Dual-fuel internal combustion engine

Abstract

To provide a dual-fuel internal combustion engine.SOLUTION: An internal combustion engine includes: cylinders capable of combusting a first liquid fuel in a first operation mode and combusting a second liquid fuel in a second operation mode; a main injection system including at least one main injector for each cylinder, in which through the system, the first liquid fuel relatively easy to ignite can be supplied to the cylinders in the first operation mode and, through the system, the second liquid fuel relatively hard to ignite can be supplied to the cylinders in the second operation mode; and a pilot injection system including at least one pilot injector for each cylinder, in which through the system, the first liquid fuel can be supplied to the cylinders of the internal combustion engine to ignite the second liquid fuel in the second operation mode.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a dual-fuel internal combustion engine.

[0002] In particular, the present invention relates to the field of so-called large engines or large internal combustion engines, the cylinders of which have a piston diameter of at least 140 mm, in particular at least 175 mm. Such large internal combustion engines are, for example, marine engines.

Background Art

[0003] Dual-fuel internal combustion engines as marine engines are already known. The dual-fuel internal combustion engines known from the prior art can be operated in a first operating mode in which the engine burns a liquid fuel and in a second operating mode in which the engine burns a gaseous fuel or another liquid fuel.

[0004] From Patent Document 1, a dual-fuel internal combustion engine equipped with a dual-fuel injector is known. Each fuel is delivered in the direction of the dual-fuel injector through a separate fuel pump. Furthermore, it is equipped with a separate seal and a separate lubricating oil system.

[0005] There is a need for a new type of dual-fuel internal combustion engine with a simple structure.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Starting from this, the present invention is based on the purpose of creating a new type of dual-fuel internal combustion engine.

Means for Solving the Problems

[0008] This object is solved by a dual-fuel internal combustion engine according to claim 1.

[0009] The dual-fuel internal combustion engine comprises cylinders, in which a first liquid fuel can be combusted in a first operating mode and a second liquid fuel can be combusted in a second operating mode. The dual-fuel internal combustion engine is a main injection system having at least one main injector for each cylinder, through which a first liquid fuel that is relatively easy to ignite is supplied to the cylinder in the first operating mode, and through which a second liquid fuel that is relatively difficult to ignite can be supplied to the cylinder in the second operating mode. The dual-fuel internal combustion engine is a pilot injection system having at least one pilot injector for each cylinder, through which the first liquid fuel can be supplied to the cylinder of the internal combustion engine to ignite the second liquid fuel in the second operating mode. The main injection system and the pilot injection system of the dual-fuel internal combustion engine according to the invention are connected such that the first fuel discharged from the pilot injection system in the second operating mode can be supplied to the individual main injectors of the main injection system as an operating fluid and / or a barrier fluid.

[0010] Thus, the two injection systems are connected to each other. This achieves that the first liquid fuel discharged from the pilot injection system in the second operating mode is supplied to the individual main injectors of the main injection system, and through the main injectors, the second liquid fuel is introduced into the cylinder in the second operating mode, in which process the first liquid fuel is supplied as an operating fluid and / or a barrier fluid into the individual main injectors. Such an operating fluid or barrier fluid contributes to sealing or actuating the valves of the individual main injectors.

[0011] In a dual-fuel internal combustion engine according to the present invention, each liquid fuel is combusted in both operating modes. The first liquid fuel for the first operating mode is relatively easy to ignite. The second liquid fuel for the second operating mode is relatively difficult to ignite. The first liquid fuel contributes to igniting the second liquid fuel in the second operating mode. The dual-fuel internal combustion engine includes a main injection system having at least one main injector for each cylinder and a pilot injection system having at least one pilot injector for each cylinder. Via the main injection system, the first liquid fuel can be supplied to the cylinder in the first operating mode, and the second liquid fuel can be supplied to the cylinder in the second operating mode. In the second operating mode, the first liquid fuel has two functions. First, the function of igniting the second fuel. Second, the function as a working fluid and / or a barrier fluid within the area of the individual main injectors. The main injection system is connected to the pilot injection system to also use the ignition fluid as a working fluid and / or a barrier fluid.

[0012] According to a further development of the present invention, the individual branch lines branch off from the pilot injection system downstream of the individual pilot injectors and preferentially open into the main injection system in the area of the individual main injectors of the main injection system. In the second operating mode, the pressure in the individual branch lines leading from the pilot injection system to the main injection system is greater than the pressure in the area of the individual main injectors of the main injection system. Such a connection of the two injection systems through the individual branch lines is particularly suitable. Thus, the first fuel contributing as a working fluid and / or a barrier fluid within the area of the individual main injectors can be easily supplied from the pilot injection system to the main injection system in the second operating mode.

[0013] According to a further development of the present invention, a pressure reducing valve is integrated into the individual branch lines to limit the pressure in the individual branch lines. The pressure in the individual branch lines is limited through the pressure reducing valve.

[0014] According to a further development of the invention, the main injection system comprises a main pump through which a first liquid fuel can be supplied to the cylinder in a first operating mode and through which a second liquid fuel can be supplied to the cylinder in a second operating mode. The pilot injection system comprises a pilot pump through which the first liquid fuel can be supplied to the cylinder in the second operating mode to ignite the second liquid fuel. A first fuel tank for the first fuel can be connected to the main pump through a first fuel line. A second fuel tank for the second fuel can be connected to the main pump through a second fuel line. The shuttle valve contributes to connecting the main pump to the first fuel tank through the first fuel line in the first operating mode and to connecting the main pump to the second fuel tank through the second fuel line in the second operating mode. This further development of the invention particularly simplifies the structure of the dual-fuel internal combustion engine according to the invention.

[0015] A preferred further development of the invention results from the dependent claims and the following description. Exemplary embodiments of the invention are described in more detail with reference to the figures, but are not limited thereto.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0017] Figure 1 shows a highly simplified ship propulsion system 10, which includes a dual-fuel internal combustion engine 11 with a plurality of cylinders 12. The fuel is burned in the cylinders 12 with the first liquid fuel in the first operating mode of the dual-fuel internal combustion engine and the second liquid fuel in the second operating mode of the dual-fuel internal combustion engine.

[0018] During the combustion of each fuel, the dual-fuel internal combustion engine generates the driving force utilized in Figure 1 to drive the generator 13. In the generator 13, electrical energy is generated, and this energy contributes to driving the ship's propeller 14.

[0019] Figure 1 further shows the fuel supply system 15 of the dual-fuel internal combustion engine 11. Figure 2 shows a further assembly of the fuel supply system 15. Through the fuel supply system 15, the individual liquid fuels can be supplied to the cylinders 12 of the dual-fuel internal combustion engine 11 in the individual operating modes of the dual-fuel internal combustion engine. The fuel supply system 15 of the dual-fuel internal combustion engine 11 includes a main injection system and a pilot injection system.

[0020] Through a main injection system with at least one main injector 16 for each cylinder 12 (see FIG. 2), a first liquid fuel that is relatively easy to ignite is supplied to the cylinder 12 in a first operating mode, and a second fuel that is relatively difficult to ignite can be supplied in a second operating mode. Thus, FIG. 2 shows the main injector 16 of the cylinder 12. Through this main injector 16, the first liquid fuel can be injected into the cylinder 12 in the first operating mode, and the second liquid fuel can be injected into the cylinder 12 in the second operating mode. For cost reasons, it is preferred to inject the first liquid fuel in the first operating mode and the second liquid fuel in the second operating mode through the same main injector 16 into the individual cylinders 12 of the dual-fuel internal combustion engine, but it is also alternatively possible for each cylinder 12 to be equipped with a separate main injector for each of the two liquid fuels. However, in the embodiment shown in FIG. 2, the same main injector 16 is utilized to inject the first liquid fuel in the first operating mode and the second liquid fuel in the second operating mode into the individual cylinders, which is preferred.

[0021] According to FIG. 2, the individual liquid fuels can be supplied to the individual main injectors 16 through the main pump 17, and thus, the first liquid fuel in the first operating mode and the second liquid fuel in the second operating mode can be delivered in the direction of the individual main injectors 16.

[0022] FIG. 1 shows a first fuel tank 18 for holding the first liquid fuel and a second fuel tank 19 for holding the second liquid fuel. The first fuel tank 18 is connected to the main pump 17 through the first fuel line 20, and the second fuel tank 19 can be connected to the main pump 17 through the second fuel line 21, i.e., via the shuttle valve 22.

[0023] In the first operating mode, the shuttle valve 22 connects the first fuel tank 18 or the first fuel line 20 to the main pump 17 to supply the first fuel to the cylinder 12 of the dual-fuel internal combustion engine. In this first operating mode, the shuttle valve 22 disconnects the second fuel tank 19 from the main pump 17 of the main injection system.

[0024] In contrast, in the second operating mode, the shuttle valve 22 assumes a switching position, in which the second fuel tank 19 is connected to the main pump 17 through the second fuel line 22 to supply the second fuel to the cylinder 12 of the dual-fuel internal combustion engine 11 in the second operating mode. In this second operating mode, the first fuel tank 18 is then disconnected from the main pump 17 of the main injection system.

[0025] As already explained, the first liquid fuel is relatively easy to ignite, and the second liquid fuel is relatively difficult to ignite. In order to ignite the second liquid fuel in the second operating mode within the region of each individual cylinder 12, the dual-fuel internal combustion engine is equipped with a pilot injection system, and each cylinder 12 is equipped with at least one pilot injector 23.

[0026] Through the pilot injection system, in order to ignite the second liquid fuel in the second operating mode, the first liquid fuel can be supplied to the cylinder 12 of the dual-fuel internal combustion engine 11.

[0027] Therefore, the pilot injection system includes a pilot pump 24 in addition to at least one pilot injector 23 for each cylinder 12. Then, through this pump, each individual pilot injector 23 can be supplied with the first liquid fuel discharged from the first fuel tank 18 in the second operating mode. A further fuel line 27 extends from the first fuel tank 18 in the direction of the cylinder 12, and the pilot pump 24 is connected within this further fuel line 27.

[0028] In the dual-fuel internal combustion engine 11 according to the present invention, the main injection system and the pilot injection system are connected as is clear from FIG. 2, i.e., the first liquid fuel can be discharged from the pilot injection system in the second operating mode and supplied to the individual main injectors 16 of the main injection system. Each cylinder 12 is provided with at least one pilot injector 23 and a pilot pump 24. The first liquid fuel contributes as a working fluid and / or a barrier fluid in the region of the individual main injectors 16 in the second operating mode.

[0029] Appropriately, FIG. 2 shows a branch line 25 which branches off from the pilot injection system upstream of the individual pilot injectors 23 and preferentially continues directly to the individual main injectors 16 of the main injection system of the individual cylinders 12 and opens preferentially into the main injection system within the region of the individual main injectors 16. Here, the branch line 25 branches off from the pilot injection system downstream of the pilot pump 24 and upstream of the individual pilot injectors 23 in order to supply the first fluid as a working fluid and / or a barrier fluid to the individual main injectors 16 of the main injection system in the second operating mode, when viewed in the delivery direction of the pilot injection system.

[0030] Here, in the second operating mode, the pressure in the individual branch lines 25 continuing from the pilot injection system to the main injection system is preferentially greater than the pressure in the region of the individual main injectors 16 by a defined pressure offset. Through this, it is ensured that the first liquid fuel is always reliably supplied to the individual main injectors 16 in the second operating mode.

[0031] In FIG. 2, it is shown that a pressure reducing valve 26 is integrated into the branch line 25. The pressure reducing valve limits the pressure in the individual branch lines 25 to a defined level downstream of the pressure reducing valve 26.

[0032] The first liquid fuel, which is relatively easy to ignite, is a liquid fuel having lubricity preferably between 100 μm and 300 μm, particularly advantageously between 100 μm and 200 μm in terms of WSD. The second fuel, which is relatively difficult to ignite, is a liquid fuel having lubricity preferably between 300 μm and 820 μm, particularly advantageously between 400 μm and 820 μm in terms of WSD. The first liquid fuel is preferably diesel fuel. The second liquid fuel is preferably ethanol or methanol.

[0033] In the dual-fuel internal combustion engine 11 according to the present invention, each liquid fuel is burned in both operating modes. The first liquid fuel contributes, on the one hand, to igniting the second liquid fuel in the second operating mode and, on the other hand, contributes as a working fluid and / or a barrier fluid in the region of the individual main injectors 16. Appropriately, in the second operating mode, the main injectors 16 and the pilot injectors 23 of the individual cylinders 12 use the first liquid fuel introduced into the cylinder 12 through the individual pilot injectors 23 as ignition oil, and on the other hand, use the first liquid fuel as working oil and / or barrier oil in the region of the main injectors 16.

[0034] This relates in particular to the field of so-called large engines or large internal combustion engines, the cylinders of which have a piston diameter of at least 140 mm, particularly 175 mm. Such large internal combustion engines are, for example, marine engines. In the present invention, these are embodied as dual-fuel internal combustion engines.

Explanation of Reference Numerals

[0035] 10 ··· Ship propulsion system 11 ··· Dual-fuel internal combustion engine 12 ··· Cylinder 13 ··· Generator 14 ··· Ship propeller 15 ··· Fuel supply system 16 ··· Main injector 17 ··· Main pump 18 ··· Fuel tank 19 ··· Fuel tank 20 ··· Fuel line 21 ··· Fuel line 22 ··· Shuttle valve 23 ··· Pilot injector 24 ··· Pilot pump 25 ··· Branch line 26 ··· Pressure reducing valve 27 ··· Fuel line

Claims

1. A dual-fuel internal combustion engine, comprising a cylinder (12) capable of burning a first liquid fuel in a first operating mode and a second liquid fuel in a second operating mode, a main injection system comprising at least one main injector (16) for each cylinder (12), through which the first liquid fuel, which is relatively easy to ignite, is supplied to the cylinder (12) in the first operating mode, and the second liquid fuel, which is relatively difficult to ignite, is supplied to the cylinder (12) in the second operating mode through the main injection system, a pilot injection system comprising at least one pilot injector (23) for each cylinder (12), through which the first liquid fuel can be supplied to the cylinder (12) of the internal combustion engine to ignite the second liquid fuel in the second operating mode, a dual-fuel internal combustion engine, wherein the main injection system and the pilot injection system are connected such that the first liquid fuel discharged from the pilot injection system in the second operating mode can be supplied to the individual main injectors (16) of the main injection system as an operating fluid and / or a barrier fluid.

2. Upstream of each of the pilot injectors (23), an individual branch line (25) branches off from the pilot injection system, through which the first liquid fuel can be supplied to the individual main injectors (16) as an operating fluid and / or a barrier fluid in the second operating mode, according to the dual-fuel internal combustion engine of Claim 1.

3. The dual-fuel internal combustion engine according to Claim 2, wherein the individual branch lines (25) open into the main injection system in the region of the individual main injectors (16).

4. The dual-fuel internal combustion engine according to Claim 2 or 3, wherein a pressure reducing valve (26) is integrated into each of the individual branch lines (25) to limit the pressure in the individual branch lines (25).

5. In the second operating mode, the pressure in each of the individual branch lines (25) leading from the pilot injection system to the main injection system is greater than the pressure in the region of each of the individual main injectors (16) of the main injection system. A dual-fuel internal combustion engine according to any one of claims 2 to 4.

6. The main injection system comprises a main pump (17), and through the main injection system, in the first operating mode, the first liquid fuel is supplied to the cylinder (12), and through the main injection system, in the second operating mode, the second liquid fuel can be supplied to the cylinder (12). The pilot injection system comprises a pilot pump (24), and through the pilot injection system, in the second operating mode, the first liquid fuel can be supplied to the cylinder (12) for ignition of the second liquid fuel. A dual-fuel internal combustion engine according to any one of claims 1 to 5.

7. Comprising a first fuel tank (18) for the first liquid fuel, which can be connected to the main pump (17) through a first fuel line (20). Comprising a second fuel tank (19) for the second liquid fuel, which can be connected to the main pump (17) through a second fuel line (21). In the first operating mode, a shuttle valve (22) for connecting the main pump (17) to the first fuel tank (18) through the first fuel line (20), and in the second operating mode, for connecting the main pump (17) to the second fuel tank (19) through the second fuel line (21). A dual-fuel internal combustion engine according to claim 6.

8. Each of the individual branch lines (25) branches off from the pilot injection system upstream of each of the individual pilot injectors (23) and downstream of the pilot pump (24). A dual-fuel internal combustion engine according to claim 6 dependent on claim 2 or claim 7 dependent on claim 2.

9. The first liquid fuel has a lubricity between WSD 100 μm and 300 μm, preferably between 100 μm and 200 μm. The second liquid fuel has a lubricity between WSD 300 μm and 820 μm, preferably between 400 μm and 820 μm. A dual-fuel internal combustion engine according to any one of claims 1 to 8.

10. The binary fuel internal combustion engine according to any one of claims 1 to 9, wherein the first liquid fuel is diesel fuel and the second liquid fuel is ethanol or methanol.

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