WO2017021583A1 - Fuel injection system and method for operating a piston engine - Google Patents

Fuel injection system and method for operating a piston engine Download PDF

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Publication number
WO2017021583A1
WO2017021583A1 PCT/FI2015/050516 FI2015050516W WO2017021583A1 WO 2017021583 A1 WO2017021583 A1 WO 2017021583A1 FI 2015050516 W FI2015050516 W FI 2015050516W WO 2017021583 A1 WO2017021583 A1 WO 2017021583A1
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WO
WIPO (PCT)
Prior art keywords
fuel
compartment
pressure
engine
injection system
Prior art date
Application number
PCT/FI2015/050516
Other languages
French (fr)
Inventor
Antti VUOHIJOKI
Jaakko Koivula
Original Assignee
Wärtsilä Finland Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wärtsilä Finland Oy filed Critical Wärtsilä Finland Oy
Priority to PCT/FI2015/050516 priority Critical patent/WO2017021583A1/en
Publication of WO2017021583A1 publication Critical patent/WO2017021583A1/en

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/44Details, components parts, or accessories not provided for in, or of interest apart from, the apparatus of groups F02M59/02 - F02M59/42; Pumps having transducers, e.g. to measure displacement of pump rack or piston
    • F02M59/447Details, components parts, or accessories not provided for in, or of interest apart from, the apparatus of groups F02M59/02 - F02M59/42; Pumps having transducers, e.g. to measure displacement of pump rack or piston means specially adapted to limit fuel delivery or to supply excess of fuel temporarily, e.g. for starting of the engine
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/04Introducing corrections for particular operating conditions
    • F02D41/06Introducing corrections for particular operating conditions for engine starting or warming up
    • F02D41/062Introducing corrections for particular operating conditions for engine starting or warming up for starting
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/30Controlling fuel injection
    • F02D41/38Controlling fuel injection of the high pressure type
    • F02D41/3809Common rail control systems
    • F02D41/3836Controlling the fuel pressure
    • F02D41/3845Controlling the fuel pressure by controlling the flow into the common rail, e.g. the amount of fuel pumped
    • F02D41/3854Controlling the fuel pressure by controlling the flow into the common rail, e.g. the amount of fuel pumped with elements in the low pressure part, e.g. low pressure pump
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/40Fuel-injection apparatus with fuel accumulators, e.g. a fuel injector having an integrated fuel accumulator
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/60Fuel-injection apparatus having means for facilitating the starting of engines, e.g. with valves or fuel passages for keeping residual pressure in common rails
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/04Feeding by means of driven pumps
    • F02M37/14Feeding by means of driven pumps the pumps being combined with other apparatus
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M59/00Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps
    • F02M59/02Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type
    • F02M59/10Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type characterised by the piston-drive
    • F02M59/107Pumps specially adapted for fuel-injection and not provided for in groups F02M39/00 -F02M57/00, e.g. rotary cylinder-block type of pumps of reciprocating-piston or reciprocating-cylinder type characterised by the piston-drive pneumatic drive, e.g. crankcase pressure drive
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02NSTARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N19/00Starting aids for combustion engines, not otherwise provided for
    • F02N2019/002Aiding engine start by acting on fuel

Definitions

  • the present invention relates to a fuel injection system for a piston engine in accordance with the preamble of claim 1 .
  • the invention also concerns a meth- od for operating a piston engine as defined in the other independent claim.
  • High-pressure pumps which pressurize the fuel for fuel injection
  • low-pressure pumps which feed the fuel to the high-pressure pumps.
  • the high-pressure pumps can be either common-rail pumps or individual fuel injection pumps.
  • ship engines the classification rules require that there are two parallel methods of feeding fuel to the high-pressure pumps.
  • the fuel injection system is provided with an engine-driven low-pressure pump, which is used during the normal operation of the engine, and with a separate stand-by pump, which can be electrically driven. The stand-by pump is used when the engine is started and the engine- driven pump does not yet deliver sufficient fuel flow to the high-pressure pumps.
  • An object of the present invention is to provide an improved fuel injection system for a piston engine, which comprises a high-pressure pump for supplying liquid fuel to a fuel injector and a low-pressure pump for feeding fuel to the high-pressure pump.
  • the characterizing features of the fuel injection system according to the invention are given in the characterizing part of claim 1 .
  • Another object of the invention is to provide an improved method for operating a piston engine, which is provided with a fuel injection system comprising a high- pressure pump for supplying fuel to a fuel injector and a low-pressure pump for feeding fuel to the high-pressure pump.
  • the fuel injection system according to the invention comprises a fuel accumulator that is configured to receive fuel from the low-pressure pump during running of the engine and to feed fuel to the high-pressure pump during start of the engine.
  • fuel from the low-pressure pump is supplied to a fuel accumulator during running of the engine, and fuel from the fuel accumulator is fed to the high-pressure pump during start of the engine.
  • the engine can be started without a stand-by pump. Energy consumption during start is reduced and the startability of the engine is also improved, since the fuel is quickly pressurized.
  • the fuel accumulator comprises a first compartment for storing the fuel, a second compartment and a fluid-tight wall separating the first compartment from the second compartment, the wall being configured to expel fuel from the first compartment when fluid pressure in the second compartment exceeds the pressure in the first compartment.
  • the delivery of fuel from the fuel accumulator can thus be controlled by controlling the pressure in the second compartment.
  • the second compartment of the fuel accumulator is configured to receive pressure medium for increasing the pressure in the second compartment and to expel fuel from the first compartment.
  • the pressure medium can be, for instance, pressurized air from a pressure medium source, such as the compressed air system of the engine.
  • the second compartment of the fuel accumulator is connected to a pressure medium source via a control valve having a first position, in which position the pressure of the second compartment is released and a second position, in which position pressure medium is supplied into the second compartment from the pressure medium source.
  • a control valve having a first position, in which position the pressure of the second compartment is released and a second position, in which position pressure medium is supplied into the second compartment from the pressure medium source.
  • fuel can be supplied into the fuel accumulator and the volume of the first compartment is maximized.
  • the control valve is switched to the second position when the engine is started.
  • the second compartment of the fuel accumulator is pressureless and leakages are thus reduced.
  • the system needs to be pressurized only for the start of the engine.
  • the control valve is preferably electrically operable.
  • the control valve can be provided with an option for manual operation, which allows starting of the engine also in a blackout situation.
  • Fig. 1 shows schematically a fuel injection system of a piston engine.
  • FIG 1 a fuel injection system of a piston engine 1 .
  • the engine 1 is a large internal combustion engine, such as a main or an auxiliary engine of a ship or an engine that is used at a power plant for producing electricity.
  • the cylinder bore of the engine is at least 150 mm.
  • the rated power of the engine is at least 150 kW/cylinder.
  • the engine 1 comprises six cylinders 2, but the engine 1 can comprise any reasonable number of cylinders 2.
  • Figure 1 shows a fuel injection system for injecting liquid fuel, such as light fuel oil, heavy fuel oil or marine diesel oil into the cylinders 2 of the engine 1 .
  • the engine 1 can also comprise an ad- ditional fuel injection system for gaseous fuel.
  • the engine 1 can also comprise a further fuel injection system for liquid fuel, such as a fuel injection system for liquid pilot fuel that is used for igniting gaseous fuel.
  • the fuel injection system is provided with one high-pressure pump 3 for each cylinder 2 of the engine 1 .
  • the fuel injection pumps 3 are conventional fuel injection pumps, which are provided with rotata- ble plungers for adjusting the fuel injection timing and the amount of the injected fuel.
  • Each high-pressure pump 3 supplies fuel to one fuel injector 4.
  • Each fuel injector 4 is arranged to inject the fuel directly into a cylinder 2 of the engine 1 .
  • the term "high-pressure pump” refers here to a fuel injection pump, which is capable of raising the pressure of the fuel to a level that is sufficient for fuel injection in a large internal combustion engine.
  • the pressure of the fuel after the high-pressure pump 3 is at least 500 bar.
  • the fuel injectors 4 are pressure-controlled and open when the pressure of the fuel exceeds a certain limit value and close when the pressure drops below the limit value.
  • the fuel injection system comprises a low-pressure pump 9 for feeding fuel to the high-pressure pumps 3.
  • the fuel is supplied to the high-pressure pumps 3 from a tank 1 1 .
  • the expression "low-pressure pump” refers here to a feed pump, which raises the pressure of the fuel to a level that is suitable for reliably feeding the high-pressure pumps 3.
  • the pressure after the low-pressure pump 9 is in the range of 5 to 15 bar.
  • the low-pressure pump 9 thus raises the pressure of the fuel to a first pressure level, and the high-pressure pumps 3 raise the pressure of the fuel from the first pressure level to a second pressure level, which is higher than the first pressure level.
  • only one low-pressure pump 9 is shown, but the fuel injection system could comprise two or more low-pressure pumps 9.
  • low-pressure pumps 9 can be arranged in parallel to feed all the high-pressure pumps 3, or one low-pressure pump 9 can feed a group of high-pressure pumps 3. It is also possible that the fuel injection system comprises one low-pressure pump 9 for each high-pressure pump 3.
  • the low-pressure pump 9 can be engine-driven, i.e. the power required by the pump 9 is taken from the crankshaft of the engine 1 . However, it is also possible that the low-pressure pump 9 is e.g. electrically or hydraulically driven.
  • the low-pressure pump 9 is connected to the high-pressure pumps 3 through a fuel supply line 12.
  • the fuel injection system needs to be provided with additional means for supplying fuel to the high-pressure pumps 3 during start of the engine 1 .
  • the fuel injection system according to the invention is provided with a fuel accumulator 5, which can store fuel and supply fuel to the high-pressure pumps 3 during the start of the engine 1 .
  • the fuel accumulator 5 comprises a first compartment 5a and a second compartment 5b.
  • the first compartment 5a can receive fuel and deliver it to the high-pressure pumps 3.
  • the first compartment 5a of the fuel accumulator 5 is connected to the fuel supply line 12 through a connecting line 13.
  • the first compartment 5a is separated from the second compartment 5b with a wall 5c.
  • the second compartment 5b of the fuel accumulator 5 can receive pressurized fluid.
  • fuel is expelled from the first compartment 5a.
  • pressure of the fuel in the first com- partment 5a exceeds the pressure in the second compartment 5b
  • fluid is expelled from the second compartment 5b.
  • the wall 5b between the first compartment 5a and the second compartment 5b can be movable or deformable for allowing changes in the volumes of the first compartment 5a and the sec- ond compartment 5b.
  • the wall 5c can be a flexible diaphragm.
  • the wall 5 can be formed by a movable piston.
  • the fuel injection system comprises a check valve 8, which is arranged in the fuel supply line 12 between the connecting line 13 and the low-pressure pump 9.
  • the check valve 8 prevents flow from the fuel accumulator 5 to the low-pressure pump 9.
  • the second compartment 5b of the fuel accumulator 5 is connected to a pressure medium source 10, from which pressurized fluid can be supplied into the second compartment 5b of the fuel accumulator 5.
  • the pressurized fluid is pressurized air.
  • the pressure medium source 10 can be a tank containing compressed air, or it can be the compressed air system of the engine 1 , which supplies pressurized air to various components of the engine 1 .
  • the pressure of the pressure medium should be approximately the same as the pressure produced by the low- pressure pump 9.
  • a suitable pressure range is thus 5 to 15 bar.
  • the pressure is typically 7 to 10 bar, which is suitable for the fuel accumulator 5.
  • the second compartment 5b of the fuel accumulator 5 is connected to the pressure medium source 10 through a pressure medium line 14.
  • the pressure medium line 14 is provided with a control valve 6, which can be used for controlling the pressure medium flow into the second compartment 5b of the fuel accumulator 5 and out of the second compartment 5b.
  • the control valve 6 has a first position and a second position. In the first position of the control valve 6, outflow from the second compartment 5b is allowed.
  • the control valve 6 con- nects the pressure medium line 14 to an outlet 15, through which the pressure medium can flow out of the second compartment 5b of the fuel accumulator 5 and the pressure in the second compartment 5b is thus released. In the first position of the control valve 6, flow from the pressure medium source 10 into the second compartment 5b of the fuel accumulator 5 is prevented.
  • the pressure medium line 14 is provided with a check valve 7, which is ar- ranged between the pressure medium source 10 and the control valve 6.
  • the check valve 7 prevents flow from the second compartment 5b of the fuel accumulator 5 into the pressure medium source 10 in case the pressure in the second compartment 5b is higher than the pressure of the pressure medium source 10. This can be the case when the fuel pressure in the fuel supply line 12 and in the first compartment 5a of the fuel accumulator 5 is higher than the pressure of the pressure medium source 10.
  • the control valve 6 is provided with both electrical and manual control. The control valve 6 is normally controlled electrically, but in case of a blackout, the control valve 6 can be switched manually from one position to another position and in particular from the first position to the second position.
  • the control valve 6 is in the first posi- tion.
  • the low-pressure pump 9 supplies fuel to the high-pressure pumps 3, but part of the fuel flows into the first compartment 5a of the fuel accumulator 5, until the volume of the first compartment 5a is maximized and the fuel accumulator 5 stores an amount of fuel that corresponds the maximum capacity of the fuel accumulator 5. Since the second compartment 5b of the fuel accumulator 5 is open to atmospheric pressure, the fluid in the second compartment 5b does not significantly resist fuel flow into the fuel accumulator 5. After shutting down the engine 1 , the control valve 6 is kept in the first position. The fuel in the fuel accumulator 5 is thus stored in the pressure that prevailed in the first compartment 5a of the fuel accumulator 5 before the shut-down.
  • the control valve 6 When the engine 1 is started, the control valve 6 is switched to the second po- sition, in which the compressed air is allowed to flow from the pressure medium source 10 into the second compartment 5b of the fuel accumulator 5. Normally, the control valve 6 can be switched to the second position electrically. However, in a blackout situation, where electric power is not available, the control valve 6 can be operated manually. When the flow of pressurized air into the second compartment 5b of the fuel accumulator 5 is allowed, the pressure of the air pushes or deforms the wall 5c of the fuel accumulator 5 and forces the fuel to flow from the first compartment 5a of the fuel accumulator 5 into the fuel supply line 12.
  • the check valve 8 in the fuel supply line 12 prevents flow towards the low-pressure pump 9, and the fuel thus flows to the high-pressure pumps 3. Because of the fuel accumulator 5, a separate stand-by pump is not needed, but the engine 1 can be started by using the fuel stored in the fuel accumulator 5. Since pressurized air is supplied from the pressure medium source 10 at a constant pressure to the second compartment 5b of the fuel accumulator 5, the fuel is supplied at a constant pressure from the fuel accumula- tor 5 to the high-pressure pumps 3.
  • the engine-driven low- pressure pump 9 starts pumping fuel.
  • the check valve 8 in the fuel supply line 12 opens and the low- pressure pump 9 starts to feed the high-pressure pumps 3 and the fuel accumulator 5.
  • the control valve 6 can be switched back to the first position. The supply of compressed air from the pressure medium source 10 into the second compartment 5b of the fuel accumulator 5 is thus prevented and flow from the second compartment 5b into the outlet 15 is allowed.
  • the low-pressure pump 9 thus starts to effectively fill the first compartment 5a of the fuel accumulator 5.
  • the volume of the fuel accumulator 5 depends on the engine.
  • the fuel accumulator 5 should be sized such that a sufficient amount of fuel can be stored for starting of the engine with a sufficient safety margin. It is also possible that the fuel injection system is provided with two or more fuel accumulators 5.
  • the fuel accumulators 5 can be arranged in parallel to feed the same high-pressure pumps 3, or one fuel accumulator 5 can feed a certain group of high-pressure pumps 3.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fuel-Injection Apparatus (AREA)

Abstract

The fuel injection system for a piston engine (1) comprises a high-pressure pump (3) for supplying liquid fuel to a fuel injector (4), a low-pressure pump (9) for feeding fuel to the high-pressure pump (3) and a fuel accumulator (5) that is configured to receive fuel from the low-pressure pump (9) during running of the engine (1) and to feed fuel to the high-pressure pump (3) during start of the engine (1).

Description

Fuel injection system and method for operating a piston engine Technical field of the invention
The present invention relates to a fuel injection system for a piston engine in accordance with the preamble of claim 1 . The invention also concerns a meth- od for operating a piston engine as defined in the other independent claim.
Background of the invention
Large internal combustion engines, such as power plant or ship engines, which are operated using liquid fuel, are provided with high-pressure pumps, which pressurize the fuel for fuel injection, and with low-pressure pumps, which feed the fuel to the high-pressure pumps. The high-pressure pumps can be either common-rail pumps or individual fuel injection pumps. In ship engines, the classification rules require that there are two parallel methods of feeding fuel to the high-pressure pumps. Often the fuel injection system is provided with an engine-driven low-pressure pump, which is used during the normal operation of the engine, and with a separate stand-by pump, which can be electrically driven. The stand-by pump is used when the engine is started and the engine- driven pump does not yet deliver sufficient fuel flow to the high-pressure pumps.
Summary of the invention
An object of the present invention is to provide an improved fuel injection system for a piston engine, which comprises a high-pressure pump for supplying liquid fuel to a fuel injector and a low-pressure pump for feeding fuel to the high-pressure pump. The characterizing features of the fuel injection system according to the invention are given in the characterizing part of claim 1 . Another object of the invention is to provide an improved method for operating a piston engine, which is provided with a fuel injection system comprising a high- pressure pump for supplying fuel to a fuel injector and a low-pressure pump for feeding fuel to the high-pressure pump. The fuel injection system according to the invention comprises a fuel accumulator that is configured to receive fuel from the low-pressure pump during running of the engine and to feed fuel to the high-pressure pump during start of the engine. In the method according to the invention, fuel from the low-pressure pump is supplied to a fuel accumulator during running of the engine, and fuel from the fuel accumulator is fed to the high-pressure pump during start of the engine.
Because of the fuel accumulator, the engine can be started without a stand-by pump. Energy consumption during start is reduced and the startability of the engine is also improved, since the fuel is quickly pressurized.
According to an embodiment of the invention, the fuel accumulator comprises a first compartment for storing the fuel, a second compartment and a fluid-tight wall separating the first compartment from the second compartment, the wall being configured to expel fuel from the first compartment when fluid pressure in the second compartment exceeds the pressure in the first compartment. The delivery of fuel from the fuel accumulator can thus be controlled by controlling the pressure in the second compartment.
According to an embodiment of the invention, the second compartment of the fuel accumulator is configured to receive pressure medium for increasing the pressure in the second compartment and to expel fuel from the first compartment. The pressure medium can be, for instance, pressurized air from a pressure medium source, such as the compressed air system of the engine.
According to an embodiment of the invention, the second compartment of the fuel accumulator is connected to a pressure medium source via a control valve having a first position, in which position the pressure of the second compartment is released and a second position, in which position pressure medium is supplied into the second compartment from the pressure medium source. In the first position of the control valve, fuel can be supplied into the fuel accumulator and the volume of the first compartment is maximized. The control valve is switched to the second position when the engine is started. In the first position of the control valve, the second compartment of the fuel accumulator is pressureless and leakages are thus reduced. The system needs to be pressurized only for the start of the engine. The control valve is preferably electrically operable. The control valve can be provided with an option for manual operation, which allows starting of the engine also in a blackout situation.
Brief description of the drawings
Embodiments of the invention are described below in more detail with reference to the accompanying drawing, in which
Fig. 1 shows schematically a fuel injection system of a piston engine.
Description of embodiments of the invention
In figure 1 is shown a fuel injection system of a piston engine 1 . The engine 1 is a large internal combustion engine, such as a main or an auxiliary engine of a ship or an engine that is used at a power plant for producing electricity. The cylinder bore of the engine is at least 150 mm. The rated power of the engine is at least 150 kW/cylinder. In the example of figure 1 , the engine 1 comprises six cylinders 2, but the engine 1 can comprise any reasonable number of cylinders 2. Figure 1 shows a fuel injection system for injecting liquid fuel, such as light fuel oil, heavy fuel oil or marine diesel oil into the cylinders 2 of the engine 1 . If the engine 1 is a dual-fuel engine, the engine 1 can also comprise an ad- ditional fuel injection system for gaseous fuel. The engine 1 can also comprise a further fuel injection system for liquid fuel, such as a fuel injection system for liquid pilot fuel that is used for igniting gaseous fuel.
In the embodiment of figure 1 , the fuel injection system is provided with one high-pressure pump 3 for each cylinder 2 of the engine 1 . The fuel injection pumps 3 are conventional fuel injection pumps, which are provided with rotata- ble plungers for adjusting the fuel injection timing and the amount of the injected fuel. Each high-pressure pump 3 supplies fuel to one fuel injector 4. Each fuel injector 4 is arranged to inject the fuel directly into a cylinder 2 of the engine 1 . The term "high-pressure pump" refers here to a fuel injection pump, which is capable of raising the pressure of the fuel to a level that is sufficient for fuel injection in a large internal combustion engine. The pressure of the fuel after the high-pressure pump 3 is at least 500 bar. The fuel injectors 4 are pressure-controlled and open when the pressure of the fuel exceeds a certain limit value and close when the pressure drops below the limit value.
The fuel injection system comprises a low-pressure pump 9 for feeding fuel to the high-pressure pumps 3. The fuel is supplied to the high-pressure pumps 3 from a tank 1 1 . The expression "low-pressure pump" refers here to a feed pump, which raises the pressure of the fuel to a level that is suitable for reliably feeding the high-pressure pumps 3. The pressure after the low-pressure pump 9 is in the range of 5 to 15 bar. The low-pressure pump 9 thus raises the pressure of the fuel to a first pressure level, and the high-pressure pumps 3 raise the pressure of the fuel from the first pressure level to a second pressure level, which is higher than the first pressure level. In the embodiment of figure 1 , only one low-pressure pump 9 is shown, but the fuel injection system could comprise two or more low-pressure pumps 9. If several low-pressure pumps 9 are provided, they can be arranged in parallel to feed all the high-pressure pumps 3, or one low-pressure pump 9 can feed a group of high-pressure pumps 3. It is also possible that the fuel injection system comprises one low-pressure pump 9 for each high-pressure pump 3. The low-pressure pump 9 can be engine-driven, i.e. the power required by the pump 9 is taken from the crankshaft of the engine 1 . However, it is also possible that the low-pressure pump 9 is e.g. electrically or hydraulically driven. The low-pressure pump 9 is connected to the high-pressure pumps 3 through a fuel supply line 12.
If the low-pressure pump 9 is engine-driven, it cannot effectively pressurize the fuel during start of the engine 1 . To ensure reliable start of the engine 1 , the fuel injection system needs to be provided with additional means for supplying fuel to the high-pressure pumps 3 during start of the engine 1 . The fuel injection system according to the invention is provided with a fuel accumulator 5, which can store fuel and supply fuel to the high-pressure pumps 3 during the start of the engine 1 . The fuel accumulator 5 comprises a first compartment 5a and a second compartment 5b. The first compartment 5a can receive fuel and deliver it to the high-pressure pumps 3. The first compartment 5a of the fuel accumulator 5 is connected to the fuel supply line 12 through a connecting line 13. The first compartment 5a is separated from the second compartment 5b with a wall 5c. The second compartment 5b of the fuel accumulator 5 can receive pressurized fluid. When the fluid pressure in the second compartment 5b exceeds the pressure in the first compartment 5a, fuel is expelled from the first compartment 5a. Conversely, when the pressure of the fuel in the first com- partment 5a exceeds the pressure in the second compartment 5b, fluid is expelled from the second compartment 5b. The wall 5b between the first compartment 5a and the second compartment 5b can be movable or deformable for allowing changes in the volumes of the first compartment 5a and the sec- ond compartment 5b. For instance, the wall 5c can be a flexible diaphragm. Alternatively, the wall 5 can be formed by a movable piston. The fuel injection system comprises a check valve 8, which is arranged in the fuel supply line 12 between the connecting line 13 and the low-pressure pump 9. The check valve 8 prevents flow from the fuel accumulator 5 to the low-pressure pump 9. The second compartment 5b of the fuel accumulator 5 is connected to a pressure medium source 10, from which pressurized fluid can be supplied into the second compartment 5b of the fuel accumulator 5. In the embodiment of figure 1 , the pressurized fluid is pressurized air. The pressure medium source 10 can be a tank containing compressed air, or it can be the compressed air system of the engine 1 , which supplies pressurized air to various components of the engine 1 . It is preferable to connect the fuel accumulator 5 to the compressed air system of the engine 1 to ensure that a sufficient amount of pressure medium is available for starting of the engine 1 . The pressure of the pressure medium should be approximately the same as the pressure produced by the low- pressure pump 9. A suitable pressure range is thus 5 to 15 bar. In the compressed air system of an engine the pressure is typically 7 to 10 bar, which is suitable for the fuel accumulator 5.
The second compartment 5b of the fuel accumulator 5 is connected to the pressure medium source 10 through a pressure medium line 14. The pressure medium line 14 is provided with a control valve 6, which can be used for controlling the pressure medium flow into the second compartment 5b of the fuel accumulator 5 and out of the second compartment 5b. The control valve 6 has a first position and a second position. In the first position of the control valve 6, outflow from the second compartment 5b is allowed. The control valve 6 con- nects the pressure medium line 14 to an outlet 15, through which the pressure medium can flow out of the second compartment 5b of the fuel accumulator 5 and the pressure in the second compartment 5b is thus released. In the first position of the control valve 6, flow from the pressure medium source 10 into the second compartment 5b of the fuel accumulator 5 is prevented. When the control valve 6 is in the first position, the pressure in the second compartment In the second position of the control valve 6 flow from the pressure medium source 10 into the second compartment 5b of the fuel accumulator 5 is allowed. Flow from the pressure medium line 14 into the outlet 15 is prevented. The pressure medium line 14 is provided with a check valve 7, which is ar- ranged between the pressure medium source 10 and the control valve 6. The check valve 7 prevents flow from the second compartment 5b of the fuel accumulator 5 into the pressure medium source 10 in case the pressure in the second compartment 5b is higher than the pressure of the pressure medium source 10. This can be the case when the fuel pressure in the fuel supply line 12 and in the first compartment 5a of the fuel accumulator 5 is higher than the pressure of the pressure medium source 10. The control valve 6 is provided with both electrical and manual control. The control valve 6 is normally controlled electrically, but in case of a blackout, the control valve 6 can be switched manually from one position to another position and in particular from the first position to the second position.
When the control valve 6 is in the first position, fuel flows from the fuel supply line 12 into the first compartment 5a of the fuel accumulator 5, provided that the pressure of the fuel in the fuel supply line 12 is higher than the atmospheric pressure. The volume of the first compartment 5a of the fuel accumulator 5 in- creases and fuel is stored in the fuel accumulator 5. The volume of the second compartment 5b decreases. When the control valve 6 is in the second position, and the pressure in the fuel supply line 12 is lower than the pressure of the pressure medium source 10, pressurized fluid flows into the second compartment 5b of the fuel accumulator 5. The volume of the second compartment 5b increases and the volume of the first compartment 5a decreases. Fuel is thus expelled from the fuel accumulator 5 into the fuel supply line 12. Since the check valve 8 in the fuel supply line 12 prevents flow to the low-pressure pump 9 and the tank 1 1 , fuel is supplied to the high-pressure pumps 3.
During normal operation of the engine 1 , the control valve 6 is in the first posi- tion. The low-pressure pump 9 supplies fuel to the high-pressure pumps 3, but part of the fuel flows into the first compartment 5a of the fuel accumulator 5, until the volume of the first compartment 5a is maximized and the fuel accumulator 5 stores an amount of fuel that corresponds the maximum capacity of the fuel accumulator 5. Since the second compartment 5b of the fuel accumulator 5 is open to atmospheric pressure, the fluid in the second compartment 5b does not significantly resist fuel flow into the fuel accumulator 5. After shutting down the engine 1 , the control valve 6 is kept in the first position. The fuel in the fuel accumulator 5 is thus stored in the pressure that prevailed in the first compartment 5a of the fuel accumulator 5 before the shut-down.
When the engine 1 is started, the control valve 6 is switched to the second po- sition, in which the compressed air is allowed to flow from the pressure medium source 10 into the second compartment 5b of the fuel accumulator 5. Normally, the control valve 6 can be switched to the second position electrically. However, in a blackout situation, where electric power is not available, the control valve 6 can be operated manually. When the flow of pressurized air into the second compartment 5b of the fuel accumulator 5 is allowed, the pressure of the air pushes or deforms the wall 5c of the fuel accumulator 5 and forces the fuel to flow from the first compartment 5a of the fuel accumulator 5 into the fuel supply line 12. The check valve 8 in the fuel supply line 12 prevents flow towards the low-pressure pump 9, and the fuel thus flows to the high-pressure pumps 3. Because of the fuel accumulator 5, a separate stand-by pump is not needed, but the engine 1 can be started by using the fuel stored in the fuel accumulator 5. Since pressurized air is supplied from the pressure medium source 10 at a constant pressure to the second compartment 5b of the fuel accumulator 5, the fuel is supplied at a constant pressure from the fuel accumula- tor 5 to the high-pressure pumps 3.
As the crankshaft of the engine 1 starts rotating, also the engine-driven low- pressure pump 9 starts pumping fuel. When the pressure produced by the low- pressure pump 9 exceeds the pressure in the first compartment 5a of the fuel accumulator 5, the check valve 8 in the fuel supply line 12 opens and the low- pressure pump 9 starts to feed the high-pressure pumps 3 and the fuel accumulator 5. After a predetermined rotation speed of the engine 1 has been reached, the control valve 6 can be switched back to the first position. The supply of compressed air from the pressure medium source 10 into the second compartment 5b of the fuel accumulator 5 is thus prevented and flow from the second compartment 5b into the outlet 15 is allowed. The low-pressure pump 9 thus starts to effectively fill the first compartment 5a of the fuel accumulator 5.
The volume of the fuel accumulator 5 depends on the engine. The fuel accumulator 5 should be sized such that a sufficient amount of fuel can be stored for starting of the engine with a sufficient safety margin. It is also possible that the fuel injection system is provided with two or more fuel accumulators 5. The fuel accumulators 5 can be arranged in parallel to feed the same high-pressure pumps 3, or one fuel accumulator 5 can feed a certain group of high-pressure pumps 3.
It will be appreciated by a person skilled in the art that the invention is not lim- ited to the embodiments described above, but may vary within the scope of the appended claims. For instance, although a fuel injection system with individual fuel injection pumps has been described above, the invention is also applicable to common-rail fuel injection systems.

Claims

Claims
1 . A fuel injection system for a piston engine (1 ), the fuel injection system comprising a high-pressure pump (3) for supplying liquid fuel to a fuel injector
(4) and a low-pressure pump (9) for feeding fuel to the high-pressure pump (3), characterized in that the fuel injection system comprises a fuel accumulator
(5) that is configured to receive fuel from the low-pressure pump (9) during running of the engine (1 ) and to feed fuel to the high-pressure pump (3) during start of the engine (1 ).
2. A fuel injection system according to claim 1 , wherein the fuel accumulator (5) comprises a first compartment (5a) for storing the fuel, a second compartment (5b) and a fluid-tight wall (5c) separating the first compartment (5a) from the second compartment (5b), the wall (5c) being configured to expel fuel from the first compartment (5a) when fluid pressure in the second compartment (5b) exceeds the pressure in the first compartment (5a).
3. A fuel injection system according to claim 2, wherein the second compartment (5b) of the fuel accumulator (5) is configured to receive pressure medium for increasing the pressure in the second compartment (5b) and to expel fuel from the first compartment (5a).
4. A fuel injection system according to claim 3, wherein the second com- partment (5b) of the fuel accumulator (5) is configured to receive pressurized air from a pressure medium source (10).
5. A fuel injection system according to claim 3 or 4, wherein the second compartment (5b) of the fuel accumulator (5) is connected to a pressure medium source (10) via a control valve (6) having a first position, in which position the pressure of the second compartment (5b) is released and a second position, in which position pressure medium is supplied into the second compartment (5b) from the pressure medium source (10).
6. A fuel injection system according to claim 5, wherein the control valve (6) is manually operable.
7. A fuel injection system according to any of the preceding claims, wherein the control valve (6) is electrically operable.
8. A method for operating a piston engine (1 ), which engine is provided with a fuel injection system comprising a high-pressure pump (3) for supplying fuel to a fuel injector (4) and a low-pressure pump (9) for feeding fuel to the high- pressure pump (3), characterized in that the method comprises the steps of supplying fuel from the low-pressure pump (9) to a fuel accumulator (5) during running of the engine (1 ), and feeding fuel from the fuel accumulator (5) to the high-pressure pump (3) during start of the engine (1 ).
9. A method according to claim 8, wherein the fuel accumulator (5) comprises a first compartment (5a) for storing the fuel, a second compartment (5b) and a fluid-tight wall (5c) separating the first compartment (5a) from the second compartment (5b), the wall (5c) being configured to expel fuel from the first compartment (5a) when fluid pressure in the second compartment (5b) exceeds the pressure in the first compartment (5a), the fuel being expelled from the fuel accumulator (5) by introducing pressure medium into the second com- partment (5b).
10. A method according to claim 9, wherein the pressure medium is pressurized air.
1 1 . A method according to claim 9 or 10, wherein the second compartment (5b) of the fuel accumulator (5) is kept at atmospheric pressure after the en- gine (1 ) has reached a predetermined rotation speed during the start of the engine (1 ).
PCT/FI2015/050516 2015-08-06 2015-08-06 Fuel injection system and method for operating a piston engine WO2017021583A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20190368449A1 (en) * 2018-06-01 2019-12-05 GM Global Technology Operations LLC Returnless fuel system with accumulator

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GB2308157A (en) * 1995-12-11 1997-06-18 Caterpillar Inc Fuel injection system for i.c. engines with actuating fluid accumulator
JP2002310038A (en) * 2001-04-12 2002-10-23 Toyota Motor Corp High pressure fuel supply device of internal combustion engine
US20090120397A1 (en) * 2007-11-13 2009-05-14 Gm Global Technology Operations, Inc. Internal Combustion Engine Starting System and Method
EP2476890A1 (en) * 2011-01-13 2012-07-18 Hydac Filtertechnik GmbH Supply device with a fuel transport device and use of such a supply device
WO2015024638A1 (en) * 2013-08-23 2015-02-26 L'orange Gmbh Flush/start method for an internal combustion engine, and flush/start system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2308157A (en) * 1995-12-11 1997-06-18 Caterpillar Inc Fuel injection system for i.c. engines with actuating fluid accumulator
JP2002310038A (en) * 2001-04-12 2002-10-23 Toyota Motor Corp High pressure fuel supply device of internal combustion engine
US20090120397A1 (en) * 2007-11-13 2009-05-14 Gm Global Technology Operations, Inc. Internal Combustion Engine Starting System and Method
EP2476890A1 (en) * 2011-01-13 2012-07-18 Hydac Filtertechnik GmbH Supply device with a fuel transport device and use of such a supply device
WO2015024638A1 (en) * 2013-08-23 2015-02-26 L'orange Gmbh Flush/start method for an internal combustion engine, and flush/start system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20190368449A1 (en) * 2018-06-01 2019-12-05 GM Global Technology Operations LLC Returnless fuel system with accumulator

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