internal combustion engine

Abstract

Internal combustion engine, with at least one adjustable piston in an engine block (2), with an intake manifold (4) and an exhaust manifold (5), wherein hydrogen can be supplied to the internal combustion engine (1) as fuel, characterized in that the fuel is a metal hydride (MgH2) which has a carrier medium with hydrogen, wherein the fuel is stored in a fuel tank (6) and can be dissolved from the carrier medium in a hydrogen reactor (7) by supplying water, and that a water separator (13) is arranged in the exhaust manifold (5) and the separated water can be supplied to the hydrogen reactor (7).

Description

The invention relates to an internal combustion engine to which hydrogen can be supplied as fuel. Hydrogen combustion engines are well-known; these engines use hydrogen as fuel instead of gasoline or diesel, with the hydrogen being burned in the combustion chambers. The hydrogen is typically stored in gaseous form under high pressure in pressurized tanks. For combustion, the hydrogen pressure is first reduced, and then the gaseous hydrogen is fed into the combustion chamber, either via the intake manifold or directly into the cylinder. The hydrogen must be stored under high pressure, for example 700 bar, in the pressure tank, which is quite heavy for stability and safety reasons. Furthermore, due to the chemical properties of hydrogen, there are safety concerns regarding its transport in vehicles that access underground parking garages, car ferries, or car trains. The invention is based on the objective of providing a hydrogen combustion engine with simple measures that meets high safety requirements and is characterized by a wide range of applications while simultaneously reducing costs. This problem is solved according to the invention by the features of claim 1. The dependent claims specify advantageous further developments. The internal combustion engine according to the invention is designed to use hydrogen as fuel. The engine comprises at least one adjustable piston in an engine block, an intake manifold for supplying combustion air, and an exhaust manifold for removing combustion products generated during hydrogen combustion. The engine is preferably designed as a reciprocating internal combustion engine and includes one or more cylinders with combustion chambers directly above them, each with a reciprocating piston that moves up and down within the cylinder. Alternatively, the engine can also be designed as a rotary engine (Wankel engine) and has a rotary piston in the engine block. The internal combustion engine can be used in a wide variety of applications. According to one advantageous embodiment, the internal combustion engine is used in ground-based vehicles, such as passenger cars and trucks, but also in single-track vehicles like motorcycles. Furthermore, it can also be used in off-road vehicles, particularly aircraft. Finally, the internal combustion engine can also be operated in stationary installations. In the following, the term "internal combustion engine" includes both the engine block with one or more pistons and the peripheral components and equipment required for operation, such as intake manifold, exhaust system, fuel tank, hydrogen reactor, water separator, etc. In the internal combustion engine, hydrogen is combusted, causing the piston to move in a manner known per se, which serves as a working motion, in particular to drive a crankshaft. In the internal combustion engine according to the invention, a metal hydride is used as fuel in the initial state, which comprises a carrier medium containing hydrogen. The fuel is stored in a fuel tank of the internal combustion engine, and the hydrogen can be dissolved from the carrier medium in a downstream hydrogen reactor by adding water, resulting in the hydrogen being present in a pure and gaseous state. A water separator is arranged in the exhaust stream of the internal combustion engine, and the water separated in the exhaust stream can be fed from the water separator to the hydrogen reactor. This internal combustion engine offers several advantages. Firstly, the fuel is in the form of a metal hydride, readily available at ambient temperatures, thus eliminating the need for pressurized hydrogen storage tanks. The fuel tanks themselves are not subject to stringent requirements, allowing for the use of conventional fuel tanks, similar to those found in gasoline or diesel engines. However, unlike hydrogen pressure vessels, these tanks are significantly lighter and require considerably less pressure resistance. Vehicles equipped with this type of engine can also operate in environments with heightened safety requirements, such as parking garages, car ferries, or car trains. The metal hydride comprises the carrier medium in which the hydrogen is chemically bound. In the hydrogen reactor, which is located downstream of the fuel tank, the hydrogen is dissolved from the carrier medium with the addition of water and is then present in a pure form, ready to be fed into the combustion chamber of the internal combustion engine. On the exhaust side, the combustion of hydrogen produces essentially only water vapor, which is routed through the exhaust system past a water separator where it is collected. This collected water is then fed from the exhaust system to the hydrogen reactor, where it is used to extract the hydrogen from the carrier medium. This creates a closed water cycle: first, the supplied water reacts with the metal hydride in the hydrogen reactor to form hydrogen and a metal hydroxide; then, the hydrogen is combusted in the engine; and finally, the resulting water vapor is collected in the exhaust system and returned to the hydrogen reactor via a recirculation line. The recirculated water can be introduced into the hydrogen reactor, particularly under ambient conditions, where the reaction with the metal hydride to extract the hydrogen also takes place under ambient conditions.During the reaction in the hydrogen reactor, a metal hydroxide is deposited from the metal hydride, which can be extracted from the hydrogen reactor and fed into a collection device. Overall, the hydrogen combustion engine according to the invention results in an engine that can be operated with environmentally friendly hydrogen without increased safety measures for carrying the hydrogen. In this way, high-performance combustion engines can be realized that are also suitable for use in heavy-duty transport, among other applications. A further advantage arises from the fact that no complex cleaning measures are required on the exhaust gas side. Any nitrogen oxides that may be produced can be filtered out or converted using existing exhaust gas cleaning systems. Furthermore, virtually no gaseous, solid, or liquid exhaust gas components are generated that require separation or conversion for environmental reasons. According to an advantageous embodiment, the fuel carrier is an alkaline earth metal from group 2 of the periodic table. Advantageously, the fuel carrier is magnesium. However, other alkaline earth metals from group 2 of the periodic table, such as beryllium, calcium, strontium, or barium, are also suitable. The metal hydride used as fuel is present in solid form, especially under ambient conditions, for example in the form of a fuel paste, which has the advantage that the pasty fuel can be conveyed from the fuel tank into the hydrogen reactor under mechanical pressure, for example via a hydraulic cylinder. According to a further advantageous embodiment, a receiving vessel is arranged downstream of the hydrogen reactor, which serves to collect the hydrogen extracted in the hydrogen reactor. This receiving vessel is, in particular, designed as a pressure vessel to hold the gaseous hydrogen at a pressure higher than ambient pressure. This increased pressure is, for example, 8 bar and can be generated by means of a compressor, which is arranged between the hydrogen reactor and the receiving vessel and serves to compress the hydrogen supplied from the hydrogen reactor. The increased pressure represents the operating pressure at which the gaseous hydrogen is fed directly or indirectly to the combustion chamber of the internal combustion engine. It may be advantageous, if necessary, to compress the hydrogen in the compressor to up to 10 bar. According to a further advantageous embodiment, the hydrogen from the storage tank can be directed towards the engine via a control valve. This can be achieved either by intake manifold injection, where the hydrogen is introduced directly into the intake manifold and mixed with the intake air, or alternatively, by injecting the hydrogen directly into the piston chamber via a nozzle. On the exhaust side, it can be advantageous to provide a suction pump for removing the separated water from the exhaust stream. According to yet another advantageous embodiment, a water storage tank is located between the exhaust stream and the hydrogen reactor, in which the separated water from the exhaust stream can be collected and from which it can be fed to the hydrogen reactor as needed. In this case, it can be advantageous to feed the separated water to the hydrogen reactor via a metering pump. The metering pump is located, in particular, between the water storage tank for the separated water and the hydrogen reactor. In a further advantageous embodiment, the metal hydroxide Mg(OH)₂, which is released in the hydrogen reactor during the dissolution of hydrogen from the metal hydride MgH₂, is extracted from the hydrogen reactor and subjected to a chemical reaction with the addition of heat, causing the metal hydroxide Mg(OH)₂ to decompose into magnesium oxide MgO and water. The magnesium oxide MgO can then be fed into a collection device where it is collected as a byproduct. The process temperature at which the reaction takes place is at least 350°C and is preferably derived from the exhaust gas stream of the internal combustion engine. After being extracted from the hydrogen reactor, the metal hydroxide Mg(OH)₂ is directed towards the exhaust gas stream so that the heat from the exhaust gas stream triggers the reaction. Subsequently, the magnesium oxide MgO can be fed into the collection device. The metal hydroxide Mg(OH)₂ is not routed through the exhaust stream, but rather along or above it, to avoid direct contact with the exhaust gas and simultaneously ensure that the heat from the exhaust stream is transferred to the metal hydroxide Mg(OH)₂ to trigger the desired reaction. The magnesium oxide MgO, a byproduct, has a molecular weight of 40.3 g / mol, which is over 30% lower than that of the metal hydroxide Mg(OH)₂. Consequently, the weight of the magnesium oxide MgO collected in the receiving tank is less than that of the metal hydroxide Mg(OH)₂ generated in the hydrogen reactor. The water produced during the decomposition of the metal hydroxide Mg(OH)2 to magnesium oxide MgO either escapes as water vapor or is added to the exhaust gas to be returned to the hydrogen reactor as process water in the water separator. The invention further relates to the use of a fuel with a carrier medium containing embedded hydrogen, present under ambient conditions, in a previously described internal combustion engine. The fuel is preferably, as stated, a metal hydride. Further advantages and practical embodiments can be found in the further claims, the description of the figures, and the drawings. Figure 1 shows a schematic representation of a hydrogen internal combustion engine including various peripheral devices, and Figure 2 shows a variant embodiment of the hydrogen internal combustion engine. In the figures, identical components are labelled with the same reference symbols. Fig. 1 shows a reciprocating internal combustion engine 1 with an engine block 2 in which, by way of example, four cylinders 3 are arranged in a row, with a piston in each cylinder 3 being movable up and down. The internal combustion engine 1 is designed as a hydrogen engine, in which hydrogen is the fuel that is burned in the cylinders 3 and drives the pistons. The internal combustion engine 1 is equipped with an intake manifold 4 for the introduction of fresh air and an exhaust manifold 5 for the removal of combustion products from the cylinders 3. The fuel is hydrogen, which in its initial state is bound in a metal hydride, in particular magnesium hydride (MgH2), present as a fuel paste and stored under ambient conditions in a fuel tank 6. The fuel paste is either introduced into the fuel tank 6 or, alternatively, the fuel tank 6 is designed to be replaceable and exchanged as needed. The fuel is a metal hydride with a carrier medium in which the hydrogen is absorbed, wherein the carrier medium is preferably an alkaline earth metal from the second main group of the periodic table, in particular magnesium. Accordingly, the metal hydride is a magnesium hydride MgH₂. The fuel from fuel tank 6 can be fed into a hydrogen reactor 7, in which, under ambient conditions, hydrogen (H₂) is extracted from the magnesium hydride (MgH₂). This occurs with the addition of water according to the reaction equation MgH₂ + 2H₂O = 2H₂ + Mg(OH)₂, whereby metal hydroxide (Mg(OH)₂) is released, which, as indicated by arrow 8, is fed into a collection device. The hydrogen H2 extracted in the hydrogen reactor is in gaseous form and is fed to a downstream compressor 9, in which the hydrogen H2 is compressed to an operating pressure of, for example, 8 bar. Under this pressure, the hydrogen H2 is collected in a receiving tank 10, from which the hydrogen H2 is blown into the intake manifold 4 via a control valve 11 and mixed with incoming fresh air, whereby the mixture of fresh air and hydrogen is supplied to the combustion chambers in the cylinders 3. As an alternative to the shown intake manifold injection of hydrogen into the intake tract 4, it is also possible, as indicated by arrow 12, to carry out direct injection of hydrogen H2 into the cylinders 3 via a nozzle. During combustion in cylinders 3, hydrogen is burned with oxygen according to the following reaction, leaving water as the reaction product: 2H2 + 2O2 = 2H2O In the exhaust stream 5, there is a water separator 13, indicated by arrow 13. The exhaust gases produced during combustion and routed into the exhaust stream 5 pass through this separator, and water vapor is separated from the exhaust gases. The water is conveyed via a return line 14, which contains a suction pump 15, to a water reservoir 16 and collected there. This reservoir is connected to the hydrogen reactor 7 via another line 17, which contains a metering pump 18. The metering pump 18 pumps water from the reservoir 16 into the hydrogen reactor 7 as needed. In the hydrogen reactor 7, the reaction described above takes place to release the hydrogen from the magnesium alloy. Thus, a water cycle exists in which water vapor is produced during the combustion of hydrogen in the engine. Water is then separated from this vapor and returned to the hydrogen reactor, where hydrogen is produced again. The water storage tank 16 is connected to the exhaust system 5 via a vent line 19. If necessary, the water storage tank 16 is vented via the vent line 19 towards the exhaust, which connects to the exhaust system 5. The water storage tank 16 can also be equipped with an overflow device and a sensor to determine the current fill level. The suction pump 15 and the metering pump 18 can also be equipped with sensors to deliver water as needed. The suction pump 15 can also be equipped with a filter for water purification. Fig. 2 shows a variant embodiment of Fig. 1. In Fig. 2, the internal combustion engine 1 is also designed as a hydrogen internal combustion engine, in which hydrogen is the fuel. The hydrogen is bound in a metal hydride, in particular magnesium hydride (MgH₂), in the form of a fuel paste, which is stored in the fuel tank 6 under ambient conditions. For the basic structure of the internal combustion engine 1, reference is made to the description of Fig. 1. The treatment of the metal hydroxide Mg(OH)₂, which is released in the hydrogen reactor 7 and represents a waste product, differs in Fig. 2. The metal hydroxide Mg(OH)₂ is routed along the exhaust gas line 5 to be heated to at least 350° Celsius. For the sake of simplicity, the exhaust gas line 5 is shown as a dashed line below the hydrogen reactor 7 in Fig. 2. There is no direct contact between the exhaust gas in the exhaust gas line 5 and the metal hydroxide Mg(OH)₂; rather, only the heat from the exhaust gas line 5 is transferred as process heat to the metal hydroxide Mg(OH)₂, which decomposes into magnesium oxide MgO and water. The magnesium oxide MgO has a lower molecular weight than the metal hydroxide Mg(OH)₂ and is fed into a collection device 20, where it is collected as a waste product.Due to its lower molecular weight, the weight of magnesium oxide MgO in the collection device 20 is also lower than the weight of metal hydroxide Mg(OH)2. The water produced during the decomposition of the metal hydroxide Mg(OH)2 to magnesium oxide MgO either escapes into the environment as water vapor or is fed to the exhaust gas line 5 in order to be returned to the hydrogen reactor 7 as process water via the water separator 13, the return line 14, the suction pump 15, the water storage tank 16, the line 17 and the metering pump 18.

Claims

Internal combustion engine, with at least one adjustable piston in an engine block (2), with an intake manifold (4) and an exhaust manifold (5), wherein hydrogen can be supplied to the internal combustion engine (1) as fuel, characterized in that the fuel is a metal hydride (MgH2) which has a carrier medium with hydrogen, wherein the fuel is stored in a fuel tank (6) and can be dissolved from the carrier medium in a hydrogen reactor (7) by supplying water, and that a water separator (13) is arranged in the exhaust manifold (5) and the separated water can be supplied to the hydrogen reactor (7). Internal combustion engine according to claim 1, characterized in that the carrier medium of the fuel is an alkaline earth metal from the second main group of the periodic table. Internal combustion engine according to claim 1 or 2, characterized in that the carrier medium of the fuel is magnesium. Internal combustion engine according to one of claims 1 to 3, characterized in that the fuel can be stored as fuel paste in the fuel tank (6). Internal combustion engine according to one of claims 1 to 4, characterized in that in the hydrogen reactor (7) the water is soluble from the carrier medium under ambient conditions. Internal combustion engine according to one of claims 1 to 5, characterized in that a receiving container (10) for receiving the hydrogen is arranged downstream of the hydrogen reactor (7). Internal combustion engine according to claim 6, characterized in that the receiving container (10) is designed as a pressure vessel. Internal combustion engine according to claim 7, characterized in that a compressor (9) for compressing the supplied hydrogen is arranged between the hydrogen reactor (7) and the receiving container (10). Internal combustion engine according to claim 8, characterized in that the hydrogen in the compressor (9) is to be compressed to a maximum of 10 bar. Internal combustion engine according to one of claims 6 to 9, characterized in that a control valve (11) is arranged downstream of the receiving container (10) for receiving the hydrogen. Internal combustion engine according to one of claims 1 to 10, characterized in that the hydrogen can be introduced into the intake tract (4). Internal combustion engine according to one of claims 1 to 10, characterized in that the hydrogen can be introduced into the piston receiving chamber via a nozzle. Internal combustion engine according to one of claims 1 to 12, characterized in that a suction pump (15) for suctioning the separated water is arranged between the exhaust gas stream (5) and the hydrogen reactor (7). Internal combustion engine according to one of claims 1 to 13, characterized in that the separated water from the exhaust stream (5) can be supplied to a water storage tank (16). Internal combustion engine according to one of claims 1 to 14, characterized in that the separated water can be supplied to the hydrogen reactor (7) via a metering pump (18). Internal combustion engine according to one of claims 1 to 15, characterized in that in the hydrogen reactor (7) when the hydrogen is dissolved from the metal hydride (MgH2) metal hydroxide (Mg(OH)2) is released which can be derived from the hydrogen reactor (7). Internal combustion engine according to claim 16, characterized in that the metal hydroxide (Mg(OH)2) from the hydrogen reactor is directed to the exhaust gas line (5), wherein the heat of the exhaust gas line (5) causes the metal hydroxide (Mg(OH)2) to decompose into magnesium oxide (MgO) and water, and the magnesium oxide (MgO) can be supplied to a collection device (20). Internal combustion engine according to one of claims 1 to 17, characterized by a design as a reciprocating piston engine. Use of a fuel with a carrier medium present under ambient conditions with embedded hydrogen in an internal combustion engine (1) according to any one of claims 1 to 18.

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