Prechamber type gas engine

Abstract

This prechamber type gas engine, which is configured to be capable of burning hydrocarbon gas and hydrogen gas as fuel gas, comprises: a main combustion chamber forming portion that forms a main combustion chamber; a pre-combustion chamber forming portion that forms a pre-combustion chamber communicating with the main combustion chamber via at least one injection hole; at least one main spark plug configured to ignite the fuel gas in the main combustion chamber; at least one auxiliary spark plug configured to ignite the fuel gas in the pre-combustion chamber; and an ignition control device configured to control ignition of each of the main spark plug and the auxiliary spark plug on the basis of the hydrogen gas co-firing ratio.

Description

Pre-chamber gas engine

[0001] This disclosure relates to a pre-chamber gas engine. This application claims priority under Japanese Patent Application No. 2025-049495, filed with the Japan Patent Office on March 25, 2025, the contents of which are incorporated herein by reference.

[0002] Conventionally, a pre-chamber gas engine is known that includes a main combustion chamber defined between the piston and the cylinder head, and a sub-combustion chamber connected to the main combustion chamber via a nozzle (for example, Patent Document 1). In a pre-chamber gas engine, the fuel gas in the sub-combustion chamber is ignited by igniting a spark plug located in the sub-combustion chamber. The combustion flame generated by the ignition is ejected from the nozzle, burning the air-fuel mixture in the main combustion chamber. In a pre-chamber gas engine, hydrocarbon gases such as natural gas are sometimes used as the fuel gas supplied to the sub-combustion chamber.

[0003] Japanese Patent Publication No. 2024-075018

[0004] By the way, CO during hydrocarbon gas combustion ２ From the perspective of reducing emissions, it is conceivable to burn a fuel gas containing hydrocarbon gas and hydrogen gas. However, Patent Document 1 does not disclose any knowledge regarding the co-combustion of a fuel gas containing hydrocarbon gas and hydrogen gas in a pre-chamber gas engine.

[0005] The inventors have found that in a pre-chamber gas engine, when a combustion flame ejected from a pre-combustion chamber burns a fuel gas containing hydrocarbon gas and hydrogen gas in the main combustion chamber, a high hydrogen co-combustion ratio results in a steep combustion of the fuel gas in the main combustion chamber, leading to a decrease in thermal efficiency and NO production. ｘ We have gained insights that this could lead to an increase in emissions.

[0006] In view of the above circumstances, at least some embodiments of the present invention address the reduction in thermal efficiency and NO when hydrocarbon gas and hydrogen gas are co-fired as fuel gas. ｘ The objective is to provide a pre-chamber type gas engine that can suppress the increase in emissions.

[0007] A pre-chamber gas engine according to at least some embodiments of the present invention is configured to combust hydrocarbon gas and hydrogen gas as fuel gas and comprises: a main combustion chamber forming section that forms a main combustion chamber; a pre-combustion chamber forming section that forms a pre-combustion chamber that communicates with the main combustion chamber via at least one injection hole; at least one main spark plug configured to ignite the fuel gas in the main combustion chamber; at least one sub-spark plug configured to ignite the fuel gas in the pre-combustion chamber; and an ignition control device configured to control the ignition of the main spark plug and the sub-spark plug based on the combustion ratio of hydrogen gas.

[0008] In at least some embodiments of the present invention, when hydrocarbon gas and hydrogen gas are co-fired as fuel gas, a decrease in thermal efficiency and NO are observed. ｘ A pre-chamber gas engine is provided that can suppress the increase in emissions.

[0009] This is a schematic diagram showing the configuration of a pre-chamber gas engine according to one embodiment. This is a schematic diagram showing the configuration of a pre-chamber gas engine according to another embodiment. This is a diagram showing the ignition timing of the main spark plug and auxiliary spark plug by the ignition control device according to one embodiment. This is a diagram showing the ignition timing of the main spark plug and auxiliary spark plug by the ignition control device according to another embodiment. This is a flowchart showing the flow from intake to exhaust of a pre-chamber gas engine according to one embodiment. This is a schematic diagram showing the arrangement of the ignition part of the main spark plug in the main combustion chamber another embodiment.

[0010] Hereinafter, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0011] Figure 1 is a schematic diagram showing the configuration of a pre-chamber gas engine according to one embodiment. Figure 2 is a schematic diagram showing the configuration of a pre-chamber gas engine according to another embodiment. Hereinafter, a pre-chamber gas engine may be abbreviated as "gas engine".

[0012] Several embodiments of the sub-chamber gas engine 1 (1A, 1B) are gas engines configured to combust hydrocarbon gas and hydrogen gas as fuel gas. In the combustion of fuel gas in the gas engine 1 (1A, 1B), the hydrogen gas co-combustion ratio R takes a value from 0% to 100%. That is, when R = 0%, the gas engine 1 (1A, 1B) is in a state of pure hydrocarbon gas combustion, when 0% < R < 100%, it is in a state of mixed combustion of hydrocarbon gas and hydrogen gas, and when R = 100%, it is in a state of pure hydrogen gas combustion. Hydrocarbon gas is a gas whose main components are methane gas, ethane gas, propane gas, etc. Natural gas is an example of hydrocarbon gas.

[0013] In some embodiments, the gas engine 1 (1A, 1B), as shown in Figures 1 and 2, includes a main combustion chamber forming section 10, a sub-combustion chamber forming section 30, at least one main spark plug 40 (40A, 40B), at least one sub-spark plug 50, and an ignition control device 60.

[0014] The main combustion chamber forming section 10 is a component that forms the main combustion chamber MC. The main combustion chamber MC is a combustion chamber for burning the first mixture A1. The first mixture A1 is a gas containing an oxidizing gas and a hydrocarbon gas or hydrogen gas. In one embodiment, the oxidizing gas is air. In this case, the ratio of air to fuel gas in the first mixture A1 is set so that the proportion of air is higher than that of the stoichiometric air-fuel ratio. In other words, the first mixture is a lean mixture.

[0015] As shown in Figure 1, the main combustion chamber forming section 10 communicates with the main combustion chamber MC and forms an intake passage 12 for guiding the first air-fuel mixture A1 into the main combustion chamber MC. The gas engine 1 (1A, 1B) further includes an intake valve 70 that is positioned to open and close the intake passage 12 relative to the main combustion chamber MC. Similarly, the main combustion chamber forming section 10 communicates with the main combustion chamber MC and forms an exhaust passage 14 for guiding exhaust gas A3 generated by combustion in the main combustion chamber MC to the outside of the main combustion chamber MC. The gas engine 1 (1A, 1B) further includes an exhaust valve 72 that is positioned to open and close the exhaust passage 14 relative to the main combustion chamber MC.

[0016] In the embodiments shown in Figures 1 and 2, the main combustion chamber forming section 10 includes a cylinder liner 16, a piston 18 reciprocally arranged within the cylinder liner 16, and a cylinder head 20 that forms the main combustion chamber MC between the cylinder liner 16 and the piston 18. In other words, the main combustion chamber MC is formed by the cylinder liner 16, the piston 18, and the cylinder head 20. In the embodiments illustrated in Figures 1 and 2, the main combustion chamber MC is defined by the crown surface 18a of the piston 18 and the wall surface 20a of the cylinder head 20. In other embodiments not shown, the main combustion chamber MC may be defined by the wall surface 16a of the cylinder liner 16, the crown surface 18a of the piston 18, and the wall surface 20a of the cylinder head 20.

[0017] The sub-combustion chamber forming section 30 is a member that forms the sub-combustion chamber PC. The sub-combustion chamber PC communicates with the main combustion chamber MC through at least one injection hole 32 formed in the sub-combustion chamber forming section 30. The number of injection holes 32 is not particularly limited; one injection hole 32 may be formed in the sub-combustion chamber forming section 30, or multiple injection holes 32 may be formed in the sub-combustion chamber forming section 30. The sub-combustion chamber PC is a combustion chamber for burning the second mixture A2. The second mixture A2 is a gas containing an oxidizing gas and a hydrocarbon gas. In one embodiment, the oxidizing gas is air. In this case, the ratio of air to hydrocarbon gas in the second mixture A2 is set to be close to the stoichiometric air-fuel ratio. In other embodiments not shown, the second mixture A2 in the sub-combustion chamber PC may be a mixture obtained by mixing the first mixture A1 that flows in through the injection hole 32 formed in the sub-combustion chamber forming section 30 with the hydrocarbon gas. The second mixture A2 may be a mixture containing hydrogen gas or a mixture that does not contain hydrogen gas.

[0018] As shown in Figures 1 and 2, the sub-combustion chamber forming section 30 communicates with the sub-combustion chamber PC and forms an intake passage 34 for guiding the second air-fuel mixture A2 into the sub-combustion chamber PC. The gas engine 1 (1A, 1B) further includes an intake valve 74 that is positioned to open and close the intake passage 34 relative to the sub-combustion chamber PC. In other embodiments not shown, the intake passage 34 may also be a flow path for guiding fuel gas into the sub-combustion chamber PC.

[0019] In the embodiments shown in Figures 1 and 2, the sub-combustion chamber forming section 30 is positioned such that the central axis O1 of the main combustion chamber MC coincides with the central axis O2 of the sub-combustion chamber PC. In other embodiments not shown, the sub-combustion chamber forming section 30 may be positioned such that the central axis O1 of the main combustion chamber MC and the central axis O2 of the sub-combustion chamber PC do not coincide.

[0020] At least one main spark plug 40 (40A, 40B) is configured to ignite the fuel gas in the main combustion chamber MC. In other words, the main spark plug 40 (40A, 40B) is configured to ignite the hydrocarbon gas or hydrogen gas contained in the first mixture A1 in the main combustion chamber MC.

[0021] In the embodiments shown in Figures 1 and 2, the main spark plug 40 (40A, 40B) includes a main body portion 42 (42A, 42B) and an ignition unit 44 (44A, 44B) attached to the main body portion 42 (42A, 42B). The main body portion 42 (42A, 42B) is installed so that the ignition unit 44 (44A, 44B) is located within the main combustion chamber MC. The ignition unit 44 (44A, 44B) is not particularly limited and may be a spark plug that generates a spark discharge, or other known ignition technology may be used. As will be described in detail later, in the embodiment shown in Figure 1, the main spark plug 40 includes a central main spark plug 40A. Similarly, in the embodiment shown in Figure 2, the main spark plug 40 includes an outer-circumferential main spark plug 40B.

[0022] At least one auxiliary spark plug 50 is configured to ignite the fuel gas in the auxiliary combustion chamber PC. In other words, the auxiliary spark plug 50 is configured to ignite the hydrocarbon gas contained in the second mixture A2 in the auxiliary combustion chamber PC. As will be described in detail later, the auxiliary spark plug 50 may also ignite the first mixture A1 that flows into the auxiliary combustion chamber PC from the injection hole 32 formed in the auxiliary combustion chamber forming section 30.

[0023] In the embodiments shown in Figures 1 and 2, the auxiliary spark plug 50 includes a main body 52 and an ignition unit 54 attached to the main body 52. ​​The main body 52 is installed such that the ignition unit 54 is located inside the auxiliary combustion chamber PC. The ignition unit 54 is not particularly limited and may be a spark plug that generates a spark discharge, or other known ignition technologies may be used.

[0024] The ignition control device 60 is configured to control the ignition of the main spark plugs 40 (40A, 40B) and the auxiliary spark plugs 50 based on the hydrogen gas co-firing ratio R. Specifically, the ignition control device 60 is configured to control the ignition of the main spark plugs 40 (40A, 40B) or the auxiliary spark plugs 50, and to control the ignition timing of the main spark plugs 40 (40A, 40B) and the auxiliary spark plugs 50. The hydrogen gas co-firing ratio R is the ratio of the heat energy of hydrogen gas to the heat energy of the total fuel gas. The hydrogen gas co-firing ratio R may be calculated, for example, by measuring or estimating the flow rate of hydrocarbon gas supplied from a hydrocarbon gas supply source and the flow rate of hydrogen gas supplied from a hydrogen gas supply source.

[0025] As shown in Figures 1 and 2, the ignition control device 60 includes a processor 62 and a memory 64 for controlling the ignition of the main spark plugs 40 (40A, 40B) and the auxiliary spark plugs 50, respectively. The processor 62 is configured to refer to the ignition timing of the main spark plugs 40 (40A, 40B) or the auxiliary spark plugs 50 recorded in the memory 64. The processor 62 is configured to transmit a signal to the main spark plugs 40 (40A, 40B) or the auxiliary spark plugs 50 to perform ignition according to the hydrogen gas mixture ratio R. The processor 62 is not particularly limited and is, for example, a CPU (Central Processing Unit). The memory 64 is not particularly limited and is, for example, a RAM (Random Access Memory).

[0026] In the embodiments shown in Figures 1 and 2, the ignition control device 60 is connected to the main spark plugs 40 (40A, 40B) via a first ignition line 66 and to the auxiliary spark plugs 50 via a second ignition line 68. The first ignition line 66 is a line for transmitting signals generated by the ignition control device 60 to the main spark plugs 40 (40A, 40B). Similarly, the second ignition line 68 is a line for transmitting signals generated by the ignition control device 60 to the auxiliary spark plugs 50.

[0027] According to the above configuration, the ignition of the main spark plugs 40 (40A, 40B) and the auxiliary spark plugs 50 is controlled by the ignition control device 60 based on the hydrogen gas combustion ratio R. By controlling the presence or absence and timing of ignition of the main spark plugs 40 (40A, 40B) and the auxiliary spark plugs 50 based on the hydrogen gas combustion ratio R, the reduction in thermal efficiency and NO emissions during fuel gas combustion, as described later, can be reduced. ｘ Ignition control that suppresses increases in emissions is also possible.

[0028] Here, with further reference to Figures 3 and 4, the ignition control of the main spark plugs 40 (40A, 40B) and auxiliary spark plugs 50 by the ignition control device 60 will be described. Figure 3 is a diagram showing the ignition timing of the main spark plugs and auxiliary spark plugs by an ignition control device according to one embodiment. Figure 4 is a diagram showing the ignition timing of the main spark plugs and auxiliary spark plugs by an ignition control device according to another embodiment.

[0029] Figures 3 and 4 are graphs showing an example of the relationship between the ignition timing θ (θ1, θ2) of the main spark plug 40 (40A, 40B) or auxiliary spark plug 50 and the hydrogen gas co-combustion ratio R. The ignition timing θ is advanced as it moves towards the top of the graph and retarded as it moves towards the bottom of the graph. A solid line indicates that ignition occurs, and a dashed line indicates that ignition may or may not occur.

[0030] In some embodiments, as shown in Figures 3 and 4, the ignition control device 60 is configured to ignite the auxiliary spark plug 50 before the main spark plug 40 (40A, 40B) or to ignite only the auxiliary spark plug 50 when the hydrogen gas co-combustion ratio R is less than a first threshold R_th1. In other words, when the ignition control device 60 ignites both the main spark plug 40 (40A, 40B) and the auxiliary spark plug 50, it controls the ignition so that the ignition timing θ2 of the auxiliary spark plug 50 is advanced more than the ignition timing θ1 of the main spark plug 40 (40A, 40B). Furthermore, the ignition control device 60 is configured to ignite the main spark plug 40 (40A, 40B) before the auxiliary spark plug 50 or to ignite only the main spark plug 40 (40A, 40B) when the hydrogen gas co-combustion ratio R is equal to or greater than the first threshold R_th1. In other words, when the ignition control device 60 ignites the main spark plugs 40 (40A, 40B) and the auxiliary spark plugs 50, it controls the ignition so that the ignition timing θ1 of the main spark plugs 40 (40A, 40B) is advanced more than the ignition timing θ2 of the auxiliary spark plugs 50.

[0031] The first threshold R_th1 is set as the hydrogen gas co-combustion ratio R at which the combustion of the fuel gas begins to become steeper as the hydrogen gas co-combustion ratio R increases. Furthermore, according to the inventors' findings, when the combustion of the fuel gas becomes steeper as the hydrogen gas co-combustion ratio R increases, the thermal efficiency decreases and NO emissions decrease. ｘ The increase in emissions becomes significant. Therefore, the first threshold R_th1 is such that when the hydrogen gas co-firing ratio R is increased, the thermal efficiency decreases or NO emissions increase. ｘ This may be set as the hydrogen gas co-firing ratio R at which emissions begin to increase significantly. The first threshold R_th1 is recorded in the memory 64 of the ignition control device 60 described above and is referenced in the processing of the processor 62.

[0032] According to the above configuration, when the hydrogen gas co-combustion ratio R is equal to or greater than the first threshold R_th1, the ignition control device 60 ignites the fuel gas in the main combustion chamber MC by igniting the main spark plugs 40 (40A, 40B). Therefore, compared to the case where the fuel gas in the main combustion chamber MC is burned by the flame caused by the ignition of the auxiliary spark plug 50, the combustion of the combustion gas can be slowed down. This reduces the decrease in thermal efficiency and NOx ｘ This helps to suppress increases in emissions. Furthermore, the ignition control device 60 burns the fuel gas in the main combustion chamber MC with the flame caused by the ignition of the auxiliary spark plug 50 when the hydrogen gas co-combustion ratio R is less than the first threshold R_th1. Therefore, compared to the case where the fuel gas in the main combustion chamber MC is burned by the ignition of the main spark plug 40 (40A, 40B), the decrease in thermal efficiency during fuel gas combustion can be suppressed. Moreover, when the ignition control device 60 ignites the main spark plug 40 (40A, 40B) after the ignition of the auxiliary spark plug 50, the unburned fuel gas in the main combustion chamber MC can be effectively burned.

[0033] In one embodiment, the gas engine 1 is configured not to supply fuel gas to the sub-combustion chamber PC when the hydrogen gas co-combustion ratio R is equal to or greater than a first threshold R_th1. In this case, as shown in Figures 3 and 4, the ignition control device 60 may be configured to ignite only the main spark plugs 40 (40A, 40B), or it may be configured to ignite the sub-spark plugs 50 after the main spark plugs 40 (40A, 40B). In other words, when the hydrogen gas co-combustion ratio R is equal to or greater than the first threshold R_th1, the ignition control device 60 may perform ignition control so that the ignition timing θ2 of the sub-spark plugs 50 is retarded compared to the ignition timing θ1 of the main spark plugs 40 (40A, 40B).

[0034] In the embodiments illustrated in Figures 3 and 4, when the auxiliary spark plug 50 is ignited after the main spark plugs 40 (40A, 40B), the ignition timing θ2 of the auxiliary spark plug 50 may be controlled to be constant regardless of the hydrogen gas mixture ratio R when the hydrogen gas mixture ratio R is equal to or greater than a first threshold R_th1. In other embodiments not shown, the ignition timing θ2 of the auxiliary spark plug 50 may be controlled to advance or retard as the hydrogen gas mixture ratio R increases. In this case, the ignition timing θ2 of the auxiliary spark plug 50 may be controlled to advance or retard at a constant rate as the hydrogen gas mixture ratio R increases, or the degree of advance or retardation may be controlled to change.

[0035] In the embodiments shown in Figures 3 and 4, the ignition control device 60 is configured to retard the ignition timing θ1 of the main spark plugs 40 (40A, 40B) as the hydrogen gas co-combustion ratio R increases when the co-combustion ratio R is equal to or greater than a first threshold R_th1. In other words, the ignition timing θ1 of the main spark plugs 40 (40A, 40B) is controlled to be most advanced when the hydrogen gas co-combustion ratio R is at the first threshold R_th1, and most retarded when the hydrogen gas co-combustion ratio R is 100%.

[0036] In the embodiments illustrated in Figures 3 and 4, the ignition timing θ1 of the main spark plugs 40 (40A, 40B) is controlled to retard by a constant rate as the hydrogen gas co-combustion ratio R increases. In other embodiments not shown, the ignition timing θ1 of the main spark plugs 40 (40A, 40B) may be controlled so that the degree of retardation changes as the hydrogen gas co-combustion ratio R increases.

[0037] In the embodiment shown in FIG. 4, the ignition control device 60 is configured to ignite the auxiliary spark plug 50 before the main spark plugs 40 (40A, 40B) when the mixed combustion rate R of hydrogen gas is less than a first threshold R_th1 and greater than or equal to a second threshold R_th2. That is, the ignition control device 60 performs ignition control such that the ignition timing θ2 of the auxiliary spark plug 50 is advanced relative to the ignition timing θ1 of the main spark plugs 40 (40A, 40B) when the mixed combustion rate R of hydrogen gas is less than the first threshold R_th1 and greater than or equal to the second threshold R_th2. The second threshold R_th2 is set as a mixed combustion rate R of hydrogen gas that is smaller than the first threshold R_th1. Further, the second threshold R_th2 is set as the mixed combustion rate R of hydrogen gas at which knocking starts to occur in the main combustion chamber MC due to an increase in the mixed combustion rate R of hydrogen gas. The second threshold R_th2 is stored in the memory 64 of the aforementioned ignition control device 60 and referred to in processing by the processor 62.

[0038] In the embodiments shown in FIGS. 3 and 4, the ignition control device 60 is configured to discontinuously advance the ignition timing θ1 of the main spark plugs 40 (40A, 40B) at the first threshold R_th1 when increasing the mixed combustion rate R of hydrogen gas from below the first threshold R_th1 to equal to or above the first threshold R_th1. That is, the ignition control device 60 is configured to execute control such that the ignition timing θ1 of the main spark plugs 40 (40A, 40B) at the first threshold R_th1 is advanced relative to the ignition timing θ1 of the main spark plugs 40 (40A, 40B) when the mixed combustion rate R is less than the first threshold R_th1.

[0039] In the embodiment shown in FIG. 4, the ignition control device 60 is configured to ignite only the auxiliary spark plug 50 when the mixed combustion rate R of hydrogen gas is less than the second threshold R_th2.

[0040] In the embodiments shown in FIGS. 3 and 4, the ignition control device 60 is configured to retard the ignition timing θ2 of the auxiliary spark plug 50 as the mixed combustion rate R of hydrogen gas increases, when the mixed combustion rate R of hydrogen gas is less than the first threshold R_th1. That is, the ignition timing θ2 of the auxiliary spark plug 50 is controlled to be most advanced when the mixed combustion rate R of hydrogen gas is 0%.

[0041] In the embodiment illustrated in FIGS. 3 and 4, the ignition timing θ2 of the auxiliary spark plug 50 is controlled such that the degree of ignition retardation increases as the mixing ratio R of hydrogen gas increases. In another embodiment not shown, the ignition timing θ2 of the auxiliary spark plug 50 may be controlled to be retarded at a constant rate as the mixing ratio R of hydrogen gas increases.

[0042] Further, in the embodiment illustrated in FIGS. 3 and 4, the ignition timing θ2 of the auxiliary spark plug 50 is controlled such that the difference between the ignition timing θ2 and the ignition timing θ1 of the main spark plugs 40 (40A, 40B) decreases as the mixing ratio R of hydrogen gas increases. That is, the difference between the ignition timing θ2 of the auxiliary spark plug 50 and the ignition timing θ1 of the main spark plugs 40 (40A, 40B) is controlled to be maximum when the mixing ratio R of hydrogen gas is 0%, and minimum when the mixing ratio R of hydrogen gas approximates the first threshold value R_th1.

[0043] Here, a specific example of ignition control of the main spark plugs 40 (40A, 40B) or the auxiliary spark plug 50 by the ignition control device 60 will be described with reference to FIG. 5. FIG. 5 is a flowchart showing a flow from intake to exhaust of a pre-chamber gas engine according to one embodiment.

[0044] First, the case where the mixing ratio R of hydrogen gas is less than the first threshold value R_th1 (Yes in step S10) will be described. When the mixing ratio R is less than the first threshold value R_th1, a first air-fuel mixture A1 is supplied to the main combustion chamber MC of the gas engine 1 (step S20), and a second air-fuel mixture A2 is supplied to the pre-combustion chamber PC of the gas engine 1 (step S22). The order of step S20 and step S22 is not particularly limited. Step S20 may be performed after step S22 is performed, or step S20 and step S22 may be performed substantially simultaneously.

[0045] After steps S20 and S22, the ignition control device 60 ignites the auxiliary spark plug 50 (step S24). If the hydrogen gas combustion ratio R is less than the second threshold R_th2 (Yes in step S26), the first mixture A1 after combustion is exhausted from the main combustion chamber MC as exhaust A3 (step S40). On the other hand, if the hydrogen gas combustion ratio R is greater than or equal to the second threshold R_th2 (No in step S26), after igniting the auxiliary spark plug 50, the ignition control device 60 ignites the main spark plugs 40 (40A, 40B) (step S28). After step S28, the first mixture A1 after combustion is discharged from the main combustion chamber MC as exhaust A3 (step S40).

[0046] Returning to step S10, the case where the hydrogen gas combustion ratio R is greater than or equal to the first threshold R_th1 (No. in step S10) will be explained. When the hydrogen gas combustion ratio R is greater than or equal to the first threshold R_th1, the first mixture A1 is supplied to the main combustion chamber MC of the gas engine 1 (step S30). Note that the second mixture A2 is not supplied to the sub-combustion chamber PC of the gas engine 1. After step S30, the ignition control device 60 ignites the main spark plugs 40 (40A, 40B) (step S32).

[0047] After step S32, if there is residual gas in the sub-combustion chamber PC as unburned fuel gas (Yes in step S34), the ignition control device 60 ignites the auxiliary spark plug 50 (step S36). The residual gas burned by the ignition of the auxiliary spark plug 50 and the fuel gas burned by the ignition of the main spark plugs 40 (40A, 40B) are discharged from the main combustion chamber MC as exhaust A3 (step S40). On the other hand, if there is no residual gas in the sub-combustion chamber PC as unburned fuel gas (Yes in step S34), the auxiliary spark plug 50 is not ignited, and the fuel gas burned by the ignition of the main spark plugs 40 (40A, 40B) is discharged from the main combustion chamber MC as exhaust A3 (step S40).

[0048] From here, with reference to Figures 1, 2, 6, and 7, the specific arrangement of the main spark plugs 40 (40A, 40B) in the pre-chamber type gas engine 1 (1A, 1B) described above will be explained. Figure 6 is a schematic diagram showing the arrangement of the ignition part of the main spark plug in the main combustion chamber according to one embodiment. Figure 7 is a schematic diagram showing the arrangement of the ignition part of the main spark plug in the main combustion chamber according to another embodiment.

[0049] The pre-chamber type gas engine 1 (1A, 1B), as described above with reference to Figures 1 and 2, includes a cylinder liner 16, a piston 18, and a cylinder head 20 as the main combustion chamber forming part 10. As shown in Figures 6 and 7, the central axis O1 of the cylinder liner 16 is defined as the 0% position X_0%, and the wall surface 16a of the cylinder liner 16 is defined as the 100% position X_100%.

[0050] In some embodiments, as shown in Figures 1 and 6, at least one main spark plug 40 includes a central main spark plug 40A having an ignition section 44A positioned between the 0% position X_0% and the 20% position X_20%.

[0051] In the embodiments shown in Figures 1 and 6, the main spark plug 40 includes one central main spark plug 40A. In other embodiments not shown, the main spark plug 40 may include multiple central main spark plugs 40A.

[0052] In some embodiments, as shown in Figures 2 and 7, at least one main spark plug 40 includes an outer-circumferential main spark plug 40B having an ignition portion 44B positioned between the 60% position X_60% and the 100% position X_100%.

[0053] In the embodiments shown in Figures 2 and 7, the outer-circumferential main spark plugs 40B are installed at different positions in the circumferential direction φ1 of the main combustion chamber MC.

[0054] In the embodiment illustrated in Figure 7, the gas engine 1B includes four outer-circumferential main spark plugs 40B. In other embodiments not shown, the number of outer-circumferential main spark plugs 40B is not particularly limited. Note that each of the multiple outer-circumferential main spark plugs 40B may be at the same distance from the central axis O1 of the cylinder liner 16, or they may be at different distances.

[0055] In the embodiment shown in Figure 7, at least one injection hole 32 includes a plurality of injection holes 32 that are each formed at different positions in the circumferential direction φ2 of the sub-combustion chamber forming portion 30. Furthermore, each of the ignition portions 44B of the plurality of outer peripheral main spark plugs 40B is installed at a circumferential position between adjacent injection holes 32 in the circumferential direction φ2 of the sub-combustion chamber forming portion 30.

[0056] In the embodiment illustrated in Figure 7, the ignition portion 44B of one outer-circumferential main spark plug 40B is installed between adjacent injection holes 32 in the circumferential direction φ2 of the sub-combustion chamber forming portion 30. In other embodiments not shown, multiple ignition portions 44B of outer-circumferential main spark plugs 40B may be installed between adjacent injection holes 32 in the circumferential direction φ2 of the sub-combustion chamber forming portion 30.

[0057] The characteristic configurations of the pre-chamber type gas engine 1 (1A, 1B) according to some of the embodiments described above can be summarized as follows.

[0058] [1] A pre-chamber gas engine (1; 1A, 1B) according to some embodiments is a pre-chamber gas engine (1; 1A, 1B) configured to be capable of combusting hydrocarbon gas and hydrogen gas as fuel gas, comprising: a main combustion chamber forming portion (10) that forms a main combustion chamber (MC); a pre-combustion chamber forming portion (30) that forms a pre-combustion chamber (PC) communicating with the main combustion chamber (10) via at least one injection hole (32); at least one main spark plug (40; 40A, 40B) configured to ignite fuel gas in the main combustion chamber (MC); at least one pre-chamber spark plug (50) configured to ignite fuel gas in the pre-combustion chamber (PC); and an ignition control device (60) configured to control ignition of each of the main spark plug (40; 40A, 40B) and the pre-chamber spark plug (50) based on a hydrogen co-firing rate (R).

[0059] According to the configuration of the above [1], the pre-chamber gas engine (1; 1A, 1B) includes the main spark plug (40; 40A, 40B) configured to ignite fuel gas in the main combustion chamber (MC), and the pre-chamber spark plug (50) configured to ignite fuel gas in the pre-combustion chamber (PC). Ignition of each of the main spark plug (40; 40A, 40B) and the pre-chamber spark plug (50) is controlled by the ignition control device (60) based on the hydrogen co-firing rate (R). By controlling the presence or absence and timing of ignition of each of the main spark plug (40; 40A, 40B) and the pre-chamber spark plug (50) based on the hydrogen co-firing rate (R), as described later, a decrease in thermal efficiency and NO ｘ It is also possible to perform ignition control that suppresses an increase in exhaust emissions.

[0060] For example, when the hydrogen co-firing rate (R) is high, combusting the fuel gas in the main combustion chamber (MC) by ignition from the main spark plug (40; 40A, 40B) makes combustion of the combustion gas in the main combustion chamber (MC) slower compared to a case where the fuel gas in the main combustion chamber (MC) is combusted by a flame ejected from the injection hole (32) formed in the pre-combustion chamber forming portion (30). This reduces a decrease in thermal efficiency and NO ｘThis can suppress the increase in emissions. On the other hand, when the hydrogen gas co-combustion ratio (R) is low, if the fuel gas in the main combustion chamber (MC) is burned by ignition of the main spark plug (40; 40A, 40B), the combustion of the combustion gas in the main combustion chamber (MC) becomes slow, and the thermal efficiency during the combustion of the fuel gas may decrease. Therefore, for example, when the hydrogen gas co-combustion ratio (R) is low, the decrease in thermal efficiency during the combustion of the fuel gas can be suppressed by burning the combustion gas in the main combustion chamber (MC) with a flame caused by ignition of the auxiliary spark plug (50).

[0061] [2] In some embodiments, in the configuration of [1] above, the ignition control device (60) is configured to ignite the auxiliary spark plug (50) before the main spark plug (40; 40A, 40B) or ignite only the auxiliary spark plug (50) when the hydrogen gas co-firing ratio (R) is less than a first threshold (R_th1), and to ignite the main spark plug (40; 40A, 40B) before the auxiliary spark plug (50) or ignite only the main spark plug (40; 40A, 40B) when the hydrogen gas co-firing ratio is equal to or greater than the first threshold (R_th1).

[0062] According to the configuration described in [2] above, the ignition control device (60) burns the fuel gas in the main combustion chamber (MC) by igniting the main spark plugs (40; 40A, 40B) when the hydrogen gas co-combustion ratio (R) is equal to or greater than the first threshold (R_th1). Therefore, compared to the case where the fuel gas in the main combustion chamber (MC) is burned by the flame caused by the ignition of the auxiliary spark plug (50), the combustion of the combustion gas can be made slower. This reduces the decrease in thermal efficiency and NO ｘ This helps to suppress increases in emissions. Furthermore, the ignition control device (60) burns the fuel gas in the main combustion chamber (MC) with a flame caused by the ignition of the auxiliary spark plug (50) when the hydrogen gas co-combustion ratio (R) is less than the first threshold (R_th1). Therefore, compared to the case where the fuel gas in the main combustion chamber (MC) is burned by the ignition of the main spark plug (40; 40A, 40B), the decrease in thermal efficiency during fuel gas combustion can be suppressed.

[0063] [3] In some embodiments, in the configuration of [2] above, the pre-chamber gas engine (1; 1A, 1B) is configured not to supply fuel gas into the pre-combustion chamber (PC) when the hydrogen gas co-combustion ratio (R) is equal to or greater than a first threshold (R_th1), and the ignition control device (60) is configured to ignite the pre-ignition spark plug (50) after the main spark plug (40; 40A, 40B) when the hydrogen gas co-combustion ratio (R) is equal to or greater than a first threshold (R_th1).

[0064] As described in [2] above, when the hydrogen gas co-combustion ratio (R) is equal to or greater than the first threshold (R_th1), the fuel gas in the main combustion chamber (MC) is combusted by ignition of the main spark plugs (40; 40A, 40B). At this time, the fuel gas in the main combustion chamber (MC) flows from the main combustion chamber (MC) to the sub-combustion chamber (PC) through the injection holes (32) formed in the sub-combustion chamber forming section (30). If the fuel gas that flows into the sub-combustion chamber (PC) remains uncombusted, knocking may occur in the sub-combustion chamber (PC). According to the configuration in [3] above, the fuel gas that flows into the sub-combustion chamber (PC) can be combusted by ignition of the sub-main spark plug (50). Therefore, the possibility of knocking occurring in the sub-combustion chamber (PC) can be reduced.

[0065] [4] In some embodiments, in the configuration of [2] or [3] above, the ignition control device (60) is configured to ignite the auxiliary spark plug (50) before the main spark plug (40; 40A, 40B) when the hydrogen gas co-firing ratio (R) is less than a first threshold (R_th1) and is equal to or greater than a second threshold (R_th2) which is smaller than the first threshold (R_th1).

[0066] As described in [2] above, when the hydrogen gas co-combustion ratio (R) is less than the first threshold (R_th1), the fuel gas in the main combustion chamber (MC) is burned by the flame caused by the ignition of the auxiliary spark plug (50). However, depending on the hydrogen gas co-combustion ratio (R), unburned fuel gas may remain in the main combustion chamber (MC), and knocking may occur in the main combustion chamber (MC). According to the configuration in [4] above, the unburned gas in the main combustion chamber (MC) can be burned by the ignition of the main spark plug (40; 40A, 40B). Therefore, the possibility of knocking occurring in the main combustion chamber (MC) can be reduced.

[0067] [5] In some embodiments, in the configuration of [4] above, the ignition control device (60) is configured to discontinuously advance the ignition timing (θ1) of the main spark plugs (40; 40A, 40B) at the first threshold (R_th1) when increasing the hydrogen gas co-firing ratio (R) from less than the first threshold (R_th1) to the first threshold (R_th1) or more.

[0068] As described in [2] above, when the hydrogen gas co-combustion ratio (R) is above the first threshold (R_th1), the combustion of the fuel gas becomes steep. For this reason, it is preferable to advance the ignition timing (θ1) of the main spark plugs (40; 40A, 40B). In this respect, the configuration in [5] above allows for a more effective advancement of the timing of flame generation caused by the ignition of the main spark plugs (40; 40A, 40B) compared to the case where the ignition timing (θ1) of the main spark plugs (40; 40A, 40B) is continuously advanced before and after the first threshold (R_th1). Therefore, the reduction in thermal efficiency and NO during fuel gas combustion is reduced. ｘ This will allow for a more effective reduction in emissions.

[0069] [6] In some embodiments, in the configuration of [4] or [5] above, the ignition control device (60) is configured to ignite only the auxiliary spark plug (50) when the hydrogen gas co-firing ratio (R) is less than the second threshold (R_th2).

[0070] According to the configuration described in [6] above, when the hydrogen gas co-firing ratio (R) is less than the second threshold (R_th2), only the auxiliary spark plug (50) is ignited, thus simplifying the ignition control by the ignition control device (60).

[0071] [7] In some embodiments, in any of the configurations described in [2] to [6] above, the ignition control device (60) is configured to retard the ignition timing (θ1) of the main spark plugs (40; 40A, 40B) as the combustion ratio (R) of hydrogen gas increases when the combustion ratio (R) is equal to or greater than a first threshold (R_th1).

[0072] Since the combustion rate of hydrogen gas is faster than that of hydrocarbon gas, the combustion rate of the fuel gas increases as the hydrogen gas co-combustion ratio (R) increases. Therefore, when the hydrogen gas co-combustion ratio (R) increases, there is a risk that the timing of fuel gas combustion may advance excessively relative to the expansion timing of the main combustion chamber (MC). In this regard, the configuration of [7] above can suppress excessive advancement of the ignition timing (θ1) of the main spark plugs (40; 40A, 40B), thereby reducing the decrease in thermal efficiency and NO during fuel gas combustion. ｘ Emissions can be reduced more effectively.

[0073] [8] In some embodiments, in any of the configurations described in [2] to [7] above, the ignition control device (60) is configured to retard the ignition timing (θ2) of the auxiliary spark plug (50) as the combustion ratio (R) of hydrogen gas increases when the combustion ratio (R) is less than a first threshold (R_th1).

[0074] As described in [7] above, depending on the hydrogen gas co-combustion ratio (R), there is a risk that the timing of fuel gas combustion may be excessively advanced. In this regard, the configuration in [8] above can suppress the excessive advance of the ignition timing (θ2) of the auxiliary spark plug (50), thereby reducing the thermal efficiency during fuel gas combustion and NO ｘ Emissions can be reduced more effectively.

[0075] [9] In some embodiments, in any of the configurations of [1] to [8] above, the main combustion chamber forming section (10) includes a cylinder liner (16), a piston (18) reciprocally arranged within the cylinder liner (16), and a cylinder head (20) that forms a main combustion chamber (MC) between the cylinder liner (16) and the piston (18), wherein, when the central axis (O1) of the cylinder liner (16) is at the 0% position (X_0%) and the wall surface (16a) of the cylinder liner (16) is at the 100% position (X_100%), at least one main spark plug (40) includes a central main spark plug (40A) having an ignition section (44A) positioned between the 0% position (X_0%) and the 20% position (X_20%).

[0076] According to the configuration described in [9] above, by igniting the central main spark plug (40A) having an ignition unit (44A) positioned between the 0% position (X_0%) and the 20% position (X_20%), a hemispherical flame can be propagated from near the central axis (O1) of the cylinder liner (16). Therefore, the fuel gas in the main combustion chamber (MC) can be burned effectively.

[0077]

[10] In some embodiments, in any of the configurations of [1] to [9] above, the main combustion chamber forming section (10) includes a cylinder liner (16), a piston (18) reciprocally arranged within the cylinder liner (16), and a cylinder head (20) that forms a main combustion chamber (MC) between the cylinder liner (16) and the piston (18), wherein, when the central axis (O1) of the cylinder liner (16) is at the 0% position (X_0%) and the wall surface (16a) of the cylinder liner (16) is at the 100% position (X_100%), at least one main spark plug (40) includes an outer peripheral main spark plug (40B) having an ignition section (44B) positioned between the 60% position (X_60%) and the 100% position (X_100%).

[0078] According to the configuration described in

[10] above, by igniting the outer-circumferential main spark plug (40B) having an ignition section (44B) positioned between the 60% position (X_60%) and the 100% position (X_100%), unburned fuel gas remaining near the wall surface (16a) of the cylinder liner (16) can be effectively burned. Therefore, the occurrence of knocking in the main combustion chamber (MC) can be suppressed.

[0079]

[11] In some embodiments, in the configuration of

[10] above, the outer-circumferential main spark plugs (40B) are installed at different positions in the circumferential direction (φ1) of the main combustion chamber (MC).

[0080] According to the configuration described in

[11] above, the outer-circumferential main spark plugs (40B) are installed at different positions in the circumferential direction (φ1) of the main combustion chamber (MC), so that unburned fuel gas remaining near the wall surface (16a) of the cylinder liner (16) can be burned more effectively. Therefore, the occurrence of knocking can be suppressed more effectively.

[0081]

[12] In some embodiments, in the configuration of

[11] above, at least one nozzle (32) includes a plurality of nozzles (32) each formed at different positions in the circumferential direction (φ2) of the sub-combustion chamber forming portion (30), and each of the ignition portions (44B) of the plurality of outer peripheral main spark plugs (40B) is installed at a circumferential position between adjacent nozzles (32) in the circumferential direction (φ2) of the sub-combustion chamber forming portion (30) among the plurality of nozzles (32).

[0082] According to the configuration described in

[12] above, the flames ejected from the multiple nozzles (32) and the flames propagating from the ignition part (44B) of the outer-circumferential main spark plug (40B) are less likely to overlap within the main combustion chamber (MC). Since the flames can be effectively propagated within the main combustion chamber (MC), knocking can be suppressed more effectively.

[0083] Although several embodiments of the present invention have been described above, it goes without saying that modifications to the above embodiments are permitted as long as they do not deviate from the spirit of the present invention.

[0084] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances sufficient to achieve the same function. For example, expressions describing things being in an equal state such as "identical," "equal," and "homogeneous" shall not only describe states of being strictly equal, but also describe states where tolerances or differences exist to the extent that the same function is achieved. Furthermore, in this specification, expressions describing shapes such as quadrilaterals or cylindrical shapes shall not only describe geometrically precise quadrilaterals or cylindrical shapes, but also describe shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect is achieved. In addition, in this specification, expressions such as "equipment," "includes," or "possesses" a component are not exclusive expressions that exclude the existence of other components.

[0085] 1 (1A, 1B): Pre-chamber gas engine 10: Main combustion chamber forming section 16: Cylinder liner 16a: Wall surface 18: Piston 20: Cylinder head 30: Sub-combustion chamber forming section 32: Injection hole 40: Main spark plug 40A: Central main spark plug 40B: Outer circumference main spark plug 44 (44A, 44B): Ignition section 50: Sub-spark plug 54: Ignition section 60: Ignition control device MC: Main combustion chamber O1: Central axis PC: Sub-combustion chamber R: Co-combustion ratio R_th1: First threshold R_th2: Second threshold θ1, θ2: Ignition timing φ1, φ2: Circumferential direction

Claims

1. A pre-chamber gas engine configured to combust hydrocarbon gas and hydrogen gas as fuel gas, comprising: a main combustion chamber forming section that forms a main combustion chamber; a sub-combustion chamber forming section that forms a sub-combustion chamber that communicates with the main combustion chamber via at least one injection hole; at least one main spark plug configured to ignite the fuel gas in the main combustion chamber; at least one sub-spark plug configured to ignite the fuel gas in the sub-combustion chamber; and an ignition control device configured to control the ignition of the main spark plug and the sub-spark plug based on the combustion ratio of the hydrogen gas.

2. The sub-chamber type gas engine according to claim 1, wherein the ignition control device is configured to ignite the auxiliary spark plug before the main spark plug, or ignite only the auxiliary spark plug, when the combustion ratio of the hydrogen gas is less than a first threshold, and to ignite the main spark plug before the auxiliary spark plug, or ignite only the main spark plug, when the combustion ratio of the hydrogen gas is equal to or greater than the first threshold.

3. The sub-chamber type gas engine according to claim 2, wherein the fuel gas is not supplied to the sub-combustion chamber when the co-combustion ratio of the hydrogen gas is equal to or greater than a first threshold, and the ignition control device is configured to ignite the sub-spark plug later than the main spark plug when the co-combustion ratio of the hydrogen gas is equal to or greater than a first threshold.

4. The sub-chamber type gas engine according to claim 2 or 3, wherein the ignition control device is configured to ignite the sub-spark plug before the main spark plug when the co-combustion rate of the hydrogen gas is less than the first threshold and greater than or equal to a second threshold that is smaller than the first threshold.

5. The sub-chamber type gas engine according to claim 4, wherein the ignition control device is configured to discontinuously advance the ignition timing of the main spark plug at the first threshold when the co-combustion ratio of the hydrogen gas is increased from below a first threshold to above a first threshold.

6. The sub-chamber type gas engine according to claim 4, wherein the ignition control device is configured to ignite only the sub-spark plug when the co-combustion rate of the hydrogen gas is less than the second threshold.

7. The sub-chamber type gas engine according to claim 2 or 3, wherein the ignition control device is configured to retard the ignition timing of the main spark plug as the co-combustion ratio of the hydrogen gas increases when the co-combustion ratio is equal to or greater than a first threshold.

8. The sub-chamber type gas engine according to claim 2 or 3, wherein the ignition control device is configured to retard the ignition timing of the auxiliary spark plug as the co-combustion ratio of the hydrogen gas increases when the co-combustion ratio is less than a first threshold.

9. The pre-chamber gas engine according to any one of claims 1 to 3, wherein the main combustion chamber forming section includes a cylinder liner, a piston reciprocally disposed within the cylinder liner, and a cylinder head that forms the main combustion chamber between the cylinder liner and the piston, and the at least one main spark plug includes a central main spark plug having an ignition portion located between the 0% position and the 20% position, when the central axis of the cylinder liner is at the 0% position and the wall surface of the cylinder liner is at the 100% position.

10. The pre-chamber gas engine according to any one of claims 1 to 3, wherein the main combustion chamber forming section includes a cylinder liner, a piston reciprocally disposed within the cylinder liner, and a cylinder head that forms the main combustion chamber between the cylinder liner and the piston, and the at least one main spark plug includes an outer-circumferential main spark plug having an ignition portion positioned between the 60% and 100% positions, with the central axis of the cylinder liner at the 0% position and the wall surface of the cylinder liner at the 100% position.

11. The sub-chamber type gas engine according to claim 10, wherein the outer-circumferential main spark plugs are each installed at different positions in the circumferential direction of the main combustion chamber.

12. The pre-chamber gas engine according to claim 11, wherein the at least one injection hole includes a plurality of injection holes each formed at different positions in the circumferential direction of the pre-combustion chamber forming portion, and each of the ignition portions of the plurality of outer peripheral main spark plugs is installed at a circumferential position between adjacent injection holes in the circumferential direction of the pre-combustion chamber forming portion among the plurality of injection holes.

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