Engine intake and exhaust systems

Abstract

To suppress the discharge of unburnt ammonia.SOLUTION: An intake and exhaust system 1 for an engine 100 includes an engine 100 having a plurality of cylinders, intake flow paths 200 communicated with combustion chambers 108 of the respective cylinders of the engine 100, ammonia injection valves provided for the respective cylinders, a supply flow path 500 communicating an exhaust port 104b of the partial cylinder (the sixth cylinder #6) out of the plurality of cylinders with intake ports 104a of the other cylinders (the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5) than the partial cylinder, and a control device 600 for making an ammonia equivalence ratio as the ratio of an ammonia amount to an air amount in the partial cylinder smaller than an ammonia equivalence ratio in each of the other cylinders.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an intake and exhaust system for an engine. [Background technology]

[0002] Various proposals have been made in the past regarding engines. For example, as disclosed in Patent Document 1, a technology has been proposed that uses ammonia as engine fuel. By using ammonia as engine fuel, carbon dioxide emissions are suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-148198 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when ammonia is used as engine fuel, if the ammonia equivalence ratio, which is the ratio of the amount of ammonia supplied to the engine's combustion chamber to the amount of air supplied, is low, a large amount of nitrous oxide (NO), a greenhouse gas, will be emitted. Therefore, it is necessary to increase the ammonia equivalence ratio to a certain extent. However, increasing the ammonia equivalence ratio increases the amount of unburned ammonia emitted. Therefore, it is desirable to suppress the emission of unburned ammonia.

[0005] An object of the present disclosure is to provide an intake and exhaust system for an engine that can suppress the emission of unburned ammonia. [Means for solving the problem]

[0006] In order to solve the above problems, the intake and exhaust system of the engine of the present disclosure includes an engine having a plurality of cylinders, an intake flow path communicating with the combustion chamber of each cylinder of the engine, an ammonia injector provided for each cylinder, a supply flow path communicating with the exhaust ports of some of the plurality of cylinders and the intake ports of the other cylinders other than the some of the cylinders, and a control device that makes the ammonia equivalence ratio, which is the ratio of the amount of ammonia to the amount of air in some of the cylinders, smaller than the ammonia equivalence ratio in the other cylinders.

[0007] The engine may be provided with an exhaust flow path communicating with the combustion chambers of the other cylinders, a connecting flow path communicating the exhaust flow path and the supply flow path, and a switching valve that switches between a first state in which the exhaust ports of some of the cylinders are connected to the exhaust flow path via the connecting flow path and the exhaust ports of some of the cylinders are not connected to the intake ports of other cylinders via the supply flow path, and a second state in which the exhaust ports of some of the cylinders are not connected to the exhaust flow path via the connecting flow path and the exhaust ports of some of the cylinders are connected to the intake ports of other cylinders via the supply flow path.

[0008] When the engine load is lower than a reference load, the control device may cause the switching valve to switch to the second state, and make the ammonia equivalence ratio in some cylinders smaller than the ammonia equivalence ratio in other cylinders.

[0009] When the intake air temperature is lower than a reference temperature, the control device may cause the switching valve to switch to the second state, and make the ammonia equivalence ratio in some cylinders smaller than the ammonia equivalence ratio in other cylinders. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to suppress the emission of unburned ammonia. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an intake and exhaust system according to an embodiment of the present disclosure. [Figure 2]FIG. 2 is a schematic diagram showing the configuration of each cylinder of the engine according to the embodiment of the present disclosure. [Figure 3] FIG. 3 is a flowchart illustrating an example of a flow of processing performed by the control device according to the embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of an intake and exhaust system according to a modified example. [Figure 5] FIG. 5 is a schematic diagram showing the gas flow when the communication state is in the first state in the intake and exhaust system according to the modified example. [Figure 6] FIG. 6 is a schematic diagram showing the gas flow when the communication state is in the second state in the intake and exhaust system according to the modified example. [Figure 7] FIG. 7 is a flowchart showing the flow of a first processing example performed by a control device according to a modified example. [Figure 8] FIG. 8 is a flowchart showing the flow of a second example of processing performed by a control device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for ease of understanding and, unless otherwise specified, do not limit the present disclosure. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0013] Fig. 1 is a schematic diagram showing the configuration of an intake and exhaust system 1 according to this embodiment. The intake and exhaust system 1 is a system related to the intake and exhaust of an engine 100. As shown in Fig. 1, the intake and exhaust system 1 includes the engine 100, an intake passage 200, an exhaust passage 300, a supercharger 400, a supply passage 500, and a control device 600.

[0014] Engine 100 is a diesel engine. Engine 100 has multiple cylinders. In the example of Fig. 1, engine 100 has a first cylinder #1, a second cylinder #2, a third cylinder #3, a fourth cylinder #4, a fifth cylinder #5, and a sixth cylinder #6. However, the number of cylinders of engine 100 may be other than six.

[0015] Fig. 2 is a schematic diagram showing the configuration of each cylinder of engine 100 according to this embodiment. In Fig. 2, intake port 104a, exhaust port 104b, ammonia injector 112, and non-ammonia fuel injector 114 are illustrated on the same cross section. However, intake port 104a, exhaust port 104b, ammonia injector 112, and non-ammonia fuel injector 114 do not have to be located on the same cross section.

[0016] 2, the engine 100 includes a cylinder liner 102, a cylinder head 104, and a piston 106. The piston 106 is housed within the cylinder liner 102. The cylinder liner 102, the cylinder head 104, and the piston 106 form a combustion chamber 108.

[0017] An intake port 104a and an exhaust port 104b are formed in the cylinder head 104. The intake port 104a and the exhaust port 104b open to the combustion chamber 108. The intake valve 110a opens and closes the opening of the intake port 104a on the combustion chamber 108 side. The exhaust valve 110b opens and closes the opening of the exhaust port 104b on the combustion chamber 108 side. The opening and closing operations of the intake valve 110a and the exhaust valve 110b are performed in accordance with the rotation of a camshaft (not shown).

[0018] A pipe that forms a branch flow path 202 of an intake flow path 200 (described later) is connected to the intake port 104a. Intake air flows into the combustion chamber 108 via the intake port 104a. A pipe that forms a branch flow path 302 of an exhaust flow path 300 (described later) is connected to the exhaust port 104b. Exhaust gas is discharged from the combustion chamber 108 via the exhaust port 104b. As will be described later, a pipe that forms a supply flow path 500 is connected to the exhaust port 104b of the sixth cylinder #6 among the multiple cylinders, rather than a pipe that forms the exhaust flow path 300.

[0019] The ammonia injector 112 is connected to a supply source of ammonia used as fuel. The supply source of ammonia is, for example, an ammonia tank (not shown). In the example of FIG. 2, the ammonia injector 112 is provided in a branch flow path 202 of the intake flow path 200. The tip of the ammonia injector 112 faces the intake port 104a. The ammonia injector 112 injects ammonia as a fuel gas into the intake port 104a. Gaseous ammonia is injected from the ammonia injector 112. In this way, the engine 100 is an engine that uses ammonia as fuel.

[0020] However, the ammonia injector 112 may be provided in the combustion chamber 108. In this case, the ammonia injector 112 is provided in the cylinder head 104 so as to face the inside of the combustion chamber 108, and injects ammonia directly into the combustion chamber 108. In this case, gaseous or liquid ammonia is injected from the ammonia injector 112. In this way, the ammonia injector 112 is provided in the intake passage 200 or the combustion chamber 108 for each cylinder.

[0021] The non-ammonia fuel injector 114 is connected to a supply source of non-ammonia fuel, which is a fuel other than ammonia. For example, diesel is used as the non-ammonia fuel. In this case, the supply source of the non-ammonia fuel is, for example, a diesel tank (not shown). However, a fuel other than diesel, such as heavy oil, may also be used as the non-ammonia fuel. The non-ammonia fuel injector 114 is provided in the combustion chamber 108. In the example of FIG. 2 , the non-ammonia fuel injector 114 is provided in the cylinder head 104 so as to face the inside of the combustion chamber 108, and directly injects the non-ammonia fuel into the combustion chamber 108. For example, liquid non-ammonia fuel is injected from the non-ammonia fuel injector 114.

[0022] Ammonia is less combustible than other fuels, so in order to ensure combustibility in the combustion chamber 108, the engine 100 uses a non-ammonia fuel in addition to ammonia.

[0023] The engine 100 is a four-stroke engine. During the intake stroke, ammonia is injected from the ammonia injector 112, the intake valve 110a opens, and the exhaust valve 110b closes. The piston 106 moves toward bottom dead center, and intake air and ammonia are drawn into the combustion chamber 108 through the intake port 104a. During the compression stroke, the intake valve 110a and the exhaust valve 110b close. The piston 106 moves toward top dead center, and the air-fuel mixture in the combustion chamber 108 is compressed. When the piston 106 reaches near top dead center, non-ammonia fuel is injected from the non-ammonia fuel injector 114, which enhances combustibility in the combustion chamber 108. This ignites and burns the air-fuel mixture in the combustion chamber 108. During the expansion stroke, the piston 106 is pressed toward the bottom dead center. During the exhaust stroke, the intake valve 110a closes and the exhaust valve 110b opens. As the piston 106 approaches top dead center, the exhaust gases after combustion are expelled from the combustion chamber 108 through the exhaust port 104b. Returning to FIG. 1, the following explanation will be continued.

[0024] The intake passage 200 communicates with the combustion chamber 108 of each cylinder of the engine 100. Intake air, which is air supplied to the combustion chamber 108, flows through the intake passage 200. An intake port (not shown) is provided at the upstream end of the intake passage 200, through which air is taken in from the outside. The intake passage 200 has multiple branch passages 202, each communicating with the combustion chamber 108 of each cylinder. The multiple branch passages 202 are provided downstream of the intake passage 200. The combustion chamber 108 of each cylinder and the intake passage 200 are connected by the multiple branch passages 202. As described above, the piping that forms the branch passages 202 is connected to the intake port 104a of the engine 100. The intake port 104a corresponds to the downstream end of the branch passages 202. The intake port 104a is included in the intake passage 200.

[0025] The branch flow path 202 connected to the sixth cylinder #6 branches off at a first position P1 in the intake flow path 200. The branch flow paths 202 connected to the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 each branch off at a second position P2 in the intake flow path 200 that is downstream of the first position P1.

[0026] The exhaust passage 300 communicates with the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. Exhaust gas discharged from the combustion chambers 108 flows through the exhaust passage 300. An exhaust port (not shown) is provided at the downstream end of the exhaust passage 300, through which the exhaust gas is discharged to the outside. The exhaust passage 300 has multiple branch passages 302 that respectively communicate with the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. The multiple branch passages 302 are provided upstream of the exhaust passage 300. As described above, the pipes that form the branch passages 302 are connected to the exhaust port 104b of the engine 100. The exhaust ports 104b of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 correspond to the upstream ends of the branch flow passages 302. The exhaust ports 104b of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 are included in the exhaust flow passage 300.

[0027] The supercharger 400 has a compressor 402 and a turbine 404. The impeller of the compressor 402 and the impeller of the turbine 404 rotate as a unit. The impeller of the compressor 402 and the impeller of the turbine 404 are connected by a shaft.

[0028] The compressor 402 is provided upstream of the first position P1 in the intake passage 200. The compressor 402 compresses the intake air taken in through the intake port and sends it downstream. The intake air sent out from the compressor 402 is sent to each combustion chamber 108 via each branch passage 202.

[0029] The turbine 404 is provided in the exhaust flow path 300 downstream of the branch flow paths 302. The exhaust gas discharged from the engine 100 is sent to the turbine 404 via each branch flow path 302. The turbine 404 generates rotational power when an impeller of the turbine 404 is rotated by the exhaust gas. The rotational power generated by the turbine 404 is transmitted to the compressor 402 via a shaft. The exhaust gas that has passed through the turbine 404 is discharged from an exhaust port.

[0030] The supply passage 500 connects the exhaust port 104b of the sixth cylinder #6 with the intake ports 104a of the first cylinder #1, second cylinder #2, third cylinder #3, fourth cylinder #4, and fifth cylinder #5. Exhaust gas discharged from the exhaust port 104b of the sixth cylinder #6 is sent to the supply passage 500. In the supply passage 500, the side of the exhaust port 104b of the sixth cylinder #6 is called the upstream side, and the side opposite the exhaust port 104b of the sixth cylinder #6 is called the downstream side.

[0031] The upstream end of the supply passage 500 is connected to the exhaust port 104b of the sixth cylinder #6. In the example of FIG. 1, the downstream end of the supply passage 500 is connected to a portion of the intake passage 200 downstream of the first position P1 and upstream of the second position P2. Therefore, exhaust gas discharged from the exhaust port 104b of the sixth cylinder #6 passes through the supply passage 500 and is sent to a portion of the intake passage 200 downstream of the first position P1 and upstream of the second position P2. The exhaust gas sent from the supply passage 500 to the intake passage 200 is then supplied to the combustion chambers 108 of the first cylinder #1, second cylinder #2, third cylinder #3, fourth cylinder #4, and fifth cylinder #5 through the intake ports 104a of these cylinders.

[0032] The control device 600 includes a central processing unit (CPU), a ROM storing programs and the like, a RAM as a work area, etc. The control device 600 controls the operation of each device in the intake and exhaust system 1. For example, the control device 600 controls the operation of each device in the engine 100.

[0033] The control device 600 also acquires information from sensors in the intake and exhaust system 1. For example, in the intake and exhaust system 1, an intake pressure sensor 204 is provided in the intake flow path 200. The intake pressure sensor 204 detects the intake pressure, which is the pressure of the intake air in the intake flow path 200. In the example of FIG. 1, the intake pressure sensor 204 is provided in the intake flow path 200 upstream of the first position P1.

[0034] In particular, the control device 600 can control the ammonia equivalence ratio of each cylinder by controlling the ammonia injection amount, which is the injection amount of ammonia injected from the ammonia injector 112. The ammonia equivalence ratio is the ratio of the amount of ammonia supplied to the combustion chamber 108 to the amount of air supplied. By appropriately controlling the ammonia equivalence ratio of each cylinder, the emission of unburned ammonia is suppressed, as will be described later. Hereinafter, the control of the ammonia equivalence ratio by the control device 600 will be described with reference to FIG. 3.

[0035] 3 is a flowchart showing an example of the flow of processing performed by the control device 600 according to this embodiment. For example, the control flow shown in FIG. 3 is repeatedly executed at preset time intervals.

[0036] 3 starts, in step S101, control device 600 estimates the amount of air supplied to combustion chamber 108 of each cylinder. Control device 600 can estimate the amount of air supplied to combustion chamber 108 of each cylinder based on the detection result of intake pressure sensor 204, for example.

[0037] After step S101, in step S102, the control device 600 controls the ammonia injection amount of each cylinder so that the ammonia equivalence ratio in the sixth cylinder #6 is smaller than the ammonia equivalence ratios in the other cylinders, and the control flow shown in Fig. 3 ends. The other cylinders are the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5.

[0038] For example, the control device 600 controls the ammonia equivalence ratio in each of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 to a value high enough to suppress N2O emissions. On the other hand, the control device 600 controls the ammonia equivalence ratio in the sixth cylinder #6 to a value low enough to allow a large amount of N2O to be emitted. Therefore, the exhaust gas discharged from the exhaust port 104b of the sixth cylinder #6 contains a large amount of N2O. The exhaust gas containing N2O is then sent to the supply passage 500, passes through the supply passage 500, and is supplied to the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5.

[0039] Here, the N2O supplied to the combustion chambers 108 of the first cylinder #1, second cylinder #2, third cylinder #3, fourth cylinder #4, and fifth cylinder #5 promotes combustion in the combustion chambers 108. Specifically, N2O is decomposed into N2 and O2 in the high-temperature environment of the combustion chambers 108. The O2 produced by this decomposition reaction promotes combustion in the combustion chambers 108. This suppresses the emission of unburned ammonia from the first cylinder #1, second cylinder #2, third cylinder #3, fourth cylinder #4, and fifth cylinder #5.

[0040] As described above, in the intake and exhaust system 1, the control device 600 sets the ammonia equivalence ratio in one of the cylinders, the sixth cylinder #6, to be smaller than the ammonia equivalence ratios in the other cylinders, the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. This suppresses the emission of unburned ammonia from each of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. Furthermore, since the ammonia equivalence ratio in each of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 can be made sufficiently high, NO emissions are also appropriately suppressed.

[0041] 1, an example has been described in which the supply passage 500 is connected to the exhaust port 104b of the sixth cylinder #6. However, the supply passage 500 may be connected to the exhaust port 104b of a cylinder other than the sixth cylinder #6. Furthermore, the supply passage 500 may be connected to the exhaust ports 104b of two or more cylinders.

[0042] 1, an example has been described in which the downstream end of the supply flow path 500 is connected to the intake flow path 200 on the downstream side of the first position P1 and the upstream side of the second position P2. However, the downstream side of the supply flow path 500 may branch and be connected to each of the branch flow paths 202.

[0043] An intake and exhaust system 1A according to a modified example will be described below with reference to FIGS.

[0044] Fig. 4 is a schematic diagram showing the configuration of an intake and exhaust system 1A according to a modified example. As shown in Fig. 4, the intake and exhaust system 1A according to the modified example is different from the intake and exhaust system 1 described above mainly in that a connection flow path 700 and a switching valve 800 are further provided.

[0045] 4, in the intake and exhaust system 1A, the exhaust flow path 300 and the supply flow path 500 communicate with each other via a connection flow path 700. In the example of Fig. 4, the connection flow path 700 is connected to the exhaust flow path 300 on the upstream side of the joining portion of the branch flow paths 302. However, the connection flow path 700 may also be connected to the exhaust flow path 300 on the upstream side of the joining portion of the branch flow paths 302.

[0046] The switching valve 800 is provided at a connection portion of the supply flow path 500 with the connection flow path 700. The switching valve 800 is, for example, a three-way valve. The switching valve 800 switches the communication state of the intake / exhaust system 1A between a first state in which the portion of the supply flow path 500 upstream of the switching valve 800 communicates with the connection flow path 700, and a second state in which the portion of the supply flow path 500 upstream of the switching valve 800 communicates with the portion of the supply flow path 500 downstream of the switching valve 800.

[0047] 5 is a schematic diagram showing the gas flow when the communication state is in the first state in the intake / exhaust system 1A according to the modified example. In the first state, the portion of the supply passage 500 upstream of the switching valve 800 communicates with the connection passage 700. On the other hand, the portion of the supply passage 500 upstream of the switching valve 800 does not communicate with the portion of the supply passage 500 downstream of the switching valve 800. In other words, in the first state, the exhaust port 104b of the sixth cylinder #6 communicates with the exhaust passage 300 via the connection passage 700, but the exhaust port 104b of the sixth cylinder #6 does not communicate with the intake ports 104a of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 via the supply passage 500. Therefore, as shown in FIG. 5, exhaust gas discharged from the exhaust port 104b of the sixth cylinder #6 passes through the connecting passage 700 and is sent to the exhaust passage 300.

[0048] 6 is a schematic diagram showing the gas flow when the communication state is in the second state in the intake / exhaust system 1A according to the modified example. In the second state, the portion of the supply passage 500 upstream of the switching valve 800 communicates with the portion of the supply passage 500 downstream of the switching valve 800. On the other hand, the portion of the supply passage 500 upstream of the switching valve 800 does not communicate with the connection passage 700. In other words, in the second state, the exhaust port 104b of the sixth cylinder #6 does not communicate with the exhaust passage 300 via the connection passage 700, and the exhaust port 104b of the sixth cylinder #6 communicates with the intake ports 104a of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 via the supply passage 500. Therefore, as shown in FIG. 6, exhaust gas discharged from the exhaust port 104b of the sixth cylinder #6 passes through the supply passage 500 and is sent to the intake ports 104a of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5, and is supplied to the combustion chambers 108 of these cylinders.

[0049] 4, the intake and exhaust system 1A is further provided with an intake air temperature sensor 206 in the intake air flow path 200. The intake air temperature sensor 206 detects the intake air temperature, which is the temperature of the intake air in the intake air flow path 200. Since the intake air temperature is approximately the same as the outside air temperature, for example, a sensor that detects the outside air temperature can be used as the intake air temperature sensor 206. The intake air temperature sensor 206 may be provided in the intake air flow path 200 or at a location other than the intake air flow path 200. The detection result of the intake air temperature sensor 206 is output to the control device 600.

[0050] As described above, in the intake and exhaust system 1A, the switching valve 800 switches between a first state in which the exhaust port 104b of the sixth cylinder #6 is connected to the exhaust passage 300 via the connecting passage 700, and the exhaust port 104b of the sixth cylinder #6 is not connected to the intake ports 104a of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 via the supply passage 500, and a second state in which the exhaust port 104b of the sixth cylinder #6 is not connected to the exhaust passage 300 via the connecting passage 700, and the exhaust port 104b of the sixth cylinder #6 is connected to the intake ports 104a of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 via the supply passage 500.

[0051] In the first state, the ammonia equivalence ratio in the sixth cylinder #6 is made approximately the same as that in the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5, thereby increasing the output of the sixth cylinder #6 to the same level as that of the other cylinders. In the second state, similar to the above-described intake and exhaust system 1, the ammonia equivalence ratio in the sixth cylinder #6 is made smaller than that in the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5, thereby promoting combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. This suppresses the emission of unburned ammonia.

[0052] Therefore, when it is not necessary to promote combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5, the communication state of the intake and exhaust system 1A is set to the first state, thereby increasing the output of the engine 100. On the other hand, when it is necessary to promote combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5, the communication state of the intake and exhaust system 1A is set to the second state, thereby appropriately suppressing the emission of unburned ammonia.

[0053] Hereinafter, a first processing example and a second processing example relating to switching of the communication state in the intake / exhaust system 1A and control of the ammonia equivalence ratio will be described with reference to FIGS.

[0054] Fig. 7 is a flowchart showing the flow of a first processing example performed by the control device 600. For example, the control flow shown in Fig. 7 is repeatedly executed at preset time intervals.

[0055] When the control flow shown in FIG. 7 starts, control device 600 acquires the load on engine 100 in step S201.

[0056] After step S201, in step S202, the control device 600 determines whether the load of the engine 100 is lower than a reference load. Here, the lower the load of the engine 100, the lower the combustibility in the combustion chambers 108, and the more likely unburned ammonia is to be produced. Therefore, the need for promoting combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 increases. The reference load is set to a load low enough to determine the need for promoting combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5.

[0057] When the load of the engine 100 is lower than the reference load, it becomes necessary to promote combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. On the other hand, when the load of the engine 100 is equal to or higher than the reference load, it becomes unnecessary to promote combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5.

[0058] If it is determined that the load on the engine 100 is equal to or greater than the reference load (step S202 / NO), the process proceeds to step S203. In step S203, the control device 600 causes the switching valve 800 to switch to the first state, thereby switching the communication state of the intake and exhaust system 1A to the first state.

[0059] After step S203, in step S204, control device 600 makes the ammonia equivalence ratio in the sixth cylinder #6 approximately the same as the ammonia equivalence ratios in the other cylinders, and the control flow shown in FIG. 7 ends.

[0060] On the other hand, if it is determined that the load of the engine 100 is lower than the reference load (step S202 / YES), the process proceeds to step S205. In step S205, the control device 600 causes the switching valve 800 to switch to the second state, and switches the communication state of the intake and exhaust system 1A to the second state.

[0061] After step S205, in step S206, control device 600 makes the ammonia equivalence ratio in the sixth cylinder #6 smaller than the ammonia equivalence ratios in the other cylinders, and the control flow shown in FIG. 7 ends.

[0062] Specifically, the control of the ammonia equivalence ratio of each cylinder in steps S204 and S206 is performed based on the estimated value of the amount of air supplied to the combustion chamber 108 of each cylinder, as described above.

[0063] As described above, in the first processing example of FIG. 7 , when the load of engine 100 is lower than the reference load, control device 600 causes switching valve 800 to switch to the second state, thereby making the ammonia equivalence ratio in one of the cylinders, i.e., sixth cylinder #6, smaller than the ammonia equivalence ratios in the other cylinders, i.e., first cylinder #1, second cylinder #2, third cylinder #3, fourth cylinder #4, and fifth cylinder #5. This allows control device 600 to appropriately determine whether combustion promotion is necessary or unnecessary in the combustion chambers 108 of first cylinder #1, second cylinder #2, third cylinder #3, fourth cylinder #4, and fifth cylinder #5, based on the load of engine 100, and then switch the communication state of intake / exhaust system 1A. Therefore, when combustion promotion is unnecessary, the output of engine 100 is increased, while when combustion promotion is necessary, the emission of unburned ammonia is appropriately suppressed.

[0064] Fig. 8 is a flowchart showing the flow of a second processing example performed by the control device 600. For example, the control flow shown in Fig. 8 is repeatedly executed at preset time intervals.

[0065] The second processing example in FIG. 8 differs from the first processing example in FIG. 7 described above in that steps S201 and S202 are replaced with steps S301 and S302.

[0066] 8 starts, in step S301, the control device 600 acquires the intake air temperature. The intake air temperature can be acquired from the intake air temperature sensor 206, for example.

[0067] Following step S301, in step S302, control device 600 determines whether the intake air temperature is lower than a reference temperature. Here, the lower the intake air temperature, the lower the combustibility in the combustion chambers 108, making it more likely that unburned ammonia will be generated. Therefore, the need for promoting combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5 increases. The reference temperature is set to a temperature low enough to determine the need for promoting combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5.

[0068] When the intake temperature is lower than the reference temperature, it becomes necessary to promote combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. On the other hand, when the intake temperature is equal to or higher than the reference temperature, it becomes unnecessary to promote combustion in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5.

[0069] If it is determined that the intake air temperature is equal to or higher than the reference temperature (step S302 / NO), the process proceeds to step S203. Then, similar to the first processing example in Fig. 7 described above, steps S203 and S204 are performed, and the control flow shown in Fig. 8 ends.

[0070] On the other hand, if it is determined that the intake air temperature is lower than the reference temperature (step S302 / YES), the process proceeds to step S205. Then, similarly to the first processing example of Fig. 7 described above, steps S205 and S206 are performed, and the control flow shown in Fig. 8 ends.

[0071] As described above, in the second process example of FIG. 8 , when the intake-air temperature is lower than the reference temperature, the control device 600 causes the switching valve 800 to switch to the second state, thereby making the ammonia equivalence ratio in one of the cylinders, the sixth cylinder #6, smaller than the ammonia equivalence ratios in the other cylinders, the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5. This makes it possible to appropriately determine, based on the intake-air temperature, whether combustion promotion is necessary or unnecessary in the combustion chambers 108 of the first cylinder #1, the second cylinder #2, the third cylinder #3, the fourth cylinder #4, and the fifth cylinder #5, and then switch the communication state of the intake / exhaust system 1A. Therefore, when combustion promotion is unnecessary, the output of the engine 100 is increased, while when combustion promotion is necessary, the emission of unburned ammonia is appropriately suppressed.

[0072] Note that the control device 600 may use both the load of the engine 100 being lower than a reference load and the intake air temperature being lower than a reference temperature as conditions for switching the communication state of the intake and exhaust system 1A to the second state. For example, the control device 600 may cause the switching valve 800 to switch to the second state when the load of the engine 100 is lower than the reference load and the intake air temperature is lower than the reference temperature. For example, the control device 600 may cause the switching valve 800 to switch to the second state when either the load of the engine 100 is lower than the reference load or the intake air temperature is lower than the reference temperature is satisfied.

[0073] In the above, an example has been described in which the switching valve 800 is a three-way valve. However, the switching valve 800 is not limited to the above example as long as it can switch the communication state of the intake and exhaust system 1A between the first state and the second state. For example, a first on-off valve provided in the connection flow path 700 and a second on-off valve provided in the supply flow path 500 downstream of the connection portion with the connection flow path 700 may be used as the switching valve 800. In this case, by opening the first on-off valve and closing the second on-off valve, the communication state of the intake and exhaust system 1A becomes the first state. On the other hand, by opening the second on-off valve and closing the first on-off valve, the communication state of the intake and exhaust system 1A becomes the second state.

[0074] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present disclosure.

[0075] This disclosure can contribute, for example, to Goal 7 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "Ensure access to affordable, reliable, sustainable and modern energy." [Explanation of symbols]

[0076] 1. Intake and exhaust system 1A Intake and Exhaust System 100 Engine 104a Intake port 104b Exhaust port 108 Combustion chamber 112 Ammonia injector 200 Intake passage 300 Exhaust passage 500 supply channel 600 control device 700 connecting flow channel 800 Switching valve

Claims

1. an engine having multiple cylinders; an intake passage communicating with the combustion chamber of each cylinder of the engine; an ammonia injector provided for each cylinder; a supply passage communicating exhaust ports of some of the cylinders with intake ports of other cylinders; a control device that sets an ammonia equivalence ratio, which is a ratio of an amount of ammonia to an amount of air in the part of the cylinders, to be smaller than the ammonia equivalence ratio in the other cylinders; Equipped with Engine intake and exhaust system.

2. an exhaust passage communicating with the combustion chamber of the other cylinder; a connecting flow path that connects the exhaust flow path and the supply flow path; a switching valve that switches between a first state in which the exhaust ports of the some of the cylinders and the exhaust flow passages communicate with each other via the connecting flow passages, and the exhaust ports of the some of the cylinders and the intake ports of the other cylinders do not communicate with each other via the supply flow passages, and a second state in which the exhaust ports of the some of the cylinders and the exhaust flow passages do not communicate with each other via the connecting flow passages, and the exhaust ports of the some of the cylinders and the intake ports of the other cylinders communicate with each other via the supply flow passages; Equipped with 2. The engine intake and exhaust system according to claim 1.

3. the control device causes the switching valve to switch to the second state when a load of the engine is lower than a reference load, and makes the ammonia equivalence ratio in the some of the cylinders smaller than the ammonia equivalence ratio in the other cylinders.

3. The engine intake and exhaust system according to claim 2.

4. the control device causes the switching valve to switch to the second state when the intake air temperature is lower than a reference temperature, and makes the ammonia equivalence ratio in the some of the cylinders smaller than the ammonia equivalence ratio in the other cylinders.

4. The engine intake and exhaust system according to claim 2 or 3.

Images