Gas engine

Abstract

To achieve both promotion of diffusion and combustion of liquid fuel and gas fuel, and suppression of coking of an injection port in a gas injection valve.SOLUTION: The engine 1 combusts the gas fuel and the liquid fuel in the same cylinder 16. The engine 1 includes the cylinder 16 that forms the combustion chamber 17, the scavenge port 14a that generates the swirling flow by the air by regulating the flow of the air sucked into the cylinder 16, and the gas injector 30 that injects the hydrogen gas into the combustion chamber 17 so that the hydrogen gas flows in accordance with the swirling flow. When viewed along the center line C of the cylinder 16, the length (first length R1) between the gas injector 30 and the center line C is longer than the length (second length R2) between the liquid injector 40 and the center line C.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to gas engines. [Background technology]

[0002] For example, Patent Document 1 discloses an engine that burns gas fuel and oil fuel in a cylinder. The engine according to Patent Document 1 injects a small amount of pilot oil into the combustion chamber together with a sufficient amount of high-pressure gas fuel.

[0003] According to Patent Document 1, the engine according to the document can be configured to supply pilot oil from a dedicated pilot oil valve separate from the fuel injection valve that injects high-pressure gas fuel. In this case, both the fuel injection valve and the pilot oil valve are arranged on the cylinder cover. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-11871 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present application have considered diffusing gas fuel and oil fuel into the combustion chamber by a swirl flow. In this case, it is conceivable to arrange an injection valve for injecting oil fuel (hereinafter referred to as an "oil injection valve") and an injection valve for injecting gas fuel (hereinafter referred to as a "gas injection valve") adjacent to each other along the flow direction of the swirl flow.

[0006] However, when two injection valves are adjacent to each other as described above, there is a possibility that the oil fuel injected from the upstream oil injection valve will be sprayed onto the downstream gas injection valve. In this case, the oil fuel will burn at the tip of the gas injection valve, which may cause so-called coking at the injection port of the gas injection valve.

[0007] In order to prevent such clogging, it is possible to devise an ingenious arrangement for the oil injection valve and the gas injection valve, but rather than simply changing the arrangement, it is advantageous to avoid interfering with the diffusion of the oil fuel and the gas fuel by the swirl flow, and ultimately with the ignition of the gas fuel by the oil fuel.

[0008] These problems are not limited to oil fuels and oil injection valves, but are common to liquid fuels containing organic compounds and liquid injection valves that inject such liquid fuels.

[0009] The present disclosure has been made in consideration of these points, and its purpose is to achieve both the promotion of diffusion and combustion of liquid fuel and gas fuel and the suppression of coking of the injection port in the gas injection valve. [Means for solving the problem]

[0010] A first aspect of the present disclosure relates to a gas engine that combusts gaseous fuel and liquid fuel containing an organic compound in the same cylinder. The gas engine includes a cylinder that forms a combustion chamber, a rectifying means that rectifies the flow of air drawn into the cylinder to generate a swirl flow of the air, a gas injector that injects the gaseous fuel into the combustion chamber so that the gaseous fuel flows along the swirl flow, and a liquid injector that is adjacent to the gas injector on the upstream side of the swirl flow and injects the liquid fuel into the combustion chamber.

[0011] According to the first aspect, when viewed along the central axis of the cylinder, the distance between the gas injection valve and the central axis is longer than the distance between the liquid injection valve and the central axis.

[0012] According to the first aspect, the distance between the gas injector and the central axis (hereinafter also referred to as the "first distance") is longer than the distance between the liquid injector and the central axis (hereinafter also referred to as the "second distance"). That is, in the radial direction perpendicular to the central axis, the liquid injector is located more inward than the gas injector. This makes it possible to prevent the liquid fuel from being sprayed onto the gas injector located downstream when the liquid injector located upstream injects liquid fuel. This prevents coking of the injection port.

[0013] Furthermore, the first aspect can be realized while maintaining the gas injector and the liquid injector adjacent to each other in the swirl direction (the direction of the swirl flow) as much as possible, which is effective in maintaining the diffusion of the liquid fuel and the gas fuel by the swirl flow and the ignition of the gas fuel by the liquid fuel.

[0014] Furthermore, by locating the gas injection valve relatively outward, the gas fuel injected from the gas injection valve travels largely around the side wall of the combustion chamber, thereby enabling the gas fuel to be uniformly dispersed throughout the combustion chamber.

[0015] Furthermore, by arranging the liquid injection valve inside the gas injection valve, the liquid fuel injected from the liquid injection valve is more likely to collide with the gas fuel injected from the gas injection valve, which is advantageous for igniting the gas fuel with the liquid fuel.

[0016] In this way, according to the first aspect, it is possible to both promote the diffusion and combustion of the liquid fuel and the gas fuel and suppress coking of the injection port of the gas injection valve.

[0017] According to the second aspect, the gas fuel may be hydrogen gas, and the nozzle of the gas injection valve may be larger than the nozzle of the liquid injection valve.

[0018] Generally, considering the lower heating value of each fuel, hydrogen gas needs to be injected in larger quantities than liquid fuels, LNG, etc. Therefore, when hydrogen gas is used as the gas fuel, the nozzle of the gas injection valve tends to be larger than when other fuels are used. When the nozzle is larger, the problem of coking described above becomes more pronounced.

[0019] The configuration according to the present disclosure is particularly useful in a configuration such as the second aspect.

[0020] According to the third aspect, the cylinder may have a cylinder cover that serves as a lid for the cylinder, and both the gas injection valve and the liquid injection valve may be inserted into the cylinder cover. If an insertion angle of the gas injection valve with respect to the central axis is defined as a first insertion angle and an insertion angle of the liquid injection valve with respect to the central axis is defined as a second insertion angle, both the first insertion angle and the second insertion angle may be acute angles, and the first insertion angle may be smaller than the second insertion angle.

[0021] One way to increase the first distance is to move the entire gas injector outward in the radial direction, but moving the entire gas injector raises concerns about interference with other components of the engine.

[0022] In contrast, according to the third aspect, the gas injection valve is positioned more along the central axis than the liquid injection valve. In this position, the lower end of the gas injection valve is farther from the central axis than the lower end of the liquid injection valve. This makes it possible to lengthen the first distance.

[0023] Furthermore, by adopting the above-mentioned position, the upper end of the gas injector is closer to the central axis than the upper end of the liquid injector, which reduces interference between the parts near the upper end of the gas injector and other parts that make up the engine.

[0024] According to the fourth aspect, the gas engine may include a plurality of the cylinders, and the gas injection valve may be located between the central axis and another cylinder adjacent to the cylinder in a plan view along the central axis.

[0025] According to the fourth aspect, by arranging the gas injection valve along the central axis, it is possible to reduce interference between the gas injection valve and other components of the cylinder while increasing the first distance.

[0026] According to the fifth aspect, in a plan view taken along the central axis, a flow path through which a heat exchange medium flows is arranged between the gas injection valve and the liquid injection valve, and if a straight line extending along the gas injection valve is defined as a first imaginary line and a straight line extending along the liquid injection valve is defined as a second imaginary line, at least one of the first imaginary line and the second imaginary line may extend away from the central axis in the plan view.

[0027] According to the fifth aspect, the flow path is disposed in the space between the first virtual line and the second virtual line, and this space can be expanded, thereby making it possible to secure the space for disposing the flow path without disrupting the layout in which the gas injection valve and the liquid injection valve are adjacent to each other. [Effects of the Invention]

[0028] As described above, according to the present disclosure, it is possible to suppress coking of the injection port by liquid fuel without interfering with the diffusion and combustion of fuel and gas fuel. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a gas engine. [Figure 2] FIG. 2 is an enlarged view of a combustion chamber of a gas engine. [Figure 3] FIG. 3 is a vertical cross-sectional view illustrating the structure of a cylinder liner. [Figure 4]FIG. 4 is a cross-sectional view illustrating the structure of a cylinder liner. [Figure 5] FIG. 5 is a diagram illustrating an example of the ceiling surface of the combustion chamber. [Figure 6] FIG. 6 is a plan view illustrating the peripheral configuration of the cylinder cover. [Figure 7A] FIG. 7A is a vertical cross-sectional view for explaining the insertion angle of the oil injection valve. [Figure 7B] FIG. 7B is a vertical cross-sectional view for explaining the insertion angle of the gas injection valve. [Figure 8] FIG. 8 is a block diagram illustrating the configuration of a controller for a gas engine. [Figure 9] FIG. 9 is a flowchart showing a specific example of engine control. [Figure 10A] FIG. 10A is a diagram for explaining the first-stage injection of oil fuel. [Figure 10B] FIG. 10B is a diagram for explaining the second-stage injection of hydrogen gas. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the following description is an example. Fig. 1 is a schematic diagram illustrating the configuration of a gas engine (hereinafter also simply referred to as "engine") 1.

[0031] <Overall structure> The engine 1 is an in-line multi-cylinder gas engine. The engine 1 is configured as a uniflow scavenging two-stroke one-cycle engine, and is installed on large ships such as tankers, container ships, and car carriers.

[0032] The engine 1 is configured to combust gas fuel and liquid fuel containing organic compounds in the same cylinder 16. In other words, the engine 1 is capable of performing multi-combustion using both gas fuel and liquid fuel.

[0033] In this embodiment, hydrogen gas is used as the gas fuel, but liquefied natural gas (LNG) may also be used as the gas fuel.

[0034] In this embodiment, oil fuel is used as the liquid fuel. Marine fuel oil such as light oil or heavy oil may be used as the oil fuel. The liquid fuel may be a mixture of oil fuel and other liquid fuels. It is not essential to use a liquid fuel containing oil fuel. An alcohol fuel containing methanol, ethanol, or the like may be used as the liquid fuel.

[0035] An engine 1 mounted on a ship is used as a main engine for propelling the ship. The output shaft of the engine 1 as the main engine is connected to a propeller (not shown) of the ship via a propeller shaft (not shown). When the engine 1 is operating, its output is transmitted to the propeller, propelling the ship.

[0036] <Main configuration> 1, the engine 1 includes an engine body 10 having a cylinder 16, and a controller 100 electrically connected to the engine body 10. The cylinder 16 forms a combustion chamber 17 for combusting gas fuel.

[0037] (1) Engine body 10 Fig. 2 is an enlarged view of the combustion chamber 17 of the engine 1, Fig. 3 is a longitudinal cross-sectional view illustrating the structure of the cylinder liner 14, and Fig. 4 is a transverse cross-sectional view illustrating the structure of the cylinder liner 14. Fig. 4 corresponds to the cross section taken along line III-III in Fig. 3. As shown in Fig. 3, Fig. 4 corresponds to a cross-sectional view looking down from above along the axial direction.

[0038] The engine body 10 includes a plurality of the cylinders 16 (only one is illustrated in FIGS. 1 to 3), and is installed in the engine room of the ship.

[0039] The engine body 10 according to this embodiment is configured as a so-called crosshead type internal combustion engine in order to achieve a long stroke. That is, in this engine body 10, a piston rod 22 that supports a piston 21 from below and a connecting rod 24 that is connected to a crankshaft 23 are connected by a crosshead 25.

[0040] Specifically, the engine body 10 includes a base plate 11 located below, a frame 12 provided on the base plate 11, and a cylinder jacket 13 provided on the frame 12. Each cylinder 16 is provided inside the cylinder jacket 13. The engine body 10 also includes a piston 21 disposed in each cylinder 16, and an output shaft (e.g., a crankshaft 23) that rotates in conjunction with the reciprocating motion of the piston 21.

[0041] Here, the base plate 11 constitutes the crankcase of the engine 1 and houses a crankshaft 23 and a bearing 26 that rotatably supports the crankshaft 23. The lower end of a connecting rod 24 is connected to the crankshaft 23 via a crank 27.

[0042] The frame 12 houses a pair of guide plates 28, a connecting rod 24, and a crosshead 25. The pair of guide plates 28 are arranged at an interval in the width direction of the engine 1 (the left-right direction on the paper surface of FIG. 1). The connecting rod 24 is arranged between the pair of guide plates 28 with its lower end connected to the crankshaft 23. The upper end of the connecting rod 24 is connected to the lower end of the piston rod 22 via the crosshead 25.

[0043] The crosshead 25 is disposed between a pair of guide plates 28 and slides up and down along each of the guide plates 28. That is, the pair of guide plates 28 guide the sliding movement of the crosshead 25. The crosshead 25 is connected to the piston rod 22 and the connecting rod 24 via a crosshead pin 29. The crosshead pin 29 is connected to the piston rod 22 so as to move up and down integrally therewith, and is connected to the connecting rod 24 so as to rotate the connecting rod 24 around the upper end of the connecting rod 24 as a fulcrum.

[0044] The cylinder jacket 13 supports a cylinder liner 14 as an inner cylinder. The aforementioned piston 21 is disposed inside the cylinder liner 14. This piston 21 reciprocates up and down along the inner wall of the cylinder liner 14. A cylinder cover 15 is fixed to the top of the cylinder liner 14. The cylinder cover 15 and the cylinder liner 14 form a cylinder 16.

[0045] The cylinder cover 15 is also provided with an exhaust valve 18 that is operated by a valve train (not shown). The exhaust valve 18, together with a cylinder 16 made up of the cylinder liner 14 and the cylinder cover 15 and the top surface of a piston 21, form a combustion chamber 17 (see FIG. 2). The exhaust valve 18 opens and closes the connection between the combustion chamber 17 and an exhaust pipe 19. The exhaust pipe 19 has an exhaust port that communicates with the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

[0046] As shown in Figures 2 and 3, the cylinder cover 15 serves as a lid for the cylinder 16. The cylinder cover 15 also forms a ceiling surface 17a of the combustion chamber 17. As shown in Figure 2, this ceiling surface 17a is inclined downward in the vertical direction as it moves away from the central axis C of the piston 21 in the radial direction. In other words, the ceiling surface 17a is inclined so as to gradually descend as it moves away from the central axis C of the piston 21 and the exhaust valve 18.

[0047] Hereinafter, the central axis C of the piston 21 will be simply referred to as the "central axis C" (see Figures 2 and 3 for the central axis C). This central axis C can also be considered as the central axis of the cylinder liner 14 and the cylinder 16. The direction along the central axis C will be referred to as the "axial direction" or the above-mentioned "vertical direction." In this vertical direction, the direction from the piston 21 toward the exhaust valve 18 will be referred to as the "upward direction," and the direction from the exhaust valve 18 toward the piston 21 will be referred to as the "downward direction."

[0048] Furthermore, a direction perpendicular to the central axis C and extending toward or away from the central axis C (a direction extending radially from the central axis C) is referred to as the "radial direction," and a direction circumferentially around the central axis C is referred to as the "circumferential direction."

[0049] Air is supplied to the combustion chamber 17 from the cylinder liner 14, and hydrogen gas is supplied from the gas injection valve 30 shown in Figure 2. In order to operate the engine 1 properly, it is advantageous if the hydrogen gas supplied from the gas injection valve 30 is uniformly dispersed within the combustion chamber 17.

[0050] Therefore, the engine 1 utilizes the flow of air flowing in the circumferential direction, i.e., the swirl flow of the air, to uniformly diffuse the hydrogen gas within the combustion chamber 17. The engine 1 is equipped with a straightening means for generating such a swirl flow.

[0051] The flow straightening means is a means for generating a swirl flow of the air by adjusting the flow of the air taken into the cylinder 16. The flow straightening means according to this embodiment is configured by the above-mentioned cylinder liner 14, in particular, the multiple scavenging ports 14a provided in the cylinder liner 14.

[0052] The term "air" as used herein refers to the air supplied into the combustion chamber 17, and in particular refers to air composed of at least one of fresh air taken in from outside the engine body 10 and exhaust gas (so-called "EGR gas") recirculated by an EGR system (not shown).

[0053] Specifically, as shown in FIGS. 3 and 4, the cylinder liner 14 has a plurality of scavenging ports 14a provided in the lower part of the cylinder liner 14 and an inner wall portion 14b that defines the internal space of the cylinder liner 14.

[0054] The scavenging ports 14a are arranged in a line along the circumferential direction. Each scavenging port 14a is formed as a scavenging hole penetrating the inner wall portion 14b of the cylinder liner 14.

[0055] In addition, in the axial direction, each scavenging port 14a is arranged in a portion of the cylinder liner 14 that is inserted into the cylinder jacket 13 (a portion corresponding to a lower part of the cylinder liner 14). Although not shown in the drawing, each scavenging port 14a is arranged so as to be located above the piston 21 that is located at the bottom dead center.

[0056] 4, each of the scavenging ports 14a causes the air drawn in from the cylinder jacket 13 to flow in a swirling manner in a predetermined flow direction D1, which is one of the circumferential directions, when viewed in a cross section perpendicular to the central axis C. On the plane of FIG. 4 (on a cross section viewed from above downward), the flow direction D1 is equal to the counterclockwise direction around the central axis C. To achieve such a flow, each scavenging port 14a is inclined clockwise in the circumferential direction from the outside to the inside in the radial direction.

[0057] The flow direction D1 is not limited to the counterclockwise direction as shown in the illustrated example. The counterclockwise direction about the central axis C may also be set as the flow direction D1. In this case, the inclination direction of each scavenging port 14a will be inclined counterclockwise in the circumferential direction from the outer side to the inner side in the radial direction (the inclination will be inclined in the opposite direction to the illustrated example).

[0058] Each scavenging port 14a is opened when the piston 21 is positioned near the bottom dead center, and communicates between a scavenging trunk (not shown) and the combustion chamber 17 via the cylinder jacket 13 and the cylinder liner 14.

[0059] The swirl flow generated by the multiple scavenging ports 14a flows into the combustion chamber 17 of the cylinder 16. Hydrogen gas is supplied to the combustion chamber 17 so as to flow along with the swirl flow.

[0060] Fig. 5 is a diagram illustrating an example of the ceiling surface of the combustion chamber 17. Fig. 6 is a plan view illustrating an example of the peripheral configuration of the cylinder cover 15. Fig. 7A is a vertical cross-sectional view for explaining the insertion angle of the oil injection valve 40. Fig. 7B is a vertical cross-sectional view for explaining the insertion angle of the gas injection valve 30.

[0061] 5 corresponds to the AA cross section of FIGS. 7A and 7B. This AA cross section is a cross section passing through a gas injection port 30a and an oil injection port 40a, which will be described later. As shown in this AA cross section, unlike FIG. 4, FIG. 5 corresponds to a view looking up from below along the axial direction.

[0062] The cylinder cover 15 is provided with one or more gas injection valves 30 that inject hydrogen gas into the combustion chamber 17 so that the hydrogen gas flows according to the swirl flow. In particular, in this embodiment, as illustrated in FIGS. 1 to 2, 5, and 6, two gas injection valves 30 are provided for each cylinder 16. Hereinafter, one of the two gas injection valves 30 may be referred to as a "first gas injection valve 31," and the other may be referred to as a "second gas injection valve 32."

[0063] Each gas injection valve 30 has a gas injection port 30a located in the combustion chamber 17. Each gas injection valve 30 injects hydrogen gas from its gas injection port 30a. Each gas injection valve 30 is indirectly connected to the controller 100, for example, via a solenoid valve (not shown). The solenoid valve operates in accordance with a control signal input from the controller 100, thereby controlling the hydraulic oil supplied to each gas injection valve 30. Each gas injection valve 30 opens and closes by controlling the hydraulic oil.

[0064] Furthermore, the cylinder cover 15 is provided with one or more oil injection valves 40 that inject oil fuel into the combustion chamber 17. The one or more oil injection valves 40 are adjacent to the gas injection valve 30 on the upstream side of the swirl flow. The one or more oil injection valves 40 are examples of the "liquid injection valve" in this embodiment.

[0065] 5 and 6, it is preferable that one or more oil injection valves 40 are provided for each cylinder 16 in the same number as the gas injection valves 30 (i.e., two in this embodiment). Hereinafter, one of the two oil injection valves 40 may be referred to as the "first oil injection valve 41," and the other may be referred to as the "second oil injection valve 42."

[0066] Each oil injection valve 40 has an oil injection port 40a located in the combustion chamber 17. Each oil injection valve 40 injects oil fuel from the oil injection port 40a. The oil fuel functions as "pilot oil" that ignites hydrogen gas. Each oil injection valve 40 is indirectly connected to the controller 100, for example, via a solenoid valve (not shown). The solenoid valve operates in accordance with a control signal input from the controller 100, thereby controlling the hydraulic oil supplied to the fuel pump. The fuel pump is controlled via the hydraulic oil, thereby opening and closing each oil injection valve 40.

[0067] The first gas injector 31 is arranged circumferentially offset by a predetermined angle from the first oil injector 41 (see FIG. 5). Similarly, the second gas injector 32 is arranged circumferentially offset by a predetermined angle from the second oil injector 42.

[0068] In this embodiment, the predetermined angle is set to be equal to or greater than 10° and equal to or less than 45°. The magnitude of the predetermined angle can be set depending on the dimensions of each part of the engine body 10, the performance of the first gas injection valve 31, control parameters of the first gas injection valve 31 (for example, parameters that characterize the injection amount of hydrogen gas), etc. The predetermined angle is preferably set to be equal to or less than 90°, and more preferably set to be equal to or less than 45°.

[0069] Furthermore, in this embodiment, the relative angle of the second gas injector 32 with respect to the second oil injector 42 is set to the same value as the predetermined angle, but is not limited to such a setting. For example, if there is a difference in specifications between the first gas injector 31 and the second gas injector 32, the relative angle may be set to a value different from the predetermined angle.

[0070] In addition, the gas injection port 30a is larger than the oil injection port 40a in this embodiment. Specifically, the opening area (area of ​​the opening) of the gas injection port 30a is larger than the opening area of ​​the oil injection port 40a in this embodiment.

[0071] 5, the first gas injector 31 is disposed downstream in the flow direction D1 from the first oil injector 41. Similarly, the second gas injector 32 is disposed downstream in the flow direction D1 from the second oil injector 42.

[0072] In addition, in this embodiment, the first gas injection valve 31 and the first oil injection valve 41 are arranged so as to be point-symmetrical about the central axis C with respect to the second gas injection valve 32 and the second oil injection valve 42, as shown in FIG.

[0073] In the above-described configuration, when each scavenging port 14a is opened, the air drawn into the cylinder liner 14 flows in a swirling manner in the flow direction D1, as shown by the arrow A1 in Fig. 4. The swirling air then flows toward the combustion chamber 17 as a swirling flow around the central axis C, i.e., a swirl flow, as shown by the arrow A in Fig. 3.

[0074] The hydrogen gas injected from the gas injection valve 30 flows in a swirling manner in the flow direction D1 following the swirl flow of the air. This flow causes the hydrogen gas to diffuse to various parts within the combustion chamber 17. The hydrogen gas burns when the oil fuel is ignited.

[0075] As described above, by utilizing the swirl flow, the hydrogen gas can be diffused widely and uniformly within the combustion chamber 17. Furthermore, in this embodiment, the layout of the gas injection valves 30 and the oil injection valves 40 is devised to further promote the diffusion of the hydrogen gas and to eliminate the inconvenience that may arise when oil fuel is also used.

[0076] These improvements will be described in detail below.

[0077] (2) Details of the gas injection valve 30 and the oil injection valve 40 As shown in Fig. 6, both the gas injection valve 30 and the oil injection valve 40 are inserted into the cylinder cover 15. In addition, in a plan view seen along the central axis C, the gas injection valve 30 and the oil injection valve 40 are located between the central axis C and another cylinder 16 adjacent to the cylinder 16 (see the double-headed arrow A4 in Fig. 6).

[0078] 6, in a plan view taken along the central axis C, a flow path 15f is disposed between the gas injector 30 and the oil injector 40, through which the heat exchange medium flows.

[0079] More specifically, the flow paths 15f according to this embodiment are formed inside the cylinder cover 15. The flow paths 15f extend radially along the radial direction so as to pass through the central axis C. The heat exchange medium flowing through the flow paths 15f is, for example, cooling water. The heat exchange medium cools the cylinder cover 15.

[0080] Since the gas injection valve 30 has a generally cylindrical shape as shown in Fig. 7B, its central axis (hereinafter referred to as the "gas central axis") Cg can be defined. Similarly, since the oil injection valve 40 has a generally cylindrical shape as shown in Fig. 7A, its central axis (hereinafter referred to as the "oil central axis") Cf can be defined.

[0081] 6 and 7B, a line extending along the gas injector 30, i.e., a line extending along the gas central axis Cg, is defined as a first imaginary line Lx1. Similarly, as shown in FIGS. 6 and 7A, a line extending along the oil injector 40, i.e., a line extending along the oil central axis Cf, is defined as a second imaginary line Lx2.

[0082] In this embodiment, at least one of the first virtual line Lx1 and the second virtual line Lx2 extends so as to move away from the central axis C in the plan view of FIG.

[0083] In the illustrated example, the second imaginary line Lx2 of the oil injector 40 extends to pass through the central axis C. On the other hand, the first imaginary line Lx1 of the gas injector 30 does not pass through the central axis C and extends downward as shown in Figures 7A and 7B, moving away from the second imaginary line Lx2.

[0084] If the first virtual line Lx1 is extended so as to pass through the central axis C, the first virtual line Lx1 and the second virtual line Lx2 will intersect on the central axis C in a plan view. On the other hand, if the first virtual line Lx1 is extended as shown in the example, the first virtual line Lx1 and the second virtual line Lx2 will not intersect at the central axis C, but will intersect at a position away from the central axis C.

[0085] With this configuration, the distance between the first virtual line Lx1 and the second virtual line Lx2 (particularly the distance on the radially inner side) can be increased (see the double-headed arrow A3 in FIG. 6).

[0086] The following provides a more detailed description of the configurations of the first gas injector 31 and the first oil injector 41. The following description is also applicable to the second gas injector 32 and the second oil injector .

[0087] That is, in the following description, the first gas injector 31 can be replaced with the second gas injector 32, and the first oil injector 41 can be replaced with the second oil injector .

[0088] As shown in Fig. 6, the upper ends of the first gas injection valve 31 and the first oil injection valve 41 protrude above the cylinder cover 15. On the other hand, as shown in Figs. 7A and 7B, the lower ends of the first gas injection valve 31 and the first oil injection valve 41 protrude into the combustion chamber 17.

[0089] The gas injection port 30a and the oil injection port 40a are formed at the lower end of the corresponding injection valve. As described above, the gas injection port 30a and the oil injection port 40a face the inside of the combustion chamber 17, respectively.

[0090] Specifically, the gas injection port 30a is arranged to protrude from the ceiling surface 17a that defines the combustion chamber 17 or from the inner wall surface 17b on the side of the combustion chamber 17. Similarly, the oil injection port 40a is arranged to protrude from the ceiling surface 17a.

[0091] In this embodiment, when viewed along the central axis C of the cylinder 16, the distance between the first gas injection valve 31 and the central axis C (first distance R1) is longer than the distance between the first oil injection valve 41 and the central axis C (second distance R2).

[0092] 5, the "first distance R1" here refers to the distance (particularly, the radial length) between the central axis C and the gas injection port 30a. Similarly, the "second distance R2" refers to the distance (particularly, the radial length) between the central axis C and the oil injection port 40a.

[0093] In this embodiment, the insertion angle of the first gas injection valve 31 (first insertion angle θg) is devised to provide a difference between the first distance R1 and the second distance R2.

[0094] First, as shown in Figures 7A and 7B, the insertion angle of the first gas injection valve 31 with respect to the central axis C is referred to as the first insertion angle θg, and the insertion angle of the first oil injection valve 41 with respect to the central axis C is referred to as the second insertion angle θf.

[0095] The first insertion angle θg may be the relative angle of the gas central axis Cg with respect to the central axis C, or may be the relative angle of the first virtual line Lx1 with respect to the central axis C. Similarly, the second insertion angle θf may be the relative angle of the oil central axis Cf with respect to the central axis C, or may be the relative angle of the second virtual line Lx2 with respect to the central axis C.

[0096] In this case, the first insertion angle θg and the second insertion angle θf are both acute angles in this embodiment. While the first insertion angle θg has conventionally been set equal to the second insertion angle θf, the first insertion angle θg in this embodiment is set to be smaller than the second insertion angle θf.

[0097] Furthermore, as shown by arrows A1 and A2 in FIGS. 6 and 7B, when the first insertion angle θg is reduced, the lower end of the first gas injection valve 31 is displaced more than the upper end thereof.

[0098] By displacing the lower end of the first gas injection valve 31 relatively greatly, the lower end, and therefore the gas injection port 30a, is displaced significantly radially outward relative to the central axis C (see arrow A1). As a result, the first distance R1 becomes longer than the second distance R2.

[0099] Furthermore, the lower end of the first gas injection valve 31 is displaced in a direction away from the central axis C (see, in particular, arrow A1 in FIG. 6). This makes it possible to expand the space between the central axis C and the first gas injection valve 31.

[0100] On the other hand, by displacing the upper end of the first gas injection valve 31 by a relatively small amount, the upper end protruding from the cylinder cover 15 is displaced slightly radially inward relative to the central axis C (see arrow A2).

[0101] As a result, the upper end of the first gas injection valve 31 is displaced in a direction away from another cylinder 16 adjacent to the cylinder 16 into which the first gas injection valve 31 is inserted (see particularly arrow A2 in FIG. 6), thereby suppressing interference between the upper end of the first gas injection valve 31 and the adjacent other cylinder 16.

[0102] 5, the center line of the gas injection port 30a is referred to as the "first center line F1," and the center line of the oil injection port 40a is referred to as the "second center line F2." Note that the "first center line F1" here refers to an imaginary line that is perpendicular to the opening surface of the gas injection port 30a (particularly, the center of the opening surface) and extends in a direction away from the first gas injection valve 31. Similarly, the "second center line F2" here refers to an imaginary line that is perpendicular to the opening surface of the oil injection port 40a (particularly, the center of the opening surface) and extends in a direction away from the first oil injection valve 41.

[0103] In this case, the first center line F1 extends linearly toward the downstream side of the swirl flow, and similarly, the second center line F2 extends linearly toward the downstream side of the swirl flow.

[0104] Furthermore, the second center line F2 is located radially inward from the gas ejection port 30a and radially outward from the central axis C. In other words, the second center line F2 extends between the gas ejection port 30a and the central axis C.

[0105] The second center line F2 intersects with the first center line F1. The intersection of the second center line F2 and the first center line F1 is closer to the gas ejection port 30a than the central axis C.

[0106] (3) Controller 100 8 is a block diagram illustrating the configuration of the controller 100 of the engine 1. The controller 100 has a processor, a volatile memory, a non-volatile memory, and an input / output bus. Connected to the controller 100 are, for example, a gas flow sensor Sw1 that detects the flow rate of hydrogen gas supplied to the engine 1 from a hydrogen tank (not shown), a gas pressure sensor Sw2 that detects the pressure of the hydrogen gas supplied to the engine 1, a rotation speed sensor Sw3 that detects the output rotation speed of the engine 1, and a telegraph 101. The various sensors Sw1 to Sw3 and the telegraph 101 are only shown in FIG. 8.

[0107] The controller 100 generates control signals based on signals input from these sensors and devices, and inputs the control signals to solenoid valves and the like for operating the gas injection valve 30 and the oil injection valve 40. The controller 100 controls the opening and closing of the gas injection valve 30 and the oil injection valve 40 through these control signals.

[0108] For example, the controller 100 according to this embodiment injects oil fuel into the oil injection valve 40, and then injects hydrogen gas into the gas injection valve 30 from the downstream side of the swirl flow, thereby allowing the hydrogen gas to flow along with the oil fuel in accordance with the swirl flow.

[0109] <Engine control details> Fig. 9 is a flowchart showing a specific example of engine control. Fig. 10A is a diagram for explaining the injection of oil fuel in the first stage, and Fig. 10B is a diagram for explaining the injection of hydrogen gas in the second stage. Figs. 10A and 10B, like Fig. 5, correspond to the AA cross section of Figs. 7A and 7B, and correspond to views looking up from below along the axial direction.

[0110] 9 shows the processing and operations from the downstroke in the nth combustion cycle to the upstroke and downstroke in the (n+1)th combustion cycle, where n is an integer greater than or equal to 1. This flow is repeatedly executed by the engine 1 as long as operation using hydrogen gas continues.

[0111] First, in step S1 of Fig. 9, the engine 1 introduces air flowing in a lateral vortex (swirl) into the combustion chamber 17. In this step S1, the engine 1 executes the downstroke in the nth combustion cycle and subsequently starts the upstroke in the (n+1)th combustion cycle.

[0112] Specifically, in the downward stroke of step S1, hydrogen gas is burned in the combustion chamber 17, causing the piston 21 to descend toward bottom dead center. At this time, the exhaust valve 18 opens to open the combustion chamber 17, and the scavenging ports 14a open as the piston 21 descends. As a result, air is introduced into the combustion chamber 17 from the scavenging ports 14a, and the air pushes the exhaust gas into the exhaust pipe 19. The air introduced at this time is rectified by the scavenging ports 14a, which function as rectifying means. The air rectified by the scavenging ports 14a becomes a swirl (horizontal vortex) in a cross-sectional view transverse to the central axis C. Air flowing in a horizontal vortex shape flows into the combustion chamber 17.

[0113] Furthermore, when the piston 21 changes from descending to ascending in step S1, the upstroke in the (n+1)th combustion cycle begins. In the first half of this upstroke, the scavenging ports 14a and the exhaust valves 18 are successively closed as the piston 21 rises. On the other hand, in the second half of the upstroke, the air introduced into the combustion chamber 17 is compressed as the piston 21 rises.

[0114] The "first half" and "second half" of the ascent stroke correspond to the first and second halves of the ascent stroke. The "first half" and "second half" of the descent stroke are defined in the same way.

[0115] 9 are executed within a predetermined period from the latter half of the upstroke to the first half of the downstroke in the (n+1)th combustion cycle. This predetermined period corresponds to the period from just before to just after TDC. The controller 100 may execute all of the processing related to steps S2 to S4 immediately after TDC, or may execute only some of the processing related to steps S2 to S4 immediately after TDC.

[0116] In step S2 following step S1, the controller 100 injects oil fuel from the oil injector 40 along the second center line F2 as shown in FIG. 10A (see spray Gf in the figure).

[0117] Next, in step S3, the controller 100 injects hydrogen gas from the gas injector 30 along the first center line F1, as shown in Fig. 10B, to cause the hydrogen gas to flow in a swirl flow (see spray Gh in the figure). The injected hydrogen gas flows in a vortex together with the oil fuel along the flow direction D1 and diffuses into the combustion chamber 17. This step corresponds to the gas injection step performed during the (n+1)th combustion cycle.

[0118] As shown in the sequence of steps S2 and S3, during the (n+1)th combustion cycle, the controller 100 injects oil fuel from the oil injector 40 (step S2), and then injects hydrogen gas from the gas injector 30 (step S3).

[0119] Next, in step S4, the oil fuel injected in step S2 is ignited, which ignites the hydrogen gas injected in step S3. This causes the hydrogen gas to burn in the combustion chamber 17, and the combustion generates power to reciprocate the piston 21. The downward movement of the piston 21 is promoted, and the aforementioned downward stroke progresses.

[0120] <Significance of the layout of the gas injection valve 30 and the oil injection valve 40> As described above, according to the embodiment, the first distance R1 is longer than the second distance R2 as illustrated in Fig. 5. That is, in the radial direction perpendicular to the central axis C, the oil injection valve 40 is positioned more inward than the gas injection valve 30. As a result, as illustrated in Fig. 10A, when oil fuel is injected from the oil injection valve 40 located upstream, it is possible to suppress the oil fuel from being sprayed onto the gas injection valve 30 located downstream. This suppresses coking of the gas injection port 30a.

[0121] 5, the configuration according to the embodiment can be realized while maintaining the positional relationship of the gas injector 30 and the oil injector 40 adjacent to each other in the swirl direction (swirl flow direction D1) as much as possible. This is effective in maintaining the diffusion of oil fuel and gas fuel by the swirl flow and the ignition of gas fuel by the oil fuel.

[0122] Furthermore, by arranging the gas injector 30 relatively outward (outward in the radial direction), the hydrogen gas injected from the gas injector 30 travels largely around the side wall (inner wall surface 17b) of the combustion chamber 17, as shown by the spray Gh in Fig. 10B. This allows the hydrogen gas to be uniformly diffused throughout the combustion chamber 17.

[0123] Furthermore, by arranging the oil injection valve 40 inside the gas injection valve 30, the oil fuel injected from the oil injection valve 40 is more likely to collide with the hydrogen gas injected from the gas injection valve 30, as shown in spray Gf in Fig. 10B. This is advantageous in igniting the hydrogen gas with the oil fuel.

[0124] As described above, according to the embodiment, it is possible to promote the diffusion and combustion of the oil fuel and hydrogen gas while suppressing the coking of the gas injection port 30a.

[0125] Generally, considering the lower heating value of each fuel, hydrogen gas needs to be injected in larger quantities than oil fuel, LNG, etc. Therefore, when hydrogen gas is used as the gas fuel, the gas injection port 30a tends to be larger than when other fuels are used. When the injection port is larger, the problem of coking becomes more pronounced.

[0126] The configuration according to the present disclosure is particularly useful in a configuration such as the second aspect.

[0127] In order to increase the first distance R1, it is possible to move the entire gas injector 30 radially outward. However, if the entire gas injector 30 is moved, there is a concern that it may interfere with other components that configure the engine 1.

[0128] In contrast, as can be seen from a comparison of the gas central axis Cg and the oil central axis Cf in Fig. 7B, the gas injector 30 is oriented more along the central axis C than the oil injector 40. In this orientation, the lower end of the gas injector 30 is farther from the central axis than the lower end of the oil injector 40 (see arrow A1 in Fig. 7B). This makes it possible to lengthen the first distance R1.

[0129] Furthermore, by adopting the above-described posture, the upper end of the gas injection valve 30 is closer to the central axis C than the upper end of the oil injection valve 40. This reduces interference between the parts near the upper end of the gas injection valve 30 and other components that make up the engine 1.

[0130] Furthermore, when multiple cylinders 16 are adjacent to each other as shown in Figure 6, by aligning the gas injection valve 30 along the central axis C, it is possible to lengthen the first distance R1 while suppressing interference between the gas injection valve 30 and components of other cylinders 16.

[0131] Furthermore, by separating the lower end of the gas injection valve 30 from the central axis C, the tip (nozzle portion) where the gas injection port 30a is formed is buried in the ceiling surface 17a, which reduces the amount of protrusion of the nozzle portion from the ceiling surface 17a and is advantageous in suppressing coking.

[0132] 5, the flow path 15f is disposed in the space between the first imaginary line Lx1 and the second imaginary line Lx2, but this space can be expanded, thereby ensuring the space for disposing the flow path 15f without disrupting the layout in which the gas injector 30 and the oil injector 40 are adjacent to each other.

[0133] <Other embodiments> In the above embodiment, the "first distance R1" refers to the distance (particularly, the radial length) between the central axis C and the gas ejection port 30a, and the "second distance R2" refers to the distance (particularly, the radial length) between the central axis C and the oil ejection port 40a. However, the present disclosure is not limited to such a configuration.

[0134] For example, the distance between the central axis C and the tip of the gas injector 30 may be defined as the "first distance R1," and the distance between the central axis C and the tip of the oil injector 40 may be defined as the "second distance R2." [Explanation of symbols]

[0135] 1 Engine (gas engine) 14 Cylinder liner 14a Scavenging port (flow rectification means) 15 Cylinder cover 15f Flow path 16 cylinders 17 Combustion chamber 30 Gas injection valve 30a Gas nozzle 31 First gas injection valve 32 Second gas injection valve 40 Oil injection valve (liquid injection valve) 40a Oil injection port 41 First oil injection valve 42 No. 2 oil injection valve 100 Controllers C Cylinder central axis Cg Gas central axis Cf oil center axis D1 Flow direction of swirl flow Gf Oil fuel spray Gh Hydrogen gas spray Lx1 First virtual line Lx2 Second virtual line R1 First distance (distance between the gas injection valve and the center axis) R2 Second distance (distance between the oil injection valve and the center axis) θg First insertion angle θf Second insertion angle

Claims

1. A gas engine that burns a gas fuel and a liquid fuel containing an organic compound in the same cylinder, a cylinder forming a combustion chamber; a flow straightening unit that straightens the flow of air drawn into the cylinder to generate a swirl flow of the air; a gas injection valve that injects the gas fuel into the combustion chamber so that the gas fuel flows along the swirl flow; a liquid injection valve that is adjacent to the gas injection valve on the upstream side of the swirl flow and that injects the liquid fuel into the combustion chamber, When viewed along the central axis of the cylinder, the distance between the gas injection valve and the central axis is longer than the distance between the liquid injection valve and the central axis. A gas engine characterized by:

2. 2. The gas engine according to claim 1, the gas fuel is hydrogen gas; The nozzle of the gas injection valve is larger than the nozzle of the liquid injection valve. A gas engine characterized by:

3. 2. The gas engine according to claim 1, The cylinder has a cylinder cover that serves as a lid for the cylinder, The gas injection valve and the liquid injection valve are both inserted into the cylinder cover, When an insertion angle of the gas injection valve with respect to the central axis is defined as a first insertion angle, and an insertion angle of the liquid injection valve with respect to the central axis is defined as a second insertion angle, the first insertion angle and the second insertion angle are both acute angles; The first insertion angle is smaller than the second insertion angle. A gas engine characterized by:

4. 4. The gas engine according to claim 3, The gas engine includes a plurality of the cylinders, The gas injection valve is located between the central axis and another cylinder adjacent to the cylinder in a plan view along the central axis. A gas engine characterized by:

5. 4. The gas engine according to claim 3, a flow path through which a heat exchange medium flows is disposed between the gas injection valve and the liquid injection valve in a plan view along the central axis; If a straight line extending along the gas injection valve is defined as a first imaginary line, and a straight line extending along the liquid injection valve is defined as a second imaginary line, In the plan view, at least one of the first virtual line and the second virtual line extends so as to move away from the central axis. A gas engine characterized by:

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