Multi-fuel engine system and its control method

Abstract

One aspect of the present invention is a control method for a multi-fuel engine system configured to use gaseous fuel and hydrogen, wherein the maximum pressure of the cylinder and the mid-combustion timing are detected during the operation of the multi-fuel engine system, and the ratio of hydrogen to be mixed with the gaseous fuel is determined based on the detected maximum pressure of the cylinder and the mid-combustion timing.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority under Korean Patent Application No. 10-2023-0052949 dated April 21, 2023, and all content disclosed in the documents of the said Korean Patent Application is incorporated herein by reference.

[0002] The present invention relates to a multi-fuel engine system and a method for controlling the same, and more particularly to a multi-fuel engine system and a method for controlling the same that can reduce greenhouse gas emissions by adjusting the ratio of environmentally friendly fuels such as hydrogen by adjusting the EGR rate. [Background technology]

[0003] A dual-fuel engine system is configured to selectively or simultaneously use liquid fuel (e.g., diesel) and gaseous fuel (e.g., natural gas), and can satisfy both economic and environmental requirements.

[0004] The dual-fuel engine system has a gas-fueled operating mode that uses gaseous fuel and a liquid-fueled operating mode that uses liquid fuel.

[0005] Liquid fuel is injected into the combustion chamber by a main injector located in each cylinder head, while gaseous fuel is distributed from the main feed pipe to individual cylinder distribution pipes before being injected into the intake port of the cylinder head via a gas admission valve (GAV).

[0006] The dual fuel engine system is based on a diesel engine that compresses intake air to high temperature and pressure and causes self-ignition, unlike a gasoline engine that spark-ignites fuel with a spark plug. Therefore, it has a micro pilot injector for igniting gas fuel. Gas fuels such as natural gas have a low flash point but a high self-ignition temperature of around 550°C. Therefore, just before injecting the gas fuel, which is the main fuel, in the gas fuel operation mode (main injection process), a small amount of pilot fuel (e.g., diesel) is injected through the pilot injector to induce ignition (pilot injection process), and stable ignition of the gas fuel can be induced. Also, even in the liquid fuel operation mode, just before injecting the liquid fuel, a small amount of pilot fuel is injected through the pilot injector, and by improving the combustion environment in the combustion chamber, NOx can be improved and combustion performance can be enhanced.

[0007] However, the dual fuel engine system has limitations in appropriately responding to the strengthened greenhouse gas emission regulations by simply using gas fuel and / or liquid fuel.

[0008] The matters described in this background art section are created to enhance the understanding of the background of the invention and may include matters that are not prior art already known to those with ordinary knowledge in the field to which this technology belongs.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been derived in consideration of the above points, and an object thereof is to provide a multi-fuel engine system and a control method thereof that can reduce greenhouse gas emissions by adjusting the ratio of environmentally friendly fuel, the EGR rate, and the like.

[0010] The problems that this embodiment aims to solve are not limited to those described here, and can also include the means and embodiments for solving the problems described below, as well as the objectives and effects that can be understood from these embodiments. [Means for solving the problem]

[0011] One aspect of the present invention for achieving the above objectives is a control method for a multi-fuel engine system configured to use gaseous fuel and hydrogen, wherein the maximum pressure and mid-combustion timing of the cylinder are detected during operation of the multi-fuel engine system, and the ratio of hydrogen to be mixed with the gaseous fuel is determined based on the detected maximum pressure and mid-combustion timing of the cylinder.

[0012] According to one embodiment, during the operation of the multi-fuel engine system, it is possible to determine whether conditions are permissible for hydrogen to be mixed with the gaseous fuel, and depending on whether conditions are permissible for hydrogen to be mixed with the gaseous fuel, the ratio of hydrogen to be mixed with the gaseous fuel can be determined.

[0013] According to the embodiment, the conditions under which hydrogen is permitted to be mixed with gaseous fuel may be that the detected maximum pressure of the cylinder is less than or equal to the design pressure of the cylinder, and the detected mid-combustion timing is greater than or equal to the set mid-combustion timing.

[0014] According to one embodiment, when conditions allow for the mixing of hydrogen with gaseous fuel, the hydrogen ratio can be increased so that the hydrogen ratio remains below a set ratio.

[0015] According to the embodiment, after the hydrogen ratio is increased, it is determined again whether the conditions for mixing hydrogen with the gaseous fuel are permissible, and if the conditions for mixing hydrogen with the gaseous fuel are not permissible after the hydrogen ratio is increased, the hydrogen ratio can be reduced to the hydrogen ratio before the increase.

[0016] According to one embodiment, the multi-fuel engine system can detect EGR during operation, increase the EGR rate to maintain it below a set EGR rate, and increase the hydrogen ratio based on the increased EGR rate.

[0017] According to the embodiment, when conditions are not permitted for hydrogen to be mixed with the gaseous fuel, the EGR rate can be increased to maintain the EGR rate below a set EGR rate, and after the EGR rate has been increased, it can be determined again whether conditions are permitted for hydrogen to be mixed with the gaseous fuel.

[0018] According to one embodiment, when conditions are in which it is permissible for hydrogen to be mixed with the gaseous fuel after the EGR rate has increased, the proportion of hydrogen can be increased based on the increased EGR rate so as to maintain the proportion of hydrogen at or below a set ratio.

[0019] According to one embodiment, when the conditions for hydrogen mixing with the gaseous fuel are not permissible after the EGR rate has been increased, the EGR rate can be reduced to the rate before the increase.

[0020] According to the embodiment, after the EGR rate has increased, when conditions are in which it is permissible for hydrogen to be mixed with the gaseous fuel, it is determined whether the temperature on the turbine inlet side of the turbocharger is below a set temperature. If the temperature on the turbine inlet side is below the set temperature, the hydrogen ratio is increased based on the increased EGR rate so as to maintain the hydrogen ratio below the set ratio. If the temperature on the turbine inlet side exceeds the set temperature, the EGR rate can be reduced to the EGR rate before the increase.

[0021] A multi-fuel engine system according to an embodiment of the present invention may include a cylinder having a combustion chamber, an intake port communicating with the combustion chamber, and an exhaust port communicating with the combustion chamber; a gaseous fuel; a gas inlet valve configured to inject at least one of a mixture of the gaseous fuel and hydrogen into the intake port; and a controller configured to determine the ratio of hydrogen mixed with the gaseous fuel based on the maximum pressure of the cylinder and the mid-combustion timing.

[0022] A multi-fuel engine system according to an embodiment of the present invention may further include a gas fuel supply source fluidly connected to the gas inlet valve via a gas fuel supply pipe, a gas fuel control valve located in the gas fuel supply pipe, a hydrogen supply source fluidly connected to the gas inlet valve via a hydrogen supply pipe, and a hydrogen control valve located in the hydrogen supply pipe. The controller may be configured to control the flow control valve of the gas fuel supply pipe and the flow control valve of the hydrogen supply pipe.

[0023] The gas fuel supply pipe and the hydrogen supply pipe can merge into a main supply pipe, and the main supply pipe can be connected to the gas inlet valve.

[0024] The controller may be configured to detect the EGR rate during the operation of the multi-fuel engine system, increase the EGR rate to maintain it below a set EGR rate, and increase the hydrogen ratio based on the increased EGR rate.

[0025] The controller can be configured to determine whether the conditions for mixing hydrogen with gaseous fuel are permissible during the operation of the multi-fuel engine system, and to determine the ratio of hydrogen to be mixed with gaseous fuel depending on whether the conditions for mixing hydrogen with gaseous fuel are permissible. [Effects of the Invention]

[0026] According to the present invention, by operating a multi-fuel engine system using a mixture of gaseous fuel and hydrogen, which is an environmentally friendly fuel (decarbonized fuel), greenhouse gas emissions (such as nitrogen oxides and methane gas) can be reduced.

[0027] In particular, by optimally determining the ratio of hydrogen mixed with gaseous fuel based on the maximum cylinder pressure, mid-burn timing, and EGR rate, the maximum pressure inside the cylinder can be reduced and the combustion speed (mid-burn timing) can be relatively delayed, thereby reducing greenhouse gas emissions (nitrogen oxides, methane, etc.).

[0028] According to the present invention, by increasing the EGR rate so that the EGR rate remains below a set EGR rate, and by increasing the hydrogen ratio so that the hydrogen ratio remains below a set ratio, the combustion efficiency of the multi-fuel engine system can be improved, and greenhouse gas emissions (nitrogen oxides, methane gas, etc.) can be drastically reduced. [Brief explanation of the drawing]

[0029] [Figure 1] This figure illustrates a multi-fuel engine system according to an embodiment of the present invention. [Figure 2] This figure illustrates a control method for a multi-fuel engine system according to an embodiment of the present invention. [Figure 3] This figure illustrates a control method for a multi-fuel engine system according to a specific embodiment of the present invention. [Figure 4] This diagram illustrates that the detected combustion midpoint is equal to or greater than the set combustion midpoint. [Figure 5] This diagram illustrates that the maximum detected cylinder pressure is below the cylinder's design pressure. [Modes for carrying out the invention]

[0030] Hereinafter, some embodiments of the present invention will be described in detail with reference to illustrative drawings. When assigning reference numerals to the components in each drawing, it should be noted that, as far as possible, the same component will have the same reference numeral even if it is shown in other drawings. Furthermore, when describing embodiments of the present invention, if it is determined that a specific description of a related known configuration or function would interfere with understanding the embodiments of the present invention, such a detailed description will be omitted.

[0031] Furthermore, when describing the components of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc., can be used. Such terms are used to distinguish a component from other components, and the terms do not limit the essence, order, or sequence of the component.

[0032] In embodiments of the present invention, the singular type may also include the plural type unless otherwise specified in the text, and when it is written as "A and / or at least one of B and C", it may include one or more of all possible combinations of A, B, and C.

[0033] Furthermore, when it is stated that a component is “linked,” “joined,” or “connected” to another component, this may include not only cases where the component is directly linked, joined, or connected to the other component, but also cases where yet another component between that component and the other component is “linked,” “joined,” or “connected.”

[0034] Furthermore, when describing something as being formed or positioned "above" or "below" each component, "above" or "below" includes not only cases where two components are in direct contact with each other, but also cases where one or more other components are formed or positioned between the two components. Also, when expressed as "above" or "below," it can include not only an upward direction but also a downward direction relative to one component.

[0035] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not as ideal or overly formal unless expressly defined herein.

[0036] Referring to Figure 1, a multi-fuel engine system 10 according to an embodiment of the present invention may include one or more cylinders 11 having a combustion chamber 13. The cylinder 11 may have a combustion chamber 13 confined within it, and a piston 19 may be configured to reciprocate within the combustion chamber 13. The cylinder 11 may have an intake port 12 communicating with the combustion chamber 13 and an exhaust port 14 communicating with the combustion chamber 13. An intake valve 15 may be configured to open and close the intake port 12, and an exhaust valve 16 may be configured to open and close the exhaust port 14.

[0037] An intake pipe 17 and an intake manifold (not shown) are connected to the intake port 12, allowing intake air to flow into the intake port 12 via the intake pipe 17 and intake manifold. When the intake valve 15 is opened, intake air can flow into the combustion chamber 13 via the intake port 12.

[0038] An exhaust pipe 18 and an exhaust manifold (not shown) are connected to the exhaust port 14, allowing exhaust gas to be discharged into the exhaust pipe 18 via the exhaust port 14 and the exhaust manifold. When the exhaust valve 16 is opened, exhaust gas can be discharged from the combustion chamber 13 through the exhaust port 14.

[0039] Referring to Figure 1, the multi-fuel engine system 10 according to an embodiment of the present invention may include a main injector 21 positioned on the combustion chamber 13, a pilot injector 22 spaced apart from the main injector 21, and a gas inlet valve 23 attached to the intake port 12.

[0040] The main injector 21 can be configured to inject liquid fuel into the combustion chamber 13. The main injector 21 can be fluidically connected to a liquid fuel supply source 31 via a common rail, a pump, or the like. For example, the liquid fuel may be diesel.

[0041] The pilot injector 22 can be configured to inject pilot fuel into the combustion chamber 13. According to one embodiment, the pilot fuel may be a liquid fuel such as diesel. The pilot injector 22 can be fluidically connected to a liquid fuel supply source 31 via a common rail, a pump, or the like.

[0042] The gas inlet valve 23 can be configured to inject at least one of gaseous fuel or a mixture of gaseous fuel and hydrogen into the intake port 12. In particular, the gas inlet valve 23 can be located upstream of the intake valve 15 on the intake port 12. For example, the gaseous fuel may be natural gas.

[0043] A gas fuel supply source 32 and a hydrogen supply source 33 can be fluidly connected to a gas inlet valve 23. Gas fuel can be supplied from the gas fuel supply source 32 to the gas inlet valve 23, and hydrogen can be supplied from the hydrogen supply source 33 to the gas inlet valve 23. As the hydrogen supply flow rate is determined, the gas fuel supply flow rate can be adjusted relatively, thereby determining the mixing ratio of gas fuel and hydrogen. In particular, when the proportion of hydrogen, which is a decarbonized fuel, is relatively increased, greenhouse gas emissions can be minimized by sufficiently burning unburned greenhouse gases in the combustion chamber 13.

[0044] The gas fuel supply source 32 can be fluidly connected to the gas inlet valve 23 via the gas fuel supply pipe 32a. A pressure regulating valve, a gas fuel regulating valve 32b, an on / off valve, various sensors, etc., can be placed in the gas fuel supply pipe 32a.

[0045] The hydrogen supply source 33 can be fluidly connected to the gas inlet valve 23 via the hydrogen supply pipe 33a. A pressure regulating valve, a hydrogen regulating valve 33b, an on / off valve, various sensors, etc., can be placed in the hydrogen supply pipe 33a.

[0046] As the hydrogen control valve 33b adjusts the hydrogen supply flow rate, the gas fuel control valve 32b can relatively adjust the gas fuel supply flow rate, thereby determining the mixing ratio of gas fuel and hydrogen.

[0047] The gas fuel supply pipe 32a and the hydrogen supply pipe 33a can be fluidically connected to the gas inlet valve 23 via the main supply pipe 35. Specifically, the gas fuel supply pipe 32a and the hydrogen supply pipe 33a can merge at the first end (inlet) of the main supply pipe 35, and the second end (outlet) of the main supply pipe 35 can be connected to the gas inlet valve 23. As a result, the gas fuel supplied via the gas fuel supply pipe 32a and the hydrogen supplied via the hydrogen supply pipe 33a can be mixed in a predetermined ratio in the main supply pipe 35.

[0048] Referring to Figure 1, the multi-fuel engine system 10 according to an embodiment of the present invention may include a turbocharger 25 that runs across the intake pipe 17 and the exhaust pipe 18. The turbocharger 25 may include a compressor 26 that compresses outside air flowing in through the intake pipe 17, a turbine 27 that is rotated by exhaust gas discharged through the exhaust pipe 18, and a common shaft 28 that connects the compressor 26 and the turbine 27. A charge air cooler 29 may be located downstream of the compressor 26 on the intake pipe 17.

[0049] Referring to Figure 1, the multi-fuel engine system 10 according to an embodiment of the present invention may include an exhaust gas recirculation system 40 that recirculates a portion of the exhaust gas discharged from the exhaust port 14 to the intake port 12.

[0050] The exhaust gas recirculation system 40 may include an EGR conduit 41 that crosses the exhaust pipe 18 and intake pipe 17 to recirculate the exhaust gas for mixing with fresh air, and an EGR cooler 42 located in the EGR conduit 41.

[0051] According to the embodiment shown in Figure 1, the inlet of the EGR conduit 41 is connected to the exhaust pipe 18 downstream of the turbine 27, and the outlet of the EGR conduit 41 is connected to the intake pipe 17 upstream of the compressor 26, thereby enabling the EGR conduit 41 to form a low-pressure EGR path.

[0052] The EGR cooler 42 may be configured to cool the EGR gas passing through the EGR conduit 41. An on-off valve 43 may be located upstream of the EGR cooler 42, allowing the EGR gas to pass through the EGR conduit 41 when the on-off valve 43 is open, and preventing the EGR gas from passing through the EGR conduit 41 when the on-off valve 43 is closed. An EGR valve 44 may be located downstream of the EGR cooler 42, and the EGR valve 44 may be configured to regulate the flow rate of the EGR gas discharged from the EGR cooler 42.

[0053] The EGR rate can be calculated using the CO2 concentration measured by an exhaust gas analyzer. The exhaust gas analyzer measures the CO2 concentration on the exhaust side at point 18a downstream of the turbine 27 of the turbocharger 25. e It is possible to measure the intake side CO2 concentration at the upstream point 17a of the compressor 26 of the turbocharger 25. i It is possible to measure the CO2 concentration on the atmospheric side at the upstream point 17a of the compressor 26 when the exhaust gas is not recirculated. amb It is possible to measure the following. The CO2 concentration can be measured in vol%, and the EGR rate can be calculated using the following mathematical formula (1).

[0054]

number

[0055] The controller 100 can be configured to control the operation of the intake valve 15, exhaust valve 16, gas fuel control valve 32b, hydrogen control valve 33b, main injector 21, pilot injector 22, gas inlet valve 23, etc., based on various fuel modes.

[0056] According to the embodiment, the controller 100 uses various sensors to determine the maximum pressure P of the cylinder 11 while the multi-fuel engine system 10 is operating using liquid or gaseous fuel. m The system can be configured to detect the center of combustion (COC) and the EGR rate E, and to determine the ratio R of hydrogen mixed with the gas fuel based on the detected internal pressure P of the cylinder 11, the center of combustion (COC), and the EGR rate E. The center of combustion (COC) may be the point at which half of the fuel supplied into the cylinder 11 has completely burned. The controller 100 can adjust the hydrogen ratio and the gas fuel ratio relative to each other by adjusting the hydrogen control valve 33b and the gas fuel control valve 32b, thereby determining the mixture ratio of gas fuel and hydrogen.

[0057] Figure 2 illustrates a control method for a multi-fuel engine system according to an embodiment of the present invention.

[0058] Referring to Figure 2, the multi-fuel engine system 10 operates when liquid or gaseous fuel is supplied to the combustion chamber 13 of the cylinder 11 and burned (S1).

[0059] In liquid fuel mode, air flows into the intake port 12, and the intake valve 15 opens, allowing air to flow into the combustion chamber 13 of the cylinder 11, after which the intake valve 15 closes. As the piston 19 rises to top dead center, the air that has flowed into the combustion chamber 13 is compressed. Subsequently, the main injector 21 injects liquid fuel into the combustion chamber 13, causing the liquid fuel to burn by compression ignition.

[0060] In gas fuel mode, air flows in through the intake port 12, the gas inlet valve 23 injects gas fuel into the intake port 12, the intake valve 15 opens, allowing air and gas fuel to flow into the combustion chamber 13, after which the intake valve 15 is closed. As the piston 19 rises to top dead center, the gas fuel and air that have flowed into the combustion chamber 13 are compressed, and the pilot injector 22 injects pilot fuel into the combustion chamber 13, causing the gas fuel to ignite and burn within the combustion chamber 13.

[0061] The controller 100 uses various sensors to determine the maximum pressure P of the cylinder 11 while the multi-fuel engine system 10 is operating using liquid or gaseous fuel. m The center of combustion (COC) and the EGR rate E are detected (S2). The center of combustion (COC) may be the point at which half of the fuel supplied into the cylinder 11 has been completely burned.

[0062] The controller 100 determines the ratio R of hydrogen to be mixed with the gas fuel based on the detected internal pressure P of the cylinder 11, the center of combustion (COC), and the EGR rate E (S3). The hydrogen ratio R is determined by adjusting the hydrogen control valve 33b to a predetermined opening, and the gas fuel ratio is determined by relatively adjusting the gas fuel control valve 32b based on the predetermined hydrogen ratio, thereby determining the volumetric mixing ratio of gas fuel and hydrogen. For example, if the hydrogen ratio is determined to be 5 vol%, the gas fuel ratio can be determined to be 95 vol%.

[0063] According to the embodiment, the EGR rate E detected in step S3 is set to the EGR rate E t The EGR rate E can be relatively increased to maintain the following, and the hydrogen ratio R can be increased based on the increased EGR rate E. The EGR rate E can be relatively increased by the controller 100 controlling the EGR valve 44 to relatively increase the opening degree of the EGR valve 44.

[0064] The controller 100 operates the multi-fuel engine system 10 using a mixture of gas fuel and hydrogen (S4). Air flows into the intake port 12, the gas inlet valve 23 injects the mixture of gas fuel and hydrogen into the intake port 12, and when the intake valve 15 is opened, the mixture of gas fuel and hydrogen and air flow into the combustion chamber 13, and then the intake valve 15 closes. As the piston 19 rises to top dead center, the mixture of gas fuel and hydrogen and air that has flowed into the combustion chamber 13 is compressed, and the pilot injector 22 injects pilot fuel into the combustion chamber 13, causing the mixture of gas fuel and hydrogen in the combustion chamber 13 to ignite and burn.

[0065] Figure 3 is a flowchart illustrating a control method for a multi-fuel engine system according to a specific embodiment of the present invention.

[0066] The multi-fuel engine system 10 operates (S11) by supplying and burning liquid fuel or gas fuel to the combustion chamber 13 of the cylinder 11.

[0067] During the operation of the multi-fuel engine system 10, the controller 100 can determine whether it is a condition where hydrogen is allowed to be mixed with the gas fuel (or a condition where the ratio of hydrogen mixed with the gas fuel is an acceptable ratio). According to an embodiment, the gas fuel may be a gas fuel such as natural gas, and the hydrogen may be hydrogen. Since hydrogen has a high flame speed, when the mixture of hydrogen (hydrogen) and gas fuel (gas fuel) burns in the combustion chamber 13 of the cylinder 11, its combustion speed and the center of combustion timing COC can become relatively rapid. Here, the maximum pressure P of the cylinder 11 m can increase relatively. In particular, when the ratio R of hydrogen (hydrogen) exceeds the set ratio R t , the center of combustion timing COC may be less than the set center of combustion timing COC t (the center of combustion timing becomes more rapid than the set center of combustion timing), whereby the maximum pressure P of the cylinder 11 m can be the design pressure P of the cylinder 11 dThis allows the maximum pressure of cylinder 11 to be exceeded by the design pressure P of cylinder 11. d Compared to the detected Combustion Center of Cess (COC), set the Combustion Center of Cess (COC). t By comparing this with the following, it is possible to determine whether the conditions under which hydrogen is mixed with gaseous fuel are acceptable. (Setting the center of combustion time (COC)) t This may also be the combustion center timing detected when the multi-fuel engine system 10 is operating without hydrogen being supplied.

[0068] Specifically, the conditions under which hydrogen can be mixed with gaseous fuel are the maximum pressure P detected in cylinder 11. m The design pressure P of cylinder 11 d The following applies: The detected combustion center time (COC) is the set combustion center time (COC). t The above conditions may also be met.

[0069] Referring to Figure 3, the controller 100 detects the maximum pressure P of cylinder 11. m The design pressure P of cylinder 11 d The following (see Figure 4) shows that the detected combustion center time (COC) is equal to the set combustion center time (COC). t By determining whether the above conditions (see Figure 5) are met, it is possible to determine whether the conditions for mixing hydrogen with gaseous fuel are permissible (S12).

[0070] The maximum pressure P of cylinder 11 detected in step S12 m The design pressure P of cylinder 11 d The following applies: The detected combustion center time (COC) is the set combustion center time (COC). tIf the above conditions are determined, the controller 100 can determine that the conditions for mixing hydrogen with the gaseous fuel are permissible, and thereby increases the hydrogen ratio R by a predetermined value (a vol%) (S13). Under operating conditions in which the multi-fuel engine system 10 operates using only liquid fuel or gaseous fuel, no hydrogen is added, so the hydrogen ratio R mixed with the gaseous fuel is 0 vol%, and the hydrogen ratio R can be gradually increased from 0 vol% by a predetermined value (a vol%).

[0071] In step S13, after the hydrogen ratio R has increased by a predetermined value (a vol%), the controller 100 can re-determine whether the conditions are acceptable for hydrogen to be mixed with the gaseous fuel. Specifically, the controller 100 determines the maximum pressure P of the cylinder 11 detected. m The design pressure P of cylinder 11 d The following applies: The detected combustion center time (COC) is the set combustion center time (COC). t By determining whether the above conditions apply, it is possible to re-determine whether the conditions for mixing hydrogen with gaseous fuel are permissible (S14).

[0072] The maximum pressure P of cylinder 11 detected in step S14 m The design pressure P of cylinder 11 d If it exceeds the set COC, the detected COC is set to the COC. t If it is determined that the hydrogen ratio R is less than the set EGR rate, the controller 100 can determine that the conditions for mixing hydrogen with the gaseous fuel are not permissible and can subtract a predetermined value (a vol%) from the hydrogen ratio R (S14-1). That is, by subtracting a predetermined value (a vol%) from the hydrogen ratio R, it can be reduced to the hydrogen ratio before the increase in step S12 (i.e., the hydrogen ratio detected in step S12). Subsequently, the controller 100 determines that the detected EGR rate E is less than the set EGR rate E t Determine if the following applies (S15): The combustion center time (COC) is set. t If it is less than the set Combustion Center of Cessation (COC), then the Combustion Center of Cessation (COC) is set. tThis means it will be faster. The setting of the center of combustion (COC) is the COC. t If it is less than, the maximum pressure P of cylinder 11 becomes relatively faster as the combustion center timing (COC) becomes shorter. m The design pressure P of cylinder 11 d It can exceed the maximum pressure P of cylinder 11. m The design pressure P of cylinder 11 d If it exceeds this value, the proportion of hydrogen mixed into the gaseous fuel cannot be relatively increased.

[0073] Setting EGR rate E t This may be a reference EGR rate for determining whether or not combustion of the multi-fuel engine system 10 is performed stably, and the set EGR rate E t The EGR rate E can be set in various ways depending on the specifications and operating conditions of the multi-fuel engine system 10. t The combustion of the multi-fuel engine system 10 is stable and the EGR rate E is set to the EGR rate E if the following conditions are met. t If this value is exceeded, the combustion of the multi-fuel engine system 10 may become unstable.

[0074] The EGR rate E detected in step S15 is set to the EGR rate E t If it is determined that the following conditions apply, the EGR rate E is increased by a predetermined value (b%) (S16). The controller 100 controls the EGR valve 44 so that the opening degree of the EGR valve 44 is relatively increased, thereby relatively increasing the EGR rate E. As the EGR rate E relatively increases, the oxygen concentration in the combustion chamber 13 of the cylinder 11 can become relatively lower, which relatively delays the combustion center timing, so that the combustion center timing COC can become greater than or equal to the set combustion center timing COCt (see Figure 4), and the maximum pressure P of the cylinder 11 is reached. m This can be relatively reduced (see Figure 5). Thus, when the EGR rate E increases relatively, the combustion center timing COC is relatively delayed, and the maximum pressure P of the cylinder 11 is reduced. m It can be relatively lower.

[0075] After the EGR rate E increases by a predetermined value (b%) in step S16, the controller 100 can again determine whether the conditions are acceptable for hydrogen to be mixed with the gaseous fuel. Specifically, the controller 100 determines the maximum pressure P of the cylinder 11 detected. m The design pressure P of cylinder 11 d The following applies: The detected combustion center time (COC) is the set combustion center time (COC). t By determining whether the above conditions apply, it is possible to determine whether the conditions for mixing hydrogen with gaseous fuel are permissible (S17).

[0076] The maximum pressure P of cylinder 11 detected in step S17 m The design pressure P of cylinder 11 d The following applies: The detected combustion center time (COC) is the set combustion center time (COC). t If the above conditions are met, the controller 100 can determine that the conditions for hydrogen to be mixed with the gaseous fuel are acceptable, and the temperature T on the inlet side of the turbine 27 of the turbocharger 25 is set to the set temperature T. a It can be determined that the following is true (S18): Set temperature T a This temperature may also be a safe temperature for determining whether or not the turbine 27 will be damaged.

[0077] In step S18, the temperature T on the inlet side of turbine 27 is set to the set temperature T. a If it is determined that the hydrogen ratio R is set to the set ratio R, the controller 100 will determine that the hydrogen ratio R is set to the set ratio R. t It can be determined that the following applies (S19).

[0078] In step S19, the hydrogen ratio R is set to the set ratio R t If it is determined that the following is true, the control method of the present invention can return to step S13. In this case, the controller 100 increases the hydrogen ratio R by a predetermined mixing ratio (a vol%) (S13). That is, the hydrogen ratio R can be increased stepwise by a predetermined mixing ratio (a vol%) based on the EGR rate E and the temperature T on the inlet side of the turbine 27.

[0079] As mentioned above, the set EGR rate E t After increasing the EGR rate E, maintain the following, set ratio R t By increasing the hydrogen ratio R to maintain the following, the combustion efficiency of the multi-fuel engine system 10 can be improved, and greenhouse gas emissions (nitrogen oxides, methane gas, etc.) can be drastically reduced.

[0080] The maximum pressure P of cylinder 11 detected in step S14 m The design pressure P of cylinder 11 d The following applies: The detected combustion center time (COC) is the set combustion center time (COC). t If it is determined that the hydrogen ratio R is set to the set ratio R, the controller 100 will determine that the hydrogen ratio R is set to the set ratio R. t It can be determined that the following applies (S19).

[0081] In step S18, the temperature T on the inlet side of turbine 27 is set to the set temperature T. a If it is determined that the EGR rate E exceeds a certain value, the controller 100 can subtract a predetermined value (b%) from the EGR rate E (S20). The controller 100 controls the EGR valve 44 to reduce its opening by a predetermined opening, thereby subtracting a predetermined value (b%) from the EGR rate E. By subtracting a predetermined value (b%) from the EGR rate E, the EGR rate E can be reduced to the EGR rate before it increased in step S16 (i.e., the EGR rate detected in step S15).

[0082] After subtracting a predetermined value (b%) from the EGR rate E, the controller 100 determines whether the multi-fuel engine system 10 is in an abnormal condition (S21).

[0083] Abnormal conditions for the multi-fuel engine system 10 can include various causes that result in the multi-fuel engine system 10 operating abnormally, such as a gas trip, an emergency shut-down, the multi-fuel engine system 10 stopping, or a change in the multi-fuel engine system 10's mode. Here, a gas trip refers to the phenomenon in which fuel in the combustion chamber 13 of the cylinder 11 cannot be completely burned due to abnormal combustion and is discharged from the exhaust pipe.

[0084] If the multi-fuel engine system 10 is determined to be in an abnormal condition in step S21, the hydrogen control valve 33b can be completely closed to shut off the hydrogen supply, and the on / off valve 43 of the exhaust gas recirculation system 40 can be completely closed to shut off the EGR (S22).

[0085] If, in step S21, it is determined that the multi-fuel engine system 10 is in a normal condition and not an abnormal condition, the control method of the present invention returns to step S12.

[0086] The maximum pressure P of cylinder 11 detected in step S12 m The design pressure P of cylinder 11 d If it exceeds the set COC, the detected COC is set to the COC. t If it is determined that the value is less than the specified value, the controller 100 determines whether the multi-fuel engine system 10 is in an abnormal condition (S21).

[0087] In step S15, the EGR rate E is set. t If it is determined that the limit has been exceeded, the controller 100 determines whether the multi-fuel engine system 10 is in an abnormal condition (S21).

[0088] The above description is merely illustrative of the technical concept of the present invention, and any person with ordinary skill in the art to which the present invention belongs can make various modifications and alterations without departing from the essential characteristics of the present invention.

[0089] Therefore, the embodiments disclosed in this invention are for illustrative purposes only, and not to limit the technical concept of the invention, and the scope of the technical concept of the invention is not limited by such embodiments. The scope of protection of this invention should be interpreted in accordance with the following claims, and all technical concepts within an equivalent scope should be interpreted as being included within the scope of the rights of this invention.

Claims

1. A control method for a multi-fuel engine system configured to use gaseous fuel and hydrogen, During operation of the multi-fuel engine system, the maximum cylinder pressure and mid-combustion timing are detected. A control method for a multi-fuel engine system that determines the ratio of hydrogen mixed with gaseous fuel based on the detected maximum pressure of the cylinder and the mid-combustion timing.

2. During operation of the multi-fuel engine system, it is determined whether the conditions are acceptable for hydrogen to be mixed with the gaseous fuel. A control method for a multi-fuel engine system according to claim 1, which determines the ratio of hydrogen to be mixed with gaseous fuel depending on whether the conditions under which the mixing of hydrogen with gaseous fuel is permissible.

3. The control method for a multi-fuel engine system according to claim 2, wherein the conditions under which hydrogen is permitted to be mixed with gaseous fuel are that the maximum pressure of the detected cylinder is less than or equal to the design pressure of the cylinder, and the detected mid-combustion timing is greater than or equal to the set mid-combustion timing.

4. A control method for a multi-fuel engine system according to claim 2, which involves increasing the ratio of hydrogen so that the ratio of hydrogen remains below a set ratio when conditions are permitted for the mixing of hydrogen with gaseous fuel.

5. After the proportion of hydrogen is increased, reassess whether the conditions under which hydrogen is mixed with gaseous fuel are acceptable. A control method for a multi-fuel engine system according to claim 4, wherein, after an increase in the hydrogen ratio, when conditions are not permitted for the hydrogen to be mixed with the gaseous fuel, the hydrogen ratio is reduced to the hydrogen ratio before the increase.

6. A control method for a multi-fuel engine system according to claim 2, comprising detecting EGR during operation of the multi-fuel engine system, increasing the EGR rate to maintain the EGR rate below a set EGR rate, and increasing the hydrogen ratio based on the increased EGR rate.

7. When conditions are not permitted for hydrogen to be mixed with gaseous fuel, the EGR rate is increased so that the EGR rate remains below the set EGR rate. A control method for a multi-fuel engine system according to claim 6, comprising determining again whether the conditions for mixing hydrogen with gaseous fuel are permissible after the EGR rate has increased.

8. A control method for a multi-fuel engine system according to claim 7, wherein, after an increase in the EGR rate, when conditions are in which it is permissible for hydrogen to be mixed with the gaseous fuel, the hydrogen ratio is increased based on the increased EGR rate so as to maintain the hydrogen ratio at or below a set ratio.

9. A control method for a multi-fuel engine system according to claim 7, wherein, after an increase in the EGR rate, when conditions are not in which it is permissible for hydrogen to be mixed with the gaseous fuel, the EGR rate is reduced to the EGR rate before the increase.

10. After the EGR rate increases, when conditions are in place for hydrogen to be mixed with the gaseous fuel, it is determined whether the temperature on the inlet side of the turbocharger turbine is below the set temperature. If the temperature at the turbine inlet is below the set temperature, the hydrogen ratio is increased based on the increased EGR rate so that the hydrogen ratio remains below the set ratio. A control method for a multi-fuel engine system according to claim 7, wherein when the temperature on the turbine inlet side exceeds a set temperature, the EGR rate is reduced to the EGR rate before it was increased.

11. A cylinder having a combustion chamber, an intake port communicating with the combustion chamber, and an exhaust port communicating with the combustion chamber, A gaseous fuel, and a gas inlet valve configured to inject at least one of a mixture of the gaseous fuel and hydrogen into the intake port, A multi-fuel engine system including a controller configured to determine the ratio of hydrogen mixed with gaseous fuel based on the maximum pressure of the cylinder and the mid-combustion timing.

12. A gas fuel supply source is fluidly connected to the gas inlet valve via a gas fuel supply pipe, A gas fuel control valve located in the aforementioned gas fuel supply pipe, A hydrogen supply source fluidly connected to the gas inlet valve via a hydrogen supply pipe, The system further includes a hydrogen control valve arranged in the hydrogen supply pipe, The multi-fuel engine system according to claim 11, wherein the controller is configured to control the flow control valve of the gas fuel supply pipe and the flow control valve of the hydrogen supply pipe.

13. The multi-fuel engine system according to claim 12, wherein the gas fuel supply pipe and the hydrogen supply pipe merge into a main supply pipe, and the main supply pipe is connected to the gas inlet valve.

14. The multi-fuel engine system according to claim 11, wherein the controller is configured to detect the EGR rate during the operation of the multi-fuel engine system, increase the EGR rate so that the EGR rate remains below a set EGR rate, and increase the hydrogen ratio based on the increased EGR rate.

15. The multi-fuel engine system according to claim 11, wherein the controller is configured to determine whether conditions are permissible for hydrogen to be mixed with gaseous fuel during the operation of the multi-fuel engine system, and to determine the ratio of hydrogen to be mixed with gaseous fuel depending on whether conditions are permissible for hydrogen to be mixed with gaseous fuel.

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