Engine system, ship, and method for controlling engine system

Abstract

To suppress deterioration of a methane oxidation catalyst.SOLUTION: An engine system comprises: an engine that is driven using, as fuel, methane fuel containing methane; a turbocharger that is driven by exhaust gas discharged from an exhaust part of the engine, and supplies air to the engine; a discharge pipe through which the exhaust gas discharged from the turbocharger flows; an oxidation treatment part into which the exhaust gas is introduced through the discharge pipe, and in which a methane oxidation catalyst is received; a turbocharger bypass pipe that causes the exhaust gas discharged from the exhaust part to bypass the turbocharger and join the discharge pipe; an exhaust bypass valve that is provided in the turbocharger bypass pipe and can be opened and closed; and a control device that performs control of switching the exhaust bypass valve from a closed state to an open state when the load on the engine is decreased.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an engine system, a ship, and a method for controlling an engine system. [Background technology]

[0002] Methane oxidation catalysts that oxidize methane contained in engine exhaust gas are known. In engine systems equipped with a turbocharger, such methane oxidation catalysts are often disposed downstream of the turbocharger in the exhaust gas discharge direction.

[0003] Patent Document 1 discloses an engine system (reciprocating piston internal combustion engine) that includes an engine, a supercharger (exhaust gas turbocharger), and a methane oxidation catalyst (catalytic converter). The supercharger is driven by exhaust gas from the engine and supplies air to the engine. A line equipped with the methane oxidation catalyst is provided between the engine and the supercharger. Exhaust gas from the engine is passed through the line equipped with the methane oxidation catalyst. The methane oxidation catalyst oxidizes methane contained in the exhaust gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-214970 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when methane is used as the fuel for an engine, fuel oil is supplied to the combustion chamber of the engine together with the methane in order to improve the ignition ability of the fuel. Therefore, even when methane is used as the fuel, the exhaust gas from the engine contains sulfur. In an engine with such a configuration, when the load decreases, the temperature of the exhaust gas sent to the catalyst may decrease. When the temperature of the exhaust gas sent to the catalyst decreases, the moisture contained in the exhaust gas condenses, and the water containing sulfur adheres to the catalyst surface, which causes the methane oxidation catalyst to deteriorate.

[0006] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide an engine system, a ship, and a control method for an engine system that can suppress deterioration of a methane oxidation catalyst. [Means for solving the problem]

[0007] In order to solve the above problems, an engine system according to the present disclosure includes an engine, a turbocharger, an exhaust pipe, an oxidation treatment unit, a turbocharger bypass pipe, an exhaust bypass valve, and a control device. The engine is driven by a methane fuel containing methane as a main fuel. The turbocharger is driven by exhaust gas discharged from an exhaust unit of the engine to supply air to the engine. The exhaust gas discharged from the turbocharger flows through the exhaust pipe. The oxidation treatment unit receives the exhaust gas via the exhaust pipe and contains a methane oxidation catalyst. The turbocharger bypass pipe causes the exhaust gas discharged from the exhaust unit to merge with the exhaust pipe, bypassing the turbocharger. The exhaust bypass valve is provided in the turbocharger bypass pipe and is capable of being opened and closed. The control device controls the exhaust bypass valve to be switched from a closed state to an open state when the load on the engine decreases.

[0008] The engine system according to the present disclosure includes an engine, a turbocharger, an exhaust pipe, an oxidation treatment unit, and a temperature-raising gas supply unit. The engine is driven by a methane fuel containing methane. The turbocharger supplies air to the engine by being driven by exhaust gas discharged from an exhaust unit of the engine. The exhaust gas discharged from the turbocharger flows through the exhaust pipe. The oxidation treatment unit receives the exhaust gas via the exhaust pipe and contains a methane oxidation catalyst. The temperature-raising gas supply unit is connected to the exhaust pipe and supplies gas that raises the temperature of the methane oxidation catalyst of the oxidation treatment unit from the outside into the exhaust pipe.

[0009] A vessel according to the present disclosure is equipped with the engine system described above.

[0010] The control method for an engine system according to the present disclosure is a control method for an engine system as described above, and includes the steps of driving the engine, increasing the temperature of the exhaust gas, and stopping the engine. In the step of driving the engine, the exhaust bypass valve is closed and the engine is driven using methane fuel containing methane as fuel. In the step of increasing the temperature of the exhaust gas, when the load of the engine decreases, the exhaust bypass valve is switched from a closed state to an open state, and the temperature of the exhaust gas introduced from the exhaust pipe to the oxidation treatment unit is increased. In the step of stopping the engine, the engine is stopped after increasing the temperature of the exhaust gas. Effect of the Invention

[0011] According to the engine system, ship, and engine system control method disclosed herein, deterioration of the methane oxidation catalyst can be suppressed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a side view of a vessel including an engine system according to an embodiment of the present disclosure. [Diagram 2]1 is a diagram showing a configuration of an engine system according to a first embodiment of the present disclosure. FIG. [Diagram 3] FIG. 2 is a diagram illustrating a hardware configuration of a control device according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is a functional block diagram of a control device according to an embodiment of the present disclosure. [Diagram 5] 4 is a flowchart illustrating the procedure of a control method for an engine system according to an embodiment of the present disclosure. [Figure 6] FIG. 4 is a diagram showing changes in engine load when operating an engine system according to an embodiment of the present disclosure. [Figure 7] FIG. 2 is a diagram showing a flow of exhaust gas when fuel oil is used as fuel in the engine system according to the first embodiment of the present disclosure. [Figure 8] 2 is a diagram showing a flow of exhaust gas in an engine system according to a first embodiment of the present disclosure, when a methane fuel containing methane is used as fuel and the exhaust gas is introduced into an oxidation treatment unit. FIG. [Figure 9] 4 is a diagram showing a flow of exhaust gas when the temperature of exhaust gas introduced into an oxidation treatment unit is increased in the engine system according to the first embodiment of the present disclosure. FIG. [Figure 10] FIG. 4 is a diagram showing a configuration of an engine system according to a second embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram showing a flow of exhaust gas when the temperature of exhaust gas introduced into an oxidation treatment unit is increased in an engine system according to a second embodiment of the present disclosure. [Figure 12] FIG. 11 is a diagram showing a configuration of an engine system according to a modified example of the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First Embodiment Hereinafter, an engine system, a ship, and a control method for an engine system according to an embodiment of the present disclosure will be described with reference to FIGS. (Vessel configuration) 1, the ship 1 of the first embodiment includes at least a hull 2 ​​and an engine system 10A. Examples of the type of ship 1 include a bulk carrier, a carrier for liquefied gases such as liquefied natural gas (LNG), carbon dioxide, and ammonia, a ferry, a roll-on / roll-off ship (RO-RO ship), a pure car & truck carrier (PCTC), and a passenger ship.

[0014] (Hull configuration) The hull 2 ​​has a pair of side walls 3A, 3B, a bottom wall 4, an upper deck 5, and a bottom deck 6, which form the outer hull of the hull. The side walls 3A, 3B have a pair of side wall shells forming the starboard and port sides, respectively. The bottom wall 4 has a bottom shell plate connecting the side walls 3A, 3B. The upper deck 5 illustrated in this first embodiment is a full deck exposed to the outside. The bottom deck 6 is provided inside the hull 2 ​​and forms a double bottom together with the bottom shell plate. The hull 2 ​​has a superstructure 7 having an accommodation area formed on the upper deck 5, for example, on the stern 2b side. The position and size of the superstructure 7 can be changed as appropriate.

[0015] (Engine system configuration) FIG. 2 is a diagram showing a configuration of the engine system according to the first embodiment of the present disclosure. The engine system 10A is provided within the hull 2. As shown in FIG. 2, the engine system 10A includes at least an engine 20, a turbocharger 30, an oxidation treatment unit 40, a turbocharger bypass pipe 103, a control device 60, and an engine control device 80.

[0016] The engine 20 is provided on the bottom deck 6 inside the hull 2. Examples of the engine 20 include a main engine that generates driving force to propel the hull 2, and an engine that drives a generator that supplies power to the inside of the hull 2. The engine 20 is driven by burning fuel. The engine 20 emits exhaust gas generated by burning fuel. The engine 20 used in this first embodiment is capable of switching between methane fuel containing methane and fuel oil as fuel. Examples of methane fuel containing methane include a mixture of methane mainly and a small amount of oil fuel. Examples of fuel oil include heavy oil such as heavy oil A and heavy oil C, and diesel fuel.

[0017] The engine 20 includes an engine body 21 and an exhaust section 22. The engine body 21 has, for example, a plurality of cylinders (not shown). Fuel is introduced from the outside into each cylinder of the engine body 21 via a fuel supply section 27. The fuel supply section 27 has a methane supply system 27a that supplies methane fuel as fuel, and a fuel oil supply system 27b that supplies fuel oil as fuel. The fuel supply section 27 is capable of adjusting the amount of fuel supplied by the methane supply system 27a and the amount of fuel supplied by the fuel oil supply system 27b based on the control of the engine control device 80. The fuel introduced into the engine body 21 is mixed with air and combusted in each cylinder of the engine body 21. This combustion drives the engine body 21. Exhaust gas generated by driving the engine body 21 is discharged to the outside via the exhaust section 22.

[0018] The exhaust section 22 discharges exhaust gas from each cylinder of the engine body 21 to the turbocharger 30 and the oxidation treatment section 40. The exhaust section 22 includes a connecting pipe 23 and a manifold 24. The connecting pipes 23 are provided corresponding to each of the multiple cylinders. Each connecting pipe 23 connects an exhaust port (not shown) of each cylinder to the manifold 24. Exhaust gas flows into the manifold 24 from the multiple connecting pipes 23. The manifold 24 collects the exhaust gas discharged from the multiple connecting pipes 23 and sends it to the turbocharger 30 and the oxidation treatment section 40.

[0019] The turbocharger 30 is connected to an end of the manifold 24 on the downstream side in the flow direction of the exhaust gas. The exhaust gas flowing through the manifold 24 is introduced into the turbocharger 30. The turbocharger 30 has a compressor (not shown) that supplies air to the engine 20, and an exhaust turbine (not shown). The exhaust turbine (not shown) of the turbocharger 30 is driven by the exhaust gas discharged from the exhaust section 22, and drives the compressor (not shown). The exhaust gas that has passed through the turbocharger 30 is discharged to an exhaust pipe 102.

[0020] The discharge pipe 102 forms a flow path that guides the exhaust gas discharged from the turbocharger 30 to the oxidation treatment unit 40. That is, the exhaust gas discharged from the turbocharger 30 flows through the discharge pipe 102. One end of the discharge pipe 102 is connected to a discharge port (not shown) of the turbocharger 30. The other end of the discharge pipe 102 is connected to the oxidation treatment unit 40. The discharge pipe 102 of this embodiment is provided with a temperature sensor 102s that detects the temperature of the exhaust gas flowing through the discharge pipe 102.

[0021] The oxidation treatment unit 40 performs a process of oxidizing methane contained in the exhaust gas. The exhaust gas is introduced into the oxidation treatment unit 40 via an exhaust pipe 102. The oxidation treatment unit 40 has a housing 41 and a methane oxidation catalyst 42.

[0022] The housing 41 forms the outer shell of the oxidation treatment unit 40. The other end of the exhaust pipe 102 is connected to the lower end of the housing 41. Meanwhile, an exhaust duct 43 is connected to the upper end of the housing 41. The exhaust duct 43 leads to a funnel 9 shown in FIG. 1. The funnel 9 is provided on the upper deck 5 on the stern 2b side of the hull 2, has a cylindrical shape extending in the vertical direction Dv, and extends so as to protrude upward from the upper deck 5.

[0023] 2, the methane oxidation catalyst 42 is accommodated in a housing 41. The methane oxidation catalyst 42 oxidizes unburned methane contained in the exhaust gas. The methane oxidation catalyst 42 includes, for example, a catalyst support and an active component made of catalytic metal particles fixed to the catalyst support.

[0024] The turbocharger bypass pipe 103 allows a portion of the exhaust gas discharged from the exhaust section 22 to bypass the turbocharger 30 and merge with the discharge pipe 102. A first end 103a of the turbocharger bypass pipe 103 is connected to the exhaust section 22. The first end 103a is connected to the manifold 24 of the exhaust section 22 downstream in the flow direction of the exhaust gas from a position where the multiple connection pipes 23 are connected to the manifold 24. A second end 103b of the turbocharger bypass pipe 103 is connected to the discharge pipe 102.

[0025] The turbocharger bypass pipe 103 is provided with an exhaust bypass valve 104. The exhaust bypass valve 104 opens and closes the flow path of exhaust gas from the exhaust section 22 to the turbocharger bypass pipe 103.

[0026] The engine system 10A further includes an oxidation treatment unit bypass pipe 105 and a switching unit 110. The oxidation treatment unit bypass pipe 105 forms a flow path for exhaust gas that bypasses the oxidation treatment unit 40. One end of the oxidation treatment unit bypass pipe 105 branches off from the exhaust pipe 102. The other end of the oxidation treatment unit bypass pipe 105 merges with the exhaust duct 43.

[0027] The switching unit 110 switches the introduction destination of the exhaust gas discharged from the turbocharger 30 between the discharge pipe 102 and the oxidation treatment unit bypass pipe 105. The switching unit 110 has a first switching valve 111 and a second switching valve 112. The first switching valve 111 is disposed in the discharge pipe 102 between a portion to which one end of the oxidation treatment unit bypass pipe 105 is connected and the oxidation treatment unit 40. The second switching valve 112 is provided in the oxidation treatment unit bypass pipe 105. The first switching valve 111 and the second switching valve 112 may be opened and closed by remote control or the like. In addition to the first switching valve 111, a switching valve may be provided downstream of the oxidation treatment unit 40.

[0028] (Hardware configuration diagram) FIG. 3 is a diagram illustrating a hardware configuration of the control device according to the embodiment of the present disclosure. 3, the control device 60 is a computer including a CPU 61 (Central Processing Unit), a ROM 62 (Read Only Memory), a RAM 63 (Random Access Memory), a storage 64 including an HDD (Hard Disk Drive), and a signal transmission / reception module 65. The signal transmission / reception module 65 receives a detection signal of the load (revolutions per minute, etc.) of the engine body 21 output from the engine body 21, and a detection signal of the temperature of the exhaust gas output from the temperature sensor 102s.

[0029] (Function block diagram) FIG. 4 is a functional block diagram of a control device according to an embodiment of the present disclosure. As shown in FIG. 4, the CPU 61 of the control device 60 executes a program previously stored in the RAM 63, storage 64, etc., thereby realizing the functional configurations of a signal input section 70, an operation command receiving section 71, a valve control section 72, and an output section 73. The signal input unit 70 receives detection signals from the engine control device 80 and the temperature sensor 102s via the signal transmitting / receiving module 65.

[0030] The operation command receiving unit 71 receives an operation command from an operator of the engine system 10A. An example of the input of the operation command from the operator is an operation input from a command input means (not shown) such as an operation button. Based on the operation command received by the operation command receiving unit 71, the valve control unit 72 controls the exhaust bypass valve 104, the first switching valve 111, and the second switching valve 112, as will be described in detail later. The output unit 73 outputs control signals for controlling each of the exhaust bypass valve 104, the first switching valve 111, and the second switching valve 112 to the exhaust bypass valve 104, the first switching valve 111, and the second switching valve 112 via the signal transmission / reception module 65.

[0031] (Engine system control method procedure) FIG. 5 is a flowchart showing the procedure of a control method for an engine system according to an embodiment of the present disclosure. As shown in FIG. 5, the control method S10 of the engine system according to this embodiment includes step S11 of starting the engine, step S12 of switching the fuel from fuel oil to methane fuel, step S13 of raising the temperature of the exhaust pipe, step S14 of operating the engine normally, step S15 of starting a process to stop the engine, step S16 of raising the temperature of the exhaust gas introduced into the oxidation treatment unit, step S17 of switching the fuel from methane fuel to fuel oil, and step S18 of stopping the engine.

[0032] Fig. 6 is a diagram showing a change in engine load when the engine system according to the embodiment of the present disclosure is operated. Fig. 7 is a diagram showing a flow of exhaust gas when fuel oil is used as fuel in the engine system according to the first embodiment of the present disclosure. When an operator operates a predetermined command input means (for example, a start button) to start the engine system 10A, the operation command receiving unit 71 receives the input of a command to start the engine 20 (engine body 21). When the control device 60 and the engine control device 80 receive the input of the start command, they execute step S11 to start the engine (timing T1 in FIG. 6). In step S11 to start the engine, as shown in FIG. 7, first, the valve control unit 72 performs control to close the exhaust bypass valve 104 and the first switching valve 111 and to open the second switching valve 112. Thereafter, the engine control device 80 performs control to start the engine 20.

[0033] At the start of the engine system 10A, fuel oil is supplied to the engine 20 as fuel through the fuel oil supply system 27b of the fuel supply unit 27. Exhaust gas discharged from the exhaust unit 22 of the engine 20 is introduced into the turbocharger 30 from the manifold 24 of the exhaust unit 22. The turbocharger 30 is driven by the exhaust gas introduced into the turbocharger 30, and air is supplied to the engine 20. The exhaust gas discharged from the turbocharger 30 flows from the exhaust pipe 102 into the oxidation treatment unit bypass pipe 105, bypasses the oxidation treatment unit 40, and is released into the atmosphere from the funnel 9 through the exhaust duct 43. This prevents exhaust gas containing sulfur from flowing into the oxidation treatment unit 40 by burning fuel oil as fuel. Thereafter, when the load (revolutions per minute) of the engine 20 reaches a preset load (timing T2 in FIG. 6), the load is maintained until the load of the engine 20 becomes stable (timing T3 in FIG. 6).

[0034] After the load of the engine 20 has stabilized, step S12 is executed to switch the fuel from fuel oil to methane fuel. In step S12 to switch the fuel from fuel oil to methane fuel, the load of the engine 20 is increased to or above a preset threshold value (timing T3 to T4 in FIG. 6). The threshold value set here is set to a lower limit value of the load at which the engine 20 operates stably when methane fuel is supplied as the fuel. When the load of the engine 20 reaches or exceeds a threshold value, the fuel supplied to the engine 20 is switched from fuel oil to methane fuel (timing T4 to T5 in FIG. 6). To achieve this, methane fuel is supplied as fuel to the engine 20 via the methane supply system 27a of the fuel supply unit 27. Note that even after the fuel supplied to the engine 20 is switched from fuel oil to methane fuel, the supply of a small amount of fuel oil as pilot oil is maintained.

[0035] In step S13 for increasing the temperature of the exhaust pipe, the fuel supplied to the engine 20 is switched from fuel oil to methane fuel, and then the temperature of the exhaust gas flowing through the exhaust pipe 102 is increased to a preset lower limit temperature or higher (timings T5 to T6 in FIG. 6). To achieve this, the load of the engine 20 is maintained until the temperature of the exhaust gas increases to a preset lower limit temperature or higher while the control device 60 monitors the temperature of the exhaust gas flowing through the exhaust pipe 102 detected by the temperature sensor 102s. Also, in step S13, the temperature of the exhaust pipe 102 may be increased until it is determined that the exhaust gas has been sufficiently replaced with that derived from dual combustion.

[0036] FIG. 8 is a diagram showing the flow of exhaust gas in the engine system according to the first embodiment of the present disclosure, when methane fuel is used as the fuel and the exhaust gas is introduced into the oxidation treatment unit. After completion of step S13, the valve control unit 72 performs control to open the first switching valve 111 and close the second switching valve 112 and the exhaust bypass valve 104, as shown in Fig. 8. As a result, the introduction destination of the exhaust gas discharged from the turbocharger 30 is switched from the oxidation treatment unit bypass pipe 105 to the exhaust pipe 102. The exhaust gas discharged from the turbocharger 30 is introduced from the exhaust pipe 102 to the oxidation treatment unit 40. In the oxidation treatment unit 40, the methane oxidation catalyst 42 oxidizes the unburned methane contained in the introduced exhaust gas. As a result, the exhaust gas with a sufficiently increased temperature is introduced into the oxidation treatment unit 40. The exhaust gas that has passed through the oxidation treatment unit 40 is discharged into the atmosphere from the funnel 9 through the exhaust duct 43.

[0037] Thereafter, in step S14 where the engine is operated normally, the engine system 10A performs normal operation while adjusting the load on the engine 20 as necessary (timings T6 to T7 in FIG. 6). Note that the adjustment of the load on the engine 20 may be performed automatically under the control of the engine control device 80, or may be appropriately performed by an operator.

[0038] To stop the engine system 10A after the normal operation of the engine system 10A, the operator operates a predetermined command input means (e.g., a stop button). Then, the operation command receiving unit 71 of the control device 60 receives the input of a command to stop the engine 20 (engine body 21). In step S15 for starting the process to stop the engine, the control device 60 and the engine control device 80 start the process to stop the engine 20 based on the input of the stop command. Specifically, in step S15 for starting the process to stop the engine, the engine control device 80 reduces the load on the engine 20 (timing T7 to T8 in FIG. 6). When the load on the engine 20 is reduced, the temperature of the exhaust gas introduced into the oxidation treatment device 40 also decreases.

[0039] FIG. 9 is a diagram showing the flow of exhaust gas when the temperature of the exhaust gas introduced into the oxidation treatment unit is increased in the engine system according to the first embodiment of the present disclosure. In step S16 for raising the temperature of the exhaust gas introduced into the oxidation treatment unit, the valve control unit 72 controls the exhaust bypass valve 104 to switch from an open state to a closed state (timing T9 to T10 in FIG. 6). To this end, the valve control unit 72 controls the exhaust bypass valve 104 and the first switching valve 111 to be open, and the second switching valve 112 to be closed, as shown in FIG.

[0040] Then, a portion of the exhaust gas discharged from the exhaust section 22 of the engine 20 flows from the manifold 24 into the turbocharger bypass pipe 103. The exhaust gas that has flowed into the turbocharger bypass pipe 103 flows into the exhaust pipe 102. The exhaust gas flowing from the turbocharger bypass pipe 103 into the exhaust pipe 102 is at a higher temperature than the exhaust gas that has passed through the turbocharger 30 because it has not done any work in the turbocharger 30. Therefore, by introducing the exhaust gas that has flowed from the turbocharger bypass pipe 103 into the exhaust pipe 102 into the oxidation treatment unit 40, the temperature of the exhaust gas in the exhaust pipe 102, which has decreased with the decrease in the load of the engine 20, increases. This increases the temperature of the methane oxidation catalyst 42, and suppresses the condensation of moisture contained in the exhaust gas. In addition, if the temperature of the methane oxidation catalyst 42 is increased to a temperature equal to or higher than a preset reference temperature, the sulfur content adhering to the surface of the methane oxidation catalyst 42 can be burned off. Such step S16 of increasing the temperature of the methane oxidation catalyst 42 is continued for a predetermined time or more. Moreover, step S16 of increasing the temperature of the methane oxidation catalyst 42 may be continued until the temperature of the methane oxidation catalyst 42 becomes equal to or higher than a predetermined reference temperature.

[0041] After completing step S16 of increasing the temperature of the exhaust gas introduced into the oxidation treatment unit, in order to further reduce the load on the engine 20, step S17 of switching the fuel from methane fuel to fuel oil is executed (timing T10 to T11 in FIG. 6). In step S17 of switching the fuel from methane fuel to fuel oil, the valve control unit 72 performs control to close the exhaust bypass valve 104 and the first switching valve 111 and open the second switching valve 112, as shown in FIG. 7. As a result, the exhaust gas discharged from the turbocharger 30 flows from the exhaust pipe 102 into the oxidation treatment unit bypass pipe 105, bypasses the oxidation treatment unit 40, and is released into the atmosphere from the funnel 9 through the exhaust duct 43. Next, the fuel supplied to the engine 20 is switched from methane fuel to fuel oil. To do this, fuel oil is supplied as fuel to the engine 20 via the fuel oil supply system 27b of the fuel supply unit 27. By burning the fuel oil as fuel, exhaust gas containing sulfur flows into the oxidation treatment unit bypass pipe 105 and bypasses the oxidation treatment unit 40.

[0042] In step S18 for stopping the engine, after the fuel supplied to the engine 20 is switched to fuel oil in step S17, the engine control device 80 reduces the load on the engine 20 and stops the engine 20 (timing T11 to T12 in FIG. 6). In this case, since fuel oil is used as the fuel, the engine 20 operates stably until it is stopped. This ends the operation of the engine system 10A.

[0043] (Action and effect) In the engine system 10A and the ship 1 of the first embodiment, when the load on the engine 20 decreases, the exhaust bypass valve 104 is switched from a closed state to an open state by the control device 60. As a result, the exhaust gas discharged from the exhaust section 22 of the engine 20 passes through the turbocharger bypass pipe 103, bypasses the turbocharger 30, and merges into the exhaust pipe 102. The exhaust gas merged into the exhaust pipe 102 is introduced into the oxidation treatment unit 40, where methane contained in the exhaust gas is oxidized by the methane oxidation catalyst. Here, the exhaust gas that passes through the turbocharger bypass pipe 103 and bypasses the turbocharger 30 is not performing work in the turbocharger 30, and therefore a drop in temperature is suppressed. As a result, the exhaust gas introduced into the oxidation treatment unit 40 becomes hotter than when it passes through the turbocharger 30. This suppresses condensation of moisture contained in the exhaust gas, and suppresses adhesion of sulfur-containing water contained in the exhaust gas to the surface of the methane oxidation catalyst 42. As a result, deterioration of the methane oxidation catalyst 42 can be suppressed. Furthermore, the higher the temperature of the exhaust gas introduced into the methane oxidation catalyst 42, the higher the oxidation rate of methane. Therefore, even if the load on the engine 20 is reduced, the oxidation treatment unit 40 can efficiently oxidize methane.

[0044] Furthermore, if sulfur has already adhered to the methane oxidation catalyst 42, it is possible to remove the sulfur from the surface of the methane oxidation catalyst 42 by increasing the temperature of the exhaust gas to a temperature at which the sulfur can be heated and burned off.

[0045] In the above embodiment, when the control device 60 reduces the load on the engine 20 based on a command to stop the engine 20, the control device 60 switches the exhaust bypass valve 104 from a closed state to an open state. This makes it possible to automatically introduce high-temperature exhaust gas into the oxidation treatment device 40 when the load on the engine 20 is reduced.

[0046] In the above embodiment, the control device 60 controls the exhaust bypass valve 104 to switch from a closed state to an open state, and then controls the fuel to be switched from methane fuel to fuel oil. As a result, when the load on the engine 20 decreases, high-temperature exhaust gas is introduced into the oxidation treatment unit 40 to suppress deterioration of the methane oxidation catalyst 42, and then the fuel is switched from methane fuel to fuel oil. When the load on the engine 20 decreases, the engine 20 can be operated stably by using fuel oil as fuel.

[0047] In the above embodiment, the switching unit 110 can switch the introduction destination of the exhaust gas discharged from the turbocharger 30 between the exhaust pipe 102 and the oxidation treatment unit bypass pipe 105 . As a result, for example, when methane fuel is used as the fuel, the switching unit 110 causes the exhaust gas discharged from the turbocharger 30 to be introduced into the oxidation treatment unit 40 via the exhaust pipe 102, so that the unburned methane contained in the exhaust gas can be oxidized in the oxidation treatment unit 40, as described above. On the other hand, when fuel oil is used as the fuel, the switching unit 110 causes the exhaust gas discharged from the turbocharger 30 to be introduced into the oxidation treatment unit bypass pipe 105, so that the exhaust gas is not introduced into the oxidation treatment unit 40 and can be efficiently discharged through the oxidation treatment unit bypass pipe 105.

[0048] Second Embodiment Next, a second embodiment of the engine system and the ship according to the present disclosure will be described. Since the second embodiment differs from the first embodiment only in a part of the configuration of the engine system, the same parts as those in the first embodiment are denoted by the same reference numerals and will not be described again. (Engine system configuration) FIG. 10 is a diagram showing a configuration of an engine system according to the second embodiment of the present disclosure. 10, an engine system 10B illustrated in the second embodiment includes a warm-up gas supply unit 50 in addition to the engine system 10A of the first embodiment. That is, the engine system 10B includes an engine 20, a turbocharger 30, an oxidation treatment unit 40, a turbocharger bypass pipe 103, and a warm-up gas supply unit 50.

[0049] The temperature-raising gas supply unit 50 is connected to the exhaust pipe 102. The temperature-raising gas supply unit 50 supplies gas for raising the temperature of the methane oxidation catalyst 42 of the oxidation treatment unit 40 from the outside into the exhaust pipe 102. An example of the temperature-raising gas supply unit 50 is a configuration including a blower 51 that sends air from the outside of the exhaust pipe 102 into the exhaust pipe 102, and a heater 52 such as a burner that heats the air sent by the blower 51.

[0050] FIG. 11 is a diagram showing the flow of exhaust gas when the temperature of the methane oxidation catalyst is increased in the engine system according to the second embodiment of the present disclosure. As shown in FIG. 11, in such an engine system 10B, in step S16 (see FIG. 5) for raising the temperature of the exhaust gas introduced into the oxidation treatment unit, a gas for raising the temperature of the methane oxidation catalyst 42 of the oxidation treatment unit 40 is supplied from the outside to the exhaust pipe 102 by the temperature raising gas supply unit 50. Specifically, air sent from the outside into the exhaust pipe 102 by the blower 51 is heated by the heater 52 and sent into the exhaust pipe 102. This raises the temperature of the exhaust gas introduced into the oxidation treatment unit 40. In this step S16, as in the first embodiment, the exhaust gas discharged from the exhaust unit 22 of the engine 20 is introduced into the oxidation treatment unit 40 via the turbocharger bypass pipe 103 and the exhaust pipe 102, so that the temperature of the methane oxidation catalyst 42 is further raised.

[0051] In the engine system 10B and ship 1 of the second embodiment, when the load on the engine 20 decreases, the temperature-raising gas supply unit 50 supplies gas for raising the temperature of the methane oxidation catalyst 42 of the oxidation treatment unit 40 from the outside into the exhaust pipe 102. This increases the temperature of the exhaust gas introduced into the oxidation treatment unit 40 via the exhaust pipe 102. This prevents the moisture contained in the exhaust gas introduced into the oxidation treatment unit 40 from condensing, and prevents the adhesion of sulfur-containing water contained in the exhaust gas to the surface of the methane oxidation catalyst 42. As a result, deterioration of the methane oxidation catalyst 42 can be suppressed. Furthermore, the higher the temperature of the exhaust gas introduced into the methane oxidation catalyst 42, the higher the oxidation rate of methane. Therefore, even if the load on the engine 20 is reduced, the oxidation treatment unit 40 can efficiently oxidize methane. Furthermore, if sulfur has already adhered to the methane oxidation catalyst 42, it is possible to remove the sulfur from the surface of the methane oxidation catalyst 42 by raising the temperature of the exhaust gas to a temperature at which the sulfur can be heated and burned off.

[0052] Furthermore, in the engine system 10B of the second embodiment, similarly to the first embodiment, when the load on the engine 20 decreases, the control device 60 switches the exhaust bypass valve 104 from a closed state to an open state. As a result, the exhaust gas introduced into the oxidation treatment unit 40 becomes hotter than when the exhaust gas passes through the turbocharger 30. This prevents the moisture contained in the exhaust gas from condensing, and prevents the sulfur-containing water contained in the exhaust gas from adhering to the surface of the methane oxidation catalyst 42. As a result, deterioration of the methane oxidation catalyst 42 can be suppressed.

[0053] (Modification of the second embodiment) In the second embodiment, the engine system 10B includes the turbocharger bypass pipe 103, the exhaust bypass valve 104, and the warm-up gas supply unit 50. However, the present invention is not limited to this. FIG. 12 is a diagram showing a configuration of an engine system according to a modified example of the second embodiment of the present disclosure. For example, as shown in FIG. 12, an engine system 10C may not include the supercharger bypass pipe 103 and the exhaust bypass valve 104, and may include only the warm gas supply unit 50. In this case, in step S16 (see FIG. 5) for raising the temperature of the exhaust gas introduced into the oxidation treatment unit, the temperature-raising gas supply unit 50 supplies gas for raising the temperature of the methane oxidation catalyst 42 in the oxidation treatment unit 40 from the outside into the exhaust pipe 102. This raises the temperature of the methane oxidation catalyst 42, making it possible to suppress deterioration of the methane oxidation catalyst 42.

[0054] (Other embodiments) Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not depart from the gist of the present disclosure are also included. The configurations of the engine systems 10A to 10C shown in the above embodiments are merely examples, and the configurations of the various components can be modified as appropriate. Furthermore, the uses of the engine systems 10A to 10C are not limited in any way and can be used for a variety of purposes. In addition, in each of the above embodiments, the engine systems 10A to 10C are provided on the boat 1, but the engine systems 10A to 10C are not limited to being provided on the boat 1. The engine systems 10A to 10C are also applicable to engine systems used in various facilities on land, for example. In addition, in each of the above embodiments, the control device 60 and the engine control device 80 are provided, but a part of the configuration of the control device 60 may be provided in the engine control device 80, or a part of the engine control device 80 may be provided in the control device 60. Furthermore, the control device 60 and the engine control device 80 are not necessarily provided separately in terms of hardware, and a single computer may be provided with the functions of the control device 60 and the engine control device 80.

[0055] <Additional Notes> The engine systems 10A to 10C, the boat 1, and the control method for the engine systems 10A to 10C described in each embodiment can be understood, for example, as follows.

[0056] (1) An engine system 10A, 10B according to a first aspect includes an engine 20 driven by a methane fuel containing methane, a turbocharger 30 driven by exhaust gas discharged from an exhaust section 22 of the engine 20 to supply air to the engine 20, an exhaust pipe 102 through which the exhaust gas discharged from the turbocharger 30 flows, an oxidation treatment section 40 into which the exhaust gas is introduced via the exhaust pipe 102 and which houses a methane oxidation catalyst 42, a turbocharger bypass pipe 103 that causes the exhaust gas discharged from the exhaust section 22 to merge with the exhaust pipe 102, bypassing the turbocharger 30, an exhaust bypass valve 104 provided in the turbocharger bypass pipe 103 and capable of being opened and closed, and a control device 60 that controls the exhaust bypass valve 104 to be switched from a closed state to an open state when a load on the engine 20 decreases.

[0057] As a result, exhaust gas discharged from the exhaust section 22 of the engine 20 passes through the turbocharger bypass pipe 103, bypasses the turbocharger 30, and merges into the exhaust pipe 102. The exhaust gas merged into the exhaust pipe 102 is introduced into the oxidation treatment section 40. The methane oxidation catalyst 42 oxidizes methane contained in the exhaust gas. Here, the exhaust gas that passes through the turbocharger bypass pipe 103 and bypasses the turbocharger 30 is not performing work in the turbocharger 30, and therefore a drop in temperature is suppressed. As a result, the exhaust gas introduced into the oxidation treatment unit 40 becomes hotter than when it passes through the turbocharger 30. This suppresses condensation of moisture contained in the exhaust gas, and suppresses adhesion of sulfur-containing water contained in the exhaust gas to the surface of the methane oxidation catalyst 42. As a result, deterioration of the methane oxidation catalyst 42 can be suppressed. Furthermore, the higher the temperature of the exhaust gas introduced into the methane oxidation catalyst 42, the higher the oxidation rate of methane. Therefore, even if the load on the engine 20 is reduced, the oxidation treatment unit 40 can efficiently oxidize methane.

[0058] (2) The engine systems 10A, 10B according to a second aspect are the engine systems 10A, 10B of (1), in which the control device 60 controls the exhaust bypass valve 104 to switch from a closed state to an open state when the load on the engine 20 is reduced based on a command to stop the engine 20.

[0059] This makes it possible to automatically introduce high-temperature exhaust gas into the oxidation treatment unit 40 when the load on the engine 20 decreases.

[0060] (3) The engine systems 10A, 10B according to a third aspect are the engine systems 10A, 10B of (1) or (2), in which the engine 20 is capable of using methane fuel and fuel oil as fuel, and the control device 60 controls the exhaust bypass valve 104 to switch from a closed state to an open state, and then controls the fuel to be switched from methane fuel to fuel oil.

[0061] As a result, when the load on the engine 20 decreases, high-temperature exhaust gas is introduced into the oxidation treatment unit 40 to suppress deterioration of the methane oxidation catalyst 42, and then the fuel is switched from methane fuel to fuel oil.As a result, when the load on the engine 20 decreases, the fuel oil can be used as fuel, allowing the engine 20 to operate stably.

[0062] (4) The engine system 10B according to a fourth aspect is any one of the engine systems 10B of (1) to (3), and further includes a temperature-raising gas supply unit 50 connected to the exhaust pipe 102 and supplying a gas for raising the temperature of the methane oxidation catalyst 42 of the oxidation treatment unit 40 from the outside into the exhaust pipe 102.

[0063] This prevents the moisture contained in the exhaust gas introduced into the oxidation treatment unit 40 from condensing, and prevents the sulfur-containing water contained in the exhaust gas from adhering to the surface of the methane oxidation catalyst 42. As a result, deterioration of the methane oxidation catalyst 42 can be suppressed.

[0064] (5) The engine systems 10B and 10C according to a fifth aspect include an engine 20 driven by a methane fuel containing methane, a turbocharger 30 driven by exhaust gas discharged from an exhaust section 22 of the engine 20 to supply air to the engine 20, an exhaust pipe 102 through which the exhaust gas discharged from the turbocharger 30 flows, an oxidation treatment section 40 into which the exhaust gas is introduced via the exhaust pipe 102 and in which a methane oxidation catalyst 42 is housed, and a temperature-raising gas supply section 50 connected to the exhaust pipe 102 to supply a gas for raising the temperature of the methane oxidation catalyst 42 of the oxidation treatment section 40 from the outside into the exhaust pipe 102.

[0065] This prevents the moisture contained in the exhaust gas introduced into the oxidation treatment unit 40 from condensing, and prevents the sulfur-containing water contained in the exhaust gas from adhering to the surface of the methane oxidation catalyst 42. As a result, deterioration of the methane oxidation catalyst 42 can be suppressed. Furthermore, the higher the temperature of the exhaust gas introduced into the methane oxidation catalyst 42, the higher the oxidation rate of methane. Therefore, even if the load on the engine 20 is reduced, the oxidation treatment unit 40 can efficiently oxidize methane.

[0066] (6) A boat 1 according to a sixth aspect includes any one of the engine systems 10A to 10C according to (1) to (5).

[0067] As a result, the ship 1 equipped with the engine systems 10A to 10C capable of suppressing deterioration of the methane oxidation catalyst 42 can be provided.

[0068] (7) A control method S10 for engine systems 10A, 10B according to a seventh aspect is a control method S10 for engine systems 10A, 10B of any one of (1) to (4), and includes a step S14 of closing the exhaust bypass valve 104 and driving the engine 20 using methane fuel containing methane as fuel, a step S16 of switching the exhaust bypass valve 104 from the closed state to an open state when the load on the engine 20 decreases, and raising the temperature of the exhaust gas introduced from the exhaust pipe to the oxidation treatment unit 40, and a step S18 of stopping the engine 20 after raising the temperature of the exhaust gas.

[0069] This prevents moisture contained in the exhaust gas from condensing. Then, engine 20 is stopped, which prevents sulfur-containing water contained in the exhaust gas from adhering to the surface of methane oxidation catalyst 42 when engine 20 is stopped. As a result, deterioration of methane oxidation catalyst 42 can be suppressed. [Explanation of symbols]

[0070] 1...ship 2...hull 2b...stern 3A, 3B...shipside 4...ship bottom 5...upper deck 6...bottom deck 7...superstructure 9...funnel 10A-10C...engine system 20...engine 21...engine body 22...exhaust section 23...connecting pipe 24...manifold 27...fuel supply section 27a...methane supply system 27b...fuel oil supply system 30...turbocharger 40...oxidation treatment section 41...housing 42...methane oxidation catalyst 43...exhaust duct 50...heating gas supply section 51...blower 52...heater 60...control device 61...CPU 62...ROM 63...RAM 64...storage 65...signal transmission / reception module 70...signal input section 71...operation command reception section 72...valve control section 73...output section 80...engine control device 102...exhaust pipe 102s...Temperature sensor 103...Turbocharger bypass pipe 103a...First end 103b...Second end 104...Exhaust bypass valve 105...Oxidation treatment unit bypass pipe 110...Switching unit 111...First switching valve 112...Second switching valve Dv...Up-down direction

Claims

1. an engine driven by a methane fuel containing methane; a turbocharger that is driven by exhaust gas discharged from an exhaust portion of the engine to supply air to the engine; an exhaust pipe through which the exhaust gas discharged from the turbocharger flows; an oxidation treatment unit into which the exhaust gas is introduced via the exhaust pipe and which accommodates a methane oxidation catalyst; a turbocharger bypass pipe that causes the exhaust gas discharged from the exhaust portion to bypass the turbocharger and join the exhaust pipe; an exhaust bypass valve provided in the turbocharger bypass pipe and configured to be openable and closable; a control device that controls the exhaust bypass valve to switch from a closed state to an open state when a load on the engine decreases; An engine system comprising:

2. The control device performs control to switch the exhaust bypass valve from a closed state to an open state when the load of the engine is reduced based on a command to stop the engine. The engine system of claim 1 .

3. The engine can use methane fuel and fuel oil as fuel, The control device performs control to switch the exhaust bypass valve from a closed state to an open state, and then performs control to switch the fuel from methane fuel to fuel oil.

3. An engine system according to claim 1 or 2.

4. a temperature-raising gas supply unit connected to the exhaust pipe and supplying a gas for raising the temperature of the methane oxidation catalyst in the oxidation treatment unit from the outside into the exhaust pipe.

3. An engine system according to claim 1 or 2.

5. an engine driven by a methane fuel containing methane; a turbocharger that is driven by exhaust gas discharged from an exhaust portion of the engine to supply air to the engine; an exhaust pipe through which the exhaust gas discharged from the turbocharger flows; an oxidation treatment unit into which the exhaust gas is introduced via the exhaust pipe and which accommodates a methane oxidation catalyst; a temperature-raising gas supply unit connected to the exhaust pipe and configured to supply a gas for raising the temperature of the methane oxidation catalyst in the oxidation treatment unit from the outside into the exhaust pipe; An engine system comprising:

6. The engine system according to claim 1 or 2 is provided. ship.

7. 3. A method for controlling an engine system according to claim 1, comprising: closing the exhaust bypass valve and driving the engine using methane fuel containing methane as fuel; When a load of the engine decreases, the exhaust bypass valve is switched from a closed state to an open state, thereby increasing a temperature of the exhaust gas introduced from the exhaust pipe to the oxidation treatment unit; stopping the engine after increasing the temperature of the exhaust gas; A method for controlling an engine system comprising:

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