WO2013045756A1

WO2013045756A1 - Fuel injection pump arrangement and method for operating an internal combustion engine

Info

Publication number: WO2013045756A1
Application number: PCT/FI2012/050886
Authority: WO
Inventors: Esa Ylivainio; Matti Koivunen; Tom Nordman
Original assignee: Wärtsilä Finland Oy
Priority date: 2011-09-30
Filing date: 2012-09-13
Publication date: 2013-04-04
Also published as: CN104755744A; KR20140069080A; FI124006B; EP2761163B1; KR101791732B1; EP2761163A1; FI20115954A; FI20115954A0; CN104755744B

Abstract

The fuel injection pump arrangement for a dual-fuel internal combustion engine comprises a pump body (1), at least one fuel chamber (10) that is arranged inside the pump body (1), at least one reciprocating plunger (2) that protrudes into the fuel chamber (10) for pressurizing liquid fuel in the chamber (10), a plunger moving mechanism (5, 11) for establishing mechanical connection between the plunger (2) and a rotating cam that drives the fuel injection pump, and means (4, 6, 7) for breaking the mechanical connection between the plunger (2) and the cam when the fuel injection pump is not used for pressurizing fuel. The invention also concerns a method for operating a dual-fuel engine.

Description

FUEL INJECTION PUMP ARRANGEMENT AND METHOD FOR OPERATING AN INTERNAL COMBUSTION

ENGINE

Technical field of the invention

The present invention relates to a fuel injection pump arrangement for a dual-fuel inter- 5 nal combustion engine according to the preamble of claim 1. The invention also concerns a method for operating a dual-fuel internal combustion engine that comprises a cam-driven fuel injection pump for each cylinder of the engine, as defined in the preamble of the other independent claim.

10 Background of the invention

So-called dual-fuel engines that can be operated both on gaseous and liquid fuel provide high efficiency and fuel flexibility. In certain types of large dual-fuel engines, each cylinder of the engine is provided with an own fuel injection pump that is used for pressurizing fuel when the engine is operated in a liquid fuel mode. Each fuel injection pump is

15 driven by a rotating cam that moves one or more plungers inside the pump. When operated on gaseous fuel, the engine can utilize either an Otto combustion process or a Diesel combustion process. In the gaseous fuel mode, a common rail system is used for injecting a small amount of liquid pilot fuel into the cylinder or a pre-chamber. Since a common rail system is used for injecting the liquid pilot fuel, the separate fuel injection

20 pumps of each cylinder are not needed in the gaseous fuel mode. This kind of engines can be used, for instance, in offshore applications and ships or at power plants. In many applications, the engines are operated mostly on gaseous fuel, and the liquid fuel mode is only used when the gaseous fuel is not available. Therefore, the fuel injection pumps may be run most of the time unnecessarily. Due to mechanical losses, this increases fuel

25 consumption of the engine and also leads in wear of the fuel injection pumps.

Summary of the invention

An object of the present invention is to provide an improved fuel injection pump arrangement for a dual-fuel internal combustion engine. The characterizing features of the 30 arrangement according to the present invention are given in the characterizing part of claim 1. Another object of the invention is to provide an improved method for operating a dual-fuel internal combustion engine, which engine comprises a cam-driven fuel injection pump for each cylinder of the engine. In the fuel injection pump, liquid fuel is pressurized by at least one reciprocating plunger that is in mechanical connection with a rotating cam. The method is characterized by the characterizing part of the other independent claim.

According to the invention, the fuel injection pump arrangement comprises a pump body, at least one fuel chamber that is arranged inside the pump body, at least one recip- rocating plunger that protrudes into the fuel chamber for pressurizing liquid fuel in the fuel chamber, a plunger moving mechanism for establishing mechanical connection between the plunger and a rotating cam that drives the fuel injection pump, and means for breaking the mechanical connection between the plunger and the cam when the fuel injection pump is not used for pressurizing fuel.

In the method for operating a dual-fuel internal combustion engine in accordance with the invention, the mechanical connection between the plunger of each fuel injection pump and the respective cam is broken for preventing moving of the plunger when the engine is operated on gaseous fuel.

With the fuel injection pump arrangement according to the invention, the fuel injection pump can be taken out of use when the engine is operated on gaseous fuel. With the arrangement and the method according to the invention, fuel economy of the engine can be improved and the life cycle of the fuel injection pumps can be extended.

According to an embodiment of the invention, the arrangement comprises a hydraulic fluid chamber and a piston that is arranged in the hydraulic fluid chamber for moving the plunger away from the cam. According to another embodiment of the invention, the plunger moving mechanism comprises a cam follower unit and a push rod that is arranged between the plunger and the cam follower unit, and the hydraulic fluid chamber is arranged around the push rod. According to another embodiment of the invention, the piston is a sleeve-like part that is arranged around the push rod.

According to another embodiment of the invention, the hydraulic fluid is lube oil of the engine. According to another embodiment of the invention, the hydraulic fluid is fuel that is used in the engine.

According to another embodiment of the invention, the arrangement comprises a hydraulic pump for pressurizing the hydraulic fluid.

According to an embodiment of the invention, in the method the plunger is moved away from the cam by introducing hydraulic fluid into a hydraulic fluid chamber between the end of the chamber and a piston that is in mechanical connection with the plunger.

According to another embodiment of the invention, the hydraulic fluid is pressurized by a hydraulic pump.

According to another embodiment of the invention, the hydraulic pump is operated when the engine is operated on gaseous fuel and pressure in the hydraulic fluid chamber is below a predetermined level.

Brief description of the drawings

Fig. 1 shows a fuel injection pump arrangement according to an embodiment of the invention.

Detailed description of the invention

Embodiments of the invention are now described in more detail with reference to the accompanying drawings.

In figure 1 is shown a fuel injection pump arrangement according to an embodiment of the present invention. The engine where the arrangement is used is a large dual-fuel internal combustion engine, such as a ship engine or an engine that is used for produc- ing electricity at a power plant. The engine can be operated both on liquid fuel, such as light or heavy fuel oil, and gaseous fuel, such as natural gas or biogas.

The engine is provided with one fuel injection pump for each cylinder of the engine. The fuel injection pumps are used when the engine is operated on liquid fuel. With a separate fuel injection pump for each cylinder of the engine, the amount of the injected fuel and the injection timing can be individually adjusted in each cylinder. The fuel injection pump comprises a pump body 1. Inside the pump body 1, there is a fuel chamber 10, into which liquid fuel can be introduced through fuel inlets 3 from a fuel channel 23. The engine is provided with a fuel supply pump for introducing the liquid fuel into the fuel chamber 10 at a relatively low pressure. A reciprocating plunger 2 protrudes into the fuel chamber 10 for pressurizing the fuel that is introduced into the fuel chamber 10. Each fuel injection pump could also be provided with two fuel chambers 10 and two plungers 2. In that case, one of the plungers 2 can be used for adjusting the injection timing and the other plunger 2 can be used for adjusting the amount of the injected fuel. The fuel injection pump is driven by a cam that is attached to a rotating camshaft (not shown). The fuel injection pump arrangement comprises a plunger moving mechanism 5, 11 that establishes mechanical connection between the cam and the plunger 2. The plunger moving mechanism 5, 11 transforms the rotating movement of the cam into the reciprocating movement of the plunger 2. In the embodiment of figure 1, the plunger moving mechanism comprises a cam follower unit 11 and a push rod 5 that is arranged between the cam follower unit 11 and the plunger 2. The cam follower unit 11 comprises a cam follower wheel 12 that follows the surface of the rotating cam. The push rod 5 transmits the movement of the cam follower unit 11 to the plunger 2. A spring 8 that is arranged around the plunger 2 pushes the plunger 2 and the push rod 5 towards the cam follower unit 11 and the cam. The camshaft end of the spring 8 is supported against a spring support plate 9 that is attached to the plunger 2. The bottom part of the fuel injection pump is provided with a second spring 13 that pushes the cam follower unit 11 against the cam of the camshaft. The pressurized fuel is supplied to the cylinder of the engine through a fuel outlet (not shown in Fig. 1) that is arranged in the upper part of the fuel chamber 10. The injection of the liquid fuel and the adjustment of the injection timing and the amount of the injected fuel by a rack 18 and a pinion 19 work in a conventional manner and are therefore not described in more detail here. When the engine is operated on gaseous fuel, a small amount of liquid pilot fuel is used for igniting the gaseous fuel. For injecting the pilot fuel into the cylinders of the engine or into pre-chambers, the engine is provided with a common rail system. The fuel injec- tion pumps are therefore not needed when the engine is in the gas mode. Each fuel injection pump arrangement is provided with means 4, 6, 7 for breaking the mechanical connection between the cam and the plunger 2 when the fuel injection pump is not used for pressurizing fuel. The reciprocating movement of the plungers 2 can thus be prevented and the fuel injection pumps can be taken out of use when the engine is operated on gaseous fuel. This reduces the fuel consumption of the engine and wear of the fuel injection pumps.

In the embodiment of figure 1, the means for breaking the mechanical connection between the plunger 2 and the cam comprise a hydraulic fluid chamber 6, a piston 4, and means, i.e. a fluid supply line 7, for introducing hydraulic fluid into the hydraulic fluid chamber 6. The hydraulic fluid chamber 6 is arranged below the plunger 2 and surrounds the push rod 5. The piston 4 is a sleeve-like part that is arranged in the hydraulic fluid chamber 6 around the push rod 5. Through the fluid supply line 7, hydraulic fluid can be introduced into the hydraulic fluid chamber 6 between the piston 4 and the camshaft end of the chamber 6. The hydraulic fluid can be, for instance, lube oil of the engine, or fuel that is used in the engine. When the hydraulic fluid is introduced into the chamber 6 at a sufficiently high pressure, the piston 4 is moved together with the plunger 2 away from the cam. The pressure needs to be high enough to overcome the force that is created by the spring 8 that pushes the plunger 2 towards the cam. The inner and outer surfaces of the piston 4 are provided with seals 21, 22 for preventing leakage between the push rod 5 and the piston 4 and between the wall of the hydraulic fluid chamber 6 and the piston 4. A seal 20 is arranged also between the bottom aperture of the hydraulic fluid chamber 6 and the push rod 5. When the engine is running in the gas mode, hydraulic fluid is introduced into the hydraulic fluid chamber 6. The piston 4 and the plunger 2 are thus pushed away from the cam. The push rod 5 moves together with the piston 4 and the plunger 2 and is thus separated from the cam follower unit 11. The second spring 13 keeps the cam follower unit 11 in contact with the cam. The pressure in the hydraulic fluid chamber 6 is maintained until the engine is to be operated on liquid fuel again. Before operating the engine again on liquid fuel, hydraulic fluid is released from the hydraulic fluid chamber 6. The piston 4 and the plunger 2 can thus return to their original positions and the mechanical con- nection between the plunger 2 and the cam is re-established. The fluid supply line 7 can be used for releasing the hydraulic fluid from the hydraulic fluid chamber 6, as in the embodiment of figure 1, or the chamber 6 can be provided with a separate outlet. In the embodiment of figure 1, the engine is provided with a separate hydraulic pump 14 for pressurizing the hydraulic fluid. A valve 16 is arranged in the fluid supply line 7 be- tween the hydraulic pump 14 and the hydraulic fluid chamber 6. When the valve 16 is in the position shown in the figure, the hydraulic pump 14 can be used for supplying hydraulic fluid from a tank 17 into the hydraulic fluid chamber 6. A check valve 15 is arranged between the hydraulic pump 14 and the valve 16 for preventing backflow to the pump 14. Therefore, the hydraulic pump 14 does not need to be operated continuously, but it can be switched on when the pressure in the fluid supply line 7 drops below a certain predetermined limit. By switching the valve 16 into a second position, hydraulic fluid can be released from the hydraulic fluid chamber 6 back into the tank 17.

It will be appreciated by a person skilled in the art that the invention is not limited to the embodiments described above, but may vary within the scope of the appended claims. For instance, instead of lifting only the plunger for breaking the mechanical connection between the cam and the plunger, also the cam follower can be lifted from the cam.

Claims

1. A fuel injection pump arrangement for a dual-fuel internal combustion engine, which fuel injection pump arrangement comprises

a pump body (1),

- at least one fuel chamber (10) that is arranged inside the pump body (1),

at least one reciprocating plunger (2) that protrudes into the fuel chamber (10) for pressurizing liquid fuel in the chamber (10), and

a plunger moving mechanism (5, 11) for establishing mechanical connection between the plunger (2) and a rotating cam that drives the fuel injection pump, characterized in that the arrangement further comprises means (4, 6, 7) for breaking the mechanical connection between the plunger (2) and the cam when the fuel injection pump is not used for pressurizing fuel.

2. An arrangement according to claim 1, characterized in that the arrangement comprises a hydraulic fluid chamber (6), a piston (4) that is arranged in the hydraulic fluid chamber (6), and means (7) for introducing hydraulic fluid into the hydraulic fluid chamber (6) for moving the plunger (2) away from the cam.

3. An arrangement according to claim 2, characterized in that the plunger moving mechanism comprises a cam follower unit (11) and a push rod (5) that is arranged between the plunger (2) and the cam follower unit (11), and that the hydraulic fluid chamber (6) is arranged around the push rod (5).

4. An arrangement according to claim 3, characterized in that the piston (4) is a sleeve-like part that is arranged around the push rod (5).

5. An arrangement according to any of claims 2-4, characterized in that the hydraulic fluid is lube oil of the engine.

6. An arrangement according to any of claims 2-4, characterized in that the hydraulic fluid is fuel that is used in the engine.

7. An arrangement according to any of the preceding claims, characterized in that the arrangement comprises a hydraulic pump (14) for pressurizing the hydraulic fluid.

8. A method for operating a dual-fuel internal combustion engine, which engine comprises a cam-driven fuel injection pump for each cylinder of the engine, in which fuel injection pump liquid fuel is pressurized by at least one reciprocating plunger (2) that is in mechanical connection with a rotating cam, characterized in that when the engine is operated on gaseous fuel, the mechanical connection between the plunger (2) of each fuel injection pump and the respective cam is broken for preventing moving of the plunger (2).

9. A method according to claim 8, characterized in that the plunger (2) is moved away from the cam by introducing hydraulic fluid into a hydraulic fluid chamber (6) between the end of the chamber (6) and a piston (4) that is in mechanical connection with the plunger (2).

10. A method according to claim 9, characterized in that the hydraulic fluid is pressurized by a hydraulic pump.

11. A method according to claim 10, characterized in that the hydraulic pump is operated when the engine is operated on gaseous fuel and pressure in the hydraulic fluid chamber (6) is below a predetermined level.