Internal combustion engine

Abstract

To provide an internal combustion engine that can inhibit fuel from remaining half-burned.SOLUTION: An internal combustion engine comprises a cylinder, a piston that is received in the cylinder and reciprocatively driven along the axial direction of the cylinder, a main fuel supply unit that is provided at one end side of the cylinder and supplies main fuel into the cylinder, and a control unit for controlling the main fuel supply unit. The main fuel supply unit or the control unit is configured so that the main fuel supply unit is injecting main fuel into the cylinder when the piston is at an intake bottom dead center.SELECTED DRAWING: Figure 2

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] Japanese Patent Application Publication No. 2019-178623 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 heat loss, which may result in ammonia remaining unburned.

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

[0006] One aspect of the present invention is A cylinder; a piston accommodated in the cylinder and reciprocatingly driven along the axial direction of the cylinder; a main fuel supply unit provided at one end side of the cylinder and supplying main fuel into the cylinder; a control unit that controls 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 so that the main fuel supply unit injects the main fuel into the cylinder when the piston is at intake bottom dead center.

[0007] This configuration can prevent the main fuel from remaining unburned. In an internal combustion engine, the combustion flame comes into contact with the piston during the expansion stroke, and heat is transferred from the combustion flame to the piston, resulting in heat loss, which can cause the main fuel to remain unburned. In contrast, this configuration allows the main fuel supply unit to inject the main fuel into the cylinder when the piston is at bottom dead center of the intake stroke, where the volume of the combustion chamber is greatest. Therefore, a layer of air with a lean fuel content is formed on the top surface of the piston during the expansion stroke. This air layer 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 can be prevented from remaining unburned.

[0008] Another aspect of the present invention is A cylinder; a piston accommodated in the cylinder and reciprocatingly driven along the axial direction of the cylinder; a main fuel supply unit provided at one end side of the cylinder and supplying main fuel into the cylinder; an intake valve that opens and closes an intake port for supplying air into the cylinder; a control unit that controls 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 when the intake valve closes the intake port, the main fuel supply unit injects the main fuel into the cylinder.

[0009] With this configuration, the main fuel supply unit injects main fuel into the cylinder when the intake valve closes the intake port, so a layer of air with a lean fuel content is formed above the piston during the expansion stroke. This air layer 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.

[0010] In one embodiment, the angular range of crank angles corresponding to the duration 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] With this configuration, the main fuel is supplied from the main fuel supply unit into the cylinder in a short time, which more reliably forms a layer of air with a lean fuel content 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 so 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 of the piston side in the cylinder.

[0013] With this configuration, the concentration of the main fuel in the combustion chamber during the compression stroke increases with increasing distance from the piston in the axial direction of the piston. As a result, a layer of air with a lean fuel content is formed on the upper surface of the piston during the expansion stroke. This air layer 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. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an internal combustion engine that can suppress unburned fuel. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine according to one embodiment of the present invention. [Figure 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. [Figure 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 one 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 one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[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 an internal combustion engine for a ship. 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 to 900 rpm. Referring to FIG. 1, the internal combustion engine 1 includes a cylinder 10, a piston 20, a main fuel injector 30, and a pilot fuel injector 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 the 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 the 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 is in communication 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, and air is supplied 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 burned 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 that opens and closes the exhaust port 18. During the exhaust stroke, the exhaust valve 19 opens, discharging the burned 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, thereby driving the generator.

[0024] An angle sensor 22 for detecting 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 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 in the axial direction A (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 of this embodiment is an example of a main fuel supply unit according to the present invention.

[0028] The pilot fuel injector 40 is attached to the cylinder head 12 so as to face the combustion chamber 13. The pilot fuel injector 40 is disposed on one end side of the cylinder 10. In other words, the pilot fuel injector 40 is disposed on one side of the cylinder 10 in the axial direction A. Pilot fuel is supplied to the pilot fuel injector 40 from a pilot fuel source 41. The pilot fuel in this embodiment is heavy oil or light oil. The pilot fuel injector 40 injects the pilot fuel supplied from the pilot fuel source 41 into the combustion chamber 13. The pilot fuel injector 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 illustrating the timing at which the main fuel injection device 30 supplies main fuel. FIG. 2 shows one cycle of the internal combustion engine 1, which consists of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The horizontal axis of FIG. 2 represents the crank angle θ [°]. Note that on the horizontal axis of FIG. 2, BDC1 represents the intake bottom dead center, and BDC2 represents the expansion bottom dead center. Also on the horizontal axis of FIG. 2, TDC1 represents the compression top dead center, and TDC2 represents the exhaust top dead center. FIG. 2 also shows the timing at which the main fuel injection device 30 supplies main fuel, the timing at which the pilot fuel injection device 40 injects pilot fuel, the timing at which the intake valve 16 opens and closes, and the timing at which the exhaust valve 19 opens and closes. Specifically, FIG. 2 shows the injection amount IM1 of the main fuel, the injection amount IM2 of the pilot fuel, the valve opening OP1 of the intake valve 16, and the valve opening 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 is thinner than the concentration of the main fuel on the opposite side of the cylinder 10 from the piston 20 side. 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 on the piston 20 side in the axial direction A during the compression stroke is thinner than the concentration of the main fuel 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 spanning from the intake stroke to the compression stroke. In more 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 spanning from the intake stroke to the compression stroke.

[0033] In this embodiment, a portion of the injection period T overlaps with the intake stroke, and another portion of the injection period T overlaps with the compression stroke. The entire angular range of the crank angle θ of the crankshaft 21 corresponding to the main fuel injection period T is preferably within the range from 30° before bottom dead center to 30° after bottom dead center. That is, the crank angle θ when the main fuel injection device 30 starts injecting the main fuel is preferably within 30° before bottom dead center, and the crank angle θ when the fuel injection device 30 finishes injecting the main fuel is preferably within 30° after bottom dead center. More preferably, the crank angle θ when the main fuel injection device 30 starts injecting the main fuel is preferably within 20° before bottom dead center. More preferably, the crank angle θ when the main fuel injection device 30 finishes injecting the main fuel is preferably within 25° after 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°. The angle range of the crank angle θ of the crankshaft 21 corresponding to the injection period T of the main fuel is preferably greater than 0° and not greater 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 not greater than 30°.

[0035] In this embodiment, as shown in FIG. 2, 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. Specifically, 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. Because 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 has difficulty reaching 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 (the cylinder head 12 side) of the cylinder 10 in the axial direction A, while a layer AL (shown in FIG. 1) of air with a lean main fuel is formed on the other side (the piston 20 side) of the cylinder 10 in the axial direction A.

[0036] In this embodiment, as shown in FIG. 2, the main fuel injection device 30 injects the main fuel when the intake valve 16 closes the intake port 15. In other words, the main fuel injection device 30 injects the main fuel when the valve opening of the intake valve 16 becomes zero. Specifically, 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 maximized. Therefore, the main fuel injected from the main fuel injection device 30 when the intake valve 16 closes the intake port 15 does not easily 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 cylinder 10 in the axial direction A, while an air layer AL with a low concentration of the main fuel is formed on the other side of the cylinder 10 in the axial direction A.

[0037] (effect) The internal combustion engine 1 of this embodiment can prevent 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 heat is transferred from the combustion flame to the piston, resulting in heat loss, which can cause the main fuel to remain unburned. In contrast, in the internal combustion engine 1 of this embodiment, the main fuel injection device 30 injects the main fuel into the cylinder 10 at the intake bottom dead center, when the volume of the combustion chamber 13 is at its maximum. Therefore, a layer of air AL containing a lean amount of main fuel is formed above the top 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, thereby reducing the amount of heat transferred from the combustion flame to the piston 20. As a result, the main fuel can be prevented from remaining unburned.

[0038] In this embodiment, the main fuel injector 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 above 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, 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.

[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 time, which more reliably forms a fuel-lean air layer AL 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 with increasing distance 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 air layer 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 main fuel is formed on one side in the axial direction A where pilot fuel injection device 40 serving as an ignition device is disposed, and therefore the main fuel can be burned at a higher temperature compared to when the main fuel is uniformly distributed within 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, making it difficult for the main fuel injected from the main fuel injection device 30 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 (the cylinder head 12 side) in the cylinder 10, while an air layer AL (shown in FIG. 1) with a lean main fuel is formed on the other side of the axial direction A (the piston 20 side) in the cylinder 10. This makes it possible to suppress unburned main fuel.

[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 the main fuel injector 30 injects the main fuel so that the main fuel moves laterally outward as it approaches the piston 20 in the axial direction A. This prevents the generation of combustion products such as carbon monoxide or soot, even if the main fuel adheres to the cylinder liner 11. In other words, even if the main fuel injector 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 are to be understood as 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 injector 30 so that the main fuel injector 30 injects the main fuel both when the piston 20 is at the intake bottom dead center and when the intake valve 16 closes the intake port 15. However, this is not limited to this. The control unit 50 may also control the main fuel injector 30 so that the main fuel injector 30 injects the main fuel either when the piston 20 is at the intake bottom dead center 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 injector 30 may start injecting the main fuel when the piston 20 is at the intake bottom dead center, or as in a modified example shown in FIG. 4 , the main fuel injector 30 may start injecting the main fuel when the intake valve 16 closes the intake port 15. Also, although not shown, the main fuel injector 30 may finish injecting the main fuel immediately after the piston 20 passes the intake bottom dead center, or 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 limiting. The timing at which the main fuel injection device 30 injects the main fuel may be controlled without 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 this is not limiting. 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 pistons 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. A cylinder; a piston accommodated in the cylinder and reciprocatingly driven along the axial direction of the cylinder; a main fuel supply unit provided at one end side of the cylinder and supplying main fuel into the cylinder; a control unit that controls the main fuel supply unit; Equipped with 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.

2. A cylinder; a piston accommodated in the cylinder and reciprocatingly driven along the axial direction of the cylinder; a main fuel supply unit provided at one end side of the cylinder and supplying main fuel into the cylinder; an intake valve that opens and closes an intake port for supplying air into the cylinder; a control unit that controls 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 the crank angle range corresponding to the injection period of the main fuel from the main fuel supply portion into the cylinder is greater than 0° and equal to or less than 40°.

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

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

Images