Engine System

Abstract

To provide an engine system capable of preventing deterioration of a catalyst of a reformer when a turbocharger is mounted.SOLUTION: An engine system 1 includes: a turbocharger 10 having a turbine 11 disposed in an exhaust passage 4 and a compressor 12 disposed in an intake passage 3; a reformer 23 having a reforming catalyst 33 for decomposing ammonia gas into hydrogen and reforming the ammonia gas; an air flow passage 24 that is connected to a space between the compressor 12 and a main throttle valve 6 in the intake passage 3 and in which air to be supplied to the reformer 23 flows; a temperature sensor 39 detecting a temperature of the air flowing in the air flow passage 24; a reforming throttle valve 25 for controlling a temperature of the reforming catalyst 33 of the reformer 23; and a temperature control section 43 for controlling the reforming throttle valve 25 so that the temperature of the reforming catalyst 33 does not exceed a specified temperature, on the basis of the air temperature detected by the temperature sensor 39.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine system. [Background technology]

[0002] A known conventional engine system is disclosed, for example, in Patent Document 1. The engine system described in Patent Document 1 includes an engine body, an intake path that supplies air to the combustion chambers of each cylinder of the engine body, an exhaust path that releases exhaust gas discharged from the combustion chambers of each cylinder into the atmosphere, a fuel reformer that generates reformed fuel from a specified fuel and supplies the reformed fuel to the intake path, and a turbocharger. The turbocharger has a turbine disposed in the exhaust path between the exhaust manifold and the exhaust purification device, a rotating shaft that rotates in synchronization with the turbine, and a compressor disposed in the intake path between the air cleaner and the throttle valve and that rotates together with the turbine via the rotating shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-263039 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional technology has the following problem: Because the temperature of the air supercharged by the turbocharger is high, the air supplied to the reformer may cause the catalyst in the reformer to overheat and deteriorate.

[0005] An object of the present invention is to provide an engine system that can prevent deterioration of the catalyst in the reformer when a turbocharger is installed. [Means for solving the problem]

[0006] an intake passage through which air flows to be supplied to the engine; an exhaust passage through which exhaust gas generated by the engine flows; a main flow control valve disposed in the intake passage and controlling the flow rate of air supplied to the engine; a main fuel supply valve that supplies fuel to the engine; a turbocharger having a turbine disposed in the exhaust passage and a compressor disposed in the intake passage; a reformer having a catalyst that decomposes fuel into hydrogen and that reforms the fuel to produce a reformed gas containing hydrogen; an air flow path connected between the compressor and the main flow control valve in the intake passage and through which air flows to be supplied to the reformer; a reformed fuel supply valve that supplies fuel to the reformer; a reformed gas flow path through which the reformed gas produced by the reformer flows toward the engine; an air temperature detection unit that detects the temperature of air flowing in the air flow path; a catalyst temperature adjustment unit that adjusts the temperature of the catalyst in the reformer; and a temperature control unit that controls the catalyst temperature adjustment unit based on the air temperature detected by the air temperature detection unit so that the temperature of the catalyst does not exceed a specified temperature.

[0007] In such an engine system, fuel and air are supplied to the reformer, where the reformed gas containing hydrogen is generated by the reformer's catalyst, and the reformed gas flows through a reformed gas flow path and is supplied to the engine. Then, fuel and air are supplied to the engine, where the fuel is mixed with hydrogen and burned, generating exhaust gas. At this time, the exhaust gas flowing through the exhaust passage drives the turbine to rotate, which in turn drives the compressor. Therefore, the air flowing through the intake passage is compressed, increasing the temperature of the air flowing through the air flow path toward the reformer. The temperature of the air flowing through the air flow path is detected. Then, based on the air temperature, a catalyst temperature adjustment unit is controlled to prevent the temperature of the reformer catalyst from exceeding a specified temperature. This prevents the catalyst from overheating. This prevents deterioration of the reformer catalyst when a turbocharger is installed.

[0008] The catalyst temperature adjustment unit is a reforming flow control valve disposed in the air flow path that controls the flow rate of air supplied to the reformer, and the temperature control unit may control the aperture of the reforming flow control valve based on the air temperature detected by the air temperature detection unit so that the catalyst temperature does not exceed a specified temperature. In this configuration, when the temperature of the air flowing through the air flow path is high, the aperture of the reforming flow control valve is reduced, thereby reducing the flow rate of air supplied to the reformer. Therefore, excessive temperature rise of the catalyst is suppressed.

[0009] The catalyst temperature adjustment unit is a variable cooler disposed in the air flow path that cools the air supplied to the reformer, and the temperature control unit may control the variable cooler based on the temperature of the air detected by the air temperature detection unit so that the temperature of the catalyst does not exceed a specified temperature. In this configuration, when the temperature of the air flowing through the air flow path is high, the variable cooler is controlled so that the temperature of the air supplied to the reformer itself decreases. Therefore, excessive temperature rise of the catalyst is suppressed.

[0010] The temperature control unit may determine whether the air temperature detected by the air temperature detection unit is equal to or higher than a threshold value, and when the air temperature is equal to or higher than the threshold value, control the catalyst temperature adjustment unit based on the air temperature so that the catalyst temperature does not exceed a specified temperature. In this configuration, when the temperature of the air flowing through the air flow path is lower than the threshold value, control of the catalyst temperature adjustment unit is not executed, thereby simplifying the control process. [Effects of the Invention]

[0011] According to the present invention, when a turbocharger is installed, deterioration of the catalyst in the reformer can be prevented. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing an engine system according to a first embodiment of the present invention. [Figure 2] 3 is a flowchart showing the procedure of a temperature control process executed by a temperature control unit shown in FIG. [Figure 3]4 is a graph showing an example of opening degree map data. [Figure 4] 1 is a graph showing a comparison of the temperature of the reforming catalyst when a turbocharger is present and when no turbocharger is present. [Figure 5] 10 is a graph showing the temperature of the reforming catalyst when the process of the temperature control unit is executed in the case where a turbocharger is present. [Figure 6] FIG. 4 is a schematic configuration diagram showing an engine system according to a second embodiment of the present invention. [Figure 7] 7 is a flowchart showing the procedure of a temperature control process executed by a temperature control unit shown in FIG. 6. [Figure 8] FIG. 2 is a schematic configuration diagram showing a modified example of the engine system shown in FIG. [Figure 9] FIG. 2 is a schematic configuration diagram showing another modified example of the engine system shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0014] Fig. 1 is a schematic diagram showing an engine system according to a first embodiment of the present invention. In Fig. 1, the engine system 1 of this embodiment is mounted on a vehicle (not shown). 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.

[0015] The ammonia engine 2 is an engine that uses ammonia gas (NH3 gas) as fuel. In the ammonia engine 2, hydrogen (H2) is mixed with the ammonia gas as a combustion improver to make the flame-retardant ammonia gas easier to burn. In other words, in the ammonia engine 2, the ammonia gas is burned together with the hydrogen to generate exhaust gas. Here, the ammonia engine 2 is a four-cylinder engine.

[0016] The intake passage 3 is connected to the ammonia engine 2. The intake passage 3 is a passage through which air flows to be supplied to the ammonia engine 2. An air cleaner 7 is disposed in the intake passage 3 to remove foreign matter such as dust and dirt contained in the air.

[0017] The exhaust passage 4 is connected to the ammonia engine 2. The exhaust passage 4 is a passage through which exhaust gas generated by the ammonia engine 2 flows. The exhaust passage 4 is provided with a three-way catalyst 8 that purifies carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx), which are harmful components contained in the exhaust gas, and an SCR catalyst 9 that removes NOx contained in the exhaust gas.

[0018] The main injector 5 is an electromagnetic fuel injection valve that injects ammonia gas toward the ammonia engine 2. The main injector 5 constitutes a main fuel supply valve that supplies ammonia gas to the ammonia engine 2.

[0019] The main throttle valve 6 is disposed in the intake passage 3. The main throttle valve 6 is an electromagnetic main flow rate control valve that controls the flow rate of air supplied to the ammonia engine 2.

[0020] The engine system 1 also includes a turbocharger 10. The turbocharger 10 has a turbine 11 disposed in the exhaust passage 4, a compressor 12 disposed in the intake passage 3, and a turbine shaft 13 connecting the turbine 11 and the compressor 12.

[0021] The turbine 11 is disposed in the exhaust passage 4 between the ammonia engine 2 and the three-way catalyst 8. The turbine 11 is rotationally driven by the exhaust gas flowing through the exhaust passage 4. The compressor 12 is disposed in the intake passage 3 between the air cleaner 7 and the main throttle valve 6. The compressor 12 is rotationally driven by the turbine 11 via a turbine shaft 13, and compresses and sends out the air flowing through the intake passage 3.

[0022] An intercooler 14 is disposed in the intake passage 3 between the compressor 12 and the main throttle valve 6. The intercooler 14 exchanges heat with the air whose temperature has increased as a result of being compressed by the compressor 12, thereby cooling the air.

[0023] The engine system 1 also includes an ammonia cylinder 21, a vaporizer 22, a reformer 23, an air flow path 24, a reforming throttle valve 25, a reforming injector 26, a reformed gas flow path 27, a cooler 28, and a stop valve 29.

[0024] The ammonia cylinder 21 is a container that stores ammonia in a liquid state. That is, the ammonia cylinder 21 stores liquid ammonia.

[0025] The vaporizer 22 vaporizes the liquid ammonia stored in the ammonia cylinder 21 to generate ammonia gas. The ammonia gas generated in the vaporizer 22 flows through the ammonia flow path 30 and is supplied to the main injector 5, and also flows through the ammonia flow path 31 and is supplied to the reforming injector 26.

[0026] The reformer 23 has a cylindrical housing 32, and a reforming catalyst 33 and an electric heater 34 housed in the housing 32. The reformer 23 produces a reformed gas containing hydrogen by reforming ammonia gas using heat generated by burning the ammonia gas. The housing 32 is made of stainless steel or the like that is resistant to corrosion by ammonia gas.

[0027] The reforming catalyst 33 has, for example, a honeycomb structure. The reforming catalyst 33 is a catalyst that burns ammonia gas and decomposes the ammonia gas into hydrogen. The reforming catalyst 33 is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst. As the reforming catalyst 33, for example, a cobalt-based catalyst, a rhodium-based catalyst, a ruthenium-based catalyst, a palladium-based catalyst, or the like is used.

[0028] The electric heater 34 is disposed upstream of the reforming catalyst 33 inside the housing 32. The electric heater 34 heats the ammonia gas and air supplied to the reforming catalyst 33, thereby heating (warming) the reforming catalyst 33 through the ammonia gas and air.

[0029] The air flow path 24 connects the intake passage 3 and the reformer 23. One end of the air flow path 24 is connected to the intake passage 3 between the intercooler 14 and the main throttle valve 6. In other words, one end of the air flow path 24 is connected to the intake passage 3 between the compressor 12 and the main throttle valve 6. The other end of the air flow path 24 is connected to the inlet of the housing 32 of the reformer 23. The air flow path 24 is an air flow path through which air supplied to the reformer 23 flows.

[0030] The reforming throttle valve 25 is disposed in the air flow path 24. The reforming throttle valve 25 is an electromagnetic reforming flow control valve that controls the flow rate of air supplied to the reformer 23.

[0031] The reforming injector 26 is an electromagnetic fuel injection valve that injects ammonia gas into the air flow path 24. The reforming injector 26 injects ammonia gas into the air flow path 24 between the reforming throttle valve 25 and the reformer 23. The reforming injector 26 constitutes a reforming fuel supply valve that supplies ammonia gas to the reformer 23.

[0032] The reformed gas flow path 27 connects the reformer 23 and the intake passage 3. One end of the reformed gas flow path 27 is connected to an outlet portion of the housing 32 of the reformer 23. The other end of the reformed gas flow path 27 is connected to a portion of the intake passage 3 between the main throttle valve 6 and the ammonia engine 2. The reformed gas flow path 27 is a flow path through which the reformed gas generated by the reformer 23 flows toward the ammonia engine 2.

[0033] The cooler 28 is disposed in the reformed gas passage 27. The cooler 28 cools the reformed gas flowing through the reformed gas passage 27 by heat exchange.

[0034] The stop valve 29 is disposed downstream of the cooler in the reformed gas passage 27. The stop valve 29 is, for example, an electromagnetic on-off valve (ON / OFF valve) that opens and closes the reformed gas passage 27.

[0035] The engine system 1 also includes a temperature sensor 39 and a controller 40. The temperature sensor 39 is an air temperature detection unit that detects the temperature of the air flowing through the air flow path .

[0036] The controller 40 is composed of a CPU, RAM, ROM, an input / output interface, etc. The controller 40 has a reforming control unit 41, a combustion control unit 42, and a temperature control unit 43. The reforming control unit 41, the combustion control unit 42, and the temperature control unit 43 are executed when an ignition switch (not shown) is turned on.

[0037] The reforming control unit 41 controls the electric heater 34, the reforming throttle valve 25, and the reforming injector 26 so that reforming is performed by the reformer 23. At this time, the reforming control unit 41 controls the electric heater 34 to be ON for only the required time. The reforming control unit 41 also controls the openings of the reforming throttle valve 25 and the reforming injector 26 so that an air-fuel ratio suitable for the reforming operation by the reformer 23 is obtained.

[0038] The combustion control unit 42 controls the openings of the main injector 5 and the main throttle valve 6 based on the load of the ammonia engine 2 (not shown). The load of the ammonia engine 2 includes the engine speed and accelerator opening of the ammonia engine 2.

[0039] The temperature control unit 43 controls the reforming throttle valve 25 based on the air temperature detected by the temperature sensor 39 so that the temperature of the reforming catalyst 33 in the reformer 23 does not exceed a specified temperature. The specified temperature is the degradation temperature (see FIGS. 4 and 5) at which the reforming catalyst 33 deteriorates due to heat. The reforming throttle valve 25 constitutes a catalyst temperature adjustment unit that adjusts the temperature of the reforming catalyst 33. The temperature control unit 43 controls the opening of the reforming throttle valve 25 so that the temperature of the reforming catalyst 33 does not exceed the specified temperature.

[0040] Fig. 2 is a flowchart showing the procedure of the temperature control process executed by the temperature control unit 43. In Fig. 2, the temperature control unit 43 first acquires the detection value of the temperature sensor 39 (step S101).

[0041] Next, the temperature control unit 43 determines whether the temperature of the air flowing through the air flow path 24 is equal to or higher than a predetermined threshold (step S102). When the temperature control unit 43 determines that the temperature of the air flowing through the air flow path 24 is lower than the threshold, it executes the above-described step S101 again.

[0042] When the temperature control unit 43 determines that the temperature of the air flowing through the air flow path 24 is equal to or higher than the threshold value, the temperature control unit 43 reads the opening degree map data MD as shown in Fig. 3 (step S103). The opening degree map data MD is stored in a memory (not shown) of the controller 40.

[0043] 3, the opening map data MD is map data that represents the relationship between the temperature of the air flowing through the air flow path 24 and the opening of the reforming throttle valve 25. The opening map data MD is set so that the opening of the reforming throttle valve 25 is constant when the temperature of the air flowing through the air flow path 24 is equal to or lower than a threshold value Ts. The opening map data MD is set so that when the temperature of the air flowing through the air flow path 24 becomes equal to or higher than the threshold value Ts, the opening of the reforming throttle valve 25 gradually decreases as the air temperature increases.

[0044] At this time, the opening map data MD is set so that when the temperature of the air flowing through the air flow path 24 becomes equal to or higher than the threshold value Ts, the opening of the reforming throttle valve 25 decreases linearly or in steps as the air temperature increases, for example.

[0045] After executing step S103, the temperature control unit 43 uses the opening map data MD to determine (step S104) the opening of the reforming throttle valve 25 that corresponds to the temperature of the air flowing through the air flow path 24. Then, the temperature control unit 43 controls the opening of the reforming throttle valve 25 (step S105).

[0046] Then, the temperature control unit 43 controls the opening of the reforming injector 26 in accordance with the opening of the reforming throttle valve 25 (step S106). Specifically, when the opening of the reforming throttle valve 25 becomes smaller, the temperature control unit 43 controls the opening of the reforming injector 26 to become smaller by that amount. Thereafter, the temperature control unit 43 executes the above step S101 again.

[0047] In the engine system 1 as described above, when the vehicle's ignition switch (not shown) is turned ON, the starter (not shown) is turned ON, thereby cranking the ammonia engine 2. In addition, the stop valve 29, the reforming injector 26, the reforming throttle valve 25, the main injector 5, and the main throttle valve 6 are opened. Then, ammonia gas and air are supplied to the reformer 23 and the ammonia engine 2.

[0048] When ammonia gas and air are supplied to the reformer 23, the ammonia gas and air are heated by the electric heater 34. Therefore, the reforming catalyst 33 is heated by the heat of the ammonia gas and air, and the temperature of the reforming catalyst 33 rises. Then, when the temperature of the reforming catalyst 33 reaches an activation temperature (combustible temperature), the ammonia gas is burned by the reforming catalyst 33. Specifically, a chemical reaction (exothermic reaction) occurs between ammonia and oxygen in the air, as shown in the following formula. NH3 + 3 / 4O2 → 1 / 2N2 + 3 / 2H2O + Q1 (exothermic) ... (A)

[0049] Then, the heat of combustion of the ammonia gas further increases the temperature of the reforming catalyst 33. Then, when the temperature of the reforming catalyst 33 reaches the reaction temperature (reformable temperature), the ammonia gas is reformed by the reforming catalyst 33. Specifically, as shown in the following formula, a decomposition reaction of ammonia occurs (endothermic reaction), and a reformed gas containing hydrogen is produced. NH3→3 / 2H2+1 / 2N2-Q2 (endothermic) …(B)

[0050] The reformed gas flows through the reformed gas flow path 27 and the intake passage 3 and is supplied to the ammonia engine 2. Then, in the ammonia engine 2, the state shifts to a steady state in which the ammonia gas is burned together with the hydrogen in the reformed gas.

[0051] Incidentally, since the calorific value of ammonia is small, the output of the ammonia engine 2 is small compared to a gasoline engine or the like of the same displacement. As a countermeasure, the output of the ammonia engine 2 can be increased by providing the ammonia engine 2 with a turbocharger 10. However, since the intake air is compressed by the compressor 12 of the turbocharger 10, the pressure of the air flowing through the intake passage 3 increases, and the temperature of the air becomes high. When high-temperature air flows through the air flow path 24 and is supplied to the reformer 23, the reforming catalyst 33 of the reformer 23 overheats, making the reforming catalyst 33 prone to deterioration.

[0052] Specifically, when the ammonia engine 2 is not equipped with the turbocharger 10, the temperature of the reforming catalyst 33 rarely exceeds the degradation temperature Tr (described above), as shown in Fig. 4(a). In terms of the in-plane distribution of the reforming catalyst 33, the temperature on the upstream side of the reforming catalyst 33 is higher than the temperature on the downstream side of the reforming catalyst 33.

[0053] On the other hand, when the ammonia engine 2 is equipped with a turbocharger 10, the turbine 11 is rotationally driven by the exhaust gas flowing through the exhaust passage 4, which in turn rotates the compressor 12 via the turbine shaft 13, compressing the air flowing through the intake passage 3. Therefore, as shown in Fig. 4(b), the temperature of the air supplied to the reformer 23 increases due to the pressurization of the intake air, and the temperature of the reforming catalyst 33 may exceed the degradation temperature Tr.

[0054] Here, when the intercooler 14 is disposed downstream of the compressor 12 as in this embodiment, the air pressurized and heated by the compressor 12 is cooled. However, in order to generate a desired amount of hydrogen in the reformer 23, it is necessary to heat the reforming catalyst 33 to the reaction temperature. Therefore, if the air is cooled too much by the intercooler 14, the time required for heating the reforming catalyst 33 by the electric heater 34 will inevitably become longer. For this reason, it is difficult to use the intercooler 14 to cool the air more than necessary. Furthermore, a malfunction of the intercooler 14 may occur.

[0055] Therefore, if the intercooler 14 does not sufficiently cool the air or if the intercooler 14 fails, the temperature of the air supplied to the reformer 23 will rise, which may cause the temperature of the reforming catalyst 33 to exceed the degradation temperature Tr.

[0056] The reaction of the reforming catalyst 33 is a combination of the above formulas (A) and (B). The temperature of the reforming catalyst 33 is determined by the balance between the exothermic reaction and the endothermic reaction of the reforming catalyst 33. To lower the temperature of the reforming catalyst 33, there are methods to reduce the amount of heat generated Q1 in the above formula (A) or to increase the amount of heat absorbed Q2 in the above formula (B). However, the amount of heat absorbed Q2 is difficult to control because it is determined by the catalytic performance of the reforming catalyst 33. On the other hand, the amount of heat generated Q1 can be controlled by changing the flow rate of air supplied to the reformer 23.

[0057] Therefore, in this embodiment, the temperature sensor 39 detects the temperature of the air flowing through the air flow path 24. When the temperature of the air flowing through the air flow path 24 is equal to or higher than the threshold value Ts, the opening of the reforming throttle valve 25 is controlled to decrease according to the air temperature. Therefore, the flow rate of air supplied to the reformer 23 decreases, and the amount of heat Q1 generated in the reforming catalyst 33 decreases. As a result, as shown in Fig. 5, the temperature rise of the reforming catalyst 33 is suppressed, and the temperature of the reforming catalyst 33 is prevented from exceeding the degradation temperature Tr.

[0058] As described above, according to this embodiment, when ammonia gas and air are supplied to the reformer 23, the reforming catalyst 33 of the reformer 23 generates a reformed gas containing hydrogen, and the reformed gas flows through the reformed gas flow path 27 and is supplied to the ammonia engine 2. When ammonia gas and air are supplied to the ammonia engine 2, the ammonia gas is mixed with hydrogen and combusted in the ammonia engine 2, generating exhaust gas. At this time, the turbine 11 is rotationally driven by the exhaust gas flowing through the exhaust passage 4, which in turn rotationally drives the compressor 12. Therefore, the air flowing through the intake passage 3 is compressed, and the temperature of the air flowing through the air flow path 24 toward the reformer 23 increases. Here, the temperature of the air flowing through the air flow path 24 is detected. Then, based on the air temperature, the reforming throttle valve 25 is controlled so that the temperature of the reforming catalyst 33 of the reformer 23 does not exceed a specified temperature. This suppresses excessive temperature rise of the reforming catalyst 33. As a result, when a turbocharger 10 is installed, deterioration of the reforming catalyst 33 of the reformer 23 is prevented.

[0059] Furthermore, in this embodiment, the opening of the reforming throttle valve 25 is controlled based on the air temperature detected by the temperature sensor 39 so that the temperature of the reforming catalyst 33 does not exceed a specified temperature. When the temperature of the air flowing through the air flow path 24 is high, the opening of the reforming throttle valve 25 is reduced, thereby reducing the flow rate of air supplied to the reformer 23. Therefore, excessive temperature rise of the reforming catalyst 33 is suppressed.

[0060] Furthermore, in this embodiment, when the temperature of the air detected by the temperature sensor 39 is equal to or higher than the threshold value Ts, the reforming throttle valve 25 is controlled based on the air temperature so that the temperature of the reforming catalyst 33 does not exceed a specified temperature. In this configuration, when the temperature of the air flowing through the air flow path 24 is lower than the threshold value Ts, the reforming throttle valve 25 is not controlled, which simplifies the control process.

[0061] Furthermore, in this embodiment, when the temperature of the air flowing through the air flow passage 24 is high, the flow rate of the air supplied to the reformer 23 is reduced, and therefore the amount of ammonia gas to be oxidized in the reforming catalyst 33 is reduced. Therefore, the flow rate of ammonia gas supplied to the reformer 23 can be reduced, and fuel efficiency can be improved.

[0062] 6 is a schematic diagram showing an engine system according to a second embodiment of the present invention. In FIG. 6, an engine system 1A of this embodiment includes a variable cooler 45 in addition to the configuration of the first embodiment.

[0063] The variable cooler 45 is disposed upstream of the reforming throttle valve 25 in the air flow path 24. The variable cooler 45 cools the air flowing through the air flow path 24. The variable cooler 45 constitutes a catalyst temperature adjustment unit that adjusts the temperature of the reforming catalyst 33 of the reformer 23.

[0064] Variable cooler 45 has a drive unit 46 that adjusts the cooling degree of the air flowing through air flow path 24. Variable cooler 45 may be water-cooled or air-cooled. In a water-cooled variable cooler 45, drive unit 46 is, for example, a pump that pressurizes cooling water, and adjusts the rotation speed of the pump to adjust the cooling degree of the air flowing through air flow path 24. In an air-cooled variable cooler 45, drive unit 46 is, for example, a fan that blows cooling air, and adjusts the rotation speed of the fan to adjust the cooling degree of the air flowing through air flow path 24.

[0065] Furthermore, the engine system 1A includes a controller 40A instead of the controller 40 in the first embodiment. The controller 40A includes the reforming control unit 41 and combustion control unit 42, as well as a temperature control unit 43A.

[0066] The temperature control unit 43A controls the variable cooler 45 based on the air temperature detected by the temperature sensor 39 so that the temperature of the reforming catalyst 33 of the reformer 23 does not exceed a specified temperature.

[0067] FIG. 7 is a flowchart showing the procedure of the temperature control process executed by the temperature control unit 43A, and corresponds to FIG.

[0068] 7, after executing steps S101 and S102, temperature control unit 43A reads drive amount map data (step S103A). Although not specifically shown, drive amount map data is map data that represents the relationship between the temperature of air flowing through air flow path 24 and the drive amount (rotation speed) of drive unit 46 of variable cooler 45.

[0069] Temperature control unit 43A uses the drive amount map data to determine the drive amount of drive unit 46 of variable cooler 45 that corresponds to the temperature of air flowing through air flow path 24 (step S104A). Temperature control unit 43A then controls drive unit 46 of variable cooler 45 according to the determined drive amount (step S105A). Thereafter, temperature control unit 43A executes step S101 again.

[0070] In this embodiment, the variable cooler 45 is controlled based on the air temperature detected by the temperature sensor 39 so that the temperature of the reforming catalyst 33 does not exceed a specified temperature. When the temperature of the air flowing through the air flow path 24 is high, the variable cooler 45 is controlled so that the temperature of the air supplied to the reformer 23 itself decreases. Therefore, an excessive temperature rise of the reforming catalyst 33 is suppressed.

[0071] The present invention is not limited to the above embodiment. For example, in the above embodiment, the intercooler 14 is disposed in the intake passage 3 downstream of the compressor 12 of the turbocharger 10 and upstream of the connection point with the air flow path 24, but the present invention is not particularly limited to such an embodiment. The intercooler 14 may be disposed in the intake passage 3 downstream of the connection point with the air flow path 24 and upstream of the main throttle valve 6, as shown in FIG. 8 .

[0072] Furthermore, in the above embodiment, the cooler 28 is disposed in the reformed gas passage 27, but the present invention is not limited to such a configuration. For example, as shown in Fig. 9, a cooler 49 may be disposed downstream of the connection point with the reformed gas passage 27 in the intake passage 3 and upstream of the ammonia engine 2, and the intercooler 14 and the cooler 28 may be replaced by the cooler 49. In this case, the number of parts can be reduced.

[0073] Furthermore, in the above embodiment, the reforming throttle valve 25 or the variable cooler 45 is controlled based on the air temperature detected by the temperature sensor 39 so that the temperature of the reforming catalyst 33 does not exceed a specified temperature, but this is not limited to a particular form, and both the reforming throttle valve 25 and the variable cooler 45 may be controlled so that the temperature of the reforming catalyst 33 does not exceed a specified temperature.

[0074] Furthermore, in the above embodiment, the reforming catalyst 33 of the reformer 23 is heated by the electric heater 34 when the ammonia engine 2 is started, but this is not a particular limitation, and the reforming catalyst 33 may be heated by a combustor such as a tubular flame burner, for example. Furthermore, if compression heat from the compressor 12 of the turbocharger 10 is available, the compression heat may be used to heat the reforming catalyst 33. In this case, the electric heater 34 and the combustor are not required.

[0075] Furthermore, in the above embodiment, the temperature sensor 39 detects the temperature of the air flowing through the air flow path 24, but this is not a particular limitation, and for example, a pressure sensor may be used to detect the pressure of the air flowing through the air flow path 24 and estimate the temperature of the air flowing through the air flow path 24. In this case, for example, map data representing the relationship between the pressure and temperature of the air flowing through the air flow path 24 may be stored, and the temperature of the air flowing through the air flow path 24 may be detected from the map data.

[0076] In the above embodiment, the reformer 23 has the reforming catalyst 33 that has both the function of burning ammonia gas and the function of decomposing the ammonia gas into hydrogen, but is not limited to this particular form. The reformer 23 may have a combustion catalyst that burns ammonia gas and a reforming catalyst that decomposes the ammonia gas into hydrogen separately.

[0077] Furthermore, in the above embodiment, ammonia gas is used as the fuel, but the present invention is also applicable to engine systems that use hydrocarbons or the like as fuel. [Explanation of symbols]

[0078] 1, 1A...engine system, 2...ammonia engine (engine), 3...intake passage, 4...exhaust passage, 5...main injector (main fuel supply valve), 6...main throttle valve (main flow control valve), 10...turbocharger, 11...turbine, 12...compressor, 23...reformer, 24...air flow path, 25...reforming throttle valve (reformed flow control valve, catalyst temperature adjustment unit), 26...reforming injector (reformed fuel supply valve), 27...reformed gas flow path, 33...reforming catalyst (catalyst), 39...temperature sensor (air temperature detection unit), 43, 43A...temperature control unit, 45...variable cooler (catalyst temperature adjustment unit).

Claims

1. an engine in which fuel is combusted with hydrogen; an intake passage through which air supplied to the engine flows; an exhaust passage through which exhaust gas generated by the engine flows; a main flow control valve disposed in the intake passage for controlling the flow rate of air supplied to the engine; a main fuel supply valve for supplying the fuel to the engine; a turbocharger having a turbine disposed in the exhaust passage and a compressor disposed in the intake passage; a reformer having a catalyst for decomposing the fuel into the hydrogen and reforming the fuel to generate a reformed gas containing the hydrogen; an air flow path connected between the compressor and the main flow control valve in the intake passage, through which air to be supplied to the reformer flows; a reformed fuel supply valve that supplies the fuel to the reformer; a reformed gas flow path through which the reformed gas generated by the reformer flows toward the engine; an air temperature detection unit that detects the temperature of air flowing through the air flow path; a catalyst temperature adjusting unit that adjusts the temperature of the catalyst in the reformer; a temperature control unit that controls the catalyst temperature adjustment unit based on the air temperature detected by the air temperature detection unit so that the temperature of the catalyst does not exceed a specified temperature, The temperature control unit determines whether the temperature of the air detected by the air temperature detection unit is equal to or higher than a threshold value, and when the temperature of the air is equal to or higher than the threshold value, controls the catalyst temperature adjustment unit based on the temperature of the air so that the temperature of the catalyst does not exceed the specified temperature.

2. An engine in which fuel is combusted with hydrogen; an intake passage through which air supplied to the engine flows; an exhaust passage through which exhaust gas generated by the engine flows; a main flow control valve disposed in the intake passage for controlling the flow rate of air supplied to the engine; a main fuel supply valve for supplying the fuel to the engine; a turbocharger having a turbine disposed in the exhaust passage and a compressor disposed in the intake passage; a reformer having a catalyst for decomposing the fuel into the hydrogen and reforming the fuel to generate a reformed gas containing the hydrogen; an air flow path connected between the compressor and the main flow control valve in the intake passage, through which air to be supplied to the reformer flows; a reformed fuel supply valve that supplies the fuel to the reformer; a reformed gas flow path through which the reformed gas generated by the reformer flows toward the engine; an air temperature detection unit that detects the temperature of air flowing through the air flow path; a catalyst temperature adjusting unit that adjusts the temperature of the catalyst in the reformer; a temperature control unit that controls the catalyst temperature adjustment unit based on the air temperature detected by the air temperature detection unit so that the temperature of the catalyst does not exceed a specified temperature, the catalyst temperature adjustment unit has a variable cooler disposed in the air flow path and configured to cool the air supplied to the reformer; The temperature control unit controls the variable cooler based on the air temperature detected by the air temperature detection unit so that the temperature of the catalyst does not exceed the specified temperature.

3. The catalyst temperature adjustment unit has a reforming flow rate control valve disposed in the air flow path and controlling the flow rate of air supplied to the reformer, 3. The engine system according to claim 1, wherein the temperature control unit controls the opening degree of the reforming flow control valve based on the air temperature detected by the air temperature detection unit so that the temperature of the catalyst does not exceed the specified temperature.

4. The catalyst temperature adjustment unit is a variable cooler disposed in the air flow path and cooling the air supplied to the reformer, 2. The engine system according to claim 1, wherein the temperature control unit controls the variable cooler based on the air temperature detected by the air temperature detection unit so that the temperature of the catalyst does not exceed the specified temperature.

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