JP7655802B2 - Engine System - Google Patents

Description

The present invention relates to an engine system.

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

JP 2014-211155 A

However, in the above conventional technology, depending on the state of the surrounding environment, the reforming rate of the cracker (reforming section) decreases, and the required amount of hydrogen cannot be obtained. Specifically, when the engine body (engine) is started, the starter is rotated. When the temperature of the surrounding environment is low, the viscosity of the lubricating and cooling oil in the starter is high, so the starter rotation speed is low. In this case, the amount of air intake into the engine is reduced, and the flow rate of air supplied to the reforming section is reduced accordingly. Therefore, the air-fuel ratio of the reforming section is reduced, so the temperature of the reforming section is reduced, and the reforming rate of the reforming section is reduced. As a result, the required amount of hydrogen is not generated by the reforming section. In addition, when the flow rate of air supplied to the reforming section is reduced, it takes time for the reforming section to reach a reaction temperature at which reforming is possible, so the time required to start the reforming section is increased.

The object of the present invention is to provide an engine system that can start the reforming section early while ensuring the reforming performance of the reforming section regardless of the state of the surrounding environment.

An engine system according to one aspect of the present invention includes an engine, a starter for starting the engine, an intake passage through which air supplied to the engine flows, a first flow control valve for controlling the flow rate of air flowing through the intake passage, a first fuel supply valve for supplying fuel to the engine, a reforming section for generating reformed gas containing hydrogen by reforming the fuel using heat generated by burning the fuel, a heating section for heating the reforming section, an air flow path through which air supplied to the reforming section flows, a second flow control valve for controlling the flow rate of air flowing through the air flow path, and a fuel supply valve for supplying fuel to the reforming section. The engine includes a second fuel supply valve that supplies fuel, a reformed gas flow path through which the reformed gas generated by the reforming unit flows toward the engine, a state detection unit that detects the state of the surrounding environment, an air-fuel ratio setting unit that sets the air-fuel ratio of the reforming unit according to the state of the surrounding environment detected by the state detection unit, and a start control unit that controls the starter, the first flow control valve, the first fuel supply valve, the second flow control valve, and the second fuel supply valve when the engine is started. The start control unit controls the second flow control valve and the second fuel supply valve according to the air-fuel ratio of the reforming unit set by the air-fuel ratio setting unit.

In such an engine system, when the engine is started by the starter, the reforming section is heated by the heating section, and the first flow control valve, the first fuel supply valve, the second flow control valve, and the second fuel supply valve are opened, so that air and fuel are supplied to the engine and the reforming section, respectively. Then, when the temperature of the reforming section reaches a desired temperature, the fuel is burned and reformed in the reforming section, and reformed gas containing hydrogen is generated. The reformed gas flows through the reformed gas flow path and is supplied to the engine. Then, in the engine, the fuel is burned together with the hydrogen in the reformed gas. Here, the state of the surrounding environment is detected, and the air-fuel ratio (set air-fuel ratio) of the reforming section according to the state of the surrounding environment is set. Then, the second flow control valve and the second fuel supply valve are controlled according to the set air-fuel ratio, so that air and fuel are supplied to the reforming section at a flow rate according to the set air-fuel ratio. Therefore, the temperature of the reforming section becomes a temperature suitable for the state of the surrounding environment, and the reforming rate of the reforming section becomes a reforming rate suitable for the state of the surrounding environment. This ensures the reforming performance of the reforming section regardless of the state of the surrounding environment. Also, because air and fuel are supplied to the reforming section at flow rates according to the set air-fuel ratio, the temperature of the reforming section quickly reaches the desired temperature. This allows the reforming section to be started up quickly regardless of the state of the surrounding environment.

The state detection unit may detect the temperature of the surrounding environment as the state of the surrounding environment, and the air-fuel ratio setting unit may increase the air-fuel ratio of the reforming unit as the temperature of the surrounding environment decreases. In such a configuration, the air-fuel ratio of the reforming unit is set to be higher as the temperature of the surrounding environment decreases. Therefore, even when the temperature of the surrounding environment is low, the starter rotation speed is low, and the amount of air intake into the engine is small, the temperature of the reforming unit increases by increasing the air-fuel ratio of the reforming unit, and the reforming rate of the reforming unit increases.

The start control unit may control the second fuel supply valve so that the flow rate of fuel supplied to the reforming unit decreases as the temperature of the surrounding environment decreases. In this configuration, the lower the temperature of the surrounding environment, the lower the flow rate of fuel supplied to the reforming unit, and the higher the air-fuel ratio of the reforming unit. When the temperature of the surrounding environment decreases, the rotation speed of the starter decreases, so the amount of air intake into the engine decreases, and the flow rate of air supplied to the reforming unit decreases accordingly. For this reason, it is difficult to increase the air-fuel ratio of the reforming unit by increasing the flow rate of air supplied to the reforming unit. Therefore, the air-fuel ratio of the reforming unit can be easily increased by decreasing the flow rate of fuel supplied to the reforming unit.

The start control unit may control the first fuel supply valve so that the flow rate of fuel supplied to the engine increases as the temperature of the surrounding environment decreases. In this configuration, the flow rate of fuel supplied to the engine increases as the temperature of the surrounding environment decreases. When the air-fuel ratio of the reforming unit increases, the reforming rate of the reforming unit increases, and the flow rate of the reformed gas generated by the reforming unit increases. As a result, the flow rate of the reformed gas supplied to the engine increases. Therefore, by increasing the flow rate of fuel supplied to the engine as the temperature of the surrounding environment decreases, the fuel can be stably burned together with the hydrogen in the reformed gas.

The engine system may further include a memory unit that stores air-fuel ratio table data that indicates the relationship between the temperature of the surrounding environment and the air-fuel ratio of the reforming section, and the air-fuel ratio setting unit may set the air-fuel ratio of the reforming section to an air-fuel ratio that corresponds to the temperature of the surrounding environment based on the air-fuel ratio table data stored in the memory unit. In such a configuration, it is possible to set a large number of data for the air-fuel ratio of the reforming section that correspond to the temperature of the surrounding environment. Therefore, an air-fuel ratio of the reforming section that is optimal for the temperature of the surrounding environment is obtained, and therefore a reforming rate of the reforming section that is optimal for the temperature of the surrounding environment is obtained.

The air-fuel ratio setting unit may set the air-fuel ratio of the reforming unit to a first air-fuel ratio when the temperature of the surrounding environment is equal to or higher than a specified temperature, and may set the air-fuel ratio of the reforming unit to a second air-fuel ratio higher than the first air-fuel ratio when the temperature of the surrounding environment is lower than the specified temperature. In such a configuration, the air-fuel ratio of the reforming unit is set by comparing the temperature of the surrounding environment with the specified temperature, so that a small memory capacity is required. Therefore, an inexpensive memory medium can be used.

The engine system may further include a temperature setting unit that sets the temperature of the heating unit according to the temperature of the surrounding environment, and the temperature setting unit may increase the temperature of the heating unit as the temperature of the surrounding environment decreases. In such a configuration, even when the temperature of the surrounding environment is low, causing the starter rotation speed to be low and the amount of air intake into the engine to be small, and the flow rate of air supplied to the reforming unit to be small accordingly, the temperature of the heating unit is increased, so that the temperature of the reforming unit reaches the desired temperature more quickly. This allows the reforming unit to be started up more quickly, regardless of the temperature of the surrounding environment.

The heating unit may be an electric heater, and the temperature setting unit may lengthen the time the electric heater is energized as the temperature of the surrounding environment decreases. In this configuration, even if the power input to the electric heater is constant, the temperature of the electric heater increases by lengthening the time the electric heater is energized.

The heating unit may be an electric heater, and the temperature setting unit may increase the power input to the electric heater as the temperature of the surrounding environment decreases. In this configuration, even if the time the electric heater is energized is constant, the temperature of the electric heater increases by increasing the power input to the electric heater.

According to the present invention, the reforming section can be started early while ensuring the reforming performance of the reforming section regardless of the state of the surrounding environment.

1 is a schematic configuration diagram showing an engine system according to a first embodiment of the present invention. 2 is a table showing air-fuel ratio table data stored in a storage unit shown in FIG. 1 . 2 is a flowchart showing details of a procedure for air-fuel ratio setting processing executed by an air-fuel ratio setting unit shown in FIG. 1 . 4 is a flowchart showing details of a procedure of a startup control process executed by a startup control unit shown in FIG. 1 . 4 is a graph showing the reforming characteristics of the reforming section together with control points at room temperature. 6 is a graph showing how a control point is changed at a low temperature in the reforming characteristics of the reforming section shown in FIG. 5 . 4 is a flowchart showing a modified example of the procedure of the air-fuel ratio setting process shown in FIG. 3 . FIG. 5 is a schematic configuration diagram showing an engine system according to a second embodiment of the present invention. 9 is a table showing current application time table data stored in the storage unit shown in FIG. 8 . 9 is a flowchart showing details of a procedure of a current-flow time setting process executed by a current-flow time setting unit shown in FIG. 8 . 11 is a flowchart showing a modified example of the procedure of the current application time setting process shown in FIG. 10 . FIG. 11 is a schematic configuration diagram showing an engine system according to a third embodiment of the present invention. 13 is a table showing input power table data stored in a storage unit shown in FIG. 12 . 13 is a flowchart showing details of a procedure of an input power setting process executed by an input power setting unit shown in FIG. 12 . 15 is a flowchart showing a modified example of the procedure of the input power setting process shown in FIG. 14 .

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

Figure 1 is a schematic diagram showing an engine system according to a first embodiment of the present invention. In Figure 1, the engine system 1 of this embodiment is mounted on, for example, a vehicle. The engine system 1 includes an ammonia engine 2, an intake passage 3, an exhaust passage 4, a main injector 5, a main throttle valve 6, and a starter 7.

The ammonia engine 2 is an engine that uses ammonia gas ( _NH3 gas) as fuel. In the ammonia engine 2, hydrogen ( _H2 ) is mixed into the ammonia gas in order to make the flame-retardant ammonia gas easier to combust. The ammonia engine 2 has a combustion chamber 8 in which the ammonia gas is burned together with the hydrogen to generate exhaust gas.

The intake passage 3 and the exhaust passage 4 are connected to the combustion chamber 8 of the ammonia engine 2. The intake passage 3 is a passage through which air supplied to the combustion chamber 8 flows. The exhaust passage 4 is a passage through which exhaust gas generated in the combustion chamber 8 flows.

The main injector 5 is an electromagnetic fuel injection valve that injects ammonia gas toward the combustion chamber 8 of the ammonia engine 2. The main injector 5 constitutes a first fuel supply valve that supplies ammonia gas to the ammonia engine 2.

The main throttle valve 6 is disposed in the intake passage 3. The main throttle valve 6 is an electromagnetic first flow control valve that controls the flow rate of air supplied to the combustion chamber 8 of the ammonia engine 2. An air cleaner 9 that removes foreign matter such as dust and dirt contained in the air is disposed upstream of the main throttle valve 6 in the intake passage 3.

The starter 7 starts the ammonia engine 2. Although not shown in the figure, the starter 7 has a motor and multiple gears. The starter 7 contains oil for lubrication and cooling.

The engine system 1 also includes a reforming system 10. The reforming system 10 includes a reformer 11, an air passage 12, a sub-throttle valve 13, a sub-injector 14, a reformed gas passage 15, and a cooler 16.

The reformer 11 has a cylindrical housing 17 and a reforming section 18 and an electric heater 19 housed within the housing 17. The housing 17 is made of a metal material such as stainless steel that is resistant to corrosion by ammonia gas.

The reforming unit 18 produces reformed gas containing hydrogen by reforming ammonia gas using heat generated by burning the ammonia gas. The reforming unit 18 has a reforming catalyst 18a, for example, having a honeycomb structure. The reforming catalyst 18a is a catalyst that burns ammonia gas and decomposes the ammonia gas into hydrogen. The reforming catalyst 18a is, for example, an ATR (Autothermal Reformer) type ammonia reforming catalyst. As the reforming catalyst 18a, for example, a cobalt-based catalyst, a rhodium-based catalyst, a ruthenium-based catalyst, or a palladium-based catalyst is used.

The electric heater 19 is disposed upstream of the reforming section 18 within the housing 17. The electric heater 19 is a heating section that heats the reforming section 18. When power is applied to the electric heater 19, it generates heat, which heats the reforming section 18. Specifically, the heat generated by the electric heater 19 is transmitted to the reforming section 18 through the housing 17, and is also transmitted to the reforming section 18 through the ammonia gas and air flowing within the housing 17.

The air flow path 12 connects the intake passage 3 and the reformer 11. One end of the air flow path 12 is connected between the air cleaner 9 and the main throttle valve 6 in the intake passage 3. The other end of the air flow path 12 is connected to the inlet 17a of the housing 17 of the reformer 11. The air flow path 12 is a flow path through which air supplied to the reformer section 18 flows.

The sub-throttle valve 13 is disposed in the air flow path 12. The sub-throttle valve 13 is an electromagnetic second flow control valve that controls the flow rate of air supplied to the reforming section 18.

The sub-injector 14 is an electromagnetic fuel injection valve that injects ammonia gas into the air flow path 12. The sub-injector 14 injects ammonia gas between the sub-throttle valve 13 and the reformer 11 in the air flow path 12. The sub-injector 14 constitutes a second fuel supply valve that supplies ammonia gas to the reforming section 18.

The reformed gas flow passage 15 connects the reformer 11 and the intake passage 3. One end of the reformed gas flow passage 15 is connected to the outlet 17b of the housing 17 of the reformer 11. The other end of the reformed gas flow passage 15 is connected between the main throttle valve 6 and the ammonia engine 2 in the intake passage 3. The reformed gas flow passage 15 is a flow passage through which the reformed gas generated by the reforming section 18 flows toward the ammonia engine 2.

The cooler 16 is disposed in the reformed gas flow passage 15. The cooler 16 cools the reformed gas flowing through the reformed gas flow passage 15, for example, by using engine cooling water that cools the ammonia engine 2.

The engine system 1 also includes a temperature sensor 20, a temperature sensor 21, a memory unit 22, and a controller 23.

The temperature sensor 20 is a sensor that detects the temperature of the surrounding environment (hereinafter simply referred to as the surrounding environment) of the engine system 1 including the ammonia engine 2 and the reformer 11. The temperature sensor 20 constitutes a state detection unit that detects the state of the surrounding environment. The temperature sensor 20 detects the outside air temperature of the surrounding environment, etc., as the state of the surrounding environment.

The temperature sensor 21 is a sensor that detects the temperature of the reforming section 18. The temperature sensor 21 may detect the temperature of the reforming catalyst 18a, or may detect the temperature of the gas supplied to the reforming section 18.

As shown in FIG. 2, the memory unit 22 stores various data including air-fuel ratio table data D1 that represents the relationship between the temperature of the surrounding environment and the air-fuel ratio (AFR) of the reformer 18. The air-fuel ratio of the reformer 18 is the ratio of the flow rates of ammonia gas and air supplied to the reformer 18 (air flow rate/ammonia gas flow rate).

The air-fuel ratio table data D1 is set so that the lower the temperature of the surrounding environment, the higher the air-fuel ratio of the reforming section 18. At this time, the air-fuel ratio of the reforming section 18 may, for example, increase stepwise as the temperature of the surrounding environment decreases, or may increase continuously (for example, linearly) as the temperature of the surrounding environment decreases.

The controller 23 is composed of a CPU, RAM, ROM, an input/output interface, etc. The controller 23 has an air-fuel ratio setting unit 24 and a start control unit 25.

The air-fuel ratio setting unit 24 sets the air-fuel ratio of the reforming unit 18 according to the temperature of the surrounding environment detected by the temperature sensor 20. The air-fuel ratio setting unit 24 sets the air-fuel ratio of the reforming unit 18 to an air-fuel ratio that corresponds to the temperature of the surrounding environment based on the air-fuel ratio table data D1 stored in the memory unit 22.

Figure 3 is a flowchart showing the details of the procedure for the air-fuel ratio setting process executed by the air-fuel ratio setting unit 24. This process is executed when the ignition switch (not shown) is turned ON.

In FIG. 3, the air-fuel ratio setting unit 24 first acquires the detection value of the temperature sensor 20 (step S101). Next, the air-fuel ratio setting unit 24 reads the air-fuel ratio table data D1 stored in the memory unit 22 (step S102). Then, the air-fuel ratio setting unit 24 selects an air-fuel ratio value in the air-fuel ratio table data D1 that corresponds to the temperature of the surrounding environment (step S103). Then, the air-fuel ratio setting unit 24 sets the selected air-fuel ratio value as the air-fuel ratio of the reformer unit 18 to be used in the control process of the start control unit 25 (step S104).

When the ammonia engine 2 is started, the start control unit 25 controls the main injector 5, main throttle valve 6, starter 7, sub-throttle valve 13, sub-injector 14, and electric heater 19 based on the detection value of the temperature sensor 21. The start control unit 25 controls the sub-throttle valve 13 and sub-injector 14 according to the air-fuel ratio of the reformer unit 18 set by the air-fuel ratio setting unit 24.

Figure 4 is a flowchart showing the details of the procedure for the start control process executed by the start control unit 25. This process is also executed when the ignition switch (described above) is turned ON. Note that before this process is executed, the main injector 5, main throttle valve 6, sub-throttle valve 13, and sub-injector 14 are all in a closed state.

In FIG. 4, the start-up control unit 25 first controls the electric heater 19 to be turned ON (step S111). Then, power is supplied to the electric heater 19, and the electric heater 19 is energized, so that the temperature of the electric heater 19 rises. At this time, the power supplied to the electric heater 19 is a predetermined constant value.

The start-up control unit 25 then determines whether the time that the electric heater 19 has been energized has reached a specified time (step S112). The specified time is the time during which the electric heater 19 heats the reforming unit 18, causing the temperature of the reforming unit 18 to reach or exceed the activation temperature. Here, the specified time is a predetermined constant value. The activation temperature is the temperature at which ammonia gas can be burned by the reforming catalyst 18a.

When the start-up control unit 25 determines that the time that the electric heater 19 has been energized has reached the specified time, it controls the electric heater 19 to be turned OFF (step S113). Then, the electric heater 19 is de-energized, and the temperature of the electric heater 19 drops.

Then, the start control unit 25 controls the starter 7 to rotate (step S114). Then, the start control unit 25 controls the main throttle valve 6 to open (step S115). Then, air is supplied into the combustion chamber 8 of the ammonia engine 2.

Then, the start control unit 25 controls the sub-injector 14 and the sub-throttle valve 13 to open (step S116). Then, ammonia gas and air are supplied to the reforming unit 18. At this time, the start control unit 25 controls the opening degree of the sub-injector 14 and the sub-throttle valve 13 so that the air-fuel ratio of the reforming unit 18 becomes the air-fuel ratio set by the air-fuel ratio setting unit 24.

Then, the start-up control unit 25 acquires the detection value of the temperature sensor 21 (step S117). Then, the start-up control unit 25 determines whether the temperature of the reforming unit 18 is equal to or higher than the reaction temperature based on the detection value of the temperature sensor 21 (step S118). The reaction temperature is the temperature at which the reforming catalyst 18a can reform ammonia gas. The reaction temperature is higher than the activation temperature.

When the start control unit 25 determines that the temperature of the reforming unit 18 is not equal to or higher than the reaction temperature, it executes step S117 again. When the start control unit 25 determines that the temperature of the reforming unit 18 is equal to or higher than the reaction temperature, it controls the opening degree of the sub-injector 14 (step S119). At this time, the start control unit 25 controls the opening degree of the sub-injector 14 so that the air-fuel ratio of the reforming unit 18 becomes an air-fuel ratio suitable for the reforming operation of ammonia gas. The start control unit 25 may control the opening degree of the sub-throttle valve 13 together with the opening degree of the sub-injector 14.

Then, the start control unit 25 controls the opening degree of the main injector 5 (step S120). As a result, ammonia gas is supplied into the combustion chamber 8 of the ammonia engine 2, and the ammonia gas is burned together with the hydrogen in the reformed gas in the combustion chamber 8.

In the engine system 1 described above, when the ignition switch (not shown) is turned on, the electric heater 19 is energized, causing the temperature of the electric heater 19 to rise. Then, the electric heater 19 heats the reforming section 18, causing the temperature of the reforming section 18 to rise.

The starter 7 is then rotated and the main throttle valve 6 is opened, supplying air to the combustion chamber 8 of the ammonia engine 2. The sub-injector 14 and the sub-throttle valve 13 are also opened, supplying ammonia gas and air to the reforming section 18.

When the temperature of the reforming section 18 reaches the activation temperature, the ammonia gas is burned by the reforming catalyst 18a. Specifically, ammonia and oxygen in the air undergo a chemical reaction (exothermic reaction) as shown in the following formula.
_NH3 +3/ _4O2 →1/ _2N2 +3/ _2H2O ...(A)

Then, the temperature of the reforming section 18 is further increased by the heat of combustion of the ammonia gas. Then, when the temperature of the reforming section 18 reaches the reaction temperature, the ammonia gas is reformed by the reforming catalyst 18a. Specifically, as shown in the following formula, a decomposition reaction of ammonia occurs (endothermic reaction), and a reformed gas containing hydrogen is generated.
NH ₃ → 3/2H ₂ + 1/2N ₂ …(B)

The reformed gas flows through the reformed gas flow passage 15 and the intake passage 3 and is supplied to the combustion chamber 8 of the ammonia engine 2. Then, in the combustion chamber 8, the system transitions to a steady state in which the ammonia gas is combusted together with the hydrogen in the reformed gas.

The reforming section 18 has reforming characteristics as shown in FIG. 5. The reforming characteristics represent the relationship between the air-fuel ratio (AFR) of the reforming section 18 and the temperature and reforming rate of the reforming section 18. The reforming rate of the reforming section 18 is the ratio of the flow rate of hydrogen generated in the reforming section 18 to the flow rate of ammonia gas supplied to the reforming section 18. The higher the air-fuel ratio of the reforming section 18, the higher the temperature and reforming rate of the reforming section 18. When the reforming section 18 is started up, the reforming section 18 basically operates at a control point P at which a desired reforming rate is obtained. For this reason, the opening degree of the sub-injector 14 and the sub-throttle valve 13 is controlled so that the air-fuel ratio of the reforming section 18 corresponds to the control point P. Here, when the temperature of the surrounding environment is normal temperature, the reforming section 18 operates at the control point P, and therefore an appropriate amount of hydrogen is generated by the reforming section 18.

However, when the temperature of the surrounding environment is low, the following problem occurs. That is, when the engine system 1 is started, the viscosity of the lubricating and cooling oil contained in the starter 7 is high, so the rotation speed of the starter 7 is low when the starter 7 is rotated. In this case, the amount of air intake into the combustion chamber 8 of the ammonia engine 2 is reduced, and the flow rate of air supplied to the reformer 18 is reduced accordingly. Therefore, as shown in FIG. 6(a), the air-fuel ratio of the reformer 18 is reduced, and the reforming rate of the reformer 18 is reduced (see control point Q*). As a result, the amount of hydrogen generated by the reformer 18 is reduced.

Therefore, in step S116 (see FIG. 4) above, when the temperature of the surrounding environment is low, the start-up control unit 25 of the controller 23 controls the opening degree of the sub-injector 14 so that the air-fuel ratio in the reforming section is higher than at room temperature, as shown in FIG. 6(b) (see control point Q).

Specifically, when the temperature of the surrounding environment is low, the start control unit 25 reduces the opening of the sub-injector 14 compared to normal temperature. In other words, the start control unit 25 controls the sub-injector 14 so that the flow rate of ammonia gas supplied to the reforming unit 18 decreases. At this time, the start control unit 25 controls the sub-injector 14 so that the flow rate of ammonia gas supplied to the reforming unit 18 decreases as the temperature of the surrounding environment decreases. Therefore, the air-fuel ratio of the reforming unit 18 increases, and the reforming rate of the reforming unit 18 increases. As a result, the amount of hydrogen generated by the reforming unit 18 increases compared to when the reforming unit 18 operates at control point Q*.

In addition, in the above step S120 (see FIG. 4), when the temperature of the surrounding environment is low, the start control unit 25 increases the opening of the main injector 5 compared to normal temperature. In other words, the start control unit 25 controls the main injector 5 so as to increase the flow rate of ammonia gas supplied to the combustion chamber 8 of the ammonia engine 2. At this time, the start control unit 25 controls the main injector 5 so that the flow rate of ammonia gas supplied to the ammonia engine 2 increases as the temperature of the surrounding environment decreases. Therefore, the flow rate of ammonia gas supplied to the ammonia engine 2 increases by the amount that the flow rate of ammonia gas supplied to the reformer 18 decreases.

As described above, in this embodiment, when the ammonia engine 2 is started by the starter 7, the reforming section 18 is heated by the electric heater 19, and the main throttle valve 6, the main injector 5, the sub-throttle valve 13, and the sub-injector 14 are opened, so that air and ammonia gas are supplied to the ammonia engine 2 and the reforming section 18, respectively. Then, when the temperature of the reforming section 18 reaches a desired temperature, the ammonia gas is burned and reformed in the reforming section 18, and a reformed gas containing hydrogen is generated. The reformed gas flows through the reformed gas flow path 15 and is supplied to the ammonia engine 2. Then, in the ammonia engine 2, the ammonia gas is burned together with the hydrogen in the reformed gas. Here, the temperature of the surrounding environment is detected, and the air-fuel ratio (set air-fuel ratio) of the reforming section 18 according to the temperature of the surrounding environment is set. Then, the sub-throttle valve 13 and the sub-injector 14 are controlled according to the set air-fuel ratio, so that air and ammonia gas are supplied to the reforming section 18 at flow rates according to the set air-fuel ratio. Therefore, the temperature of the reforming unit 18 becomes suitable for the temperature of the surrounding environment, and the reforming rate of the reforming unit 18 becomes suitable for the temperature of the surrounding environment. This ensures the reforming performance of the reforming unit 18 regardless of the temperature of the surrounding environment. In addition, because air and ammonia gas are supplied to the reforming unit 18 at flow rates according to the set air-fuel ratio, the temperature of the reforming unit 18 quickly reaches the desired temperature. This allows the reforming unit 18 to be started up early, regardless of the temperature of the surrounding environment.

In addition, in this embodiment, the air-fuel ratio of the reforming section 18 is set to be higher as the temperature of the surrounding environment becomes lower. Therefore, even when the temperature of the surrounding environment is low, the rotation speed of the starter 7 is low, and the amount of air intake into the ammonia engine 2 is small, the temperature of the reforming section 18 is increased by increasing the air-fuel ratio of the reforming section 18, and the reforming rate of the reforming section 18 is increased.

In addition, in this embodiment, the lower the temperature of the surrounding environment, the lower the flow rate of ammonia gas supplied to the reforming section 18, and therefore the higher the air-fuel ratio of the reforming section 18. When the temperature of the surrounding environment is lower, the rotation speed of the starter 7 is lowered, so the amount of air intake into the ammonia engine 2 is reduced, and the flow rate of air supplied to the reforming section 18 is reduced accordingly. For this reason, it is difficult to increase the air-fuel ratio of the reforming section 18 by increasing the flow rate of air supplied to the reforming section 18. Therefore, by reducing the flow rate of ammonia gas supplied to the reforming section 18, the air-fuel ratio of the reforming section 18 can be easily increased.

In addition, in this embodiment, the lower the temperature of the surrounding environment, the higher the flow rate of ammonia gas supplied to the ammonia engine 2. When the air-fuel ratio of the reforming unit 18 becomes higher, the reforming rate of the reforming unit 18 becomes higher, and the flow rate of the reformed gas generated by the reforming unit 18 increases. As a result, the flow rate of the reformed gas supplied to the ammonia engine 2 increases. Therefore, by increasing the flow rate of ammonia gas supplied to the ammonia engine 2 as the temperature of the surrounding environment becomes lower, the ammonia gas can be stably burned together with the hydrogen in the reformed gas.

In addition, in this embodiment, the air-fuel ratio of the reforming section 18 is set to an air-fuel ratio that corresponds to the temperature of the surrounding environment based on air-fuel ratio table data D1 that represents the relationship between the temperature of the surrounding environment and the air-fuel ratio of the reforming section 18. Therefore, it is possible to set a large number of air-fuel ratio data for the reforming section 18 that correspond to the temperature of the surrounding environment. Therefore, the air-fuel ratio of the reforming section 18 that is optimal for the temperature of the surrounding environment is obtained, and therefore the reforming rate of the reforming section 18 that is optimal for the temperature of the surrounding environment is obtained.

Figure 7 is a flowchart showing a modified example of the procedure for the air-fuel ratio setting process shown in Figure 3. In Figure 7, after executing the above-mentioned step S101, the air-fuel ratio setting unit 24 determines whether the temperature of the surrounding environment is equal to or higher than a predetermined specified temperature (step S106).

When the air-fuel ratio setting unit 24 determines that the temperature of the surrounding environment is equal to or higher than the specified temperature, it sets the air-fuel ratio of the reforming unit 18 to a predetermined first air-fuel ratio (step S107). When the air-fuel ratio setting unit 24 determines that the temperature of the surrounding environment is not equal to or higher than the specified temperature, it sets the air-fuel ratio of the reforming unit 18 to a predetermined second air-fuel ratio (step S108). The second air-fuel ratio is a higher value than the first air-fuel ratio.

In this modified example, the air-fuel ratio of the reforming unit 18 is set by comparing the temperature of the surrounding environment with a specified temperature, so that the memory capacity of the memory unit 22 can be reduced. Therefore, an inexpensive storage medium can be used as the memory unit 22.

Figure 8 is a schematic diagram showing an engine system according to a second embodiment of the present invention. In Figure 8, in the engine system 1 of this embodiment, the controller 23 has the above-mentioned air-fuel ratio setting unit 24, the current supply time setting unit 26, and the above-mentioned start control unit 25.

The power supply time setting unit 26 sets the power supply time of the electric heater 19 according to the temperature of the surrounding environment detected by the temperature sensor 20. The longer the power supply time of the electric heater 19, the higher the temperature of the electric heater 19. Therefore, the power supply time setting unit 26 constitutes a temperature setting unit that sets the temperature of the electric heater 19 according to the temperature of the surrounding environment.

The current supply time setting unit 26 sets the current supply time of the electric heater 19 to a current supply time corresponding to the temperature of the surrounding environment based on the current supply time table data D2 as shown in FIG. 9. The current supply time table data D2 is stored in the memory unit 22 together with the air-fuel ratio table data D1 described above.

The power supply time table data D2 is table data that represents the relationship between the temperature of the surrounding environment and the power supply time of the electric heater 19. The power supply time table data D2 is set so that the power supply time of the electric heater 19 becomes longer as the temperature of the surrounding environment becomes lower. Therefore, the power supply time setting unit 26 increases the temperature of the electric heater 19 as the temperature of the surrounding environment becomes lower.

Figure 10 is a flowchart showing the details of the procedure for the power supply time setting process executed by the power supply time setting unit 26. This process is executed when the ignition switch (not shown) is turned ON.

In FIG. 10, the current conduction time setting unit 26 first acquires the detection value of the temperature sensor 20 (step S121). Next, the current conduction time setting unit 26 reads the current conduction time table data D2 stored in the memory unit 22 (step S122). Then, the current conduction time setting unit 26 selects a current conduction time value corresponding to the temperature of the surrounding environment in the current conduction time table data D2 (step S123). Then, the current conduction time setting unit 26 sets the selected current conduction time value as the current conduction time (prescribed time for determination) of the electric heater 19 used in the control process of the start control unit 25 (step S124).

In step S112 (see FIG. 4) above, the start control unit 25 determines whether the power supply time of the electric heater 19 has reached the specified time set by the power supply time setting unit 26. Other processing by the start control unit 25 is similar to that in the first embodiment.

In this embodiment, when the temperature of the surrounding environment is low, the rotation speed of the starter 7 is low and the amount of air intake into the ammonia engine 2 is small, and the flow rate of air supplied to the reforming section 18 is accordingly small. Even when this is the case, the temperature of the electric heater 19 is increased so that the temperature of the reforming section 18 reaches the desired temperature more quickly. This allows the reforming section 18 to be started up more quickly, regardless of the temperature of the surrounding environment.

In addition, in this embodiment, even if the power input to the electric heater 19 is constant, the temperature of the electric heater 19 increases by extending the time that the electric heater 19 is energized.

In addition, in this embodiment, the energization time of the electric heater 19 is set to a power supply time corresponding to the temperature of the ambient environment based on the power supply time table data D2, which represents the relationship between the temperature of the ambient environment and the power supply time of the electric heater 19. Therefore, it is possible to set a large number of data on the power supply time of the electric heater 19 corresponding to the temperature of the ambient environment. Therefore, the temperature of the electric heater 19 suitable for the temperature of the ambient environment can be obtained.

Figure 11 is a flowchart showing a modified example of the procedure for the power supply time setting process shown in Figure 10. In Figure 11, after executing the above-mentioned step S121, the power supply time setting unit 26 determines whether the temperature of the surrounding environment is equal to or higher than a predetermined specified temperature (step S126).

When the power-on time setting unit 26 determines that the temperature of the surrounding environment is equal to or higher than the specified temperature, it sets the power-on time of the electric heater 19 to a predetermined first time (step S127). When the power-on time setting unit 26 determines that the temperature of the surrounding environment is not equal to or higher than the specified temperature, it sets the power-on time of the electric heater 19 to a predetermined second time (step S128). The second time is longer than the first time.

In this modified example, the temperature of the surrounding environment is compared with a specified temperature to set the time for which the electric heater 19 is energized, so the memory unit 22 does not require a large memory capacity. Therefore, an inexpensive storage medium can be used as the memory unit 22.

Figure 12 is a schematic diagram showing an engine system according to a third embodiment of the present invention. In Figure 12, in the engine system 1 of this embodiment, the controller 23 has the above-mentioned air-fuel ratio setting unit 24, the input power setting unit 27, and the above-mentioned starting control unit 25.

The input power setting unit 27 sets the input power to the electric heater 19 according to the temperature of the surrounding environment detected by the temperature sensor 20. The greater the input power to the electric heater 19, the higher the temperature of the electric heater 19. Therefore, the input power setting unit 27 constitutes a temperature setting unit that sets the temperature of the electric heater 19 according to the temperature of the surrounding environment.

The input power setting unit 27 sets the input power to the electric heater 19 to an input power corresponding to the temperature of the surrounding environment based on the input power table data D3 as shown in FIG. 13. The input power table data D3 is stored in the memory unit 22 together with the above-mentioned air-fuel ratio table data D1.

The input power table data D3 is table data that represents the relationship between the temperature of the surrounding environment and the power input to the electric heater 19. The input power table data D3 is set so that the lower the temperature of the surrounding environment, the greater the power input to the electric heater 19. Therefore, the input power setting unit 27 will increase the temperature of the electric heater 19 as the temperature of the surrounding environment decreases.

Figure 14 is a flowchart showing the details of the procedure for the input power setting process executed by the input power setting unit 27. This process is executed when the ignition switch (not shown) is turned ON.

In FIG. 14, the input power setting unit 27 first acquires the detection value of the temperature sensor 20 (step S131). Next, the input power setting unit 27 reads the input power table data D3 stored in the memory unit 22 (step S132). Then, the input power setting unit 27 selects the input power value corresponding to the temperature of the surrounding environment in the input power table data D3 (step S133). Then, the input power setting unit 27 sets the selected input power value as the input power to the electric heater 19 to be used in the control process of the start control unit 25 (step S134).

In step S111 (see FIG. 4 ), the start control unit 25 supplies the input power set by the input power setting unit 27 to the electric heater 19. Other processing by the start control unit 25 is the same as in the first embodiment.

Even in this embodiment, when the ambient temperature is low, the rotation speed of the starter 7 is low and the amount of air intake into the ammonia engine 2 is small, and the flow rate of air supplied to the reforming section 18 is accordingly small, the temperature of the electric heater 19 is increased so that the temperature of the reforming section 18 reaches the desired temperature more quickly. This allows the reforming section 18 to be started up more quickly, regardless of the ambient temperature.

In addition, in this embodiment, even if the time that the electric heater 19 is energized is constant, the temperature of the electric heater 19 increases by increasing the power input to the electric heater 19.

In addition, in this embodiment, the power input to the electric heater 19 is set to a power input corresponding to the temperature of the ambient environment based on the input power table data D3, which represents the relationship between the temperature of the ambient environment and the power input to the electric heater 19. Therefore, it is possible to set a large number of data for the power input to the electric heater 19 corresponding to the temperature of the ambient environment. Therefore, the temperature of the electric heater 19 suitable for the temperature of the ambient environment can be obtained.

Figure 15 is a flowchart showing a modified example of the procedure for the input power setting process shown in Figure 14. In Figure 15, after executing the above-mentioned step S131, the input power setting unit 27 determines whether the temperature of the surrounding environment is equal to or higher than a predetermined specified temperature (step S136).

When the input power setting unit 27 determines that the temperature of the ambient environment is equal to or higher than the specified temperature, it sets the input power to the electric heater 19 to a predetermined first power (step S137). When the input power setting unit 27 determines that the temperature of the ambient environment is not equal to or higher than the specified temperature, it sets the input power to the electric heater 19 to a predetermined second power (step S138). The second power is greater than the first power.

In this modified example, the temperature of the surrounding environment is compared with a specified temperature to set the input power to the electric heater 19, so the memory capacity of the memory unit 22 can be small. Therefore, an inexpensive storage medium can be used as the memory unit 22.

The present invention is not limited to the above embodiment. For example, in the above embodiment, when the time that the electric heater 19 is energized reaches a specified time, the electric heater 19 is turned off, but the present invention is not limited to this form, and the electric heater 19 may be turned off when the temperature of the reforming section 18 rises to a specified temperature (e.g., activation temperature).

In addition, in the above embodiment, the reforming section 18 is heated by the electric heater 19, but the heating section for heating the reforming section 18 is not limited to the electric heater 19, and a combustion heater or the like may be used. In this case, in the above second and third embodiments, the lower the temperature of the surrounding environment, the higher the temperature of the combustion heater or the like may be.

In the above embodiment, the temperature of the surrounding environment, such as the outside air temperature, is directly detected by the temperature sensor 20, but the sensor for detecting the temperature of the surrounding environment is not limited to this form, and the temperature of the surrounding environment may be detected, for example, by measuring the temperature of the engine oil that lubricates the ammonia engine 2 or the temperature of the engine coolant that cools the ammonia engine 2.

In addition, in the above embodiment, the temperature of the surrounding environment is detected as the state of the surrounding environment, and the air-fuel ratio of the reforming unit 18 is set to be higher as the temperature of the surrounding environment decreases, but the state of the surrounding environment to be detected is not limited to the temperature of the surrounding environment. For example, the oxygen state of the surrounding environment may be detected, and the air-fuel ratio of the reforming unit 18 may be set according to the oxygen state of the surrounding environment. In this case, the lower the oxygen content of the surrounding environment, the higher the air-fuel ratio of the reforming unit 18 is set.

In the above embodiment, the reforming unit 18 has a reforming catalyst 18a that has both the function of burning ammonia gas and the function of decomposing ammonia gas into hydrogen, but is not limited to such a form. The reforming unit 18 may have a combustion catalyst that burns ammonia gas and a reforming catalyst that decomposes ammonia gas into hydrogen separately.

In addition, in the above embodiment, ammonia is used as the fuel, but the present invention can also be applied to engine systems that use hydrocarbons or the like as fuel.

1...engine system, 2...ammonia engine (engine), 3...intake passage, 5...main injector (first fuel supply valve), 6...main throttle valve (first flow control valve), 7...starter, 12...air flow path, 13...sub throttle valve (second flow control valve), 14...sub injector (second fuel supply valve), 15...reformed gas flow path, 18...reforming section, 19...electric heater (heating section), 20...temperature sensor (state detection section), 22...storage section, 24...air-fuel ratio setting section, 25...start control section, 26...power supply time setting section (temperature setting section), 27...input power setting section (temperature setting section), D1...air-fuel ratio table data, D2...power supply time table data, D3...input power table data.

Claims (7)

The engine,
A starter for starting the engine;
an intake passage through which air supplied to the engine flows;
a first flow control valve that controls a flow rate of air flowing through the intake passage;
a first fuel supply valve for supplying fuel to the engine;
a reforming unit that generates a reformed gas containing hydrogen by reforming the fuel using heat generated by burning the fuel;
A heating unit that heats the reforming unit;
an air flow path through which air supplied to the reforming unit flows;
a second flow control valve that controls a flow rate of air flowing through the air flow path;
a second fuel supply valve that supplies fuel to the reforming section;
a reformed gas flow path through which the reformed gas generated by the reforming unit flows toward the engine;
A state detection unit that detects an outside air temperature of the surrounding environment;
an air-fuel ratio setting unit that sets an air-fuel ratio of the reforming unit according to an outside air temperature of the surrounding environment detected by the state detection unit;
a start control unit that controls the first flow control valve, the first fuel supply valve, the second flow control valve, and the second fuel supply valve when the engine is started by the starter ;
a storage unit that stores air-fuel ratio table data that represents a relationship between an outside temperature of the surrounding environment and an air-fuel ratio of the reformer ,
the air-fuel ratio table data is set so that the lower the outside temperature of the surrounding environment, the higher the air-fuel ratio of the reforming section;
the air-fuel ratio setting unit sets the air-fuel ratio of the reforming unit to an air-fuel ratio corresponding to an outside air temperature of the surrounding environment based on the air-fuel ratio table data stored in the memory unit;
The starting control unit controls the second flow control valve and the second fuel supply valve in accordance with the air-fuel ratio of the reformer unit that is set by the air-fuel ratio setting unit. The engine,
A starter for starting the engine;
an intake passage through which air supplied to the engine flows;
a first flow control valve that controls a flow rate of air flowing through the intake passage;
a first fuel supply valve for supplying fuel to the engine;
a reforming unit that generates a reformed gas containing hydrogen by reforming the fuel using heat generated by burning the fuel;
A heating unit that heats the reforming unit;
an air flow path through which air supplied to the reforming unit flows;
a second flow control valve that controls a flow rate of air flowing through the air flow path;
a second fuel supply valve that supplies fuel to the reforming section;
a reformed gas flow path through which the reformed gas generated by the reforming unit flows toward the engine;
A state detection unit that detects an outside air temperature of the surrounding environment;
an air-fuel ratio setting unit that sets an air-fuel ratio of the reforming unit according to an outside air temperature of the surrounding environment detected by the state detection unit;
a start control unit that controls the first flow control valve, the first fuel supply valve, the second flow control valve, and the second fuel supply valve when the engine is started by the starter,
the air-fuel ratio setting unit sets the air-fuel ratio of the reforming unit to a first air-fuel ratio when the outside air temperature of the surrounding environment is equal to or higher than a specified temperature, and sets the air-fuel ratio of the reforming unit to a second air-fuel ratio higher than the first air-fuel ratio when the outside air temperature of the surrounding environment is lower than the specified temperature;
The starting control unit controls the second flow control valve and the second fuel supply valve in accordance with the air-fuel ratio of the reformer unit that is set by the air-fuel ratio setting unit. 3. The engine system according to claim 1 , wherein the start control section controls the second fuel supply valve so that a flow rate of the fuel supplied to the reforming section decreases as an outside temperature of the surrounding environment decreases. The engine system according to claim 3 , wherein the start control unit controls the first fuel supply valve so that a flow rate of the fuel supplied to the engine increases as the outside air temperature of the surrounding environment decreases. A temperature setting unit that sets a temperature of the heating unit according to an outside air temperature of the surrounding environment,
The engine system according to any one of claims 1 to 4 , wherein the temperature setting unit increases the temperature of the heating unit as the outside air temperature of the surrounding environment decreases. The heating unit is an electric heater,
6. The engine system according to claim 5 , wherein the temperature setting unit extends a power supply time of the electric heater as the outside air temperature of the surrounding environment decreases. The heating unit is an electric heater,
6. The engine system according to claim 5 , wherein the temperature setting unit increases the electric power supplied to the electric heater as the outside air temperature of the surrounding environment decreases.

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