Ammonia mixed combustion engine

Abstract

To provide an ammonia mixed combustion engine that enables operation at any ammonia mixed fuel burning ratio and can improve a combustion stability and an exhaust gas property.SOLUTION: An ammonia mixed combustion engine 1, which operates by combusting ammonia and hydrocarbon system liquid fuel, causes a control unit 2 to implement at least one of lowering or raising the air excess ratio in the fuel, advancing or retarding the injection timing of the liquid fuel, and lowering or raising the injection pressure of the liquid fuel, in accordance with an increase or decrease in a mixed fuel combustion ratio of ammonia in the fuel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ammonia co-fuel engine that operates by burning ammonia and a hydrocarbon liquid fuel. [Background technology]

[0002] Conventionally, there are ammonia co-fuel engines that operate by burning ammonia and hydrocarbon liquid fuel such as diesel. In ammonia co-fuel engines, it is required to improve the properties of the exhaust gas emitted.

[0003] For example, the ammonia co-fuel engine disclosed in Patent Document 1 includes a combustion chamber, an ammonia supply means for supplying ammonia to the combustion chamber, an air intake means for supplying air to the combustion chamber, a liquid fuel supply means for supplying liquid fuel to the combustion chamber, a fuel ratio setting means for setting the ratio of the amount of ammonia supplied to the total amount of liquid fuel and ammonia supplied, and a supply timing control means for controlling the timing of liquid fuel supply by the liquid fuel supply means in accordance with the ratio set by the fuel ratio setting means. The ammonia co-fuel engine delays the timing of liquid fuel supply to the combustion chamber relative to the timing of start of supply of ammonia and air, and controls the supply timing control means to advance the timing of liquid fuel supply as the ratio of the amount of ammonia supplied set by the fuel ratio setting means increases.

[0004] According to Patent Document 1, the supply timing control means controls the supply of liquid fuel by the liquid fuel supply means to inject the liquid fuel in multiple stages. In the ammonia co-fuel engine, the advance angle as the liquid fuel supply timing is set in the range of -25° to -70° relative to the top dead center (TDC) of the engine. The ratio of the ammonia supply amount to the total supply amount of liquid fuel and ammonia is in the range of 1% to 95%. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-155927 Summary of the Invention [Problem to be solved by the invention]

[0006] In an ammonia co-firing engine, as the ammonia supply amount is increased and the co-firing ratio is increased from 0 to 95%, combustion stability may decrease, exhaust gas properties may deteriorate, and the amounts of NH3 and NO contained in the exhaust gas may increase. In a conventional ammonia co-firing engine such as that disclosed in Patent Document 1, exhaust gas properties are improved by controlling the timing of supplying liquid fuel to the combustion chamber, but it is difficult to simultaneously increase the ammonia co-firing ratio and improve combustion stability and exhaust gas properties by simply controlling the timing of supplying liquid fuel.

[0007] An object of the present invention is to provide an ammonia co-firing engine that enables operation at any ammonia co-firing ratio and that can improve combustion stability and exhaust gas properties. [Means for solving the problem]

[0008] In order to solve the above problems, the ammonia-mixed combustion engine of the present invention is an ammonia-mixed combustion engine that operates by burning ammonia and a hydrocarbon-based liquid fuel, and is characterized in that, in response to an increase or decrease in the ammonia mixing ratio in the fuel, at least one of decreasing or increasing an excess air ratio in the fuel, advancing or retarding an injection timing of the liquid fuel, and decreasing or increasing an injection pressure of the liquid fuel is carried out. [Effects of the Invention]

[0009] According to the present invention, an ammonia co-fuel engine is provided which enables operation at any ammonia co-fuel ratio and can improve combustion stability and exhaust gas properties. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a schematic diagram showing an ammonia-mixed combustion engine according to an embodiment of the present invention. FIG. [Figure 2] 1 is a graph showing a map of combustion instability in relation to the ammonia co-fuel ratio and excess air ratio in an ammonia co-fuel engine. [Figure 3] 1 is a graph showing a map of combustion instability in relation to the liquid fuel injection timing and the excess air ratio in an ammonia co-fuel engine. [Figure 4] 1 is a graph showing the relationship between liquid fuel injection pressure and combustion instability in an ammonia co-fuel engine. [Figure 5] 1 is a graph showing a map of unburned ammonia in relation to the ammonia co-fuel ratio and excess air ratio in an ammonia co-fuel engine. [Figure 6] 1 is a graph showing a map of N2O in relation to the ammonia co-fuel ratio and excess air ratio in an ammonia co-fuel engine. [Figure 7] 1 is a graph showing an example of an excess air ratio set with respect to an ammonia co-fuel ratio in an ammonia co-fuel engine according to an embodiment of the present invention. [Figure 8] 4 is a graph showing an example of a liquid fuel injection timing set with respect to an ammonia co-fuel ratio in an ammonia co-fuel engine according to an embodiment of the present invention. [Figure 9] 1 is a graph showing an example of a liquid fuel injection pressure set with respect to an ammonia co-fuel ratio in an ammonia co-fuel engine according to an embodiment of the present invention. [Figure 10] FIG. 1 is a schematic diagram showing an ammonia-mixed combustion engine according to another embodiment of the present invention. [Figure 11] 1 is a graph showing a map of unburned ammonia in relation to the combustion temperature and fuel-air equivalence ratio in an ammonia co-fuel combustion engine. [Figure 12] 1 is a graph showing a map of N2O in relation to the combustion temperature and fuel-air equivalence ratio in an ammonia co-fuel combustion engine. DETAILED DESCRIPTION OF THE INVENTION

[0011] An ammonia-mixed combustion engine 1 according to an embodiment of the present invention will be described with reference to the drawings. The ammonia-mixed combustion engine 1 (engine) operates by burning at least one fuel selected from ammonia and hydrocarbon liquid fuel such as diesel. The ammonia-mixed combustion engine 1 controls the supply of ammonia and liquid fuel by a control unit 2. The ammonia-mixed combustion engine 1 is configured with a cylinder block (not shown) having multiple cylinders 10, but FIG. 1 shows only one cylinder 10. As shown in FIG. 1, each cylinder 10 includes a cylinder 11, a piston 12, a cylinder head 13, an ammonia supply device 14, and a liquid fuel supply device 15.

[0012] The cylinder 11 is formed in a cylindrical shape within, for example, a cylinder block, the piston 12 is slidably housed within the cylinder 11, and the cylinder head 13 is attached to the upper side of the cylinder 11. Within the cylinder 11, a combustion chamber 20 is formed between the piston 12 and the cylinder head 13.

[0013] Below the cylinder 11 , a crankshaft 17 is connected to the piston 12 via a connecting rod 16 , and the reciprocating motion of the piston 12 is converted into the rotational motion of the crankshaft 17 via the connecting rod 16 .

[0014] The cylinder head 13 also has an intake port 21 and an exhaust port 22 that communicate with the combustion chamber 20 of the cylinder 11, and is equipped with an intake valve 23 and an exhaust valve 24 that open and close the intake port 21 and the exhaust port 22 to the combustion chamber 20, respectively.

[0015] The intake port 21 is connected to the intake passage 3 and introduces air supplied from the intake passage 3 into the combustion chamber 20, while the exhaust port 22 is connected to the exhaust passage 4 and discharges exhaust gas generated in the combustion chamber 20 into the exhaust passage 4. By opening the intake valve 23, intake air can be taken into the combustion chamber 20 through the intake port 21, while by opening the exhaust valve 24, exhaust gas generated in the combustion chamber 20 can be exhausted through the exhaust port 22.

[0016] 1 shows an example in which the intake passage 3 and the intake port 21 are directly connected, but in order to connect the intake passage 3 to each of the intake ports 21 of the multiple cylinders 10, an intake manifold having branch passages branching from the intake passage 3 to the multiple cylinders 10 may be provided between the intake passage 3 and the cylinder head 13. Also, while FIG. 1 shows an example in which the exhaust passage 4 and the exhaust port 22 are directly connected, in order to connect the exhaust passage 4 to each of the exhaust ports 22 of the multiple cylinders 10, an exhaust manifold having branch passages branching from the exhaust passage 4 to the multiple cylinders 10 may be provided between the exhaust passage 4 and the cylinder head 13.

[0017] The ammonia supplier 14 is controlled by the control unit 2, and supplies ammonia, which is supplied from an ammonia tank 25 that stores ammonia, toward the combustion chamber 20. For example, the ammonia supplier 14 is composed of a gas admission valve, a gas injector, and the like.

[0018] 1 illustrates an example in which the ammonia supply device 14 is provided in the intake port 21 and injects ammonia into the intake port 21, thereby supplying the ammonia to the combustion chamber 20 via the intake port 21. Alternatively, the ammonia supply device 14 may be provided in the intake passage 3 and injects ammonia into the intake passage 3, thereby supplying the ammonia to the combustion chamber 20 via the intake passage 3 or the intake port 21, or the ammonia supply device 14 may be provided in the cylinder 11 or the cylinder head 13 and supply ammonia by directly injecting it into the combustion chamber 20.

[0019] An air-fuel mixture of air supplied from the intake passage 3 and ammonia supplied by the ammonia supplier 14, the injection amount of which is controlled by the control unit 2, is supplied from the intake port 21 to the combustion chamber 20, thereby controlling the excess air ratio. The ammonia supplier 14 is controlled by the control unit 2 in terms of the injection amount of ammonia as well as the injection pressure, injection timing, etc.

[0020] Liquid fuel supply device 15 is controlled by control unit 2 and supplies liquid fuel supplied from liquid fuel tank 26, which stores hydrocarbon liquid fuel such as diesel, to combustion chamber 20. For example, liquid fuel supply device 15 is configured with a device such as a micro-pilot type injector that injects a small amount of liquid fuel.

[0021] 1 illustrates an example in which the liquid fuel supply device 15 is provided in the cylinder head 13 and supplies liquid fuel by injecting it directly into the combustion chamber 20. Alternatively, the liquid fuel supply device 15 may be provided in the intake port 21 and inject liquid fuel into the intake port 21 to supply it to the combustion chamber 20 via the intake port 21, or the liquid fuel supply device 15 may be provided in the intake passage 3 and inject liquid fuel into the intake passage 3 to supply it to the combustion chamber 20 via the intake passage 3 and the intake port 21.

[0022] The liquid fuel supply device 15 is controlled by the control unit 2 in terms of the injection amount, injection pressure, injection timing, etc. of the liquid fuel. The liquid fuel supply device 15 compresses and auto-ignites the mixture of ammonia and air in the combustion chamber 20 with the hydrocarbon liquid fuel and burns it.

[0023] The control unit 2 is a computer such as an ECU (Engine Control Unit) that controls the operation of the ammonia-mixed combustion engine 1, and is equipped with a CPU, ROM, RAM, etc., and is configured to control each part of the ammonia-mixed combustion engine 1. The control unit 2 may store various programs for controlling the ammonia-mixed combustion engine 1, and control the ammonia-mixed combustion engine 1 by reading and executing the programs.

[0024] Next, the supply control of ammonia and liquid fuel in the ammonia-mixed combustion engine 1 will be described.

[0025] In Fig. 2, the ammonia co-firing ratio (the proportion of ammonia in a fuel consisting of ammonia and liquid fuel) burned in the combustion chamber 20 is shown on the horizontal axis, and the excess air ratio relative to ammonia in the mixture supplied to the combustion chamber 20 is shown on the vertical axis. Fig. 2 also shows a stable region 30 in which the ammonia co-firing engine 1 can be operated stably from the perspective of combustion stability, with respect to the relationship between the ammonia co-firing ratio and the excess air ratio, and also shows a map of combustion instability within the stable region 30, with instability increasing in the direction indicated by the white arrow 31. According to Fig. 2, when the excess air ratio is relatively high, as the ammonia co-firing ratio increases, combustion instability increases and the engine 1 falls outside the stable region 30. Therefore, the ammonia co-firing engine 1 can be operated stably by reducing the excess air ratio as the ammonia co-firing ratio increases.

[0026] In Fig. 3, the horizontal axis indicates the injection timing of liquid fuel into the combustion chamber 20, and the vertical axis indicates the excess air ratio relative to ammonia in the mixture supplied to the combustion chamber 20. Fig. 3 also shows the relationship between the liquid fuel injection timing and the excess air ratio, the liquid fuel injection timing, and a stable region 32 in which the ammonia co-firing engine 1 can be operated stably, as well as a map of combustion instability within the stable region 32, with instability increasing in the direction indicated by the white arrow 33. According to Fig. 3, when the liquid fuel injection timing is relatively retarded, combustion instability increases as the ammonia co-firing ratio increases. Therefore, the ammonia co-firing engine 1 can be operated stably by advancing the liquid fuel injection timing as the ammonia co-firing ratio increases.

[0027] In Fig. 4, the horizontal axis represents the injection pressure of the liquid fuel into the combustion chamber 20, and the vertical axis represents the combustion instability in the combustion chamber 20 (for example, COV Pmax, which is an index of combustion instability). According to Fig. 4, when the liquid fuel injection pressure is relatively high, the combustion instability increases, so by lowering the liquid fuel injection pressure, the ammonia co-fuel engine 1 can be operated stably.

[0028] In Fig. 5, the horizontal axis represents the ammonia co-firing ratio burned in the combustion chamber 20, and the vertical axis represents the excess air ratio relative to the ammonia in the mixture supplied to the combustion chamber 20. Fig. 5 also shows a stable region 34 in which the ammonia co-firing engine 1 can be operated stably from the perspective of exhaust gas properties, relative to the ammonia co-firing ratio, for the relationship between the ammonia co-firing ratio and the excess air ratio. It also shows a map of the unburned ammonia contained in the exhaust gas discharged from the combustion chamber 20 within the stable region 34, with the amount of unburned ammonia increasing in the direction indicated by the white arrow 35. According to Fig. 5, when the excess air ratio is relatively high, as the ammonia co-firing ratio increases, the amount of unburned ammonia increases and the engine 1 falls outside the stable region 34. Therefore, by decreasing the excess air ratio as the ammonia co-firing ratio increases, the ammonia co-firing engine 1 can be operated with less unburned ammonia.

[0029] In Fig. 6, the horizontal axis represents the ammonia co-firing ratio burned in the combustion chamber 20, and the vertical axis represents the excess air ratio relative to the ammonia in the mixture supplied to the combustion chamber 20. Fig. 6 also shows a stable region 36 in which the ammonia co-firing engine 1 can be stably operated from the perspective of exhaust gas properties, relative to the ammonia co-firing ratio and the excess air ratio. Fig. 6 also shows a map of N2O (nitrous oxide or nitrous oxide) contained in the exhaust gas emitted from the combustion chamber 20 within the stable region 36, with N2O increasing in the direction indicated by the white arrow 37. According to Fig. 6, when the excess air ratio is relatively high, increasing the ammonia co-firing ratio increases the N2O content, causing the engine to deviate from the stable region 36. Therefore, by decreasing the excess air ratio as the ammonia co-firing ratio increases, the ammonia co-firing engine 1 can be operated with reduced N2O.

[0030] Based on the relationship between the ammonia co-firing ratio, excess air ratio, liquid fuel injection timing, and liquid fuel injection pressure in the ammonia co-firing engine 1 as described above, the control unit 2 controls each parameter (excess air ratio, liquid fuel injection timing, and liquid fuel injection pressure) so as to simultaneously improve combustion stability and exhaust gas properties when operated at a given ammonia co-firing ratio. The control unit 2 performs control to implement at least one of decreasing the excess air ratio, advancing (advancing) the liquid fuel injection timing, and decreasing the liquid fuel injection pressure as the ammonia co-firing ratio increases. In the ammonia co-firing engine 1 of this embodiment, the ammonia co-firing ratio may be set to a value greater than 0%, preferably about 5% or greater.

[0031] For example, as shown in Fig. 7, the control unit 2 controls the supply of ammonia by the ammonia supplier 14 and the intake of air through the intake passage 3 so that the excess air ratio of the mixture supplied to the combustion chamber 20 decreases as the ammonia co-firing ratio increases. Specifically, the control unit 2 reduces the excess air ratio by 0.1 to 0.5, preferably by 0.1, while the co-firing ratio increases by 10%. The control unit 2 presets a minimum value for the excess air ratio (e.g., 1.0) and reduces the excess air ratio to this minimum value. The control unit 2 may also control the supply of ammonia by the ammonia supplier 14 and the intake of air through the intake passage 3 so that the excess air ratio increases as the ammonia co-firing ratio decreases.

[0032] As shown in Fig. 8, the control unit 2 controls the supply of liquid fuel by the liquid fuel supply device 15 so that the injection timing of the liquid fuel supplied to the combustion chamber 20 is advanced (advanced) as the ammonia mixing ratio increases. Specifically, the control unit 2 advances the liquid fuel injection timing by 0.1 to 5.0 degrees, preferably by 1.1 degrees, while the mixing ratio increases by 10%. Also, the control unit 2 preferably controls the supply of liquid fuel by the liquid fuel supply device 15 so that the liquid fuel injection timing is retarded as the ammonia mixing ratio decreases.

[0033] 9, the control unit 2 controls the supply of liquid fuel by the liquid fuel supply device 15 so that the injection pressure of the liquid fuel supplied to the combustion chamber 20 decreases as the ammonia mixing ratio increases. Specifically, the control unit 2 decreases the liquid fuel injection pressure by 1 to 30 MPa, preferably by 17 MPa, while the mixing ratio increases by 10%. Also, the control unit 2 preferably controls the supply of liquid fuel by the liquid fuel supply device 15 so that the liquid fuel injection pressure increases as the ammonia mixing ratio decreases.

[0034] The control unit 2 may control at least two of the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure simultaneously in response to an increase or decrease in the ammonia co-firing ratio. The control unit 2 may control the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure in this order of priority.

[0035] As described above, according to the present invention, the ammonia co-firing engine 1 that operates by burning ammonia and hydrocarbon liquid fuel performs at least one of decreasing or increasing the excess air ratio in the fuel, advancing or retarding the injection timing of the liquid fuel, and decreasing or increasing the injection pressure of the liquid fuel, depending on an increase or decrease in the co-firing ratio of ammonia in the fuel, using the control unit 2.

[0036] As a result, the ammonia co-fuel engine 1 of the present invention can set an appropriate excess air ratio, liquid fuel injection timing, and / or liquid fuel injection pressure even when the ammonia co-fuel ratio changes depending on the operating mode. Therefore, when operating by burning ammonia and hydrocarbon liquid fuel, the ammonia co-fuel engine 1 can be operated at any ammonia co-fuel ratio and can simultaneously improve combustion stability and exhaust gas properties. Furthermore, the ammonia co-fuel engine 1 can improve its marketability regardless of the operating mode, even when the operating mode is selected depending on the remaining amount of various fuels or regulations of the operating sea area.

[0037] Furthermore, the ammonia co-firing engine 1 of the present invention reduces the excess air ratio by 0.1 to 0.5 while the ammonia co-firing ratio increases by 10% by the control unit 2. This allows the ammonia co-firing engine 1 to set an appropriate excess air ratio to simultaneously improve combustion stability and exhaust gas properties, even when the ammonia co-firing ratio is increased.

[0038] Furthermore, the ammonia co-fuel engine 1 of the present invention advances the liquid fuel injection timing by 0.1 to 5.0 degrees while the ammonia co-fuel ratio increases by 10% by the control unit 2. This allows the ammonia co-fuel engine 1 to set an appropriate liquid fuel injection timing to simultaneously improve combustion stability and exhaust gas properties, even when the ammonia co-fuel ratio is increased.

[0039] Furthermore, the ammonia co-firing engine 1 of the present invention reduces the liquid fuel injection pressure by 1 to 30 MPa while the ammonia co-firing ratio increases by 10% by the control unit 2. This allows the ammonia co-firing engine 1 to set an appropriate liquid fuel injection pressure to simultaneously improve combustion stability and exhaust gas properties, even when the ammonia co-firing ratio is increased.

[0040] Furthermore, the ammonia co-firing engine 1 of the present invention simultaneously controls at least two of the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure in response to an increase or decrease in the ammonia co-firing ratio by the control unit 2. This allows the ammonia co-firing engine 1 to appropriately select parameters that need to be set from the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure in order to more appropriately achieve both combustion stability and exhaust gas properties in response to an arbitrary ammonia co-firing ratio.

[0041] In the above-described embodiment, an example is described in which the control unit 2 controls the reduction of the excess air ratio, the advancement of the liquid fuel injection timing, and / or the reduction of the liquid fuel injection pressure as the ammonia mixing ratio increases. FIGS. 7, 8, and 9 illustrate examples in which the reduction of the excess air ratio, the advancement of the liquid fuel injection timing, and / or the reduction of the liquid fuel injection pressure are performed in proportion to the increase in the ammonia mixing ratio, but the present invention is not limited to this example.

[0042] In another example, the control unit 2 may determine the ammonia co-firing ratio based on a threshold value, and determine whether to reduce the excess air ratio, advance the liquid fuel injection timing, and / or reduce the liquid fuel injection pressure based on the determination result. For example, the control unit 2 may set multiple threshold values ​​for the ammonia co-firing ratio in advance, and set the excess air ratio, liquid fuel injection timing, and / or liquid fuel injection pressure corresponding to each threshold value. The control unit 2 may then compare the ammonia co-firing ratio with the multiple threshold values ​​to determine which level the ammonia co-firing ratio corresponds to, and set the excess air ratio, liquid fuel injection timing, and / or liquid fuel injection pressure corresponding to the level determined.

[0043] In the above embodiment, an example has been described in which the ammonia co-fuel engine 1 performs at least one of decreasing or increasing the excess air ratio in the fuel, advancing or retarding the injection timing of the liquid fuel, and decreasing or increasing the injection pressure of the liquid fuel in response to an increase or decrease in the ammonia co-fuel ratio in the fuel by the control unit 2, but the present invention is not limited to this example.

[0044] 10, the ammonia-mixed combustion engine 1 includes an intake throttle 40, a supercharger 41, an intercooler 42, and a recirculation device 43 (EGR device) in addition to the configuration of the above embodiment. The ammonia-mixed combustion engine 1 also includes an intake bypass passage 44 and a wastegate 45.

[0045] The ammonia co-fuel engine 1 is configured to perform at least one of the following in response to an increase in the ammonia co-fuel ratio in the fuel: an increase in the temperature of the air supplied from the intake passage 3 to the cylinder 10 (i.e., intake temperature); an increase in the number of injections of liquid fuel from the liquid fuel supply device 15 in one combustion cycle of the piston 12 in the cylinder 10; a change in the closing timing of the intake valve 23 in the cylinder 10 toward bottom dead center; an increase in the amount of air bypassed from the intake passage 3 to the exhaust passage 4 through the intake bypass passage 44 (i.e., intake bypass amount); a change in the opening of the wastegate 45 of the turbocharger 41 in the valve opening direction; and an increase in the passage area by adjusting the variable nozzle 41c of the turbocharger 41.

[0046] Specifically, the ammonia mixed combustion engine 1 is provided with a supercharger 41, an intercooler 42, and an intake throttle 40 in this order from the upstream side of the intake passage 3 in the intake direction.

[0047] The turbocharger 41 has a turbine 41a arranged in the exhaust passage 4 and a compressor 41b arranged in the exhaust passage 4, and the turbine 41a is provided with a variable nozzle 41c that adjusts the passage area of ​​the exhaust gas flowing through the turbine 41a. The turbocharger 41 rotates the turbine 41a with the exhaust gas flowing through the exhaust passage 4, and drives the compressor 41b with the rotational force of the turbine 41a, thereby compressing the air flowing through the intake passage 3.

[0048] The recirculation device 43 includes a recirculation passage 43a, a recirculation cooler 43b, and a recirculation valve 43c. The recirculation passage 43a is connected to the exhaust passage 4 upstream of the turbocharger 41 (turbine 41a) in the exhaust direction, and is connected to the intake passage 3 downstream of the intercooler 42 in the intake direction. The recirculation device 43 cools and recirculates exhaust gas flowing into the exhaust passage 4 upstream of the turbocharger 41 in the exhaust direction using the recirculation cooler 43b, and supplies the cooled exhaust gas to the intake passage 3 downstream of the intercooler 42 in the intake direction. The recirculation device 43 adjusts the opening of the recirculation valve 43c using the control unit 2 to adjust the flow rate of the recirculated exhaust gas flowing into the intake passage 3, thereby adjusting the amount of oxygen in the air flowing into the intake passage 3.

[0049] The ammonia-mixed combustion engine 1 is also provided with an intake bypass passage 44 that bypasses the downstream side of the turbocharger 41 in the intake direction of the intake passage 3 and the upstream side of the turbocharger 41 in the exhaust direction of the exhaust passage 4, and the intake bypass passage 44 is provided with an intake bypass valve 44a that adjusts the intake bypass amount. The ammonia-mixed combustion engine 1 is also provided with a wastegate 45 that bypasses the upstream side and downstream side of the turbocharger 41 in the exhaust direction of the exhaust passage 4, and the wastegate 45 is provided with a wastegate valve 45a that adjusts the exhaust bypass amount.

[0050] In the ammonia co-fuel engine 1, the control unit 2 controls the intercooler 42 in response to an increase in the ammonia co-fuel ratio in the fuel, thereby increasing the temperature of the air (i.e., intake temperature) supplied to the cylinder 10 from the intake passage 3. This increases the in-cylinder temperature of the cylinder 10, thereby increasing the combustion temperature in the combustion chamber 20, reducing unburned ammonia and NOx (NH3, N2O, etc.) in the exhaust gas, thereby achieving low emissions.

[0051] Alternatively, the ammonia co-fuel engine 1 controls the liquid fuel supply device 15 by the control unit 2 in accordance with an increase in the ammonia co-fuel ratio in the fuel, thereby increasing the number of injections of liquid fuel from the liquid fuel supply device 15 in one combustion cycle of the piston 12 in the cylinder 10. This optimizes the arrangement of the liquid fuel relative to the combustion chamber 20, thereby increasing the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (NH3, NO, etc.) in the exhaust gas, thereby achieving low emissions.

[0052] Alternatively, the ammonia co-fuel engine 1 controls the intake valve 23 by the control unit 2 in accordance with an increase in the ammonia co-fuel ratio in the fuel, and changes the closing timing of the intake valve 23 toward bottom dead center timing. This increases the effective compression ratio in the combustion chamber 20, thereby raising the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (NH3, N2O, etc.) in the exhaust gas, thereby achieving low emissions.

[0053] Alternatively, the ammonia co-fuel engine 1 controls the intake bypass valve 44a by the control unit 2 in response to an increase in the ammonia co-fuel ratio in the fuel, thereby increasing the intake bypass amount of the intake bypass passage 44. This reduces the proportion of air in the intake air and increases the proportion of fuel, raising the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (NH3, NO, etc.) in the exhaust gas, thereby achieving low emissions.

[0054] Alternatively, the ammonia co-fuel engine 1 controls the wastegate valve 45a by the control unit 2 to change the opening of the wastegate 45 in the valve opening direction in response to an increase in the ammonia co-fuel ratio in the fuel. This increases the amount of residual gas and reduces the amount of air compressed by the turbocharger 41, thereby decreasing the proportion of air in the intake air and increasing the proportion of fuel, raising the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (NH3, NO, etc.) in the exhaust gas, thereby achieving low emissions.

[0055] Alternatively, the ammonia co-fuel engine 1 adjusts the variable nozzle 41c by the control unit 2 in response to an increase in the ammonia co-fuel ratio in the fuel, thereby increasing the passage area of ​​the turbine 41a of the turbocharger 41. This increases the amount of residual gas in the exhaust passage 4 and reduces the amount of air compressed by the turbocharger 41, thereby decreasing the proportion of air in the intake air and increasing the proportion of fuel, thereby raising the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (NH3, NO, etc.) in the exhaust gas, thereby achieving low emissions.

[0056] 11 and 12, the horizontal axis represents the combustion temperature in the combustion chamber 20, and the vertical axis represents the fuel-air equivalence ratio of the fuel to the air in the air-fuel mixture supplied to the combustion chamber 20. FIG. 11 shows a map of unburned ammonia contained in the exhaust gas of the ammonia-mixed combustion engine 1 versus the relationship between combustion temperature and fuel-air equivalence ratio, with unburned ammonia decreasing in the direction indicated by the white arrow 50. FIG. 12 shows a map of N2O contained in the exhaust gas of the ammonia-mixed combustion engine 1 versus the relationship between combustion temperature and fuel-air equivalence ratio, with N2O decreasing in the direction indicated by the white arrow 51. According to FIG. 11, the higher the combustion temperature, the less unburned ammonia there is, and according to FIG. 12, the higher the combustion temperature, the less N2O there is.

[0057] Thus, according to another example, in response to an increase in the ammonia co-fuel ratio in the fuel, exhaust gas properties can be improved by implementing at least one of the following: increasing the intake air temperature; increasing the number of injections of liquid fuel in one combustion cycle; shifting the closing timing of the intake valve 23 toward bottom dead center; increasing the intake bypass amount; shifting the opening of the wastegate 45 toward opening; and increasing the passage area by adjusting the variable nozzle 41c.

[0058] The present invention can be modified as appropriate within the scope of the claims and the gist or idea of ​​the invention that can be read from the entire specification, and an ammonia co-fuel engine accompanied by such modifications is also included in the technical idea of ​​the present invention.

[0059] [Appendix to the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0060] <Appendix 1> In an ammonia co-fuel engine that operates by burning ammonia and hydrocarbon liquid fuel, an ammonia co-fuel engine, characterized in that at least one of decreasing or increasing an excess air ratio in the fuel, advancing or retarding an injection timing of the liquid fuel, and decreasing or increasing an injection pressure of the liquid fuel is carried out in response to an increase or decrease in the ammonia co-fuel ratio in the fuel.

[0061] <Appendix 2> 2. The ammonia co-fuel engine according to claim 1, wherein the excess air ratio is reduced by 0.1 to 0.5 while the co-fuel ratio is increased by 10%.

[0062] <Appendix 3> 3. The ammonia mixed combustion engine according to claim 1, wherein the injection timing is advanced by 0.1 to 5.0 degrees while the mixed combustion ratio increases by 10%.

[0063] <Appendix 4> 4. The ammonia co-fuel engine according to any one of claims 1 to 3, wherein the injection pressure is reduced by 1 to 30 MPa while the co-fuel ratio increases by 10%.

[0064] <Appendix 5> 5. The ammonia co-fuel engine according to claim 1, wherein at least two of the excess air ratio, the injection timing, and the injection pressure are simultaneously controlled in accordance with an increase or decrease in the co-fuel ratio.

[0065] <Appendix 6> An ammonia-mixed combustion engine that operates by burning ammonia and a hydrocarbon liquid fuel, characterized in that, in response to an increase in the ammonia mixture ratio in the fuel, at least one of an increase in intake air temperature, an increase in the number of injections of the liquid fuel in one combustion cycle, a change in the closing timing of the intake valve toward bottom dead center, an increase in the intake bypass amount, a change in the opening of a wastegate of a turbocharger in the closing direction, and a reduction in passage area by adjusting a variable nozzle of the turbocharger. [Explanation of symbols]

[0066] 1. Ammonia co-fuel engine 2. Control Unit 3 Intake passage 4 Exhaust passage 10 cylinders 11 cylinders 12 pistons 13 Cylinder head 14 Ammonia supply device 15 Liquid fuel supply system 16 Connecting rod 17. Crankshaft 20 Combustion chamber 21 Intake port 22 Exhaust port 23 Intake valve 24 Exhaust valve 25 Ammonia Tank 26 Liquid fuel tank 40 intake throttle 41 Supercharger 41a Turbine 41b Compressor 41c Variable Nozzle 42 Intercooler 43 Recirculation device 43a Recirculation passageway 43b Recirculation Cooler 43c Recirculation Valve 44 Intake bypass passage 44a Intake bypass valve 45 Westgate 45a wastegate valve

Claims

1. In an ammonia co-fuel engine that operates by burning ammonia and hydrocarbon liquid fuel, an ammonia co-fuel engine, characterized in that at least one of decreasing or increasing an excess air ratio in the fuel, advancing or retarding an injection timing of the liquid fuel, and decreasing or increasing an injection pressure of the liquid fuel is carried out in response to an increase or decrease in the ammonia co-fuel ratio in the fuel.

2. 2. The ammonia co-fuel engine according to claim 1, wherein the excess air ratio is decreased by 0.1 to 0.5 while the co-fuel ratio is increased by 10%.

3. 2. The ammonia mixed combustion engine according to claim 1, wherein the injection timing is advanced by 0.1 to 5.0 degrees while the mixed combustion ratio increases by 10%.

4. The ammonia co-fuel engine according to claim 1, wherein the injection pressure is reduced by 1 to 30 MPa while the co-fuel ratio is increased by 10%.

5. 2. The ammonia mixed combustion engine according to claim 1, wherein at least two of the excess air ratio, the injection timing, and the injection pressure are simultaneously controlled in accordance with an increase or decrease in the mixed combustion ratio.

6. In an ammonia co-fuel engine that operates by burning ammonia and hydrocarbon liquid fuel, an ammonia co-fuel engine, wherein, in response to an increase in the ammonia co-fuel ratio in fuel, at least one of an increase in intake air temperature, an increase in the number of injections of the liquid fuel in one combustion cycle, a change in the closing timing of the intake valve toward bottom dead center, an increase in the intake bypass amount, a change in the opening of the wastegate of the turbocharger in the valve opening direction, and an increase in passage area by adjusting a variable nozzle of the turbocharger.

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