JP2006152901A - Hybrid system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hybrid system uniformly cooling the inside of a combustion chamber of an internal combustion engine. <P>SOLUTION: The hybrid system comprises: an internal combustion engine 2 including a fuel cell 4 whose operating temperature is not less than a boiling temperature of water and a combustion chamber, and burning fuel and oxygen in the combustion chamber; and generated water supply means 106, 107 supplying water generated by the fuel cell 4 to the combustion chamber of the internal combustion engine 2. In this case, the water generated by the fuel cell 4 turns into water vapor to be supplied to the combustion chamber of the internal combustion engine 2 through the generated water supply means 106, 107. The water vapor is uniformly dispersed in the combustion chamber of the internal combustion engine 2. Therefore, the combustion chamber of the internal combustion engine 2 is uniformly cooled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hybrid system including an internal combustion engine and a fuel cell.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. This fuel cell has been developed widely as a future energy supply system because it is environmentally friendly and can realize high energy efficiency.

  In many fuel cells, a reforming section generates reformed gas containing hydrogen from a hydrocarbon-based fuel such as gasoline, natural gas, or methanol, and supplies the reformed gas to the anode of the fuel cell. In this reforming section, reforming is performed by a steam reforming reaction using steam or the like.

In recent years, a polymer electrolyte fuel cell / motor combination system has been developed that enables high-efficiency output by combining the electric power generated by the fuel cell and an internal combustion engine that operates on fuel such as gasoline (for example, , See Patent Document 1). In this polymer electrolyte fuel cell / motor combination system, water generated by a chemical reaction between hydrogen and oxygen in the polymer electrolyte fuel cell is supplied to the intake system of the internal combustion engine. According to this technique, the nitrogen oxide concentration in the exhaust gas is reduced by lowering the combustion temperature in the internal combustion engine.
JP 2002-117873 A

  However, since the operating temperature of the polymer electrolyte fuel cell is around 80 ° C., the generated water discharged from the polymer electrolyte fuel cell is in a gas-liquid mixed state. The generated water in the gas-liquid mixed state is less diffusible than water vapor. Therefore, even if the produced water discharged from the polymer electrolyte fuel cell is supplied into the combustion chamber of the internal combustion engine, the combustion chamber cannot be cooled uniformly.

  An object of this invention is to provide the hybrid system which can cool the combustion chamber of an internal combustion engine uniformly.

  A hybrid system according to the present invention includes a fuel cell having an operating temperature equal to or higher than the boiling point of water, an internal combustion engine that includes a combustion chamber and burns with fuel and oxygen in the combustion chamber, and burns generated water generated in the fuel cell Product water supply means for supplying to the chamber.

  In the hybrid system according to the present invention, the generated water generated in the fuel cell becomes steam, and the steam is supplied to the combustion chamber of the internal combustion engine by the generated water supply means. In this case, since water vapor has a higher diffusibility than the produced water in the gas-liquid mixed state, the water vapor diffuses uniformly in the combustion chamber of the internal combustion engine. As a result, the combustion chamber of the internal combustion engine can be cooled more uniformly than a hybrid system that supplies the generated water in the gas-liquid mixed state to the combustion chamber of the internal combustion engine.

  There may be further provided avoiding means for avoiding supply of liquid water in the generated water into the combustion chamber of the internal combustion engine. In this case, liquid water is prevented from being supplied into the combustion chamber of the internal combustion engine. As a result, non-uniform cooling of the combustion chamber is prevented.

  The avoiding means may be a gas-liquid separator. In this case, the generated water is separated into water vapor and liquid water. Therefore, liquid water is reliably prevented from being supplied to the combustion chamber of the internal combustion engine.

  A determination unit that determines whether or not the fuel cell is in a warm-up state, and a generation unit that stops supply of generated water to the combustion chamber when the determination unit determines that the fuel cell is in a warm-up state. Control means for controlling the water supply means may be further provided. In this case, the generated water becomes steam and is supplied to the combustion chamber of the internal combustion engine. Therefore, liquid water is more reliably prevented from being supplied to the combustion chamber.

  The fuel cell may be a hydrogen separation membrane fuel cell. In this case, since the operating temperature of the hydrogen separation membrane battery is about 300 ° C. to 600 ° C., the generated water generated in the fuel cell is surely steam. Thereby, the generated water diffuses uniformly in the combustion chamber of the internal combustion engine.

  According to the present invention, the combustion chamber of the internal combustion engine is uniformly cooled. Therefore, generation of nitrogen oxides due to fuel combustion is suppressed. Further, the combustion efficiency in the combustion chamber of the internal combustion engine is improved. As a result, the system efficiency of the hybrid system is improved.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is an overall configuration diagram of a hybrid system 100 according to the present invention. As shown in FIG. 1, the hybrid system 100 includes a fuel tank 1, an internal combustion engine 2, a reforming unit 3, a fuel cell 4, an exhaust catalyst 5, a gas-liquid separator 6, and a control unit 7. The fuel cell 4 comprises a hydrogen separation membrane cell and includes a cathode 41 and an anode 42.

  Here, the hydrogen separation membrane battery is a fuel cell provided with a hydrogen separation membrane layer. The hydrogen separation membrane layer is a layer formed of a metal having hydrogen permeability, and can be formed of, for example, palladium, a palladium alloy, or the like. The hydrogen separation membrane battery has a structure in which the hydrogen separation membrane layer and an electrolyte having proton conductivity are laminated. Hydrogen supplied to the anode of the hydrogen separation membrane battery is converted into protons via a catalyst, moves through proton conductive electrolyte, and combines with oxygen at the cathode to become water. Therefore, most of the water or water vapor generated from the fuel cell 4 is contained in the cathode offgas.

  The fuel tank 1 is connected to the internal combustion engine 2 via a pipe 101. The fuel tank 1 is connected to the middle of the pipe 102 via the pipe 103. The internal combustion engine 2 is connected to the reforming unit 3 via a pipe 102. The reforming unit 3 is connected to the anode 42 of the fuel cell 4 via a pipe 104. The anode 42 is connected to the exhaust catalyst 5 via a pipe 105. The cathode 41 is connected to the gas-liquid separator 6 via a pipe 106. The gas-liquid separator 6 is connected to the internal combustion engine 2 via a pipe 107.

  Next, the operation of the hybrid system 100 will be described. The fuel tank 1 supplies a required amount of fuel to the internal combustion engine 2 via the pipe 101 in accordance with an instruction from the control unit 7. Further, the fuel tank 1 supplies a necessary amount of fuel to the reforming unit 3 via the pipes 103 and 102 in accordance with an instruction from the control unit 7. As the fuel, hydrocarbon fuels such as gasoline and methanol can be used.

  The internal combustion engine 2 operates by generating an air-fuel mixture with a predetermined air-fuel ratio from the fuel and air supplied from the fuel tank 1 and burning the air-fuel mixture in accordance with instructions from the control unit 7. High-temperature flue gas generated by the combustion of the air-fuel mixture is supplied to the reforming unit 3 via the pipe 102. The combustion exhaust gas contains water vapor and the like.

  In the reforming unit 3, reformed gas containing hydrogen gas is generated from the fuel supplied from the fuel tank 1 and the combustion exhaust gas. First, a steam reforming reaction occurs from the fuel and the steam in the combustion exhaust gas, and hydrogen and carbon monoxide are generated. Next, the produced carbon monoxide and the water vapor in the combustion exhaust gas react to produce hydrogen and carbon dioxide. In this case, since the combustion exhaust gas is at a high temperature, fuel vaporization and steam reforming reaction are promoted. Thereby, it is not necessary to newly provide a means for heating the reforming unit 3. As a result, the system efficiency of the hybrid system 100 is improved.

  In addition, since the combustion exhaust gas of the internal combustion engine 2 contains a large amount of water vapor, it is possible to prevent a shortage of water vapor necessary for the steam reforming reaction. Furthermore, the atmosphere in the reforming unit 3 becomes a hydrogen reduction atmosphere due to hydrogen in the reformed gas. Thereby, nitrogen oxides in the combustion exhaust gas of the internal combustion engine 2 are reduced in the reforming unit 3. Therefore, the purification reaction in the exhaust catalyst 5 described later is simplified. As a result, the structure of the exhaust catalyst 5 can be simplified.

  The reformed gas generated in the reforming unit 3 is supplied to the anode 42 of the fuel cell 4 via the pipe 104. At the anode 42, hydrogen in the reformed gas is converted into hydrogen ions. Hydrogen that has not been converted into hydrogen ions at the anode 42 and carbon monoxide that has not reacted in the reforming unit 3 are supplied to the exhaust catalyst 5 through the pipe 105 as anode off-gas. In the exhaust catalyst 5, the anode off gas is oxidized through the catalyst while generating heat, and is discharged to the outside of the hybrid system 100. The oxidation heat of the anode off gas is used for the steam reforming reaction in the reforming unit 3. Therefore, it is not necessary to newly provide heat generation means for generating heat necessary for the steam reforming reaction in the reforming unit 3. As a result, the hybrid system 100 can be reduced in size. Further, the system efficiency of the hybrid system 100 is improved.

  Air is supplied to the cathode 41 from the outside by an air pump (not shown) or the like. In the cathode 41, water is generated and electric power is generated by a reaction between hydrogen ions generated in the anode 42 and oxygen in the air supplied to the cathode 41. This generated water is hereinafter referred to as generated water. The generated water becomes water vapor by heat generated in the fuel cell 4. In this embodiment, since the fuel cell 4 is a hydrogen separation membrane cell, the operating temperature of the fuel cell 4 is about 300 to 600 ° C. As a result, the generated water is surely steam. The generated water and the air that has not reacted with the hydrogen ions are supplied to the gas-liquid separator 6 through the pipe 106 as cathode off gas.

  The gas-liquid separator 6 separates the gas and the liquid in the cathode off gas, discharges the separated liquid to the outside of the hybrid system 100, and supplies the separated gas to the internal combustion engine 2 via the pipe 107. As a result, even if the temperature of the fuel cell 4 does not reach the operating temperature of the fuel cell 4, even if the generated water contains liquid water, the liquid water is supplied to the internal combustion engine 2. Is prevented. As a result, the generated water supplied to the combustion chamber of the internal combustion engine 2 does not contain liquid water.

  From the above, the diffusibility of the generated water supplied to the combustion chamber of the internal combustion engine 2 is improved. Thereby, the generated water is uniformly diffused in the combustion chamber of the internal combustion engine 2. Therefore, the combustion chamber of the internal combustion engine 2 is uniformly cooled. As a result, generation of nitrogen oxides due to fuel combustion is suppressed. Further, the generated water is supplied into the combustion chamber of the internal combustion engine 2, thereby improving the combustion efficiency in the combustion chamber of the internal combustion engine 2. As a result, the system efficiency of the hybrid system 100 is improved.

  In this embodiment, a hydrogen separation membrane battery is used as the fuel cell 4, but other fuel cells can be used as long as the operating temperature is equal to or higher than the boiling point of water. In this case, when a fuel cell in which water is generated from hydrogen ions and oxygen at the anode, such as a solid oxide fuel cell, is used, if the anode off gas is supplied to the internal combustion engine 2, the hybrid according to the present embodiment The same effect as the system 100 can be obtained.

  In this embodiment, the pipes 106 and 107 correspond to the generated water supply means, and the gas-liquid separator 6 corresponds to the avoidance means.

  Next, a hybrid system 100a according to a second embodiment of the present invention will be described. FIG. 2 is a diagram illustrating an overall configuration of the hybrid system 100a. As shown in FIG. 2, the hybrid system 100 a is different from the hybrid system 100 in that a switching valve 8 is provided instead of the gas-liquid separator 6 and a temperature sensor 9 is provided in the fuel cell 4. It is. The switching valve 8 is composed of a three-way cock or the like, and is connected to the pipes 106 and 107 and communicates with the outside of the hybrid system 100a. Other configurations of the hybrid system 100a are the same as the configurations of the hybrid system 100. The temperature sensor 9 may be provided in the pipe 106. In this case, the temperature of the cathode off gas can be detected more accurately.

  Next, the operation of the hybrid system 100a will be described. The temperature sensor 9 detects the temperature of the fuel cell 4 and gives the detected value to the control unit 7. For example, the temperature sensor 9 can detect the temperature of the cathode 41. Thereby, the control part 7 can detect the temperature of cathode off gas. The switching valve 8 supplies or discharges the cathode off gas supplied from the cathode 41 to one or both of the pipe 107 and the outside of the hybrid system 100a in accordance with an instruction from the control unit 7. Other operations of the hybrid system 100a are the same as the operations of the hybrid system 100.

  FIG. 3 is a flowchart showing how the control unit 7 controls the switching valve 8 after the operation of the fuel cell 4 is started. As shown in FIG. 3, the control unit 7 receives the temperature detection value from the temperature sensor 9 (step S1). Next, the control unit 7 determines whether or not the temperature of the fuel cell 4 has reached a predetermined temperature (step S2). In this case, the predetermined temperature is not particularly limited as long as the temperature is equal to or higher than the boiling point of water, and can be set to 100 ° C., for example.

  When it is determined in step S2 that the temperature of the fuel cell 4 has reached a predetermined temperature, the control unit 7 controls the switching valve 8 to supply cathode offgas to the internal combustion engine 2 (step S3). Hereinafter, the control part 7 repeats from the operation | movement of step S1.

  If it is not determined in step S2 that the temperature of the fuel cell 4 has reached the predetermined temperature, the control unit 7 controls the switching valve 8 to discharge the cathode off gas to the outside of the hybrid system 100a (step S4). ). Hereinafter, the control part 7 repeats from the operation | movement of step S1.

  As described above, if the temperature of the fuel cell 4 does not reach the boiling point of water or more, the cathode off gas is discharged to the outside of the hybrid system 100a. This prevents liquid water from being supplied to the combustion chamber of the internal combustion engine 2. As a result, uneven cooling in the combustion chamber of the internal combustion engine 2 can be prevented.

  In this embodiment, the pipes 106 and 107 and the switching valve 8 correspond to the generated water supply unit, the control unit 7 and the temperature sensor 9 correspond to the determination unit, and the control unit 7 corresponds to the control unit. The warm-up state refers to a state where the temperature of the fuel cell 4 is at a temperature below the boiling point of water or a state where the temperature of the pipe 106 is at a temperature below the boiling point of water.

  Next, a hybrid system 100b according to a third embodiment of the present invention will be described. FIG. 4 is a diagram illustrating an overall configuration of the hybrid system 100b. As shown in FIG. 4, the hybrid system 100 b is different from the hybrid system 100 in that a switching valve 8 is provided instead of the gas-liquid separator 6, a temperature sensor 9 is provided in the pipe 106, and This is the point that a pipe 108 is provided.

  The switching valve 8 is composed of a three-way cock or the like, and is connected to the pipes 106 and 107 and is connected to the reforming unit 3 via the pipe 108. Other configurations of the hybrid system 100 b are the same as the configurations of the hybrid system 100. The temperature sensor 9 may be provided in the fuel cell 4. In this case, the temperature of the cathode off gas can be detected from the temperature of the fuel cell 4.

  Next, the operation of the hybrid system 100b will be described. The temperature sensor 9 detects the temperature of the pipe 106 and gives the detected value to the control unit 7. Thereby, the control part 7 can detect the temperature of cathode off gas more correctly. The switching valve 8 supplies the cathode off gas supplied from the cathode 41 to one or both of the pipe 107 and the pipe 108 in accordance with an instruction from the control unit 7. The cathode off gas supplied to the pipe 108 is supplied to the reforming unit 3. The generated water in the cathode offgas is used for the steam reforming reaction in the reforming unit 3. Accordingly, water vapor shortage in the reforming unit 3 is prevented. Other operations of the hybrid system 100b are the same as the operations of the hybrid system 100.

  FIG. 5 is a diagram illustrating a flowchart in which the control unit 7 controls the switching valve 8 after the operation of the fuel cell 4 is started. As shown in FIG. 5, the control unit 7 receives the temperature detection value from the temperature sensor 9 (step S11). Next, the control unit 7 determines whether or not the temperature of the pipe 106 has reached a predetermined temperature (step S12). In this case, the predetermined temperature is not particularly limited as long as the temperature is equal to or higher than the boiling point of water, and can be set to 100 ° C., for example.

  When it is determined in step S <b> 12 that the temperature of the pipe 106 has reached a predetermined temperature, the control unit 7 controls the switching valve 8 to supply the cathode off gas to the internal combustion engine 2. Hereinafter, the control part 7 repeats from the operation | movement of step S11.

  When it is not determined in step S12 that the temperature of the pipe 106 has reached the predetermined temperature, the control unit 7 controls the switching valve 8 to supply the cathode offgas to the reforming unit 3 via the pipe 108. . Hereinafter, the control part 7 repeats from the operation | movement of step S11.

  As described above, if the temperature of the pipe 106 does not reach the boiling point of water or higher, the cathode off gas is supplied to the reforming unit 3. This prevents liquid water from being supplied to the combustion chamber of the internal combustion engine 2. As a result, uneven cooling in the combustion chamber of the internal combustion engine 2 can be prevented. Moreover, the lack of water vapor in the reforming unit 3 is prevented. Furthermore, if the cathode off gas is supplied to the reforming unit 3, a shortage of water vapor in the reforming unit 3 is prevented.

  In this embodiment, the pipes 106 and 107 and the switching valve 8 correspond to the generated water supply unit, the control unit 7 and the temperature sensor 9 correspond to the determination unit, and the control unit 7 corresponds to the control unit. The warm-up state refers to a state where the temperature of the fuel cell 4 is at a temperature below the boiling point of water or a state where the temperature of the pipe 106 is at a temperature below the boiling point of water.

1 is an overall configuration diagram of a hybrid system according to the present invention. It is a figure which shows the whole structure of a hybrid system. It is a figure which shows the flowchart which controls a switching valve after the operation | movement of a fuel cell starts. It is a figure which shows the whole structure of a hybrid system. It is a figure which shows the flowchart which controls a switching valve after the operation | movement of a fuel cell starts.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Internal combustion engine 3 Reforming part 4 Fuel cell 41 Cathode 42 Anode 5 Exhaust catalyst 6 Gas-liquid separator 7 Control part 8 Switching valve 9 Temperature sensor 100, 100a, 100b Hybrid system

Claims (5)

A fuel cell whose operating temperature is above the boiling point of water;
An internal combustion engine that includes a combustion chamber and that burns with fuel and oxygen in the combustion chamber;
A hybrid system comprising: generated water supply means for supplying generated water generated in the fuel cell to the combustion chamber. The hybrid system according to claim 1, further comprising avoidance means for avoiding supply of liquid water in the generated water to the combustion chamber. The hybrid system according to claim 2, wherein the avoiding means is a gas-liquid separator. Determining means for determining whether or not the fuel cell is in a warm-up state;
And a control means for controlling the generated water supply means to stop the supply of the generated water to the combustion chamber when the determining means determines that the fuel cell is in a warm-up state. The hybrid system according to claim 1. The hybrid system according to claim 1, wherein the fuel cell is a hydrogen separation membrane fuel cell.

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