Ammonia co-firing method in engines, ammonia co-firing engine, and a ship equipped with an ammonia co-firing engine.

Abstract

To provide an ammonia mixing combustion method in an engine capable of increasing an ammonia mixing combustion ratio in an engine that mixes and combusts ammonia and liquid fuel, and improving properties of exhaust gas compared to conventional methods, an ammonia mixing combustion engine, and a vessel equipped with an ammonia mixing combustion engine.SOLUTION: When supplying air, ammonia, and liquid fuel to a combustion chamber of an engine and igniting them by compression ignition to cause mixing combustion, by supplying hydrogen to the combustion chamber and mixing and combusting it, a variable range is expanded in a direction of advancing the supply timing of the liquid fuel, and the supply timing of the liquid fuel to the combustion chamber is set later than the supply timing of ammonia and hydrogen.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an ammonia co - firing method in an engine that co - fires ammonia and liquid fuel, an ammonia co - firing engine, and a ship equipped with an ammonia co - firing engine.

Background Art

[0002] Regarding marine diesel engines, research and development for using ammonia (NH3) as fuel and the development of actual engines are in progress. Since ammonia has poor flammability, heavy oil or the like is used as a pilot fuel for ignition. Here, Patent Document 1 discloses a configuration in an ammonia - fired internal combustion engine that enables the supply of ammonia and highly flammable substances other than ammonia, such as GTL light oil and hydrogen, into the combustion chamber. Also, Patent Documents 2 to 4 disclose devices for controlling an internal combustion engine that uses ammonia and a combustion - promoting fuel for the ammonia as fuel, and it is described that hydrogen may be used as the combustion - promoting fuel. Further, Patent Document 5 discloses a technique for purifying nitrogen oxides contained in the exhaust gas of an internal combustion engine using ammonia generated based on aqueous urea, generating hydrogen based on the further - generated ammonia, and effectively using ammonia and hydrogen as fuel to improve the combustion efficiency of the internal combustion engine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0004] When ammonia is used as fuel, unburned ammonia and nitrous oxide (N2O), a greenhouse gas, are emitted. Furthermore, the ratio of ammonia to pilot fuel's calorific value is important; a high ammonia ratio can lead to unstable engine operation and increased levels of unburned ammonia and nitrous oxide. Patent documents 1-5 also describe the unburned ammonia and NO contained in exhaust gases. X Although there are mentions of purification measures, further improvements in the properties of exhaust gases are needed. Therefore, the present invention aims to provide an ammonia co-firing method in an engine, an ammonia co-firing engine, and a ship equipped with an ammonia co-firing engine, which can increase the co-firing rate of ammonia in an engine that co-fires ammonia and liquid fuel, thereby improving the properties of the exhaust gas compared to conventional methods. [Means for solving the problem]

[0005] The ammonia co-firing method in an engine corresponding to claim 1 is an ammonia co-firing method in an engine that co-fires ammonia and liquid fuel, characterized in that when supplying air, ammonia, and liquid fuel to the combustion chamber of the engine and igniting them by compression ignition for co-firing, hydrogen is further supplied to the combustion chamber for co-firing, thereby expanding the variable range in the direction of advancing the timing of liquid fuel supply, and setting the timing of liquid fuel supply to the combustion chamber to be later than the timing of ammonia and hydrogen supply. According to the present invention as described in claim 1, by co-firing hydrogen, the timing of liquid fuel supply can be advanced compared to conventional methods, thereby increasing the co-firing rate of ammonia and improving the properties of exhaust gas by reducing ammonia slip and nitrogen oxides such as nitrous oxide.

[0006] The present invention as described in claim 2 is characterized in that the liquid fuel is supplied by multi-stage injection. According to the present invention as described in claim 2, the properties of the exhaust gas can be further improved compared to single injection.

[0007] The present invention as described in claim 3 is characterized in that the liquid fuel is diesel fuel. According to the present invention as described in claim 3, the properties of the exhaust gas can be further improved in an ammonia co-firing method using diesel fuel, which is a common liquid fuel.

[0008] The present invention as described in claim 4 is characterized by supplying air to the combustion chamber with a pre-mixed mixture of ammonia and hydrogen. According to the present invention as described in claim 4, the properties of the exhaust gas can be further improved.

[0009] The present invention as described in claim 5 is characterized by supplying ammonia stored in a liquid state by vaporizing it. According to the present invention as described in claim 5, it is possible to prevent a drop in the temperature of the supply air and further improve the properties of the exhaust gas.

[0010] The present invention as described in claim 6 is characterized by obtaining hydrogen by decomposing a portion of ammonia. According to the present invention as described in claim 6, the properties of the exhaust gas can be improved by co-firing hydrogen obtained from ammonia, eliminating the need to store ammonia and hydrogen separately.

[0011] The present invention as described in claim 7 is characterized in that the advance angle as the timing for supplying liquid fuel is set in the range of -25 degrees to -70 degrees after ATDC (top dead center). According to the present invention as described in claim 7, the properties of the exhaust gas can be further improved while maintaining stable combustion.

[0012] The present invention as described in claim 8 is characterized in that the ratio of the supply amount of ammonia and hydrogen to the total supply amount of liquid fuel, ammonia and hydrogen is in the range of 1% to 95%. According to the present invention as described in claim 8, the properties of the exhaust gas can be further improved while increasing the co-combustion ratio of ammonia and hydrogen.

[0013] The present invention as described in claim 9 is characterized by purifying NOx in exhaust gas discharged from a combustion chamber using ammonia and SCR (selective catalytic reduction). According to the present invention as described in claim 9, nitrogen oxides (NOx) in exhaust gas can be reduced by utilizing slipped ammonia contained in the exhaust gas and ammonia supplied from the same source as for combustion.

[0014] An ammonia co-firing engine corresponding to claim 10 is a compression ignition type ammonia co-firing engine using an ammonia co-firing method in an engine, characterized by comprising: a combustion chamber; an ammonia supply means for supplying ammonia to the combustion chamber; an air supply means for supplying air to the combustion chamber; a liquid fuel supply means for supplying liquid fuel to the combustion chamber; a hydrogen supply means for supplying hydrogen to the combustion chamber; a fuel ratio setting means for setting the ratio of the supply amounts of ammonia and hydrogen to the total supply amount of liquid fuel, ammonia and hydrogen; and a supply timing control means for controlling the supply timing of liquid fuel by the liquid fuel supply means according to the ratio setting of the fuel ratio setting means. According to the present invention as described in claim 10, by co-firing hydrogen, the timing of liquid fuel supply can be advanced compared to conventional methods, thereby increasing the co-firing rate of ammonia and reducing ammonia slip and nitrogen oxides such as nitrous oxide, thereby improving the properties of exhaust gas.

[0015] The present invention as described in claim 11 is characterized in that the supply timing control means controls the supply of liquid fuel by the liquid fuel supply means to supply it by multi-stage injection. According to the present invention as described in claim 11, the properties of the exhaust gas can be further improved compared to single injection.

[0016] The present invention according to claim 12 is characterized in that ammonia and hydrogen are injected into the air supply path of the air supply means, and air, ammonia, and hydrogen are mixed in advance and supplied to the combustion chamber. According to the present invention described in claim 12, the properties of the exhaust gas can be further improved.

[0017] The present invention according to claim 13 is characterized in that a vaporizing means for vaporizing ammonia stored in a liquid state is provided in the air supply path of the air supply means. According to the present invention described in claim 13, it is possible to prevent a temperature drop of the supplied air and further improve the properties of the exhaust gas.

[0018] The present invention according to claim 14 is characterized in that the supply timing control means controls the supply timing of the liquid fuel supply means to an advance angle as the supply timing of the liquid fuel from ATDC (after top dead center) -25 degrees to -70 degrees. According to the present invention described in claim 14, it is possible to further improve the properties of the exhaust gas while maintaining stable combustion.

[0019] The present invention according to claim 15 is characterized in that the fuel ratio setting means sets the ratio of the supply amounts of ammonia and hydrogen to the total supply amount of the liquid fuel, hydrogen, and ammonia in the range of 1% to 95%. According to the present invention described in claim 15, it is possible to further improve the properties of the exhaust gas while increasing the co-combustion ratio of ammonia and hydrogen.

[0020] The present invention according to claim 16 is characterized in that a SCR (selective catalytic reduction) system for purifying NOx in the exhaust gas discharged from the combustion chamber using ammonia is provided in the exhaust path of the exhaust gas. According to the present invention described in claim 16, nitrogen oxides (NOx) in the exhaust gas can be reduced by using the slipped ammonia contained in the exhaust gas and the ammonia supplied from the same supply source as that for combustion.

[0021] A vessel equipped with an ammonia co-firing engine corresponding to claim 17 is characterized in that the ammonia co-firing engine is installed on the vessel. According to the present invention as described in claim 17, it is possible to realize a ship that increases the co-firing rate of ammonia and improves the properties of the exhaust gas. [Effects of the Invention]

[0022] According to the ammonia co-firing method in the engine of the present invention, by co-firing hydrogen, the timing of liquid fuel supply can be advanced compared to conventional methods, thereby increasing the ammonia co-firing rate and improving the properties of exhaust gas by reducing ammonia slip and nitrogen oxides such as nitrous oxide.

[0023] Furthermore, when liquid fuel is supplied by multi-stage injection, the properties of the exhaust gas can be improved compared to single injection.

[0024] Furthermore, when the liquid fuel is diesel fuel, the properties of the exhaust gas can be further improved in the ammonia co-firing method using diesel fuel, which is a common liquid fuel.

[0025] Furthermore, if ammonia and hydrogen are pre-mixed with air before being supplied to the combustion chamber, the properties of the exhaust gas can be further improved.

[0026] Furthermore, when ammonia stored in liquid form is vaporized and supplied, it is possible to prevent a drop in the temperature of the supplied air and further improve the properties of the exhaust gas.

[0027] Furthermore, when hydrogen is obtained by decomposing part of the ammonia, the hydrogen obtained from the ammonia can be co-fired to improve the properties of the exhaust gas, eliminating the need to store ammonia and hydrogen separately.

[0028] Furthermore, by setting the advance angle for liquid fuel supply timing to a range of -25 to -70 degrees after ATDC (top dead center), it is possible to maintain stable combustion while further improving the properties of the exhaust gas.

[0029] Furthermore, when the ratio of ammonia and hydrogen supply to the total supply of liquid fuel, ammonia, and hydrogen is set between 1% and 95%, the exhaust gas properties can be further improved while increasing the co-combustion rate of ammonia and hydrogen.

[0030] Furthermore, when NOx in exhaust gas discharged from the combustion chamber is purified using SCR (Selective Catalytic Reduction) with ammonia, nitrogen oxides (NOx) in the exhaust gas can be reduced by utilizing the slipped ammonia contained in the exhaust gas or ammonia supplied from the same source as for combustion.

[0031] Furthermore, with the ammonia co-firing engine of the present invention, by co-firing hydrogen, the timing of liquid fuel supply can be advanced compared to conventional engines, thereby increasing the ammonia co-firing rate and improving the properties of exhaust gas by reducing ammonia slip and nitrogen oxides such as nitrous oxide.

[0032] Furthermore, when the supply timing control means controls the supply of liquid fuel by the liquid fuel supply means to be supplied by multi-stage injection, the properties of the exhaust gas can be improved compared to single injection.

[0033] Furthermore, if ammonia and hydrogen are injected into the air intake path of the air supply means, and the air, ammonia, and hydrogen are mixed in advance and supplied to the combustion chamber, the properties of the exhaust gas can be further improved.

[0034] Furthermore, if a vaporization means for vaporizing ammonia stored in liquid state is provided in the air supply path of the air supply means, a decrease in the temperature of the supplied air can be prevented, thereby further improving the properties of the exhaust gas.

[0035] Furthermore, when the supply timing control means controls the advance angle of the liquid fuel supply timing from -25 degrees to -70 degrees after ATDC (top dead center), it is possible to maintain stable combustion while further improving the properties of the exhaust gas.

[0036] Furthermore, when the fuel ratio setting means sets the ratio of the supply amount of ammonia to the supply amount of hydrogen to the total supply amount of liquid fuel, hydrogen, and ammonia in the range of 1% to 95%, it is possible to further improve the properties of the exhaust gas while increasing the co-combustion rate of ammonia and hydrogen.

[0037] Furthermore, if a selective catalytic reduction (SCR) system, which purifies NOx in exhaust gas discharged from the combustion chamber using ammonia, is installed in the exhaust gas path, nitrogen oxides (NOx) in the exhaust gas can be reduced by utilizing the slipped ammonia contained in the exhaust gas and ammonia supplied from the same source as for combustion.

[0038] Furthermore, a ship equipped with the ammonia co-firing engine of the present invention can be realized that increases the ammonia co-firing rate and improves the properties of the exhaust gas. [Brief explanation of the drawing]

[0039] [Figure 1] Schematic diagram of an ammonia co-firing engine according to an embodiment of the present invention [Figure 2] The injection timing chart (supply timing) [Figure 3] The same injection timing chart (variable range). [Figure 4-1] Diagram showing test results [Figure 4-2] Diagram showing test results [Modes for carrying out the invention]

[0040] This paper describes an ammonia co-firing method in an engine according to embodiments of the present invention, an ammonia co-firing engine, and a vessel equipped with an ammonia co-firing engine. Figure 1 is a schematic diagram of an ammonia co-firing engine according to this embodiment. The ammonia co-firing engine used in the ammonia co-firing method of this embodiment is a diesel engine and comprises a piston 10, a cylinder 11, a combustion chamber 12, an ammonia supply means 13 for supplying ammonia to the combustion chamber 12, an air supply means 14 for supplying air to the combustion chamber 12, a liquid fuel supply means 15 for supplying liquid fuel to the combustion chamber 12, a liquid fuel pressurizing means 16 for pressurizing the liquid fuel, a hydrogen supply means 17 for supplying hydrogen to the combustion chamber 12, a vaporization means 18 for vaporizing the ammonia stored in liquid state, an exhaust means 19 for guiding the exhaust gas discharged from the combustion chamber 12 to the outside, an SCR (Selective Catalytic Reduction) system 20 for purifying NOx in the exhaust gas discharged from the combustion chamber 12 using ammonia, and a control device 21 for controlling the ammonia co-firing engine. The control device 21 is configured to include, for example, a programmable computer and a signal generation circuit for generating signals to be sent to various parts of the ammonia co-firing engine, and has a fuel ratio setting means 21a for setting the ratio of the supply amounts of ammonia and hydrogen to the total supply amount of liquid fuel, ammonia and hydrogen, and a supply timing control means 21b for controlling the timing of liquid fuel supply by the liquid fuel supply means 15 according to the ratio setting of the fuel ratio setting means 21a. An ammonia-fired engine can be installed on a ship, for example, and function as a main engine or an auxiliary engine that drives a load device 1 such as a propeller.

[0041] In each cylinder of an ammonia-fired engine, the combustion chamber 12 is formed by the piston 10 and the cylinder 11. Specifically, the cylinder 11 is constructed by combining a cylinder block and a cylinder head, with the piston 10 positioned to reciprocate within the bore of the cylinder block, and the cylinder head connected to the piston 10 so as to surround the bore. The space enclosed by the piston 10 and the cylinder 11 becomes the combustion chamber 12.

[0042] The air supply means 14 has an air supply path (also called an intake path) 14a and an air supply valve (also called an intake valve) 14b, and the exhaust means 19 has an exhaust path 19a and an exhaust valve 19b. Each cylinder of the ammonia-fired engine is provided with an intake passage 14a and an exhaust passage 19a. An intake valve 14b is provided in the intake passage 14a at the connection point with the combustion chamber 12, and an exhaust valve 19b is provided in the exhaust passage 19a at the connection point with the combustion chamber 12. Each cylinder is equipped with a crank angle sensor (not shown) that detects the rotational angle position of the crankshaft in accordance with the movement of the piston 10. The control device 21 controls the opening and closing of the intake valve 14b and the exhaust valve 19b according to the detected rotational angle position. In other words, the intake valve 14b is opened and closed according to the rotational angle position of the crankshaft, thereby controlling the timing of air supply to the cylinder. Similarly, the exhaust valve 19b is opened and closed according to the rotational angle position of the crankshaft, thereby controlling the exhaust from the cylinder. The air intake may be naturally aspirated using an ammonia-co-firing engine or pressurized air intake using a turbocharger. Furthermore, for experimental purposes, as shown in Figure 1, an exhaust gas analyzer 2, such as an FTIR (Fourier Transform Infrared Spectroscopy) analyzer, can be connected to the exhaust path 19a.

[0043] The ammonia supply means 13 is installed in the air supply path 14a. A liquefied ammonia cylinder 3, which stores liquefied ammonia (NH3), is connected to the ammonia supply means 13. The ammonia supply means 13 is equipped with a flow meter and an injector (injection valve) and injects ammonia into the air supply path 14a. The flow rate of ammonia supplied from the ammonia supply means 13 is controlled by the control device 21. The vaporization means (vaporizer) 18 is located downstream of the ammonia supply means 13 in the air intake path 14a, and the injector of the ammonia supply means 13 is located near the inlet of the vaporization means 18. The vaporization means 18 is not essential, but if it is not provided, the temperature will drop and the amount of ammonia and nitrous oxide discharged will increase. Therefore, by vaporizing the ammonia stored in liquid state using the vaporization means 18 and supplying it as in this embodiment, it is possible to prevent a drop in the temperature of the intake air and further improve the properties of the exhaust gas. Furthermore, the vaporization means 18 can also be installed upstream of the ammonia supply means 13. Also, since the ammonia supplied from the ammonia supply means 13 is vaporized by the vaporization means 18, gaseous ammonia can be used instead of liquefied ammonia. In addition, the system can be configured to decompose a portion of the ammonia to obtain hydrogen, in which case the hydrogen obtained from the ammonia can be co-fired to improve the properties of the exhaust gas, eliminating the need to store ammonia and hydrogen separately.

[0044] In this way, by injecting ammonia into the air intake path 14a, the supplied ammonia can be mixed with air, which acts as an oxidizing agent, and supplied to the combustion chamber 12. Note that other oxidizing agents such as oxygen-enriched air or pure oxygen may be used instead of air. Furthermore, other auxiliary fuels such as hydrogen (H2), natural gas, or LPG may be added. The supply of the ammonia-air mixture to the combustion chamber 12 occurs in conjunction with the intake stroke in an ammonia-fired engine and begins before the pilot injection of liquid fuel.

[0045] Each cylinder of the ammonia-co-fired engine is connected to a liquid fuel supply means 15 and a liquid fuel pressurizing means 16. The liquid fuel supply means 15 is equipped with an electronic fuel injector and receives pressurized liquid fuel from the liquid fuel pressurizing means 16, such as a high-pressure pump, and injects the liquid fuel into the combustion chamber 12. The liquid fuel can be, for example, diesel fuel, heavy oil A, GTL (Gas to Liquids) fuel, or biodiesel fuel such as FAME (Fatty Acid Methyl Ester) or HVO (Hydrotreated Vegetable Oil). In particular, when diesel fuel is used as the liquid fuel, the properties of the exhaust gas can be further improved in the ammonia co-firing method. When the liquid fuel is diesel fuel, it is preferable to pressurize the liquid fuel by the liquid fuel pressurizing means 16 to about 100 MPa. The amount of liquid fuel supplied from the liquid fuel supply means 15 is controlled by the control device 21. The timing of liquid fuel injection by the liquid fuel supply means 15 is controlled by the supply timing control means 21b. Pilot injection of liquid fuel is performed in the compression stroke of the ammonia-co-fired engine before top dead center (TDC).

[0046] When operating an ammonia-fired engine, pilot injection of liquid fuel can be multi-stage. For example, if pilot injection is performed in two stages, the sub-injection is followed by the main injection between -60 and -10 degrees of crank angle after the engine's top dead center (ATDC). By supplying liquid fuel through multi-stage injection, the properties of the exhaust gas can be further improved compared to single injection.

[0047] The SCR system 20 is installed in the exhaust path 19a and filters nitrogen oxides (NOx) from the exhaust gas. X Post-treatment is performed to reduce ) by the SCR system 20. By providing the SCR system 20, nitrogen oxides can be reduced to nitrogen (N2) and water (H2O) by using the action of a catalyst and the slipped ammonia contained in the exhaust gas, thereby suppressing the amount of nitrogen oxides emitted from the exhaust gas. Furthermore, if a reduction ammonia supply line is provided in the middle of the piping connecting the liquefied ammonia gas cylinder 3 and the ammonia supply means 13, with one end connected to the upstream side of the SCR system 20 in the exhaust path 19a, and the ammonia from the liquefied ammonia cylinder 3 can also be supplied to the SCR system 20 by controlling a valve, etc., then the ammonia used as fuel (ammonia supplied from the same supply source as for combustion) can also be used as ammonia for the reduction reaction in the SCR system 20 to reduce nitrogen oxides in the exhaust gas. In addition, by sharing the ammonia supply source and part of the supply system between combustion and reduction, the piping and supply source of the ammonia co-firing engine can be simplified. Furthermore, the amount of ammonia used as fuel supplied to the ammonia-co-fired engine can be increased and supplied to the SCR system 20 as unburned, slipped ammonia for the reduction of nitrogen oxides. However, in this case, precise ratio control is required, so it is preferable to provide an ammonia detection means in the exhaust path 19a and precisely control the amount of ammonia supplied by the supply timing control means 21b of the control device 21.

[0048] The hydrogen supply means 17 is located downstream of the vaporization means 18 in the air intake path 14a. A hydrogen gas cylinder 4 containing hydrogen (H2) is connected to the hydrogen supply means 17. The hydrogen supply means 17 is equipped with a flow meter and an injector (injection valve) and injects hydrogen into the air intake path 14a. Note that if the vaporization means 18 is located upstream of the ammonia supply means 13 or if gaseous ammonia is used, it is not necessary to install the hydrogen supply means 17 downstream of the vaporization means 18 in the air intake path 14a. The supply of hydrogen to the combustion chamber 12 is carried out together with the air intake stroke in the ammonia co-firing engine and starts before the pilot injection of liquid fuel. As in this embodiment, when supplying air, ammonia, and liquid fuel to the combustion chamber 12 of the engine and igniting them by compression ignition for co-combustion, further supplying hydrogen to the combustion chamber 12 for co-combustion expands the variable range of the liquid fuel supply timing in the advance direction. By operating at this expanded operating point, the co-combustion rate of ammonia can be increased, and the properties of the exhaust gas can be improved by reducing ammonia slip and nitrogen oxides such as nitrous oxide. In this case, as described above, the supply timing of liquid fuel to the combustion chamber 12 is set to be later than the supply timing of ammonia and hydrogen. Furthermore, by pre-mixing ammonia and hydrogen with air in the intake passage 14a and supplying it to the combustion chamber 12, the properties of the exhaust gas can be further improved. Note that the ammonia and hydrogen mixture can also be prepared outside the intake passage 14a and supplied to the intake passage 14a. Alternatively, ammonia and hydrogen can be supplied directly to the engine's combustion chamber 12.

[0049] In an ammonia-fired engine, the fuel ratio setting means 21a adjusts the ratio of the supply amount of ammonia to the supply amount of hydrogen used as fuel, thereby controlling the ratio of each amount of ammonia and hydrogen to the total supply amount of liquid fuel, ammonia, and hydrogen to a desired value. It is preferable to set the ratio of ammonia and hydrogen supply to the total supply of liquid fuel, ammonia, and hydrogen in the range of 1% to 95%. This allows for an increased co-combustion rate of ammonia and hydrogen while further improving the properties of the exhaust gas. The ratio of ammonia and hydrogen supply to the total supply of liquid fuel, ammonia, and hydrogen may be set to a fixed value before operation, or it may be set according to the operating conditions of the ammonia co-firing engine. For example, the ratio of ammonia supply to the total supply of liquid fuel, ammonia, and hydrogen may be set according to the output values ​​of sensors that detect the liquid fuel supply, ammonia supply, and hydrogen supply, respectively. Alternatively, the ratio of ammonia and hydrogen supply may be controlled according to the load on the ammonia co-firing engine. For example, if the load suddenly increases, the ratio of liquid fuel (diesel oil), which has a high calorific value and a fast combustion rate, may be increased.

[0050] The supply timing control means 21b controls the supply timing of liquid fuel by the liquid fuel supply means 15, as well as the supply timing of ammonia by the ammonia supply means 13 and the supply timing of hydrogen by the hydrogen supply means 17, according to the ratio of the supply amounts of ammonia and hydrogen to the total supply amount of liquid fuel, ammonia and hydrogen set by the fuel ratio setting means 21a. The supply timing includes the supply start timing and the supply period.

[0051] Figures 2 and 3 are injection timing charts. Figure 2 shows the timing of ammonia supply (injection) to the intake path (intake pipe) 14a and its variable range, the timing of hydrogen supply (injection) to the intake path 14a and its variable range, and the timing of liquid fuel supply (direct injection) into the cylinder 11 and its variable range. The horizontal axis of Figure 2 represents the engine cycle and crank angle. Figure 3 shows the variable range for each supply timing. The horizontal axis of Figure 3 represents the engine cycle. The supply of ammonia and hydrogen to path 14a occurs during the intake stroke of the ammonia-co-firing engine. The timing of the supply of ammonia and hydrogen is variable within the range of crank angle -360 degrees (top dead center) to -180 degrees (bottom dead center). In Figure 2, hydrogen supply is started during ammonia supply and ends after ammonia supply ends, but as shown in Figure 3, the order of ammonia supply timing and hydrogen supply timing does not matter. The pilot injection of liquid fuel into the combustion chamber 12 is performed in the intake stroke of an ammonia-co-firing engine at a timing before top dead center. As described above, by further supplying hydrogen to the combustion chamber 12 and co-firing it in an ammonia-co-firing engine, the variable range of the liquid fuel supply timing can be expanded. In Figure 3, the solid arrows in the liquid fuel injection timing show the variable range when hydrogen is not supplied, and the dotted arrows show the variable range when hydrogen is supplied. By supplying hydrogen, the liquid fuel supply timing can be varied within the range of crank angle ATDC (after top dead center) -70 degrees to -10 degrees.

[0052] [Mixed Combustion Test] The following describes a mixed combustion test using an ammonia-co-firing engine. The main specifications of the ammonia-co-firing engine used in the test are shown in Table 1 below. [Table 1]

[0053] In the test, ammonia, which had been kept at approximately 40°C and liquefied in a liquefied ammonia cylinder 3, was supplied to the injector of the ammonia supply means 13. To prevent ammonia condensation, the supply piping connecting the liquefied ammonia cylinder 3 and the ammonia supply means 13 was maintained at a temperature of 264K or higher. In addition, the amount of ammonia supplied was adjusted by adjusting the opening time of the injector valve. Diesel fuel was used as the liquid fuel. The diesel fuel was pressurized to 100 MPa and supplied to the fuel accumulator by the liquid fuel pressurizing means 16, and injected into the combustion chamber 12 at the desired crank angle by the electronic fuel injection valve of the liquid fuel supply means 15.

[0054] During the test, the torque was automatically controlled by an electric load device connected to the ammonia-fired engine to maintain the set rotational speed. Furthermore, regarding the exhaust gas components, total hydrocarbons (THC) were measured using an FID-type analyzer (600HFID CAI). Other gases besides THC, such as nitric oxide (CO), carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2), ammonia (NH3), and water (H2O), were measured using an FTIR-type exhaust gas analyzer (FAST2200 Iwata Electric). The gas analyzer measured multiple components simultaneously at high temperatures. The sampling line and sampling filter were heated to 191°C, enabling accurate detection of ammonia in exhaust gas containing water.

[0055] In the experiment, the difference between reducing diesel fuel emissions using ammonia alone and reducing them using ammonia and hydrogen was compared at the same co-firing ratio. Comparative Examples A and B involved co-firing only ammonia with diesel fuel, with a co-firing ratio of 68% for Comparative Example A and 79% for Comparative Example B. Examples C and D of this embodiment involve co-firing ammonia and hydrogen with diesel fuel. The co-firing ratio for Example C was 67% (43% ammonia + 24% hydrogen), and the co-firing ratio for Example D was 80% (56% ammonia + 24% hydrogen). When ammonia-co-fired engines were operated using Comparative Examples A and B and Examples C and D as fuel, tests were conducted on the lower heating value (LHV fraction), net thermal efficiency (Brake thermal efficiency), variation in maximum in-cylinder combustion pressure (COV Pmax), and emissions of carbon dioxide (CO2), unburned ammonia (NH3), nitrous oxide (N2O), greenhouse gases (GHG), carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx).

[0056] In the test, diesel fuel, a liquid fuel, was injected from the liquid fuel supply means 15. The diesel fuel was injected as a pilot injection during the compression stroke, in the range of crank angle -60 to -10 degrees after top dead center (ATDC), after supplying ammonia and hydrogen to the combustion chamber 12 during the intake stroke. In other words, the timing of the diesel fuel supply to the combustion chamber 12 was set to be later than the timing of the supply of the ammonia and air mixture and hydrogen.

[0057] The engine speed was kept constant during the test. In addition, the ratio of the supply of ammonia and hydrogen to the total supply of diesel fuel, ammonia, and hydrogen was set and maintained using the fuel ratio setting means 21a. The timing of the diesel pilot injection was varied in 5° increments of crank angle from -10° to -60° after the engine's top dead center (ATDC) (a negative angle indicates before top dead center). During the test, combustion in the ammonia-co-fired engine was stable, and fluctuations in the mean effective pressure were below the specified value.

[0058] Figures 4-1 and 4-2 show the test results, illustrating the lower heating value and emissions of various gases in response to changes in the timing of diesel fuel pilot injection. Figure 4-1(a) shows the lower heating value fraction [%], Figure 4-1(b) shows carbon dioxide [%], Figure 4-1(c) shows the variation in maximum in-cylinder combustion pressure [%], Figure 4-1(d) shows unburned ammonia [ppm], Figure 4-1(e) shows nitrous oxide [ppm], Figure 4-1(f) shows greenhouse gases [g / kWh], Figure 4-2(a) shows carbon monoxide [ppm], Figure 4-2(b) shows hydrocarbons [ppm], Figure 4-2(c) shows nitrogen oxides [ppm], and Figure 4-2(d) shows the net thermal efficiency [%]. Note that the nitrogen oxide emission concentration in Figure 4-2(c) represents the sum of nitric oxide (NO) and nitrogen dioxide (NO2). Figures 4-1 and 4-2 plot the results of Comparative Example A with "*", the results of Comparative Example B with "●", the results of Example C with "▲", and the results of Example D with "■". The horizontal axis represents the diesel fuel supply timing (SOI: Start of Injection) [CAD (Crank Angle Degree)].

[0059] As shown in Figures 4-1(d) and (e), in the case of Comparative Example B (ammonia co-firing rate of 79%), the ignition timing could only be advanced to -30 degrees, and the concentrations of unburned ammonia and nitrous oxide remained relatively high. This indicates that if the co-firing rate with ammonia alone is set to approximately 80% or higher, the ignition timing cannot be advanced before the reduction effect of ammonia and nitrous oxide due to ignition timing can be obtained. Furthermore, when comparing the case of co-firing ammonia alone with the case of co-firing ammonia and hydrogen at equivalent co-firing ratios, such as Comparative Example A (ammonia co-firing ratio 68%) and Example C (ammonia and hydrogen co-firing ratio 67%), and Comparative Example B and Example D (ammonia and hydrogen co-firing ratio 80%), the case of supplying hydrogen showed a suppression of the increase in the rate of fluctuation of the average maximum in-cylinder combustion pressure (Pmax) due to ignition timing advance, as shown in Figure 4-1(c), and the range in which ignition timing could be advanced was widened. As a result, in Examples C and D, operation under conditions of further ignition timing advance was possible, and unburned ammonia and nitrous oxide were reduced (see the circled areas in Figures 4-1(d) and (e)).

[0060] As shown in Figures 4-2(a) and (b), in Example D, where ammonia and hydrogen were co-fired at a co-firing ratio of 80%, the increase in emissions was smaller than in Comparative Example B, where only ammonia was co-fired at a co-firing ratio of 79%.

[0061] Based on the test results, it is preferable to set the advance angle for liquid fuel supply timing in the range of -25 to -70 degrees after ATDC (top dead center). This allows for stable combustion while further improving the properties of the exhaust gas. Furthermore, the supply ratio of ammonia to hydrogen is preferably about 2:1. Moreover, when ammonia and hydrogen are supplied in a ratio of about 2:1 and the co-firing rate relative to the total supply amount including liquid fuel is 60-70%, it is even more preferable to set the ATDC (after top dead center) in the range of -40 to -60 degrees. When ammonia and hydrogen are co-fired in a ratio of about 2:1 and the co-firing rate is 71-80%, it is preferable to set the ATDC (after top dead center) in the range of -30 to -40 degrees. [Industrial applicability]

[0062] By installing an ammonia co-firing engine using the ammonia co-firing method in the engine of the present invention on a ship, it is possible to increase the ammonia co-firing rate and realize a ship with improved exhaust gas properties. Furthermore, this invention can be widely applied not only to power-requiring devices such as generators used as main engines or auxiliary engines in ships, but also to ammonia co-firing engines throughout the industrial sector. [Explanation of Symbols]

[0063] 12 Combustion chamber 13 Ammonia supply means 14. Air supply means 14a Air supply path 15 Liquid fuel supply means 17. Means of supplying hydrogen 18. Vaporization means 19a Exhaust path 20. SCR (Selective Catalytic Reduction) System 21a Fuel ratio setting means 22b Supply timing control means

Claims

1. A method for co-firing ammonia in an engine that co-fires ammonia and liquid fuel, characterized in that when supplying air, ammonia, and liquid fuel to the combustion chamber of the engine and igniting them by compression ignition for co-firing, hydrogen is further supplied to the combustion chamber for co-firing, thereby expanding the variable range in the direction of advancing the supply timing of the liquid fuel, and setting the supply timing of the liquid fuel to the combustion chamber to be later than the supply timing of the ammonia and hydrogen.

2. The ammonia co-firing method in the engine according to claim 1, characterized in that the liquid fuel is supplied by multi-stage injection.

3. The method for co-firing ammonia in an engine according to claim 1, characterized in that the liquid fuel is diesel fuel.

4. A method for co-firing ammonia in an engine according to claim 1, characterized in that the ammonia and hydrogen are pre-mixed with the air and supplied to the combustion chamber.

5. A method for co-firing ammonia in an engine according to claim 1, characterized in that the ammonia stored in a liquid state is vaporized and supplied.

6. A method for co-firing ammonia in an engine according to claim 1, characterized in that a portion of the ammonia is decomposed to obtain hydrogen.

7. The ammonia co-firing method in an engine according to claim 1, characterized in that the advance angle as the supply timing of the liquid fuel is set in the range of -25 degrees to -70 degrees after ATDC (top dead center).

8. The ammonia co-firing method in an engine according to claim 1, characterized in that the ratio of the supply amounts of ammonia and hydrogen to the total supply amount of the liquid fuel, ammonia and hydrogen is in the range of 1% to 95%.

9. The ammonia co-firing method in an engine according to claim 1, characterized in that NOx in the exhaust gas discharged from the combustion chamber is purified using ammonia by SCR (selective catalytic reduction).

10. A compression-ignition ammonia co-firing engine using the ammonia co-firing method in an engine according to any one of claims 1 to 9, comprising: a combustion chamber; an ammonia supply means for supplying ammonia to the combustion chamber; an air supply means for supplying air to the combustion chamber; a liquid fuel supply means for supplying liquid fuel to the combustion chamber; a hydrogen supply means for supplying hydrogen to the combustion chamber; a fuel ratio setting means for setting the ratio of the supply amounts of ammonia and hydrogen to the total supply amount of the liquid fuel, ammonia and hydrogen; and a supply timing control means for controlling the supply timing of the liquid fuel by the liquid fuel supply means according to the setting of the ratio by the fuel ratio setting means.

11. The ammonia co-firing engine according to claim 10, referencing claim 2, characterized in that the supply timing control means controls the supply of the liquid fuel by the liquid fuel supply means to be supplied by multi-stage injection.

12. The ammonia co-firing engine according to claim 10, which references claim 4, characterized in that the ammonia and hydrogen are injected into the air intake path of the air supply means, and the air, ammonia, and hydrogen are mixed in advance and supplied to the combustion chamber.

13. The ammonia co-firing engine according to claim 10, which references claim 5, characterized in that a vaporization means for vaporizing the ammonia stored in a liquid state is provided in the air supply path of the air supply means.

14. The ammonia co-firing engine according to claim 10, referencing claim 7, characterized in that the supply timing control means controls the supply timing of the liquid fuel supply means to advance the angle of advance of the liquid fuel supply timing from -25 degrees to -70 degrees after ATDC (top dead center).

15. The ammonia co-firing engine according to claim 10, referencing claim 8, characterized in that the fuel ratio setting means sets the ratio of the supply amount of ammonia and hydrogen to the total supply amount of the liquid fuel, hydrogen and ammonia in the range of 1% to 95%.

16. The ammonia co-firing engine according to claim 10, which references claim 9, further comprising an SCR (selective catalytic reduction) system in the exhaust path of the exhaust gas for purifying NOx in the exhaust gas discharged from the combustion chamber using the ammonia.

17. A ship equipped with an ammonia co-firing engine, characterized in that the ammonia co-firing engine described in claim 10 is installed on the ship.

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