Engine system, ship having same, and engine system control method

Abstract

Provided is an engine system comprising: an engine driven by combusting fuel; a fuel supply system for supplying the fuel to the engine through a fuel supply pipe; a fuel recovery pipe for recovering, to the fuel supply system, the fuel that is not combusted in the engine; a fuel valve train which is positioned between the fuel supply system and the engine, and which controls the flow of the fuel supplied to the engine; and a control unit for controlling the fuel supply system, the fuel valve train and the engine, wherein the engine includes: an injector for driving the engine by injecting the fuel into a combustion chamber; a fuel discharge pipe for discharging unused fuel in the engine to the fuel recovery pipe; a purge valve for opening and closing the fuel discharge pipe; and a rear inert gas supply module which is positioned at the rear end of the purge valve and which supplies inert gas to the fuel recovery pipe.

Description

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

[0001] The present invention relates to an engine system using low flashpoint fuel and a ship equipped with the same.

[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 capable of efficiently utilizing low flashpoint fuel, a ship equipped with the same, and a control method thereof.

[0009] An engine system is provided, comprising: an engine that operates by combusting fuel; a fuel supply system that supplies fuel to the engine through a fuel supply pipe; a fuel recovery pipe that recovers unburned fuel from the engine to the fuel supply system; a fuel valve train located between the fuel supply system and the engine and controlling the flow of fuel supplied to the engine; and a control unit that controls the fuel supply system, the fuel valve train, and the engine, wherein the engine includes: an injector that injects the fuel into a combustion chamber to drive the engine; a fuel discharge pipe that discharges unused fuel within the engine to the fuel recovery pipe; a purge valve that opens and closes the fuel discharge pipe; and a rear-end inert gas supply module located at a rear end of the purge valve and supplying an inert gas to the fuel recovery pipe.

[0010] Before driving the engine, the control unit can close the purge valve and control the rear inert gas supply module to fill the fuel recovery pipe with inert gas.

[0011] The above control unit can control the rear inert gas supply module so that the pressure of the inert gas in the fuel recovery pipe is constant when the engine is driven.

[0012] The fuel valve train may include a supply valve train positioned on the fuel supply pipe; and a return valve train positioned on the fuel return pipe.

[0013] The above supply valve train includes a front-end inert gas supply module for supplying an inert gas to the engine, and the front-end inert gas supply module can selectively supply one of a high-pressure inert gas that maintains the fuel in a liquid state and a low-pressure inert gas that vaporizes the fuel.

[0014] The fuel may contain ammonia, which vaporizes at room temperature.

[0015] The above control unit can supply high-pressure inert gas through the front-end inert gas supply module before charging fuel to the engine.

[0016] The above control unit can supply sealing oil to the injector before charging the engine with the high-pressure inert gas.

[0017] The above-mentioned shear inert gas supply module can supply high-pressure inert gas to discharge liquid fuel from the engine after the engine has stopped operating, and supply low-pressure inert gas to discharge gaseous fuel from the engine after recovering the liquid fuel.

[0018] The fuel supply system includes a pump that pressurizes the fuel to medium pressure, the supply valve train includes a bypass line that selectively reduces the pressure of the medium pressure fuel to low pressure, and the control unit can supply low pressure fuel to the engine through the bypass line before the engine is driven and supply medium pressure fuel to the engine through the fuel supply pipe when the engine is driven.

[0019] The fuel valve train may include a double block bleed valve comprising a pair of block valves and a bleed line, and the fuel supply system may include a knockout drum connected to the bleed line.

[0020] In a method for driving an engine system, an engine system control method is provided, including a first inert gas padding step (S312) of charging an inert gas into a fuel pipe of the engine; a fuel charging step (S315) of supplying fuel to fill a fuel pipe inside the engine; an engine closing step (S316) of closing a purge valve located at the rear end of the fuel pipe of the engine; a fuel pressurizing step (S317) of pressurizing the fuel to high pressure in a fuel pressurizing device of the engine; a second inert gas padding step (S318) of supplying an inert gas to the rear end of the purge valve to recover the fuel in a fuel recovery pipe and fill the inert gas; and an engine driving step (S320) of supplying the high-pressure fuel to a combustion chamber by an injector and combusting it.

[0021] Before the first inert gas padding step, a preparatory step of supplying sealing oil to the injector may be included.

[0022] In the above fuel pressurization step, the pressure of the silicon oil supplied to the injector can be increased.

[0023] When the pressure of the inert gas in the fuel recovery pipe decreases during the above engine operation stage, the inert gas can be replenished.

[0024] The pressure of the fuel supplied to the engine in the fuel pressurization step may be higher than the pressure of the fuel supplied to the engine in the fuel charging step.

[0025] Before the engine shut-off step, the step of driving a fuel pressurization device; and the step of increasing the pressure of the sealing oil of the injector may be included, and the engine shut-off step may include the step of supplying the sealing oil of the increased pressure to the purge valve to close the purge valve.

[0026] The present invention provides an engine system comprising: an engine that operates by combusting fuel; a fuel supply system that supplies fuel to the engine through a fuel supply pipe; a fuel recovery pipe that recovers unburned fuel from the engine to the fuel supply system; a fuel valve train positioned between the fuel supply system and the engine and controlling the flow of fuel supplied to the engine; and a control unit that controls the fuel supply system, the fuel valve train, and the engine, wherein the fuel supply system includes a separator that separates liquid fuel and gaseous inert gas; and a knockout drum that separates gaseous fuel and liquid fuel.

[0027] The fuel valve train includes a supply valve train positioned on the fuel supply pipe; and a return valve train positioned on the fuel recovery pipe, wherein the return valve train can selectively supply fuel on the fuel recovery pipe to either the separator or the knockout drum.

[0028] The above return valve train can recover liquid fuel to the knockout drum if no liquid fuel is detected in the fuel recovery pipe.

[0029] In an emergency stop situation, the return valve train can close the fuel recovery pipe connected to the separator and recover fuel to the knockout drum.

[0030] The above supply valve train includes a front-end inert gas supply module for supplying an inert gas to the engine, and the front-end inert gas supply module can selectively supply one of a high-pressure inert gas that maintains the fuel in a liquid state and a low-pressure inert gas that vaporizes the fuel.

[0031] The fuel may contain ammonia, which vaporizes at room temperature.

[0032] The above-mentioned shear inert gas supply module can supply high-pressure inert gas to discharge liquid fuel from the engine after the engine has stopped operating, and supply low-pressure inert gas to discharge gaseous fuel from the engine after recovering the liquid fuel.

[0033] Liquid fuel separated from the knockout drum can be recovered to the separator, and gaseous fuel separated from the knockout drum can be moved to the exhaust treatment unit.

[0034] The fuel valve train includes a double block bleed valve including a pair of block valves and a bleed line, wherein the bleed line can be connected to the knockout drum.

[0035] A method for driving an engine system includes an engine driving step (S320) of supplying high-pressure fuel to a combustion chamber by an injector and combusting it; and a step (S330) of terminating the driving of the engine, wherein the step of terminating the engine driving may include an engine opening step (S332) of opening a purge valve located at the rear end of a fuel pipe of the engine; a liquid fuel recovery step of discharging liquid fuel remaining in the engine; and a gaseous fuel recovery step of discharging gaseous fuel remaining in the engine.

[0036] The above liquid fuel recovery step supplies the liquid fuel to a separator to separate it from an inert gas, and the above gaseous fuel recovery step supplies the gaseous fuel to a knockout drum to separate it into gaseous fuel and liquid fuel.

[0037] The above liquid fuel recovery step may include a step of supplying a high-pressure inert gas that maintains the fuel in a liquid state, and the above gaseous fuel recovery step may include a step of supplying a low-pressure inert gas that vaporizes the fuel.

[0038] The step of terminating the engine operation may omit the liquid fuel recovery step and perform only the gaseous fuel recovery step in an emergency stop situation of the engine.

[0039] According to at least one embodiment of the present invention, stable operation of an engine system using ammonia as fuel is possible.

[0040] Additionally, the engine system according to at least one embodiment of the present invention can minimize vaporization of ammonia and increase the reuse rate of ammonia.

[0041] Additionally, the engine system according to at least one embodiment of the present invention can quickly discharge fuel inside the engine during emergency braking.

[0042] 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.

[0043] FIG. 1 is a diagram illustrating an engine system according to a first embodiment of the present invention.

[0044] FIG. 2 is a diagram illustrating an engine system according to a second embodiment of the present invention.

[0045] FIG. 3 is a diagram illustrating an engine system according to a third embodiment of the present invention.

[0046] Figure 4 is a flowchart illustrating a control method of an engine system according to a third embodiment of the present invention.

[0047] Figures 5 to 15 are diagrams illustrating a control method of an engine system according to a third embodiment of the present invention.

[0048] Figure 16 is a flowchart illustrating an emergency braking control method of an engine system according to a third embodiment of the present invention.

[0049] Figures 17 and 18 are diagrams illustrating the emergency braking control method of Figure 16.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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).

[0062] The present embodiment includes a methanol engine (10) that uses methanol (CH3OH) as fuel.

[0063] 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).

[0064] 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.

[0065] 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.

[0066] 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).

[0067] 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).

[0068] 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.

[0069] 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.

[0070] 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).

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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).

[0076] 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.

[0077] 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).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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).

[0082] 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).

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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).

[0088] 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.

[0089] 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.

[0090] 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).

[0091] 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.

[0092] 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).

[0093] 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.

[0094] The purge valve (141) is included in the safety valve unit (140) (SVT: 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 (Operation Mode), the control unit can close the purge valve (141) to block the flow of fuel to the fuel recovery pipe (L6).

[0095] 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).

[0096] 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.

[0097] 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.

[0098] 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).

[0099] 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.

[0100] 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).

[0101] 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).

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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).

[0110] 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).

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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).

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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).

[0120] FIG. 3 is a diagram illustrating an ammonia engine system (3) according to a third embodiment of the present invention.

[0121] 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.

[0122] 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.

[0123] 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. 3. The same engine (10) can be applied to both the methanol engine system (2) and the ammonia engine system (3), thereby improving manufacturing efficiency.

[0124] 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.

[0125] 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.

[0126] 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).

[0127] The engine system (3) according to the third embodiment of FIG. 3 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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).

[0133] 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).

[0134] 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.

[0135] 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.

[0136] 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).

[0137] 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.

[0138] 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).

[0139] 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).

[0140] 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).

[0141] 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.

[0142] 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).

[0143] 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.

[0144] The supply valve train (31) may include a pre-stage inert gas supply module (33) that supplies an inert gas such as nitrogen. The pre-stage 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.

[0145] 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.

[0146] 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).

[0147] 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).

[0148] 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).

[0149] 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.

[0150] As shown in Fig. 3, 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).

[0151] Fig. 4 is a flowchart illustrating a control method of an engine system (3) according to a third embodiment of the present invention. Figs. 5 to 15 are diagrams illustrating a control method of an engine system (3) according to a third embodiment of the present invention, and will be examined together with the description of the flowchart of Fig. 4.

[0152] This embodiment is an engine system (3) that uses ammonia as fuel, and may be composed of a preparation step (S310) before driving the engine (10), an engine (10) driving step (S320) injecting fuel into a combustion chamber from an injector (110) and combusting it, and a step (S330) of recovering fuel inside the engine (10) after the engine (10) is shut down.

[0153] Figures 5 to 11 are drawings illustrating the preparatory steps prior to operation. Since ammonia easily vaporizes at room temperature and pressure, the pressure in the fuel pipe (L4-L5) within the engine (10) must be maintained above a certain level before supplying fuel to the engine (10).

[0154] An inert gas, such as nitrogen, can be used to increase the pressure within the fuel pipe (L4-L5) above atmospheric pressure. Inert gases do not readily react with fuel and do not liquefy easily at room temperature and high pressure, so they have the advantage of not reacting even when mixed with fuel.

[0155] Before supplying fuel to the engine (10), an inert gas of 32-40 bar can be supplied to the engine (10) from the upstream inert gas supply module (33) of the supply valve train (31) so that the pressure of the fuel pipe (L4-L5) can be made 30 bar or higher.

[0156] The shear inert gas supply module (33) of this embodiment may include a high-pressure inert gas supply valve (SV33-1) that supplies a high-pressure inert gas of 30 bar or more and a low-pressure inert gas supply valve (SV33-3) that supplies a low-pressure inert gas of 5-10 bar.

[0157] The pre-fuel inert gas supply module (33) can supply an inert gas (high-pressure nitrogen) at a pressure (32-40 bar) that does not vaporize ammonia by opening the high-pressure inert gas supply valve (SV33-1). The high-pressure inert gas can be filled into the injector pipe (L4) and fuel discharge pipe (L5) inside the engine (10) through the fuel supply pipe (L3).

[0158] At this time, the working oil pump (130) and the hydraulic pump (151) can supply sealing oil having a pressure higher than the pressure of the inert gas (32-40 bar) to prevent the inert gas from leaking through the piston of the injector (110) and the fuel pressurization device (120). For example, the working oil pump (130) and the hydraulic pump (151) can supply sealing oil of about 50 bar-70 bar to the injector (110) and the engine (10) pressurization device.

[0159] When filling the inert gas with the purge valve (141) closed, air existing inside the engine (10) may remain, so the purge valve (141) can be opened to fill all fuel pipes (L4, L5) inside the engine with the inert gas.

[0160] When the inert gas is returned to the fuel supply system, the pressure in the fuel pipes (L4, L5) inside the engine does not increase, so the second double-block bleed valve (37) of the return valve train (36) can be closed and the inert gas can be supplied.

[0161] When the pressure of the pressure gauge (PT81R) at the rear end of the inert gas supply module (33) and the front end of the second double block bleed valve (37) of the return valve train (36) becomes higher than the reference pressure, it is determined that padding is complete and the supply of inert gas can be stopped.

[0162] The performance of the second double block bleed valve (37) of the return valve train (36) before driving the engine (10) can be tested. ① Confirm that the pressure gauge (PT37) between a pair of valves (SV37-1, SV37-2) remains at 0 until the inert gas padding is completed.

[0163] Next, ② as shown in Fig. 6, the valve (SV37-1) of the front end of the return valve train (36) can be opened and the pressure gauge (PT37) can be checked to see if the pressure of the supplied inert gas rises to 32 bar. ③ After closing the valve (SV37-1) of the front end, it can be checked to see if the pressure between a pair of valves is maintained to see if a leak occurs in the second double block bleed valve (37).

[0164] When the inert gas is filled in the engine (10) and the fuel pipes (L4, L5) of the engine (10), the fuel supply system (20) can start supplying fuel (S313) as shown in Fig. 7. The pump (51) in the fuel tank (50) can supply fuel at a low pressure at which ammonia does not vaporize, and the pump (25) of the fuel supply system (20) can pressurize the fuel to a pressure of 50 bar or more and supply it to the supply valve train (31).

[0165] The supply valve train (31) can test the performance of the first double-block bleed valve (32) before supplying fuel to the engine (10). As with the performance test of the second double-block bleed valve (37) of the return valve train (36), the change in the pressure sensor (PT32) between a pair of valves according to the opening and closing of the valve (SV32-1) in front of the first double-block bleed valve (32) is measured.

[0166] With the valve (SV32-1) of the front end closed, the valve (SV32-1) of the front end opened and fuel injected into the first double block bleed valve (32), the pressure and the valve (SV32-1) of the front end closed again, and the change in pressure measured, can be used to check whether a leak occurs in the first double block bleed valve (32).

[0167] After confirming the normal operation of the first double block bleed valve (32), the rear valve (SV32-2) can be opened as shown in Fig. 8 to fill the engine (10) with fuel (S315).

[0168] Since the pressure of the sealing oil supplied to the injector (110) and the fuel pressurization device (120) of the engine (10) is still in a low pressure state, it is preferable to supply fuel to the engine (10) at a pressure lower than the medium pressure (50 to 83 bar) pressurized by the pump (25) of the fuel supply device when supplying fuel before driving the engine (10).

[0169] As illustrated in Fig. 8, the second double-block bleed valve (37) of the return valve train (36) can be opened to reduce the pressure within the fuel pipes (L4, L5). Additionally, the supply valve train (31) can include a bypass line including an orifice (34) to reduce the pressure of the fuel.

[0170] In the step of charging fuel to the engine (10) before driving the engine (10), the pressure of the fuel can be lowered by closing the valve (SV34) on the fuel supply pipe (L3) to allow the fuel to pass through the orifice (34).

[0171] Fuel is filled into the fuel pipes (L4, L5) and the fuel recovery pipe (L6) inside the engine (10), and the return valve train (36) is opened, so that the inert gas filled in the fuel pipes (L4, L5, L6) can be discharged to the knockout drum (21) through the inert gas / fuel separator (23) of the fuel supply system (20).

[0172] When the fuel is fully filled in the engine (10), the purge valve (141) at the rear end of the engine (10) can be closed as shown in Fig. 9. The control unit can increase the pressure of the working oil supplied by the working oil pump (130) and open the working oil valve (SV145) of the safety valve unit (140) to close the purge valve (141) (S316)

[0173] The purge valve (141) divides the space between the fuel pipes (L4, L5) inside the engine (10) and the fuel recovery pipe (L6) at the rear end of the engine (10), so that the pressure in front of the purge valve (141), i.e., inside the engine (10), can be independently increased.

[0174] Before closing the purge valve (141), the supply valve (SV34) of the supply valve train (31) can be opened to supply the fuel that was supplied at a lower pressure by first bypassing the orifice (34) at a medium pressure again.

[0175] The hydraulic pump (151) supplies high-pressure hydraulic oil (200 bar-320 bar) to the fuel pressurization device (120), so that the fuel pressurization device (120) can pressurize the fuel to a level of 400 bar-600 bar (S317).

[0176] The hydraulic motor of the fuel pressurization device (120) can be pre-driven when the hydraulic pump (151) is supplying low-pressure hydraulic oil before closing the purge valve (141). By pre-driving the hydraulic motor with low-pressure hydraulic oil, the torque shortage phenomenon of the hydraulic motor can be alleviated.

[0177] Since the purge valve (141) is closed, fuel does not flow out of the engine (10), and high-pressure fuel can be supplied to the injector pipe (L4).

[0178] After the purge valve (141) is closed, an inert gas is supplied through the rear inert gas supply module (146) located at the rear end of the purge valve (141), thereby discharging the low-pressure fuel filled in the fuel recovery pipe (L6) and filling the fuel recovery pipe (L6) with the inert gas (S318).

[0179] Referring to Fig. 10, by supplying high-pressure inert gas of 30 bar or more while the second double-block bleed valve (37) of the return valve train (36) is open, the low-pressure fuel remaining in the fuel recovery pipe (L6) can be pushed out to the inert gas / fuel separator (23).

[0180] If no fuel is detected by the liquid detection sensor (LS1) at the rear end of the purge valve (141) and after a predetermined period of time, it is determined that all fuel has been discharged in the fuel recovery pipe (L6), the second double block bleed valve (37) of the return valve train (36) can be closed as shown in FIG. 11, and the supply of inert gas from the front inert gas supply module (33) can be stopped.

[0181] The fuel recovery pipe (L6) forms a closed space filled with high-pressure inert gas from the purge valve (141) to the supply valve, and the pressure inside the fuel recovery pipe (L6) can be maintained at 30 bar or more.

[0182] When the engine (10) is stopped from operating and the purge valve (141) is opened, or a leak occurs in the purge valve (141) and fuel flows into the fuel recovery pipe (L6), the fuel recovery pipe (L6) can be filled with an inert gas (inert gas padding) to prevent the fuel pressure from rapidly decreasing and vaporizing. The inert gas between the second double block bleed valves (37) can be recovered to the knockout drum (21) by opening the bleed valve (SV37-3).

[0183] When the fuel is pressurized in the fuel supply device (120) and the inert gas padding is completed in the fuel recovery pipe (L6) at the rear end of the engine, the engine (10) is ready for operation in the driving mode. In the driving mode, the injector (110) can inject high-pressure fuel into the combustion chamber and produce energy (S320).

[0184] When the driving mode of an ammonia engine (10) that runs on ammonia as fuel is terminated (S330), the following sequence can be sequentially terminated.

[0185] When a command to terminate engine (10) operation is input, the injector (110) stops fuel injection and opens the purge valve (141) (S332). When the engine (10) operation is terminated, the operating oil valve is closed as shown in FIG. 12 to open the purge valve (141), and the motor of the fuel pressurization device (120) is turned off. The first double block bleed valve (32) of the supply valve train (31) is closed to stop fuel supply to the engine (10).

[0186] The second double-block bleed valve (37) of the return valve train (36) can be opened to discharge unburned fuel inside the engine (10) into the inert gas / fuel separator (23). When the second double-block bleed valve (37) of the return valve train (36) is opened, the pressure inside the engine (10) can be lowered.

[0187] When the purge valve (141) is opened, the fuel recovery pipe (L6) is filled with an inert gas, so the fuel does not vaporize and the low-pressure liquid fuel can move to the inert gas / fuel separator (23) (S333).

[0188] When the second double block bleed valve (37) is opened, the liquid fuel moves to the inert gas / fuel separator (23) due to the pressure difference, but when the pressure becomes equal, the liquid fuel remains in the fuel pipes (L4, L5) of the engine (10). In order to discharge the liquid fuel remaining in the fuel pipes (L4, L5), as illustrated in FIG. 13, the inert gas can be supplied from the upstream inert gas supply module (33) of the supply valve train (31).

[0189] To recover the fuel in a liquid state, the inert gas can be supplied at a pressure of 30 bar or more. The high-pressure inert gas moves the liquid fuel to the inert gas / fuel separator (23). If no liquid is detected by the liquid detection sensor (LS1) at the rear end of the purge valve (141) and the liquid detection sensor (LS2) of the return valve train (36), the discharge of the liquid fuel is determined to be complete, and the supply of the inert gas can be stopped as shown in FIG. 14.

[0190] When the supply of the inert gas is interrupted, the pressure within the fuel pipes (L3, L4, L5, L6) decreases, causing the fuel to vaporize and convert to a gaseous fuel state. The second double-block bleed valve (37) of the return valve train closes to block the fuel converted to a gaseous state from moving to the inert gas / fuel separator (23).

[0191] Instead, the vent line (392a) located at the front end of the second double-block bleed valve (37) can be opened to supply gaseous fuel to the knockout drum (21) (S334). Since the pressure of the knockout drum is maintained at 0.5 bar, the remaining fuel in the engine (10) pipe can be naturally vaporized.

[0192] The bleed line can be opened to supply gaseous fuel between the second double block bleed valve (37) to the knockout drum (21).

[0193] Gaseous fuel may remain in the fuel pipes (L3, L4, L5, L6) that have been brought to atmospheric pressure. As illustrated in Fig. 15, the front-end inert gas supply module (33) can supply inert gas to discharge all gaseous fuel in the fuel pipes (L4, L5, L6). High-pressure inert gas was supplied when discharging liquid fuel, but high-pressure inert gas is not necessary to discharge gaseous fuel. To reduce inert gas consumption, low-pressure inert gas of 5-10 bar can be supplied.

[0194] A sensor that detects the presence of residual gaseous ammonia may be used, but because it is low pressure, its reliability is low, so the supply of low pressure inert gas may be stopped after a certain period of time to terminate operation of the engine system (3).

[0195] The control method of the engine system (3) discussed above is the operation when the engine (10) is operating normally using ammonia as fuel. When an emergency situation such as a malfunction or fuel leak of the engine (10) occurs (S325), the engine system (3) can be subjected to emergency braking (S350) to immediately shut down the engine (10) and quickly discharge the fuel inside the fuel pipe within a short period of time.

[0196] FIG. 16 is a flowchart illustrating a method for controlling an engine system (3) during emergency braking according to one embodiment of the present invention, and FIGS. 17 and 18 are diagrams illustrating a method for controlling an engine system (3) during emergency braking of FIG. 16.

[0197] In addition to an abnormality in the engine (10), emergency braking can be performed when an abnormality is detected in the inert gas / fuel separator (23) on the fuel supply system (20) or the selective catalytic reduction device (SCR: Selective Catalytic Reduction) of the exhaust gas treatment device.

[0198] When entering emergency braking mode, the engine (10) is shut down and the purge valve (141) is opened (S352). Similar to the engine (10) shutdown step in normal operation of Fig. 12, the operating oil valve is closed to open the purge valve (141), and the motor of the fuel pressurization device (120) is shut down. The first double-block bleed valve (32) of the supply valve train (31) is closed to stop the fuel supply to the engine (10).

[0199] However, since the fuel inside the engine (10) is discharged directly to the knockout drum (21) without a liquid fuel discharge stage in the event of emergency braking, the second double block bleed valve remains closed and the valve (SV36) of the return valve train is opened so that the fuel can be discharged to the vent line (392a). Since the pressure in the knockout drum (21) is low, the pressure inside the fuel pipe is quickly reduced and the liquid fuel can vaporize. The non-vaporized liquid fuel can also be recovered from the knockout drum (21) and returned to the regeneration tank.

[0200] Since the fuel in the fuel pipe must be discharged within a short period of time (e.g., 2 minutes) in case of emergency braking, the residual fuel in the fuel pipe can be quickly discharged by supplying inert gas from the rear inert gas supply module (146) as shown in FIG. 18.

[0201] When normal operation is terminated, low-pressure inert gas is supplied to discharge the fuel gas, but when emergency braking is required, rapid discharge of fuel is required, so high-pressure inert gas is supplied to enable rapid discharge.

[0202] As described above, according to at least one embodiment of the present invention, stable operation of the engine system (3) is possible using ammonia as fuel.

[0203] In addition, the engine system (3) according to at least one embodiment of the present invention can minimize vaporization of ammonia and increase the reuse rate of ammonia.

[0204] Additionally, the engine system (3) according to at least one embodiment of the present invention can rapidly discharge fuel inside the engine (10) during emergency braking. The above detailed description should not be construed as limiting in all respects but should be considered illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are intended to be included within the scope of the present invention.

[0205] 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.

[0206] The present invention is applicable to engines and ships in various fields, and thus its industrial applicability is recognized.

Claims

1. An engine that operates by burning fuel; A fuel supply system that supplies fuel to the engine through a fuel supply pipe; A fuel recovery pipe for recovering unburned fuel from the engine to the fuel supply system; A fuel valve train located between the fuel supply system and the engine and controlling the flow of fuel supplied to the engine; and Including the fuel supply system, the fuel valve train and the control unit that controls the engine, The above engine, An injector that injects the fuel into the combustion chamber to drive the engine; A fuel discharge pipe for discharging unused fuel within the engine to the fuel recovery pipe; A purge valve that opens and closes the above fuel discharge pipe; and An engine system including a rear inert gas supply module located at the rear end of the purge valve and supplying an inert gas to the fuel recovery pipe.

2. In paragraph 1, Before driving the above engine The above control unit, An engine system characterized in that the purge valve is closed and the rear inert gas supply module is controlled to fill the fuel recovery pipe with inert gas.

3. In paragraph 2, The above control unit, An engine system characterized in that the rear inert gas supply module is controlled so that the pressure of the inert gas in the fuel recovery pipe is constant when the engine is driven.

4. In paragraph 1, The above fuel valve train, a supply valve train positioned on the fuel supply pipe; and An engine system characterized by comprising a return valve train positioned on the fuel recovery pipe.

5. In paragraph 4, The above fuel contains ammonia which vaporizes at room temperature, The above supply valve train includes a front inert gas supply module for supplying inert gas to the engine, The above shear inert gas supply module An engine system characterized in that it selectively supplies one of a high-pressure inert gas that maintains the fuel in a liquid state and a low-pressure inert gas that vaporizes the fuel.

6. In paragraph 5, The above control unit Before charging fuel to the engine, sealing oil is supplied to the injector before charging the engine with the high-pressure inert gas, An engine system characterized in that a high-pressure inert gas is supplied through the above-mentioned shear inert gas supply module.

7. In paragraph 5, The above shear inert gas supply module After the above engine has stopped operating, high pressure inert gas is supplied to discharge the liquid fuel from the engine, An engine system characterized in that after recovering the liquid fuel, a low-pressure inert gas is supplied to discharge the gaseous fuel from the engine.

8. In paragraph 4, The above fuel supply system includes a pump that pressurizes the fuel to medium pressure, The above supply valve train includes a bypass line for selectively reducing the pressure of the medium-pressure fuel to low pressure, The above control unit Before the engine is driven, low-pressure fuel is supplied to the engine through the bypass line. An engine system characterized in that when the above engine is driven, high-pressure fuel is supplied to the engine through a fuel supply pipe.

9. In paragraph 1, The fuel valve train is Includes a double block bleed valve with a pair of block valves and a bleed line; The above fuel supply system An engine system characterized by comprising a knockout drum connected to the bleed line.

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

11. In the method of driving the engine system, A first inert gas padding step (S312) of charging an inert gas into the fuel pipe of the above engine; A fuel charging step (S315) for supplying fuel and filling the fuel pipe inside the engine with fuel; Engine shut-off step (S316) that closes the purge valve located at the rear end of the engine's fuel pipe; A fuel pressurization step (S317) of pressurizing the fuel to high pressure in the fuel pressurization device of the engine; A second inert gas padding step (S318) of supplying an inert gas to the rear end of the above purge valve to recover fuel in the fuel recovery pipe and fill it with the inert gas; and An engine system control method including an engine driving step (S320) of supplying high-pressure fuel to a combustion chamber through an injector and combusting it.

12. In paragraph 11, An engine system control method comprising a preparatory step of supplying sealing oil to the injector before the first inert gas padding step.

13. In paragraph 12, An engine system control method characterized in that the pressure of sealing oil supplied to the injector is increased in the fuel pressurization step.

14. In paragraph 11, The pressure of the fuel supplied to the engine in the above fuel pressurization step is An engine system control method characterized in that the pressure is higher than that of the fuel supplied to the engine in the above fuel charging step.

15. In paragraph 11, Before the above engine shutdown step, a step of driving a fuel pressurization device; and A step of increasing the pressure of the sealing oil of the above injector is included, An engine system control method characterized in that the engine closing step includes a step of supplying sealing oil of the increased pressure to the purge valve and closing the purge valve.

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