Fuel injector

Abstract

The present application concerns fuel injectors, fuel injection systems, a fuel treatment system, a large combustion engine and a method for operating such a large combustion engine. A fuel injector defining an actuation chamber and a pressure chamber, wherein an actuating piston is disposed within the injector body and movable therein, wherein a supply of an actuating fluid to the actuation chamber moves the actuating piston to pressurize the fuel in the pressure chamber wherein at least one leakage line is arranged in the injector body which at least partially surrounds and is in contact with the actuating piston, the leakage line being fluidly connected or connectable to a low-pressure source, such that leaked fuel present in the leakage line is guidable out of the injector body.

Description

[0001] Fuel Injector

[0002] The present application concerns fuel inj ectors, a pressure amplifier for a fuel inj ector, fuel inj ection systems, an ammonia treatment system, a large combustion engine, and a method for operating such a large combustion engine .

[0003] Technical Field

[0004] Large engines, which can be configured as two-stroke or four-stroke engines, e . g. as longitudinally scavenged two-stroke large engines or two-stroke cross-head engines, are often used as drive units for ships, particularly large ships and vessels for the transport of goods, or in stationary operations such as driving large generators for generating electrical energy. The engines usually run for considerable periods in continuous operation, which places high demands on operational safety and availability .

[0005] Within the framework of this application, the term "large engine" designates an internal combustion engine with a bore of the cylinder (s) that is at least 200 mm and preferably at least 300 mm. Engine speed is preferably below 800 RPM, especially for four-stroke engines, and more preferably below 200 RPM for two-stroke engines, which indicates the designation of low-speed engines .

[0006] Large engines are classically configured as large diesel engines, which are operated with heavy fuel oil . The engine can be a diesel or a gas engine, a dual-fuel or a multi-fuel engine . Under the aspects of economic and efficient operation, compliance with exhaust-gas limit values, sustainability, reduction of CO2- and NOx- emissions, and the availability of resources, alternatives to heavy fuel oil are now also being sought for large engines . In this respect, both liquid fuels, i . e . fuels that areintroduced into the combustion chamber in the liquid state, and gaseous fuels, i . e . fuels that are introduced into the combustion chamber in the gaseous state, are used.

[0007] Examples of liquid fuels as known alternatives to heavy fuel oil are other heavy hydrocarbons, which are particularly left over as residues from oil refining; alcohols, in particular methanol or ethanol; ammonia; gasoline; diesel; or also emulsions or suspensions such as slurries . Biological fuels, such as oil made from algae or seaweed, HVO (hydro-treated vegetable oil) , and FAME ( fatty acid methyl ester) based fuels are also possible . For example, it is known to use emulsions known as MSAR (Multiphase Superfine Atomized Residue) as fuel . As gaseous fuels, natural gases such as LNG (liquefied natural gas) , liquefied gases such as LPG (liquefied petroleum gas) , natural gas (NG) , petrol gas (PG) , ethane, or hydrogen are known. Further possible fuels comprise LBG (liquefied biogas) , hydrogen, ammonia, and synthetic fuels from CO2(e . g. , made by Power-To-Gas or Power-To-Liquid processes) .

[0008] In particular, large engines are also known which can be operated with at least two or even more different fuels, whereby the engine is operated either with one fuel or with the other fuel depending on the operating situation or environment . It is also known to concurrently inj ect the two different fuels into the combustion chamber of the cylinder .

[0009] For this, fuel inj ectors are used. However, prior art fuel inj ectors can suffer from leaked fuel .

[0010] Large engines that can be operated with two or more different fuels are referred to as dual-fuel or multi-fuel large engines . Depending on the fuels, these engines may be operated in a liquid mode, in which a liquid fuel is introduced into the cylinderfor combustion, and / or in a gas mode, in which a gas is introduced into the cylinder as fuel .

[0011] Large engines, which can be operated with at least two or even more different liquid or gaseous fuels, are often operated in different operating modes depending on the fuel currently in use . In the operating mode often referred to as diesel operation, the combustion of the fuel generally takes place according to the principle of compression ignition or self-ignition of the fuel . In the mode often referred to as Otto operation, combustion takes place by induced ignition. This induced ignition can take place, for example, by an electrical spark (e . g. , with a spark plug) or by the self-ignition of a small inj ected amount of fuel (pilot fuel) , which then causes the induced ignition of another fuel . The small amount of fuel intended for self-ignition is directly inserted into the combustion chamber or inj ected into a pre-chamber connected to the combustion chamber . Forced ignition can thus be achieved by use of a pre-chamber, a spark plug, and / or a pilot fuel . The process of induced ignition by self-ignition of a small amount of a liquid or another selfigniting fuel is sometimes referred to as pilot inj ection.

[0012] Furthermore, mixed forms using both Otto and diesel operation are also known.

[0013] In particular, in view of attempts to reduce greenhouse gas emissions, the reduction of CO2production, and sustainability goals, a reduction in the use of fossil fuels is strived for . Thus, alternatives are investigated to at least reduce or even completely avoid the use of fossil fuels in large engines .

[0014] Alternatives to fossil fuel are, for example, methanol or ammonia . However, there is the risk that these fuels escape from the engine, e . g. , as vapor, into the space which is accessible to engine maintenance or operating personnel . This constitutes ahealth hazard requiring comprehensive mitigation measures . The escaping of gaseous fuel into the atmosphere are usually referred to as fuel slip or fugitive emissions . When methanol or ammonia is used as a fuel in a large engine, most of the methanol or ammonia is consumed in the combustion process . However, some of the fuel remains unburned and may escape into the atmosphere, e . g. , by passing through the exhaust gas system of the large engine ( fuel slip) . All upstream losses are summarized as fugitive emissions . Methanol or ammonia is hazardous for the environment as well as for humans and animals . Therefore, great efforts are made to reduce the fuel slip and fugitive emissions occurring in large engines, such as those used for ship propulsion .

[0015] The reduction of nitrogen oxides and nitrous oxide in the exhaust gas of an ammonia fueled engine is for example disclosed in DE 102022119570 Al . The exhaust gas aftertreatment system has an Fe-beta-zeolite catalytic converter for the simultaneous reduction of nitrogen oxides NOXand decomposition of dinitrogen monoxide N2O in the exhaust gas, which is set up to use an ammonia slip in the exhaust gas at least proportionately as a reducing agent for the reduction of nitrogen oxides NOXin the exhaust gas . The exhaust gas aftertreatment system furthermore has an ammonia catalyst which is set up to convert ammonia not used as a reducing agent into water and into nitrogen.

[0016] Disclosure of the Invention

[0017] It is an obj ective of the present invention to at least in part overcome the drawbacks of the prior art solutions and, in particular, to provide fuel inj ectors, a fuel inj ector system, an internal combustion engine, an ammonia treatment system and a method for operating such an internal combustion engine, which allow a safer and / or more effective operation.This obj ective is achieved by fuel inj ectors, a fuel inj ection system, a fuel treatment system, an internal combustion engine, and a method for operating such an internal combustion engine, according to the independent claims .

[0018] According to a first aspect of the invention, the fuel inj ector for inj ecting a fuel into a combustion chamber of a large combustion engine, preferably a large engine dual fuel engine and preferably a two-stroke engine, comprises a nozzle .

[0019] The fuel inj ector comprises an inj ector body defining an actuation chamber and a pressure chamber . The fuel inj ector on one side comprises the actuation chamber and on the other side the pressure chamber .

[0020] An actuating piston is arranged for a reciprocating movement between the actuation chamber and the pressure chamber .

[0021] Within this context the fuel is preferably a low flashpoint fuel, more preferably is selected from the group consisting of methanol, ammonia, ethanol, and dimethyl ether (DME) , and advantageously comprises or is ammonia .

[0022] The actuating piston is disposed within the inj ector body and movable therein. In particular the actuating piston is moveable within a pressure cylinder .

[0023] The actuating piston has a first side with a first cross-sectional area facing the actuation chamber and a second side with a second cross-sectional area facing the pressure chamber .

[0024] A supply of an actuating fluid to the actuation chamber moves the actuating piston to pressurize the fuel in the pressure chamber .

[0025] The actuating fluid preferably is a hydraulic oil .The nozzle comprises a nozzle tip having at least one spray hole, through which the fuel is inj ectable into the combustion chamber .

[0026] The spray hole is fluidly connectable to the pressure chamber . The nozzle further comprises at least one high-pressure fuel duct, through which the fuel can be guided from the pressure chamber to the at least one spray hole .

[0027] Preferably, a valve needle is loaded with a spring and interacts with a valve seat for opening and closing a fluid connection between the high-pressure fuel duct and the at least one spray hole .

[0028] Then, preferably, the valve needle moves to an open position, thus allowing the fuel to be inj ected into the combustion chamber through the at least one spray hole, when the pressure of the fuel in the pressure chamber exceeds a threshold sufficient to overcome the biasing force of the spring.

[0029] According to the invention, at least one leakage line is arranged in the inj ector body.

[0030] In a preferred embodiment the leakage line at least partially surrounds the actuating piston and is in contact with the actuating piston.

[0031] The leakage line may be open towards (i . e . in a fluid communication with) the actuating piston.

[0032] The leakage line may be arranged between the pressure chamber and the actuation chamber, preferably in a longitudinal direction of the actuating piston. The leakage line advantageously comprises an annular opening in the inj ector body, which opening surrounds and is open towards the actuating piston.The leakage line is fluidly connected or connectable to a low-pressure source and / or to a high-pressure source, typically arranged outside the fuel inj ector and / or inj ector body, such that leaked fuel present in the leakage line is guidable out of the inj ector body.

[0033] Thus, leaked fuel that leaks from the pressure chamber within the narrow gap between the actuating piston and the inj ector body towards the leakage line is guidable out of the inj ector body by the low-pressure source and / or by a high-pressure source .

[0034] Pressurized fuel present in the pressure chamber is mainly guided towards the nozzle tip . However, a small part of the pressurized fuel may get into the pressure cylinder in a region between the actuating piston and the inj ector body.

[0035] Depending on the kind of fuel, even a small amount of this leaked fuel such as ammonia may be too much to allow it to escape into the environment .

[0036] The low-pressure source, in particular a vacuum ej ector, may provide for creating a pressure that is below the pressure around the actuating piston, preferably a pressure below the atmospheric pressure, such that leaked fuel may not escape into the environment .

[0037] Preferably, the low-pressure source is adapted to create a pressure of below or equal to 0.8 bar inside the leakage line .

[0038] When the leaked fuel gets into the leakage line, it may be sucked out of the inj ector body and may be collected for disposal and / or subsequent use .

[0039] Additionally or alternatively, the high-pressure source may provide for purging the leaked fuel through at least one leakageline and away from the inj ector body by a pressurized inert gas, such as nitrogen.

[0040] Two or more leakage lines may be arranged in parallel around the actuating piston. The leakage lines can be annular in shape and may be connected such that leakage gas is merged into one common outlet line for guiding the leakage gas away.

[0041] In particular, the fuel may be ammonia, which is hazardous and for which it is particularly important not to release any leaked fuel into the environment .

[0042] A fuel supply line may be fluidly connected or connectable to the pressure chamber, such that the pressure chamber can repeatedly be filled with fuel . Fuel may be supplied with a pressure of 85 bar .

[0043] The actuating piston may comprise at least one sealing ring.

[0044] Preferably, the at least one leakage line is located in a region of the inj ector body, which is closer to the pressure chamber than the region where the sealing rings move towards the pressure chamber and away from the actuation chamber on the one hand and towards the actuation chamber and away from the pressure chamber on the other hand.

[0045] According to the invention the leakage line can be arranged at least partially surrounding and / or in contact with a moveable part of the fuel inj ector, preferably arranged within the inj ector body.

[0046] Preferably, the first cross-sectional area facing the actuation chamber is larger than the second cross-sectional area facing the pressure chamber . Thus, the actuating piston acts as a pressure amplifier .The actuation piston may have a first cylindrical part with a first diameter facing the actuation chamber and a second cylindrical part with a second diameter smaller than the first diameter facing the pressure chamber .

[0047] The inj ector body may define a first pressure cylinder part with an inner diameter corresponding to the first diameter and second pressure cylinder part with an inner diameter corresponding to the second diameter . The at least one leakage line may be arranged in the second pressure cylinder part .

[0048] For example, actuating fluid, such as hydraulic oil ("system oil") , is released to the actuation chamber with a pressure of approximately 300 bar, achieving a pressure on the to be inj ected fuel in the pressure chamber of 500-800 bar . The valve needle may open at a pressure of at least approximately 300 bar .

[0049] By a pressure equalizing chamber, it may be prevented that the inj ection pressure is applied to the sealing rings around the actuating piston. Such a pressure equalizing chamber is preferably arranged between the pressure chamber and the sealing ring on the pressure chamber side of the leakage line . The pressure equalizing chamber is preferably in a fluid communication with the fuel supply line . Thus, any overpressure is at least partially released into the fuel supply line .

[0050] A pressure amplifier comprising the pressure chamber, the actuating piston, and the actuation chamber may be arranged adj acent to the nozzle and form part of the fuel inj ector or it may form a separate device .

[0051] The valve needle and / or the spring and / or the high-pressure fuel duct may be arranged in the same inj ector body as the pressure chamber and the actuation chamber, such that the valve needle and the pressure amplifier may share the same inj ector body.The inj ector body may comprise several, preferably axially aligned, body parts, tightly connected to each other .

[0052] The pressure amplifier may comprise an amplifier body which is adj acent to or part of the inj ector body.

[0053] The leakage line may be connected or connectable to a fuel treatment system, to a fuel supply system and / or to an SCR reactor, for example by an outlet line, for guiding the leaked fuel thereto .

[0054] The nozzle may comprise a double walled sleeve . The double walled sleeve may be adapted to allow an air flow for leakage detection and / or removal .

[0055] The fuel inj ector may further comprise at least one first sealing ring arranged between the actuation chamber and the leakage line . The first sealing ring may at least partially surround and be in contact with the actuating piston.

[0056] The first sealing ring further reduces the risk for any fuel escaping towards the actuation chamber .

[0057] The fuel inj ector may as an alternative or in addition comprise at least one second sealing ring arranged between the pressure chamber and the leakage line . The second sealing ring may at least partially surround and be in contact with the actuating piston .

[0058] The second sealing ring further reduces the risk for any fuel escaping from the pressure chamber towards the leakage line .

[0059] The inj ector body and / or the amplifier body may provide annular seats for the at least one first and / or the at least second sealing ring.The fuel inj ector may further comprise a channel, preferably in the second pressure cylinder, for providing sealing air to the actuating piston.

[0060] The fuel inj ector may comprise a purge line fluidly connected or connectable with the nozzle tip . Residuals of fuel in the fuel inj ector, in particular downstream a valve needle, may be guided out of the fuel inj ector via a purge fluid, in particular a purge gas .

[0061] A purge valve may be arranged in the purge line for opening and closing the purge line . Preferably the fuel inj ector may comprise the purge valve, such that the purge valve is arranged close to the spray hole .

[0062] The purge valve may comprise a purge valve body integrated in the inj ector body and a moveable purge valve plug. The purge valve may be a one-way valve .

[0063] The leakage line may at least partially surround and be in contact with the purge valve, in particular with the moveable purge valve plug.

[0064] Thus, leaked fuel, that leaks from the nozzle tip towards the purge line is guidable out of the inj ector body through the leakage line, for example in cases when a large fuel pressure is applied downstream the purge valve for opening the fuel valve .

[0065] The leakage line in the nozzle tip may be additional or alternative to the leakage line as described above, which at least partially surrounds the actuating piston. In case of more than one leakage line in the fuel inj ector, the leakage lines may be fluidly connected or connectable to the same low-pressure source and / or to the same high-pressure source or may be fluidly connected or connectable to a respective low-pressure source and / or to a respective high-pressure source .According to a further aspect of the invention, a fuel inj ector, preferably as described above, for inj ecting a fuel into a combustion chamber of a large engine comprises a nozzle and a pressure amplifier .

[0066] The fuel inj ector further comprises an inj ector body defining an actuation chamber and a pressure chamber .

[0067] The pressure amplifier comprises an actuating piston disposed within the inj ector body and movable therein. The actuating piston has a first side with a first cross-sectional area facing the actuation chamber and a second side with a second cross-sectional area smaller than the first cross-sectional area facing the pressure chamber . A supply of an actuating fluid to the actuation chamber moves the actuating piston to pressurize the fuel in the pressure chamber .

[0068] The nozzle comprises a valve needle biased by a spring toward a closed position against a valve seat . The valve needle is configured to open and close a fluid connection between the pressure chamber and a nozzle tip of the fuel inj ector . The nozzle tip having at least one spray hole through which the fuel can be inj ected into the combustion chamber . When the pressure of the fuel in the pressure chamber exceeds a threshold sufficient to overcome the biasing force of the spring, the valve needle moves to an open position, allowing the fuel to be inj ected into the combustion chamber through the at least one spray hole .

[0069] The fuel inj ector according to the second aspect of the invention comprises at least a first sensor for determining at least a first sensor signal indicative of a position and / or of a velocity of the actuating piston.

[0070] The first sensor is advantageously selected from the group consisting of an inductive sensor, a capacitive sensor, an acoustic sensor, and an optical sensor . The first sensor preferably isarranged in an opening within the inj ector body, such that a sensing surface or a sensing spot of the sensor is directed towards the actuating piston. The first sensor may be arranged in the pressure chamber and / or in the actuation chamber and / or in the first pressure cylinder part and / or in the second pressure cylinder part .

[0071] The first sensor may be arranged closer to the actuation chamber than the at least one leakage line .

[0072] The actuating piston may comprise at least one marker, preferably a set of grooves, and the sensor may be configured to determine the sensor signal based on the marker .

[0073] The presence of a marker, having a structure or color different from the rest of the actuating piston may be detected by the sensor .

[0074] An optical sensor may detect a marker with a different reflexivity, due to a different color or different surface structure, whereas an acoustical, an inductive sensor, or a capacitive sensor may detect a changed distance of a different structure .

[0075] The sensor signal based on the marker may be used for determining a signal representative for the moving way of the actuating position per inj ection and / or a signal representative for the velocity of the actuating position. Based on the sensor signal and the dimensions of the fuel inj ector, information about the amount of pressure amplification and / or the amount of inj ected fuel can thus be obtained more easily.

[0076] Preferably, the fuel inj ector further comprises a second sensor configured to determine at least a respective first and second sensor signal, preferably based on markers on the actuating piston, preferably on grooves . The position and / or the velocity of the actuating piston may then be determined based on the firstand the second sensor signal . This helps to provide more information .

[0077] The first and the second sensor, and optionally further sensors, may be of the same sensor type as described above . Alternatively, the different sensors may detect the marker in different ways .

[0078] The actuating piston may comprise a cone-shaped portion and the sensor may be configured to determine the sensor signal based on a distance between the first and / or second sensor and the cone-shaped portion.

[0079] It should be noted here that the inventive concept comprising a low-pressure impinged leakage line also extends to a pressure amplifier that is separate from (and connectable via a high-pressure line to) the fuel inj ector itself, i . e . a pressure amplifier for a fuel inj ector for a large combustion engine, the pressure amplifier comprising an amplifier body defining an actuation chamber and a pressure chamber, wherein an actuating piston is disposed within the amplifier body and movable therein. The actuating piston has a first side with a first cross-sectional area facing the actuation chamber and a second side with a second cross-sectional area smaller than the first cross-sectional area facing the pressure chamber, wherein a supply of an actuating fluid to the actuation chamber moves the actuating piston to pressurize the fuel in the pressure chamber . At least one leakage line is arranged in the amplifier body, which leakage line at least partially surrounds and is in contact with the actuating piston. The leakage line is fluidly connected or connectable to a low-pressure source and / or to a high-pressure source, such that leaked fuel present in the leakage line is guidable out of the amplifier body.The pressure amplifier may be arranged in contact with an inj ector body or may be fluidly connected with an inj ector body by a high-pressure line, such as a fuel line .

[0080] All the advantages, technical effects and possible combinations and advantageous embodiment remain the same as discussed above and shall not be repeated here for the sake of clarity.

[0081] According to the further aspect of the invention, a fuel inj ection system comprises at least one fuel inj ector as described above and / or pressure amplifier as described above and at least one low-pressure source and / or at least one high-pressure source .

[0082] Advantageously, the low-pressure source is or comprises at least one of a suction pump, a vacuum compressor, and a vacuum ej ector .

[0083] The vacuum ej ector, which is based on the Venturi effect, is advantageously driven by compressed air . This has the advantage that the mechanical design is simplified and that no additional heat is created (as e . g. by a compressor) .

[0084] Preferably, the low-pressure source is controlled in such a way, e . g. by a control unit being part of a main engine control unit or being a separate control unit, that a predefined low pressure below atmospheric pressure, e . g. 0.8 bar or below is created. It is also possible to have a control loop for adjusting and / or maintaining this low pressure depending on demand, e . g. based on an amount of leaked fuel in the leakage line, as e . g. measured by a sensor .

[0085] Preferably, the high-pressure source is controlled in such a way, e . g. by a control unit being part of a main engine control unit or being a separate control unit, that an inert gas, suchas nitrogen, is provided at a predefined high pressure for purging the leaked fuel through the leakage line . It is also possible to have a control loop for adjusting and / or maintaining this pressurized inert gas depending on demand, e . g. based on an amount of leaked fuel in the leakage line, as e . g. measured by a sensor .

[0086] The fuel inj ection system may comprise an outlet line for fluidly connecting the leakage line and the low-pressure source or for fluidly connecting the leakage line and the high-pressure source .

[0087] The outlet line is preferably double walled. A low pressure and / or a high-pressure source and / or an airflow may be provided between the walls in addition to the low pressure inside the outlet line or to the pressurized inert gas inside the outlet line . Fuel leaking from the outlet line may thus be detected and / or purged.

[0088] The outlet line may comprise at least one valve .

[0089] The valve may close or open the connection between the leakage line and the low-pressure source and / or the high-pressure source .

[0090] The valve may allow to vent or purge the outlet line .

[0091] A pressurizing system may be fluidly connected to the outlet line, such that the leaked fuel may be pressurized if needed, for example for facilitating a mixing with a pressurized exhaust gas .

[0092] The fuel inj ection system may comprise a fuel supply system, which is connected or connectable to a fuel supply line of the fuel inj ector .

[0093] The fuel supply system may comprise a fuel tank.The fuel inj ection system may comprise a fuel treatment system connected or connectable to the leakage line .

[0094] In the fuel treatment system, the leaked fuel may be treated for further use and / or for storing and / or venting. For example, the fuel treatment system may comprise a cleaning stage to remove oil residuals .

[0095] The fuel treatment system may be fluidly connected or connectable to the fuel supply system. Thus, leaked fuel can be reused more easily.

[0096] Alternatively, the fuel treatment system may be fluidly connected or connectable to the exhaust gas manifold and / or to an exhaust gas outlet .

[0097] The fuel treatment system may comprise water and / or an acid for absorbing leaked fuel . The leaked fuel can be chemically bound.

[0098] The fuel treatment system may comprise a liquifying system, preferably comprising a cooling system for condensation of gaseous leaked fuel . The cooling system may comprise a direct contact condenser or an indirect heat exchanger . It may use the low temperature of liquid fuel, such as ammonia, in the fuel supply system. The cooling system may comprise a heat pump .

[0099] Alternatively or in addition, the liquifying system may comprise a compression liquefier .

[0100] Liquified leaked fuel may be directed to and used in the fuel supply system and / or a reducing agent dosing system of an SCR reactor .

[0101] The fuel treatment system may comprise an incinerating system for burning the leaked fuel . The incineration system may comprise an ignition plug. The combustion products of the leakedfuel leaving the incinerating system may be discharged into the environment .

[0102] The fuel treatment system may comprise a catalyst, for example as described below.

[0103] The fuel treatment system may comprise a dilution gas inlet for providing gas, such as air or exhaust gas . The gas provides for diluting the leaked fuel and for supplying oxygen.

[0104] The dilution gas inlet may be fluidly connected or connectable to an exhaust gas manifold of the internal combustion engine .

[0105] Alternatively or in addition, the outlet line may be fluidly connected or connectable to the exhaust gas manifold.

[0106] The leaked fuel, in particular leaked ammonia fuel, from the outlet line or from the fuel treatment system, may be used as a reducing agent in an SCR reactor arranged downstream the exhaust gas manifold, in particular a high-pressure SCR reactor arranged upstream a turbine of a turbocharger .

[0107] The regular urea dosing of the SCR reactor unit may be controlled in such a way, e . g. by a control unit being part of a main engine control unit or being a separate control unit, that there is no extended ammonia slip . In other words, when leaked ammonia fuel is used as reducing agent, regular urea dosing is decreased which helps to save costs . According to a further aspect of the invention, a fuel treatment system, preferably an ammonia treatment system, preferably for a fuel inj ection system as described above, is configured for reducing an ammonia content of leaked fuel in a large combustion engine, preferably an ammonia fueled combustion engine .The fuel treatment system comprises a leaked fuel inlet for receiving leaked fuel, for example for receiving leaked fuel sucked off a fuel inj ection system of an ammonia-fueled engine .

[0108] Such leaked fuel can contain ammonia and a small amount of oil . However, the leaked fuel may have an ammonia content of more than 90 percent .

[0109] However, in order for the leaked fuel to be vented into the environment, the ammonia content must be less than 10 ppm or less

[0110] Ammonia may also leak from other parts of the combustion engine . Such ammonia can be fed to the fuel treatment system as well .

[0111] According to the invention, the fuel treatment system comprises at least one ammonia slip catalyst, also called ammonia oxidation catalyst, configured to oxidize leaked ammonia and at least one metal-zeolite catalyst, arranged downstream the ammonia slip catalyst .

[0112] The gas hourly space velocities (GHSV) defined by the flowrate and the volume of a catalyst, of the at least one ammonia slip catalyst and the at least one metal-zeolite catalyst is configured to practically remove the complete ammonia content or at least to substantially reduce the ammonia content of the leaked fuel at a given temperature and pressure .

[0113] In the ammonia slip catalyst, the ammonia is oxidized and nitrogen N2, NOX, in particular NO and NO2, as well as nitrous oxide N2O are produced.

[0114] Nitrous oxide N2O is involved in ozone depletion and has high global warming potential . Thus, nitrous oxide should not be released into the environment .The ammonia slip catalyst may operate at a high temperature window, for example between 350°C and 500°C .

[0115] The metal-zeolite catalyst provides for reducing residuals of NO as well as for reducing nitrous oxide, in particular at temperatures in a range from 500°C to 650°C . The oxidation heat produced in the ammonia slip catalyst may warm up the metal-zeolite catalyst, such that the metal-zeolite catalyst is at an appropriate temperature . Such a thermal coupling can help to reduce energy consumption.

[0116] It should be noted, that the concept of the invention can be adapted to other fuels such as methanol as well by selecting appropriate catalysts .

[0117] The fuel treatment system may comprise a dilution gas inlet arranged upstream the ammonia slip catalyst for introducing a dilution gas, preferably exhaust gas .

[0118] Within this context, the meaning of the terms upstream / down-stream refers to the flow direction of leaked fuel, for example from a fuel inj ection system towards a funnel .

[0119] Less than 1% of the exhaust gas of the combustion engine may be branched off to dilute the leaked ammonia .

[0120] The amount of dilution gas is advantageously controlled (e . g. depending on the amount of leaked ammonia) such that an outlet temperature after the last metal-zeolite catalyst is maintained within a predetermined range or value, e . g. below 550°C .

[0121] The leaked ammonia may also be diluted with air or another gas such as an inert gas .

[0122] The exhaust gas or the air may heat up the leaked fuel .The exhaust gas or the air may be heated up by a heater, preferably an electrical heater, to bring the temperature of the flow of diluted leaked fuel to an appropriate temperature for the function of the ammonia slip catalyst, e . g. 400 or 450°C . The heater may be arranged in a dilution gas line upstream of the dilution gas inlet .

[0123] Preferably, the dilution gas inlet is configured to dilute the leaked ammonia by a factor in a range of 70-210.

[0124] The fuel treatment system may comprise more than one catalyst combination, each of which comprises at least one ammonia slip catalyst and at least one metal-zeolite catalyst, which may be passed successively, for stepwise reducing the ammonia content of the leaked fuel .

[0125] A stepwise reducing of ammonia may prevent overheating of the metal-zeolite catalyst as in each step only a part of the ammonia is oxidized and correspondingly a lower amount of oxidation heat is produced.

[0126] Alternatively or additionally, the fuel treatment system may comprise a recirculation line for repeatedly passing a catalyst combination comprising one ammonia slip catalyst and one metalzeolite catalyst . This may also provide for a stepwise reduction of the ammonia content .

[0127] When the ammonia content is reduced in a plurality of steps, smaller catalysts may be used, as compared to a substantial reduction of the ammonia content in one step .

[0128] Preferably, at least one ammonia slip catalyst and at least one metal-zeolite catalyst, preferably a catalyst combination of one ammonia slip catalyst and one metal-zeolite catalyst, are thermally coupled, such that oxidation heat produced in the ammonia slip catalyst warms up the metal-zeolite catalyst .The ammonia slip catalyst and the metal-zeolite catalyst may be placed in contact with each other, preferably forming a catalyst combination .

[0129] Adj acent catalyst combinations may be placed in contact to each other .

[0130] The ammonia slip catalyst and the metal-zeolite catalyst may be arranged in a common housing.

[0131] The dilution gas inlet may be connected or connectable to the exhaust line, preferably to an exhaust gas manifold, more preferably upstream a turbine of a turbocharger .

[0132] The metal-zeolite catalyst may be a Fe-zeolite-catalyst and / or a Cu-zeolite-catalyst , in particular a Fe-beta-zeolite-catalyst .

[0133] The leaked ammonia inlet of the fuel treatment system may be fluidly connected or connectable to a leakage line of a fuel inj ector as described above .

[0134] The fuel treatment system may comprise a housing, in particular encompassing the at least ammonia slip catalyst and the metal zeolite catalyst . The housing may be double walled.

[0135] The container may be arranged close to, on and / or within an exhaust gas pipe, in particular an exhaust gas manifold. This has the benefit that the housing is preheated from the exhaust gas and that a second enclosure may be omitted.

[0136] The leaked fuel inlet may also be arranged inside the exhaust gas pipe .

[0137] According yet another aspect of the invention, a fuel inj ection system, preferably as described above, comprises a fuel inj ector with at least one sensor as described above, and a control unit . The control unit is configured to determine at least one of thegroup consisting of a start of inj ection, an end of inj ection, and a quantity of inj ected fuel .

[0138] The control unit is configured to determine based on the position and / or based on the velocity of the actuating piston of the fuel inj ector .

[0139] The control unit may be part of the engine control unit or it may be a separate control unit .

[0140] According to a further aspect of the invention, a large combustion engine, in particular a longitudinally scavenged two-stroke large engine, comprises at least one cylinder having a combustion chamber, wherein a piston is arranged in the cylinder for a reciprocating movement between a top dead center position and a bottom dead center position. Each cylinder comprises at least one fuel inj ector and / or at least one fuel inj ection system as described above .

[0141] Each cylinder comprises at least one exhaust gas outlet which outlets may be fluidly connected or connectable to an exhaust gas manifold.

[0142] The at least one cylinder may comprise a second fuel inj ector for inj ecting a second fuel into the combustion chamber, wherein the second fuel is different from the fuel . In particular, the second fuel is a diesel fuel for self-ignition and / or pilot ignition of the fuel in the combustion chamber .

[0143] Additionally or alternatively, the large combustion engine comprises a fuel treatment system as described above .

[0144] The fuel treatment system may provide for the reducing of the ammonia content of leaked fuel, in particular leaked in a fuel inj ection system.According to a further aspect of the invention, a method for operating the large combustion engine, in particular as described above, comprises the following steps :

[0145] A pressure below atmospheric pressure is created in the leakage line, in particular by means of a vacuum ej ector, preferable a pressure lower than 0.8 bar . Leaked fuel, present in the leakage line, is guided out of the inj ector body.

[0146] Alternatively or additionally, a pressurized inert gas is guided through the leakage line to purge leaked fuel and to guide the leaked fuel out of the inj ector body.

[0147] The method may comprise a step of guiding the leaked fuel into an exhaust gas stream of the large combustion engine .

[0148] Additionally or alternatively, the method may comprise a step of guiding the leaked fuel into a scavenge air inlet upstream of a compressor of a turbocharger .

[0149] Additionally or alternatively, in particular, in cases when the leakage exceeds a predetermined limit, the method may comprise a step of guiding the leaked fuel into a fuel inj ection system, preferably as described above, and / or into a fuel treatment system , preferably as described above .

[0150] According to a further aspect of the invention, a method for reducing the ammonia content of leaked fuel in a large combustion engine comprises steps of oxidizing ammonia and producing oxidation heat in an ammonia slip catalyst and preferably using the oxidation heat to heat up a metal zeolite catalyst, preferably to temperature of equal or above 500°C, and removing nitrous oxide in the metal zeolite catalyst, produced during the previous step of oxidization of ammonia . Preferably, said steps of oxidizing and removal of nitrous oxide may be repeated for a step-wise reduction of the ammonia content .In the metal zeolite catalyst also the NOXcontent may be reduced .

[0151] Preferably, the leaked ammonia may be diluted, preferably with exhaust gas, before it is passed through the catalysts .

[0152] The method for reducing the ammonia content of leaked ammonia may be applied to leaked fuel, which is guided out of the inj ector body, as described above .

[0153] Brief Description of the Drawings

[0154] The invention will be better understood and obj ects other than those set forth above will become apparent when consideration is given to the following detailed description thereof . Such description makes reference to the annexed drawings, wherein:

[0155] Figure 1 shows a schematic representation of an embodiment of a large combustion engine;

[0156] Figure 2 shows a schematic representation of an embodiment of a fuel inj ector;

[0157] Figure 3 shows a schematic representation of an embodiment of a detail of a fuel inj ector;

[0158] Figure 4 shows a schematic representation of an embodiment of a large combustion engine comprising a fuel treatment system;

[0159] Figure 5 shows a vacuum ej ector as a low-pressure source to generate a low-pressure in the leakage line;

[0160] Figure 6 shows a detail of a fuel inj ector having a purge line and a purge valve .

[0161] In figure 1, only one of the cylinders 210 of the large engine 200 is shown. Usually, the large engine 200 comprises a plurality of cylinders 210, for example at least four and up to twelve cylinders 210 or even more . The term "large combustion engine"refers to internal combustion engines that are typically used as drive units for ships or in stationary operations, such as driving large generators for generating electrical energy.

[0162] Typically, the cylinders 210 of a large engine 200 each have an inner diameter (bore) of at least about 200 mm. Large engines 200 are known in various configurations, for example as two-stroke engines or four-stroke engines .

[0163] In the following description, reference is made by way of example to a large engine 200 configured as a longitudinally scavenged two-stroke large engine having a plurality of cylinders 210. Each cylinder 210 has a combustion chamber 211. Furthermore, in each cylinder 210, a piston 220 is arranged for reciprocating movement between a top dead center and a bottom dead center .

[0164] The term "longitudinally scavenged" means that the scavenging or charging air is introduced into the cylinder 210 in the area of the lower end, and an exhaust valve 230 is arranged in or at the cylinder cover 212 located at the upper end of the cylinder 210.

[0165] In particular, reference is made to a large longitudinally scavenged two-stroke engine that can be operated with different fuels, namely with a first fuel and with a second fuel .

[0166] According to a preferred configuration, the large engine 200 can be operated with methanol or ammonia as a first fuel and with a self-igniting and liquid second fuel . For this, the large engine 200 comprises a first fuel inj ection system 100 and a second fuel supply system 250.

[0167] Each cylinder 110 comprises at least one, but preferably a plurality of, first fuel inj ector systems 100 for inj ecting thefirst fuel, as well as at least one, but preferably a plurality of, second fuel inj ectors 250 for inj ecting the second fuel .

[0168] In each cylinder 210, the piston 220 is connected in a manner known per se to a crosshead 222 via a piston rod 221. The crosshead 222 is connected to a crankshaft 224 via a push rod or connecting rod 223, so that the movement of the piston 220 is transmitted via the piston rod 221, the crosshead 222, and the connecting rod 223 to the crankshaft 224 to rotate it . The upper side of the piston 220, together with the cylinder cover 212, delimits the combustion chamber 211 into which the first fuel and / or the second fuel is introduced.

[0169] In the embodiment of a longitudinally scavenged two-stroke large diesel engine 200, scavenging air slots 215 are usually provided in the lower region of each cylinder 210 or cylinder liner .

[0170] These slots are periodically closed and opened by the movement of the piston 220 in the cylinder 210, allowing the scavenging air provided by the turbocharger under charging pressure to flow into the cylinder 210 through the scavenging air slots 215 when they are open. In the cylinder cover 212, the usually centrally arranged exhaust valve 230 is provided, through which the exhaust gases can be discharged from the cylinder 210 into the exhaust system after the combustion process .

[0171] The first fuel inj ection system 100 comprises an outlet line 101 which fluidly connects the first fuel inj ector 1 and a low-pressure source 30. By means of the low-pressure source 30, leaked fuel can be sucked out of a leakage line 20 (see figure 2 ) of the first fuel inj ector 1. The leaked fuel may be guided to a fuel treatment system 40, where the fuel leaked fuel may be liquified and subsequently be guided to a fuel supply system 17.

[0172] It is noted that the invention is not restricted to this specific type of a longitudinally scavenged two-stroke large engine200, which can be operated with the first fuel and / or with the second fuel . The large engine can also be any other type of large engine . In particular, it is possible that the large engine is configured for the combustion of only one fuel .

[0173] Figure 2 shows a schematic representation of an embodiment of a fuel inj ector 1, for example a first fuel inj ector 1 as shown in figure 1 .

[0174] The fuel inj ector 1 comprises a nozzle 2 and a pressure amplifier 4 .

[0175] The fuel inj ector 1 comprises an inj ector body 3 defining an actuation chamber 5 and a pressure chamber 6.

[0176] An actuating piston 7 is disposed within the inj ector body 3 and movable therein. The actuating piston 7 has a first side 9 with a first cross-sectional area facing the actuation chamber 5 and a second side 8 with a second cross-sectional area smaller than the first cross sectional area facing the pressure chamber 6.

[0177] A supply of an actuating fluid, such as a hydraulic oil, to the actuation chamber 5 moves the actuating piston 7 to pressurize the fuel in the pressure chamber 6.

[0178] The nozzle 2 comprises a nozzle tip 10 having at least one spray hole 11, through which the fuel is inj ectable into the combustion chamber 211 (see figure 1 ) . The nozzle 2 further comprises at least one high-pressure fuel duct 12, through which the fuel can be guided from the pressure chamber 6 to the at least one spray hole 11.

[0179] A valve needle 13 is loaded with a spring 14 and interacts with a valve seat 15 for opening and closing a fluid connection between the high-pressure fuel duct 12 and the at least one spray hole 11.Typically, the valve needle 13 moves to an open position, allowing the fuel to be inj ected into the combustion chamber 211 (see figure 1 ) through the at least one spray hole 11, when the pressure of the fuel in the pressure chamber 6 exceeds a threshold sufficient to overcome the biasing force of the spring 14.

[0180] At least one leakage line 20 is arranged in the inj ector body 3 which surrounds and is in contact with the actuating piston 7.

[0181] The leakage line 20 is fluidly connected or connectable to a low-pressure source 30 (see figure 1 ) , such that leaked fuel present in the leakage line 20 is guidable out of the inj ector body 3 .

[0182] High pressure fuel in the pressure chamber 6 may escape from the pressure chamber 6 in direction to the actuation chamber 5 through the narrow space between the actuating piston 7 and the inj ector body 3. By applying a low pressure in the leakage line 20, the leaked fuel may be removed from the fuel inj ector 1 and be prevented from escaping into the environment .

[0183] The nozzle 2 comprises a double walled sleeve 18.

[0184] The fuel inj ector further comprises a first sealing ring 19.1 and a second sealing ring 19.2. The sealing rings 19.1, 19.2 surround and are in contact with the actuating piston 7.

[0185] The first sealing ring 19.1 is arranged between the actuation chamber 5 and the leakage line 20. The second sealing ring 19.2 is arranged between the pressure chamber 6 and the leakage line 20. This helps to reduce the amount of leaked fuel .

[0186] Figure 3 shows a schematic representation of an embodiment of a detail of a fuel inj ector 1, for example as shown in figures 1 or 2 .The fuel inj ector 1 comprises a first sensor 50 and a second sensor 51 for determining at least a first and a second sensor signal indicative of a position and / or of a velocity of the actuating piston 7.

[0187] The sensors 50, 51 may be selected from the group consisting of inductive sensors, capacitive sensors, acoustic sensors, and optical sensors .

[0188] The actuating piston 7 comprises two markers 55, preferably grooves . The sensors 50, 51 are configured to detect the markers 55, when they pass a respective sensor and to determine the sensor signal based on the markers 55, which have a defined distance d. The speed of the actuating piston 7 may be determined.

[0189] A control unit 260 (see figure 1 ) is configured to determine a start of an inj ection, an end of the inj ection and / or a quantity of inj ected fuel based on the position and / or based on the velocity of the actuating piston 7 of the fuel inj ector 1.

[0190] The sensors may for example detect time stamps of the passing markers 55 during the reciprocating movement of the actuating piston and determine time differences .

[0191] Based on these time differences and / or based on dimensions, such as the distance d of the markers 55, the diameters of the actuating piston 7, the volumes of the pressure chamber 6 and the actuation chamber 5 and / or based on the amount and / or the compressibility of the hydraulic oil, a pressure difference and / or an amount of the inj ected fuel gas may be derived.

[0192] Figure 4 shows a schematic representation of an embodiment of a large combustion engine 200 comprising a fuel treatment system which is an ammonia treatment system 40.In this case, the large combustion engine 200 comprises six cylinders 210 and respective ammonia fuel inj ectors 1.

[0193] Leaked ammonia is sucked off by a low-pressure source comprising a compressed-air driven vacuum ej ector 30 (see Fig. 5) and passed to the ammonia treatment system 40.

[0194] The ammonia treatment system 40 comprises a leaked ammonia inlet 41, a dilution gas inlet 42, ammonia slip catalysts 43, configured to oxidize leaked ammonia, and metal-zeolite catalysts 44.

[0195] Each metal-zeolite catalyst 44 is arranged downstream a respective ammonia slip catalyst 43.

[0196] In this example, the ammonia treatment system 40 comprises three catalyst combinations 47 arranged in series, each comprising one ammonia slip catalyst 43 and one metal-zeolite catalyst 44.

[0197] The ammonia treatment system 40 may be arranged within an exhaust gas manifold 45 of the large engine 200.

[0198] Exhaust gas is branched off the exhaust gas manifold 45, is passed over a heater 46 and guided to the dilution gas inlet 42 to dilute the leaked ammonia .

[0199] Within the ammonia treatment system 40, the ammonia content is reduced, such that the resulting gas may be merged with the exhaust gas, in this case downstream the turbocharger 240, for example in a low-pressure exhaust gas treatment device 245.

[0200] Alternatively, the resulting gas may be redirected into the exhaust gas manifold 45 by a return line (not shown in the figures) .

[0201] In such a case, the branched off exhaust gas from the exhaust gas manifold 45 is pressurized by a blower before being passedover the heater 46 and being guided to the dilution gas inlet 42 .

[0202] The leaked ammonia may be pressurized as well to facilitate mixing with the exhaust gas .

[0203] Energy that is added to the mixture may thus advantageously be kept in the system and at least in part be reused in the turbocharger .

[0204] The large combustion engine 200 may also comprise a purge system 270. The purge system 270 may provide for purging the fuel inj ection system 100 (not shown in this figure) , in particular for removing residual fuel from the leakage line 20 (see figure 2 ) .

[0205] The purge system 270 may comprise a high-pressure source (not shown in the figure) .

[0206] Nitrogen may be used as a purging gas, which is supplied to the leakage line 20 (see figure 2 ) in the fuel inj ector 1 and sucked off by the low-pressure source 30.

[0207] Figure 5 shows a vacuum ej ector as a low-pressure source 30 to generate a low-pressure in the leakage line . The low-pressure source 30 has a first inlet 31 for the leaked ammonia comprising fuel from the leakage line, for which a low pressure is to be created. The first inlet 31 at least partially encircles the second inlet 32. Furthermore, the outlet 33 comprises a diffuser 34. The second inlet 32 for compressed air comprises a nozzle 35 which accelerates the compressed air . The outlet 33 of the vacuum ej ector combines the leaked fuel from the first inlet 31 and the accelerated compressed air from the second inlet 32 such that in combination with the diffuser 34 a low-pressure is generated in the leakage line connected to the first inlet 31.Figure 6 shows a detail of a fuel inj ector 1. The fuel inj ector 1 comprises a purge line 271 fluidly connected or connectable with the nozzle tip 10, and a purge valve 272 for opening and closing the purge line 271. A purge fluid, in particular a purge gas, may be guided though the purge line when the purge valve 272 is open, to purge residual fuel out of the nozzle tip 10.

[0208] The purge valve is integrated in the inj ector body 3.

[0209] Typically, the purge gas is pressurized to approximately 30bar .

[0210] Residuals of fuel remaining close to the purge valve 272 may be guided away through the leakage line 20 which surrounds the purge valve 272. The leaked fuel may be sucked up with a low-pressure source 30 (see for example figure 5, not shown in this figure) , in particular when the purge valve 272 is closed.

[0211] Any embodiments described with respect to the device shall similarly pertain to the method and the computer program product . Synergetic effects may arise from different combinations of the embodiments although they might not be described in detail .

[0212] While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims .

Claims

Claims1 . A fuel inj ector ( 1 ) for inj ecting a fuel into a combustion chamber of a large combustion engine , the fuel inj ector ( 1 ) comprising a noz zle ( 2 ) and an inj ector body ( 3 ) defining an actuation chamber ( 5 ) and a pressure chamber ( 6 ) , wherein- an actuating piston ( 7 ) is disposed within the inj ector body ( 3 ) and movable therein, the actuating piston ( 7 ) having a first side ( 9 ) with a first cross-sectional area facing the actuation chamber ( 5 ) and a second side ( 8 ) with a second cross-sectional area facing the pressure chamber ( 6 ) , wherein a supply of an actuating fluid to the actuation chamber ( 5 ) moves the actuating piston ( 7 ) to pressuri ze the fuel in the pressure chamber ( 6 ) ;- the noz zle ( 2 ) comprising a noz zle tip ( 10 ) having a spray hole ( 11 ) , through which the fuel is inj ectable into the combustion chamber ( 211 ) , the noz zle ( 2 ) further comprising a high-pressure fuel duct ( 12 ) , through which the fuel can be guided from the pressure chamber ( 6 ) to the spray hole ( 11 ) ,characteri zed in thatat least one leakage line ( 20 ) is arranged in the inj ector body ( 3 ) ,the leakage line ( 20 ) being fluidly connected or connectable to a low-pressure source ( 30 ) , such that leaked fuel present in the leakage line ( 20 ) is guidable out of the in- j ector body ( 3 ) .2 . The fuel inj ector according to claim 1 , wherein the first cross-sectional area facing the actuation chamber ( 5 ) islarger than the second cross-sectional area facing the pressure chamber ( 6) .

3. The fuel inj ector according to any one of the preceding claims, wherein the leakage line (20) is connected or connectable to a fuel treatment system (40) and / or to a fuel supply system ( 17 ) and / or an SCR reactor for guiding at least a part of the leaked fuel thereto .

4. The fuel inj ector according to any one of the preceding claims, wherein the nozzle (2 ) comprises a double walled sleeve ( 18 ) .

5. The fuel inj ector according to any one of the preceding claims, wherein the leakage line (20) at least partially surrounds and is in contact with the actuating piston (7 ) .

6. The fuel inj ector according to claim 5, further comprising at least one of the group consisting of- at least one first sealing ring ( 19.1 ) arranged between the actuation chamber (5) and the leakage line (20) and at least partially surrounding and in contact with the actuating piston (7 ) and- at least one second sealing ring ( 19.2 ) arranged between the pressure chamber ( 6) and the leakage line (20) and at least partially surrounding and in contact with the actuating piston ( 7 ) .

7. The fuel inj ector according to any one of the preceding claims, wherein the fuel inj ector ( 1 ) comprises a purge line (271 ) fluidly connected or connectable with the nozzle tip ( 10) , and a purge valve (272 ) for opening and closing the purge line (271 ) .

8. The fuel inj ector according to claim 7, wherein the leakage line (20) at least partially surrounds and is in contact with the purge valve (272 ) .

9. A fuel inj ector, preferably according to any one of the preceding claims, for inj ecting a fuel into a combustion chamber of a large engine, the fuel inj ector comprising a nozzle ( 1 ) and a pressure amplifier (4 ) , the fuel inj ector further comprising an inj ector body defining an actuation chamber and a pressure chamber;the pressure amplifier (4 ) comprising an actuating piston disposed within the inj ector body and movable therein, the actuating piston having a first side with a first cross-sectional area facing the actuation chamber and a second side with a second cross-sectional area smaller than the first cross-sectional area facing the pressure chamber, wherein a supply of an actuating fluid to the actuation chamber moves the actuating piston to pressurize the fuel in the pressure chamber;the nozzle (2 ) comprising a valve needle biased by a spring toward a closed position against a valve seat, the valve needle configured to open and close a fluid connection between the pressure chamber and a nozzle tip of the fuel inj ector, the nozzle tip having a spray hole through which the fuel can be inj ected into the combustion chamber; wherein, when the pressure of the fuel in the pressure chamber exceeds a threshold sufficient to overcome the biasing force of the spring, the valve needle moves to an open position, allowing the fuel to be inj ected into the combustion chamber through the spray hole,characterized in thatthe fuel inj ector comprises a first sensor (50) for determining a first sensor signal indicative of a position and / or of a velocity of the actuating piston (7 ) .

10. The fuel inj ector of claim 9, wherein the first sensor (50) is selected from the group consisting of an inductive sensor, a capacitive sensor, an acoustic sensor, and an optical sensor .

11. The fuel inj ector of any one of the claims 9 to 10, wherein the actuating piston (7 ) comprises a marker (55) , preferably a set of grooves, and wherein the first sensor (50) is configured to determine the first sensor signal based on the marker (55) .

12. The fuel inj ector of any one of the claims 9 to 11 further comprising a second sensor (51 ) configured to determine a second sensor signal, in particular based on a marker (55) on the actuating piston (7 ) , preferably a set of grooves, and wherein the position and / or the velocity of the actuating piston is determined based on the first and the second sensor signal .

13. The fuel inj ector of any one of the claims 9 to 12, wherein the actuating piston comprises a cone-shaped portion and wherein the first sensor is configured to determine the sensor signal based on a distance between the sensor and the cone-shaped portion.14 . A pressure amplifier for a fuel inj ector ( 1 ) for a large combustion engine, in particular of any one of the preceding claims, the pressure amplifier comprising an amplifierbody (3) defining an actuation chamber (5) and a pressure chamber ( 6) , wherein- an actuating piston (7 ) is disposed within the amplifier body (3) and movable therein, the actuating piston (7 ) having a first side ( 9) with a first cross-sectional area facing the actuation chamber (5) and a second side ( 8 ) with a second cross-sectional area smaller than the first cross-sectional area facing the pressure chamber ( 6) , wherein a supply of an actuating fluid to the actuation chamber (5) moves the actuating piston (7 ) to pressurize the fuel in the pressure chamber ( 6) ;characterized in thatat least one leakage line (20) is arranged in the amplifier body (3) , which leakage line (20) at least partially surrounds and is in contact with the actuating piston (7 ) , the leakage line (20) being fluidly connected or connectable to a low-pressure source (30) , such that leaked fuel present in the leakage line (20) is guidable out of the amplifier body (3) .

15. A fuel inj ection system ( 100) comprising- at least one fuel inj ector ( 1 ) according to any one of the claims 1 to 13 and / or at least one pressure amplifier according to claim 14and- a low-pressure source (30) .

16. The fuel inj ection system ( 100) according to claim 15, wherein the low-pressure source (30) comprises at least one of the group consisting of a suction pump, a vacuum ej ector, and a vacuum compressor .

17. The fuel inj ection system ( 100) according to any one of the claims 15 to 16, comprising an outlet line ( 101 ) for fluidly connecting the leakage line (20) and the low-pressure source (30) , the outlet line ( 101 ) preferably being double walled, more preferably providing a low pressure between the walls .

18. The fuel inj ection system ( 100) according to any one of the claims 15 to 17 comprising a fuel treatment system (40) connected or connectable to the leakage line (20) .

19. The fuel inj ection system ( 100) according to claim 18, wherein the fuel treatment system (40) comprises water and / or an acid for absorbing at least a part of the leaked fuel .

20. The fuel inj ection system ( 100) according to any one of the claims 18 to 19, wherein the fuel treatment system (40) comprises a liquifying system, preferably comprising a cooling system for condensation of gaseous leaked fuel .

21. The fuel inj ection system ( 100) according to any one of the claims 18 to 20, wherein the fuel treatment system (40) comprises an incinerating system.

22. The fuel inj ection system ( 100) according to any one of the claims 18 to 21, wherein the fuel treatment system (40) comprises a catalyst (43, 44 ) .

23. A fuel inj ection system ( 100) , preferably according to any one of the claims 15 to 22, comprising a fuel inj ector of any one of the claims 9 to 13, and a control unit (260) configured to determine at least one of the group consist- ing ofa start of inj ection,an end of inj ection, and- a quantity of inj ected fuelbased on the position and / or based on the velocity of the actuating piston of the fuel inj ector .

24. The fuel inj ection system ( 100) according to any one of the claims 15 to 23, comprising a fuel supply system ( 17 ) , which is connected or connectable to a fuel supply line ( 16) .

25. A fuel treatment system (40) , preferably an ammonia treatment system (40) , preferably a fuel treatment system (40) for a fuel inj ection system ( 100) according to any one of the claims 15-24, for reducing an ammonia content of leaked fuel in a large combustion engine (200) , comprising- a leaked fuel inlet (41 ) ,- at least one ammonia slip catalyst (43) configured to oxidize leaked ammonia, and- at least one metal-zeolite catalyst (44 ) arranged downstream the ammonia slip catalyst (43) .

26. The fuel treatment system (40) according to claim 25 comprising a dilution gas inlet (42 ) for introducing a dilution gas, preferably exhaust gas, arranged upstream the ammonia slip catalyst, and in particular wherein an amount of dilution gas is controlled such that an outlet temperature downstream the metal-zeolite catalyst (44 ) is maintained in a predetermined range .

27. The fuel treatment system (40) according to claim 26, wherein the dilution gas inlet (41 ) is connected or connectable to an exhaust line of the large combustion engine (200) , preferably to an exhaust gas manifold (45) , preferably upstream a turbine of a turbocharger (240) .

28. The fuel treatment system (40) according to any one of the claims 25 to 27, comprising more than one catalyst combination (47 ) , each comprising an ammonia slip catalyst (43) and a metal-zeolite catalyst (44 ) , for a stepwise reduction of the ammonia content of the leaked fuel .

29. The fuel treatment system (40) according to any one of the claims 25 to 28, wherein at least one ammonia slip catalyst (43) and at least one metal-zeolite catalyst (44 ) are thermally coupled in such a way that oxidation heat produced in the ammonia slip catalyst (43) warms up the metal-zeolite catalyst ( 44 ) .

30. The fuel treatment system (40) according to any one of the claims 25 to 29, wherein the metal-zeolite catalyst (44 ) is a Fe-beta-zeolite-catalyst or a Cu-zeolite-catalyst .

31. The fuel treatment system (40) according to any one of the claims 25 to 30, wherein the fuel treatment system (40) is fluidly connected or connectable to a leakage line (20) of a fuel inj ector ( 1 ) according to any one of the claims 1 to 8 or to a pressure amplifier according to claim 14.

32. A large combustion engine (200) , in particular a longitudinally scavenged two-stroke large engine, comprising at least one cylinder (210) having a combustion chamber (211 ) , wherein a piston (220) is arranged in the cylinder (210) for a reciprocating movement between a top dead center position and a bottom dead center position, wherein the engine (200) comprises at least one of- at least one fuel inj ector ( 1 ) according to any one of the claims 1-13 and / or at least one pressure amplifier according to claim 14,- a fuel inj ection system ( 100) according to any one of the claims 15 to 24, and- a fuel treatment system (40) according to any one of the claims 25-31 .

33. A method for operating the large combustion engine of claim 32 comprising steps of- Creating, in particular by means of a vacuum ej ector, a pressure below atmospheric pressure, preferable a pressure lower than 0.8 bar, in the leakage line (20) , and- guiding leaked fuel out of the inj ector body (3) and / or out of the amplifier body.

34. The method of claim 33 comprising a step of- Guiding the leaked fuel into an exhaust gas stream of the large combustion engine;and / or- Guiding the leaked fuel into a scavenge air inlet upstream of a compressor of a turbocharger (240) ;and / or- Guiding the leaked fuel into a fuel inj ection system ( 100) , preferably according to any one of the claims 15 to 24 ;and / or- Guiding the leaked fuel into a fuel treatment system (40) , preferably according to any one of the claims 25- 31 .

35. A method for reducing the ammonia content of leaked fuel in a large combustion engine, preferably the large combustion engine of claim 32, comprising steps of(i) preferably diluting the leaked ammonia, preferably with exhaust gas,(ii) oxidizing ammonia and producing oxidation heat in an ammonia slip catalyst,(iii) preferably using the oxidation heat to warm up a metal zeolite catalyst, preferably to a temperature of equal or above 500°C,(iv) removing nitrous oxide as produced during the step of oxidization of ammonia in the metal zeolite catalyst,(v) preferably repeating at least steps (ii) and (iv) .

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