Engine intake and exhaust systems

Abstract

To suppress discharging of unburned fuel.SOLUTION: An intake / exhaust system 1 of an engine 100 includes an intake flow passage 200, a plurality of branch flow passages 202 connecting each of a plurality of combustion chambers 108 of the engine 100 having a plurality of cylinders to the intake flow passage 200 and provided with fuel injection valves, and a connection flow passage 500 connecting the branch flow passages 202 different from each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] There is an engine having a combustion chamber, an intake valve, and an exhaust valve. In such an engine, as disclosed in Patent Document 1, for example, an intake port communicating with the combustion chamber is opened and closed by the intake valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 049878 Summary of the Invention [Problem to be solved by the invention]

[0004] In a system in which a fuel injection valve is provided in the intake passage, some of the fuel injected from the fuel injection valve may remain in the intake port when the intake valve is closed. When switching from the exhaust stroke to the intake stroke, both the intake valve and the exhaust valve may be open. When both the intake valve and the exhaust valve are open, unburned fuel remaining in the intake port may be discharged through the exhaust port, a phenomenon known as "blow-by." From the perspective of improving thermal efficiency or reducing greenhouse gas emissions, it is desirable to reduce the discharge of unburned fuel due to blow-by.

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

[0006] In order to solve the above-described problems, an intake and exhaust system for an engine according to the present disclosure includes an intake passage, a plurality of branch passages that connect each of a plurality of combustion chambers of an engine having a plurality of cylinders to the intake passage and in which fuel injection valves are provided, and a connecting passage that connects different branch passages to each other. The opening periods of the intake valves of the cylinders connected via the connecting passages do not overlap with each other. .

[0007] An on-off valve may be provided in the connecting flow path.

[0008] The engine may further include a control device that opens the on-off valve during the opening period of the intake valve of any one of the cylinders connected via the connecting flow path. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to suppress the emission of unburned fuel. [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 diagram showing the opening period of the intake valve of each cylinder of the engine according to the embodiment of the present disclosure. 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 flow path 200, an exhaust flow path 300, a turbocharger 400, connection flow paths 500a, 500b, and 500c, and a control device 600. Hereinafter, when there is no need to distinguish between the connection flow paths 500a, 500b, and 500c, they will also be simply referred to as connection flow paths 500.

[0014] 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 in engine 100 may be other than six. 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, fuel injection valve 112, and ignition device 114 are illustrated on the same cross section. However, intake port 104a, exhaust port 104b, fuel injection valve 112, and ignition device 114 do not have to be located on the same cross section.

[0015] 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.

[0016] 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).

[0017] A pipe that forms a branch passage 202 of an intake passage 200 (described later) is connected to the intake port 104a. An air-fuel mixture flows into the combustion chamber 108 via the intake port 104a. A pipe that forms a branch passage 302 of an exhaust passage 300 (described later) is connected to the exhaust port 104b. Exhaust gas is discharged from the combustion chamber 108 via the exhaust port 104b.

[0018] The fuel injection valve 112 is connected to a fuel supply source. The fuel supply source is, for example, a fuel tank (not shown) or a pipeline for city gas or the like. The fuel injection valve 112 is provided in a branch flow path 202 of the intake flow path 200. The tip of the fuel injection valve 112 faces the intake port 104a. The fuel injection valve 112 injects fuel gas into the intake port 104a. The fuel gas is generated, for example, by gasifying LNG (liquefied natural gas). The fuel gas is not limited to LNG, and may be, for example, gasified LPG (liquefied petroleum gas), light oil, heavy oil, ammonia, hydrogen, or the like. The engine 100 is a gas engine that uses fuel gas as fuel. Hereinafter, fuel gas may also be simply referred to as fuel.

[0019] The ignition device 114 is provided in the cylinder head 104. The tip of the ignition device 114 protrudes into the combustion chamber .

[0020] The engine 100 is a four-stroke engine. During the intake stroke, fuel is injected from the fuel injector 112, the intake valve 110a opens, and the exhaust valve 110b closes. As the piston 106 moves toward bottom dead center, intake air and fuel 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. As the piston 106 moves toward top dead center, the air-fuel mixture in the combustion chamber 108 is compressed. The air-fuel mixture is ignited and combusted by the ignition device 114, and during the combustion 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 moves toward top dead center, the burned exhaust gas is discharged from the combustion chamber 108 through the exhaust port 104b. Returning to Figure 1, the explanation will be continued below.

[0021] The intake passage 200 communicates with the combustion chambers 108 of the engine 100. Intake air, which is air supplied to the combustion chambers 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 a plurality of branch passages 202 that communicate with the plurality of combustion chambers 108, respectively. The plurality of branch passages 202 are provided downstream of the intake passage 200. Each of the plurality of combustion chambers 108 and the intake passage 200 are connected by the plurality of 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.

[0022] The exhaust flow path 300 communicates with the combustion chambers 108 of the engine 100. Exhaust gas discharged from the combustion chambers 108 flows through the exhaust flow path 300. An exhaust port (not shown) is provided at the downstream end of the exhaust flow path 300, through which the exhaust gas is discharged to the outside. The exhaust flow path 300 has a plurality of branch flow paths 302 that communicate with the plurality of combustion chambers 108, respectively. The plurality of branch flow paths 302 are provided on the upstream side of the exhaust flow path 300. As described above, the pipe that forms the branch flow path 302 is connected to the exhaust port 104b of the engine 100. The exhaust port 104b corresponds to the upstream end of the branch flow path 302. The exhaust port 104b is included in the exhaust flow path 300.

[0023] 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.

[0024] The compressor 402 is provided in the intake air flow path 200, upstream of the branch flow path 202. The compressor 402 compresses the intake air taken in through the intake port and sends it downstream. An intercooler C1 is provided in the intake air flow path 200, upstream of the branch flow path 202 and downstream of the compressor 402. The intake air flowing through the intercooler C1 is cooled by heat exchange with air outside the intercooler C1. The intake air that has passed through the intercooler C1 is sent to each combustion chamber 108 via each branch flow path 202. Note that the intercooler C1 may also be one that uses cooling water, such as engine cooling water or industrial water, to cool the intake air.

[0025] 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 exhaust gas sent to the turbine 404 passes through the turbine 404 and is discharged from an exhaust port. 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.

[0026] The connection flow path 500 connects different branch flow paths 202 to each other. In the example of Fig. 1, connection flow path 500 includes connection flow path 500a, connection flow path 500b, and connection flow path 500c. As will be described later, the connection flow path 500 is provided to send fuel remaining in intake port 104a of engine 100 to other cylinders.

[0027] The connection flow path 500a connects the branch flow path 202 connected to the first cylinder #1 with the branch flow path 202 connected to the sixth cylinder #6. That is, the first cylinder #1 and the sixth cylinder #6 are connected via the connection flow path 500a. The connection flow path 500b connects the branch flow path 202 connected to the second cylinder #2 with the branch flow path 202 connected to the fifth cylinder #5. That is, the second cylinder #2 and the fifth cylinder #5 are connected via the connection flow path 500b. The connection flow path 500c connects the branch flow path 202 connected to the third cylinder #3 with the branch flow path 202 connected to the fourth cylinder #4. That is, the third cylinder #3 and the fourth cylinder #4 are connected via the connection flow path 500c.

[0028] 2, the connection passages 500 are connected to the intake ports 104a. That is, each connection passage 500 connects the intake ports 104a of two cylinders. However, the position at which the connection passages 500 are connected in the intake passage 200 is not limited to the example in FIG. 2, as will be described later.

[0029] As shown in Fig. 1, each connection flow path 500 is provided with an on-off valve 502. The on-off valve 502 is capable of opening and closing the connection flow path 500. In the example of Fig. 1, on-off valves 502a, 502b, and 502c are provided as the on-off valves 502. On-off valve 502a is provided in connection flow path 500a. On-off valve 502b is provided in connection flow path 500b. On-off valve 502c is provided in connection flow path 500c.

[0030] The control device 600 includes a central processing unit (CPU), a ROM storing programs and the like, a RAM as a work area, and the like. 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 the engine 100. For example, the control device 600 controls the operation of each on-off valve 502.

[0031] Here, when the intake valve 110a is closed, some of the fuel injected from the fuel injection valve 112 may remain in the intake port 104a. In the intake and exhaust system 1, the fuel remaining in the intake port 104a is sent to other cylinders via a connecting flow path 500. The movement of fuel via the connecting flow path 500 is achieved by the opening and closing operation of an on-off valve 502. The movement of fuel via the connecting flow path 500 will be described below with reference to FIG. 3.

[0032] FIG. 3 shows the opening period of the intake valve 110a of each cylinder of the engine 100. In FIG. 3, the opening period of the intake valve 110a of each cylinder is indicated by the crank angle. In FIG. 3, the crank angle at the start of the intake stroke of the first cylinder #1 is set to 0 degrees. The period indicated by the arrow in FIG. 3 is the opening period of the intake valve 110a. In the engine 100, combustion occurs in the following order: first cylinder #1, third cylinder #3, fifth cylinder #5, sixth cylinder #6, fourth cylinder #4, and second cylinder #2. Therefore, the intake stroke is performed and the intake valve 110a opens in the following order: first cylinder #1, third cylinder #3, fifth cylinder #5, sixth cylinder #6, fourth cylinder #4, and second cylinder #2.

[0033] As shown in FIG. 3, the opening period of the intake valve 110a is approximately 180° in crank angle. For example, the opening period of the first cylinder #1 is from approximately 0° to 180° in crank angle. The opening period of the third cylinder #3 is from approximately 120° to 300° in crank angle. The opening period of the fifth cylinder #5 is from approximately 240° to 420° in crank angle. The opening period of the sixth cylinder #6 is from approximately 360° to 540° in crank angle. The opening period of the fourth cylinder #4 is from approximately 480° to 660° in crank angle. The opening period of the second cylinder #2 is from approximately 600° to 60° in crank angle. In this way, the start timing of the opening period of the intake valve 110a of each cylinder is shifted by 120° in crank angle.

[0034] Here, the control device 600 opens the on-off valve 502 provided in the connection flow path 500 while the intake valve 110a of one of the cylinders connected via the connection flow path 500 is open. This allows fuel remaining in the intake port 104a of each cylinder to be sent to the other cylinders via the connection flow path 500. On the other hand, when the intake valve 110a of none of the cylinders connected via the connection flow path 500 is open, the control device 600 closes the on-off valve 502 provided in the connection flow path 500.

[0035] The control device 600 opens the on-off valve 502 provided in the connection flow path 500, for example, from the start to the end of an opening period of the intake valve 110a of one of the cylinders connected via the connection flow path 500. However, it is sufficient that the control device 600 opens the on-off valve 502 for at least a part of the opening period.

[0036] The control device 600 opens the on-off valve 502a provided in the connection passage 500a while the intake valve 110a of one of the first cylinder #1 and the sixth cylinder #6 connected via the connection passage 500a is open.

[0037] As shown in FIG. 3, the on-off valve 502a opens while the intake valve 110a of the first cylinder #1 is open. At this time, the intake valve 110a of the sixth cylinder #6 is closed, so the pressure in the intake port 104a of the first cylinder #1 is lower than the pressure in the intake port 104a of the sixth cylinder #6. As a result, fuel remaining in the intake port 104a of the sixth cylinder #6, whose intake valve 110a is closed, is drawn into the connecting passage 500a and sent to the intake port 104a of the first cylinder #1 through the connecting passage 500a. Therefore, when the sixth cylinder #6 switches from the exhaust stroke to the intake stroke, if both the intake valve 110a and the exhaust valve 110b are open, the blow-by phenomenon, in which unburned fuel is discharged through the exhaust port 104b, is suppressed.

[0038] As shown in FIG. 3, the on-off valve 502a is open even when the intake valve 110a of the sixth cylinder #6 is open. At this time, the intake valve 110a of the first cylinder #1 is closed, so the pressure in the intake port 104a of the sixth cylinder #6 is lower than the pressure in the intake port 104a of the first cylinder #1. As a result, fuel remaining in the intake port 104a of the first cylinder #1, whose intake valve 110a is closed, is drawn into the connecting passage 500a and sent through the connecting passage 500a to the intake port 104a of the sixth cylinder #6. Therefore, blow-by of unburned fuel is suppressed in the first cylinder #1 as well.

[0039] The control device 600 opens the on-off valve 502b provided in the connection flow path 500b during the open period of the intake valve 110a of one of the second cylinder #2 and the fifth cylinder #5, which are connected via the connection flow path 500b. As a result, as shown in Fig. 3, the on-off valve 502b is open during the open period of the intake valve 110a of the second cylinder #2 and the open period of the intake valve 110a of the fifth cylinder #5. Therefore, as described above, the blow-by of unburned fuel is suppressed in the second cylinder #2 and the fifth cylinder #5.

[0040] The control device 600 opens the on-off valve 502c provided in the connecting flow path 500c during the open period of the intake valve 110a of one of the third cylinder #3 and the fourth cylinder #4, which are connected via the connecting flow path 500c. As a result, as shown in Fig. 3, the on-off valve 502c is open during the open period of the intake valve 110a of the third cylinder #3 and the open period of the intake valve 110a of the fourth cylinder #4. Therefore, as described above, the blow-by of unburned fuel is suppressed in the third cylinder #3 and the fourth cylinder #4.

[0041] In the above example, an example in which the on-off valve 502 is provided in each connection flow path 500 has been described. In the above example, the movement of fuel through the connection flow path 500 is appropriately achieved by the opening and closing operation of the on-off valve 502. For example, as described above, by opening the on-off valve 502, the fuel remaining in the intake port 104a of each cylinder can be sent to the other cylinders through the connection flow path 500. Furthermore, by closing the on-off valve 502 after the fuel has been moved through the connection flow path 500, the fuel sent to the other cylinders is prevented from flowing back through the connection flow path 500.

[0042] However, the on-off valve 502 does not have to be provided in the connection passage 500. Even in this case, a difference in pressure occurs in the intake port 104a between the cylinders connected via the connection passage 500 while the intake valve 110a of one of the cylinders is open. This causes fuel to move via the connection passage 500, and fuel remaining in the intake port 104a of each cylinder is sent to the other cylinders via the connection passage 500.

[0043] As described above, in the intake and exhaust system 1, different branch passages 202 are connected to each other by the connecting passage 500. This allows fuel remaining in the intake port 104a of each cylinder to be sent to the other cylinders via the connecting passage 500. This prevents unburned fuel from being discharged through the exhaust port 104b, thereby improving thermal efficiency and reducing greenhouse gas emissions.

[0044] In particular, in the intake / exhaust system 1, the opening periods of the intake valves 110a of the multiple cylinders connected via the connection flow path 500 do not overlap with each other. Specifically, as shown in Fig. 3, the opening periods of the intake valves 110a of the first cylinder #1 and the sixth cylinder #6 connected via the connection flow path 500a do not overlap with each other. The opening periods of the intake valves 110a of the second cylinder #2 and the fifth cylinder #5 connected via the connection flow path 500b do not overlap with each other. The opening periods of the intake valves 110a of the third cylinder #3 and the fourth cylinder #4 connected via the connection flow path 500c do not overlap with each other.

[0045] Therefore, when the intake valve 110a of one cylinder connected via the connecting flow path 500 is open, the intake valve 110a of the other cylinder is closed. This appropriately creates a situation in which a difference in pressure occurs in the intake port 104a between the cylinders when the intake valve 110a of one cylinder connected via the connecting flow path 500 is open. For example, this appropriately creates a situation in which a difference in pressure occurs in the intake port 104a between the cylinders from the start to the end of the opening period of the intake valve 110a of one cylinder connected via the connecting flow path 500. This more appropriately creates a situation in which fuel remaining in the intake port 104a of each cylinder is sent to the other cylinder via the connecting flow path 500.

[0046] However, the opening periods of the intake valves 110a of the multiple cylinders connected via the connecting passage 500 may partially overlap. Even in this case, a situation may occur in which the intake valve 110a of one cylinder connected via the connecting passage 500 is open while the intake valve 110a of the other cylinder is closed. Therefore, fuel remaining in the intake port 104a can be sent to the other cylinders via the connecting passage 500.

[0047] In the above example, the position at which the connection passage 500 is connected in the intake passage 200 is the intake port 104a. However, the position at which the connection passage 500 is connected in the intake passage 200 may be other than the intake port 104a. From the viewpoint of effectively sending fuel remaining in the intake port 104a to the connection passage 500, it is preferable that the position at which the connection passage 500 is connected in the intake passage 200 be as close as possible to the intake port 104a.

[0048] However, when connecting the connection flow passage 500 to the intake port 104a, the connection flow passage 500 needs to pass through the cylinder head 104. If it is difficult to pass the connection flow passage 500 through the cylinder head 104 due to design considerations, for example, the connection flow passage 500 may be connected to a portion of the branch flow passage 202 of the intake flow passage 200 that is outside the cylinder head 104. In this case, the position at which the connection flow passage 500 is connected in the intake flow passage 200 may be closer to the cylinder head 104 than the fuel injection valve 112, or may be on the opposite side of the fuel injection valve 112 from the cylinder head 104. In other words, the connection flow passage 500 may be connected to a portion of the branch flow passage 202 between the fuel injection valve 112 and the intake port 104a, or may be connected to a portion of the branch flow passage 202 upstream of the fuel injection valve 112.

[0049] In the above example, two cylinders are connected by the connection flow path 500. However, the number of cylinders connected by the connection flow path 500 may be other than two. For example, if the engine 100 has six cylinders as in the above example, two connection flow paths 500 may be provided, and each connection flow path 500 may connect three cylinders. In this case, for example, one connection flow path 500 may connect the first cylinder #1, the fourth cylinder #4, and the fifth cylinder #5, and the other connection flow path 500 may connect the second cylinder #2, the third cylinder #3, and the sixth cylinder #6. This prevents the opening periods of the intake valves 110a of the multiple cylinders connected via the connection flow paths 500 from overlapping with each other.

[0050] 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. [Explanation of symbols]

[0051] 1. Intake and exhaust system 100 Engine 108 Combustion chamber 110a intake valve 112 Fuel injection valve 200 Intake passage 202 Branch channel 500 connecting channels 500a connecting channel 500b connecting channel 500c connecting channel 502 On-off valve 502a On-off valve 502b On-off valve 502c On-off valve 600 control device

Claims

1. an intake flow path; a plurality of branch passages each connecting a plurality of combustion chambers of an engine having a plurality of cylinders to the intake passage, the branch passages being provided with fuel injection valves; a connecting flow path that connects the different branch flow paths; Equipped with The opening periods of the intake valves of the plurality of cylinders connected via the connecting flow passages do not overlap with each other. Engine intake and exhaust system.

2. An on-off valve is provided in the connecting flow path.

2. The engine intake and exhaust system according to claim 1.

3. a control device that opens the on-off valve during an opening period of an intake valve of any one of the plurality of cylinders connected via the connection flow path; 3. The engine intake and exhaust system according to claim 2.

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