Internal combustion engine

Abstract

To provide an internal combustion engine capable of suppressing unburned fuel. [Solution] The internal combustion engine includes a cylinder, a piston housed in the cylinder and reciprocatingly driven along the axial direction of the cylinder, a main fuel supply unit provided at one end of the cylinder and supplying main fuel into the cylinder, and a control unit that controls the main fuel supply unit. The main fuel supply unit or the control unit is configured so that the main fuel supply unit injects main fuel into the cylinder when the piston is at intake bottom dead center.

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine. [Background technology]

[0002] Patent Document 1 discloses an internal combustion engine that uses ammonia as fuel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-178623 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the internal combustion engine of Patent Document 1, the combustion flame comes into contact with the piston during the expansion stroke, and heat is transferred from the combustion flame to the piston, causing a heat loss, which may result in ammonia remaining unburned.

[0005] An object of the present invention is to provide an internal combustion engine capable of suppressing unburned fuel. [Means for solving the problem]

[0006] One aspect of the present invention is A cylinder; A piston that is accommodated in the cylinder and is driven to reciprocate along an axial direction of the cylinder; a main fuel supply unit provided on one end side of the cylinder and supplying a main fuel into the cylinder; a control unit for controlling the main fuel supply unit; Equipped with The present invention provides an internal combustion engine, wherein the main fuel supply unit or the control unit is configured such that the main fuel supply unit injects the main fuel into the cylinder when the piston is at intake bottom dead center.

[0007] According to this configuration, it is possible to suppress the main fuel from remaining unburned. In an internal combustion engine, the main fuel may remain unburned due to heat loss caused by the combustion flame contacting the piston during the expansion stroke and heat being transferred from the combustion flame to the piston. In contrast, according to this configuration, the main fuel supply unit injects the main fuel into the cylinder when the piston is at the intake bottom dead center, where the volume of the combustion chamber is maximum, so that a layer of air with a lean fuel content is formed on the upper surface of the piston during the expansion stroke. This layer of air suppresses the combustion flame from coming into contact with the piston, so that the amount of heat transferred from the combustion flame to the piston can be reduced. As a result, it is possible to suppress the main fuel from remaining unburned.

[0008] Another aspect of the present invention is A cylinder; A piston that is accommodated in the cylinder and is driven to reciprocate along an axial direction of the cylinder; a main fuel supply unit provided on one end side of the cylinder and supplying a main fuel into the cylinder; an intake valve that opens and closes an intake port for supplying air into the cylinder; a control unit for controlling the main fuel supply unit; Equipped with The present invention provides an internal combustion engine, wherein the main fuel supply or the control unit is configured such that when the intake valve closes the intake port, the main fuel supply injects the main fuel into the cylinder.

[0009] According to this configuration, since the main fuel supply unit injects the main fuel into the cylinder when the intake valve closes the intake port, a layer of air with a lean fuel content is formed on the upper surface of the piston during the expansion stroke. This layer of air prevents the combustion flame from coming into contact with the piston, thereby reducing the amount of heat transferred from the combustion flame to the piston. As a result, the main fuel is prevented from remaining unburned.

[0010] In one embodiment, the angular range of crank angles corresponding to the period of injection of the main fuel from the main fuel supply into the cylinder is greater than 0° and less than or equal to 40°.

[0011] According to this configuration, the main fuel is supplied from the main fuel supply unit into the cylinder in a short time, so that a layer of air with a thin fuel content can be more reliably formed on the upper surface of the piston during the expansion stroke, thereby more reliably preventing the main fuel from remaining unburned.

[0012] In one embodiment, the main fuel supply unit or the control unit is configured such that, when the main fuel is compressed in the cylinder, the concentration of the main fuel on the piston side in the cylinder is thinner than the concentration of the main fuel on the opposite side to the piston side in the cylinder.

[0013] According to this configuration, the concentration of the main fuel in the combustion chamber during the compression stroke becomes denser the further away from the piston in the axial direction of the piston. Therefore, a layer of air with a lean fuel content is formed on the upper surface of the piston during the expansion stroke. This layer of air prevents the combustion flame from coming into contact with the piston, thereby reducing the amount of heat transferred from the combustion flame to the piston. As a result, it is possible to prevent the main fuel from remaining unburned.

[0014] In one embodiment, the primary fuel is ammonia or methanol. Effect of the Invention

[0015] According to the present invention, it is possible to provide an internal combustion engine capable of suppressing unburned fuel. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic configuration diagram of an internal combustion engine according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram for explaining the timing of supplying the main fuel in the internal combustion engine according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram for explaining the timing of supplying the main fuel in an internal combustion engine according to a modified example of an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram for explaining the timing of supplying the main fuel in an internal combustion engine according to another modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0018] FIG. 1 is a schematic diagram of an internal combustion engine according to this embodiment. The internal combustion engine 1 according to this embodiment is a marine internal combustion engine. The internal combustion engine 1 according to this embodiment is a medium-speed engine. For example, the internal combustion engine 1 according to this embodiment is an internal combustion engine having a rotation speed of 600 [rpm] to 900 [rpm]. Referring to FIG. 1, the internal combustion engine 1 includes a cylinder 10, a piston 20, a main fuel injection device 30, and a pilot fuel injection device 40.

[0019] The cylinder 10 is cylindrical and accommodates the piston 20. The cylinder 10 extends in an axial direction A. In the following description, the axial direction A of the cylinder 10 may be simply referred to as the axial direction A, and a direction perpendicular to the axial direction A may be referred to as the lateral direction.

[0020] The cylinder 10 includes a cylinder liner 11 for accommodating a piston 20, and a cylinder head 12 disposed on the cylinder liner 11. The cylinder head 12 is disposed on one side of the cylinder 10 in the axial direction A (the upper side in FIG. 1 ). The cylinder liner 11, the cylinder head 12, and the piston 20 define a combustion chamber 13 of the internal combustion engine 1. In other words, the combustion chamber 13 of the internal combustion engine 1 is a space surrounded by the cylinder liner 11, the cylinder head 12, and the piston 20.

[0021] The cylinder head 12 is provided with an intake passage 14 for supplying air into the combustion chamber 13. The intake passage 14 communicates with the combustion chamber 13 via an intake port 15. The cylinder head 12 is provided with an intake valve 16 that opens and closes the intake port 15. During the intake stroke, the intake valve 16 opens, thereby supplying air into the combustion chamber 13 via the intake passage 14 and the intake port 15.

[0022] The cylinder head 12 is provided with an exhaust passage 17 for discharging the burnt mixture from the combustion chamber 13. The exhaust passage 17 is in communication with the combustion chamber 13 via an exhaust port 18. The cylinder head 12 is provided with an exhaust valve 19 for opening and closing the exhaust port 18. During the exhaust stroke, the exhaust valve 19 opens, discharging the burnt mixture from the combustion chamber 13 via the exhaust passage 17 and the exhaust port 18.

[0023] The piston 20 is housed in the cylinder 10 and reciprocates within the cylinder 10 along the axial direction A of the cylinder 10. The volume of the combustion chamber 13 changes as the piston 20 reciprocates within the cylinder 10 along the axial direction A. A crankshaft 21 is connected to the piston 20. The crankshaft 21 converts the reciprocating motion of the piston 20 into rotational motion. The crankshaft 21 is connected to a generator (not shown). The rotational motion of the crankshaft 21 is transmitted to the generator to drive it.

[0024] An angle sensor 22 that detects the crank angle θ is attached to the crankshaft 21.

[0025] The crankshaft 21 is mechanically connected to the intake valve 16. As a result, the intake valve 16 opens and closes the intake port 15 in accordance with the crank angle θ of the crankshaft 21. Similarly, the crankshaft 21 is mechanically connected to the exhaust valve 19. As a result, the exhaust valve 19 opens and closes the exhaust port 18 in accordance with the crank angle θ of the crankshaft 21.

[0026] The main fuel injection device 30 is attached to the cylinder head 12 so as to face the combustion chamber 13. The main fuel injection device 30 is disposed on one end side of the cylinder 10. In other words, the main fuel injection device 30 is disposed on one side of the cylinder 10 in the axial direction A (the upper side in FIG. 1).

[0027] The main fuel injection device 30 is supplied with a main fuel from a main fuel source 31. The main fuel in this embodiment is ammonia. The main fuel injection device 30 vaporizes the main fuel supplied from the main fuel supply source 31 and injects it into the combustion chamber 13. More specifically, the main fuel injection device 30 injects the main fuel so that the main fuel moves laterally outward as it approaches from one side to the other side in the axial direction A (as it approaches from the upper side to the lower side in FIG. 1). In other words, the main fuel injection device 30 injects the main fuel so that the main fuel moves laterally outward as it approaches the piston 20 in the axial direction A. The main fuel injection device 30 is configured to inject the main fuel in a direction in which an angle α with respect to the axial direction A is equal to or greater than 45° and less than 90° in a cross section along the axial direction A (for example, the cross section shown in FIG. 1). The main fuel injection device 30 in this embodiment is an example of a main fuel supply unit according to the present invention.

[0028] The pilot fuel injection device 40 is attached to the cylinder head 12 so as to face the combustion chamber 13. The pilot fuel injection device 40 is disposed on one end side of the cylinder 10. In other words, the pilot fuel injection device 40 is disposed on one side of the cylinder 10 in the axial direction A. Pilot fuel is supplied to the pilot fuel injection device 40 from a pilot fuel source 41. The pilot fuel in this embodiment is heavy oil or light oil. The pilot fuel injection device 40 injects the pilot fuel supplied from the pilot fuel source 41 into the combustion chamber 13. The pilot fuel injection device 40 functions as an ignition device.

[0029] The internal combustion engine 1 includes a control unit 50 that controls the main fuel injector 30 and the pilot fuel injector 40 .

[0030] The control unit 50 is composed of a microcomputer, an input / output circuit, etc. The control unit 50 is electrically connected to each of the main fuel injection device 30, the pilot fuel injection device 40, and the angle sensor 22. A signal indicating the crank angle θ of the crankshaft 21 is input to the control unit 50 from the angle sensor 22. The control unit 50 controls the timing at which the main fuel injection device 30 injects main fuel and the timing at which the pilot fuel injection device 40 injects pilot fuel based on the crank angle θ of the crankshaft 21.

[0031] FIG. 2 is a diagram for explaining the timing at which the main fuel injection device 30 supplies the main fuel. FIG. 2 shows one cycle of the internal combustion engine 1, which is composed of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The horizontal axis of FIG. 2 is the crank angle θ [°]. In addition, on the horizontal axis of FIG. 2, BDC1 indicates the intake bottom dead center, and BDC2 indicates the expansion bottom dead center. In addition, on the horizontal axis of FIG. 2, TDC1 indicates the compression top dead center, and TDC2 indicates the exhaust top dead center. In addition, FIG. 2 shows the timing at which the main fuel injection device 30 supplies the main fuel, the timing at which the pilot fuel injection device 40 injects the pilot fuel, the timing at which the intake valve 16 is opened and closed, and the timing at which the exhaust valve 19 is opened and closed. Specifically, FIG. 2 shows the injection amount IM1 of the main fuel, the injection amount IM2 of the pilot fuel, the valve opening degree OP1 of the intake valve 16, and the valve opening degree OP2 of the exhaust valve 19. FIG. 2 also shows the internal pressure CP of the cylinder 10.

[0032] The control unit 50 controls the main fuel injection device 30 so that, when the main fuel is compressed in the cylinder 10, the concentration of the main fuel on the piston 20 side in the cylinder 10 becomes thinner than the concentration of the main fuel on the opposite side of the piston 20 side in the cylinder 10. In other words, the control unit 50 controls the timing at which the main fuel injection device 30 injects the main fuel so that the concentration of the main fuel in the cylinder 10 in the compression stroke becomes thinner on the piston 20 side in the axial direction A than on the cylinder head 12 side. Specifically, as shown in FIG. 2, in this embodiment, the main fuel injection device 30 injects the main fuel during an injection period T that spans from the intake stroke to the compression stroke. In detail, the control unit 50 in this embodiment controls the main fuel injection device 30 so that the main fuel injection device 30 injects the main fuel during an injection period T that spans from the intake stroke to the compression stroke.

[0033] In this embodiment, a part of the injection period T overlaps with the intake stroke, and another part of the injection period T overlaps with the compression stroke. It is preferable that the entire angle range of the crank angle θ of the crankshaft 21 corresponding to the injection period T of the main fuel is included in the range from 30° before the intake bottom dead center to 30° after the intake bottom dead center. That is, it is preferable that the crank angle θ when the main fuel injection device 30 starts injecting the main fuel is within 30° before the intake bottom dead center, and the crank angle θ when the fuel injection device 30 finishes injecting the main fuel is within 30° after the intake bottom dead center. It is more preferable that the crank angle θ when the main fuel injection device 30 starts injecting the main fuel is within 20° before the intake bottom dead center. It is more preferable that the crank angle θ when the main fuel injection device 30 finishes injecting the main fuel is within 25° after the intake bottom dead center.

[0034] The control unit 50 controls the main fuel injection device 30 so that the injection period T is short. Specifically, in this embodiment, the angle range of the crank angle θ of the crankshaft 21 corresponding to the injection period T of the main fuel is 30°. It is preferable that the angle range of the crank angle θ of the crankshaft 21 corresponding to the injection period T of the main fuel is greater than 0° and equal to or less than 40°. It is more preferable that the angle range of the crank angle θ of the crankshaft 21 corresponding to the injection period T of the main fuel is greater than 5° and equal to or less than 30°.

[0035] In this embodiment, as shown in FIG. 2, when the piston 20 is at the intake bottom dead center, that is, when the crank angle θ is BDC1, the main fuel injection device 30 injects the main fuel. In detail, the control unit 50 of this embodiment controls the main fuel injection device 30 so that the main fuel injection device 30 injects the main fuel when the piston 20 is at the intake bottom dead center, that is, when the crank angle θ is BDC1. Since the volume of the combustion chamber 13 is maximum at the intake bottom dead center, the main fuel injected from the main fuel injection device 30 at the intake bottom dead center is unlikely to reach the piston 20. As a result, a fuel layer FL (shown in FIG. 1) having a high concentration of the main fuel is formed on one side (cylinder head 12 side) in the axial direction A in the cylinder 10, while an air layer AL (shown in FIG. 1) having a low concentration of the main fuel is formed on the other side (piston 20 side) in the axial direction A in the cylinder 10.

[0036] In this embodiment, as shown in FIG. 2, when the intake valve 16 closes the intake port 15, the main fuel injection device 30 injects the main fuel. In other words, when the valve opening degree of the intake valve 16 becomes zero, the main fuel injection device 30 injects the main fuel. In detail, the control unit 50 of this embodiment controls the main fuel injection device 30 so that the main fuel injection device 30 injects the main fuel when the intake valve 16 closes the intake port 15. As shown in FIG. 2, the intake valve 16 closes the intake port 15 near the intake bottom dead center where the volume of the combustion chamber 13 is maximum. For this reason, the main fuel injected from the main fuel injection device 30 when the intake valve 16 closes the intake port 15 is unlikely to reach the piston 20. As a result, a fuel layer FL (shown in FIG. 1) with a high concentration of the main fuel is formed on one side of the axial direction A in the cylinder 10, while an air layer AL with a low concentration of the main fuel is formed on the other side of the axial direction A in the cylinder 10.

[0037] (effect) According to the internal combustion engine 1 of the present embodiment, it is possible to suppress the main fuel from remaining unburned. In the internal combustion engine 1, the combustion flame comes into contact with the piston 20 during the expansion stroke, and the main fuel may remain unburned due to heat loss caused by the transfer of heat from the combustion flame to the piston. In contrast, according to the internal combustion engine 1 of the present embodiment, the main fuel injection device 30 injects the main fuel into the cylinder 10 at the intake bottom dead center where the volume of the combustion chamber 13 is maximum, so that an air layer AL in which the main fuel is lean is formed on the upper surface of the piston 20 during the expansion stroke. This air layer AL suppresses the combustion flame from coming into contact with the piston 20, so that the amount of heat transferred from the combustion flame to the piston 20 can be reduced. As a result, it is possible to suppress the main fuel from remaining unburned.

[0038] In this embodiment, the main fuel injection device 30 injects the main fuel into the cylinder 10 when the intake valve 16 closes the intake port 15, so that an air layer AL in which the main fuel is lean is formed on the upper surface of the piston 20 during the expansion stroke. This air layer AL prevents the combustion flame from coming into contact with the piston 20, so the amount of heat transferred from the combustion flame to the piston 20 can be reduced. As a result, the main fuel can be prevented from remaining unburned.

[0039] In this embodiment, the angle range of the crank angle θ corresponding to the injection period T of the main fuel from the main fuel injection device 30 into the cylinder 10 is greater than 0° and equal to or less than 40°. With this configuration, the main fuel is supplied from the main fuel injection device 30 into the cylinder 10 in a short period of time, so that the layer AL of air with a thin fuel content can be more reliably formed on the upper surface of the piston 20 during the expansion stroke. As a result, it is possible to more reliably prevent the main fuel from remaining unburned.

[0040] According to this configuration, the concentration of the main fuel in the combustion chamber 13 during the compression stroke becomes denser as it moves away from the piston 20 in the axial direction A. Therefore, during the expansion stroke, a layer of air AL with lean fuel is formed on the upper surface of the piston 20. This layer of air AL prevents the combustion flame from coming into contact with the piston 20, thereby reducing the amount of heat transferred from the combustion flame to the piston 20. As a result, it is possible to prevent the main fuel from remaining unburned.

[0041] It is generally known that when ammonia is burned at a high temperature, the generation of nitrous oxide is suppressed compared to when ammonia is burned at a low temperature. In this embodiment, a fuel layer FL having a high concentration of the main fuel is formed on one side in the axial direction A where the pilot fuel injection device 40 serving as an ignition device is disposed, so that the main fuel can be burned at a higher temperature compared to when the main fuel is uniformly distributed in the combustion chamber 13. As a result, when ammonia is used as the main fuel as in this embodiment, the generation of nitrous oxide can be suppressed.

[0042] In this embodiment, the main fuel injection device 30 injects the main fuel so that the main fuel moves laterally outward as it approaches the piston 20 in the axial direction A. In particular, the main fuel injection device 30 is configured to inject the main fuel in a direction inclined by 45° or more with respect to the axial direction in a cross section along the axial direction A. With this configuration, the axial direction A component of the direction in which the main fuel is injected is smaller than the lateral direction component, so that the main fuel injected from the main fuel injection device 30 is unlikely to reach the piston 20. As a result, a fuel layer FL (shown in FIG. 1) in which the concentration of the main fuel is high is formed on one side (cylinder head 12 side) in the axial direction A in the cylinder 10, while an air layer AL (shown in FIG. 1) in which the main fuel is lean is formed on the other side (piston 20 side) in the axial direction A in the cylinder 10. This makes it possible to suppress the main fuel from remaining unburned.

[0043] When a hydrocarbon fuel is used as the main fuel, if the main fuel injected into the cylinder 10 adheres to the wall surface of the cylinder liner 11, combustion products such as carbon monoxide or soot may be generated. In contrast, in this embodiment, ammonia is used as the main fuel, and therefore the main fuel injection device 30 injects the main fuel so that the main fuel moves laterally outward as it approaches the piston 20 in the axial direction A, and therefore no combustion products such as carbon monoxide or soot are generated even if the main fuel adheres to the cylinder liner 11. In other words, even if the main fuel injection device 30 injects the main fuel toward the cylinder liner 11, no combustion products such as carbon monoxide or soot are generated.

[0044] Although the present invention has been fully described in connection with the preferred embodiments with reference to the accompanying drawings, various changes and modifications will be apparent to those skilled in the art, and such changes and modifications should be understood to be included within the scope of the present disclosure as defined by the appended claims unless they depart therefrom.

[0045] In the above embodiment, the control unit 50 controls the main fuel injection device 30 so that the main fuel injection device 30 injects the main fuel both when the piston 20 is at the bottom dead center of the intake stroke and when the intake valve 16 closes the intake port 15, but this is not limited to the above. The control unit 50 may control the main fuel injection device 30 so that the main fuel injection device 30 injects the main fuel either when the piston 20 is at the bottom dead center of the intake stroke or when the intake valve 16 closes the intake port 15. For example, as in a modified example shown in FIG. 3, the main fuel injection device 30 may start injecting the main fuel when the piston 20 is at the bottom dead center of the intake stroke, or as in a modified example shown in FIG. 4, the main fuel injection device 30 may start injecting the main fuel when the intake valve 16 closes the intake port 15. Also, although not shown, the main fuel injection device 30 may finish injecting the main fuel immediately after the piston 20 passes the intake bottom dead center, or the main fuel injection device 30 may finish injecting the main fuel immediately after the intake valve 16 closes the intake port 15.

[0046] In the above embodiment, the timing at which the main fuel injection device 30 injects the main fuel is controlled by the control unit 50, but this is not limited to the above. The timing at which the main fuel injection device 30 injects the main fuel may be controlled without using the control unit 50. For example, the timing at which the main fuel injection device 30 injects the main fuel may be controlled using a mechanical mechanism.

[0047] In the above embodiment, ammonia is used as the main fuel, but the present invention is not limited to this. For example, methanol may be used as the main fuel. [Explanation of symbols]

[0048] 1. Internal combustion engine 10 Cylinders 11 Cylinder liner 12. Cylinder head 13 Combustion chamber 14 Intake passage 15 Intake port 16 Intake valve 17 Exhaust passage 18 Exhaust port 19 Exhaust valve 20 Piston 21 Crankshaft 22 Angle Sensor 30 Main fuel injection device (main fuel supply section) 31 Main fuel source 40 Pilot fuel injector 41 Pilot Fuel Source 50 Control section

Claims

1. An internal combustion engine that is a medium speed engine having an engine speed of 600 to 900 rpm, A cylinder; A piston that is accommodated in the cylinder and is driven to reciprocate along an axial direction of the cylinder; a main fuel supply unit provided on one end side of the cylinder and supplying a main fuel into the cylinder; a pilot fuel supply unit provided on one end side of the cylinder and supplying pilot fuel into the cylinder; a control unit for controlling the main fuel supply unit; Equipped with An internal combustion engine, wherein the main fuel supply or the control unit is configured such that the main fuel supply injects the main fuel into the cylinder when the piston is at intake bottom dead center.

2. An internal combustion engine that is a medium speed engine having an engine speed of 600 to 900 rpm, A cylinder; A piston that is accommodated in the cylinder and is driven to reciprocate along an axial direction of the cylinder; a main fuel supply unit provided on one end side of the cylinder and supplying a main fuel into the cylinder; a pilot fuel supply unit provided on one end side of the cylinder and supplying pilot fuel into the cylinder; an intake valve that opens and closes an intake port for supplying air into the cylinder; a control unit for controlling the main fuel supply unit; Equipped with An internal combustion engine, wherein the main fuel supply or the control unit is configured such that when the intake valve closes the intake port, the main fuel supply injects the main fuel into the cylinder.

3. 3. The internal combustion engine according to claim 1, wherein an angle range of crank angles corresponding to a period during which the main fuel is injected from the main fuel supply into the cylinder is greater than 0° and is equal to or smaller than 40°.

4. 3. The internal combustion engine according to claim 1, wherein the main fuel supply unit or the control unit is configured such that, when the main fuel is compressed in the cylinder, a concentration of the main fuel on a side of the piston in the cylinder is thinner than a concentration of the main fuel on a side of the cylinder opposite to the piston side.

5. 3. The internal combustion engine according to claim 1, wherein the main fuel is ammonia or methanol.

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