Control device for internal combustion engine and control method for internal combustion engine

Abstract

To provide a control device and a control method for internal combustion engine which can perform control such that amounts of discharge of nitrogen oxide and ammonia satisfy limit values even when an environment condition changes.SOLUTION: A control device for an internal combustion engine includes: a nitrogen oxide acquiring unit for acquiring an amount of nitrogen oxide in exhaust gas discharged from the internal combustion engine; an ammonia amount acquiring unit for acquiring an amount of ammonia in the exhaust gas discharged from the internal combustion engine; and a flow rate control unit which gives a flow adjustment instruction to adjust a flow rate of combustion gas directed to the internal combustion engine, to a flow rate adjustment device which adjusts a flow rate of combustion gas introduced into the internal combustion engine, such that the nitrogen oxide amount acquired by the nitrogen oxide amount acquiring unit and the ammonia amount acquired by the ammonia amount acquiring unit do not exceed threshold values in a state where the internal combustion engine is being operated in a mixed combustion operation mode using both liquid fuel and ammonia gas as fuel.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a control device and a control method for an internal combustion engine.

Background Art

[0002] An internal combustion engine capable of a premixed combustion operation using both a liquid fuel such as light oil and ammonia gas as a fuel is known. For the internal combustion engine, an air excess ratio λ is set so that the emission amounts of nitrogen oxides and ammonia satisfy the limit values under standard environmental conditions and assumed operating conditions (including transient operating conditions), and the amount of air introduced into the internal combustion engine so as to achieve the set air excess ratio λ is controlled by a device capable of operating the amount of air (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The relationships between the emission amounts of nitrogen oxides and ammonia with respect to the air excess ratio λ can vary depending on changes in combustion states and exhaust gas catalyst performances associated with changes in environmental conditions and the like. For this reason, it is difficult to set the air excess ratio λ that can be established under various conditions. Further, in control to bring the air excess ratio λ closer to the set value, there is a risk that the emission amounts of nitrogen oxides and ammonia may exceed the limit values due to changes in environmental conditions and the like.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a control device and a control method for an internal combustion engine that can control the emission amounts of nitrogen oxides and ammonia to satisfy the limit values even when changes in environmental conditions and the like occur.

Means for Solving the Problems

[0006] A control device for an internal combustion engine according to at least one embodiment of the present disclosure is a control device for an internal combustion engine configured to control the operation of an internal combustion engine capable of switching between a plurality of operating modes, wherein the plurality of operating modes include a dedicated combustion operation mode using liquid fuel as the fuel to be used, and a mixed combustion operation mode using both the liquid fuel and ammonia gas as the fuel to be used, the control device of the internal combustion engine includes a nitrogen oxide amount acquisition unit configured to acquire the amount of nitrogen oxides in the exhaust gas discharged from the internal combustion engine, an ammonia amount acquisition unit configured to acquire the amount of ammonia in the exhaust gas discharged from the internal combustion engine, a flow rate control unit configured to give a flow rate adjustment instruction to adjust the flow rate of the combustion gas introduced into the internal combustion engine to the flow rate adjustment device configured to adjust the flow rate of the combustion gas introduced into the internal combustion engine so that each of the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit and the amount of ammonia acquired by the ammonia amount acquisition unit does not exceed a threshold value in a state where the internal combustion engine is operating in the mixed combustion operation mode.

[0007] A control method for an internal combustion engine according to at least one embodiment of the present disclosure is a control method for an internal combustion engine configured to control the operation of an internal combustion engine capable of switching between a plurality of operating modes, wherein the plurality of operating modes include a dedicated combustion operation mode using liquid fuel as the fuel to be used, and a mixed combustion operation mode using both the liquid fuel and ammonia gas as the fuel to be used, the control method of the internal combustion engine includes a nitrogen oxide amount acquisition step of acquiring the amount of nitrogen oxides in the exhaust gas discharged from the internal combustion engine, an ammonia amount acquisition step of acquiring the amount of ammonia in the exhaust gas discharged from the internal combustion engine, In a state where the internal combustion engine is operating in the co-firing operation mode, a flow rate control step is performed to give a flow rate adjustment instruction to a flow rate adjustment device configured to adjust the flow rate of combustion gas introduced into the internal combustion engine so that each of the amount of nitrogen oxides acquired in the nitrogen oxide amount acquisition step and the amount of ammonia acquired in the ammonia amount acquisition step does not exceed a threshold value.

Advantages of the Invention

[0008] According to at least one embodiment of the present disclosure, there is provided a control device and a control method for an internal combustion engine that can control the exhaust amounts of nitrogen oxides and ammonia to satisfy the limit values even when environmental conditions change or the like.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

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

[0011] (Internal Combustion Engine System) FIG. 1 is a schematic diagram of an internal combustion engine system 1 including a control device 3 for an internal combustion engine 2 according to an embodiment of the present disclosure. As shown in FIG. 1, the internal combustion engine system 1 includes an internal combustion engine (engine) 2 configured to generate power by burning fuel used therein, and a control device 3 configured to perform operation control and combustion control of the internal combustion engine 2. In the following embodiments, the case where the internal combustion engine 2 is a four-stroke engine will be described, but some embodiments of the present disclosure are also applicable to the case where the internal combustion engine 2 is a two-stroke engine.

[0012] (Internal Combustion Engine) As shown in FIG. 1, the internal combustion engine 2 includes at least one (a plurality in the illustrated example) cylinder 21. Each of the plurality of cylinders 21 has a combustion chamber 22 for burning the fuel used. Although not shown, the combustion chamber 22 is formed between a cylinder body and a piston housed inside the cylinder body.

[0013] The internal combustion engine 2 is configured to be able to switch between a plurality of operation modes. The plurality of operation modes include a dedicated combustion operation mode using liquid fuel as the fuel used, and a mixed combustion operation mode using both the liquid fuel and ammonia gas as the fuel used. When the internal combustion engine 2 is operating in the dedicated combustion operation mode, it is configured to burn liquid fuel and combustion gas in each combustion chamber 22 of the plurality of cylinders 21. When the internal combustion engine 2 is operating in the mixed combustion operation mode, it is configured to burn liquid fuel, ammonia gas, and combustion gas in each combustion chamber 22 of the plurality of cylinders 21. Specific examples of the liquid fuel include, for example, light oil, gasoline, bioethanol, and the like.

[0014] As shown in FIG. 1, the internal combustion engine 2 further includes a liquid fuel introduction line 4, a combustion gas introduction line 5, an ammonia gas introduction line 6, an exhaust gas discharge line 7, a plurality of liquid fuel side injectors 8, and a plurality of ammonia side injectors 9.

[0015] (Liquid fuel side injector) The plurality of liquid fuel side injectors 8 are for injecting liquid fuel into the combustion chambers 22 of the respective plurality of cylinders 21. The liquid fuel side injectors 8 are provided individually for each cylinder 21. Each of the plurality of liquid fuel side injectors 8 includes a fuel injection valve configured to inject liquid fuel into the corresponding combustion chamber 22.

[0016] (Liquid fuel introduction line) The liquid fuel introduction line 4 forms a flow path for supplying liquid fuel to each of the plurality of liquid fuel side injectors 8, and is formed by, for example, a pipe or the like. In the illustrated embodiment, the liquid fuel introduction line 4 includes a common rail 41 capable of storing liquid fuel, a plurality of branch pipes 42 for introducing liquid fuel from the common rail 41 to each of the plurality of liquid fuel side injectors 8, a liquid fuel pipe 44 for guiding liquid fuel from a liquid fuel supply source (for example, a storage tank for storing liquid fuel) 43 to the common rail 41, and a pressure boosting device (for example, a pressure boosting pump) 45 configured to boost the liquid fuel guided to the common rail 41.

[0017] One end of each of the plurality of branch pipes 42 is connected to the common rail 41, and the other end is connected to the liquid fuel side injector 8 corresponding to the branch pipe 42. One end of the liquid fuel pipe 44 is connected to the common rail 41, and the other end is connected to the liquid fuel supply source 43. The pressure boosting device 45 is provided on the liquid fuel pipe 44. In a state where the internal combustion engine 2 is operated in a dedicated combustion operation mode and a mixed combustion operation mode, the liquid fuel boosted by the pressure boosting device 45 is introduced into the liquid fuel side injector 8 via the liquid fuel introduction line 4.

[0018] (Combustion gas introduction line) The combustion gas introduction line 5 forms a flow path for guiding combustion gas to each of the plurality of combustion chambers 22, and is formed by, for example, piping or the like. In the illustrated embodiment, the combustion gas introduction line 5 includes a compressor 51 configured to boost the pressure of the combustion gas, a first combustion gas pipe 52 for guiding the combustion gas to the compressor 51, a second combustion gas pipe 53 for guiding the combustion gas from the compressor 51, and a plurality of air supply branch pipes 54 for introducing the combustion gas from the second combustion gas pipe 53 to each of the plurality of combustion chambers 22.

[0019] One end of each of the plurality of air supply branch pipes 54 is connected to a common second combustion gas pipe 53, and the other end is connected to the combustion chamber 22 corresponding to the air supply branch pipe 54. One end of each of the first combustion gas pipe 52 and the second combustion gas pipe 53 is connected to the compressor 51. The other end (upstream end) of the first combustion gas pipe 52 may be open to the atmosphere or may be connected to a storage tank for storing the combustion gas. In a state where the internal combustion engine 2 is operated in a dedicated combustion operation mode and a mixed combustion operation mode, the combustion gas boosted by the compressor 51 is introduced into each of the plurality of combustion chambers 22 via the combustion gas introduction line 5.

[0020] The internal combustion engine 2 may include a throttle valve (flow rate adjustment device) 55 configured to be able to adjust the flow rate of the combustion gas flowing through the second combustion gas pipe 53. The throttle valve 55 has a valve disposed in the second combustion gas pipe 53. The throttle valve 55 can increase the flow rate of the combustion gas flowing through the second combustion gas pipe 53 by increasing the opening degree of the valve, and can decrease the flow rate of the combustion gas flowing through the second combustion gas pipe 53 by decreasing the opening degree of the valve.

[0021] The internal combustion engine 2 may include an intercooler 56 for cooling the combustion gas flowing through the second combustion gas pipe 53. The intercooler 56 performs heat exchange between the combustion gas flowing through the second combustion gas pipe 53 and the cooling heat medium, and is configured to cool the combustion gas flowing through the second combustion gas pipe 53. In the illustrated embodiment, the intercooler 56 is disposed on the downstream side of the throttle valve 55 in the flow direction of the combustion gas.

[0022] (Ammonia-side injector) The plurality of ammonia-side injectors 9 are for injecting ammonia gas into the intake air side branch pipes 54 connected to the respective plurality of combustion chambers 22. The ammonia-side injectors 9 are provided individually for each intake air side branch pipe 54. Each of the plurality of ammonia-side injectors 9 includes a fuel injection valve configured to inject ammonia gas into the corresponding intake air side branch pipe 54.

[0023] (Ammonia gas introduction line) The ammonia gas introduction line 6 forms a flow path for supplying ammonia gas to each of the plurality of ammonia-side injectors 9, and is formed by, for example, a pipe or the like. In the illustrated embodiment, the ammonia gas introduction line 6 includes a supply source of ammonia gas (for example, a gas tank for storing ammonia gas) 61, an ammonia gas pipe 62 for guiding ammonia gas from the supply source 61 of ammonia gas, and a plurality of ammonia gas side branch pipes 63 for introducing ammonia gas from the ammonia gas pipe 62 to each of the plurality of ammonia-side injectors 9. Note that the supply source 61 of ammonia gas may store ammonia in a gaseous state or in a liquid state.

[0024] Each of the plurality of ammonia gas branch pipes 63 has one end connected to a common ammonia gas pipe 62, and the other end is connected to the ammonia side injector 9 corresponding to the ammonia gas branch pipe 63. One end of the ammonia gas pipe 62 is connected to a supply source 61 of ammonia gas. When the internal combustion engine 2 is operating in the premixed combustion mode, ammonia gas is introduced into each of the plurality of intake air branch pipes 54 via the ammonia gas introduction line 6 and the ammonia side injector 9. Then, the ammonia gas is introduced into the combustion chamber 22 in a mixed gas state mixed with the combustion gas and burns in the mixed gas state. In the illustrated embodiment, the ammonia gas stored in the supply source 61 of ammonia gas is at a higher pressure than the combustion chamber 22 which is the gas supply destination, and is introduced into the combustion chamber 22 via the ammonia gas introduction line 6 due to the pressure difference.

[0025] (Exhaust gas discharge line) The exhaust gas discharge line 7 forms a flow path through which the exhaust gas discharged from the internal combustion engine 2 flows, and is formed by, for example, a pipe or the like. In the illustrated embodiment, the exhaust gas discharge line 7 includes an exhaust gas pipe 71 for guiding the exhaust gas, and a plurality of exhaust gas branch pipes 72 for discharging the exhaust gas from each of the plurality of combustion chambers 22 to the exhaust gas pipe 71. One end of each of the plurality of exhaust gas branch pipes 72 is connected to a common exhaust gas pipe 71, and the other end is connected to the combustion chamber 22 corresponding to the exhaust gas branch pipe 72. The exhaust gas discharged from each of the plurality of combustion chambers 22 flows through the exhaust gas discharge line 7. When the internal combustion engine 2 is operating in the premixed combustion mode, nitrogen oxides and ammonia may be contained in the exhaust gas flowing through the exhaust gas discharge line 7.

[0026] The internal combustion engine 2 may include a turbine 73 provided in the exhaust gas discharge line 7 and configured to be driven by the exhaust gas flowing through the exhaust gas discharge line 7. In the illustrated embodiment, the turbine 73 is connected to one end of the exhaust gas pipe 71 and is configured to be driven by the exhaust gas guided through the exhaust gas pipe 71. The internal combustion engine 2 is equipped with a supercharger 11 including the above-described compressor 51, the above-described turbine 73, and a rotating shaft 74 that coaxially connects the compressor 51 and the turbine 73. The rotating shaft 74 has the turbine 73 attached to one side and the compressor 51 attached to the other side, and is configured to rotate together with the compressor 51 in conjunction with the rotation of the turbine 73. Further, the internal combustion engine 2 may include a generator 75 that is mechanically connected to the drive shaft of the turbine 73 and is configured to convert the rotational force of the turbine 73 into electric power.

[0027] The internal combustion engine 2 may include a denitration catalyst 77 for removing nitrogen oxides in the exhaust gas flowing through the exhaust gas discharge line 7 and an ammonia decomposition catalyst 78 for removing ammonia in the exhaust gas flowing through the exhaust gas discharge line 7. In the illustrated embodiment, the denitration catalyst 77 and the ammonia decomposition catalyst 78 are arranged on the downstream side of the turbine 73 in the flow direction of the exhaust gas in the exhaust gas discharge line 7. The exhaust gas discharge line 7 further includes an exhaust gas connection pipe 76 for guiding the exhaust gas from the turbine 73 to the denitration catalyst 77 and the ammonia decomposition catalyst 78, and an exhaust gas discharge pipe 79 for discharging the exhaust gas that has passed through the denitration catalyst 77 and the ammonia decomposition catalyst 78. The downstream end of the exhaust gas discharge pipe 79 may be open to the atmosphere or may be connected to a facility for discharging exhaust gas such as a chimney.

[0028] FIG. 2 is an explanatory diagram for explaining the relationship between the amount of nitrogen oxides in the exhaust gas, the amount of ammonia in the exhaust gas, and the air excess ratio. In FIG. 2, a graph is shown with the amount of nitrogen oxides in the exhaust gas (nitrogen oxide emission amount) flowing through the exhaust gas discharge line 7 on the vertical axis and the amount of ammonia in the exhaust gas (ammonia emission amount) flowing through the exhaust gas discharge line 7 on the horizontal axis. In the graph shown in FIG. 2, there are shown a target region A1 where both the nitrogen oxide emission amount and the ammonia emission amount are below the limit values, and a curve L1 showing the relationship between the nitrogen oxide emission amount and the ammonia emission amount with respect to the air excess ratio λ. As shown by the curve L1 in FIG. 2, when the air excess ratio λ is increased and the flow rate of the combustion gas introduced into the combustion chamber 22 is increased, the nitrogen oxide emission amount can be reduced, but the ammonia emission amount tends to increase. Also, when the air excess ratio λ is decreased and the flow rate of the combustion gas introduced into the combustion chamber 22 is decreased, the ammonia emission amount can be reduced, but the nitrogen oxide emission amount tends to increase.

[0029] FIG. 3 is an explanatory diagram for explaining the relationship between the exhaust gas temperature, the amount of ammonia in the exhaust gas, and the air excess ratio. In FIG. 3, a graph is shown with the temperature of the exhaust gas (exhaust gas temperature) flowing through the exhaust gas discharge line 7 on the vertical axis and the amount of ammonia in the exhaust gas (ammonia emission amount) flowing through the exhaust gas discharge line 7 on the horizontal axis. In the graph shown in FIG. 3, there are shown a target region A2 where both the exhaust gas temperature and the ammonia emission amount are below the limit values, and a curve L2 showing the relationship between the exhaust gas temperature and the ammonia emission amount with respect to the air excess ratio λ. As shown by the curve L2 in FIG. 3, when the air excess ratio λ is increased and the flow rate of the combustion gas introduced into the combustion chamber 22 is increased, the exhaust gas temperature can be reduced, but the ammonia emission amount tends to increase. Also, when the air excess ratio λ is decreased and the flow rate of the combustion gas introduced into the combustion chamber 22 is decreased, the ammonia emission amount can be reduced, but the exhaust gas temperature tends to increase.

[0030] The curves L1 shown in FIG. 2 and the curve L2 shown in FIG. 3 (the relationships between the exhaust gas temperature, nitrogen oxide emissions, and ammonia emissions with respect to the air excess ratio λ) can change according to changes in environmental conditions, unexpected transient operations, equipment deterioration, etc., as indicated by the arrows in the figures, in response to changes in the combustion state and exhaust gas catalyst performance. For example, when exhaust gas catalysts (denitration catalyst 77 and ammonia decomposition catalyst 78) are provided in the exhaust gas discharge line 7, these exhaust gas catalysts have a high temperature dependence and exhibit complex behaviors such as a sharp increase in nitrogen oxide emissions when the exhaust gas temperature increases when the air excess ratio λ is lowered. Therefore, even if the air excess ratio λ is determined so that the nitrogen oxide emissions and ammonia emissions satisfy the limit values (are below the limit values) under standard environmental conditions, and the flow rate of the combustion gas introduced into the combustion chamber 22 is adjusted to achieve this determined air excess ratio λ, there is a risk that the nitrogen oxide emissions and ammonia emissions may exceed the limit values. Also, it is difficult to pre-determine an air excess ratio λ that can cope with changes in environmental conditions, unexpected transient operations, equipment deterioration, etc.

[0031] The control device 3 of the internal combustion engine 2 is an electronic control unit that controls the operation of each device provided in the internal combustion engine 2, such as the liquid fuel side injector 8, the ammonia side injector 9, and the throttle valve 55 (flow rate adjustment device 10). The control device 3 may be configured as a microcomputer including a central processing unit (CPU) including a processor, a random access memory (RAM), a read only memory (ROM), and an I / O interface. In the illustrated embodiment, the control device 3 consists of an engine control unit. Note that in some other embodiments, the control device 3 may be implemented as one of the functions (programs and circuits) provided in the engine control unit. Also, in some other embodiments, the control device 3 may be configured as an electronic control unit different from the engine control unit.

[0032] As shown in FIG. 1, a control device 3 for an internal combustion engine 2 according to some embodiments includes a nitrogen oxide amount acquisition unit 31, an ammonia amount acquisition unit 32, and a flow rate control unit 33. The nitrogen oxide amount acquisition unit 31 is configured to acquire the amount of nitrogen oxides (nitrogen oxide emission amount) in the exhaust gas discharged from the internal combustion engine 2. The ammonia amount acquisition unit 32 is configured to acquire the amount of ammonia (ammonia emission amount) in the exhaust gas discharged from the internal combustion engine 2. A control method for an internal combustion engine 2 according to some embodiments includes a nitrogen oxide amount acquisition step of acquiring the nitrogen oxide emission amount and an ammonia amount acquisition step of acquiring the ammonia emission amount. In the following embodiments, the nitrogen oxide amount acquisition step is performed by the nitrogen oxide amount acquisition unit 31 of the control device 3, and the ammonia amount acquisition step is performed by the ammonia amount acquisition unit 32 of the control device 3.

[0033] In the illustrated embodiment, the internal combustion engine 2 includes a nitrogen oxide sensor 12 that measures the amount of nitrogen oxides in the exhaust gas flowing through the exhaust gas discharge line 7, and an ammonia sensor 13 that measures the amount of ammonia in the exhaust gas flowing through the exhaust gas discharge line 7. The amount of nitrogen oxides in the exhaust gas measured by the nitrogen oxide sensor 12 is sent from the nitrogen oxide sensor 12 to the nitrogen oxide amount acquisition unit 31 at all times. The amount of ammonia in the exhaust gas measured by the ammonia sensor 13 is sent from the ammonia sensor 13 to the ammonia amount acquisition unit 32 at all times. The nitrogen oxide sensor 12 and the ammonia sensor 13 are not limited to those that physically measure the amount of the detection target (nitrogen oxides, ammonia) in the exhaust gas, and may calculate the amount of the detection target in the exhaust gas by calculation or estimate it from the measurement values of other sensors.

[0034] While the internal combustion engine 2 is operating in the premixed combustion mode, the flow rate control unit 33 gives a flow rate adjustment instruction to adjust the flow rate of the combustion gas introduced into the internal combustion engine 2 so that the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 and the amount of ammonia acquired by the ammonia amount acquisition unit 32 do not exceed their respective threshold values. In the illustrated embodiment, the flow rate adjustment device 10 is the throttle valve 55 described above. However, in other embodiments, the flow rate adjustment device 10 may be a device provided with a flow rate adjustment mechanism other than the throttle valve 55. Specific examples of the device provided with the flow rate adjustment mechanism include an electric compressor (not shown) provided in the combustion gas introduction line 5 and a variable nozzle (not shown) that changes the exhaust gas passage area of a variable displacement supercharger provided in the exhaust gas discharge line 7. The control method for the internal combustion engine 2 according to some embodiments includes a flow rate control step of giving a flow rate adjustment instruction to adjust the flow rate of the combustion gas introduced into the internal combustion engine 2 to the flow rate adjustment device 10. In the following embodiments, the flow rate control step is performed by the flow rate control unit 33 of the control device 3.

[0035] When changes in environmental conditions or the like occur, the combustion state and the like also change. Therefore, the relationship between the emission amounts of nitrogen oxides and ammonia with respect to the air excess ratio λ always changes. The control device 3 uses, as control parameters for adjusting the flow rate of the combustion gas introduced into the internal combustion engine 2, the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 and the amount of ammonia acquired by the ammonia amount acquisition unit 32, rather than the air excess ratio λ. Such a control device 3 enables adjustment of the flow rate of the combustion gas so that the emission amounts of nitrogen oxides and ammonia satisfy the limit values even when changes in environmental conditions or the like occur.

[0036] As shown in FIG. 1, the internal combustion engine 2 may include a selection device (switch) 15 for manually selecting the operation mode of the internal combustion engine 2. The control device 3 is configured to perform operation control and combustion control of the internal combustion engine 2 according to information (signal) regarding the operation mode sent from the selection device 15. When the internal combustion engine 2 is operating in the premixed combustion operation mode, the control device 3 monitors the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 that changes moment by moment and the amount of ammonia acquired by the ammonia amount acquisition unit 32, respectively.

[0037] In some embodiments, as shown in FIG. 1, the above-described nitrogen oxide amount acquisition unit 31 is configured to acquire the amount of nitrogen oxides in the exhaust gas flowing on the downstream side of the denitration catalyst 77 for removing nitrogen oxides in the exhaust gas discharge line 7. In the illustrated embodiment, the nitrogen oxide sensor 12 is provided in the exhaust gas discharge pipe 79 through which the exhaust gas that has passed through the denitration catalyst 77 and the ammonia decomposition catalyst 78 flows, and is configured to measure the amount of nitrogen oxides in the exhaust gas flowing through the exhaust gas discharge pipe 79. The nitrogen oxide amount acquisition unit 31 acquires the measurement result of the nitrogen oxide sensor 12.

[0038] The amount of nitrogen oxides in the exhaust gas flowing on the downstream side of the denitration catalyst 77 in the exhaust gas discharge line 7 is equivalent to the nitrogen oxide emission amount actually discharged into the atmosphere. By using the amount of nitrogen oxides in the exhaust gas flowing on the downstream side of the denitration catalyst 77 in the exhaust gas discharge line 7 acquired by the nitrogen oxide amount acquisition unit 31 for control in the control device 3, the control device 3 can more appropriately perform control such that the nitrogen oxide emission amount satisfies the limit value.

[0039] In some embodiments, as shown in FIG. 1, the ammonia amount acquisition unit 32 described above is configured to acquire the amount of ammonia in the exhaust gas flowing downstream of the ammonia decomposition catalyst 78 for removing ammonia in the exhaust gas discharge line 7. In the illustrated embodiment, the ammonia sensor 13 is provided in the exhaust gas discharge pipe 79 through which the exhaust gas that has passed through the denitration catalyst 77 and the ammonia decomposition catalyst 78 flows, and is configured to measure the amount of ammonia in the exhaust gas flowing through the exhaust gas discharge pipe 79. The ammonia amount acquisition unit 32 acquires the measurement result of the ammonia sensor 13.

[0040] The amount of ammonia in the exhaust gas flowing downstream of the ammonia decomposition catalyst 78 in the exhaust gas discharge line 7 is equivalent to the ammonia discharge amount actually discharged into the atmosphere. By using the amount of ammonia in the exhaust gas flowing downstream of the ammonia decomposition catalyst 78 in the exhaust gas discharge line 7 acquired by the ammonia amount acquisition unit 32 for control in the control device 3, the control device 3 can more appropriately perform control such that the ammonia discharge amount satisfies the limit value.

[0041] FIG. 4 is a control flowchart of an internal combustion engine according to an embodiment of the present disclosure. The internal combustion engine 2 operates in a premixed combustion operation mode upon receiving an instruction to start the premixed combustion operation from the control device 3 (step S1).

[0042] (Flow rate reduction control) In some embodiments, as shown in FIG. 4, in a state where the above-described flow rate control unit 33 operates the internal combustion engine 2 in the premixed combustion operation mode, when the amount of nitrogen oxides ANO acquired by the nitrogen oxide amount acquisition unit 31 satisfies the flow rate reduction condition that the amount of nitrogen oxides is equal to or less than the first nitrogen oxide threshold value NOT1 (Yes in step S2), the flow rate control unit 33 gives a flow rate reduction instruction to the flow rate adjustment device 10 to reduce the flow rate of the combustion gas led to the internal combustion engine 2 (step S3). In a range where the amount of nitrogen oxides ANO acquired by the nitrogen oxide amount acquisition unit 31 does not exceed the first nitrogen oxide threshold value NOT1, the flow rate of the combustion gas led to the internal combustion engine 2 can be reduced. By reducing the flow rate of the combustion gas led to the internal combustion engine 2, the emission amount of ammonia can be reduced as much as possible while the emission amount of nitrogen oxides satisfies the limit value.

[0043] In the embodiment shown in FIG. 4, when the amount of nitrogen oxides ANO acquired by the nitrogen oxide amount acquisition unit 31 exceeds the first nitrogen oxide threshold value NOT1 (No in step S2), the control device 3 determines whether the amount of ammonia AA acquired by the ammonia amount acquisition unit 32 is equal to or less than the ammonia threshold value AT (step S4).

[0044] (Transition to the dedicated combustion operation mode) In some embodiments, the control device 3 of the internal combustion engine 2 includes a first operation mode control unit 34. As shown in FIG. 4, when the internal combustion engine 2 is operating in the premixed combustion operation mode, the first operation mode control unit 34 determines that the amount of nitrogen oxides ANO acquired by the nitrogen oxide amount acquisition unit 31 exceeds the first nitrogen oxide threshold value NOT1 ( "No" in step S2), and the amount of ammonia AA acquired by the ammonia amount acquisition unit 32 exceeds the ammonia threshold value AT ( "No" in step S4). When the premixed combustion operation stop condition including both of these conditions is satisfied, the operation mode of the internal combustion engine 2 is configured to be switched to the dedicated combustion operation mode. The internal combustion engine 2 receives an instruction from the control device 3, stops the premixed combustion operation, and shifts to the dedicated combustion operation (step S8). The control method of the internal combustion engine 2 according to some embodiments includes a first operation mode control step of switching the operation mode of the internal combustion engine 2 to the dedicated combustion operation mode when the above-described premixed combustion operation stop condition is satisfied. In the following embodiments, the first operation mode control step is performed by the first operation mode control unit 34 of the control device 3.

[0045] When the above-described premixed combustion operation stop condition is satisfied, in the flow rate adjustment of the combustion gas, it is difficult to continue the premixed combustion operation such that both the nitrogen oxide emission amount and the ammonia emission amount satisfy the limit values. When the control device 3 satisfies the above-described premixed combustion operation stop condition, the control device 3 promptly terminates the premixed combustion operation and switches to the dedicated combustion operation, thereby promptly improving (reducing) the nitrogen oxide emission amount and the ammonia emission amount.

[0046] (Flow Rate Increase Control) In some embodiments, as shown in FIG. 4, in a state where the above-described flow rate control unit 33 operates the internal combustion engine 2 in the premixed combustion operation mode, when the amount AA of ammonia acquired by the ammonia amount acquisition unit 32 is equal to or less than the ammonia threshold value AT ( “Yes” in step S4), and the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 exceeds the second nitrogen oxide threshold value NOT2 ( “Yes” in step S5), the flow rate control unit 33 is configured to give an instruction to increase the flow rate of the combustion gas led to the internal combustion engine 2 to the flow rate adjustment device 10 (step S6). The second nitrogen oxide threshold value NOT2 is the same as or greater than the first nitrogen oxide threshold value NOT1.

[0047] The control device 3 reduces the flow rate of the combustion gas led to the internal combustion engine 2 as much as possible so as to reduce the ammonia emission as much as possible, but the nitrogen oxide emission may suddenly increase due to changes in environmental conditions or the like. When the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 exceeds the second nitrogen oxide threshold value NOT2, by giving the above-described flow rate increase instruction, the flow rate of the combustion gas led to the internal combustion engine 2 can be increased so that the nitrogen oxide emission amount satisfies the limit value.

[0048] As shown in FIG. 4, when determining whether or not the flow rate increase condition is satisfied, if the amount AA of ammonia acquired by the ammonia amount acquisition unit 32 is equal to or less than the ammonia threshold value AT ( “Yes” in step S4), and the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 is less than the second nitrogen oxide threshold value NOT2 ( “No” in step S5), the control device 3 continues the premixed combustion operation without giving the above-described flow rate increase instruction (step S7).

[0049] In some of the above-described embodiments, the control device 3 adjusts the flow rate of the combustion gas introduced into the combustion chamber 22 so that the nitrogen oxide emission amount and the ammonia emission amount satisfy the limit values. If the temperature of the exhaust gas flowing through the exhaust gas discharge line 7 becomes excessively high, there is a risk of damage to the equipment, piping, etc. constituting the exhaust gas discharge line 7 due to the heat of the exhaust gas. Therefore, it is preferable that the control device 3 adjusts the flow rate of the combustion gas introduced into the combustion chamber 22 so that the exhaust gas temperature also satisfies the limit value.

[0050] In some embodiments, the control device 3 of the internal combustion engine 2 includes an exhaust gas temperature acquisition unit 35 configured to acquire the temperature of the exhaust gas flowing through the exhaust gas discharge line 7, as shown in FIG. 1. In the illustrated embodiment, the internal combustion engine 2 includes a temperature sensor 14 that measures the temperature of the exhaust gas flowing through the exhaust gas discharge line 7. The temperature of the exhaust gas measured by the temperature sensor 14 is sent to the exhaust gas temperature acquisition unit 35 at all times. The temperature sensor 14 is not limited to physically measuring the exhaust gas temperature, and may calculate the exhaust gas temperature or estimate it from the measured values of other sensors. The control device 3 monitors the exhaust gas temperature acquired by the exhaust gas temperature acquisition unit 35, which changes from moment to moment, when the internal combustion engine 2 is operating in the dual-fuel operation mode. The control method of the internal combustion engine 2 according to some embodiments includes an exhaust gas temperature acquisition step of acquiring the temperature of the exhaust gas flowing through the exhaust gas discharge line 7. In the following embodiments, the exhaust gas temperature acquisition step is performed by the exhaust gas temperature acquisition unit 35.

[0051] FIG. 5 is a control flowchart of an internal combustion engine according to an embodiment of the present disclosure. In some embodiments, the above-described flow rate reduction condition further includes a determination condition that the temperature GT of the exhaust gas acquired by the exhaust gas temperature acquisition unit 35 is equal to or lower than the first temperature threshold value TT1. That is, as shown in FIG. 5, the above-described flow rate control unit 33, in a state where the internal combustion engine 2 is operating in the premixed combustion mode, when the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 satisfies both the determination condition that the amount ANO of nitrogen oxides is equal to or lower than the first nitrogen oxide threshold value NOT1 and the determination condition that the temperature GT of the exhaust gas acquired by the exhaust gas temperature acquisition unit 35 is equal to or lower than the first temperature threshold value TT1 (in step S2, “Yes”), the flow rate reduction instruction for reducing the flow rate of the combustion gas introduced into the internal combustion engine 2 is given to the flow rate adjustment device 10 (step S3).

[0052] In this case, within a range where the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 does not exceed the first nitrogen oxide threshold value NOT1 and the temperature GT of the exhaust gas acquired by the exhaust gas temperature acquisition unit 35 does not exceed the first temperature threshold value TT1, the flow rate of the combustion gas introduced into the internal combustion engine 2 can be reduced. By reducing the flow rate of the combustion gas introduced into the internal combustion engine 2, the emission amount of nitrogen oxides and the temperature of the exhaust gas can satisfy the limit values, and the emission amount of ammonia can be reduced as much as possible. The control device 3 can suppress damage to the devices and pipes constituting the exhaust gas discharge line 7 due to the heat of the exhaust gas by performing control so that the temperature of the exhaust gas satisfies the limit value.

[0053] In the embodiment shown in FIG. 5, when the control device 3 satisfies either the determination condition that the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 exceeds the first nitrogen oxide threshold value NOT1 or the determination condition that the temperature GT of the exhaust gas acquired by the exhaust gas temperature acquisition unit 35 exceeds the first temperature threshold value TT1 (in step S2, “No”), it is configured to determine whether the amount AA of ammonia acquired by the ammonia amount acquisition unit 32 is equal to or lower than the ammonia threshold value AT (step S4).

[0054] In the embodiment shown in FIG. 5, in a state where the above-described first operation mode control unit 34 operates the internal combustion engine 2 in the premixed combustion operation mode, when the determination condition that the temperature GT of the exhaust gas acquired by the exhaust gas temperature acquisition unit 35 exceeds the first temperature threshold value TT1 ( "No" in step S2) and the determination condition that the amount AA of ammonia acquired by the ammonia amount acquisition unit 32 exceeds the ammonia threshold value AT ( "No" in step S4) are satisfied, the operation mode of the internal combustion engine 2 is configured to be switched to the dedicated combustion operation mode. The internal combustion engine 2 receives an instruction from the control device 3, stops the premixed combustion operation, and shifts to the dedicated combustion operation (step S8).

[0055] In some embodiments, as shown in FIG. 5, in a state where the above-described flow rate control unit 33 operates the internal combustion engine 2 in the premixed combustion operation mode, when the determination condition that the amount AA of ammonia acquired by the ammonia amount acquisition unit 32 is less than or equal to the ammonia threshold value AT ( "Yes" in step S4) and the determination condition that the temperature GT of the exhaust gas acquired by the exhaust gas temperature acquisition unit 35 exceeds the second temperature threshold value TT2 ( "Yes" in step S5) are satisfied, the flow rate control unit 33 is configured to give an instruction to increase the flow rate of the combustion gas guided to the internal combustion engine 2 to the flow rate adjustment device 10 (step S6). The second temperature threshold value TT2 is the same as or greater than the first temperature threshold value TT1.

[0056] In the embodiment shown in FIG. 5, when the internal combustion engine 2 is operating in the dual-fuel operation mode, the flow rate control unit 33 issues a flow rate increase instruction to increase the flow rate of the combustion gas led to the internal combustion engine 2 with respect to the flow rate adjustment device 10 even when the following flow rate increase conditions including both the determination condition that the amount AA of ammonia acquired by the ammonia amount acquisition unit 32 is less than or equal to the ammonia threshold value AT (Yes in step S4) and the determination condition that the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 exceeds the second nitrogen oxide threshold value NOT2 (Yes in step S5) are satisfied. In other words, the flow rate control unit 33 is configured to issue the above flow rate increase instruction (step S6) when any of the above determination conditions regarding the exhaust gas temperature GT or the above determination conditions regarding the amount ANO of nitrogen oxides is satisfied (Yes in step S5) and the above determination conditions regarding the amount AA of ammonia are satisfied (Yes in step S4) in a state where the internal combustion engine 2 is operating in the dual-fuel operation mode.

[0057] The control device 3 reduces the flow rate of the combustion gas led to the internal combustion engine 2 as much as possible so as to reduce the ammonia emission amount as much as possible, but the exhaust gas temperature may rapidly increase due to changes in environmental conditions or the like. When the exhaust gas temperature GT acquired by the exhaust gas temperature acquisition unit 35 exceeds the second temperature threshold value TT2, the flow rate of the combustion gas led to the internal combustion engine 2 can be increased so that the exhaust gas temperature GT satisfies the limit value.

[0058] As shown in FIG. 5, when determining whether or not the flow rate increase conditions are satisfied, if the amount AA of ammonia acquired by the ammonia amount acquisition unit 32 is less than or equal to the ammonia threshold value AT (Yes in step S4), the amount ANO of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit 31 is less than the second nitrogen oxide threshold value NOT2, and the exhaust gas temperature GT acquired by the exhaust gas temperature acquisition unit 35 is less than the second temperature threshold value TT2 (No in step S5), the control device 3 continues the dual-fuel operation without issuing the above flow rate increase instruction (step S7).

[0059] In some embodiments, as shown in FIG. 1, the exhaust gas temperature acquisition unit 35 described above is configured to acquire the temperature of the exhaust gas flowing upstream of the turbine 73 in the exhaust gas discharge line 7. In the illustrated embodiment, the temperature sensor 14 is provided in the exhaust gas pipe 71 and measures the temperature of the exhaust gas flowing through the exhaust gas pipe 71. The exhaust gas temperature acquisition unit 35 acquires the measurement result of the temperature sensor 14.

[0060] The upstream side of the turbine 73 in the exhaust gas discharge line 7 is at a higher temperature than the downstream side of the turbine 73. By using the temperature of the exhaust gas flowing upstream of the turbine 73 in the relatively high-temperature exhaust gas discharge line 7 for the control in the control device 3, the control device 3 can perform the control such that the exhaust gas temperature satisfies the limit value more appropriately. Thereby, damage due to the heat of the exhaust gas of the equipment, piping, etc. constituting the exhaust gas discharge line 7 can be more effectively suppressed.

[0061] In some embodiments, as shown in FIG. 1, the control device 3 of the internal combustion engine 2 includes a parameter acquisition unit 36, an association information acquisition unit 37, and an operation condition determination unit 38. The control method of the internal combustion engine 2 according to some embodiments includes a parameter acquisition step of acquiring a plurality of parameters related to the operation state of the internal combustion engine 2, an association information acquisition step of acquiring association information associating the plurality of parameters with the operation conditions enabling the co-firing operation mode, and an operation condition determination step of determining, based on the association information, whether or not the plurality of parameters acquired in the parameter acquisition step satisfy the operation conditions enabling the co-firing operation mode. In the following embodiments, the parameter acquisition step is performed by the parameter acquisition unit 36. The association information acquisition step is performed by the association information acquisition unit 37. The operation condition determination step is performed by the operation condition determination unit 38.

[0062] The parameter acquisition unit 36 is configured to acquire a plurality of parameters related to the operating state of the internal combustion engine 2. The parameter acquisition unit 36 is adapted to acquire the plurality of parameters from the internal combustion engine 2, devices mounted on the internal combustion engine 2, sensors, etc. The sensors for acquiring parameters are not limited to those that physically measure parameters, and may be those calculated by calculation or estimated from the measured values of other sensors. The plurality of parameters related to the operating state of the internal combustion engine 2 include parameters related to the rotational speed of the internal combustion engine 2 and parameters related to the load of the internal combustion engine 2. Specifically, as the above parameters, the rotational speed of the internal combustion engine 2, the load of the internal combustion engine 2, the fuel injection amount of the liquid fuel side injector 8, the intake pressure (such as the pressure on the downstream side of the throttle valve 55 in the flow direction of the combustion gas in the second combustion gas pipe 53), the output of the generator 75, etc. are included.

[0063] The association information acquisition unit 37 is configured to acquire association information that associates a plurality of parameters with operating conditions under which a mixed combustion operation mode is possible. The above association information indicates the correspondence between the plurality of parameters and the operating conditions under which a mixed combustion operation mode is possible, and when two or more types of a plurality of parameters are input information, the operating conditions corresponding to the plurality of parameters as the input information can be acquired as output information regarding whether or not they are operating conditions under which a mixed combustion operation mode is possible. The above association information includes a list, table, map, function, machine learning model, etc. that indicate the correspondence between the input information and the output information. The above association information may be created based on steady test data, or may be created based on past performance values, experimental values, numerical analysis results, etc. other than steady test data.

[0064] FIG. 7 is a control flowchart of an internal combustion engine according to an embodiment of the present disclosure. In a state where the internal combustion engine 2 is operating in the dedicated combustion operation mode (the portion surrounded by the dotted line in FIG. 7), the operation condition determination unit 38 determines whether or not the plurality of parameters acquired by the parameter acquisition unit 36 satisfy the operation conditions based on the association information acquired by the association information acquisition unit 37 (step S9).

[0065] When the operation condition determination unit 38 operates the internal combustion engine 2 in the dedicated combustion operation mode, it monitors the plurality of parameters acquired by the parameter acquisition unit 36 that changes moment by moment, and determines whether or not the operation conditions enabling the mixed combustion operation mode are satisfied.

[0066] FIG. 6 is an explanatory diagram for explaining a control map showing the relationship between the rotational speed and load of the internal combustion engine 2 according to an embodiment of the present disclosure and the operation conditions enabling the mixed combustion operation. In some embodiments, the above-described association information is a control map showing the relationship between a plurality of parameters and the operation conditions enabling the mixed combustion operation mode as shown in FIG. 6, and includes a control map in which a region A3 enabling the mixed combustion operation mode is set on a map constituted by a plurality of parameters. The above-described operation condition determination unit 38 is configured to determine whether or not the plurality of parameters acquired by the parameter acquisition unit 36 satisfy the operation conditions by referring to the above control map.

[0067] FIG. 6 shows a two-dimensional map with the rotational speed of the internal combustion engine 2, which is one of the above parameters, on the horizontal axis and the load of the internal combustion engine 2, which is one of the above parameters, on the vertical axis. In the two-dimensional map shown in FIG. 6, a region A3 enabling the mixed combustion operation mode under standard environmental conditions and a line L3 indicating the specified maximum torque are preset. By referring to the two-dimensional map shown in FIG. 6, the operation condition determination unit 38 can determine whether or not the operation state of the internal combustion engine 2 enables the mixed combustion operation mode (whether or not it belongs to the region A3) from the rotational speed and load of the internal combustion engine 2 acquired by the parameter acquisition unit 36.

[0068] When determining whether the plurality of parameters acquired by the parameter acquisition unit 36 satisfy the operating conditions, the operating condition determination unit 38 may refer to a two-dimensional map in which at least one parameter is different from the two-dimensional map shown in FIG. 6, a three-dimensional map showing the relationship between three types of parameters and the operating conditions enabling the co-firing operation mode, and association information other than the control map. The operating condition determination unit 38 may refer to the association information stored in the storage unit 30 of the control device 3, or may refer to the association information stored in a device external to the control device 3.

[0069] In the operating condition determination unit 38, it can be determined whether the plurality of parameters acquired by the parameter acquisition unit 36 satisfy the operating conditions enabling the co-firing operation mode. When the determination result in the operating condition determination unit 38 is favorable, the control device 3 permits the switching operation to the co-firing operation mode, thereby suppressing the attempt of co-firing operation in an operating state where there is no expectation of the establishment of the co-firing operation mode and the wasteful discharge of ammonia. Further, by using a control map in which an area where the co-firing operation mode is possible is set under standard environmental conditions for the determination in the operating condition determination unit 38, it is possible to appropriately and quickly determine whether the operating state of the internal combustion engine 2 is appropriate for the co-firing operation mode.

[0070] In some embodiments, as shown in FIG. 1, the control device 3 of the internal combustion engine 2 includes a second operation mode control unit 39. As shown in FIG. 7, the second operation mode control unit 39 is configured to switch the operation mode of the internal combustion engine 2 to the dual-fuel operation mode when the dual-fuel operation possible condition including the determination condition that the above-described plurality of parameters satisfy the operation conditions enabling the dual-fuel operation mode is satisfied in a state where the internal combustion engine 2 is operating in the dedicated-fuel operation mode. The second operation mode control unit 39 of the control device 3 may be configured to automatically switch the operation mode of the internal combustion engine 2 to the dual-fuel operation mode when the dual-fuel operation possible condition is satisfied. The internal combustion engine 2 is configured to receive an instruction from the control device 3, stop the dedicated-fuel operation, and shift to the dual-fuel operation (step S10). The control method of the internal combustion engine 2 according to some embodiments includes a second operation mode control step of switching the operation mode of the internal combustion engine 2 to the dual-fuel operation mode when it is determined in the operation condition determination step that the dual-fuel operation possible condition is satisfied. In the following embodiments, the second operation mode control step is performed by the second operation mode control unit 39 of the control device 3.

[0071] The dual-fuel operation possible condition may further include a determination condition that the dual-fuel operation mode is selected in the selection device. In this case, the second operation mode control unit 39 of the control device 3 is configured to switch the operation mode of the internal combustion engine 2 to the dual-fuel operation mode when the dual-fuel operation mode is manually selected in the selection device in a state where the above-described plurality of parameters satisfy the operation conditions enabling the dual-fuel operation mode (step S10).

[0072] When the determination result in the operation condition determination unit 38 is good, the control device 3 permits the switching operation to the co-firing operation mode, so that when the operation state of the internal combustion engine 2 is in a state appropriate for the co-firing operation mode, the switching to the co-firing operation mode can be performed. Note that even after the co-firing operation mode is not established and the dedicated firing operation mode is switched, the control device 3 can return to the co-firing operation mode when the determination result in the operation condition determination unit 38 is good. Further, the control device 3 may limit the permission of the switching operation to the co-firing operation mode only when the determination result in the operation condition determination unit 38 is good even when first attempting to switch to the co-firing operation mode after driving the internal combustion engine 2.

[0073] The above-described storage unit 30 may store the above-described threshold values (the first nitrogen oxide threshold value NOT1, the second nitrogen oxide threshold value NOT2, the ammonia threshold value AT, the first temperature threshold value TT1, the second temperature threshold value TT2). Each part (the flow rate control unit 33, the first operation mode control unit 34, the second operation mode control unit 39) of the above-described control device 3 may refer to the above-described threshold values stored in the storage unit 30.

[0074] In this specification, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent a state of being relatively displaced with tolerances or at an angle or distance such that the same function can be obtained. For example, expressions representing that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent a state in which there are tolerances or differences such that the same function can be obtained. Further, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent the shapes such as a rectangular shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. Further, in this specification, the expression that one component "comprises", "includes", or "has" is not an exclusive expression excluding the existence of other components.

[0075] The present disclosure is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0076] The content described in some of the above-described embodiments is understood as follows, for example.

[0077] 1) The control device (3) of the internal combustion engine (2) according to at least one embodiment of the present disclosure is a control device (3) of an internal combustion engine (2) for controlling the operation of the internal combustion engine (2) configured to be able to switch between a plurality of operation modes, wherein the plurality of operation modes include a dedicated combustion operation mode using liquid fuel as the fuel to be used, and a mixed combustion operation mode using both the liquid fuel and ammonia gas as the fuel to be used, and the control device (3) of the internal combustion engine (2) includes a nitrogen oxide amount acquisition unit (31) configured to acquire the amount of nitrogen oxides in the exhaust gas discharged from the internal combustion engine (2), an ammonia amount acquisition unit (32) configured to acquire the amount of ammonia in the exhaust gas discharged from the internal combustion engine (2), and a flow rate control unit (33) configured to give a flow rate adjustment instruction to adjust the flow rate of the combustion gas introduced into the internal combustion engine (2) to the flow rate adjustment device (10) configured to adjust the flow rate of the combustion gas introduced into the internal combustion engine (2) so that each of the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit (31) and the amount of ammonia acquired by the ammonia amount acquisition unit (32) does not exceed a threshold value in a state where the internal combustion engine (2) is operating in the mixed combustion operation mode.

[0078] According to the configuration of 1) above, when changes in environmental conditions or the like occur, the combustion state and the like also change. Therefore, the relationship between the emission amount of nitrogen oxides and the emission amount of ammonia with respect to the air excess ratio always changes. The control device (3) uses the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit (31) and the amount of ammonia acquired by the ammonia amount acquisition unit (33) as control parameters for adjusting the flow rate of the combustion gas introduced into the internal combustion engine (2), rather than the air excess ratio. Such a control device (3) enables adjustment of the flow rate of the combustion gas so that the emission amounts of nitrogen oxides and ammonia satisfy the limit values even when changes in environmental conditions or the like occur.

[0079] 2) In some embodiments, it is the control device (3) of the internal combustion engine (2) described in 1) above, The flow rate control unit (33) In a state where the internal combustion engine (2) is operating in the co-firing operation mode, when the amount of nitrogen oxides (ANO) acquired by the nitrogen oxide amount acquisition unit (31) satisfies a flow rate reduction condition including at least a determination condition that the amount of nitrogen oxides is equal to or less than a first nitrogen oxide threshold value (NOT1), the flow rate adjustment device (10) is configured to give an instruction to reduce the flow rate of the combustion gas introduced into the internal combustion engine (2).

[0080] According to the configuration of 2) above, within a range where the amount of nitrogen oxides (ANO) acquired by the nitrogen oxide amount acquisition unit (31) does not exceed the first nitrogen oxide threshold value (NOT1), the flow rate of the combustion gas introduced into the internal combustion engine (2) can be reduced. By reducing the flow rate of the combustion gas introduced into the internal combustion engine (2), the emission amount of nitrogen oxides can satisfy the limit value while minimizing the emission amount of ammonia.

[0081] 3) In some embodiments, it is the control device (3) of the internal combustion engine (2) described in 1) above, The flow rate control unit (33) In a state where the internal combustion engine is operating in the co - firing operation mode, when the flow - rate increase condition including both the determination condition that the amount of ammonia (AA) acquired by the ammonia amount acquisition unit (32) is less than or equal to the ammonia threshold value (AT), and the determination condition that the amount of nitrogen oxides (ANO) acquired by the nitrogen oxide amount acquisition unit (31) exceeds a second nitrogen oxide threshold value (NOT2) which is equal to or greater than the first nitrogen oxide threshold value (NOT1) is satisfied, a flow - rate increase instruction for increasing the flow rate of the combustion gas led to the internal combustion engine (2) is given to the flow - rate adjustment device (10).

[0082] According to the configuration of 3) above, when the amount of nitrogen oxides (ANO) acquired by the nitrogen oxide amount acquisition unit (31) exceeds the second nitrogen oxide threshold value (NOT2), the flow rate of the combustion gas led to the internal combustion engine (2) can be increased so that the emission amount of nitrogen oxides satisfies the limit value.

[0083] 4) In some embodiments, a control device (3) for the internal combustion engine (2) described in any one of 1) to 3) above, In a state where the internal combustion engine (2) is operating in the co - firing operation mode, when the co - firing operation stop condition including both the determination condition that the amount of nitrogen oxides (ANO) acquired by the nitrogen oxide amount acquisition unit (31) exceeds the first nitrogen oxide threshold value (NOT1), and the determination condition that the amount of ammonia (AA) acquired by the ammonia amount acquisition unit (32) exceeds the ammonia threshold value (AT) is satisfied, it further includes a first operation mode control unit (34) configured to switch the operation mode of the internal combustion engine (2) to the dedicated - firing operation mode.

[0084] According to the configuration of 4) above, when the co-firing operation stop condition is satisfied, in the flow rate adjustment of the combustion gas, it is difficult to continue the co-firing operation such that both the nitrogen oxide emission amount and the ammonia emission amount satisfy the limit values. When the co-firing operation stop condition is satisfied, the control device (3) promptly terminates the co-firing operation and switches to the dedicated firing operation, thereby enabling prompt improvement (reduction) of the nitrogen oxide emission amount and the ammonia emission amount.

[0085] 5) In some embodiments, it is the control device (3) of the internal combustion engine (2) described in 2) or 3) above, further comprising an exhaust gas temperature acquisition unit (35) configured to acquire the temperature of the exhaust gas, wherein the flow rate reduction condition further includes a determination condition that the temperature (GT) of the exhaust gas acquired by the exhaust gas temperature acquisition unit (35) is equal to or lower than a first temperature threshold value (TT1).

[0086] According to the configuration of 5) above, within a range where the amount of nitrogen oxides (ANO) acquired by the nitrogen oxide amount acquisition unit (31) does not exceed the first nitrogen oxide threshold value (NOT1) and the temperature (GT) of the exhaust gas acquired by the exhaust gas temperature acquisition unit (35) does not exceed the first temperature threshold value (TT1), the flow rate of the combustion gas introduced into the internal combustion engine (2) can be reduced. By reducing the flow rate of the combustion gas introduced into the internal combustion engine (2), while the nitrogen oxide emission amount and the exhaust gas temperature satisfy the limit values, the ammonia emission amount can be reduced as much as possible. The control device (3) performs control such that the temperature of the exhaust gas satisfies the limit value, thereby suppressing damage to devices, pipes, etc. constituting the exhaust gas discharge line (7) through which the exhaust gas discharged from the internal combustion engine (2) flows due to the heat of the exhaust gas.

[0087] 6) In some embodiments, it is the control device (3) of the internal combustion engine (2) described in 5) above, wherein the flow rate control unit (33) In a state where the internal combustion engine (2) is operating in the co-firing operation mode, when the determination condition that the amount of ammonia (AA) acquired by the ammonia amount acquisition unit (32) is equal to or less than the ammonia threshold value (AT) and the determination condition that the temperature of the exhaust gas (GT) acquired by the exhaust gas temperature acquisition unit (35) exceeds the second temperature threshold value (TT2) which is the same as or greater than the first temperature threshold value (TT1) are both satisfied, it is configured to give an instruction to increase the flow rate of the combustion gas guided to the internal combustion engine (2) to the flow rate adjustment device (10).

[0088] According to the configuration of 6) above, when the temperature of the exhaust gas (GT) acquired by the exhaust gas temperature acquisition unit (35) exceeds the second temperature threshold value (TT2), the flow rate of the combustion gas guided to the internal combustion engine (2) can be increased so that the temperature of the exhaust gas (GT) satisfies the limit value.

[0089] 7) In some embodiments, it is a control device (3) for the internal combustion engine (2) described in any one of 1) to 6) above, a parameter acquisition unit (36) that acquires a plurality of parameters related to the operating state of the internal combustion engine (2); an association information acquisition unit (37) that acquires association information associating the plurality of parameters with the operating conditions in which the co-firing operation mode is possible; and a driving condition determination unit (38) that determines whether or not the plurality of parameters acquired by the parameter acquisition unit (36) satisfy the driving conditions based on the association information acquired by the association information acquisition unit (37) in a state where the internal combustion engine (2) is operating in the dedicated firing operation mode.

[0090] According to the configuration of 7) above, in the operation condition determination unit (38), it can be determined whether or not the plurality of parameters acquired by the parameter acquisition unit (36) satisfy the operation conditions enabling the co-firing operation mode. When the determination result in the operation condition determination unit (38) is good, the control device (3) permits the switching operation to the co-firing operation mode, thereby suppressing the attempt of co-firing operation in an operation state where there is no expectation of the establishment of the co-firing operation mode and discharging ammonia wastefully.

[0091] 8) In some embodiments, it is the control device (3) of the internal combustion engine (2) described in 7) above, In a state where the internal combustion engine (2) is operating in the dedicated firing operation mode, when the co-firing operation possible condition including the determination condition that the plurality of parameters satisfy the operation conditions is satisfied, it further includes a second operation mode control unit (39) configured to switch the operation mode of the internal combustion engine (2) to the co-firing operation mode.

[0092] According to the configuration of 8) above, when the determination result in the operation condition determination unit (38) is good, the control device (3) permits the switching operation to the co-firing operation mode, so that when the operation state of the internal combustion engine (2) is appropriate for the co-firing operation mode, the switching to the co-firing operation mode can be performed. Note that even after the co-firing operation mode fails to be established and the operation mode is switched to the dedicated firing operation mode, when the determination result in the operation condition determination unit (38) is good, the control device (3) can return to the co-firing operation mode.

[0093] 9) In some embodiments, it is the control device (3) of the internal combustion engine (2) described in 7) or 8) above, The associated information is a control map showing the relationship between the plurality of parameters and the operation conditions, and includes a control map in which a region where the co-firing operation mode is possible is set on a map constituted by the plurality of parameters.

[0094] According to the configuration of the above (9), by using a control map in which an area where the co-firing operation mode is possible under standard environmental conditions is set for the determination in the operation condition determination unit (38), it is possible to appropriately and quickly determine whether the operation state of the internal combustion engine (2) is in a state appropriate for the co-firing operation mode.

[0095] 10) In some embodiments, it is a control device (3) of the internal combustion engine (2) described in any one of the above (1) to (9), The nitrogen oxide amount acquisition unit (31) is configured to acquire the amount of nitrogen oxides in the exhaust gas flowing through the downstream side of a denitration catalyst (77) for removing the nitrogen oxides in an exhaust gas discharge line (7) through which the exhaust gas discharged from the internal combustion engine (2) flows.

[0096] According to the configuration of the above (10), the amount of nitrogen oxides in the exhaust gas flowing through the downstream side of the denitration catalyst (77) in the exhaust gas discharge line (7) is equivalent to the nitrogen oxide emission amount actually discharged into the atmosphere. By using the amount of nitrogen oxides in the exhaust gas flowing through the downstream side of the denitration catalyst (77) in the exhaust gas discharge line (7) acquired by the nitrogen oxide amount acquisition unit (31) for the control in the control device (3), it becomes possible for the control device (3) to more appropriately perform control such that the nitrogen oxide emission amount satisfies the limit value.

[0097] 11) In some embodiments, it is a control device (3) of the internal combustion engine (2) described in any one of the above (1) to (10), The ammonia amount acquisition unit (32) is configured to acquire the amount of ammonia in the exhaust gas flowing through the downstream side of an ammonia decomposition catalyst (78) for removing the ammonia in an exhaust gas discharge line (7) through which the exhaust gas discharged from the internal combustion engine (2) flows.

[0098] According to the configuration of the above (11), the amount of ammonia in the exhaust gas flowing downstream of the ammonia decomposition catalyst (78) in the exhaust gas discharge line (7) is equivalent to the ammonia emission amount actually discharged into the atmosphere. By using the amount of ammonia in the exhaust gas flowing downstream of the ammonia decomposition catalyst (78) in the exhaust gas discharge line (7) acquired by the ammonia amount acquisition unit (32) for control in the control device (3), the control device (3) can perform control such that the ammonia emission amount satisfies the limit value more appropriately.

[0099] 12) In some embodiments, it is the control device (3) of the internal combustion engine (2) described in the above (5) or (6), The exhaust gas temperature acquisition unit (35) is configured to acquire the temperature of the exhaust gas flowing upstream of the turbine (73) in the exhaust gas discharge line (7) through which the exhaust gas discharged from the internal combustion engine (2) flows.

[0100] According to the configuration of the above (12), the upstream side of the turbine (73) in the exhaust gas discharge line (7) is at a higher temperature than the downstream side of the turbine (73). By using the temperature of the exhaust gas flowing upstream of the turbine (73) in the relatively high-temperature exhaust gas discharge line (7) for control in the control device (3), the control device (3) can perform control such that the exhaust gas temperature satisfies the limit value more appropriately.

[0101] 13) The control method of the internal combustion engine (2) according to at least one embodiment of the present disclosure is A control method of an internal combustion engine (2) for controlling the operation of the internal combustion engine (2) configured to be able to switch between a plurality of operation modes, The plurality of operation modes are A dedicated combustion operation mode using liquid fuel as the fuel to be used, and A mixed combustion operation mode using both the liquid fuel and ammonia gas as the fuel to be used, and The control method of the internal combustion engine (2) is A nitrogen oxide amount acquisition step of acquiring the amount of nitrogen oxides in the exhaust gas discharged from the internal combustion engine (2), An ammonia amount acquisition step of acquiring the amount of ammonia in the exhaust gas discharged from the internal combustion engine (2); A flow rate control step of giving a flow rate adjustment instruction to a flow rate adjustment device configured to adjust the flow rate of combustion gas introduced into the internal combustion engine (2) so that, in a state where the internal combustion engine (2) is operating in the co-firing operation mode, each of the amount of nitrogen oxides acquired in the nitrogen oxide amount acquisition step and the amount of ammonia acquired in the ammonia amount acquisition step does not exceed a threshold value. It is provided with.

[0102] According to the method of 13) above, when environmental conditions change, etc., the combustion state also changes, so the relationship between the nitrogen oxide emission amount and the ammonia emission amount with respect to the air excess ratio always changes. In the above control method, instead of the air excess ratio, the amount of nitrogen oxides acquired in the nitrogen oxide amount acquisition step and the amount of ammonia acquired in the ammonia amount acquisition step are used as control parameters for adjusting the flow rate of combustion gas introduced into the internal combustion engine (2). Such a control method enables adjustment of the flow rate of combustion gas so that the emission amounts of nitrogen oxides and ammonia satisfy the limit values even when environmental conditions change.

Explanation of symbols

[0103] 1 Internal combustion engine system 2 Internal combustion engine 3 Control device 4 Liquid fuel introduction line 5 Combustion gas introduction line 6 Ammonia gas introduction line 7 Exhaust gas discharge line 8 Liquid fuel side injector 9 Ammonia side injector 10 Flow rate adjustment device 11 Supercharger 12 Nitrogen oxide sensor 13 Ammonia sensor 14 Temperature sensor 15 Selection device 21 Cylinder 22 Combustion chamber 30 Memory unit 31 Nitrogen oxide amount acquisition unit 32 Ammonia amount acquisition unit 33 Flow control unit 34 First operation mode control unit 35 Exhaust gas temperature acquisition unit 36 Parameter acquisition unit 37 Association information acquisition unit 38 Operation condition determination unit 39 Second operation mode control unit 41 Common rail 42 Branch pipe 43 Liquid fuel supply source 44 Liquid fuel pipe 45 Boosting device 51 Compressor 52 Gas pipe for first combustion 53 Gas pipe for second combustion 54 Intake side branch pipe 55 Throttle valve 56 Intercooler 61 Ammonia gas supply source 62 Ammonia gas pipe 63 Ammonia gas side branch pipe 71 Exhaust gas pipe 72 Exhaust gas side branch pipe 73 Turbine 74 Rotating shaft 75 Generator 76 Exhaust gas connection pipe 77 Denitration catalyst 78 Ammonia decomposition catalyst 79 Exhaust gas discharge pipe AA Amount of ammonia ANO Amount of nitrogen oxides AT Ammonia threshold value GT Exhaust gas temperature NOT1 First nitrogen oxide threshold value NOT2 Second nitrogen oxide threshold value TT1 First temperature threshold value TT2 Second temperature threshold value

Claims

1. A control device for an internal combustion engine for controlling the operation of the internal combustion engine configured to be able to switch between a plurality of operating modes, wherein the plurality of operating modes include a dedicated combustion operation mode using liquid fuel as the fuel to be used, and a mixed combustion operation mode using both the liquid fuel and ammonia gas as the fuel to be used, and the control device of the internal combustion engine includes a nitrogen oxide amount acquisition unit configured to acquire the amount of nitrogen oxides in the exhaust gas discharged from the internal combustion engine, an ammonia amount acquisition unit configured to acquire the amount of ammonia in the exhaust gas discharged from the internal combustion engine, and a flow rate control unit configured to give a flow rate adjustment instruction to adjust the flow rate of the combustion gas introduced into the internal combustion engine to the flow rate adjustment device configured to adjust the flow rate of the combustion gas introduced into the internal combustion engine so that each of the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit and the amount of ammonia acquired by the ammonia amount acquisition unit does not exceed a threshold value in a state where the internal combustion engine is operating in the mixed combustion operation mode. A control device for an internal combustion engine.

2. The flow rate control unit is configured to give a flow rate reduction instruction to reduce the flow rate of the combustion gas introduced into the internal combustion engine to the flow rate adjustment device when a flow rate reduction condition including at least a determination condition that the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit is equal to or less than a first nitrogen oxide threshold value is satisfied in a state where the internal combustion engine is operating in the mixed combustion operation mode. The control device for an internal combustion engine according to Claim 1.

3. The flow rate control unit is configured to give a flow rate increase instruction to increase the flow rate of the combustion gas introduced into the internal combustion engine to the flow rate adjustment device when a flow rate increase condition including both a determination condition that the amount of ammonia acquired by the ammonia amount acquisition unit is equal to or less than an ammonia threshold value and a determination condition that the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit exceeds a second nitrogen oxide threshold value that is equal to or greater than the first nitrogen oxide threshold value is satisfied in a state where the internal combustion engine is operating in the mixed combustion operation mode. The control device for an internal combustion engine according to Claim 2.

4. In a state where the internal combustion engine is operating in the co-firing operation mode, when a co-firing operation stop condition including both a determination condition that the amount of nitrogen oxides acquired by the nitrogen oxide amount acquisition unit exceeds a first nitrogen oxide threshold value and a determination condition that the amount of ammonia acquired by the ammonia amount acquisition unit exceeds an ammonia threshold value is satisfied, the internal combustion engine is further provided with a first operation mode control unit configured to switch the operation mode of the internal combustion engine to the dedicated firing operation mode. The control device for an internal combustion engine according to any one of claims 1 to 3.

5. The exhaust gas temperature acquisition unit is further provided and configured to acquire the temperature of the exhaust gas. The flow rate reduction condition further includes a determination condition that the temperature of the exhaust gas acquired by the exhaust gas temperature acquisition unit is equal to or lower than a first temperature threshold value. The control device for an internal combustion engine according to claim 2 or 3.

6. In a state where the internal combustion engine is operating in the co-firing operation mode, when a flow rate increase condition including both a determination condition that the amount of ammonia acquired by the ammonia amount acquisition unit is equal to or less than an ammonia threshold value and a determination condition that the temperature of the exhaust gas acquired by the exhaust gas temperature acquisition unit exceeds a second temperature threshold value that is equal to or greater than the first temperature threshold value is satisfied, the internal combustion engine is configured to give an instruction to increase the flow rate of the combustion gas led to the internal combustion engine to the flow rate adjustment device. The control device for an internal combustion engine according to claim 5.

7. A parameter acquisition unit configured to acquire a plurality of parameters related to the operation state of the internal combustion engine; An association information acquisition unit configured to acquire association information associating the plurality of parameters with operation conditions in which the co-firing operation mode is possible; In a state where the internal combustion engine is operating in the dedicated firing operation mode, an operation condition determination unit configured to determine whether or not the plurality of parameters acquired by the parameter acquisition unit satisfy the operation conditions based on the association information acquired by the association information acquisition unit. The control device for an internal combustion engine according to any one of claims 1 to 3.

8. In a state where the internal combustion engine is operating in the dedicated combustion operation mode, when a co-combustion operation enable condition including a determination condition that the plurality of parameters satisfy the operation conditions is satisfied, a second operation mode control unit configured to switch the operation mode of the internal combustion engine to the co-combustion operation mode is further provided. The control device for an internal combustion engine according to claim 7.

9. The associated information is a control map showing the relationship between the plurality of parameters and the operation conditions, and includes a control map in which an area where the co-combustion operation mode is possible is set on a map constituted by the plurality of parameters. The control device for an internal combustion engine according to claim 7.

10. The nitrogen oxide amount acquisition unit is configured to acquire the amount of nitrogen oxides in the exhaust gas flowing downstream of a denitration catalyst for removing the nitrogen oxides in an exhaust gas discharge line through which the exhaust gas discharged from the internal combustion engine flows. The control device for an internal combustion engine according to any one of claims 1 to 3.

11. The ammonia amount acquisition unit is configured to acquire the amount of ammonia in the exhaust gas flowing downstream of an ammonia decomposition catalyst for removing the ammonia in an exhaust gas discharge line through which the exhaust gas discharged from the internal combustion engine flows. The control device for an internal combustion engine according to any one of claims 1 to 3.

12. The exhaust gas temperature acquisition unit is configured to acquire the temperature of the exhaust gas flowing upstream of a turbine in an exhaust gas discharge line through which the exhaust gas discharged from the internal combustion engine flows. The control device for an internal combustion engine according to claim 5.

13. An internal combustion engine control method for controlling the operation of an internal combustion engine configured to be able to switch between a plurality of operation modes, wherein the plurality of operation modes include a dedicated combustion operation mode using liquid fuel as the fuel to be used, and a co-combustion operation mode using both the liquid fuel and ammonia gas as the fuel to be used, and the control method of the internal combustion engine includes a nitrogen oxide amount acquisition step of acquiring the amount of nitrogen oxides in the exhaust gas discharged from the internal combustion engine, and an ammonia amount acquisition step of acquiring the amount of ammonia in the exhaust gas discharged from the internal combustion engine. In a state where the internal combustion engine is operating in the co-firing operation mode, a flow rate control step of giving a flow rate adjustment instruction to adjust the flow rate of the combustion gas introduced into the internal combustion engine is performed for a flow rate adjustment device configured to adjust the flow rate of the combustion gas introduced into the internal combustion engine so that the amount of nitrogen oxides obtained in the nitrogen oxide amount acquisition step and the amount of ammonia obtained in the ammonia amount acquisition step do not exceed the threshold values, respectively. A method for controlling an internal combustion engine.

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