Engine system

Abstract

An engine system is provided. An engine system is provided with: a first flow rate control valve that controls the flow rate of air supplied to an engine; a first fuel injection valve that injects fuel toward the engine; a reformer that reforms the fuel to generate a reformed gas containing hydrogen; a second flow rate control valve that controls the flow rate of air supplied to the reformer; a second fuel injection valve that injects fuel toward the reformer; and a control unit that controls the first flow control valve, the first fuel injection valve, the second flow control valve, and the second fuel injection valve on the basis of a command value for the engine. When the command value changes during operation of the engine, the control unit sets a target opening degree corresponding to the command value of the first flow rate control valve to a first target opening degree, and sets a target opening degree corresponding to the command value of the second flow rate control valve to a second target opening degree. The first flow rate control valve and the second flow rate control valve are controlled such that the point in time at which the opening degree of the first flow rate control valve reaches the first target opening degree is delayed than the point in time at which the opening degree of the second flow rate control valve reaches the second target opening degree.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an engine system. BACKGROUND

[0002] As a conventional engine system, for example, the technology described in Patent Literature 1 is known. The engine system described in Patent Literature 1 is provided with a main reformer that is attached to an exhaust pipe of an internal combustion engine and reforms fuel by a reforming catalyst, a reforming gas supply pipe that supplies reforming gas generated by the main reformer, a gas injection valve that injects the supplied reforming gas into an intake pipe, and a plurality of fuel injection valves with a sub-reformer that are provided at branch portions of the intake pipe per cylinder. In the case where the supply of reforming gas from the main reformer and the gas injection valve is insufficient, the insufficient portion is supplemented by the fuel injection valves with a sub-reformer. Thereby, even in a transient state such as sudden acceleration, the internal combustion engine can be supplied with sufficient reforming gas.

[0003] Patent Literature 1: Japanese Patent Application Publication No. 2001-12321

[0004] However, in the above-described conventional technology, in addition to the main reformer and the gas injection valve, the fuel injection valves with a sub-reformer are required per cylinder of the engine (internal combustion engine). Further, with the addition of the fuel injection valves with a sub-reformer, a temperature sensor that detects the temperature of the reforming catalyst in the sub-reformer and a pressure sensor that detects the pressure of the reforming gas in the sub-reformer, and the like are required. Therefore, the structure of the engine system becomes complicated. Therefore, it is desirable to achieve simplification of the engine system structure and to ensure an appropriate air-fuel ratio at the transition of the engine. SUMMARY

[0005] An object of the present disclosure is to provide an engine system that can achieve simplification of the system structure and ensure an appropriate air-fuel ratio at the transition of the engine.

[0006] (1) An engine system according to one aspect of this disclosure comprises: an engine for burning fuel together with hydrogen; an intake air passage for supplying air to the engine; a first flow control valve disposed in the intake air passage for controlling the flow rate of air supplied to the engine; a first fuel injection valve for injecting fuel toward the engine; a reformer having a catalyst for decomposing fuel into hydrogen and reforming the fuel to generate reformed gas containing hydrogen; an upstream reforming passage for supplying air to the reformer; a downstream reforming passage for supplying gas generated by the reformer toward the engine; a second flow control valve disposed in the upstream or downstream reforming passage for controlling the flow rate of air supplied to the reformer; and a second fuel injection valve for injecting fuel toward the engine. The system includes: a fuel injection unit for the reformer; a command value output unit that outputs a command value for the engine after engine startup; and a control unit that controls a first flow control valve, a first fuel injection valve, a second flow control valve, and a second fuel injection valve based on the command value output from the command value output unit. If the command value output from the command value output unit changes during engine operation, the control unit sets the target opening degree of the first flow control valve corresponding to the command value as a first target opening degree and sets the target opening degree of the second flow control valve corresponding to the command value as a second target opening degree. The control unit controls the first and second flow control valves in such a way that the time point at which the opening degree of the first flow control valve reaches the first target opening degree is delayed compared to the time point at which the opening degree of the second flow control valve reaches the second target opening degree.

[0007] In such an engine system, fuel and air are supplied to the reformer, thereby generating hydrogen-containing reformed gas using the reformer's catalyst, which is then supplied to the engine. Fuel and air are supplied to the engine, where the fuel and hydrogen are mixed and combusted. At this time, on one hand, air flows in the intake airflow path and is supplied to the engine, and fuel is injected into the engine from the first fuel injection valve. On the other hand, air flows in the upstream reforming airflow path and is supplied to the reformer, and fuel is injected into the reformer from the second fuel injection valve. Reformed gas is generated in the reformer, which flows in the downstream reforming airflow path and is supplied to the engine. Therefore, while air flowing in the intake airflow path is rapidly supplied to the engine, the reformed gas is supplied with a delay compared to the air. Consequently, when engine operating commands change, the flow rate of the reformed gas supplied to the engine changes with a delay compared to the flow rate of the air supplied to the engine. At this time, a proper air-fuel ratio cannot be ensured in the engine.

[0008] Therefore, if the engine command value changes during engine operation, the target opening degree of the first flow control valve corresponding to that command value is set to the first target opening degree, and the target opening degree of the second flow control valve corresponding to that command value is set to the second target opening degree. Furthermore, the first and second flow control valves are controlled such that the time when the opening degree of the first flow control valve reaches the first target opening degree is delayed compared to the time when the opening degree of the second flow control valve reaches the second target opening degree. Thus, the time when the opening degree of the first flow control valve reaches the first target opening degree is delayed compared to the time when the opening degree of the second flow control valve reaches the second target opening degree. Therefore, even during transitions where engine operating conditions change, reformed gas and air are appropriately supplied to the engine, thus ensuring an appropriate air-fuel ratio. Furthermore, it is not necessary to install a secondary reformer for each cylinder of the engine, therefore, valves that inject fuel towards the secondary reformer are also unnecessary. Therefore, the engine system structure is simplified.

[0009] (2) Alternatively, in (1) above, if the command value output from the command value output unit changes in the direction of increasing during engine operation, the control unit sets a first target opening degree and a second target opening degree that increase in accordance with the command value.

[0010] In this structure, if the command value for the engine changes in an increasing direction during engine operation, a first target opening degree and a second target opening degree are set to increase accordingly. Therefore, the time point at which the opening degree of the first flow control valve increases to the first target opening degree is delayed compared to the time point at which the opening degree of the second flow control valve increases to the second target opening degree. This ensures an appropriate air-fuel ratio, thereby suppressing misfires caused by a decrease in the flow rate of hydrogen contained in the reformed gas compared to the air flow rate.

[0011] (3) Alternatively, in (1) or (2) above, if the command value output by the command value output unit changes in the direction of decreasing during engine operation, a first target opening degree and a second target opening degree that decrease in accordance with the command value are set.

[0012] In this structure, if the command value for the engine changes in a decreasing direction during engine operation, a first target opening degree and a second target opening degree are set to decrease accordingly. Therefore, the time point at which the opening of the first flow control valve decreases to the first target opening degree is delayed compared to the time point at which the opening of the second flow control valve decreases to the second target opening degree. This ensures an appropriate air-fuel ratio, thus suppressing the instability in engine control caused by an excess of hydrogen flow rate in the reformed gas compared to the air flow rate, which leads to overly rich combustion.

[0013] (4) Alternatively, in any of (1) to (3) above, the control unit controls the first flow control valve and the second flow control valve in such a way that the start time of the change in the opening of the first flow control valve is delayed compared to the start time of the change in the opening of the second flow control valve.

[0014] In this configuration, the start time of the opening change of the first flow control valve is delayed compared to the start time of the opening change of the second flow control valve. Therefore, the time when the opening of the first flow control valve reaches the first target opening is indeed delayed compared to the time when the opening of the second flow control valve reaches the second target opening. Furthermore, the rapid change in the opening of the first flow control valve facilitates control of the air flow supplied to the engine.

[0015] (5) Alternatively, in any of (1) to (3) above, the control unit controls the first flow control valve and the second flow control valve in such a way that the opening and closing speed of the first flow control valve is slower than that of the second flow control valve.

[0016] In this structure, the opening and closing speed of the first flow control valve is slower than that of the second flow control valve. Therefore, the time when the opening degree of the first flow control valve reaches the first target opening degree is actually delayed compared to the time when the opening degree of the second flow control valve reaches the second target opening degree. Furthermore, the opening degree of the first flow control valve changes gradually, thereby enabling the first flow control valve to perform its opening and closing actions smoothly.

[0017] (6) Alternatively, in any of (1) to (5) above, the second flow control valve is installed at the downstream reforming flow path to control the flow rate of the reforming gas supplied to the engine together with the flow rate of the air supplied to the reformer.

[0018] In this configuration, air flowing in the upstream reforming path is supplied to the reformer to generate reformed gas, which then flows in the downstream reforming path and is supplied to the engine. A second flow control valve is located in the downstream reforming path. Therefore, compared to the case where the second flow control valve is located in the upstream reforming path, increasing the opening of the second flow control valve allows for a rapid increase in the amount of reformed gas supplied to the engine. Conversely, decreasing the opening of the second flow control valve allows for a rapid decrease in the amount of reformed gas supplied to the engine.

[0019] According to this disclosure, the system structure can be simplified, and the appropriate air-fuel ratio can be ensured during engine transitions. Attached Figure Description

[0020] Figure 1 This is a schematic structural diagram of an engine system according to one embodiment of the present disclosure.

[0021] Figure 2 It means by Figure 1 The flowchart shows the steps of the control processing performed by the control unit.

[0022] Figure 3 It means Figure 2 The flowchart shows the details of the control process when the throttle opening increases in step S104.

[0023] Figure 4 It means Figure 2 The flowchart shows the details of the control process when the throttle opening decreases in step S105.

[0024] Figure 5 (a) is a timing diagram representing the switching of the throttle from off to on. Figure 5 (b) is a timing diagram showing the action of the main injector when the throttle switches from off to on. Figure 5 (c) is a timing diagram showing the action of the reformer injector when the throttle switches from off to on. Figure 5 (d) is a timing diagram representing the action of the main throttle valve when the throttle is switched from off to on. Figure 5 (e) is a timing diagram representing the action of the throttle resetting valve when the throttle is switched from off to on.

[0025] Figure 6 (a) is a timing diagram representing the switching of the throttle from on to off. Figure 6 (b) is a timing diagram showing the action of the main injector when the throttle switches from on to off. Figure 6 (c) is a timing diagram showing the action of the reformer injector when the throttle switches from on to off. Figure 6 (d) is a timing diagram representing the action of the main throttle valve when the throttle is switched from on to off. Figure 6 (e) is a timing diagram representing the action of the throttle resetting valve when the throttle is switched from on to off.

[0026] Figure 7 (a) is a timing diagram representing the switching of the throttle from off to on. Figure 7 (b) is a timing diagram showing a variation of the action of the main injector when the throttle switches from off to on. Figure 7 (c) is a timing diagram representing a variation of the action of the reformer when the throttle switches from off to on. Figure 7 (d) is a timing diagram representing a variation of the action of the main throttle valve when the throttle is switched from off to on. Figure 7 (e) is a timing diagram representing a variation of the action of the re-regulating throttle valve when the throttle is switched from off to on.

[0027] Figure 8 This is a schematic structural diagram of the engine system involved in other embodiments of this disclosure. Detailed Implementation

[0028] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent elements are labeled with the same reference numerals, and repeated descriptions are omitted.

[0029] Figure 1 This is a schematic structural diagram of an engine system according to one embodiment of the present disclosure. Figure 1 In this embodiment, the engine system 1 is mounted on a vehicle (not shown). The engine system 1 includes an ammonia engine 2, an intake air passage 3, an exhaust air passage 4, a main throttle valve 5, and a main injector 6.

[0030] Ammonia engine 2 is an engine that uses ammonia gas (NH3 gas) as fuel. In ammonia engine 2, hydrogen gas (H2) is mixed with the ammonia gas as a combustion accelerant to make the non-flammable ammonia gas easier to burn. In other words, in each cylinder of ammonia engine 2, ammonia gas and hydrogen gas burn together to produce combustion gases. Ammonia engine 2 is, for example, a four-cylinder engine.

[0031] The intake air passage 3 is connected to each cylinder of the ammonia engine 2 via the intake manifold 7. The intake air passage 3 is the flow path for supplying air to the ammonia engine 2. An air filter 8 is installed on the intake air passage 3 to remove dust, dirt and other foreign matter contained in the air.

[0032] Exhaust path 4 is connected to each cylinder of ammonia engine 2 via exhaust manifold 9. Exhaust path 4 is the flow path for the exhaust gas generated by ammonia engine 2. Exhaust path 4 is equipped with a three-way catalyst 10 for purifying NH3 and NOx contained in the exhaust gas, and an SCR catalyst 11 for adsorbing NH3 that passes through the three-way catalyst 10.

[0033] The main throttle valve 5 is located in the intake air passage 3. The main throttle valve 5 is an electromagnetic first flow control valve that controls the flow rate of air supplied to each cylinder of the ammonia engine 2.

[0034] The main injector 6 is an electromagnetic first fuel injection valve that intermittently injects ammonia into each cylinder of the ammonia engine 2. The main injector 6 injects ammonia into the intake manifold 7, for example. The number of main injectors 6 is the same as the number of cylinders in the ammonia engine 2 (four in this case). The amount of ammonia injected can be adjusted by changing the opening of the main injector 6.

[0035] In addition, the engine system 1 includes a reformer 12, an upstream reforming flow path 13, a reforming throttle valve 14, an ammonia cylinder 15, a carburetor 16, a carburetor 17, an ammonia flow path 18, an ammonia flow path 19, a reforming injector 20, a downstream reforming flow path 21, a cooler 22, and a shut-off valve 23.

[0036] The reformer 12 reforms ammonia by utilizing the heat generated from the combustion of ammonia gas, thereby producing a reformed gas containing hydrogen. The reformer 12 has a cylindrical shell 24. The reformer 12 includes a combustion catalyst 25, a reforming catalyst 26, and an electric heater 27 housed within the shell 24. The shell 24 is made of stainless steel or the like, which is corrosion-resistant to ammonia gas.

[0037] Combustion catalyst 25 and reforming catalyst 26, for example, have a honeycomb structure. Combustion catalyst 25 is a catalyst for burning ammonia. Reforming catalyst 26 is disposed downstream of combustion catalyst 25 within housing 24. Reforming catalyst 26 is a catalyst for decomposing ammonia into hydrogen. Combustion catalyst 25 and reforming catalyst 26 are, for example, ATR (Autothermal Reformer) type catalysts.

[0038] An electric heater 27 is disposed upstream of the combustion catalyst 25 within the housing 24. The electric heater 27 heats the combustion catalyst 25 by heating the ammonia and air introduced into the housing 24 (warm-up).

[0039] The upstream rectifier flow path 13 is connected to the inlet of the housing 24 of the rectifier 12. The upstream rectifier flow path 13 is the flow path for the air supplied to the rectifier 12. An air filter 28 is provided in the upstream rectifier flow path 13 to remove foreign matter such as dust and dirt contained in the air. The upstream rectifier flow path 13 is, for example, branched into the inlet flow path 3.

[0040] The reforming throttle valve 14 is located in the upstream reforming flow path 13. The reforming throttle valve 14 is an electromagnetic second flow control valve that controls the flow rate of air supplied to the reformer 12.

[0041] Ammonia cylinder 15 is a container for storing ammonia in a liquid state. In other words, ammonia cylinder 15 stores liquid ammonia.

[0042] Vaporizers 16 and 17 are connected to ammonia cylinder 15 via ammonia flow path 29. Ammonia flow path 29 is a flow path for the liquid ammonia stored in ammonia cylinder 15. Vaporizers 16 and 17 vaporize the liquid ammonia to generate ammonia gas.

[0043] Ammonia flow path 18 connects vaporizer 16 to each main injector 6. Ammonia flow path 18 is a flow path for the ammonia gas generated by vaporizer 16 to flow toward each main injector 6. Ammonia flow path 19 connects vaporizer 17 to reformer injector 20. Ammonia flow path 19 is a flow path for the ammonia gas generated by vaporizer 17 to flow toward reformer injector 20.

[0044] The reformer injector 20 is an electromagnetic second fuel injection valve that intermittently injects ammonia towards the reformer 12. The reformer injector 20 injects ammonia into the portion of the upstream reforming flow path 13 between the reforming throttle valve 14 and the reformer 12. The amount of ammonia injected can be adjusted by changing the opening of the reformer injector 20.

[0045] The downstream-side reforming path 21 connects the reformer 12 to the intake airflow path 3. One end of the downstream-side reforming path 21 is connected to the outlet of the housing 24 of the reformer 12. The other end of the downstream-side reforming path 21 is connected between the main throttle valve 5 of the intake airflow path 3 and the ammonia engine 2. The downstream-side reforming path 21 is a flow path for the reformed gas generated by the reformer 12 to flow towards the ammonia engine 2.

[0046] Cooler 22 is provided in the downstream reforming flow path 21. Cooler 22 cools the reformed gas flowing in the downstream reforming flow path 21.

[0047] The shut-off valve 23 is installed on the downstream side of the downstream rectifier flow path 21, near the downstream side of the cooler 22. The shut-off valve 23 is an on / off valve that opens and closes the downstream rectifier flow path 21.

[0048] Here, the intake airflow path 3, the main throttle valve 5, and the main injector 6 constitute the main pipeline 38. The upstream reforming flow path 13, the reformer 12, the downstream reforming flow path 21, the reforming throttle valve 14, the reforming injector 20, the cooler 22, and the shut-off valve 23 constitute the reforming pipeline 39.

[0049] In addition, engine system 1 includes throttle sensor 30 and control unit 31.

[0050] The throttle sensor 30 is a sensor that detects the throttle opening (ped weight) of the vehicle and outputs the detected throttle opening value as an electrical signal. The electrical signal output from the throttle sensor 30 corresponds to a command value for the ammonia engine 2. Therefore, the throttle sensor 30 constitutes a command value output unit that outputs a command value for the ammonia engine 2 after the ammonia engine 2 is started. The change in throttle opening during the operation of the ammonia engine 2 corresponds to a transitional state in which the operating conditions of the ammonia engine 2 change.

[0051] The control unit 31 consists of a CPU, RAM, ROM, and input / output interfaces. The control unit 31 constitutes a control unit, which controls the main throttle valve 5, the main injector 6, the reforming throttle valve 14, and the reforming injector 20 based on the detection value (command value) of the throttle sensor 30.

[0052] If the throttle sensor 30 changes its detection value during the operation of the ammonia engine 2, the control unit 31 sets the target opening of the main throttle valve 5 corresponding to the detection value of the throttle sensor 30 as the first target opening. If the throttle sensor 30 changes its detection value during the operation of the ammonia engine 2, the control unit 31 sets the target opening of the reforming throttle valve 14 corresponding to the detection value of the throttle sensor 30 as the second target opening. The control unit 31 controls the main throttle valve 5 and the reforming throttle valve 14 in a manner that delays the time when the opening of the main throttle valve 5 reaches the first target opening compared to the time when the opening of the reforming throttle valve 14 reaches the second target opening.

[0053] At this time, the control unit 31 controls the main throttle valve 5 and the reforming throttle valve 14 in such a way that the start time of the change in the opening of the main throttle valve 5 is delayed compared with the start time of the change in the opening of the reforming throttle valve 14.

[0054] The control unit 31 has an opening change determination unit 32, an opening increase control unit 33, and an opening decrease control unit 34.

[0055] The throttle opening change determination unit 32 determines whether the throttle opening has changed based on the detection value of the throttle sensor 30.

[0056] If the opening change determination unit 32 determines that the throttle opening has changed in the increasing direction, the control unit 33 sets a first target opening and a second target opening that follow the detection value of the throttle sensor 30 when the opening increases. When the opening increases, the control unit 33 controls the main throttle valve 5 and the resetting throttle valve 14 in a manner that delays the time when the opening of the main throttle valve 5 reaches the first target opening compared with the time when the opening of the resetting throttle valve 14 reaches the second target opening.

[0057] If the throttle opening determination unit 32 determines that the throttle opening has changed in the direction of decreasing, the control unit 34 sets a first target opening and a second target opening that follow the detection value of the throttle sensor 30 when the opening decreases. When the opening decreases, the control unit 34 controls the main throttle valve 5 and the resetting throttle valve 14 in a manner that delays the time when the opening of the main throttle valve 5 reaches the first target opening compared with the time when the opening of the resetting throttle valve 14 reaches the second target opening.

[0058] Figure 2This is a flowchart illustrating the steps of the control process executed by control unit 31. This process is executed if ammonia engine 2 is started. If ammonia engine 2 is started, shut-off valve 23 opens.

[0059] exist Figure 2 In this process, the control unit 31 first acquires the detection value of the throttle sensor 30 (step S101). Then, the control unit 31 determines whether the throttle opening has changed based on the detection value of the throttle sensor 30 (step S102). Alternatively, the control unit 31 determines that the throttle opening has changed when the throttle opening changes by more than a predetermined amount.

[0060] When the control unit 31 determines that the throttle opening has changed, it determines whether the throttle opening has changed in the direction of increasing (step S103). When the control unit 31 determines that the throttle opening has changed in the direction of increasing, it executes the control process for increasing the throttle opening (step S104). When the control unit 31 determines that the throttle opening has changed in the direction of decreasing, it executes the control process for decreasing the throttle opening (step S105).

[0061] After executing step S104 or step S105, control unit 31 executes step S101 again. Even if control unit 31 determines in step S102 that the throttle opening has not changed, control unit 31 executes step S101 again.

[0062] Here, the opening change determination unit 32 performs steps S101 to S103 as described above. When the opening increases, the control unit 33 performs step S104 as described above. When the opening decreases, the control unit 34 performs step S105 as described above.

[0063] Figure 3 This is a flowchart detailing the steps of the control process when the throttle opening increases in step S104.

[0064] exist Figure 3 In step S111, the control unit 31 first calculates the increase in ammonia and air based on the detection value of the throttle sensor 30. The increase in ammonia and air is calculated, for example, based on mapping data representing the relationship between the throttle opening and the flow rate of ammonia and air.

[0065] Next, the control unit 31 sets the target opening degree of each injector (main injector 6 and reformer injector 20) and each throttle valve (main throttle valve 5 and reformer throttle valve 14) based on the increase in ammonia and air (step S112). The target opening degree of the main injector 6, main throttle valve 5, reformer injector 20 and reformer throttle valve 14 is obtained, for example, based on mapping data representing the relationship between the increase in ammonia and air and each target opening degree.

[0066] Next, the control unit 31 controls the reforming injector 20 to increase its opening to a target opening (step S113). The control unit 31 also controls the reforming throttle valve 14 to increase its opening to a target opening (second target opening) (step S114). Furthermore, the order in which steps S113 and S114 are executed is not particularly limited; step S114 may be executed before step S113, or steps S113 and S114 may be executed simultaneously.

[0067] Next, the control unit 31 determines whether a predetermined time T has elapsed since the reforming throttle valve 14 was controlled in step S114 (step S115). The predetermined time T is a time predetermined considering the delay in the supply of reforming gas compared to the air supplied to the ammonia engine 2 (described later) (see reference). Figure 5 (a) ~ Figure 5 (e)).

[0068] When the control unit 31 determines that a predetermined time T has elapsed, it controls the main injector 6 to increase its opening to a target opening (step S116). The control unit 31 controls the main throttle valve 5 to increase its opening to a target opening (first target opening) (step S117). Furthermore, the order in which steps S116 and S117 are executed is not particularly limited; step S117 may be executed before step S116, or steps S116 and S117 may be executed simultaneously.

[0069] Figure 4 This is a flowchart detailing the steps of the control process when the throttle opening decreases in step S105.

[0070] exist Figure 4 In this process, the control unit 31 first calculates the amount of ammonia and air reduction based on the detection value of the throttle sensor 30 (step S121). For the amount of ammonia and air reduction, for example, the same as in step S111 above, the calculation is performed based on mapping data representing the relationship between the throttle opening and the flow rate of ammonia and air.

[0071] Next, the control unit 31 sets the target opening degree of each injector (main injector 6 and reformer injector 20) and each throttle valve (main throttle valve 5 and reformer throttle valve 14) based on the reduction amount of ammonia and air (step S122). The target opening degree of the main injector 6, main throttle valve 5, reformer injector 20 and reformer throttle valve 14 is obtained, for example, based on mapping data representing the relationship between the reduction amount of ammonia and air and each target opening degree.

[0072] Next, the control unit 31 controls the reforming injector 20 to reduce its opening to a target opening (step S123). The control unit 31 then controls the reforming throttle valve 14 to reduce its opening to a target opening (second target opening) (step S124). Furthermore, the order in which steps S123 and S124 are executed is not particularly limited; step S124 may be executed before step S123, or steps S123 and S124 may be executed simultaneously.

[0073] Next, the control unit 31 determines whether a predetermined time T has elapsed since the reforming throttle valve 14 was controlled in step S124 (step S125). The predetermined time T is a time predetermined taking into account the delay in the supply of reformed gas relative to the air supplied to the ammonia engine 2 (described later) (see reference). Figure 6 (a) ~ Figure 6 (e)). The specified time T is the same as the specified time T used in step S115 above.

[0074] When the control unit 31 determines that a predetermined time T has elapsed, it controls the main injector 6 to reduce its opening to a target opening (step S126). The control unit 31 also controls the main throttle valve 5 to reduce its opening to a target opening (first target opening) (step S127). Furthermore, the order in which steps S126 and S127 are executed is not particularly limited; step S127 may be executed before step S126, or steps S126 and S127 may be executed simultaneously.

[0075] In the engine system 1 described above, the vehicle's ignition switch (not shown) is operated to turn it on, starting the ammonia engine 2. Then, the reformer injector 20, reformer throttle valve 14, main injector 6, and main throttle valve 5 open. Thus, ammonia and air are supplied to the reformer 12 and the ammonia engine 2.

[0076] If ammonia and air are supplied to the reformer 12, they are heated by an electric heater 27. The heat from the ammonia and air then heats the combustion catalyst 25, causing its temperature to rise. If the temperature of the combustion catalyst 25 reaches its activation temperature (combustible temperature), the ammonia is burned through the combustion catalyst 25. Specifically, the ammonia reacts chemically with oxygen in the air (exothermic reaction) as shown in the following formula.

[0077] NH3 + 3 / 4O2 → 1 / 2N2 + 3 / 2H2O + Q1 (exothermic) ... (A)

[0078] If ammonia is burned, the heat of combustion raises the temperature of the reforming catalyst 26. Furthermore, if the temperature of the reforming catalyst 26 reaches the reaction temperature (reformable temperature), the ammonia is reformed by the reforming catalyst 26. Specifically, as shown in the following formula, a decomposition reaction (endothermic reaction) of ammonia is initiated, generating a reformed gas containing hydrogen.

[0079] NH3→3 / 2H2+1 / 2N2-Q2 (endothermic) ... (B)

[0080] The reformed gas flows in the downstream reforming flow path 21. At this time, the reformed gas, cooled by the cooler 22, flows in the intake flow path 3 and is supplied to the ammonia engine 2. Moreover, in the ammonia engine 2, it is transferred to a stable state in which the ammonia gas and the hydrogen in the reformed gas are burned together.

[0081] Figure 5 This is a timing diagram illustrating the actions of the main injector 6, reformer injector 20, main throttle valve 5, and reformer throttle valve 14 as the throttle switches from off to on, as an example of increasing throttle opening. Throttle off refers to the state where the throttle is not operated, such as at idle. Throttle on refers to the state where the throttle is operated, such as during steady operation.

[0082] In a steady state, such as Figure 5 As shown in (a), when the throttle is switched from off to on, the target opening degree of the main throttle valve 5, main injector 6, reforming throttle valve 14, and reforming injector 20 is set to increase the flow rate of ammonia and air supplied to the ammonia engine 2 and the reformer 12. Furthermore, when the throttle is off, the main throttle valve 5, main injector 6, reforming throttle valve 14, and reforming injector 20 are in a slightly open state.

[0083] Moreover, such as Figure 5 As shown in (c), the opening of the reformer 20 increases sharply to the target opening, and as... Figure 5 As shown in (e), the opening of the reforming throttle valve 14 increases sharply to the target opening (the second target opening).

[0084] Subsequently, if a specified time T elapses, then as follows: Figure 5 As shown in (b), the opening of the main injector 6 increases sharply to the target opening, and as Figure 5 As shown in (d), the opening of the main throttle valve 5 increases sharply to the target opening (first target opening). In other words, the opening of the main injector 6 and the main throttle valve 5 increases at a time point that is delayed compared to the opening of the reformer injector 20 and the reformer throttle valve 14.

[0085] Figure 6As an example of a reduction in throttle opening, a timing diagram is shown of the actions of the main injector 6, the reformer injector 20, the main throttle valve 5, and the reformer throttle valve 14 when the throttle is switched from on to off.

[0086] In a steady state, such as Figure 6 As shown in (a), if the throttle is switched from on to off, the target opening is set such that the flow rates of ammonia and air supplied to the ammonia engine 2 and the reformer 12 are reduced by the main throttle valve 5, the main injector 6, the reformer throttle valve 14 and the reformer injector 20.

[0087] Moreover, such as Figure 6 As shown in (c), the opening of the reformer 20 is drastically reduced to the target opening, and as... Figure 6 As shown in (e), the opening of the reforming throttle valve 14 is drastically reduced to the target opening (the second target opening).

[0088] Subsequently, if a specified time T elapses, then as follows: Figure 6 As shown in (b), the opening of the main injector 6 decreases sharply to the target opening, and as Figure 6 As shown in (d), the opening of the main throttle valve 5 decreases sharply to the target opening (first target opening). In other words, the opening of the main injector 6 and the main throttle valve 5 decreases at a time point that is delayed compared to the opening of the reformer injector 20 and the reformer throttle valve 14.

[0089] However, during the transitional operation of the ammonia engine 2, such as when switching the throttle from off to on or from on to off, if the opening of the main throttle valve 5 and the reforming throttle valve 14 are not properly adjusted in the main line 38 and the reforming line 39, air may be drawn into the ammonia engine 2 undesirably. In this case, without ensuring a proper air-fuel ratio in the ammonia engine 2, it is difficult to achieve good combustion.

[0090] Specifically, the pressure losses in the main pipeline 38 and the reforming pipeline 39 differ. The main pipeline 38 responds rapidly to changes in the opening of the main throttle valve 5. However, the reforming pipeline 39 contains a combustion catalyst 25, a reforming catalyst 26, and a cooler 22, all of which experience significant pressure losses. This results in a delay in the flow of the reformed gas. Furthermore, for the reforming pipeline 39, ammonia is supplied upstream of the reformer 12, where it is reformed to generate reformed gas. This reformed gas flows in the downstream reforming path 21 and merges with the intake path 3.

[0091] Therefore, on the one hand, when the throttle is switched from off to on, the opening of the main throttle valve 5 and the reforming throttle valve 14 increases at the same time. In this case, the air volume increases rapidly at the main line 38, but the increase in reformed gas volume at the reforming line 39 is delayed compared to the main line 38. Therefore, in the ammonia engine 2, there is a situation where the air flow rate is high and the hydrogen flow rate of the reformed gas is low. As a result, misfire may occur. At this time, unburned ammonia gas flows out of the ammonia engine 2.

[0092] On the other hand, when the throttle is switched from on to off, the openings of the main throttle valve 5 and the reforming throttle valve 14 decrease simultaneously. In this case, the air volume at the main line 38 decreases rapidly, but the reduction of reformed gas at the reforming line 39 is delayed compared to the main line 38. Therefore, the supply of reformed gas to the ammonia engine 2 continues for a period of time. Consequently, in the ammonia engine 2, the air flow rate is relatively low, while the flow rate of hydrogen contained in the reformed gas is relatively high. As a result, fuel combustion becomes rapid and active, leading to instability in the control of the ammonia engine 2.

[0093] Therefore, for example, when switching the throttle from off to on, it is possible to increase the injection quantity of ammonia from the main injector 6 by increasing the opening of the main injector 6, thereby homogenizing the A / F ratio and preventing lean combustion. However, in this case, there is no contribution to the increase in the auxiliary fuel used to promote ammonia combustion, namely hydrogen, thus resulting in a delayed ammonia combustion.

[0094] To address this issue, in this embodiment, if the throttle sensor 30's detection value (the command value for the ammonia engine 2) changes during the operation of the ammonia engine 2, the target opening degree of the main throttle valve 5 corresponding to the throttle sensor 30's detection value is set as the first target opening degree, and the target opening degree of the reforming throttle valve 14 corresponding to the throttle sensor 30's detection value is set as the second target opening degree. Furthermore, the main throttle valve 5 and the reforming throttle valve 14 are controlled such that the time point at which the main throttle valve 5 reaches the first target opening degree is delayed compared to the time point at which the reforming throttle valve 14 reaches the second target opening degree. Therefore, the time point at which the main throttle valve 5 reaches the first target opening degree is delayed compared to the time point at which the reforming throttle valve 14 reaches the second target opening degree. As a result, even during transitions in the operating conditions of the ammonia engine 2, reformed gas and air are appropriately supplied to the ammonia engine 2, thus ensuring an appropriate air-to-fuel (A / F) ratio. Consequently, a good combustion state is obtained. Furthermore, since there is no need to install a secondary reformer for each cylinder of the ammonia engine 2, there is also no need for valves or the like that inject ammonia gas toward the secondary reformer. Therefore, the structure of the engine system 1 is simplified.

[0095] In this embodiment, if the throttle sensor 30 detects an increasing value during the operation of the ammonia engine 2, a first target throttle opening and a second target throttle opening are set to increase in accordance with the detected value of the throttle sensor 30. The time point at which the opening of the main throttle valve 5 increases to the first target throttle opening is delayed compared to the time point at which the opening of the reforming throttle valve 14 increases to the second target throttle opening. Therefore, by ensuring an appropriate air-to-fuel (A / F) ratio, misfires caused by a situation where the flow rate of hydrogen contained in the reformed gas becomes less than the flow rate of air are suppressed.

[0096] In this embodiment, if the throttle sensor 30 detects a decrease in value during the operation of the ammonia engine 2, a first target throttle opening and a second target throttle opening are set to decrease in accordance with the detected value of the throttle sensor 30. The time point at which the opening of the main throttle valve 5 decreases to the first target throttle opening is delayed compared to the time point at which the opening of the reforming throttle valve 14 decreases to the second target throttle opening. Therefore, by ensuring proper air-to-fuel (A / F) ratio, overly rich combustion and engine control instability caused by a state where the flow rate of hydrogen contained in the reformed gas becomes greater than the flow rate of air are suppressed.

[0097] In this embodiment, the start time of the change in the opening of the main throttle valve 5 is delayed compared to the start time of the change in the opening of the reforming throttle valve 14. Therefore, the time when the opening of the main throttle valve 5 reaches the first target opening is indeed delayed compared to the time when the opening of the reforming throttle valve 14 reaches the second target opening. Furthermore, by making the opening of the main throttle valve 5 change drastically, the air flow supplied to the ammonia engine 2 can be easily controlled.

[0098] Furthermore, in this embodiment, the start time of the change in the opening of the main throttle valve 5 is delayed compared to the start time of the change in the opening of the reforming throttle valve 14, but it is not particularly limited to this method, and can be implemented as follows: Figure 7 It deforms as shown.

[0099] exist Figure 7 In the modified example shown, the control unit 31 controls the main throttle valve 5 and the resetting throttle valve in such a way that the opening and closing speed of the main throttle valve 5 is delayed compared to the opening and closing speed of the resetting throttle valve 14. Therefore, the control unit 31 controls the main throttle valve 5 and the resetting throttle valve 14 in such a way that the time point at which the opening degree of the main throttle valve 5 reaches the first target opening degree is delayed compared to the time point at which the opening degree of the resetting throttle valve 14 reaches the second target opening degree.

[0100] If the throttle is switched from off to on (see reference) Figure 7 (a) then the opening of the reforming injector 20 and the reforming throttle valve 14 increases sharply to the target opening (refer to...). Figure 7 (c) Figure 7 (e)), and the opening of the main injector 6 and the main throttle valve 5 begins to increase (see reference).Figure 7 of (b) Figure 7 (d) Moreover, after a specified time T0, the opening of the main injector 6 and the main throttle valve 5 reaches the target opening.

[0101] If the throttle is switched from on to off, the opening of the reformer injector 20 and the reformer throttle valve 14 decreases sharply to the target opening, and the opening of the main injector 6 and the main throttle valve 5 begins to decrease. Moreover, after a specified time T0, the opening of the main injector 6 and the main throttle valve 5 reaches the target opening.

[0102] At this time, when the opening degree of the control unit 31 increases, the control unit 33 does not execute. Figure 3 Step S115, in Figure 3 In step S116, the opening speed of the main injector 6 is made slower than the opening speed of the reforming injector 20, and... Figure 3 In step S117, the opening speed of the main throttle valve 5 is made slower than the opening speed of the reforming throttle valve 14.

[0103] When the opening degree of control unit 31 decreases, control unit 34 does not perform. Figure 4 Step S125, in Figure 4 In step S126, the closing speed of the main injector 6 is made slower than the closing speed of the reformer injector 20, and... Figure 4 In step S127, the closing speed of the main throttle valve 5 is made slower than the closing speed of the reforming throttle valve 14.

[0104] As described above, in this modified example, the opening and closing speed of the main throttle valve 5 is slower than that of the re-regulating throttle valve 14. Therefore, the time when the main throttle valve 5 reaches the first target opening is indeed delayed compared to the time when the re-regulating throttle valve 14 reaches the second target opening. The opening of the main throttle valve 5 changes gradually, thereby allowing the main throttle valve 5 to open and close smoothly.

[0105] Figure 8 This is a schematic structural diagram illustrating the engine system involved in another embodiment of this disclosure. Figure 8 In this embodiment, the engine system 1A differs from the engine system 1 of the previous embodiment in that the locations of the reforming throttle valve 14 and the shut-off valve 23 are interchanged. In other words, the reforming throttle valve 14 is located in the downstream reforming flow path 21, and the shut-off valve 23 is located in the upstream reforming flow path 13.

[0106] The reforming throttle valve 14 controls the flow rate of reformed gas supplied to the ammonia engine 2 together with the flow rate of air supplied to the reformer 12. Specifically, the reforming throttle valve 14 controls the flow rate of air supplied to the reformer 12 before reformed gas is generated by the reformer 12. After reformed gas is generated by the reformer 12, the reforming throttle valve 14 controls the flow rate of both air and reformed gas supplied to the reformer 12.

[0107] In this embodiment, air flowing in the upstream reforming path 13 is supplied to the reformer 12 to generate reformed gas. The reformed gas flows in the downstream reforming path 21 and is supplied to the ammonia engine 2. A reforming throttle valve 14 is disposed on the downstream reforming path 21. Therefore, compared to the case where the reforming throttle valve 14 is disposed on the upstream reforming path 13, by increasing the opening of the reforming throttle valve 14, the supply amount of reformed gas to the ammonia engine 2 can be rapidly increased. By decreasing the opening of the reforming throttle valve 14, the supply amount of reformed gas to the ammonia engine 2 can be rapidly decreased.

[0108] This disclosure is not limited to the embodiments described above. For example, in the embodiments described above, the start time of the change in the opening of the main injector 6 is equal to the start time of the change in the opening of the main throttle valve 5, but it is not particularly limited to this manner. As long as the start time of the change in the opening of the main injector 6 is delayed compared to the start time of the change in the opening of the reformer injector 20, the start time of the change in the opening of the main injector 6 may also be different from the start time of the change in the opening of the main throttle valve 5.

[0109] In the above embodiments, as long as the opening and closing speed of the main injector 6 is slower than the opening and closing speed of the reformer injector 20, the opening and closing speed of the main injector 6 can also be equal to the opening and closing speed of the main throttle valve 5, or the opening and closing speed of the main injector 6 can be different from the opening and closing speed of the main throttle valve 5.

[0110] In the above embodiments, the reformer 12 has a combustion catalyst 25 for burning ammonia and a reforming catalyst 26 for decomposing ammonia into hydrogen, but is not particularly limited to this configuration. Alternatively, the reformer 12 may have a catalyst that functions both for burning ammonia and for decomposing ammonia into hydrogen.

[0111] In the above embodiment, air filters 8 and 28 are respectively provided on the main pipeline 38 and the reforming pipeline 39, but it is not particularly limited to this method. For example, it is also possible that a branch in the intake airflow path 3 between the air filter 8 and the main throttle valve 5 is connected to the upstream reforming path 13, and the air filter 28 is not present. In this case, the system structure can be simplified.

[0112] In the above embodiment, the ammonia gas generated by the vaporizer 16 flows in the ammonia flow path 18 and is supplied to the main injector 6, and the ammonia gas generated by the vaporizer 17 flows in the ammonia flow path 19 and is supplied to the reforming injector 20, but it is not particularly limited to this method. For example, it is also possible to set the number of vaporizers to one, and connect the ammonia flow paths 18 and 19 to the vaporizer. In this case, the system structure can also be simplified.

[0113] In the above embodiment, each cylinder of the ammonia engine 2 is equipped with a main injector 6 that injects ammonia gas toward the ammonia engine 2. However, the number of main injectors 6 is not particularly limited to multiple, and may be one. In this case, the main injector 6 is configured to inject ammonia gas toward the vicinity of the ammonia engine 2 in the intake air passage 3.

[0114] The engine system 1 described above is mounted on a vehicle, but is not particularly limited to this method; for example, it can also be mounted on a ground-based power generation device. In this case, for example, an operator inputting the operation constitutes a command value output unit that outputs command values ​​for the ammonia engine 2 after the ammonia engine 2 is started.

[0115] In the above embodiments, ammonia is used as fuel, but this disclosure can also be applied to engine systems that use hydrocarbons or the like as fuel.

[0116] Explanation of reference numerals in the attached figures

[0117] 1. 1A... Engine system; 2... Ammonia engine (engine); 3... Intake airflow path; 5... Main throttle valve (first flow control valve); 6... Main injector (first fuel injection valve); 12... Reformer; 13... Upstream reforming flow path; 14... Reforming throttle valve (second flow control valve); 20... Reforming injector (second fuel injection valve); 21... Downstream reforming flow path; 25... Combustion catalyst (catalyst); 26... Reforming catalyst (catalyst); 30... Throttle sensor (command value output unit); 31... Control unit (control unit).

Claims

1. An engine system, characterized in that, have: An engine that supplies fuel, which is burned together with hydrogen; An intake airflow path, which supplies airflow to the engine; The first flow control valve is disposed in the intake air passage to control the flow rate of air supplied to the engine; The first fuel injection valve injects fuel toward the engine; A reformer having a catalyst that decomposes the fuel into hydrogen and reforms the fuel to generate reformed gas containing the hydrogen; The upstream rectifier flow path supplies airflow to the rectifier; The downstream reforming flow path supplies reformed gas generated by the reformer to flow toward the engine. The second flow control valve is installed in the upstream rectifier path or the downstream rectifier path to control the flow rate of air supplied to the rectifier. The second fuel injection valve injects fuel toward the reformer; The command value output unit outputs a command value for the engine after the engine is started; as well as The control unit controls the first flow control valve, the first fuel injection valve, the second flow control valve, and the second fuel injection valve based on the command value output from the command value output unit. If the command value output by the command value output unit changes during the operation of the engine, the control unit sets the target opening degree of the first flow control valve corresponding to the command value as the first target opening degree, and sets the target opening degree of the second flow control valve corresponding to the command value as the second target opening degree, so that the time point when the opening degree of the first flow control valve reaches the first target opening degree is delayed compared with the time point when the opening degree of the second flow control valve reaches the second target opening degree.

2. The engine system according to claim 1, characterized in that, If the command value output from the command value output unit changes in the direction of increase during the operation of the engine, the control unit sets the first target opening degree and the second target opening degree to increase in accordance with the command value.

3. The engine system according to claim 1, characterized in that, If the command value output from the command value output unit changes in the direction of decrease during the operation of the engine, the control unit sets the first target opening and the second target opening to decrease in accordance with the command value.

4. The engine system according to claim 1, characterized in that, The control unit controls the first flow control valve and the second flow control valve in such a way that the start time of the change in the opening of the first flow control valve is delayed compared to the start time of the change in the opening of the second flow control valve.

5. The engine system according to claim 1, characterized in that, The control unit controls the first flow control valve and the second flow control valve in such a way that the opening and closing speed of the first flow control valve is slower than that of the second flow control valve.

6. The engine system according to claim 1, characterized in that, The second flow control valve is located in the downstream reforming flow path and controls the flow rate of the reforming gas supplied to the engine together with the flow rate of the air supplied to the reformer.

Images