Fuel injector for first and second fuels, combustion engine and vehicle

Abstract

A fuel injector (1) configured to inject a first fuel and a second fuel into a combustion chamber (4) of an internal combustion engine (10) is disclosed. The fuel injector (1) comprises a nozzle portion (3) provided with a plurality of first fuel injection holes (h1) for injecting the first fuel into the combustion chamber (4), where the first fuel injection holes (h1) are circumferentially distributed on the nozzle portion (3) around a central axis (ax1) of the nozzle portion (3). The nozzle portion (3) is further provided with a second fuel injection hole (h2) for injecting the second fuel into the combustion chamber (4). The second fuel injection hole (h2) is configured to inject the second fuel in a main fuel injection direction (md) substantially coincident with the central axis (ax1) of the nozzle portion (3). The present disclosure also relates to an internal combustion engine (10) and a vehicle (2).

Description

Technical Field

[0001] The present disclosure relates to a fuel injector configured to inject two different fuels into a combustion chamber of an internal combustion engine. The present disclosure also relates to an internal combustion engine including the fuel injector and a vehicle including the internal combustion engine. Background Art

[0002] An internal combustion engine, such as a four-stroke internal combustion engine, includes one or more cylinders and pistons disposed in each cylinder. The pistons are connected to the crankshaft of the engine and are arranged to reciprocate within the cylinders as the crankshaft rotates. The engine typically also includes one or more intake valves and outlet valves and one or more fuel supply devices. The one or more intake valves and outlet valves are controlled by respective valve control devices, which typically include one or more camshafts rotatably connected to the crankshaft of the engine via a belt, chain, gear, or the like. A four-stroke internal combustion engine completes four separate strokes while rotating the crankshaft. A stroke refers to the full travel of the piston along the cylinder in either direction.

[0003] The strokes are completed in the following order: intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke of the piston within the cylinder in a traditional four-stroke internal combustion engine, the intake valve control device controls the intake valve of the cylinder to an open state to allow air or a mixture of air and fuel to enter the cylinder. During the compression stroke, all valves should be closed to allow compression of the air or the mixture of air and fuel in the cylinder. If the engine is in a power generation state, then typically near the end of the compression stroke, the fuel in the cylinder is ignited, for example, by a spark plug or by the compression heat in the cylinder.

[0004] The combustion of the fuel in the cylinder significantly increases the pressure and temperature within the cylinder. The combustion of the fuel typically continues through most of the subsequent expansion stroke. The increased pressure and temperature in the cylinder obtained by combustion are partially converted into mechanical work supplied to the crankshaft during the expansion stroke. The expansion stroke is also commonly referred to as the combustion stroke because typically most of the combustion occurs during the expansion stroke. During the subsequent exhaust stroke, the exhaust valve control device controls the exhaust valve of the cylinder to an open state to allow the exhaust gas to exit the cylinder into the exhaust system of the combustion engine.

[0005] A fuel injector is a device for supplying fuel to a combustion chamber of an internal combustion engine. Compression ignition engines such as diesel engines and some spark ignition engines such as Otto engines use fuel injectors configured to supply fuel to the combustion chamber. A gasoline engine having a fuel injector for supplying fuel to the combustion chamber is commonly referred to as a gasoline direct injection engine. In a diesel engine, the injected fuel is ignited by compression heat or by a glow plug. In an Otto engine, the injected fuel is ignited by the spark of a spark plug.

[0006] Fuel injectors configured to inject fuel into a combustion chamber of an internal combustion engine typically include a nozzle having a nozzle portion protruding into the combustion chamber. The nozzle portion typically includes a plurality of fuel injection holes for injecting fuel into the combustion chamber. In addition, the nozzle portion typically includes a valve seat and a needle, the valve seat being located at an inner surface of the nozzle portion, the needle being configured to interact with the valve seat to open and close a fluid connection between a fuel chamber of the fuel injector and the plurality of fuel injection holes.

[0007] Some fuel injectors have been developed that are capable of injecting two different fuels into a combustion chamber of an internal combustion engine. An example of an engine utilizing such a fuel injector is a dual-fuel engine configured to operate on a first fuel and a second fuel, where the second fuel has a lower research octane number than the first fuel.

[0008] The research octane number of a fuel indicates the ability of the fuel to withstand compression in a combustion chamber without knocking. In this context, the term "knocking" means autoignition, i.e., a type of spontaneous combustion caused by the compression heat and pressure in the combustion chamber. The higher the octane number, the greater the compression the fuel can withstand before knocking / ignition. In other words, a fuel with a high research octane number has a high ability to withstand compression before knocking / ignition, while a fuel with a low research octane number has a low ability to withstand compression before knocking / ignition.

[0009] As indicated above, in a compression ignition engine, it is desirable for the fuel to autoignite at the end of the compression stroke. Thus, in a compression ignition engine operating on a fuel with a high research octane number such as natural gas or hydrogen fuel, a fuel with a lower research octane number such as diesel can be injected into the cylinder, where the combustion of the fuel with the lower research octane number ignites the fuel with the higher research octane number.

[0010] A fuel injector for injecting two different fuels typically includes the same number of fuel injection holes for the two different fuels, where the fuel injection holes are arranged and oriented such that a pair of adjacent fuel flow formations are obtained in the combustion chamber. In this way, the combustion of the fuel in the fuel flow formation with the lower research octane number can ignite the fuel in the fuel flow formation with the higher research octane number.

[0011] Hydrogen fuel refers to hydrogen that can produce zero hydrocarbon emissions, provided that the hydrogen is produced in a process that does not involve fossil carbon. Some compression ignition engines have been developed that operate on both hydrogen fuel and diesel fuel, in which the diesel fuel is ignited and injected into the combustion chamber according to the fuel injector described above to ignite the hydrogen fuel. One problem with these types of engines is that a relatively large amount of diesel fuel is required to ignite the hydrogen fuel. Studies have shown that when using a fuel injector as described above, several percent of diesel fuel is required to ignite the hydrogen fuel.

[0012] If the hydrogen fuel is produced in a process that does not involve fossil carbon, then this relatively large amount of diesel fuel can be the sole contributing factor to the emission of fossil hydrocarbons from the engine. The same problem occurs in engines configured to operate on other types of fuels, such as a combination of natural gas and diesel, for example. This is because natural gas can provide a lower carbon footprint than diesel fuel.

[0013] Therefore, in an engine configured to operate on two different fuels, such as a first fuel with a higher research octane number and a second fuel with a lower research octane number, for environmental reasons, it may be desirable to minimize the injection of the second fuel. However, fuel injectors typically have mechanical and fluid limitations, which make it difficult to reduce the amount of the second fuel injected into the combustion chamber.

[0014] One possible way to reduce the amount of the second fuel injected into the combustion chamber could be to reduce the number of holes for the second fuel. However, such a solution risks impairing the ignition process of the first fuel, which may increase the emissions of unburned fuel from the engine and increase the fuel consumption of the engine. Another possible way to reduce the amount of the second fuel injected into the combustion chamber could be to provide fuel injection holes with a smaller cross-sectional area for the second fuel. However, the cross-sectional area of the fuel injection holes is limited by the manufacturing method, and it may be difficult to manufacture fuel injection holes with a small cross-sectional area. Summary of the Invention

[0015] The object of the present invention is to overcome or at least mitigate at least some of the above problems and disadvantages.

[0016] According to a first aspect of the present invention, the object is achieved by a fuel injector configured to inject a first fuel and a second fuel into a combustion chamber of an internal combustion engine, wherein the second fuel is different from the first fuel. The fuel injector includes a nozzle portion provided with a plurality of first fuel injection holes for injecting the first fuel into the combustion chamber, wherein the first fuel injection holes are circumferentially distributed on the nozzle portion around the central axis of the nozzle portion. The fuel injector further includes a second fuel injection hole for injecting the second fuel into the combustion chamber. The second fuel injection hole is configured to inject the second fuel in a main fuel injection direction substantially coincident with the central axis of the nozzle portion.

[0017] Since the second fuel injection hole is configured to inject the second fuel in a main fuel injection direction substantially coincident with the central axis of the nozzle portion, a fuel injector is provided in which the second fuel can be redirected by the top surface of the piston of the engine including the fuel injector. Thus, the second fuel can reach the portion of the combustion chamber into which the first fuel is injected. In other words, by being redirected by the top surface of the piston, the second fuel can be distributed to various parts of the combustion chamber to reach the fuel flow formation containing the first fuel, i.e., the fuel flow formation containing the first fuel, from the plurality of first fuel injection holes.

[0018] In this way, a smaller amount of the second fuel can be injected into the combustion chamber while ensuring contact between the fuel flow formations from the first fuel and the second fuel injection holes. In this way, the fuel injector can be used, for example, to inject a first fuel having a higher research octane number than the second fuel, wherein the combustion of the second fuel can effectively ignite the first fuel while reducing the consumption of the second fuel.

[0019] As a further result, a fuel injector is provided that is capable of reducing the total carbon footprint of an engine including the fuel injector.

[0020] Thus, a fuel injector is provided that overcomes or at least mitigates at least some of the above problems and disadvantages. Thus, the above object is achieved.

[0021] Optionally, the second fuel injection hole is configured such that the angle between the main fuel injection direction of the second fuel and the central axis of the nozzle portion is less than 15 degrees or less than 10 degrees. Thereby, it can be ensured that the fuel flow formation from the second fuel injection hole impinges on the piston top of the engine piston at an angle that provides for the second fuel to be evenly distributed to various parts of the combustion chamber. Thereby, it can be further ensured that the combustion of the second fuel ignites each fuel flow formation of the plurality of first fuel injection holes.

[0022] Optionally, the central axis of the nozzle portion extends through at least a part of the second fuel injection hole. Thereby, it can be ensured that the fuel flow formation from the second fuel injection hole is evenly distributed into various parts of the combustion chamber, such that the combustion of the second fuel ignites each fuel flow formation of the plurality of first fuel injection holes.

[0023] Optionally, the geometric centerline of the second fuel injection hole is parallel to the central axis of the nozzle portion. Thereby, it can be ensured that the fuel flow formation from the second fuel injection hole impacts the piston top of the engine piston at an angle, and the angle provides for the second fuel to be evenly distributed into various parts of the combustion chamber. Thereby, it can be further ensured that the combustion of the second fuel ignites each fuel flow formation of the plurality of first fuel injection holes.

[0024] Optionally, the fuel injector includes only one second fuel injection hole. Thereby, it can be ensured that only a small amount of the second fuel is required to ensure the combustion of the first fuel. As a further result, a fuel injector is provided that can further reduce the carbon footprint of an engine including the fuel injector.

[0025] Optionally, the plurality of first fuel injection holes includes at least three first fuel injection holes. Thereby, it can be ensured that the overall volume of the combustion chamber can be used for the effective combustion of the fuel.

[0026] Optionally, each of the plurality of first fuel injection holes is configured such that the angle between the main fuel injection direction of the first fuel and the central axis of the nozzle portion is greater than 30 degrees or greater than 50 degrees. Thereby, it can be ensured that the first fuel reaches various parts of the combustion chamber, while ensuring the ignition of the first fuel through the combustion of the second fuel.

[0027] Optionally, the fuel injector includes a fuel injector body, the fuel injector body including a first fuel chamber configured to accommodate the first fuel and a second fuel chamber configured to accommodate the second fuel, and wherein the fuel injector includes: a first needle seat; a first needle configured to interact with the first needle seat to open and close the fluid connection between the first fuel chamber and the plurality of first fuel injection holes; a second needle seat; and a second needle configured to interact with the second needle seat to open and close the fluid connection between the second fuel chamber and the second fuel injection hole. Thereby, a fuel injector is provided that has conditions for highly controllable injection of the first fuel and the second fuel.

[0028] Optionally, at least a part of the second needle is disposed inside the first needle. Thereby, a compact fuel injector can be provided that has conditions for highly controllable injection of the first fuel and the second fuel.

[0029] Optionally, at least a portion of the second fuel chamber is disposed inside the first needle. Thereby, a compact fuel injector can be provided that has conditions for highly controllable injection of the first fuel and the second fuel.

[0030] Optionally, the second fuel injection holes extend through a portion of the first needle. Thereby, a compact fuel injector can be provided that has conditions for highly controllable injection of the first fuel and the second fuel.

[0031] Optionally, the second needle seat is formed by the inner surface of the first needle. Thereby, a compact fuel injector can be provided that has conditions for highly controllable injection of the first fuel and the second fuel.

[0032] Optionally, the first and second needles are configured to open and close the respective fluid connections by moving in a direction parallel to the central axis of the nozzle portion. Thereby, highly controllable injection of the first fuel and the second fuel can be ensured while providing conditions for a compact fuel injector.

[0033] According to a second aspect of the present invention, the object is achieved by an internal combustion engine comprising a cylinder, a piston disposed in the cylinder and arranged to reciprocate along the cylinder axis of the cylinder, a combustion chamber formed between the wall of the cylinder and the piston top of the piston, and a fuel injector according to some embodiments of the present disclosure. The fuel injector is configured to inject a first fuel and a second fuel into the combustion chamber.

[0034] Since the internal combustion engine includes a fuel injector configured to inject a first fuel and a second fuel into the combustion chamber of the internal combustion engine according to some embodiments, an internal combustion engine is provided that has conditions for using a smaller amount of the second fuel while ensuring contact between the fuel flow formations from the first fuel and second fuel injection holes. This is because the second fuel injected from the second fuel injection holes can be redirected by the piston top of the piston into various parts of the combustion chamber, thereby reaching the fuel flow formations of a plurality of first fuel injection holes.

[0035] Thus, in this way, the internal combustion engine can be configured to operate on a first fuel having a higher research octane number than the second fuel, where the combustion of the second fuel can effectively ignite the first fuel while reducing the consumption of the second fuel. Accordingly, an internal combustion engine is provided that has conditions for reducing the total carbon footprint.

[0036] Accordingly, an internal combustion engine is provided that overcomes or at least mitigates at least some of the above problems and disadvantages. Thus, the above object is achieved.

[0037] Optionally, the angle between the main fuel injection direction of the second fuel and the cylinder axis of the cylinder is less than 15 degrees or less than 10 degrees. Thereby, it can be ensured that the fuel stream formation from the second fuel injection holes impacts the piston top of the engine piston at an angle that provides for the second fuel to be evenly distributed to various parts of the combustion chamber. Thereby, it can further be ensured that the combustion of the second fuel ignites each fuel stream formation of the plurality of first fuel injection holes.

[0038] Optionally, the central axis of the nozzle portion is parallel to the cylinder axis of the cylinder. Thereby, it can be ensured that the fuel stream formation from the second fuel injection holes impacts the piston top of the engine piston at an angle that provides for the second fuel to be evenly distributed to various parts of the combustion chamber. Thereby, it can further be ensured that the combustion of the second fuel ignites each fuel stream formation of the plurality of first fuel injection holes.

[0039] Optionally, the central axis of the nozzle portion coincides with the cylinder axis of the cylinder. Thereby, it can be ensured that the fuel stream formation from the second fuel injection holes impacts the piston top of the engine piston at an angle that provides for the second fuel to be evenly distributed to various parts of the combustion chamber. Thereby, it can further be ensured that the combustion of the second fuel ignites each fuel stream formation of the plurality of first fuel injection holes.

[0040] Optionally, the piston top includes a piston bowl and a protrusion protruding from the bottom surface of the piston bowl, and wherein the protrusion includes a fuel impact surface facing the fuel injector. Thereby, it can further be ensured that the second fuel is distributed to various parts of the combustion chamber in an effective manner, thereby igniting each fuel stream formation of the plurality of first fuel injection holes.

[0041] Optionally, the fuel impact surface is substantially flat. Thereby, it can provide for the second fuel to be evenly distributed to various parts of the combustion chamber of the internal combustion engine.

[0042] Optionally, the fuel impact surface is convex. Thereby, it can be ensured that the second fuel redirected by the fuel impact surface reaches the radially outer portions of the fuel stream formations of the plurality of first fuel injection holes.

[0043] Optionally, the fuel impact surface is concave. Thereby, it can be ensured that the second fuel redirected by the fuel impact surface reaches the radially inner portions of the fuel stream formations of the plurality of first fuel injection holes.

[0044] Optionally, the fuel impingement surface includes a first portion located at the radial center of the fuel impingement surface and a second portion surrounding the first portion, and wherein the first portion is convex and the second portion is concave. Thereby, the fuel in the radially inner portion of the fuel flow formation of the second fuel injection hole impinging on the first portion of the fuel impingement surface can be guided in a more radial direction, and the fuel in the radially outer portion of the fuel flow formation of the second fuel injection hole impinging on the second portion can be guided in a more axial direction toward the cylinder head of the cylinder. In this way, it is further ensured that the combustion of the second fuel ignites all the fuel flow formations of the plurality of first fuel injection holes.

[0045] Optionally, the fuel impingement surface is patterned. Thereby, an internal combustion engine is provided in which the reflection and direction of the second fuel can be controlled by the design of the pattern of the fuel impingement surface. In this way, it is further ensured that the redirected second fuel can reach all the fuel flow formations of the plurality of first fuel injection holes in an effective manner.

[0046] Optionally, the internal combustion engine is a compression ignition engine. Thereby, the internal combustion engine can be configured to operate on a first fuel having a higher research octane number than the second fuel, wherein the second fuel is ignited by a compression hot spot in the combustion chamber to thereby ignite the first fuel. Since the second fuel injection holes are configured to inject the second fuel in a main fuel injection direction that is substantially coincident with the central axis of the nozzle portion, conditions are provided for reducing the consumption of the second fuel while ensuring the combustion of the first fuel.

[0047] Optionally, the first fuel has a higher research octane number than the second fuel. Thereby, the second fuel can be ignited, for example, by a compression hot spot in the combustion chamber to thereby ignite the first fuel. Since the second fuel injection holes are configured to inject the second fuel in a main fuel injection direction that is substantially coincident with the central axis of the nozzle portion, conditions are provided for reducing the consumption of the second fuel while ensuring the combustion of the first fuel.

[0048] Optionally, the first fuel has a research octane number higher than 50, and wherein the second fuel has a research octane number lower than 50. Thereby, the second fuel can be ignited, for example, by a compression hot spot in the combustion chamber to thereby ignite the first fuel. Since the second fuel injection holes are configured to inject the second fuel in a main fuel injection direction that is substantially coincident with the central axis of the nozzle portion, conditions are provided for reducing the consumption of the second fuel while ensuring the combustion of the first fuel.

[0049] Optionally, the first fuel is a gaseous fuel and the second fuel is a liquid fuel. Thereby, a dual fuel engine is provided that has conditions for effectively igniting the gaseous fuel while using only a small amount of liquid fuel. As a further result, a dual fuel engine is provided that has conditions for reducing the carbon footprint.

[0050] Optionally, the first fuel comprises hydrogen and / or natural gas, and wherein the second fuel comprises diesel and / or diesel-like fuel. Thereby, a dual-fuel engine is provided that has the condition to ignite hydrogen and / or natural gas in an efficient manner while using only a small amount of diesel and / or diesel-like fuel. As a further result, a dual-fuel engine is provided that has the condition to reduce the carbon footprint.

[0051] According to a third aspect of the present invention, the object is achieved by a vehicle comprising an internal combustion engine according to some embodiments of the present disclosure. Since the vehicle comprises an internal combustion engine according to some embodiments, a vehicle is provided that overcomes or at least mitigates at least some of the above problems and disadvantages. Thus, the above object is achieved.

[0052] Further features and advantages of the present invention will become apparent when studying the appended claims and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Various aspects of the present invention, including its particular features and advantages, will be readily understood from the following detailed description and the example embodiments discussed in the drawings, wherein:

[0054] Figure 1 A vehicle according to some embodiments is schematically shown,

[0055] Figure 2 is schematically shown Figure 1 the internal combustion engine of the vehicle shown in

[0056] Figure 3 shows Figure 1 and Figure 2 a perspective view of the piston of the internal combustion engine shown in

[0057] Figure 4 is schematically shown Figure 1 and Figure 2 a part of the internal combustion engine shown in

[0058] Figure 5 is schematically shown Figure 1 , Figure 2 and Figure 4 the fuel flow formations of the first fuel and the fuel flow formations of the second fuel in the combustion chamber of the internal combustion engine shown in

[0059] Figure 6 is schematically shown Figure 4 a cross-section of a part of the internal combustion engine shown in

[0060] Figure 7Schematically shows a part of an internal combustion engine according to some additional embodiments.

[0061] Figure 8 Schematically shows a part of an internal combustion engine according to some additional embodiments, and

[0062] Figure 9 Schematically shows a part of an internal combustion engine according to some additional embodiments. Detailed Description

[0063] Aspects of the present invention will now be described more fully. Like reference numerals always refer to like elements. For brevity and / or clarity, well-known functions or constructions will not be described in detail.

[0064] Figure 1 Schematically shows a vehicle 2 according to some embodiments. According to the illustrated embodiment, the vehicle 2 is a truck, i.e., a type of heavy vehicle. According to additional embodiments, the vehicle 2 as referred to herein can be another type of heavy or lighter type of manned or unmanned vehicle for land-based or water-based propulsion, such as a freight truck, a bus, a construction vehicle, a tractor, an automobile, a ship, a boat, etc.

[0065] The vehicle 2 includes an internal combustion engine 10. According to the illustrated embodiment, the internal combustion engine 10 is configured to provide motive power to the vehicle 2 via the wheels 47 of the vehicle 2.

[0066] The vehicle 2 includes a first fuel tank t1 configured to store a first fuel and a second fuel tank t2 configured to store a second fuel, where the second fuel is different from the first fuel. As further explained herein, the internal combustion engine 10 of the vehicle 2 is a so-called dual-fuel engine configured to operate on each of the first fuel and the second fuel.

[0067] In addition to the internal combustion engine 10, the vehicle 2 may further include one or more electric propulsion motors for providing motive power to the vehicle 2. Thus, the vehicle 2 as referred to herein may include a so-called hybrid electric powertrain that includes one or more electric propulsion motors in addition to the combustion engine 10 for providing motive power to the vehicle 2.

[0068] Figure 2 Schematically shows Figure 1 the internal combustion engine 10 of the vehicle 2 shown in. For reasons of brevity and clarity, the internal combustion engine 10 is referred to herein in some places as the "combustion engine 10" or simply as the "engine 10". In the following, if not otherwise indicated, reference is made simultaneously to Figure 1 and Figure 2 .

[0069] According to the illustrated embodiment, the internal combustion engine 10 includes six cylinders 7 arranged in a row. Thus, the internal combustion engine 10 according to the illustrated embodiment can be referred to as an in-line six-cylinder engine. However, according to additional embodiments, the internal combustion engine 10 as mentioned herein can include another number of cylinders 7. In addition, the cylinders 7 of the internal combustion engine 10 can be arranged in another configuration different from a row, for example, arranged in two rows or more rows.

[0070] The internal combustion engine 10 includes pistons 5 arranged in each cylinder 7, wherein the pistons 5 are connected to the crankshaft of the internal combustion engine 10. The pistons 5 are configured to reciprocate within the cylinders 7 when the crankshaft rotates. A combustion chamber 4 is formed between the piston top of each piston 5 and the cylinder wall of the cylinder 7 of the internal combustion engine 10. For reasons of simplicity and clarity, only one piston 5 of one cylinder 7 and the combustion chamber 4 of this cylinder 7 are schematically indicated in Figure 2 . However, as explained above, the internal combustion engine 10 includes one piston 5 arranged in each cylinder 7, and the combustion chamber 4 is formed between the piston top of each piston 5 and the cylinder wall of the cylinder 7 of the internal combustion engine 10.

[0071] The internal combustion engine 10 includes a plurality of fuel injectors 1, wherein each fuel injector 1 is configured to inject a first fuel and a second fuel into the combustion chamber 4 of the internal combustion engine 10. According to the illustrated embodiment, the internal combustion engine 10 includes the same number of fuel injectors 1 as the number of cylinders 7. In addition, according to the illustrated embodiment, each fuel injector 1 is configured to directly inject the first fuel and the second fuel into the combustion chamber 4 of the internal combustion engine 10.

[0072] According to the illustrated embodiment, the internal combustion engine 10 is a four-stroke compression-ignition engine 10. As understood from the above, according to the illustrated embodiment, the engine 10 is configured to provide motive power to a vehicle including the engine 10. However, according to additional embodiments, the engine 10 as mentioned herein can be configured to provide power to another type of unit, device, or system (e.g., a generator) other than a vehicle.

[0073] Figure 3 Is shown Figure 1 And Figure 2 A perspective view of the piston 5 of the internal combustion engine 10 shown in. In the following, if not otherwise indicated, reference is made simultaneously to Figures 1 - 3 . The piston 5 is configured to reciprocate along the cylinder axis of the cylinder 7 of the engine 10. The piston 5 includes a central axis ax3. When the piston 5 is arranged in the cylinder 7, the central axis ax3 of the piston 5 coincides with the cylinder axis of the cylinder 7.

[0074] The piston 5 includes a piston top 5'. When the piston 5 is disposed in the cylinder 7, the piston top 5' faces the cylinder head of the cylinder 7. Further, when the piston 5 is disposed in the cylinder 7, the piston top 5' faces the fuel injector 1 of the cylinder. According to the illustrated embodiment, the piston top 5' includes a piston bowl 31 and a protrusion 33 protruding from the bottom surface 31' of the piston bowl 31. The protrusion 33 includes a fuel impact surface 35 which faces the fuel injector 1 when the piston 5 is disposed in the cylinder 7. The features, functions and advantages of the fuel impact surface 35 are further explained below.

[0075] Figure 4 is schematically shown Figure 1 and Figure 2 a part of the internal combustion engine 10 shown in. In Figure 4 a part of the piston 5 can be seen. The piston 5 is a piston according to the embodiment shown in Figure 3 . The piston 5 is disposed in the cylinder such that the central axis ax3 of the piston 5 coincides with the cylinder axis ax2 of the cylinder. Further, in Figure 4 the cylinder wall 7' of the cylinder is indicated. In Figure 4 the cylinder wall 7' of the cylinder is the inner wall of the cylinder head of the cylinder. A combustion chamber 4 is formed between the wall 7' of the cylinder and the piston top 5' of the piston 5.

[0076] The cylinder head of the cylinder may include a plurality of inlet valves and a plurality of outlet valves, wherein the plurality of inlet valves may be arranged to control the air flow into the combustion chamber 4, and wherein the plurality of outlet valves may be configured to control the gas flow out of the combustion chamber 4. The plurality of outlet valves may also be referred to as a plurality of exhaust valves. For reasons of simplicity and clarity, Figure 4 these types of valves are not shown in.

[0077] Further, Figure 4 the fuel injector 1 is schematically shown. The fuel injector 1 is attached to the cylinder head of the cylinder and includes a nozzle portion 3. The nozzle portion 3 of the fuel injector 1 protrudes into the combustion chamber 4.

[0078] The fuel injector 1 is configured to inject a first fuel and a second fuel into the combustion chamber 4. More specifically, the nozzle portion 3 of the fuel injector 1 is provided with a plurality of first fuel injection holes h1 for injecting the first fuel into the combustion chamber 4. As can be seen in Figure 4 the first fuel injection holes h1 among the plurality of first fuel injection holes h1 are circumferentially distributed on the nozzle portion 3 around the central axis ax1 of the nozzle portion 3.

[0079] The nozzle portion 3 of the fuel injector 1 is also provided with second fuel injection holes h2 for injecting the second fuel into the combustion chamber 4. In Figure 4In [the figure], the control section 1' of the fuel injector 1 is schematically indicated by a box. As further explained herein, the control section 1' of the fuel injector 1 may include connections for the respective first fuel and second fuel, and may include hydraulic, electrical, and / or pneumatic control arrangements for controlling the injection of the respective first fuel and second fuel into the combustion chamber 4.

[0080] In addition, a vehicle including the fuel injector 1, such as Figure 1 the vehicle 2 shown in [the figure], may include a first fuel supply system configured to supply the first fuel from a first fuel tank t1 to the fuel injector 1, and a second fuel supply system for supplying the second fuel from a second fuel tank t2 to the fuel injector 1.

[0081] According to the illustrated embodiment, the first fuel is a gaseous fuel and the second fuel is a liquid fuel. According to further embodiments, each of the first fuel and the second fuel may be a liquid fuel. In addition, according to some further embodiments, each of the first fuel and the second fuel may be a gaseous fuel. Moreover, according to some embodiments, the first fuel as mentioned herein may be a liquid fuel and the second fuel may be a gaseous fuel.

[0082] The gaseous fuel may include hydrogen, natural gas, biogas, methane, propane, butane, and / or mixtures thereof. The liquid fuel may include diesel or diesel-like fuels such as biodiesel, biomass-to-liquid (BTL), or gas-to-liquid (GTL) diesel. Diesel-like fuels (such as biodiesel) may be obtained from renewable resources such as vegetable oils mainly including fatty acid methyl esters (FAME). Diesel-like fuels may be produced from many types of oils (such as rapeseed oil (rapeseed methyl ester, RME) and soybean oil (soybean methyl ester, SME)). As an alternative or in addition, the liquid fuel may include gasoline, alcohols such as ethanol or methanol, volatile fuel-like substances, or combinations thereof. Alcohols such as ethanol or methanol may be derived from renewable biomass.

[0083] According to embodiments herein, the first fuel has a higher Research Octane Number (RON) than the second fuel. According to some embodiments, the first fuel has a RON higher than 50 and the second fuel has a RON lower than 50. The Research Octane Number of a fuel indicates the ability of the fuel to withstand compression in the combustion chamber 4 without ignition. The term "Research Octane Number" is sometimes abbreviated as "RON". The higher the RON, the greater the compression the fuel can withstand before ignition. In other words, a fuel with a high RON has a high ability to withstand compression before ignition, while a fuel with a low RON has a low ability to withstand compression before ignition. Diesel and diesel-like fuels typically have a RON of about 15 - 25. Hydrogen fuel typically has a RON of over 130. Methane, which is the main component of natural gas, has a RON of about 120.

[0084] As Figure 4 seen, the second fuel injection hole h2 is configured to inject the second fuel in a main fuel injection direction md that substantially coincides with the central axis ax1 of the nozzle portion 3. The fuel injector 1 can be controlled to inject the second fuel when the piston 5 of the cylinder is in the region of top dead center. In this way, the second fuel can be redirected by the top surface of the piston 5 (e.g., the fuel impact surface 35 of the projection 33 of the piston 5) to be distributed to various parts of the combustion chamber 4, and thus reach the fuel flow formation, i.e., the fuel flow formation containing the first fuel, from the plurality of first fuel injection holes h1.

[0085] Figure 5 Schematically shown are Figure 4 the fuel flow formation s1 of the first fuel and the fuel flow formation s2 of the second fuel in the combustion chamber 4 as shown. In Figure 5 it, as seen in the direction coinciding with the cylinder axis ax2 of the cylinder, the fuel flow formations s1, s2 are shown. In addition, in Figure 5 it, the fuel injector 1 and the fuel impact surface 35 are schematically indicated.

[0086] As mentioned, according to the illustrated embodiments, the engine is a compression ignition engine and the second fuel has a lower Research Octane Number than the second fuel. In addition, the engine is configured such that the second fuel is ignited by a compression hot spot generated during the compression stage of the cylinder. Therefore, the fuel flow formation s2 of the second fuel redirected by the fuel impact surface 35 will be ignited by the compression hot spot generated during the compression stage of the cylinder.

[0087] Therefore, Figure 5The dashed circle denoted by reference numeral s2 in FIG. 1 can be said to represent the combustion flame of the second fuel. Since the second fuel is redirected to reach the fuel flow formation s1 of the first fuel, the fuel flow formation s1 of the first fuel can be ignited at least substantially simultaneously by the combustion flame of the second fuel.

[0088] In this way, a smaller amount of the second fuel can be injected into the combustion chamber 4 while ensuring the ignition of the fuel flow formation s1 of the first fuel. That is, the prior art fuel injectors for injecting two different fuels into the combustion chamber usually include the same number of fuel injection holes for the two different fuels, wherein the fuel injection holes are arranged and oriented so that a pair of adjacent fuel flow formations are obtained in the combustion chamber. In this way, the combustion of the fuel of the fuel flow formation with a lower research octane number can ignite the fuel of the fuel flow formation with a higher research octane number. However, such fuel injectors need to inject a relatively large amount of fuel with a lower research octane number in order to ensure the ignition of all fuel flow formations of the other fuel.

[0089] Therefore, since the nozzle part of the fuel injector 1 according to the embodiment of the present invention is provided with a second fuel injection hole, and the second fuel injection hole is configured to inject the second fuel in the main fuel injection direction substantially coinciding with the central axis of the nozzle part, the second fuel can be redirected by a part of the piston (for example, the fuel impact surface 35 of the piston), thereby using a small amount of the second fuel to ignite the first fuel.

[0090] Figure 6 Schematically shows Figure 4 A cross section of a portion of an internal combustion engine is shown in FIG. Figure 4 Similar to Figure 6 A portion of the piston 5 can be seen in Figure 4 and Figure 6 In the figure, the piston is shown in the region of top dead center. Figure 4 Similar to Figure 6 The cylinder wall 7' of the cylinder is schematically indicated in FIG. Figure 4 Similar to Figure 6 The fuel injector 1 can be seen in Figure 6 In FIG. 1 , a fuel injector 1 is shown in cross section. Figure 6 The cross section is taken in a plane including the cylinder axis ax2 of the cylinder.

[0091] According to the illustrated embodiment, the fuel injector 1 is attached to the cylinder of the engine so that the center axis ax1 of the nozzle portion 3 is parallel to the cylinder axis ax2 of the cylinder 7. In addition, according to the illustrated embodiment, the fuel injector 1 is attached to the cylinder of the engine so that the center axis ax1 of the nozzle portion 3 coincides with the cylinder axis ax2 of the cylinder 7.

[0092] In Figure 6 it can be seen that two of the first fuel injection holes h1 among the second fuel injection hole h2 and the plurality of first fuel injection holes h1. According to the illustrated embodiment, the plurality of first fuel injection holes h1 includes eight first fuel injection holes h1. However, according to another embodiment, the plurality of first fuel injection holes h1 may include another number of first fuel injection holes h1, such as 3 - 25 first fuel injection holes h1 or 3 - 16 first fuel injection holes h1.

[0093] Furthermore, according to the illustrated embodiment, the fuel injector 1 includes only one second fuel injection hole h2. However, according to another embodiment, the fuel injector 1 may include two or more adjacent second fuel injection holes.

[0094] According to the illustrated embodiment, the second fuel injection hole h2 is configured to inject the second fuel in a main fuel injection direction md that coincides with the central axis ax1 of the nozzle portion 3. In other words, according to the illustrated embodiment, the second fuel injection hole h2 is configured such that the angle between the main fuel injection direction md of the second fuel and the central axis ax1 of the nozzle portion 3 is zero degrees.

[0095] According to another embodiment, the second fuel injection hole h2 may be configured to inject the second fuel in a main fuel injection direction md that substantially coincides with the central axis ax1 of the nozzle portion 3. The feature that the main fuel injection direction md substantially coincides with the central axis ax1 of the nozzle portion 3 may cover an angle between the main fuel injection direction md of the second fuel and the central axis ax1 of the nozzle portion 3 that is less than 15 degrees or less than 10 degrees. In other words, the second fuel injection hole h2 may be configured such that the angle between the main fuel injection direction md of the second fuel and the central axis ax1 of the nozzle portion 3 is less than 15 degrees or less than 10 degrees. Furthermore, the fuel injector 1 may be attached to a cylinder of an internal combustion engine such that the angle between the main fuel injection direction md of the second fuel and the cylinder axis ax2 of the cylinder is less than 15 degrees or less than 10 degrees.

[0096] As Figure 6 seen, the central axis ax1 of the nozzle portion 3 extends through the second fuel injection hole h2. Furthermore, according to the illustrated embodiment, the geometric centerline Cl of the second fuel injection hole h2 coincides with the central axis ax1 of the nozzle portion 3. In other words, according to the illustrated embodiment, the geometric centerline Cl of the second fuel injection hole h2 is parallel to the central axis ax1 of the nozzle portion 3.

[0097] The geometric centerline Cl of the second fuel injection hole h2 is a line positioned such that the radial distance from the line to the inner bounding surface of the second fuel injection hole h2 is maximized in all radial directions. The main fuel injection direction md of the second fuel coincides with the geometric centerline Cl of the second fuel injection hole h2. The main fuel injection direction md as referred to herein may also be referred to as the average fuel injection direction of the fuel.

[0098] In addition, in Figure 6 it indicates the respective centerlines Cl' of the two first fuel injection holes h1. Similar to the above, the geometric centerline Cl' of the first fuel injection hole h1 is a line positioned such that the radial distance from the line of the first fuel injection hole h1 to the inner bounding surface is maximized in all radial directions. The main fuel injection direction md' of the first fuel from the first fuel injection hole h1 coincides with the geometric centerline Cl' of the first fuel injection hole h1.

[0099] According to the illustrated embodiment, each of the plurality of first fuel injection holes h1 is configured such that the angle between the main fuel injection direction md' of the first fuel and the central axis ax1 of the nozzle portion 3 is approximately 80 degrees. According to a further embodiment, each of the plurality of first fuel injection holes h1 may be configured such that the angle between the main fuel injection direction md' of the first fuel and the central axis ax1 of the nozzle portion 3 is greater than 30 degrees or greater than 50 degrees. Additionally, according to some embodiments, each of the plurality of first fuel injection holes h1 may be configured such that the angle between the main fuel injection direction md' of the first fuel and the central axis ax1 of the nozzle portion 3 is in the range of 30 - 130 degrees, or in the range of 50 - 110 degrees.

[0100] According to the illustrated embodiment, the second fuel injection hole h2 has a much smaller diameter than each of the plurality of first fuel injection holes h1. By way of example only, each of the plurality of first fuel injection holes h1 may have a diameter in the range of 0.2 - 1 mm or in the range of 0.5 - 0.8 mm. Additionally, the second fuel injection hole h2 may have a diameter in the range of 0.07 - 0.18 mm or in the range of 0.07 - 0.13 mm. Furthermore, according to some embodiments, each of the plurality of first fuel injection holes h1 may have a diameter that is at least twice the diameter of the second fuel injection hole h2. The diameters of the fuel injection holes h1, h2 may be measured in a plane perpendicular to the geometric centerlines Cl, Cl' of the fuel injection holes h1, h2.

[0101] In the following, some structural parts of the fuel injector 1 are explained. The fuel injector 1 includes a fuel injector body 6, and the fuel injector body includes a first fuel chamber 11 and a second fuel chamber 12. The first fuel chamber 11 is configured to accommodate a first fuel, and the second fuel chamber 12 is configured to accommodate a second fuel. An engine including the fuel injector 1 may include a first fuel supply system configured to supply the first fuel to the first fuel chamber 11, and may include a second fuel supply system configured to supply the second fuel to the second fuel chamber 12.

[0102] Also in Figure 6 it, the control portion 1' of the fuel injector 1 is schematically indicated by a box. The control portion 1' of the fuel injector 1 may include a first connection connected to the first fuel chamber 11 and a second connection connected to the second fuel chamber 12. One or both of the first fuel supply system and the second fuel supply system may be configured to supply pressurized fuel to the respective first connection and second connection, that is, to the respective first fuel chamber 11 and second fuel chamber 12.

[0103] The fuel injector 1 includes a first needle seat 15 and a first needle 17, and the first needle is configured to interact with the first needle seat 15 to open and close the fluid connection between the first fuel chamber 11 and a plurality of first fuel injection holes h1. According to the illustrated embodiment, the fuel injector 1 includes an outer sleeve-shaped portion 24, and the first needle seat 15 is provided on a part of the outer sleeve-shaped portion 24. In addition, according to the illustrated embodiment, a plurality of first fuel injection holes h1 are provided in the outer sleeve-shaped portion 24 and extend through the outer sleeve-shaped portion.

[0104] The fuel injector 1 further includes a second needle seat 20 and a second needle 23, and the second needle is configured to interact with the second needle seat 20 to open and close the fluid connection between the second fuel chamber 12 and the second fuel injection hole h2. As Figure 6 can be seen, according to the illustrated embodiment, the second needle seat 20 is formed by the inner surface of the first needle 17. In addition, according to the illustrated embodiment, the second fuel injection hole h2 is provided in a part of the first needle 17 and extends through the part.

[0105] As Figure 6 can be seen, according to the illustrated embodiment, at least a part of the second needle 23 is disposed inside the first needle 17. In addition, at least a part of the second fuel chamber 12 is disposed inside the first needle 17. According to the illustrated embodiment, the first needle 17 and the second needle 23 are configured to open and close the respective fluid connections by moving in directions d1, d2 parallel to the central axis ax1 of the nozzle portion 3.

[0106] More specifically, the first needle 17 is movably arranged relative to the fuel injector body 6 between a closed position and an open position. In the closed position, a part of the first needle 17 abuts against the first needle seat 15 to close the fluid connection between the first fuel chamber 11 and the plurality of first fuel injection holes h1. In the open position, the said part of the first needle 17 is lifted from the first needle seat 15 to open the fluid connection between the first fuel chamber 11 and the plurality of first fuel injection holes h1. In Figure 6 , the first needle 17 is shown in the closed position and is movably arranged from the closed position in the direction d2 shown in Figure 6 .

[0107] Similarly, the second needle 23 is movably arranged relative to the fuel injector body 6 between a closed position and an open position. In the closed position, a part of the second needle 23 abuts against the second needle seat 20 to close the fluid connection between the second fuel chamber 12 and the second fuel injection hole h2. In the open position, the said part of the second needle 23 is lifted from the second needle seat 20 to open the fluid connection between the second fuel chamber 12 and the second fuel injection hole h2. In Figure 6 , the second needle 13 is shown in the closed position and is movably arranged from the closed position in the direction d2 shown in Figure 6 .

[0108] The control part 1' of the fuel injector 1 may include hydraulic, electrical and / or pneumatic control means for moving the first needle 17 and the second needle 23 between the open position and the closed position. Since the second needle 23 is arranged inside the first needle 17 and since the second needle seat 20 is formed by the inner surface of the first needle 17, the second needle 23 moves towards the open position by moving relative to the first needle 17 in the direction d2. Similarly, the second needle 23 moves towards the closed position by moving relative to the first needle 17 in the direction d1. Furthermore, as understood from the above, when the first needle 17 moves towards the open position, the first needle 17 and the second needle 23 move in unison in the direction d2.

[0109] According to some embodiments, in the injection program of the fuel injector 1, the second needle 23 moves towards the open position before the first needle 17. Thus, before the first fuel, the second fuel is injected into the combustion chamber 4 in the first main fuel injection direction md indicated in Figure 6 .

[0110] In Figure 4 , the dashed arrow r2 schematically indicates that the radially outer part of the fuel flow formation of the second fuel from the second fuel injection hole h2 is reflected on the fuel impact surface 35. Since the engine 10 is a compression ignition engine and since the second fuel has a relatively low research octane number according to the illustrated embodiment, the second fuel is ignited by the compression heat in the combustion chamber 4.

[0111] According to some embodiments, the first needle 17 may move towards the open position after the second fuel is ignited. When the first needle 17 moves to the open position, the first fuel is injected into the combustion chamber 4. In Figure 4 , the dashed arrow r1 indicates the radially outer portion of the fuel flow formation of the first fuel from the first fuel injection hole h1. As Figure 4 can be seen, the second fuel is redirected by the fuel impact surface 35 such that the second fuel reaches the first fuel in the combustion chamber 4. In this way, the combustion of the second fuel can ignite the first fuel in an efficient manner.

[0112] The second needle 23 may move to the closed position before moving the first needle 17 to the open position. In other words, the fuel injection of the second fuel may be stopped before the injection of the first fuel begins. The fuel injection of the second fuel may also be referred to as the pilot fuel injection of the second fuel.

[0113] According to some embodiments, the control portion 1' of the fuel injector 1 may be configured to move the second needle 23 between the open position and the closed position using the hydraulic pressure of the second fuel. Similarly, the control portion 1' of the fuel injector 1 may be configured to move the first needle 17 between the open position and the closed position using the hydraulic pressure of the second fuel. The second fuel supply system mentioned above may be a so-called common rail fuel supply system configured to supply the second fuel to the second fuel chamber 12 at a high fuel pressure, for example, a fuel pressure exceeding 50 bar.

[0114] As Figure 4 can be seen, according to the illustrated embodiment, the fuel injector 1 and the protrusion 33 are configured such that the fuel flow formation of the first fuel is not redirected by the fuel impact surface 35. One reason for this is that the protrusion 33 including its fuel impact surface 35 is relatively narrow. In this way, it can be ensured that the second fuel is redirected by the fuel impact surface 35 while the first fuel is not redirected by the fuel impact surface 35. According to the illustrated embodiment, as measured in a plane perpendicular to the central axis ax3 of the piston 5, the diameter of the fuel impact surface 35 is approximately 12 mm. However, as measured in a plane perpendicular to the central axis ax3 of the piston 5, the diameter of the fuel impact surface 35 may be in the range of 6 - 25 mm, or may be in the range of 8 - 16 mm.

[0115] Furthermore, according to some additional embodiments, the piston 5 may include a relatively large protrusion 33 having a relatively large fuel impact surface 35. According to such embodiments and other embodiments herein, the fuel injector 1 and the protrusion 33 may be configured such that the fuel flow formation of each of the first fuel and the second fuel is redirected by the fuel impact surface 35 of the protrusion 33.

[0116] According to Figure 3 、 Figure 4 and Figure 6 the embodiments shown in, the fuel impact surface 35 is substantially flat. As used herein, the phrase "substantially flat" can encompass a deviation of the fuel impact surface 35 from the shape of a flat plane oriented perpendicular to the central axis ax3 of the piston 5 of less than 7%.

[0117] Figure 7 Figure schematically shows a part of an internal combustion engine according to some further embodiments. The internal combustion engine may include the same features, functions and advantages as the internal combustion engine 10 explained with reference to Figures 1 - 6 wherein some differences are pointed out below. In addition, Figure 7 the fuel injector 1 of the internal combustion engine shown in may include the same features, functions and advantages as the fuel injector 1 explained with reference to Figures 2 - 6 Figure

[0118] Figure 7 The piston 5 of the internal combustion engine shown in includes a protrusion 33, wherein the fuel impact surface 35' is convex. As seen when comparing Figure 4 and Figure 7 when compared with the substantially flat fuel impact surface 35 shown in Figure 4 Figure Figure 7 the convex shape of the fuel impact surface 35' in Figure causes the fuel flow formation of the second fuel to be redirected to obtain a different redirection angle.

[0119] More specifically, compared with the substantially flat shape of the fuel impact surface 35 shown in Figure 4 Figure Figure 7 the convex shape of the fuel impact surface 35' shown in Figure causes the second fuel to be redirected to obtain more movement in the radial direction relative to the cylinder axis ax2 of the cylinder and less movement in the axial direction relative to the cylinder axis ax2 of the cylinder.

[0120] In other words, compared with the substantially flat shape of the fuel impact surface 35 shown in Figure 4 Figure Figure 7 the convex shape of the fuel impact surface 35' shown in Figure causes the second fuel to be redirected to reach further radially into the combustion chamber 4. According to Figure 7 the convex shape of the embodiment shown in Figure may be utilized, for example, when it is desired to further distribute the second fuel in the radial direction relative to the cylinder axis ax2 of the cylinder into the combustion chamber 4.

[0121] In addition, when it is desired to slightly delay the ignition timing of the first fuel and / or when it is desired to ignite the first fuel at a position further away from the plurality of first fuel injection holes h1 of the fuel injector 1, the one caused byFigure 7 The convex shape of the fuel impact surface 35' shown in [reference] causes a more radial redirection of the second fuel.

[0122] Figure 8 Part of an internal combustion engine according to some additional embodiments is schematically shown. Figure 8 The internal combustion engine shown in [reference] may include the same features, functions, and advantages as the internal combustion engine 10 explained with reference to Figures 1 - 6 wherein some differences are pointed out below. Additionally, Figure 8 The fuel injector 1 of the internal combustion engine shown in [reference] may include the same features, functions, and advantages as the fuel injector 1 explained with reference to Figures 2 - 6 The piston 5 of the internal combustion engine shown in [reference] includes a protrusion 33, wherein the fuel impact surface 35'' is concave. As can be seen when comparing

[0123] Figure 8 with Figure 4 and Figure 8 when Figure 4 compared to the substantially flat fuel impact surface 35 shown in [reference], Figure 8 the concave shape of the fuel impact surface 35'' in [reference] causes the fuel flow formation of the second fuel to be redirected to obtain a different redirection angle.

[0124] More specifically, compared to the substantially flat shape of the fuel impact surface 35 shown in [reference], Figure 4 the concave shape of the fuel impact surface 35'' in [reference] causes the second fuel to be redirected to obtain less movement in the radial direction with respect to the cylinder axis ax2 of the cylinder and greater movement in the axial direction with respect to the cylinder axis ax2 of the cylinder. Figure 8 In other words, compared to the substantially flat shape of the fuel impact surface 35 shown in [reference],

[0125] the concave shape of the fuel impact surface 35'' in [reference] causes the second fuel to be redirected to reach the combustion chamber 4 less radially. According to Figure 4 the embodiment shown in [reference], the concave shape can be utilized, for example, when it is desired to distribute the second fuel more towards the plurality of first fuel injection holes h1 in the radial direction with respect to the cylinder axis ax2 of the cylinder and less to the combustion chamber 4. Figure 8 In addition, when it is desired to slightly advance the ignition timing of the first fuel and / or when it is desired to ignite the first fuel at a position closer to the plurality of first fuel injection holes h1 of the fuel injector 1, the more radial redirection of the second fuel caused by the concave shape of the fuel impact surface 35'' shown in [reference] can be utilized. Figure 8 The concave shape according to the embodiment shown in [reference] can be utilized, for example, when it is desired to distribute the second fuel more towards the plurality of first fuel injection holes h1 in the radial direction with respect to the cylinder axis ax2 of the cylinder and less to the combustion chamber 4.

[0126] Furthermore, when it is desired to slightly advance the ignition timing of the first fuel and / or when it is desired to ignite the first fuel at a position closer to the plurality of first fuel injection holes h1 of the fuel injector 1, the more radial redirection of the second fuel caused by the concave shape of the fuel impact surface 35'' shown in [reference] can be utilized. Figure 8 The concave shape of the fuel impact surface 35'' shown in [reference] causes a more radial redirection of the second fuel.

[0127] Figure 9 Schematically shows a part of an internal combustion engine according to some additional embodiments. Figure 9 The internal combustion engine shown in may include the same features, functions and advantages as the internal combustion engine 10 explained with reference to Figures 1 - 6 Some differences are pointed out below. In addition, Figure 9 The fuel injector 1 of the internal combustion engine shown in may include the same features, functions and advantages as the fuel injector 1 explained with reference to Figures 2 - 6 The piston 5 of the internal combustion engine shown in includes a protrusion 33 having a fuel impact surface 35''', the protrusion including a first portion 37 located at the radial center of the fuel impact surface 35''' and a second portion 39 surrounding the first portion 37, wherein the first portion 37 is convex and the second portion 39 is concave. As used herein, the term "radial center" means the center seen radially with respect to the central axis ax3 of the piston 5. According to the illustrated embodiment, the radius of the radial center of the fuel impact surface 35''' is approximately 13% of the total radius of the fuel impact surface 35'''.

[0128] Figure 9 In, the first dashed arrow r2 schematically indicates that the second fuel from the second fuel injection hole h2 is redirected on the concave second portion 39 of the fuel impact surface 35''', while the second dashed arrow r2' schematically indicates that the second fuel from the second fuel injection hole h2 is redirected on the convex first portion 37 of the fuel impact surface 35'''.

[0129] In Figure 9 As seen in, compared to the redirection of the second fuel on the second portion 39 of the fuel impact surface 35''',

[0130] As Figure 9 seen in, the convex shape of the first portion 37 of the fuel impact surface 35''' shown in Figure 9 causes the second fuel to be redirected to obtain more movement in the radial direction with respect to the cylinder axis ax2 of the cylinder.

[0131] In this way, the fuel impact surface 35''' according to the embodiment shown in Figure 9 redirects the second fuel to various parts of the combustion chamber 4 in a more efficient manner, which can cause early ignition of the first fuel and further radial distribution of the second fuel into the combustion chamber 4, as Figure 9 indicated in.

[0132] According to Figures 3 - 9In the embodiments shown, the fuel impact surfaces 35, 35', 35", 35'" are substantially smooth surfaces. However, according to additional embodiments, one or more of these fuel impact surfaces 35, 35', 35", 35'" may be patterned. The pattern may include a plurality of protrusions protruding from the fuel impact surfaces 35, 35', 35", 35'" and / or a plurality of recesses provided in the fuel impact surfaces 35, 35', 35", 35'". According to some embodiments, the pattern of the fuel impact surfaces 35, 35', 35", 35'" includes a plurality of protrusions and / or valleys extending radially across the fuel impact surfaces 35, 35', 35", 35'" in a direction starting from the central axis ax3 of the piston 5.

[0133] As used herein, the feature "fuel flow formation" may also be referred to as a fuel spray, a fuel jet, etc.

[0134] It should be understood that the foregoing is illustrative of various exemplary embodiments, and the invention is defined only by the appended independent claims. Those skilled in the art will recognize that the exemplary embodiments may be modified without departing from the scope of the invention defined by the appended independent claims, and different features of the exemplary embodiments may be combined to produce embodiments other than those described herein.

[0135] As used herein, the term "comprising" or "comprises" is open-ended and includes one or more of the stated features, elements, steps, components or functions, but does not exclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof.

Claims

1. A fuel injector (1) configured to inject a first fuel and a second fuel into a combustion chamber (4) of an internal combustion engine (10), wherein the second fuel is different from the first fuel, and wherein the fuel injector (1) comprises a nozzle part (3) provided with the following: - A plurality of first fuel injection holes (h1) for injecting the first fuel into the combustion chamber (4), wherein the first fuel injection holes (h1) are circumferentially distributed on the nozzle part (3) around a central axis (ax1) of the nozzle part (3), and - A second fuel injection hole (h2) for injecting the second fuel into the combustion chamber (4), wherein the second fuel injection hole (h2) is configured to inject the second fuel in a main fuel injection direction (md) substantially coinciding with the central axis (ax1) of the nozzle part (3).

2. The fuel injector (1) according to claim 1, wherein the second fuel injection hole (h2) is configured such that an angle between the main fuel injection direction (md) of the second fuel and the central axis (ax1) of the nozzle part (3) is less than 15 degrees or less than 10 degrees.

3. The fuel injector (1) according to claim 1 or 2, wherein the central axis (ax1) of the nozzle part (3) extends through at least a part of the second fuel injection hole (h2).

4. The fuel injector (1) according to any one of the preceding claims, wherein a geometric center line (Cl) of the second fuel injection hole (h2) is parallel to the central axis (ax1) of the nozzle part (3).

5. The fuel injector (1) according to any one of the preceding claims, wherein the fuel injector (1) comprises only one second fuel injection hole (h2).

6. The fuel injector (1) according to any one of the preceding claims, wherein the plurality of first fuel injection holes (h1) comprises at least three first fuel injection holes (h1).

7. The fuel injector (1) according to any one of the preceding claims, wherein each of the plurality of first fuel injection holes (h1) is configured such that an angle between the main fuel injection direction (md') of the first fuel and the central axis (ax1) of the nozzle part (3) is greater than 30 degrees or greater than 50 degrees.

8. The fuel injector (1) according to any one of the preceding claims, wherein the fuel injector (1) comprises a fuel injector body (6), the fuel injector body comprising: - A first fuel chamber (11) configured to accommodate the first fuel, and - A second fuel chamber (12) configured to accommodate the second fuel, and wherein the fuel injector (1) comprises: - A first needle seat (15), - a first needle (17) configured to interact with the first needle seat (15) to open and close the fluid connection between the first fuel chamber (11) and the plurality of first fuel injection holes (h1), - a second needle seat (20), and - a second needle (23) configured to interact with the second needle seat (20) to open and close the fluid connection between the second fuel chamber (12) and the second fuel injection hole (h2).

9. The fuel injector (1) according to claim 8, wherein at least a portion of the second needle (23) is disposed inside the first needle (17).

10. The fuel injector (1) according to claim 8 or 9, wherein at least a portion of the second fuel chamber (12) is disposed inside the first needle (17).

11. The fuel injector (1) according to any one of claims 8 to 10, wherein the second fuel injection hole (h2) extends through a portion of the first needle (17).

12. The fuel injector (1) according to any one of claims 8 to 11, wherein the second needle seat (20) is formed by the inner surface of the first needle (17).

13. The fuel injector (1) according to any one of claims 8 to 12, wherein the first and second needles (17, 23) are configured to open and close the respective fluid connections by moving in a direction (d1, d2) parallel to the central axis (ax1) of the nozzle portion (3).

14. An internal combustion engine (10) comprising: - a cylinder (7), - a piston (5) disposed in the cylinder (7) and arranged to reciprocate along the cylinder axis (ax2) of the cylinder (7), - a combustion chamber (4) formed between the wall (7') of the cylinder (7) and the piston top (5') of the piston (5), and - a fuel injector (1) according to any one of the preceding claims, wherein the fuel injector (1) is configured to inject the first fuel and the second fuel into the combustion chamber (4).

15. The internal combustion engine (10) according to claim 14, wherein the angle between the main fuel injection direction (md) of the second fuel and the cylinder axis (ax2) of the cylinder (7) is less than 15 degrees or less than 10 degrees.

16. The internal combustion engine (10) according to claim 14 or 15, wherein the central axis (ax1) of the nozzle portion (3) is parallel to the cylinder axis (ax2) of the cylinder (7).

17. The internal combustion engine (10) according to any one of claims 14 to 16, wherein the central axis (ax1) of the nozzle portion (3) coincides with the cylinder axis (ax2) of the cylinder (7).

18. The internal combustion engine (10) according to any one of claims 14 to 17, wherein the piston top (5') includes a piston bowl (31) and a protrusion (33) protruding from the bottom surface (31') of the piston bowl (31), and wherein the protrusion (33) includes a fuel impact surface (35, 35', 35'', 35''') facing the fuel injector (1).

19. The internal combustion engine (10) according to claim 18, wherein the fuel impact surface (35) is substantially flat.

20. The internal combustion engine (10) according to claim 18, wherein the fuel impact surface (35') is convex.

21. The internal combustion engine (10) according to claim 18, wherein the fuel impact surface (35'') is concave.

22. The internal combustion engine (10) according to claim 18, wherein the fuel impact surface (35''') includes a first portion (37) located at the radial center of the fuel impact surface (35''') and a second portion (39) surrounding the first portion (37), and wherein the first portion (37) is convex and the second portion (39) is concave.

23. The internal combustion engine (10) according to any one of claims 18 to 22, wherein the fuel impact surface (35, 35', 35'', 35''') is patterned.

24. The internal combustion engine (10) according to any one of claims 18 to 23, wherein the internal combustion engine (10) is a compression ignition engine.

25. The internal combustion engine (10) according to any one of claims 14 to 24, wherein the first fuel has a higher research octane number than the second fuel.

26. The internal combustion engine (10) according to any one of claims 14 to 25, wherein the first fuel has a research octane number higher than 50, and wherein the second fuel has a research octane number lower than 50.

27. The internal combustion engine (10) according to any one of claims 14 to 26, wherein the first fuel is a gaseous fuel and the second fuel is a liquid fuel.

28. The internal combustion engine (10) according to any one of claims 14 to 27, wherein the first fuel includes hydrogen and / or natural gas, and wherein the second fuel includes diesel and / or diesel-like fuel.

29. A vehicle (2) comprising the internal combustion engine (10) according to any one of claims 14 to 28.

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