CN116357449A

CN116357449A - Gas engine

Info

Publication number: CN116357449A
Application number: CN202211250532.1A
Authority: CN
Inventors: 上田哲司
Original assignee: Japan Engine Corp
Current assignee: Japan Engine Corp
Priority date: 2021-12-27
Filing date: 2022-10-12
Publication date: 2023-06-30
Also published as: JP2023096412A; KR20230099624A

Abstract

The invention discloses a gas engine. Only the hydrogen cluster (α) injected from the fuel injection valve a (30) is ignited by the ignition plug a (32). Then, a flame (α) generated by combustion of the hydrogen cluster (α) is made to surround a half cycle in the cylinder (10), catches up with the hydrogen cluster (β) injected from the fuel injection valve B (31), ignites the hydrogen cluster (β), and then causes the hydrogen cluster (β) to also burn. The present invention provides a gas engine capable of combusting a gas having good combustibility, wherein a plurality of fuel injection valves for injecting a fuel gas are provided in a cylinder of a cylinder to improve combustibility, and a large heat load is not applied to the cylinder or the like, so that the rigidity of the engine itself does not need to be improved, and the emission amount of NOx can be suppressed.

Description

Gas engine

Technical Field

The present invention relates to a gas engine that burns a gas having good combustibility such as hydrogen.

Background

In recent years, there has been a demand for realizing so-called zero emission in which the emission amount of carbon dioxide is zero due to a problem such as global warming. Accordingly, it is difficult to achieve zero emission in existing engines using fossil fuels such as heavy oil as fuel, and gas engines using combustible gases having no carbon in molecular structures such as hydrogen have been recently developed in a large number.

For example, patent document 1 below proposes a hydrogen fuel engine using hydrogen gas as a fuel. Patent document 1 describes the following: in a hydrogen-fuelled engine, in order to suppress a temperature rise in the vicinity of a spark plug and reduce the concentration of NOx in combustion gas, two spark plugs and two fuel injection valves are provided in a cylinder of a cylinder so as to face each other, and the two spark plugs are simultaneously ignited, whereby the propagation distance of combustion flame is shortened and the temperature rise in the vicinity of the spark plugs is suppressed.

Of course, when a gas having good combustibility such as hydrogen is combusted, the fuel is abruptly combusted and the temperature around the ignition plug is abruptly increased, as compared with a conventional engine using fossil fuel as the fuel, and therefore the NOx amount in the combustion gas (exhaust gas) is increased, and therefore, it is necessary to reduce the total amount of fuel around each ignition plug by providing two ignition plugs as in patent document 1, and thereby reduce the combustion temperature.

Patent document 1: japanese laid-open patent publication No. Sho 58-12457

Disclosure of Invention

Technical problem to be solved by the invention

As described in patent document 1, if two fuel injection valves and two spark plugs are provided in the cylinder of the cylinder and the two spark plugs are simultaneously ignited, the propagation distance of the combustion flame is surely shortened.

However, since two combustions occur simultaneously in one cylinder, the pressure in the cylinder increases sharply, and a large heat load may be applied to the cylinder. If a large heat load is applied to the cylinder in this way, there is a problem that the pressure resistance of the cylinder inner surface, such as the piston, or the mounting strength of the spark plug, needs to be improved, the rigidity of the engine itself needs to be improved, the manufacturing cost of the engine increases, and NOx emissions as harmful substances remain large because of rapid combustion.

The present invention has been made to solve the above-mentioned problems, and has an object of: a gas engine capable of combusting a gas having excellent combustibility is provided, in which a plurality of fuel injection valves for injecting a fuel gas are provided in cylinders of a cylinder to improve combustibility, and in which a large heat load is not applied to the cylinder or the like, so that the rigidity of the engine itself does not need to be improved, and the emission amount of NOx can be suppressed.

Technical solution for solving the technical problems

In order to achieve the object, the present invention relates to a gas engine for combusting a gas having good combustibility such as hydrogen, comprising: a plurality of fuel injection valves for injecting fuel gas are provided in a cylinder of a cylinder, and the gas engine includes an ignition member for burning one of a plurality of gas clusters injected from the plurality of fuel injection valves before the other gas clusters.

Specifically, the present invention relates to a gas engine for combusting a gas having good combustibility such as hydrogen, the gas engine comprising: the gas engine is provided with a cylinder which is cylindrical and has a combustion chamber inside, and a plurality of fuel injection valves for injecting gas are provided at positions separated from each other in the cylinder, and the gas engine includes an ignition member for burning at least one of the plurality of gas clusters injected from the plurality of fuel injection valves before the other gas clusters.

According to this configuration, a plurality of fuel injection valves that inject the gas are provided at positions separated from each other in the cylinder, and the ignition member that burns one of the plurality of gas clusters injected from the plurality of fuel injection valves earlier than the other gas clusters is provided, whereby the plurality of gas clusters are burned one by one in sequence. That is, instead of a plurality of gas clusters being burned simultaneously, one gas cluster is burned first, and then the other gas clusters are burned under the influence of the flame of the burned gas cluster.

Therefore, the plurality of gas clusters are burned one by one in sequence, combustion becomes slow, and the pressure caused by combustion in the cylinder gradually rises.

The ignition member may be a general ignition plug, or may be an ignition member that promotes combustion of gas, such as a glow plug or a hot bulb (hot bulb).

The number of ignition members is not limited to one, and a plurality of ignition members may be provided depending on the number of fuel injection valves or the like. In the case where a plurality of ignition members are provided in this way, only one ignition member may be operated in one combustion cycle. In this case, the ignition member may be switched to operate at regular intervals.

In a second aspect of the invention, it is characterized in that: in the gas engine, a swirling flow generating means is provided that generates a swirling flow of air sucked into the cylinder, and the gas aggregate injected by the fuel injection valve swirls by the swirling flow of air.

According to this configuration, the swirling flow is generated in the air sucked into the cylinder by the swirling flow generating means, and the gas agglomerate injected from the fuel injection valve is swirled in the cylinder by the swirling flow of the air.

Therefore, when one gas agglomerate burns first and other gas agglomerates burn under the influence of the first burnt gas agglomerate, the other gas agglomerates are more easily influenced by the flame under the effect of the air swirling flow, so that the combustion interval can be shortened.

Therefore, the interval between the combustions when the plurality of gas clusters are burned in sequence can be shortened, and the pressure fluctuation is smoothly generated with the pressure rise, so that the rotation of the engine is not adversely affected.

In the invention of the third aspect, it is characterized in that: the fuel injection valve is constituted by a first fuel injection valve that injects a gas agglomerate that burns first and a second fuel injection valve that injects a gas agglomerate that burns second, and the gas engine includes a control means that causes the amount of gas agglomerate injected from the first fuel injection valve to be smaller than the amount of gas agglomerate injected from the second fuel injection valve.

According to this configuration, since the amount of gas of the gas agglomerate of the pre-combustion is small and the amount of gas agglomerate of the post-combustion is large, the heat release rate by the combustion, that is, the waveform of the heat per unit time (ROHR rate of heat release) generated by the combustion in the engine is small in the first half of the combustion and becomes large in the second half of the combustion.

Therefore, in the initial combustion stage in which the piston is located near the top dead center and the combustion chamber is small, the heat loss is suppressed by reducing the heat quantity, and the combustion temperature is also suppressed, whereby the generation of NOx is reduced, and in the later combustion stage in which the piston is located away from the top dead center and the combustion chamber is large, the effect of heat energy is obtained to the maximum extent by increasing the heat quantity, and the combustion temperature is not so high, and NOx is also difficult to generate.

Therefore, a more desirable combustion state of the engine can be obtained.

Effects of the invention

As described above, according to the present invention, a plurality of gas clusters are burned one by one in sequence, and the pressure rise due to the combustion in the cylinder is gradually generated.

Therefore, in a gas engine that burns a gas having good combustibility, a plurality of fuel injection valves that inject a fuel gas are provided in the cylinder of the cylinder to make the combustibility good, and a large heat load is not applied to the cylinder or the like, so that it is not necessary to increase the rigidity of the engine itself. The amount of NOx emission can be suppressed.

Drawings

Fig. 1 is a schematic diagram showing the structure of a gas engine according to a first embodiment of the present invention;

fig. 2 is a view illustrating a uniflow scavenging method of the gas engine, fig. 2 (a) is a detailed sectional view of a lower portion of the cylinder, and fig. 2 (b) is a lateral sectional view of the lower portion of the cylinder;

fig. 3 is a detailed sectional view of the cylinder head of the first embodiment;

fig. 4 is a view showing the top surface of the cylinder head of the first embodiment;

fig. 5 is a system block diagram of a control system of the gas engine of the first embodiment;

fig. 6 is a diagram showing a combustion state of the gas engine according to the first embodiment, fig. 6 (a) is a diagram of an initial stage of combustion, and fig. 6 (b) is a diagram of a later stage of combustion;

fig. 7 is a graph showing a change in the heat release rate (ROHR) generated by the combustion of the first embodiment;

fig. 8 is a diagram showing a combustion state of the gas engine of the second embodiment, fig. 8 (a) is a diagram of an initial stage of combustion, and fig. 8 (b) is a diagram of a later stage of combustion;

fig. 9 is a graph showing a change in the heat release rate (ROHR) caused by the combustion of the second embodiment.

Symbol description-

1-a gas engine; 10-cylinder; 30-a fuel injection valve a; 31-combustion injection valve B; 32-spark plug a (ignition member); 33-spark plug B; 40-scavenging holes; alpha, beta, gamma, lambda-hydrogen clusters (gas clusters).

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following preferred embodiments are merely illustrative of the present invention in nature and are not intended to limit the present invention, its application, or uses.

(first embodiment)

Fig. 1 is a schematic diagram illustrating the structure of a gas engine 1 for a ship, and a brief structure of the gas engine 1 will be described with reference to the diagram. Hereinafter, the gas engine 1 for a ship will be simply referred to as "engine 1".

The engine 1 is an in-line multi-cylinder gas engine including a plurality of cylinders 10. The engine 1 is configured as a two-cycle engine employing a uniflow scavenging system, and is mounted on a large vessel such as a tanker, a container ship, or an automobile carrier. Note that, the uniflow scavenging method will be described below with reference to fig. 2.

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

In particular, the engine 1 according to the present embodiment is configured as a so-called crosshead engine in order to achieve a longer stroke. That is, in the engine 1, a piston rod 22 supporting a piston 21 from below and a connecting rod 24 connected to a crankshaft 23 are coupled together by a cross head 25.

The engine 1 includes a frame 11 located below, a frame 12 provided on the frame 11, and a cylinder jacket (cylinder jacket) 13 provided on the frame 12. The housing 11, the frame 12, and the cylinder water jacket 13 are fastened by a plurality of tie bolts (tie bolts) B … … and nuts extending in the up-down direction. The engine 1 further includes: a cylinder 10 provided in the cylinder water jacket 13, a piston 21 provided in the cylinder 10, and an output shaft (e.g., a crankshaft 23) that rotates in conjunction with the reciprocating motion of the piston 21.

The housing 11 constitutes a so-called crankcase of the engine 1, and a crankshaft 23 and a bearing 26 for rotatably supporting the crankshaft 23 are housed in the housing 11. The lower end of the connecting rod 24 is coupled to the crankshaft 23 via a crank 27.

A pair of guide plates 28, a link 24, and a cross head 25 are housed in the frame 12. Wherein the pair of

guide plates

28, 28 are constituted by a pair of plate-like members provided along the piston axial direction, and are arranged with a space therebetween in the width direction of the engine 1 (the left-right direction of the paper surface of fig. 1). The connecting rod 24 is disposed between a pair of

guide plates

28, 28 in a state where its lower end portion is connected 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.

Specifically, the crosshead 25 is arranged between a pair of guide plates 28, and slides in the up-down direction along each

guide plate

28, 28. That is, the pair of

guide plates

28, 28 are configured to guide sliding 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 cross pin 29 is connected to the piston rod 22 to move up and down integrally, and on the other hand, the cross pin 29 is connected to the link 24 to rotate the link 24 with the upper end portion of the link 24 as a fulcrum.

The cylinder water jacket 13 is arranged with a cylinder liner 14 as an inner cylinder. Inside the cylinder liner 14, the above-described piston 21 is disposed. The piston 21 reciprocates in the up-down direction along the inner wall of the cylinder liner 14. A cylinder head 15 is also fixed to an upper portion of the cylinder liner 14. The cylinder head 15 constitutes the cylinder 10 together with the cylinder liner 14.

An exhaust valve 18 is provided in the cylinder head 15, and the exhaust valve 18 is operated by a valve train device, not shown. The exhaust valve 18 delimits a combustion chamber 17 together with the cylinder 10 and the top surface of the piston 21, wherein the cylinder 10 is formed by 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 (not shown) communicating with the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

The cylinder head 15 delimits a top surface 16 of a combustion chamber 17. As described below, a plurality of fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31 are provided on the top surface 16. In this embodiment, two fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31 are provided for each cylinder 10.

Fig. 2 is a view illustrating a uniflow scavenging system for generating a swirling flow of air in the cylinder 10, fig. 2 (a) is a detailed cross-sectional view of the lower part of the cylinder, and fig. 2 (b) is a transverse cross-sectional view of the lower part of the cylinder.

As shown in fig. 2, the cylinder liner 14 in the lower portion of the cylinder 10 is provided with a plurality of scavenging holes 40, … …, and the plurality of scavenging holes 40, … … suck air from the outside of the cylinder liner 14. As shown in fig. 2 (b), the scavenging hole 40 … … is opened in a slightly inclined manner with respect to the tangential direction of the cylinder liner 14.

Therefore, as shown in fig. 2, when air is sucked into the cylinder 10 through the scavenging holes 40 and … …, a swirling flow of air is generated in the cylinder 10.

As described above, the swirling flow of air is generated in the cylinder 10, and thus, an effective function in combustion of gas is exerted as described below.

Next, a detailed structure in the vicinity of the cylinder head 15 of the engine according to the present embodiment will be described with reference to fig. 3 and 4. Fig. 3 is a detailed cross-sectional view of the cylinder head of the first embodiment, and fig. 4 is a diagram showing the top surface of the cylinder head of the first embodiment.

In the cylinder head 15, as described above, the exhaust valve 18 is provided at the center portion of the top surface 16, and a plurality of fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31 are provided on the top surface 16. Specifically, two fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31 are provided at substantially diagonal positions of the inclined surface of the top surface 16. Hydrogen gas as a combustible gas is injected from these fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31. Since the supply paths and the like for supplying hydrogen gas to these

fuel injection valves

30 and 31 are well known, detailed description thereof is omitted.

On the top surface 16 of the cylinder head 15, spark plugs (spark plugs a,

B)

32, 33 as ignition members are further provided, and the spark plugs (spark plugs a,

B)

32, 33 are provided at positions slightly offset from the fuel injection valves (fuel injection valves a,

B)

30, 31 in the circumferential direction. Like the above-described fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31, a plurality of spark plugs 32, 33 (spark plugs a, B) are provided.

In the present embodiment, the offset amounts of the spark plugs (spark plugs a,

B)

32, 33 from the fuel injection valves (fuel injection valves a,

B)

30, 31 in the circumferential direction are set to about 10 ° to 45 °. However, the amount of the circumferential deviation is preferably set appropriately according to the performance of the fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31, the amount of injected hydrogen, the injection speed, the swirl speed of the air swirling flow, and the like.

The spark plugs (spark plugs a,

B)

32, 33 burn the hydrogen gas (hydrogen gas clusters) injected from the fuel injection valves (fuel injection valves a,

B)

30, 31 by applying sparks to the hydrogen gas. As described above, the engine 1 can be appropriately burned as a gas engine by burning hydrogen with the spark plugs (spark plugs a,

B)

32, 33.

Next, an outline of system blocks of the control system of the engine 1 according to the present embodiment will be described.

As shown in fig. 5, the engine control system of the present embodiment includes: a start switch 51 for starting the engine 1, a joystick 52 for controlling the rotation speed of the engine 1, a selection switch 53 for switching the mode of the combustion state, and an environment sensor 54 for detecting the external environment and inputting information of the external environment are used as input means. Based on the information from these input means, an engine control unit 50 performs arithmetic processing. The engine control unit 50 is connected to a storage unit 55, and various data to be used in the arithmetic processing, predetermined map information, and the like are extracted from the storage unit 55.

The output signals calculated by the engine control unit 50 are sent to the fuel injection valve a30, the fuel injection valve B31, the spark plug a32, and the spark plug B33 as output members, respectively.

The control system of the engine 1 of the present embodiment has the above-described configuration, so that the operating state of the engine 1 is appropriately controlled.

Next, the operation state of the engine according to the present embodiment will be described with reference to fig. 6 and 7. Fig. 6 is a diagram showing a combustion state, fig. 6 (a) is a diagram showing an initial stage of combustion, and fig. 6 (b) is a diagram showing a later stage of combustion. Fig. 7 is a graph showing a change in the heat release rate (ROHR) caused by the combustion of the present embodiment.

As shown in fig. 6 (a), at the initial stage of combustion, hydrogen gas as fuel is injected from two fuel injection valves, specifically, from the fuel injection valve a30 and the fuel injection valve B31, respectively, in equal amounts. The injected hydrogen gas forms hydrogen gas clusters α and β in the cylinder 10.

In which only the hydrogen cluster α injected from the fuel injection valve a30 is ignited by the ignition plug a 32. As described above, when only one hydrogen cluster α is ignited to burn, it is possible to suppress the pressure rise caused by the combustion, as compared with the case where two hydrogen clusters α, β are ignited at the same time to burn.

Then, as shown in fig. 6 (B), the flame α generated by the combustion of the hydrogen cluster α is surrounded by the cylinder 10 in half a cycle, catches up with the hydrogen cluster β injected from the fuel injection valve B31, and then ignites the hydrogen cluster β, and then the hydrogen cluster β is also combusted. That is, the hydrogen cluster β is not ignited by the ignition plug B33 (refer to fig. 6 (a)), but is ignited by the flame α of the hydrogen cluster that is burned first to burn.

In the engine 1 of the present embodiment, the heat release rate (ROHR) changes as shown in fig. 7 because of such a combustion state. In the figure, the vertical axis represents the value of the heat release rate (ROHR), and the horizontal axis represents the value of the time elapsed when the piston 21 moves from near the top dead center toward the bottom dead center.

In the figure, the value shown by the solid line is the value when the two hydrogen clusters α, β are burned by the two spark plugs (spark plug a, spark plug B) 32, 33 simultaneously, and the value shown by the broken line is the value when burned in the present embodiment.

As is clear from the figure, in the case where the two hydrogen-gas clusters α, β are simultaneously ignited by the two spark plugs (spark plug a, spark plug B) 32, 33 (solid line case), the value of the heat release rate (ROHR) increases sharply and then decreases in a short time. As described above, when the heat release rate (ROHR) increases sharply, there is a possibility that a large heat load is applied to the cylinder interior of the cylinder 10. Accordingly, there is a problem in that the engine manufacturing cost increases because it is necessary to improve the pressure resistance of the cylinder 10, the inner surface of the cylinder 21, and the like, the mounting strength of the spark plugs 32, 33, and the like, and the rigidity of the engine 1 itself. Moreover, since the fuel is burned off in a relatively small area, the temperature of the local space rises, resulting in a state where much NOx is still generated.

In contrast, in the case of the present embodiment (the case of the broken line), the value of the heat release rate (ROHR) gradually increases, then temporarily decreases, but again increases, and then gradually decreases. As described above, by gradually increasing the value of the heat release rate (ROHR) and maintaining it for a long period of time, a large heat load is not applied to the cylinder interior of the cylinder 10 in the present embodiment. Therefore, it is not necessary to improve the pressure resistance of the cylinder 10, the in-cylinder inner surface of the piston 2I, etc., the mounting strength of the ignition plugs 32, 33, etc., and thus it is not necessary to improve the rigidity of the engine 1 itself. Since the diffusion region of the fuel is enlarged and the combustion region is enlarged, the amount of temperature rise is reduced as compared with the case where both spark plugs are simultaneously ignited, and thus NOx generation can be suppressed.

Therefore, the cost of manufacturing the engine can be suppressed. That is, according to the present embodiment, even when a gas having good combustibility such as hydrogen is combusted, it is not necessary to increase the rigidity of the engine 1 itself.

As described above, the present embodiment relates to an engine 1 for combusting hydrogen gas having good combustibility, characterized in that: the engine 1 is provided with a cylinder 10, the cylinder 10 having a cylindrical shape and being provided with a combustion chamber 17 therein, and a plurality of fuel injection valves (fuel injection valves a,

B)

30, 31 for injecting hydrogen gas are provided at positions separated from each other in the cylinder 10, and the engine 1 includes a spark plug (spark plug a) 32, and the spark plug (spark plug a) 32 burns one hydrogen gas cluster α of a plurality of hydrogen gas clusters α, β injected from the plurality of fuel injection valves (fuel injection valves a,

B)

30, 31 earlier than the other hydrogen gas clusters β.

Thus, the plurality of hydrogen clusters α, β are burned one by one. That is, instead of the plurality of hydrogen clusters α, β being burned simultaneously, one hydrogen cluster α is burned first, and then the other hydrogen clusters β are burned under the influence of the flame of the previously burned hydrogen cluster α.

Therefore, the plurality of hydrogen clusters α, β are burned one by one in sequence, and the combustion becomes slow, so that the pressure in the cylinder 10 slowly rises.

Therefore, in the engine 1 that burns hydrogen gas having good combustibility, the plurality of fuel injection valves (fuel injection valve a, fuel injection valve B) 30, 31 that inject hydrogen gas, which is fuel, are provided in the cylinder 10 to make combustibility good, and a large heat load is not applied to the cylinder 10 or the like, so that it is not necessary to increase the rigidity of the engine 1 itself. The amount of NOx emission can be suppressed.

In the present embodiment, the scavenging holes 40 and … … for generating a swirling flow in the air taken into the cylinder 10 are provided in the lower portion of the cylinder 10, and the hydrogen clusters α and β injected by the fuel injection valves (fuel injection valves a and B) 30 and 31 are swirled by the swirling flow of the air.

In this way, the hydrogen clusters α and β injected from the fuel injection valves (fuel injection valve a and fuel injection valve B) 30 and 31 swirl in the cylinder 10 by the swirling flow of the air.

Therefore, when one hydrogen aggregation group α burns first and the other hydrogen aggregation groups β burn under the influence of the first burnt hydrogen aggregation group α, the other hydrogen aggregation groups β are more easily influenced by the flame under the effect of the air swirling flow, so that the combustion interval can be shortened.

Therefore, even in a state where the combustion period is longer than the combustion period in which the plurality of hydrogen clusters are simultaneously ignited, the interval between the combustions when the plurality of hydrogen clusters α, β are sequentially combusted can be shortened, and pressure fluctuation is smoothly generated with the pressure rise, so that the rotation of the engine 1 is not adversely affected.

(second embodiment)

Next, a second embodiment will be described with reference to fig. 8 and 9. Fig. 8 is a diagram showing a combustion state of the second embodiment, fig. 8 (a) is a diagram showing an initial stage of combustion, and fig. 8 (b) is a diagram showing a later stage of combustion, as in fig. 6. Fig. 9 is a graph showing a change in the heat release rate (ROHR) caused by the combustion of the second embodiment, as in fig. 7. The structure of the engine 1 to be used as a premise is the same as that of the first embodiment, and therefore, the description thereof is omitted.

In the second embodiment, the injection amount of hydrogen gas from the fuel injection valve a30 is smaller than that from the fuel injection valve B31. Therefore, as shown in fig. 8 (a), the hydrogen cluster γ injected from the fuel injection valve a30 is smaller than the hydrogen cluster λ injected from the fuel injection valve B31.

In this second embodiment, only the hydrogen cluster γ injected from the fuel injection valve a30 is ignited by the ignition plug 32. In this case, the pressure rise can be suppressed as compared with the case where the two hydrogen clusters γ, λ are simultaneously ignited and burned.

Then, as shown in fig. 8 (B), in this second embodiment, too, the flame γ generated by the combustion of the hydrogen cluster γ surrounds the cylinder 10 by half a circle, and after the hydrogen cluster λ ejected from the fuel injection valve B31 is caught up, the hydrogen cluster λ is ignited, and the hydrogen cluster λ is also combusted.

In this second embodiment, as shown by the broken line in fig. 9, the heat release rate (ROHR) is low when only the first hydrogen cluster γ burns, and becomes high when the second hydrogen cluster λ is also added to burn.

This is different from the first embodiment. As described above, the heat release rate (ROHR) when the first hydrogen cluster γ burns is low, and the heat release rate (ROHR) when the second hydrogen cluster λ is also added to burn becomes high, whereby the ideal combustion state of the engine can be obtained.

That is, the combustion state of the engine is theoretically: all combustion occurs when the piston is at top dead center and the explosion energy is converted entirely into kinetic energy of the piston lowering, but in an actual engine, a part of the explosion energy escapes as thermal energy into the cylinder, piston, etc. Therefore, it is not efficient to have all combustion take place when the piston is at top dead center. If all of the combustion is caused to occur near the top dead center, the combustion temperature increases sharply, and thus the amount of NOx produced increases.

Therefore, when the piston is lowered from the top dead center and the volume of the combustion chamber is increased, more combustion is generated (the second heat release rate (ROHR) is increased as compared with the first heat release rate (ROHR)), whereby a part of energy lost as thermal energy can be used as kinetic energy. By causing a large amount of combustion to occur after reaching the top dead center, the combustion temperature can also be suppressed, and thus the amount of NOx generated can also be suppressed.

Thus, according to the combustion of the second embodiment, an ideal combustion state of the engine can be obtained.

As described above, in the present embodiment, the following control is performed: the amount of the hydrogen cluster γ injected from the fuel injection valve a30 is made smaller than the amount of the hydrogen cluster λ injected from the fuel injection valve B31.

In this way, the waveform of the heat release rate (ROHR) generated by combustion is smaller in the first half of combustion and becomes larger in the second half of combustion.

Therefore, in the initial combustion stage in which the piston is located near the top dead center and the combustion chamber is small, the heat loss is suppressed by reducing the heat quantity, and the combustion temperature is also suppressed, whereby the generation of NOx is reduced, and in the later combustion stage in which the piston is located away from the top dead center and the combustion chamber is large, the effect of heat energy is obtained to the maximum extent by increasing the heat quantity, and the combustion temperature is also less elevated, and therefore NOx is also difficult to generate.

Therefore, a more desirable combustion state of the engine can be obtained.

(other embodiments)

Next, other embodiments will be described.

First, the ignition member is a general spark plug used in the first embodiment and the like, but may be a glow plug, a thermal ball, or the like as long as it is an ignition member that promotes gas combustion.

In the above embodiment, two ignition members are provided corresponding to the fuel injection valve, but one ignition member may be provided. Further, in the case where two ignition members are provided, for example, control may be performed as follows: the ignition means is switched to operate at the timing of engine start or at regular intervals.

The combustion gas is not limited to hydrogen, and may be a combustible gas such as methane, propane, or isobutane.

Industrial applicability

As described above, the present invention is useful in a gas engine that burns a gas having good combustibility such as hydrogen.

Claims

1. A gas engine for combusting a gas having excellent combustibility such as hydrogen, the gas engine comprising:

the gas engine is provided with a cylinder which is cylindrical and has a combustion chamber inside,

at positions separated from each other in the cylinder, a plurality of fuel injection valves that inject the gas are provided,

the gas engine includes an ignition member that burns at least one of a plurality of gas clusters injected from the plurality of fuel injection valves earlier than the other gas clusters.

2. The gas engine of claim 1, wherein:

the gas engine is provided with a swirling flow generating means for generating a swirling flow of air sucked into the cylinder,

the gas agglomerate injected by the fuel injection valve is swirled by the swirling flow of the air.

3. The gas engine according to claim 1 or 2, characterized in that:

the fuel injection valve is composed of a first fuel injection valve injecting a gas aggregate of pre-combustion and a second fuel injection valve injecting a gas aggregate of post-combustion,

the gas engine includes a control means that causes the amount of gas agglomerate injected from the first fuel injection valve to be smaller than the amount of gas agglomerate injected from the second fuel injection valve.