Hydrogen engine and vehicle comprising a hydrogen engine

Abstract

A hydrogen engine (1, 1', 1'') is disclosed comprising one or more cylinders (3), a piston (12) arranged in each cylinder (3) to delimit a combustion chamber (5) inside the cylinder (3), an exhaust outlet (7) and a gas inlet (9) each connected to the combustion chamber (5), and a loop assembly (11) connecting the exhaust outlet (7) to the gas inlet (9), thereby forming a closed loop (11') that includes the exhaust outlet (7), the gas inlet (9), and the combustion chamber (5). The hydrogen engine (1, 1', 1'') further comprises an inert gas (Ar) contained within the closed loop (11') and a gas supply arrangement (6, 6', 6'') configured to supply hydrogen (H2) to the combustion chamber (5). The gas supply arrangement (6, 6', 6'') is further configured to supply an ozone (O3) enriched gaseous mixture to the combustion chamber (5). The present disclosure further relates to a vehicle (2) comprising a hydrogen engine (1, 1', 1'').

Description

[0001] Hydrogen Engine and Vehicle comprising a Hydrogen Engine

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a hydrogen engine. The present disclosure further relates to a vehicle comprising a hydrogen engine.

[0004] BACKGROUND

[0005] Internal combustion engines are used to provide motive power to vehicles, commonly via a drivetrain and driven wheels of the vehicle. In many vehicles, the drivetrain comprises a transmission controllable between at least two different gears to provide at least two different transmission ratios between the engine and the driven wheels of the vehicle.

[0006] Internal combustion engines, such as four-stroke internal combustion engines, comprise one or more cylinders and a piston arranged in each cylinder. The pistons are connected to a crankshaft of the engine via a respective connecting rod and normally each comprise one or more piston rings to seal the area between the piston and the cylinder. The pistons are arranged to reciprocate within the cylinders upon rotation of the crankshaft.

[0007] The engine usually further comprises one or more inlet valves and one or more exhaust valves as well as one or more fuel supply arrangements. The one or more inlet valves and exhaust valves are controlled by a respective valve control arrangement usually comprising one or more camshafts rotatably connected to a crankshaft of the engine, via a belt, chain, gears, push rods, or similar. A four-stroke internal combustion engine completes four separate strokes while turning a crankshaft two revolutions. A stroke refers to the full travel of the piston along the cylinder, in either direction. The uppermost position of the piston in the cylinder is usually referred to as the top dead centre TDC, and the lowermost position of the piston in the cylinder is usually referred to as the bottom dead centre BDC.

[0008] The strokes are completed in the following order, inlet stroke, compression stroke, expansion stroke and exhaust stroke. During operation of a conventional four-stroke internal combustion engine, the inlet valve control arrangement controls inlet valves of a cylinder to an open state during the inlet stroke of a piston within the cylinder, to allow air, or a mixture of air and fuel, to enter the cylinder. During the compression stroke, all valves should be closed to allow compression of the air, or the mixture of the air and fuel, in the cylinder. If the engine is in a power producing state, fuel in the cylinder is ignited, usually towards the end of the compression stroke, by the ignition device. The combustion of fuel within the cylinder significantly increases pressure and temperature in the cylinder. The combustion of the fuel usually continues into a significant portion of the subsequent expansion stroke. The increased pressure and temperature in the cylinder obtained by the combustion is partially converted into mechanical work supplied to the crankshaft in the expansion stroke.

[0009] Obviously, all valves should remain closed during the expansion stroke to allow the increased pressure and temperature to be converted into mechanical work. The expansion stroke is also usually referred to as the combustion stroke, because usually, the majority of the combustion takes place during the expansion stroke. In the subsequent exhaust stroke, the exhaust valve control arrangement controls exhaust valves of the cylinder to an open state to allow exhaust gases to be expelled out of the cylinder into an exhaust system. The exhaust stroke is then followed by an inlet stroke.

[0010] General problems when designing an internal combustion engine is the emission levels from the engine as well as the fuel consumption of the engine. Emissions generated by an internal combustion engine normally comprise a range of gaseous and particulate substances. A primary constituent of exhaust gases is carbon dioxide (CO2), which results from the combustion of hydrocarbons present in the fuel. While carbon dioxide is not directly harmful in low concentrations, its release in significant quantities contributes to the greenhouse effect and global climate change by trapping heat in the Earth's atmosphere.

[0011] In addition to carbon dioxide, exhaust gases contain carbon monoxide (CO), which is produced by incomplete combustion when there is insufficient oxygen present to fully oxidize the carbon in the fuel. Carbon monoxide is a toxic gas that can be harmful to both humans and animals.

[0012] Nitrogen oxides (NOx), another significant component of exhaust emissions, are formed due to the high temperatures and pressures within the engine cylinder, where nitrogen from the air reacts with oxygen. Nitrogen oxides contribute to the formation of smog and acid rain and are also linked to respiratory problems in humans and animals.

[0013] Unburned hydrocarbons (HC) are released when fuel does not completely combust within the cylinder. These hydrocarbons can contribute to the formation of ground-level ozone, which is a major component of smog. Ground-level ozone can irritate the respiratory system and reduce lung function. Additionally, some hydrocarbons are classified as carcinogens, presenting long-term health risks. Particulate matter (PM), consisting of microscopic solid or liquid particles, is primarily generated by incomplete combustion of fuel, particularly in engines running on diesel. These particulates can penetrate deep into the lungs and can be harmful to both humans and animals. Furthermore, particulate matter contributes to environmental issues such as air quality degradation and reduced visibility.

[0014] Each of these emissions, individually and collectively, contributes to environmental degradation and poses health risks to humans and animals. Due to environmental concerns, almost all vehicles for sale today comprise some sort of exhaust aftertreatment system.

[0015] Examples are catalytic converters, particulate filters, and Selective catalytic reduction (SCR) arrangements. These exhaust aftertreatment systems are efficient in reducing the amount of carbon monoxide (CO), nitrogen oxides (NOx), unburned hydrocarbons (HC), and particulate matter (PM) exhausted from vehicles.

[0016] However, such exhaust aftertreatment systems cannot reduce the amount of carbon dioxide (CO2) in the exhaust gas because carbon dioxide is a direct product of the combustion process itself, resulting from the oxidation of carbon in the fuel. Unlike other harmful emissions that can be chemically transformed or filtered out, the formation of carbon dioxide is an inherent aspect of burning hydrocarbons, and its reduction requires alternative strategies. These strategies typically include improving the overall efficiency of the engine to reduce fuel consumption, thereby lowering carbon dioxide (CO2) output, or transitioning to alternative, low-carbon energy sources, such as electric propulsion or hybrid systems that rely less on internal combustion engines.

[0017] Despite the advancements in aftertreatment technology, the rising global focus on climate change and stringent emissions regulations are pushing the automotive industry toward the development of more efficient engines and alternative powertrains. Electrification, in particular, is seen as a key solution to minimize or eliminate tailpipe emissions, as electric vehicles (EVs) do not produce exhaust gases during operation. Nonetheless, internal combustion engines continue to play a critical role in the automotive market, especially in hybrid systems or in regions where charging infrastructure for electric vehicles is still underdeveloped.

[0018] One promising alternative is the hydrogen engine, which is an internal combustion engine operating on hydrogen instead of conventional hydrocarbon-based fuels. In a hydrogen engine, the combustion of hydrogen with oxygen produces water vapor as the primary byproduct. The chemical reaction between hydrogen and oxygen produce no carbon dioxide (CO2). However, hydrogen internal combustion engines typically utilize a pilot injection of diesel or a diesel-like fuel to initiate combustion. This small quantity of diesel is injected into the cylinder just before the main injection of hydrogen to create the necessary conditions for combustion. The pilot diesel fuel serves as an ignition source because, unlike conventional fuels, hydrogen has a higher ignition temperature and a faster flame propagation speed. These characteristics make it more challenging to ignite hydrogen reliably under typical engine operating conditions. The pilot injection ensures stable combustion by creating a localized high-temperature region within the cylinder, where the hydrogen can then be ignited. Without this small amount of diesel or diesel-like fuel, the hydrogen might not ignite as consistently, especially in low-temperature or part-load conditions.

[0019] The use of a pilot injection of diesel or a diesel-like fuel does introduce a small amount of carbon emissions. Even the small amount of carbon emissions generated by the pilot injection of diesel or diesel-like fuel poses a problem. While hydrogen combustion itself is free from carbon dioxide emissions, the use of a carbon-based fuel for ignition introduces a source of greenhouse gases, undermining the full potential of a zero-emission solution. This is especially concerning as regulatory bodies worldwide push for stricter emissions standards, with many aiming for complete decarbonization of vehicle exhausts. Moreover, in these hydrogen engines, nitrogen oxides (NOx) can still be produced due to the high combustion temperatures and the presence of nitrogen from the air entering the combustion chambers.

[0020] Some hydrogen engines use spark ignition, meaning they are equipped with a spark ignition device in the combustion chambers to initiate hydrogen combustion. A drawback of these engines is that they generally have lower efficiency compared to hydrogen engines operating with compression ignition.

[0021] An alternative to these traditional hydrogen engines is the closed-loop hydrogen engine, which operates with an inert gas and added oxygen within a sealed loop system. In this configuration, the inert gas circulates within the engine, replacing the atmospheric air used in conventional combustion processes. While closed-loop hydrogen engines offer many advantages, they also come with some problems and drawbacks. One significant problem is the difficulty of reliably initiating combustion, particularly in low-temperature or part-load conditions.

[0022] Despite the addition of oxygen to support combustion, the presence of the inert gas alters the thermal properties of the mixture, making consistent ignition more difficult under certain conditions. That is, the inert gas absorbs heat, reducing the overall temperature in the combustion chamber, which can prevent reaching the high ignition temperatures required for hydrogen combustion. This challenge is heightened in low-temperature or part-load conditions, where the available energy is already limited. As a result, the engine may struggle to initiate or maintain combustion reliably, which can lead to unreliable performance and reduced efficiency. Furthermore, the use of diesel pilot ignition in closed-loop hydrogen engines is not feasible due to the rapid increase in carbon dioxide (CO2) levels in the closed- loop system. Carbon dioxide (CO2) contamination in the inert gas would significantly reduce engine performance and would hinder prolonged operation of the engine.

[0023] Another problem associated with closed-loop hydrogen engines is that if the hydrogen is not completely combusted in the combustion chambers, oxygen may follow the closed loop to be introduced again into the combustion chambers. Such introduced oxygen tends to increase the risk of pre-ignition and knocking, which can damage the hydrogen engine and can cause combustion instabilities.

[0024] SUMMARY

[0025] It is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks. The object is achieved by the subject-matter of the appended independent claim(s).

[0026] According to a first aspect of the present disclosure, the object is achieved by a hydrogen engine comprising one or more cylinders, a piston arranged in each cylinder to delimit a combustion chamber inside the cylinder, an exhaust outlet and a gas inlet each connected to the combustion chamber, and a loop assembly connecting the exhaust outlet to the gas inlet, thereby forming a closed loop that includes the exhaust outlet, the gas inlet, and the combustion chamber. The hydrogen engine further comprises an inert gas contained within the closed loop and a gas supply arrangement configured to supply hydrogen to the combustion chamber. The gas supply arrangement is further configured to supply an ozone enriched gaseous mixture to the combustion chamber.

[0027] Thereby, a hydrogen engine is provided with the ability to efficiently initiate and maintain hydrogen combustion under a wide range of operating conditions, including low-temperature and part-load scenarios.

[0028] This is because ozone is an unstable gas and contribute to formation of oxygen atoms and hydroxyl radicals that substantially improve the chain reactions between hydrogen and oxygen. The ozone increases the rate of reactions in the limited residence time that oxygen and hydrogen molecules have in the combustion chamber. Faster reaction leads to higher closed cycle efficiency as well as a more complete combustion in which more oxygen molecules will be consumed compared to when ozone is not present. Accordingly, as a result, a hydrogen engine is provided with a reduced risk of pre-ignition and knocking, which helps prevent engine damage and ensures smoother operation of the hydrogen engine. In addition, the supplied ozone enriched gaseous mixture can improve the transient behaviour of the hydrogen engine and can facilitate cold starts.

[0029] Moreover, since the gas supply arrangement is configured to supply the ozone enriched gaseous mixture to the combustion chamber, the need for utilizing a pilot injection of diesel or a diesel-like fuel is circumvented for initiating combustion. Accordingly, conditions are provided for obtaining a zero-emission hydrogen engine. In this context, the wording a zeroemission hydrogen engine means that no emissions, other than pure water, are exhausted from the hydrogen engine.

[0030] That is, since the hydrogen engine comprises the inert gas contained within the closed loop, the hydrogen inside the combustion chamber can be combusted without the presence of atmospheric air, and thereby also the presence of nitrogen, which prevents the formation of nitrogen oxides (NOx). Additionally, by eliminating the need for any carbon-based pilot fuels, the hydrogen engine eliminates the release of carbon dioxide (CO2), carbon monoxide (CO), unburned hydrocarbons (HC), and particulate matter (PM) typically associated with traditional combustion engines.

[0031] As a further result, the need for one or more exhaust aftertreatment systems on the engine is circumvented. In this manner, the complexity and cost associated with maintaining and integrating systems such as catalytic converters, particulate filters, and selective catalytic reduction (SCR) units are eliminated. This simplifies the overall design of the hydrogen engine and contributes to enhanced efficiency and reliability. Additionally, by removing the dependence on exhaust aftertreatment systems, the engine can achieve a lower overall weight, further improving fuel efficiency and performance.

[0032] Accordingly, a hydrogen engine is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved. Optionally, the gas supply arrangement is configured to supply at least one of the hydrogen and the ozone enriched gaseous mixture directly into the combustion chamber. Thereby, the ability to efficiently initiate and maintain hydrogen combustion can be further ensured under a wide range of operating conditions, including low-temperature and part-load scenarios.

[0033] Optionally, the gas supply arrangement is configured to supply the at least one of the hydrogen and the ozone enriched gaseous mixture at the end, or near the end, of a compression stroke of the piston. Thereby, a hydrogen engine is provided that is capable of operating with compression ignition, and thereby a high efficiency, while ensuring efficient initiation and maintenance of hydrogen combustion under a wide range of operating conditions, including low-temperature and part-load scenarios.

[0034] Optionally, the gas supply arrangement is configured to supply one of the hydrogen and the ozone enriched gaseous mixture at the end, or near the end, of a compression stroke of the piston, and the other of the hydrogen and the ozone enriched gaseous mixture during an intake stroke of the piston. Thereby, a hydrogen engine is provided that is capable of operating with compression ignition, and thereby a high efficiency, while having conditions for being manufactured and assembled in a cost-efficient manner.

[0035] Optionally, the gas supply arrangement is configured to supply hydrogen to the combustion chamber during an intake stroke of the piston and is configured to supply an ozone enriched gaseous mixture to the combustion chamber at the end, or near the end, of a compression stroke of the piston. Thereby, a hydrogen engine is provided circumventing the need for a compressor configured to compress the hydrogen prior to supplying the hydrogen to the hydrogen engine. This is because the pressure inside the combustion chamber is considerably lower during an intake stroke of the piston as compared to at the end, or near the end, of a compression stroke of the piston.

[0036] Furthermore, the liquefaction of oxygen is much easier than the liquefaction of hydrogen since it has higher critical temperature compared to hydrogen, -147°C for oxygen vs -240°C for hydrogen. This means that the need for arranging a compressor for compressing the ozone enriched gaseous mixture also can be circumvented by storing oxygen in liquified state for use by the hydrogen engine. As indicated, the liquefaction of oxygen is much easier than liquefaction of hydrogen. Also, the boil off rate of liquified oxygen is less of a problem compared to the boil off rate of liquified hydrogen. The term boil off rate refers to the amount of liquid that is evaporating from a storage tank due to heat leakage. A compressor configured to compress gas prior to supplying the gas to the combustion chamber at the end, or near the end, of a compression stroke of the piston requires the input of energy that has parasite effect on the hydrogen engine which reduces the overall efficiency of the hydrogen engine. Accordingly, by circumventing the need for such a compressor, the overall energy efficiency of the hydrogen engine can be significantly improved.

[0037] Another potential problem with supplying hydrogen to the combustion chamber during the intake stroke and supplying oxygen to the combustion chamber at the end, or near the end, of the compression stroke could be that that the oxygen won’t have enough time to completely react with hydrogen inside the cylinder. If so, some oxygen will end-up in the exhaust outlet which will be sent back to the gas inlet in the closed loop engine solution. This will result in pre-ignition or knocking in the engine. One potential solution to this could be to operate the hydrogen engine at very high concentrations of hydrogen. Nevertheless, the higher excess hydrogen in the intake manifold would significantly decrease the efficiency of the engine.

[0038] However, this potential problem is overcome by the hydrogen engine, according to embodiments herein, since the gas supply arrangement of the hydrogen engine is configured to supply the ozone enriched gaseous mixture to the combustion chamber which can ensure that the oxygen completely reacts with the supplied hydrogen. Thus, as a result, a hydrogen engine is provided having conditions for increased efficiency and a reduced tendency of preignition and knocking.

[0039] The wording “at the end, or near the end, of a compression stroke of the piston”, as used herein, may encompass that the gaseous mixture referred to is supplied within a maximum of 70 crank angle degrees, or a maximum of 40 crank angle degrees, from the top dead centre of the piston. According to some embodiments, this may include supplying the gaseous mixture within a maximum of 70 crank angle degrees, or a maximum of 40 crank angle degrees, before the top dead centre, and within a maximum of 40 crank angle degrees, or a maximum of 20 crank angle degrees, after the top dead centre of the piston.

[0040] Optionally, the engine is a compression ignition engine. Thereby, a hydrogen engine is provided that is capable of operating with compression ignition, while ensuring efficient initiation and maintenance of hydrogen combustion under a wide range of operating conditions, including low-temperature and part-load scenarios. Optionally, the gas supply arrangement comprises an oxygen gas source and an ozone generator, and wherein the ozone generator is configured to generate ozone using oxygen gas from the oxygen gas source. Since the ozone generator is configured to generate ozone using oxygen gas from the oxygen gas source, the ozone generator can generate ozone at a high conversion efficiency using a low amount of inputted energy. Moreover, it can be ensured that the ozone enriched gaseous mixture supplied to the combustion chamber is composed of pure oxygen O2 being enriched with ozone O3.

[0041] The oxygen gas source, as referred to herein, may comprise a pressure tank, and / or a cryogenic tank, configured to accommodate oxygen gas O2. The oxygen gas O2 may be a byproduct of hydrogen H2 production, for example using a renewable energy source, such as solar, wind, or hydroelectric power.

[0042] In embodiments in which the hydrogen engine is configured to provide motive power to a vehicle, the oxygen gas source may be arranged on the vehicle. Likewise, such a vehicle may comprise a pressure tank, and / or a cryogenic tank, configured to accommodate hydrogen H2 for supply to the combustion chamber of the hydrogen engine by the gas supply arrangement.

[0043] However, as is further explained herein, the hydrogen engine, as referred to herein, may be configured to power a unit, system, or arrangement other than a vehicle, such as, for example, an electric generator.

[0044] Optionally, the ozone generator comprises at least one of an electrical discharge unit and an ultraviolet radiation unit. Thereby, the ozone generator has conditions for operating at a high conversion efficiency using a low amount of inputted energy.

[0045] Optionally, the loop assembly comprises a separator unit configured to separate water from the inert gas. Thereby, reliable and efficient operation of the hydrogen engine can be ensured while obtaining water as the only emission from the hydrogen engine.

[0046] Optionally, the inert gas is argon. Thereby, the use of argon, due to its chemical inertness and non-reactive properties, ensures that it does not interfere with the combustion process within the hydrogen engine. Argon is also more cost-effective compared to other noble gases, such as helium or neon, making it an economical choice while maintaining safety and performance in high-temperature operating conditions. According to a second aspect of the present disclosure, the object is achieved by a vehicle comprising a hydrogen engine according to the first aspect of the present disclosure. Since the vehicle comprises a hydrogen engine according to the first aspect of the present disclosure, a vehicle is provided comprising a hydrogen engine having zero-emission potential with the ability to efficiently initiate and maintain hydrogen combustion under a wide range of operating conditions, including low-temperature and part-load scenarios.

[0047] Moreover, a vehicle is provided comprising a hydrogen engine with improved transient behaviour and cold start performance, as well as a reduced risk of pre-ignition and knocking, which helps prevent engine damage and ensures smoother operation of the hydrogen engine.

[0048] Furthermore, the need for one or more exhaust aftertreatment systems on the vehicle is circumvented. In this manner, the complexity and cost associated with maintaining and integrating systems such as catalytic converters, particulate filters, and selective catalytic reduction (SCR) units are eliminated. This simplifies the overall design of the vehicle and contributes to enhanced efficiency and reliability.

[0049] Accordingly, a vehicle is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

[0050] Optionally, the vehicle is a heavy wheeled vehicle, such as a truck or a bus. Thereby, a heavy wheeled vehicle is provided having at least some of the above mentioned advantages.

[0051] It will be appreciated that the various embodiments described for the method are all combinable with the control arrangement as described herein. That is, the control arrangement according to the fourth aspect of the invention may be configured to perform any one of the method steps of the method according to the first aspect of the invention.

[0052] Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.

[0053] BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Various aspects of the present disclosure, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which: Fig. 1 schematically illustrates a vehicle according to some embodiments,

[0055] Fig. 2 illustrates a cross sectional view of a hydrogen engine of the vehicle illustrated in Fig. 1,

[0056] Fig. 3 illustrates a cross sectional view of a hydrogen engine according to some further embodiments, and

[0057] Fig. 4 illustrates a cross sectional view of a hydrogen engine according to some further embodiments.

[0058] DETAILED DESCRIPTION

[0059] Aspects of the present disclosure will now be described more fully. Like reference signs refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity.

[0060] Fig. 1 schematically illustrates a vehicle 2 according to some embodiments. According to the illustrated embodiments, the vehicle 2 is a truck, i.e. , a type of heavy road vehicle as well as a heavy commercial vehicle. According to further embodiments, the vehicle 2, as referred to herein, may be another type of heavy or lighter manned or unmanned vehicle for land or water propulsion, such as a lorry, bus, construction vehicle, tractor, car, boat, ship, or similar.

[0061] The vehicle 2 comprises a hydrogen engine 1. As is further explained herein, the hydrogen engine 1 is a type of internal combustion engine configured to operate on hydrogen H2. Therefore, throughout this disclosure, the wording “hydrogen engine 1” may be replaced by the wording “internal combustion engine”. According to the illustrated embodiments, the hydrogen engine 1 is operably connected to driven wheels 27 of the vehicle 2. In other words, the hydrogen engine 1 is configured to provide motive power to the vehicle 2 via the driven wheels 27 of the vehicle 2.

[0062] According to the illustrated embodiments, the vehicle 2 comprises two driven wheels 27 which constitute rear-wheels of the vehicle 2. The vehicle 2 further comprises two non-driven wheels 27’, which according to the illustrated embodiments constitute front-wheels of the vehicle 2. However, according to further embodiments, the vehicle 2 may comprise another configuration of driven and non-driven wheels.

[0063] Fig. 2 illustrates a cross sectional view of the hydrogen engine 1 of the vehicle 2 illustrated in

[0064] Fig. 1. For the reason of brevity and clarity, the hydrogen engine 1 is in some places herein referred to as “the combustion engine”, or simply “the engine 1”. Below, simultaneous reference is made to Fig. 1 and Fig. 2, if not indicated otherwise.

[0065] Even though the engine 1 is described as being configured to provide motive power to a vehicle 2 according to embodiments herein, the engine 1, as referred to herein, may be configured to power a unit, system, or arrangement other than a vehicle, such as, for example, an electric generator.

[0066] The engine 1 comprises one or more cylinders 3 and a piston 12 arranged in each cylinder 3 to delimit a combustion chamber 5 inside the cylinder 3. In Fig. 2, only one cylinder 3 of the engine 1 is seen and consequently also only one combustion chamber 5 and one piston 12. However, the engine 1 may comprise more than one cylinder 3 each delimiting a combustion chamber 5 together with a piston 12 arranged in the cylinder 3. The engine 1 may for example comprise four, six, or eight cylinders 3.

[0067] The engine 1 further comprises a crankshaft 16. Each piston 12 of the engine 1 is connected to the crankshaft 16 via a respective connecting rod 13. The pistons 12 move forwards and backwards in the respective cylinder 3 between a top dead centre and a bottom dead centre upon rotation of the crankshaft 16.

[0068] The engine 1 further comprises an exhaust outlet 7 and a gas inlet 9 each connected to the combustion chambers 5 of the engine 1. The exhaust outlet 7 may also be referred to as an exhaust outlet manifold, an exhaust manifold, or the like. Likewise, the gas inlet 9 may also be referred to as a gas inlet manifold, an inlet manifold, or the like.

[0069] According to the illustrated embodiments, the engine 1 is a four-stroke hydrogen engine 1 which comprises at least one inlet valve 19 arranged in each cylinder 3. The at least one inlet valve 19 is configured to control the transfer of gas from the gas inlet 9 into the combustion chamber 5 as is further explained herein. The engine 1 further comprises an inlet valve control arrangement 29 configured to control each inlet valve 19 on the basis of a rotational position of the crankshaft 16.

[0070] The engine 1 further comprises at least one exhaust valve 17 arranged in each cylinder 3. The at least one exhaust valve 17 is configured to control the transfer of gas from the combustion chamber 5 into the exhaust outlet 7. The engine 1 further comprises an exhaust valve control arrangement 27 configured to control each exhaust valve 17 on the basis of the rotational position of the crankshaft 16. In Fig. 2, the at least one inlet valve 19 is illustrated in an open position and the at least one exhaust valve 17 is illustrated in a closed position. In a closed position, each valve 17, 19 abuts against a respective valve seat to close fluid connection between the combustion chamber 5 and the respective gas inlet 9 and the exhaust outlet 7 respectively.

[0071] The inlet valve control arrangement 29 is arranged to control the at least one inlet valve 19 between the closed position and an open position by displacing the at least one inlet valve 19 in a direction into the cylinder 3. A fluid connection is thereby opened between the gas inlet 9 and the combustion chamber 5. Likewise, the exhaust valve control arrangement 27 is arranged to control the at least one exhaust valve 17 between the closed position and an open position by displacing the at least one exhaust valve 17 in a direction into the cylinder 3. Thereby, a fluid connection is opened between the combustion chamber 5 and the exhaust outlet 7. Upon displacement of a valve 17, 19 from the closed position to the open position, the valve 17, 19 is lifted from its valve seat.

[0072] The exhaust valve control arrangement 27 and the inlet valve control arrangement 29 may each comprise one or more camshafts rotatably connected to the crankshaft 16, wherein the camshafts comprise cam lobes arranged to displace valves 17, 19 to an open position by pressing on valve stems of the valves 17, 19 upon rotation of the camshaft. The exhaust valve control arrangement 27, and / or the inlet valve control arrangement 29, may according to further embodiments comprise electric, pneumatic, or hydraulic actuators arranged to control valves on the basis of the rotational position of the crankshaft 16. The rotational position of the crankshaft 16 may be obtained using data from a crank angle sensor.

[0073] Moreover, the hydrogen engine 1 may comprise an inlet valve phase-shifting device and an exhaust valve phase-shifting device. The inlet valve phase-shifting device and the exhaust valve phase-shifting device may each comprise a hydraulic arrangement, for example using engine oil as hydraulic fluid, to phase-shift control of the valves 17, 19 in relation to the crankshaft 16. Such hydraulic arrangement may form part of a belt pulley (not illustrated) arranged to transfer rotation from the crankshaft 16 to a camshaft of the exhaust valve control arrangement 27 and / or the inlet valve control arrangement 29, wherein the hydraulic arrangement is arranged to regulate an angular relationship between a first portion of the belt pulley, being connected to the crankshaft 16, and a second portion of the belt pulley, being connected to the camshaft, in order to phase-shift control of the at least one inlet valve 19 and / or the at least one exhaust valve 17. In embodiments wherein the exhaust valve control arrangement 27 and / or the inlet valve control arrangement 29 comprises electric, pneumatic, or hydraulic actuators, the exhaust valve phase-shifting device and / or the inlet valve phase-shifting device may phase-shift control of the at least one valve 17, 19 in another manner, for example by an electronic phase-shift of control.

[0074] According to the illustrated embodiments, the engine 1 is a compression ignition engine, i.e. , a type of engine 1 that ignites the fuel, i.e., the hydrogen according to embodiments herein, through the heat generated by compressing the air in the cylinder, rather than relying on a spark. However, according to further embodiments, the engine 1 as referred to herein may be an Otto engine with a spark-ignition device configured to ignite the hydrogen in the combustion chamber 5.

[0075] The hydrogen engine 1 comprises a loop assembly 11 connecting the exhaust outlet 7 to the gas inlet 9, thereby forming a closed loop 1 T that includes the exhaust outlet 7, the gas inlet 9, and the combustion chamber 5. Moreover, the hydrogen engine 1 comprises an inert gas Ar contained within the closed loop 1 T. In other words, the loop assembly 11 connects the exhaust outlet 7 to the gas inlet 9 such that the inert gas Ar is circulated within the closed loop 1 T upon operation of the hydrogen engine 1, as is further explained herein.

[0076] According to the illustrated embodiments, the inert gas Ar is Argon. However, according to further embodiments, the hydrogen engine 1 may comprise another type of inert gas contained within the closed loop 1 T. The term “inert gas” means a gas that does not undergo chemical reactions under a set of given conditions. In general, inert gases are chemically stable and non-reactive because their outer electron shells are full, making them unlikely to form chemical bonds with other elements. The most common inert gases are the noble gases, such as helium, neon, argon, krypton, xenon, and radon. In some cases, other gases like nitrogen (N2) may be considered inert under specific conditions, though they are not true noble gases. The term is often used in contexts like engine design, where the gas must not participate in combustion or cause corrosion or other chemical reactions.

[0077] The hydrogen engine 1 further comprises a gas supply arrangement 6. As is further explained herein, the gas supply arrangement 6 is configured to supply hydrogen H2to the combustion chamber 5 of the hydrogen engine 1. Moreover, as is further explained herein, the gas supply arrangement 6 is configured to supply an ozone O3 enriched gaseous mixture to the combustion chamber 5. In more detail, according to the embodiments illustrated in Fig. 2, the gas supply arrangement 6 comprises a hydrogen tank H2t configured to accommodate hydrogen H2. The hydrogen tank H2t is also indicated in Fig. 1. The hydrogen tank H2t may be a cryogenic tank configured to accommodate hydrogen H2in liquid form or a pressure tank configured to accommodate pressurized hydrogen H2.

[0078] The hydrogen engine 1 comprises a first injector i1. According to the embodiments illustrated in Fig. 2, the first injector i1 is configured to inject hydrogen H2from the hydrogen tank H2t into the gas inlet 9 of the hydrogen engine 1.

[0079] As mentioned, the piston 12 is configured to reciprocate in the cylinder 3 between a top dead centre and a bottom dead centre. During an intake stroke of the piston 12, the piston 12 moves from the top dead centre towards the bottom dead centre. Moreover, the at least one inlet valve 19 is controlled to the open position during the intake stroke of the piston 12. In this manner, the inert gas Ar and the hydrogen H2gas is sucked from the gas inlet 9 into the combustion chamber 5 during the intake stroke of the piston 12. Therefore, according to the embodiments illustrated in Fig. 2, the gas supply arrangement 6 can be said to be configured to supply hydrogen H2to the combustion chamber 5 during an intake stroke of the piston 12.

[0080] The at least one inlet valve 19 is closed when the piston 12 is at the bottom dead centre. The compression stroke of the piston 12 refers to the subsequent stroke of the piston 12, in which the piston 12 moves from the bottom dead centre towards the top dead centre. Each of the at least one inlet valve 19 and the at least one exhaust valve 17 is controlled to the closed position during the compression stroke of the piston 12. In this manner, the inert gas Ar and the hydrogen H2is compressed in the combustion chamber 5 during the compression stroke of the piston 12.

[0081] According to the embodiments illustrated in Fig. 2, the gas supply arrangement 6 of the hydrogen engine 1 comprises an oxygen gas source O2t. The oxygen gas source O2t is also indicated in Fig. 1. The oxygen gas source O2t may comprise a cryogenic tank configured to accommodate oxygen O2in liquid form or a pressure tank configured to accommodate pressurized oxygen O2.

[0082] Moreover, the gas supply arrangement 6 comprises an ozone generator O2g. The ozone generator O3g may comprise at least one of an electrical discharge unit and an ultraviolet radiation unit. As can be seen in the schematic illustration of Fig. 1 , the ozone generator O3g is configured to generate ozone O3using oxygen gas from the oxygen gas source O2t. In this manner, the ozone generator O3g can operate with high ozone production efficiency while using a low amount of input energy. As understood from the above described, an ozone O3 enriched gaseous mixture is formed in the gas supply arrangement 6 downstream of the ozone generator Osg. The ozone O3 enriched gaseous mixture, as referred to herein, is a gaseous mixture between oxygen O2 gas and ozone O3.

[0083] Furthermore, according to the embodiments illustrated in Fig. 2, the hydrogen engine 1 comprises a second injector i2. The second injector i2 is configured to supply the ozone O3 enriched gaseous mixture from the ozone generator Chg and the oxygen gas source C>2t directly into the combustion chamber 5 at the end, or near the end, of a compression stroke of the piston 12.

[0084] Thereby, a hydrogen engine 1 is provided with the ability to efficiently initiate and maintain hydrogen combustion under a wide range of operating conditions, including low-temperature and part-load scenarios. This is because ozone O3 is an unstable gas and contribute to formation of oxygen atoms and hydroxyl radicals that substantially improve the chain reactions between hydrogen H2and oxygen O2. The ozone O3 increases the rate of reactions in the limited residence time that oxygen O3 and hydrogen H2 molecules have in the combustion chamber 5. Faster reaction leads to higher closed cycle efficiency as well as a more complete combustion in which more oxygen O2 molecules will be consumed compared to when ozone O3 is not present.

[0085] Accordingly, as a result, a hydrogen engine 1 is provided with a reduced risk of pre-ignition and knocking, which helps prevent engine damage and ensures smoother operation of the hydrogen engine 1. In addition, the supplied ozone O3 enriched gaseous mixture can improve the transient behaviour of the hydrogen engine 1 and can facilitate cold starts.

[0086] Moreover, since the gas supply arrangement 6 is configured to supply the ozone O3 enriched gaseous mixture to the combustion chamber 5, the need for utilizing a pilot injection of diesel or a diesel-like fuel is circumvented for initiating combustion. Accordingly, conditions are provided for obtaining a zero-emission hydrogen engine 1. In this context, the wording a zero-emission hydrogen engine 1 means that no emissions, other than pure water H2O, are exhausted from the hydrogen engine 1 .

[0087] That is, since the hydrogen engine 1 comprises the inert gas Ar contained within the closed loop, the hydrogen H2inside the combustion chamber 5 can be combusted without the presence of atmospheric air, and thereby also the presence of nitrogen, which eliminates the formation of nitrogen oxides (NOx). Additionally, by eliminating the need for any carbonbased pilot fuels, the hydrogen engine 1 eliminates the release of carbon dioxide (CO2), carbon monoxide (CO), unburned hydrocarbons (HC), and particulate matter (PM) typically associated with traditional combustion engines.

[0088] As a further result, the need for one or more exhaust aftertreatment systems on the engine 1 is circumvented. In this manner, the complexity and cost associated with maintaining and integrating systems such as catalytic converters, particulate filters, and selective catalytic reduction (SCR) units are eliminated. This simplifies the overall design of the hydrogen engine 1 and contributes to enhanced efficiency and reliability. Additionally, by removing the dependence on exhaust aftertreatment systems, the engine 1 can achieve a lower overall weight, further improving fuel efficiency and performance.

[0089] Moreover, since the gas supply arrangement 6 is configured to supply the ozone O3 enriched gaseous mixture into the combustion chamber 5 at the end, or near the end, of a compression stroke of the piston 12, and the hydrogen H2during the intake stroke of the piston 12, a hydrogen engine 1 is provided circumventing the need for a compressor configured to compress the hydrogen H2prior to supplying the hydrogen to the hydrogen engine 1. This is because the pressure inside the combustion chamber 5 is considerably lower during an intake stroke of the piston 12 as compared to at the end, or near the end, of a compression stroke of the piston 12.

[0090] Furthermore, the liquefaction of oxygen O2is much easier than the liquefaction of hydrogen H2since it has higher critical temperature compared to hydrogen, -147°C for oxygen vs - 240°C for hydrogen. This means that the need for arranging a compressor for compressing the ozone O3 enriched gaseous mixture also can be circumvented by storing oxygen O2in liquified state for use by the hydrogen engine 1. As indicated, the liquefaction of oxygen O2is much easier than liquefaction of hydrogen H2. Also, the boil off rate of liquified oxygen O2is less of a problem compared to the boil off rate of liquified hydrogen. The term boil off rate refers to the amount of liquid that is evaporating from a storage tank due to heat leakage.

[0091] A compressor configured to compress gas prior to supplying the gas to the combustion chamber 5 at the end, or near the end, of a compression stroke of the piston 12 requires the input of energy that has parasite effect on the hydrogen engine 1 which reduces the overall efficiency of the hydrogen engine 1 . Accordingly, by circumventing the need for such a compressor, the overall energy efficiency of the hydrogen engine 1 can be significantly improved. Another potential problem with supplying hydrogen H2to the combustion chamber 5 during the intake stroke of the piston 12 and supplying oxygen O2to the combustion chamber 5 at the end, or near the end, of the compression stroke could be that that the oxygen O2won’t have enough time to completely react with hydrogen H2inside the combustion chamber 5. If so, some oxygen will end-up in the exhaust outlet 7 which will be sent back to the gas inlet 9 in the closed loop 11’ engine solution. This will result in pre-ignition or knocking in the engine 1. One potential solution to this could be to operate the hydrogen engine 1 at very high concentrations of hydrogen H2. Nevertheless, the higher excess hydrogen H2in the gas inlet 9 would significantly decrease the efficiency of the engine 1 .

[0092] However, this potential problem is overcome by the hydrogen engine 1 according to the embodiments illustrated in Fig. 2, since the gas supply arrangement 6 is configured to supply the ozone O3 enriched gaseous mixture to the combustion chamber 5 which can ensure that the oxygen O2completely reacts with the supplied hydrogen H2. Thus, as a result, a hydrogen engine 1 is provided having conditions for increased efficiency and a reduced tendency of pre-ignition and knocking.

[0093] As understood from the above described, the compression heat and the ozone O3 enriched gaseous mixture initiate combustion of the hydrogen H2inside the combustion chamber 5. The expansion stroke refers to the stroke following the compression stroke, during which the piston 12 moves from the top dead centre to the bottom dead centre. During the expansion stroke, each of the at least one inlet valve 19 and at least one exhaust valve 17 is controlled to remain in the closed position. In this manner, at least part of the increased pressure and temperature resulting from the combustion of hydrogen can be transferred to the crankshaft 16 of the hydrogen engine 1 to perform useful work.

[0094] The exhaust stroke refers to the stroke following the expansion stroke, during which the piston 12 moves from the bottom dead centre to the top dead centre. During this stroke, the at least one exhaust valve 17 is controlled to open, allowing the combustion gases to be expelled from the combustion chamber 5 into the exhaust outlet 7. The at least one inlet valve 19 remains in the closed position during the exhaust stroke. This process enables the removal of exhaust gases from the combustion chamber 5, preparing the combustion chamber 5 for the next intake of hydrogen H2in the subsequent intake stroke.

[0095] The combustion of hydrogen H2, i.e. , the chemical reaction between hydrogen H2and oxygen O2results in water H2O. Accordingly, the exhaust gas expelled from the combustion chamber 5 into the exhaust outlet 7 during the exhaust stroke of the piston 12 is composed of water H2O vapor and the inert gas Ar. As can be seen in Fig. 2, according to the illustrated embodiments, the hydrogen engine 1 comprises a separator unit 15. The separator unit 15 is configured to separate water H2O from the inert gas Ar in the closed-loop 1 T.

[0096] In other words, the separator 15 is configured to remove water H2O from the closed-loop 1 T as the inert gas Ar circulates within the closed-loop 1 T. As can be seen in Fig. 2, according to the illustrated embodiments, the separator 15 is arranged within the loop assembly 11 such that the exhaust gas circulating in the closed-loop 1 T flows through the separator 15. The separator 15 may comprise a heat exchanger for cooling the exhaust gas flowing through the separator to thereby condense water H2O in the exhaust gas thereby separating the water H2O from the inert gas Ar. The heat exchanger of the separator 15 may comprise an evaporator or may be cooled using an evaporator. The evaporator may be part of a heat pump circuit that comprises the evaporator, a condenser, a compressor, an expansion valve arranged upstream of the evaporator, and the like components. As an alternative, or in addition, the separator 15 may employ centrifugal forces or cyclonic action and / or coalescing filters to isolate and collect the water H2O, preventing it from remaining in the inert gas flow. The separated water H2O is either stored in a designated reservoir or expelled from the hydrogen engine 1 as required.

[0097] Fig. 3 illustrates a cross sectional view of a hydrogen engine T according to some further embodiments. As indicated in Fig. 1, the vehicle 2 may comprise a hydrogen engine T according to the embodiments illustrated in Fig. 3. The hydrogen engine T according to the embodiments illustrated in Fig. 3 comprises the same features, functions, and advantages as the hydrogen engine 1 according to the embodiments illustrated in Fig. 2, with some differences explained below. For reasons of brevity and clarity, only the differences are explained in detail below.

[0098] According to the embodiments illustrated in Fig. 3, the gas supply arrangement 6’ of the hydrogen engine T is configured to supply the ozone O3 enriched gaseous mixture during an intake stroke of the piston 12 and the hydrogen H2at the end, or near the end, of a compression stroke of the piston 12.

[0099] That is, in more detail, according to the embodiments illustrated in Fig. 3, the first injector i1 is connected to the oxygen gas source O2t and the ozone generator Osg. The ozone O3 enriched gaseous mixture therefrom is thus injected by the first injector i1 into the gas inlet 9. When the at least one inlet valve 19 is opened during the intake stroke of the piston 12, the ozone O3 enriched gaseous mixture is transferred from the gas inlet 9 into the combustion chamber 5.

[0100] Each of the at least one inlet valve 19 and the at least one exhaust valve 17 is controlled to the closed position in the subsequent compression stroke of the piston 12. In this manner, the inert gas Ar and the ozone O3 enriched gaseous mixture is compressed in the combustion chamber 5 during the compression stroke of the piston 12 according to the embodiments illustrated in Fig. 3.

[0101] As can be seen in Fig. 3, the hydrogen tank H2t is connected to the second injector i2, wherein the second injector i2 is configured to supply the hydrogen H2 directly into the cylinder at the end, or near the end, of a compression stroke of the piston 12. In this manner, combustion of the hydrogen H2 is initiated by the compression heat in the combustion chamber 5, with the aid of the ozone O3 of the ozone O3 enriched gaseous mixture supplied to the combustion chamber 5 during the intake stroke of the piston 12.

[0102] Thus, also in this manner, a hydrogen engine T is provided with the ability to efficiently initiate and maintain hydrogen combustion under a wide range of operating conditions, including low-temperature and part-load scenarios.

[0103] A drawback with the engine T according to the embodiments illustrated in Fig. 3, as compared to the engine 1 according to the embodiments illustrated in Fig. 2, is that the hydrogen H2 is injected into the combustion chamber 5 when the pressure in the combustion chamber 5 is relatively high. Therefore, the hydrogen engine T according to the embodiments illustrated in Fig. 3 may need a compressor for compressing the hydrogen H2 before it is injected into the combustion chamber 5, and / or a cryogenic storage solution for the hydrogen H2 in the hydrogen tank H2t.

[0104] Fig. 4 illustrates a cross sectional view of a hydrogen engine 1” according to some further embodiments. As indicated in Fig. 1 , the vehicle 2 may comprise a hydrogen engine 1” according to the embodiments illustrated in Fig. 4. The hydrogen engine 1” according to the embodiments illustrated in Fig. 4 comprises the same features, functions, and advantages as the hydrogen engine 1 according to the embodiments illustrated in Fig. 2, with some differences explained below. For reasons of brevity and clarity, only the differences are explained in detail below. According to the embodiments illustrated in Fig. 4, each of the first and second injectors i1 , i2 of the gas supply arrangement 6” is configured to supply gas directly into the combustion chamber 5 of the hydrogen engine 1”.

[0105] In these embodiments, the gas supply arrangement 6” may be configured to supply one of the hydrogen H2 and the ozone O3 enriched gaseous mixture during an intake stroke of the piston 12, and the other of the hydrogen H2 and the ozone O3 enriched gaseous mixture at the end, or near the end, of a compression stroke of the piston 12.

[0106] According to the embodiments illustrated in Fig. 4, only the inert gas Ar is conducted into the combustion chamber 5 from the gas inlet 9 during the intake stroke of the piston 12, wherein one of the hydrogen H2 and the ozone O3 enriched gaseous mixture is supplied directly into the combustion chamber 5 during the intake stroke of the piston 12.

[0107] Preferably, the hydrogen H2is supplied directly into the combustion chamber 5 during the intake stroke of the piston 12 using the second injector i2, wherein the ozone O3 enriched gaseous mixture is supplied directly into the combustion chamber 5 by the first injector i1 at the end, or near the end, of a compression stroke of the piston 12.

[0108] In this manner, the need for a compressor compressing the hydrogen H2prior to supplying it to the combustion chamber 5 is eliminated, as well as the need for storing the hydrogen H2using a cryogenic storage solution.

[0109] However, according to some further embodiments, the engine 1” according to the embodiments illustrated in Fig. 4 may be configured to supply the ozone O3 enriched gaseous mixture directly into the combustion chamber 5 during the intake stroke of the piston 12 using the first injector i1 , wherein hydrogen H2 is supplied directly into the combustion chamber 5 by the second injector i2 at the end, or near the end, of a compression stroke of the piston 12.

[0110] Since the hydrogen engine 1” according to the embodiments illustrated in Fig. 4 is configured to supply the ozone O3 enriched gaseous mixture to the combustion chamber 5, a hydrogen engine 1” is provided with the ability to efficiently initiate and maintain hydrogen combustion under a wide range of operating conditions, including low-temperature and part-load scenarios. As indicated above, even though the engine 1 , T, 1” is described as being configured to provide motive power to a vehicle 2 according to the illustrated embodiments, the engine 1, T, 1”, as referred to herein, may be configured to power a unit, system, or arrangement other than a vehicle, such as, for example, an electric generator.

[0111] The wording “at the end, or near the end, of a compression stroke of the piston 12”, as used herein, may encompass that the gaseous mixture referred to is supplied within a maximum of 70 crank angle degrees, or a maximum of 40 crank angle degrees, from the top dead centre of the piston 12. According to some embodiments, this may include supplying the gaseous mixture within a maximum of 70 crank angle degrees, or a maximum of 40 crank angle degrees, before the top dead centre, and within a maximum of 40 crank angle degrees, or a maximum of 20 crank angle degrees, after the top dead centre of the piston 12.

[0112] Since each of the first injector i1 and the second injector i2 is configured to supply a gaseous substance, each of the first injector i1 and the second injector i2 may also be referred to as a gas injector, a gas injector nozzle, a gas nozzle, or similar.

[0113] It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended independent claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended independent claims.

[0114] As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components, or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims

CLAIMS1. A hydrogen engine (1 , T, 1”) comprising: one or more cylinders (3), a piston (12) arranged in each cylinder (3) to delimit a combustion chamber (5) inside the cylinder (3), an exhaust outlet (7) and a gas inlet (9) each connected to the combustion chamber (5), a loop assembly (11) connecting the exhaust outlet (7) to the gas inlet (9), thereby forming a closed loop (1 T) that includes the exhaust outlet (7), the gas inlet (9), and the combustion chamber (5), an inert gas (Ar) contained within the closed loop (1 T), and a gas supply arrangement (6, 6’, 6”) configured to supply hydrogen (H2) to the combustion chamber (5), wherein the gas supply arrangement (6, 6’, 6”) is further configured to supply an ozone (O3) enriched gaseous mixture to the combustion chamber (5).

2. The engine (1 , T, 1”) according to claim 1 , wherein the gas supply arrangement (6, 6’, 6”) is configured to supply at least one of the hydrogen (H2) and the ozone (O3) enriched gaseous mixture directly into the combustion chamber (5).

3. The engine (1 , T, 1”) according to claim 1 or 2, wherein the gas supply arrangement (6, 6’, 6”) is configured to supply the at least one of the hydrogen (H2) and the ozone (O3) enriched gaseous mixture at the end, or near the end, of a compression stroke of the piston (12).

4. The engine (1 , T, 1”) according to any one of the preceding claims, wherein the gas supply arrangement (6, 6’, 6”) is configured to supply one of the hydrogen (H2) and the ozone (O3) enriched gaseous mixture at the end, or near the end, of a compression stroke of the piston (12), and the other of the hydrogen (H2) and the ozone (O3) enriched gaseous mixture during an intake stroke of the piston (12).

5. The engine (1 , 1”) according to any one of the preceding claims, wherein the gas supply arrangement (6, 6”) is configured to supply hydrogen (H2) to the combustion chamber (5) during an intake stroke of the piston (12), and is configured to supply an ozone (O3) enriched gaseous mixture to the combustion chamber (5) at the end, or near the end, of a compression stroke of the piston (12).

6. The engine (1 , T, 1”) according to any one of the preceding claims, wherein the engine (1 , T, 1”) is a compression ignition engine.

7. The engine (1 , T, 1”) according to any one of the preceding claims, wherein the gas supply arrangement (6, 6’, 6”) comprises an oxygen gas source (C>2t) and an ozone generator (Chg), and wherein the ozone generator (Osg) is configured to generate ozone (O3) using oxygen gas from the oxygen gas source (C>2t) .

8. The engine (1 , T, 1”) according to claim 7, wherein the ozone generator (Chg) comprises at least one of an electrical discharge unit and an ultraviolet radiation unit.

9. The engine (1 , T, 1”) according to any one of the preceding claims, wherein the loop assembly (11) comprises a separator unit (15) configured to separate water (H2O) from the inert gas (Ar).

10. The engine (1 , T, 1”) according to any one of the preceding claims, wherein the inert gas (Ar) is argon.

11. A vehicle (2) comprising a hydrogen engine (1 , T, 1”) according to any one of the preceding claims.

12. The vehicle (2) according to claim 11 , wherein the vehicle (2) is a heavy wheeled vehicle, such as a truck or a bus.

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