CN118361337A

CN118361337A - Hydrogen engine

Info

Publication number: CN118361337A
Application number: CN202410035376.XA
Authority: CN
Inventors: 上田哲司
Original assignee: Japan Engine Corp
Current assignee: Japan Engine Corp
Priority date: 2023-01-18
Filing date: 2024-01-09
Publication date: 2024-07-19
Also published as: JP2024101802A; KR20240115173A

Abstract

The invention discloses a hydrogen engine. The engine (1) comprises: a scavenging port (14 a) that generates a vortex formed by air sucked into the cylinder (16); a gas injection valve (30) for injecting hydrogen gas into the combustion chamber (17); a water injection valve (50) for injecting water into the combustion chamber (17); and a controller (100) that controls the gas injection valve (30) and the water injection valve (50). The controller (100) causes the hydrogen gas to flow along with the vortex by causing the gas injection valve (30) to inject the hydrogen gas, and causes the spray (W2) of water to collide with the hydrogen gas by causing the water injection valve (50) to inject the water from the upstream side of the vortex. In this way, in the hydrogen engine capable of injecting water, abnormal combustion is suppressed more preferably than before.

Description

Hydrogen engine

Technical Field

The present disclosure relates to a HYDROGEN ENGINE (HYDROGEN ENGINE) that burns HYDROGEN gas.

Background

Patent document 1 discloses an example of an internal combustion engine capable of injecting water. Specifically, the gasoline engine disclosed in patent document 1 includes: a fuel injection injector that injects fuel into a cylinder; and water injection injectors provided in both side regions with the fuel injection injector interposed therebetween, and injecting water to the vicinity of the both side regions. According to patent document 1, by injecting water according to the operation conditions, the inside of the cylinder can be cooled effectively, and combustion in the vicinity of the theoretical air-fuel ratio can be achieved.

Patent document 1: japanese laid-open patent publication No. 2021-143629

Disclosure of Invention

Technical problem to be solved by the invention

However, in a so-called hydrogen engine, there is a possibility that abnormal combustion such as knocking and pre-ignition occurs due to the combustibility of hydrogen gas. In order to suppress such abnormal combustion, a water injection device as disclosed in patent document 1 may be used.

The present inventors have conducted intensive studies on further suppression of abnormal combustion, and as a result of the studies: a new structure of a hydrogen engine capable of injecting water was devised, and the present disclosure was thereby derived.

The technology disclosed herein has been completed to solve the above technical problems, and it is an object of the present invention to: in a hydrogen engine capable of injecting water, abnormal combustion is suppressed more preferably than before.

Technical solution for solving the technical problems

A first aspect of the present disclosure relates to a hydrogen engine that combusts hydrogen gas. The hydrogen engine includes a cylinder that defines a combustion chamber, a gas injection valve that injects the hydrogen gas into the combustion chamber, a rectifying mechanism that generates a vortex of the air sucked into the cylinder by adjusting a flow of the air, a water injection valve that injects water into the combustion chamber in a flow direction of the vortex, and a controller that controls the gas injection valve and the water injection valve.

Further, according to the first aspect, the controller causes the hydrogen gas to flow along with the vortex by causing the gas injection valve to inject the hydrogen gas, and causes the water injection valve to spray the water in a mist form from an upstream side of the vortex to collide with the hydrogen gas.

According to the first aspect, the controller causes the water spray to collide with the hydrogen gas by spraying the water in a mist form from the upstream side of the vortex flow. Since the spray is sprayed along the flow direction of the vortex, the hydrogen can be stirred by the penetrating force thereof. This promotes the flow of hydrogen gas in the cylinder of the hydrogen engine, and suppresses the occurrence of uneven concentration of hydrogen gas in the combustion chamber. As a result, abnormal combustion can be suppressed more effectively than in the conventional case.

In addition, according to a second aspect of the present disclosure, it may be configured to: the water injection valve is disposed adjacent to the gas injection valve at a position on an upstream side of the gas injection valve in the flow direction of the swirl flow, and the water injection valve injects the water toward a downstream side of the flow direction of the swirl flow.

According to the second aspect, by disposing the water injection valve on the upstream side of the gas injection valve, the water injected from the upstream side of the vortex flow is liable to collide with the hydrogen gas. Further, by injecting water toward the downstream side in the flow direction of the swirl flow, the water can collide with the hydrogen gas immediately after being injected from the gas injection valve. As a result, stirring of the hydrogen gas can be started at an earlier timing. The stirring is started at an earlier timing, and accordingly, the hydrogen gas can be stirred for a longer time. This is advantageous in suppressing abnormal combustion.

Further, according to a third aspect of the present disclosure, it may be configured to: in a predetermined combustion cycle, the controller causes the water to be injected from the water injection valve after causing the hydrogen gas to be injected from the gas injection valve.

According to the third aspect, the controller causes water to be injected after injecting the hydrogen gas. This makes it possible to more reliably collide the water injected with the hydrogen gas. As a result, the hydrogen gas can be stirred with water more reliably, which is advantageous in suppressing abnormal combustion.

In addition, according to a fourth aspect of the present disclosure, it may be configured to: the hydrogen engine includes a spark plug that is controlled by the controller and ignites the hydrogen gas, and the controller operates the spark plug after injecting the water from the water injection valve in the predetermined combustion cycle.

According to the fourth aspect, the controller operates the spark plug after causing water to be injected. This makes it possible to burn the hydrogen gas after the concentration of the hydrogen gas is suppressed from being uneven by the water. As a result, it is advantageous in suppressing abnormal combustion.

Further, according to a fifth aspect of the present disclosure, it may be configured to: the water injection valve has a water injection port opening along a flow direction of the swirl flow, the water injection port being arranged such that a center line of the water injection port does not intersect the spark plug when a cross section taken transversely to a center axis of the cylinder is observed.

According to the fifth aspect, the center line of the water injection port does not intersect the spark plug. This can reduce the amount of water sprayed onto the spark plug. As a result, the hydrogen gas can be ignited more reliably. In addition, abrupt temperature changes of the spark plug can be suppressed, and the reliability can be improved.

Further, according to a sixth aspect of the present disclosure, it may be configured to: the hydrogen engine includes a fuel injection valve that is controlled by the controller and injects an oil fuel for igniting the hydrogen gas, and in the prescribed combustion cycle, the controller causes the oil fuel to be injected from the fuel injection valve after causing the water to be injected from the water injection valve.

According to the sixth aspect, the controller causes the oil fuel to be injected after causing the water to be injected. This makes it possible to burn the hydrogen gas after the concentration of the hydrogen gas is suppressed from being uneven by the water. As a result, it is advantageous in suppressing abnormal combustion.

In addition, according to a seventh aspect of the present disclosure, it may be configured to: the water injection valve has a water injection port opening along a flow direction of the swirl flow, the water injection port being arranged such that a center line of the water injection port does not intersect the fuel injection valve when a cross section taken transversely to a center axis of the cylinder is observed.

According to the seventh aspect, the centerline of the water injection port does not intersect the fuel injection valve. This can reduce the amount of water sprayed onto the fuel injection valve. As a result, the hydrogen gas can be ignited more reliably. In addition, abrupt temperature changes of the fuel injection valve can be suppressed, and reliability can be improved.

In addition, according to an eighth aspect of the present disclosure, it may be configured to: in the predetermined combustion cycle, the controller sequentially executes a first water injection step in which the controller causes the water injection valve to inject the water so that the water reaches an inner wall surface of the cylinder, a gas injection step in which the controller causes the gas injection valve to inject the hydrogen gas, and a second water injection step in which the controller causes the water injection valve to spray the water in a mist so that the water spray collides with the hydrogen gas.

According to the eighth aspect, the water injected in the first water injection step reaches the inner wall surface of the cylinder before the hydrogen injected in the gas injection step reaches the inner wall surface. By allowing water to reach the inner wall surface before hydrogen gas, the water absorbs heat from deposits (for example, deposits formed by combustion residues in the cylinder and cylinder oil residues) in the vicinity of the inner wall surface, and the temperature of the deposits can be reduced in advance. This can suppress abnormal combustion with deposits or the like as a source of pre-ignition. Further, a water vapor film is formed in the vicinity of the wall surface, and as a result, heat loss due to heat transfer to the wall surface can be suppressed.

Effects of the invention

As described above, according to the present disclosure, in a hydrogen engine capable of injecting water, abnormal combustion can be suppressed more preferably than before.

Drawings

Fig. 1 is a schematic diagram illustrating a structure of a hydrogen engine;

fig. 2 is a diagram showing the combustion chamber of the hydrogen engine in an enlarged manner;

Fig. 3 is a view showing an upper structure of the combustion chamber;

FIG. 4 is a longitudinal cross-sectional view illustrating the structure of a cylinder liner;

FIG. 5 is a transverse cross-sectional view illustrating the construction of a cylinder liner;

fig. 6 is a block diagram illustrating the structure of a controller of the hydrogen engine;

FIG. 7 is a flowchart showing a specific example of engine control;

FIG. 8A is a diagram for explaining the first stage water injection;

Fig. 8B is a diagram for explaining hydrogen injection;

FIG. 8C is a diagram for explaining the second stage water injection;

Fig. 9 is a diagram showing a modification of the ignition member, corresponding to fig. 3;

fig. 10 is a diagram for explaining water injection in the modification, and corresponds to fig. 8C.

Symbol description-

1-Engine (hydrogen engine); 14-cylinder sleeve; 14 a-scavenging port (rectifying mechanism); 16-cylinder; 17-combustion chamber; 30-a gas injection valve; 31-a first gas injection valve; 32-a second gas injection valve; 40-spark plug; 41-a first spark plug; 42-a second spark plug; 50-a water injection valve; 50 a-water jet ports; 51-a first water injection valve; 52-a second water injection valve; 60-fuel injection valve; 60 a-fuel injection ports; 61-a first fuel injection valve; 62-a second fuel injection valve; 100-a controller; a central shaft of the C-cylinder; c1-the center line of the water jet port; d1—the flow direction of the vortex; g1-spraying of hydrogen; w2-spraying of water.

Detailed Description

Embodiments of the present disclosure will be described below based on the drawings. The following description is merely illustrative. Fig. 1 is a schematic diagram illustrating a structure of a hydrogen engine (hereinafter also simply referred to as "engine") 1.

< Integral Structure >

The engine 1 is an in-line multi-cylinder hydrogen engine that burns hydrogen. The engine 1 is configured as a uniflow scavenged two-cycle engine mounted on a large vessel such as a tanker, a container ship, or an automobile carrier.

The engine 1 is configured to use hydrogen gas as a gaseous fuel, and can burn the hydrogen gas in the cylinders 16. The engine 1 may be one capable of performing at least one of combustion of hydrogen alone and combustion of a mixture of hydrogen and an oil fuel simultaneously.

The engine 1 mounted on the ship is used as a main engine for propelling the ship. An output shaft of the engine 1 as a main engine is coupled to a propeller (not shown) of a ship via a propeller shaft (not shown). By the operation of the engine 1, the output of the engine 1 is transmitted to the propeller, thereby propelling the ship.

< Principal Structure >

As shown in fig. 1, engine 1 includes an engine body 10 having cylinders 16, and a controller 100 electrically connected to engine body 10. Cylinder 16 defines a combustion chamber 17 for combusting gaseous fuel.

(1) Engine body 10

Fig. 2 is an enlarged view of the combustion chamber 17 of the engine 1, and fig. 3 is a view illustrating an upper structure (a surrounding structure of the top surface 17 a) of the combustion chamber 17. Fig. 4 is a longitudinal sectional view illustrating the structure of the cylinder liner 14, and fig. 5 is a transverse sectional view illustrating the structure of the cylinder liner 14.

The engine body 10 has a plurality of (only one is illustrated in fig. 1 to 3) cylinders 16, and is provided in an engine room of a ship.

The engine body 10 according to the present embodiment constitutes a so-called crosshead type internal combustion engine in order to achieve a longer stroke. That is, in the engine main body 10, a piston rod 22 supporting the piston 21 from below and a connecting rod 24 connected to the crankshaft 23 are connected by a cross head 25.

Specifically, the engine body 10 includes: a lower housing 11, a frame 12 provided on the housing 11, and a cylinder jacket (cylinder pocket) 13 provided on the frame 12. Each cylinder 16 is disposed within the cylinder water jacket 13. In addition, the engine main body 10 further includes: a piston 21 disposed in the cylinder 16, and an output shaft (e.g., a crankshaft 23) that rotates in conjunction with the reciprocating motion of the piston 21.

Here, the housing 11 constitutes a crankcase of the engine 1, and the housing 11 houses a crankshaft 23 and a bearing 26 that rotatably supports the crankshaft 23. The lower end of the connecting rod 24 is coupled to the crankshaft 23 via a crank 27.

The frame 12 accommodates a pair of guide plates 28, a link 24, and a cross head 25. The pair of guide plates 28 are provided with a gap therebetween in the width direction of the engine 1 (the left-right direction of the paper surface in fig. 1). The connecting rod 24 is disposed between a pair of guide plates 28 in a state where its lower end portion is coupled to the crankshaft 23. The upper end of the link 24 is connected to the lower end of the piston rod 22 via a cross head 25.

The crosshead 25 is arranged between a pair of guide plates 28, and slides in the up-down direction along each guide plate 28. That is, the pair of guide plates 28 guide the cross head 25 to slide. The crosshead 25 is connected to the piston rod 22 and the connecting rod 24 via a crosshead pin 29. The cross pin 29 is connected to the piston rod 22 so as to move up and down integrally therewith, and the cross pin 29 is connected to the link 24 so as to pivot the link 24 about the upper end of the link 24.

The cylinder water jacket 13 supports a cylinder liner (CYLINDER LINER) 14 as an inner cylinder. The piston 21 is disposed inside the cylinder liner 14. The piston 21 reciprocates in the up-down direction along the inner wall of the cylinder liner 14. Further, a cylinder head 15 is fixed to an upper portion of the cylinder liner 14. The cylinder head 15 constitutes a cylinder 16 together with the cylinder liner 14.

The cylinder head 15 is provided with an exhaust valve 18, and the exhaust valve 18 is driven to operate by a valve train device, not shown. The exhaust valve 18 defines a combustion chamber 17 (see fig. 2) together with a top surface of a piston 21 and a cylinder 16 formed of a cylinder liner 14 and a cylinder head 15. The exhaust valve 18 opens or closes the combustion chamber 17 and the exhaust pipe 19. The exhaust pipe 19 has an exhaust port communicating with the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

Further, one or more gas injection valves 30 for injecting hydrogen into the combustion chamber 17 are provided in the cylinder head 15. In particular, in the present embodiment, as shown in fig. 1 to 3, two gas injection valves 30 are provided for each cylinder 16. Hereinafter, one of the two gas injection valves 30 is sometimes referred to as "first gas injection valve 31", and the other of the two gas injection valves 30 is sometimes referred to as "second gas injection valve 32".

Each gas injection valve 30 faces the chamber of the combustion chamber 17 through the top surface 17a, and has an injection port (not shown) for injecting hydrogen gas. Each gas injection valve 30 is indirectly connected to the controller 100 via, for example, a solenoid valve (not shown). The solenoid valves operate in accordance with control signals input from the controller 100 to open or close the respective gas injection valves 30.

Further, one or a plurality of ignition members that ignite the hydrogen gas supplied into the combustion chamber 17 are provided in the cylinder head 15. The ignition member according to the present embodiment is constituted by two spark plugs 40 provided for each cylinder 16. Hereinafter, one of the two spark plugs 40 is sometimes referred to as "first spark plug 41", and the other of the two spark plugs 40 is sometimes referred to as "second spark plug 42".

Each spark plug 40 faces the chamber of the combustion chamber 17 through the top surface 17 a. Each spark plug 40 is electrically connected to the controller 100. Each of the spark plugs 40 operates in accordance with a control signal input from the controller 100, thereby generating a spark in the combustion chamber 17.

The first spark plug 41 is arranged so as to be offset from the first gas injection valve 31 by a predetermined first angle θa in the circumferential direction (see fig. 3). Similarly, the second spark plug 42 is arranged to be offset from the second gas injection valve 32 by a predetermined angle (not shown) in the circumferential direction.

In the present embodiment, the first angle θa is set to about 10 ° to 90 °. The magnitude of the first angle θa can be set in accordance with the dimensions of the respective portions of the engine body 10, the performance of the first gas injection valve 31, control parameters of the first gas injection valve 31 (e.g., parameters characterizing the injection amount of hydrogen), and the like.

In the present embodiment, the relative angle (the predetermined angle described above) of the second spark plug 42 with respect to the second gas injection valve 32 is set to the same value as the first angle θa, but the present invention is not limited to this setting. For example, when there is a difference in specification or the like between the first gas injection valve 31 and the second gas injection valve 32, the predetermined angle may be set to a value different from the first angle θa.

The term "circumferential direction" refers to a direction of rotation about the central axis C of the cylinder liner 14, the cylinder 16, and the piston 21 (see fig. 2 and 3 for the central axis C). Both the first angle θa and the predetermined angle correspond to angles when a cross section intersecting the central axis C is observed, that is, angles in the cross-sectional view of fig. 3.

Here, the direction extending along the central axis C is defined as "axial direction", and the direction extending radially from the central axis C is defined as "radial direction". In this case, the tip ends (injection ports) of the first gas injection valve 31 and the second gas injection valve 32 are arranged equidistantly in the axial direction and the radial direction. Similarly, the tip ends of the first spark plug 41 and the second spark plug 42 are disposed equidistantly in the axial direction and the radial direction. The term "distance" as used herein means: as shown in fig. 2 and 3, the distance from a point (reference point C0) on the central axis C to the distal end portion is set.

As described above, in the case where the gas injection valve 30 and the spark plug 40 are arranged in the circumferential direction, it is preferable to provide a mechanism that smoothly guides the hydrogen gas injected from the gas injection valve 30 to the spark plug 40.

In the engine 1, in order to guide the hydrogen gas to the ignition plug 40, an air flow flowing in the above-described circumferential direction, that is, a vortex of the air is utilized. The engine 1 includes a rectifying mechanism for generating such a vortex.

The rectifying mechanism is a mechanism that generates a vortex of air sucked into the cylinder 16 by adjusting the flow of the air. The rectification mechanism according to the present embodiment is constituted by the cylinder liner 14, and particularly a plurality of scavenging ports 14a provided in the cylinder liner 14.

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

Specifically, as shown in fig. 4 and 5, the cylinder liner 14 includes a plurality of scavenging ports 14a provided at a lower portion of the cylinder liner 14, and an inner wall portion 14b that partitions an inner space of the cylinder liner 14.

Wherein the plurality of scavenging ports 14a are arranged in a circumferential direction, respectively. Each scavenging port 14a is formed as a scavenging hole penetrating the inner wall portion 14b of the cylinder liner 14.

In addition, in the axial direction, each scavenging port 14a is arranged at a portion of the cylinder liner 14 that is inserted into the cylinder water jacket 13 (a portion corresponding to a lower portion of the cylinder liner 14). The scavenging ports 14a are disposed above the piston 21 at the bottom dead center, and are not shown.

As shown in fig. 5, when viewed in a cross section perpendicular to the central axis C, the plurality of scavenging ports 14a cause the air sucked from the cylinder water jacket 13 to flow in a swirl manner in a predetermined flow direction D1, which is either one of the directions in the circumferential direction. On the paper surface of fig. 5, the flow direction D1 is equal to the clockwise direction centered on the central axis C. To achieve such flow, each of the scavenging ports 14a is inclined in the circumferential direction clockwise as going from the outside to the inside in the radial direction.

The flow direction D1 is not limited to the clockwise direction illustrated in the drawing. A counterclockwise direction about the central axis C may be used as the flow direction D1. In this case, the inclination direction of each scavenging port 14a is: as going from the outside to the inside in the radial direction, it is inclined in the circumferential direction counterclockwise (corresponding to the inclination toward the opposite direction of the illustration).

When the piston 21 is located near the bottom dead center, each scavenging port 14a is opened, so that a scavenging box (not shown) communicates with the combustion chamber 17 via the cylinder water jacket 13 and the cylinder liner 14.

The air sucked into the cylinder liner 14 when each scavenging port 14a becomes in an open state flows in such a manner as to form a vortex in the flow direction D1 as indicated by an arrow A1 in fig. 5. The air thus swirled becomes a swirling flow around the central axis C, i.e., a vortex flow, as indicated by an arrow a in fig. 4, and flows into the combustion chamber 17.

The hydrogen gas ejected from the gas injection valve 30 flows along with the vortex of the air in such a manner as to form a vortex in the flow direction D1. The hydrogen gas diffuses through this flow to various portions within the combustion chamber 17. In order to suppress abnormal combustion of hydrogen, it is preferable to spread hydrogen uniformly over a wide range.

The engine 1 according to the present embodiment injects water into the combustion chamber 17 in order to promote diffusion of hydrogen gas. Accordingly, the engine 1 includes one or more water injection valves 50 (see fig. 3) that inject water into the combustion chamber 17. Preferably, the number of water injection valves 50 is the same as the number of gas injection valves 30 on each cylinder 16. One or more water injection valves 50 have water injection ports 50a for injecting water. The water injection valve 50 injects water into the combustion chamber 17 in the swirl flow direction D1.

For example, in the present embodiment, two water injection valves 50 are provided for each cylinder 16. Hereinafter, one of the two water injection valves 50 is sometimes referred to as "first water injection valve 51", and the other of the two water injection valves 50 is sometimes referred to as "second water injection valve 52".

The structure of the first water injection valve 51 and the relative positional relationship among the first water injection valve 51, the first gas injection valve 31, and the first spark plug 41 will be described in detail below. The following description is applicable to the structure of second water injection valve 52 and the relative positional relationship among second water injection valve 52, second gas injection valve 32, and second spark plug 42.

For example, in the following description, the first water injection valve 51, the first gas injection valve 31, and the first spark plug 41 may be replaced with the second water injection valve 52, the second gas injection valve 32, and the second spark plug 42, respectively.

The first water injection valve 51 according to the present embodiment is disposed in the combustion chamber 17. Specifically, the first water injection valve 51 is arranged along the top surface 17a that partitions the combustion chamber 17 or the inner wall surface 17b that is on the side of the combustion chamber 17.

The first water injection valve 51 is disposed adjacent to the first gas injection valve 31 at a position on the upstream side in the flow direction D1 from the first gas injection valve 31. Specifically, the first water injection valve 51 according to the present embodiment is disposed upstream of the first gas injection valve 31 and downstream of the second gas injection valve 32 in the flow direction D1. The interval between the first water injection valve 51 and the first gas injection valve 31 in the circumferential direction is smaller than the interval between the first water injection valve 51 and the second gas injection valve 32 in the circumferential direction.

For example, the first water injection valve 51 is arranged to be offset from the first gas injection valve 31 by a predetermined second angle θb in the circumferential direction. Similarly, the first water injection valve 51 is arranged to be offset from the second gas injection valve 32 by a predetermined third angle θc in the circumferential direction. When the interval is set as described above, the third angle θc according to the present embodiment is larger than the second angle θb as shown in fig. 3. Preferably, both the second angle θb and the third angle θc are set to be smaller than 180 °. The second angle θb is preferably set to 90 ° or less, more preferably 45 ° or less.

Further, as shown in fig. 3, the first spark plug 41 is arranged on the downstream side in the flow direction D1 with respect to both the first gas injection valve 31 and the first water injection valve 51. In view of the positional relationship between the first spark plug 41 and the first water injection valve 51 and the first gas injection valve 31, it is known that the first water injection valve 51, the first gas injection valve 31, and the first spark plug 41 are arranged in this order from the upstream side to the downstream side in the flow direction D1.

Specifically, the first spark plug 41 according to the present embodiment is disposed downstream of the first gas injection valve 31 and upstream of the second water injection valve 52 in the flow direction D1. The interval between the first gas injection valve 31 and the first spark plug 41 in the circumferential direction is smaller than the interval between the first spark plug 41 and the second water injection valve 52 in the circumferential direction.

In addition, in the flow direction D1, the first gas injection valve 31 may be disposed closer to the first water injection valve 51 than to the first spark plug 41 as in fig. 3, or may be disposed opposite thereto closer to the first spark plug 41 than to the first water injection valve 51. The magnitude relation of the first angle θa and the second angle θb can be changed according to the arrangement condition of the first gas injection valve 31. For example, in the case of ignition from the top of the hydrogen jet, an arrangement such as the former (first angle θa > second angle θb) is effective. On the other hand, in the case of ignition from the rear end (root) of the hydrogen jet, the arrangement as the latter (first angle θa < second angle θb) is effective.

The first water injection valve 51 injects water toward a space near the first gas injection valve 31 adjacent to the first water injection valve 51, out of the first gas injection valve 31 and the second gas injection valve 32. Specifically, the first water injection valve 51 injects water toward the downstream side in the flow direction D1 (in particular, the downstream side in the flow direction D1 with respect to the first water injection valve 51). In order to spray water toward the space near the first gas injection valve 31, the water injection port 50a of the first water injection valve 51 according to the present embodiment is opened along the flow direction D1 of the swirl flow. By opening the water injection port 50a in this way, the first water injection valve 51 can inject water in the flow direction D1 of the swirl flow.

Here, when a cross section intersecting the central axis C is viewed, the center line C1 of the water jet port 50a extends so as to intersect with a predetermined portion (see the surface to be jetted 17C of fig. 3) of the inner wall surface 17 b. The center line C1 here is a virtual line that is perpendicular to the opening surface (particularly, the center portion of the opening surface) of the water injection port 50a and extends in a direction away from the first water injection valve 51 so as not to intersect the first spark plug 41.

For example, in the case of the arrangement shown in fig. 3 (the first angle θa > the second angle θb), in the cross-sectional view described above, the center line C1 extends so as not to intersect at least the first spark plug 41 of the first gas injection valve 31 and the first spark plug 41. In the example shown in fig. 3, the center line C1 extends so as not to intersect both the first gas injection valve 31 and the first spark plug 41 but to pass between the first gas injection valve 31 and the first spark plug 41.

In addition, in the above-described axial direction, the center line C1 extends so as to intersect with the upper side portion of the combustion chamber 17. The upper part here means: a portion of the upper side portion of the inner wall surface 17b that is closer to the top surface 17a than the top surface of the piston 21 when the piston 21 is positioned at the top dead center. The ejection target surface 17c corresponds to the upper portion.

In the flow direction D1, the injected surface 17c is set closer to the first gas injection valve 31, the first spark plug 41, and the first water injection valve 51 than to the second gas injection valve 32, the second spark plug 42, and the second water injection valve 52.

Specifically, in the flow direction D1, the injected surface 17c is set closer to the first gas injection valve 31 and the first spark plug 41 than to the first water injection valve 51. In more detail, in the flow direction D1, the injected surface 17c may be set closer to the first spark plug 41 than to the first gas injection valve 31.

(2) Controller 100

Fig. 6 is a block diagram illustrating the structure of a controller of the hydrogen engine. The controller 100 has a processor, a volatile memory, a nonvolatile memory, and an input-output bus. The controller 100 is connected to, for example, a gas flow sensor Sw1 that detects a flow rate of hydrogen supplied from a hydrogen storage tank (not shown) to the engine 1, a gas pressure sensor Sw2 that detects a pressure of hydrogen supplied to the engine 1, a rotation speed sensor Sw3 that detects an output rotation speed of the engine 1, and a clock 101. The various sensors Sw1 to Sw3 and the car clock 101 are shown only in fig. 6.

The controller 100 generates a control signal based on signals input from these sensors and devices, and inputs the control signal directly to the spark plug 40 or to a solenoid valve or the like for operating the gas injection valve 30 and the water injection valve 50. The controller 100 directly or indirectly controls the gas injection valve 30, the spark plug 40, and the water injection valve 50 through these control signals.

By controlling the respective parts of the engine 1 by the controller 100, it is possible to supply hydrogen gas into the combustion chamber 17 or to inject water into the combustion chamber 17 together with the hydrogen gas supply.

However, in the conventionally known hydrogen engine, abnormal combustion such as knocking and pre-ignition may occur due to the combustibility of hydrogen gas. In order to suppress such abnormal combustion, water injection as described above may be considered.

The present inventors have conducted intensive studies on further suppression of abnormal combustion, and as a result of the studies: in terms of the layout of the water injection valve 50, the structure as described above is invented; in terms of its injection timing, a new control pattern is created, and thus the present inventors have arrived at the present disclosure.

The engine control according to the present embodiment will be described below centering on the relationship between the engine control and the water injection.

< Details of Engine control >

Fig. 7 is a flowchart showing a specific example of engine control. Fig. 8A is a view for explaining the first stage water injection, fig. 8B is a view for explaining the hydrogen gas injection, and fig. 8C is a view for explaining the second stage water injection.

The flow illustrated in fig. 7 represents: when n is an integer of 1 or more, the processing and operation starts from the downstroke in the nth combustion cycle to the upstroke and downstroke in the (n+1) th combustion cycle. If the engine 1 is continuously operated with hydrogen, the flow is repeatedly executed by the engine 1.

First, in step S1 of fig. 7, the engine 1 introduces air flowing in a lateral vortex into the combustion chamber 17. In this step S1, the engine 1 performs a downstroke in the nth combustion cycle, and then starts an upstroke in the n+1th combustion cycle.

Specifically, in the descending stroke of step S1, the hydrogen gas burns in the combustion chamber 17, and as a result, the piston 21 descends toward the bottom dead center. At this time, the exhaust valve 18 is opened so that the combustion chamber 17 is opened, and the piston 21 is lowered so that the scavenging port 14a is opened. Thereby, air is introduced into the combustion chamber 17 from the scavenging port 14a, and exhaust gas is extruded into the exhaust pipe 19 by the air. The air introduced at this time is rectified by the scavenging port 14a as the rectifying mechanism. When a cross section intersecting the central axis C is observed, the air rectified by the scavenging port 14a becomes a vortex (transverse vortex). Air flowing in a cross vortex shape flows into the combustion chamber 17.

In addition, in step S1, when the piston 21 is changed from descending to ascending, the ascending stroke in the n+1th combustion cycle is started. In the first half of the upward stroke, the scavenging port 14a and the exhaust valve 18 are closed in this order as the piston 21 rises. On the other hand, in the latter half of the upward stroke, the air introduced into the combustion chamber 17 is compressed by the upward movement of the piston 21.

The "first half" and "second half" of the upstroke correspond to the first half and the second half of the upstroke when halving the upstroke. The same is defined with respect to the "first half" and "second half" of the downstroke.

Steps S2 to S5 in fig. 7 are executed within a predetermined period from the second half of the upward stroke to the first half of the downward stroke in the (n+1) -th combustion cycle. The predetermined period corresponds to a period from just before reaching TDC (top DEAD CENTER ) until just after reaching TDC. The controller 100 may execute all of the processing in steps S2 to S5 immediately after reaching TDC, or may execute some of the processing in steps S2 to S5 immediately after reaching TDC.

In the case where the engine is a high-speed engine for an automobile, the engine is operated at a rotational speed of about 2000rpm, and thus the time required for the piston to be positioned at TDC (more specifically, the time required for a change from TDC to1 deg.ca) is short, about 80 to 100 μs. In this case, in consideration of the ignition delay of the hydrogen, it is necessary to inject the hydrogen in advance of TDC so as to be adjusted such that the combustion peak occurs immediately after TDC is reached.

In contrast, when the engine is a low-speed and large-sized marine engine as in the present embodiment, the engine is operated at a rotational speed of about 100rpm, and thus the time for which the piston is located at TDC is long, about 1 to 2 ms. In this case, it is not necessary to inject hydrogen before TDC, and hydrogen can be injected at a timing based on the specification, the operating state, and the like of the engine 1. The same is true with respect to the injection timing of water. It is also possible to inject hydrogen and water in the downstroke after TDC. In this case, it is allowed to adjust to reach the combustion peak at a time slightly later than TDC.

As described above, the degree of freedom in the injection timing of the hydrogen gas and water of the engine 1 according to the present embodiment is greater than that of the high-speed engine. Since the arrival time of the combustion peak is allowed to be delayed, a longer stirring time for stirring the hydrogen gas by the water can be ensured as compared with a high-speed engine.

In step S2 subsequent to step S1, as shown in fig. 8A, the controller 100 causes water to be sprayed from the water spray valve 50 along the center line C1 (see spray W1 in the figure). The water injection is for causing the water injection valve 50 to inject water so that the water reaches the cylinder 16, particularly the inner wall surface (the injected surface 17 c) of the cylinder liner 14 in the (n+1) -th combustion cycle, and corresponds to the first stage water injection (the first water injection step).

The water injected in step S2 reaches the inner wall surface 17b before the hydrogen gas injected from the gas injection valve 30 reaches the inner wall surface 17b. By allowing water to reach the inner wall surface 17b before hydrogen gas, the water absorbs heat from deposits (for example, deposits formed by combustion residues in the cylinder and cylinder oil residues) near the inner wall surface 17b, and the temperature of the deposits can be reduced in advance. This can suppress abnormal combustion with deposits or the like as a source of pre-ignition.

In addition, by injecting water at a relatively early timing as in the first stage water injection described above, it is possible to cause water to reach the inner wall surface 17b before the flame generated by the hydrogen combustion reaches the inner wall surface 17b. This can form a water vapor film in the vicinity of the inner wall surface 17b. Since water does not have combustion supporting properties, the quenching distance can be extended by the water vapor film. By extending the quenching distance, heat loss can be reduced. This can suppress a decrease in the circulation efficiency caused by the combustion of hydrogen. This also makes it possible to maintain the exhaust gas energy and to operate the engine 1 without changing the operating point of a supercharger (not shown), which is advantageous in maintaining λ. The maintenance of lambda is effective in maximizing the effect of the EGR system (not shown). Further, by increasing the amount of water to increase the thickness of the water vapor film, heat loss can be further reduced, circulation efficiency can be improved, and exhaust gas energy can be increased, so that the operating point of the supercharger is shifted to the high-pressure large-air-volume side. Thus, λ can be made larger than before, and lean combustion of hydrogen can be achieved. By realizing lean combustion, the generation of nitrogen oxides in the exhaust gas can also be suppressed.

Next, in step S3 subsequent to step S2, as shown in fig. 8B, the controller 100 causes the gas injection valve 30 to inject hydrogen gas, thereby causing the hydrogen gas to flow along with the swirling flow (see the spray G1 in the figure). The hydrogen gas thus injected flows so as to form a vortex along the flow direction D1, and diffuses in the combustion chamber 17. This step corresponds to the gas injection step performed in the (n+1) th combustion cycle.

Next, in step S4 subsequent to step S3, as shown in fig. 8C, the controller 100 causes the water injection valve 50 to inject water from the upstream side of the vortex flow, thereby causing the spray W2 of the water to collide with hydrogen gas (more specifically, the spray G1 of hydrogen gas). The water injection is used to inject water into the water injection valve 50 in the (n+1) th combustion cycle so that the water spray W2 collides with the hydrogen gas, and corresponds to the second stage water injection (second water injection step).

As shown in the tandem relation between step S3 and step S4, in the (n+1) th combustion cycle, the controller 100 causes the hydrogen gas to be injected from the gas injection valve 30 (step S3) and then causes the water to be injected from the water injection valve 50 (step S4).

The water sprayed in step S4 flows along the center line C1. The spray W2 of water collides with the spray G1 of hydrogen gas from the upstream side of the vortex. The water after colliding with the spray G1 of hydrogen gas agitates the hydrogen gas by its penetrating power. Since the center line C1 extends along the flow direction D1, the hydrogen gas can be stirred by the penetrating power of the water so as not to obstruct the flow of the vortex flow. The hydrogen diffusion is promoted by this stirring. This can suppress occurrence of uneven concentration of hydrogen gas, and can suppress abnormal combustion.

In addition, the temperature rise in the cylinder 16 can be suppressed by the heat of vaporization of the water itself. This can prevent the energy density required for abnormal combustion from being reached, and is advantageous in suppressing abnormal combustion.

Next, in step S5 subsequent to step S4, the controller 100 ignites the hydrogen gas by operating the ignition plug 40 as an ignition member.

As shown in the front-rear relationship between step S4 and step S5, in the (n+1) th combustion cycle, the controller 100 operates the ignition plug 40 (step S5) after injecting water from the water injection valve 50 (step S4).

The hydrogen ignited in step S5 is combusted in the combustion chamber 17. By this combustion, power for reciprocating the piston 21 is obtained. The piston 21 is promoted to descend to perform the above-described descending stroke.

In the case where the hydrogen gas is continuously combusted, the steps from step S1 to step S5 are repeated as described above, and the illustration is omitted.

Meaning of water injection according to the present embodiment

As described above, the controller 100 according to the present embodiment causes the water spray W2 to collide with the hydrogen gas (spray G1) by spraying water from the upstream side of the vortex flow as described with reference to fig. 8C. Since the spray W2 is sprayed along the flow direction of the vortex, the hydrogen gas can be stirred by the penetrating force. This promotes the flow of hydrogen gas in the cylinder of the engine 1, and suppresses the occurrence of the concentration unevenness of hydrogen gas in the combustion chamber 17. As a result, abnormal combustion can be suppressed more effectively than in the conventional case.

In addition, by stirring the hydrogen gas with the spray W2 of water, the room temperature of the combustion chamber 17 can be reduced. Thus, the maximum combustion temperature that can be achieved by burning hydrogen is reduced, and the NOx emission amount can be reduced.

In addition, by disposing the water injection valve 50 on the upstream side of the gas injection valve 30 as illustrated in fig. 3 and the like, water injected from the upstream side of the vortex flow is likely to collide with the hydrogen gas phase. Further, by injecting water toward the gas injection valve 30, the water can collide with the hydrogen gas just injected from the gas injection valve 30 (see fig. 8C). As a result, stirring of the hydrogen gas can be started at an earlier timing. The stirring is started at an earlier timing, and accordingly, the hydrogen gas can be stirred for a longer time. This is advantageous in suppressing abnormal combustion.

As illustrated in steps S3 to S4 of fig. 7, the controller 100 injects water after injecting hydrogen gas. This makes it possible to more reliably collide the water injected with the hydrogen gas. As a result, the hydrogen gas can be stirred with water more reliably, which is advantageous in suppressing abnormal combustion.

As illustrated in steps S4 to S5 of fig. 7, the controller 100 causes the spark plug 40 to operate after injecting water. This makes it possible to burn the hydrogen gas after the concentration of the hydrogen gas is suppressed from being uneven by the water. As a result, it is advantageous in suppressing abnormal combustion.

In addition, as illustrated in fig. 3, the center line C1 of the water injection port 50a does not intersect the spark plug 40. This can reduce the amount of water sprayed onto the spark plug 40. As a result, the hydrogen gas can be ignited more reliably. In addition, abrupt temperature changes of the spark plug 40 can be suppressed, and the reliability can be improved.

< Modification of ignition Member >

Fig. 9 is a diagram showing a modification of the ignition member, and corresponds to fig. 3. Fig. 10 is a diagram for explaining water injection in the modification, and corresponds to fig. 8C. In fig. 9 and 10, components substantially identical to those illustrated in fig. 1 to 8 are given the same reference numerals.

The ignition member according to the above embodiment is constituted by the ignition plugs 40, and two ignition plugs 40 are provided for each cylinder 16, but the present disclosure is not limited to this configuration. For example, the ignition means may be constituted by one or a plurality of fuel injection valves 60, and the fuel injection valves 60 may inject a pilot oil (oil fuel) for igniting the hydrogen gas. In the case of the example of the drawing, two fuel injection valves 60 are provided on each cylinder 16, and the fuel injection valves 60 constitute ignition means. Hereinafter, one of the two fuel injection valves 60 is sometimes referred to as a "first fuel injection valve 61", and the other of the two fuel injection valves 60 is sometimes referred to as a "second fuel injection valve 62".

Each fuel injection valve 60 faces the chamber of the combustion chamber 17 through the top surface 17 a. Each fuel injection valve 60 is electrically connected to the controller 100 via a solenoid valve (not shown) or the like. The solenoid valve operates in accordance with a control signal input from the controller 100 to open or close each fuel injection valve 60. Each fuel injection valve 60 is indirectly controlled by the controller 100.

The relative positional relationship of the first water injection valve 51, the first gas injection valve 31, and the first fuel injection valve 61, and the injection timing of the first fuel injection valve 61 and the like will be described in order. The following description is applicable to the second water injection valve 52, the second gas injection valve 32, and the second fuel injection valve 62.

For example, in the following description, the first water injection valve 51, the first gas injection valve 31, and the first fuel injection valve 61 may be replaced with the second water injection valve 52, the second gas injection valve 32, and the second fuel injection valve 62, respectively.

As shown in fig. 9, the first fuel injection valve 61 is arranged between the first gas injection valve 31 and the first water injection valve 51 in the circumferential direction. In other words, in the above-described flow direction D1, the first fuel injection valve 61 is arranged at a position on the downstream side of the first water injection valve 51 and on the upstream side of the first gas injection valve 31.

In addition, the fuel injection ports 60a of the first fuel injection valve 61 are opened along the flow direction D1 of the swirl flow. By opening the fuel injection port 60a in this way, the first fuel injection valve 61 can inject the pilot oil in the flow direction D1 of the swirl flow.

When a cross section intersecting the central axis of the cylinder 16 is observed, the water injection ports 50a of the first water injection valve 51 are arranged such that the center line C1 of the water injection ports 50a does not intersect with the first fuel injection valve 61. By this arrangement, as with the structure illustrated in fig. 3, the amount of water sprayed onto the first fuel injection valve 61 can be reduced. As a result, the hydrogen gas can be ignited more reliably by the pilot oil injected from the first fuel injection valve 61 (more precisely, the flame generated by the pilot oil reaching the ignition point). Further, abrupt temperature change of the first fuel injection valve 61 can be suppressed, and reliability can be improved.

As in the above embodiment, the injection timing of the pilot oil by first fuel injection valve 61 is controlled in accordance with the flow chart shown in fig. 7. That is, in a predetermined combustion cycle, the controller 100 causes the oil fuel to be injected from the first fuel injection valve 61 after causing water to be injected from the first water injection valve 51 (see the spray G2 in fig. 10).

By adopting such injection timing, it is possible to combust hydrogen after the concentration unevenness of hydrogen is suppressed by water. As a result, it is advantageous in suppressing abnormal combustion.

< Other modifications >

In the above embodiment, the first stage water injection for making the water reach the vicinity of the inner wall surface 17b is performed before the second stage water injection for stirring the hydrogen gas is performed, but the present disclosure is not limited to this configuration. For example, the structure may be as follows: the spray range of the second stage water spray is enlarged to replace the first stage water spray. In the case of such a configuration, the spray range of water may be enlarged so that the inner wall surface 17b closer to the water injection valve 50 than to the spark plug 40 or the fuel injection valve 60 is included in the spray range of water; alternatively, the center line C1 of the water jet port 50a may be set to be directed toward such an inner wall surface 17b.

In the above embodiment, the case where water is injected in a predetermined combustion cycle (n+1th combustion cycle) has been described, but it is not necessary to inject water in all the combustion cycles. For example, the controller 100 may distinguish between a control scheme using water injection together with hydrogen gas and a control scheme using only hydrogen gas according to the operating state of the engine 1, the external environment, and the like.

In addition, the ignition member constituted by the ignition plug 40 or the fuel injection valve 60 is illustrated, but the structure of the ignition member is not limited to the above-described example. The ignition member may be constituted by a glow plug or by a so-called hot bulb.

Claims

1. A hydrogen engine that burns hydrogen gas, characterized in that:

the hydrogen engine comprises a cylinder, a gas injection valve, a rectifying mechanism, a water injection valve and a controller,

The cylinder defines a combustion chamber,

The gas injection valve injects the hydrogen gas into the combustion chamber,

The rectifying mechanism generates a vortex of the air by regulating the flow of the air sucked into the cylinder,

The water injection valve injects water into the combustion chamber along the flow direction of the swirl flow,

The controller controls the gas injection valve and the water injection valve,

The controller causes the hydrogen gas to flow along with the vortex by causing the gas injection valve to inject the hydrogen gas, and causes the water injection valve to spray the water in a mist form from an upstream side of the vortex to collide the spray of the water with the hydrogen gas.

2. The hydrogen engine of claim l, wherein:

The water injection valve is disposed adjacent to the gas injection valve at a position on the upstream side of the gas injection valve in the flow direction of the swirl flow,

The water injection valve injects the water toward a downstream side in a flow direction of the vortex flow.

3. The hydrogen engine according to claim 2, characterized in that:

In a predetermined combustion cycle, the controller causes the water to be injected from the water injection valve after causing the hydrogen gas to be injected from the gas injection valve.

4. A hydrogen engine according to claim 3, characterized in that:

the hydrogen engine includes a spark plug that is controlled by the controller and ignites the hydrogen gas,

In the predetermined combustion cycle, the controller may operate the spark plug after injecting the water from the water injection valve.

5. The hydrogen engine according to claim 4, characterized in that:

the water injection valve has a water injection port opening along a flow direction of the swirl flow,

The water injection ports are arranged such that a center line of the water injection ports does not intersect the spark plug when a cross section taken transversely to a center axis of the cylinder is observed.

6. A hydrogen engine according to claim 3, characterized in that:

the hydrogen engine includes a fuel injection valve that is controlled by the controller and injects an oil fuel for igniting the hydrogen gas,

In the predetermined combustion cycle, the controller causes the oil fuel to be injected from the fuel injection valve after causing the water to be injected from the water injection valve.

7. The hydrogen engine according to claim 6, characterized in that:

The water injection ports are arranged such that a center line of the water injection ports does not intersect the fuel injection valve when a cross section taken transversely to a center axis of the cylinder is observed.

8. The hydrogen engine according to any one of claims 3 to 7, characterized in that:

in the predetermined combustion cycle, the controller sequentially executes a first water injection step, a gas injection step, and a second water injection step,

In the first water injection process, the controller causes the water injection valve to inject the water so that the water reaches an inner wall surface of the cylinder,

In the gas injection process, the controller causes the gas injection valve to inject the hydrogen gas,

In the second water injection step, the controller causes the water injection valve to spray the water in a mist form so that the spray of the water collides with the hydrogen gas.