Reciprocating engine

Abstract

A reciprocating engine using ammonia as fuel, the engine comprising: a cylinder that forms a combustion chamber; an exhaust channel through which exhaust gas from the combustion chamber is discharged; an exhaust treatment device that is provided in the exhaust channel and that treats unburned ammonia; a piston that reciprocates in the cylinder; a crank that is linked to the piston; a crankcase that houses the crank and into which blow-by gas flows from the combustion chamber; and a suction device that performs negative-pressure suction in the crankcase, wherein unburned ammonia contained in the blow-by gas suctioned from the crankcase by the suction device is treated by the exhaust treatment device.

Description

[Technical field]

[0001] The present invention relates to a reciprocating engine. This application claims priority based on Japanese Patent Application No. 2023-013146, filed on January 31, 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] The following Patent Document 1 discloses a blow-by gas treatment system applied to an engine system having an engine, a turbocharger having a compressor disposed in an intake passage of the engine and a turbine disposed in an exhaust passage of the engine, and an oxidation catalyst disposed in the exhaust passage downstream of the turbine. This blow-by gas treatment system includes a blow-by gas introduction switching mechanism that introduces blow-by gas discharged from the engine to the oxidation catalyst when the conditions that the load of the engine is in a high load state greater than a predetermined load and the oxidation catalyst is in an active state are satisfied, and introduces the blow-by gas discharged from the engine to the compressor when the conditions are not satisfied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-76779 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand to reduce emissions of carbon dioxide (CO2), a greenhouse gas, as a measure against global warming. Ammonia (NH3) has been attracting attention as a new fuel that does not emit carbon dioxide when burned. However, because ammonia is toxic, when it is used as fuel for a reciprocating engine, safety issues may arise if the blow-by gas remains in the crankcase or leaks out of the crankcase.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to improve the safety of reciprocating engines that use ammonia as fuel. [Means for solving the problem]

[0006] A reciprocating engine according to one embodiment of the present invention is a reciprocating engine that uses ammonia as fuel, and includes a cylinder that forms a combustion chamber, an exhaust passage through which exhaust gas is discharged from the combustion chamber, an exhaust treatment device that is provided in the exhaust passage and treats unburned ammonia, a piston that reciprocates within the cylinder, a crank connected to the piston, a crankcase that houses the crank and into which blow-by gas flows from the combustion chamber, and a suction device that creates negative pressure inside the crankcase, and the unburned ammonia contained in the blow-by gas sucked from the crankcase by the suction device is treated by the exhaust treatment device.

[0007] In the above reciprocating engine, the exhaust treatment device may be a catalytic treatment device that treats unburned ammonia using a catalyst.

[0008] In the above-mentioned reciprocating engine, the suction device may include a pressure gauge that measures the pressure inside the crankcase, and a blower that draws the inside of the crankcase to negative pressure and pressurizes the drawn-in gas and sends it to the exhaust passage, and the blower may be driven so that the measurement result of the pressure gauge becomes a predetermined negative pressure value.

[0009] In the above reciprocating engine, the suction device may draw negative pressure into the crankcase through a suction port provided in a gas retention section that communicates with the inside of the crankcase.

[0010] In the above reciprocating engine, the gas retention portion may be formed in a cylinder head.

[0011] In the above-mentioned reciprocating engine, a gas inlet port is provided in a gas retention section that communicates with the inside of the crankcase, and the suction device may draw negative pressure into the crankcase through a suction port provided at a location other than the gas retention section in which the gas inlet port is provided.

[0012] The above reciprocating engine may further include a gas supply device that supplies gas from the gas inlet to the gas retention section.

[0013] The above reciprocating engine may further include a first exhaust route that connects the inside of the crankcase to the exhaust passage via the suction device, a second exhaust route that opens the inside of the crankcase to the atmosphere without connecting it to the exhaust passage, and a switching device that switches between the first exhaust route and the second exhaust route depending on an operating condition of the reciprocating engine.

[0014] In the above reciprocating engine, the reciprocating engine may be switchable between a first operation mode in which a fuel containing ammonia is used and a second operation mode in which a fuel other than ammonia is used, and the switching device may switch to the first exhaust route in the first operation mode and switch to the second exhaust route in the second operation mode.

[0015] In the above reciprocating engine, the switching device may switch from the first exhaust route to the second exhaust route after a certain time has elapsed since the first operating mode was switched to the second operating mode.

[0016] In the above reciprocating engine, the switching device may immediately switch from the second exhaust route to the first exhaust route when the operating mode is switched from the second operating mode to the first operating mode.

[0017] In the above reciprocating engine, an oil mist separator may be provided on the suction side of the suction device. Effect of the Invention

[0018] According to the above aspect of the present invention, it is possible to improve the safety of a reciprocating engine that uses ammonia as fuel. [Brief description of the drawings]

[0019] [Figure 1] 1 is a configuration diagram of a reciprocating engine according to an embodiment. FIG. [Diagram 2] FIG. 2 is an explanatory diagram illustrating the operation of a diesel operation mode of the reciprocating engine according to one embodiment. [Diagram 3] FIG. 2 is an explanatory diagram illustrating an operation in an ammonia operation mode of the reciprocating engine according to one embodiment. [Figure 4] FIG. 2 is a cross-sectional view of an engine body according to one embodiment. [Diagram 5] FIG. 1 is a schematic configuration diagram of an engine body according to an embodiment. [Figure 6] FIG. 11 is a schematic configuration diagram of an engine body according to another embodiment. [Figure 7] FIG. 1 is a diagram showing an exhaust system for exhaust gas and blow-by gas of a reciprocating engine according to an embodiment of the present invention. [Figure 8] FIG. 2 is a schematic diagram showing a discharge destination of blow-by gas in a reciprocating engine according to one embodiment. [Figure 9] FIG. 2 is a diagram showing the destinations of blow-by gas (mist) discharged in different situations in a reciprocating engine according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] FIG. 1 is a configuration diagram of a reciprocating engine 1 according to one embodiment. As shown in Fig. 1, the reciprocating engine 1 includes an engine body 2 and a control device 3. The reciprocating engine 1 is a marine engine that directly or indirectly drives a propeller. Note that the reciprocating engine 1 may also be a power generation engine that drives a generator.

[0022] The reciprocating engine 1 generally comprises a cylinder 11 that forms a combustion chamber 10, a piston 12 that reciprocates within the cylinder 11, a crank 13 connected to the piston 12, a rotation detection sensor 14 that detects the rotation of the crank 13, and a torque detection sensor 15 that detects the torque of the crank 13. The shaft of the crank 13 is connected to, for example, a propeller of a ship.

[0023] An intake passage 20 and an exhaust passage 30 are connected to a cylinder head 16 of the cylinder 11. An intake valve 21 for opening and closing the intake passage 20 and an exhaust valve 31 for opening and closing the exhaust passage 30 are also provided in the cylinder head 16. A liquid fuel injection valve 53 for injecting liquid auxiliary fuel into the combustion chamber 10 and an ignition device 55 are also provided in the cylinder head 16. The ignition device 55 is, for example, a micro pilot oil injection valve, and is used in an ammonia operation mode (first operation mode) described later.

[0024] The intake passage 20 includes a compressor 22 that compresses air for combustion, an air cooler 23 installed downstream of the compressor 22, and a fuel gas injector 43 installed downstream of the air cooler 23. The fuel gas injector 43 injects gaseous ammonia as fuel into the intake passage 20. The gaseous ammonia is premixed with compressed air in the intake passage 20 to form an air-fuel mixture, which is then supplied into the cylinder 11.

[0025] The air cooler 23 may be an air cooler / heater having not only the function of cooling air with cold water but also the function of heating air with hot water, a heater, or the like. If necessary, an air heater 24 may be installed upstream of the compressor 22 in the intake passage 20. The air heater 24 may have, for example, a cooling / heating system 25 that uses a refrigerant that has exchanged heat with the engine body 2 as a heat source.

[0026] The exhaust passage 30 includes a turbine 33 that is rotated by the exhaust gas discharged from the combustion chamber 10, and a catalytic treatment device 60 that is installed downstream of the turbine 33 and treats substances contained in the exhaust gas. The rotating shaft of the turbine 33 is connected to the compressor 22, and the exhaust gas serves as a rotation source to rotate the compressor 22. In other words, the turbine 33 and the compressor 22 constitute a turbocharger 4.

[0027] The catalytic treatment device 60 uses a catalyst to treat specific substances such as nitrogen oxides (NOx), nitrous oxide, and unburned ammonia that are generated by the combustion of ammonia and liquid auxiliary fuel. The catalytic treatment device 60 is equipped with a detection sensor 60a that detects the specific substances.

[0028] The engine body 2 includes an ammonia fuel supply device 40 that supplies ammonia into the cylinder 11, and a liquid auxiliary fuel supply device 50 that supplies liquid auxiliary fuel that ignites the ammonia into the cylinder 11. The ammonia fuel supply device 40 generally includes an ammonia tank 41, a vaporizer 42, and a fuel gas injector 43.

[0029] The ammonia tank 41 contains liquid ammonia. The vaporizer 42 vaporizes the liquid ammonia discharged from the ammonia tank 41 to generate gaseous ammonia. The vaporizer 42 may include a pressure pump that pressurizes the gaseous ammonia. The vaporizer 42 is connected to the fuel gas injection valve 43 via an ammonia supply path 44. The ammonia supply path 44 includes a regulator 44a and a pressure sensor 44b installed downstream of the regulator 44a.

[0030] The ammonia supply path 44 further includes a second ammonia supply path 45 branched off upstream of the regulator 44a. The second ammonia supply path 45 is connected to the above-mentioned catalytic treatment device 60. The second ammonia supply path 45 includes a regulator 45a and a pressure sensor 45b disposed downstream of the regulator 45a.

[0031] The liquid auxiliary fuel supply device 50 includes a liquid auxiliary fuel tank 51, a first liquid fuel supply pump 52, a liquid fuel injection valve 53, a second liquid fuel supply pump 54, and an ignition device 55. The liquid auxiliary fuel tank 51 stores liquid auxiliary fuel such as heavy oil, light oil, gasoline, etc. The first liquid fuel supply pump 52 supplies the liquid auxiliary fuel stored in the liquid auxiliary fuel tank 51 to the liquid fuel injection valve 53.

[0032] The liquid fuel injector 53 is, for example, a mechanical fuel injection device used in a diesel operation mode (second operation mode) described later. The second liquid fuel supply pump 54 supplies the liquid auxiliary fuel stored in the liquid auxiliary fuel tank 51 to the ignition device 55. The ignition device 55 is, for example, a common rail type fuel injection device used in the ammonia operation mode.

[0033] The control device 3 is realized by, for example, a processor such as a CPU (Central Processing Unit) executing a program stored in a storage unit. The control device 3 may also be realized by hardware such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array).

[0034] The storage unit is realized by, for example, a hard disk drive (HDD), a flash memory, an electrically erasable programmable read only memory (EEPROM), a read only memory (ROM), a random access memory (RAM), etc. The storage unit stores firmware, programs executed by the processor, etc.

[0035] In the control device 3, for example, the output (work load [kW]) for the current load is derived based on the rotation speed detected by the rotation detection sensor 14 and the torque detected by the torque detection sensor 15, and the load factor is derived based on this current output and the rated output previously stored in the storage unit. The load factor is derived, for example, by dividing the current output by the rated output.

[0036] The control device 3 performs feedback control of boost pressure based on the derived boost pressure target value based on the load factor of the engine body 2 and the boost pressure measured by a pressure gauge (not shown). The boost pressure target value derivation information is information indicating a relationship between a predetermined load factor and a boost pressure target value. This information is stored in advance in a storage unit as, for example, a map or a function. Thus, the control device 3 supplies fuel based on the load factor of the internal combustion engine during operation.

[0037] The reciprocating engine 1 having the above configuration can be switched between an ammonia operation mode (first operation mode) in which the fuel used includes ammonia, and a diesel operation mode (second operation mode) in which a liquid auxiliary fuel (heavy oil, etc.) is used. Since ammonia is more difficult to burn than liquid auxiliary fuel (heavy oil, etc.), ammonia operation mode performs a mixed combustion operation using ammonia and liquid auxiliary fuel. For this reason, the ammonia operation mode is also called a mixed combustion operation mode.

[0038] In addition, in the ammonia operation mode (co-firing operation mode), the maximum co-firing rate of ammonia near the maximum output is 80% or more in terms of heat ratio.

[0039] FIG. 2 is an explanatory diagram for explaining the operation of the reciprocating engine 1 in the diesel operation mode according to one embodiment. 2, in the diesel operation mode, liquid auxiliary fuel is injected from the liquid fuel injector 53 into the combustion chamber 10 and is ignited and burned in the compressed air compressed by the piston 12. At this time, the fuel gas injector 43 is stopped.

[0040] FIG. 3 is an explanatory diagram illustrating the operation of the reciprocating engine 1 in the ammonia operation mode according to one embodiment. As shown in Fig. 3, in the ammonia operation mode, gaseous ammonia is injected from the fuel gas injector 43 into the intake passage 20 and premixed with air just before the combustion chamber 10. Next, liquid auxiliary fuel for ignition is injected from the ignition device 55 into the combustion chamber 10, and the mixture compressed by the piston 12 is ignited and burned. At this time, the liquid fuel injector 53 is stopped.

[0041] FIG. 4 is a cross-sectional configuration diagram of the engine body 2 according to one embodiment. As shown in Fig. 4, the engine body 2 includes a cylinder 11 that forms a combustion chamber 10, a piston 12 that reciprocates in the cylinder 11, a crank 13 connected to the piston 12, and a crankcase 70 that houses the crank 13 and into which blow-by gas flows from the combustion chamber 10. The crank 13 is connected to the piston 12 via a connecting rod 13a. The dotted arrows in Fig. 4 indicate the flow of blow-by gas. The blow-by gas is gas that leaks out from the gap between the piston 12 and the cylinder 11.

[0042] The bottom of the crankcase 70 is formed by an oil pan 71. The oil pan 71 stores lubricating oil to be supplied to sliding parts such as the crank 13. A crank chamber 72 and a cam chamber 73 are provided inside the crankcase 70. The crank chamber 72 houses the crank 13. The cam chamber 73 houses a cam mechanism 80 that drives the exhaust valve 31. The cam chamber 73 is located above the crank chamber 72 and is in communication with the crank chamber 72.

[0043] The cam mechanism 80 includes a cam 81 that rotates in conjunction with the crank 13, a tappet roller mechanism 82 that contacts the peripheral surface of the cam 81, and a push rod 83 that is pushed up by the tappet roller mechanism 82. The push rod 83 is disposed in a through hole 74 formed in the cylinder head 16, and its tip extends into the head cover 17 attached to the upper surface of the cylinder head 16.

[0044] A rocker arm 84 and a valve spring 85 are housed within the head cover 17. The valve spring 85 urges the exhaust valve 31 upward to close the exhaust communication passage 30a that communicates with the exhaust path 30. When the rocker arm 84 is pushed up by the tip of the push rod 83, it pushes the exhaust valve 31 down against the urging of the valve spring 85, opening the exhaust communication passage 30a. Although not shown, the cam mechanism 80 also drives the intake valve 21 (see FIG. 1) by a similar mechanism.

[0045] The inside of the head cover 17 is in communication with the crank chamber 72 via the through hole 74 and the cam chamber 73. Blow-by gas accompanied by oil mist flows into the head cover 17 from the crank chamber 72 via the cam chamber 73 and the through hole 74. Therefore, the inside of the head cover 17 serves as a gas retention section 16A where the blow-by gas is likely to be retained. A suction port 90 is formed in the head cover 17. A suction pipe 91 is connected to the suction port 90.

[0046] FIG. 5 is a schematic configuration diagram of the engine body 2 according to one embodiment. As shown in Fig. 5, the engine body 2 is provided with a plurality of head covers 17 (six in the example of Fig. 4). That is, the engine body 2 is provided with a plurality of cylinders (six cylinders 11). The number of cylinders in the engine body 2 is not limited to six. A crankcase 70 is provided in common to each cylinder, and blow-by gas from each cylinder flows into a crank chamber 72. A main suction port 75 communicating with the crank chamber 72 is provided in the crankcase 70 at a location separate from the suction ports 90 of each head cover 17.

[0047] The main suction port 75 and the suction ports 90 of each head cover 17 are connected to a suction path 100. A suction device 110 and an oil mist separator 120 are provided in the suction path 100. The suction device 110 creates negative pressure in the crankcase 70 via the suction path 100. The oil mist separator 120 is disposed on the suction side (upstream side) of the suction device 110, and separates oil mist contained in the sucked blow-by gas.

[0048] The suction device 110 includes a blower 111, a motor 112, and a pressure gauge 113. The blower 111 is driven by the motor 112 and sucks the inside of the crankcase 70 to a negative pressure. The pressure gauge 113 measures the pressure inside the crankcase 70. The suction device 110 drives the blower 111 so that the measurement result of the pressure gauge 113 becomes a negative pressure (for example, −0.2 kPa).

[0049] According to the above configuration, by negatively suctioning the inside of the crankcase 70, it is possible to suppress leakage of blow-by gas to the outside of the engine body 2. In addition, by negatively suctioning the blow-by gas from inside each head cover 17 (gas retention portion 16A), it is possible to suppress retention of the blow-by gas inside each head cover 17. This ensures safety even if an operator opens the head cover 17 during maintenance.

[0050] The following configuration may also be adopted.

[0051] FIG. 6 is a schematic configuration diagram of an engine body 2 according to another embodiment. 6, the inside of the crankcase 70 is negatively suctioned from the main suction port 75, and a gas inlet port 92 is provided in each head cover 17. Gas is supplied to the gas inlet port 92 from a gas supply device 130.

[0052] A gas introduction pipe 93 is connected to each gas introduction port 92. A gas supply device 130 supplies gas to each gas introduction pipe 93 from a gas supply path 131. The gas is preferably a gas that does not react with the unburned ammonia contained in the blow-by gas, and may be air or an inert gas such as nitrogen. Examples of the gas supply device 130 include a fan, a blower, a compressor, and the like, and the gas supply device 130 may also be used in combination with another gas supply device (such as the compressor 22) inside the ship.

[0053] According to the above configuration, while negative pressure is applied to the crankcase 70 from the main suction port 75, gas is supplied to the inside of each head cover 17 (gas retention portion 16A) and the blow-by gas is expelled from the inside of the head cover 17, thereby making it possible to prevent the blow-by gas from retention in each head cover 17. This ensures safety even if an operator opens the head cover 17 during maintenance.

[0054] If the inside of the crankcase 70 can be constantly kept negative pressure by the suction device 110, it is sufficient to simply form the gas inlet 92 for taking in outside air in the head cover 17. In other words, the gas supply device 130 does not have to be provided. Also, in order to reliably prevent leakage of blow-by gas from the gas inlet 92, a check valve may be provided in the gas inlet pipe 93 connected to the gas inlet 92 or the gas supply path 131, and the end of the check valve may be opened to the atmosphere.

[0055] FIG. 7 is a diagram showing an exhaust system for exhaust gas and blow-by gas of the reciprocating engine 1 according to one embodiment. 7, a catalytic treatment device 60 is provided in the exhaust passage 30 through which exhaust gas is discharged from the engine body 2. A suction passage 100 that draws in the inside of the crankcase 70 branches into a first exhaust passage 101 and a second exhaust passage 102 upstream of the oil mist separator 120.

[0056] An oil mist separator 120 and a suction device 110 are provided in the first discharge path 101. The first discharge path 101 is connected to the upstream side of the catalytic treatment device 60 in the exhaust passage 30. The oil mist separator 120 includes a first separation section 121 and a second separation section 122, and includes a return flow path 124 that returns the oil separated in each separation section into the crankcase 70. A differential pressure gauge 123 is connected to the upstream side and downstream side of the oil mist separator 120. The differential pressure gauge 123 detects abnormalities such as clogging of the oil mist separator 120 by measuring the differential pressure between the upstream side and the downstream side of the oil mist separator 120.

[0057] The suction device 110 includes an inverter 114 in addition to a blower 111, a motor 112, and a pressure gauge 113. The inverter 114 drives the motor 112 based on the measurement result of the pressure gauge 113. The pressure inside the exhaust path 30 is, for example, 5 kPa. It is preferable that the pressure on the discharge side (downstream side) of the suction device 110 is set to a pressure that does not allow gas to flow back from the exhaust path 30. If backflow from the exhaust path 30 occurs, a check valve may be provided on the discharge side (downstream side) of the suction device 110.

[0058] A switching device 140 is provided at the branch point between the first exhaust path 101 and the second exhaust path 102. The switching device 140 switches the connection destination of the suction path 100 between the first exhaust path 101 and the second exhaust path 102. When the suction path 100 is connected to the first exhaust path 101, the blow-by gas in the crankcase 70 is sucked in by the suction device 110, introduced into the catalytic treatment device 60 of the exhaust passage 30, treated, and then released to the atmosphere. When the suction path 100 is connected to the second exhaust path 102, the blow-by gas in the crankcase 70 is released to the atmosphere as it is without being introduced into the exhaust passage 30 (catalytic treatment device 60) and treated.

[0059] FIG. 8 is a schematic diagram showing the destination of blow-by gas in the reciprocating engine 1 according to one embodiment. As shown in Fig. 8, the catalytic treatment device 60 includes a first treatment tank 61 for treating unburned ammonia (NH3) and nitrous oxide (N2O), and a second treatment tank 62 for treating nitrogen oxides (NOx). A flow path switching valve 34 is provided in the exhaust passage 30 upstream of the catalytic treatment device 60, and is capable of switching between a first exhaust path 30A connected to the first treatment tank 61 and a second exhaust path 30B connected to the second treatment tank 62. Reference numeral 103 in Fig. 8 denotes a check valve provided downstream of the suction device 110.

[0060] In the diesel operation mode, the exhaust passage 30 is normally connected to the second exhaust path 30B, and the exhaust gas (including nitrogen oxides) is introduced into the second treatment tank 62 for treatment. In the second treatment tank 62, the nitrogen oxides contained in the exhaust gas are subjected to reduction treatment. In addition, in the diesel operation mode, the suction path 100 that draws in the inside of the crankcase 70 is normally connected to the second exhaust path 102, and the blow-by gas is released to the atmosphere.

[0061] On the other hand, in the ammonia operation mode, the exhaust passage 30 is normally connected to the first exhaust path 30A, and the exhaust gas (including unburned ammonia and nitrous oxide) is introduced into the first treatment tank 61 for treatment. In the first treatment tank 61, the unburned ammonia acts as a reducing agent that removes oxygen from the nitrous oxide. When the generation rate of unburned ammonia is insufficient compared to the generation rate of nitrous oxide, the shortage of gaseous ammonia is injected into the first treatment tank 61 from the second ammonia supply passage 45 (see FIG. 1).

[0062] In the first treatment tank 61, nitrogen oxides are reduced by unburned ammonia, and the unburned ammonia is oxidized by oxygen in the exhaust gas to be rendered harmless. In the ammonia operation mode, the suction path 100 that normally draws in the crankcase 70 is connected to the first exhaust path 101, and the blow-by gas (containing unburned ammonia) is introduced into the exhaust passage 30 and treated in the first treatment tank 61.

[0063] In this way, the reciprocating engine 1 is provided with a first exhaust route F1 that connects the inside of the crankcase 70 to the exhaust passage 30 via the suction device 110, and a second exhaust route F2 that opens the inside of the crankcase 70 to the atmosphere without connecting it to the exhaust passage 30. The switching device 140 switches between the first exhaust route F1 and the second exhaust route F2 depending on the operating conditions of the reciprocating engine 1.

[0064] Typically, the switching device 140 switches to the first exhaust route F1 in the ammonia operation mode, and switches to the second exhaust route F2 in the diesel operation mode. Also, the switching device 140 switches between the first exhaust route F1 and the second exhaust route F2 depending on various conditions of the reciprocating engine 1.

[0065] FIG. 9 is a diagram showing the destinations of blow-by gas (mist) discharged in different situations in the reciprocating engine 1 according to one embodiment. 9, the switching device 140 switches the blow-by gas (mist) discharge destination to the first discharge route F1 or the second discharge route F2 under the conditions of No. 1 to No. 9. Note that the following No. 1 to No. 9 are merely examples.

[0066] <No.1> In the diesel operation mode (normal operation), the switching device 140 switches to the second exhaust route F2. In the diesel operation mode, the blow-by gas does not contain unburned ammonia (NH3: none), so the blow-by gas is caused to flow through the second exhaust route F2 and released to the atmosphere.

[0067] <No.2> In the ammonia operation mode (normal operation), the switching device 140 switches to the first exhaust route F1. In the ammonia operation mode, the blow-by gas contains unburned ammonia (NH3: present), so the blow-by gas is made to flow through the first exhaust route F1 and is detoxified by the catalytic treatment device 60 before being released to the atmosphere.

[0068] <No.3> Immediately after the diesel operation mode is stopped (normally), the switching device 140 maintains the switch to the second exhaust route F2. Since the blow-by gas immediately after the diesel operation mode is stopped does not contain unburned ammonia (NH3: no), the blow-by gas is caused to flow into the second exhaust route F2 and released to the atmosphere.

[0069] <No.4> Immediately after the ammonia operation mode is stopped in an emergency (in an emergency), the switching device 140 maintains the switch to the first discharge route F1 for several minutes. Also, it is preferable to drive the suction device 110 for several minutes immediately after the ammonia operation mode is stopped in an emergency. This allows the blow-by gas (NH3: present) remaining in the crankcase 70 to flow into the first discharge route F1 and be rendered harmless by the catalytic treatment device 60.

[0070] <No.5> When switching from the diesel operation mode to the ammonia operation mode (normal operation), the switching device 140 immediately switches from the second exhaust route F2 to the first exhaust route F1. In the ammonia operation mode, the blow-by gas contains unburned ammonia (NH3: present), so the blow-by gas is immediately caused to flow into the first exhaust route F1 and is rendered harmless by the catalytic treatment device 60.

[0071] <No.6> When switching from the ammonia operation mode to the diesel operation mode (normally), the switching device 140 switches from the first exhaust route F1 to the second exhaust route F2 after a certain time has elapsed since the switching. Even when the operation mode is switched from the ammonia operation mode to the diesel operation mode, blow-by gas (NH3: present) remains in the crankcase 70. Therefore, it is preferable to let the blow-by gas flow through the first exhaust route F1 for several minutes after the switching and to make it harmless in the catalytic treatment device 60.

[0072] <No.7> In the ammonia operation mode, when the pressure difference measured by the differential pressure gauge 123 (see FIG. 7) of the oil mist separator 120 rises (emergency), the switching device 140 maintains the switch to the first exhaust route F1. This allows the blow-by gas (NH3: present) remaining in the crankcase 70 to flow into the first exhaust route F1 and be rendered harmless by the catalytic treatment device 60. It is also advisable to issue an alarm and render the blow-by gas harmless by the catalytic treatment device 60 for several minutes, and then replace the parts of the oil mist separator 120.

[0073] <No.8> In the ammonia operation mode, when a failure of the suction device 110 (blower 111) is detected and the operation mode is switched to the diesel operation mode (emergency), the switching device 140 immediately switches from the first discharge route F1 to the second discharge route F2. This is because the first discharge route F1 cannot be used when the suction device 110 fails.

[0074] <No.9> In the ammonia operation mode, when ammonia leaks from the engine body 2 or the internal pressure of the engine body 2 rises, the switching device 140 switches from the first exhaust route F1 to the second exhaust route F2 after a certain time has passed since the switching. Even when the ammonia operation mode is switched to the diesel operation mode, blow-by gas (NH3: present) remains in the crankcase 70. Therefore, it is preferable to let the blow-by gas flow through the first exhaust route F1 for several minutes after the switching and to make it harmless with the catalytic treatment device 60.

[0075] As described above, the reciprocating engine 1 according to this embodiment is a reciprocating engine 1 that uses ammonia as fuel, and includes a cylinder 11 that forms a combustion chamber 10, an exhaust passage 30 through which exhaust gas is discharged from the combustion chamber 10, an exhaust treatment device (catalytic treatment device 60) that is provided in the exhaust passage 30 and treats unburned ammonia, a piston 12 that reciprocates in the cylinder 11, a crank 13 connected to the piston 12, a crankcase 70 that houses the crank 13 and into which blow-by gas flows from the combustion chamber 10, and a suction device 110 that negatively sucks the inside of the crankcase 70, and the unburned ammonia contained in the blow-by gas sucked from the crankcase 70 by the suction device 110 is treated by the exhaust treatment device (catalytic treatment device 60). According to this configuration, since the inside of the crankcase 70 can be negatively sucked, retention of ammonia in the reciprocating engine 1 and leakage to the surroundings of the reciprocating engine 1 can be suppressed, and the safety of the reciprocating engine 1 that uses ammonia as fuel can be improved. As the exhaust gas treatment device, in addition to the catalytic treatment device 60, a scrubber or the like can also be used.

[0076] In this embodiment, the exhaust treatment device is a catalytic treatment device 60 that treats unburned ammonia using a catalyst. By using the catalytic treatment device 60, unburned ammonia can be effectively treated without the need for wash water or waste liquid treatment.

[0077] In this embodiment, the suction device 110 includes a pressure gauge 113 for measuring the pressure inside the crankcase 70, and a blower 111 for sucking the inside of the crankcase 70 to a negative pressure and pressurizing the sucked gas and sending it to the exhaust path 30, and the blower 111 is driven so that the measurement result of the pressure gauge 113 becomes a predetermined negative pressure value. With this configuration, even if there is a fluctuation in the pressure in the exhaust path 30, the blower 111 is driven so as to maintain the inside of the crankcase 70 at the predetermined negative pressure value accordingly. It is desirable that this predetermined negative pressure value be a negative pressure value as close to 0 as possible while maintaining the inside of the crankcase 70 at a negative pressure, and can be set preferably in the range of 0 kPa > predetermined value ≧ -0.25 kPa.

[0078] In this embodiment, the suction device 110 negatively suctions the inside of the crankcase 70 through a suction port 90 provided in the gas retention section 16A that communicates with the inside of the crankcase 70. This configuration makes it possible to prevent the blow-by gas from being retained in the gas retention section 16A.

[0079] In this embodiment, the gas retention portion 16A is formed in the cylinder head 16. According to this configuration, the blow-by gas is sucked under negative pressure from inside the head cover 17 of the cylinder head 16 (gas retention portion 16A), thereby preventing the blow-by gas from being retained inside the head cover 17, and safety can be ensured even if an operator opens the head cover 17 during maintenance.

[0080] In this embodiment, a gas inlet 92 is provided in gas retention section 16A communicating with the inside of crankcase 70, and suction device 110 negatively suctions the inside of crankcase 70 via main suction port 75 provided in a location other than gas retention section 16A where gas inlet 92 is provided. With this configuration, outside air is introduced into head cover 17 (gas retention section 16A) and blow-by gas is expelled from inside head cover 17, thereby making it possible to prevent blow-by gas from accumulating in head cover 17.

[0081] Moreover, in this embodiment, a gas supply device 130 is provided that supplies gas to the gas retention portion 16A from the gas inlet 92. According to this configuration, gas is actively introduced into the head cover 17 (gas retention portion 16A) and blow-by gas is expelled from inside the head cover 17, thereby making it possible to suppress retention of blow-by gas inside the head cover 17.

[0082] In this embodiment, the engine is provided with a first exhaust route F1 that connects the inside of the crankcase 70 to the exhaust passage 30 via the suction device 110, a second exhaust route F2 that opens the inside of the crankcase 70 to the atmosphere without connecting it to the exhaust passage 30, and a switching device 140 that switches between the first exhaust route F1 and the second exhaust route F2 depending on the operating condition of the reciprocating engine 1. With this configuration, the exhaust route of the blow-by gas can be switched depending on the presence or absence of unburned ammonia contained in the blow-by gas.

[0083] In this embodiment, the reciprocating engine 1 can be switched between an ammonia operation mode (first operation mode) in which the fuel used contains ammonia and a diesel operation mode (second operation mode) in which fuel other than ammonia, such as heavy oil, is used, and the switching device 140 switches to the first exhaust route F1 in the ammonia operation mode and switches to the second exhaust route F2 in the diesel operation mode. In the ammonia operation mode, the blow-by gas contains unburned ammonia, so the blow-by gas can be made to flow through the first exhaust route F1 and released to the atmosphere after being rendered harmless by the catalytic treatment device 60. In the diesel operation mode, the blow-by gas does not contain unburned ammonia, so the blow-by gas can be made to flow through the second exhaust route F2 and released to the atmosphere.

[0084] In this embodiment, the switching device 140 switches from the first exhaust route F1 to the second exhaust route F2 a certain time after the ammonia operation mode is switched to the diesel operation mode. According to this configuration, even when the ammonia operation mode is switched to the diesel operation mode, blow-by gas remains in the crankcase 70. Therefore, the blow-by gas can be rendered harmless by the catalytic treatment device 60 by flowing it through the first exhaust route F1 for several minutes after the switching.

[0085] In this embodiment, the switching device 140 immediately switches from the second exhaust route F2 to the first exhaust route F1 when the diesel operation mode is switched to the ammonia operation mode. According to this configuration, since the blow-by gas contains unburned ammonia in the ammonia operation mode, the blow-by gas is immediately caused to flow into the first exhaust route F1 and can be rendered harmless by the catalytic treatment device 60.

[0086] In this embodiment, an oil mist separator 120 is provided on the suction side of the suction device 110. With this configuration, the oil mist contained in the blow-by gas can be separated, and the suction device 110 can be protected.

[0087] While preferred embodiments of the present invention have been described and illustrated, it should be understood that they are illustrative of the present invention and should not be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Although a four-stroke engine has been described as a preferred embodiment, the same principles apply to a two-stroke engine. Thus, the present invention should not be considered as limited by the foregoing description, but rather by the scope of the appended claims.

[0088] 6, for example, the gas inlet port 92 is provided in each of the gas retention sections 16A of the six cylinders 11, but, for example, five of the six gas retention sections 16A may be provided with the gas inlet port 92 and one gas retention section 16A may be provided with the suction port 90. In other words, it is sufficient for the suction device 110 to be able to negatively suck the inside of the crankcase 70 via the suction port 90 provided in a location other than the gas retention section 16A in which the gas inlet port 92 is provided.

[0089] Furthermore, for example, the above embodiment has been described assuming the use of the suction device 110, but a configuration without the suction device 110 may also be adopted. That is, the form shown in the appendix may be adopted. <Additional Notes> A reciprocating engine that uses ammonia as fuel, A cylinder forming a combustion chamber; an exhaust passage through which exhaust gas is discharged from the combustion chamber; a catalytic treatment device provided in the exhaust passage for treating unburned ammonia using a catalyst; A piston that reciprocates within the cylinder; a crank connected to the piston; a crankcase that houses the crank and into which blow-by gas flows from the combustion chamber; a first exhaust route connecting the inside of the crankcase with the exhaust passage; a second exhaust route that is not connected to the exhaust passage and is open to the atmosphere; A switching device that switches between the first exhaust route and the second exhaust route depending on an operating condition of the reciprocating engine. Reciprocating engine. [Explanation of symbols]

[0090] 1 Reciprocating engine 2 Engine body 3. Control device 4. Turbocharger 10 Combustion chamber 11 Cylinders 12 Piston 13. Crank 13a Connecting rod 14 Rotation detection sensor 15 Torque detection sensor 16 Cylinder head 16A Gas retention section 17 Head Cover 20 Intake passage 21 Intake valve 22 Compressor 23 Air cooler 24 Air heating device 25 Cooling and heating system 30 Exhaust duct 30a Exhaust passage 30A First exhaust route 30B Second exhaust route 31 Exhaust valve 33 Turbine 34 Flow path switching valve 40 Ammonia fuel supply device 41 Ammonia Tank 42 Vaporizer 43 Fuel gas injection valve 44 Ammonia supply line 44a regulator 44b Pressure sensor 45 Ammonia second supply line 45a regulator 45b Pressure sensor 50 Liquid auxiliary fuel supply system 51 Liquid Auxiliary Fuel Tank 52 No. 1 liquid fuel supply pump 53 Liquid fuel injection valve 54 No. 2 liquid fuel supply pump 55 Ignition device 60 Catalyst treatment device (exhaust treatment device) 60a Detection sensor 61 First treatment tank 62 Second treatment tank 70 Crankcase 71 Oil pan 72 Crankcase 73 Cam chamber 74 Through hole 75 Main suction port 80 Cam mechanism 81 Cam 82 Tappet roller mechanism 83 Push rod 84 Rocker arm 85 Valve spring 90 Suction port 91 Suction tube 92 Gas inlet 93 Gas introduction pipe 100 Suction Path 101 First Discharge Path 102 Secondary Discharge Path 103 sign 110 Suction device 111 Blower 112 Motor 113 Pressure Gauge 114 Inverter 120 Oil Mist Separator 121 1st separation section 122 2nd separation section 123 Differential pressure gauge 124 Return Channel 130 Gas supply equipment 131 Gas supply route 140 Switching Device F1 First Emission Route F2 Secondary Emission Route

Claims

1. A reciprocating engine that uses ammonia as fuel, A cylinder forming a combustion chamber; an exhaust passage through which exhaust gas is discharged from the combustion chamber; an exhaust gas treatment device provided in the exhaust passage for treating unburned ammonia; A piston that reciprocates within the cylinder; a crank connected to the piston; a crankcase that houses the crank and into which blow-by gas flows from the combustion chamber; a suction device that creates a negative pressure inside the crankcase, unburned ammonia contained in the blow-by gas sucked from the crankcase by the suction device is treated by the exhaust treatment device. Reciprocating engine.

2. The exhaust treatment device is a catalytic treatment device that treats unburned ammonia using a catalyst.

2. The reciprocating engine according to claim 1.

3. The suction device includes a pressure gauge that measures the pressure inside the crankcase, and a blower that draws the inside of the crankcase to a negative pressure and pressurizes the drawn gas and sends it to the exhaust path, and the blower is driven so that the measurement result of the pressure gauge becomes a predetermined negative pressure value.

3. The reciprocating engine according to claim 2.

4. The suction device suctions the inside of the crankcase to create a negative pressure through a suction port provided in a gas retention section communicating with the inside of the crankcase.

4. The reciprocating engine according to claim 3.

5. The gas retention portion is formed in a cylinder head.

5. The reciprocating engine according to claim 4.

6. A gas inlet port is provided in the gas retention section communicating with the inside of the crankcase, The suction device suctions the inside of the crankcase to create a negative pressure through a suction port provided at a location other than the gas retention portion in which the gas inlet port is provided.

4. The reciprocating engine according to claim 3.

7. a gas supply device for supplying gas from the gas inlet to the gas retention section, 7. The reciprocating engine according to claim 6.

8. a first exhaust route that connects the inside of the crankcase to the exhaust passage via the suction device; a second exhaust route that is not connected to the exhaust passage and is open to the atmosphere; a switching device that switches between the first exhaust route and the second exhaust route depending on an operating condition of the reciprocating engine, A reciprocating engine according to any one of claims 1 to 7.

9. The reciprocating engine is switchable between a first operation mode in which a fuel containing ammonia is used and a second operation mode in which a fuel other than ammonia is used; The switching device is When in the first operating mode, switching to the first discharge route; When in the second operating mode, the discharge route is switched to the second discharge route.

9. The reciprocating engine according to claim 8.

10. the switching device switches from the first discharge route to the second discharge route after a certain time has elapsed since the first operation mode was switched to the second operation mode, 10. The reciprocating engine according to claim 9.

11. the switching device immediately switches from the second discharge route to the first discharge route when the operation mode is switched from the second operation mode to the first operation mode.

10. The reciprocating engine according to claim 9.

12. An oil mist separator is provided on the suction side of the suction device. A reciprocating engine according to any one of claims 1 to 7.

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