Engine system

Abstract

To suppress the impact of equipment responsiveness and avoid deterioration of the exhaust gas purification catalyst. [Solution] The engine system comprises an engine having a first fuel supply unit that supplies a first fuel to a combustion chamber and a second fuel supply unit that supplies a second fuel; an exhaust gas purification catalyst disposed in the exhaust passage of the engine and purifying components derived from the second fuel; a bypass passage connected to the exhaust passage and avoiding passage through the exhaust gas purification catalyst; a control valve that adjusts the ratio of the engine's exhaust passing through the exhaust gas purification catalyst and the bypass passage; and a controller that controls the control valve. The system is configured to allow selection between a first mode in which the first fuel supply unit operates and a second mode in which the operation of the first fuel supply unit is stopped and the second fuel supply unit operates. When the controller detects the selection of the first mode while operating in the second mode, it controls the control valve to increase the ratio of the exhaust passing through the bypass passage.

Description

Technical Field

[0001] The present invention relates to an engine system.

Background Art

[0002] Conventionally, engines that use gas fuel containing a methane component such as natural gas are known. In such engines, it is known that methane slip, in which unburned methane is discharged into the atmosphere, occurs, and countermeasures against methane slip are required from the viewpoint of reducing greenhouse gases.

[0003] As a countermeasure against methane slip, it is known to use a methane oxidation catalyst (see, for example, Patent Documents 1 and 2). However, methane oxidation catalysts are known to cause sulfur-derived catalyst deactivation (sulfur poisoning), and when using a methane oxidation catalyst, countermeasures against sulfur poisoning are required. Patent Document 2 discloses, as a countermeasure against sulfur poisoning, bringing a gas stream containing methane into contact with an SO2 absorbent before coming into contact with the methane oxidation catalyst.

[0004] Further, conventionally, a technique for suppressing sulfur poisoning of NOx catalysts is known (see, for example, Patent Document 3). Patent Document 3 discloses that when an SOx concentration detection means detects SOx at a concentration higher than a predetermined value, the exhaust gas control valve is controlled so that exhaust gas passes through a bypass passage, thereby suppressing sulfur poisoning of the catalyst.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of Invention

Problem to be Solved by the Invention

[0006] Incidentally, when designing an engine that can switch between liquid fuels containing sulfur components, such as heavy oil, and gaseous fuels containing methane components, such as natural gas, the problem of methane slip arises when using gaseous fuel. While the use of a methane oxidation catalyst can be considered as a countermeasure against methane slip, in this case, sulfur poisoning of the methane oxidation catalyst due to the use of liquid fuels containing sulfur components becomes a problem.

[0007] Based on the technology disclosed in Patent Document 3, it is conceivable to detect the SOx concentration in exhaust gas using an SOx concentration sensor, pass exhaust gas with a high SOx concentration through a bypass passage, and pass exhaust gas with a low SOx concentration through a methane oxidation catalyst. This is thought to solve both the methane slip problem and the sulfur poisoning problem.

[0008] However, when considering applications such as those in large ships, the system, including the engine and catalyst, tends to be larger. In larger systems, the responsiveness of the equipment decreases. For this reason, in a configuration where SOx concentration is measured by a sensor and the exhaust passage is switched according to the result, there is a concern that delays may occur in switching the passage. For example, as a result of delays in switching the passage, exhaust containing a large amount of sulfur may pass through the methane oxidation catalyst, causing the methane oxidation catalyst to deteriorate due to sulfur poisoning.

[0009] In view of the above, the present invention aims to provide a technology that can suppress the influence of equipment responsiveness and avoid deterioration of exhaust gas purification catalysts. [Means for solving the problem]

[0010] An exemplary engine system of the present invention comprises an engine having a first fuel supply unit for supplying a first fuel to a combustion chamber and a second fuel supply unit for supplying a second fuel to the combustion chamber; an exhaust gas purification catalyst disposed in the exhaust passage of the engine for purifying components derived from the second fuel; a bypass passage connected to the exhaust passage and avoiding passage through the exhaust gas purification catalyst; a control valve for adjusting the ratio of the engine's exhaust passing through the exhaust gas purification catalyst and the bypass passage; an EGR device connected to the exhaust passage upstream of the control valve for recirculating a portion of the exhaust gas to the engine's intake passage; and a controller for controlling the control valve and the EGR device. The engine system is provided in a selectable manner between a first mode in which the first fuel supply unit operates and a second mode in which the operation of the first fuel supply unit is stopped and the second fuel supply unit operates. When the controller detects the selection of the second mode, it activates the EGR device, and when it detects the selection of the first mode during operation in the second mode, it controls the control valve to increase the ratio of the exhaust gas passing through the bypass passage. [Effects of the Invention]

[0011] According to an exemplary engine system of the present invention, the impact of equipment responsiveness can be suppressed, thereby avoiding the degradation of the exhaust gas purification catalyst. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic diagram showing the general configuration of the engine system. [Figure 2] Diagram to explain engine operating modes [Figure 3] A diagram showing the usage status of the exhaust gas purification catalyst in the engine system for each operating mode. [Figure 4] Diagram showing an overview of the control system included in the engine system. [Figure 5] Block diagram illustrating the control system in the engine. [Figure 6] A flowchart illustrating the control flow of the control valves in an engine system. [Figure 7] Time chart showing a specific example of operation when switching from the first mode to the second mode and from the second mode to the first mode Detailed Description of the Embodiments

[0013] Exemplary embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and repeated description thereof will be omitted where not necessary for explanation.

[0014] <1. Overview of Engine System> Figure 1 is a schematic diagram showing a general configuration of an engine system 100 according to an embodiment of the present invention. As shown in Figure 1, the engine system 100 includes an engine 1 and a catalyst system 2. The engine system 100 is, for example, a power generation engine system used on land, on a ship, or the like. For this purpose, the engine system 100 further includes a power generation device 3 that generates electric power using the output of the engine 1. However, the engine system of the present invention may be applied to other uses such as ship propulsion, for example. When applied to other uses in this manner, the engine system does not necessarily need to include the power generation device.

[0015] In Figure 1, thick outlined arrows indicate the direction in which supply air (supply gas) flows in the engine system 100, and thick solid black arrows indicate the direction in which exhaust gas flows in the engine system 100.

[0016] [1-1. Engine] The engine 1 is configured to be able to use a first fuel and a second fuel of mutually different types. For this purpose, the engine 1 has a first fuel supply unit that supplies the first fuel to a combustion chamber (not shown), and a second fuel supply unit that supplies the second fuel to the combustion chamber. Although not an essential configuration, the present embodiment further includes a third fuel supply unit that supplies the first fuel to the combustion chamber for a purpose different from that of the first fuel supply unit. Specific examples of the first fuel supply unit, the second fuel supply unit, and the third fuel supply unit will be described below.

[0017] In the present embodiment, the first fuel is a liquid fuel containing a sulfur component. Specific examples of the liquid fuel are petroleum fuels such as heavy oil, light oil, and gasoline. The second fuel is a gaseous fuel containing a methane component. A specific example of the gaseous fuel is natural gas. The natural gas used as fuel is, in detail, prepared in the form of liquefied LNG. Hereinafter, in the present specification, for the convenience of description, the first fuel is referred to as liquid fuel, and the second fuel is referred to as gaseous fuel.

[0018] The first fuel supply unit and the third fuel supply unit described above directly supply liquid fuel such as heavy oil to the combustion chamber. The first fuel supply unit and the third fuel supply unit differ in the injection amount of the liquid fuel into the combustion chamber. Since the first fuel supply unit is intended to operate the engine 1 with the liquid fuel, it has an injection valve (injector) that injects a larger amount of liquid fuel into the combustion chamber as compared with the third fuel supply unit. On the other hand, the third fuel supply unit has an injection valve (micro pilot injector) that injects a small amount of liquid fuel as ignition fuel into the combustion chamber. Hereinafter, in the present specification, for the convenience of description, the first fuel supply unit is referred to as a main injection valve, and the third fuel supply unit is referred to as a pilot injection valve.

[0019] The second fuel supply unit described above supplies gaseous fuel such as natural gas, which is the second fuel, to the combustion chamber. Specifically, the second fuel supply unit supplies the gaseous fuel to the combustion chamber via an intake port provided in the engine 1. The second fuel supply unit has a gaseous fuel supply valve (injector) that supplies the gaseous fuel to the intake port. Hereinafter, in the present specification, for the convenience of description, the second fuel supply unit is referred to as a gaseous fuel supply valve.

[0020] Each of the main injection valve, the pilot injection valve, and the gaseous fuel supply valve is provided for each combustion chamber (cylinder). The number of main injection valves and the like included in the engine 1 is changed in accordance with the number of cylinders of the engine 1.

[0021] Figure 2 is a diagram illustrating the operating modes of engine 1. As shown in Figure 2, engine 1 is configured to be switchable between multiple operating modes. Specifically, engine 1 is configured to allow selection of diesel mode, gas mode, mixed combustion mode, and backup mode as operating modes.

[0022] The diesel mode is a mode in which engine 1 is operated using liquid fuel such as heavy oil. In diesel mode, the main injector and pilot injector operate, and the gas fuel supply valve is deactivated (not operating). The gas mode is a mode in which engine 1 is operated using gaseous fuel such as natural gas. In gas mode, the gas fuel supply valve and pilot injector operate, and the main injector is deactivated. In gas mode, a very small amount of liquid fuel is used in addition to the gaseous fuel because the pilot injector operates.

[0023] The mixed-fuel mode is a mode in which engine 1 is operated using both liquid fuel and gaseous fuel. In mixed-fuel mode, the ratio of liquid fuel to gaseous fuel is higher than in gaseous mode. In mixed-fuel mode, the main injector, pilot injector, and gaseous fuel supply valve are operational. The backup mode is an operating mode used when the pilot injector fails. In backup mode, the main injector operates, and the pilot injector and gaseous fuel supply valve are deactivated.

[0024] As can be seen from the above, the engine system 100 is provided with selectable modes: a first mode in which the main injection valve (first fuel supply unit) operates, and a second mode in which the operation of the main injection valve is stopped and the gas fuel supply valve (second fuel supply unit) operates. In this embodiment, as can be seen from Figure 2, the first mode includes a diesel mode, a mixed combustion mode, and a backup mode. The second mode is the gas mode. Hereafter, in this specification, the terms first mode and second mode may be used in this sense. Note that the mixed combustion mode and the backup mode are not essential configurations in the engine system of the present invention.

[0025] In this embodiment, the engine 1 is equipped with a supercharger 11, an intercooler 12, and an EGR device 13 (see Figure 1). That is, the engine system 100 comprises a supercharger 11, an intercooler 12, and an EGR device 13. Note that the engine 1 (engine system 100) does not necessarily have to be equipped with these auxiliary devices 11 to 13. Also, if the engine system 100 does not have a supercharger 11, "intake" may be read as "intake."

[0026] The supercharger 11 includes a turbine 111 and a compressor 112. The turbine 111 is rotated using the exhaust from the engine 1. The rotational power of the turbine 111 is transmitted to the compressor 112. The compressor 112 pressurizes and compresses the intake air, such as air supplied from outside the engine 1. The pressurized and compressed intake air is supplied to the combustion chamber of the engine 1 via the intercooler 12. The intercooler 12 is supplied with coolant by a coolant pump (not shown), and cools the intake air by exchanging heat between the coolant supplied by the coolant pump and the pressurized and compressed intake air.

[0027] The EGR (Exhaust Gas Recirculation) device 13 is connected to the exhaust passage 4 of the engine 1 and recirculates a portion of the engine 1's exhaust gases into the engine 1's intake passage 5. The EGR device 13 is connected to the exhaust passage 4 downstream of the turbine 111. The EGR device 13 is connected to the intake passage 5 upstream of the compressor 112. The EGR device 13 has an EGR valve 131. Specifically, the EGR valve 131 is located on the inlet side connected to the exhaust passage 4 and the outlet side connected to the intake passage 5 of the EGR device 13. The EGR device 13 switches between an operating state and a non-operating state by opening and closing the EGR valve 131. Details of the opening and closing control of the EGR valve 131 will be described later.

[0028] In this embodiment, the fluid passages through which the supply and exhaust air pass (such as the exhaust passage 4 and the supply air passage 5) are constructed using hollow members such as pipes.

[0029] [1-2. Catalytic Systems] The catalytic converter system 2 is a system provided for the purpose of purifying components derived from the gaseous fuel (second fuel) contained in the exhaust of engine 1. As described above, the gaseous fuel contains methane components, and the catalytic converter system 2 is a system provided as a measure against methane slip. As shown in Figure 1, the catalytic converter system 2 includes an exhaust purification catalyst 21, a bypass passage 22, and a control valve 23. In other words, the engine system 100 is equipped with an exhaust purification catalyst 21, a bypass passage 22, and a control valve 23.

[0030] The exhaust gas purification catalyst 21 is located in the exhaust passage 4 of the engine 1. That is, the exhaust gas from the engine 1 is provided to pass through the exhaust gas purification catalyst 21. More specifically, the exhaust gas purification catalyst 21 purifies components derived from the gaseous fuel (second fuel). More specifically, the exhaust gas purification catalyst 21 is a methane oxidation catalyst. The exhaust gas purification catalyst 21 oxidizes the methane contained in the gaseous fuel. By passing the exhaust gas from the engine 1 through the exhaust gas purification catalyst 21 (methane oxidation catalyst), the amount of methane contained in the exhaust gas discharged to the outside of the engine system 100 can be reduced.

[0031] The bypass passage 22 is connected to the exhaust passage 4. More specifically, one end and the other end of the bypass passage 22 are connected to the exhaust passage 4. The bypass passage 22 is a passage that avoids passing through the exhaust purification catalyst 21. In other words, in the engine system 100, the provision of the bypass passage 22 makes it possible to discharge the exhaust from the engine 1 to the outside of the engine system 100 without passing through the exhaust purification catalyst 21.

[0032] In this embodiment, the bypass passage 22 is configured so that both the exhaust inlet and outlet sides are connected to the exhaust passage 4, but this is merely an example. The exhaust outlet side of the bypass passage 22 may not be connected to the exhaust passage 4. In this case, the engine system 100 will have two outlets for discharging exhaust to the outside of the engine system 100.

[0033] The control valve 23 adjusts the ratio of the exhaust gas from the engine 1 passing through the exhaust gas purification catalyst 21 and the bypass passage 22. The control valve 23 may be a valve whose flow rate can be arbitrarily adjusted by command, or it may be configured to only switch the opening and closing of the valve by command. In this embodiment, the control valve 23 includes a plurality of control valves 231 to 233. The number of control valves 23 may be appropriately changed depending on, for example, the type of valve and the configuration of the bypass passage 22.

[0034] In this embodiment, the control valve 23 includes a catalyst upstream valve 231, a catalyst downstream valve 232, and a bypass upstream valve 233. The catalyst upstream valve 231 is located upstream of the exhaust gas purification catalyst 21 in the exhaust passage 4. The catalyst downstream valve 232 is located downstream of the exhaust gas purification catalyst 21 in the exhaust passage 4. The bypass upstream valve 233 is located upstream of the bypass passage 22. The upstream portion of the bypass passage 22 is near the exhaust gas inlet portion of the bypass passage 22.

[0035] For example, suppose the catalytic converter upstream valve 231 and catalytic converter downstream valve 232 are open (100% open), and the bypass upstream valve 233 is closed (0% open). In this case, the exhaust from engine 1 passes through the exhaust purification catalyst 21 and is discharged outside the engine system 100, and does not pass through the bypass passage 22. Alternatively, suppose the catalytic converter upstream valve 231 and catalytic converter downstream valve 232 are closed (0% open), and the bypass upstream valve 233 is open (100% open). In this case, the exhaust from engine 1 passes through the bypass passage 22 and is discharged outside the engine system 100, and does not pass through the exhaust purification catalyst 21.

[0036] Figure 3 shows the usage status of the exhaust gas purification catalyst 21 in the engine system 100 for each operating mode. As shown in Figure 3, the exhaust gas purification catalyst 21 is used in gas mode. On the other hand, the exhaust gas purification catalyst 21 is not used in diesel mode, co-firing mode, and backup mode.

[0037] In detail, in gas mode, the opening degrees of the catalyst upstream valve 231 and catalyst downstream valve 232 are set to 100% and the opening degree of the bypass upstream valve 233 is set to 0% so that the exhaust from engine 1 passes through the exhaust purification catalyst 21. This prevents unburned methane from being discharged outside the engine system 100 through the action of the exhaust purification catalyst (methane oxidation catalyst) 21. In other words, the engine system 100 is configured to prevent methane slip.

[0038] On the other hand, in diesel mode, co-firing mode, and backup mode, unburned methane is basically not generated. Also, in diesel mode, co-firing mode, and backup mode, liquid fuel containing sulfur is used, so the amount of SOx contained in the exhaust cannot be ignored, and deterioration of the exhaust purification catalyst (methane oxidation catalyst) 21 due to sulfur poisoning becomes a problem. Taking these points into consideration, in diesel mode, co-firing mode, and backup mode, the control valve 23 is controlled so that the exhaust from engine 1 passes through the bypass passage 22 without passing through the exhaust purification catalyst 21. Specifically, in diesel mode, co-firing mode, and backup mode, the opening degree of the catalyst upstream valve 231 and the catalyst downstream valve 232 is set to 0%, and the opening degree of the bypass upstream valve 233 is set to 100%.

[0039] As shown in the notes section of Figure 3, in this embodiment, the bypass passage 22 is always used in diesel mode, co-firing mode, and backup mode, and in these modes, the exhaust from engine 1 does not pass through the exhaust purification catalyst 21. On the other hand, in gas mode, the bypass passage 22 is not used in principle, but it may be switched to a state in which the bypass passage 22 is used depending on the usage status of the engine system 100. This point will be described later.

[0040] Furthermore, in this embodiment, each control valve 231 to 233 is configured to be controlled to either have an opening of 0% or 100%, but this is not a mandatory configuration. For example, in gas mode, a portion (a small amount) of the exhaust from engine 1 may pass through the bypass passage 22 at a level where methane emission is not a problem. Also, for example, in diesel mode, a portion (a small amount) of the exhaust from engine 1 may pass through the exhaust purification catalyst 21 at a level where sulfur poisoning is not a problem.

[0041] [1-3. Control System] Figure 4 shows an overview of the control system provided by the engine system 100. As shown in Figure 4, the engine system 100 includes an engine control panel 14, a catalyst control panel 24, and a power generation control panel 31.

[0042] The engine control panel 14 is a control panel primarily provided for controlling engine 1. The engine control panel 14 allows the user to operate settings related to engine 1. The engine control panel 14 also includes a main ECU (Electronic Control Unit) 141 that manages the entire engine system 100, including management related to engine 1. The main ECU 141 is composed of, for example, a controller having an arithmetic unit, an input / output unit, and a memory unit.

[0043] The above-described arithmetic unit is composed of, for example, a processor or a microprocessor. The above-described storage unit is a main memory such as ROM (Read Only Memory) and RAM (Random Access Memory). The storage unit may further include an auxiliary storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive). Various programs and data are stored in the storage unit. The arithmetic unit performs various functions by reading various programs from the storage unit and executing arithmetic processing according to the programs. The programs stored in the storage unit may be provided, for example, on a computer-readable non-volatile recording medium. As another example, programs may be provided from a program provision server via a communication line such as the Internet.

[0044] The catalyst control panel 24 is a control panel for controlling the catalyst system 2. The catalyst control panel 24 allows the user to operate settings related to the catalyst system 2. The catalyst control panel 24 also includes a catalyst ECU 241 that manages the catalyst system 2. The catalyst ECU 241 is composed of, for example, a controller having a calculation unit, an input / output unit, and a memory unit. The general configuration of the calculation unit, etc., is the same as that of the main ECU 141, so a description is omitted here.

[0045] The power generation control panel 31 is a control panel for controlling the power generation device 3. The power generation control panel 31 allows the user to operate settings related to the power generation device 3. The power generation control panel 31 also includes a power generation ECU 311 that manages the power generation device 3. The power generation ECU 311 is composed of, for example, a controller having an arithmetic unit, an input / output unit, and a memory unit. The general configuration of the arithmetic unit, etc., is the same as in the case of the main ECU 141, so the explanation is omitted here.

[0046] The main ECU 141 and the catalytic converter ECU 241 can communicate with each other using a communication network. Similarly, the main ECU 141 and the power generator ECU 311 can communicate with each other using a communication network. A specific example of this communication network is a LAN (Local Area Network). The LAN applied to the engine system 100 may be either a wired or wireless LAN. The main ECU 141 issues commands to the catalytic converter ECU 241 and receives information from the catalytic converter ECU 241. The main ECU 141 also issues commands to the power generator ECU 311 and receives information from the power generator ECU 311.

[0047] For example, in this embodiment, the catalytic converter ECU 241 controls the control valve 23 and other components of the catalytic converter system 2. However, the catalytic converter ECU 241 does not control the control valve 23 and other components based on its own judgment, but rather controls them in response to commands from the main ECU 141. Furthermore, if an abnormality occurs in the catalytic converter system 2, information about the abnormality is transmitted from the catalytic converter ECU 241 to the main ECU 141. The main ECU 141 then performs appropriate processing according to the received abnormality information.

[0048] In this embodiment, the engine control panel 14 and the catalyst control panel 24 are provided separately, but this is merely an example. The engine control panel 14 and the catalyst control panel 24 may be combined into one. Similarly, the engine control panel 14 and the power generation control panel 31 may be combined into one. Furthermore, the engine control panel 14, the catalyst control panel 24, and the power generation control panel 31 may all be combined into one. Also, as described above, the power generation device 3 is not essential in the engine system of the present invention, and if the engine system 100 is configured without the power generation device 3, the power generation control panel 31 is unnecessary.

[0049] <2. Control operation of the engine system> Next, the control operations performed by the engine system 100 will be described.

[0050] [2-1. Overview] Figure 5 is a block diagram illustrating the control system in the engine system 100. Note that Figure 5 primarily shows the elements related to the control operation of the present invention, and general elements are omitted from the illustration.

[0051] As shown in Figure 5, the engine system 100 includes a controller 6. Here, the controller 6 is assumed to be the controller of the main ECU 141 described above. However, as stated above, in this embodiment, the main ECU 141 and the catalyst ECU 241 cooperate to control the catalyst system 2. For this reason, the controller 6 may be understood to consist of a controller for the main ECU 141 and a controller for the catalyst ECU 241.

[0052] As shown in Figure 5, the controller 6 controls various elements of the engine system 100 as appropriate based on information received from sensors and the like. Specifically, the controller 6 controls the main injection valve 15, the gas fuel supply valve 16, and the pilot injection valve 17 of the engine 1. The explanation of the main injection valve 15, the gas fuel supply valve 16, and the pilot injection valve 17 is as described above, so it will be omitted here. The controller 6 also controls the EGR valve 131 of the EGR device 13. The explanation of the EGR valve 131 is as described above, so it will be omitted here.

[0053] Furthermore, the controller 6 controls the control valves 23 provided in the catalytic converter system 2. More specifically, the controller 6 controls the control valves 23 in cooperation with the controller of the catalytic converter ECU 241. As described above, the control valves 23 include the catalytic converter upstream valve 231, the catalytic converter downstream valve 232, and the bypass upstream valve 233. Since these have been explained above, a further explanation will be omitted here.

[0054] As shown in Figure 5, the controller 6 receives information from the operating mode control panel 142, the in-cylinder pressure sensor 71, the UEGO (Universal Exhaust Gas Oxygen) sensor 72, various temperature sensors 73, various pressure sensors 74, the methane concentration sensor 75, and the load setting control panel 312. These will be briefly explained below.

[0055] The operating mode control panel 142 is located on the engine control panel 14. The user can switch between operating modes by operating the operating mode control panel 142. The controller 6 can obtain information about the operating mode set by the user from the operating mode control panel 142.

[0056] The in-cylinder pressure sensor 71 is a pressure sensor provided for each combustion chamber of the engine 1. The controller 6 is configured to calculate the misfire rate of each cylinder based on the combustion pressure obtained from the in-cylinder pressure sensor 71.

[0057] The UEGO (Universal Exhaust Gas Oxygen) sensor 72 is installed in the exhaust passage 4 and is configured to detect the oxygen concentration contained in the exhaust gas of the engine 1. In other words, the engine system 100 is equipped with an oxygen concentration sensor. The controller 6 can obtain the air-fuel ratio in the engine 1 based on the value detected by the UEGO sensor 72.

[0058] The various temperature sensors 73 refer to the various temperature sensors provided by the engine system 100. In this embodiment, the various temperature sensors 73 include a turbocharger outlet temperature sensor 731, a pre-catalytic converter temperature sensor 732, a catalytic converter temperature sensor 733, and a post-catalytic converter temperature sensor 734. The turbocharger outlet temperature sensor 731 measures the temperature of the exhaust gas near the outlet of the turbocharger 11 (turbine 111). The pre-catalytic converter temperature sensor 732 measures the temperature between the upstream catalytic converter valve 231 and the exhaust gas purification catalyst 21. The catalytic converter temperature sensor 733 measures the temperature of the exhaust gas purification catalyst 21. The post-catalytic converter temperature sensor 734 measures the temperature between the exhaust gas purification catalyst 21 and the downstream catalytic converter valve 232. The controller 6 can acquire the temperatures measured by each of the temperature sensors 731 to 734.

[0059] The various pressure sensors 74 refer to the various pressure sensors provided by the engine system 100. In this embodiment, the various pressure sensors 74 include an intake pressure sensor 741, a pre-catalytic converter pressure sensor 742, and a post-catalytic converter pressure sensor 743. The intake pressure sensor 741 is located downstream of the compressor 112 in the intake passage 5 and measures the intake air pressure. The pre-catalytic converter pressure sensor 742 measures the pressure between the exhaust catalytic converter upstream valve 231 and the exhaust gas purification catalyst 21. The post-catalytic converter pressure sensor 743 measures the pressure between the exhaust gas purification catalyst 21 and the catalytic converter downstream valve 232. The controller 6 can acquire the pressures measured by each of the pressure sensors 741 to 743.

[0060] Furthermore, the values ​​measured by the intake pressure sensor 741 can be used to calculate the air-fuel ratio in engine 1. In other words, from the standpoint of obtaining the air-fuel ratio, the engine system 100 only needs to be equipped with at least one of the following: an intake pressure device (intake pressure sensor 741) installed in the intake passage 5 and an oxygen concentration detection device (UEGO sensor 72) installed in the exhaust passage 4.

[0061] The methane concentration sensor 75 is installed in the passage 25 (see Figure 1) connected to the exhaust passage 4 on both the upstream and downstream sides of the exhaust gas purification catalyst 21, and measures the methane concentration in the exhaust gas. The controller 6 can acquire the measured value from the methane concentration sensor 75.

[0062] The load setting operation panel 312 is provided on the power generation control panel 31. The user can set the load factor of the power generation device 3 by operating the load setting operation panel 312. The controller 6 can obtain the load factor of the power generation device 3 set by the user from the load setting operation panel 312.

[0063] As shown in Figure 5, the controller 6 performs the functions of an operating mode setting unit 61, an EGR management unit 62, a catalyst usage permission determination unit 63, and an exhaust gas flow state management unit 64 through the cooperation of hardware and software. The functions of each functional unit 61 to 64 are realized by having the arithmetic unit (processor) execute calculation processing according to the program.

[0064] Furthermore, at least one of the functions of each of the functional units 61 to 64 may be implemented using, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). In other words, at least one of the functions of each of the functional units 61 to 64 may be implemented in hardware using a dedicated IC or the like. Also, at least one of the functions of each of the functional units 61 to 64 may be implemented using a combination of software and hardware. Moreover, each of the functional units 61 to 64 is a conceptual component. The function performed by one component may be distributed among multiple components. Also, the functions of multiple components may be integrated into one component.

[0065] The operating mode setting unit 61 sets the operating mode of the engine 1 in response to instructions from the operating mode operation panel 142. The operating mode setting unit 61 appropriately sets the operation of the main injection valve 15, the gas fuel supply valve 16, and the pilot injection valve 17 so that the engine 1 operates in the specified operating mode. The operating mode setting unit 61 also appropriately sets the fuel supply so that the engine 1 operates in the specified operating mode. Once the operating mode setting by the operating mode setting unit 61 is complete, the engine 1 starts operating in the set operating mode.

[0066] When the operating mode setting unit 61 detects the selection of another operating mode while the engine 1 is operating in a certain operating mode, it executes the necessary processes to change the setting from one operating mode to another. For example, if the engine 1 is operating in diesel mode and the operating mode setting unit 61 detects a change to gas mode based on an instruction from the operating mode operation panel 142, the operating mode setting unit 61 performs the process to change the setting from diesel mode to gas mode. At this time, the operating mode setting unit 61 appropriately adjusts the operating settings of the main injection valve 15, the gas fuel supply valve 16, and the pilot injection valve 17, as well as the amount of fuel supplied.

[0067] The EGR management unit 62 manages the operation of the EGR device 13, which is connected to the exhaust passage 4 upstream of the control valve 23. In other words, the controller 6 controls the EGR device 13. In this embodiment, when the EGR management unit 62 (controller 6) detects the selection of the second mode (gas mode), it activates the EGR device 13. Here, "activating the EGR device 13" means opening the EGR valve to a predetermined opening. It also includes changing the opening depending on the engine operating state, etc. The selection of the second mode can be detected by information from the operating mode operation panel 142.

[0068] When the EGR device 13 is activated in the second mode, the methane components contained in the exhaust of the engine 1 can be re-introduced into the combustion chamber of the engine 1 and burned. This reduces the amount of methane components that pass through the exhaust purification catalyst (methane oxidation catalyst) 21 located in the exhaust passage 4. As a result, the size of the methane oxidation catalyst can be suppressed, and furthermore, the size of the control valve 23 can also be suppressed. By suppressing the size of the control valve 23, the responsiveness of the control valve 23 can be improved.

[0069] In this embodiment, the EGR control unit 62 does not activate the EGR device 13 when it detects the selection of the first mode (diesel mode, co-firing mode, or backup mode). Here, "do not activate the EGR device 13" means closing the EGR valve. However, this is an example, and the EGR device 13 may be configured to operate regardless of which operating mode is selected.

[0070] The catalyst usage permission determination unit 63 makes a determination regarding the requirements for permission to use the exhaust gas purification catalyst 21. As shown in Figure 3 above, the exhaust gas purification catalyst 21 is used only when the second mode (gas mode) is selected, and is not used when the first mode (diesel mode, co-firing mode, or backup mode) is selected. For this reason, the catalyst usage permission determination unit 63 makes a determination regarding the requirements for permission to use the exhaust gas purification catalyst 21 when the second mode is selected. The catalyst usage permission determination unit 63 does not make a determination regarding the requirements for permission to use the exhaust gas purification catalyst 21 when the first mode is selected.

[0071] The catalyst usage permission determination unit 63 may or may not permit the use of the exhaust purification catalyst 21. If permission is granted, the exhaust from engine 1 will pass through the exhaust purification catalyst 21. If permission is not granted, the exhaust from engine 1 will pass through the bypass passage 22 so that it does not pass through the exhaust purification catalyst 21.

[0072] The requirements for permitting the use of the exhaust gas purification catalyst 21 are predetermined with the aim of preventing deterioration of the exhaust gas purification catalyst 21. The types and number of permit requirements are determined in advance through experiments and simulations. The permit requirements include, for example, requirements related to the engine 1 and requirements related to the catalyst system 2.

[0073] Specific examples of requirements for permitting the use of the exhaust gas purification catalyst 21 include the following, and if all of these are met, the use of the exhaust gas purification catalyst 21 will be permitted. (Requirements for permission to use) A predetermined time has elapsed since the completion of the transition from the first mode to the second mode, the load rate of the engine 1 is above a predetermined value, the misfire rate of each cylinder is below a predetermined value, the air-fuel ratio is below a predetermined value, the load fluctuation rate is below a predetermined value, the EGR device 13 is operating, the exhaust supercharger outlet temperature is within a predetermined range, the methane concentration in the exhaust is below a predetermined value, the catalyst temperature is within a predetermined range, and the components of the catalytic converter system 2 are functioning normally.

[0074] The exhaust flow state management unit 64 manages the flow state of the exhaust gas from engine 1. More specifically, the exhaust flow state management unit 64 determines the proportion of the exhaust gas from engine 1 that passes through the exhaust purification catalyst 21 and the bypass passage 22. Once the exhaust flow state management unit 64 has determined this proportion, it instructs the catalyst ECU 241 to achieve the determined proportion. In response to this instruction, the catalyst ECU 241 controls the control valve 23. From this point of view, it can be said that the exhaust flow state management unit 64 (controller 6) controls the control valve 23.

[0075] The exhaust flow state management unit 64 determines the proportion of the exhaust from engine 1 that passes through the exhaust purification catalyst 21 and the bypass passage 22 based on the operating mode. Specifically, the exhaust flow state management unit 64 changes the proportion of the exhaust from engine 1 that passes through the exhaust purification catalyst 21 and the bypass passage 22 depending on whether it is in the first mode (diesel mode, etc.) or the second mode (gas mode).

[0076] Furthermore, as described above, even if the second mode is selected, if the requirements for permission to use the exhaust gas purification catalyst 21 are not met, the exhaust gas will not be allowed to pass through the exhaust gas purification catalyst 21. For this reason, when the second mode is selected, the exhaust gas flow state management unit 64 determines the pass-through rate based on the determination result of the catalyst usage permission determination unit 63 regarding the requirements for permission to use the exhaust gas purification catalyst 21.

[0077] Furthermore, in this embodiment, the determination of the pass-through ratio is a choice between setting the pass-through ratio of the exhaust gas purification catalyst 21 to 100% (the pass-through ratio of the bypass passage 22 to 0%) or setting the pass-through ratio of the bypass passage 22 to 100% (the pass-through ratio of the exhaust gas purification catalyst 21 to 0%).

[0078] When the exhaust gas flow state management unit 64 detects the selection of the first mode while operating in the second mode, it controls the control valve 23 to increase the proportion of exhaust gas passing through the bypass passage 22. In other words, when the exhaust gas flow state management unit 64 detects the selection of the first mode while operating in the second mode, it controls the control valve 23 to decrease the proportion of exhaust gas passing through the exhaust gas purification catalyst 21. In this embodiment, the proportion of exhaust gas passing through the exhaust gas purification catalyst 21 is set to 0%, and the proportion of exhaust gas passing through the bypass passage 22 is set to 100%.

[0079] In this configuration, the proportion of exhaust gas passing through the exhaust gas purification catalyst 21 can be reduced in response to a switching instruction from the second mode (gas mode) to the first mode (diesel mode, etc.). Compared to a configuration in which the concentration of catalyst poison (sulfur component in this embodiment) in the exhaust gas is detected before the exhaust gas purification catalyst 21 and the proportion of exhaust gas passing through the catalyst 21 is reduced according to the detection result, the operation of the control valve 23 to suppress the effects of catalyst poison can be started earlier. As a result, even if the engine system 100 is large, for example, the impact of equipment responsiveness can be suppressed, and catalyst poisoning (catalyst degradation) by catalyst poison components (sulfur component in this embodiment) derived from the first fuel (heavy oil, etc.) used in the first mode can be avoided.

[0080] Furthermore, when the exhaust gas flow state management unit 64 detects the selection of the second mode while operating in the first mode, it controls the control valve 23 after a predetermined period has elapsed since the detection of the selection of the second mode to reduce the proportion of exhaust gas passing through the bypass passage 22. In other words, when the exhaust gas flow state management unit 64 detects the selection of the second mode while operating in the first mode, it controls the control valve 23 after a predetermined period has elapsed since the detection of the selection of the second mode to increase the proportion of exhaust gas passing through the exhaust gas purification catalyst 21. In this embodiment, the proportion of exhaust gas passing through the exhaust gas purification catalyst 21 is set to 100%, and the proportion of exhaust gas passing through the bypass passage 22 is set to 0%.

[0081] If the exhaust gas passes through the exhaust gas purification catalyst 21 immediately upon receiving a switching instruction from the first mode to the second mode, then unless the main injection valve 15 is immediately deactivated, there is a possibility that catalyst poison components (sulfur components in this embodiment) derived from the first fuel (heavy oil, etc.) may pass through the exhaust gas purification catalyst 21. On the other hand, if the main injection valve 15 is immediately deactivated in response to the switching instruction from the first mode to the second mode, there is a concern that the combustion state will become unstable. If the combustion state becomes unstable, there is a concern that undesirable situations may occur, such as an excessive amount of unburned components (methane) of the gas fuel used in the second mode, which may adversely affect the exhaust gas purification catalyst 21. In this configuration, a predetermined grace period is provided after the switching instruction from the first mode to the second mode, so that the exhaust gas passes through the exhaust gas purification catalyst 21 after the grace period has elapsed. With such a configuration, the grace period can be used to switch the operation from the main injection valve 15 to the gas fuel supply valve 16 without immediately deactivating the main injection valve 15, thereby avoiding the occurrence of the undesirable situations described above.

[0082] [2-2. Control of the operation of the control valve] Figure 6 is a flowchart showing the flow of operation control for the control valve 23 of the engine system 100. The operation control process shown in Figure 6 starts when the engine system 100 is started.

[0083] In step S1, the controller 6 (an information acquisition unit, etc., not shown) acquires various types of information. This information includes setting information for the operating mode using the operating mode operation panel 142, and information necessary to determine whether or not the requirements for permission to use the exhaust gas purification catalyst 21 are met (permission requirement determination information). The permission requirement determination information includes, for example, information about the engine 1 (load factor information, misfire rate information for each cylinder, air-fuel ratio information, etc.), operating information of the EGR device 13, exhaust information (temperature, methane concentration information, etc.), and information about the catalyst system 2 (catalyst temperature, differential pressure information before and after the catalyst, information about the control valve 23, etc.). Once the various types of information are acquired, the process proceeds to the next step S2.

[0084] In step S2, the controller 6 (catalyst usage permission determination unit 63) uses the information acquired in step S1 to determine whether the operating mode is the second mode (gas mode). If the operating mode is the second mode (Yes in step S2), the process proceeds to the next step S3. On the other hand, if the operating mode is the first mode (diesel mode, etc.) (No in step S2), the process proceeds to step S6.

[0085] In step S3, the controller 6 (catalyst usage permission determination unit 63) determines whether the exhaust gas purification catalyst 21 meets the usage permission requirements. The usage requirements are as described above. If it is determined that the usage permission requirements are met (Yes in step S3), the process proceeds to the next step S4. If it is determined that the usage permission requirements are not met (No in step S3), the process proceeds to step S6.

[0086] In step S4, the controller 6 (exhaust flow state management unit 64) sets (determines) the pass-through ratio of the engine 1's exhaust to 100% for the exhaust purification catalyst 21 and 0% for the bypass passage. Once this setting is complete, the process proceeds to the next step S5.

[0087] In step S5, the controller 6 (exhaust flow state management unit 64) instructs the control valve 23 to achieve the pass-through ratio set in step S4. In this embodiment, the controller 6 instructs the control valve 23 via the catalyst ECU 241. In response to this instruction, the control valve 23 operates, and the exhaust from the engine 1 passes through the exhaust purification catalyst 21 and not through the bypass passage 22. Specifically, the catalyst upstream valve 231 and catalyst downstream valve 232 are opened to 100%, and the bypass upstream valve 233 is opened to 0%. Once the processing in step S5 is completed, the process returns to step S1, and the processing from step S1 onward is repeated.

[0088] In step S6, the controller 6 (exhaust flow state management unit 64) sets (determines) the pass-through ratio of the engine 1's exhaust to 0% for the exhaust purification catalyst 21 and 100% for the bypass passage. Once this setting is complete, the process proceeds to the next step S7.

[0089] In step S7, the controller 6 (exhaust flow state management unit 64) instructs the control valve 23 to achieve the pass-through ratio set in step S6. In this embodiment, the controller 6 instructs the control valve 23 via the catalyst ECU 241. In response to this instruction, the control valve 23 operates, and the exhaust from the engine 1 passes through the bypass passage 22 instead of the exhaust purification catalyst 21. Specifically, the catalyst upstream valve 231 and catalyst downstream valve 232 are opened to 0%, and the bypass upstream valve 233 is opened to 100%. Once the processing in step S7 is complete, the process returns to step S1, and the processing from step S1 onward is repeated.

[0090] As can be seen from the above explanation, in the engine system 100, even when operating in the second mode (gas mode), if the requirements for permission to use the exhaust purification catalyst 21 are not met, the exhaust from engine 1 may pass through the bypass passage 22 instead of the exhaust purification catalyst 21. However, if operation in the second mode is maintained, even if the exhaust passes through the bypass passage 22, the exhaust will return to passing through the exhaust purification catalyst 21 once the requirements for permission to use the exhaust purification catalyst 21 are met.

[0091] To give a specific example, when the controller 6 is operating in the second mode, if it detects that the load factor setting of the power generator 3 has changed by a predetermined value or more, it may be configured to control the control valve 23 to increase the proportion of exhaust passing through the exhaust bypass passage 22. Here, a change in the load factor of the power generator 3 by a predetermined value or more specifically means that the difference (absolute value) between the first load factor, which is the current load factor set on the load setting operation panel 312 (see Figure 5), and the second load factor, which was set immediately before, becomes a predetermined value or more.

[0092] When the load factor fluctuates significantly, the operation of engine 1 tends to become temporarily unstable. For example, when the load factor drops suddenly, the amount of unburned gaseous fuel may exceed the amount allowed by the exhaust gas purification catalyst 21. Also, for example, when the load factor increases suddenly, the amount of liquid fuel (heavy oil, etc.) injected by the pilot injection valve 17 may temporarily increase, and the SOx concentration in the exhaust may increase to a level where sulfur poisoning of the exhaust gas purification catalyst 21 cannot be ignored. In this respect, with the above configuration, even in the second mode, when the load factor fluctuates significantly, the exhaust gas can be prevented from passing through the exhaust gas purification catalyst 21, thereby suppressing the deterioration of the exhaust gas purification catalyst 21.

[0093] Furthermore, when the controller 6 detects that the load ratio of the engine 1 is below a predetermined load ratio during operation in the second mode, it may be configured to control the control valve 23 to increase the proportion of exhaust passing through the exhaust bypass passage 22. For example, the load ratio of the engine 1 may be a value calculated according to the setting information of the power generator 3. Alternatively, the load ratio of the engine 1 may be determined from torque information of the output shaft of the engine 1, etc.

[0094] If the load rate of engine 1 is too low, the excess air ratio in the combustion chamber may become too large, exceeding the flammability range of the gaseous fuel. When this occurs, the sulfur-containing fuel injected from the pilot injection valve 17 may be included in the exhaust gas in an unburned state, potentially causing sulfur poisoning of the exhaust gas purification catalyst 21. In this respect, the above configuration makes it possible to prevent the exhaust gas from passing through the exhaust gas purification catalyst 21 even in the second mode when the load rate of engine 1 is below a predetermined load rate, thereby suppressing the deterioration of the exhaust gas purification catalyst 21. In particular, in the configuration in which the load rate of engine 1 is acquired according to the setting information of the power generator 3, the possibility of sulfur poisoning can be quickly predicted from the setting information of the power generator 3, and the control valve 23 can be switched accordingly. This makes it possible to suppress the influence of equipment responsiveness and avoid sulfur poisoning of the exhaust gas purification catalyst 21.

[0095] Furthermore, the controller 6 may be configured to control the control valve 23 using the detection value of at least one of the intake pressure detection device (intake pressure sensor 741) and the oxygen concentration detection device (UEGO sensor 72). With such a configuration, it is possible to infer from the detection value that the air-fuel ratio is high and, even in the second mode, control the control valve 23 to increase the proportion of exhaust passing through the exhaust bypass passage 22. If the air-fuel ratio in the combustion chamber becomes too high, as described above, there is a concern about sulfur poisoning of the exhaust purification catalyst 21. In this regard, with this configuration, when it is inferred from the detection value of the intake pressure detection device, etc. that the air-fuel ratio is high, the control valve 23 can be switched so that the exhaust does not pass through the exhaust purification catalyst 21, thereby suppressing sulfur poisoning of the exhaust purification catalyst 21.

[0096] Furthermore, if the exhaust gas purification catalyst 21 is not used despite being in the second mode, it is preferable to notify the user of this. This allows the user to recognize that the exhaust gas purification catalyst 21 should be used but is unavailable, and to take appropriate action. In addition, if the exhaust gas purification catalyst 21 remains unusable for a predetermined period of time despite being in the second mode, the system may be configured to automatically switch from the second mode to the first mode.

[0097] [2-3. Specific examples of engine system operation] Figure 7 is a time chart showing specific examples of operation when switching from the first mode to the second mode, and from the second mode to the first mode. In the example shown in Figure 7, the first mode is the diesel mode, but the operation is generally similar even when the first mode is the mixed-fuel mode or backup mode.

[0098] In the example shown in Figure 7, at time t0, the engine system 100 is in diesel mode. In this case, the gas fuel supply valve 16 is in a deactivated state (OFF), and the main injector 15 and pilot injector 17 are in an activated state (ON). Note that the pilot injector 17 is used in both diesel and gas modes, so in the example shown in Figure 7, it is always ON. The catalyst usage permission requirement is not met because the operating mode is not gas mode (OFF). In diesel mode, the EGR device 13 is not used, so the opening of the EGR valve 131 is 0%. Liquid fuel such as heavy oil is used as fuel, and gaseous fuel is not used. To avoid sulfur poisoning of the exhaust gas purification catalyst 21, the percentage of engine 1 exhaust passing through the catalyst is 0%, and the percentage passing through the bypass passage is 100%.

[0099] At time t1, the operating mode (instructed mode) specified by the user is changed from diesel mode to gas mode, and the controller 6 detects the selection of gas mode. Upon detecting the selection of gas mode, the controller 6 begins preparations to switch to gas mode.

[0100] At time t2, the controller 6 confirms that the equipment related to the supply of gas fuel is functioning correctly and activates (turns on) the gas fuel supply valve 16. At this point, the controller 6 maintains the main injection valve 15 in the ON state. However, the controller 6 begins to gradually increase the supply amount of gas fuel (second fuel) and gradually decrease the supply amount of liquid fuel (first fuel).

[0101] At time t3, the controller 6 detects that the supply amounts of gaseous and liquid fuel, which had been gradually changing, have reached the target values, and stops the operation of the main injection valve 15 (turns it OFF). This completes the transition from diesel mode (first mode) to gas mode (second mode). In other words, when the controller 6 detects the selection of the second mode while operating in the first mode, it executes a transition mode in which the supply amount of first fuel by the first fuel supply unit is reduced while the supply amount of second fuel by the second fuel supply unit is increased, and then starts the second mode.

[0102] As shown in Figure 7, during the transition mode, the controller 6 controls the control valve 23 to prevent the engine 1 exhaust from passing through the exhaust purification catalyst 21. During the transition mode, the engine 1 exhaust contains a relatively large amount of sulfur components derived from liquid fuel. In this embodiment, since the exhaust is configured to prevent the passage of the exhaust through the exhaust purification catalyst 21 during the transition mode, sulfur poisoning of the exhaust purification catalyst 21 can be avoided.

[0103] Furthermore, as shown in Figure 7, the controller 6 increases the opening of the EGR valve 131 after the transition mode is completed. In other words, the EGR device 13 is put into use after the transition mode is completed.

[0104] At time t4, the controller 6 detects the operation of the EGR device 13 and also detects that the other catalyst usage permission requirements are met (catalyst usage permission requirements are turned ON). Accordingly, the controller 6 decides to set the flow state of the exhaust gas from engine 1 so that 100% passes through the exhaust purification catalyst 21 and 0% passes through the bypass passage 22. The controller 6 then instructs the catalyst ECU 241 of this decision. As a result, the catalyst ECU 241 controls the control valve 23 so that 100% of the exhaust gas from engine 1 passes through the catalyst and 0% passes through the bypass passage.

[0105] As can be seen from the above, the controller 6 increases the proportion of exhaust gas passing through the exhaust gas purification catalyst 21 after a predetermined time has elapsed since the transition from the first mode to the second mode was completed. This reduces the possibility of sulfur poisoning of the exhaust gas purification catalyst 21. In addition, the controller 6 controls the control valve 23 to increase the proportion of exhaust gas passing through the exhaust gas purification catalyst 21 after the opening of the EGR valve 131 is increased. Since the exhaust gas purification catalyst 21 is used after the operation of the EGR device 13, the possibility of a large amount of methane components passing through the exhaust gas purification catalyst 21 is reduced, and catalyst degradation can be suppressed.

[0106] In the example shown in Figure 7, at time t5, the instruction mode is changed from gas mode to diesel mode, and the controller 6 detects the selection of diesel mode. Accordingly, the controller 6 stops the operation of the gas fuel supply valve 16 (turns it OFF) and starts the operation of the main injection valve 15 (turns it ON). The controller 6 also turns OFF the catalyst usage permission requirement because it does not need to determine the catalyst usage permission requirement. The controller 6 also sets the opening of the EGR valve 131 to 0% in order to stop the operation of the EGR device 13. The controller 6 also immediately switches the supplied fuel from gas fuel to liquid fuel. The controller 6 also decides on the flow state of the exhaust gas from the engine 1, setting the pass rate through the exhaust purification catalyst 21 to 0% and the pass rate through the bypass passage 22 to 100%. The controller 6 then instructs the catalyst ECU 241 of this decision. As a result, the catalyst ECU 241 controls the control valve 23 to change the pass rate of the engine 1's exhaust gas through the catalyst to 0% and the pass rate through the bypass passage to 100%.

[0107] As can be seen from the above, when the controller 6 detects the selection of the first mode while operating in the second mode, it immediately completes the transition from the second mode to the first mode, unlike when switching from the first mode to the second mode. Also, when the controller 6 detects the selection of the first mode while operating in the second mode, it immediately controls the control valve 23 to increase the proportion of exhaust passing through the exhaust bypass passage 22. By configuring it in this way, the possibility of sulfur components passing through the exhaust purification catalyst 21 can be reduced as much as possible, and sulfur poisoning of the exhaust purification catalyst 21 can be suppressed.

[0108] <3. Things to keep in mind> Various technical features disclosed herein can be modified in various ways without departing from the spirit of the technical creation. Furthermore, the multiple embodiments, examples, and modifications shown herein may be combined as possible.

[0109] <4. Addendum> An exemplary engine system of the present invention comprises an engine having a first fuel supply unit that supplies a first fuel to a combustion chamber and a second fuel supply unit that supplies a second fuel to the combustion chamber; an exhaust gas purification catalyst disposed in the exhaust passage of the engine for purifying components derived from the second fuel; a bypass passage connected to the exhaust passage and avoiding passage through the exhaust gas purification catalyst; a control valve that adjusts the ratio of the engine's exhaust passing through the exhaust gas purification catalyst and the bypass passage; an EGR device connected to the exhaust passage upstream of the control valve for recirculating a portion of the exhaust gas to the engine's intake passage; and a controller that controls the control valve and the EGR device, wherein the system is configured to allow selection between a first mode in which the first fuel supply unit operates and a second mode in which the operation of the first fuel supply unit is stopped and the second fuel supply unit operates, and the controller may be configured to activate the EGR device when it detects the selection of the second mode, and to control the control valve to increase the ratio of the exhaust gas passing through the bypass passage when it detects the selection of the first mode while operating in the second mode (first configuration).

[0110] In the engine system of the first configuration described above, the controller may be configured such that, when it detects the selection of the second mode while operating in the first mode, it controls the control valve after a predetermined period of time has elapsed since the detection of the selection of the second mode to reduce the proportion of the exhaust passing through the bypass passage (second configuration).

[0111] The engine system according to the first or second configuration described above includes a power generation device that generates electricity using the output of the engine, and the controller may be configured to control the control valve to increase the proportion of the exhaust passing through the bypass passage when it detects that the load factor setting of the power generation device has changed by more than a predetermined value during operation in the second mode (third configuration).

[0112] In an engine system with any of the first to third configurations described above, the controller may be configured to control the control valve to increase the proportion of exhaust passing through the bypass passage when it detects that the load rate of the engine is below a predetermined load rate during operation in the second mode (fourth configuration).

[0113] An engine system according to any of the first to fourth configurations described above may include at least one of an intake pressure detection device provided in the intake passage of the engine and an oxygen concentration detection device arranged in the exhaust passage, and the controller may be configured to control the control valve using the detection value of at least one of the intake pressure detection device and the oxygen concentration detection device (fifth configuration).

[0114] In an engine system with any of the first to fifth configurations described above, the controller may, upon detecting the selection of the second mode while operating in the first mode, execute a transition mode in which the amount of first fuel supplied by the first fuel supply unit is reduced while the amount of second fuel supplied by the second fuel supply unit is increased, and then start the second mode, and during the execution of the transition mode, control the control valve to prevent the exhaust gas from passing through the exhaust gas purification catalyst (sixth configuration).

[0115] In the engine system of the sixth configuration described above, the EGR device may have an EGR valve, and the controller may increase the opening degree of the EGR valve after the transition mode is completed, and after the opening degree of the EGR valve is increased, control the control valve to increase the proportion of the exhaust gas that passes through the exhaust gas purification catalyst (seventh configuration).

[0116] In an engine system according to any of the above configurations 1 to 7, the first fuel may be a liquid fuel containing a sulfur component, the second fuel may be a gaseous fuel containing a methane component, and the exhaust gas purification catalyst may be a methane oxidation catalyst (configuration 8). [Explanation of Symbols]

[0117] 1. Engine 3. Power generation equipment 4. Exhaust passage 5. Air intake passage 6. Controller 13...EGR device 15. Main injection valve (first fuel supply unit) 16. Gas fuel supply valve (second fuel supply section) 21. Exhaust purifying catalyst 22... Bypass passage 23. Control valve 100... Engine System 131...EGR valve

Claims

1. An engine having a first fuel supply unit that supplies first fuel to the combustion chamber, and a second fuel supply unit that supplies second fuel to the combustion chamber, An exhaust gas purification catalyst is placed in the exhaust passage of the engine and purifies components derived from the second fuel, A bypass passage connected to the exhaust passage and avoiding passage through the exhaust purification catalyst, A control valve that adjusts the ratio of the exhaust gas of the engine passing through the exhaust gas purification catalyst and the bypass passage, An EGR device is connected to the exhaust passage upstream of the control valve and recirculates a portion of the exhaust gas into the engine's intake passage. A controller that controls the control valve and the EGR device, Equipped with, A first mode in which the first fuel supply unit operates, and a second mode in which the operation of the first fuel supply unit is stopped and the second fuel supply unit operates, are provided to be selectable. The engine system wherein the controller activates the EGR device when it detects the selection of the second mode, and when it detects the selection of the first mode while operating in the second mode, it controls the control valve to increase the proportion of the exhaust passing through the bypass passage.

2. The engine system according to claim 1, wherein the controller, when operating in the first mode, detects the selection of the second mode, controls the control valve after a predetermined period of time has elapsed since the detection of the selection of the second mode to reduce the proportion of the exhaust passing through the bypass passage.

3. The system includes a power generation device that generates electricity using the output of the aforementioned engine, The engine system according to claim 1, wherein when the controller detects that the load factor setting of the power generator has changed by more than a predetermined value while operating in the second mode, it controls the control valve to increase the proportion of the exhaust passing through the bypass passage.

4. The engine system according to claim 1, wherein when the controller detects that the load rate of the engine is below a predetermined load rate during operation in the second mode, it controls the control valve to increase the proportion of the exhaust passing through the bypass passage.

5. The engine comprises at least one of the following: an intake pressure detection device provided in the intake passage of the engine, and an oxygen concentration detection device arranged in the exhaust passage. The engine system according to claim 1, wherein the controller controls the control valve using the detection value of at least one of the air supply pressure detection device and the oxygen concentration detection device.

6. The aforementioned controller, When the selection of the second mode is detected during operation in the first mode, a transition mode is executed in which the amount of first fuel supplied by the first fuel supply unit is reduced while the amount of second fuel supplied by the second fuel supply unit is increased, and then the second mode is started. The engine system according to claim 1, wherein during the execution of the transition mode, the control valve is controlled to prevent the exhaust gas from passing through the exhaust gas purification catalyst.

7. The EGR device has an EGR valve, The aforementioned controller, After the transition mode is completed, the opening degree of the EGR valve is increased. The engine system according to claim 6, wherein, after increasing the opening of the EGR valve, the control valve is controlled to increase the proportion of the exhaust gas that passes through the exhaust gas purification catalyst.

8. The first fuel is a liquid fuel containing sulfur components. The second fuel is a gaseous fuel containing methane, The engine system according to any one of claims 1 to 7, wherein the exhaust gas purification catalyst is a methane oxidation catalyst.

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