (non-supercharged) internal combustion engine installation with direct injection using partially or totally hydrogen as fuel. The elements identical to the are not re-detailed. For this embodiment, the intake line does not include a compressor. In addition, the capture line 29 includes a single branch 11 connected to the intake line 6.

There illustrates, schematically and in a non-limiting manner, an internal combustion engine installation according to a fourth embodiment. This embodiment concerns an atmospheric (non-supercharged) internal combustion engine installation with indirect injection using partially or totally hydrogen as fuel. The elements identical to the are not re-detailed. For this fourth embodiment, the hydrogen injector 25 is arranged in the intake line 6 upstream of the intake valve 15, and downstream of the connection between the capture line 29 and the intake line 6.

Claims (11)

Internal combustion engine installation using partially or totally hydrogen as fuel, said installation comprising an air intake line (6), a hydrogen capture line (29) present within a casing (20) of said internal combustion engine, said capture line (29) comprising a de-oiling system (8) and being connected to said air intake line (6) upstream of the internal combustion engine, characterized in that said air intake line (6) comprises a scavenging pipe (4) of said casing (20) with air at atmospheric pressure coming from said air intake line (6), and in that said capture line (29) comprises a hydrogen concentration sensor (9) at the outlet of said de-oiling system (8). Internal combustion engine installation according to claim 1, in which said intake line (6) comprises a valve (14), in particular a butterfly valve, controlled as a function of said measured hydrogen concentration (9). Internal combustion engine installation according to one of the preceding claims, wherein said scavenging line (4) and/or said intake line (6) comprises a pilot valve (2; 3) for controlling an air flow at atmospheric pressure in said scavenging line (4). Internal combustion engine installation according to one of the preceding claims, in which said intake line (6) comprises a compressor (13), in particular a compressor of a turbocharger, and said capture line (29) is connected to said intake line (6) upstream and/or downstream of said compressor (13). Internal combustion engine installation according to one of the preceding claims, in which said intake line comprises a hydrogen injector (25). Internal combustion engine installation according to one of the preceding claims, wherein said scavenging pipe (4) comprises a non-return valve (5). Internal combustion engine installation according to one of the preceding claims, wherein said scavenging pipe (4) comprises a flow meter (17). Internal combustion engine installation according to one of the preceding claims, in which said intake line (6) comprises air flow measuring means (16). Internal combustion engine installation according to one of the preceding claims, in which said collection line (29) comprises a non-return valve (10). Method for controlling an internal combustion engine system according to one of the preceding claims, in which at least the following steps are implemented:

1. The hydrogen concentration in said collection line (29) is measured by means of said hydrogen concentration sensor (9); and
2. Air at atmospheric pressure is injected into said crankcase (20) of the internal combustion engine to sweep said crankcase (20), depending on the measurement of hydrogen concentration in said capture line (29).

Control method according to claim 10, wherein the wear of at least one segment (22) of a piston (28) of said internal combustion engine is further diagnosed as a function of said hydrogen concentration measured by said hydrogen concentration sensor (9).