Ammonia mixed combustion engine

Abstract

To provide an ammonia mixed combustion engine capable of improving exhaust gas property by appropriately mixing and combusting ammonia and hydrocarbon-based liquid fuel.SOLUTION: An ammonia mixed combustion engine 1, which is operated by combusting ammonia and hydrocarbon-based liquid fuel, comprises a main combustion chamber 20, an auxiliary combustion chamber 21 that communicates with the main combustion chamber 20, and a fuel supply device 14 that supplies ammonia and liquid fuel to the auxiliary combustion chamber 21. For example, the fuel supply device 14 comprises an ammonia injector 27 for supplying ammonia and a liquid fuel injector 28 for supplying hydrocarbon-based liquid fuel, as separate bodies.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventionally, there is an ammonia co-fuel engine that operates by burning ammonia and a hydrocarbon liquid fuel such as diesel oil.

[0003] For example, Patent Document 1 discloses a large turbocharged two-stroke uniflow crosshead dual-fuel internal combustion engine that has an Otto cycle mode in which the engine is operated using a first fuel such as ammonia and fuel oil for ignition of the first fuel, and a Diesel cycle mode in which the engine is operated using only fuel oil. This engine is equipped with a fuel inlet valve located in the cylinder cover for introducing the first fuel during the piston's stroke from bottom dead center to top dead center, a fuel injection valve located in the cylinder cover or cylinder liner for injecting fuel oil when the piston is at or near top dead center, and a pilot ignition subchamber located in the cylinder cover or cylinder liner and having a subchamber port opening to the combustion chamber, for igniting the mixture of the first fuel and scavenging gas in the combustion chamber with the fuel oil introduced into the subchamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7329713 Summary of the Invention [Problem to be solved by the invention]

[0005] A conventional engine such as that disclosed in Patent Document 1 is equipped with a fuel inlet valve for ammonia, a fuel injection valve for fuel oil, and a pilot ignition sub-chamber, and is configured so that, when the engine is operating in an Otto cycle mode, the fuel injector introduces fuel oil into the pilot ignition sub-chamber and the fuel inlet valve supplies a first fuel such as ammonia to the combustion chamber. However, because the supply of the first fuel to the combustion chamber and the supply of fuel oil to the pilot ignition sub-chamber are carried out separately, it is not possible to form a premixture in which the first fuel and fuel oil are uniformly mixed, and the fuel burns locally and violently in the combustion chamber, emitting large amounts of particulate matter (PM), nitrogen oxides (NOx), etc., which may deteriorate exhaust gas properties.

[0006] An object of the present invention is to provide an ammonia co-fuel engine that can appropriately mix ammonia and hydrocarbon liquid fuel and burn them, thereby improving exhaust gas properties. [Means for solving the problem]

[0007] In order to solve the above problems, the ammonia co-fuel engine of the present invention is an ammonia co-fuel engine that operates by burning ammonia and a hydrocarbon-based liquid fuel, and is characterized by comprising: a main combustion chamber; an auxiliary combustion chamber that communicates with the main combustion chamber; and a fuel supply device that supplies the ammonia and the liquid fuel to the auxiliary combustion chamber. [Effects of the Invention]

[0008] According to the present invention, there is provided an ammonia co-fuel engine that can improve exhaust gas properties by appropriately mixing ammonia and hydrocarbon liquid fuel and burning them. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an ammonia-mixed combustion engine according to an embodiment of the present invention. FIG. [Figure 2] 1 is a graph showing an example of the relationship between the excess air ratio of hydrogen burned in an ammonia co-fuel engine and nitrogen oxides produced in exhaust gas. [Figure 3] 1 is a graph showing a map of the generation region of NO+NO2 and the generation region of unburned NH3 generated by combustion in the relationship between the equivalence ratio of ammonia in the mixture supplied to the pre-combustion chamber of an ammonia co-fuel engine and the combustion temperature of ammonia, and also showing the combustion temperature of ammonia when the mixture is combusted. DETAILED DESCRIPTION OF THE INVENTION

[0010] An ammonia-mixed combustion engine 1 according to an embodiment of the present invention will be described with reference to the drawings. The ammonia-mixed combustion engine 1 (engine) operates by burning ammonia and a hydrocarbon liquid fuel such as diesel. The ammonia-mixed combustion engine 1 is configured with a cylinder block (not shown) having multiple cylinders 10, but FIG. 1 shows only one cylinder 10. As shown in FIG. 1, each cylinder 10 has a cylinder 11, a piston 12, a cylinder head 13, and a fuel supply device 14.

[0011] The cylinder 11 is formed in a cylindrical shape within a cylinder block, for example, and the piston 12 is slidably housed within the cylinder 11 . The cylinder head 13 is attached to the upper side of the cylinder 11 .

[0012] A main combustion chamber 20 is formed in the cylinder 11 between the piston 12 and the cylinder head 13, and an auxiliary combustion chamber 21 is formed in the lower part of the cylinder head 13 and communicates with the main combustion chamber 20 via an auxiliary chamber port 22.

[0013] Below the cylinder 11 , a crankshaft 16 is connected to the piston 12 via a connecting rod 15 , and the reciprocating motion of the piston 12 is converted into the rotational motion of the crankshaft 16 via the connecting rod 15 .

[0014] The cylinder head 13 also has an intake port 23 and an exhaust port 24 that communicate with the main combustion chamber 20 of the cylinder 11, and is equipped with an intake valve 25 and an exhaust valve 26 that open and close the intake port 23 and the exhaust port 24, respectively, to the main combustion chamber 20.

[0015] 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, while 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. By opening the intake valve 25, intake air can be taken into the main combustion chamber 20 through the intake port 23, while by opening the exhaust valve 26, exhaust gas generated in the main combustion chamber 20 can be exhausted through the exhaust port 24.

[0016] The fuel supply device 14 supplies ammonia and hydrocarbon liquid fuel separately to the pre-combustion chamber 21 to generate a first mixture corresponding to the ammonia and the liquid fuel in the pre-combustion chamber 21. The fuel supply device 14 is controlled by the control device 2 in terms of the supply pressure (injection pressure), supply timing (injection timing), supply period (injection period), etc. of the ammonia and the liquid fuel to the pre-combustion chamber 21.

[0017] The control device 2 is a computer such as an ECU (Engine Control Unit) that controls the operation of the engine 1, and is equipped with a CPU, ROM, RAM, etc., and is configured to control each part of the engine 1. The control device 2 may store various programs for controlling the engine 1, and control the engine 1 by reading and executing the programs.

[0018] For example, the fuel supply device 14 includes an ammonia injector 27 connected to an ammonia tank 29 that stores ammonia, and a liquid fuel injector 28 connected to a liquid fuel tank 30 that stores a hydrocarbon-based liquid fuel.

[0019] For example, in a state where air is supplied from the main combustion chamber 20 into the pre-combustion chamber 21 via the pre-combustion port 22, the fuel supply device 14 injects and supplies ammonia into the pre-combustion chamber 21 using the ammonia injector 27, thereby generating a first mixture of ammonia and air in the pre-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, air is introduced from the intake passage 3 into the main combustion chamber 20 when the piston 12 descends toward bottom dead center. Thereafter, during the compression stroke of the combustion cycle, with the intake port 23 and the exhaust port 24 closed, the fuel supply device 14 supplies ammonia into the pre-combustion chamber 21 using the ammonia injector 27 before the piston 12 reaches top dead center.

[0020] The fuel supply device 14 supplies ammonia to the pre-combustion chamber 21 so that the ammonia mixed combustion ratio in the pre-combustion chamber 21 is relatively high, and at this time, the fuel supply device 14 sets the amount of ammonia supplied (for example, the supply pressure, supply timing, and supply period) so that the first air-fuel mixture generated in the pre-combustion chamber 21 is rich in ammonia (excess fuel relative to air). For example, the fuel supply device 14 supplies ammonia to the pre-combustion chamber 21 so that the excess air ratio of ammonia is 0.4 to 0.7.

[0021] FIG. 3 shows the relationship between the equivalence ratio of ammonia in the first air-fuel mixture supplied to the auxiliary combustion chamber 21 and the combustion temperature of the ammonia. In FIG. 3, a map of the generation region of NO+NO2 generated by the combustion of the first air-fuel mixture relative to the relationship between the equivalence ratio of ammonia and the combustion temperature is shown by a solid line, with the amount of NO+NO2 generated increasing in the direction indicated by the outline arrow 50. Also in FIG. 3, a map of the generation region of N2O generated by the combustion of the first air-fuel mixture relative to the relationship between the equivalence ratio of ammonia and the combustion temperature is shown by a dashed-dot line, with the amount of N2O generated increasing in the direction indicated by the outline arrow 51. Also in FIG. 3, a map of the generation region of unburned NH3 generated by the combustion of the first air-fuel mixture relative to the relationship between the equivalence ratio of ammonia and the combustion temperature is shown by a two-dot chain line, with the amount of unburned NH3 generated increasing in the direction indicated by the outline arrow 52.

[0022] Furthermore, Fig. 3 shows, in a broken line graph, the combustion temperature of ammonia when the first air-fuel mixture is combusted versus the equivalence ratio of ammonia in the first air-fuel mixture supplied to the pre-combustion chamber 21 when the engine 1 is operating. As shown in the line graph in Fig. 3, by setting the equivalence ratio of ammonia in the pre-combustion chamber 21 to 2.5 to 1.5, that is, by setting the excess air ratio of ammonia to 0.4 to 0.7, it is possible to avoid the generation of N2O and NO+NO2 in the pre-combustion chamber 21. Note that at this excess air ratio, unburned NH3 is generated, but this unburned NH3 is reformed into H2 during the combustion process.

[0023] Furthermore, in a state in which the first air-fuel mixture of ammonia and air is compressed and heated to a high temperature in the auxiliary combustion chamber 21, the fuel supply device 14 injects and supplies liquid fuel into the auxiliary combustion chamber 21 by the liquid fuel injector 28, and the first air-fuel mixture of ammonia and air is compressed and auto-ignited with the hydrocarbon liquid fuel to burn. Specifically, in the combustion stroke of the combustion cycle, with the intake port 23 and the 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 by the liquid fuel injector 28, and ignites the first air-fuel mixture of ammonia and air.

[0024] In the combustion stroke of the combustion cycle, the engine 1 burns ammonia in the auxiliary combustion chamber 21 to decompose and reform the ammonia to produce reformed fuel (e.g., hydrogen) and generate fuel gas containing rich reformed fuel. Note that the engine 1 can also burn hydrocarbon liquid fuel in the auxiliary combustion chamber 21 to decompose and reform the liquid fuel to produce reformed fuel (e.g., hydrogen).

[0025] Furthermore, the engine 1 increases the pressure in the auxiliary combustion chamber 21 by burning the first air-fuel mixture containing ammonia, and then injects and supplies the second air-fuel mixture (fuel gas) containing the reformed fuel in the auxiliary combustion chamber 21 into the main combustion chamber 20 via the auxiliary combustion port 22. During the combustion stroke of the combustion cycle, the engine 1 ejects the generated fuel gas containing the reformed fuel from the auxiliary combustion chamber 21 into the main combustion chamber 20 via the auxiliary combustion port 22 when the piston 12 descends toward bottom dead center with the intake port 23 and exhaust port 24 closed. In the main combustion chamber 20, a second air-fuel mixture of the reformed fuel and air is generated, and the oxygen in the air spontaneously ignites due to the high temperature and richness of the reformed fuel, burning the second air-fuel mixture of the reformed fuel and air.

[0026] At this time, the fuel supply device 14 sets the supply amounts (for example, supply pressure, supply timing, and supply period) of ammonia and liquid fuel so that the reformed fuel of the second air-fuel mixture generated in the main combustion chamber 20 is mixed with the air in the main combustion chamber 20 and gradually becomes lean (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 becomes 1.8 or more.

[0027] By burning the second air-fuel mixture containing lean reformed fuel in the main combustion chamber 20, the combustion temperature in the main combustion chamber 20 is lowered, and the amount of nitrogen oxides produced in the exhaust gas is reduced. Figure 2 shows an example of the relationship between the excess air ratio of hydrogen in the second air-fuel mixture generated in the main combustion chamber 20 and the amount of nitrogen oxides produced in the exhaust gas when the second air-fuel mixture is burned in the main combustion chamber 20. As shown in this example of the relationship, the higher the excess air ratio of hydrogen, the lower the amount of nitrogen oxides emitted.

[0028] As described above, according to the present invention, the ammonia co-fuel engine 1 that operates by combusting ammonia and hydrocarbon-based liquid fuel includes the main combustion chamber 20, the auxiliary combustion chamber 21 that communicates with the main combustion chamber 20, and the fuel supply device 14 that supplies ammonia and liquid fuel to the auxiliary combustion chamber 21.

[0029] As a result, according to the ammonia co-fuel engine 1 of the present invention, by supplying ammonia and hydrocarbon liquid fuel to the pre-combustion chamber 21, an ammonia-rich first mixture is generated in the pre-combustion chamber 21, and the ammonia can be burned uniformly in the pre-combustion chamber 21.

[0030] Furthermore, in the ammonia-mixed combustion engine 1 of the present invention, the fuel supply device 14 is provided with an ammonia injector 27 that supplies ammonia and a liquid fuel injector 28 that supplies hydrocarbon liquid fuel, which are separate bodies. This makes it possible to realize a configuration in which ammonia and hydrocarbon liquid fuel are supplied separately to the pre-combustion chamber 21.

[0031] Furthermore, the ammonia co-fuel engine 1 of the present invention produces reformed fuel such as hydrogen in the auxiliary combustion chamber 21 by burning ammonia and / or hydrocarbon liquid fuel in the auxiliary combustion chamber 21. As a result, by burning the reformed fuel produced in the auxiliary combustion chamber 21 in the main combustion chamber 20, combustion with good exhaust gas properties can be achieved.

[0032] Furthermore, the ammonia-mixed combustion engine 1 of the present invention performs combustion at an excess air ratio of 0.4 to 0.7 in the auxiliary combustion chamber 21 to which ammonia is supplied. This allows rich ammonia to be instantly decomposed to produce reformed fuel such as hydrogen, and this reformed fuel is then burned in the main combustion chamber 20, thereby suppressing the production of nitrous oxide (N2O) (a greenhouse gas 265 times more potent than CO2). Note that while reformed fuel such as hydrogen can be produced in the auxiliary combustion chamber 21 by burning hydrocarbon liquid fuel in the auxiliary combustion chamber 21, there is a risk of soot and other particles being generated due to excessive combustion of the liquid fuel. Therefore, the use of rich ammonia can suppress the generation of soot and other particles.

[0033] Furthermore, the ammonia co-fuel engine 1 of the present invention supplies the reformed fuel produced in the auxiliary combustion chamber 21 to the main combustion chamber 20, and burns the reformed fuel in the main combustion chamber 20 at a lean excess air ratio exceeding 1. For example, the excess air ratio in the main combustion chamber 20 is 1.8 or more. By burning the second air-fuel mixture containing lean reformed fuel in the main combustion chamber 20, the combustion temperature in the main combustion chamber 20 can be lowered and the amount of nitrogen oxides produced in the exhaust gas can be suppressed.

[0034] Furthermore, in the combustion cycle of the ammonia-mixed combustion engine 1 of the present invention, after ammonia is supplied to the pre-combustion chamber 21, hydrocarbon liquid fuel is supplied to the pre-combustion chamber 21. At this time, combustion occurs in the combustion cycle by supplying the liquid fuel to the pre-combustion chamber 21. As a result, the ammonia is burned in a state where it is sufficiently mixed with air in the pre-combustion chamber 21, and therefore the ammonia can be burned more uniformly in the pre-combustion chamber 21.

[0035] In the above embodiment, an example has been described in which the fuel supply device 14 is provided with the ammonia injector 27 and the liquid fuel injector 28 separately in order to supply ammonia and hydrocarbon liquid fuel separately to the pre-combustion chamber 21, but the present invention is not limited to this example.

[0036] For example, fuel supply device 14 may be configured to include an integrated dual-fuel injector that supplies ammonia and a hydrocarbon-based liquid fuel. This dual-fuel injector may be configured, for example, to include a single valve body with a first valve chamber for supplying ammonia and a second valve chamber for supplying liquid fuel, and to be able to supply ammonia and liquid fuel separately by driving valve elements provided in each valve chamber to open and close. Alternatively, the dual-fuel injector may be configured to include a single valve body with a first passage for supplying ammonia and a second passage for supplying liquid fuel, and with nozzle holes communicating with each passage, and to be able to supply ammonia and liquid fuel separately by switching the nozzle hole between the first passage and the second passage.

[0037] In the above embodiment, an example has been described in which the second mixture is a mixture of reformed fuel and air, but the present invention is not limited to this example, and the second mixture may be a mixture containing unreformed ammonia and hydrocarbon fuel in addition to the reformed fuel and air.

[0038] The present invention can be modified as appropriate within the scope of the claims and the gist or idea of ​​the invention that can be read from the entire specification, and an ammonia co-fuel engine accompanied by such modifications is also included in the technical idea of ​​the present invention.

[0039] [Appendix to the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0040] <Appendix 1> In an ammonia co-fuel engine that operates by burning ammonia and hydrocarbon liquid fuel, A main combustion chamber; an auxiliary combustion chamber communicating with the main combustion chamber; a fuel supply device that supplies the ammonia and the liquid fuel to the auxiliary combustion chamber; An ammonia co-fuel engine comprising:

[0041] <Appendix 2> 2. The ammonia-mixed combustion engine according to claim 1, wherein the fuel supply device includes an ammonia injector that supplies the ammonia, and a liquid fuel injector that supplies the liquid fuel.

[0042] <Appendix 3> 2. The ammonia co-fuel engine according to claim 1, wherein the fuel supply device includes a dual fuel injector that supplies the ammonia and the liquid fuel.

[0043] <Appendix 4> 4. An ammonia co-fuel engine according to any one of claims 1 to 3, wherein the ammonia and / or the liquid fuel is combusted in the auxiliary combustion chamber to produce reformed fuel in the auxiliary combustion chamber.

[0044] <Appendix 5> 5. An ammonia co-fuel engine according to any one of claims 1 to 4, wherein combustion is carried out in the auxiliary combustion chamber to which the ammonia is supplied at an excess air ratio of 0.4 to 0.7.

[0045] <Appendix 6> The reformed fuel produced in the auxiliary combustion chamber is supplied to the main combustion chamber; 6. An ammonia co-fuel engine according to claim 4 or 5, characterized in that combustion is carried out in the main combustion chamber supplied with the reformed fuel at a lean air excess ratio exceeding 1.

[0046] <Appendix 7> 7. The ammonia co-fuel engine according to claim 6, wherein an excess air ratio in the main combustion chamber is 1.8 or more.

[0047] <Appendix 8> 8. The ammonia co-fuel engine according to any one of claims 1 to 7, wherein in a combustion cycle, the ammonia is supplied to the auxiliary combustion chamber, and then the liquid fuel is supplied to the auxiliary combustion chamber.

[0048] <Appendix 9> 9. The ammonia co-fuel engine according to claim 8, wherein combustion occurs by supplying the liquid fuel to the auxiliary combustion chamber in a combustion cycle. [Explanation of symbols]

[0049] 1. Ammonia co-fuel engine 2. Control device 3 Intake passage 4 Exhaust passage 10 cylinders 11 cylinders 12 pistons 13 Cylinder head 14 Fuel supply system 15 Connecting rod 16 crankshaft 20 Main combustion chamber 21 Pre-combustion chamber 22 Antechamber port 23 Intake port 24 exhaust port 25 Intake valve 26 Exhaust valve 27 Ammonia injector 28 Liquid fuel injector 29 Ammonia Tank 30 Liquid fuel tank

Claims

1. In an ammonia co-fuel engine that operates by burning ammonia and hydrocarbon liquid fuel, A main combustion chamber; an auxiliary combustion chamber communicating with the main combustion chamber; a fuel supply device that supplies the ammonia and the liquid fuel to the auxiliary combustion chamber; An ammonia co-fuel engine comprising:

2. 2. The ammonia-mixed combustion engine according to claim 1, wherein the fuel supply device comprises an ammonia injector that supplies the ammonia, and a liquid fuel injector that supplies the liquid fuel.

3. 2. The ammonia co-fuel engine according to claim 1, wherein the fuel supply device includes a dual fuel injector that supplies the ammonia and the liquid fuel.

4. 2. The ammonia co-fuel engine according to claim 1, wherein the ammonia and / or the liquid fuel is combusted in the auxiliary combustion chamber to produce reformed fuel in the auxiliary combustion chamber.

5. 2. The ammonia co-fuel engine according to claim 1, wherein combustion is carried out in the auxiliary combustion chamber to which the ammonia is supplied at an excess air ratio of 0.4 to 0.

7.

6. 5. The ammonia co-fuel engine according to claim 4, wherein the reformed fuel produced in the auxiliary combustion chamber is supplied to the main combustion chamber, and combustion is performed in the main combustion chamber to which the reformed fuel is supplied at a lean air excess ratio exceeding 1.

7. 7. The ammonia co-fuel engine according to claim 6, wherein an excess air ratio in the main combustion chamber is 1.8 or more.

8. 2. The ammonia co-fuel engine according to claim 1, wherein in a combustion cycle, the ammonia is supplied to the auxiliary combustion chamber, and then the liquid fuel is supplied to the auxiliary combustion chamber.

9. 9. The ammonia-mixed combustion engine according to claim 8, wherein combustion occurs by supplying the liquid fuel to the auxiliary combustion chamber in the combustion cycle.

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