Device with hydrogen collector unit

Abstract

An apparatus (100, 200) suitable for hydrogen applications, comprising: a hydrogen preparation unit (102) suitable for supplying a gaseous medium containing hydrogen at a pressure between a lower limit and an upper limit, the gaseous medium containing at least 85 volume percent hydrogen; a hydrogen collector unit (101, 201) comprising one or more duct elements (300, 301), which together define an internal space delimited by a wall portion; a hydrogen treatment unit (103) adapted to treat and / or use a hydrogen-containing medium wherein the apparatus (100, 200) is adapted to: feed the hydrogen-containing medium from the hydrogen production unit (102) to the hydrogen collector unit (101, 201); the hydrogen-containing medium is supplied from the hydrogen collector unit (101, 201) to the hydrogen treatment unit (103), where the upper limit is at most 50 bar, and each of the one or more conduit elements (300, 301) is a casting made of nodular cast iron having a tensile strength of at most 600 MPa.

Description

Technical Field

[0001] The present invention relates generally to collectors in hydrogen applications, and more particularly to fuel rails in hydrogen internal combustion engines. The present invention particularly provides a solution for a collector that, through appropriate material selection, is sufficiently resistant to hydrogen embrittlement while allowing limited material costs and good feasibility. Background Art

[0002] In recent years, hydrogen has emerged as a promising alternative fuel and energy carrier. For example, hydrogen internal combustion engines, in which hydrogen is used as fuel, have been developed as vehicle drive systems, and fuel cells, which use hydrogen to generate electricity, have been developed.

[0003] However, the use of hydrogen in engines and other applications presents additional challenges at the material level used in the system. Indeed, a substantial risk associated with the use of hydrogen is the development of hydrogen embrittlement or hydrogen embrittlement: a phenomenon in which hydrogen diffuses into the material structure, causing localized embrittlement and the risk of cracking or brittle fracture. In particular, parameters that promote a certain increase in activation energy, such as elevated pressure or temperature, increase the risk of hydrogen embrittlement.

[0004] Therefore, particular attention should be paid to selecting suitable materials for components that come into contact with hydrogen-containing media during storage, transportation, or processing. For example, in hydrogen internal combustion engines, the collector or fuel rail is a critical component. The fuel rail forms part of the hydrogen supply system and provides a temporary buffer for the nearly pure hydrogen before mixing with air and supplying the hydrogen-air mixture to the cylinders. While the pressure levels within the collector or fuel rail are admittedly not as high as those in, for example, a hydrogen storage tank, there is a real risk of hydrogen embrittlement due to the collector walls being in constant contact with the nearly pure hydrogen. Consequently, inspection requirements for such components are particularly stringent, and resistance to hydrogen embrittlement must be guaranteed even at the highest pressure levels that can occur in the fuel rail (e.g., 10 bar), not just at the lower pressure levels experienced during nominal operation (e.g., 3.5 bar). Furthermore, even though hydrogen may only buffer and flow briefly within the fuel rail in practice, resistance to hydrogen embrittlement must be guaranteed under nearly constant static exposure to hydrogen.

[0005] In general, the prior art teaches that certain more porous materials (such as cast iron) are not suitable for use with hydrogen due to their high sensitivity to hydrogen embrittlement. For example, an online article entitled “Identifying Unique Hydrogen Fuel Cell System Demands and How to Meet Them” (October 22, 2020, https: / / www.oemoffhighway.com / engines / fuels-fluids / fuel-tanks-systems / article / 21199105 / identifying-unique-hydrogen-fuel-cell-system-demands-and-how-to-meet-them) describes materials suitable for key components in hydrogen fuel cells. The article points out that lower-grade traditional stainless steel behaves similarly to cast iron and therefore exhibits a high risk of hydrogen embrittlement. Furthermore, in a scientific article titled "Hydrogen embrittlement of nodular cast iron" (Patrik Sahiluoma et al., 2020), the susceptibility of ferritic ductile iron to hydrogen embrittlement was investigated for the selection of materials for containers used in the long-term geological storage of spent nuclear fuel. The experimental studies conducted, focusing on high temperatures as an activator for hydrogen, indicate that the cast iron studied belongs to a material grade with a high sensitivity to hydrogen embrittlement.

[0006] To limit the risk of hydrogen embrittlement, the prior art recommends the use of specific high-grade materials in hydrogen applications. For example, the article entitled "Review: Hydrogen Embrittlement of Metals and Alloys in Combustion Engines" (Maricruz Saborio González et al., 2017) provides an overview of the materials currently used in various components of internal combustion engines using hydrogen-rich fuels. In general, the article states that non-porous materials should be selected to avoid hydrogen permeation. In particular, the use of specific metals, alloys, and steel grades is recommended, such as aluminum, aluminum alloys, titanium steel, stainless steel, copper, bronze, monel, inconel, titanium, austenitic stainless steel, and alloy steels containing titanium oxide and aluminum oxide.

[0007] In the aforementioned online article titled “Identifying Unique Hydrogen Fuel Cell System Demands and How to Meet Them” (October 22, 2020, https: / / www.oemoffhighway.com / engines / fuels-fluids / fuel-tanks-systems / article / 21199105 / identifying-unique-hydrogen-fuel-cell-system-demands-and-how-to-meet-them), suitable materials for key components in hydrogen fuel cells are mentioned. In this case, higher-grade stainless steel grades, such as stainless steel with a certain nickel content, are recommended, which are more resistant to hydrogen embrittlement and therefore more reliable as a material choice for components in hydrogen fuel cells.

[0008] US2018 / 0058312A1 proposes a "hydrogen fuel reformer" that converts fuel into hydrogen, which can then be used, for example, in a fuel cell or supplied to a combustion chamber. The hydrogen flowing out of the reformer is at a high temperature and must therefore be cooled in a so-called "fuel reforming cooler". The hydrogen is therefore temporarily retained in the cooler, where there is a risk of hydrogen diffusing into the walls. In order to limit the risk of hydrogen embrittlement, the application of a special layer or coating is proposed in this patent application. Examples of such "anti-hydrogen embrittlement layers" are nitride films (e.g., silicon nitride films) or nickel-based alloy layers or coatings.

[0009] In summary, the above-mentioned prior art recommends the use of high-grade materials (such as stainless steel and alloy steel) or the use of special coatings in combination with hydrogen. However, in this way, the reduction in hydrogen embrittlement sensitivity is accompanied by the introduction of additional disadvantages, such as disadvantages in terms of cost and feasibility. In fact, high-grade materials (such as stainless steel and alloy steel) are expensive, so when these expensive materials must be used in large engines, it will have a significant impact on the cost price. In addition, for components such as hydrogen collectors or fuel rails that require a double-wall structure, in order to limit the occupied space and facilitate the integration of the collector in the engine, it is preferred to make the double wall thinner. However, the above-mentioned high-grade materials are not suitable for thin wall casting, so components such as collectors have to be manufactured by welding. Therefore, the compact design of the collector and simple integration in the engine become difficult. Finally, any existing welds always constitute weak points of the manufactured components, which is disadvantageous in terms of strength and durability.

[0010] The object of the present invention is to propose a solution that overcomes one or more of the drawbacks of prior art solutions. More specifically, the object of the present invention is to propose a collector for hydrogen applications that is sufficiently resistant to hydrogen embrittlement through a suitable choice of materials, while having limited material costs and good feasibility. Summary of the Invention

[0011] According to a first aspect of the present invention, the above object is achieved by a device suitable for hydrogen applications as defined in claim 1, wherein the device comprises:

[0012] a hydrogen production unit adapted to supply a hydrogen-containing gaseous medium at a pressure corresponding to the operating state of the apparatus, the gaseous medium containing at least 85% by volume of hydrogen;

[0013] - a hydrogen collector unit in communication with the hydrogen production unit, comprising one or more conduit elements which together define an interior space bounded by a wall;

[0014] a hydrogen treatment unit in communication with the hydrogen collector unit, which is suitable for treating and / or using the hydrogen-containing medium,

[0015] The device is suitable for:

[0016] - supplying the hydrogen-containing medium from the hydrogen production unit to the hydrogen collector unit for achieving a flow and / or temporary buffering of the hydrogen-containing medium in the inner space, wherein the wall is in contact with the hydrogen-containing medium, and wherein the pressure in the inner space is at most equal to an upper limit and the temperature in the inner space is at most 100° C.;

[0017] - supplying the hydrogen-containing medium from the hydrogen collector unit to the hydrogen treatment unit,

[0018] in:

[0019] - the upper limit of the pressure is at most 50 bar, and

[0020] Each of the one or more piping elements is a casting made of ductile iron having a tensile strength of at most 600 MPa.

[0021] In other words, the present invention relates to a device suitable for hydrogen applications. Hydrogen applications refer to applications or systems in which a medium containing hydrogen is used, such as for processing, use, transport, storage, etc. In one possible embodiment, the device is a hydrogen internal combustion engine. In other embodiments, the device is equipment in which hydrogen is processed or handled, such as a fuel cell, turbine, compressor, etc.

[0022] The apparatus includes a hydrogen production unit for supplying a gaseous medium containing hydrogen. The hydrogen-containing medium is a gas or gas mixture containing at least 85% hydrogen by volume. In one embodiment, the volume percentage of hydrogen in the medium is, for example, 85%, 90%, or 95%. The production unit serves as a hydrogen supply, supplying the hydrogen-containing medium under desired conditions. Specifically, the production unit supplies the medium at a predetermined pressure. For example, the hydrogen production unit includes one or more supply lines and one or more pressure controllers. Depending on the operating state of the apparatus, the pressure delivered by the production unit can assume various values. For example, if one or more pressure reducing valves or pressure regulating valves are present, the pressure is adjusted to a set value or a desired value based on the actual power. In a low-power operating mode, the production unit then delivers the hydrogen-containing medium at a set pressure lower than the nominal power. For example, an overpressure valve may be provided to release excess pressure once a certain discharge value is reached if the pressure reducing valve is no longer in operation. In this way, the pressure of the hydrogen-containing medium delivered by the production unit is always between a lower and upper limit, depending on the current operating state. In other words, during operation of the apparatus, the hydrogen production unit supplies the hydrogen-containing medium at a pressure at least equal to a lower limit and at most equal to an upper limit. For example, when the pressure reaches a certain discharge value, the upper pressure limit is reached when the overpressure valve activates. In this case, the hydrogen-containing medium is delivered by the hydrogen production unit at a pressure equal to the discharge value, where the discharge value corresponds to the upper pressure limit that may occur. Depending on the current operating state, a certain pressure level can be achieved, varying between the lower and upper limits. In one embodiment, the lower and upper limits may be equal, so that the production unit always delivers at the same pressure during operation.

[0023] The device includes a hydrogen collector unit. The collector unit is a component in which a medium containing hydrogen can flow and / or can be temporarily buffered or stored. The collector unit is composed of one or more pipe elements, ducts or pipes. These pipe elements together define an internal space in which the medium is present. The internal space is defined by an inner wall portion or a wall portion, which is in contact with the medium in the presence of the medium. In one embodiment, the hydrogen collector unit corresponds to a gas rail, a hydrogen rail or a fuel rail used in a hydrogen internal combustion engine. The hydrogen collector unit is connected to a hydrogen preparation unit, which means that the preparation unit and the collector unit are fluidically connected so that the medium transported by the preparation unit ultimately flows into the collector unit via a direct connection or through one or more intermediate supply lines or pipes.

[0024] The apparatus includes a hydrogen processing unit adapted to process and / or utilize a hydrogen-containing medium. In one embodiment, the hydrogen processing unit is configured to correspond to a cylinder and injector combination, such as that found in a hydrogen internal combustion engine. The hydrogen processing unit is connected to a hydrogen collector unit, meaning that the collector unit and the processing unit are in fluid communication such that the medium can flow from the collector unit to the processing unit via a direct connection or via one or more intermediate supply lines or conduits.

[0025] During operation of the system, the hydrogen collector unit is supplied with a hydrogen-containing medium delivered by the hydrogen production unit. Furthermore, the hydrogen-containing medium is supplied or distributed from the hydrogen collector unit to the hydrogen processing unit. During operation, the hydrogen-containing medium is temporarily buffered or stored in the collector unit before flowing through it and / or being distributed to the processing unit. While the hydrogen-containing medium is in the collector unit, the inner wall of the collector unit comes into contact with the hydrogen-containing medium. Inside the hydrogen collector unit, the temperature of the hydrogen-containing medium is a maximum of 100°C. For example, at temperatures between -20°C and 100°C, hydrogen is in a gaseous state. Inside the hydrogen collector unit, the hydrogen-containing medium is under a certain pressure. This pressure is equal to the pressure of the medium delivered by the hydrogen production unit, achieved, for example, by an expansion system or pressure controller. Therefore, during operation, the pressure in the hydrogen collector unit ranges between a lower limit and an upper limit, depending on the operating state of the system. The pressure level in the hydrogen collector unit is therefore at most equal to the upper limit. All stated pressure values (in bar) are relative or gauge pressures measured relative to atmospheric pressure.

[0026] The upper limit of pressure is at most 50 bar. For example, the upper limit is equal to 50 bar, which means that during the operation of the equipment, according to the current operating state, the pressure delivered by the preparation unit and in the collector unit is between the lower limit and 50 bar, wherein the lower limit is less than or equal to 50 bar. In another embodiment, the upper limit is equal to 10 bar, which means that during the operation of the equipment, according to the current operating state, the above-mentioned pressure is between the lower limit and 10 bar. For example, the lower limit is equal to 0.3 bar, so that the pressure in the collector unit can change between 0.3 bar and 10 bar. In a possible embodiment, the upper limit of pressure is at most 50 bar and is at least 5 bar. For example, this upper limit is equal to 5 bar, 10 bar, 20 bar, 30 bar, 40 bar or 50 bar.

[0027] The hydrogen collector unit consists of one or more piping elements. Each of these piping elements is a casting made of ductile iron. Cast iron is an iron-carbon alloy with a carbon content typically exceeding 2% by weight. The casting is obtained by pouring liquid cast iron into a mold and then solidifying the material. The solidification rate, the presence of certain alloying elements, and any heat treatment applied together determine the final material structure and, therefore, the material's ultimate properties. Ductile iron is a grade of cast iron in which free, unbound carbon is present in the form of globules or spheroids within the solidified cast iron. In English, this is known as "nodular cast iron," "ductile cast iron," "ductile iron," "spheroidal graphite iron," or "spheroidal graphite cast iron." The matrix comprises ferrite and / or pearlite. Ductile iron refers to a class of materials whose internal material properties differ depending on their microstructure. For example, the microstructure of the matrix may be predominantly ferrite or predominantly pearlite.

[0028] The hydrogen collector unit is constructed from one or more castings, each of which is made of a material having a tensile strength of at most 600 MPa or 600 N / mm 2 In one embodiment, the ductile iron is ductile iron according to standard EN-GJS-400, having a tensile strength between 400 MPa and 500 MPa. In another embodiment, the ductile iron is ductile iron according to standard EN-GJS-500, having a tensile strength between 500 MPa and 600 MPa.

[0029] This type of cast iron is a commonly used, common material that offers advantages in terms of cost and availability. In particular, components made of this material can be easily cast into various shapes and sizes, eliminating the need for welding to produce certain components. However, cast iron also has a porous structure, so when in contact with hydrogen, hydrogen easily diffuses into the porous structure of the material, making this material very sensitive to hydrogen embrittlement. Therefore, in the prior art, it is not recommended to use such porous materials in conjunction with hydrogen. Instead, it is recommended to use higher-grade materials (such as stainless steel and alloy steel) or to apply special coatings.

[0030] Surprisingly, however, it has been discovered that, despite the material's porous structure, cast iron can be used in conjunction with hydrogen, provided certain pressure and temperature conditions are met and the appropriate type of cast iron is selected. In fact, for cast iron of the ductile iron type with a tensile strength of up to 600 MPa, it has been found that even under steady-state conditions, long-term exposure to nearly pure hydrogen at temperatures up to 100°C and pressures up to 50 bar results in very low hydrogen absorption. Furthermore, for this type of material under these hydrogen conditions, only minimal effects are observed within the plastic zone, with no reduction in tensile strength and only a slight decrease in elongation.

[0031] Therefore, it is possible to use this material in hydrogen collector units where the above-mentioned conditions apply. For example, in hydrogen internal combustion engines, where nearly pure hydrogen is typically present in the fuel rail, ductile iron can be used to manufacture the fuel rail at temperatures up to 100°C and pressures typically up to 10 bar. In fact, even with common materials such as cast iron, the present invention can meet the stringent inspection requirements currently imposed on such components. Inspection requirements include ensuring resistance to hydrogen embrittlement at the highest pressure levels that can occur in the fuel rail (e.g., 10 bar), not just at the lower pressure levels (e.g., 3.5 bar) encountered during nominal operation. Furthermore, even in actual use, where hydrogen only buffers and flows briefly within the fuel rail, resistance to hydrogen embrittlement should be guaranteed even during stationary conditions, when the fuel rail is exposed to hydrogen gas almost continuously.

[0032] In summary, in the present invention it has surprisingly been found that despite the challenging nature of the application, with the significant risk of hydrogen embrittlement under the activation energy of continuous exposure to nearly pure hydrogen and the overpressure present, common materials can still be used.

[0033] This offers the advantage that the material costs of the hydrogen collector unit are significantly lower than when using higher-grade materials. Furthermore, the use of cast iron contributes to good feasibility. Specifically, it allows the collector to be cast with thin walls, thus enabling a compact design and simple integration into the engine, even when double-walled sections are required. Finally, welds are eliminated in the collector unit, contributing to improved robustness and durability.

[0034] Optionally, according to claim 2, the upper limit of the pressure is at least 5 bar and at most 50 bar. In a possible embodiment of the device, the pressure delivered by the hydrogen production unit and actually in the hydrogen collector unit is, for example, between the lower limit and 5 bar, or between the lower limit and 10 bar, or between the lower limit and 20 bar, or between the lower limit and 30 bar, or between the lower limit and 40 bar, or between the lower limit and 50 bar. This means that the hydrogen-containing medium present in the collector unit is always at a certain overpressure, or in any case there are certain operating states in which this overpressure is applicable. The increased pressure is associated with giving the hydrogen a certain activation energy, which increases the risk of hydrogen diffusing into the wall material. Despite this increased risk associated with the pressure increase, it was surprisingly found that ductile iron can be used for the collector wall.

[0035] Optionally, the upper limit of the pressure is at least 9 bar, so that in a possible embodiment the actual pressure in the collector unit is always greater than or equal to 9 bar.

[0036] Optionally, the upper limit of the pressure is equal to 10 bar, so that for the device in this embodiment, the actual pressure in the hydrogen collector unit is between the lower limit and 10 bar depending on the operating state of the device. For example, the lower limit is 0.3 bar and the pressure level in nominal operation is about 3.5 bar.

[0037] Optionally, according to claim 3, the device is a hydrogen internal combustion engine, wherein

[0038] A hydrogen-containing gaseous medium is used as the gaseous fuel, the gaseous medium comprising at least 85% by volume of hydrogen;

[0039] - one or more piping elements of the hydrogen collector unit together forming a fuel rail, and

[0040] - the hydrogen processing unit comprises one or more injectors and a combustion chamber for each injector,

[0041] and wherein the hydrogen internal combustion engine is adapted to, during operation:

[0042] - temporarily buffering the hydrogen-containing medium in the fuel rail at a temperature of at most 100° C. and a pressure between a lower limit and an upper limit depending on the operating mode of the hydrogen internal combustion engine, and

[0043] - Distributing the hydrogen-containing medium from the fuel rail to the injector for combustion in the combustion chamber.

[0044] A hydrogen internal combustion engine is an internal combustion engine in which hydrogen or a mixture containing hydrogen is used as a fuel. Various types of hydrogen internal combustion engines can be employed in various configurations. For example, a hydrogen internal combustion engine may be a dual-fuel type, in which the engine can run on either diesel or a mixture of hydrogen and diesel, and in which, in hydrogen mode, the diesel is used to ignite the hydrogen. In another embodiment, the present invention relates to an engine that runs solely on hydrogen, in which spark ignition or electric ignition is used to initiate the ignition of the hydrogen.

[0045] In hydrogen internal combustion engines, there is a fuel rail or gas rail which serves as a hydrogen collector unit and forms part of the hydrogen supply system. Typically, hydrogen or a hydrogen-containing gas mixture is provided from a storage tank, in which the gas is stored at high pressure, for example at least 200 bar. Then, in a hydrogen preparation unit, for example a hydrogen preparation unit comprising an expansion system or a pressure controller, the hydrogen-containing fuel is increased to the desired pressure, depending on the operating mode of the engine. Depending on the operating mode, the pressure delivered by the preparation unit varies between a lower limit and an upper limit, wherein the upper limit is at most 50 bar. For example, in nominal operation of the engine, the delivered pressure is 3.5 bar, and the delivered pressure can be a maximum of 10 bar, wherein the value of 10 bar mentioned is achieved when the overpressure valve starts to operate.

[0046] After the preparation unit, the hydrogen-containing fuel is collected in the fuel rail, where it is temporarily buffered. The temperature within the fuel rail reaches a maximum of 100°C, and the pressure is equal to the pressure delivered by the hydrogen preparation equipment. During buffering and flow in the fuel rail, the hydrogen-containing fuel contacts the inner wall of the fuel rail. The fuel rail is composed of one or more piping elements, each of which is a casting made of ductile iron with a tensile strength of up to 600 MPa. The hydrogen-containing fuel is supplied from the fuel rail to the injectors, for example, via one or more supply lines. Thus, the fuel rail serves to accumulate or temporarily store the hydrogen-containing fuel and distribute it to the injectors.

[0047] Each injector has a combustion chamber (e.g., a cylinder) for burning fuel, thereby providing driving force. Typically, hydrogen-containing fuel (which has a high hydrogen content) is mixed with air before the hydrogen-air mixture is drawn through the cylinder's intake valve. The injector and combustion chamber thus form part of a hydrogen processing unit, and the driving force is generated by the combustion of the fuel, as is known from conventional internal combustion engines. The fuel can be ignited in various ways, such as by injecting diesel or by spark ignition.

[0048] Optionally, according to claim 4, the ductile iron complies with the European standard DIN EN 1563, grades EN-GJS-400, EN-GJS-450, or EN-GJS-500. Within each specified grade, several variations are possible, such as EN-GJS-400-15, EN-GJS-400-18-LT, EN-GJS-450-15, EN-GJS-450-10, and so on. Other designations may be used to refer to the same material according to other specifications or standards. For example, according to the older standard DIN 1693, EN-GJS-400 is equivalent to GGG40. Other equivalent grades to EN-GJS-400 include: ISO 1083 400-15, China GB1348 QT400-15, US ASTM A536 60-40-18, Japan FCD400, Italy GS400-12, France FGS400-12, Spain FGE42-12, Belgium FNG42-12, Australia AS1831 400-12, and Norway SJK-400. For cast iron grades below EN-GJS-400, the tensile strength is at least 400 MPa and at most 500 MPa. For cast iron grades below EN-GJS-500, the tensile strength is at least 500 MPa and at most 600 MPa. On the one hand, the cast iron should be spherical, not flake graphite, and on the other hand, the tensile strength should be sufficiently low. Typically, this grade of cast iron is a material that necks under load before breaking.

[0049] Optionally, according to claim 5, the tensile strength of the ductile iron is between 400 MPa and 500 MPa. For example, the cast iron complies with the European standard DIN EN 1563, grade EN-GJS-400.

[0050] In one embodiment, one or more castings are made of ferritic or pearlitic ductile iron. For example, it relates to ferritic cast iron with a predominantly ferritic microstructure, which means that the ductile iron consists of ductile graphite and a matrix, wherein the content of ferrite in the matrix is greater than the content of another structure (such as pearlite). For example, the ferrite content in the cast iron is at least 75%, which means that the cast iron consists of graphite, ferrite and other components, and the volume percentage of ferrite in the entire material is at least 75%. For example, in terms of volume percentage, the graphite content is between 12% and 13%, the ferrite content is between 75% and 85%, and the pearlite content is between 2% and 10%. In another embodiment, during the casting process, pearlitic cast iron is produced with a predominantly pearlitic matrix, and in this way a cast iron with a desired tensile strength of up to 600 MPa or between 400 and 500 MPa is obtained. For example, a cast iron with a pearlite content of at least 55% means that the cast iron consists of graphite, pearlite, and other components, with pearlite accounting for at least 55% by volume of the entire material. For example, the graphite content is between 12% and 13%, the pearlite content is between 55% and 65%, and the ferrite content is between 20% and 35% by volume.

[0051] Optionally, according to claim 6, the hydrogen production unit is adapted to supply the gaseous medium containing hydrogen at a pressure between 3 and 4 bar, for example 3.5 bar, in a nominal operating state of the device. For example, the device is a hydrogen internal combustion engine, wherein at nominal engine load the pressure in the gas rail is between 3 and 4 bar, for example 3.5 bar.

[0052] Optionally, according to claim 7, the lower limit of the pressure is at least 0.1 bar and at most 1 bar, for example 0.3 bar. The lower limit of the pressure is the lowest pressure value occurring in the collector unit, for example the lowest pressure value occurring during low power operation. In a possible embodiment of the device, the lower limit is equal to 0.3 bar, so that in the hydrogen collector unit, during operation of the device, the pressure is always greater than or equal to 0.3 bar.

[0053] Optionally, according to claim 8, each conduit element is made as a double-walled section, wherein the conduit element comprises a second wall section arranged around a first wall section, and wherein the second wall section is at least partially separated from the first wall section by a cavity. The collector unit is thus made as a double-walled section, wherein the first wall section is in contact with the hydrogen-containing medium and the second wall section is separated from the first wall section by an intermediate cavity. Optionally, the two walls are connected together at one or more locations along the circumference or length, so that the two walls are not completely separated from each other, but there is an intermediate cavity over a considerable part. The double-walled section structure of the collector has the advantage that if there is a leak through the first wall section, the second wall section forms an additional barrier so that the hydrogen does not end up in the environment. This helps to improve safety. In some applications, the double-walled section structure is a requirement imposed by the inspection standards.

[0054] Optionally, according to claim 9, the pipeline element is composed of a pipe and a branch, wherein:

[0055] - each pipe element comprises a sleeve, wherein the sleeve has an end adapted to be connected to an adjacent pipe element so that the pipe elements connected together form a continuous tube, and wherein the pipe elements have a transverse opening made in the sleeve,

[0056] Each branching element comprises a sleeve having an end adapted to be connected to a pipe element at the location of the transverse opening, thereby forming a branch on the continuous pipe.

[0057] Therefore, the pipeline element includes two types of components. The first type involves pipe fittings, which usually extend in the longitudinal direction and are open at one or both ends. The common connection of multiple pipe fittings forms a continuous pipe. The second type involves branching pieces, for example configured as elbow-shaped elements. Each pipe fitting has a transverse opening to which a branching piece can be connected. In this way, by assembling pipe fittings and branching pieces, a continuous pipe with one or more branches is formed. Typically, the continuous pipe transports a hydrogen-containing medium supplied by the hydrogen preparation unit and distributes this medium to the hydrogen treatment unit via branches. For example, each branching piece forms a supply to an injector and an associated cylinder.

[0058] Alternatively, according to claim 10, the hydrogen preparation unit includes an expansion system arranged between the high-pressure pipeline and the low-pressure pipeline and including one or more pressure controllers, wherein the expansion system is suitable for reducing the pressure of the medium containing hydrogen transported via the high-pressure pipeline to the pressure between the lower limit and the upper limit in the low-pressure pipeline, wherein the low-pressure pipeline is connected to the hydrogen collector unit. The hydrogen preparation unit therefore includes a high-pressure pipeline, an expansion system and a low-pressure pipeline. In one embodiment, the high-pressure pipeline of the device is directly supplied with a limited supply pressure by the main pipeline of hydrogen. In another embodiment, the device includes a storage tank connected to the high-pressure pipeline, which is used to store a medium containing hydrogen at a pressure higher than 50 bar. Typically, the gaseous medium containing hydrogen is stored in a storage tank at high pressure, such as 200 bar, 350 bar, 500 bar or 700 bar. For example, the medium containing hydrogen is transported from the storage tank by a high-pressure pipeline (such as a high-pressure fuel line). The expansion system includes one or more pressure controllers (such as pressure regulating valves and overpressure valves), using which the pressure controller is reduced to a lower level via the pressure of the medium transported by the high-pressure pipeline. The resulting lower pressure level is according to the actual state of the equipment, and for example, changes between 0.3 bar and 50 bar, or changes between 0.3 bar and 10 bar. The low-pressure pipeline connected to the expansion system allows the medium containing hydrogen to be supplied to the hydrogen collector unit at a lower pressure level. For example, a storage tank, a high-pressure pipeline, an expansion system, a low-pressure pipeline and a hydrogen collector unit form a hydrogen supply system together, which is suitable for supplying a medium containing hydrogen to the hydrogen treatment unit under appropriate conditions.

[0059] Optionally, according to claim 11, one or more pressure controllers include one or more pressure regulating valves, which are suitable for reducing the pressure of the hydrogen-containing medium transported via the high-pressure pipeline to a set value between a lower limit and an upper limit. For example, there are one or more pressure regulating valves or pressure reducing valves, which reduce the pressure to a certain desired value or set the pressure between 0.3 bar and 3.5 bar according to the actual power. Optionally, also according to claim 11, the pressure controller includes one or more overpressure valves, which are suitable for reducing the pressure of the hydrogen-containing medium transported via the high-pressure pipeline to a discharge value equal to the upper limit. This means that there is an overpressure valve, which is set to a certain discharge value; if the overpressure valve starts to work, for example because the pressure regulating valve fails, the overpressure is discharged to the discharge value, and the pressure in the hydrogen collector unit is also at this discharge value. The discharge value set by the overpressure valve is therefore consistent with the above-mentioned upper pressure limit value.

[0060] Optionally, according to claim 12, the device is a hydrogen internal combustion engine with a power of at least 500 kW. The present invention thus relates to high-power engines, such as those used in ships, rail transport, and power plants. In various embodiments, it relates to hydrogen internal combustion engines, such as those with 6, 8, 12, or 16 cylinders and a power of between 1000 kW and 3000 kW.

[0061] According to a second aspect of the present invention, the above object is achieved by the use of a hydrogen collector unit as defined in claim 13, wherein the use comprises:

[0062] - providing a hydrogen collector unit comprising one or more conduit elements which together define an interior space bounded by a wall;

[0063] - providing a hydrogen-containing gaseous medium, the gaseous medium containing at least 85 volume percent hydrogen;

[0064] - flowing the hydrogen-containing medium in the inner space and / or temporarily buffering the hydrogen-containing medium and / or storing the hydrogen-containing medium at a temperature of at most 100° C. and a pressure between a lower limit and an upper limit, wherein the wall is in contact with the hydrogen-containing medium, and wherein the lower limit is less than or equal to the upper limit;

[0065] And among them:

[0066] - the upper limit of the pressure is at most 50 bar, and

[0067] Each of the one or more piping elements is a casting made of ductile iron having a tensile strength of at most 600 MPa.

[0068] Therefore, the present invention relates to the use of a hydrogen collector unit, wherein during use, a gaseous medium containing hydrogen, comprising at least 85% by volume of hydrogen, is present. The medium is buffered or stored in the collector, and / or the medium flows in the collector. In one embodiment, the hydrogen collector unit is a fuel rail or gas rail in an internal combustion engine. In another embodiment, the hydrogen collector unit is a storage tank in which the hydrogen-containing medium is stored. During use of the hydrogen collector unit, the pressure of the gaseous medium containing hydrogen is between a lower limit and an upper limit. In one embodiment, the pressure in the collector varies depending on the specific operating conditions. In another embodiment, the lower limit is equal to the upper limit, and the pressure is the same while the medium is in the collector. The upper limit of the pressure in the hydrogen collector unit is at most 50 bar. In one embodiment, the upper limit of the pressure is at least 5 bar and at most 50 bar, for example, an upper limit of 10 bar. The hydrogen collector unit is composed of one or more conduit elements that together define an interior space bounded by walls. The pipe element may thus have two open ends, or one open end and one closed end, or the pipe element may be closed at both ends.

[0069] Optionally, according to claim 14, the use comprises:

[0070] - providing a hydrogen production unit in communication with the hydrogen collector unit;

[0071] - providing a hydrogen processing unit in communication with the hydrogen production unit;

[0072] - supplying the hydrogen-containing medium by the hydrogen production unit at a pressure according to the operating state of the device, the pressure varying between the lower limit and the upper limit;

[0073] - supplying the hydrogen-containing medium from the hydrogen preparation unit to the hydrogen collector unit, wherein the hydrogen-containing medium flows and / or is temporarily buffered in the inner space;

[0074] - supplying the hydrogen-containing medium from the hydrogen collector unit to the hydrogen treatment unit;

[0075] - treating and / or using the hydrogen-containing medium in the hydrogen treatment unit.

[0076] Hence, the hydrogen collector unit is for use in an apparatus for hydrogen applications, wherein the apparatus is defined in accordance with the first aspect of the invention.

[0077] Optionally, according to claim 15, the hydrogen collector unit is a fuel rail for a hydrogen internal combustion engine, wherein

[0078] - the hydrogen-containing medium is used as fuel, the medium containing at least 85% by volume of hydrogen;

[0079] - the hydrogen processing unit comprises one or more injectors and a combustion chamber for each injector,

[0080] and wherein the use includes:

[0081] - temporarily buffering the hydrogen-containing medium in the fuel rail at a temperature of at most 100° C. and at a pressure varying between the lower limit and the upper limit depending on the operating mode of the hydrogen-burning engine;

[0082] - distributing the hydrogen-containing medium from the fuel rail to the injector;

[0083] - Combusting the hydrogen-containing medium in the combustion chamber.

[0084] The hydrogen collector unit is therefore a fuel rail or gas rail used in a hydrogen internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 is a schematic diagram of an apparatus suitable for hydrogen application according to an embodiment of the present invention.

[0086] Figure 2 、 Figure 3 、 Figure 4 and Figure 5A hydrogen internal combustion engine according to an embodiment of the present invention is shown. Figure 2 and Figure 3 They are three-dimensional views, where Figure 3 In this image, the exhaust assembly has been removed to allow visibility of the internal components. Figure 4 and Figure 5 They are the front view and the back view respectively.

[0087] Figure 6 and Figure 7 A three-dimensional view and a cross-sectional view of a pipe according to an embodiment of the present invention are respectively shown.

[0088] Figure 8 and Figure 9 A three-dimensional view and a cross-sectional view of a branch member according to an embodiment of the present invention are respectively shown.

[0089] Figure 10 A three-dimensional view of a branch member connected to a pipe member according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0090] Figure 1 The apparatus 100 suitable for hydrogen application according to an embodiment of the present invention is schematically shown. For example, the apparatus 100 is a hydrogen internal combustion engine 200. Figure 2-Figure 5 1. The device 100 includes a hydrogen preparation unit 102, a hydrogen collection unit 101 and a hydrogen treatment unit 103. The hydrogen preparation unit 102 includes a high-pressure pipeline 109, an expansion system 106 and a low-pressure pipeline 110. The high-pressure pipeline 109 is connected to the storage tank 104. The low-pressure pipeline 110 is connected to the hydrogen collector unit 101. The storage tank 104 stores a gaseous hydrogen-containing medium containing at least 85% volume percentage hydrogen. Storage in the storage tank is usually carried out under high pressure (e.g., 200 bar, 350 bar, 500 bar or 700 bar). The expansion system 106 includes a pressure controller so that the pressure of the hydrogen-containing medium is reduced to a lower value in the low-pressure pipeline 110. The pressure reached in the low-pressure pipeline 110 is determined according to the operating state of the device 100 and is always between a lower limit and an upper limit. The upper limit is 50 bar or lower, for example, 10 bar. The hydrogen-containing medium is supplied to the hydrogen collector unit 101 via the low-pressure line 110 at the obtained lower pressure.

[0091] In the collector unit 101, the medium is temporarily buffered and distributed to the hydrogen processing unit 103. The storage tank 104, high-pressure line 109, expansion system 106, low-pressure line 110, and hydrogen collector unit 101 together form a hydrogen supply system 105, which is suitable for supplying the hydrogen-containing medium to the hydrogen processing unit 103 under appropriate conditions. The hydrogen-containing medium is processed or used in the hydrogen processing unit 103. In the embodiment shown, the hydrogen-containing medium is used in the cylinders 111 of an internal combustion engine. The hydrogen-containing medium is supplied to the engine cylinders 111 via intake valves (gas injectors) 108. Before entering the cylinders 111, the hydrogen-containing medium is mixed with air 107.

[0092] Figure 2-Figure 5 A hydrogen internal combustion engine 200 is shown. The embodiment shown relates to an engine with 12 V-shaped cylinders, with a power of up to 2000 kW, typically used for propulsion of large ships or trains.

[0093] The hydrogen internal combustion engine 200 includes a fuel rail 201 or a gas rail 201 corresponding to Figure 1 The hydrogen collector unit 101 is provided with a gaseous hydrogen-containing fuel from a low-pressure fuel line 202. The gaseous fuel comprises at least 85% hydrogen by volume, and in a possible embodiment may comprise 90% or 95% hydrogen, so that the gaseous fuel is almost pure hydrogen. The low-pressure fuel line 202 forms Figure 2-Figure 5 For this purpose, a part of the hydrogen production unit not shown in FIG. Figure 1 , the hydrogen preparation unit 102 includes a high-pressure fuel pipeline 109 and a pressure controller 106. Figure 1 , fuel is stored at high pressure in Figure 2-Figure 5 In the storage tank 104 not shown.

[0094] Depending on the operating state of hydrogen engine 200, the hydrogen-containing fuel is brought to a lower pressure level by means of pressure controller 106. In the illustrated embodiment, pressure controller 106 includes at least one pressure regulating or reducing valve. Based on this pressure regulating or reducing valve, a desired or setpoint pressure is achieved, depending on the actual engine power. This desired pressure level is approximately 3.5 bar in nominal operation and approximately 0.3 bar in low power. The preparation unit also includes at least one overpressure valve, which activates when the pressure no longer decreases as expected, for example due to a fault in the pressure regulating valve. The overpressure valve is set to a discharge value of 10 bar, so that the maximum possible pressure after pressure controller 106 is 10 bar. Therefore, the pressure of the gaseous fuel supplied via low-pressure fuel line 202 is always between 0.3 bar and 10 bar. This is also the actual pressure in fuel rail 201. The temperature in fuel rail 201 typically does not exceed ambient temperature by much and is at most 100°C.

[0095] exist Figure 3 For clarity, the exhaust assembly 205 has been omitted. Figure 3 As shown, fuel rail 201 is composed of a plurality of piping elements 300, 301. There are two different types of piping elements: pipes 300 and branching elements 301. Pipes 300 are connected together to form a continuous tube. One end of the continuous tube is connected to low-pressure fuel line 202, and the other end is closed by an end plate 303. Furthermore, a branching element 301 for supplying hydrogen to one of the cylinders is secured to each pipe 300.

[0096] Tubing elements 300 and 301 together define an interior space within which gaseous fuel can flow and be temporarily buffered. This interior space is bounded by walls whose inner surfaces come into contact with the hydrogen-containing fuel. Consequently, the inner walls of fuel rail 201 are in constant contact with nearly pure hydrogen, creating a significant risk of hydrogen diffusion into the wall material unless the wall is constructed of a hydrogen-compatible material. The pressure present in fuel rail 201 further increases this risk, with inspections requiring guaranteed resistance to hydrogen embrittlement at the highest possible pressure level—in this case, 10 bar.

[0097] Hydrogen is supplied from the gas rail 201 to 12 injectors, one for each cylinder. Figure 2 and Figure 3 Before entering the cylinder 203, the hydrogen is mixed with air supplied through line 204. Figure 4, in which the hydrogen flow is schematically indicated as 400 and the air flow as 401. The hydrogen-air mixture 402 is drawn into the cylinder and then compressed and ignited. In various embodiments, ignition can occur in different ways. In the case of a dual-fuel engine, ignition is performed by injecting a pilot fuel (e.g. 15% diesel). In the case of a spark-ignition engine, spark ignition is used. The situation in the fuel rail is similar for both embodiments, as almost pure hydrogen is buffered in the fuel rail at a pressure of up to 10 bar. After ignition, the hydrogen in the cylinder burns, producing the working stroke. The exhaust gases then pass as Figure 3 Line 302 is shown exiting the cylinder.

[0098] Figure 6 and Figure 7 A pipe 300 is shown. The pipe 300 is constructed as a double-walled structure, wherein a first wall 701 defines an interior space 600. The inner surface of the first wall 701 contacts the hydrogen-containing fuel. A second wall 702 surrounds the first wall 701, with a cavity 703 between the two walls 701, 702. The pipe 300 also includes a sleeve 603 having open ends 601 and 602. The ends 601 and 602 are adapted to be connected to another pipe 300. An end plate 303 may also be placed on the ends 601, 602. The sleeve 603 is provided with a transverse opening 604 and a transverse opening 700.

[0099] Figure 8 and Figure 9 The figure shows a branching member 301 configured as an elbow. The branching member 301 is constructed as a double-walled structure, wherein a first wall 801 defines an interior space 800. The inner surface of the first wall 801 contacts the hydrogen-containing fuel. A second wall 802 surrounds the first wall 801, with a cavity 803 defined between the two walls 801 and 802. The two walls 811 and 812 are connected at two locations 805 and 806. The branching member 301 also includes a sleeve 813 having open ends 811 and 812. The end 811 is adapted to connect to the pipe 300.

[0100] like Figure 3 As shown, a plurality of pipe members 300 are connected together to form a continuous pipe in which hydrogen gas is supplied. Figure 10 The diagram shows how branching piece 301 is connected to pipe 300 at the location of transverse opening 604. In this way, hydrogen can be supplied from the pipe to the cylinders in the first row of six cylinders. Similarly, branching piece 301 can be connected to another transverse opening 700 for supplying the cylinders in the second row of six cylinders.

[0101] Safety requirements necessitate a double-walled structure for pipes 300 and 301. On the other hand, a compact design for fuel rail 201 is also essential to facilitate its integration into engine 200. In particular, the distance between the two cylinder heads, determined by the engine's V-angle, imposes a constraint: the intake and exhaust collectors must also be placed in the space between the two cylinder heads, between the two cylinder banks. To achieve a compact design for fuel rail 201 despite its double-walled structure, sufficiently thin walls are required for pipe elements 300 and 301. In the illustrated embodiment, this is achieved through thin-wall casting: pipe 300 and branching element 301 are each formed as a casting and made of cast iron. Furthermore, given the risk of hydrogen diffusion into the wall of fuel rail 201, a material that provides sufficient resistance to hydrogen embrittlement under realistic pressure and temperature conditions should be selected. Therefore, in the present invention, ductile iron with a tensile strength of up to 600 MPa is selected.

[0102] In particular, in the embodiment shown, each pipe element 300, 301 is made of ductile iron conforming to grade EN-GJS-400-15. Typical properties of this material are:

[0103] Yield point: minimum 250 MPa; Tensile strength: minimum 400 MPa; Elongation: minimum 15%. A typical stress-strain curve measured in air shows necking before fracture.

[0104] Density: 7.3g / cm 3 , Brinell hardness: 130-180.

[0105] Typical chemical composition: Carbon: 2.5-3.8%; Silicon: 0.5-2.5%; Manganese: 0.2-0.5%; Phosphorus: ≤0.08%; Sulfur: ≤0.02%.

[0106] To arrive at the surprising discovery that the cast iron material is sufficiently resistant to hydrogen embrittlement and thus suitable for use in fuel rails of hydrogen internal combustion engines, the inventors conducted experimental studies involving a first series of tests and a second series of tests.

[0107] In the first test series, the compatibility of various materials with hydrogen was investigated. Specifically, the following material grades were studied: EN-GJS-400-15, EN-GJS-700, Mk11C, and RVS316. The last-mentioned material grade is related to a stainless steel grade with an austenitic microstructure and was included in the study as a reference material compatible with hydrogen environments. The first three material grades were related to cast iron, and the microstructure of the specimens, which measured 5 × 8 × 50 mm, was analyzed. The following microstructure was found in the cast iron studied:

[0108] EN-GJS-400-15: Spheroidal graphite (13%), ferrite (77%), pearlite (10%). This refers to a ductile iron with a predominantly ferrite phase. Most of the graphite particles were between 60 and 120 microns in size; some smaller particles, ranging from 15 to 30 microns, were also found. In terms of density, a total particle density of 126 graphite particles / mm was found. 2 , including 73 particles / mm 2 Spherical particles. Titanium-rich inclusions were found in the material.

[0109] EN-GJS-700: Spheroidal graphite (13%), ferrite (1%), pearlite (86%). This refers to a ductile iron with a tensile strength of at least 700 MPa, primarily composed of pearlite. Most of the graphite particles are between 15 and 30 microns in size; only a few smaller particles were found. In terms of density, a total particle density of 171 graphite particles / mm was found. 2 , including 150 particles / mm 2 The inclusions are mainly magnesium oxides.

[0110] Mk11C: Flake graphite (12%), pearlite (88%). Therefore, this refers to a flake graphite cast iron. 34% of the graphite particles were between 30 and 60 microns in size, and 33% were between 60 and 120 microns in size. Some smaller graphite particles were also found. In terms of density, a total particle density of 1026 graphite particles / mm was found. 2 The presence of MnS (manganese sulfide) and molybdenum-rich particles was detected.

[0111] For each material grade, several specimens were exposed to hydrogen at room temperature and a pressure of 10 bar for 1000 hours. This pressure level of 10 bar was chosen because it represents the design pressure in the proposed hydrogen internal combustion engine and the maximum pressure that could occur in the gas rail. During the hydrogen exposure, the specimens were unloaded. For each material grade, several specimens were also tested without exposure to hydrogen.

[0112] After exposure to hydrogen, a first round of evaluation tests determined which samples showed hydrogen absorption. To do this, measurements were performed on two samples of 5 × 8 × 50 mm for each grade of material: one sample was exposed to hydrogen, the other not. The hydrogen concentration was determined using the G8 GALILEO (Brüker) melt extraction method.

[0113] The measurement results are summarized in the following table (Table 1). It can be seen that the EN-GJS-700 (pearlitic ductile iron, minimum tensile strength 700 MPa) and Mk11C (flake graphite cast iron) materials show a certain amount of hydrogen absorption; both materials absorb about 0.3 ppm of hydrogen. This sensitivity to hydrogen absorption is consistent with the teachings of the prior art, that is, cast iron is generally sensitive to hydrogen absorption. For RVS316 (stainless steel), it was determined that no significant hydrogen absorption occurred; the difference measured between the exposed and unexposed samples was within the standard deviation of the measurement. This result is also in line with expectations, as stainless steel is generally considered to have good resistance to hydrogen absorption. However, surprisingly, the EN-GJS-400-15 (ferritic ductile iron, minimum tensile strength 400 MPa) material also showed almost no hydrogen absorption, despite being a cast iron material with a porous structure.

[0114]

[0115] Table 1

[0116] In a further evaluation of the first test series, tensile tests were performed on specimens exposed to hydrogen and the results were compared with identical tensile tests performed on specimens that had not been exposed to hydrogen. In this case, circular tensile specimens were used and tested according to standard NBN ISO 6892-1 Method B.

[0117] In this case, RVS316 (stainless steel) specimens exposed to hydrogen exhibited similar behavior to specimens not exposed to hydrogen. RVS316 therefore appears to be insensitive to hydrogen embrittlement, as expected.

[0118] Specimens of EN-GJS-700 (pearlitic ductile iron with a minimum tensile strength of 700 MPa) and Mk11C (flaky graphite cast iron) exposed to hydrogen exhibited significant degradation in mechanical properties compared to unexposed specimens of the same materials. The hydrogen-exposed specimens experienced premature fracture accompanied by brittle fracture. For example, the Rm value and elongation at break of Mk11C after hydrogen exposure were 271 MPa and 0.16%, respectively, compared to 291 MPa and 0.29%, respectively, for the unexposed specimen. For example, the Rm value and elongation at break of EN-GJS-700 specimens exposed to hydrogen were 617 MPa and 1.5%, respectively, compared to 696 MPa and 3.1%, respectively, for the unexposed specimen. Therefore, both cast irons are clearly susceptible to hydrogen embrittlement, consistent with the general teachings of the prior art regarding the combination of cast iron and hydrogen.

[0119] Finally, for samples of EN-GJS-400-15 (ferritic ductile iron with a minimum tensile strength of 400 MPa) exposed to hydrogen, no degradation of mechanical properties was observed compared to samples of the same material not exposed to hydrogen: hydrogen exposure did not lead to premature fracture, and at maximum load, the samples exhibited ductile fracture. Contrary to expectations based on prior art teachings, this cast iron appears to be less susceptible to hydrogen embrittlement under these test conditions.

[0120] In the second test series, the hydrogen compatibility of material EN-GJS-400-15 was further verified. For this purpose, the ISO 11114-4 Method A fracture test, more specifically the "disc burst test," was employed. This test allows the calculation of the "Embrittiness Index (EI)." An EI value of 2 or less indicates that the material is suitable for use in cylinders containing compressed hydrogen. The tests were conducted using helium and hydrogen as test gases, with an applied pressure increment of 10 bar / minute. The specimens were discs with a diameter of 58 mm and a thickness of 2 mm. Under helium, the burst pressure was 605 bar (pR_He), and under hydrogen, the burst pressure was 485 bar (pR_H2). After applying the thickness correction factor described in EN ISO 11114-4, the corrected p'R_He and p'R_H2 values were calculated, resulting in the EI value (EI = p'R_He / p'R_H2). The measured EI value for the EN-GJS-400-15 material sample was 1.2, so the material can be considered hydrogen-compatible. The disc burst test was also repeated on EN-GJS-400-15 material samples at a pressure rise rate of 1.5 bar / minute, yielding similar results, with EI values between 1.2 and 1.3.

[0121] In the aforementioned tests, EN-GJS-400-15, a predominantly ferrite material, was used; for example, various specimens had 77% or 82% ferrite. Through appropriate casting techniques, ductile iron with a predominantly pearlite structure can also be produced while maintaining the same tensile strength level (400 to 500 MPa). Similar tests were conducted on EN-GJS-400, a predominantly pearlite structure (i.e., 12% graphite, 61% pearlite, and 27% ferrite). These tests also revealed that this material is hydrogen-compatible.

[0122] Finally, a third test series was carried out in which the influence of pressure on the development of hydrogen embrittlement was further investigated. In this case, tensile tests were used, more specifically "slow strain rate tests" (SSRT), which were carried out in air and in a hydrogen atmosphere at 10 bar and 50 bar. The SSRT tests were carried out at a constant deformation rate ds / dt = 0.018 mm / min, which corresponds to an elongation of 0.036% / min. Several specimens were tested, all made of cast iron grade EN-GJS-400-15. For these specimens, the graphite content was between 12% and 13%, the ferrite content was between 83% and 85%, and the pearlite content was between 2% and 5%.

[0123] During the SSRT test, stress-elongation curves were measured and mechanical properties were determined upon completion. The results are summarized in the table below (Table 2).

[0124]

[0125]

[0126] Table 2

[0127] In test (1), carried out in air, the highest elongation at break (Epsilon_break) and necking were measured, demonstrating the high plasticity of the material. Test (2), also carried out in air, showed a lower elongation at break compared to test (1), confirming that for cast materials, there may be a certain degree of dispersion in the material properties. Tests (3), (4) and (5) were carried out in hydrogen at a pressure of 10 bar. In each case, the measured tensile strength (Rm, ultimate tensile strength) was greater than 420 MPa and the elongation at break was greater than 10%. Therefore, the material does not seem to exhibit brittleness in a hydrogen environment at 10 bar. Test (6) was carried out in hydrogen at a pressure of 50 bar. The measured values of elongation at break and necking at break were both lower than the values tested at 10 bar. This indicates that hydrogen embrittlement increases with increasing hydrogen pressure, but does not reach the level where completely brittle behavior is observed in test (6). Therefore, the pressure value of 50 bar can be regarded as the upper limit of the permissible pressure for EN-GJS-400-15 material when used in combination with hydrogen. This is also confirmed by the shape of the measured tension-elongation curve of test (6): in the plastic stage, the curve does not show complete continuity, but discontinuities at three time points, which are manifested as a sudden drop in tension at almost the same elongation, followed by fracture.

[0128] Finally, the fracture surfaces of each specimen were studied by fractographic analysis. For the test under 50 bar, a larger brittle fracture area was found on the fracture surface than for the test under 10 bar, while no brittle fracture area was observed on the fracture surface in the test in air.

[0129] Based on a series of tests conducted, the inventors realized that flake graphite cast iron is not suitable for use with hydrogen, just as ductile iron with high tensile strength (i.e., greater than 600 MPa) is not suitable for use with hydrogen. Typically, these unsuitable cast iron materials do not neck before fracture in an air environment (i.e., when not exposed to hydrogen). In contrast, ductile iron with sufficiently low tensile strength (i.e., up to 600 MPa) appears to be suitable for use with hydrogen under the conditions present in a hydrogen collector. Both ferrite-based and pearlite-based ductile irons are considered, as long as their tensile strength does not exceed 600 MPa. These ductile irons appear to be suitable for use with hydrogen, despite their porous structures, which is generally not recommended in the prior art. The suitability of these ductile irons with sufficiently low tensile strength may be explained by the fact that hydrogen accumulated in the cavities around the carbides significantly reduces the material's ductility and promotes the development of a more brittle fracture mode. However, in ductile iron with sufficiently low tensile strength, the matrix around the carbides can compensate for the reduction in ductility caused by hydrogen without significantly reducing the tensile strength, thereby effectively avoiding the occurrence of brittle fracture.

[0130] While the present invention has been described based on specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the details of the foregoing illustrative embodiments and that various modifications and adaptations may be made while remaining within the scope of the present invention. The present embodiments should therefore be considered in all respects as illustrative and not restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description. All modifications that come within the meaning and scope of the claims are intended to be included within the present invention. In other words, this includes all modifications, variations, or equivalents that fall within the scope of the basic principles and whose essential attributes are claimed in this patent application. Furthermore, readers of this patent application will understand that the terms "comprise" or "include" do not exclude other elements or steps, and that the term "a" or "includes" does not exclude plural references. Any reference in a claim should not be construed as limiting that claim. When used in the specification or claims, the terms "first," "second," "third," "a," "b," "c," etc., are used to distinguish similar elements or steps and do not necessarily describe a sequential or chronological order. Similarly, the terms "upper," "lower," "above," "below," etc., are used for descriptive purposes and do not necessarily refer to relative positions. It is to be understood that these terms are interchangeable under appropriate circumstances and that embodiments of the invention are capable of functioning in orders or orientations other than those described or illustrated.

Claims

1. A device (100, 200) suitable for hydrogen application, the device (100, 200) comprising: a hydrogen production unit (102) adapted to supply a hydrogen-containing gaseous medium, said gaseous medium containing at least 85% by volume of hydrogen, at a pressure according to the operating state of the apparatus (100, 200), said pressure being between a lower limit and an upper limit, wherein said lower limit is less than or equal to said upper limit; - a hydrogen collector unit (101, 201) in communication with the hydrogen production unit (102), comprising one or more conduit elements (300, 301), said one or more conduit elements (300, 301) jointly defining an interior space delimited by a wall; - a hydrogen treatment unit (103) in communication with the hydrogen collector unit (101, 201), which is suitable for treating and / or using a medium containing hydrogen, The device (100, 200) is adapted to: - supplying the hydrogen-containing medium from the hydrogen production unit (102) to the hydrogen collector unit (101, 201) for achieving a flow and / or temporary buffering of the hydrogen-containing medium in the inner space, wherein the wall is in contact with the hydrogen-containing medium, and wherein the pressure in the inner space is at most equal to the upper limit and the temperature in the inner space is at most 100° C.; - supplying the hydrogen-containing medium from the hydrogen collector unit (101, 201) to the hydrogen treatment unit (103), Its characteristics are: The upper limit of the pressure is at most 50 bar, and Each of the one or more pipe elements (300, 301) is a casting made of ductile iron having a tensile strength of at most 600 MPa.

2. The device (100, 200) according to claim 1, The upper limit of the pressure is at least 5 bar and at most 50 bar, for example equal to 10 bar.

3. The device (200) according to one of the preceding claims, The device is a hydrogen internal combustion engine (200), wherein: - the hydrogen-containing gaseous medium is used as gaseous fuel, the gaseous medium containing at least 85% by volume of hydrogen; - the one or more pipe elements (300, 301) of the hydrogen collector unit (101) together form a fuel rail (201), and - the hydrogen processing unit (103) comprises one or more injectors and a combustion chamber (203) for each injector, and wherein the hydrogen internal combustion engine (200) is adapted to, during operation: - temporarily buffering the hydrogen-containing medium in the fuel rail (201) at a temperature of at most 100° C. and at a pressure between the lower limit and the upper limit depending on the operating mode of the hydrogen internal combustion engine (200), and - distributing the hydrogen-containing medium from the fuel rail (201) to the injectors for combustion in the combustion chamber (203).

4. The device (100, 200) according to one of the preceding claims, The ductile iron complies with the EN-GJS-400, EN-GJS-450 or EN-GJS-500 grade according to the European standard DIN EN 1563, preferably complies with the EN-GJS-400 grade according to the European standard DIN EN 1563.

5. The device (100, 200) according to one of the preceding claims, The tensile strength of the ductile iron is between 400 MPa and 500 MPa.

6. The device (100, 200) according to one of the preceding claims, The hydrogen production unit (102) is adapted to supply the hydrogen-containing gaseous medium at a pressure between 3 and 4 bar, for example 3.5 bar, under a nominal operating state of the apparatus (100, 200).

7. The device (100, 200) according to one of the preceding claims, The lower limit of the pressure is at least 0.1 bar and at most 1 bar, for example 0.3 bar.

8. The device (100, 200) according to one of the preceding claims, Each of the pipe elements (300, 301) is made into a double-walled portion, wherein the pipe element (300, 301) comprises a second wall portion (702, 802) arranged around the wall portion (701, 801), wherein the second wall portion (702, 802) is at least partially separated from the wall portion (701, 801) by a cavity (703, 803).

9. The device (100, 200) according to one of the preceding claims, The pipeline element (300, 301) is composed of a pipe (300) and a branch (301), wherein: - each of said pipe elements (300) comprises a sleeve (603), wherein said sleeve (603) has ends (601, 602) suitable for being connected to adjacent pipe elements (300) so that the pipe elements (300) connected together form a continuous tube, and wherein said pipe elements (300) have transverse openings (604) made in said sleeve (603), Each of said branching elements (301) comprises a sleeve (813) having an end (811) suitable for being connected to the pipe element (300) at the location of said transverse opening (604), thereby forming a branch on said continuous pipe.

10. The device (100, 200) according to one of the preceding claims, The hydrogen preparation unit (102) comprises an expansion system (106) arranged between a high-pressure pipeline (109) and a low-pressure pipeline (110) and comprising one or more pressure controllers, wherein the expansion system (106) is suitable for reducing the pressure of the hydrogen-containing medium transported via the high-pressure pipeline (109) to a pressure between the lower limit and the upper limit in the low-pressure pipeline (110), wherein the low-pressure pipeline (110) is connected to the hydrogen collector unit (101).

11. The device (100, 200) according to claim 10, wherein the one or more pressure controllers include: one or more pressure regulating valves adapted to reduce the pressure to a set value between the lower limit and the upper limit, and / or one or more overpressure valves adapted to reduce the pressure to a discharge value equal to the upper limit.

12. The device (200) according to claim 3, The power of the hydrogen internal combustion engine (200) is at least 500 kilowatts.

13. A use of a hydrogen collector unit (101, 201), the use comprising: - providing a hydrogen collector unit (101, 201) comprising one or more conduit elements (300, 301) which together define an interior space bounded by a wall; - providing a hydrogen-containing gaseous medium, said gaseous medium containing at least 85 volume percent hydrogen; - flowing a hydrogen-containing medium in the inner space and / or temporarily buffering the hydrogen-containing medium and / or storing the hydrogen-containing medium at a temperature of at most 100° C. and a pressure between a lower limit and an upper limit, wherein the wall is in contact with the hydrogen-containing medium, and wherein the lower limit is less than or equal to the upper limit; Its characteristics are: The upper limit of the pressure is at most 50 bar, and Each of the one or more pipe elements (300, 301) is a casting made of ductile iron having a tensile strength of at most 600 MPa.

14. The use according to claim 13, The uses described include: - providing a hydrogen production unit (102) in communication with the hydrogen collector unit (101, 201); - providing a hydrogen processing unit (103) in communication with the hydrogen production unit (102); - supplying the hydrogen-containing medium from the hydrogen production unit (102) at a pressure according to the operating state of the device (100, 200), the pressure varying between the lower limit and the upper limit; - supplying the hydrogen-containing medium from the hydrogen production unit (102) to the hydrogen collector unit (101, 201), wherein the hydrogen-containing medium flows and / or is temporarily buffered in the inner space; - supplying the hydrogen-containing medium from the hydrogen collector unit (101, 201) to the hydrogen treatment unit (103); - treating and / or using the hydrogen-containing medium in the hydrogen treatment unit (103).

15. The use according to claim 14, wherein the hydrogen collector unit (101) is a fuel rail (201) for a hydrogen internal combustion engine (200), And among them - the hydrogen-containing medium is used as fuel, the medium containing at least 85% by volume of hydrogen; - the hydrogen processing unit (103) comprises one or more injectors and a combustion chamber (203) for each injector, The uses include: - temporarily buffering the hydrogen-containing medium in the fuel rail (201) at a temperature of at most 100° C. and at a pressure varying between the lower limit and the upper limit depending on the operating mode of the hydrogen internal combustion engine (200); - distributing the hydrogen-containing medium from the fuel rail (201) to the injectors; - Combusting the hydrogen-containing medium in the combustion chamber (203).

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