Fuel injector, use of a fuel injector, piston engine and method of operating a piston engine

Abstract

A fuel injector (1) for injecting fuel directly into a main combustion chamber (14) of a piston engine comprises nozzle holes (2, 3, 5) for introducing fuel into the main combustion chamber (14), and a fuel injector needle (4, 6) for controlling fuel injection via the nozzle holes (2, 3, 5), the nozzle holes (2, 3, 5) comprising at least one non-axial nozzle hole (3, 5) configured to inject fuel into a direction deviating from a radial direction of the fuel injector needle (4, 6) when projected onto a plane perpendicular to an axial direction of the fuel injector needle (4, 6).

Description

Technical Field

[0001] This invention relates to a fuel injector as defined in claim 1 and its use. The invention also relates to a piston engine and a method of operating the piston engine. Background Technology

[0002] Many large piston engines (such as those used in ships and power plants) operate using pilot fuel injection. The main fuel is introduced into the cylinder via an inlet channel or through direct injection. The main fuel typically forms a lean air-fuel mixture. The pilot fuel is a liquid fuel, such as light fuel oil. The liquid pilot fuel is injected into the cylinder through a pilot fuel injector. The pilot fuel ignites spontaneously, and its ignition triggers or promotes the combustion of the main fuel. The main fuel can be a fuel with lower reactivity and lower energy density, while the pilot fuel can be a fuel with higher reactivity and typically higher energy density.

[0003] Ignition fuel injection has traditionally been used in engines that operate using natural gas as their primary fuel. However, ignition fuel injection can also be used in engines that operate using novel fuels (such as ammonia, methanol, or hydrogen) or mixtures of different fuels.

[0004] Traditionally, ignition fuel is injected into the cylinder near top dead center during the compression stroke. However, if the engine operates with a particularly low-reactivity fuel and / or a very lean mixture, a single ignition fuel injection event near top dead center may not be sufficient to achieve reliable ignition and the desired combustion phasing and speed. This problem can occur, for example, if the engine is running on ammonia. Similar issues can arise when using other fuels, such as hydrogen. While hydrogen has a high auto-ignition temperature and a high octane number, its low ignition energy makes it sensitive to the formation of a spontaneous combustion zone, leading to undesirable combustion such as knocking. The risks of auto-ignition and other undesirable combustion can be mitigated to some extent by using a leaner air-fuel mixture, but lean mixtures involve emissions risks from incomplete combustion and ignition difficulties.

[0005] To address the aforementioned issues and other challenges leading to abnormal combustion or improper phasing of the main fuel, the amount of pilot fuel can be increased and / or the timing of pilot fuel introduction can be altered. Typically, pilot fuel is introduced into the cylinder through multiple injection events, some of which may occur very early. While early pilot fuel injection and increased pilot fuel quantity enhance charge responsiveness, they can also lead to increased interaction between the fuel spray and the combustion chamber walls. When this wall wetting occurs on the cylinder liner, it affects the properties of the lubricating film on the cylinder liner surface and can lead to oil contamination, which in turn significantly shortens oil life. If oil change intervals are not shortened accordingly, oil contamination can cause serious damage to engine components.

[0006] Similar wall wetting problems may also be encountered with direct injection of the main fuel. Summary of the Invention

[0007] The object of this invention is to provide an improved fuel injector for directly injecting fuel into the main combustion chamber of a piston engine cylinder. Other objects of this invention include providing uses for such a fuel injector, an improved piston engine, and a method of operating the piston engine.

[0008] The fuel injector according to the invention includes one or more nozzle orifices for introducing fuel into the main combustion chamber, and at least one movable fuel injector needle for controlling fuel injection via the one or more nozzle orifices. The one or more nozzle orifices include at least one non-axial nozzle orifice configured to inject fuel in a direction that, when projected onto a plane perpendicular to the axial direction of the respective fuel injector needle, deviates from the radial direction of the fuel injector needle.

[0009] The nozzle orifice, configured to inject fuel in a direction deviating from the radial direction of the fuel injector needle, reduces fuel jet penetration into the combustion chamber. The interaction between the fuel spray and the walls of the main combustion chamber is thus reduced, and problems caused by wall wetting are avoided.

[0010] According to one embodiment of the invention, the angle between the central axis of the at least one non-axial nozzle orifice, when projected onto a plane perpendicular to the axial direction of the corresponding fuel injector needle, and the radius at which the fuel injector needle intersects the central axis at the inner end of the non-axial nozzle orifice, is between 10 and 50 degrees. Angles within this range maintain the penetration depth within a suitable range and contribute to the generation of suitable vortices in the main combustion chamber.

[0011] According to one embodiment of the invention, the outer end of the at least one non-axial nozzle orifice has a portion with a diameter larger than the inner end of the non-axial nozzle orifice. Together with the non-radial direction, the enlarged outer portion helps reduce fuel jet penetration into the main combustion chamber.

[0012] According to one embodiment of the invention, the diameter of the outer end of the at least one non-axial nozzle orifice is 200% to 400% of the diameter of the inner end of the non-axial nozzle orifice. According to one embodiment of the invention, the diameter of the outer end of the at least one non-axial nozzle orifice is 10% to 30% of the length of the non-axial nozzle orifice. According to one embodiment of the invention, the length of the portion having the larger diameter is 30% to 70% of the total length of the non-axial nozzle orifice. Each of the above parameters contributes to achieving suitable jet penetration in the main combustion chamber.

[0013] According to one embodiment of the invention, the angle between the axial direction of the at least one non-axial nozzle orifice and the axial direction of the corresponding injector needle is 30 to 90 degrees. This helps to avoid interaction between the fuel jet and both the cylinder wall and the piston.

[0014] According to one embodiment of the invention, the at least one non-axial nozzle orifice opens inside the fuel injector into a sac volume, located in the uppermost third of the sac volume; or opens into the region of the needle valve seat. This also helps to reduce fuel jet penetration into the main combustion chamber.

[0015] According to one embodiment of the invention, the one or more nozzle orifices include one or more ignition fuel nozzle orifices, the one or more ignition fuel nozzle orifices include one or more non-axial ignition fuel nozzle orifices, the one or more ignition fuel nozzle orifices are configured to inject liquid ignition fuel into the main combustion chamber, and the at least one fuel injector needle includes an ignition fuel injector needle for controlling fuel injection via the one or more ignition fuel nozzle orifices.

[0016] Especially when a portion of the ignition fuel is injected into the combustion chamber early, the ignition fuel does not ignite immediately. Therefore, avoiding wall interaction is important. Thus, the fuel injector according to the invention is advantageous, particularly for ignition fuel injection, especially when at least a portion of the ignition fuel is injected very early. Furthermore, since the ignition fuel injection duration is much shorter than the main fuel injection duration, dynamic effects play a greater role in ignition fuel injection. This allows for the regulation of the fuel jet behavior through minute changes in the orientation and size of the nozzle orifice.

[0017] According to one embodiment of the invention, the one or more ignition fuel nozzle orifices include axial nozzle orifices configured to inject fuel in the axial direction of the ignition fuel injector needle. Using axial ignition fuel orifices, a portion of the ignition fuel can be injected toward the piston, and the risk of wall wetting can be further reduced.

[0018] According to one embodiment of the invention, the fuel injector is configured such that the ignition fuel injector needle has a closed state, a fully raised state, and at least one partially raised state, and in the at least one partially raised state, a greater portion of the ignition fuel is injected through the axial nozzle orifice compared to the fully raised state. The partially raised state can be used for early ignition fuel injection to avoid wall wetting. In the fully raised state, more fuel is injected through the non-axial ignition fuel nozzle orifice to promote the ignition of the main fuel.

[0019] According to one embodiment of the invention, the ignition fuel injector needle has at least one partially raised state in which ignition fuel is injected entirely or primarily through an axial nozzle orifice. This effectively prevents wall wetting and is particularly useful for very early ignition fuel injection.

[0020] According to one embodiment of the invention, the fuel injector is configured such that, in the fully raised state of the ignition fuel injector needle, ignition fuel is injected entirely or primarily through the one or more non-axial ignition fuel nozzle orifices. This facilitates ignition and helps avoid contact between the ignition fuel jet and the piston.

[0021] According to one embodiment of the invention, the ignition fuel injector needle is configured to protrude into the axial nozzle orifice in the closed state of the ignition fuel injector needle. Therefore, the fuel injector can have a pintle-type design. For example, this allows for control of the flow pattern through the axial nozzle orifice based on the injector needle lift.

[0022] According to one embodiment of the invention, the ignition fuel injector needle is configured to protrude beyond the axial nozzle orifice in the closed state, and the diameter of the portion protruding beyond the axial nozzle orifice increases toward the outer end of the ignition fuel injector needle. This shape allows for reduced flow through the axial nozzle orifice when the injector needle is at full lift, or even complete closure of the axial nozzle orifice. However, many other shapes of the protruding portion can also be used to achieve the desired spray pattern.

[0023] According to one embodiment of the invention, the axial nozzle orifice has a larger flow area than the one or more non-axial ignition fuel nozzle orifices. Therefore, a relatively large amount of fuel can be injected through a single axial nozzle orifice.

[0024] According to one embodiment of the invention, the fuel injector is configured to be positioned such that the ignition fuel injector needle is deviated from the central axis of the cylinder, and the one or more non-axial ignition fuel nozzle orifices are positioned such that more ignition fuel is directed to the side further away from the cylinder wall. This allows for further reduction of the contact between the fuel spray and the cylinder wall.

[0025] According to one embodiment of the invention, the fuel injector includes a plurality of non-axial ignition fuel nozzle holes, and on the side configured closer to the cylinder wall, the angular distance between two consecutive non-axial ignition fuel nozzle holes is greater than the angular distance on the side configured further away from the cylinder wall. Therefore, more ignition fuel nozzle holes can be arranged on the side further away from the cylinder wall, and less fuel is injected near the wall.

[0026] According to one embodiment of the present invention, the fuel injector is a dual-fuel injector, which includes one or more main fuel nozzle orifices, one or more ignition fuel nozzle orifices, a main fuel injector needle for controlling the injection of main fuel through the main fuel nozzle orifices, and an ignition fuel injector needle for controlling the injection of ignition fuel through the ignition fuel nozzle orifices.

[0027] In dual-fuel injectors, at least one of the injector needles is typically offset from the central axis of the cylinder, and the nozzle orifices are arranged asymmetrically about the central axis of the cylinder. With the nozzle orifice configuration according to the invention, wall wetting can be prevented even when some of the nozzle orifices are positioned closer to the cylinder wall.

[0028] According to the present invention, the aforementioned fuel injector can be used to inject liquid ignition fuel into the main combustion chamber of a piston engine cylinder that uses ammonia or other gaseous fuels, ethanol, or methanol as the primary fuel. Ammonia, many other gaseous fuels, ethanol, and methanol are fuels that require large amounts of ignition fuel and / or very early ignition fuel injection. By using the fuel injector according to the present invention to inject ignition fuel, the interaction between the fuel and the cylinder wall can be reduced.

[0029] The piston engine according to the invention includes a plurality of cylinders, a cylinder head for each cylinder of the engine, and the aforementioned fuel injector mounted in each cylinder head for injecting fuel directly into the main combustion chamber of the cylinder.

[0030] According to one embodiment of the invention, the engine is configured to operate using ammonia or other gaseous fuels, ethanol or methanol as the primary fuel.

[0031] The method according to the invention includes the step of directly injecting fuel into the main combustion chamber of the engine using the aforementioned fuel injector.

[0032] According to one embodiment of the invention, the method includes the step of introducing main fuel into a cylinder of an engine, and in the step of directly injecting fuel into the main combustion chamber, using the fuel injector to inject liquid ignition fuel into the main combustion chamber of the cylinder to promote the ignition and / or combustion of the main fuel. The main fuel may be ammonia or other gaseous fuels, ethanol, or methanol. Attached Figure Description

[0033] The embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, wherein: Figure 1 The diagram schematically shows a portion of the cylinder head and cylinder of a piston engine. Figure 2 A front view of a fuel injector according to one embodiment of the present invention is shown. Figure 3 It shows Figure 2 Bottom view of the fuel injector Figure 4 It shows along Figure 3 A cross-sectional view taken from line BB. Figure 5 It shows Figure 4 A magnified view of detail A. Figure 6 A nozzle orifice of a fuel injector according to one embodiment of the present invention is shown. Figure 7 A nozzle orifice of a fuel injector according to another embodiment of the present invention is shown. Figure 8 A cross-sectional view of a fuel injector according to yet another embodiment of the present invention is shown. Figure 9 It shows Figure 8 Details of the fuel injectors Figure 10 A nozzle orifice configuration according to one embodiment of the present invention is shown. Figure 11 An illustration shows the spray pattern of fuel injected through radial nozzle orifices. Figure 12 An illustration shows the spray pattern of fuel injected through a non-radial nozzle orifice, and Figures 13A to 13D Different shapes of needles for needle fuel injectors are shown. Detailed Implementation

[0034] Figure 1A portion of cylinder 10 of a piston engine is schematically shown. The engine is a large piston engine. The term "large piston engine" here refers to an engine with cylinder diameters of at least 150 mm. The engine can be, for example, used as a main or auxiliary engine in a ship, or as an engine used to drive generators in a power plant. The engine is a four-stroke engine. The engine may include multiple cylinders 10. The cylinders 10 may be arranged, for example, in an inline or V-shaped configuration.

[0035] Cylinder 10 may be formed by cylinder liner 11 inserted into engine block. Each cylinder 10 is provided with piston 12, which is configured to move in a reciprocating manner within cylinder 10. Piston 12 moves between top dead center (TDC) and bottom dead center (BDC). Piston 12 is connected to crankshaft (not shown).

[0036] The upper end of each cylinder 10 is closed by the cylinder head 13. The term "upper end" here refers to the end closer to top dead center. Cylinder 10 does not need to be in a vertical position, but can be tilted from the vertical direction, for example in a V-type engine.

[0037] The piston 12, cylinder head 13, and cylinder 10 walls define the main combustion chamber 14.

[0038] The cylinder head 13 is provided with an intake passage 15 and an exhaust passage 16. The intake passage 15 is configured to introduce intake air into the main combustion chamber 14. A portion of the fuel used in the engine may also be introduced into the main combustion chamber 14 via the intake passage 15. The engine's intake air may be pressurized by one or more turbochargers. The exhaust passage 16 is configured to discharge exhaust gases from the main combustion chamber 14.

[0039] Each cylinder 10 is provided with one or more intake valves 17 and one or more exhaust valves 18. The intake valves 17 are configured to control the supply of intake air (and possibly fuel) from the intake passage 15 to the main combustion chamber 14. The exhaust valves 18 are configured to control the discharge of exhaust gases from the main combustion chamber 14. The number of intake valves 17 can range from one to three. The number of exhaust valves 18 can also range from one to three. Each cylinder 10 may, for example, be provided with two intake valves 17 and two exhaust valves 18. Alternatively, each cylinder 10 may be provided with three intake valves 17 and two exhaust valves 18. The opening and closing of the intake valves 17 and exhaust valves 18 can be controlled mechanically, hydraulically, electrically, pneumatically, or by a combination of two or more of the above. Valve timing can be fixed or variable.

[0040] The engine also includes at least one fuel injector 1 for each cylinder 10 of the engine. The fuel injector 1 is mounted to the cylinder head 13. The fuel injector 1 is configured to inject fuel directly into the main combustion chamber 14.

[0041] exist Figure 1 In the example, fuel injector 1 is a dual-fuel injector. Dual-fuel injector 1 is configured to inject both main fuel and ignition fuel into the main combustion chamber 14. The fuel injector includes an ignition fuel nozzle 8 and a main fuel nozzle 9. The ignition fuel is a liquid fuel, meaning, in this context, a fuel that is liquid at atmospheric pressure and at a temperature of 20°C. The ignition fuel can be, for example, light fuel oil.

[0042] The primary fuel can be a liquid fuel or a gaseous fuel; the term "gaseous fuel" here refers to a fuel that is a gas at atmospheric pressure and a temperature of 20°C. Even if the primary fuel is a gas, it can be introduced into the fuel injector 1 in a liquid phase. The primary fuel can be, for example, ammonia, ethanol, or methanol. However, the primary fuel can also be some other fuel that requires or benefits from ignition fuel injection, particularly a gaseous fuel. The engine can be configured to operate using two or more different primary fuels. Therefore, the engine can be a dual-fuel or multi-fuel engine. The engine can have different operating modes, and ignition fuel injection can be used only in some operating modes. For example, ignition fuel injection can be used only when using a certain primary fuel.

[0043] The engine can be configured to operate using a lean mixture (i.e., a mixture containing more air than is required for complete combustion of the fuel). The stoichiometric mixture has just enough air for complete combustion of the fuel, and the air-fuel equivalence ratio λ = 1.0. The engine can, for example, operate using a mixture with an air-fuel equivalence ratio of at least 1.5.

[0044] Figure 2 A fuel injector 1 according to one embodiment of the present invention is shown. Figures 3 to 6 It shows Figure 2 Different views of fuel injector 1. Figure 7 It shows Figures 2 to 6 Alternative nozzle orifice configuration for fuel injectors. Figure 8 A fuel injector 1 according to yet another embodiment of the present invention is shown. Details of the fuel injector according to an embodiment of the present invention are shown below. Figure 9 and Figure 10 Not all features of different embodiments are essential features of the present invention. Furthermore, features of different embodiments may be combined and / or replaced by features of other embodiments.

[0045] Figure 2 and Figure 8The fuel injector 1 is a dual-fuel injector. Therefore, each fuel injector 1 is configured to inject two different fuels into the main combustion chamber 14. The fuel injector 1 is configured to inject both main fuel and pilot fuel into the main combustion chamber 14. The combustion of the main fuel constitutes the majority of the heat release in the cylinder 10, preferably at least 85%. Pilot fuel is injected into the main combustion chamber 14 to promote the ignition and / or combustion of the main fuel.

[0046] In the embodiment shown in the accompanying drawings, the fuel injector 1 includes a main fuel injection section and an ignition fuel injection section. The ignition fuel injection section includes a plurality of ignition fuel nozzle orifices 2, 3 for introducing ignition fuel into the main combustion chamber 14. The ignition fuel injection section also includes a movable ignition fuel injector needle 4 (shown in the figure) for controlling the fuel injection through the ignition fuel nozzle orifices 2, 3. Figures 8 to 10 (Middle). Ignition fuel nozzle holes 2 and 3 are arranged in the ignition fuel nozzle 8, which is configured to protrude into the main combustion chamber 14.

[0047] The main fuel injection section includes multiple main fuel nozzle orifices 5 for introducing main fuel into the main combustion chamber 14. The main fuel injection section also includes a movable main fuel injector needle 6 (only in use with respect to controlling fuel injection via the main fuel nozzle orifices 5). Figure 8 (As shown in the figure). The main fuel nozzle orifice 5 is arranged in the main fuel nozzle 9, which is configured to protrude into the main combustion chamber 14.

[0048] Fuel injector needles 4 and 6 can be electrically controlled. Each fuel injector needle 4 and 6 can move in the axial direction of the fuel injector needle 4 and 6, and has at least a closed state and an open state with lifting. In the open state, it allows the flow into the sac-like volume 20 and further through the corresponding nozzle orifices 2, 3, and 5.

[0049] Figure 9 The ignition fuel injector needle 4 is shown in the off state, and Figure 10 The ignition fuel injector needle 4 is shown in the raised position. When injector needles 4 and 6 are closed, the injector needle rests against the needle valve seat 21.

[0050] With the fuel injector 1 installed, the axial direction of the fuel injector needles 4 and 6 can be parallel to the axial direction of the cylinder 10.

[0051] Ignition fuel nozzle orifices 2 and 3 include non-axial nozzle orifices 3. The axial direction of the non-axial ignition fuel nozzle orifices 3 differs from the axial direction of the ignition fuel injector needle 4. Furthermore, the axial direction of each non-axial ignition fuel nozzle orifice 3 deviates from the radial direction of the ignition fuel injector needle 4 when projected onto a plane perpendicular to the axial direction of the ignition fuel injector needle 4. Therefore, the central axis C of the non-axial ignition fuel nozzle orifice 3 does not intersect with the central axis of the ignition fuel injector needle 4. Because the axial direction of the non-axial ignition fuel nozzle orifice 3 differs from the radial direction of the ignition fuel injector needle 4, the non-axial ignition fuel nozzle orifice 3 is configured to inject fuel in a direction that deviates from the radial direction of the ignition fuel injector needle 4 when projected onto a plane perpendicular to the axial direction of the ignition fuel injector needle 4. Due to the orientation of the non-axial ignition fuel nozzle orifices 3, wall wetting caused by ignition fuel injection can be reduced.

[0052] The main fuel nozzle orifice 5 is a non-axial nozzle orifice. The main fuel nozzle orifice 5 can also be configured such that the axial direction of each non-axial main fuel nozzle orifice 5 deviates from the radial direction of the main fuel injector needle 6 when projected onto a plane perpendicular to the axial direction of the main fuel injector needle 6. Therefore, the non-axial main fuel nozzle orifice 5 can be configured to inject fuel in a direction that, when projected onto a plane perpendicular to the axial direction of the main fuel injector needle 6, deviates from the radial direction of the main fuel injector needle 6.

[0053] exist Figures 2 to 6 In this embodiment, the angle θ between the central axis C of each non-axial ignition fuel nozzle orifice 3, when projected onto a plane perpendicular to the axial direction of the ignition fuel injector needle 4, and the radius R of the ignition fuel injector needle 4 intersecting the central axis C at the inner end 3a of the non-axial ignition fuel nozzle orifice 3, is approximately 30 degrees. The angle θ can be, for example, in the range of 10 degrees to 50 degrees.

[0054] The main fuel nozzle orifice 5 can be configured in a similar manner. The central axis C of the non-axial ignition fuel nozzle orifice 3 is offset from the central axis of the ignition fuel injector needle 4 by a distance L3, which depends on the angle θ. Therefore, the orientation of the non-axial ignition fuel nozzle orifice 3 can also be described by the offset L3.

[0055] The effect of the non-radial orientation of the ignition fuel nozzle orifice 3 is due to Figure 11 and Figure 12 As shown. Figure 11 A prior art configuration is shown, in which the ignition fuel nozzle orifice is arranged radially. Figure 12An ignition fuel injector according to one embodiment of the invention is shown. Utilizing the nozzle orifice configuration according to the invention, the fuel jet diffuses more effectively upon exiting the fuel injector, which reduces jet penetration into the main combustion chamber 14. A line through the nozzle orifice depicts the streamline. The non-radial orientation of the nozzle orifice 3 generates controlled cavitation on the side of the nozzle orifice 3 where the wall of the nozzle orifice 3 forms an acute angle with the inner side of the ignition fuel nozzle. The diffusion of the fuel jet is at least partially caused by the cavitation occurring in the nozzle orifice 3. The diffusion of the fuel jet is achieved through the nozzle orifice 3 having a constant diameter. However, this effect can be further improved by providing a portion with a diameter larger than that of the inner end of the nozzle orifice 3 at its outer end.

[0056] exist Figures 2 to 7 In this embodiment, the outer end of each non-axial ignition fuel nozzle orifice 3 is provided with a portion 3B whose diameter is larger than that of the inner end 3A of the non-axial ignition fuel nozzle orifice 3. The larger diameter in the outer end of the non-axial ignition fuel nozzle orifice 3 reduces the penetration of the ignition fuel jet in the main combustion chamber 14.

[0057] exist Figures 2 to 7 In this embodiment, the diameter D2 of the outer end of the non-axial ignition fuel nozzle orifice 3 is approximately 300% of the diameter D1 of the inner end 3a of the non-axial ignition fuel nozzle orifice. The diameter D2 of the outer end of the non-axial ignition fuel nozzle orifice 3 can be in the range of 200% to 400% of the diameter D1 of the inner end of the non-axial ignition fuel nozzle orifice 3.

[0058] exist Figures 2 to 7 In this embodiment, the length L2 of the portion 3B with the larger diameter is approximately half the total length L1 of the non-axial ignition fuel nozzle orifice 3. The length L2 can be 30% to 70% of the total length L1 of the non-axial ignition fuel nozzle orifice 3.

[0059] exist Figures 2 to 7 In this embodiment, the diameter D2 of the outer end of the non-axial ignition fuel nozzle orifice 3 is approximately 20% of the length L1 of the non-axial ignition fuel nozzle orifice 3. The diameter D2 of the outer end of the non-axial ignition fuel nozzle orifice 3 can be in the range of 10% to 30% of the length L1 of the non-axial ignition fuel nozzle orifice 3.

[0060] exist Figures 2 to 7 In this embodiment, each non-axial ignition fuel nozzle orifice 3 is formed by an outer portion 3B and an inner portion 3A. The outer portion 3B and the inner portion 3A each have a constant diameter.

[0061] The outer end of each non-axial main fuel nozzle orifice 5 may be provided with a portion having a diameter larger than that of the inner end of the non-axial main fuel nozzle orifice 5 in a similar manner.

[0062] exist Figures 2 to 7In this embodiment, the angle γ (gamma) between the axial direction C of the non-axial ignition fuel nozzle orifice 3 and the axial direction of the ignition fuel injector needle 4 is 60 degrees. This angle can be, for example, in the range of 30 to 90 degrees. The angle between the axial direction of the main fuel nozzle orifice 5 and the axial direction of the main fuel injector needle 6 is 75 degrees. However, this angle can be within the same range as that of the non-axial ignition fuel nozzle orifice 3.

[0063] In the attached diagram, the dual fuel injector 1 is positioned such that its central axis is aligned with the central axis of the cylinder 10. Therefore, the ignition fuel nozzle 8 and the ignition fuel injector needle 4 are offset from the central axis of the cylinder 10. Figures 2 to 6 In this embodiment, the non-axial ignition fuel nozzle orifice 3 is positioned such that more ignition fuel is directed to the side further away from the wall of cylinder 10. Figure 6 In this configuration, the left-hand side of the fuel injector is positioned closer to the wall of cylinder 10. On the left-hand side, the angular distance between the two consecutive non-axial ignition fuel nozzle orifices 3 is greater than the angular distance on the right-hand side, which is positioned further away from the wall of cylinder 10. The angular distance 'a' between the two consecutive non-axial ignition fuel nozzle orifices 3 is 45 degrees on the side positioned further away from the wall of cylinder 10. On the side positioned closer to the wall of cylinder 10, there is an angle of 135 degrees between the two consecutive non-axial ignition fuel nozzle orifices 3.

[0064] Figure 7 An alternative embodiment is shown in which the non-axial ignition fuel nozzle orifices 3 are uniformly distributed along the periphery of the ignition fuel nozzle 8. The fuel injector 1 includes six non-axial ignition fuel nozzle orifices 3, and therefore the angular distance α between two consecutive non-axial ignition fuel nozzle orifices is 60 degrees.

[0065] exist Figure 8In this embodiment, the ignition fuel injection section further includes an axial ignition fuel nozzle orifice 2, which is configured to inject fuel along the axial direction of the ignition fuel injector needle 4. The ignition fuel injector needle 4 has a closed state and a fully raised state. Between the closed state and the fully raised state, the ignition fuel injector needle 4 has a partially raised state. In at least one partially raised state, a larger portion of the ignition fuel is injected through the axial nozzle orifice 2 compared to the fully raised state. The ignition fuel injection section can be configured such that in at least one partially raised state, the ignition fuel is injected entirely or primarily through the axial ignition fuel nozzle orifice 2. The ignition fuel injection section can be further configured such that in the fully raised state of the ignition fuel injector needle 4, the ignition fuel is injected entirely or primarily through the non-axial ignition fuel nozzle orifice 3. The axial ignition fuel nozzle orifice 2 allows more fuel to be directed to the piston 12 during early ignition fuel injection events. This further reduces wall wetting problems. With the ignition fuel injector needle 4 fully raised, the ignition fuel can be guided to the upper part of the cylinder 10 to better promote the ignition of the main fuel.

[0066] exist Figure 8 In this embodiment, the ignition fuel injector needle 4 is a needle-type needle. Therefore, the ignition fuel injector needle 4 is configured to protrude into the axial ignition fuel nozzle orifice 2 in the closed state, as from... Figure 9 The enlarged view best shows this. The axial nozzle orifice 2 has a larger diameter and flow area than the non-axial ignition fuel nozzle orifice 3. This allows a sufficient portion of the ignition fuel to be injected through the axial nozzle orifice 2. By appropriately shaping the needle-type ignition fuel injector needle 4 and the axial nozzle orifice 2, the fuel injector 1 can be configured to inject different portions of the ignition fuel through the axial nozzle orifice 2 and the non-axial nozzle orifice 3 at different lifts of the ignition fuel injector needle 4.

[0067] Figures 13A to 13D Examples of different shapes of the protruding portion 4A of the ignition fuel injector needle 4 are shown. Figure 13A In this embodiment, the protruding portion 4A has a truncated conical shape and tapers towards the outer end of the ignition fuel injector needle 4. Utilizing this shape, the flow area through the axial nozzle orifice 2 increases with the lift of the ignition fuel injector needle 4. Therefore, at the full lift of the ignition fuel injector needle 4, a larger portion of the fuel is injected through the axial nozzle orifice compared to a partial lift. Figure 13B and Figure 13C In this embodiment, the protruding portion 4A also tapers towards the outer end of the ignition fuel injector needle 4. However, in Figure 13B and Figure 13C In the implementation method, the protruding part 4A is unlike Figure 13A Instead of a continuous tapering, it tapers gradually. Figure 13B In the middle, the protruding portion 4A comprises two parts with different diameters. The outer portion of the protruding portion 4A has a smaller diameter than the inner portion. Figure 13C In the middle, the protruding part 4A comprises three sections with different diameters. The outermost section has the smallest diameter, and the innermost section has the largest diameter. Utilizing... Figure 13B and Figure 13C The ignition fuel injector needle, through the axial nozzle orifice 2, injects fuel as a function of the lift of the ignition fuel injector needle 4, in order to utilize... Figure 13A The ignition fuel injector needle 4 changes in a similar manner.

[0068] exist Figure 13D In this embodiment, the diameter of the protruding portion 4A increases toward the outer end of the ignition fuel injector needle 4. The protruding portion 4A is configured to protrude beyond the axial nozzle orifice 2, at least in the closed state of the ignition fuel injector needle 4. As the lift of the ignition fuel injector needle 4 increases, the flow area through the axial nozzle orifice 2 decreases. Therefore, during partial lift of the ignition fuel injector needle 4, a larger portion of the fuel is injected through the axial nozzle orifice 2 compared to full lift. The protruding portion 4A can be configured to close the axial nozzle orifice 2 even during full lift.

[0069] Many other shapes of the protrusion 4A can also be used to achieve the desired spray pattern at different lifts. The axial nozzle orifice 2 does not need to have a constant diameter, but can have a special shape suitable for cooperating with the protrusion 4A of the ignition fuel injector needle 4 to produce the desired spray pattern.

[0070] exist Figure 8 and Figure 9 In one embodiment, the non-axial ignition fuel nozzle orifice 3 has a constant diameter. However, even when using a needle-type ignition fuel injector needle 4, the outer end of the non-axial ignition fuel nozzle orifice 3 can have a portion with a larger diameter.

[0071] Figure 10 A portion of a fuel injector 1 according to yet another embodiment of the invention is shown. A non-axial ignition fuel nozzle orifice 3 opens internally into a sac-like volume 20 within the fuel injector 1. The term "sac-like volume" refers to the space located below the needle valve seat 21, i.e., downstream of the needle valve seat 21. In the closed state of the ignition fuel injector needle 4, the sac-like volume 20 is therefore in fluid communication with the main combustion chamber 14. Figure 10In this embodiment, the non-axial ignition fuel nozzle orifice 3 opens into the sac-like volume 20 near the needle valve seat 21. The non-axial ignition fuel nozzle orifice 3 opens into the uppermost quarter of the sac-like volume 20. The positioning of the inner end of the non-axial ignition fuel nozzle orifice 3 affects the flow from the sac-like volume 20 into the main combustion chamber 14 and reduces jet penetration in the main combustion chamber 14. The non-axial ignition fuel nozzle orifice 3 can even open into the region of the needle valve seat 21. Figure 10 A nozzle orifice 3 with a constant diameter is shown, but... Figure 10 In one embodiment, the nozzle hole 3 may also be provided with an outer end having a larger diameter.

[0072] Although dual-fuel injectors have been described above, the fuel injector according to the invention can be a main fuel injector configured to inject primary fuel, or an ignition fuel injector configured to inject ignition fuel. In the case of an ignition fuel injector, primary fuel can be introduced into the main combustion chamber 14 via a separate fuel injector configured to inject fuel directly into the main combustion chamber 14. Alternatively, primary fuel or a portion thereof can be introduced into the main combustion chamber 14 via the intake passage 15.

Claims

1. A fuel injector (1) for directly injecting fuel into the main combustion chamber (14) of a cylinder (10) of a piston engine, said fuel injector (1) comprising: - For introducing fuel into one or more nozzle holes (2, 3, 5) of the main combustion chamber (14), and - At least one movable fuel injector needle (4, 6) for controlling fuel injection through the one or more nozzle orifices (2, 3, 5), wherein - The one or more nozzle holes (2, 3, 5) include at least one non-axial nozzle hole (3, 5) which is configured to inject fuel in a direction that, when projected onto a plane perpendicular to the axial direction of the respective fuel injector needle (4, 6), deviates from the radial direction (R) of the fuel injector needle (4, 6).

2. The fuel injector (1) according to claim 1, wherein, The angle (θ) between the central axis (C) of the at least one non-axial nozzle orifice (3, 5) and the radius (R) of the fuel injector needle (4, 6) intersecting the central axis (C) at the inner end of the non-axial nozzle orifice (3, 5) when projected onto the plane perpendicular to the axial direction of the corresponding fuel injector needle (4, 6) is between 10 and 50 degrees.

3. The fuel injector (1) according to claim 1 or 2, wherein, The outer end of at least one non-axial nozzle hole (3, 5) is provided with a portion (3B) with a diameter larger than that of the inner end of the non-axial nozzle hole (3, 5).

4. The fuel injector (1) according to claim 3, wherein, The diameter (D2) of the outer end of the at least one non-axial nozzle orifice (3, 5) is 200% to 400% of the diameter (D1) of the inner end of the non-axial nozzle orifice (3, 5).

5. The fuel injector (1) according to claim 3 or 4, wherein, The diameter (D2) of the outer end of the at least one non-axial nozzle hole (3, 5) is 10% to 30% of the length (L1) of the non-axial nozzle hole (3, 5).

6. The fuel injector (1) according to any one of claims 3 to 5, wherein, The length (L2) of the portion (3B) with the larger diameter is 30% to 70% of the total length (L1) of the non-axial nozzle orifice (3, 5).

7. The fuel injector (1) according to any one of the preceding claims, wherein, The angle (γ) between the axial direction of the at least one non-axial nozzle orifice (3, 5) and the axial direction of the corresponding injector needle (4, 6) is 30 to 90 degrees.

8. The fuel injector (1) according to any one of the preceding claims, wherein, The at least one non-axial nozzle orifice (3, 5) opens inside the fuel injector (1) into the sac-like volume (20), located in the uppermost third of the sac-like volume (20); or opens into the region of the needle valve seat (21).

9. The fuel injector (1) according to any one of the preceding claims, wherein, The one or more nozzle orifices (2, 3, 5) include one or more ignition fuel nozzle orifices (2, 3), the one or more ignition fuel nozzle orifices (2, 3) include one or more non-axial ignition fuel nozzle orifices (3), the one or more ignition fuel nozzle orifices (2, 3) are configured to inject liquid ignition fuel into the main combustion chamber (14), and the at least one fuel injector needle (4) includes an ignition fuel injector needle (4) for controlling fuel injection via the one or more ignition fuel nozzle orifices (2, 3).

10. The fuel injector (1) according to claim 9, wherein, The one or more ignition fuel nozzle holes (2, 3) include an axial nozzle hole (2) configured to inject fuel in the axial direction of the ignition fuel injector needle (4).

11. The fuel injector (1) according to claim 10, wherein, The fuel injector (1) is configured such that the ignition fuel injector needle (4) has a closed state, a fully raised state, and at least one partially raised state, and in the at least one partially raised state, a greater portion of the ignition fuel is injected through the axial nozzle orifice (2) compared to the fully raised state.

12. The fuel injector (1) according to claim 11, wherein, The ignition fuel injector needle (4) has at least one partially raised state in which the ignition fuel is injected completely or mainly through the axial nozzle orifice (2).

13. The fuel injector (1) according to claim 11 or 12, wherein, The fuel injector (1) is configured such that, in the fully raised state of the ignition fuel injector needle (4), the ignition fuel is injected entirely or primarily through the one or more non-axial ignition fuel nozzle orifices (3).

14. The fuel injector (1) according to any one of claims 10 to 13, wherein, The ignition fuel injector needle (4) is configured to protrude into the axial nozzle orifice (2) in the closed state of the ignition fuel injector needle (4).

15. The fuel injector (1) according to claim 14, wherein, The ignition fuel injector needle (4) is configured to protrude beyond the axial nozzle orifice (2) in the closed state, and the diameter of the portion (4A) protruding beyond the axial nozzle orifice (2) increases toward the outer end of the ignition fuel injector needle (4).

16. The fuel injector (1) according to any one of claims 10 to 15, wherein, The axial nozzle orifice (2) has a larger flow area than the one or more non-axial ignition fuel nozzle orifices (3).

17. The fuel injector (1) according to any one of claims 9 to 16, wherein, The fuel injector (1) is configured to be positioned such that the ignition fuel injector needle (4) is offset from the central axis of the cylinder (10), and the one or more non-axial ignition fuel nozzle holes (3) are positioned such that more ignition fuel is directed to the side further away from the wall of the cylinder (10).

18. The fuel injector (1) according to claim 17, wherein, The fuel injector (1) includes a plurality of non-axial ignition fuel nozzle holes (3), and on the side configured closer to the wall of the cylinder (10), the angular distance (α) between two consecutive non-axial ignition fuel nozzle holes (3) is greater than the angular distance on the side configured further away from the wall of the cylinder (10).

19. The fuel injector (1) according to any one of the preceding claims, wherein, The fuel injector (1) is a dual-fuel injector, which includes one or more main fuel nozzle holes (5), one or more ignition fuel nozzle holes (2, 3), a main fuel injector needle (6) for controlling the injection of main fuel through the main fuel nozzle holes (5), and an ignition fuel injector needle (4) for controlling the injection of ignition fuel through the ignition fuel nozzle holes (2, 3).

20. Use of the fuel injector (1) according to any one of the preceding claims for injecting liquid ignition fuel into the main combustion chamber (14) of a cylinder (10) of a piston engine that uses ammonia or other gaseous fuels, ethanol or methanol as the main fuel.

21. A piston engine comprising a plurality of cylinders (10), a cylinder head (13) for each cylinder (10) of the engine, and a fuel injector (1) mounted in each cylinder head (13) for injecting fuel directly into a main combustion chamber (14) of the cylinder (10) according to any one of claims 1 to 19.

22. The piston engine according to claim 21, wherein, The engine is configured to operate using ammonia or other gaseous fuels, ethanol, or methanol as the primary fuel.

23. A method of operating a piston engine, the method comprising the step of injecting fuel directly into the main combustion chamber (14) of the engine using a fuel injector (1) according to any one of claims 1 to 19.

24. The method according to claim 23, wherein, The method includes the step of introducing main fuel into the cylinder (10) of the engine, and in the step of injecting fuel directly into the main combustion chamber (14), using the fuel injector (1) to inject liquid ignition fuel into the main combustion chamber (14) of the cylinder (10) to promote the ignition and / or combustion of the main fuel.

25. The method according to claim 24, wherein, The primary fuel is ammonia or other gaseous fuels, ethanol, or methanol.

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