Engine system, ship comprising same, and method for controlling engine system

Abstract

Provided is an engine system comprising: a fuel tank storing fuel; an engine which is driven by combusting the fuel; a fuel valve train which is located between the fuel tank and the engine and controls the flow of fuel supplied to the engine; and a controller controlling the fuel valve train and the engine, wherein the engine comprises: a fuel pressurizing device pressurizing, with a high pressure, the fuel of low temperature supplied from the fuel tank; a hydraulic pump supplying pressurized hydraulic oil to the fuel pressurizing device; an injector injecting the pressurized fuel to a combustion chamber; an injector pipe supplying, to the injector, the fuel pressurized by the fuel pressurizing device; a fuel discharge pipe branched from the injector pipe and discharging unused fuel in the engine; an operating oil pump supplying pressurized operating oil to the injector; and a safety valve unit comprising a purge valve opening / closing the fuel discharge pipe, wherein the purge valve closes the fuel discharge pipe by using the pressure of the operating oil supplied from the operating oil pump.

Description

Engine system, vessel equipped with same, and engine system control method

[0001] The present invention relates to an engine system, a ship, and a control method thereof using low flashpoint fuel.

[0002] Typically, ships are propelled by diesel engines that generate driving force using diesel oil, gas engines that generate driving force using gas such as LNG, and dual fuel engines that generate driving force using a mixture of diesel oil and gas.

[0003] Recently, with the growing demand for eco-friendly / high-efficiency engines due to the strengthening of IMO environmental regulations, research on propulsion systems using various fuels is actively underway.

[0004] Compared to diesel, methanol emits less sulfur oxides (SOx) and particulate matter (PM) during combustion, and also produces relatively low carbon dioxide (CO2) emissions. When produced from biomethanol or renewable feedstocks (carbon dioxide + hydrogen), methanol can achieve carbon neutrality, attracting attention as an eco-friendly fuel.

[0005] Ammonia is attracting attention as an environmentally friendly fuel because it does not contain carbon. Technology for a ship using ammonia as fuel is published in Republic of Korea Patent Publication No. 10-2022-0051098.

[0006] Low flashpoint fuels such as methanol and ammonia have low ignition and combustion rates, requiring a dual-fuel engine system that uses a fuel with high ignition points such as diesel as auxiliary fuel.

[0007] Meanwhile, methanol and ammonia can cause a slip phenomenon in which unburned fuel inside the engine is mixed with the exhaust gas and released into the atmosphere, and are toxic, so a system that takes into account the safety of workers in the event of a leak must be established.

[0008] The present invention provides an engine system, a ship, and a control method thereof that can efficiently utilize low flashpoint fuel.

[0009] The present invention provides an engine system comprising: a fuel tank for storing fuel; an engine for driving by combusting the fuel; a fuel valve train positioned between the fuel tank and the engine and controlling the flow of fuel supplied to the engine; and a control unit for controlling the fuel valve train and the engine, wherein the engine comprises: a fuel pressurization device for pressurizing low-pressure fuel supplied from the fuel tank to high pressure; a hydraulic pump for supplying pressurized hydraulic oil to the fuel pressurization device; an injector for injecting the pressurized fuel into a combustion chamber; an injector pipe for supplying the pressurized fuel from the fuel pressurization device to the injector; a fuel discharge pipe branched from the injector pipe for discharging unused fuel in the engine; a hydraulic pump for supplying pressurized hydraulic oil to the injector; and a safety valve unit including a purge valve for opening and closing the fuel discharge pipe, wherein the purge valve closes the fuel discharge pipe using the pressure of the hydraulic oil supplied from the hydraulic oil pump.

[0010] It may include an operating oil valve located between the purge valve and the operating oil pump and selectively supplying the operating oil.

[0011] The above-mentioned operating fluid pump may include an electric motor.

[0012] The above-mentioned operating fluid can provide driving force to the plunger of the injector and prevent the fuel from flowing back from the plunger.

[0013] The fuel pressurization device includes a plunger that compresses the fuel using the pressurized hydraulic oil; a hydraulic motor that supplies hydraulic oil to the plunger; and a pressure reducing valve that supplies low-pressure hydraulic oil that lowers the pressure of the hydraulic oil and drives the hydraulic motor, wherein the depressurized hydraulic oil can be sealed with the operating oil and sealing oil of the plunger.

[0014] The above safety valve unit includes a liquid detection sensor located on the fuel discharge pipe at the rear end of the purge valve, and the control unit can close the purge valve when liquid is detected by the liquid detection sensor when fuel is filled into the engine with the purge valve open.

[0015] The above liquid detection sensor may be located below the purge valve.

[0016] The above safety valve unit includes a rear inert gas supply module that supplies an inert gas to the fuel discharge pipe at the rear end of the purge valve and a front inert gas supply module that supplies an inert gas to the fuel pipe passing through the fuel valve train, and the control unit can control the rear inert gas supply module to supply an inert gas before the engine is driven, and control the front inert gas supply module to supply an inert gas after the engine has finished driving.

[0017] It includes a rear-end inert gas supply module for supplying an inert gas to the fuel discharge pipe at the rear end of the purge valve, and the rear-end inert gas supply module includes: an inert gas line connected to the rear end of the purge valve; a pair of inert gas block valves located in the inert gas line; an inert gas bleed valve for opening and closing an inert gas bleed line connected between the inert gas block valves; and a control air valve for selectively supplying air for opening and closing the pair of inert gas block valves and the inert gas bleed valve, wherein when the control air valve is opened, the pair of inert gas block valves are opened and the inert gas bleed valve is closed, and when the control air valve is blocked, the pair of inert gas block valves are closed and the inert gas bleed valve is opened.

[0018] The fuel includes a low flashpoint fuel, and the control unit can control the hydraulic pump and the operating oil pump so that the pressures of the hydraulic oil and the operating oil are different depending on the type of the fuel when the fuel is charged into the engine before driving the engine.

[0019] In a method for driving an engine system, the present invention provides an engine control method comprising: an engine driving preparation step of driving an engine's working oil pump to supply low-pressure working oil to an injector and driving a hydraulic pump to supply low-pressure hydraulic oil to a fuel pressurization device; a fuel filling step (S215) of supplying low-pressure fuel to fill a fuel pipe inside the engine; an engine closing step (S216) of closing a purge valve located at the rear end of a fuel pipe of the engine; a fuel pressurization step (S217) of pressurizing the low-pressure fuel to high pressure in the fuel pressurization device; and an engine driving step (S220) of supplying the high-pressure fuel to a combustion chamber by the injector and combusting it, wherein the step of closing the purge valve includes a step of receiving the working oil from the working oil pump.

[0020] The fuel pressurization step may include a step of supplying high-pressure hydraulic oil from the hydraulic pump to the fuel pressurization device; and a step of supplying high-pressure hydraulic oil from the hydraulic oil pump to the injector.

[0021] The fuel pipe further includes a liquid sensor located at the rear end of the purge valve, and if liquid fuel is detected by the liquid sensor for a reference time or longer after the fuel charging step (S215), the purge valve can be closed.

[0022] After the above purge valve closing step, an engine exhaust purge step may be included in which an inert gas is supplied to the rear end of the engine's purging valve to recover fuel to the fuel tank through a fuel recovery pipe.

[0023] The fuel pipe further includes a liquid sensor located at the rear end of the purge valve, and if no liquid is detected by the liquid sensor after the purging step, the supply of the inert gas can be stopped.

[0024] The engine operation may include a step of stopping fuel supply from the injector; a step of stopping the operation of the engine pressurization device; a step of reducing the pressure of the operating oil supplied from the operating oil pump and the hydraulic oil supplied from the hydraulic pump; and a step of opening the purge valve to discharge fuel from the fuel pipe of the engine.

[0025] The step of discharging the fuel may include an engine purging step of supplying the inert gas to a fuel pipe of the engine.

[0026] The above fuel may contain methanol.

[0027] The present invention provides an engine system comprising: a fuel tank for storing fuel; an engine for driving by combusting the fuel; a fuel valve train positioned between the fuel tank and the engine and controlling the flow of fuel supplied to the engine; and a control unit for controlling the fuel valve train and the engine, wherein the engine comprises: an injector for driving the engine by injecting the fuel into a combustion chamber; an injector pipe for supplying fuel pressurized in the fuel pressurization device to the injector; a fuel discharge pipe branched from the injector pipe for discharging unused fuel within the engine; a purge valve for opening and closing the fuel discharge pipe; and the fuel discharge pipe at the rear end of the purge valve includes a U-shaped pipe bent downward.

[0028] The liquid detection sensor is located in the U-shaped pipe, and the control unit opens the fuel valve train while the purge valve is open to fill fuel into the engine, and when the liquid detection sensor detects liquid fuel for a predetermined period of time or longer, the purge valve is closed and the engine can be driven.

[0029] The fuel is ammonia, and the fuel valve train can inject an inert gas before supplying fuel to the engine.

[0030] The above control unit can stop the operation of the engine or provide an abnormal alarm of the purge valve when the fuel is detected by the liquid detection sensor while the engine is running.

[0031] The fuel is ammonia, and includes an inert gas supply module connected between the purge valve of the fuel discharge pipe and the U-shaped pipe, and when the engine is running, the fuel discharge pipe can be filled with the inert gas.

[0032] The above inert gas can have a pressure of 30 bar or more.

[0033] The fuel is methanol, and the U-shaped pipe may include a double pipe including an outer space and an auxiliary liquid detection sensor disposed in the outer space.

[0034] The above liquid detection sensor may include a level switch.

[0035] A vessel including the above engine system is provided.

[0036] An engine system according to at least one embodiment of the present invention is capable of stable engine operation using methanol / ammonia.

[0037] Additionally, the engine system according to at least one embodiment of the present invention can be applied to both an engine system using methanol as fuel and an engine system using ammonia as fuel.

[0038] Additionally, the engine according to at least one embodiment of the present invention can accurately determine the opening and closing timing of the purge valve during fuel charging. Furthermore, the engine according to at least one embodiment of the present invention can detect leaks in the purge valve and prevent safety accidents.

[0039] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0040] FIG. 1 is a diagram illustrating an engine system according to a first embodiment of the present invention.

[0041] FIG. 2 is a diagram illustrating an engine system according to a second embodiment of the present invention.

[0042] Figure 3 is a flowchart illustrating a control method of an engine system according to a second embodiment of the present invention.

[0043] Figures 4 to 9 are diagrams illustrating a control method of an engine system according to a second embodiment of the present invention.

[0044] Fig. 10 is a diagram illustrating an engine system according to a third embodiment of the present invention.

[0045] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components are given the same reference numbers and redundant descriptions thereof will be omitted.

[0046] The suffixes "module" and "part" used in the following description are assigned or used interchangeably solely for the convenience of writing the specification, and do not in themselves have distinct meanings or roles. Furthermore, when describing the embodiments disclosed herein, if a detailed description of a related known technology is deemed to obscure the gist of the embodiments disclosed herein, the detailed description will be omitted.

[0047] In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0048] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0049] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0050] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0051] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0052] A low-flashpoint fuel engine system (1) refers to a system that operates an engine using fuel other than traditional fuels like heavy oil or diesel. Representative examples of low-flashpoint fuels include ammonia and methanol, which are attracting attention as next-generation, eco-friendly fuels.

[0053] Environmentally friendly fuels such as methanol and ammonia are low-flashpoint fuels with a flashpoint lower than 60℃, which can easily ignite and pose a significant risk in the engine room of a ship. They are also toxic to the human body, so the fuel equipment must be installed in a sealed space that blocks gas emissions. In consideration of corrosiveness, storage tanks and fuel transport pipes must be made of corrosion-resistant materials.

[0054] Dual-fuel technology can be applied to low-flashpoint fuels, utilizing them alongside diesel fuel to enhance combustion efficiency. This relates to an engine system that utilizes methanol or ammonia as fuel, and may additionally include a diesel supply system for supplying diesel.

[0055] The low flash point engine system (1) according to the embodiments will be described in detail with reference to the attached drawings below, and description of overlapping parts will be omitted.

[0056] Figure 1 is a diagram illustrating an engine system according to a first embodiment of the present invention. This diagram depicts piping and equipment such as valves and sensors installed in the piping, and is also called a piping & instrumentation drawing (P&ID).

[0057] The present embodiment includes a methanol engine (10) that uses methanol (CH3OH) as fuel.

[0058] Methanol emits less sulfur oxides (SOx) and particulate matter (PM) when burned, and has relatively low carbon dioxide (CO2) emissions. It can be carbon neutral when produced from biomethanol or renewable raw materials (carbon dioxide + hydrogen).

[0059] Methanol has a high octane rating, excellent knock resistance, and generates less carbon dioxide (CO2) and harmful exhaust gases during combustion, attracting attention as an environmentally friendly fuel.

[0060] Methanol has a lower energy density than gasoline, which results in higher fuel consumption, but can be used in dual-fuel technology, either by mixing it with hydrogen fuel or using it with diesel, to improve fuel efficiency and power output.

[0061] Referring to FIG. 1, the engine system (1) of the present invention may include an engine (10) that obtains propulsion using methanol, a fuel tank (50) for supplying fuel to the engine (10), a fuel supply system (20) (FSS: Fuel Supply System), and a fuel valve train (30) (FVT: Fuel Valve Train).

[0062] Although not shown in the drawing, it may include a control unit that controls each device (110, 120, 130, 140, 151) of the engine (10), the pump and heater of the fuel supply system (20), and the valves (32, 33) of the fuel valve train (30). The control unit may control the engine system (1) based on information detected by a pressure sensor and a liquid detection sensor within the engine system (1).

[0063] Each component can be connected to fuel pipes (L2, L4, L5, L6) through which fuel flows. For safety reasons, the fuel pipes can be double-piped. Since methanol is liquid at room temperature, the methanol inside the fuel pipes (L2, L4, L5, L6) can move in a liquid state.

[0064] The fuel pipe may include a fuel supply pipe (L2) that supplies fuel from a fuel tank to the engine, an injector pipe (L4) that supplies fuel to an injector within the engine, and a fuel discharge pipe (L5) that discharges unused fuel from the injector.

[0065] The fuel discharged from the engine (10) through the fuel discharge pipe (L5) may include a fuel recovery pipe (L6) connecting the engine (10) to the fuel tank (50) to recover the fuel to the fuel tank (50).

[0066] The area where the engine (10) is located must be maintained as a safety area to ensure that the engine (10) operates normally and to protect the engine (10) and surrounding workers from hazards. The safety area may be equipped with a ventilation system consisting of an air inlet (61) and an air outlet (62) to ensure continuous ventilation.

[0067] The ventilation system (61, 62) exhausts heat generated from the engine (10) and generates sufficient airflow so that even if fuel leaks from the engine (10), it can be exhausted to minimize exposure of workers to toxic substances. The ventilation system (61, 62) can be located at the inlet and outlet of the fuel pipe in the safety zone, respectively.

[0068] In order to check whether the engine (10) is operating normally, various sensors such as a temperature sensor, a pressure sensor, and a liquid detection sensor may be included. Since the fuel and operating fluid supplied into the engine's fuel pipe are high-pressure fuel, it is necessary to check whether the fluid pressure is within a set range.

[0069] Pressure sensors (PT11-1, PT11-2, PT12, PT13, PT14-1, PT15) can be placed on the fuel pipe or within each component within the engine.

[0070] Methanol is supplied from a fuel tank (50) storing methanol to a fuel supply system (20), and the fuel supply system (20) may include a fuel pump (25) and a temperature control system (heater / cooler, 6). The fuel pump (25) may pressurize methanol to a pressure of about 7-13 bar so that methanol is supplied to the engine (10).

[0071] Unused methanol can be recovered from the engine (10) to the fuel tank (50) and supplied back to the engine (10). Since the methanol may contain impurities (sludge, fine particles, etc.) during this process, the fuel supply system (20) may include a fuel filter (27) to remove the impurities contained in the methanol. Since methanol is vulnerable to moisture, the fuel filter can also remove moisture.

[0072] A fuel valve train (30) located between a fuel supply system (20) and an engine (10) includes a plurality of valve structures and serves to control the timing at which fuel is supplied to the engine (10). The fuel valve train (30) may include a plurality of solenoid valves (SV32-1, SV32-2, SV32-3, SV33) and a sensor (PT31, PT32) for detecting the pressure inside a fuel supply pipe (L2).

[0073] The fuel valve train (30) may include a double block and bleed valve (32) (DBB Valve: Double Block and Bleed Valve). By arranging the valves (SV32-1, SV32-2) in duplicate, the leakage of methanol supplied to the engine (10) can be blocked. The double block bleed valve (32) is a pair of valves (SV32-1, SV32-2) that are closed by default (NC) and can be opened by applying power.

[0074] A drain line (Drain) may be positioned to discharge methanol between a pair of valves (SV32-1, SV32-2) of the double block bleed valve (32) when both valves (SV32-1, SV32-2) are closed.

[0075] The fuel valve train (30) may include a front-end inert gas supply module (33) including a valve (SV33) that selectively supplies not only fuel but also an inert gas such as nitrogen to the engine (10). The inert gas removes fuel remaining in the fuel pipes (L4, L5) inside the engine (10) when the engine (10) is stopped from running or when maintenance of the engine (10) is required.

[0076] Since the inert gas has low reactivity, it does not react with methanol and methanol can be stably discharged together with the inert gas, and the unburned methanol recovered in this way can be supplied back to the fuel tank (50).

[0077] Fuel supplied from the fuel valve train (30) is supplied to the engine (10), and the interior of the engine (10) may include a fuel pressurization device (120), a hydraulic pump (151), an injector (110), a working oil pump (130), and a safety valve unit (140).

[0078] The fuel pressurization device (120) is a device that supplies fuel to the engine (10) at an appropriate pressure and can pressurize low-pressure fuel into high-pressure fuel.

[0079] The conventional fuel pressurization device (120) was installed in a separate pump room space, far away from the engine (10) room. However, in order to transport pressurized fuel to the engine (10), a long double-pipe structure capable of withstanding the pressure must be connected.

[0080] Depending on the size of the vessel, lengths exceeding 100 meters can increase costs and pose significant risks of pressure loss and leakage during transport. Additional costs arise, such as the need for additional leak detection devices and safety measures to prevent ignition or explosion of leaked gas.

[0081] Accordingly, the engine system (1) of the present invention can improve efficiency and safety by arranging a fuel pressurization device (120) inside the engine (10). The fuel pressurization device (120) can utilize a hydraulic booster pump (HBU) that uses hydraulic pressure.

[0082] The hydraulic booster pump is equipped with a solenoid valve for selectively supplying hydraulic oil, and can be selectively driven by an electric signal. A hydraulic booster pump that can be electrically controlled in this way is called an e-HBU (electro Hydraulic Booster Pump). The fuel pressurization device (120) can pressurize low-pressure fuel of 7-13 bar supplied from the fuel valve train (30) to a pressure of 400-600 bar and supply it to the injector (110).

[0083] The hydraulic pump (151) supplies high-pressure hydraulic oil to the fuel pressurization device (120), and the fuel pressurization device (120) can pressurize fuel to high pressure using the pressure of the hydraulic oil. The pressure of the hydraulic oil supplied from the hydraulic pump (151) is at the level of 200-320 bar, and the fuel pressurization device (120) can be driven using the pressure.

[0084] The hydraulic oil supplied to the fuel pressurization device (120) can be used for sealing purposes in addition to driving a piston that increases the pressure of the fuel. Considering the pressure of the low-pressure fuel supplied to the fuel pressurization device (120), the high-pressure hydraulic oil supplied from the hydraulic pump (151) can be lowered to 36-45 bar and used as sealing oil.

[0085] In order to control the injector (110) and prevent fuel backflow (seal), operating oil (C&S oil: control and sealing oil) with a pressure corresponding to the high-pressure fuel is required. The operating oil pump (130) supplies high-pressure operating oil to the injector (110), and the operating oil supplied from the operating oil pump (130) can be used as driving and lubricating oil for the injector (110).

[0086] Since the operating fluid must have a pressure equivalent to (or slightly higher than) the pressure of the fuel supplied to the injector (110) to prevent reverse flow of the fuel, when the fuel is supplied to the injector (110) at 400 to 600 bar, the operating fluid can be supplied by pressurizing it at a pressure of 400 to 650 bar.

[0087] The operating oil pump (130) of this embodiment can use a hydraulic booster that pressurizes the operating oil pressure to 400 to 650 bar using high-pressure hydraulic oil supplied from a hydraulic pump (151).

[0088] The engine (10) may further include a fuel discharge line (L5) to discharge unused fuel and residual fuel. Fuel supplied from the fuel pressurization device (120) is branched into an injector pipe (L4) supplied to the injector (110) and a fuel discharge pipe (L5), and the fuel discharge pipe (L5) may include a purge valve (141) that selectively passes fuel.

[0089] The purge valve (141) is included in the safety valve unit (140) (SVU: Safety Valve Unit), and the purge valve (141) is basically in an open state (NO) so that fuel within the engine (10) can be discharged to the fuel recovery pipe (L6). In an operation mode in which fuel is injected from the injector to generate power, the control unit can close the purge valve (141) to block the flow of fuel to the fuel recovery pipe (L6).

[0090] The purge valve (141) must be able to withstand high pressure (400-600 bar) to prevent the passage of high-pressure fuel. Since it is difficult for an electric valve to sufficiently withstand the pressure of high-pressure fuel, a hydraulic valve can be used as the purge valve (141).

[0091] The oil supplied when the purge valve (141) is driven can use hydraulic oil supplied from the hydraulic pump (151). However, as described above, the pressure (200 to 320 bar) of the oil supplied from the hydraulic pump (151) is lower than the pressure (400 to 600 bar) of the fuel pressurized in the fuel pressurization device (120), so the purge valve (141) is made larger in size to prevent the fuel from flowing into the discharge line.

[0092] The purge valve (141) is kept open before fuel is supplied, and when low-pressure fuel is supplied to the engine (10), the purge valve (141) is opened to fill the fuel pipes (L4, L5) inside the engine with fuel before the fuel pressurization device (120) pressurizes it.

[0093] When the fuel pressurization device (120) operates to supply high-pressure hydraulic oil by operating the hydraulic pump (151), the purge valve (141) closes and the high-pressure fuel can be supplied to the injector (110) without being discharged to the fuel recovery pipe (L6).

[0094] At this time, an inert gas such as nitrogen may be supplied to the rear end of the purge valve (141) to recover the fuel remaining at the rear end of the purge valve (141). The safety valve unit (140) may include an inert gas supply valve that supplies the inert gas in addition to the purge valve (141). The inert gas supply valve may be composed of multiple valves to prevent backflow.

[0095] Since the inert gas does not react with methanol, the fuel remaining in the recovery pipe (L6) at the rear end of the purge valve (141) can be pushed out and returned to the fuel tank (50). The recovery pipe (L6) can be connected from the engine (10) to the fuel tank (50).

[0096] When the engine (10) is stopped from running, the fuel supply system (20) stops the operation of the pump (25) and the double block bleed valve (32) of the fuel valve train (30) also closes, thereby stopping the fuel supply to the engine (10). The purge valve (141) of the engine (10) is opened to discharge the fuel inside the engine (10) and allow it to be recovered to the fuel tank (50) through the fuel recovery pipe (L6).

[0097] Since the injector (110) and the fuel pressure device (120) also stop operating, the hydraulic pump (151) and the operating oil pump (130) can also lower the oil pressure to prevent the operating oil from flowing back.

[0098] Since liquid methanol may remain, the fuel valve train (30) includes an inert gas supply line such as nitrogen, and supplies the inert gas to the engine (10) so that all residual inert gas inside the engine (10) can be discharged.

[0099] In the drawing, only the structure of the engine (10) connected to the fuel supply pipe (L4, L5) through which fuel is supplied is shown, and the engine (10) may include an engine block in which fuel supplied from an injector (110) is burned, an intake and combustion system, an exhaust system, a cooling system, etc.

[0100] Fig. 2 is a diagram illustrating an engine system according to a second embodiment of the present invention. The engine system (1) and fuel supply system (20) of the aforementioned embodiment and the fuel valve train (30) of the engine system (2) according to the second embodiment are identical, but the configuration within the engine (10) is different.

[0101] The operating oil pump (130) that supplies operating oil to the injector (110) is a device for pressurizing the operating oil. In the embodiment of Fig. 1, the operating oil pump (130) uses a hydraulic booster. Since the hydraulic booster operates using hydraulic oil, a pipe is required to supply high-pressure hydraulic oil to the operating oil pump (130), and it is large in volume.

[0102] In the case of the fuel pressurization device (120), a hydraulic booster is efficient because a large amount of fuel is pressurized, but the amount of operating oil supplied to the injector is relatively small, so the operating oil pump (130) can be changed to an electric oil pump to pressurize and use only a small amount of operating oil. By changing the operating oil pump (130) from a hydraulic drive type to an electric oil pump, the hydraulic pipe connecting the hydraulic pump (151) to the operating oil pump (130) can be omitted, and the size of the operating oil pump (130) can be reduced.

[0103] The embodiment of Fig. 1 is driven by supplying hydraulic oil for the operation of the purge valve (141) from a hydraulic pump (151). The operation of the fuel pressurization device (120), the operating oil of the injector, and the operation of the purge valve (141) can all be supplied through the hydraulic oil pump (151), thereby simplifying the configuration.

[0104] However, the pressure of the oil supplied from the hydraulic pump (151) is lower than the high pressure fuel pressure blocked by the purge valve (141), so there is a limit to reducing the purge valve (141).

[0105] Meanwhile, the embodiment of FIG. 2 can receive high-pressure oil for the operation of the purge valve (141) from the operating oil pump (130) rather than the hydraulic pump (151). The operating oil pump (130) pressurizes the operating oil to 450 to 650 bar so that it has a pressure equivalent to or higher than the high-pressure fuel supplied to the injector (110).

[0106] The purge valve (141) of the second embodiment can control the flow of fuel using oil at a pressure more than twice that of the aforementioned embodiment, thereby reducing the volume of the purge valve (141). The purge valve (141) is opened when filling fuel into the fuel pipe before driving the engine (10) or when purging the fuel inside the engine (10) after driving the engine (10) is completed, and the purge valve (141) is closed when driving the engine (10) to block the exhaust line.

[0107] Purging is a process of removing fuel inside the fuel pipe (L4, L5) of the engine. It refers to a step of injecting an inert gas such as nitrogen into the fuel pipe (L4, L5) of the engine and opening the purge valve (41) to discharge the fuel.

[0108] When the engine (10) is running, the operating oil pump (130) supplies high-pressure (450 to 650 bar) operating oil to the injector (110) and also supplies high-pressure operating oil to the purge valve (141) to close the purge valve (141) and block the discharge line.

[0109] However, even in the step of filling fuel into the engine (10) before driving the engine (10) with the purge valve (141) open (fuel filling step), if low-pressure fuel still exists inside the engine (10) immediately after the engine (10) is stopped (pressure reduction step), low-pressure operating fluid (15 to 50 bar) must be supplied to the injector (110).

[0110] The safety valve unit (140) may further include a working oil valve (SV145) positioned between the working oil pump (130) and the purge valve (141) to drive the purge valve (141) independently from the injector (110). The working oil valve (SV145) may employ an electrically driven solenoid valve. The working oil valve (SV145) can selectively supply working oil, so that even if the working oil pump (130) is driven to supply working oil to the injector (110), the supply to the purge valve (141) can be blocked to keep the purge valve (141) in an open state.

[0111] A fuel pressurization device (120) is a device that compresses low-pressure fuel to high-pressure by pushing a plunger with hydraulic oil. The hydraulic oil supplied to the plunger is periodically supplied and recovered, and may include a motor that manages this cycle.

[0112] Motors can be either servo or hydraulic. Servomotors utilize an electrically driven shaft that allows precise control of rotation angle, speed, and position, and offer rapid response. However, their torque (force) is weak, requiring expensive equipment to achieve sufficient torque, increasing costs.

[0113] A hydraulic motor can rotate a shaft using hydraulic oil. Compared to a servo motor, a hydraulic motor has lower precision but can produce high torque. Furthermore, the fuel pressurization device (120) of the present invention receives high-pressure hydraulic oil, which can be used to drive the hydraulic motor.

[0114] The engine system (1) according to the first embodiment of FIG. 1 illustrates an embodiment that uses a servo motor to drive the shaft of a fuel pressurization device (120), and the engine system (2) according to the second embodiment of FIG. 2 can reduce costs by using a hydraulic motor to drive the shaft of a fuel pressurization device (120).

[0115] Fig. 3 is a flowchart illustrating a control method of an engine system (2) according to a second embodiment of the present invention. Figs. 4 to 10 are diagrams illustrating a control method of an engine system (2) according to a second embodiment of the present invention, which will be examined together with the description of the flowchart of Fig. 4.

[0116] The engine system (1) control method of this embodiment is composed of a step (S213-S218) of injecting and preparing fuel based on engine operation (S220) and a step (S232, S235) of discharging fuel after engine operation ends.

[0117] The engine system (1) of this embodiment illustrates a control method for an engine (10) that uses methanol as fuel. Methanol can maintain a liquid state at room temperature and pressure, and thus does not easily vaporize.

[0118] Figure 4 is a drawing illustrating a preparation step (S213) before driving an engine (10). The fuel supply system (20) can supply methanol (fuel) from a fuel tank (50) to the engine through a pump (25).

[0119] The fuel valve train (30) of the engine (10) may include a supply valve (32) to selectively supply fuel through a fuel supply pipe (L2). The supply valve (32) may include a double-block bleed valve including a pair of block valves (SV32-1, SV32-2) to block fuel without a leak. Fuel is supplied from the fuel supply system (20) with the front valve (SV32-1) open and the rear valve (SV32-2) closed.

[0120] The double-block bleed valve can completely block the flow of fuel on the fuel pipe (L2), and the space between the pair of block valves (SV32-1, SV32-2) can release pressure through the bleed line (32c). By applying the double-block bleed valve (32) as a supply valve (32), it is possible to safely check whether the fuel valve train (30) is operating normally.

[0121] If the pressure at the pressure sensor (PT32) between a pair of block valves (SV32-1, SV32-2) is maintained at a constant level, it can be determined that the supply valve (32) is operating normally.

[0122] Before injecting fuel into the engine (10), operating oil is supplied to the injector (110) and hydraulic oil is supplied to the fuel pressurization device (120). The operating oil and hydraulic oil function as sealing oil to prevent reverse flow of fuel in the injector (110) and the fuel pressurization device (120).

[0123] The fuel supplied to the engine (10) is low-pressure fuel of 7-13 bar, and the operating oil pump (130) and the hydraulic pump (151) can supply low-pressure operating oil and hydraulic oil having a value of 15-50 bar corresponding to the pressure of the low-pressure fuel. At this stage, the injector (110) and the fuel pressurization device (120) are not operated, and the operating oil and hydraulic oil only function as sealing oil.

[0124] When the double block bleed valve (32) is operating normally and the sealing oil is filled, the double block bleed valve (32) can be opened to charge fuel into the engine (10) as shown in FIG. 5 (S215). At this time, since the fuel must be filled up to the rear end of the fuel discharge pipe (L5) located in the engine (10), i.e., the fuel discharge port of the engine (10), the purge valve (41) located at the rear end of the fuel discharge pipe (L5) can be opened to inject fuel into the engine (10).

[0125] When the fuel is full up to the purge valve (41), if the liquid detection sensor (LS87) located at the rear end of the purge valve (41) detects fuel (methanol), it can be determined that the fuel is filled up to the rear end of the engine (10), and the purge valve (41) can be closed to drive the engine (10) (S216).

[0126] Fig. 6 illustrates a state in which the purge valve (41) is closed. In the second embodiment, the purge valve (41) receives operating oil from the operating oil pump (130), so the operating oil valve (SV146) that controls the flow of operating oil between the operating oil pump (130) and the purge valve (41) can be opened.

[0127] When the purge valve (41) is closed, a pressure difference occurs between the fuel pipes (L4, L5) inside the engine (10) in front of the purge valve (41) and the fuel recovery pipe (L6) in the rear.

[0128] The fuel pressurization device (120) of the engine (10) can start driving and supply fuel pressurized to 400 bar or more to the injector (110). As the fuel pressurization device (120) is driven, the pressure of the hydraulic oil supplied to the fuel pressurization device (120) can also increase to 200-300 bar. The pressure of the fuel can be increased by driving the plunger of the fuel pressurization device (120) using high-pressure hydraulic oil. However, since the pressure of the injected fuel is low, the sealing oil of the fuel pressurization device (120) can be reduced to 35-45 bar and used as sealing oil.

[0129] The pressure of the working fluid can be increased to a pressure of 400 bar or more corresponding to the pressure of the pressurized fuel and supplied to the injector (110). The pressure of the fuel at which the purge valve (41) blocks the flow and the pressure of the working fluid supplied to the purge valve (41) are the same, so that the purge valve (41) can stably block the flow of fuel.

[0130] The step of closing the purge valve (41) and the step of pressurizing the fuel may be performed simultaneously or sequentially.

[0131] Since fuel is no longer supplied to the fuel recovery pipe (L6), the pressure decreases and the fuel in the fuel recovery pipe (L6) is recovered into the fuel tank (50). In order to recover all remaining fuel in the fuel recovery pipe (L6), an inert gas may be supplied from the rear inert gas supply module (146) located at the rear end of the purge valve (41) as illustrated in FIG. 7. Fuel purging may be performed in which the inert gas pushes the fuel at the rear end of the purge valve (41) and recovers it into the fuel tank (50) (S218).

[0132] The step of closing the purge valve (S216), the step of pressurizing the fuel (S218), and the step of purging the fuel (S218) described above may be performed sequentially or simultaneously. For example, the step of closing the purge valve (41) (S216) and the step of pressurizing the fuel (n117) may be performed simultaneously, followed by the fuel purging (S218).

[0133] Alternatively, the fuel at the rear end of the purge valve (41) can be recovered and pressurized by supplying an inert gas before closing the purge valve (41) and pressurizing the fuel. In the latter case, since the purge valve (41) is closed before pressurizing the fuel, the pressure of the working fluid supplied to the purge valve (41) is low, but the pressure of the fuel shielded by the purge valve (41) is also low, so the performance of the purge valve (41) can be maintained. Alternatively, the three steps (S216-S218) can be performed simultaneously.

[0134] If no liquid is detected by the liquid detection sensor (LS87) at the rear end of the purge valve (41) for a predetermined period of time, purging at the rear end of the engine (10) is determined to be complete, so the supply of inert gas is stopped and the engine (10) can be started (S220).

[0135] Driving of the engine (10) refers to a step of producing energy by supplying fuel from the injector (110) to the combustion chamber. The engine (10) driving step (S220) is such that pressurized fuel is supplied to the injector (110) through the injector pipe (L4), and the injector (110) consumes the fuel and can produce energy.

[0136] When the engine (10) is stopped from operating, the fuel pressurization device (120) may be stopped from operating and the purge valve (41) may be opened (S232), as shown in FIG. 8. The fuel supply system stops operating the pump and no longer supplies fuel to the engine (10). The supply of operating oil to the purge valve (41) may be stopped as the operating oil valve (SV145) closes.

[0137] As the fuel pressure device (120) stops operating and the purge valve (41) opens, the fuel pressure inside the engine (10) decreases. As the fuel pressure decreases, the operating pressure of the fuel pressure device (120) and the injector (110) may decrease. For example, the pressure of the operating oil supplied from the operating oil pump (130) and the hydraulic oil supplied from the hydraulic pump (151) may be reduced to about 15-50 bar.

[0138] After the pressure in the fuel pipes (L4, L5) inside the engine is lowered, an inert gas can be supplied to the engine (10) from the rear inert gas supply module (146) located at the front end of the engine (10) as shown in FIG. 9.

[0139] The inert gas moves toward the fuel tank (50) and can perform a step of discharging the fuel remaining inside the engine (10), which is the engine (10) purging (S235). The engine (10) purging is a fuel discharge (purging) step performed after the engine (10) is shut down, and by injecting the inert gas into the front inert gas supply module (33) located at the front end of the engine (10), all the fuel inside the engine (10) can be recovered into the fuel tank (50).

[0140] If no liquid is detected by the liquid detection sensor (LS87) at the rear end of the purge valve (41) for a predetermined period of time, purging is determined to be complete and operation of the engine system (1) can be terminated.

[0141] The operation of the engine system (1) described in FIGS. 4 to 9 is described based on a fuel circulation (supply / recovery) path using methanol, and in the case of a dual fuel system, the engine (10) can be operated by supplying a different type of fuel, such as diesel fuel, to the injector (110) through a separate system.

[0142] Since methanol, which is supplied as fuel to the engine (10), is in a liquid state, a liquid detection sensor (LS87) can be used to determine the presence or absence of fuel in the fuel pipe. The liquid detection sensor may include a level sensor. The level sensor can detect the liquid level, and can determine the presence or absence of fuel in the fuel pipe by utilizing changes in electrostatic capacity.

[0143] If a small amount of fuel remains in the fuel pipe, the liquid detection sensor (LS87) cannot detect the fuel. In particular, it cannot detect fuel remaining at a location lower than where the liquid detection sensor (LS87) is installed.

[0144] Accordingly, the fuel pipe of the present embodiment is arranged in a U-shaped pipe (L61) that is concavely bent downwards at the rear end of the purge valve (41), so that the part of the fuel pipe at the rear end of the purge valve (41) closest to the direction of gravity can be arranged. If the liquid detection sensor (LS87) is arranged in the U-shaped pipe (L61), even if a small amount of liquid is discharged at the rear end of the purge valve (41), it flows into the U-shaped pipe (L61), thereby improving the accuracy of the liquid detection sensor (LS87).

[0145] The U-shaped pipe (L61) may have a gentle slope and may be installed within the safety valve unit or on the outside of the safety valve. The liquid detection sensor (LS87) can determine whether fuel charging is complete in the step (S215) of charging fuel to the engine (10).

[0146] If an abnormality occurs in the purge valve (41) at the stage (S220) where the engine (10) is operating, fuel may leak into the fuel recovery pipe. An abnormality in the purge valve (41) can be confirmed by detecting fuel in the liquid detection sensor (LS87) of the U-shaped pipe (L61) at the rear end of the purge valve (41).

[0147] In the purging step (S218, S234) of recovering fuel inside the fuel pipe by injecting an inert gas, the completion of purging can be confirmed through the liquid detection sensor (LS87). If the liquid detection sensor (LS87) does not detect liquid in the purging step (S218) at the rear end of the engine (10) before the engine (10) is driven, purging can be determined to be complete.

[0148] After the engine (10) is driven, an inert gas is injected into the front end of the engine (10) and when the internal fuel of the engine (10) is purged (S234), it can be confirmed by the liquid detection sensor (LS87) whether the inert gas has been completely discharged.

[0149] Fig. 10 is a diagram illustrating an ammonia engine system (3) according to a third embodiment of the present invention.

[0150] This embodiment is an ammonia engine system (3) using ammonia as fuel. Ammonia (NH3) can be used as a fuel in place of existing fossil fuels and is attracting attention as a next-generation eco-friendly fuel because it does not contain carbon. However, it has a low self-ignition capacity, making it difficult to ignite, and contains toxic substances that are harmful to the human body if leaked.

[0151] The methanol engine (10) is a dual fuel engine (10) in which diesel is partially used due to combustion safety issues, similar to ammonia, and has something in common in that it has a system that takes into account the safety of workers in the event of a fuel leak, as the fuel contains toxicity.

[0152] Therefore, the engine (10) of the methanol engine system (2) according to the second embodiment of FIG. 2 can be directly applied to the engine (10) of the ammonia engine system (3) according to the first embodiment of FIG. 10. The same engine (10) can be applied to both the methanol engine system (2) and the ammonia engine system (3), thereby improving manufacturing efficiency.

[0153] However, since ammonia has a high ignition point and is in a gaseous state at room temperature, it must be maintained under high pressure to maintain a liquid state. Ammonia supplied to the engine through the fuel pressurization device (120) also differs from methanol in that it has a higher pressure of 50-83 bar than methanol.

[0154] By controlling the pressure of the sealing oil (hydraulic oil) of the fuel pressurization device (120) and the sealing oil (operating oil) of the injector (110) to match the pressure of ammonia, the engine (10) of the present embodiment can use ammonia as fuel.

[0155] In addition, the purge valve (141) can be controlled independently from the injector (110) through the operating oil valve (SV145), so that the engine (10) of the present embodiment can be applied to the ammonia engine system (3).

[0156] The engine system (3) according to the third embodiment of Fig. 10 is an ammonia engine system (3) that uses ammonia as fuel, and the engine (10) can use the same engine (10) as the embodiment of Fig. 2, but there is a slight difference in the control method.

[0157] Before injecting ammonia, an inert gas of 32-40 bar can be filled in advance into the engine (10) to increase the pressure in the fuel pipes (L4, L5, L6). In order to discharge ammonia in the engine, an inert gas can be supplied from a pre-stage inert gas supply module (33) that supplies an inert gas, and an inert gas of 30 bar or more can be filled into the fuel pipes (L4, L5, L6) at the rear end of the fuel valve train (30). At this time, the operating oil pump (130) and the hydraulic pump (151) can supply operating oil and hydraulic oil as sealing oil to the injector (110) and the fuel pressurization device (120) at a level of 50-70 bar according to the pressure of the inert gas.

[0158] After closing the purge valve (141) and recovering the ammonia at the rear end of the purge valve, in order to prevent the ammonia discharged from the engine from vaporizing, the fuel recovery pipe (L6) can be filled with an inert gas through the rear inert gas supply module (146) to maintain the internal pressure of the fuel recovery pipe (L6) above the ammonia vaporization pressure.

[0159] In the process of lowering the pressure of ammonia inside the engine (10) by terminating the operation of the engine (10), the process can be divided into a step of discharging in a liquid state and a step of discharging in a gaseous state to prevent vaporization of ammonia.

[0160] Even though the engine (10) of the ammonia engine system (3) uses the same engine (10) as the methanol engine system (2), the fuel supply system (20) and the fuel valve train (30) of the front end are different, and there are differences in the specific control method and the pressure of the fuel and operating oil.

[0161] The fuel tank (50) of the engine system (3) of the present embodiment may include a low-pressure fuel pump (51). Ammonia can be converted into a gas at room temperature, so that the ammonia can be pressurized to maintain a liquid state and supplied to the fuel supply system (20).

[0162] The fuel supply system (20) may include a temperature control device (26) to control the temperature so that the ammonia remains in a liquid state, and may include a fuel filter (27) to prevent impurities from entering the engine. Ammonia that is initially pressurized in the low-pressure pump (51) may be re-pressurized in the high-pressure pump (25) of the fuel supply system (20) so that ammonia of 50-83 bar can be supplied to the engine (10).

[0163] The fuel supply system (20) of the ammonia engine system (3) can recover ammonia in a gaseous state and can be recovered mixed with an inert gas during purging. Unlike the methanol engine system, the ammonia engine system does not directly recover the recovered ammonia into the ammonia fuel tank (50), but can be equipped with a separate recovery device (21, 22, 23) to process the recovered ammonia so that it can be reused.

[0164] It may include a knockout drum (21) (KOD: Knock Out Drum) for recovering ammonia converted to a gaseous state. The knockout drum (21) is also called a gas-liquid separator and can separate gaseous ammonia and liquid ammonia.

[0165] The knockout drum (21) can be connected to the fuel valve train (31, 36) and can recover vaporized ammonia from the fuel pipe to the vent line (391, 392a, 392b) to prevent the vaporized ammonia from being supplied to or leaked from the engine (10).

[0166] The knockout drum (21) has a wider space than the fuel pipe, and the ammonia in the gaseous and liquid states that moves into the knockout drum (21) has a slower flow rate. Inside the knockout drum (21), the liquid ammonia falls to the bottom due to gravity, and the gaseous ammonia is supplied to the exhaust gas treatment device (80) to remove toxicity and be discharged. The liquid ammonia is collected in a recovery tank (22) and can be recycled.

[0167] Ammonia can be converted to a gaseous state when the pressure is lowered when supplied to an empty fuel pipe. Therefore, the ammonia engine system (3) can be filled with an inert gas before supplying ammonia to the fuel pipes (L4, L5) of the engine (10). Alternatively, after the engine (10) is stopped from operating, the fuel recovery pipe (L6) can be filled with an inert gas to prevent the ammonia inside the engine from being vaporized due to a lower pressure when moving to the fuel recovery pipe (L6).

[0168] Since the ammonia that is unburned and recovered in the engine (10) may contain an inert gas, the fuel supply system (20) may further include an inert gas / fuel separator (23) that separates the inert gas from the recovered ammonia. The liquid ammonia and the inert gas are primarily separated in the inert gas / fuel separator (23), and the gaseous fuel mixed with the inert gas can be secondarily recovered in the knockout drum (21).

[0169] The fuel valve train (31, 36) of the ammonia engine system (3) may also include a valve train (36) at the rear end of the engine (10). The valve train located at the front end of the engine (10) is called a supply valve train (31) (SVT: Supply Valve Train), and the valve train located at the rear end of the engine (10) is called a return valve train (36) (RVT: Return Valve Train).

[0170] The supply valve train (31) and the return valve train (36) of the fuel valve train (31, 36) can be configured as a single module and can have a left-right symmetrical structure. The fuel supply pipe (L2) of the supply valve train (31) and the fuel return pipe (L6) on the return valve train (36) can be arranged horizontally adjacent to each other.

[0171] The supply valve train (31) may have a configuration similar to the fuel valve train (30) of the aforementioned methanol engine system (2). The double-block bleed valve (32) can block ammonia supplied to the engine (10), thereby isolating the engine (10) and the fuel supply system (20).

[0172] The double block bleed valve (32) includes a vent line (392b) located between a pair of valves, and the methanol engine (10) recovers liquid methanol through the vent line (392b), but the double block bleed valve (32) of the ammonia engine system (3) is connected to a knockout drum (21) where ammonia can be converted into a gaseous state.

[0173] The supply valve train (31) may include a front-end inert gas supply module (33) that supplies an inert gas, such as an inert gas. The front-end inert gas supply module (33) may include a high-pressure inert gas supply valve (33a) that supplies a high-pressure inert gas and a low-pressure inert gas supply valve (33b) that supplies a low-pressure inert gas. Since ammonia is easily vaporized under low pressure, a high-pressure inert gas is required to recover liquid ammonia, and thus a high-pressure inert gas can be supplied through the high-pressure inert gas supply valve (33a). The low-pressure inert gas supply valve (33b) can supply a lower-pressure inert gas than the inert gas supplied by the high-pressure inert gas supply valve (33a) to recover gaseous ammonia.

[0174] The ammonia engine system (3) can be filled with an inert gas (inert gas padding) before supplying ammonia to the engine (10). To prevent ammonia from vaporizing in a vacuum, the pressure of the fuel pipe within the engine (10) can be configured to be 30 bar or higher.

[0175] A return line can be closed via a return valve train (36) at the rear end of the engine (10) to allow the fuel pipes (L4, L5) inside the engine (10) to be filled with an inert gas. The return valve train (36) also includes a double-block bleed valve (37) that isolates the fuel supply system (20) and the engine (10), and a gas recovery line (392a) between a pair of valves (SV37-1, SV37-2) can be connected to a knockout drum (21).

[0176] To distinguish between the double block bleed valve (32) of the supply valve train (31) and the double block bleed valve (37) of the return valve train (36), the former is called the supply valve (32) and the latter is called the return valve (37).

[0177] The return valve train (36) can optionally supply fuel to the inert gas / fuel separator (23) or the knockout drum (21) depending on the condition of the recovered fuel. Basically, since the engine is filled with an inert gas to maintain a high pressure state, the return valve train (36) can supply fuel to the inert gas / fuel separator (23).

[0178] When the engine is shut down, the remaining fuel after the liquid fuel is recovered becomes gaseous, and the gaseous ammonia can be recovered to the knockout drum (21) through the vent line (391). In particular, in an emergency stop situation, the ammonia inside the engine (10) can be diverted to the knockout drum (21) to quickly discharge it.

[0179] As shown in Fig. 10, the return valve train (36) is provided with a plurality of vent lines (391) bypassing the knockout drum (21) to quickly recover gaseous ammonia within the engine (10).

[0180] In an engine system (3) that uses ammonia as fuel, a U-shaped pipe and a liquid detection sensor (LS87) located at the rear end of the purge valve (41) can also be used. To prevent ammonia from vaporizing, the pressure inside the fuel pipe can be maintained at 30 bar or higher by filling it with an inert gas.

[0181] Before supplying ammonia to the engine, an inert gas can be filled between the double block bleed valves (32, 37) at both ends of the fuel pipe (L3-L6) extending from the supply valve train (31) to the return valve train (36).

[0182] When ammonia fuel is injected into the fuel pipe (L3-L6), the ammonia is maintained in a liquid state by the pressure of the inert gas. Whether or not the ammonia fuel is filled up to the rear end of the engine can be detected by the liquid detection sensor (LS87). The U-shaped pipe (L61) can be configured at the lowest position on the fuel recovery pipe (L6), and the liquid detection sensor (LS87) located in the U-shaped pipe (L61) can determine whether the ammonia filling is complete before the engine (10) is driven.

[0183] In addition, when ammonia leaks while the engine (10) is running, the rear end of the purge valve (41) is filled with an inert gas, so that the ammonia does not vaporize and the leaked ammonia can be detected by the liquid detection sensor (LS87).

[0184] Also, like the purging step (S218, S234) of the methanol engine system (2), the ammonia engine system (3) can also purge ammonia in the fuel pipe by supplying an inert gas until no liquid is detected by the liquid detection sensor (LS87). The engine system according to at least one embodiment of the present invention can operate the engine stably using methanol / ammonia.

[0185] Additionally, the engine system according to at least one embodiment of the present invention can be applied to both an engine system using methanol as fuel and an engine system using ammonia as fuel.

[0186] Additionally, the engine according to at least one embodiment of the present invention can accurately determine the opening and closing timing of the purge valve during fuel charging. Furthermore, the engine according to at least one embodiment of the present invention can detect leaks in the purge valve and prevent safety accidents.

[0187] The detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are intended to be embraced therein.

[0188] With respect to various embodiments for implementing the present invention, duplicate descriptions are omitted as they have been described above in the previous table of contents, Best Mode for Carrying Out the Invention.

[0189] The present invention is applicable to engines and ships in various fields, and thus its industrial applicability is recognized.

Claims

1. Fuel tank for storing fuel; An engine that operates by burning the above fuel; A fuel valve train located between the fuel tank and the engine and controlling the flow of fuel supplied to the engine; and Including a control unit that controls the fuel valve train and the engine, The above engine, A fuel pressurization device that pressurizes low-pressure fuel supplied from the above fuel tank to high pressure; A hydraulic pump for supplying pressurized hydraulic oil to the fuel pressurization device; An injector that injects the pressurized fuel into the combustion chamber; An injector pipe for supplying pressurized fuel from the fuel pressurizing device to the injector; A fuel discharge pipe branching from the injector pipe to discharge unused fuel within the engine; An operating oil pump that supplies pressurized operating oil to the above injector; It includes a safety valve unit including a purge valve that opens and closes the above fuel discharge pipe, An engine system characterized in that the purge valve closes the fuel discharge pipe using the pressure of the operating oil supplied from the operating oil pump.

2. In paragraph 1, An engine system characterized by including an operating oil valve positioned between the purge valve and the operating oil pump and selectively supplying the operating oil.

3. In paragraph 1, An engine system characterized in that the operating fluid provides driving force to the plunger of the injector and prevents the fuel from flowing back from the plunger.

4. In paragraph 1, The above fuel pressurization device A plunger that compresses the fuel using the pressurized hydraulic oil; A hydraulic motor for supplying hydraulic oil to the plunger; and It includes a pressure reducing valve that supplies low-pressure hydraulic oil to drive the hydraulic motor by lowering the pressure of the hydraulic oil. An engine system characterized in that the depressurized hydraulic oil is sealed with the operating oil and sealing oil of the plunger.

5. In paragraph 1, The above safety valve unit includes a liquid detection sensor located on the fuel discharge pipe at the rear end of the purge valve, The above control unit, An engine system characterized in that when fuel is filled into the engine while the purge valve is open, the purge valve is closed when liquid is detected by the liquid detection sensor.

6. In paragraph 5, An engine system characterized in that the liquid detection sensor is located lower than the purge valve.

7. In paragraph 1, The above safety valve unit A rear inert gas supply module that supplies inert gas to the fuel discharge pipe at the rear end of the above purge valve, and It includes a front inert gas supply module that supplies an inert gas to a fuel pipe passing through the above fuel valve train, The above control unit Before the engine is driven, the rear inert gas supply module is controlled to supply inert gas, An engine system characterized in that the front inert gas supply module is controlled to supply inert gas after the engine has stopped driving.

8. In paragraph 1, It includes a rear inert gas supply module that supplies inert gas to the fuel discharge pipe at the rear end of the above purge valve, The above rear inert gas supply module An inert gas line connected to the rear end of the above purge valve; A pair of inert gas block valves located in the above inert gas line; An inert gas bleed valve for opening and closing an inert gas bleed line connected between the above inert gas block valves; and It includes a control air valve that selectively supplies air to open and close the pair of inert gas block valves and the inert gas bleed valve, When the above control air valve is opened, the pair of inert gas block valves are opened and the inert gas bleed valve is closed. An engine system characterized in that when the control air valve is blocked, the pair of inert gas block valves are closed and the inert gas bleed valve is opened.

9. In paragraph 1, The above fuel includes low flash point fuel, The above control unit An engine system characterized in that the hydraulic pump and the operating oil pump are controlled so that the pressure of the hydraulic oil and the operating oil are different depending on the type of the fuel when the fuel is charged into the engine before driving the engine.

10. A vessel comprising an engine system according to any one of the preceding clauses.

11. In the method of driving the engine system, An engine operation preparation step of driving the engine's operating oil pump to supply low-pressure operating oil to the injector and driving the hydraulic pump to supply low-pressure hydraulic oil to the fuel pressurization device; A fuel charging step (S215) for supplying low-pressure fuel to fill the fuel pipe inside the engine; Engine shut-off stage (S216) that closes the purge valve located at the rear end of the engine's fuel pipe; A fuel pressurization step (S217) of pressurizing the low-pressure fuel to high pressure in the fuel pressurization device; The above injector includes an engine driving step (S220) in which the high-pressure fuel is supplied to the combustion chamber and combusted. An engine system control method, characterized in that the step of closing the purge valve includes a step of supplying the operating oil from the operating oil pump.

12. In paragraph 11, The above fuel pressurization step is a step of supplying high-pressure hydraulic oil from the hydraulic pump to the fuel pressurization device; and An engine system control method characterized by comprising a step of supplying high-pressure operating oil from the operating oil pump to the injector.

13. In paragraph 11, Further comprising a liquid sensor located at the rear end of the purge valve of the fuel pipe, An engine system control method characterized in that the purge valve is closed when liquid fuel is detected by the liquid sensor for a reference time or longer after the fuel charging step (S215).

14. In paragraph 11, Further comprising a liquid sensor located at the rear end of the purge valve of the fuel pipe, An engine exhaust purging step of supplying an inert gas to the rear end of the purging valve of the engine after the step of closing the purge valve to recover fuel to the fuel tank through a fuel recovery pipe; and; An engine system control method characterized by including a step of stopping the supply of an inert gas when no liquid is detected by the liquid sensor after the purging step.

15. In paragraph 11, Engine shutdown step that stops fuel supply from the above injector; A step of stopping the operation of the fuel pressurization device; A step of lowering the pressure of the operating oil supplied from the operating oil pump and the hydraulic oil supplied from the hydraulic pump; and An engine system control method comprising a step of opening the purge valve to discharge fuel from a fuel pipe of the engine.

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