DK201770660A1

DK201770660A1 - A large two-stroke compression-ignited internal combustion engine with dual fuel systems

Info

Publication number: DK201770660A1
Application number: DKPA201770660A
Authority: DK
Inventors: Cenker Poul; Skovgaard Andersen Jørn; Kaltoft Johan
Original assignee: MAN Energy Solutions
Priority date: 2017-09-04
Filing date: 2017-09-04
Publication date: 2019-03-20
Also published as: KR102058380B1; KR20190026620A; DK179683B1; CN109281787B; CN109281787A; JP6650003B2; JP2019044774A

Abstract

A large two-stroke turbocharged compression igniting multicylinder internal combustion engine (9) of the crosshead type. The engine (9) comprises a first fuel supply and injection system (52) for delivering a first type of fuel to the cylinders (1) of the engine, the first fuel supply and injection system comprises hydraulically powered pumps (43) and/or pressure boosters for pressurizing the first type of fuel, a second fuel supply and injection system (53) for delivering a second type of fuel to the cylinders of theengine, the second fuel supply and injection system comprising hydraulically powered pumps and/or pressure boosters (39) for pressurizing the second type of fuel, and a hydraulic pumping station (22) comprising a plurality of mechanically driven hydraulic pumps (24,26), the mechanically driven pumps(25,26) being driven by power takeoff from the engine. The engine is configured to selectively operate on the first fuel or on the second fuel. The hydraulic pumping station (22) is configured to supply hydraulic power to the first fuel supply and injection system (52) when the engine is operating on thefirst fuel and the hydraulic pumping station (22) being configured to supply hydraulic power to the second fuel supply and injection system (53) when the engine is operating on the second fuel.

Description

A LARGE TWO-STROKE COMPRESSION-IGNITED INTERNAL COMBUSTION

ENGINE WITH DUAL FUEL SYSTEMS

TECHNICAL FIELD

This disclosure relates to a large two-stroke pressureigniting internal combustion engine with dual fuel systems.

BACKGROUND

Large two-stroke uniflow turbocharged compression-ignited internal combustion crosshead engines are typically used as propulsion systems for large ships or as prime mover in power plants. The sheer size, weight and power output renders them quite different from common combustion engines and places large two-stroke turbocharged compression-ignited internal combustion engines in a class for themselves.

Large two-stroke compression-ignited internal combustion engines are conventionally operated with a liquid fuel such as e.g. fuel oil or heavy fuel oil. However, increased focus on environmental aspects has led to the development towards using alternative types of fuel such as natural gas, petroleum gas, methanol, ethanol, coal slurry, petroleum coke and the like. Gas is typically stored in liquid form but injected in gaseous form.

These alternative types of fuel have characteristics that are difficult or impossible to deal with for conventional fuel pumps. Some are abrasive, such as coal slurry, some have very poor lubrication qualities such as petrol or ethanol, and

DK 2017 70660 A1 others require extremely low temperatures, such as liquefied gas - a cryogenic fuel.

In most applications, it is a required that the engine can run on a conventional fuel, such as e.g. marine diesel oil or heavy fuel oil and on one of the alternative and potentially more environmental friendly fuels, such as e.g. liquefied gas or ethanol.

Thus, a dedicated fuel supply and injection system is required for each of the fuel types used. This requirement for a two separate fuel supply and injection systems significantly increasers the initial costs for constructing the engine and increases the engines complexity and maintained costs.

There is therefore a need for an engine that can handle two different types of fuels that overcomes or at least reduces the additional costs and increase complexity.

SUMMARY

It is an object of the invention to provide an engine that overcomes or at least reduces the problems indicated above.

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.

According to a first aspect there is provided a large twostroke turbocharged compression igniting multi-cylinder

DK 2017 70660 A1 internal combustion engine of the crosshead type, the engine comprising:

a first fuel supply and injection system for delivering a first type of fuel to the cylinders of the engine, the first fuel supply and injection system comprising hydraulically powered pumps and/or pressure boosters for pressurizing the first type of fuel, a second fuel supply and injection system for delivering a second type of fuel to the cylinders of the engine, the second fuel supply and injection system comprising hydraulically powered pumps and/or pressure boosters for pressurizing the second type of fuel, and a hydraulic pumping station comprising a plurality of mechanically driven hydraulic pumps, the mechanically driven pumps being driven by power takeoff from the engine, the engine being configured to selectively operate on the first fuel or on the second fuel, and the hydraulic pumping station being configured to supply hydraulic power to the first fuel supply and injection system when the engine is operating on the first fuel and the hydraulic pumping station being configured to supply hydraulic power to the second fuel supply and injection system when the engine is operating on the second fuel.

By providing a single hydraulic pumping station that can flexibly supply power to either of the two fuel supply systems, a dedicated hydraulic pumping station for each fuel supply system can be avoided, thereby reducing costs, and complexity.

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According to a possible implementation of the first aspect the engine comprises a hydraulically powered exhaust valve actuation system that is operated both when the engine is running on the first type fuel and when the engine is running on the second type fuel, the pumping station being configured to supply the exhaust valve actuation system with hydraulic power when the engine is running on the first type fuel and when the engine is running on the second type fuel.

According to a possible implementation of the first aspect a selected group of the plurality of mechanically driven pumps is dedicated to providing hydraulic power to the exhaust valve actuation system and to the first fuel supply and injection system and wherein one or more non-dedicated pumps of the plurality of mechanically driven pumps selectively provides the second fuel supply and injection system with hydraulic power when the engine is operated with the second type fuel.

According to a possible implementation of the first aspect a first electronically controlled valve on the outlet side of the non-dedicated pump is selectively connectable to a first conduit or to a second conduit, the first conduit connecting the first electronically controlled valve to the first fuel supply and injection system and to the valve actuation system and the second conduit connecting the first electronically controlled valve to the second fuel supply and injection system.

According to a possible implementation first aspect a first hydraulic pressure P1 required by the first fuel supply and injection system is at least under certain operating

DK 2017 70660 A1 conditions of the engine lower than a second hydraulic pressure P2 required by the second fuel supply and injection system and wherein a first conduit connects the first fuel supply and injection system with the hydraulic pumping station and wherein a second conduit connects second first fuel supply and injection system with the hydraulic pumping station, the first conduit preferably also supplying the exhaust valve actuation system.

According to a possible implementation of the first aspect a hydraulic pressure booster pump is arranged in the second conduit for increasing the first pressure P1 delivered by the pumping station to the second pressure P2, the hydraulic pressure booster pump being preferably driven by a hydraulic motor or by an electric drive motor.

According to a possible implementation of the first aspect a hydraulic pressure reduction valve arrangement is arranged in the first conduit for reducing the second pressure P2 delivered by the pumping station to the first pressure P1.

According to a possible implementation of the first aspect a selected group of the plurality of mechanically driven pumps is dedicated to providing hydraulic power to the exhaust valve actuation system and to the first fuel supply and injection system and wherein one or more variable displacement dedicated pumps of the plurality of mechanically driven pumps provides the second fuel supply and injection system with hydraulic power when the engine is operated with the second type fuel.

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According to a possible implementation of the first aspect one or more of the mechanically driven pumps are variable displacement hydraulic pumps.

According to a possible implementation of the first aspect the engine comprises an electronic control unit configured to control the operation of the first fuel supply and injection system, the second fuel supply and injection system, the exhaust valve actuation system and the hydraulic pumping station, the electronic control unit being configured to:

ramp down the first fuel supply and injection system, ramp up the second fuel supply and injection system, to divert a portion of the hydraulic power supplied by the hydraulic pumping station from first fuel supply and injection system to the second fuel supply and injection system, upon receipt of an instruction to switch operation from the first type fuel to the second type fuel.

According to a possible implementation of the first aspect the electronic control unit is configured to ramp up the first fuel supply and injection system, ramp down the second fuel supply and injection system, and to divert a portion of the hydraulic power supplied by the hydraulic pumping station from second fuel supply and injection system to the first fuel supply and injection system, upon receipt of an instruction to switch operation from the first type fuel to the second type fuel.

According to a possible implementation of the first aspect the hydraulic power supplied to the second fuel supply and injection system also supplies a hydraulic rotary motor that

DK 2017 70660 A1 drives a compressor, the compressor compressing the second type fuel in gaseous form.

According to a possible implementation of the first aspect the second fuel supply and injection system comprises a hydraulically driven high-pressure pump, the high-pressure pump comprising two or more pump units, each pump unit comprising a pump piston slidably disposed in a single pump cylinder and a hydraulically powered drive piston slidably disposed in a single drive cylinder with the drive piston coupled to the pump piston for driving the pump piston.

According to a possible implementation of the first aspect the engine comprises at least one main control valve connected to the hydraulic pumping station and to tank for controlling the flow of hydraulic fluid to and from the drive cylinder of one or more of the pump units, the source of high-pressure hydraulic fluid preferably being a source with a variable and controllable pressure level.

According to a possible implementation of the first aspect the engine comprises a heat exchanger or evaporator connected to the outlet of the hydraulically driven high-pressure pump.

According to a second aspect there is provided an assembly comprising two engines the implementation above, the engines sharing a single a hydraulically driven high-pressure pump and heat exchanger or evaporator.

According to a possible implementation of the second aspect the pumping station of each engine comprises at least one

DK 2017 70660 A1 non-dedicated pump, wherein the inlet of the non-dedicated pump of the pumping station of one of the engines is provided with a selection valve for selectively connecting the inlet concerned with the tank and filtering system of the other engine or with the tank and filtering system of the engine concerned.

According to a possible implementation of the second aspect the assembly is configured to control the selection valve to connect the inlet of the non-dedicated pump provided with the selection valve to the tank and filtering system of the other engine when the other that the non-dedicated pump concerned is connected to the second fuel supply and injection system).

According to a possible implementation of the second aspect, the pumping stations of both engines each comprise at least one variable displacement dedicated pump, the inlet of the at least one variable displacement dedicated pumps being connected to the tank and filtering system of one of the two engines in the assembly.

These and other aspects of the invention will be apparent from the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

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 front view of a large two-stroke diesel engine according to an example embodiment,

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Fig. 2 is a diagrammatic representation the engine of Fig. 1 with its two fuel supply and injection systems, its exhaust valve actuation system and its hydraulic pumping station,

Fig. 3 is a diagrammatic representation in greater detail of the two fuel supply and injection systems and the valve actuation system,

Fig. 4 to 7 are a diagrammatic representations of other embodiments of the engine of Fig. 1 with its two fuel supply and injection systems, its exhaust valve actuation system and its hydraulic pumping station,

Fig. 8 to 10 are a diagrammatic representations of another embodiments of an assembly of two engines of Fig. 1 with its four fuel supply and injection systems, its exhaust valve actuation systems and its hydraulic pumping stations,

Fig. 11 is a graph illustrating fuel supply flow during a switch in operation from a first type fuel to a second type fuel in an engine according to any of the embodiments, and Fig. 12 is a graph illustrating hydraulic power consumption of the respective fuel supply and injection systems during the switch in operation from a first type fuel to a second type fuel of Fig. 11.

DETAILED DESCRIPTION

In the following detailed description, a fuel supply system for a large two-stroke low-speed turbocharged compressionignited internal combustion engine 9 with crossheads will be described with reference to the example embodiments. Fig. 1 shows a large low-speed turbocharged two-stroke diesel engine 9 with a turning wheel 7 and crossheads. In this example embodiment the engine has six cylinders in line. Large lowspeed turbocharged two-stroke diesel engines have typically

DK 2017 70660 A1 between four and fourteen cylinders in line, carried by a cylinder frame that is carried by an engine frame 6. The engine 9 may e.g. be used as the main engine in a marine 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 1,000 to 110,000 kW.

The engine 9 is in this example embodiment a compressionignited engine of the two-stroke uniflow type with scavenge ports at the lower region of the cylinder liner 1 and a central exhaust valve 4 at the top of the cylinder liners 1. The scavenge air is passed from the scavenge air receiver 2 to the scavenge ports of the individual cylinders 1. A piston in the cylinder liner 1 compresses the scavenge air, highpressure fuel such as e.g. a gaseous fuel or a liquid fuel, is injected through fuel valves in the cylinder cover, combustion follows and exhaust gas is generated.

When an exhaust valve 4 is opened, the exhaust gas flows through an exhaust duct associated with the cylinder concerned into the exhaust gas receiver 3 and onwards to a turbine of the turbocharger 5, from which the exhaust gas flows away through an exhaust conduit to the atmosphere. The turbine of the turbocharger 5 drives a compressor supplied with fresh air via an air inlet. The compressor delivers pressurized scavenge air to a scavenge air conduit leading to the scavenge air receiver 2. The scavenge air in the scavenge air conduit passes an intercooler for cooling the scavenge air.

Fig. 2 is a schematic view of the engine 9 with its fuel injection systems 52,53, its exhaust valve actuation system

DK 2017 70660 A1 and its hydraulic pumping station 22. An electronic control unit 50 controls the operation of these systems. Although shown as a single unit, the electronic control unit 50 can be of the distributed nature. The engine 9 and its systems can be installed on a marine vessel, such as e.g. an LNG carrier or a container ship.

The engine 9 is provided with a first fuel supply and injection system 53 for a first type of fuel, such as e.g. marine diesel, or heavy fuel oil.

The engine 9 is also provided with a second fuel supply and injection system 52 for a second type of fuel, such as e.g. liquefied petroleum gas (LPG), liquefied natural gas (LNG), liquefied ethane gas (LPG). These liquefied gases are evaporated before injection and injected into the engine in their gaseous form. Other examples of types of fuels that can be used for the second fuel system are low flashpoint fuel such as Ethan or methanol.

The engine 9 is provided with a hydraulically power and electronically controlled exhaust valve actuation system 54.

A hydraulic pumping station 22 supplies various consumers of hydraulic power with hydraulic power, including the first fuel supply and injection system 52, the second fuel supply and injection system 53 and the exhaust valve actuation system 54 with hydraulic power. The pumping station 22 is provided with a plurality of mechanically driven pumps 24,25. These hydraulic pumps 24,25 are driven by power takeoff from the

DK 2017 70660 A1 engine, e.g. by a chain- or gear drive connecting the hydraulic pumps 24,25 to the engine crankshaft.

The pumping station 22 is also provided with two hydraulic startup pumps 26, that are driven by an electric drive motor. These hydraulic startup pumps 26 serve to provide hydraulic power and pressure for the startup phase of the engine. These startup pumps 26 and other electrically driven pumps (not shown) may also serve to provide additional hydraulic power when the engine is running. Electric power for the startup pumps can be provided by generator sets associated with the engine or other suitable sources of electric power, such as the mains or batteries.

The engine 9 is provided with a lubrication oil system and with a low pressure hydraulic system. In an embodiment, the low-pressure hydraulic system uses filtered lubrication oil as the hydraulic liquid.

A low-pressure pump 29 pressurizes the low-pressure hydraulic system. The hydraulic pumping station 22 is provided with hydraulic liquid from the low-pressure hydraulic system via conduits that include filters 28.

The engine 9 is configured to run on either the first type fuel or on the second type fuel. A very small amount of first type fuel may be used as pilot fuel (ignition liquid) when the engine 9 is running on the second type fuel. However, this very small amount of pilot fuel is not provided with a first fuel supply and injection system 52, but instead by a

DK 2017 70660 A1 dedicated pilot oil delivery system, that is preferably an integral with the second fuel supply and injection system 53.

Fig. 11 is a graph showing fuel consumption of the first type fuel indicated by the and interrupted line and fuel consumption of the second type fuel indicated the interrupted line against time. Thus, the graph shows a transition from operating on the first type fuel to operating on the second type fuel. At the start of the graph the engine 9 is running on the first type fuel. At t1 the electronic control unit 50 receives an instruction to change operation from the first type fuel to the second type fuel, or at T1 the electronic control unit 50 decides to change operation from the first type fuel to the second type fuel. Accordingly, the control unit 50 ramps down the amount of first type fuel delivered and ramps up the amount of second type of fuel delivered until the amount of first type fuel is zero and the amount of second type fuel is at a desired level at t2.

Simultaneously, the electronic control unit 50 has, starting at t1, controlled the pumping station 22 to reduce the amount of hydraulic power supplied to the first fuel supply and injection system 52 and to increase the amount of hydraulic power supplied to the second fuel supply and injection system 53. At t2, the hydraulic power distribution is consolidated.

As diagrammatically shown in Fig. 2, the engine 9 is provided with a hydraulically powered exhaust valve actuation system 54 that is operated both when the engine is running on the first type fuel and when the engine is running on the second type fuel. The pumping 22 station is configured to supply the

DK 2017 70660 A1 exhaust valve actuation system 54 with hydraulic power both when the engine 9 is running on the first type fuel and when the engine 9 is running on the second type fuel. The hydraulically power exhaust valve actuation system 54 is controlled by the electronic control unit 50.

In the embodiment of Fig. 2 the hydraulic pumping station 22 comprises three mechanically driven hydraulic pumps 24,25. The pumps are driven by power takeoff from the engine 9. In this embodiment the mechanically driven hydraulic pumps 24,25 are variable displacement pumps that are controlled by the electronic control unit 50, i.e. There displacement is controlled by the electronic control unit 50. A selected group of the plurality of mechanically driven pumps 24 (in the shown embodiment the selected group comprises two mechanically driven pumps 24) is dedicated to providing hydraulic power to the exhaust valve actuation system 54 and to the first fuel supply and injection system 52. One or more non-dedicated pumps 25 (the shown embodiment one non-dedicated pump 25 is shown) of the plurality of mechanically driven pumps selectively provides the second fuel supply and injection system 53 with hydraulic power when the engine is operated with the second type fuel.

A first electronically controlled valve 27 on the outlet side of the non-dedicated pump 25 is selectively connectable to a first conduit 32 or to a second conduit 33. The first conduit 32 connects the first electronically controlled valve 27 to the first fuel supply and injection system 52 and to the valve actuation system 54 and the second conduit 33 connects the first electronically controlled valve 27 to the second fuel

DK 2017 70660 A1 supply and injection system 53. The electronic control unit 50 commands the first electronically controlled valve 27. Thus, the electronic control unit 50 can selectively connect the nondedicated pump 25 to either conduit 32 or to conduit 33 and thereby selectively provide hydraulic power from the non-dedicated pump 25 to either the first fuel supply and injection system 52 and the hydraulic exhaust valve actuation system 54 or to the second fuel supply and injection system 53.

The second fuel supply and injection system 53 comprises a heat exchanger or evaporator connected to an outlet of a hydraulically driven high-pressure pump, together designated by reference numeral 71.

Use hydraulic liquid is returned from the first and second fuel supply and injection systems and from the hydraulic exhaust valve actuation system to tank 61. A low-pressure pump 29 supplies hydraulic liquid two various consumers of the engine 9, including the hydraulic pumping station 22 via conduits that include filters 28.

Fig. 3 diagrammatically illustrates the first fuel supply and injection system 52, the second fuel supply and injection system 53 and the hydraulic exhaust valve actuation system 54 in greater detail.

The second fuel supply system 53 comprises a fuel storage tank 8 in which second type fuel is stored. If the fuel is liquefied gas it is stored under cryogenic conditions in the fuel storage tank 8. A feed conduit 9 connects an outlet of

DK 2017 70660 A1 the fuel or lubricant storage tank 8 to the inlet of a highpressure pump 40. A feed pump 10 assists the transport of the fuel or lubricant from the storage tank 8 to the inlet of the pump 40.

The high-pressure pump 40 pumps the liquid fuel a supply conduit 18 to the engine. The hi-pressure pump 40 is provided with two or more pump units 41,42,43, (in the present embodiment 3 pump units are shown). Each pump unit 41,42,43 includes a pump piston 62 slidably disposed in a pump cylinder 61 and a hydraulically powered drive piston 46 slidably disposed in a drive cylinder 45 with the drive piston 46 coupled to the pump piston 62 for driving the pump piston 62.

The pump piston 62 and the pump cylinder 61 form a positive displacement pump. In an embodiment, the pump piston 62 and the pump cylinder 61 form the so-called cold end of a cryogenic pump unit with a pump chamber 63 for pumping liquefied gas.

The pump cylinder 61 is connected to the drive piston of the pump unit 41,42,43 concerned via a piston rod 49. The drive piston 46 divides the interior of the drive cylinder 45 into a drive chamber 48 and a return chamber 47.

The drive cylinders 45 are connected to the hydraulic pumping station 22. Main control valves 19 control the flow of highpressure hydraulic liquid to the drive cylinders 45. The main control valves 19 are configured to selectively connect the respective drive chamber 48 to conduit 33 or to tank.

DK 2017 70660 A1

Each pump unit 41, 42, 43 comprises a pump in the form of a linear positive displacement pump formed by pump cylinder 61 with the pump piston 62 received therein to form a pump chamber 63. The pump chamber 63 is connected to the feed conduit 9 via a first one-way valve (not shown) that only allows flow to the pressure chamber 63. The pump chamber 63 is connected to a supply conduit 18 via a second one-way valve (not shown) that only allows flow out of the pressure chamber 63.

If the second type fuel is a cryogenic fuel, such as e.g. LNG or LPG the hi-pressure pump 40 is a cryogenic pump. If the second type fuel is not a cryogenic fuel, such as e.g. ethanol the high-pressure pump 40 is a regular linear positive displacement pump for pumping non-cryogenic liquids.

The second fuel supply and injection system 53 comprises a liquefied gas storage tank 8 in which e.g. natural gas is stored under cryogenic conditions (if a noncryogenic fuel is used as second type fuel a regular storage tank 8 is used). The pressure in the LNG storage tank 8 is relatively low and kept constant by allowing boil off gas to escape from the tank, e.g. for use in a boiler or a low-pressure gas injection engine, such as an auxiliary engine of the marine vessel. The boil off process also keeps the liquefied gas in the storage tank cold. The liquefied gas in storage tank 8 can be of another type than natural gas, such as e.g. ethane or methane.

A feed conduit 9 connects an outlet of the LNG storage tank 8 to the inlet of the high-pressure pump 40. A low-pressure feed pump 10 assists the transport of the liquefied gas from

DK 2017 70660 A1 the LNG storage tank 8 to the inlet of the high-pressure pump 40. Alternatively, the LNG storage tank 8 can be pressurized so that the low-pressure supply pump 10 can be dispensed with. A transfer conduit connects the outlet of the high-pressure pump 40 to the inlet of a high-pressure vaporizer 14 for transporting high-pressure liquefied gas from the highpressure pump 40 to the high-pressure vaporizer 14. If the second type fuel is not a liquefied gas, the high-pressure vaporizer is replaced by a heat exchanger 14. The highpressure pump 40 pumps liquefied gas via the transfer conduit 50 to the high-pressure vaporizer 14. The high-pressure vaporizer 14 receives the high-pressure liquefied gas and vaporizes the gas using a heat exchanger in the high-pressure vaporizer 14. The-pressure vaporizer 14 exchanges heat between a heat exchange medium, such as e.g. glycol, that circulates through a circulation circuit 15 and the liquefied gas. The circulation circuit 15 includes a circulation pump 16 and a heater 17. High-pressure vaporized gas leaves the high-pressure vaporizer 14 via the outlet of the high-pressure vaporizer 14 that is connected to a fuel supply conduit 18. The high-pressure pump 40 together with the vaporizer 14 are designated as a Pump Vaporizer Unit (PVU) and designated reference numeral 71.

The supply conduit 18 connects the outlet of the high-pressure vaporizer 14 to an inlet of the fuel injection system of second fuel supply and injection system 53. Conduits branch off from the supply conduit 18 to individual injectors 64 that are configured for the injection of the second type fuel into the cylinders 1.

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An engine cylinder 1 is provided with fuel valves 63 for injecting the second type fuel and with fuel injection valves for injecting the first type fuel.

The first fuel injection supply system 52 is supplied with hydraulic power via first conduit 32. An accumulator or compression chamber 67 ensures the stable pressure is available for the various consumers of hydraulic power and a distribution conduit 69 supplies various consumers via respective control valves 11,44,55.

The first type fuel is provided from a storage tank 12 (service tank) and transported by an electrically driven supply pump 16 via a feed conduit 73 to pressure boosters 39. The electrically driven supply pump 16 ensures that a pressure of approximately 4 bar can be maintained in the low-pressure part of the fuel system.

The fuel injection of the first type fuel is performed by the electronically controlled pressure boosters 39, one per cylinder 1. The pressure boosters 39 multiply the pressure from the low-pressure (where the hydraulic fluid is applied) side to the high-pressure side (the fuel side) by a fixed ratio.

The pressure boosters 39 are powered by pressurized hydraulic fluid. The hydraulic pumping station 22 delivers high pressure hydraulic fluid, typically a few hundred bar. Return fluid is transported from the cylinders via conduit 65 to the tank 61.

Compression chambers 67 are provided for each pair of cylinders 1 (in case the engine has an odd number of

DK 2017 70660 A1 cylinders, one of the cylinder may be served by a single compression chamber). A conduit 69 connects the compression chamber 67 to two proportional control valves 44 to two on/off valves 55 and to two proportional control valves 11.

Each cylinder 1 of the engine 9 is associated with the electronic control unit 50 which receives general synchronizing and control signals and transmits electronic control signals to the proportional control valves 44, among others, through signal lines or wires 59. There may be one management control unit 50 per cylinder 1, or several cylinders 1 may be associated with the same electronic control unit 50.

The electronic control unit 50 calculates the timing, the rate shaping and the amount of the fuel injection, in accordance with the operating conditions of the engine 9. Hereto, the electronic control unit 50 receives information about the rotational position of the crankshaft, the rotational speed of the crank shaft (which could be derived by the control unit 50 from the rotational position signal), ambient temperature, load, temperatures of various engine fluids. The electronic control unit 50 also adapts the timing of the fuel injection for reversing the engine. The movement of the spool in the proportional control valve 44 is controlled by the control unit 50.

In their rest position the proportional control valves 44 connect the pressure chamber at the low-pressure side of the pressure booster 39 to tank. When the electronic control unit 50 sends a signal to start the fuel injection for a given

DK 2017 70660 A1 cylinder, one of the proportional control valves 41 opens to a certain extend and connects thereby the low-pressure side of the pressure booster 39 to the compression chamber 67 via conduit 69, thereby applying hydraulic high-pressure from the pumping station 22 to the low-pressure side of the pressure booster 39.

The pressure at the low-pressure side of the pressure booster 39 is multiplied, typically to reach an injection pressure between approximately 400 and 1500 bar. A feed conduit 51 transports the high-pressure fuel from the pressure boosters 39 to the fuel injectors 23 which atomizes the first type fuel by injecting it in the combustion chamber via its nozzles .

The electronic control unit 50 also controls the actuation of the exhaust valves 4. The exhaust valves are open and closed against the force of an air spring by a hydraulic valve actuator 11. A proportional control valve 11 connects a hydraulic valve actuator 21 selectively and proportionally controllable to the first conduit 32 via conduit 77 and compression chamber 67 or via conduits 78 and 65 to tank 61. The electronic control unit 50 controls the proportional control valve 11 via signal lines or wires 59. The electronic control unit 50 controls timing of the lift of the exhaust valve 4 depending on the crankshaft position and in accordance with engine operating conditions. In their rest position the proportional control valves 11 connect the hydraulic exhaust valve actuator 21 to tank 61.

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The electronic control unit 50 also controls the on/off valves 55 that control the supply of pressurized cylinder lubrication oil to the cylinder lubricators 57. Based upon the operating conditions and on the position the crankshaft, the control unit 50 determines when and how much cylinder lubrication oil is pumped into the cylinders 1. In their rest position the on/off valves 55 connect the cylinder lubricators 57 to tank 61. When a given on/off valve 55 receives a signal from the control unit 50 to pump lubrication oil into a particular cylinder, the on/off valves 55 opens up to thereby connect the cylinder lubricator 57 to compression chamber 67 via conduit 69 and the cylinder lubricator will commence pumping lubrication oil into the cylinder. The control unit 50 determines the amount of lubrication oil that is pumped into the cylinder via the length of the activation of the on/off valve 55.

Thus, in an embodiment the first conduit 32 additionally supplies and engine cylinder lubrication system with hydraulic power. It is though noted that the engine cylinder lubrication system typically uses a relatively small amount of hydraulic power in comparison to the amount of hydraulic power used by the exhaust valve actuation system and the fuel injection system(s).

Fig. 4 illustrates an embodiment that is substantially identical to the embodiment of Fig. 2, except that the second conduit 33 is provided with a booster pump 34 for increasing the hydraulic pressure supplied to the second fuel supply and injection system 53. The first fuel supply and injection system 52 may in an embodiment require a lower hydraulic

DK 2017 70660 A1 supply pressure P1 compared to the hydraulic supply pressure P2 required by the second fuel supply and injection system 53. The supply pressure P1 required by the first fuel supply and injection system 52 and by the exhaust valve actuation system 54 may in an embodiment follow the engine load and be substantially equal to pressure P2 at maximum engine load. The booster pump 34 increases the output pressure of the nondedicated pump 25 from pressure P1 to pressure P2. The booster pump 34 is in this embodiment driven by a hydraulic motor 36. The hydraulic motor 36 is powered with hydraulic power from the second conduit 33.

Fig. 5 illustrates an embodiment that is substantially identical to the embodiment of Fig. 4, except that booster pump 34 is driven by an electric drive motor 38.

Fig. 6 illustrates an embodiment that is substantially identical to the embodiment of Fig. 4, except that all the mechanically driven pumps 24,25 supply the high pressure P2 and the lower pressure P1 is achieved by arranging a pressure reduction valve arrangement 31 in the first conduit 32, so that the first fuel supply and injection system 52 and the hydraulic exhaust valve actuation system 52 receive the lower pressure P1.

Fig. 7 illustrates an embodiment that is substantially identical to the embodiment of Fig. 2, except that at least one mechanically driven variable displacement pump 20 is dedicated for supplying the second fuel supply and injection system 53 via the second conduit 32. Thus, the pressure P2 supplied to the second fuel supply and injection system 53

DK 2017 70660 A1 can be regulated independently by adjusting the dedicated variable displacement pump 20 under control of the electronic control unit 50.

Fig. 8 illustrates an assembly of two engines 9 with two hydraulic pumping stations 22 that uses a common PVU 71. Both hydraulic pumping stations 22 supply hydraulic power to the single common PVU 71. In order to avoid contamination of the hydraulic system of the one engine with the other engine, the return hydraulic liquid from the single common PVU 71 is to the tank 61 of one engine and the dedicated variable displacement hydraulic pumps 20 of the pumping stations 22 for both engines receive hydraulic liquid from the tank 61of the one engine.

Fig. 8 illustrates an assembly of two engines 9 that is essentially identical to the assembly of Fig. 8, except that the pumping stations are provided with nondedicated mechanically driven pumps 25. In order avoid contamination of hydraulic oil from one to the other engine the nondedicated hydraulically driven pump 25 of the pumping station 22 of one engine is provided with an electronically controlled selection valve 30 in its inlet, so that the electronic control unit 50 can selectively provide the nondedicated mechanically driven pumps 25 concerned with hydraulic fluid from the engine to which the nondedicated mechanically driven pump 25 belongs or with hydraulic fluid from the other engine. Thus, the electronic control unit 50 will command the first electronically controlled valves 27 of both pumping stations 22 and the electronically controlled selection valve 30 of the one pumping station 22 to change position when the

DK 2017 70660 A1 nondedicated mechanically driven pumps 25 change from supplying the first fuel supply and injection system 52 to supplying to supplying the second fuel supply and injection system 53 and vice versa.

Fig. 10 illustrates an embodiment that is essentially identical to the embodiment of Fig. 7, except that this embodiment comprises additionally a hydraulic rotary motor 70 that drives a compressor 72. The compressor 72 compresses the second type fuel in gaseous form for use in the second fuel supply and injection system 53. The hydraulic power supplied to the second fuel supply and injection system 53 also powers the hydraulic rotary motor 70 that drives the compressor 72.

Fig. 11 illustrates fuel supply flow F (l/s) during a switch in operation from 100% operation on the first type fuel (illustrated by the uninterrupted line) to 100% operation on the second type fuel (illustrated by the interrupted line) against time t(s) in an engine according to any of the embodiments. At t1 the operation with the first type of fuel is rampant down and simultaneously the operation with the second type of fuel is ramped up. The process of ramping down the operation with the first type fuel and ramping down the operation with the second type fuel continues until t2 where the engine operates 100% on the second type fuel. Thus, at t2 the switch is complete.

Fig. 12 illustrates hydraulic power consumption H (kW) of the respective fuel supply and injection systems during the switch in operation from the first type fuel to the second type fuel of Fig. 11. The hydraulic power consumption of the first fuel

DK 2017 70660 A1 system and the exhaust valve actuation system is illustrated by the uninterrupted line and the hydraulic power consumption of the second fuel system is illustrated by the interrupted line. At t1 the power consumption of the first fuel system and the exhaust valve actuation system starts to decline until it reaches a stable level at t2, i.e. when the switch of the fuel is complete. The remaining fuel consumption represents the fuel consumption of the exhaust valve actuation system since the first fuel system will no longer use any hydraulic power. At t1 the power consumption of the second fuel system starts to increase and reaches a stable level at t2, i.e. when the switch is complete.

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 electronic control unit can be formed by a combination of separate electronic control units. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The reference signs used in the claims shall not be construed as limiting the scope.

Claims

1. A large two-stroke turbocharged compression igniting multi-cylinder internal combustion engine (9) of the crosshead type, said engine (9) comprising:

a first fuel supply and injection system (52) for delivering a first type of fuel to the cylinders (1) of the engine, said first fuel supply and injection system comprising hydraulically powered pumps (43) and/or pressure boosters for pressurizing said first type of fuel, a second fuel supply and injection system (53) for delivering a second type of fuel to the cylinders of the engine, said second fuel supply and injection system comprising hydraulically powered pumps and/or pressure boosters (39) for pressurizing said second type of fuel, and a hydraulic pumping station (22) comprising a plurality of mechanically driven hydraulic pumps (24,26), said mechanically driven pumps (25,26) being driven by power takeoff from said engine, said engine being configured to selectively operate on said first fuel or on said second fuel, and said hydraulic pumping station (22) being configured to supply hydraulic power to said first fuel supply and injection system (52) when said engine is operating on said first fuel and said hydraulic pumping station (22) being configured to supply

DK 2017 70660 A1 hydraulic power to said second fuel supply and injection system (53) when said engine is operating on said second fuel.

2. An engine (9) according to claim 1, comprising a hydraulically powered exhaust valve actuation system (54) that is operated both when the engine is running on said first type fuel and when the engine is running on said second type fuel, said pumping (22) station being configured to supply said exhaust valve actuation system (54) with hydraulic power when the engine is running on said first type fuel and when the engine is running on said second type fuel.

3. An engine (9) according to claim 2, wherein a selected group of said plurality of mechanically driven pumps (24) is dedicated to providing hydraulic power to said exhaust valve actuation system (54) and to said first fuel supply and injection system (52) and wherein one or more non-dedicated pumps (25) of said plurality of mechanically driven pumps selectively provides said second fuel supply and injection system (53) with hydraulic power when said engine is operated with said second type fuel.

4. An engine (9) according to claim 3, wherein a first electronically controlled valve (27) on the outlet side of said non-dedicated pump (25) is selectively connectable to a first conduit (32) or to a second conduit (33), said first conduit (32) connecting the first electronically controlled valve (27) to said first fuel supply and injection system (52) and to said valve actuation system (52) and said second conduit (33) connecting the first electronically controlled

DK 2017 70660 A1 valve (27) to said second fuel supply and injection system (53) .

5. An engine (9) according to any one of claims 1 or 4, wherein a first hydraulic pressure P1 required by said first fuel supply and injection system (52) is at least under certain operating conditions of the engine lower than a second hydraulic pressure P2 required by said second fuel supply and injection system (53) and wherein a first conduit (32) connects said first fuel supply and injection system (52) with said hydraulic pumping station (22) and wherein a second conduit (33) connects second first fuel supply and injection system (53) with said hydraulic pumping station (22), said first conduit (32) preferably also supplying said exhaust valve actuation system (54).

6. An engine (9) according to claim 5, wherein a hydraulic pressure booster pump (34) is arranged in said second conduit (33) for increasing said first pressure P1 delivered by said pumping station to said second pressure P2, said hydraulic pressure booster pump being preferably driven by a hydraulic motor (35) or by an electric drive motor (38).

7. An engine (9) according to claim 5, wherein a hydraulic pressure reduction valve arrangement (31) is arranged in said first conduit (32) for reducing said second pressure P2 delivered by said pumping station (22) to said first pressure

P1.

8. An engine (9) according to according to claim 1 or 2 wherein a selected group of said plurality of mechanically

DK 2017 70660 A1 driven pumps (25) is dedicated to providing hydraulic power to said exhaust valve actuation system (54) and to said first fuel supply and injection system (52) and wherein one or more variable displacement dedicated pumps (25) of said plurality of mechanically driven pumps provides said second fuel supply and injection system (53) with hydraulic power when said engine is operated with said second type fuel.

9. An engine (9) according to any one of claims 1 to 8, wherein one or more of said mechanically driven pumps (25,25) are variable displacement hydraulic pumps.

10. An engine (9) according to any one of claims 1 to 9, comprising an electronic control unit (50) configured to control the operation of said first fuel supply and injection system (52), said second fuel supply and injection system (53), said exhaust valve actuation system (54) and said hydraulic pumping station (22), said electronic control unit (50) being configured to:

ramp down said first fuel supply and injection system (52) , ramp up said second fuel supply and injection system (53) , and to divert a portion of the hydraulic power supplied by the hydraulic pumping station (22) from first fuel supply and injection system (52) to said second fuel supply and injection system (53), upon receipt of an instruction to switch operation from said first type fuel to said second type fuel.

11. An engine (9) according to claim 10, wherein said electronic control unit is configured to:

DK 2017 70660 A1 ramp up said first fuel supply and injection system (52), ramp down said second fuel supply and injection system (53), and to divert a portion of the hydraulic power supplied by the hydraulic pumping station (22) from second fuel supply and injection system (53) to said first fuel supply and injection system (54), upon receipt of an instruction to switch operation from said first type fuel to said second type fuel.

12. An engine (9) according to any one of claims 1 to 11, wherein said second fuel supply and injection system (53) comprises a hydraulically driven high-pressure pump (40), said high-pressure pump (40) comprising two or more pump units (41,42,43), each pump unit (41,42,43) comprising a pump piston (62) slidably disposed in a single pump cylinder (61) and a hydraulically powered drive piston (46) slidably disposed in a single drive cylinder (45) with said drive piston (46) coupled to said pump piston (62) for driving said pump piston (62).

13. An engine (9) according to of claim 12, further comprising at least one main control valve (19) connected to said hydraulic pumping station (22) and to tank for controlling the flow of hydraulic fluid to and from said drive cylinder (45) of one or more of said pump units (41,42,43), said source of high-pressure hydraulic fluid (22) preferably being a source with a variable and controllable pressure level.

14. An engine (9) according to claims 12 or 13 further comprising a heat exchanger (14) or evaporator (14) connected

DK 2017 70660 A1 to the outlet of said hydraulically driven high-pressure pump (40) .

15. An assembly comprising two engines (9) according to claim 14, said engines sharing a single a hydraulically driven highpressure pump (40) and heat exchanger (14) or evaporator (14).

16. An assembly according to claim 15, wherein the pumping station (22) of each engine comprises at least one nondedicated pump (25), wherein the inlet of the non-dedicated pump (25) of the pumping station (22) of one of the engines is provided with a selection valve (30) for selectively connecting the inlet concerned with the tank and filtering system of the other engine or with the tank and filtering system of the engine concerned.

17. An assembly according to claim 16, configured to control said selection valve (30) to connect the inlet of the nondedicated pump (20) provided with the selection valve (30) to the tank and filtering system of the other engine when the other that the non-dedicated pump concerned (25) is connected to said second fuel supply and injection system (54).