JP2024005650A - fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently increase regenerative power generated in a turbine.

SOLUTION: A fuel cell system 10 has a storage tank 30 which stores water contained in exhaust gas discharged from a fuel cell stack. The storage tank 30 has: a supply port 35 which is connected to an air layer 38 inside the storage tank 30, and which supplies the storage tank 30 with the exhaust gas discharged from the fuel cell stack; a gas-liquid separation part 36 which separates the water from the exhaust gas supplied from the supply port 35; a storage part 37 in which the water separated by the gas-liquid separation part 36 is stored; a heat exchange part 50 which exchanges heat between the water stored in the storage part 37 and air blown out from a motor compressor; and an exhaust port 39 which is connected to the air layer 38, and which discharges, to a turbine, the exhaust gas after the water has been separated therefrom by the gas-liquid separation part 36.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a fuel cell system.

The fuel cell system includes a fuel cell stack. A fuel cell stack generates electricity by causing a chemical reaction between fuel gas and oxygen in the air. Further, the fuel cell system may include an electric compressor and a turbine. The electric compressor includes a compression section and a motor. The compression section compresses air supplied to the fuel cell stack. The motor drives the compression section. The turbine has a turbine wheel. The turbine wheel is rotated by exhaust gas discharged from the fuel cell stack and assists in driving the motor. Specifically, the turbine wheel rotates as exhaust gas discharged from the fuel cell stack is supplied to the turbine. Exhaust gas supplied to the turbine is expanded by rotation of the turbine wheel. As the exhaust gas expands, the energy of the exhaust gas is converted into rotational energy. In this way, the energy of the exhaust gas is converted into rotational energy, thereby generating regenerative power in the turbine. The drive of the motor is assisted by the regenerative power generated by the turbine.

For example, the fuel cell system disclosed in Patent Document 1 includes a heat exchanger that exchanges heat between air compressed by a compression section of an electric compressor and exhaust gas discharged from a fuel cell stack. Then, the exhaust gas discharged from the fuel cell stack is heated in the heat exchanger by air compressed in the compression section. This increases the energy of the exhaust gas, so the rotational energy converted by expanding the exhaust gas in the turbine due to the rotation of the turbine wheel increases. As a result, the regenerative power generated by the turbine increases, so that the drive of the motor is efficiently assisted.

Japanese Patent Application Publication No. 2013-168308

By the way, for example, pressure loss that occurs when exhaust gas passes through a heat exchanger becomes a factor that prevents an increase in regenerative power generated in a turbine. Therefore, it is desired to efficiently increase the regenerative power generated by the turbine.

A fuel cell system that solves the above problems includes a fuel cell stack that generates electricity by chemically reacting fuel gas and oxygen in the air, a compression section that compresses air supplied to the fuel cell stack, and the compression section. and a turbine having a turbine wheel that is rotated by exhaust gas discharged from the fuel cell stack to assist in driving the motor. and a storage tank for storing water contained in the exhaust gas discharged from the fuel cell stack, the storage tank being connected to an air layer in the storage tank and for storing water contained in the exhaust gas discharged from the fuel cell stack. A supply port that supplies gas into the storage tank, a gas-liquid separation section that separates water from the exhaust gas supplied from the supply port, and a storage section that stores the water separated by the gas-liquid separation section. a heat exchange section that exchanges heat between the water stored in the storage section and the air discharged from the electric compressor; and a heat exchange section that is connected to the air layer and that separates water in the gas-liquid separation section. and an exhaust port for discharging subsequent exhaust gas to the turbine.

According to this, the exhaust gas discharged from the fuel cell stack is supplied to the air layer within the storage tank via the supply port. The gas-liquid separation section separates water from the exhaust gas supplied from the supply port. The water separated by the gas-liquid separation section is then stored in the storage section. The water stored in the storage section undergoes heat exchange with the air discharged from the electric compressor via the heat exchange section, and is evaporated into water vapor. The water vapor is discharged to the turbine through the exhaust port as exhaust gas together with the exhaust gas after water has been separated in the gas-liquid separation section. In this way, the mass of the exhaust gas supplied to the turbine increases by the amount of water vapor added. As a result, the mass of the exhaust gas that expands as the turbine wheel rotates increases, which increases the amount of work done by the turbine wheel. This increases the regenerative power generated by the turbine. Further, the exhaust gas after water has been separated in the gas-liquid separation section passes through an air layer in the storage tank and is discharged from the discharge port to the turbine. Therefore, pressure loss of the exhaust gas within the storage tank is less likely to occur, and an increase in regenerative power generated in the turbine is avoided. With the above, the regenerative power generated by the turbine can be efficiently increased.

In the fuel cell system, the storage tank includes a water storage amount control unit that controls the amount of water stored in the storage portion so that the liquid level of the water stored in the storage portion does not exceed a predetermined height. The heat exchange section has a heat exchange main body that is arranged vertically below the predetermined height, and a heat exchange main body that extends from the heat exchange main body and extends beyond the predetermined height to the air layer. It is preferable to have a protrusion that protrudes.

According to this, the protruding part can cause a capillary phenomenon that sucks up the liquid level of the water stored in the storage part, so it is possible to increase the surface area between the gas phase and the liquid phase in the storage tank. can. As a result, the water stored in the storage section can be efficiently evaporated.

In the fuel cell system, the turbine includes a turbine chamber that accommodates the turbine wheel, and a fixed nozzle that throttles the flow rate of exhaust gas supplied to the turbine chamber, and the turbine includes air discharged from the electric compressor. an introduction flow path that introduces the air into the heat exchange section; a bypass flow path that branches from the introduction flow path and supplies air flowing through the introduction flow path to the fuel cell stack by bypassing the heat exchange section; Flow rate adjustment that adjusts the flow rate of air introduced from the electric compressor to the heat exchange section via the introduction flow path by adjusting the flow rate of air that branches and flows from the introduction flow path to the bypass flow path. It would be good to have a section and.

According to this, the amount of water vapor generated by heat exchange between the water stored in the storage part and the air discharged from the electric compressor via the heat exchange part can be adjusted. Therefore, even if the flow rate of the exhaust gas supplied to the turbine chamber is uniquely determined, such as when the turbine has a fixed nozzle, the flow rate of the exhaust gas that expands due to the rotation of the turbine wheel is limited. Can be adjusted. As a result, the expansion ratio of the turbine can be adjusted, so the turbine can be operated with high turbine efficiency.

In the fuel cell system, the heat exchange section has a plurality of piping sections arranged vertically in parallel within the storage tank, and air discharged from the electric compressor flows through each of the piping sections; Each of the piping sections preferably performs heat exchange between the water stored in the storage section and the air discharged from the electric compressor.

For example, when the liquid level of the water stored in the storage section decreases, a piping section located vertically above among the plurality of piping sections may be exposed to the air layer within the storage tank. In the piping section exposed to the air layer within the storage tank, heat exchange between the water stored in the storage section and the air discharged from the electric compressor becomes difficult to occur. In this way, due to fluctuations in the liquid level of the water stored in the storage section, heat exchange occurs between the water stored in the storage section and the air discharged from the electric compressor through the heat exchange section. The amount of water vapor produced can be fine-tuned.

In the fuel cell system, the heat exchange section may include a porous material that is thermally coupled to the heat exchange main body and is disposed vertically below the predetermined height.

According to this, heat exchange is performed between the water stored in the storage part and the porous material, so that the water stored in the storage part is evaporated and becomes water vapor. Therefore, the water stored in the storage section can be efficiently evaporated.

According to this invention, the regenerative power generated by the turbine can be efficiently increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a fuel cell system in an embodiment. It is a sectional view for explaining a water storage tank. It is a sectional view for explaining a water storage tank. It is a graph which shows the relationship between the expansion ratio of a turbine, and turbine efficiency. It is a graph showing the relationship between the expansion ratio of the turbine and the corrected flow rate of exhaust gas.

An embodiment of a fuel cell system will be described below with reference to FIGS. 1 to 5. The fuel cell system of this embodiment is installed in a fuel cell vehicle.
<Overall configuration of fuel cell system 10>
As shown in FIG. 1, the fuel cell system 10 includes a fuel cell stack 11, an electric compressor 12, and a turbine 13. The fuel cell stack 11 includes, for example, a plurality of cells. Each cell is configured by stacking an oxygen electrode, a hydrogen electrode, and an electrolyte membrane disposed between the two electrodes. The fuel cell stack 11 generates power by causing a chemical reaction between hydrogen, which is a fuel gas, and oxygen in the air.

Only about 20% of the oxygen that contributes to the power generation of the fuel cell stack 11 exists in the air. Therefore, about 80% of the air supplied to the fuel cell stack 11 is discharged from the fuel cell stack 11 as exhaust gas without contributing to the power generation of the fuel cell stack 11. The exhaust gas discharged from the fuel cell stack 11 contains water generated when the fuel cell stack 11 generates power.

The fuel cell stack 11 is electrically connected to a running motor (not shown). The traveling motor is driven using electric power generated by the fuel cell stack 11 as a power source. Power from the travel motor is transmitted to the axle via a power transmission mechanism (not shown). A fuel cell vehicle travels at a vehicle speed that corresponds to the degree of opening of the accelerator pedal.

<Electric compressor 12>
The electric compressor 12 includes a compression section 14 and a motor 15. The electric compressor 12 also includes a rotating shaft 16 . The compression section 14 is connected to a first end of the rotating shaft 16. The compression unit 14 is, for example, an impeller. The compression part 14 is rotatable integrally with the rotating shaft 16. Compressor 14 compresses air supplied to fuel cell stack 11 . Motor 15 rotates rotating shaft 16 . The compression section 14 is driven by the rotation of the rotating shaft 16. Therefore, the motor 15 drives the compression section 14.

<Turbine 13>
The turbine 13 has a turbine wheel 17 and a turbine housing 18. Turbine wheel 17 is connected to the second end of rotating shaft 16 . The turbine wheel 17 is rotatable integrally with the rotating shaft 16.

The turbine housing 18 has a cylindrical shape and has a circular discharge port 19 . Turbine housing 18 is fixed to electric compressor 12. Therefore, the turbine 13 is integrated into the electric compressor 12.

The turbine 13 has a turbine chamber 20 and a fixed nozzle 21. Turbine chamber 20 is formed in turbine housing 18 . Turbine chamber 20 accommodates turbine wheel 17 . The discharge port 19 communicates with the turbine chamber 20 . The turbine 13 has a suction chamber 22 . Suction chamber 22 is formed in turbine housing 18 . The suction chamber 22 extends around the axis of the discharge port 19 around the turbine chamber 20 . The exhaust gas discharged from the fuel cell stack 11 is sucked into the suction chamber 22 .

The fixed nozzle 21 is a passage formed in the turbine housing 18 and communicating between the turbine chamber 20 and the suction chamber 22 . The fixed nozzle 21 extends in the radial direction of the rotating shaft 16. The fixed nozzle 21 supplies the exhaust gas sucked into the suction chamber 22 from the radial direction of the rotating shaft 16 to the turbine chamber 20 . The fixed nozzle 21 throttles the flow rate of exhaust gas supplied to the turbine chamber 20. The turbine wheel 17 is rotated by exhaust gas supplied to the turbine chamber 20 . Therefore, the turbine wheel 17 is rotated by the exhaust gas discharged from the fuel cell stack 11. The turbine wheel 17 is rotated by the exhaust gas and assists in driving the motor 15.

<Storage tank 30>
As shown in FIGS. 2 and 3, the fuel cell system 10 includes a storage tank 30. The storage tank 30 stores water contained in exhaust gas discharged from the fuel cell stack 11. The storage tank 30 has, for example, a square box shape. The storage tank 30 has an upper wall 31, a lower wall 32, a first side wall 33, and a second side wall 34. The upper wall 31 and the lower wall 32 face each other in the vertical direction. The first side wall 33 and the second side wall 34 face each other in the horizontal direction.

The storage tank 30 has a supply port 35 . The supply port 35 is provided at a portion of the upper wall 31 of the storage tank 30 near the first side wall 33 . The supply port 35 supplies exhaust gas discharged from the fuel cell stack 11 into the storage tank 30 .

The storage tank 30 has a gas-liquid separation section 36. The gas-liquid separation section 36 is a cylindrical section that protrudes from the inner surface of the upper wall 31. The gas-liquid separator 36 protrudes from the inner surface of the upper wall 31 while surrounding the opening of the supply port 35 to the inside of the storage tank 30 . The exhaust gas supplied into the storage tank 30 from the supply port 35 passes inside the gas-liquid separation section 36 . The water contained in the exhaust gas is centrifuged from the exhaust gas when it passes inside the gas-liquid separation section 36 . Further, the water contained in the exhaust gas is also separated from the exhaust gas when the exhaust gas collides with the inner surface of the gas-liquid separation section 36 . Therefore, the gas-liquid separator 36 separates water from the exhaust gas supplied from the supply port 35.

Water separated from the exhaust gas by the gas-liquid separator 36 is stored in the storage tank 30. Therefore, the storage tank 30 has a storage section 37 in which water separated by the gas-liquid separation section 36 is stored. In the storage tank 30, the space other than the storage section 37 in which water is stored is an air layer 38. Therefore, the upper part of the storage tank 30 forms an air layer 38. The supply port 35 is connected to an air layer 38 within the storage tank 30.

The storage tank 30 has an outlet 39 . The discharge port 39 is provided at a portion of the upper wall 31 of the storage tank 30 near the second side wall 34 . The outlet 39 is connected to the air layer 38. The exhaust port 39 discharges the exhaust gas from which water has been separated in the gas-liquid separator 36 to the turbine 13 .

The storage tank 30 has a water storage amount control section 40. The water storage amount control unit 40 controls the amount of water stored in the storage portion 37 so that the liquid level of the water stored in the storage portion 37 does not exceed a predetermined height H1. The predetermined height H1 is a preset height of the water level. The predetermined height H1 is lower than the lower end of the gas-liquid separation section 36 within the storage tank 30. Therefore, the gas-liquid separator 36 is arranged in the storage tank 30 at a position higher than the predetermined height H1.

The water storage amount control unit 40 includes a drain pipe 41 and a drain valve 42. The drain pipe 41 is provided on the first side wall 33 of the storage tank 30. The inside of the drain pipe 41 communicates with the inside of the storage tank 30. The drain pipe 41 is provided at a portion of the first side wall 33 that corresponds to a predetermined height H1. Therefore, the opening position of the drain pipe 41 relative to the inside of the storage tank 30 is a position within the storage tank 30 that corresponds to the predetermined height H1. Then, when the liquid level of the water stored in the storage section 37 reaches a predetermined height H1, the water stored in the storage section 37 flows into the drain pipe 41.

The drain valve 42 is configured to open when a preset amount of water stored in the storage portion 37 flows into the drain valve 42 through the drain pipe 41. Therefore, the drain valve 42 is configured to remain closed until the water stored in the storage section 37 flows into the drain valve 42 by a preset amount through the drain pipe 41. When the drain valve 42 is opened, the water flowing inside the drain pipe 41 is discharged to the outside. In this way, the water storage amount control section 40 controls the amount of water stored in the storage section 37 so that the liquid level of the water stored in the storage section 37 does not exceed the predetermined height H1.

The storage tank 30 has a heat exchange section 50. The heat exchange section 50 includes a heat exchange main body section 51, an upstream header 52, and a downstream header 53. The heat exchange main body part 51 has a plurality of piping parts 54. Therefore, the heat exchange section 50 has a plurality of piping sections 54.

Each piping portion 54 has, for example, a rectangular cylindrical shape. Each piping section 54 is, for example, a flat tube. Each piping section 54 is made of, for example, metal with excellent thermal conductivity. Each piping section 54 crosses inside the storage tank 30 in a state where it is bridged between the first side wall 33 and the second side wall 34 . The plurality of piping sections 54 are arranged in line in the vertical direction within the storage tank 30. The thickness direction of each piping section 54 coincides with the vertical direction. Each piping section 54 is arranged vertically below a predetermined height H1. Therefore, the heat exchange main body portion 51 is arranged below the predetermined height H1 in the vertical direction.

The upstream header 52 is connected to a first end of each piping section 54. Note that the first end portion of each piping portion 54 is an end portion of each piping portion 54 located on the second side wall 34 side. The upstream header 52 distributes air discharged from the electric compressor 12 into each piping section 54 . The air distributed from the upstream header 52 into each piping section 54 flows within each piping section 54 . Therefore, the air discharged from the electric compressor 12 flows within each piping section 54. Each piping section 54 performs heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12. Therefore, the heat exchange section 50 performs heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12.

The downstream header 53 is connected to the second end of each piping section 54. Note that the second end portion of each piping portion 54 is an end portion of each piping portion 54 located on the first side wall 33 side. Air that has passed through each piping section 54 joins the downstream header 53 . Then, the downstream header 53 causes the air from each piping section 54 to flow toward the fuel cell stack 11.

The heat exchange section 50 has a plurality of protrusions 55. Each protrusion 55 is shaped like a thin plate. Each protrusion 55 is made of, for example, metal with excellent thermal conductivity. Each protrusion 55 is arranged within the storage tank 30 with the thickness direction of each protrusion 55 aligned with the horizontal direction. The plurality of protrusions 55 are arranged at intervals in the horizontal direction within the storage tank 30. The plurality of protrusions 55 are arranged at regular intervals in the horizontal direction.

Each protrusion 55 extends from the heat exchange body 51 . Specifically, each protruding portion 55 is supported by each piping portion 54. Each piping portion 54 penetrates each protrusion 55 in the thickness direction of the protrusion 55 . Each protruding portion 55 extends upward into the storage tank 30 from each piping portion 54 . Each protruding portion 55 extends from each piping portion 54 to a position exceeding a predetermined height H1. Therefore, each protrusion 55 extends from the heat exchange main body 51 and protrudes into the air layer 38 beyond the predetermined height H1. Each protruding portion 55 is thermally coupled to each piping portion 54. Each protrusion 55 causes a capillary phenomenon that sucks up the liquid level of the water stored in the storage portion 37 .

The heat exchange section 50 has a porous material 56. Porous material 56 is thermally coupled to heat exchange body 51 . The porous material 56 is arranged in the storage tank 30 in close contact with the lowest piping part 54 among the plurality of piping parts 54 . Therefore, the porous material 56 is thermally coupled to the heat exchange main body portion 51 and is arranged below the predetermined height H1 in the vertical direction.

<Each flow path>
As shown in FIG. 1, the fuel cell system 10 includes an introduction channel 61. A first end of the introduction channel 61 is connected to a discharge chamber (not shown) of the electric compressor 12. The second end of the introduction channel 61 is connected to the upstream header 52 of the heat exchange section 50 . The introduction flow path 61 connects the electric compressor 12 and the heat exchange section 50. The introduction flow path 61 introduces air discharged from the electric compressor 12 to the upstream header 52. Therefore, the introduction flow path 61 introduces the air discharged from the electric compressor 12 into the heat exchange section 50.

The fuel cell system 10 includes an air supply channel 62. A first end of the air supply channel 62 is connected to the downstream header 53 of the heat exchange section 50 . A second end of the air supply channel 62 is connected to the fuel cell stack 11. The air supply channel 62 connects the heat exchange section 50 and the fuel cell stack 11. The air supply channel 62 supplies the air that has passed through the heat exchange section 50 to the fuel cell stack 11.

The fuel cell system 10 includes an exhaust flow path 63. A first end of the discharge flow path 63 is connected to the fuel cell stack 11 . The second end of the discharge channel 63 is connected to the supply port 35 of the storage tank 30. The discharge flow path 63 connects the fuel cell stack 11 and the supply port 35 of the storage tank 30. The exhaust flow path 63 allows exhaust gas discharged from the fuel cell stack 11 to flow toward the supply port 35 . The exhaust gas flowing through the exhaust flow path 63 is supplied to the supply port 35 .

The fuel cell system 10 includes a gas supply channel 64. A first end of the gas supply channel 64 is connected to the outlet 39 of the storage tank 30. A second end of the gas supply channel 64 is connected to the suction chamber 22 of the turbine 13 . The gas supply channel 64 connects the outlet 39 of the storage tank 30 and the suction chamber 22 of the turbine 13 . The gas supply channel 64 allows exhaust gas discharged from the exhaust port 39 to flow toward the suction chamber 22 . The exhaust gas flowing through the gas supply channel 64 is supplied to the suction chamber 22 .

The fuel cell system 10 includes a bypass flow path 65. The first end of the bypass flow path 65 is connected to the middle of the introduction flow path 61 . Therefore, the bypass flow path 65 is branched from the introduction flow path 61. The second end of the bypass flow path 65 is connected to the middle of the air supply flow path 62 . The air that branches from the introduction channel 61 to the bypass channel 65 joins the air supply channel 62 via the bypass channel 65, and then is supplied to the fuel cell stack 11 via the air supply channel 62. be done. Therefore, the bypass flow path 65 supplies the air flowing through the introduction flow path 61 to the fuel cell stack 11 by bypassing the heat exchange section 50 . Note that an intercooler 66 is provided in the bypass flow path 65. The air flowing through the bypass passage 65 is cooled by an intercooler 66.

<Flow rate adjustment section 67>
The fuel cell system 10 includes a flow rate adjustment section 67. The flow rate adjustment unit 67 is, for example, a flow control valve provided at a connection point between the introduction channel 61 and the bypass channel 65. The fuel cell system 10 also includes a controller 70. The controller 70 is electrically connected to the flow rate adjustment section 67. The controller 70 controls the valve opening degree of the flow rate adjustment section 67. The flow rate adjustment unit 67 adjusts the flow rate of the air branching from the introduction flow path 61 to the bypass flow path 65 by having the valve opening degree controlled by the controller 70 . The flow rate adjustment section 67 adjusts the flow rate of the air that branches from the introduction channel 61 to the bypass channel 65 to adjust the flow rate of the air introduced from the electric compressor 12 to the heat exchange section 50 via the introduction channel 61. Adjust the flow rate.

The fuel cell system 10 includes a rotation speed sensor 71, a flow rate sensor 72, a pressure sensor 73, and a temperature sensor 74. The rotation speed sensor 71, the flow rate sensor 72, the pressure sensor 73, and the temperature sensor 74 are electrically connected to the controller 70.

The rotation speed sensor 71 detects the rotation speed of the turbine wheel 17 . The rotation speed sensor 71 outputs a detection signal regarding the rotation speed of the turbine wheel 17 to the controller 70 . The flow rate sensor 72 detects the flow rate of air sucked into the electric compressor 12 from the outside. The flow rate sensor 72 outputs a detection signal regarding the air flow rate to the controller 70. Pressure sensor 73 detects the pressure of exhaust gas discharged from fuel cell stack 11 . The pressure sensor 73 outputs a detection signal regarding the pressure of exhaust gas to the controller 70. Temperature sensor 74 detects the temperature of exhaust gas sucked into suction chamber 22 of turbine 13 . The temperature sensor 74 outputs a detection signal regarding the temperature of exhaust gas to the controller 70.

FIG. 4 shows the relationship between the expansion ratio of the turbine 13 and the turbine efficiency. The controller 70 stores in advance a map in which the expansion ratio of the turbine 13 and the turbine efficiency are related. The relationship between the expansion ratio of the turbine 13 and the turbine efficiency is shown, for example, as a characteristic line L1 shown in FIG. 4. A characteristic line L1 indicating the relationship between the expansion ratio of the turbine 13 and the turbine efficiency is determined by the rotation speed of the turbine wheel 17. In addition, in FIG. 4, the characteristic line L1 determined by the rotation speed of the turbine wheel 17 under predetermined operating conditions is shown as an example. The controller 70 stores in advance a program for deriving a characteristic line L1 indicating the relationship between the expansion ratio of the turbine 13 and the turbine efficiency based on the rotation speed of the turbine wheel 17 detected by the rotation speed sensor 71. . Note that the controller 70 stores in advance a program for calculating the expansion ratio of the turbine 13 based on the pressure detected by the pressure sensor 73.

FIG. 5 shows the relationship between the expansion ratio of the turbine 13 and the corrected flow rate of exhaust gas. Here, the "corrected flow rate of exhaust gas" is a flow rate obtained by correcting the mass flow rate of exhaust gas flowing into the turbine 13 based on the pressure of the exhaust gas and the temperature of the exhaust gas. The corrected flow rate of exhaust gas is the flow rate before passing through the turbine wheel 17. As shown by the solid line L2 in FIG. 5, the corrected flow rate of exhaust gas increases as the expansion ratio of the turbine 13 increases. The controller 70 stores in advance a correction program that corrects the flow rate detected by the flow rate sensor 72 to a corrected flow rate based on the pressure detected by the pressure sensor 73 and the pressure detected by the temperature sensor 74. ing.

The controller 70 stores in advance a program for adjusting the valve opening degree of the flow rate adjustment section 67 so that the turbine efficiency approaches the peak value ηmax. For example, consider a case where the expansion ratio of the turbine 13 calculated by the controller 70 is lower than the expansion ratio corresponding to the peak value ηmax, as at state point P1 shown in FIG. 4. In such a case, the controller 70 adjusts the valve opening degree of the flow rate adjustment unit 67 so that the flow rate of air introduced from the electric compressor 12 into the heat exchange unit 50 via the introduction flow path 61 increases. That is, the valve opening degree of the flow rate adjustment section 67 is adjusted by the controller 70 so that the flow rate of the air branching from the introduction flow path 61 to the bypass flow path 65 is reduced.

On the other hand, consider a case where the expansion ratio of the turbine 13 calculated by the controller 70 is higher than the expansion ratio corresponding to the peak value ηmax, for example, as in state point P2 shown in FIG. 4. In such a case, the controller 70 adjusts the valve opening degree of the flow rate adjustment unit 67 so that the flow rate of air introduced from the electric compressor 12 to the heat exchange unit 50 via the introduction flow path 61 is reduced. That is, the valve opening degree of the flow rate adjustment section 67 is adjusted by the controller 70 so that the flow rate of air branching from the introduction flow path 61 to the bypass flow path 65 increases.

[Operation of embodiment]
Next, the operation of this embodiment will be explained.
Exhaust gas discharged from the fuel cell stack 11 is supplied to the air layer 38 in the storage tank 30 via the supply port 35. The gas-liquid separator 36 separates water from the exhaust gas supplied from the supply port 35. The water separated by the gas-liquid separation section 36 is stored in the storage section 37. The water stored in the storage section 37 is evaporated into water vapor by exchanging heat with the air discharged from the electric compressor 12 via the heat exchange section 50 .

Here, each protrusion 55 causes a capillary phenomenon that sucks up the liquid level of the water stored in the storage part 37. Therefore, since the surface area between the gas phase and the liquid phase in the storage tank 30 is increased, the water stored in the storage section 37 is efficiently evaporated. Furthermore, heat exchange between the water stored in the storage section 37 and the porous material 56 evaporates the water stored in the storage section 37 and turns it into water vapor. Therefore, the water stored in the storage section 37 is efficiently evaporated.

The water vapor is discharged to the turbine 13 through the exhaust port 39 as exhaust gas together with the exhaust gas after water has been separated in the gas-liquid separator 36 . In this way, the mass of the exhaust gas supplied to the turbine 13 increases by the amount of water vapor added. As a result, the mass of the exhaust gas that expands due to the rotation of the turbine wheel 17 increases, so the workload of the turbine wheel 17 increases. This increases the regenerative power generated by the turbine 13. Furthermore, the exhaust gas after water has been separated in the gas-liquid separation section 36 passes through the air layer 38 in the storage tank 30 and is discharged from the discharge port 39 to the turbine 13 . Therefore, pressure loss of the exhaust gas within the storage tank 30 is less likely to occur, and an increase in regenerative power generated in the turbine 13 is prevented from being hindered.

For example, consider a case where the expansion ratio of the turbine 13 calculated by the controller 70 is lower than the expansion ratio corresponding to the peak value ηmax, as at state point P1 shown in FIG. 4. In such a case, the controller 70 adjusts the valve opening degree of the flow rate adjustment unit 67 so that the flow rate of air introduced from the electric compressor 12 into the heat exchange unit 50 via the introduction flow path 61 increases. That is, the valve opening degree of the flow rate adjustment section 67 is adjusted by the controller 70 so that the flow rate of the air branching from the introduction flow path 61 to the bypass flow path 65 is reduced.

This increases the amount of water vapor generated by heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 via the heat exchange section 50. Therefore, since the corrected flow rate of the exhaust gas increases, the flow rate of the exhaust gas expanded by the rotation of the turbine wheel 17 increases. Therefore, the expansion ratio of the turbine 13 increases, and the expansion ratio of the turbine 13 approaches the expansion ratio corresponding to the peak value ηmax. As a result, the turbine efficiency approaches the peak value ηmax.

On the other hand, consider a case where the expansion ratio of the turbine 13 calculated by the controller 70 is higher than the expansion ratio corresponding to the peak value ηmax, for example, as in state point P2 shown in FIG. 4. In such a case, the controller 70 adjusts the valve opening degree of the flow rate adjustment unit 67 so that the flow rate of air introduced from the electric compressor 12 to the heat exchange unit 50 via the introduction flow path 61 is reduced. That is, the valve opening degree of the flow rate adjustment section 67 is adjusted by the controller 70 so that the flow rate of air branching from the introduction flow path 61 to the bypass flow path 65 increases.

Thereby, the amount of water vapor generated is reduced by heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 via the heat exchange section 50. Therefore, since the corrected flow rate of the exhaust gas is reduced, the flow rate of the exhaust gas expanded by the rotation of the turbine wheel 17 is reduced. Therefore, the expansion ratio of the turbine 13 becomes low, and the expansion ratio of the turbine 13 approaches the expansion ratio corresponding to the peak value ηmax. As a result, the turbine efficiency approaches the peak value ηmax.

In this way, by adjusting the amount of water vapor generated by heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 via the heat exchange section 50, The flow rate of the expanding exhaust gas is adjusted by the rotation of the turbine wheel 17. As a result, the expansion ratio of the turbine 13 is adjusted, so the turbine 13 operates with high turbine efficiency.

As shown in FIG. 3, the amount of water vapor generated increases as a result of heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 via the heat exchange section 50. Assume that the level of water stored in the storage section 37 has dropped. In this way, as the liquid level of the water stored in the storage section 37 decreases, the piping section 54 located vertically above among the plurality of piping sections 54 is exposed to the air layer 38 in the storage tank 30. May be exposed. In the piping section 54 exposed to the air layer 38 in the storage tank 30, heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 is difficult to occur. In this way, due to fluctuations in the liquid level of the water stored in the storage section 37, heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 via the heat exchange section 50 is caused. This fine-tunes the amount of water vapor produced.

[Effects of embodiment]
In the above embodiment, the following effects can be obtained.
(1) Exhaust gas discharged from the fuel cell stack 11 is supplied to the air layer 38 in the storage tank 30 via the supply port 35. The gas-liquid separator 36 separates water from the exhaust gas supplied from the supply port 35. The water separated by the gas-liquid separation section 36 is stored in the storage section 37. The water stored in the storage section 37 is evaporated into water vapor by exchanging heat with the air discharged from the electric compressor 12 via the heat exchange section 50 . The water vapor is discharged to the turbine 13 through the exhaust port 39 as exhaust gas together with the exhaust gas after water has been separated in the gas-liquid separator 36 . In this way, the mass of the exhaust gas supplied to the turbine 13 increases by the amount of water vapor added. As a result, the mass of the exhaust gas that expands due to the rotation of the turbine wheel 17 increases, so the workload of the turbine wheel 17 increases. This increases the regenerative power generated by the turbine 13. Furthermore, the exhaust gas after water has been separated in the gas-liquid separation section 36 passes through the air layer 38 in the storage tank 30 and is discharged from the discharge port 39 to the turbine 13 . Therefore, pressure loss of the exhaust gas within the storage tank 30 is less likely to occur, and an increase in regenerative power generated in the turbine 13 is prevented from being hindered. With the above, the regenerative power generated by the turbine 13 can be efficiently increased.

(2) The protruding portion 55 can cause a capillary phenomenon that sucks up the liquid level of the water stored in the storage portion 37, thereby increasing the surface area between the gas phase and the liquid phase in the storage tank 30. Can be done. As a result, the water stored in the storage section 37 can be efficiently evaporated.

(3) The fuel cell system 10 includes an introduction channel 61, a bypass channel 65, and a flow rate adjustment section 67. The flow rate adjustment section 67 adjusts the flow rate of the air that branches from the introduction channel 61 to the bypass channel 65 to adjust the flow rate of the air introduced from the electric compressor 12 to the heat exchange section 50 via the introduction channel 61. Adjust the flow rate. According to this, it is possible to adjust the amount of water vapor generated by heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 via the heat exchange section 50. can. Therefore, even if the flow rate of exhaust gas supplied to the turbine chamber 20 is uniquely determined, such as when the turbine 13 has a fixed nozzle 21, the exhaust gas that expands as the turbine wheel 17 rotates. Gas flow rate can be adjusted. As a result, the expansion ratio of the turbine 13 can be adjusted, so the turbine 13 can be operated with high turbine efficiency.

(4) For example, when the liquid level of the water stored in the storage section 37 decreases, the piping section 54 located vertically above among the plurality of piping sections 54 may be damaged by the air layer 3 in the storage tank 30. may be exposed to. In the piping section 54 exposed to the air layer 38 in the storage tank 30, heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 is difficult to occur. In this way, due to fluctuations in the liquid level of the water stored in the storage section 37, heat exchange between the water stored in the storage section 37 and the air discharged from the electric compressor 12 via the heat exchange section 50 is caused. By doing this, you can fine-tune the amount of water vapor produced.

(5) The heat exchange section 50 includes a porous material 56 that is thermally coupled to the heat exchange main body section 51 and disposed vertically below a predetermined height H1. According to this, heat exchange is performed between the water stored in the storage section 37 and the porous material 56, so that the water stored in the storage section 37 is evaporated and becomes water vapor. Therefore, the water stored in the storage section 37 can be efficiently evaporated.

[Example of change]
Note that 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.

(circle) In embodiment, the heat exchange part 50 does not need to have multiple protrusion parts 55. The heat exchange section 50 may have, for example, only one protrusion 55.
(circle) In embodiment, the protrusion part 55 does not need to be a thin plate shape, and may be columnar, for example. Further, the protruding portion 55 may be made of, for example, a lattice material or a mesh material. In short, the protrusion 55 only needs to extend from the heat exchange main body 51 and protrude into the air layer 38 beyond a predetermined height H1. The protruding portion 55 may have any configuration as long as it causes a capillary phenomenon to suck up the liquid level of the water stored in the storage portion 37.

(circle) In embodiment, the heat exchange part 50 does not need to have the protrusion part 55.
In the embodiment, the fuel cell system 10 may be configured without the bypass flow path 65 and the flow rate adjustment section 67.

In the embodiment, instead of the fixed nozzle 21, the turbine 13 may have a variable nozzle that can vary the flow rate of exhaust gas supplied to the turbine chamber 20.

In the embodiment, the heat exchange section 50 does not need to have a plurality of piping sections 54. For example, the heat exchange section 50 may have a configuration including only one piping section 54.
(circle) In embodiment, each piping part 54 does not need to be a flat tube, and may be a cylindrical tube, for example. In short, the shape of the piping section 54 is not particularly limited.

(circle) In embodiment, the heat exchange part 50 does not need to have the porous material 56.
In the embodiment, the fuel cell system 10 does not need to include the temperature sensor 74 that detects the temperature of the exhaust gas sucked into the suction chamber 22 of the turbine 13. In this case, for example, the temperature of the exhaust gas may be estimated from the temperature of the cooling water that adjusts the temperature of the fuel cell stack 11.

In the embodiment, the storage tank 30 may include, for example, a water level sensor that measures the height of the water level stored in the storage section 37. Further, the drain valve 42 may have a configuration in which opening and closing are controlled by the controller 70. Then, when a detection signal indicating that the water level has reached a predetermined height H1 is transmitted from the water level sensor, the controller 70 controls the drive of the drain valve 42 to open the drain valve 42. You can do it like this.

In the embodiment, the gas-liquid separation section 36 is a cylindrical section protruding from the inner surface of the upper wall 31, but is not limited thereto. In short, the specific configuration of the gas-liquid separation section 36 is not particularly limited as long as it is capable of separating water from the exhaust gas supplied from the supply port 35.

In the embodiment, the fuel cell system 10 does not need to be installed in a fuel cell vehicle. In short, the fuel cell system 10 is not limited to being mounted on a vehicle.

[Additional notes]
The above embodiment includes the configuration described in the following supplementary notes.
<Additional note 1>
A fuel cell stack that generates electricity by chemically reacting fuel gas and oxygen in the air,
an electric compressor including a compression section that compresses air supplied to the fuel cell stack, and a motor that drives the compression section;
A fuel cell system comprising: a turbine having a turbine wheel that is rotated by exhaust gas discharged from the fuel cell stack to assist in driving the motor;
comprising a storage tank that stores water contained in exhaust gas discharged from the fuel cell stack,
The storage tank is
a supply port connected to an air layer in the storage tank and supplying exhaust gas discharged from the fuel cell stack into the storage tank;
a gas-liquid separation unit that separates water from the exhaust gas supplied from the supply port;
a storage section in which water separated by the gas-liquid separation section is stored;
a heat exchange unit that exchanges heat between the water stored in the storage unit and the air discharged from the electric compressor;
A fuel cell system comprising: an outlet connected to the air layer and for discharging exhaust gas after water has been separated in the gas-liquid separation section to the turbine.

<Additional note 2>
The storage tank has a water storage amount control unit that controls the amount of water stored in the storage portion so that the liquid level of the water stored in the storage portion does not exceed a predetermined height,
The heat exchange section includes:
a heat exchange main body disposed vertically below the predetermined height;
The fuel cell system according to Supplementary Note 1, further comprising a protrusion extending from the heat exchange main body and protruding into the air layer beyond the predetermined height.

<Additional note 3>
The turbine is
a turbine chamber housing the turbine wheel;
a fixed nozzle that throttles the flow rate of exhaust gas supplied to the turbine chamber,
an introduction flow path for introducing air discharged from the electric compressor into the heat exchange section;
a bypass flow path that branches from the introduction flow path and supplies air flowing through the introduction flow path to the fuel cell stack by bypassing the heat exchange section;
A flow rate that adjusts the flow rate of air introduced from the electric compressor to the heat exchange section via the introduction flow path by adjusting the flow rate of air that branches and flows from the introduction flow path to the bypass flow path. The fuel cell system according to <Appendix 1> or <Appendix 2>, comprising: an adjustment section.

<Additional note 4>
The heat exchange section has a plurality of piping sections arranged in line in the vertical direction within the storage tank,
The air discharged from the electric compressor flows through each of the piping sections,
According to any one of <Appendix 1> to <Appendix 3>, each of the piping sections exchanges heat between the water stored in the storage section and the air discharged from the electric compressor. The fuel cell system described.

<Additional note 5>
<Additional Note 2> The heat exchange section is characterized by having a porous material that is thermally coupled to the heat exchange main body section and arranged vertically below the predetermined height. The fuel cell system described in .

DESCRIPTION OF SYMBOLS 10... Fuel cell system, 11... Fuel cell stack, 12... Electric compressor, 13... Turbine, 14... Compression part, 15... Motor, 17... Turbine wheel, 20... Turbine chamber, 21... Fixed nozzle, 30... Storage tank , 35... Supply port, 36... Gas-liquid separation section, 37... Storage section, 38... Air layer, 39... Discharge port, 40... Water storage amount control section, 50... Heat exchange section, 51... Heat exchange main body section, 54... Piping section, 55...Protrusion section, 56...Porous material, 61...Introduction channel, 65...Bypass channel, 67...Flow rate adjustment section.

Claims (5)

A fuel cell stack that generates electricity by chemically reacting fuel gas and oxygen in the air,
an electric compressor including a compression section that compresses air supplied to the fuel cell stack, and a motor that drives the compression section;
A fuel cell system comprising: a turbine having a turbine wheel that is rotated by exhaust gas discharged from the fuel cell stack to assist in driving the motor;
comprising a storage tank that stores water contained in exhaust gas discharged from the fuel cell stack,
The storage tank is
a supply port connected to an air layer in the storage tank and supplying exhaust gas discharged from the fuel cell stack into the storage tank;
a gas-liquid separation unit that separates water from the exhaust gas supplied from the supply port;
a storage section in which water separated by the gas-liquid separation section is stored;
a heat exchange unit that exchanges heat between the water stored in the storage unit and the air discharged from the electric compressor;
A fuel cell system comprising: an outlet connected to the air layer and for discharging exhaust gas after water has been separated in the gas-liquid separation section to the turbine. The storage tank has a water storage amount control unit that controls the amount of water stored in the storage portion so that the liquid level of the water stored in the storage portion does not exceed a predetermined height,
The heat exchange section includes:
a heat exchange main body disposed vertically below the predetermined height;
The fuel cell system according to claim 1, further comprising a protrusion extending from the heat exchange main body and protruding into the air layer beyond the predetermined height. The turbine is
a turbine chamber housing the turbine wheel;
a fixed nozzle that throttles the flow rate of exhaust gas supplied to the turbine chamber,
an introduction flow path for introducing air discharged from the electric compressor into the heat exchange section;
a bypass flow path that branches from the introduction flow path and supplies air flowing through the introduction flow path to the fuel cell stack by bypassing the heat exchange section;
A flow rate that adjusts the flow rate of air introduced from the electric compressor to the heat exchange section via the introduction flow path by adjusting the flow rate of air that branches and flows from the introduction flow path to the bypass flow path. The fuel cell system according to claim 1 or 2, further comprising an adjustment section. The heat exchange section has a plurality of piping sections arranged in line in the vertical direction within the storage tank,
The air discharged from the electric compressor flows through each of the piping sections,
2. The fuel cell system according to claim 1, wherein each of the piping sections exchanges heat between water stored in the storage section and air discharged from the electric compressor. 3. The heat exchanger according to claim 2, wherein the heat exchanger has a porous material that is thermally coupled to the heat exchanger main body and is arranged vertically below the predetermined height. The fuel cell system described.

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