JP7537370B2 - Engine System - Google Patents

Description

The present invention relates to an engine system.

As a conventional engine system, for example, a technology such as that described in Patent Document 1 is known. The engine system described in Patent Document 1 includes an engine body, an intake branch pipe connected to the intake port of each cylinder of the engine body, an ammonia injector that injects ammonia toward each engine intake passage of the engine body, a hydrogen generating device that generates hydrogen from liquid ammonia, and a hydrogen injector that injects hydrogen toward each engine intake passage of the engine body. The hydrogen generating device includes a tank in which liquid ammonia is stored, an evaporator that heats and vaporizes the liquid ammonia, a supply pipe through which a portion of the gaseous ammonia generated by the evaporator flows toward the ammonia injector, a cracker that decomposes the gaseous ammonia generated by the evaporator, an inlet pipe through which air supplied to the cracker flows, and a supply pipe through which hydrogen generated by the cracker flows toward the hydrogen injector.

JP 2014-211155 A

However, in the above conventional technology, the latent heat of vaporization of ammonia is large, which results in a large evaporator. In addition, when liquid ammonia is vaporized, the volume of the ammonia increases, so the diameter or number of pipes for supplying gaseous ammonia to the ammonia injector and cracker must be increased. As a result, the engine system becomes larger.

The object of the present invention is to provide an engine system that can be made compact.

The engine system according to one aspect of the present invention includes an engine having a combustion chamber in which fuel is burned, a reformer that generates a reformed gas containing hydrogen by reforming the fuel, a reformed gas flow path through which the reformed gas generated by the reformer flows toward the combustion chamber, a first fuel supply unit that supplies fuel to the combustion chamber, a first air supply unit that supplies air to the combustion chamber, a second fuel supply unit that supplies fuel to the reformer, and a second air supply unit that supplies air to the reformer. The first fuel supply unit has a first fuel injection valve that injects liquid fuel toward the combustion chamber, and the second fuel supply unit has a second fuel injection valve that is disposed upstream of the reformer and injects liquid fuel, and a heat exchanger that is disposed between the second fuel injection valve and the reformer and uses a heat medium related to the engine to heat and vaporize the liquid fuel injected from the second fuel injection valve, and the second fuel injection valve injects liquid fuel toward the heat exchanger.

In such an engine system, liquid fuel is injected from the first fuel injection valve of the first fuel supply unit toward the combustion chamber of the engine, so that liquid fuel is supplied to the combustion chamber, and air is supplied to the combustion chamber by the first air supply unit. Then, the liquid fuel is burned in the combustion chamber, and the liquid fuel is heated and vaporized by the heat capacity and combustion heat of the engine. Meanwhile, liquid fuel is injected from the second fuel injection valve of the second fuel supply unit toward the heat exchanger, so that liquid fuel is supplied to the heat exchanger. Then, in the heat exchanger, the liquid fuel is heated and vaporized by using a heat medium related to the engine. Then, fuel gas (gaseous fuel) is supplied to the reformer. Also, air is supplied to the reformer by the second air supply unit. Then, in the reformer, the fuel gas is reformed to generate a reformed gas containing hydrogen. The reformed gas flows through a reformed gas flow path and is supplied to the combustion chamber of the engine. Then, in the combustion chamber, the fuel gas is burned together with the hydrogen in the reformed gas.

In this way, the first and second fuel injection valves inject liquid fuel instead of fuel gas. This eliminates the need for a carburetor to vaporize the fuel supplied to the first and second fuel injection valves. In addition, because the fuel is supplied to the first and second fuel injection valves in a liquid state, the volume of fuel supplied to the first and second fuel injection valves is reduced. This makes it possible to reduce the diameter of the pipes through which the fuel flows and to reduce the number of pipes through which the fuel flows. As a result, the engine system can be made more compact.

The heat exchanger may be located upstream of the reformer. In this configuration, the distance from the heat exchanger to the reformer is shorter, so the fuel vaporized by the heat exchanger is less likely to cool before reaching the reformer.

The engine system further includes a cooling water circulation flow path through which engine cooling water for cooling the engine circulates, and a cooler disposed in the reformed gas flow path for cooling the reformed gas using the engine cooling water. The cooling water circulation flow path circulates the engine cooling water through the engine, the cooler, and the heat exchanger in this order, and the heat medium is the engine cooling water. The heat exchanger may heat the liquid fuel using the heat of the engine cooling water warmed in the cooler. In this configuration, the engine cooling water flows through the cooler, whereby heat exchange between the reformed gas and the engine cooling water is performed, and the reformed gas is cooled. Then, the engine cooling water warmed by the cooler flows through the heat exchanger, whereby heat exchange between the liquid fuel injected from the second fuel injection valve and the engine cooling water is performed, and the liquid fuel is heated and vaporized. In this way, by using the existing engine cooling water as a heat medium, the liquid fuel can be vaporized with a simple and inexpensive configuration.

The second air supply section has an air flow path through which air supplied to the reformer flows, and the heat exchanger is disposed in the air flow path, and the second fuel injection valve may inject liquid fuel toward an air inlet in the heat exchanger through which air is introduced. In such a configuration, liquid fuel is injected from the second fuel injection valve toward the air inlet of the heat exchanger, so that the fuel gas is mixed with the air and supplied to the reformer. Therefore, the number of gas inlets of the reformer can be minimized, simplifying the structure of the reformer.

The first fuel supply unit may have a fuel flow path through which the liquid fuel supplied to the first fuel injection valve flows, and a bubble generator disposed in the fuel flow path for generating bubbles in the liquid fuel. In this configuration, air is mixed with the liquid fuel supplied to the first fuel injection valve, making it easier for the liquid fuel to be vaporized. In addition, the liquid fuel contains air, improving the combustibility of the liquid fuel.

The present invention makes it possible to miniaturize engine systems.

1 is a schematic configuration diagram showing an engine system according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the ammonia engine shown in FIG. FIG. 2 is a cross-sectional view of the microbubble generator shown in FIG. FIG. 2 is a cross-sectional view of the heat exchanger shown in FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4. FIG. 2 is a schematic configuration diagram showing an engine system as a comparative example.

Embodiments of the present invention will now be described in detail with reference to the drawings. In the drawings, identical or equivalent elements are given the same reference numerals, and duplicate descriptions will be omitted.

Figure 1 is a schematic diagram showing an engine system according to one embodiment of the present invention. In Figure 1, the engine system 1 of this embodiment is mounted on a vehicle. The engine system 1 includes an ammonia engine 2, an intake passage 3, an exhaust passage 4, a main injector 5, and a main throttle valve 6.

The ammonia engine 2 is an engine that uses ammonia (NH ₃ ) as fuel. In the ammonia engine 2, hydrogen (H ₂ ) is mixed into ammonia in order to promote the combustion of ammonia, which is flame-resistant. The ammonia engine 2 is, for example, a four-cylinder engine.

As shown in FIG. 2, the ammonia engine 2 has a cylinder block 7, a cylinder head 8 fixed to the top surface of the cylinder block 7, and a piston 9 arranged inside the cylinder block 7 so that it can reciprocate up and down. The ammonia engine 2 also has four combustion chambers 10 in which ammonia is burned together with hydrogen to generate exhaust gas. These combustion chambers 10 are defined by the space surrounded by the cylinder block 7, the cylinder head 8, and the piston 9. Note that only one cylinder is shown in FIG. 2.

The cylinder head 8 is provided with an intake port 11 and an exhaust port 12 that are connected to the combustion chamber 10. The intake port 11 is opened and closed by an intake valve (not shown). The exhaust port 12 is opened and closed by an exhaust valve (not shown).

The intake passage 3 is connected to the intake port 11 of the ammonia engine 2. The intake passage 3 is a pipe through which air flows to be supplied to the combustion chamber 10 of the ammonia engine 2. An air cleaner 13 is disposed in the intake passage 3 to remove foreign matter such as dust and dirt contained in the air.

The exhaust flow path 4 is connected to the exhaust port 12 of the ammonia engine 2. The exhaust flow path 4 is a flow path through which exhaust gas generated in the combustion chamber 10 of the ammonia engine 2 flows. An exhaust catalyst 14 that removes harmful substances such as nitrogen oxides (NOx) contained in the exhaust gas is disposed in the exhaust flow path 4. As the exhaust catalyst 14, for example, a three-way catalyst and a selective catalytic reduction (SCR) catalyst are used.

As shown in FIG. 2, the main injector 5 injects liquid ammonia into the intake port 11 or the combustion chamber 10 of the ammonia engine 2. The main injector 5 is disposed for each cylinder of the ammonia engine 2. The main injector 5 is attached to the cylinder head 8. The main injector 5 is a first fuel injection valve that injects liquid ammonia (liquid fuel) toward the combustion chamber 10 of the ammonia engine 2.

The main throttle valve 6 is disposed between the air cleaner 13 and the ammonia engine 2 in the intake passage 3. The main throttle valve 6 is a flow control valve that controls the flow rate of air supplied to the combustion chamber 10 of the ammonia engine 2.

The intake passage 3 and the main throttle valve 6 constitute a first air supply section 15 that supplies air to the combustion chamber 10 of the ammonia engine 2.

The engine system 1 also includes an ammonia cylinder 16, a liquid pump 17, an ammonia flow path 18, a delivery pipe 19, and a microbubble generator 20.

The ammonia cylinder 16 stores ammonia in a liquid state. In other words, the ammonia cylinder stores liquid ammonia. The liquid pump 17 pumps the liquid ammonia stored in the ammonia cylinder 16 toward the main injector 5 and the reforming injector 32 (described later).

The ammonia flow path 18 connects the discharge port of the liquid pump 17 to each main injector 5 via a delivery pipe 19. The ammonia flow path 18 is a fuel flow path through which liquid ammonia pumped by the liquid pump 17 flows toward the main injectors 5. The delivery pipe 19 distributes and supplies the liquid ammonia that has flowed through the ammonia flow path 18 to each main injector 5.

The microbubble generator 20 is disposed in the ammonia flow path 18. The microbubble generator 20 generates microbubbles in the liquid ammonia flowing through the ammonia flow path 18. The microbubbles are minute bubbles with a diameter of, for example, 100 μm or less.

As shown in FIG. 3, the microbubble generator 20 has a substantially cylindrical housing 21. The housing 21 is made of a metal material such as stainless steel that is resistant to corrosion by ammonia.

The housing 21 is provided with an ammonia passage 22 through which liquid ammonia flows. The ammonia passage 22 extends in the axial direction of the housing 21. The upstream end of the housing 21 is provided with an inlet 23 that communicates with the ammonia passage 22. The inlet 23 is tapered so that its diameter gradually decreases from the upstream side to the downstream side. The downstream end of the housing 21 is provided with an outlet 24 that communicates with the ammonia passage 22. The outlet 24 is tapered so that its diameter gradually increases from the upstream side to the downstream side.

The housing 21 is also provided with an intake section 25 that is connected to the atmosphere, and an air passage 26 that guides the air drawn in by the intake section 25 to the ammonia passage 22. The intake section 25 opens to the side of the housing 21 and draws in air in the radial direction of the housing 21. The air passage 26 is arranged in an annular shape around the ammonia passage 22. The air passage 26 is also formed to guide air to the ammonia passage 22 at multiple points in the axial direction of the housing 21.

In such a microbubble generator 20, liquid ammonia flowing through the ammonia flow path 18 is introduced from the inlet 23 and supplied to the ammonia passage 22, and air drawn in from the intake 25 is supplied to the ammonia passage 22 through the air passage 26, so that air is mixed into the liquid ammonia. The liquid ammonia containing the air is then discharged from the outlet 24 and flows through the ammonia flow path 18 toward each main injector 5.

The ammonia cylinder 16, the liquid pump 17, the ammonia flow path 18, the delivery pipe 19, the microbubble generator 20, and the main injector 5 constitute a first fuel supply unit 27 that supplies ammonia, which is a fuel, to the combustion chamber 10 of the ammonia engine 2.

The engine system 1 also includes a reformer 28, an air passage 29, a reforming throttle valve 30, an ammonia passage 31, a reforming injector 32, a heat exchanger 33, a reformed gas passage 34, a cooler 35, and a stop valve 36.

The reformer 28 has a cylindrical housing 37 and a reforming section 38 and an electric heater 39 housed within the housing 37. The housing 37 is made of a metal material such as stainless steel.

The reforming section 38 produces reformed gas containing hydrogen by reforming ammonia using heat generated by burning ammonia. The reforming section 38 has a reforming catalyst 38a, for example, having a honeycomb structure. The reforming catalyst 38a is a catalyst that burns ammonia and decomposes the ammonia into hydrogen. The reforming catalyst 38a is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst. For example, a cobalt-based catalyst, a rhodium-based catalyst, a ruthenium-based catalyst, or a palladium-based catalyst is used as the reforming catalyst 38a.

The electric heater 39 is disposed upstream of the reforming section 38 inside the housing 37. The electric heater 39 heats the reforming section 38. When power is applied to the electric heater 39, it generates heat, which heats the reforming section 38. At this time, the heat generated by the electric heater 39 is transmitted to the reforming section 38 through the gas flowing inside the housing 37, and is also transmitted to the reforming section 38 through the housing 37 itself.

The air flow path 29 connects the intake flow path 3 and the reformer 28. One end of the air flow path 29 is connected to the intake flow path 3 between the air cleaner 13 and the main throttle valve 6. The other end of the air flow path 29 is connected to the gas inlet of the housing 37 of the reformer 28. The air flow path 29 is a flow path through which air supplied to the reformer 28 flows. The reforming throttle valve 30 is disposed in the air flow path 29. The reforming throttle valve 30 is a flow control valve that controls the flow rate of air supplied to the reformer 28.

The air passage 29 and the reforming throttle valve 30 constitute the second air supply section 40 that supplies air to the reformer 28.

The ammonia flow path 31 connects the discharge port of the liquid pump 17 to the reforming injector 32. The ammonia flow path 31 is a fuel flow path through which the liquid ammonia pumped by the liquid pump 17 flows toward the reforming injector 32.

The reforming injector 32 is disposed upstream of the reformer 28. The reforming injector 32 is a second fuel injection valve that injects liquid ammonia, which is a liquid fuel, toward the heat exchanger 33. The reforming injector 32 is attached to the heat exchanger 33 (see FIG. 4).

The heat exchanger 33 is disposed between the reforming throttle valve 30 and the reformer 28 in the air flow path 29. The heat exchanger 33 is also disposed between the reforming injector 32 and the reformer 28. Specifically, the heat exchanger 33 is disposed in a position upstream of the reformer 28. The position upstream of the reformer 28 refers to a position in the path (here, the air flow path 29) connecting the reforming throttle valve 30 and the reformer 28 that is closer to the reformer 28 than the reforming throttle valve 30. The distance between the heat exchanger 33 and the reformer 28 is, for example, 200 mm or less.

The heat exchanger 33 uses a heat medium related to the ammonia engine 2 to heat and vaporize the liquid ammonia injected from the reforming injector 32. The engine cooling water that cools the ammonia engine 2 is used as the heat medium related to the ammonia engine 2.

As shown in Figs. 4 and 5, the heat exchanger 33 has a housing 41, a plurality of gas supply pipes 42 arranged in the housing 41, two support plates 43 that support the gas supply pipes 42 to the housing 41, and a cooling water inlet pipe 44 and a cooling water outlet pipe 45 attached to the housing 41. The heat exchanger 33 is made of a metal material such as stainless steel. An air inlet section 46 through which air is introduced is provided at the upstream end of the housing 41. An air outlet section 47 through which air is discharged is provided at the downstream end of the housing 41.

The housing 41 has a main body 48, a connector 49 connected to the upstream end of the main body 48, and a connector 50 connected to the downstream end of the main body 48. The main body 48 has a cylindrical shape. The connector 49 has the air inlet 46 and a tapered section 51 formed so as to taper from the main body 48 side toward the air inlet 46 side. The connector 50 has the air outlet 47 and a tapered section 52 formed so as to taper from the main body 48 side toward the air outlet 47 side.

Each gas supply pipe 42 is housed within the main body 48 so as to extend in the axial direction of the housing 41. The gas supply pipe 42 is a pipe through which vaporized ammonia (ammonia gas) and air flow.

The support plate 43 has a number of circular holes 43a that fit into the gas supply pipes 42. Both ends of each gas supply pipe 42 are fitted into and fixed to the circular holes 43a of the support plate 43. Each support plate 43 is then fixed to both ends of the main body 48 via connectors 49, 50. Both ends of the main body 48 are closed by the support plate 43 except for each gas supply pipe 42. This prevents ammonia gas and air from flowing into the space outside each gas supply pipe 42 in the main body 48.

The cooling water inlet pipe 44 is attached near the upstream end of the main body 48. The cooling water inlet pipe 44 is a pipe that introduces engine cooling water, which is a heat transfer medium, into the main body 48. The cooling water outlet pipe 45 is attached near the downstream end of the main body 48. The cooling water outlet pipe 45 is a pipe that leads the engine cooling water out of the main body 48.

The space outside each gas supply pipe 42 in the main body 48 forms an engine cooling water passage 53 through which the engine cooling water introduced from the cooling water inlet pipe 44 flows toward the cooling water outlet pipe 45. The engine cooling water passage 53 is defined by the main body 48, each support plate 43, and each gas supply pipe 42.

The reforming injector 32 is attached to the housing 41 of the heat exchanger 33. The reforming injector 32 is fixed to the connector 49 of the housing 41 directly or via a support member (not shown). The reforming injector 32 is positioned so as to inject liquid ammonia toward the air inlet 46 of the heat exchanger 33.

In this heat exchanger 33, when engine cooling water is introduced from the cooling water inlet pipe 44 into the main body 48 of the housing 41, the engine cooling water flows through the engine cooling water passage 53 and is discharged from the cooling water outlet pipe 45. In this state, when liquid ammonia is injected from the reforming injector 32 into the air inlet 46, the liquid ammonia flows through each gas supply pipe 42 toward the air outlet 47. At this time, heat is exchanged between the liquid ammonia flowing through each gas supply pipe 42 and the engine cooling water flowing through the engine cooling water passage 53, and the liquid ammonia is heated and vaporized to generate ammonia gas. The ammonia gas is then discharged from the air inlet 46 to the outside of the heat exchanger 33 and flows through the air flow path 29 toward the reformer 28.

Returning to FIG. 1, the ammonia cylinder 16, the liquid pump 17, the ammonia flow path 31, the reforming injector 32, and the heat exchanger 33 constitute a second fuel supply unit 54 that supplies ammonia as fuel to the reformer 28.

The reformed gas flow passage 34 connects the reformer 28 and the intake flow passage 3. One end of the reformed gas flow passage 34 is connected to a gas outlet section of the housing 37 of the reformer 28. The other end of the reformed gas flow passage 34 is connected between the main throttle valve 6 and the ammonia engine 2 in the intake flow passage 3. The reformed gas flow passage 34 is a flow passage through which the reformed gas generated by the reforming section 38 flows toward the combustion chamber 10 of the ammonia engine 2.

The cooler 35 is disposed in the reformed gas passage 34. The cooler 35 uses engine cooling water to cool the reformed gas flowing through the reformed gas passage 34. The cooler 35 cools the reformed gas by heat exchange between the reformed gas and the engine cooling water. By providing such a cooler 35, damage to intake system components such as the main throttle valve 6 due to heat is prevented. In addition, because the volume expansion of the reformed gas is suppressed, air is more easily drawn into the combustion chamber 10 of the ammonia engine 2.

The stop valve 36 is disposed downstream of the cooler 35 in the reformed gas flow passage 34. The stop valve 36 is an opening/closing valve that opens and closes the reformed gas flow passage 34.

The engine system 1 also includes a cooling water circulation flow path 55 through which the engine cooling water circulates. The cooling water circulation flow path 55 circulates the engine cooling water so that it passes through the ammonia engine 2, the cooler 35, and the heat exchanger 33 in this order. In other words, the engine cooling water flows from the ammonia engine 2 through the cooler 35 and the heat exchanger 33 in this order, before returning to the ammonia engine 2.

At this time, the engine cooling water discharged from the ammonia engine 2 is heated by heat exchange with the reformed gas in the cooler 35. The heated engine cooling water is then cooled by heat exchange with liquid ammonia in the heat exchanger 33. The cooled engine cooling water then cools the ammonia engine 2.

Here, the amount of heat required to vaporize ammonia is 388 W/mol _-NH3 . On the other hand, under the following calculation conditions, the amount of heat recovered when the reformed gas generated by the reformer 28 is cooled by the cooler 35 is 507 W/mol _-NH3 . Therefore, the conditions for vaporizing ammonia by the heat exchanger 33 are met.
Temperature of engine cooling water at the inlet of the cooler 35=80° C.
Temperature of reformed gas at the inlet of the cooler 35=500° C.
Temperature of reformed gas at the outlet of the cooler 35=100° C.
Flow rate of engine cooling water in the cooler 35 and the heat exchanger 33 = 10 L/min
Latent heat of vaporization of ammonia = 1372 kJ/kg _-NH3 = 23.3 kJ/mol _-NH3

When an ignition switch (not shown) is turned on in the engine system 1 described above, the ammonia engine 2 starts to start, and the engine coolant circulates through the coolant circulation flow path 55. In addition, the electric heater 39 of the reformer 28 is energized, and the stop valve 36 opens.

Then, the main throttle valve 6 opens to supply air to the combustion chamber 10 of the ammonia engine 2, and the main injector 5 opens to inject liquid ammonia into the combustion chamber 10 of the ammonia engine 2. At this time, the microbubble generator 20 generates microbubbles in the liquid ammonia supplied to the main injector 5. As a result, liquid ammonia containing air is injected from the main injector 5.

Then, combustion of liquid ammonia begins in the combustion chamber 10 of the ammonia engine 2. The liquid ammonia injected from the main injector 5 is heated and vaporized by the heat capacity and combustion heat of the ammonia engine 2. At this time, the liquid ammonia contains air, so the liquid ammonia is easily vaporized.

When the reforming throttle valve 30 opens, air is supplied to the reformer 28 through the heat exchanger 33, and when the reforming injector 32 opens, liquid ammonia is injected into the heat exchanger 33. Then, in the heat exchanger 33, heat is exchanged between the liquid ammonia and the engine cooling water warmed by the ammonia engine 2, and the liquid ammonia is heated and vaporized.

Then, the mixed gas of vaporized ammonia (ammonia gas) and air is supplied to the reforming section 38 through the electric heater 39. At this time, the reforming section 38 is heated by the electric heater 39, so the temperature of the reforming section 38 rises.

When the temperature of the reforming section 38 reaches an activation temperature (a combustible temperature), the ammonia gas is combusted by the reforming catalyst 38a. Specifically, as shown in the following formula, ammonia reacts with oxygen in the air to generate combustion heat (exothermic reaction).
_NH3 +3/ _4O2 →1/ _2N2 +3/ _2H2O ...(A)

Then, the temperature of the reforming section 38 further rises due to the heat of combustion. Then, when the temperature of the reforming section 38 reaches a reforming temperature, the ammonia gas is reformed by the reforming catalyst 38a. Specifically, as shown in the following formula, a decomposition reaction of ammonia occurs (endothermic reaction), and a reformed gas containing hydrogen is generated.
_NH3 → 3/ _2H2 +1/ _2N2 ...(B)

The reformed gas flows through the reformed gas flow passage 34 toward the ammonia engine 2. At this time, the reformed gas is cooled by heat exchange between the reformed gas and engine cooling water in the cooler 35. As a result, the cooled reformed gas flows through the reformed gas flow passage 34 and the intake flow passage 3 and is supplied to the combustion chamber 10 of the ammonia engine 2. Then, in the combustion chamber 10, the ammonia gas begins to combust together with the hydrogen in the reformed gas.

In the heat exchanger 33, heat is exchanged between the liquid ammonia injected from the reforming injector 32 and the engine cooling water warmed by the cooler 35, causing the liquid ammonia to vaporize. Then, as described above, the ammonia gas is combusted and reformed in the reformer 28.

Figure 6 is a schematic diagram showing an engine system as a comparative example. In Figure 6, the engine system 100 of this comparative example has four main injectors 101 and four reforming injectors 102. The main injectors 101 inject ammonia gas (gaseous ammonia) toward the combustion chamber 10 (see Figure 2) of the ammonia engine 2. The reforming injectors 102 inject ammonia gas toward the reformer 28.

The engine system 100 also includes two carburetors 103, two carburetors 104, and a cooling water circulation flow path 105. The carburetors 103, 104 vaporize the liquid ammonia pumped by the liquid pump 17. The ammonia gas generated by the carburetor 103 flows through the ammonia flow path 106 and the delivery pipe 107 and is supplied to the main injector 101. The ammonia gas generated by the carburetor 104 flows through the ammonia flow path 108 and is supplied to the reforming injector 102.

The cooling water circulation flow path 105 circulates the engine cooling water through the ammonia engine 2, the cooler 35, and each carburetor 103, 104 in that order. Each carburetor 103, 104 heats and vaporizes liquid ammonia using the engine cooling water flowing through the cooling water circulation flow path 105.

In such an engine system 100, the latent heat of vaporization of ammonia is large, so the size of the carburetors 103, 104 is accordingly large. In addition, when liquid ammonia is vaporized, it expands, and the volume of the ammonia increases, so it is necessary to increase the number of carburetors 103, 104 and the number of pipes constituting the ammonia flow paths 106, 108, or to increase the size of the carburetors 103, 104 and the diameter of the pipes constituting the ammonia flow paths 106, 108. Increasing the number of pipes leads to an increase in the number of reforming injectors 102. Increasing the diameter of the pipes leads to an increase in the size of the reforming injectors 102. As a result, the engine system 100 becomes larger overall.

Furthermore, if the ammonia flow path 108 becomes longer, there is a risk that the ammonia gas flowing through the ammonia flow path 108 will cool and liquefy. In this case, the ammonia will no longer be reformed in the reformer 28.

In response to such a problem, in this embodiment, liquid ammonia is injected from the main injector 5 of the first fuel supply unit 27 toward the combustion chamber 10 of the ammonia engine 2, so that liquid ammonia is supplied to the combustion chamber 10, and air is supplied to the combustion chamber 10 by the first air supply unit 15. Then, the liquid ammonia is burned in the combustion chamber 10, and the liquid ammonia is heated and vaporized by the heat capacity and combustion heat of the ammonia engine 2. On the other hand, liquid ammonia is injected from the reforming injector 32 of the second fuel supply unit 54 toward the heat exchanger 33, so that liquid ammonia is supplied to the heat exchanger 33. Then, in the heat exchanger 33, the liquid ammonia is heated and vaporized using the engine cooling water. Then, ammonia gas (gaseous ammonia) is supplied to the reformer 28. Also, air is supplied to the reformer 28 by the second air supply unit 40. Then, in the reformer 28, the ammonia gas is reformed to generate a reformed gas containing hydrogen. The reformed gas flows through the reformed gas flow passage 34 and is supplied to the combustion chamber 10 of the ammonia engine 2. In the combustion chamber 10, the ammonia gas is combusted together with the hydrogen in the reformed gas.

In this way, the main injector 5 and the reforming injector 32 inject liquid ammonia instead of ammonia gas. This eliminates the need for a vaporizer to vaporize the ammonia supplied to the main injector 5 and the reforming injector 32. In addition, because ammonia is supplied to the main injector 5 and the reforming injector 32 in a liquid state, the volume of ammonia supplied to the main injector 5 and the reforming injector 32 is reduced. This makes it possible to reduce the diameter of the pipes through which ammonia flows, or to reduce the number of pipes through which ammonia flows. As a result, the engine system 1 can be made more compact.

In addition, in this embodiment, the heat exchanger 33 is disposed in a position upstream of the reformer 28. Therefore, the distance from the heat exchanger 33 to the reformer 28 is short, so that the ammonia vaporized by the heat exchanger 33 is less likely to cool before reaching the reformer 28. This prevents problems such as ammonia gas liquefying and becoming unable to be reformed.

In addition, in this embodiment, engine cooling water flows through the cooler 35, whereby heat exchange occurs between the reformed gas and the engine cooling water, and the reformed gas is cooled. Then, engine cooling water warmed by the cooler 35 flows through the heat exchanger 33, whereby heat exchange occurs between the liquid ammonia injected from the reforming injector 32 and the engine cooling water, and the liquid ammonia is heated and vaporized. In this way, by using existing engine cooling water as a heat medium, liquid ammonia can be vaporized with a simple and inexpensive configuration.

In addition, in this embodiment, liquid ammonia is injected from the reforming injector 32 toward the air inlet 46 of the heat exchanger 33, so that the ammonia gas is mixed with the air and supplied to the reformer 28. Therefore, the number of gas inlets of the reformer 28 can be kept to a minimum (one in this case), simplifying the structure of the reformer 28.

In addition, in this embodiment, a microbubble generator 20 that generates bubbles in the liquid ammonia is disposed in the ammonia flow path 18. Therefore, air is mixed with the liquid ammonia supplied to the main injector 5, making it easier for the liquid ammonia to vaporize. In addition, the liquid ammonia contains air, improving the combustibility of the liquid ammonia.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the heat exchanger 33 uses engine cooling water for cooling the ammonia engine 2 to heat and vaporize the liquid ammonia injected from the reforming injector 32. However, the heat medium for the ammonia engine 2 is not limited to engine cooling water, and may be, for example, exhaust gas generated in the combustion chamber 10 of the ammonia engine 2.

In addition, in the above embodiment, the reforming injector 32 is attached to the heat exchanger 33, but this is not particularly limited, and the reforming injector 32 may be located away from the heat exchanger 33 as long as the reforming injector 32 injects liquid ammonia toward the heat exchanger 33.

In the above embodiment, the heat exchanger 33 is disposed in the air flow path 29 through which the air supplied to the reformer 28 flows, and the reforming injector 32 injects liquid ammonia toward the air inlet 46 of the heat exchanger 33, but this is not limited to a particular form. For example, the heat exchanger 33 may be disposed on a route separate from the air flow path 29, and the ammonia gas generated by the heat exchanger 33 may be introduced into the reformer 28 or the air flow path 29 to mix the ammonia gas with the air.

In addition, in the above embodiment, a microbubble generator 20 is used to generate microbubbles in the liquid ammonia supplied to the main injector 5, but the configuration is not particularly limited, and for example, a bubble generator that generates bubbles larger than 100 μm in diameter may be used.

In addition, by arranging a bubble generator such as a microbubble generator 20 in the ammonia flow path 31 through which the liquid ammonia supplied to the reforming injector 32 flows, bubbles may also be generated in the liquid ammonia supplied to the reforming injector 32. In this case, the liquid ammonia injected from the reforming injector 32 is more likely to vaporize.

In the above embodiment, the reforming unit 38 has a reforming catalyst 38a that has both the function of burning ammonia gas and the function of decomposing ammonia gas into hydrogen, but is not limited to this form. The reforming unit 38 may have a combustion catalyst that burns ammonia gas and a reforming catalyst that decomposes ammonia gas into hydrogen separately.

In addition, in the above embodiment, ammonia is used as the fuel, but the present invention can be applied to any engine system equipped with an engine that uses a fuel with a large latent heat of vaporization.

1...engine system, 2...ammonia engine (engine), 5...main injector (first fuel injection valve), 10...combustion chamber, 15...first air supply section, 18...ammonia flow path (fuel flow path), 20...microbubble generator (bubble generator), 27...first fuel supply section, 28...reformer, 29...air flow path, 32...reforming injector (second fuel injection valve), 33...heat exchanger, 34...reformed gas flow path, 35...cooler, 40...second air supply section, 46...air introduction section, 54...second fuel supply section, 55...cooling water circulation flow path.

Claims (4)

an engine having a combustion chamber in which fuel is burned;
a reformer that generates a reformed gas containing hydrogen by reforming a fuel;
a reformed gas flow path through which the reformed gas generated by the reformer flows toward the combustion chamber;
A first fuel supply unit that supplies fuel to the combustion chamber;
A first air supply unit that supplies air to the combustion chamber;
a second fuel supply unit that supplies fuel to the reformer;
A second air supply unit that supplies air to the reformer ;
a cooling water circulation flow path through which engine cooling water for cooling the engine circulates;
a cooler disposed in the reformed gas flow passage and configured to cool the reformed gas by utilizing the engine cooling water ;
the first fuel supply unit has a first fuel injection valve that injects liquid fuel toward the combustion chamber,
the second fuel supply unit includes a second fuel injection valve that is disposed upstream of the reformer and that injects liquid fuel, and a heat exchanger that is disposed between the second fuel injection valve and the reformer and that utilizes a heat medium related to the engine to heat and vaporize the liquid fuel injected from the second fuel injection valve,
The second fuel injection valve injects liquid fuel toward the heat exchanger ,
the cooling water circulation passage circulates the engine cooling water through the engine, the cooler, and the heat exchanger in this order;
the heat medium is the engine cooling water,
The heat exchanger is an engine system that heats liquid fuel by utilizing heat of the engine cooling water warmed in the cooler . an engine having a combustion chamber in which fuel is burned;
a reformer that generates a reformed gas containing hydrogen by reforming a fuel;
a reformed gas flow path through which the reformed gas generated by the reformer flows toward the combustion chamber;
A first fuel supply unit that supplies fuel to the combustion chamber;
A first air supply unit that supplies air to the combustion chamber;
a second fuel supply unit that supplies fuel to the reformer;
a second air supply unit that supplies air to the reformer;
the first fuel supply unit has a first fuel injection valve that injects liquid fuel toward the combustion chamber,
the second fuel supply unit includes a second fuel injection valve that is disposed upstream of the reformer and that injects liquid fuel, and a heat exchanger that is disposed between the second fuel injection valve and the reformer and that utilizes a heat medium related to the engine to heat and vaporize the liquid fuel injected from the second fuel injection valve,
the second air supply unit has an air flow path through which air supplied to the reformer flows,
The heat exchanger is disposed in the air flow path,
The second fuel injection valve injects liquid fuel toward an air inlet portion into which air is introduced in the heat exchanger. 3. The engine system according to claim 1, wherein the heat exchanger is disposed upstream of the reformer. 4. The engine system according to claim 1, wherein the first fuel supply unit includes a fuel flow passage through which liquid fuel supplied to the first fuel injection valve flows, and a bubble generator disposed in the fuel flow passage and configured to generate bubbles in the liquid fuel.

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