DK179219B1

DK179219B1 - Fuel or lubrication pump for a large two-stroke compression-ignited internal combustion engine

Info

Publication number: DK179219B1
Application number: DKPA201670361A
Authority: DK
Inventors: Rasmus Borgbjerg Nielsen; Christian Curtis Veng; Jan Holst
Original assignee: Man Diesel & Turbo Filial Af Man Diesel & Turbo Se Tyskland
Priority date: 2016-05-26
Filing date: 2016-05-26
Publication date: 2018-02-12
Also published as: DK201670361A1; KR102098753B1; KR20190086647A; CN115013112A; KR20170134243A; CN107435619A; JP2019148264A; JP6902066B2; JP2017210962A; CN107435619B

Abstract

A pump for supplying fuel or lubricant to a large two-stroke compression-ignited internal combustion engine. The pump (40) comprises two or more pump units (41,42,43). Each pump unit (41,42,43) comprises 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).

Description

<¹θ> DANMARK (10)

<¹²> PATENTSKRIFT

Patent- og

Varemærkestyrelsen (51) Int.CI.: F04B 1/16(2006.01) F01M 1/02(2006.01) F02 M 59/10 (2006.01)

F16N 13/16 (2006.01) (21) Ansøgningsnummer: PA 2016 70361 (22) Indleveringsdato: 2016-05-26 (24) Løbedag: 2016-05-26 (41) Aim. tilgængelig: 2016-06-22 (45) Patentets meddelelse bkg. den: 2018-02-12 (73) Patenthaver: MAN DIESEL & TURBO, FILIAL AF MAN DIESEL & TURBO SE, TYSKLAND, Teglholmsgade 41, 2450 København SV, Danmark (72) Opfinder: Rasmus Borgbjerg Nielsen, Gillesager 264, 9. tv., 2605 Brøndby, Danmark Christian Curtis Veng, Østervænget 2, 4000 Roskilde, Danmark Jan Holst, Tingbakken 5, 2770 Kastrup, Danmark (74) Fuldmægtig: NORDIC PATENT SERVICE A/S, Bredgade 30,1260 København K, Danmark (54) Benævnelse: FUEL OR LUBRICATION PUMP FOR A LARGE TWO-STROKE COMPRESSION-IGNITED INTERNAL COMBUSTION ENGINE (56) Fremdragne publikationer:

WO 2016015732 A1 DK 177845 B1 DK 177574 B1 US 2010162989 A1 CN 104390120 A WO 2014209128 A1 US 5411374 A US 2015/0369228 A1 (57) Sammendrag:

Fortsættes ...

i

FUEL OR LUBRICATION PUMP FOR A LARGE TWO-STROKE COMPRESSIONIGNITED INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The disclosure relates to a fuel or lubrication pump for use in a large slow-running two-stroke uniflow compressionignited internal combustion engines.

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 gas, methanol, coal slurry, petroleum coke and the like.

Some of these alternative types of fuel have characteristics that are difficult to deal with conventional fuel pumps. Some are abrasive, such as coal slurry, some have very poor lubrication qualities such as petrol, and others require extremely low temperatures, such as liquefied gas.

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WO 2016/015732 discloses a cylinder lubrication system with a plurality of cylinder oil pumps. Each cylinder oil pump is provided with a drive piston coupled to a plurality of dosing plungers .

US5411374 discloses a cryogenic pump according to the preamble of claim 1.

There is therefore a need to provide pump that can handle these alternative fuels.

SUMMARY

It is an object of the invention to provide a pump 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 pump according to claim 1..

By providing pump in which each of the pump pistons is activated by linear hydraulic actuator, any suitable pump piston can be driven in a completely flexible way independent from crankshaft limitations and inertia, thereby allowing an operation profile of the pump pistons that is completely adjusted to the liquid to be pumped.

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According to a first possible implementation of the first aspect the pump further comprises at least one hydraulic control valve connected to a source of high-pressure hydraulic fluid 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 second possible implementation of the first aspect the drive cylinder comprises a drive chamber and a return chamber.

According to a third possible implementation of the first aspect the drive chamber is connected to the hydraulic control valve and the return chamber is, preferably permanently, connected to a source of hydraulic fluid with a pressure that is lower than the pressure of the source of high-pressure hydraulic fluid.

According to a fourth possible implementation of the first aspect the drive cylinder is provided with a position sensor for sensing the position of the drive piston in the drive cylinder concerned.

According to a fifth possible implementation of the first aspect the fuel supply system further comprises an electronic control unit in receipt of a signal from the position sensor, wherein the at least one hydraulic control valve is an electronic control valve coupled to the electronic control unit.

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According to a sixth possible implementation of the first aspect the electronic control unit is configured for selectively connecting the drive chambers of the pump units to the source of high-pressure hydraulic fluid or to tank.

According to a seventh possible implementation of the first aspect the electronic control unit is configured to start a pump stroke of a drive piston when the pump stroke of another drive piston is nearing its end so that there is a small overlap between the ending pump stroke and the starting pump stroke. Thus, a substantially stable flow of fuel or lubricant leaving the pump without significant pressure fluctuations can be achieved

According to an eighth possible implementation of the first aspect the electronic control unit is configured to take into account the dynamics of the ending of a pump stroke and the dynamics of the starting pump stroke in order to obtain a substantially constant flow of high-pressure fuel or lubricant from the pump.

According to a ninth possible implementation of the first aspect the electronic control unit is configured to determine when the pump stroke of one of the drive cylinders/units has to start and to determine when a pump stroke of any of the drive cylinders has to end. Thus, the point at which the pump stroke starts and especially where a pump stroke ends can be accurately controlled.

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According to a tenth possible implementation of the first aspect the electronic control unit is configured to activate the respective drive cylinders substantially consecutively, preferably with a small overlap.

According to an eleventh possible implementation of the first aspect the electronic control unit is configured to operate the drive pistons of the remaining functioning pump units when one of the pump units is out of order. Thus, redundancy is obtained and pumping action can be continued if one of the pump units is out of order.

According to a twelfth possible implementation of the first aspect the electronic control unit is configured to operate the drive pistons of the remaining functioning pump units such that the drive cylinders of the remaining functioning pump units are activated substantially consecutively, preferably with a small overlap.

According to a thirteenth possible implementation of the first aspect the electronic control unit is configured to adjust the position of the drive piston at which the drive chamber is disconnected from the source of high-pressure hydraulic fluid in relation to the magnitude of the flow of liquefied gas from the high-pressure pump to the high-pressure vaporizer. Thus, the position in which the pump stroke reverses can be kept the same, regardless of the speed and the resulting inertia of the pump piston and drive piston.

According to a fourteenth possible implementation of the first aspect the electronic control unit is configured to adjust the position of the drive piston at which the drive chamber

02586-DK-P of the drive piston concerned is disconnected from the source of high-pressure fluid in the direction opposite to the direction of the drive stroke when the flow of fuel or lubricant from the pump increases.

According to a fifteen possible implementation of the first aspect the electronic control unit is configured to adjust the position of the drive piston at which the drive chamber of the drive piston concerned is disconnected from the source of high-pressure fluid in the direction of the direction of the drive stroke when the flow of flow of fuel or lubricant from the pump decreases.

According to a sixteenth possible implementation of the first aspect the electronic control unit is configured to adjust the position of a drive piston at which the drive chamber of the drive piston concerned is disconnected from the source of high-pressure fluid according to an algorithm, plan or randomly in order to distribute the position at which the pump piston reverses over an area of the stroke of the pump piston in order to reduce wear of the pump cylinder.

According to a seventeenth possible implementation of the first aspect the electronic control unit is configured to control the pressure pumped fuel or lubricant delivered by the pump by controlling the pressure of the hydraulic fluid supplied to the drive chambers. Thus, an effective and immediately responsive control of the pressure of the pumped fuel or lubricant is achieved.

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According to an eighteen possible implementation of the first aspect the electronic control unit is configured to use a desired pressure of the pumped fuel or lubricant in a feedforward function for controlling the pressure of the hydraulic fluid supplied to the drive chambers. By using feed-forward control liquefied gas pressure via the hydraulic pressure, an even faster and stable control of the pressure in the pumped fuel or lubricant can be achieved.

According to a nineteenth possible implementation of the first aspect the electronic control unit is configured to use a measured pressure of the pumped fuel or lubricant in a feedback function for controlling the pressure of the hydraulic fluid supplied to the drive chambers. Thus, nonlinearities and transients can be accommodated by the control system.

According to a twentieth possible implementation of the first aspect the electronic control unit is configured to control the activation and deactivation of the respective drive pistons independently from the control the pressure of the hydraulic fluid supplied to the drive chambers. Thus, the control strategy for the activation of the drive pistons can be optimized by the electronic control unit independently of the pressure control.

According to a twenty-first possible implementation of the first aspect the electronic control unit is configured to use a signal representative of the position of the drive pistons to control the activation and deactivation of the drive pistons .

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According to a second aspect, there is provided a large, twostroke turbocharged compression ignited internal combustion engine with a pump according to the first aspect and any possible implementation thereof.

According to a third aspect there is provided a cargo vessel with an engine according to the second aspect.

According to a fourth aspect, there is provided a method according to claim 18. F

According to a first possible implementation of the fourth aspect the method further comprises activating one of the drive piston for a drive stroke and thereafter, deactivating the one drive piston for a return stroke.

According to a second possible implementation of the fourth aspect the pump piston and the drive piston are connected to one another to move in unison.

According to a third possible implementation of the fourth aspect the method further comprises starting a pump stroke of a drive piston when the pump stroke of another drive piston is nearing its end so that there is a small overlap between the ending pump stroke and the starting pump stroke.

According to a fourth possible implementation of the fourth aspect the method further comprises to take into account the dynamics of the ending of a pump stroke and the dynamics of the starting pump stroke in order to obtain a substantially

02586-DK-P constant flow of fuel or lubricant from the pump to the engine .

According to a fifth possible implementation of the fourth aspect the method further comprises activating the respective drive cylinders (substantially consecutively, preferably with a small overlap.

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,

Fig. 2 is a diagrammatic representation a fuel supply system for supplying high-pressure natural gas from an LNG storage tank to the large two-stroke diesel engine according to Fig.

1,

Fig. 3 is an elevated view of the high-pressure pump in the fuel supply system of Fig. 2,

Fig. 4 is a diagrammatic representation of high-pressure pump of Fig. 3,

Fig. 5 is a detailed sectional view of a pump unit of the high-pressure pump of Fig. 3,

Figs. 6 to 8 are graphs illustrating the operation of the high-pressure pump of Fig. 3,

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Fig. 9 is a diagrammatic representation of a control system for controlling the high-pressure pump of Fig. 3,

Figs. 10 and 11 are graphs illustrating the piston movements of the high-pressure pump of Fig. 3 at various speeds,

Fig. 12 is a diagrammatic representation a fuel supply system for supplying fuel or lubricant from a fuel or lubricant storage tank to the large two-stroke diesel engine according to Fig . 1.

DETAILED DESCRIPTION

In the following detailed description, a fuel supply system for a large two-stroke low-speed turbocharged compressionignited internal combustion engine with crossheads will be described with reference to the example embodiments, but it is understood that the internal combustion engine could be of another type, such as a two-stroke Otto, a four-stoke Otto or Diesel, with or without turbocharging, with or without exhaust gas recirculation or selective catalytic reduction. Also a pump for supplying fuel or lubricant to a large two-stroke low-speed turbocharged compression-ignited internal combustion engine with crossheads will be described with reference to the example embodiments, but it is understood that the internal combustion engine could be of another type, such as a two-stroke Otto, a four-stoke Otto or Diesel, with or without turbocharging, with or without exhaust gas recirculation or selective catalytic reduction.

Fig. 1 shows a large low-speed turbocharged two-stroke diesel engine with a turning wheel and crossheads. In this example embodiment the engine has six cylinders in line. Large lowspeed turbocharged two-stroke diesel engines have typically

02586-DK-P between four and fourteen cylinders in line, carried by a cylinder frame that is carried by an engine frame 6. The engine 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 is in this example embodiment a compression-ignited engine of the two-stroke uniflow type with scavenge ports at the lower region of the cylinder 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, high-pressure fuel such as e.g. a gaseous 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 1 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 7 for cooling the scavenge air.

Fig. 2 is a schematic view of a fuel or lubricant supply system for the engine. The fuel supply system can be installed

02586-DK-P on a marine vessel, such as e.g. an LNG carrier or a container ship .

The fuel supply system comprises an fuel storage tank 8 in which lubricant or fuel, such as e.g. fuel oil is stored. Alternatively, the fuel is liquefied gas that stored under cryogenic conditions. The pressure in the LNG storage tank 8 is relatively

A feed conduit 9 connects an outlet of the fuel or lubricant storage tank 8 to the inlet of a high-pressure 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 pump 40 pumps the fuel or lubricant gas via a supply conduit 18 to the engine. A valve arrangement 19 controls the connection between the fuel/lubricant supply system and the large two-stroke diesel engine.

The 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 said 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

02586-DK-P 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 a source of highpressure hydraulic liquid 20, e.g. a pump or pump station via a high-pressure hydraulic liquid supply conduit 23. In the shown embodiment the source of high-pressure hydraulic fluid 20 includes an electric drive motor 21 that drives a highpressure pump 22. The high-pressure pump 22 can e.g. be a positive displacement pump, preferably a variable displacement positive displacement pump. For redundancy purposes the source of high-pressure hydraulic fluid includes in an embodiment two high-pressure hydraulic pumps 22, each driven by its own electric drive motor 21.

Fig. 3 is an elevated view of the high-pressure pump 40, with three pump units 41, 42, 43 with their pump cylinders 61, drive cylinders 45 and control valves 24, supported by a frame 35 together with accumulators 53 for equalizing the upper pressure of the high-pressure pump 40, and for equalizing the lower pressure for the return chamber The pump units 41, 42, 43 are arranged in a compact way on the frame 35 and the components on the frame 35 have no spark generating components and only ATEX approved electrical components, thereby allowing the unit to be installed without problems in an ATEX environment.

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Fig. 4 is a diagrammatic representation of high-pressure pump 40 with its pump units 41, 42 and 43. Each pump unit 41, 42, 43 is connected to tank via a hydraulic liquid return line 26 and to the source of high pressure hydraulic liquid that includes a variable displacement positive displacement pump 22 that connects to the respective pump units 41, 42 and 43 via a hydraulic liquid supply conduit 23. Each pump unit 41, 42 and 43 is connected to the supply conduit 18.

Each pump unit 41, 42, 43 comprises hydraulic control valve 24 configured to selectively connect the respective drive chamber 48 to the source of high pressure hydraulic liquid or to tank via a control conduit 25.

Each pump unit 41, 42, 43 comprises a drive unit 44 in the form of a linear hydraulic actuator that is formed by the drive cylinder 45 with the drive piston 46 slidably arranged therein. The return chamber 47 is permanently connected to a source of hydraulic pressure, that includes a hydraulic pump 30, e.g. a variable displacement positive displacement pump, via a return chamber supply line 31, that preferably includes a flow restriction 33 and is coupled to an accumulator 32 for ensuring stable supply of pressurized hydraulic liquid to the return chamber 47. Alternatively, the source of low pressure is obtained from the high pressure hydraulic system via a pressure reduction valve. In an embodiment the pressure of the hydraulic liquid supply to the return chamber is significantly less than the pressure of the hydraulic liquid supplied to the drive chamber 48. Alternatively, the effective pressure surface of the side of the drive piston 46 facing

02586-DK-P the return chamber 47 can be arranged to be significantly smaller than the effective pressure surface of the drive piston facing the drive chamber 48. In the latter case the pressure of the hydraulic fluid in the return chamber 47 can be substantially equal to the pressure of the hydraulic fluid supply to the drive chamber 48.

Each pump unit 41, 42, 43 comprises a pump 60 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 51 that only allows flow to the pressure chamber 63. The pump chamber 63 is connected to the supply conduit 18 via a second one-way valve 52 that only allows flow from the pressure chamber 63.

Fig. 5 is a detailed sectional view of a pump unit 41, 42, 43 of the high-pressure pump 40. The pump units 41,42,43 comprises a hydraulic linear actuator 44 that includes a cylinder 45 with a drive piston 46 arranged therein. The drive piston 46 is connected to a piston shaft 47, preferably formed as one unit therewith. The piston rod 49 and the drive piston 46 are provided with a bore 58 for receiving a rod 57 of a position sensor 56. The signal of the position sensor 56 is transmitted to an electronic control unit 70. The drive piston 46 divides the interior of the drive cylinder 45 in a drive chamber 48 and a return chamber 47. In Fig. 5 the return chamber is not recognizable because the drive piston 46 as reached the end of its drive stroke. The drive chamber 48 is connected to the hydraulic control valve 24 via a bore 25.

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The return chamber 47 is permanently connected to a source of hydraulic pressure via a bore 31.

The piston rod 47 of the linear hydraulic actuator 44 is connected to the piston rod 62 of the cryogenic pump 60 (the pump60 could though just as well be a regular linear positive displacement pump for pumping non-cryogenic liquids). The connection between piston rod 47 and piston rod 62 is established by a connector piece 54, in a way that causes the piston rod 47 and the piston rod 62 to move in unison. The drive cylinder 45 is connected to the pump cylinder 61 by a bolt connection 55. The pump 60 is provided with an outlet that connects the pump chamber 63 to the transfer conduit 50.

Fig. 9 is a diagrammatic representation of a control system in the form of an electronic control unit 70 for controlling the operation of the high-pressure pump 40.

The electronic control unit 70 receives a fuel of lubricant pressure set point 71. The pressure set point 71 is transmitted to a summation point 72. At first summation point 72 the measured pressure is subtracted and the difference between the setpoint and the measured pressure at the outlet of the pump 40 is transmitted to a PI controller 74 is part of a feedback control loop.

The pressure set point is transmitted to a feed-forward piston ratio gain unit 78. The signal from the feed-forward piston ratio gain unit 78 is compared with the signal from the PI controller 74 at a second summation point 76.

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The measured fuel or lubricant pressure that is fed to the first summation point 72 can be based on a measurement of the pressure in the pipe volumes at the engine, i.e. downstream of the valve arrangement 19. The valve arrangement 19 is a double block and bleed valve arrangement that receives flow of fuel or lubricant from supply conduit 18. The measured fuel lubricant pressure is filtered in a filter 86.

The result of the comparison at the second summation point 76 is transmitted to the source of high-pressure hydraulic liquid 20. Based on the signal, the source of high-pressure hydraulic liquid 20 delivers hydraulic liquid with the correct pressure to the high-pressure pumping unit 40.

The electronic control unit 70 receives a signal representative of the position of the drive pistons and processes this position signal in a piston supervision unit 92. The piston supervision unit 92 is coupled to a piston activation strategy unit 90. The details of the operation of the piston supervision unit 92 and the piston activation strategy unit 90 will be displayed explained in greater detail further below. The signal of the piston activation strategy unit 90 is transmitted to the control valves 24 of the highpressure pump 40 for activating the drive pistons 46.

Activation of the drive pistons 46 causes fuel or lubricant to be pumped through the supply conduit 18.

The primary pressure control of the electronic control unit 70 is feed-forward. The PI (proportional integral) controller compensates for nonlinearities and assists with transients.

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The fuel or lubricant pressure is self-controlled by setting the hydraulic feed pressure to the pump units 41, 42, 43. The pressure control is on the hydraulic side, and there is no need to act on the gas side. This system makes it impossible to arrive at too high fuel or lubricant pressures when the hydraulic pressure is controlled properly.

The drive pistons 46 are controlled via a control strategy, that is not an active part of the pressure control.

Each pump unit 41,42,43 is individually controllable. Thus, it is possible to run different piston strategies and various operating conditions. Further, the possibility to run pump units 41,42,43 individually provides for redundancy since it is possible to change from three to two pump units 41,42,43 between two strokes.

The return speed can be greater than the forward (pump) speed, thereby making it possible to have overlap when running with two pump units only. The overlap between the pump units 41, 42, 43 can be adjusted in accordance to needs in order to reduce pressure spikes.

The end position of the pump stroke can be varied over time to distribute wear over an area of the pump cylinder 61, as opposed to having high wear at a fixed and position on the cylinder .

The system allows for little or no pressure overshoot, even at sudden shutdown (piston stop) since there is very low

02586-DK-P inertia and other factors that negatively affect the dynamic response .

The control valves 24 can be hydraulically controlled valves or electronically controlled valves. In the embodiment the control valve 24 is a hydraulically controlled valve there is provided an electronically controlled solenoid valve (not shown) that controls the hydraulic control signal to the control valve 24. The electronically controlled solenoid valve receives electronic control signals from the electronic control unit 70.

The electronic control unit 70, in particular the piston activation strategy unit 90, is configured for selectively connecting the drive chamber 48 of the pump units 41,42,43 to the source of high-pressure hydraulic fluid 20 or to tank.

The electronic control unit 70, in particular the piston activation strategy unit 90, is configured to start a pump stroke of a drive piston 47 when the pump stroke of another drive piston 47 is nearing its end so that there is a small overlap between the ending pump stroke and the starting pump stroke. In an embodiment the electronic control unit 70 is configured to activate the respective drive cylinders substantially consecutively, preferably with a small overlap. Thus, a substantially stable flow of LNG to the high-pressure vaporizer 14 without significant pressure fluctuations can be achieved, as illustrated in Figs. 6 and 7.

Figs. 6,7 and 8 illustrate a typical operation of the highpressure pump 40. The thin continuous line represents pump

02586-DK-P unit 41 the thick continuous line represents pump unit 42 and the dotted line represents pump unit 43. Fig. 6 is a graph illustrating the movement of the drive pistons 46/pump pistons 62 . As can be seen from the graph, the start of the pump stroke of the next pump unit starts just ahead of the end of the pump stroke of the presently active pump unit. Figure 7 illustrates the resulting pressure composed from the pressure output from the three pump units 41,42,43 transfer conduit 50. The resulting pressure is substantially constant and without fluctuations.

Fig. 8 shows the speed profile of the pump units in which can be clearly seen that the speed of the return stroke is significantly higher than the speed of the pump stroke, thus allowing for overlap between the pump units, even if only two out of three or more pump units are in use.

In an embodiment, the electronic control unit 70, in particular the piston activation strategy unit 90, is configured to take into account the dynamics of the ending of a pump stroke and the dynamics of the starting pump stroke in order to obtain a substantially constant flow of high-pressure liquefied gas from the high-pressure pump to the high-pressure vaporizer 14.

In an embodiment the electronic control unit 70, in particular the piston activation strategy unit 90, is configured to determine when the pump stroke of one of the pump units 41, 42, 43 has to start and to determine when a pump stroke of any of the drive units 41, 42, 43 has to end. Thus, the point at which the pump stroke starts and especially where it ends

02586-DK-P can be accurately controlled by the piston strategy unit 90, preferably together with the piston super vision unit 92.

In an embodiment the electronic control unit 70 is configured to operate the drive pistons of the remaining functioning pump units 41, 42, 43 when one of the pump units 41, 42, 43 is out of order. Thus, redundancy is obtained and pumping action can be continued if one of the pump units 41, 42, 43 is out of order.

In an embodiment the electronic control unit 70 is configured to adjust the position of the drive piston 46 at which the drive chamber 48 is disconnected from the source of highpressure hydraulic fluid in relation to the magnitude of the flow of liquefied gas from the high-pressure pump 40 to the high-pressure vaporizer. Thus, the position in which the pump stroke reverses can be controlled, regardless of the speed and the resulting inertia of the drive piston 46 and pump piston 62.

According to an embodiment the electronic control unit 70 is configured to adjust the position of the drive piston at which the drive chamber 48 of the drive piston 46 concerned is disconnected from the source of high-pressure fluid 20 in the direction opposite to the direction of the drive stroke when the flow of fuel or lubricant from the high-pressure pump to the engine increases and the electronic control unit 70 is configured to adjust the position of the drive piston 46 at which the drive chamber 48 of the drive piston 46 concerned is disconnected from the source of high-pressure fluid 20 in the direction of the direction of the drive stroke when the

02586-DK-P flow of fuel or lubricant from the high-pressure pump to the engine decreases. This is illustrated in Figs. 10 and 11.

Fig. 10 shows the effect of the increased speed of the drive piston 46 and pump piston 62 on the end position of the drive/pump stroke. The thin continuous line represents pump unit 41 the thick continuous line represents pump unit 42 and the dotted line represents pump unit 43. The electronic control unit 70 signals the hydraulic control valve 24 to connect the drive chamber 48 to tank when the drive piston has reached a stroke of 80 mm, regardless of the load/magnitude of the flow of liquefied gas delivered by the high-pressure pump 40. Due to the inertia and the higherspeed the stop/reverse position of the drive piston 46 changes from 85 mm at 25% load to 89 mm at 50% load to 98 mm at hundred percent load.

Fig. 11 is a graph illustrating the effect of the electronic control unit 70 compensating for the increased speed of the drive piston 46/pump piston 62 by connecting the drive chamber 48 to tank at shorter stroke when the load is high and at a longer stroke when the load is low. As can be seen in the graph, the electronic control unit 70 can in this way accurately control the end position of the drive/pump stroke.

In the example in the graph the signal for connecting the drive chamber 48 to tank for 25% load (i.e. 25% of the maximum capacity of the high-pressure pump 40) for the next drive cylinder is issued when the previous cylinder is 75 mm into the drive chamber. The drive chamber of the previous drive cylinder is connected to tank when it is 93 mm into the drive

02586-DK-P chamber. The connection to the source of high pressure of the next drive cylinder signal on and the connection to tank of the previous cylinder signal off is illustrated in table 1 below.

	25% load	45% load	70% load	100% Load
Signal on	7 5 mm	7 5 mm	7 5 mm	7 5 mm
Signal off	93 mm	8 6 mm	83 mm	80 mm
Stop position	97 mm	97 mm	97 mm	97 mm

Table 1

Of course, it is also still possible to program the electronic control unit 72 deliberately varied the start position in order to reduce wear of the pump cylinder 61.

In an embodiment the electronic control unit 70 is configured to adjust the position of a drive piston 46 at which the drive chamber 48 of the drive piston 46 concerned is disconnected from the source of high-pressure fluid 20 according to an algorithm, plan or randomly in order to distribute the position at which the pump piston 62 reverses over an area of the stroke of the pump piston 62 in order to reduce wear of the pump cylinder 61. Is known that wear on the pump cylinder 61 is highest at the position where the pump stroke ends. By varying the position in which the pump stroke ends the wear of the pump cylinder 61 can be spread over a larger area and thus the life span of the pump cylinder 61 can be significantly increased.

In an embodiment the electronic control unit 70 is configured to control the activation and deactivation of the respective

02586-DK-P drive pistons 46 independently from the control pressure of the hydraulic fluid supplied to the drive chambers 48. Thus, the control strategy for the activation of the drive pistons can be optimized by the electronic control unit 70 independently of the pressure control.

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.

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Claims

patent claims

A cryopump (40) for pumping a cryo fuel, said pump comprising two or more pump units (41, 42, 43), each pump unit (41, 42, 43) comprising a pump piston (62) slidably disposed in a a single pump cylinder (61) and a hydraulically driven drive piston (46) slidably located in a single drive cylinder (45), wherein the drive piston (46) is coupled to the pump piston (62) for driving the pump piston (62), at least one electronically control valve (24) connected to a source of high pressure hydraulic fluid (22) and a tank for controlling the flow of hydraulic fluid to and from the drive cylinder (45) to one or more of the pump units (41, 42, 43), characterized by the drive cylinder being provided with a position sensor (56) for sensing the position of the drive piston (46) in the respective drive cylinder (45), an electronic control unit (70) for receiving a signal from the position sensor (56), wherein the electronic control valve (24) is coupled to the electronic control unit (70), the n at least one electronic control unit (70) is configured to selectively connect the pump cylinders of the pump units to the source of high pressure hydraulic fluid or to the tank.

A cryopump (40) according to claim 1, wherein the source of high pressure hydraulic fluid (22) is a source of variable and controllable pressure level.

The cryopump (40) of claim 1 or 2, wherein the drive cylinder (45) comprises a drive chamber (48) and a return chamber (47).

The cryopump (40) of claim 3, wherein the drive chamber (48) is connected to the control valve (24) and the return chamber (47)

Preferably, the 02586-DK-P is associated with a source of hydraulic fluid having a pressure (30) lower than the pressure on the source (22) of high pressure hydraulic fluid.

The cryopump (40) according to any one of claims 1 to 4, wherein the electronic control unit (70) is configured to start a drive piston pump stroke as another drive piston pump stroke approaches the end so that there is a minor overlap between the final pump stroke and the starting pump stroke.

A cryopump (40) according to claim 5, wherein the electronic control unit (70) is configured to take into account the dynamics at the end of a pump stroke and the dynamics at the start of a pump stroke to obtain a substantially constant flow of fuel or lubricant. from the pump.

The cryopump (40) according to claim 6, wherein the control unit (70) is configured to correspondingly drive cylinders substantially preferably with a minor overlap.

electronically enable them consecutively,

A cryopump (40) according to any one of claims 4 to 7, wherein the electronic control unit (70) is configured to adjust the position of the drive piston (46), wherein the drive chamber (48) is disconnected from the source of high pressure hydraulic fluid (20). for increasing the amount of flow of fuel or lubricant pumped by the pump.

A cryopump (40) according to claim 8, wherein the electronic control unit (70) is configured to adjust the position of the drive piston, where the drive chamber of that drive piston is disconnected from the source of high pressure fluid in the direction.

02586-DK-P opposite the direction of the drive stroke as the flow of fuel or lubricant pumped by the pump (40) increases.

A cryopump (40) according to claim 7 or 9, wherein the electronic control unit (70) is configured to adjust the position of the drive piston, wherein the drive chamber of that drive piston is disconnected from the source of high pressure fluid in the direction of the direction of the drive stroke when the flow of fuel or lubricant pumped by pump (40) decreases.

A cryopump (40) according to any one of claims 4 to 10, wherein the electronic control unit (70) is configured to adjust the position of a drive piston according to an algorithm, plan or arbitrary to distribute the position where the pump piston turns over. part of the stroke of the pump piston to reduce wear of the pump cylinder.

A cryopump (40) according to any one of claims 4 to 11, wherein the electronic control unit (70) is configured to control the pressure of the fuel or lubricant leaving the pump by controlling the pressure of the hydraulic fluid being applied. drivkamrene.

The cryopump (40) according to claim 12, wherein the electronic control unit (70) is configured to apply a desired pressure to the fuel or lubricant leaving the pump in a forward supply function for controlling the pressure of the hydraulic fluid supplied to the drive pistons.

The cryopump (40) according to claim 12 or 15, wherein the electronic control unit (70) is configured to apply a measured pressure to the fuel or lubricant which

02586-DK-P exits the pump in a reciprocating supply function to control the pressure of the hydraulic fluid supplied to the drive pistons.

A cryopump (40) according to any one of claims 12 to 14, wherein the electronic control unit (70) is configured to control the activation and deactivation of the corresponding drive pistons (46) independently of the control of the pressure of the hydraulic fluid being applied. drivkamrene.

Cryo pump (40) 12 to 16, configured to represent representative of the actuation according to any one of the claims, the electronic controller (70) is to use a signal which is the position of the drive pistons (46) to and deactivate the drive pistons .

A large, two-stroke, turbocharged, internal combustion ignition internal combustion engine comprising a cryopump (40) according to any one of claims 1 to 16 for supplying fuel or lubricant to the engine.

A method of controlling the activation of a pump piston of a pump (40), wherein the pump (40) comprises two or more pump units (41, 42, 43), each pump unit (41, 42, 43) comprising a pump piston (62), slidingly located in a pump cylinder (61) and a hydraulically driven drive piston (46) slidingly placed in a drive cylinder (45), the drive piston (46) being coupled to the pump piston (62) to drive the pump piston (62) at least one electronic control valve (24) connected to a source of high pressure hydraulic fluid (22) and with a tank for controlling the flow of hydraulic fluid to and from the drive cylinder (45) for one or more of the pump units (41, 42, 43) , characterized by a position sensor (56) for

02586-DK-P sensing the position of the drive piston (46) in said drive cylinder (45), which comprises, activating a drive piston (46) with the electronic control valve (24) for a drive stroke and then deactivating the drive piston (46) with the electronic control valve (24) for a return stroke, measuring the position of the drive piston (46) with the position sensor (56) below the drive stroke, where the drive piston (46) is activated when the drive piston (46) is in a return position and the drive piston (46) is deactivated by a position which depends on the speed of the drive piston (46).

The method of claim 18, wherein the drive piston (46) is deactivated at a position closer to the return position with increasing speed of the drive piston (46) during the drive stroke, and wherein the drive piston (46) is deactivated at a position further away from the return position with decreasing speed of the drive piston (46). 46) during the drive stroke.

The method of claim 18 or 19, wherein the drive pistons (46) are activated substantially sequentially, with the activation of the next drive piston (46) preferably occurring immediately prior to deactivation of the currently active drive piston (46).

A method according to any one of claims 18 to 20, further comprising supplying high pressure hydraulic fluid to the drive pistons (46), wherein the pressure of the fuel or lubricant leaving the pump (40) is controlled by controlling the pressure of the hydraulic fluid which are supplied to the drive pistons (46).

02586-EN-P

A method according to any one of claims 18 to 21, comprising supplying high pressure hydraulic fluid to the drive pistons (46) and controlling the pressure of the fluid exiting the pump (40) by controlling

5, the hydraulic fluid supplied to the drive pistons (46).

The method of claim 22, wherein the drive pistons (46) are activated substantially sequentially, wherein the actuation

10 of the next drive piston (46) preferably occurs immediately prior to deactivation of the currently active drive piston (46).

02586-EN-P

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