Engine System

Abstract

To provide an engine system capable of early starting a reforming section while securing reforming performance of the reforming section regardless of a state of an ambient environment.SOLUTION: An engine system 1 includes: a reforming section 18 generating reformed gas; a temperature sensor 20 detecting a temperature of an ambient environment; a flow rate ratio setting section 24 setting a ratio of a flow rate of air to be supplied to an ammonia engine 2 and the reforming section 18 in accordance with the temperature of the ambient environment; and a start control section 25 controlling a starter 7, a main throttle valve 6, a main injector 5, a sub-throttle valve 13 and a sub-injector 14 at start of the ammonia engine 2. The flow rate ratio setting section 24 sets the ratio of the flow rate of the air so as not to reduce the flow rate of the air to be supplied to the reforming section 18 even when the temperature of the ambient environment is changed. The start control section 25 controls the main throttle valve 6 and the sub-throttle valve 13 in accordance with the ratio of the flow rate of the air.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] As a conventional engine system, for example, a technology as 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 a catalyst in the cracker. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-211155 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned 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 contained in the starter is high, so the rotation speed of the starter 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, and therefore the time required to start the reforming section is increased.

[0005] An object of the present invention is to provide an engine system that can ensure the reforming performance of the reforming section and can quickly start the reforming section regardless of the state of the surrounding environment. [Means for solving the problem]

[0006] 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 unit for generating a reformed gas containing hydrogen by reforming the fuel using heat generated by burning the fuel, a heating unit for heating the reforming unit, an air flow path through which air supplied to the reforming unit flows, a second flow control valve for controlling the flow rate of air flowing through the air flow path, a second fuel supply valve for supplying fuel to the reforming unit, a reformed gas flow path through which the reformed gas generated by the reforming unit flows toward the engine, and a surrounding The engine control system includes a condition detection unit which detects the condition of the environment, a flow rate ratio setting unit which sets the ratio of the flow rates of air supplied to the engine and the reforming unit according to the condition of the surrounding environment detected by the condition detection unit, and a start-up control unit which controls the starter, a first flow rate control valve, a first fuel supply valve, a second flow rate control valve and a second fuel supply valve when the engine is started, wherein the flow rate ratio setting unit sets the ratio of the flow rates of the air supplied to the engine and the reforming unit so that the flow rate of the air supplied to the reforming unit does not decrease even if the condition of the surrounding environment changes, and the start-up control unit controls at least the first flow rate control valve according to the ratio of the flow rates of the air supplied to the engine and the reforming unit set by the flow rate ratio setting unit.

[0007] 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 a reformed gas containing hydrogen is generated. The reformed gas flows through a 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 ratio of the flow rates of the air supplied to the engine and the reforming section is set according to the state of the surrounding environment. At this time, the ratio (set ratio) of the flow rates of the air supplied to the engine and the reforming section is set so that the flow rate of the air supplied to the reforming section does not decrease even if the state of the surrounding environment changes. Then, at least the first flow control valve is controlled according to the set ratio of the flow rates of the air. In this way, even if the state of the surrounding environment changes, the flow rate of the air supplied to the reforming section does not decrease, so that the reforming rate of the reforming section is prevented from decreasing. This ensures the reforming performance of the reforming unit regardless of the state of the surrounding environment. Also, even if the state of the surrounding environment changes, the flow rate of air supplied to the reforming unit does not decrease, so the temperature of the reforming unit quickly reaches the desired temperature. This allows the reforming unit to be started up quickly regardless of the state of the surrounding environment.

[0008] The state detection unit may detect the temperature of the surrounding environment as the state of the surrounding environment, and the flow rate ratio setting unit may increase the ratio of the flow rate of air supplied to the reforming unit to the flow rate of air supplied to the engine as the temperature of the surrounding environment decreases. In this configuration, the lower the temperature of the surrounding environment, the higher the ratio of the flow rate of air supplied to the reforming unit to the flow rate of air supplied to the engine. Therefore, even if the temperature of the surrounding environment is low, which reduces the rotation speed of the starter and reduces the amount of air intake into the engine, a decrease in the flow rate of air supplied to the reforming unit can be suppressed by increasing the ratio of the flow rate of air supplied to the reforming unit to the flow rate of air supplied to the engine.

[0009] The start control unit may control the first fuel supply valve so that the flow rate of fuel supplied to the engine decreases as the temperature of the surrounding environment decreases. In this configuration, the flow rate of fuel supplied to the engine decreases as the temperature of the surrounding environment decreases. When the ratio of the flow rate of air supplied to the reformer to the flow rate of air supplied to the engine is increased due to a low temperature of the surrounding environment, the flow rate of air supplied to the engine decreases, and the amount of fuel that flows downstream without being burned in the engine increases. Therefore, by reducing the flow rate of fuel supplied to the engine, the amount of unburned fuel discharged from the engine decreases.

[0010] The engine system may further include a storage unit that stores flow rate ratio table data that indicates the relationship between the temperature of the surrounding environment and the ratio of the flow rates of the air supplied to the engine and the reforming unit, and the flow rate ratio setting unit may set the ratio of the flow rates of the air supplied to the engine and the reforming unit to a ratio that corresponds to the temperature of the surrounding environment based on the flow rate ratio table data stored in the storage unit. In this configuration, a large number of data on the ratio of the flow rates of the air supplied to the engine and the reforming unit that correspond to the temperature of the surrounding environment can be set. Therefore, it is possible to obtain an air flow rate ratio that is suitable for the temperature of the surrounding environment.

[0011] The flow rate ratio setting unit may set the ratio of the flow rates of the air supplied to the engine and the reforming unit to a first ratio when the temperature of the ambient environment is equal to or higher than a specified temperature, and may set the ratio of the flow rates of the air supplied to the engine and the reforming unit to a second ratio higher than the first ratio when the temperature of the ambient environment is lower than the specified temperature. In this configuration, the temperature of the ambient environment is compared with the specified temperature to set the ratio of the flow rates of the air supplied to the engine and the reforming unit, so that a small memory capacity is required. Therefore, an inexpensive storage medium can be used.

[0012] 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 this configuration, even if the starter rotation speed is reduced due to a low ambient temperature, and the amount of air intake into the engine is reduced, 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.

[0013] The heating unit may be an electric heater, and the temperature setting unit may extend the time for which 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 extending the time for which the electric heater is energized.

[0014] 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 power supply time of the electric heater is constant, the temperature of the electric heater increases by increasing the power input to the electric heater.

[0015] The start control section may control the first flow control valve and the second flow control valve according to the ratio of the flow rates of air supplied to the engine and the reforming section. In this configuration, by controlling the first flow control valve and the second flow control valve, the flow rate of air supplied to the reforming section can be accurately controlled. Effect of the Invention

[0016] According to the present invention, the reforming performance of the reforming section can be ensured and the reforming section can be started up early, regardless of the state of the surrounding environment. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram showing an engine system according to a first embodiment of the present invention. [Diagram 2]2 is a table showing flow rate ratio table data stored in a storage unit shown in FIG. 1. [Diagram 3] 2 is a flowchart showing details of a procedure of a flow rate ratio setting process executed by a flow rate ratio setting unit shown in FIG. 1. [Figure 4] 2 is a flowchart showing details of a procedure of a startup control process executed by a startup control unit shown in FIG. 1. [Diagram 5] 4 is a graph showing the reforming characteristics of the reforming section. [Figure 6] 4 is a flowchart showing a modified example of the flow rate ratio setting process procedure shown in FIG. 3. [Figure 7] FIG. 4 is a schematic configuration diagram showing an engine system according to a second embodiment of the present invention. [Figure 8] 8 is a table showing power supply time table data stored in a storage unit shown in FIG. 7. [Figure 9] 8 is a flowchart showing details of a procedure for a current-flow time setting process executed by a current-flow time setting unit shown in FIG. 7. [Figure 10] 10 is a flowchart showing a modified example of the procedure of the current application time setting process shown in FIG. [Figure 11] FIG. 5 is a schematic configuration diagram showing an engine system according to a third embodiment of the present invention. [Figure 12] 12 is a table showing supplied power table data stored in a storage unit shown in FIG. 11. [Figure 13] 12 is a flowchart showing details of a procedure of an input power setting process executed by an input power setting unit shown in FIG. [Figure 14] 14 is a flowchart showing a modification of the procedure of the supplied power setting process shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0019] Fig. 1 is a schematic diagram showing an engine system according to a first embodiment of the present invention. In Fig. 1, an engine system 1 of the present 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.

[0020] 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 to make the flame-retardant ammonia gas easier to burn. The ammonia engine 2 has a combustion chamber 8 in which the ammonia gas is burned together with the hydrogen to generate exhaust gas.

[0021] The intake passage 3 and the exhaust passage 4 are connected to a 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.

[0022] 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.

[0023] 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.

[0024] The starter 7 starts the ammonia engine 2. Although not specifically shown, the starter 7 has a motor, a plurality of gears, etc. The starter 7 contains oil for lubrication and cooling.

[0025] 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.

[0026] The reformer 11 has a cylindrical housing 17, and a reforming section 18 and an electric heater 19 housed in the housing 17. The housing 17 is made of a metal material such as stainless steel that is resistant to corrosion by ammonia gas.

[0027] The reforming unit 18 generates 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 having, for example, 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, a palladium-based catalyst, or the like is used.

[0028] The electric heater 19 is disposed upstream of the reforming section 18 inside 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, the electric heater 19 generates heat, and uses the heat to heat 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 inside the housing 17.

[0029] The air flow path 12 connects the intake passage 3 and the reformer 11. One end of the air flow path 12 is connected to a position in the intake passage 3 between the air cleaner 9 and the main throttle valve 6. The other end of the air flow path 12 is connected to an inlet 17a of a 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.

[0030] The sub-throttle valve 13 is disposed in the air flow passage 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.

[0031] 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.

[0032] The reformed gas flow path 15 connects the reformer 11 and the intake passage 3. One end of the reformed gas flow path 15 is connected to an outlet portion 17b of a housing 17 of the reformer 11. The other end of the reformed gas flow path 15 is connected to a portion of the intake passage 3 between the main throttle valve 6 and the ammonia engine 2. The reformed gas flow path 15 is a flow path through which the reformed gas generated by the reforming section 18 flows toward the ammonia engine 2.

[0033] The cooler 16 is disposed in the reformed gas passage 15. The cooler 16 cools the reformed gas flowing through the reformed gas passage 15, for example, by using engine cooling water that cools the ammonia engine 2.

[0034] The engine system 1 also includes a temperature sensor 20, a temperature sensor 21, a storage unit 22, and a controller 23.

[0035] 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.

[0036] 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.

[0037] 2, the memory unit 22 stores various data including flow rate ratio table data D1 that indicates the relationship between the temperature of the surrounding environment and the ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming unit 18. The ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming unit 18 is the ratio between the flow rate of air supplied to the ammonia engine 2 and the flow rate of air supplied to the reforming unit 18.

[0038] The flow rate ratio table data D1 is set so that the lower the temperature of the surrounding environment, the higher the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2. At this time, the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2 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.

[0039] The controller 23 is composed of a CPU, a RAM, a ROM, an input / output interface, etc. The controller 23 has a flow rate ratio setting unit 24 and a start control unit 25.

[0040] The flow rate ratio setting unit 24 sets the ratio of the flow rates of the air supplied to the ammonia engine 2 and the reforming unit 18 according to the temperature of the surrounding environment detected by the temperature sensor 20. The flow rate ratio setting unit 24 sets the ratio of the flow rates of the air supplied to the ammonia engine 2 and the reforming unit 18 to a ratio corresponding to the temperature of the surrounding environment, based on flow rate ratio table data D1 stored in the memory unit 22. Therefore, the lower the temperature of the surrounding environment, the higher the flow rate ratio setting unit 24 increases the ratio of the flow rate of the air supplied to the reforming unit to the flow rate of the air supplied to the ammonia engine 2.

[0041] At this time, the flow rate ratio setting unit 24 sets the ratio of the flow rates of the air supplied to the ammonia engine 2 and the reforming unit 18 so that the flow rate of the air supplied to the reforming unit 18 does not decrease even if the temperature of the surrounding environment changes. Specifically, the flow rate ratio setting unit 24 sets the ratio of the flow rates of the air supplied to the ammonia engine 2 and the reforming unit 18 so that the flow rate of the air supplied to the reforming unit 18 is constant even if the temperature of the surrounding environment changes.

[0042] 3 is a flowchart showing details of the procedure of the flow rate ratio setting process executed by the flow rate ratio setting unit 24. This process is executed when an ignition switch (not shown) is turned ON.

[0043] 3, the flow rate ratio setting unit 24 first acquires a detection value of the temperature sensor 20 (step S101). Next, the flow rate ratio setting unit 24 reads the flow rate ratio table data D1 stored in the memory unit 22 (step S102). Then, the flow rate ratio setting unit 24 selects a value of the air flow rate ratio corresponding to the temperature of the surrounding environment in the flow rate ratio table data D1 (step S103). Then, the flow rate ratio setting unit 24 sets the selected value of the air flow rate ratio as the air flow rate ratio used in the control process of the start control unit 25 (step S104).

[0044] At the start of the ammonia engine 2, the start control unit 25 controls the main injector 5, the main throttle valve 6, the starter 7, the sub-throttle valve 13, the sub-injector 14, and the 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 the sub-injector 14 according to the ratio of the air flow rates supplied to the ammonia engine 2 and the reformer unit 18, which is set by the flow rate ratio setting unit 24.

[0045] 4 is a flowchart showing the details of the procedure of 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. 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.

[0046] 4, the start 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.

[0047] Next, the start control unit 25 judges whether the time for which the electric heater 19 has been energized has reached a specified time (step S112). The specified time is the time for which the reforming unit 18 is heated by the electric heater 19, 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 combusted by the reforming catalyst 18a.

[0048] When the start control unit 25 determines that the power supply time of the electric heater 19 has reached the specified time, it controls the electric heater 19 to be turned off (step S113). Then, the power supply to the electric heater 19 is stopped, so that the temperature of the electric heater 19 drops.

[0049] Next, the starting control unit 25 controls the starter 7 to rotate (step S114). Then, the starting 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.

[0050] Next, the starting 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, in cooperation with step S115, the starting control unit 25 controls the opening degree of the main throttle valve 6 and the sub-throttle valve 13 so as to satisfy the ratio of the air flow rates supplied to the ammonia engine 2 and the reforming unit 18 set by the flow rate ratio setting unit 24.

[0051] Next, 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 a temperature at which the reforming catalyst 18a can reform ammonia gas. The reaction temperature is higher than the activation temperature.

[0052] 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.

[0053] Then, the start control unit 25 controls the opening degree of the main injector 5 (step S120). Then, ammonia gas is supplied into the combustion chamber 8 of the ammonia engine 2, and the ammonia gas is burned in the combustion chamber 8 together with the hydrogen in the reformed gas.

[0054] In the engine system 1 as described above, when an ignition switch (not shown) is turned on, electricity is applied to the electric heater 19, causing the temperature of the electric heater 19 to rise. Then, the reforming section 18 is heated by the electric heater 19, causing the temperature of the reforming section 18 to rise.

[0055] Then, the starter 7 is rotated and the main throttle valve 6 is opened, so that air is supplied to the combustion chamber 8 of the ammonia engine 2. In addition, the sub-injector 14 and the sub-throttle valve 13 are opened, so that ammonia gas and air are supplied to the reforming section 18.

[0056] When the temperature of the reforming section 18 reaches the activation temperature, the ammonia gas is burned by the reforming catalyst 18a. Specifically, as shown in the following formula, ammonia and oxygen in the air undergo a chemical reaction (exothermic reaction). NH3+3 / 4O2→1 / 2N2+3 / 2H2O …(A)

[0057] Then, the temperature of the reforming section 18 further rises due to 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. NH3→3 / 2H2+1 / 2N2…(B)

[0058] 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 state transitions to a steady state in which the ammonia gas is combusted together with the hydrogen in the reformed gas.

[0059] Incidentally, the reforming unit 18 has reforming characteristics as shown in FIG. 5. The reforming characteristics represent the relationship between the air-fuel ratio (AFR) of the reforming unit 18 and the temperature and reforming rate of the reforming unit 18. The reforming rate of the reforming unit 18 is the ratio of the flow rate of hydrogen generated in the reforming unit 18 to the flow rate of ammonia gas supplied to the reforming unit 18. The higher the air-fuel ratio of the reforming unit 18, the higher the temperature and reforming rate of the reforming unit 18. At the start-up of the reforming unit 18, as shown in FIG. 5(a), the reforming unit 18 basically operates at a control point P at which a desired reforming rate is obtained. For this reason, the openings of the sub-injector 14 and the sub-throttle valve 13 are controlled so that the air-fuel ratio of the reforming unit 18 becomes the air-fuel ratio corresponding to the control point P. Here, when the temperature of the surrounding environment is normal temperature, the reforming unit 18 operates at the control point P, and therefore an appropriate amount of hydrogen is generated by the reforming unit 18.

[0060] 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 when the starter 7 is rotated is low. 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 accordingly reduced. Therefore, as shown in FIG. 5(b), 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.

[0061] Therefore, in the above steps S115 and S116 (see FIG. 4), the start control unit 25 of the controller 23 controls the opening degrees of the main throttle valve 6 and the sub-throttle valve 13 when the temperature of the surrounding environment is low so that the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2 becomes higher than at normal temperature.

[0062] Specifically, at normal temperature, if the total flow rate of air supplied to the ammonia engine 2 is A and the flow rate of air passing through the main throttle valve 6 is Ax, then the flow rate of air passing through the sub-throttle valve 13 and supplied to the reforming section 18 is A(1-x). On the other hand, at low temperature, if the total flow rate of air supplied to the ammonia engine 2 is B and the flow rate of air passing through the main throttle valve 6 is Bx, then the flow rate of air passing through the sub-throttle valve 13 and supplied to the reforming section 18 is B(1-x).

[0063] For example, at normal temperature, the flow rate (Ax) of air passing through the main throttle valve 6 is 70% of the total air flow rate (A), and the flow rate (A(1-x)) of air passing through the sub-throttle valve 13 and supplied to the reforming section 18 is 30% of the total air flow rate (A). On the other hand, at low temperature, the flow rate (Bx) of air passing through the main throttle valve 6 is 60% of the total air flow rate (B), and the flow rate (B(1-x)) of air passing through the sub-throttle valve 13 and supplied to the reforming section 18 is 40% of the total air flow rate (B). In this case, A>B, Ax>Bx, and A(1-x)=B(1-x) hold.

[0064] Even if the temperature of the surrounding environment drops in this way, the flow rate of air supplied to the reformer 18 remains constant. Therefore, the air-fuel ratio of the reformer 18 does not change, and the reforming rate of the reformer 18 does not change either. As a result, the reformer 18 operates at control point P, just like at room temperature, and the reformer 18 produces an appropriate amount of hydrogen.

[0065] Furthermore, in the above-mentioned step S120 (see FIG. 4), when the temperature of the surrounding environment is low, the start control unit 25 controls the main injector 5 so that the flow rate of ammonia gas supplied to the combustion chamber 8 of the ammonia engine 2 is reduced compared to that at normal temperature. 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 is reduced as the temperature of the surrounding environment decreases. As a result, the flow rate of unburned ammonia gas that flows downstream without being burned in the combustion chamber 8 is reduced.

[0066] 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 combusted and reformed in the reforming section 18, and a reformed gas containing hydrogen is generated. The reformed gas flows through the reformed gas flow passage 15 and is supplied to the ammonia engine 2. Then, in the ammonia engine 2, the ammonia gas is combusted together with the hydrogen in the reformed gas. Here, the temperature of the surrounding environment is detected as the state of the surrounding environment, and the ratio of the flow rate of the air supplied to the ammonia engine 2 and the reforming section 18 is set according to the temperature of the surrounding environment. At this time, the ratio (set ratio) of the flow rate of the air supplied to the ammonia engine 2 and the reforming section 18 is set so that the flow rate of the air supplied to the reforming section 18 does not decrease even if the temperature of the surrounding environment changes. Then, the main throttle valve 6 and the sub-throttle valve 13 are controlled according to the set ratio of the air flow rates. In this way, even if the temperature of the surrounding environment changes, the flow rate of air supplied to the reforming section 18 does not decrease, so a decrease in the reforming rate of the reforming section 18 is prevented. This ensures the reforming performance of the reforming section 18 regardless of the temperature of the surrounding environment. Also, even if the temperature of the surrounding environment changes, the flow rate of air supplied to the reforming section 18 does not decrease, so the temperature of the reforming section 18 reaches the desired temperature early. This allows the reforming section 18 to be started early, regardless of the temperature of the surrounding environment.

[0067] Furthermore, in this embodiment, the lower the temperature of the surrounding environment, the higher the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2. Therefore, even if the rotation speed of the starter 7 is lowered and the amount of air intake into the ammonia engine 2 is reduced due to a low temperature of the surrounding environment, by increasing the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2, a decrease in the flow rate of air supplied to the reforming unit 18 is suppressed.

[0068] Furthermore, in this embodiment, the lower the temperature of the surrounding environment, the smaller the flow rate of ammonia gas supplied to the ammonia engine 2. When the ratio of the flow rate of air supplied to the reformer 18 to the flow rate of air supplied to the ammonia engine 2 is increased due to the low temperature of the surrounding environment, the flow rate of air supplied to the ammonia engine 2 decreases, and the amount of ammonia gas that flows downstream without being combusted in the ammonia engine 2 increases. Therefore, by reducing the flow rate of ammonia gas supplied to the ammonia engine 2, the amount of unburned ammonia gas discharged from the ammonia engine 2 decreases.

[0069] Furthermore, in this embodiment, the ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming unit 18 is set to a ratio that corresponds to the temperature of the ambient environment based on flow rate ratio table data D1 that indicates the relationship between the temperature of the ambient environment and the ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming unit 18. Therefore, it is possible to set a large number of data for the ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming unit that correspond to the temperature of the ambient environment. Therefore, it is possible to obtain an air flow rate ratio that is suitable for the temperature of the ambient environment.

[0070] Furthermore, in this embodiment, by controlling the main throttle valve 6 and the sub-throttle valve 13 in accordance with the ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming section 18, it is possible to accurately control the flow rate of air supplied to the reforming section 18.

[0071] Fig. 6 is a flowchart showing a modified example of the procedure of the flow rate ratio setting process shown in Fig. 3. In Fig. 6, after performing the above-mentioned procedure S101, the flow rate ratio setting unit 24 determines whether the temperature of the surrounding environment is equal to or higher than a predetermined specified temperature (procedure S106).

[0072] When the flow rate ratio setting unit 24 determines that the temperature of the ambient environment is equal to or higher than the specified temperature, it sets the ratio of the air flow rates supplied to the ammonia engine 2 and the reforming unit 18 to a predetermined first ratio (step S107). When the flow rate ratio setting unit 24 determines that the temperature of the ambient environment is not equal to or higher than the specified temperature, it sets the ratio of the air flow rates supplied to the ammonia engine 2 and the reforming unit 18 to a predetermined second ratio (step S108). The second ratio is a value higher than the first ratio. In other words, when the temperature of the ambient environment is lower than the specified temperature, the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2 is higher than when the temperature of the ambient environment is equal to or higher than the specified temperature.

[0073] In such a modified example, the temperature of the surrounding environment is compared with a specified temperature to set the ratio of the flow rates of the air supplied to the ammonia engine 2 and the reformer 18, so that the storage capacity of the storage unit 22 can be reduced. Therefore, an inexpensive storage medium can be used as the storage unit 22.

[0074] Fig. 7 is a schematic diagram showing an engine system according to a second embodiment of the present invention. In Fig. 7, in the engine system 1 of this embodiment, the controller 23 has the above-mentioned flow rate ratio setting unit 24, the current supply time setting unit 26, and the above-mentioned starting control unit 25.

[0075] 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.

[0076] The power supply time setting unit 26 sets the power supply time of the electric heater 19 to a power supply time corresponding to the temperature of the surrounding environment, based on the power supply time table data D2 as shown in Fig. 8. The power supply time table data D2 is stored in the memory unit 22 together with the above-mentioned flow rate ratio table data D1.

[0077] The power supply time table data D2 is table data that represents the relationship between the temperature of the ambient environment and the power supply time of the electric heater 19. The power supply time table data D2 is set so that the lower the temperature of the ambient environment, the longer the power supply time of the electric heater 19. Therefore, the power supply time setting unit 26 increases the temperature of the electric heater 19 as the temperature of the ambient environment decreases.

[0078] 9 is a flowchart showing details of the procedure of the power supply time setting process executed by the power supply time setting unit 26. This process is executed when an ignition switch (not shown) is turned ON.

[0079] 9, the current supply time setting unit 26 first acquires a detection value of the temperature sensor 20 (step S121). Next, the current supply time setting unit 26 reads the current supply time table data D2 stored in the memory unit 22 (step S122). Then, the current supply time setting unit 26 selects a current supply time value corresponding to the temperature of the surrounding environment in the current supply time table data D2 (step S123). Then, the current supply time setting unit 26 sets the selected current supply time value as the current supply time (prescribed time for determination) of the electric heater 19 used in the control process of the start control unit 25 (step S124).

[0080] In step S112 (see FIG. 4) described above, the start control unit 25 determines whether the power supply time of the electric heater 19 reaches 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 described above.

[0081] In this embodiment, even if the ambient temperature is low, causing the rotation speed of the starter 7 to be low and the amount of air intake into the ammonia engine 2 to be small, the temperature of the electric heater 19 is increased so that the temperature of the reforming unit 18 reaches the desired temperature more quickly. This allows the reforming unit 18 to be started up more quickly, regardless of the ambient temperature.

[0082] Furthermore, 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 during which the electric heater 19 is energized.

[0083] In this embodiment, the energization time of the electric heater 19 is set to a time corresponding to the temperature of the ambient environment based on energization time table data D2 that indicates the relationship between the temperature of the ambient environment and the energization time of the electric heater 19. Therefore, it is possible to set a large number of data on the energization time of the electric heater 19 that correspond 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.

[0084] Fig. 10 is a flowchart showing a modified example of the procedure of the power supply time setting process shown in Fig. 9. In Fig. 10, after performing the above-mentioned procedure 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 (procedure S126).

[0085] When the power supply 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 supply time of the electric heater 19 to a predetermined first time (step S127). When the power supply 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 supply time of the electric heater 19 to a predetermined second time (step S128). The second time is longer than the first time.

[0086] In this modified example, the temperature of the surrounding environment is compared with the specified temperature to set the energization time of the electric heater 19, so that the storage capacity of the storage unit 22 can be small. Therefore, an inexpensive storage medium can be used as the storage unit 22.

[0087] Fig. 11 is a schematic diagram showing an engine system according to a third embodiment of the present invention. In Fig. 11, in the engine system 1 of this embodiment, the controller 23 has the above-mentioned flow rate ratio setting unit 24, the input power setting unit 27, and the above-mentioned starting control unit 25.

[0088] 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.

[0089] 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. 12. The input power table data D3 is stored in the memory unit 22 together with the above-mentioned flow rate ratio table data D1.

[0090] The input power table data D3 is table data that represents the relationship between the temperature of the ambient 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 ambient environment, the greater the power input to the electric heater 19. Therefore, the input power setting unit 27 increases the temperature of the electric heater 19 as the temperature of the ambient environment decreases.

[0091] 13 is a flowchart showing details of the procedure of the input power setting process executed by input power setting unit 27. This process is executed when an ignition switch (not shown) is turned ON.

[0092] 13, input power setting unit 27 first acquires a detection value of temperature sensor 20 (step S131). Next, input power setting unit 27 reads input power table data D3 stored in memory unit 22 (step S132). Then, input power setting unit 27 selects an input power value corresponding to the temperature of the surrounding environment in input power table data D3 (step S133). Then, input power setting unit 27 sets the selected input power value as the input power to electric heater 19 to be used in the control process of start-up control unit 25 (step S134).

[0093] In the above-mentioned step S111 (see FIG. 4), the start control unit 25 supplies the supply power set by the supply power setting unit 27 to the electric heater 19. Other processing of the start control unit 25 is similar to that in the above-mentioned first embodiment.

[0094] Even in this embodiment, even if the ambient temperature is low, causing the rotation speed of the starter 7 to be low and the amount of air intake into the ammonia engine 2 to be small, the temperature of the reforming unit 18 reaches the desired temperature more quickly by increasing the temperature of the electric heater 19. This allows the reforming unit 18 to be started up more quickly, regardless of the ambient temperature.

[0095] Furthermore, in this embodiment, even if the time for which 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 .

[0096] In this embodiment, the power supplied to the electric heater 19 is set to a value corresponding to the temperature of the ambient environment based on the power supply table data D3 indicating the relationship between the temperature of the ambient environment and the power supplied to the electric heater 19. Therefore, it is possible to set a large number of pieces of data on the power supplied 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.

[0097] Fig. 14 is a flowchart showing a modification of the procedure of the input power setting process shown in Fig. 13. In Fig. 14, after executing the above-mentioned step S131, 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).

[0098] 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.

[0099] In such a modified example, the temperature of the surrounding environment is compared with the specified temperature to set the input power to the electric heater 19, so that the storage capacity of the storage unit 22 can be small. Therefore, an inexpensive storage medium can be used as the storage unit 22.

[0100] The present invention is not limited to the above embodiment. For example, in the above embodiment, the ratio of the flow rates of the air supplied to the ammonia engine 2 and the reforming unit 18 is set so that the flow rate of the air supplied to the reforming unit 18 is constant even if the temperature of the surrounding environment drops, but the present invention is not particularly limited to such an embodiment. The ratio of the flow rates of the air supplied to the ammonia engine 2 and the reforming unit 18 may be set so that the flow rate of the air supplied to the reforming unit 18 increases when the temperature of the surrounding environment drops.

[0101] Furthermore, in the above embodiment, the main throttle valve 6 and the sub-throttle valve 13 are controlled in accordance with the ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming section 18, but the present invention is not limited to this particular form, and only the main throttle valve 6 may be controlled in accordance with the ratio of the flow rates of air supplied to the ammonia engine 2 and the reforming section 18.

[0102] In addition, 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 this 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 predetermined temperature (e.g., activation temperature).

[0103] Furthermore, 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 particularly 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.

[0104] In the above embodiment, the temperature of the surrounding environment, such as the outside air temperature, is directly detected by the temperature sensor 20. However, the sensor for detecting the temperature of the surrounding environment is not particularly limited to this form. For example, the temperature of the surrounding environment may be detected by measuring the temperature of the engine oil that lubricates the ammonia engine 2 or the temperature of the engine cooling water that cools the ammonia engine 2.

[0105] Also, in the above embodiment, the temperature of the surrounding environment is detected as the state of the surrounding environment, and the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2 is set to be higher as the temperature of the surrounding environment decreases, but the detected state of the surrounding environment 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 level of the surrounding environment, the higher the ratio of the flow rate of air supplied to the reforming unit 18 to the flow rate of air supplied to the ammonia engine 2 is set.

[0106] In the above embodiment, the reforming unit 18 has the reforming catalyst 18a that has both the function of burning ammonia gas and the function of decomposing the ammonia gas into hydrogen, but is not particularly limited to such a form. The reforming unit 18 may have a combustion catalyst that burns ammonia gas and a reforming catalyst that decomposes the ammonia gas into hydrogen separately.

[0107] Furthermore, in the above embodiment, ammonia is used as the fuel, but the present invention is also applicable to an engine system that uses a hydrocarbon or the like as the fuel. [Explanation of symbols]

[0108] 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 (status detection section), 22...memory section, 24...flow rate 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...flow rate ratio table data, D2...power supply time table data, D3...input power table data.

Claims

1. 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 the outside air temperature of the surrounding environment; a flow rate ratio setting unit that sets a ratio of flow rates of air supplied to the engine and the reforming unit in accordance with the outside air temperature of the surrounding environment detected by the state detection unit; a start control unit that controls the heating unit to heat the reforming unit when the engine is started, and then controls the starter, the first flow control valve, the first fuel supply valve, the second flow control valve, and the second fuel supply valve, the flow rate ratio setting unit sets a ratio of the flow rates of the air supplied to the engine and the reforming unit so that the flow rate of the air supplied to the reforming unit is constant and does not decrease even if the outside air temperature of the surrounding environment changes by increasing a ratio of the flow rate of the air supplied to the reforming unit to the flow rate of the air supplied to the engine as the outside air temperature of the surrounding environment decreases; The starting control unit controls the first flow control valve, the second flow control valve, and the second fuel supply valve in accordance with the ratio of the flow rates of air supplied to the engine and the reforming unit, which is set by the flow ratio setting unit, so that the air-fuel ratio of the reforming unit remains constant even if the outside air temperature of the surrounding environment changes.

2. The engine system according to claim 1 , wherein the start control unit controls the first fuel supply valve so that a flow rate of fuel supplied to the engine decreases as an outside air temperature of the surrounding environment decreases.

3. A storage unit is further provided for storing flow rate ratio table data representing a relationship between an outside temperature of the surrounding environment and a ratio of a flow rate of air supplied to the engine and the reforming unit, 3. The engine system according to claim 1, wherein the flow rate ratio setting unit sets a ratio of the flow rates of the air supplied to the engine and the reforming unit to a ratio corresponding to an outside air temperature of the surrounding environment, based on the flow rate ratio table data stored in the memory unit.

4. 3. An engine system as described in claim 1 or 2, wherein the flow rate ratio setting unit sets the ratio of the flow rates of the air supplied to the engine and the reforming unit to a first ratio when the outside air temperature of the surrounding environment is equal to or higher than a specified temperature, and sets the ratio of the flow rates of the air supplied to the engine and the reforming unit to a second ratio higher than the first ratio when the outside air temperature of the surrounding environment is lower than the specified temperature.

5. A temperature setting unit sets a temperature of the heating unit according to an outside air temperature of the surrounding environment, 5. The engine system according to claim 1, wherein the temperature setting unit increases the temperature of the heating unit as the outside air temperature of the surrounding environment decreases.

6. 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.

7. 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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