Ammonia co-combustion engine

Abstract

The present invention provides an ammonia co-combustion engine capable of improving exhaust gas properties by appropriately mixing and combusting ammonia and a hydrocarbon liquid fuel. An ammonia co-combustion engine (1) that operates by combusting liquid fuel of ammonia and hydrocarbons is provided with: a main combustion chamber (20); a sub-combustion chamber (21) communicating with the main combustion chamber (20); and a fuel supply device (14) that supplies ammonia and liquid fuel to the sub-combustion chamber (21). For example, a fuel supply device (14) is provided separately with: an ammonia injector (27) for supplying ammonia; and a liquid fuel injector (28) that supplies a hydrocarbon-based liquid fuel.

Description

Technical Field

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

[0002] Conventionally, there are ammonia co-firing engines that operate by burning ammonia and a liquid fuel of hydrocarbons such as light oil.

[0003] For example, Patent Document 1 discloses a large, turbocharged, two-stroke, single-flow, crosshead, dual-fuel internal combustion engine that operates in an Otto cycle mode using a first fuel such as ammonia and fuel oil for igniting the first fuel, and in a Diesel cycle mode using fuel oil alone. The engine includes a fuel introduction valve located within a cylinder head for introducing the first fuel during the piston's stroke from bottom dead center to top dead center; a fuel injection valve located within the cylinder head or within a cylinder liner for injecting fuel oil when the piston is at or near top dead center; and a pilot ignition sub-chamber located within the cylinder head or within a cylinder liner and having a sub-chamber port opening into a combustion chamber. The fuel oil introduced into the sub-chamber ignites a mixture of the first fuel and purge gas within the combustion chamber.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 7329713 Summary of the Invention

[0007] The conventional engine disclosed in Patent Document 1 is configured with a fuel introduction valve for ammonia, a fuel injection valve for fuel oil, and a pilot ignition sub-chamber. During operation in the Otto cycle mode of the internal combustion engine, the fuel injection valve introduces fuel oil into the pilot ignition sub-chamber, while the fuel introduction valve supplies a first fuel, such as ammonia, into the combustion chamber. However, since the first fuel is supplied to the combustion chamber and the fuel oil is supplied to the pilot ignition sub-chamber separately, a premixed gas in which the first fuel and fuel oil are uniformly mixed cannot be formed. Consequently, the fuel burns intensely in a local area of ​​the combustion chamber, emitting large amounts of particulate matter (PM) and nitrogen oxides (NOx), potentially worsening exhaust gas properties.

[0008] An object of the present invention is to provide an ammonia co-firing engine capable of properly mixing and burning ammonia and a hydrocarbon liquid fuel to improve exhaust gas properties.

[0009] In order to solve the above-mentioned problems, the ammonia co-firing engine of the present invention operates by burning ammonia and hydrocarbon liquid fuel, and is characterized in that the ammonia co-firing engine includes: a main combustion chamber; an auxiliary combustion chamber, which is connected to the main combustion chamber; and a fuel supply device, which supplies the ammonia and the liquid fuel to the auxiliary combustion chamber.

[0010] Effects of the Invention

[0011] According to the present invention, an ammonia co-firing engine is provided that can appropriately mix and burn ammonia and a hydrocarbon liquid fuel to improve exhaust gas properties. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0013] Figure 2 This is a graph showing an example of the relationship between the air excess ratio of hydrogen burned in an ammonia co-firing engine and nitrogen oxides generated in exhaust gas.

[0014] Figure 3 The present invention is a graph showing the relationship between the ammonia equivalence ratio of the mixed gas supplied to the auxiliary combustion chamber of the ammonia co-firing engine and the combustion temperature of ammonia, which shows the corresponding areas of NO+NO2 generation and unburned NH3 generation due to combustion, as well as a graph showing the combustion temperature of ammonia when the mixed gas is burned.

[0015] Description of Reference Numerals

[0016] 1…ammonia co-combustion engine; 2…control device; 3…intake passage; 4…exhaust passage; 10…cylinder; 11…cylinder block; 12…piston; 13…cylinder head; 14…fuel supply device; 15…connecting rod; 16…crankshaft; 20…main combustion chamber; 21…auxiliary combustion chamber; 22…auxiliary chamber port; 23…intake port; 24…exhaust port; 25…intake valve; 26…exhaust valve; 27…ammonia injector; 28…liquid fuel injector; 29…ammonia container; 30…liquid fuel container. DETAILED DESCRIPTION

[0017] The ammonia co-firing engine 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings. The ammonia co-firing engine 1 (engine) operates by burning ammonia and a hydrocarbon liquid fuel such as light oil. 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 Only one cylinder 10 is shown. Figure 1 As shown, each cylinder 10 includes a cylinder block 11 , a piston 12 , a cylinder head 13 , and a fuel supply device 14 .

[0018] The cylinder 11 is formed in a cylindrical shape, for example, within a cylinder body. The piston 12 is slidably accommodated in the cylinder 11 , and a cylinder head 13 is attached to an upper side of the cylinder 11 .

[0019] A main combustion chamber 20 is formed in the cylinder block 11 between the piston 12 and the cylinder head 13 , and a sub-combustion chamber 21 communicating with the main combustion chamber 20 via a sub-chamber port 22 is formed in a lower portion of the cylinder head 13 .

[0020] A crankshaft 16 is connected to the piston 12 via a connecting rod 15 below the cylinder 11 , and the reciprocating motion of the piston 12 is converted into rotational motion of the crankshaft 16 via the connecting rod 15 .

[0021] The cylinder head 13 has an intake port 23 and an exhaust port 24 communicating with the main combustion chamber 20 of the cylinder block 11 , and includes an intake valve 25 and an exhaust valve 26 for opening and closing the intake port 23 and the exhaust port 24 with respect to the main combustion chamber 20 , respectively.

[0022] The intake port 23 is connected to the intake passage 3 and introduces air supplied from the intake passage 3 into the main combustion chamber 20. The exhaust port 24 is connected to the exhaust passage 4 and discharges exhaust gas generated in the main combustion chamber 20 into the exhaust passage 4. The intake valve 25 is opened to allow intake air to be drawn into the main combustion chamber 20 via the intake port 23, while the exhaust valve 26 is opened to allow exhaust gas generated in the main combustion chamber 20 to be discharged via the exhaust port 24.

[0023] The fuel supply device 14 supplies ammonia and a hydrocarbon liquid fuel, respectively, to the auxiliary combustion chamber 21, thereby generating a first mixed gas corresponding to the ammonia and liquid fuel in the auxiliary combustion chamber 21. The fuel supply device 14 controls the supply pressure (injection pressure), supply timing (injection timing), and supply duration (injection duration) of the ammonia and liquid fuel to the auxiliary combustion chamber 21 using the control device 2.

[0024] The control device 2 is a computer such as an ECU (Engine Control Unit) that controls the operation of the engine 1. It includes a CPU, ROM, RAM, etc., and is configured to control various components of the engine 1. The control device 2 can store various programs for controlling the engine 1 and read and execute the programs to control the engine 1.

[0025] For example, the fuel supply device 14 includes an ammonia injector 27 connected to an ammonia tank 29 storing ammonia, and a liquid fuel injector 28 connected to a liquid fuel tank 30 storing hydrocarbon-based liquid fuel.

[0026] For example, the fuel supply device 14 injects ammonia into the auxiliary combustion chamber 21 using the ammonia injector 27 while air is supplied from the main combustion chamber 20 into the auxiliary combustion chamber 21 via the auxiliary chamber port 22, thereby generating a first mixture of ammonia and air in the auxiliary combustion chamber 21. Specifically, in the engine 1, during the intake stroke of the combustion cycle, with the intake port 23 open and the exhaust port 24 closed, as the piston 12 descends toward bottom dead center, air is introduced from the intake passage 3 into the main combustion chamber 20. Subsequently, during the compression stroke of the combustion cycle, with the intake port 23 and exhaust port 24 closed, before the piston 12 reaches top dead center, the fuel supply device 14 supplies ammonia into the auxiliary combustion chamber 21 using the ammonia injector 27.

[0027] The fuel supply device 14 supplies ammonia to the auxiliary combustion chamber 21 so that the ammonia combustion ratio in the auxiliary combustion chamber 21 is high. The fuel supply device 14 sets the ammonia supply amount (e.g., supply pressure, supply timing, and supply duration) so that the first air-fuel mixture generated in the auxiliary combustion chamber 21 is rich in ammonia (fuel is in excess relative to air). For example, the fuel supply device 14 supplies ammonia to the auxiliary combustion chamber 21 so that the ammonia excess ratio relative to air is 0.4 to 0.7.

[0028] exist Figure 3 , the relationship between the ammonia equivalence ratio of the first mixed gas supplied to the auxiliary combustion chamber 21 and the combustion temperature of ammonia is shown. Figure 3 In the graph of the relationship between the equivalent ratio of ammonia and the combustion temperature, the solid line represents the generation region of NO+NO2 due to the combustion of the first mixed gas, and the amount of NO+NO2 generated increases in the direction indicated by the white hollow arrow 50. Figure 3 In the diagram, the relationship between the equivalence ratio of ammonia and the combustion temperature is shown by a dot-dashed line in the corresponding diagram of the N2O generation region due to the combustion of the first mixed gas. The amount of N2O generated increases in the direction indicated by the white hollow arrow 51. Figure 3 In the corresponding diagram of the relationship between the ammonia equivalence ratio and the combustion temperature, the double-dashed chain line indicates the generation region of unburned NH 3 generated by the combustion of the first air mixture, and the generation amount of unburned NH 3 increases in the direction indicated by the white outline arrow 52.

[0029] And, in Figure 3 In FIG. 1 , when the engine 1 is operated, the combustion temperature of ammonia when the first mixed gas is combusted is represented by a dotted curve relative to the equivalent ratio of ammonia in the first mixed gas supplied to the auxiliary combustion chamber 21. Figure 3As shown in the curve, by setting the ammonia equivalence ratio in the auxiliary combustion chamber 21 to 2.5 to 1.5, that is, by setting the ammonia air excess ratio to 0.4 to 0.7, the formation of N2O and NO+NO2 in the auxiliary combustion chamber 21 can be avoided. Furthermore, unburned NH3 is generated at this air excess ratio, but this unburned NH3 is reformed to H2 during the combustion process.

[0030] Furthermore, the fuel supply device 14 compresses the first ammonia-air mixture in the auxiliary combustion chamber 21 to a high temperature. The liquid fuel injector 28 then injects and supplies liquid fuel into the auxiliary combustion chamber 21. This compression of the hydrocarbon-based liquid fuel causes the first ammonia-air mixture to self-ignite and burn. Specifically, during the combustion stroke of the combustion cycle, with the intake port 23 and exhaust port 24 closed, and the piston 12 at top dead center, the fuel supply device 14 supplies liquid fuel to the auxiliary combustion chamber 21 via the liquid fuel injector 28, igniting the first ammonia-air mixture.

[0031] In the combustion stroke of the combustion cycle, engine 1 burns ammonia in auxiliary combustion chamber 21, thereby decomposing and reforming the ammonia to produce a reformed fuel (e.g., hydrogen), thereby generating a combustion gas rich in the reformed fuel. Furthermore, engine 1 can also burn a hydrocarbon liquid fuel in auxiliary combustion chamber 21, thereby decomposing and reforming the liquid fuel to produce a reformed fuel (e.g., hydrogen).

[0032] Furthermore, the engine 1 increases the pressure within the auxiliary combustion chamber 21 by burning the first mixture containing ammonia, and then discharges the second mixture (combustion gas) containing the reformed fuel within the auxiliary combustion chamber 21 into the main combustion chamber 20 via the auxiliary chamber port 22. In the engine 1, during the combustion stroke of the combustion cycle, with the intake port 23 and the exhaust port 24 closed, as the piston 12 descends toward bottom dead center, the combustion gas containing the generated reformed fuel is discharged from the auxiliary combustion chamber 21 into the main combustion chamber 20 via the auxiliary chamber port 22. In the main combustion chamber 20, when the second mixture of the reformed fuel and air is generated, the high-temperature, rich reformed fuel spontaneously ignites oxygen in the air, causing the second mixture of the reformed fuel and air to combust.

[0033] At this time, the fuel supply device 14 sets the supply amounts (e.g., supply pressure, supply timing, and supply duration) of ammonia and liquid fuel so that the reformed fuel of the second mixed gas generated in the main combustion chamber 20 mixes with the air in the main combustion chamber 20, gradually becoming leaner (excess air). For example, the fuel supply device 14 supplies ammonia and liquid fuel to the auxiliary combustion chamber 21 so that the excess air ratio of the reformed fuel reaches 1.8 or greater.

[0034] The second mixed gas containing the lean reformed fuel is combusted in the main combustion chamber 20 to reduce the combustion temperature in the main combustion chamber 20, thereby suppressing the amount of nitrogen oxides generated in the exhaust gas. Figure 2 , shows an example of the relationship between the hydrogen-air excess ratio of the second mixed gas generated in the main combustion chamber 20 and the amount of nitrogen oxides generated in the exhaust gas when the second mixed gas is combusted in the main combustion chamber 20. As shown in this example of the relationship, the higher the hydrogen-air excess ratio, the smaller the amount of nitrogen oxides emitted.

[0035] As described above, according to the present invention, an ammonia co-combustion engine 1 that operates by burning ammonia and a hydrocarbon liquid fuel includes: a main combustion chamber 20; an auxiliary combustion chamber 21 that is connected to the main combustion chamber 20; and a fuel supply device 14 that supplies ammonia and liquid fuel to the auxiliary combustion chamber 21.

[0036] Thus, according to the ammonia co-firing engine 1 of the present invention, ammonia and hydrocarbon liquid fuel are supplied to the auxiliary combustion chamber 21 , thereby generating a first mixed gas rich in ammonia in the auxiliary combustion chamber 21 and uniformly combusting the ammonia in the auxiliary combustion chamber 21 .

[0037] In the ammonia co-firing engine 1 of the present invention, the fuel supply device 14 includes an ammonia injector 27 for supplying ammonia and a liquid fuel injector 28 for supplying hydrocarbon liquid fuel.

[0038] Furthermore, the ammonia co-firing engine 1 of the present invention generates a reformed fuel such as hydrogen in the auxiliary combustion chamber 21 by combusting ammonia and / or a hydrocarbon liquid fuel in the auxiliary combustion chamber 21. Thus, the reformed fuel generated in the auxiliary combustion chamber 21 is combusted in the main combustion chamber 20, achieving combustion with good exhaust gas properties.

[0039] Furthermore, the ammonia co-firing engine 1 of the present invention performs combustion in the auxiliary combustion chamber 21, which is supplied with ammonia, with an excess air ratio of 0.4 to 0.7. This immediately decomposes the concentrated ammonia to produce a reformed fuel such as hydrogen, which is then combusted in the main combustion chamber 20, thereby suppressing the production of nitrous oxide (N2O), a greenhouse gas 265 times more potent than CO2. Furthermore, while it is possible to produce reformed fuel such as hydrogen in the auxiliary combustion chamber 21 by combusting a hydrocarbon liquid fuel in the auxiliary combustion chamber 21, this increases the scale of liquid fuel combustion and may generate smoke. Therefore, using concentrated ammonia can suppress the generation of smoke.

[0040] Furthermore, the ammonia co-firing engine 1 of the present invention supplies the reformed fuel generated in the auxiliary combustion chamber 21 to the main combustion chamber 20. The reformed fuel is then combusted in the main combustion chamber 20 at an excess air ratio exceeding 1 in a lean state. For example, the excess air ratio in the main combustion chamber 20 is 1.8 or greater. This allows the second air mixture containing the lean reformed fuel to combust in the main combustion chamber 20, thereby lowering the combustion temperature in the main combustion chamber 20 and suppressing the amount of nitrogen oxides generated in the exhaust gas.

[0041] Furthermore, in the ammonia co-firing engine 1 of the present invention, a hydrocarbon liquid fuel is supplied to the auxiliary combustion chamber 21 after ammonia is supplied to the auxiliary combustion chamber 21 during the combustion cycle. In this case, during the combustion cycle, the liquid fuel is supplied to the auxiliary combustion chamber 21 and combustion occurs. As a result, ammonia is burned in the auxiliary combustion chamber 21 in a state where ammonia and air are thoroughly mixed, allowing ammonia to be burned more uniformly within the auxiliary combustion chamber 21.

[0042] Furthermore, in the above embodiment, an example is described in which the fuel supply device 14 includes the ammonia injector 27 and the liquid fuel injector 28 separately in order to supply ammonia and hydrocarbon liquid fuel to the auxiliary combustion chamber 21 . However, the present invention is not limited to this example.

[0043] For example, the fuel supply device 14 may be configured as a dual-fuel injector system that supplies ammonia and a hydrocarbon-based liquid fuel. These dual-fuel injectors may, for example, be configured with a first valve chamber for supplying ammonia to a single valve body and a second valve chamber for supplying liquid fuel. A valve body disposed in each valve chamber can be opened and closed to supply ammonia and liquid fuel, respectively. Alternatively, the dual-fuel injectors may be configured with a first passage for supplying ammonia to a single valve body and a second passage for supplying liquid fuel, each passage having a nozzle orifice connected to the other. Ammonia and liquid fuel can be supplied separately by switching the first and second passages relative to the nozzle orifice.

[0044] In addition, in the above embodiment, an example is described in which the second mixed gas is a mixed gas of modified fuel and air, but the present invention is not limited to this example. The second mixed gas can also be a mixed gas that contains unmodified ammonia and hydrocarbon fuel in addition to the modified fuel and air.

[0045] Furthermore, the present invention may be modified as appropriate within the scope not departing from the gist or concept of the invention as reflected in the claims and the entire specification, and an ammonia co-firing engine with such modifications is also encompassed within the technical concept of the present invention.

[0046] [Supplementary Notes on the Invention]

[0047] The following is a supplementary note on the outline of the invention extracted from the above embodiments. In addition, the various structures and processing functions described in the following supplementary notes can be selected and combined arbitrarily.

[0048] Note 1

[0049] An ammonia co-firing engine operates by burning ammonia and hydrocarbon liquid fuel, characterized in that:

[0050] The ammonia co-firing engine has:

[0051] main combustion chamber;

[0052] a secondary combustion chamber communicating with the primary combustion chamber; and

[0053] A fuel supply device supplies the ammonia and the liquid fuel to the auxiliary combustion chamber.

[0054] Note 2

[0055] The ammonia co-firing engine according to Supplementary Note 1 is characterized in that:

[0056] The fuel supply device includes an ammonia injector that supplies the ammonia and a liquid fuel injector that supplies the liquid fuel.

[0057] Note 3

[0058] The ammonia co-firing engine according to Supplementary Note 1 is characterized in that:

[0059] The fuel supply device includes two types of fuel injectors for supplying the ammonia and the liquid fuel.

[0060] Note 4

[0061] The ammonia co-firing engine according to any one of Supplementary Notes 1 to 3, characterized in that:

[0062] The ammonia and / or the liquid fuel is combusted in the auxiliary combustion chamber to generate a reformed fuel in the auxiliary combustion chamber.

[0063] <Note 5>

[0064] The ammonia co-firing engine according to any one of Supplementary Notes 1 to 4, characterized in that:

[0065] In the auxiliary combustion chamber supplied with the ammonia, combustion is performed at an excess air ratio of 0.4 to 0.7.

[0066] <Note 6>

[0067] The ammonia co-firing engine according to Supplement 4 or 5 is characterized in that:

[0068] supplying the reformed fuel generated in the auxiliary combustion chamber to the main combustion chamber,

[0069] In the main combustion chamber supplied with the reformed fuel, combustion is performed at an excess air ratio exceeding 1 in a lean state.

[0070] <Note 7>

[0071] The ammonia co-firing engine according to Supplementary Note 6 is characterized in that:

[0072] The excess air ratio in the main combustion chamber is 1.8 or more.

[0073] <Note 8>

[0074] The ammonia co-firing engine according to any one of Supplementary Notes 1 to 7, characterized in that:

[0075] In a combustion cycle, after the ammonia is supplied to the secondary combustion chamber, the liquid fuel is supplied to the secondary combustion chamber.

[0076] <Note 9>

[0077] The ammonia co-firing engine according to Supplementary Note 8 is characterized in that:

[0078] During a combustion cycle, the liquid fuel is supplied to the auxiliary combustion chamber to cause combustion.

Claims

1. An ammonia co-firing engine, which operates by burning ammonia and hydrocarbon liquid fuel, characterized in that: The ammonia co-firing engine has: main combustion chamber; a secondary combustion chamber communicating with the primary combustion chamber; and A fuel supply device supplies the ammonia and the liquid fuel to the auxiliary combustion chamber.

2. The ammonia co-firing engine according to claim 1, characterized in that: The fuel supply device includes an ammonia injector that supplies the ammonia and a liquid fuel injector that supplies the liquid fuel.

3. The ammonia co-firing engine according to claim 1, characterized in that: The fuel supply device includes two types of fuel injectors for supplying the ammonia and the liquid fuel.

4. The ammonia co-firing engine according to claim 1, characterized in that: The ammonia and / or the liquid fuel is combusted in the auxiliary combustion chamber to generate a reformed fuel in the auxiliary combustion chamber.

5. The ammonia co-firing engine according to claim 1, characterized in that: In the auxiliary combustion chamber supplied with the ammonia, combustion is performed at an excess air ratio of 0.4 to 0.

7.

6. The ammonia co-firing engine according to claim 4, characterized in that: The reformed fuel generated in the auxiliary combustion chamber is supplied to the main combustion chamber, and combustion is performed at an excess air ratio exceeding 1 in a lean state in the main combustion chamber supplied with the reformed fuel.

7. The ammonia co-firing engine according to claim 6, characterized in that: The excess air ratio in the main combustion chamber is 1.8 or more.

8. The ammonia co-firing engine according to claim 1, characterized in that: In a combustion cycle, after the ammonia is supplied to the secondary combustion chamber, the liquid fuel is supplied to the secondary combustion chamber.

9. The ammonia co-firing engine according to claim 8, characterized in that: During a combustion cycle, the liquid fuel is supplied to the auxiliary combustion chamber to cause combustion.

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