A fuel valve for injecting fuel into the cylinders of a large turbocharged two-stroke uniflow scavenged internal combustion engine and an engine with such fuel valve

Abstract

A fuel valve (30) for injection of fuel into a large two-stroke turbocharged uniflow scavenged internal combustion engine with an axially displaceable valve needle (35) cooperating with a valve seat (36) in the valve body and cylindrical distal section (39) of the valve needle (35) in a nozzle (40), the cylindrical distal section (39) being provided with a sealing ring (52).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a fuel valve for injecting liquid fuel into the cylinders of a large turbocharged two-stroke uniflow scavenged internal combustion engine.BACKGROUND

[0002] Large turbocharged two-stroke uniflow scavenged crosshead internal combustion engines are typically used as prime movers in large ocean-going ships, such as container ships or in power plants.

[0003] The cylinders of these engines are provided with a single exhaust valve centrally placed in the cylinder cover i.e., at the top of the cylinder and with a ring of piston controlled scavenge ports at the lower region of the cylinder liner. Accordingly, the direction of transport of gas through the cylinder is always from bottom to top, hence the designation uniflow scavenged. The scavenge ports are slanted to create a swirl in the gases in the combustion chamber.

[0004] Two or three fuel valves are disposed in the cylinder cover around the centrally placed exhaust valve, with their nozzles projecting into the combustion chamber. The fuel valves are peripherally disposed (i.e. not central) in the cylinder cover with the nozzle bores of the nozzles substantially directed with the swirl, away from the cylinder wall and into the combustion chamber.

[0005] Occasionally, a single nozzle hole of a nozzle is directed against the swirl in the combustion chamber.

[0006] A nozzle is attached to the forward or distal end of a fuel valve. The fuel valve comprises an elongated housing with the proximal or rear end protruding from the upper surface of the cylinder cover and with the elongated fuel valve housing extending through the cylinder cover and with the nozzle at the forward or distal end of the elongated fuel valve housing projecting into the combustion chamber.

[0007] Known nozzles for large two-stroke diesel engines of the crosshead type typically have an elongated nozzle body comprising a cylindrical section with a straight main bore leading from the base of the nozzle at a proximal end of the nozzle body to nozzle bores that are located near the tip or distal end of the nozzle body. The tip or distal end can be round or flat but is closed since the nozzle bores must not be directed downwardly towards the piston (when the piston is at top dead center, i.e. the moment of fuel injection for a compression igniting engine, the upper surface of the piston is very close to the tip of the nozzle). Thus, the nozzle bores are mainly laterally directed relative to the main axis of the nozzle / fuel valve and typically approximately at a right angle to the main axis of the engine cylinder. Typically, each nozzle is provided with three to seven nozzle bores that are all connected to the main bore.

[0008] Typically, the known fuel valves for injecting liquid fuel are provided with an axially displaceable valve needle that cooperates with a conical valve seat for controlling the flow of fuel to the nozzle. In addition, the forward section of the valve needle comprises a distal cylindrical section that is tightly received in the main bore and acts as a slide valve for closing off the nozzle bores when the valve needle is in the closed position to thereby significantly reduce the so-called sac volume, i.e. the residual volume of fuel in the space formed by the main bore in the nozzle. Without such a slide valve arrangement, the volume of residual fuel in the main bore (and in the nozzle bores) would drip into the combustion chamber after a finished fuel injection event, which has detrimental effects on fuel consumption, reliability, and emissions.

[0009] Since the nozzle body projects into the combustion chamber, it is exposed to the hot gases of the combustion chamber and parts of the nozzle body will, therefore, reach relatively high temperatures of up to approximately 400°C.

[0010] DK181704B1 discloses a fuel valve for injection of fuel into a large two-stroke turbocharged uniflow scavenged internal combustion engine, the fuel valve comprises a fuel valve housing with an axis, a proximal end and a distal end, an axially displaceable valve needle with a closed position resting on a valve seat and an open position where the valve needle has lift from the valve seat, and an atomizer nozzle disposed at the distal end of said elongated valve housing. The atomizer nozzle has a nozzle body extending along said axis from a base at a proximal end of said nozzle body to a closed distal end of said nozzle body and comprises a substantially cylindrical portion extending between said base and said closed distal end, an inlet opening to the base for receiving liquid fuel from said fuel valve, a plurality of straight nozzle bores, each nozzle bore opening to the outer surface of said nozzle body at a different radial angle, a single straight main bore extending longitudinally from said inlet into said nozzle body, the straight nozzle bores being connected to said straight main bore by an individual supply passage arranged at an angle to said straight main bore and to the straight nozzle bore concerned, the valve needle comprising a distal section with a cylindrical end section carried by a shank and which is journaled with tight fit in the straight main bore to disconnect the individual supply passages from the main straight bore when the valve needle is in the closed position.

[0011] This known design works well with conventional fuels such as fuel oil. However, the desire to reduce or even avoid CO2 has led to the use of different types of fuel components such as ammonia. Tests have shown that this conventional design does not work with ammonia or other low viscosity fuel since the barrier posed by the distal cylindrical section that is tightly received in the main bore is not enough when operating with ammonia, due to the low viscosity of ammonia and due to the fact that ammonia trapped above the distal cylindrical section will quickly heat up and boil due to the heat exposed by the combustion chamber to the nozzle, thereby creating pressure forcing ammonia past the distal cylindrical section and into the combustion chamber when the fuel valve is closed and no ammonia is supposed to enter the combustion chamber. This in turn leads to poorly combusted or uncombusted ammonia entering the exhaust system which is highly undesirable.SUMMARY

[0012] In view of the above, it is an object to provide a fuel valve for injecting liquid fuel into a large two-stroke uniflow scavenged internal combustion engine of the crosshead type that overcomes or at least reduces the problems mentioned above.

[0013] The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description, and the figures.

[0014] According to a first aspect, there is provided a fuel valve for injection of liquid fuel into a large two-stroke turbocharged uniflow scavenged internal combustion engine with crossheads, the fuel valve comprising: an elongated fuel valve housing with a longitudinal axis, a proximal end, and a distal end, an axially displaceable valve needle, the valve needle having a closed position resting on a valve seat and an open position where the valve needle has lift from the valve seat, and an atomizer nozzle disposed at the distal end of the elongated valve housing, the atomizer nozzle having a nozzle body extending along the longitudinal axis from a base at a proximal end of the nozzle body to a closed distal end of the nozzle body, the base being attached to a distal end of the fuel valve housing, the nozzle body comprising: an elongated, preferably cylindrical portion extending between the base and the closed distal end, an inlet opening to the base for receiving liquid fuel from the fuel valve, a plurality of nozzle bores, a main bore extending longitudinally from the inlet into the nozzle body, the valve needle comprising a cylindrical distal section carried by a shank, the cylindrical distal section is journaled with tight fit in a distal portion of the main bore to fluidically disconnect the nozzle bores from the main bore when the valve needle is in the closed position, wherein the cylindrical distal section is provided with a circumferential groove with a sealing ring held in the circumferential groove, wherein the main bore has an uninterrupted cylindrical surface facing the sealing ring in the closed position of the valve needle, and wherein the main bore has an interrupted cylindrical surface facing the sealing ring in the open position of the valve needle, the interruptions in the interrupted cylindrical surface being formed by a plurality of circumferentially spaced axial grooves.

[0015] By providing a sealing ring and an interrupted surface that contains the sealing ring in the circumferential groove when the valve needle is in the open position while allowing fuel to pass through the grooves, a fuel valve can be provided with a sealing ring in the cylindrical distal section that is able to seal fuels with low viscosity, thus preventing fuel from leaking into the combustion chamber when the fuel valve is closed. This, in turn, reduces undesired emissions.

[0016] According to a possible implementation form of the first aspect, the main bore has a first larger diameter proximal of the axial grooves and a second smaller diameter in the area of the axial grooves and where it forms the uninterrupted cylindrical surface facing the sealing ring in the closed position of the valve needle.

[0017] According to a possible implementation form of the first aspect, the shank has a smaller cross-sectional area than the cylindrical distal section.

[0018] According to a possible implementation form of the first aspect, the cylindrical distal section disconnects the opening of the nozzle bores from the portion of the main bore proximal to the cylindrical distal section when the valve needle is in the closed position.

[0019] According to a possible implementation form of the first aspect, the cylindrical distal section connects the opening of the nozzle bores to the portion of the main bore proximal to the cylindrical distal section when the valve needle is in the open position.

[0020] According to a possible implementation form of the first aspect, the axially displaceable valve needle is slidably received in a longitudinal bore in the elongated valve housing, the valve needle resting on the valve seat, preferably a conical valve seat, in the closed position and the valve needle having lift from the valve seat in the open position and the valve needle preferably being resiliently and / or fluidically biased towards the closed position, and preferably, a fuel chamber surrounding the valve needle and opening to the valve seat.

[0021] According to a possible implementation form of the first aspect, the fuel valve comprises a fuel inlet port in the elongated fuel valve housing for connection to a source of liquid fuel.

[0022] According to a possible implementation form of the first aspect, the nozzle bores are directed in a substantially radial direction.

[0023] According to a possible implementation form of the first aspect, the nozzle bores each have a nozzle axis, and wherein the nozzle axis of each of the nozzle bores is arranged at an obtuse angle α with the longitudinal axis X.

[0024] According to a possible implementation form of the first aspect, the radial components of each of the nozzle axes relative to the longitudinal axis are distributed, preferably substantially equally distributed, over a circular sector with an arc less than 120 deg., preferably less than 110 deg. and even more preferably less than 100 deg.

[0025] According to a possible implementation form of the first aspect, the fuel valve comprises three to twelve axial grooves.

[0026] According to a possible implementation form of the first aspect, the circumferential groove holds two or more sealing rings.

[0027] According to a possible implementation form of the first aspect, the sealing ring comprises a ring partition, preferably a labyrinth type ring partition.

[0028] According to a second aspect, there is provided a large two-stroke turbocharged uniflow scavenged internal combustion engine with crossheads comprising a fuel valve according to the first aspect or any one implementation thereof.

[0029] These and other aspects will be apparent from the examples and the embodiments described below.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the following detailed portion of the present disclosure, the invention will be explained in more detail with reference to the example embodiments shown in the drawings, in which: Fig. 1 is an elevated view showing the fore end and one lateral side of a large two-stroke unit flow scavenged turbocharged engine according to an example embodiment, Fig. 2 is an elevated view showing the aft end and the other lateral side of the engine of Fig. 1, Fig. 3 is a diagrammatic representation of the engine according to Fig. 1 with its intake and exhaust systems, Fig. 4 is a side view of an embodiment of a fuel valve for use in the engine of Figs. 1 to 3, Fig. 5 is a sectional view of the fuel valve of Fig. 4, Fig. 6 is a sectional view of a nozzle of the fuel valve of Figs. 4 and 5, Fig. 7 is an elevated view of the nozzle of Fig. 6, Fig. 8, is a sectional view of the forward section of the fuel valve of Fig. 4 and 5 with a different from the nozzle of Figs 6 and 7, Fig. 9 is a cross-sectional view through the nozzle shown in Fig. 8 showing circumferentially distributed longitudinal recesses, Fig. 10 is another cross-sectional view through the nozzle shown in Fig. 8 showing a sealing ring, Fig. 11 is another sectional view of the forward section of the fuel valve of Fig. 8, Fig. 12 is another sectional view of the forward section of the fuel valve of Fig. 8, Fig. 13 is a detailed sectional view of the nozzle of the fuel valve of Fig. 8, Fig. 14 is an elevated view of the distal section of a valve needle with the sealing ring, Fig. 15 is an elevated view of the sealing ring, and Fig. 16 is a diagrammatic representation of the position of the nozzles of the fuel valves of Fig. 5 in the cylinder cover, as seen from the side of the piston and illustrating the orientation of the nozzle bores and the resulting fuel jets. DETAILED DESCRIPTION

[0031] In the following detailed description, a fuel valve, and a large two-stroke engine in which the fuel valve is used will be described by the example embodiments. Figs. 1 to 3 show a large low speed turbocharged two-stroke internal combustion engine with a crankshaft 22 and crossheads 23. Fig. 3 shows a diagrammatic representation of a large low speed turbocharged two-stroke internal combustion engine with its intake and exhaust systems. In this example embodiment, the engine has six cylinders (that are formed by cylinder liners 1) in line. Large turbocharged two-stroke internal combustion engines have typically between five and sixteen cylinders in line, carried by an engine frame 24. The engine may e.g., be used as the 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 may, for example, range from 5,000 to 110,000 kW.

[0032] The engine can be a diesel (compression-igniting) engine of the two-stroke uniflow type with scavenge ports 19 in the form of a ring of piston-controlled ports at the lower region of the cylinder liners 1 and an exhaust valve 4 at the top of the cylinder liners 1. Thus, the flow in the combustion chamber is always from the bottom to the top and thus the engine is of the so-called uniflow type. The scavenging air is passed from the scavenging air receiver 2 to the scavenging air ports 19 of the individual cylinders that are formed by the cylinder liners 1. A reciprocating piston 21 in the cylinder liner 1 compresses the scavenging air, fuel is injected via the nozzles of two or three fuel valves 30 that are arranged in the cylinder cover 26. Combustion follows and exhaust gas is generated. When an exhaust valve 4 is opened, the exhaust gas flows through an exhaust duct 20 associated with the cylinder 1 concerned into an exhaust gas receiver 3 and onwards through a first exhaust conduit 18 to a turbine 6 of the turbocharger 5, from which the exhaust gas flows away through a second exhaust conduit 7. Through a shaft 8, the turbine 6 drives a compressor 9 supplied via an air inlet 10.

[0033] The compressor 9 delivers pressurized charging air to a charging air conduit 11 leading to the charging air receiver 2. The scavenging air in the conduit 11 passes through an intercooler 12 for cooling the charging air. The cooled charging air passes via an auxiliary blower 16 driven by an electric motor 17 that pressurizes the charging air flow in low or partial load conditions to the charging air receiver 2. At higher loads the turbocharger compressor 9 delivers sufficient compressed scavenging air and then the auxiliary blower 16 is bypassed via a nonreturn valve 15.

[0034] The cylinders are formed in a cylinder liner 1. The cylinder liners 1 are carried by a cylinder frame 25 that is supported by the engine frame 24.

[0035] Figs. 4 to 15 illustrate an embodiment of the one of the two or three fuel valves 30 that are mounted in a throughgoing bore in the cylinder cover 26 of each cylinder with the rear end 32 of the fuel valve 30 protruding from the upper side of the cylinder cover 26 and with the distal end (tip) of the nozzle 40 marginally protruding into the combustion chamber. The fuel valve 30 comprises an elongated fuel valve body 32 with a nozzle holder at its distal (forward) end 33. The nozzle holder connects the nozzle 40 to the elongated fuel valve body 32. Liquid fuel (e.g., ammonia, ethanol, methanol, diesel, heavy fuel oil) is delivered in a controlled and timed manner by the fuel valve 30 to the combustion chamber 14 via the nozzle 40. The fuel valve 30 illustrated in Fig. 4 has an elongated external housing 32 which at its proximal end 31 has a head by which the fuel valve 30 in a known manner may be mounted in the cylinder cover 26 and be connected with a fuel pump (not shown) of the internal combustion engine.

[0036] The head at the proximal end 31 includes a fuel inlet which is in flow connection with a duct extending through the valve body 32. An axially displaceable valve needle 35 is journaled in the valve housing 32 and has an open position in which the valve needle 35 has lift from a preferably conical valve seat 36 and a closed position in which a matching section of the valve needle 35 rests in a sealing fashion on the valve seat 36. The valve needle 35 is resiliently biased towards the closed position by resilient means, in the present embodiment formed by a helical spring 83. Lift of the valve needle 35 against the bias of the helical 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 of a piston or plunger operably connected to the valve needle 35. The fuel valve 30 carries at its distal end 33 a nozzle 40. The nozzle 40 is configured to project into the combustion chamber 14 of the engine cylinder liner 1, when the fuel valve 30 is mounted on the cylinder cover 26.

[0037] In the present embodiment, the fuel valve 30 comprises an axially movable valve needle 35 that comprises a conical section that cooperates with a conical seat 36 in the longitudinal housing 32 of the fuel valve 30.

[0038] Fig. 16 illustrates how the nozzles 40 are peripherally positioned in the cylinder cover 26 and illustrates the direction of the fuel jets (which corresponds to the direction of the axes I,II,II,IV, and V of nozzle bores 45 in the nozzles 40. The direction of the swirl of the gases in the combustion chamber is illustrated by the curved interrupted arrow 66.

[0039] The fuel valve 30 comprises an optional booster pump to amplify the pressure of the fuel that is supplied to the fuel valve 30. The main component of the booster pump is a booster plunger 80.

[0040] Figs. 6 to 11 illustrate the nozzle 40 and the distal section of the valve needle 35 in greater detail.

[0041] The nozzle 40 has a nozzle body that extends from a base 42 at a proximal end to a closed distal end 44 that forms the tip of the nozzle 40. A cylindrical portion 43 of the nozzle body extends from the base to the distal end 44. The nozzle body is made from a suitable material, e.g., a suitable alloy, e.g., tool steel, as is well known in the art.

[0042] An inlet 48 opens to the base 42 for receiving liquid fuel from the fuel valve 30 when the valve needle 35 is in the open position. A main bore 50 extends longitudinally from the inlet 48 into the nozzle body.

[0043] The closed distal end (tip) 44 comprises a substantially planar end surface 47 with a circular or elliptical outline. The end surface 47 connects to the cylindrical portion via a curved or rounded transition surface.

[0044] The nozzle 40 is provided with a plurality of (preferably straight) bores 45. The nozzle 40 is provided with any desirable number of nozzle bores 45, preferably between three and seven nozzle bores 45 even more preferably between three and six nozzle bores 45, and most preferably five or six nozzle bores 45. The nozzle 40 according to the present embodiment is provided with six nozzle bores 45.

[0045] Each nozzle bore 45 opens to the outer surface of the nozzle body 43 at a different radial angle to cause a fan of fuel rays (as shown in Fig. 16) to be injected into the combustion chamber when the fuel valve 30 opens. Each nozzle bore 45 opens to the outer surface of the nozzle body at a different radial angle. Preferably, the nozzle bores 45 opens to the cylindrical surface 43 and / or to the transition surface.

[0046] The nozzle holes 45 each have a nozzle axis I,II,III,IV, and V (Fig. 16). The nozzle axes I,II,III,IV, and V of each of the holes 45 is arranged at an obtuse angle α with the main axis X. The obtuse angle α can be different for each of the nozzle holes 45. The radial components of each of the nozzle axis I,II,III,IV, and V relative to the main axis X are distributed over a circular sector with an arc of less than 120 deg. preferably less than 110 deg. and even more preferably less than 100 deg. The radial components of each of the nozzle axis (I,II,III,IV, and V) relative to the main axis X are substantially evenly distributed over the circular section, to maximize the amount of nozzle body material between the individual nozzle holes 45.

[0047] The base 42 is provided with an inlet port 48 for receiving fuel from the fuel valve 30. A main bore 50 extends from the inlet port 48 into the nozzle body and into the cylindrical portion 43 in a direction along a main axis and X to a position close to the distal end 44 of the nozzle body. The main bore 50 connects to the plurality of nozzle bores 45.

[0048] The inlet port 48 is in an embodiment formed by a bore with a diameter that is larger than the diameter of the main bore 50. Alternatively, the inlet port 48 can have the same diameter as the main bore.

[0049] The valve needle 35 comprises a distal section that comprises a cylindrical distal section 39 carried by a shank 38 with a preferably lesser diameter / cross-sectional area than the cylindrical distal section 39.

[0050] The cylindrical distal section 39 is journaled with a tight fit in a distal portion of the main bore 50 to fluidically disconnect the nozzle bores 45 from the main bore 50 when the valve needle 35 is in the closed position.

[0051] The cylindrical distal section 39 is provided with a circumferential groove 54 with a sealing ring 52 held in the circumferential groove 54. The sealing ring 52 is made from a suitable alloy that is suitable for high temperature and high pressure and has a ring partition 53. The piston ring may be coated with a diamond like carbon coating (DLC coating). The main bore 50 has an uninterrupted cylindrical surface facing the sealing ring 52 in the closed position of the valve needle 35. The sealing ring 52 seals against this uninterrupted cylindrical surface and prevents fuel, also low viscosity fuel, from leaking past the cylindrical distal section 39.

[0052] The bore 50 has an interrupted cylindrical surface facing the sealing ring 52 in the open position of the valve needle 35. The interruptions in the interrupted cylindrical surface are formed a plurality of circumferentially spaced axial grooves 63. In the present embodiment there are six axial grooves but there could be as few as three axial grooves 63 or as many as twelve axial grooves 63. The interrupted cylindrical surface keeps the sealing ring 52 compressed in the circumferential groove 54 while allowing fuel to pass the sealing ring 52 through the axial grooves 63. It is advantageous to keep the sealing ring 52 compressed since the sealing ring 52 or the running surface on which it acts would otherwise be damaged when the valve needle 35 moves between the open and closed positions.

[0053] Thus, the cylindrical distal section 39 with its sealing ring 52 fluidically disconnects the nozzle bores 45 from the main bore 50 when the valve needle 35 is in the closed position. Thus, any fuel in the space between the valve seat 36 and the distal end of the main bore 50 is prevented from leaking into the combustion chamber 14 when the valve needle 35 is in the closed position.

[0054] Thus, the cylindrical distal section 39 allows fuel to flow to the nozzle holes via the axial grooves 63 when the valve needle 35 is in the open position.

[0055] The main bore has a first larger diameter proximal of the axial grooves 63 and a second smaller diameter in the area of the axial grooves 63 and where it forms the uninterrupted cylindrical surface facing the sealing ring 52 in the closed position of the valve needle 35.

[0056] The axially displaceable valve needle 35 is slidably received in a longitudinal bore 64 in the elongated valve housing 32. The valve needle 32 rests on a valve seat 36, preferably a conical valve seat, in the closed position and the valve needle 35 has lift from the valve seat 35 in the open position and the valve needle 35. A fuel chamber 68 surrounds the valve needle 35 and opens to the valve seat 36. One or more conduits 61 supply fuel to the fuel chamber 68. A sealing liquid conduit 65 supplies pressurized sealing liquid, with a pressure higher than the fuel pressure, to a bore in which the valve needle 35 is journalled.

[0057] The nozzle bores 45 are directed in a substantially radial direction.

[0058] In an embodiment, the circumferential groove 54 holds two or more sealing rings 52 to improve sealing efficiency.

[0059] In an embodiment, the ring partition 53 is a labyrinth-type ring partition to improve sealing efficiency.

[0060] The invention has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The reference signs used in the claims shall not be construed as limiting the scope.

Claims

1. A fuel valve (30) for injection of liquid fuel into a large two-stroke turbocharged uniflow scavenged internal combustion engine with crossheads, the fuel valve (30) comprising: an elongated fuel valve housing (32) with a longitudinal axis (X), a proximal end (31), and a distal end (33), an axially displaceable valve needle (35), the valve needle (35) having a closed position resting on a valve seat (36) and an open position where the valve needle (35) has lift from the valve seat (36), and an atomizer nozzle (40) disposed at the distal end (33) of the elongated valve housing (32), the atomizer nozzle (40) having a nozzle body extending along the longitudinal axis (X) from a base (42) at a proximal end (41) of the nozzle body to a closed distal end (44) of the nozzle body, the base (42) being attached to a distal end of the fuel valve housing (32), the nozzle body comprising: an elongated, preferably cylindrical portion (43) extending between the base (42) and the closed distal end (44), an inlet (48) opening to the base (42) for receiving liquid fuel from the fuel valve (30), a plurality of nozzle bores (45), a main bore (50) extending longitudinally from the inlet (48) into the nozzle body, the valve needle (35) comprising a cylindrical distal section (39) carried by a shank (38), the cylindrical distal section (39) is journaled with tight fit in a distal portion of the main bore (50) to fluidically disconnect the nozzle bores (45) from the main bore (50) when the valve needle (35) is in the closed position, characterized in that the cylindrical distal section (39) is provided with a circumferential groove (54) with a sealing ring (52) held in the circumferential groove (54), wherein the main bore (50) has an uninterrupted cylindrical surface facing the sealing ring (52) in the closed position of the valve needle (35), and wherein the main bore (50) has an interrupted cylindrical surface facing the sealing ring (52) in the open position of the valve needle (35), the interruptions in the interrupted cylindrical surface being formed by a plurality of circumferentially spaced axial grooves (63).

2. The fuel valve (30) of claim 1, wherein the main bore has a first larger diameter proximal of the axial grooves (63) and a second smaller diameter in the area of the axial grooves (63) and where it forms the uninterrupted cylindrical surface facing the sealing ring (52) in the closed position of the valve needle (35).

3. The fuel valve (30) of claim 1 or 2, wherein the shank (38) has a smaller cross-sectional area than the cylindrical distal section (39).

4. The fuel valve (30) of any one of claims 1 to 3, wherein the cylindrical distal section (39) disconnects the opening of the nozzle bores (45) from the portion of the main bore (50) proximal to the cylindrical distal section (39) when the valve needle (35) is in the closed position.

5. The fuel valve (30) of any one of claims 1 to 4, wherein the cylindrical distal section (39) connects the opening of the nozzle bores (45) to the portion of the main bore (50) proximal to the cylindrical distal section (39) when the valve needle (35) is in the open position.

6. The fuel valve (30) of any one of claims 1 to 5, wherein the axially displaceable valve needle (35) is slidably received in a longitudinal bore (64) in the elongated valve housing (32), the valve needle (32) resting on the valve seat (36), preferably a conical valve seat, in the closed position and the valve needle (35) having lift from the valve seat (36) in the open position and the valve needle (35) preferably being resiliently and / or fluidically biased towards the closed position, and preferably, a fuel chamber (68) surrounding the valve needle (35) and opening to the valve seat (36).

7. The fuel valve (30) of any one of claims 1 to 6, comprising a fuel inlet port in the elongated fuel valve housing (32) for connection to a source of liquid fuel.

8. The fuel valve (30) of any one of claims 1 to 7, wherein the nozzle bores (45) are directed in a substantially radial direction.

9. The fuel valve (30) of any one of claims 1 to 8, wherein the nozzle bores (45) each have a nozzle axis (I,II,III,IV,V), and wherein the nozzle axis (I,II,III,IV,V) of each of the nozzle bores (45) is arranged at an obtuse angle α with the longitudinal axis (X).

10. The fuel valve (30) of claim 9, wherein the radial components of each of the nozzle axes (I,II,III,IV,V) relative to the longitudinal axis (X) are distributed, preferably substantially equally distributed, over a circular sector with an arc less than 120 deg., preferably less than 110 deg. and even more preferably less than 100 deg.

11. The fuel valve (30) of any one of claims 1 to 10, comprising three to twelve axial grooves (63).

12. The fuel valve (30) of any one of claims 1 to 11, wherein the circumferential groove (54) holds two or more sealing rings (52).

13. The fuel valve (30) of any one of claims 1 to 11, wherein the sealing ring (52) comprises a ring partition (53), preferably a labyrinth-type ring partition.

14. A large two-stroke turbocharged uniflow scavenged internal combustion engine with crossheads comprising a fuel valve (30) of any one of claims 1 to 13.

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