Fuel valves for large turbocharged two-stroke unidirectional flow crosshead internal combustion engines

Abstract

A fuel valve (30) for injecting fuel into a combustion chamber (14) of a large turbocharged two-stroke unidirectional flow crosshead internal combustion engine comprises: an elongated fuel valve housing (32) having a longitudinal axis (X), a rear end (31) and a front end (33); an elongated nozzle (40) having a hole (50) and a closed end (44), the hole (50) opening into at least one through opening (45), the nozzle being at the front end of the housing; an axially displaceable valve needle (35) having a hollow shut-off shaft (37) received in the hole (50) for axial displacement between open and closed positions for opening / closing a passage to the hole, the shut-off shaft having a plurality of holes (49) for connecting / disconnecting the hole to the interior of the shut-off shaft in the open / closed position, the holes (49) having a total cross-sectional area smaller than the total cross-sectional area of ​​the openings. By providing an opening in the nozzle having a total cross-sectional area larger than the holes (49), the hole in the shut-off shaft is formed into a true nozzle hole, and problems associated with crack formation in the nozzle are reduced.

Description

Technical Field

[0001] 20. The fuel valve according to claim 19, wherein the fuel valve comprises a nozzle, a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and a nozzle, and

[0002] The invention also relates to a large two-stroke turbocharged unidirectional flow scavenged internal combustion engine having a crosshead including such a fuel valve. Background Art

[0003] A fuel valve of the type mentioned in the introduction is known from EP 2 378 109 A1.

[0004] Large turbocharged two-stroke unidirectional flow crosshead internal combustion engines are commonly used as prime movers in large ocean-going vessels (such as container ships) or power plants. Typically, heavy fuel oil or fuel oil is used to operate these engines.

[0005] The cylinders of these engines are equipped with a single exhaust valve, centrally located in the cylinder head, at the top of the cylinder, and a ring of scavenge ports in the lower area of ​​the cylinder liner, which are controlled by the movement of the piston. Therefore, the direction of gas flow through the cylinder is always from bottom to top, hence the name unidirectional scavenging. Typically, the scavenge ports are angled to create a vortex in the gases in the combustion chamber.

[0006] Two or three fuel valves are arranged in the cylinder head around a centrally located exhaust valve, with their nozzles protruding into the combustion chamber. The fuel valves are arranged peripherally (i.e., not centrally) in the cylinder head, with the nozzle orifices of the nozzles generally pointing toward the vortex, away from the cylinder wall and into the combustion chamber. Sometimes, a single nozzle orifice of the nozzle faces the vortex in the combustion chamber.

[0007] The fuel valve includes an elongated housing, a rear end of which protrudes from an upper surface of the cylinder head and extends through the cylinder head. The fuel valve includes a nozzle attached to a front end of the elongated fuel valve housing and protruding into the combustion chamber.

[0008] Known nozzles for large, two-stroke, crosshead-type diesel engines typically have an elongated nozzle body comprising a cylindrical portion with a straight main bore that leads from the nozzle base at the rear end of the nozzle body to a nozzle orifice located near the top or front end of the nozzle body. The top end may be rounded or flat, but is closed because the nozzle orifice cannot point downward toward the piston (when the piston is at top dead center, i.e., at the moment of fuel injection in a compression-ignition engine, the upper surface of the piston is very close to the nozzle tip). Consequently, the nozzle orifice is oriented primarily laterally relative to the central axis of the nozzle / fuel valve and is typically approximately at right angles to the central axis of the engine cylinder. Typically, each nozzle is provided with three to seven nozzle orifices, all of which are connected to the main orifice.

[0009] Typically, known fuel valves for injecting liquid fuels are equipped with an axially displaceable valve needle that engages a conical valve seat to control the flow of fuel to the nozzle. Furthermore, the front portion of the valve needle includes a shutoff shaft that is tightly received in the main bore and acts as a spool valve, closing the nozzle orifice when the valve needle is in the closed position. This significantly reduces the so-called pocket volume, i.e., the volume of residual fuel in the space formed by the main bore in the nozzle. Without this spool valve structure, the amount of residual fuel in the main bore (and in the nozzle bore) would drip into the combustion chamber after a fuel injection event, adversely affecting fuel consumption, reliability, and emissions.

[0010] Because the nozzle body protrudes into the combustion chamber, it is exposed to the hot combustion gases of the combustion chamber, and parts of the nozzle body will therefore reach relatively high temperatures. Recently, there has been a need to enable large two-stroke diesel engines to handle alternative types of fuels, such as methanol, LPG, ammonia, and / or other similar fuels. Such alternative fuels are relatively clean fuels that, when used as fuel for large, low-speed, unidirectional flow, turbocharged, two-stroke internal combustion engines, will result in significantly lower levels of sulfur-containing components, NOx, and CO2 in the exhaust gas compared to, for example, using heavy fuel oil as the fuel.

[0011] When this alternative fuel is injected into the cylinder's combustion chamber through the nozzle orifice, it evaporates, causing a sharp drop in temperature (due to the required heat of vaporization). Consequently, the incoming fuel exiting the nozzle through the nozzle orifice in the main bore has a significantly lower temperature than the combustion gases surrounding the outer surface of the nozzle body. Consequently, the nozzle body material is exposed to significant temperature gradients, inducing stresses in the nozzle material. Consequently, there is a higher risk of crack formation in the nozzle region where the nozzle orifice is located, when exposed to the high operating temperature of the combustion chamber gases and the high cooling effect of the injected fuel.

[0012] Ammonia is currently of great interest as an alternative fuel for internal combustion engines, primarily because it can be produced in an environmentally friendly manner by using electricity from renewable energy sources such as solar, wind and wave power, and because the combustion of ammonia itself takes place without the formation of carbon-containing greenhouse gases such as carbon dioxide.

[0013] The invention also relates to a large turbocharged two-stroke unidirectional flow crosshead internal combustion engine comprising a fuel valve as described above and as claimed in the appended claims. Summary of the Invention

[0014] It is an object of the present invention to provide a fuel valve of the type mentioned in the introduction in which the above-mentioned difficulties associated with the formation of cracks in the nozzle are at least significantly reduced.

[0015] Other implementations will become apparent from the description and accompanying drawings.

[0016] According to a first aspect, a fuel valve for injecting fuel into a combustion chamber of a large turbocharged two-stroke unidirectional flow crosshead internal combustion engine is provided, the fuel valve comprising: an elongated fuel valve housing having a longitudinal axis, a rear end and a front end; an elongated nozzle having a hole and a closed end, the hole opening in at least one through opening in the nozzle, the nozzle being arranged at the front end of the housing; an axially displaceable valve needle having a hollow shut-off shaft, the hollow shut-off shaft being axially displaceable between an open position and a closed position and being received in the hole in the nozzle for opening and closing a passage to the at least one opening, the shut-off shaft being provided with a plurality of holes so as to connect the at least one opening in the nozzle with the interior of the hollow shut-off shaft in the open position of the hollow shut-off shaft and to disconnect the at least one opening in the nozzle from the interior of the hollow shut-off shaft in the closed position of the hollow shut-off shaft, characterised in that the total cross-sectional area of ​​the plurality of holes in the shut-off shaft is smaller than the total cross-sectional area of ​​the at least one opening.

[0017] Thus, by providing an opening in the nozzle having a larger total cross-sectional area than the hole in the shut-off shaft, the hole in the shut-off shaft is made into a real nozzle hole, and the problems associated with crack formation in the nozzle are reduced. This is because the cooling effect of the evaporated fuel on the nozzle material close to the opening is therefore smaller, and the material is therefore exposed to a substantially smaller temperature gradient, which results in lower stresses in the nozzle material and a lower risk of crack formation in the region of the opening of the nozzle.

[0018] Preferably, in the open position of the hollow shut-off shaft, the plurality of holes in the shut-off shaft are arranged within the periphery of the at least one opening.

[0019] In one embodiment of the invention, the at least one opening in the nozzle can be constituted by one opening in the form of an elongated slot which, in the open position of the hollow shut-off shaft, surrounds all holes in the shut-off shaft.

[0020] In another embodiment of the present invention, the at least one opening in the nozzle can be formed by a plurality of openings. When the hollow shut-off shaft is in its open position, the opening can be an elongated slot surrounding two or more holes in the hollow shut-off shaft, or a plurality of holes, each surrounding a hole in the hollow shut-off shaft. This provides a partition wall between the openings in the nozzle, thereby strengthening the nozzle construction.

[0021] Fuel injected through a nozzle orifice (which, in the fuel valve according to the present invention, is formed by a hole in a hollow shutoff shaft) typically diverges in the form of a cone upon exiting the respective nozzle orifice. The cone angle is typically greater than 10°, and is typically approximately 20° or even greater. Therefore, to reduce the negative impact of the cooling effect of the injected fuel on the nozzle material surrounding the at least one opening in the nozzle, the at least one opening is preferably sized such that the injected fuel does not come into contact with the inner surface of the respective opening in the nozzle. To achieve this, the at least one opening should be arranged such that its inner surface is positioned outside an imaginary cone with its base at the hole in the hollow shutoff shaft and a cone angle of at least 10°, preferably at least 15°, and most preferably at least 20°. The imaginary cone is preferably concentric with the respective hole in the hollow shutoff shaft.

[0022] In the case where the inner surface of the at least one opening includes only generatrixes perpendicular to the longitudinal axis of the fuel valve housing, the most critical point is the edge of the at least one opening located farthest from the hole in the hollow shut-off shaft. In this case, preferably, the edge lies outside an imaginary cone whose base is at the hole in the hollow shut-off shaft and whose cone angle is at least 10°, preferably at least 15°, and most preferably at least 20°. The imaginary cone is preferably concentric with the corresponding hole in the hollow shut-off shaft.

[0023] In another embodiment of the present invention, the at least one opening may be provided with an inclined inner surface, wherein the cross-sectional area increases from one end of the hollow shutoff shaft toward the other end. In such an embodiment, the inner surface is preferably inclined at an angle of at least 5°, preferably at least 7°, and most preferably at least 10° relative to a centerline through the corresponding hole in the hollow shutoff shaft. The centerline through the corresponding hole in the hollow shutoff shaft is typically inclined by several degrees relative to the longitudinal axis of the fuel valve housing.

[0024] The nozzle holes in the nozzle can be distributed radially, and preferably also axially, about the nozzle. The nozzle holes can be axially positioned near the nozzle's tip, which is preferably closed. The nozzle holes can preferably be positioned within a relatively narrow range of the nozzle's circumference, for example, between approximately 50° and 120°. The nozzle holes can be radially oriented further away from the wall of the combustion chamber defined by the cylinder liner. Furthermore, the nozzle holes can be oriented so that they are generally aligned in the same direction as the swirl of the scavenging gas in the combustion chamber caused by the configuration of the scavenging ports. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will now be described in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which:

[0026] Figure 1 is a perspective view showing the front end and one lateral side of a large two-stroke unidirectional flow scavenged turbocharged engine according to an example embodiment,

[0027] Figure 2 Yes Figure 1 A perspective view of the rear end and another lateral side of the engine,

[0028] Figure 3 is based on Figure 1 Schematic diagram of an engine with its intake and exhaust systems,

[0029] Figure 4 is used for Figures 1 to 3 A cross-sectional view of an embodiment of a fuel valve in an engine,

[0030] Figure 5 is used for Figures 1 to 3 A sectional view of another embodiment of a fuel valve in an engine,

[0031] Figure 6 yes Figure 4 or a cross-sectional view of a nozzle of a fuel valve 5,

[0032] Figure 7 yes Figure 6 A cross-sectional view of the nozzle showing the fuel jet cone,

[0033] Figure 8 yes Figure 6 A cross-sectional view of the tip of the nozzle, wherein the distal cylindrical portion of the valve needle is in the closed position,

[0034] Figure 9 yes Figure 8 , wherein the distal cylindrical portion of the valve needle is in the open position, and

[0035] Figure 10 yes Figure 5Schematic diagram of the location of the fuel valve nozzle in the cylinder head (as viewed from the side of the piston), showing the orientation of the nozzle hole and the resulting fuel jet. DETAILED DESCRIPTION

[0036] In the following detailed description, the fuel valve 30 and a large two-stroke engine using the fuel valve will be described by way of example embodiments. Figures 1 to 3 A large, low speed, turbocharged, two-stroke internal combustion engine is shown having a crankshaft 22 and a crosshead 23 . Figure 3 A schematic diagram of a large, low-speed, turbocharged, two-stroke internal combustion engine and its intake and exhaust systems is shown. In this exemplary embodiment, the engine has six cylinders arranged in a straight line (formed by cylinder liners 1). Large, turbocharged, two-stroke internal combustion engines typically have between five and sixteen cylinders arranged in a straight line, supported by an engine frame 24. The engine can be used, for example, as a main engine in an ocean-going vessel or as a stationary engine for operating a generator in a power station. The total output of the engine can, for example, be in the range of 5,000 to 110,000 kW.

[0037] The engine may be a two-stroke, unidirectional-flow diesel (compression-ignition) engine, having scavenging ports 19 in the form of a ring of piston-controlled ports in the lower region of the cylinder liner 1 and exhaust valves 4 at the top of the cylinder liner 1. Consequently, flow in the combustion chamber 14 is always from bottom to top, making the engine a so-called unidirectional-flow type. Scavenging air flows from the scavenging air receiver 2 to the scavenging air ports 19 of each cylinder formed by the cylinder liner 1. Reciprocating pistons 21 in the cylinder liner 1 compress the scavenging air, and fuel is injected through the nozzles of two or three fuel valves 30 arranged in the cylinder head 26. Combustion then occurs, producing exhaust gas. When the exhaust valve 4 opens, the exhaust gas flows through the exhaust duct 20 associated with the relevant cylinder 1 into the exhaust gas receiver 3 and onward through the first exhaust duct 18 to the turbine 6 of the turbocharger 5. The exhaust gas exits the turbine 6 through the second exhaust duct 7. The turbine 6 drives the compressor 9 (which is fed by the air inlet 10) via the shaft 8.

[0038] Compressor 9 delivers pressurized intake air to intake air duct 11, which leads to intake air receiver 2. The scavenging air in duct 11 passes through intercooler 12, which cools the intake air. The cooled intake air is then passed to intake air receiver 2 via auxiliary blower 16, driven by electric motor 17. This auxiliary blower pressurizes the intake air flow under low or part load conditions. Under higher loads, turbocharger compressor 9 delivers sufficiently compressed scavenging air, which then bypasses auxiliary blower 16 via check valve 15.

[0039] The cylinder is formed in the cylinder liner 1. The cylinder liner 1 is carried by a cylinder frame 25, which is supported by the engine frame 24.

[0040] Figure 4 An embodiment of one of two or three fuel valves 30 is shown, which is mounted in a through-hole in the cylinder head 26 of each cylinder, wherein a rear end 31 of the fuel valve 30 protrudes from the upper side of the cylinder head 26 and a front end of the nozzle 40 protrudes slightly into the combustion chamber 14. The fuel valve 30 includes an elongated fuel valve body 32 having a nozzle holder at its front end 33. The nozzle holder connects the nozzle 40 to the elongated fuel valve body 32. Liquid fuel (e.g., methanol, LPG, ammonia, and / or other similar fuels) is delivered to the combustion chamber 14 through the nozzle 40 in a controlled, timed manner via the fuel valve 30. Figure 4 The fuel valve 30 shown in the figure has an elongated fuel valve housing 32, which has a head at its rear end 31, by which the fuel valve 30 can be mounted in a known manner in the cylinder head 26 and connected to a fuel pump (not shown) of the internal combustion engine.

[0041] The head portion at the rearward end 31 includes a fuel inlet 81 that is fluidly connected to a conduit extending through the valve body 32. An axially displaceable valve needle 35 is journaled in the elongated fuel valve housing 32 and has an open position, in which the valve needle 35 is lifted from a preferably conical valve seat 36, and a closed position, in which a mating portion of the valve needle 35 sealingly rests on the valve seat 36. The valve needle is resiliently biased toward the closed position by resilient means, which in this embodiment is formed by a coil spring 83. The lifting of the valve needle 35 against the bias of the coil spring 83 is caused by the pressure of the fuel supplied to the fuel valve 30 (acting on a surface of the valve needle 35 or on a surface of a piston or plunger operatively connected to the valve needle 35). The elongated fuel valve housing 32 of the fuel valve 30 carries a nozzle 40 at its forward end 33. The nozzle 40 is arranged to project into the combustion chamber 14 of the engine cylinder liner 1 when the fuel valve 30 is mounted on the cylinder head 26.

[0042] The fuel valve according to the invention may also be of the hydraulically controlled type or be part of a common rail fuel valve system.

[0043] In this embodiment, the fuel valve includes an axially movable valve needle 35 including a tapered portion that cooperates with a tapered seat 36 in the elongated fuel valve housing 32 of the fuel valve 30 .

[0044] Figure 5 A fuel valve 30 according to another embodiment is shown, which is similar to Figure 4 The embodiment of the invention differs in that a booster pump is included to increase the pressure of the fuel supplied to the fuel valve 30. The main component of the booster pump is the booster plunger 80. The other components of the fuel valve 30 and the nozzle 40 according to this embodiment are conceptually the same as those of the fuel valve 30 and the nozzle 40 according to this embodiment. Figure 4 The fuel valve is the same.

[0045] Figure 10 It shows how the nozzles 40 are positioned peripherally in the cylinder head 26 and shows the directions of the fuel jets corresponding to the directions of the axes I, II, II, IV and V. The direction of the gas swirl in the combustion chamber 14 is indicated by the curved interrupted arrows 66 .

[0046] Figures 6 to 9 The nozzle 40 and the distal portion of the valve needle 35 are shown in greater detail.

[0047] Nozzle 40 has a nozzle body extending from a base 42 at a proximal end to a closed distal end 44 forming the tip of nozzle 40. A cylindrical portion 43 of the nozzle body extends from the base to the distal end 44. The nozzle body is manufactured from a suitable material, such as a suitable alloy known in the art.

[0048] When the valve needle 35 is in the open position, an inlet 48 opens into the base 42 for receiving liquid fuel from the elongated fuel valve housing 32 of the fuel valve 30. A single straight main bore 50 extends longitudinally from the inlet 48 into the nozzle body.

[0049] The closed distal end (top) 44 includes a generally planar end surface 47 having a circular or oval profile. The end surface 47 is connected to the cylindrical portion by a curved or radiused transition surface 46.

[0050] The axially displaceable valve needle 35 comprises a hollow shutoff shaft 37 including a cylindrical end portion 39 carried by a stem 38 that moves in unison with the valve needle 35. The cylindrical end portion 39 is received in a straight main bore 50 with a tight fit and is axially displaceable therein between an open position and a closed position. The hollow shutoff shaft 37 is provided with a plurality of holes 49 disposed proximate the distal end of the cylindrical end portion 39. The hollow shutoff shaft 37 is rotatably positioned in the straight main bore 50 and is held in place, for example, by a pin (not shown).

[0051] The nozzle 40 according to the invention is provided with a through-opening 45 in the form of an elongated slot, which in the open position of the hollow shut-off shaft 37 surrounds all holes 49 in the shut-off shaft, see Figure 9 Thus, the opening 45 in the nozzle 40 is connected to the interior of the hollow shut-off shaft 37 in the open position of the hollow shut-off shaft 37 and is disconnected from the interior of the hollow shut-off shaft 37 in the closed position of the hollow shut-off shaft 37, see Figure 8 .

[0052] In other, not shown, embodiments of the present invention, the nozzle may include more openings 45. These openings 45 may be elongated slots surrounding two or more holes 49 in the hollow shutoff shaft 37 when the hollow shutoff shaft 37 is in its open position, or a plurality of holes each surrounding one hole 49 in the hollow shutoff shaft 37. In this way, partition walls are provided between the openings 45 in the nozzle 40, thereby strengthening the construction of the nozzle 40.

[0053] Therefore, in the fuel valve 30 according to the present invention, the hole 49 in the shut-off shaft 37 constitutes a nozzle hole through which fuel is injected, and the injected fuel will diverge from the outlet of the nozzle hole and enter the combustion chamber 14 through the opening 45 in the nozzle 40. Figure 7 A fuel jet is shown from the orifice 49, which enters the combustion chamber 14 in the form of a cone having a cone angle of 20°.

[0054] exist Figure 7 As can be seen in the figure, hollow shutoff shaft 37 includes a longitudinally extending bore 34 through which the fuel flows in the direction of bore 49. In the illustrated embodiment, bore 34 is drilled eccentrically with respect to the longitudinal axis X of the fuel valve housing 32. This allows the wall thickness of hollow shutoff shaft 37 to be greater in the region of bore 49, resulting in a longer length of these bores 49, which serve as nozzle openings and are therefore more optimal for proper fuel injection. A further advantage of the greater material thickness in the region of bore 49 is that the material can better withstand the high temperatures in combustion chamber 14. However, bore 34 in hollow shutoff shaft 37 can also be drilled concentrically with respect to the longitudinal axis X of the fuel valve housing 32.

[0055] exist Figure 8 , the axially displaceable valve needle 35 is shown in its closed position, wherein the hole 49 in the hollow shut-off shaft 37 is covered by the inner wall of the nozzle 40 , so that the opening 45 in the nozzle 40 is disconnected from the interior of the hollow shut-off shaft 37 .

[0056] exist Figure 9 , the axially displaceable valve needle 35 is shown in its open position, wherein a hole 49 in the hollow shut-off shaft 37 opens into an opening 45 in the nozzle 40 , thereby connecting the opening 45 in the nozzle 40 with the interior of the hollow shut-off shaft 37 and allowing fuel injection into the combustion chamber 14 .

[0057] Due to the aforementioned problems associated with stresses and possible cracks in the nozzle when the injected fuel evaporates and cools significantly, it is very important that the injected fuel does not come into contact with the material of the nozzle, or at least has reduced contact. Therefore, according to the invention, in the open position of the hollow shut-off shaft 37, the hole 49 in the shut-off shaft 37 is arranged within the circumference of the opening 45, as shown in FIG. Figure 9As best shown in FIG. 3 , the total cross-sectional area of ​​the holes 49 in the shut-off shaft 37 is also smaller than the total cross-sectional area of ​​the openings 45 .

[0058] Therefore, in order to reduce the negative impact of the cooling effect of the injected fuel on the nozzle material surrounding the opening 45 in the nozzle 40, the opening 45 is sized so that the injected fuel will not contact the inner surface of the opening 45 in the nozzle 40. Since the fuel injected through the hole 49 generally diverges in the form of a cone 27 (the angle of the cone 27 is generally greater than 10 degrees, and often greater than 20 degrees), the opening 45 should preferably be arranged so that its inner surface is located outside the imaginary cone 27, the base of the imaginary cone 27 being located at the hole 49 in the hollow stop shaft 37, and the cone angle is at least 10 degrees, preferably at least 15 degrees, and most preferably at least 20 degrees. The imaginary cone 27 is preferably concentric with the corresponding hole 49 in the hollow stop shaft 37.

[0059] Typically, the inner upper and lower surfaces 28, 29 of the opening 45 include generatrixes that are parallel and slightly inclined relative to the longitudinal axis X of the fuel valve housing 32. Therefore, the most critical points of the opening 45 are those of the edge 52 of the opening 45 that are furthest from the hole 49 in the hollow shut-off shaft 37. In this case, it is preferred that these points lie outside an imaginary cone whose base is located at the hole 49 in the hollow shut-off shaft 37 and whose cone angle is at least 10°, preferably at least 15°, and most preferably at least 20°. The imaginary cone is preferably concentric with the corresponding hole 49 in the hollow shut-off shaft 37.

[0060] In another embodiment of the present invention, the opening 45 may be provided with an inclined inner surface, wherein the cross-sectional area increases from one end proximal to the hollow stop shaft 37 toward the other end. In an embodiment not shown, the inner upper and lower surfaces of the opening 45 are preferably inclined at an angle of at least 5°, preferably at least 7°, and most preferably at least 10° relative to the center line of the corresponding hole 49 passing through the hollow stop shaft 37.

Claims

1. A fuel valve (30) for injecting fuel into a combustion chamber (14) of a large turbocharged two-stroke unidirectional flow crosshead internal combustion engine, the fuel valve (30) comprising: An elongated fuel valve housing (32) having a longitudinal axis (X), a rear end (31) and a front end (33); an elongated nozzle (40) having a hole (50) and a closed end (44), the hole (50) opening into at least one through-opening (45) in the nozzle, the nozzle (40) being arranged at the front end of the housing (32); an axially displaceable valve needle (35) having a hollow shut-off shaft (37) received in the hole (50) in the nozzle (40) axially displaceable between an open position and a closed position for opening and closing a passage to the at least one opening (45), the shut-off shaft (37) being provided with a plurality of holes (49) for enabling the hollow shut-off shaft (37) to be displaced in the open position. The invention relates to a nozzle (40) having at least one opening (45) connected to the interior of a hollow shut-off shaft (37) and disconnected from the interior of the hollow shut-off shaft (37) in the closed position of the hollow shut-off shaft (37), characterized in that the total cross-sectional area of ​​the plurality of holes (49) in the shut-off shaft (37) is smaller than the total cross-sectional area of ​​the at least one opening (45), the at least one opening (45) is sized so that injected fuel does not contact the inner surface of the at least one opening (45), and the edge (52) of the at least one opening (45) farthest from the hole (49) in the hollow shut-off shaft (37) is located outside an imaginary cone having a base at the hole (49) in the hollow shut-off shaft (37) and a cone angle of at least 10°.

2. The fuel valve (30) according to claim 1, characterized in that: In the open position of the hollow shut-off shaft (37), the plurality of holes (49) in the shut-off shaft (37) are arranged within the periphery of the at least one opening (45).

3. The fuel valve (30) according to claim 1, characterized in that: The at least one opening (45) in the nozzle (40) consists of an opening in the form of an elongated slot which, in the open position of the hollow shut-off shaft (37), surrounds all holes (49) in the shut-off shaft (37).

4. The fuel valve (30) according to claim 1, characterized in that: The at least one opening (45) in the nozzle (40) is composed of a plurality of openings.

5. The fuel valve (30) according to claim 4, characterized in that: The opening (45) is an elongated slot surrounding two or more holes (49) in the hollow shut-off shaft (37) when the hollow shut-off shaft (37) is in its open position.

6. The fuel valve (30) according to claim 4, characterized in that: When the hollow shut-off shaft (37) is in its open position, the opening (45) is a plurality of holes, each of which surrounds a hole (49) in the hollow shut-off shaft (37).

7. The fuel valve (30) according to claim 1, characterized in that: The imaginary cone is concentric with the corresponding hole (49) in the hollow stop shaft (37).

8. The fuel valve (30) according to claim 1, characterized in that: The at least one opening (45) is provided with an inclined inner surface, wherein the cross-sectional area increases from the end close to the hollow stop shaft (37) in a direction toward the other end.

9. The fuel valve (30) according to claim 8, characterized in that: The inner surface is inclined at an angle of at least 5° relative to a center line passing through a corresponding hole (49) in the hollow shut-off shaft (37).

10. The fuel valve (30) according to claim 1, characterized in that: The cone angle of the imaginary cone is at least 15°.

11. The fuel valve (30) according to claim 1, characterized in that: The cone angle of the imaginary cone is at least 20°.

12. The fuel valve (30) according to claim 8, characterized in that: The inner surface is inclined at an angle of at least 7° relative to a center line passing through a corresponding hole (49) in the hollow shut-off shaft (37).

13. The fuel valve (30) according to claim 8, characterized in that: The inner surface is inclined at an angle of at least 10° relative to a center line passing through a corresponding hole (49) in the hollow shut-off shaft (37).

14. A large turbocharged two-stroke unidirectional flow crosshead internal combustion engine comprising a fuel valve (30) according to any one of the preceding claims.

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