Fuel valve for large turbo supercharged two-stroke uniflow crosshead internal combustion engine

Abstract

To provide a fuel valve capable of reducing the risk that when a valve needle becomes stuck during the operation of an engine, fuel is excessively supplied to a combustion chamber of a cylinder so that the engine fails.SOLUTION: A fuel valve comprises: a fuel duct 7 that has an inlet end 8 communicating with a fuel inlet port 6 and an outlet end 10 communicating with a fuel injection path; and a spindle valve member 17 that is movable between at least a first position and a second position within the fuel duct 7. The spindle valve member, at the first position, allows fuel to flow through an inlet path 15 into a plunger chamber 14 to fill the plunger chamber 14 while preventing the fuel from entering the fuel injection path through an outlet path 16, and, at the second position, allows fuel to flow from the plunger chamber 14 through the outlet path 16 into the fuel injection path for supplying the fuel to a nozzle while preventing the fuel from entering the plunger chamber 14 through the inlet path 15.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a fuel valve for injecting liquid fuel into a combustion chamber of a large turbocharged two-stroke uniflow crosshead internal combustion engine, the fuel valve comprising: an elongated fuel valve housing having a rear end and a front end, a nozzle having a plurality of nozzle holes, the nozzle being located at the front end of the fuel valve housing, a fuel inlet port in the elongated fuel valve housing for connection to a source of pressurized liquid fuel, a plunger piston received in a bore of the fuel valve housing and a plunger chamber within the bore, a fuel duct having an inlet end communicating with the fuel inlet port and an outlet end communicating with a fuel injection path, a fuel inlet passage connecting the inlet end of the fuel duct to the plunger chamber, and a fuel outlet passage connecting the plunger chamber to the outlet end of the fuel duct.

[0002] The invention also relates to a large turbocharged, two-stroke, uniflow crosshead internal combustion engine equipped with such a fuel valve.

[0003] Large turbocharged two-stroke uniflow crosshead internal combustion engines are typically used as prime movers in large ocean-going ships such as container ships, and in power plants. This type of engine is very often run on heavy fuel oil or fuel oil.

[0004] In recent years, there has been a demand for large two-stroke diesel engines to be able to use other types of fuel. For example, there is a demand for gas fuels such as methanol, LPG, LNG, ethane, and ammonia. When used as fuel for large low-speed uniflow turbocharged two-stroke internal combustion engines, these fuels are relatively clean fuels because they significantly reduce sulfurous acid, NOx, and CO2 in the exhaust gas compared to when heavy oil is used as fuel.

[0005] A fuel injector of the type mentioned in the opening paragraph is known from US Pat. No. 4,398,519 A.

[0006] It is common to use different fuel valves for different types of fuel. In the following, three different known fuel valves are described, all of which have similar drawbacks. In figures 1 to 3 three different examples of a known fuel valve 1 are shown. In the three figures the same reference numbers are used for corresponding elements.

[0007] All fuel valves 1 shown in Figures 1 to 3 include an elongated fuel valve housing 2 having a rear end 3 and a front end 4. The front end of the housing 2 includes a nozzle 5 having a number of nozzle holes 9 for injecting fuel into a combustion chamber 60. The fuel valve 1 also includes a fuel inlet port 6 in the elongated fuel valve housing 2. The fuel inlet port 6 is connected to a source of pressurized liquid fuel (not shown). Fuel is supplied via a fuel duct 7 to a plunger chamber 14 located in a bore 13 in the valve housing 2. The plunger chamber 14 is defined by an axially displaceable plunger piston 12 received in the bore 13. The plunger piston 12 moves back and forth during filling and emptying of the plunger chamber 14, respectively. The known fuel valve 1 includes a fuel injection passage 11 extending from the plunger chamber 14 to a nozzle 5 at the front end 4 of the fuel valve 1. The fuel valve 1 includes an axially displaceable valve needle 30 for controlling the flow of fuel through the fuel valve 1. The valve needle 30 has a closed position and an open position. In the closed position, the valve needle 30 contacts the valve seat 31, preventing fuel from flowing to the nozzle 5. In the closed position, the valve needle 30 lifts off the valve seat 31, thereby allowing fuel to flow through the fuel valve 1 to the nozzle hole 9.

[0008] All known fuel valves 1 include an intake valve 40 disposed in the fuel path from the fuel inlet port 6 to the plunger chamber 14, and this intake valve 40 is opened by the pressure provided by the pressurized fuel when the plunger chamber 14 is filled with fuel.

[0009] If the valve needle 30 becomes stuck during engine operation, there is a risk that the cylinder combustion chamber will be overfilled with fuel, which will cause the cylinder cover to lift and result in engine failure. To prevent such overfilling of the cylinder, the fuel valve 1 shown in FIG. 1 is equipped with an external ELBI valve (Electronic Block Injection Valve) (not shown) which blocks the fuel supply to the fuel valve 1 when fuel should not be supplied to the plunger chamber. Both fuel valves 1 shown in FIGS. 2 and 3 are equipped with a check valve 41 which allows fuel to flow only from the plunger chamber 14 through the fuel injection path 11 to the nozzle 5 and not in the reverse direction towards the plunger chamber 14. The check valve 41 prevents overfilling of the cylinder if the valve needle 30 becomes stuck.

[0010] In relation to the fuel valve 1 shown in Figure 1, the ELBI cuts off the fuel supply to the fuel valve when the combustion chamber pressure falls below the fuel supply pressure, and therefore prevents over-fueling if the valve needle is stuck in the open position. However, the ELBI valve limits the filling time of the injector until the next injection, and with some fuels, it may not be possible to prevent the lifting of the cylinder cover if the volume trapped between the ELBI valve and the fuel valve contains enough energy to cause the lifting of the cylinder cover. In relation to the fuel valve 1 shown in Figures 2 and 3, the check valve cannot be monitored during operation, so if this check valve does not function properly and the fuel injector is stuck in the open position, over-fueling and therefore the lifting of the cylinder cover will occur. Summary of the Invention

[0011] SUMMARY OF THE DISCLOSURE The object of the invention is to provide a fuel valve of the type mentioned in the introduction, in which the above-mentioned problems with overfilling the combustion chamber are at least significantly reduced.

[0012] These and other objects are achieved by the features of the independent claims. Further detailed implementations will become apparent from the dependent claims, the description and the drawings.

[0013] According to a first aspect, there is provided a fuel valve for injecting liquid fuel into a combustion chamber of a large turbocharged two-stroke uniflow crosshead internal combustion engine. The fuel valve comprises: an elongated fuel valve housing having a rear end and a front end; a nozzle having a plurality of nozzle holes disposed at the forward end of the fuel valve housing; a fuel inlet port in the elongated fuel valve housing for connection to a source of pressurized liquid fuel; a plunger piston received in a bore of the fuel valve housing and a plunger chamber within the bore; a fuel duct having an inlet end communicating with the fuel inlet port and an outlet end communicating with a fuel injection path; a fuel inlet passage connecting the inlet end of the fuel duct to the plunger chamber; and a fuel outlet passage connecting the plunger chamber to the outlet end of the fuel duct. With the above in mind, a spindle valve member movable within the fuel duct between at least a first position and a second position; In the first position, the spindle valve member allows fuel to flow through the inlet passage into the plunger chamber to fill the plunger chamber with fuel while preventing fuel from entering the fuel injection passage through the outlet passage; In the second position, the spindle valve member allows fuel to flow from the plunger chamber, through the outlet passage, and into the fuel injection passage for supplying fuel to the nozzle, while preventing fuel from entering the plunger chamber through the inlet passage; The fuel valve further includes means for providing a constant leakage from the outlet passage to the fuel injection passage when the spindle valve member is in the first position to fill the plunger chamber with fuel.

[0014] The above specified fuel valve provides a self-checking safety feature that ensures that no over-injection of fuel or lifting of the cylinder cover occurs, even if the valve needle gets stuck in the open position. This is achieved by integrating the intake valve and the check valve into one component or valve. This component or valve can only stay in one of two positions: either open to fill the plunger chamber with fuel, or open to inject fuel from the plunger chamber into the combustion chamber of the cylinder. Thus, there can never be a direct open line from the fuel injection port to the combustion chamber.

[0015] To prevent fuel from flowing directly from the fuel inlet end of the fuel duct through the plunger chamber to the outlet end of the fuel duct, the spindle valve member may, at a third intermediate position between the first and second positions, block both fuel from entering the plunger chamber through the inlet passage and fuel from entering the fuel injection passage through the outlet passage. This may be made possible by providing a spindle valve member of sufficient length to simultaneously block both the inlet passage to the plunger chamber and the outlet passage from the plunger chamber. The spindle valve member does not stop at this third intermediate position.

[0016] The spindle valve member may in principle be configured in any suitable way that ensures that the only way for fuel to flow from the inlet end to the outlet end of the fuel duct is via the inlet passage, the plunger chamber and the outlet passage. Thus, in a simple embodiment, the spindle valve member may be configured with a cross section that fits tightly into the fuel duct. However, it is preferred that the spindle valve member is mounted in a stationary housing that is inserted into the fuel duct and that the spindle valve member is able to move in said housing at least between said first position and said second position. The stationary housing should preferably fit snugly into the fuel duct between the inlet and outlet ends of the fuel duct to avoid fuel leaking through gaps or spaces between the stationary housing and the fuel duct. In one embodiment, the assembly may be made as a press fit.

[0017] During operation of the fuel valve, when filling the plunger chamber with fuel, the spindle valve member is preferably moved in a direction from the inlet end towards the outlet end of the fuel duct by a force exerted by pressurized liquid fuel entering the fuel duct through the fuel inlet port. This is because at that moment the pressure at the inlet end of the fuel duct is higher than the pressure at the outlet end. When the spindle valve member is in a first position for filling said plunger chamber with fuel, due to intended leakage from the outlet path into the fuel injection path, when the plunger chamber is full, the liquid pressure is equal at the inlet and outlet ends of the fuel duct. Any suitable means may be provided for moving the spindle valve member in the opposite direction towards the second position and unblocking the outlet path from the plunger chamber when fuel has to be supplied from the plunger chamber to the fuel injection path. The fuel valve according to the invention thus preferably comprises a forcing member for exerting a force on the spindle valve member in a direction towards the inlet end of the fuel duct. The forcing member is preferably a spring.

[0018] The spindle valve member preferably further comprises an end stop surface which abuts a corresponding surface on the fuel duct or housing when the spindle valve member is in its second position, i.e. when fuel is allowed to flow from the plunger chamber through the outlet path to the fuel injection path.

[0019] The means for providing a constant leakage from the outlet passage to the fuel injection passage may in principle be any means which ensures a constant, predetermined flow of fuel from the plunger chamber to the fuel injection passage at least when the spindle valve member is in a first position for filling said plunger chamber with fuel. However, such means preferably comprise an orifice in the spindle valve member. By providing the fuel valve with leakage means such as an orifice, it is possible, as mentioned above, to obtain equal hydraulic pressures at the inlet and outlet ends of the fuel duct when the plunger chamber is fully filled, and therefore it is possible for a biasing member, such as a spring, to move the spindle valve member towards the inlet end of the fuel duct to its second position.

[0020] The orifice is preferably provided in the spindle valve member to provide a constant leakage from the outlet passage to the fuel injection passage only when the spindle valve member is in its first position filling said plunger chamber with fuel.

[0021] The fuel duct can in principle be formed with any suitable cross section, but preferably the fuel duct is a bore in the fuel valve housing.

[0022] The invention also relates to a large turbocharged, two-stroke, uniflow crosshead internal combustion engine equipped with a fuel valve as defined in the appended claims. [Brief description of the drawings]

[0023] The invention will now be explained in more detail with reference to exemplary embodiments shown in the drawings. [Figure 1] 1 shows a first example of a known fuel valve. [Diagram 2] 2 shows a second example of a known fuel valve. [Diagram 3] 2 shows a third example of a known fuel valve. [Figure 4] 1 is a diagram showing an embodiment of a fuel valve according to the present invention; [Diagram 5]5a-5c show a cross section of a fuel valve according to the present invention in more detail. Detailed explanation

[0024] In the following detailed description, the fuel valve according to the invention will be described for use in a large, crosshead, two-stroke, uniflow scavenged internal combustion engine, although it will be understood that the internal combustion engine may be of other types as well.

[0025] In Fig. 4, a fuel valve 1 according to the invention is shown. The fuel valve 1 shown in Fig. 1 has an elongated fuel valve housing 2 having a rear end 3 and a front end 4, similar to the known fuel valves shown in Figs. 1 to 3. The front end of the housing 2 is provided with a nozzle 5 having a number of nozzle holes 9 for injecting fuel into a combustion chamber 60. The fuel valve 1 also has a fuel inlet port 6 in the elongated fuel valve housing 2. The fuel inlet port 6 is connected to a source of pressurized liquid fuel, not shown. Fuel is supplied to a plunger chamber 14 provided in a bore 13 of the valve housing 2 via a fuel duct 7 and a fuel inlet passage 15. The fuel duct 7 has an inlet end 8 communicating with the fuel inlet port 6, and an outlet end 10. The plunger chamber 14 is defined by the bore 13 and an axially displaceable plunger piston 12 received in the bore 13. The plunger piston 12 moves back and forth during filling and emptying of the plunger chamber 14, respectively.

[0026] The fuel valve 1 according to the invention also comprises a fuel injection passage 11 extending from the outlet end 10 of the fuel duct 7. The fuel injection passage 11 is supplied with fuel from the plunger chamber 14 through a fuel outlet passage 16 connecting the plunger chamber 14 to the fuel duct 7. During injection of fuel into the combustion chamber 60, the fuel in the plunger chamber 14 is pressurized by the plunger piston 12 and flows through the fuel injection passage 11 towards the nozzle 5 at the front end 4 of the fuel valve 1. To control the flow of fuel through the fuel valve 1, the fuel valve 1 comprises an axially displaceable valve needle 30. The axially displaceable valve needle 30 has a closed position in which it sits on a valve seat 31. In the closed position, fuel is prevented from flowing to the nozzle 5. It also has an open position in which the axially displaceable valve needle 30 is unseated from the valve seat 31. In the open position, fuel is allowed to flow through the fuel valve 1 to the nozzle hole 9. The valve needle 30 is unseaten to the open position by fuel pressurized in the plunger chamber 14 by the plunger piston 12. During fuel injection, this pressurized fuel exerts a force on the valve needle 30. When fuel injection ends and the fuel pressure in the fuel injection passage 11 is relieved, a spring 32 biases the valve needle 30 to the closed position.

[0027] If the valve needle 30 becomes stuck during operation, as previously mentioned, there is a significant risk that the combustion chamber of the cylinder will be over-fueled, which could cause the cylinder cover to lift off and result in engine failure.

[0028] To solve this problem, the fuel valve 1 according to the invention comprises a spindle valve member 17 arranged in the fuel duct 7 and movable therein between a first position (see FIG. 5a) and a second position (see FIG. 5c). In the first position, the spindle valve member 17 is moved away from the fuel inlet port 6 by pressurized fuel provided from a fuel source, allowing fuel to flow through the inlet duct 7 and the inlet passage 15 to the plunger chamber 14, whereby fuel is filled in the plunger chamber 14. When the spindle valve member 17 is in this first position, the outlet passage 16 is closed by the spindle member 17, thus preventing fuel from entering the fuel injection passage 11. In the second position, the spindle valve member 17 is moved by a spring 18 in the direction towards the fuel inlet port 6, allowing fuel to flow through the outlet passage 16 from the plunger chamber 14 to the fuel injection passage 11 in order to supply fuel to the nozzle 5. When the spindle valve member 17 is in this second position, the inlet passage 15 is closed by the spindle member 17. Fuel is therefore prevented from entering the plunger chamber 14 through the inlet passage 15.

[0029] Thus, in the fuel valve 1 according to the invention, the intake valve and the check valve applied in known fuel valves are combined into one component or valve which can only remain in one of two positions: an open position for filling the plunger chamber 14 with fuel and an open position for injecting fuel from the plunger chamber 14 into the combustion chamber 60 of the cylinder. Thus, no open line is formed directly connecting the fuel inlet port 6 to the combustion chamber 60, and even if the valve needle gets stuck in the open position, over-injection of fuel and thus lifting of the cylinder cover does not occur.

[0030] The fuel valve 1 according to the invention comprises an orifice 21 which provides a certain leakage from the outlet passage 16 to the outlet end 10 of the fuel duct and to the fuel injection passage 11 when the spindle valve member 17 is in a first position for filling said plunger chamber 14 with fuel. By providing the fuel valve with a leakage means such as the orifice 21, when the plunger chamber 14 is filled, the hydraulic pressures at the inlet end 8 and outlet end 10 of the fuel duct 7 are equalized, thus allowing the spring 18 or other biasing member to move the spindle valve member 17 towards the inlet end 8 of the fuel duct 7 (i.e. to the second position).

[0031] With reference to Figures 5a to 5c, the fuel valve 1 according to the invention will now be described in more detail. As shown, the spindle valve member 17 is mounted in a stationary housing 20 which is inserted into the fuel duct 7. The spindle valve member 17 is movable within the housing 20 between a first position and a second position. The spindle valve member 17 also includes a spring 18 for exerting a force on the spindle valve member 17 in a direction towards the inlet end of the fuel duct 7. The spindle valve member 17 includes an end stop surface 25. As shown in Figure 5c, the end stop surface 25 abuts a corresponding surface 26 provided on the stationary housing 20 when the spindle valve member 17 is in the second position. Fuel is then allowed to flow from the plunger chamber 14 through the outlet passage 16 to the fuel injection passage 11.

[0032] In the embodiment shown, the fuel duct 7 is provided as a bore 7 in the fuel valve housing 2, and the stationary housing 20 is formed as a cylinder, which opens at both ends 37 and 38, i.e. the inlet end 8 and the outlet end 10 of the fuel duct 7, respectively. The stationary housing 20 is provided with two annular recesses 33, 34, which are arranged to communicate with the inlet passage 15 and the outlet passage 16, respectively. At the bottom of both annular recesses 33, 34, the stationary housing 20 is provided with a number of holes 35, 36, respectively. The holes 35 allow the liquid fuel to flow from the inlet end 8 of the fuel duct 7 through the open end 37 of the housing 20 at the inlet end 8, into the annular recess 33, and further through the inlet passage 15 to the plunger chamber 14, when the spindle valve member 17 is in a first position shown in FIG. 5a.

[0033] On the other hand, when the spindle valve member 17 is in the second position shown in FIG. 5c, the hole 36 allows liquid fuel to flow from the plunger chamber 14 through the outlet passage 15 to the annular recess 34, through the hole 36 and then through the open end 38 of the housing 20 to the outlet end 10 of the fuel duct 7.

[0034] In Fig. 5b, the spindle valve member 17 is shown in a third intermediate position between the first and second positions. The spindle valve member 17 passes through this intermediate position both when moving to the first position and when moving to the second position, but does not come to rest in this intermediate position. In the intermediate position, the spindle valve member 17 blocks fuel from both entering the plunger chamber 14 via the inlet passage 15 and from entering the fuel injection passage 11 via the outlet passage 16. In this way, it is further ensured that there is never a direct open path from the fuel inlet port 6 to the combustion chamber 60.

Claims

1. A fuel valve for injecting liquid fuel into a combustion chamber of a large turbocharged two-stroke uniflow crosshead internal combustion engine, comprising: an elongated fuel valve housing having a rear end and a front end; a nozzle having a plurality of nozzle holes disposed at the forward end of the fuel valve housing; a fuel inlet port in the elongated fuel valve housing for connection to a source of pressurized liquid fuel; a plunger piston received in a bore of the fuel valve housing and a plunger chamber within the bore; a fuel duct having an inlet end communicating with the fuel inlet port and an outlet end communicating with a fuel injection path; a fuel inlet passage connecting the inlet end of the fuel duct to the plunger chamber; and a fuel outlet passage connecting the plunger chamber to the outlet end of the fuel duct. With the above in mind, a spindle valve member movable within the fuel duct between at least a first position and a second position; In the first position, the spindle valve member allows fuel to flow through the inlet passage into the plunger chamber to fill the plunger chamber with fuel while preventing fuel from entering the fuel injection passage through the outlet passage; In the second position, the spindle valve member allows fuel to flow from the plunger chamber, through the outlet passage, and into the fuel injection passage for supplying fuel to the nozzle, while preventing fuel from entering the plunger chamber through the inlet passage; The fuel valve further comprises means for providing a constant leakage from the outlet passage to the fuel injection passage when the spindle valve member is in the first position to fill the plunger chamber with fuel.

2. 2. The fuel valve of claim 1, wherein the spindle valve member, in a third intermediate position between the first position and the second position, blocks fuel from entering the plunger chamber via the inlet passage and fuel from entering the fuel injection passage via the outlet passage.

3. 3. A fuel valve as claimed in claim 1 or 2, wherein the spindle valve member is mounted in a stationary housing which is inserted into the fuel duct, the spindle valve member being movable within the housing between at least the first position and the second position.

4. A fuel valve as claimed in any preceding claim, comprising a biasing member for exerting a force on the spindle valve member in a direction towards the inlet end of the fuel duct.

5. 5. The fuel valve of claim 4, wherein the biasing member is a spring.

6. 4. A fuel valve as claimed in any one of claims 1 to 3, wherein the spindle valve member is provided with an end stop surface which abuts against a corresponding surface on the fuel duct or on the housing when the spindle valve member is in the second position, i.e. when fuel is able to flow through the outlet path from the plunger chamber to the fuel injection path.

7. 2. The fuel valve of claim 1, wherein the means for providing leakage comprises an orifice in the spindle valve member.

8. 8. The fuel valve of claim 7, wherein the orifice is disposed in the spindle valve member to provide a constant leakage from the outlet passage to the fuel injection passage only when the spindle valve member is in the first position filling the plunger chamber with fuel.

9. A fuel valve according to any preceding claim, wherein the fuel duct is a bore provided in the fuel valve housing.

10. A large turbocharged two-stroke uniflow crosshead internal combustion engine comprising a fuel valve according to any one of claims 1 to 9.

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