JP2019216025A - Fuel cell system - Google Patents

Abstract

To downsize a fuel cell stack while realizing wet state of the inside of a fuel cell stack.SOLUTION: Due to heat exchange performed by an exhaust side heat exchanger 53 between exhaust gas flowing in an exhaust flow passage 15 and exhaust gas flowing in a first turbine downstream flow passage 51, the exhaust gas flowing in the exhaust flow passage 15 is cooled by the exhaust gas flowing in the first turbine downstream flow passage 51 and water vapor contained in the exhaust gas flowing in the exhaust flow passage 15 is condensed so as to generate condensed water. The condensed water flows from the first turbine downstream flow passage 51 into a second turbine downstream flow passage 52 and is supplied via the second turbine downstream flow passage 52 to a compression section upstream flow passage 12. Thereby, air flowing in the compression section upstream flow passage 12 is humidified by the condensed water supplied from the second turbine downstream flow passage 52 to the compression section upstream flow passage 12. The humidified air is supplied to a fuel cell stack 11 via a supply flow passage 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system.

  2. Description of the Related Art In recent years, a vehicle equipped with a fuel cell system including a fuel cell stack that performs power generation by chemically reacting hydrogen as fuel gas with oxygen in air has been put to practical use. The fuel cell system includes an electric compressor that compresses air. The electric compressor includes a compression unit that compresses air supplied to the fuel cell stack, and an electric motor that drives the compression unit. The air compressed by the compression unit is supplied to the fuel cell stack.

  Some fuel cell systems include a turbine having a turbine wheel that is rotated by exhaust gas discharged from the fuel cell stack. In such a fuel cell system, the turbine wheel is rotated by the kinetic energy of the exhaust gas, so that the kinetic energy of the exhaust gas is converted into the rotational energy of the turbine wheel. Thus, the rotational energy generated by the turbine reduces the load on the electric motor that drives the compression unit. Therefore, the power consumption of the electric motor necessary for driving the compression unit is reduced.

  By the way, in the fuel cell system, the inside of the fuel cell stack needs to be in a wet state in order for the fuel cell stack to generate power efficiently. Therefore, for example, in the fuel cell system of Patent Document 1, a supply flow path for supplying air compressed by an electric compressor to the fuel cell stack, a fuel cell stack and a turbine are connected, and the fuel cell stack is discharged from the fuel cell stack. A humidifier is provided so as to straddle the exhaust flow path through which the exhaust gas flows. The exhaust gas discharged from the fuel cell stack contains water vapor. The humidifier collects water vapor contained in exhaust gas discharged from the fuel cell stack and flowing through the discharge flow path. Then, the humidifier humidifies the air flowing through the supply flow path by moving the collected steam toward the supply flow path. Thereby, the air humidified by the humidifier is supplied to the fuel cell stack through the supply flow path, so that the inside of the fuel cell stack can be brought into a wet state.

JP 2012-164457 A

  However, in the fuel cell system of Patent Literature 1, since the humidifier has a larger size than components such as a heat exchanger, there is a problem that the fuel cell system becomes larger as a whole.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell system in which the inside of a fuel cell stack can be made wet and the size can be reduced. It is in.

  A fuel cell system that solves the above-mentioned problems includes a fuel cell stack that generates power by chemically reacting a fuel gas with oxygen in air, a compression unit that compresses air supplied to the fuel cell stack, and the compression unit. Compressor having an electric motor for driving the fuel cell, a turbine having a turbine wheel rotated by exhaust gas discharged from the fuel cell stack, and a supply for supplying air compressed by the electric compressor to the fuel cell stack A flow path, a discharge flow path that connects the fuel cell stack and the turbine and through which exhaust gas discharged from the fuel cell stack flows, and that is disposed in the discharge flow path or the turbine; A pressure regulating valve for regulating the pressure of air, wherein water is added to the exhaust gas discharged from the fuel cell stack. A first turbine that communicates with the atmosphere and that supplies the air from the atmosphere to the compression unit, and a first turbine through which the exhaust gas flows through the turbine wheel. A downstream flow path, a second turbine downstream flow path branched from the first turbine downstream flow path and communicating with the compression section upstream flow path, and exhaust gas flowing upstream of the pressure regulating valve in the discharge flow path And an exhaust-side heat exchanger that performs heat exchange between the exhaust gas and the exhaust gas flowing through the first turbine downstream flow path.

  According to this, the temperature of the exhaust gas flowing through the first turbine downstream flow path is reduced by reducing the pressure of the exhaust gas when passing through the pressure regulating valve and increasing the speed of the exhaust gas. The temperature is lower than the temperature of the exhaust gas flowing upstream of the regulating valve. The heat exchange between the exhaust gas flowing upstream of the pressure regulating valve in the discharge flow path and the exhaust gas flowing in the first turbine downstream flow path is performed by the discharge side heat exchanger, so that the discharge flow path in the discharge flow path is changed. The exhaust gas flowing upstream of the pressure regulating valve is cooled by the exhaust gas flowing through the first turbine downstream flow path. As a result, water vapor contained in the exhaust gas flowing upstream of the pressure regulating valve in the exhaust flow path is condensed to generate condensed water. The condensed water flows through the exhaust passage together with the exhaust gas and passes through the turbine wheel and flows through the first turbine downstream passage. At least a portion of the condensed water flows from the first turbine downstream flow path to the second turbine downstream flow path, and is supplied to the compression section upstream flow path via the second turbine downstream flow path. Thereby, the air flowing through the upstream passage of the compression unit is humidified by the condensed water supplied from the downstream passage of the second turbine to the upstream passage of the compression unit. Since the humidified air is supplied to the fuel cell stack through the supply flow path, the inside of the fuel cell stack can be brought into a wet state. Therefore, it is not necessary to provide a humidifier as in the related art so as to straddle the supply flow path and the discharge flow path in order to make the inside of the fuel cell stack wet. As a result, the size of the fuel cell system can be reduced.

In the above fuel cell system, a gas-liquid separator may be provided at a branch between the first turbine downstream flow path and the second turbine downstream flow path.
According to this, the exhaust gas and the condensed water flowing through the first turbine downstream flow path are separated from the exhaust gas and the condensed water by the gas-liquid separator at the branch between the first turbine downstream flow path and the second turbine downstream flow path. Is separated into The exhaust gas separated by the gas-liquid separator flows into the downstream flow path of the exhaust gas in the first turbine downstream flow path in the flow direction of the exhaust gas, and the condensed gas separated by the gas-liquid separator. By flowing water into the second turbine downstream flow path, the amount of condensed water supplied to the compression section upstream flow path via the second turbine downstream flow path can be increased. Therefore, the air flowing through the upstream passage of the compression unit is easily humidified, and the inside of the fuel cell stack can be efficiently brought into a wet state.

  In the above fuel cell system, heat exchange between air flowing through the supply flow path and exhaust gas flowing downstream of the exhaust heat exchanger in the first turbine downstream flow path in the flow direction of the exhaust gas is performed. It is preferable to further include a supply-side heat exchanger for performing the heat transfer.

  According to this, between the high-temperature air compressed by the electric compressor and flowing through the supply flow path and the exhaust gas flowing downstream of the exhaust-side heat exchanger in the first turbine downstream flow path in the exhaust gas flow direction. Is performed by the supply-side heat exchanger, so that the air flowing through the supply flow path is cooled by the exhaust gas flowing downstream of the exhaust-side heat exchanger in the first turbine downstream flow path in the exhaust gas flow direction. Is done. Therefore, since the temperature of the air supplied to the fuel cell stack through the supply flow path can be reduced, the power generation efficiency of the fuel cell stack can be improved.

  According to the present invention, the inside of the fuel cell stack can be made wet and the size can be reduced.

1 is a schematic configuration diagram of a fuel cell system in an embodiment.

Hereinafter, an embodiment of the fuel cell system will be described with reference to FIG. The fuel cell system according to the present embodiment is mounted on a vehicle such as a fuel cell vehicle, for example.
As shown in FIG. 1, a fuel cell system 10 includes a fuel cell stack 11, an electric compressor 21 that compresses air supplied to the fuel cell stack 11, and an electric compressor 21 connected in series and a fuel cell stack. And a turbine compressor 31 that compresses the air supplied to the compressor 11. The fuel cell stack 11 has, for example, a plurality of cells. Each cell is formed by laminating an oxygen electrode, a hydrogen electrode, and an electrolyte membrane disposed between the two electrodes. Then, the fuel cell stack 11 performs power generation by chemically reacting hydrogen as a fuel gas with oxygen in the air.

  The fuel cell stack 11 is electrically connected to a traveling motor (not shown). The traveling motor is driven by using the power generated by the fuel cell stack 11 as a power source. The power of the traveling motor is transmitted to the axle via a power transmission mechanism (not shown), and the vehicle travels at a vehicle speed corresponding to the accelerator opening of the accelerator pedal.

  Since only about 20% of the oxygen that contributes to the power generation of the fuel cell stack 11 exists in the air, about 80% of the air supplied to the fuel cell stack 11 contributes to the power generation of the fuel cell stack 11. And discharged from the fuel cell stack 11 as exhaust gas. Further, when the fuel cell stack 11 generates power, water is generated inside the fuel cell stack 11 by a chemical reaction between hydrogen and oxygen. The water generated in the fuel cell stack 11 is discharged from the fuel cell stack 11 as water vapor by heat generated by the power generation of the fuel cell stack 11. Therefore, the exhaust gas discharged from the fuel cell stack 11 contains water vapor.

  The fuel cell stack 11 has a supply port 11a to which air is supplied, a discharge port 11b from which air is discharged as exhaust gas, and an air flow path 11c connecting the supply port 11a and the discharge port 11b. . In the air passage 11c, the air supplied from the supply port 11a flows toward the discharge port 11b.

  The electric compressor 21 includes an electric compressor housing 22, an electric motor 23 housed in the electric compressor housing 22, a connection shaft 24 rotated by driving the electric motor 23, and a compression unit connected to the connection shaft 24. 25. The electric motor 23 is driven by power supplied from a battery (not shown) to rotate the connecting shaft 24. The compression unit 25 is driven by the rotation of the connecting shaft 24 and compresses the air supplied to the fuel cell stack 11. Therefore, the electric motor 23 drives the compression unit 25. In the present embodiment, the compression unit 25 is an impeller that is connected to the end of the connection shaft 24 and rotates integrally with the connection shaft 24. In the electric compressor 21, the compression operation is performed by rotating the impeller. .

  The electric compressor housing 22 has a suction port 22a through which air is sucked, and a discharge port 22b through which air is discharged. Further, the fuel cell system 10 includes a compression section upstream flow path 12 that communicates with the atmosphere and supplies air from the atmosphere to the compression section 25. The compression section upstream flow path 12 is configured by, for example, a pipe or the like. One end of the compression section upstream flow path 12 is open to the atmosphere, and the other end of the compression section upstream flow path 12 is connected to the suction port 22a. Then, air from the atmosphere flows through the upstream passage 12 of the compression unit and is sucked into the suction port 22a. The compression unit 25 compresses the air sucked from the suction port 22a. The air compressed by the compression section 25 is discharged from the discharge port 22b.

  The fuel cell system 10 includes a turbine 41. The turbine 41 has a turbine wheel 42 rotated by exhaust gas discharged from the fuel cell stack 11. The turbine 41 is integrated with the turbine compressor 31.

  The turbine compressor 31 has a housing 32, a rotating shaft 33 housed in the housing 32, and a turbine housing 34 of the turbine 41. A housing chamber 36 in which the compressor wheel 35 is housed is formed in the housing 32. Further, a turbine chamber 37 in which a turbine wheel 42 is housed is formed in the turbine housing 34. One end of the rotating shaft 33 protrudes into the storage chamber 36. A compressor wheel 35 is connected to one end of the rotating shaft 33. The other end of the rotating shaft 33 protrudes into the turbine chamber 37. The other end of the rotating shaft 33 is connected to a turbine wheel 42. The compressor wheel 35 and the turbine wheel 42 are impellers that rotate integrally with the rotating shaft 33. The compressor wheel 35 compresses air by rotating with the rotation of the rotating shaft 33.

  The housing 32 has a suction port 32a through which air is sucked, and a discharge port 32b through which air is discharged. In the housing 32, a first communication passage 321 that connects the suction port 32a and the storage chamber 36 is formed. Further, in the housing 32, a second communication passage 322 that connects the housing chamber 36 and the discharge port 32b is formed.

  The fuel cell system 10 includes a connection passage 13 that connects the electric compressor 21 and the turbine compressor 31. The connection flow path 13 is configured by, for example, a pipe. One end of the connection flow path 13 is connected to a discharge port 22 b of the electric compressor 21, and the other end of the connection flow path 13 is connected to a suction port 32 a of the turbine compressor 31. Then, the air compressed by the electric compressor 21 and discharged from the discharge port 22b to the connection channel 13 flows through the connection channel 13 and is sucked into the suction port 32a. The compressor wheel 35 compresses the air sucked from the suction port 32a and flowing into the storage chamber 36 through the first communication passage 321. The air compressed by the compressor wheel 35 is discharged from the storage chamber 36 through the discharge port 32b through the second communication path 322.

  Therefore, the turbine compressor 31 compresses the air once compressed by the electric compressor 21. Therefore, in the fuel cell system 10 of the present embodiment, two-stage compression is performed in which the air supplied to the fuel cell stack 11 is compressed by the electric compressor 21 and the turbine compressor 31, respectively.

  The fuel cell system 10 includes a supply passage 14 that connects the turbine compressor 31 and the fuel cell stack 11. The supply flow path 14 is comprised by piping etc., for example. One end of the supply passage 14 is connected to a discharge port 32 b of the turbine compressor 31, and the other end of the supply passage 14 is connected to a supply port 11 a of the fuel cell stack 11. And the air discharged from the discharge port 32b flows through the supply flow path 14, and is supplied to the supply port 11a. Therefore, the supply flow path 14 supplies the air compressed by the electric compressor 21 and the turbine compressor 31 to the fuel cell stack 11. That is, the supply flow path 14 supplies the air compressed by the electric compressor 21 to the fuel cell stack 11.

  The turbine housing 34 has an inlet 34a through which the exhaust gas is introduced, and an outlet 34b through which the exhaust gas passing through the turbine chamber 37 is exhausted. Further, the fuel cell system 10 includes an exhaust passage 15 that connects the fuel cell stack 11 and the turbine 41 and through which exhaust gas discharged from the outlet 11b of the fuel cell stack 11 flows. The discharge channel 15 is formed of, for example, a pipe. One end of the discharge channel 15 is connected to the outlet 11b, and the other end of the discharge channel 15 is connected to the inlet 34a. The exhaust gas discharged from the outlet 11b flows through the discharge channel 15 and is introduced into the inlet 34a.

  In the turbine housing 34, a communication passage 38 that connects the introduction port 34a and the turbine chamber 37 is formed. The turbine compressor 31 has a pressure adjustment valve 39 that adjusts the pressure of the air in the fuel cell stack 11 by adjusting the cross-sectional area of the communication passage 38. Therefore, in the present embodiment, the pressure regulating valve 39 is disposed on the turbine 41. The pressure regulating valve 39 has, for example, a plurality of nozzle vanes arranged in the circumferential direction at a position on the outer periphery of the turbine wheel 42, and a rotating mechanism for rotating the plurality of nozzle vanes. The cross-sectional area of the communication passage 38 is adjusted by rotating the plurality of nozzle vanes by the rotation mechanism.

  The fuel cell system 10 includes a control device 16. The control device 16 calculates the required power generation amount required for the fuel cell stack 11 based on the operation mode of the accelerator pedal and the like. The control device 16 is electrically connected to the electric motor 23. The control device 16 derives the target torque of the electric motor 23 based on the required power generation amount. Then, the control device 16 controls the driving of the electric motor 23 so that the torque of the electric motor becomes the target torque.

  Further, the control device 16 is electrically connected to the pressure regulating valve 39. The control device 16 derives a target opening of the pressure regulating valve 39 based on the required power generation amount. Then, the control device 16 controls the opening of the pressure adjusting valve 39 so that the opening of the pressure adjusting valve 39 becomes the derived target opening. The pressure of the air supplied to the fuel cell stack 11 is adjusted by controlling the opening of the pressure adjusting valve 39 by the control device 16. The opening of the pressure adjusting valve 39 is the rotation angle of the plurality of nozzle vanes. And the humidity in the fuel cell stack 11 is adjusted by adjusting the pressure of the air supplied to the fuel cell stack 11. The humidity in the fuel cell stack 11 is adjusted to a predetermined desired humidity in order to efficiently generate power in the fuel cell stack 11.

  In addition, the pressure cross-sectional area of the communication passage 38 is adjusted by the pressure adjustment valve 39, so that the pressure of the exhaust gas introduced from the communication passage 38 into the turbine chamber 37 is adjusted. The turbine wheel 42 rotates when the exhaust gas that has passed through the pressure regulating valve 39 is blown. Therefore, in the turbine 41, rotational energy is generated when the turbine wheel 42 is rotated by the exhaust gas. That is, the turbine 41 converts the kinetic energy of the exhaust gas into rotational energy by rotating the turbine wheel 42. In the turbine compressor 31, the kinetic energy of the exhaust gas rotates the turbine wheel 42 to rotate the rotating shaft 33, and the compressor wheel 35 rotates with the rotation of the rotating shaft 33 to compress the air.

  The rotating shaft 33 is rotatably supported by the housing 32 by a bearing (not shown). As the bearing, for example, an air dynamic pressure bearing is used. The air dynamic pressure bearing supports the rotating shaft 33 in contact with the rotating shaft 33 until the rotating speed of the rotating shaft 33 reaches the floating rotation speed at which the rotating shaft 33 floats by the air dynamic pressure bearing. When the rotation speed of the rotating shaft 33 reaches the floating rotation speed, the rotating shaft 33 is floated by the air dynamic pressure bearing due to the dynamic pressure generated between the rotating shaft 33 and the air dynamic pressure bearing. The rotating shaft 33 is supported in a state where the rotating shaft 33 is not in contact with the rotating shaft 33.

  The fuel cell system 10 includes a first turbine downstream flow path 51, a second turbine downstream flow path 52, and an exhaust-side heat exchanger 53. The first turbine downstream flow path 51 is configured by, for example, a pipe or the like. One end of the first turbine downstream flow path 51 is connected to an outlet 34 b of the turbine housing 34. The other end of the first turbine downstream flow path 51 is open to the atmosphere. In the first turbine downstream flow path 51, the exhaust gas that has passed through the turbine wheel 42 and has been discharged from the discharge port 34b flows. Therefore, the exhaust gas that has passed through the turbine wheel 42 flows through the first turbine downstream flow path 51.

  The first turbine downstream flow path 51 extends from the discharge port 34b toward the discharge-side heat exchanger 53. In FIG. 1, the first turbine downstream flow path 51 is illustrated as crossing the turbine compressor 31 for the sake of illustration, but in actuality, the first turbine downstream flow path 51 is It extends to a position where it does not interfere with. The internal passage 511, which is a part of the first turbine downstream passage 51, passes through the exhaust-side heat exchanger 53.

  The internal passage 151, which is a part of the discharge passage 15, passes through the inside of the discharge-side heat exchanger 53. The internal flow path 151 of the discharge flow path 15 and the internal flow path 511 of the first turbine downstream flow path 51 correspond to the exhaust gas flowing through the internal flow path 151 and the internal flow path in the discharge-side heat exchanger 53. The exhaust gas flowing through 511 is arranged so as to be able to exchange heat. Therefore, the discharge side heat exchanger 53 exchanges heat between the discharge gas flowing through the discharge passage 15 and the discharge gas flowing through the first turbine downstream flow passage 51.

  The second turbine downstream flow path 52 is branched from the first turbine downstream flow path 51 and communicates with the compression section upstream flow path 12. The second turbine downstream flow path 52 is configured by, for example, a pipe or the like. A gas-liquid separator 55 is provided at a branch 54 between the first turbine downstream flow path 51 and the second turbine downstream flow path 52. The branch portion 54 between the first turbine downstream flow path 51 and the second turbine downstream flow path 52 is located on the first turbine downstream flow path 51 on the upstream side of the internal flow path 511 in the exhaust gas flow direction. I have. The gas-liquid separator 55 is configured such that, inside the gas-liquid separator 55, the gas flows in the first turbine downstream flow path 51 toward a flow path downstream of the gas-liquid separator 55 in the exhaust gas flow direction, and The gas and the liquid are configured to be separable so that the liquid flows toward the second turbine downstream flow path 52.

  The fuel cell system 10 further includes a supply-side heat exchanger 56. The internal flow path 141, which is a part of the supply flow path 14, passes through the supply-side heat exchanger 56. Further, the internal flow path 512, which is a part of the flow path of the first turbine downstream flow path 51 on the downstream side in the exhaust gas flow direction from the discharge side heat exchanger 53, passes through the supply side heat exchanger 56. ing. The internal flow path 141 of the supply flow path 14 and the internal flow path 512 of the first turbine downstream flow path 51 are connected to the air flowing through the internal flow path 141 and the internal flow path 512 in the supply-side heat exchanger 56. And the exhaust gas flowing therethrough are arranged so as to be able to exchange heat. Accordingly, the supply-side heat exchanger 56 is provided between the air flowing through the supply flow path 14 and the exhaust gas flowing downstream of the exhaust-side heat exchanger 53 in the first turbine downstream flow path 51 in the exhaust gas flow direction. Perform heat exchange.

Next, the operation of the present embodiment will be described.
The temperature of the exhaust gas flowing through the first turbine downstream flow path 51 decreases as the pressure of the exhaust gas decreases when passing through the pressure regulating valve 39 and the speed of the exhaust gas increases. It is lower than the temperature. The heat exchange between the exhaust gas flowing through the discharge flow path 15 and the exhaust gas flowing through the first turbine downstream flow path 51 is performed by the discharge-side heat exchanger 53, so that the exhaust gas flowing through the discharge flow path 15 is reduced. The exhaust gas flowing through the first turbine downstream flow path 51 is cooled. As a result, the water vapor contained in the exhaust gas flowing through the exhaust passage 15 is condensed, and condensed water is generated. The condensed water flows with the exhaust gas through the discharge flow path 15, the inlet 34a, the communication path 38, and the turbine chamber 37, passes through the turbine wheel 42, flows through the first turbine downstream flow path 51, and flows through the gas-liquid separator 55. Leads to.

  In addition, the steam present in the exhaust gas without being condensed in the exhaust heat exchanger 53 decreases the pressure of the exhaust gas when passing through the pressure regulating valve 39 in the turbine 41, and the speed of the exhaust gas decreases. Cooling is performed by increasing the speed, and condensed water is generated by condensing the steam. Then, the condensed water flows through the communication passage 38 and the turbine chamber 37 together with the exhaust gas, passes through the turbine wheel 42, flows through the first turbine downstream flow path 51, and reaches the inside of the gas-liquid separator 55.

  The exhaust gas and the condensed water in the gas-liquid separator 55 are separated into the exhaust gas and the condensed water by the gas-liquid separator 55. In the gas-liquid separator 55, the exhaust gas flows in the first turbine downstream flow path 51 toward a flow path downstream of the gas-liquid separator 55 in the exhaust gas flow direction, and condensed water flows in the second turbine downstream flow path. They are separated from each other so as to flow toward the channel 52. Then, the exhaust gas separated by the gas-liquid separator 55 flows into the first turbine downstream flow path 51 into a flow path downstream of the gas-liquid separator 55 in the exhaust gas flow direction. Exhaust gas that has flowed into the first turbine downstream flow path 51 in a flow path downstream of the gas-liquid separator 55 in the flow direction of the exhaust gas passes through the internal flow paths 511 and 512 and is discharged to the atmosphere. .

  Here, the pressure in the gas-liquid separator 55 is higher than the atmospheric pressure, and the pressure in the compression unit upstream flow path 12 is lower than the atmospheric pressure. , Higher than the pressure in the upstream channel 12 of the compression section. Therefore, the condensed water separated by the gas-liquid separator 55 flows so as to be sucked into the second turbine downstream flow path 52 by a difference between the pressure in the gas-liquid separator 55 and the pressure in the compression section upstream flow path 12. Thus, the compressed gas is supplied to the compression section upstream flow path 12 via the second turbine downstream flow path 52. Thereby, the air flowing in the compression section upstream flow path 12 is humidified by the condensed water supplied from the second turbine downstream flow path 52 to the compression section upstream flow path 12. The humidified air is compressed by the compression unit 25 of the electric compressor 21 and the compressor wheel 35 of the turbine compressor 31, respectively, and is supplied to the fuel cell stack 11 via the supply passage 14. Thereby, the inside of the fuel cell stack 11 becomes wet.

  In addition, the high-temperature air compressed by the electric compressor 21 and the turbine compressor 31 and flowing through the supply flow path 14 and the downstream side of the exhaust-side heat exchanger 53 in the first turbine downstream flow path 51 in the flow direction of the exhaust gas flow. The heat exchange with the flowing exhaust gas is performed by the supply-side heat exchanger 56. Thereby, the air flowing through the supply flow path 14 is cooled by the exhaust gas flowing downstream of the exhaust-side heat exchanger 53 in the first turbine downstream flow path 51 in the flow direction of the exhaust gas. The temperature of the air supplied to the fuel cell stack 11 decreases.

In the above embodiment, the following effects can be obtained.
(1) The heat exchange between the exhaust gas flowing through the discharge flow path 15 and the exhaust gas flowing through the first turbine downstream flow path 51 is performed by the discharge-side heat exchanger 53, so that the exhaust gas flowing through the discharge flow path 15 Is cooled by the exhaust gas flowing through the first turbine downstream flow path 51, and the steam contained in the exhaust gas flowing through the exhaust flow path 15 is condensed to generate condensed water. Then, the condensed water flows from the first turbine downstream flow path 51 into the second turbine downstream flow path 52 and is supplied to the compression section upstream flow path 12 via the second turbine downstream flow path 52. Thereby, the air flowing in the compression section upstream flow path 12 is humidified by the condensed water supplied from the second turbine downstream flow path 52 to the compression section upstream flow path 12. Since the humidified air is supplied to the fuel cell stack 11 through the supply flow path 14, the inside of the fuel cell stack 11 can be in a wet state. Therefore, in order to make the inside of the fuel cell stack 11 wet, it is not necessary to provide a humidifier as in the related art so as to straddle the supply passage 14 and the discharge passage 15. As a result, the size of the fuel cell system 10 can be reduced.

  (2) A gas-liquid separator 55 is provided at a branch portion 54 between the first turbine downstream flow path 51 and the second turbine downstream flow path 52. According to this, the exhaust gas and the condensed water flowing through the first turbine downstream flow path 51 are discharged by the gas-liquid separator 55 at the branch portion 54 between the first turbine downstream flow path 51 and the second turbine downstream flow path 52. Separated into gas and condensed water. Then, the exhaust gas separated by the gas-liquid separator 55 flows into the first turbine downstream flow path 51 into a flow path downstream of the gas-liquid separator 55 in the flow direction of the exhaust gas, and is discharged by the gas-liquid separator 55. The separated condensed water flows into the second turbine downstream flow path 52. Thereby, the amount of condensed water supplied to the compression section upstream flow path 12 via the second turbine downstream flow path 52 can be increased. Therefore, since the air flowing through the compression section upstream flow path 12 is easily humidified, the inside of the fuel cell stack 11 can be efficiently wetted.

  (3) The fuel cell system 10 performs heat transfer between the air flowing through the supply flow path 14 and the exhaust gas flowing downstream of the exhaust heat exchanger 53 in the first turbine downstream flow path 51 in the exhaust gas flow direction. A supply-side heat exchanger 56 for performing exchange is further provided. According to this, the high-temperature air compressed by the electric compressor 21 and flowing through the supply flow path 14 is discharged from the first turbine downstream flow path 51 downstream of the discharge-side heat exchanger 53 in the exhaust gas flow direction. Cooled by gas. Therefore, the temperature of the air supplied to the fuel cell stack 11 via the supply flow path 14 can be lowered, so that the power generation efficiency of the fuel cell stack 11 can be improved.

  (4) The condensed water supplied from the second turbine downstream flow path 52 to the compression section upstream flow path 12 becomes steam by the heat generated in the compression section 25 by compressing the air. Since the air compressed by the compression unit 25 is cooled by the latent heat of evaporation of the condensed water, the temperature of the air discharged from the electric compressor 21 can be lowered, and the power generation efficiency of the fuel cell stack 11 is improved. be able to.

  (5) Since the exhaust gas separated by the gas-liquid separator 55 flows into the first turbine downstream flow path 51 into a flow path downstream of the gas-liquid separator 55 in the exhaust gas flow direction, the first turbine downstream flow It is possible to reduce the amount of exhaust gas flowing from the passage 51 through the second turbine downstream passage 52 to the compression section upstream passage 12. As a result, the amount of exhaust gas that flows through the compression unit upstream flow path 12 and is supplied to the compression unit 25 decreases, and therefore the amount of exhaust gas compressed by the compression unit 25 decreases. As a result, the compression efficiency of air in the compression unit 25 can be improved.

  (6) As in the prior art, the humidifier provided so as to straddle the supply flow path 14 and the discharge flow path 15 is provided with, for example, a moisture-exchangeable hollow fiber membrane, and a fuel cell stack is provided via the hollow fiber membrane. Since the air supplied to the humidifier 11 is humidified, the pressure loss of the exhaust gas by the humidifier is likely to occur, and the kinetic energy of the exhaust gas for rotating the turbine wheel 42 is reduced. Then, since the rotation energy generated by the rotation of the turbine wheel 42 decreases, it is necessary to increase the compression work performed by the compression unit 25 of the electric compressor 21. Therefore, the load on the electric motor 23 that drives the compression unit 25 increases, and the power consumption of the electric motor 23 required to drive the compression unit 25 increases.

  The fuel cell system 10 of the present embodiment employs a configuration in which the discharge-side heat exchanger 53 and the supply-side heat exchanger 56 in which no hollow fiber membrane or the like is provided are used. And the pressure loss of the exhaust gas can be suppressed. Therefore, since the kinetic energy of the exhaust gas for rotating the turbine wheel 42 is suppressed from being reduced due to the pressure loss of the exhaust gas, the rotational energy generated by the rotation of the turbine wheel 42 is reduced. Is suppressed. As a result, the power consumption of the electric motor 23 required to drive the compression unit 25 is easily reduced.

  The above embodiment can be modified and implemented as follows. The above embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

  In the embodiment, the fuel cell system 10 may have a configuration in which the gas-liquid separator 55 is not provided at the branch portion 54 between the first turbine downstream channel 51 and the second turbine downstream channel 52. Even in this case, a part of the condensed water flows from the first turbine downstream flow path 51 to the second turbine downstream flow path 52 and is supplied to the compression section upstream flow path 12 via the second turbine downstream flow path 52. Is done. In short, in the fuel cell system 10, at least a part of the condensed water flows from the first turbine downstream flow path 51 to the second turbine downstream flow path 52 and passes through the second turbine downstream flow path 52 to the compression section upstream flow path. 12 may be used.

In the embodiment, the fuel cell system 10 may be configured not to include the supply-side heat exchanger 56.
In the embodiment, the positional relationship between the electric compressor 21 and the turbine compressor 31 may be reversed. That is, the electric compressor 21 may compress the air compressed once by the turbine compressor 31.

  In the embodiment, the turbine compressor 31 may include an electric motor that rotates the rotating shaft 33. In this case, the electric motor is provided between the compressor wheel 35 and the turbine wheel 42 on the rotating shaft 33. Then, in the fuel cell system 10, the electric compressor 21 may be deleted, and the turbine compressor 31 may function as an electric compressor included in the fuel cell system 10. In this case, the compressor wheel 35 functions as a compression unit of the electric compressor.

  In the embodiment, the fuel cell system 10 does not need to include the turbine compressor 31 and only needs to include at least the turbine 41. Then, using the rotational energy generated by the rotation of the turbine wheel 42 in the turbine 41, for example, a regenerative electric power is generated in the generator, and the regenerative electric power generated in the generator is used for driving the compressor 25. It may be used as power supplied to the motor 23.

  In the embodiment, the specific configuration of the pressure regulating valve 39 is not particularly limited. In short, the pressure adjusting valve 39 may be any valve that can adjust the pressure of the air supplied to the fuel cell stack 11 by adjusting the cross-sectional area of the communication passage 38.

  In the embodiment, the pressure regulating valve 39 is provided in the turbine compressor 31. However, the present invention is not limited to this, and the pressure regulating valve 39 may be provided between the discharge heat exchanger 53 and the turbine housing 34 in the discharge flow path 15. Good. In short, the pressure regulating valve 39 may not be arranged in the turbine 41 but may be arranged in the discharge passage 15. In this case, the exhaust-side heat exchanger 53 exchanges heat between the exhaust gas flowing upstream of the pressure regulating valve 39 in the exhaust flow path 15 and the exhaust gas flowing through the first turbine downstream flow path 51.

In the embodiment, the specific type of the compression unit 25 is not limited to the impeller type as in the present embodiment, and may be any type, such as a scroll type or a roots type.
In the embodiment, the fuel cell system 10 may be mounted on a device other than the vehicle.

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell system, 11 ... Fuel cell stack, 12 ... Compression part upstream flow path, 14 ... Supply flow path, 15 ... Discharge flow path, 21 ... Electric compressor, 23 ... Electric motor, 25 ... Compression part, 39 ... Pressure regulating valve, 41 ... Turbine, 42 ... Turbine wheel, 51 ... First turbine downstream flow path, 52 ... Second turbine downstream flow path, 53 ... Discharge side heat exchanger, 54 ... Branch part, 55 ... Gas-liquid separator , 56 ... supply side heat exchanger.

Claims (3)

A fuel cell stack that performs a chemical reaction between fuel gas and oxygen in the air to generate power,
A compression unit that compresses air supplied to the fuel cell stack, and an electric compressor including an electric motor that drives the compression unit;
A turbine having a turbine wheel rotated by exhaust gas discharged from the fuel cell stack;
A supply channel for supplying air compressed by the electric compressor to the fuel cell stack,
An exhaust passage connecting the fuel cell stack and the turbine and through which exhaust gas discharged from the fuel cell stack flows,
A pressure regulating valve arranged in the exhaust passage or the turbine and regulating a pressure of air in the fuel cell stack,
A fuel cell system in which the exhaust gas discharged from the fuel cell stack contains water vapor,
A compression section upstream flow path that communicates with the atmosphere and supplies air from the atmosphere to the compression section;
A first turbine downstream flow path through which the exhaust gas that has passed through the turbine wheel flows;
A second turbine downstream flow path branched from the first turbine downstream flow path and communicating with the compression section upstream flow path;
A discharge-side heat exchanger for performing heat exchange between exhaust gas flowing upstream of the pressure regulating valve in the discharge flow path and exhaust gas flowing in the first turbine downstream flow path. And a fuel cell system.   The fuel cell system according to claim 1, wherein a gas-liquid separator is provided at a branch between the first turbine downstream flow path and the second turbine downstream flow path.   A supply-side heat exchanger that performs heat exchange between air flowing through the supply passage and exhaust gas flowing downstream of the exhaust-side heat exchanger in the first turbine downstream passage in the flow direction of the exhaust gas. The fuel cell system according to claim 1, further comprising: