Ammonia co-combustion engine

Abstract

The invention provides an ammonia co-combustion engine which can operate at any ammonia co-combustion rate and can improve combustion stability and exhaust gas properties. An ammonia co-combustion engine that operates by combusting ammonia and a hydrocarbon-based liquid fuel is implemented by a control means (2) in accordance with an increase or decrease in the co-combustion rate of ammonia in the fuel: a decrease or increase in the excess air rate in the fuel; an advance or lag in the injection timing of the liquid fuel; and at least one of a decrease and an increase in the injection pressure of the liquid fuel.

Description

Technical Field

[0001] The present invention relates to an ammonia co-firing engine which operates by burning ammonia and hydrocarbon-based liquid fuel. Background Art

[0002] Conventionally, there are ammonia-co-firing engines that operate by burning ammonia with a hydrocarbon-based liquid fuel such as light oil. Ammonia-co-firing engines are required to improve the properties (quality and state) of the exhaust gas discharged.

[0003] For example, the ammonia co-firing engine disclosed in Patent Document 1 includes a combustion chamber, an ammonia supply mechanism for supplying ammonia to the combustion chamber, an air supply mechanism for supplying air to the combustion chamber, a liquid fuel supply mechanism for supplying liquid fuel to the combustion chamber, a fuel ratio setting mechanism for setting the ratio of the ammonia supply amount to the total supply amount of the liquid fuel and ammonia, and a supply timing control mechanism for controlling the timing of liquid fuel supply from the liquid fuel supply mechanism based on the ratio set by the fuel ratio setting mechanism. The ammonia co-firing engine performs control such that the timing of liquid fuel supply to the combustion chamber is delayed relative to the start timing of ammonia and air supply, and the supply timing control mechanism advances the liquid fuel supply timing as the ammonia supply amount ratio set by the fuel ratio setting mechanism increases.

[0004] Furthermore, according to Patent Document 1, the supply timing control mechanism performs control such that the liquid fuel supplied by the liquid fuel supply mechanism is supplied in a multi-stage injection manner. In an ammonia-fueled engine, the advance angle for liquid fuel supply timing is set within a range of -25° to -70° relative to engine top dead center (TDC). The ratio of the ammonia supply amount to the total supply amount of liquid fuel and ammonia is within a range of 1% to 95%.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-155927 Summary of the Invention

[0008] In an ammonia co-firing engine, increasing the ammonia supply rate and the combustion ratio toward 0-95% can reduce combustion stability, worsen exhaust gas properties, and increase the amount of NH3 and N2O contained in the exhaust gas. Conventional ammonia co-firing engines, such as those disclosed in Patent Document 1, improve exhaust gas properties by controlling the timing of liquid fuel supplied to the combustion chamber. However, controlling only the liquid fuel supply timing makes it difficult to simultaneously achieve both an increase in the ammonia co-firing ratio and improvements in combustion stability and exhaust gas properties.

[0009] An object of the present invention is to provide an ammonia co-firing engine that can be operated at any ammonia co-firing ratio and that can improve combustion stability and exhaust gas properties.

[0010] In order to solve the above-mentioned problems, the ammonia co-firing engine of the present invention is an engine that operates by burning ammonia and a hydrocarbon-based liquid fuel. The ammonia co-firing engine is characterized in that at least one of the following is implemented: a reduction or increase in the excess air ratio in the fuel, an advancement or delay in the injection period of the liquid fuel, and a reduction or increase in the injection pressure of the liquid fuel according to an increase or decrease in the mixing ratio of the ammonia in the fuel.

[0011] According to the present invention, it is possible to provide an ammonia co-firing engine that can be operated at any ammonia co-firing ratio and that can improve combustion stability and exhaust gas properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a simulation diagram showing an ammonia co-firing engine according to an embodiment of the present invention.

[0013] Figure 2 This is a graph showing a map of combustion instability in the relationship between the ammonia co-firing ratio and the excess air ratio in an ammonia co-firing engine.

[0014] Figure 3 This is a graph showing a map of combustion instability in the relationship between the liquid fuel injection timing and the excess air ratio in an ammonia co-firing engine.

[0015] Figure 4 This is a graph showing the relationship between liquid fuel injection pressure and combustion instability in an ammonia co-firing engine.

[0016] Figure 5 This is a graph showing a map of unburned ammonia in the relationship between the ammonia co-firing ratio and the excess air ratio in an ammonia co-firing engine.

[0017] Figure 6 This is a graph showing a map of N2O in the relationship between the ammonia co-firing ratio and the excess air ratio in an ammonia co-firing engine.

[0018] Figure 7 This is a graph showing an example of an excess air ratio set for an ammonia co-firing ratio in an ammonia co-firing engine according to an embodiment of the present invention.

[0019] Figure 8 This is a graph showing an example of the liquid fuel injection timing set with respect to the ammonia co-firing ratio in the ammonia co-firing engine according to the embodiment of the present invention.

[0020] Figure 9 This is a graph showing an example of the liquid fuel injection pressure set for the ammonia co-firing ratio in the ammonia co-firing engine according to the embodiment of the present invention.

[0021] Figure 10 This is a simulation diagram showing an ammonia co-firing engine according to another example of the present invention.

[0022] Figure 11 This is a graph showing a map of unburned ammonia in relation to the combustion temperature and the fuel-air equivalence ratio in an ammonia co-firing engine.

[0023] Figure 12 This is a graph showing a map of N2O in relation to the relationship between the combustion temperature and the fuel-air equivalence ratio in an ammonia co-firing engine.

[0024] Description of Reference Numerals

[0025] 1--Ammonia co-firing engine, 2--Control unit, 3--Intake passage, 4--Exhaust passage, 10--Cylinder, 11--Cylinder barrel, 12--Piston, 13--Cylinder head, 14--Ammonia supply device, 15--Liquid fuel supply device, 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 valve, 41--Supercharger, 41a--Turbine, 41b--Compressor, 41c--Variable nozzle, 42--Intercooler, 43--Recirculation device, 43a--Recirculation passage, 43b--Recirculation cooler, 43c--Recirculation valve, 44--Intake bypass passage, 44a--Intake bypass valve, 45--Wastegate, 45a--Wastegate valve. DETAILED DESCRIPTION

[0026] Referring to the accompanying drawings, an ammonia co-firing engine 1 according to an embodiment of the present invention will be described. The ammonia co-firing engine 1 (engine) is an engine that operates by burning at least one fuel, ammonia and a hydrocarbon-based liquid fuel such as light oil. The ammonia co-firing engine 1 controls the supply of ammonia and liquid fuel by a control unit 2. The ammonia co-firing engine 1 is configured such that a plurality of cylinders 10 are provided in a cylinder block (not shown). Figure 1 In the figure, only one cylinder 10 is shown. Figure 1 As shown, each cylinder 10 includes a cylinder bore 11 , a piston 12 , a cylinder head 13 , an ammonia supply device 14 , and a liquid fuel supply device 15 .

[0027] The cylinder tube 11 is formed in a cylindrical shape, for example, within a cylinder block, and the piston 12 is slidably accommodated in the cylinder tube 11. The cylinder head 13 is mounted on the upper side of the cylinder tube 11. A combustion chamber 20 is formed in the cylinder tube 11 between the piston 12 and the cylinder head 13.

[0028] 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 .

[0029] The cylinder head 13 has an intake port 21 and an exhaust port 22 communicating with the combustion chamber 20 of the cylinder 11 , and includes an intake valve 23 and an exhaust valve 24 for opening and closing the intake port 21 and the exhaust port 22 with respect to the combustion chamber 20 , respectively.

[0030] 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. 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 introduced into the combustion chamber 20 through the intake port 21. On the other hand, by opening the exhaust valve 24, exhaust gas generated in the combustion chamber 20 can be discharged through the exhaust port 22.

[0031] in addition, Figure 1 In the figure, although the example in which the intake passage 3 and the intake port 21 are directly connected is shown, in order to connect the intake passage 3 to the intake ports 21 of the plurality of cylinders 10, an intake manifold having branched flow paths branching from the intake passage 3 toward the plurality of cylinders 10 may be provided between the intake passage 3 and the cylinder head 13. Figure 1 Although an example in which the exhaust passage 4 and the exhaust port 22 are directly connected is illustrated, when the exhaust passage 4 and the exhaust ports 22 of the plurality of cylinders 10 are connected, an exhaust manifold having a branch flow path branching from the exhaust passage 4 toward the plurality of cylinders 10 may be provided between the exhaust passage 4 and the cylinder head 13.

[0032] The ammonia supply device 14 is controlled by the control unit 2 and supplies ammonia supplied from an ammonia tank 25 storing ammonia toward the combustion chamber 20. For example, the ammonia supply device 14 is composed of a gas supply valve, a gas injector, and the like.

[0033] Figure 1, the figure shows an example in which the ammonia supply device 14 is provided at the intake port 21 to inject ammonia into the intake port 21 and supply ammonia to the combustion chamber 20 via the intake port 21. Alternatively, the ammonia supply device 14 may be provided at the intake passage 3 to inject ammonia into the intake passage 3 and supply ammonia to the combustion chamber 20 via the intake passage 3 and the intake port 21. Alternatively, the ammonia supply device 14 may be provided at the cylinder bore 11 or the cylinder head 13 to inject ammonia directly into the combustion chamber 20 for supply.

[0034] A mixture of air supplied from the intake passage 3 and ammonia supplied by the ammonia supply device 14, the injection rate of which is controlled by the control unit 2, is supplied to the combustion chamber 20 from the intake port 21, with the air excess ratio controlled. The ammonia supply device 14 controls the injection rate of ammonia, as well as the injection pressure, injection timing, and other factors, through the control unit 2.

[0035] The liquid fuel supply device 15 is controlled by the control unit 2 and supplies liquid fuel supplied from a liquid fuel tank 26 storing hydrocarbon-based liquid fuel such as diesel toward the combustion chamber 20. For example, the liquid fuel supply device 15 is composed of a device such as an injector of a droplet injection type that injects a small amount of liquid fuel.

[0036] Figure 1 , the figure shows an example in which the liquid fuel supply device 15 is provided in the cylinder head 13 and supplies the 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 to inject the liquid fuel into the intake port 21 and supply the liquid fuel to the combustion chamber 20 via the intake port 21. Alternatively, the liquid fuel supply device 15 may be provided in the intake passage 3 to inject the liquid fuel into the intake passage 3 and supply the liquid fuel to the combustion chamber 20 via the intake passage 3 and the intake port 21.

[0037] The liquid fuel supply device 15 controls the injection amount, injection pressure, injection timing, etc. of the liquid fuel via the control unit 2. The liquid fuel supply device 15 compresses and auto-ignites the mixture of ammonia and air in the combustion chamber 20 using hydrocarbon-based liquid fuel to cause combustion.

[0038] The control unit 2 is a computer such as an ECU (Engine Control Unit) that controls the operation of the ammonia-burning engine 1. It includes a CPU, ROM, RAM, and other components and is configured to control various components of the ammonia-burning engine 1. The control unit 2 can store various programs for controlling the ammonia-burning engine 1 and controls the ammonia-burning engine 1 by reading and executing the programs.

[0039] Next, supply control of ammonia and liquid fuel in the ammonia co-firing engine 1 will be described.

[0040] Figure 2 In FIG, the horizontal axis represents the ammonia combustion rate (the ratio of ammonia in the fuel composed of ammonia and liquid fuel) of the ammonia burned in the combustion chamber 20, and the vertical axis represents the excess air ratio relative to the ammonia in the mixed gas supplied to the combustion chamber 20. Figure 2 In FIG. 1 , the relationship between the ammonia co-firing ratio and the excess air ratio is shown, from the perspective of combustion stability, as a stable region 30 in which the ammonia co-firing engine 1 can operate stably. Furthermore, a map of combustion instability within the stable region 30 is shown, where the instability increases in the direction indicated by the white arrow 31. Figure 2 When the excess air ratio is relatively high, once the ammonia co-combustion ratio becomes high, the combustion instability increases and it will deviate from the stable area 30. Therefore, the higher the ammonia co-combustion ratio, the lower the excess air ratio must be, so that the ammonia co-combustion engine 1 can operate stably.

[0041] Figure 3 In FIG. 1 , the horizontal axis represents the injection timing of the liquid fuel into the combustion chamber 20, and the vertical axis represents the excess air ratio relative to ammonia in the air-fuel mixture supplied to the combustion chamber 20. Figure 3 In FIG. 1 , the relationship between the liquid fuel injection timing and the excess air ratio is shown, showing the liquid fuel injection timing and the stable region 32 in which the ammonia co-firing engine 1 can operate stably. In addition, the map of combustion instability within the stable region 32 is shown, and the instability increases in the direction indicated by the white arrow 33. Figure 3 When the liquid fuel injection timing is relatively delayed, once the ammonia combustion rate becomes higher, combustion instability increases. Therefore, the higher the ammonia combustion rate, the earlier the liquid fuel injection timing should be, thereby enabling the ammonia combustion engine 1 to operate stably.

[0042] Figure 4 In FIG. 1 , the horizontal axis represents the injection pressure of the liquid fuel injected 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). Figure 4 When the liquid fuel injection pressure is relatively high, combustion instability increases. Therefore, by reducing the liquid fuel injection pressure, the ammonia co-firing engine 1 can be operated stably.

[0043] Figure 5 In FIG. 1 , the horizontal axis represents the combustion rate of ammonia burned in the combustion chamber 20, and the vertical axis represents the excess air rate relative to the ammonia in the mixed gas supplied to the combustion chamber 20. Figure 5, the relationship between the ammonia co-firing ratio and the excess air ratio is shown, from the perspective of exhaust gas properties, as a stable region 34 in which the ammonia co-firing engine 1 can operate stably. Furthermore, the map of unburned ammonia contained in the exhaust gas discharged from the combustion chamber 20 within the stable region 34 shows that the amount of unburned ammonia increases in the direction indicated by the white arrow 35. Figure 5 When the excess air ratio is relatively high, once the ammonia co-combustion ratio becomes higher, the unburned ammonia will increase and will deviate from the stable area 34. Therefore, the higher the ammonia co-combustion ratio, the lower the excess air ratio must be, thereby reducing the unburned ammonia and allowing the ammonia co-combustion engine 1 to operate.

[0044] Figure 6 In FIG. 1 , the horizontal axis represents the combustion rate of ammonia burned in the combustion chamber 20, and the vertical axis represents the excess air rate relative to the ammonia in the mixed gas supplied to the combustion chamber 20. Figure 6 In the figure, the relationship between the ammonia co-firing ratio and the excess air ratio is shown, from the perspective of exhaust gas properties, as follows: a stable region 36 in which the ammonia co-firing engine 1 can operate stably is shown, and a map of N2O (nitrous oxide or nitrous oxide) contained in the exhaust gas discharged from the combustion chamber 20 within the stable region 36 is shown, where N2O increases in the direction indicated by the white arrow 37. Figure 6 When the excess air ratio is relatively high, once the ammonia co-combustion ratio becomes higher, N2O will increase and deviate from the stable area 36. Therefore, the higher the ammonia co-combustion ratio, the lower the excess air ratio must be, thereby reducing N2O and allowing the ammonia co-combustion engine 1 to operate.

[0045] Based on the aforementioned relationship between the ammonia combustion ratio, excess air ratio, liquid fuel injection timing, and liquid fuel injection pressure in the ammonia co-firing engine 1, the control unit 2 controls each parameter (excess air ratio, liquid fuel injection timing, and liquid fuel injection pressure) to simultaneously maintain and improve combustion stability and exhaust gas properties when operating at any ammonia combustion ratio. The control unit 2 controls the engine to reduce the excess air ratio, advance (or shorten) the liquid fuel injection timing, or reduce the liquid fuel injection pressure in response to an increase in the ammonia combustion ratio. Furthermore, in the ammonia co-firing engine 1 of this embodiment, the ammonia combustion ratio can be set to a value exceeding 0%, or preferably to a value of approximately 5% or greater.

[0046] For example, the control unit 2 may be Figure 7As shown, the supply of ammonia by the ammonia supply device 14 and the intake of air on the intake passage 3 are controlled in such a manner that the excess air ratio of the mixed gas supplied to the combustion chamber 20 decreases as the ammonia mixing ratio increases. Specifically, the control unit 2 reduces the excess air ratio by 0.1 to 0.5 during a period in which the mixing ratio increases by 10%, preferably reducing it by 0.1 at a time. In addition, the control unit 2 pre-sets a minimum value of the excess air ratio (for example, 1.0) and reduces the excess air ratio to the minimum value. In addition, the control unit 2 may also control the supply of ammonia by the ammonia supply device 14 and the intake of air on the intake passage 3 in such a manner that the excess air ratio increases as the ammonia mixing ratio decreases.

[0047] Control unit 2 Figure 8 As shown, the liquid fuel supply from the liquid fuel supply device 15 is controlled so that the injection timing of the liquid fuel supplied to the combustion chamber 20 is advanced (earlier) 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, as the mixing ratio increases by 10%. Alternatively, the control unit 2 may control the liquid fuel supply from the liquid fuel supply device 15 so that the injection timing of the liquid fuel is delayed as the ammonia mixing ratio decreases.

[0048] Control unit 2 Figure 9 As shown, the supply of liquid fuel by the liquid fuel supply device 15 is controlled 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 reduces the liquid fuel injection pressure by 1 to 30 MPa, preferably by 17 MPa at a time, while the mixing ratio increases by 10%. Alternatively, the control unit 2 may control the supply of liquid fuel by the liquid fuel supply device 15 so that the injection pressure increases as the ammonia mixing ratio decreases.

[0049] Furthermore, the control unit 2 may also perform control so that at least two of the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure are simultaneously implemented in accordance with an increase or decrease in the ammonia mixing ratio. The control unit 2 may also perform control by setting a priority in the order of the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure.

[0050] As described above, according to the present invention, an ammonia co-combustion engine 1 that operates by burning ammonia with a hydrocarbon-based liquid fuel implements, through a control unit 2, at least one of the following: a decrease or increase in the excess air ratio in the fuel, an advance or retardation of the injection period of the liquid fuel, and a decrease or increase in the injection pressure of the liquid fuel, in response to an increase or decrease in the mixing ratio of ammonia in the fuel.

[0051] Thus, the ammonia co-firing 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-firing ratio changes in response to changes in the operating mode. Therefore, the ammonia co-firing engine 1 can operate at any ammonia co-firing ratio while combusting ammonia with a hydrocarbon-based liquid fuel, while achieving both combustion stability and improved exhaust gas properties. Furthermore, the ammonia co-firing engine 1 is not restricted to a specific operating mode, even when selecting an operating mode based on various fuel levels or navigation area restrictions, thereby enhancing market appeal.

[0052] Furthermore, the ammonia co-firing engine 1 of the present invention reduces the excess air ratio by 0.1 to 0.5 when the ammonia co-firing ratio increases by 10%, using the control unit 2. Thus, the ammonia co-firing engine 1 can set an appropriate excess air ratio to achieve both improved combustion stability and exhaust gas properties, even when the ammonia co-firing ratio is increased.

[0053] Furthermore, the ammonia co-firing engine 1 of the present invention advances the liquid fuel injection timing by 0.1 to 5.0 degrees during a period in which the ammonia co-firing ratio increases by 10%, using the control unit 2. Thus, the ammonia co-firing engine 1 can set an appropriate liquid fuel injection timing to achieve both improved combustion stability and improved exhaust gas properties, even when the ammonia co-firing ratio is increased.

[0054] Furthermore, the ammonia co-firing engine 1 of the present invention reduces the liquid fuel injection pressure by 1 to 30 MPa during a period in which the ammonia co-firing ratio increases by 10%, using the control unit 2. Thus, the ammonia co-firing engine 1 can set an appropriate liquid fuel injection pressure to achieve both improved combustion stability and improved exhaust gas properties, even when the ammonia co-firing ratio is increased.

[0055] Furthermore, the ammonia co-firing engine 1 of the present invention simultaneously controls at least two of the following: the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure, in response to increases or decreases in the ammonia co-firing ratio, via the control unit 2. Consequently, the ammonia co-firing engine 1 can appropriately select the desired parameters from the excess air ratio, the liquid fuel injection timing, and the liquid fuel injection pressure to more appropriately balance combustion stability and exhaust gas properties at any ammonia co-firing ratio.

[0056] In addition, in the above embodiment, an example is described in which the control unit 2 performs control in such a manner that the excess air ratio is reduced, the liquid fuel injection timing is advanced, and / or the liquid fuel injection pressure is reduced as the ammonia mixing rate is increased. Figure 7 、 Figure 8 as well as Figure 9 , although an example is shown in which the excess air ratio is reduced, the liquid fuel injection timing is advanced, and / or the liquid fuel injection pressure is reduced in proportion to the increase in the ammonia mixing ratio, the present invention is not limited to this example.

[0057] In another example, control unit 2 may also perform a threshold determination on the ammonia combustion ratio and, based on the determination result, determine whether to reduce the excess air ratio, advance the liquid fuel injection timing, and / or reduce the liquid fuel injection pressure. For example, control unit 2 may pre-set multiple levels of thresholds for the ammonia combustion ratio and pre-set the excess air ratio, liquid fuel injection timing, and / or liquid fuel injection pressure corresponding to each threshold level. Furthermore, control unit 2 may compare the ammonia combustion ratio with the multiple levels of thresholds to determine the level to which the ammonia combustion ratio corresponds, and then set the excess air ratio, liquid fuel injection timing, and / or liquid fuel injection pressure corresponding to the level determined by the determination result.

[0058] In addition, in the above-mentioned embodiment, although an example is described in which the ammonia co-combustion engine 1 implements at least one of a reduction or increase in the excess air ratio in the fuel, an advancement or delay in the injection period of the liquid fuel, and a reduction or increase in the injection pressure of the liquid fuel in accordance with an increase or decrease in the co-combustion rate of ammonia in the fuel through the control unit 2, the present invention is not limited to this example.

[0059] In other examples, the ammonia co-firing engine 1 is Figure 10 As shown, in addition to the configuration of the above-mentioned embodiment, the engine 1 further includes an intake throttle valve 40 , a supercharger 41 , an intercooler 42 , and a recirculation device 43 (EGR device). Furthermore, the ammonia co-firing engine 1 includes an intake bypass passage 44 and a waste gate 45 .

[0060] Moreover, the ammonia co-firing engine 1 is constructed such that, corresponding to an increase in the combustion ratio of ammonia in the fuel, at least one of the following contents is implemented, namely: an increase in the temperature of the air supplied from the intake passage 3 to the cylinder 10 (i.e., the intake air temperature), an increase in the number of injections of the liquid fuel by the liquid fuel supply device 15 during one combustion cycle of the piston 12 in the cylinder 10, a change in the closing timing of the intake valve 23 of the cylinder 10 toward the bottom dead center timing, an increase in the amount of air bypassed from the intake passage 3 to the exhaust passage 4 using the intake bypass passage 44 (i.e., the intake bypass amount), a change in the opening of the waste gate 45 of the supercharger 41 toward the valve opening direction, and an increase in the passage area due to adjustment of the variable nozzle 41c of the supercharger 41.

[0061] Specifically, in the ammonia co-firing engine 1 , a supercharger 41 , an intercooler 42 , and an intake throttle valve 40 are provided in this order from the upstream side in the intake direction of the intake passage 3 .

[0062] The supercharger 41 includes a turbine 41a and a compressor 41b located in the exhaust passage 4. 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 supercharger 41 uses the exhaust gas flowing through the exhaust passage 4 to rotate the turbine 41a. The rotational force of the turbine 41a drives the compressor 41b, thereby compressing the air flowing through the intake passage 3.

[0063] 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 supercharger 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 uses the recirculation cooler 43b to cool the exhaust gas flowing through the exhaust passage 4 upstream of the supercharger 41 in the exhaust direction, recirculates the gas, and supplies it to the intake passage 3 downstream of the intercooler 42 in the intake direction. The recirculation device 43 uses the control unit 2 to adjust the opening of the recirculation valve 43c and the flow rate of the recirculated exhaust gas flowing into the intake passage 3, thereby adjusting the oxygen content of the air flowing through the intake passage 3.

[0064] Furthermore, the ammonia-co-firing engine 1 is provided with an intake bypass passage 44 that connects a position downstream of the supercharger 41 in the intake direction of the intake passage 3 and a position upstream of the supercharger 41 in the exhaust direction of the exhaust passage 4, thereby providing a bypass. An intake bypass valve 44a for adjusting the amount of intake bypass is provided in the intake bypass passage 44. A wastegate 45 is provided in the ammonia-co-firing engine 1 that connects a position upstream of the supercharger 41 and a position downstream of the supercharger 41 in the exhaust direction of the exhaust passage 4, thereby providing a bypass. A wastegate valve 45a for adjusting the amount of exhaust bypass is provided in the wastegate 45.

[0065] Furthermore, in the ammonia co-firing engine 1, the control unit 2 controls the intercooler 42 in response to an increase in the ammonia co-firing ratio in the fuel, thereby increasing the temperature of the air supplied from the intake passage 3 to the cylinder 10 (i.e., the intake air temperature). This increases the temperature inside the cylinder 10, thereby raising the combustion temperature inside the combustion chamber 20. This reduces unburned ammonia and NOx (such as NH3 or N2O) in the exhaust gas, thereby achieving lower emissions.

[0066] Alternatively, in the ammonia co-firing engine 1, the control unit 2 controls the liquid fuel supply device 15 in response to an increase in the ammonia co-firing ratio in the fuel, thereby increasing the number of injections of liquid fuel from the liquid fuel supply device 15 during one combustion cycle of the piston 12 of the cylinder 10. This optimizes the distribution of the liquid fuel within the combustion chamber 20, thereby increasing the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (such as NH3 or N2O) in the exhaust gas, thereby achieving lower emissions.

[0067] Alternatively, in the ammonia co-firing engine 1, the control unit 2 controls the intake valve 23 in response to an increase in the ammonia co-firing ratio in the fuel, changing the closing timing of the intake valve 23 toward bottom dead center timing. This increases the effective compression ratio within the combustion chamber 20, raising the combustion temperature within the combustion chamber 20. This reduces unburned ammonia and NOx (NH3, N2O, etc.) in the exhaust gas, thereby achieving lower emissions.

[0068] Alternatively, the ammonia co-firing engine 1 controls the intake bypass valve 44a via the control unit 2 in response to an increase in the ammonia co-firing 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, thereby increasing the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (NH3, N2O, etc.) in the exhaust gas, thereby achieving lower emissions.

[0069] Alternatively, in the ammonia co-firing engine 1, the control unit 2 controls the wastegate valve 45a in response to an increase in the ammonia co-firing ratio in the fuel, changing the opening of the wastegate 45 toward the open position. This increases the amount of residual gas, reduces the amount of air compressed by the supercharger 41, and thereby reduces the proportion of air in the intake air. Furthermore, the proportion of fuel is increased, raising the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (such as NH3 or N2O) in the exhaust gas, thereby achieving lower emissions.

[0070] Alternatively, in the ammonia co-firing engine 1, the control unit 2 adjusts the variable nozzle 41c to increase the passage area of ​​the turbine 41a of the supercharger 41 in response to an increase in the ammonia co-firing ratio in the fuel. This increases the amount of residual gas in the exhaust passage 4, reduces the amount of air compression in the supercharger 41, and thereby reduces the proportion of air in the intake air. Furthermore, it increases the proportion of fuel, raising the combustion temperature in the combustion chamber 20 and reducing unburned ammonia and NOx (such as NH3 or N2O) in the exhaust gas, thereby achieving lower emissions.

[0071] exist Figure 11 as well as Figure 12 In FIG. 2 , 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 of the mixture supplied to the combustion chamber 20 . Figure 11, regarding the relationship between the combustion temperature and the fuel-air equivalence ratio, a map of unburned ammonia contained in the exhaust gas of the ammonia co-firing engine 1 is shown. In the direction indicated by the white arrow 50, the unburned ammonia decreases. Figure 12 In FIG. 1 , the relationship between the combustion temperature and the fuel-air equivalence ratio is shown as follows: the map of N2O contained in the exhaust gas of the ammonia co-firing engine 1 shows that N2O decreases in the direction indicated by the white arrow 51. Figure 11 , the higher the combustion temperature, the less unburned ammonia. Figure 12 , the higher the combustion temperature, the less N2O will be produced.

[0072] Thus, according to other examples, corresponding to the increase in the mixing rate of ammonia in the fuel, at least one of the following is implemented: an increase in the intake temperature, an increase in the number of injections of liquid fuel during one combustion cycle, a change in the closing timing of the intake valve 23 toward the bottom dead center timing, an increase in the intake bypass volume, a change in the opening of the exhaust valve 45 toward the opening direction, and an increase in the passage area due to adjustment of the variable nozzle 41c, thereby improving the exhaust gas properties.

[0073] Furthermore, the present invention may be appropriately modified without departing from the spirit or concept of the invention as can be read from the claims and the entire contents of the specification, and an ammonia co-firing engine with such modifications is also included in the technical concept of the present invention.

[0074] [Supplementary Notes on the Invention]

[0075] The following is a summary of the invention extracted from the above-mentioned embodiment as a supplementary note. In addition, each configuration and each processing function described in the following supplementary notes can be selected and discarded, and can be combined arbitrarily.

[0076] Note 1

[0077] An ammonia co-firing engine is an ammonia co-firing engine that operates by burning ammonia and a hydrocarbon-based liquid fuel. The ammonia co-firing engine is characterized in that, corresponding to an increase or decrease in the mixing ratio of the ammonia in the fuel, at least one of the following is implemented: a decrease or increase in the excess air ratio in the fuel, an advancement or delay in the injection period of the liquid fuel, and a decrease or increase in the injection pressure of the liquid fuel.

[0078] Note 2

[0079] The ammonia co-firing engine according to Supplementary Note 1 is characterized in that the excess air ratio is reduced by 0.1 to 0.5 while the co-firing ratio is increased by 10%.

[0080] Note 3

[0081] In the ammonia co-firing engine according to Supplement 1 or 2, it is characterized in that the injection timing is advanced by 0.1 to 5.0 degrees while the co-firing ratio increases by 10%.

[0082] Note 4

[0083] The ammonia co-firing engine according to any one of Supplementary Notes 1 to 3 is characterized in that the injection pressure is reduced by 1 to 30 MPa while the co-firing ratio is increased by 10%.

[0084] Note 5

[0085] The ammonia co-firing engine according to any one of Supplements 1 to 4 is characterized in that at least two of the excess air ratio, the injection timing, and the injection pressure are controlled simultaneously in accordance with an increase or decrease in the co-firing ratio.

[0086] <Note 6>

[0087] An ammonia co-firing engine operates by burning ammonia and a hydrocarbon-based liquid fuel. The ammonia co-firing engine is characterized in that, corresponding to an increase in the mixing ratio of the ammonia in the fuel, at least one of the following is implemented: an increase in the intake temperature, an increase in the number of injections of the liquid fuel during one combustion cycle, a change in the closing timing of the intake valve toward the bottom dead center timing, an increase in the intake bypass amount, a change in the opening of the waste gate of the supercharger toward the closing direction, and a reduction in the passage area due to adjustment of the variable nozzle of the supercharger.

Claims

1. An ammonia co-firing engine which operates by burning ammonia and a hydrocarbon-based liquid fuel, characterized in that: Corresponding to an increase or decrease in the ammonia combustion ratio in the fuel, at least one of a decrease or increase in the air excess ratio in the fuel, an advance or retardation in the injection timing of the liquid fuel, and a decrease or increase in the injection pressure of the liquid fuel is implemented.

2. The ammonia co-firing engine according to claim 1, characterized in that: While the co-firing ratio is increased by 10%, the excess air ratio is reduced by 0.1 to 0.

5.

3. The ammonia co-firing engine according to claim 1, characterized in that: While the co-firing rate is increased by 10%, the injection timing is advanced by 0.1 to 5.0 degrees.

4. The ammonia co-firing engine according to claim 1, characterized in that: While the co-firing ratio is increased by 10%, the injection pressure is reduced by 1 to 30 MPa.

5. The ammonia co-firing engine according to claim 1, characterized in that: At least two or more of the excess air ratio, the injection timing, and the injection pressure are simultaneously controlled in accordance with an increase or decrease in the combustion ratio.

6. An ammonia co-firing engine which operates by burning ammonia and a hydrocarbon-based liquid fuel, characterized in that: Corresponding to the increase in the mixing ratio of the ammonia in the fuel, at least one of the following is implemented: an increase in the intake temperature, an increase in the number of injections of the liquid fuel during one combustion cycle, a change in the closing timing of the intake valve toward the bottom dead center timing, an increase in the intake bypass amount, a change in the opening of the exhaust valve of the supercharger toward the valve opening direction, and an increase in the passage area due to adjustment of the variable nozzle of the supercharger.

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