Fuel cell systems and unmanned aerial vehicles

Abstract

The present invention relates to a fuel cell system and an unmanned aerial vehicle equipped with the fuel cell system. The fuel cell system of the present invention is characterized by comprising: a fuel cell stack; an air supply path for supplying air to the fuel cell stack; an air compressor disposed in the air supply path and pressurizing air to the fuel cell stack; an air exhaust path for exhausting exhaust gas, including air exhausted from the fuel cell stack, to the atmosphere; an air bypass path that branches from the air supply path between the fuel cell stack and the air compressor and merges with the air exhaust path; and a flow hole formed at the connection between the air bypass path and the air exhaust path.

Description

Technical Field

[0001] The present invention relates to a fuel cell system and an unmanned aerial vehicle equipped with the fuel cell system. Background Art

[0002] Unmanned aerial vehicles equipped with fuel cell systems are known (e.g., Japanese Patent Application Laid-Open No. 2018-181576). In such fuel cell systems, an air compressor is used to draw air as an oxidant gas from the atmosphere and pressurize it to the fuel cell stack.

[0003] In air compressors, especially turbine-type air compressors, it is important to avoid surge, a phenomenon in which the flow rate and pressure of air fluctuate drastically and periodically. Surge is likely to occur when the flow rate of air flowing through the air compressor is relatively low. If the flow rate of air flowing through the air compressor is increased in order to avoid surge, there is a possibility that the flow rate of air supplied to the fuel cell stack becomes excessive. Therefore, it is possible to consider detouring a portion of the air compressed by the air compressor and discharging it into the atmosphere. However, discharging the detouring air into the atmosphere increases the power consumption of the air compressor, resulting in a deterioration in the fuel efficiency of the unmanned aerial vehicle. Summary of the Invention

[0004] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a fuel cell system capable of suppressing the power consumption of an air compressor, and an unmanned aerial vehicle equipped with the fuel cell system.

[0005] In order to solve the above-mentioned problems, the fuel cell system of the present invention is characterized in that it comprises: a fuel cell group; a supply path for supplying air to the above-mentioned fuel cell group; a compressor, which is arranged in the above-mentioned supply path and pressurizes air to the above-mentioned fuel cell group; an exhaust path for discharging exhaust gas including air exhausted from the above-mentioned fuel cell group into the atmosphere; a bypass path, which branches off from the above-mentioned supply path between the above-mentioned fuel cell group and the above-mentioned compressor and merges with the above-mentioned exhaust path; and a flow hole, which is formed at the connection portion of the above-mentioned bypass path with the above-mentioned exhaust path.

[0006] According to this structure, the flow rate of air passing through the connection portion formed with the flow hole is faster than the flow rate of air flowing in the bypass path upstream of the connection portion. The pressure of the air passing through the connection portion formed with the flow hole is lower than the pressure of the air flowing in the bypass path upstream of the connection portion. The air whose pressure is reduced by passing through the connection portion merges with the exhaust gas flowing in the exhaust path, thereby lowering the pressure of the exhaust path near the connection portion compared to when no flow hole is formed. Therefore, when the flow hole is formed in the connection portion, the exhaust gas flowing in the exhaust path upstream of the connection portion is more easily drawn toward the vicinity of the connection portion. As a result, the flow rate of air flowing in the fuel cell stack connected to the exhaust path can be increased. Even without increasing the output of the compressor, the flow rate of air supplied to the fuel cell stack can be increased. Even if the output of the compressor is suppressed, the fuel cell system can still supply the desired flow rate of air to the fuel cell stack. Therefore, the fuel cell system can suppress the power consumption of the compressor.

[0007] As a more preferred embodiment, the discharge path includes a throttle portion at a position upstream of the connection portion.

[0008] According to this configuration, the flow rate of the exhaust gas passing through the throttle portion is faster than the flow rate of the exhaust gas flowing in the exhaust path upstream of the throttle portion. The difference in flow rate between the exhaust gas passing through the throttle portion and flowing in the exhaust path near the connection portion and the air passing through the connection portion and flowing into the exhaust path can be reduced. The confluence loss between the exhaust gas flowing in the exhaust path near the connection portion and the air passing through the connection portion can be reduced. Therefore, the fuel cell system can further suppress the output of the compressor required to supply the desired flow of air to the fuel cell stack, thereby further suppressing the power consumption of the compressor.

[0009] As a more preferred embodiment, the bypass path is inclined at an acute angle with respect to the flow direction of the exhaust gas flowing in the exhaust path, and merges with the exhaust path at an acute angle with respect to the merged exhaust path.

[0010] According to this aspect, the merging loss between the exhaust gas flowing in the discharge path near the connection portion and the air passing through the connection portion can be reduced. The fuel cell system can further suppress the required compressor output, thereby further suppressing the power consumption of the compressor.

[0011] As a more preferred embodiment, the supply path directly supplies the air compressed by the compressor to the fuel cell stack. For example, the supply path directly supplies the air compressed by the compressor to the fuel cell without passing through an intercooler.

[0012] This configuration enables a fuel cell system to be smaller and lighter. Furthermore, the fuel cell system can operate the compressor at a speed that allows for the timely direct supply of air from the compressor to the fuel cell stack while also enabling appropriate power generation. This further reduces compressor power consumption.

[0013] Furthermore, the unmanned aerial vehicle of the present invention is characterized by being equipped with the above-mentioned fuel cell system.

[0014] This structure reduces the amount of power supplied from the fuel cell stack to the compressor, thereby increasing the amount of power supplied from the fuel cell stack to the unmanned aerial vehicle's drive system. Consequently, the unmanned aerial vehicle can achieve improved fuel efficiency, for example, extending its range and flight time.

[0015] According to the present invention, it is possible to provide a fuel cell system capable of suppressing the power consumption of an air compressor and an unmanned aerial vehicle equipped with the fuel cell system.

[0016] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention are described below with reference to the accompanying drawings, wherein like reference numerals denote like elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a perspective view schematically showing the unmanned aerial vehicle according to this embodiment.

[0018] Figure 2 yes Figure 1 A top view of the unmanned aerial vehicle is shown.

[0019] Figure 3 yes Figure 1 A side view of the unmanned aerial vehicle is shown.

[0020] Figure 4 It is mounted on Figure 1 System diagram of the fuel cell system of the unmanned aerial vehicle shown.

[0021] Figure 5 Yes Figure 2 The diagram shows the structure of each air path.

[0022] Figure 6 yes Figure 5 A cross-sectional view taken along line VI-VI is shown. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present invention will be described using the drawings. In each embodiment, unless otherwise specified, components denoted by the same reference numerals have the same functions in each embodiment, and their description will be omitted.

[0024] Figure 1 It is a perspective view schematically showing the unmanned aerial vehicle 1 according to this embodiment. Figure 2 yes Figure 1 A top view of the UAV 1 is shown. Figure 3 yes Figure 1 The side view of the unmanned aerial vehicle 1 is shown. Figure 2 and Figure 3 In the figure, the arm 4 and the propeller device 5 are omitted.

[0025] Unmanned aerial vehicle 1 is equipped with a fuel cell stack 11 of a fuel cell system 10 as its power source. Unmanned aerial vehicle 1 uses the electricity generated by the fuel cell stack 11 to rotate blades 7, enabling it to fly in various modes, including ascent, descent, rotation, forward movement, backward movement, and hovering. Unmanned aerial vehicle 1 can be flown autonomously or by remote control. Unmanned aerial vehicle 1 may also be a multi-rotor drone.

[0026] The unmanned aerial vehicle 1 includes a body 2 having a box-shaped frame 3 , arms 4 protruding left and right from the front and rear of the frame 3 , and propeller devices 5 attached to the front ends of the arms 4 .

[0027] The body 2 includes a fuel cell system 10; a control device (not shown) that controls the operation of the unmanned aerial vehicle 1; a communication device (not shown) that wirelessly communicates with the outside of the unmanned aerial vehicle 1; and sensors (not shown) that detect the surrounding environment of the unmanned aerial vehicle 1. The body 2 is constructed by mounting the various components of the fuel cell system 10, the control device, the communication device, and the sensors inside or outside the frame 3. For example, the fuel cell stack 11, secondary battery 12, air supply path 21, and air compressor 22 (described later) of the fuel cell system 10 are mounted inside the frame 3. The radiator 62 (described later) of the fuel cell system 10 is mounted on the front outer surface of the frame 3 in a forward-inclined position. The hydrogen tank 41 (described later) of the fuel cell system 10 is mounted on the upper outer surface of the frame 3 with the axis of the cylindrical hydrogen tank 41 aligned in the front-to-back direction.

[0028] The propeller device 5 includes a motor 6 driven by electric power generated by the fuel cell stack 11 , and blades 7 rotated by the drive of the motor 6 .

[0029] Figure 4 It is mounted on Figure 1 A system diagram of the fuel cell system 10 of the unmanned aerial vehicle 1 is shown.

[0030] The fuel cell system 10 includes a fuel cell stack 11 formed by stacking a plurality of fuel cell units, such as membrane electrode assemblies (MEAs), and a secondary battery 12. The power generated by the fuel cell stack 11 is stored in the secondary battery 12. The power generated by the fuel cell stack 11 may be supplied directly to a load such as the motor 6 of the propeller device 5 without being stored in the secondary battery 12. The fuel cell system 10 further includes an air supply system 20 for supplying air to the fuel cell stack 11, a hydrogen supply system 40 for supplying hydrogen as fuel gas to the fuel cell stack 11, and a cooling system 60 for cooling the fuel cell stack 11.

[0031] The air supply system 20 is a system that supplies air to the fuel cell stack 11 and discharges exhaust gas including air that has not been used for the electrochemical reaction in the fuel cell stack 11 from the fuel cell stack 11 .

[0032] The air supply system 20 includes an air supply path 21 for supplying air to the fuel cell stack 11, and an air cleaner 23 disposed in the air supply path 21 to remove dust contained in the air introduced from the atmosphere. The air supply system 20 includes an air compressor 22 disposed in the air supply path 21 to pressurize the air that has passed through the air cleaner 23 to the fuel cell stack 11. The air compressor 22 is a turbine-type air compressor. The air compressor 22 is driven by a motor 22a driven by the electricity generated by the fuel cell stack 11 and compresses the sucked air.

[0033] The air supply system 20 includes an air discharge path 24 for discharging exhaust gas, including air discharged from the fuel cell stack 11, into the atmosphere. The air supply system 20 includes an air bypass path 25 that branches from the air supply path 21 between the fuel cell stack 11 and the air compressor 22 and merges with the air discharge path 24. Specifically, the air bypass path 25 includes a branching portion 26 that branches from the air supply path 21 and a connecting portion 27 that connects to the air discharge path 24 to merge with the air discharge path 24. The air bypass path 25 allows a portion of the air pumped by the air compressor 22 to flow in a roundabout way toward the air discharge path 24.

[0034] The air supply system 20 includes a pressure sensor 28 and a temperature sensor 29 for measuring the pressure and temperature of the air, respectively, and an air flow meter 30 for measuring the air flow rate. The pressure sensor 28 may be located near the air inlet of the air supply path 21, between the air compressor 22 and the branching portion 26. The temperature sensor 29 may be located in the air cleaner 23. The air flow meter 30 may also be located in the air supply path 21 near the outlet of the air cleaner 23.

[0035] In addition, the air supply system 20 may not include an intercooler for cooling the air compressed by the air compressor 22. That is, the air supply path 21 of the air supply system 20 may also directly supply the air compressed by the air compressor 22 to the fuel cell stack 11. As a result, the fuel cell system 10 can reduce the number of components, thereby achieving miniaturization and lightweight. The unmanned aerial vehicle 1 can achieve miniaturization and lightweight. In addition, the fuel cell system 10 can operate the air compressor 22 at a rotation speed that achieves a pressure ratio that allows the fuel cell stack 11 to generate appropriate power even if the air compressed by the air compressor 22 is directly supplied to the fuel cell stack 11. The fuel cell system 10 can suppress the power consumption of the air compressor 22. The fuel cell system 10 can further improve the fuel efficiency of the unmanned aerial vehicle 1 equipped with the fuel cell system 10.

[0036] The hydrogen supply system 40 is a system that supplies hydrogen to the fuel cell stack 11 and discharges exhaust gas including hydrogen that has not been used for the electrochemical reaction in the fuel cell stack 11 from the fuel cell stack 11 .

[0037] The hydrogen supply system 40 includes a hydrogen tank 41 filled with high-pressure hydrogen and a hydrogen supply path 42 that supplies hydrogen to the fuel cell stack 11. The hydrogen supply system 40 includes a main stop valve 43, which is located near the outlet of the hydrogen tank 41 on the hydrogen supply path 42 and switches between introducing and stopping the hydrogen filled in the hydrogen tank 41 into the hydrogen supply path 42. The hydrogen supply system 40 includes a regulator 44, which is located on the hydrogen supply path 42 and regulates the pressure of the hydrogen introduced from the hydrogen tank 41. The hydrogen supply system 40 includes an ejector 45, which is located on the hydrogen supply path 42 between the regulator 44 and the fuel cell stack 11 and discharges the hydrogen, whose pressure has been regulated by the regulator 44, toward the fuel cell stack 11. The hydrogen supply system 40 includes a safety valve 46 for relieving excess pressure that may occur in the hydrogen supply path 42 near the outlet of the regulator 44 , and a safety valve 47 for relieving excess pressure that may occur in the hydrogen supply path 42 near the outlet of the ejector 45 .

[0038] The hydrogen supply system 40 includes a hydrogen discharge path 48 that discharges exhaust gas from the fuel cell stack 11 to the air discharge path 24. The hydrogen supply system 40 includes a gas-liquid separator 49 disposed in the hydrogen discharge path 48 and separating generated water from the exhaust gas discharged from the fuel cell stack 11. The hydrogen supply system 40 includes a hydrogen circulation path 50 that circulates hydrogen contained in the exhaust gas that has passed through the gas-liquid separator 49 to the ejector 45 (or the hydrogen supply path 42). Furthermore, a hydrogen pump may be provided in the hydrogen circulation path 50 to pressurize the hydrogen that has passed through the gas-liquid separator 49 to the ejector 45 (or the hydrogen supply path 42). The hydrogen supply system 40 includes an exhaust / drain valve 51 disposed in the hydrogen discharge path 48 near the outlet of the gas-liquid separator 49 (between the gas-liquid separator 49 and the air discharge path 24) to switch between discharging and stopping the exhaust gas and generated water that have passed through the gas-liquid separator 49 to the air discharge path 24.

[0039] The hydrogen supply system 40 includes a pressure sensor 52 for measuring the pressure of the hydrogen gas. The pressure sensor 52 may also be provided in the hydrogen supply path 42 near the outlet of the hydrogen tank 41, the hydrogen supply path 42 between the safety valve 46 and the ejector 45, and the hydrogen supply path 42 between the safety valve 47 and the fuel cell stack 11.

[0040] The cooling system 60 circulates cooling water to cool the fuel cell stack 11 .

[0041] The cooling system 60 includes a cooling water circulation path 61 that circulates cooling water between the fuel cell stack 11 and a radiator 62, and a radiator 62 that cools the cooling water discharged from the fuel cell stack 11. The cooling system 60 includes a water pump 63 that pumps the cooling water cooled by the radiator 62 to the fuel cell stack 11. The water pump 63 is driven by a motor 63a that is driven by the electricity generated by the fuel cell stack 11. The cooling system 60 also includes a storage tank 64 that stores and regulates the pressure of the reserved cooling water, and a fan 65 that cools the radiator 62.

[0042] The cooling system 60 includes a compressor cooling path 66 that diverts the cooling water flowing through the cooling water circulation path 61 to the air compressor 22 to cool the air compressor 22. The compressor cooling path 66 supplies a portion of the cooling water pumped from the water pump 63 to the air compressor 22 and discharges the cooling water discharged from the air compressor 22 to the radiator 62.

[0043] The cooling system 60 includes a temperature sensor 67 for measuring the temperature of the cooling water. The temperature sensor 67 may also be provided in the cooling water circulation path 61 near the outlet of the fuel cell stack 11. The cooling system 60 may also include an ion exchanger provided in parallel with the radiator 62 in the cooling water circulation path 61 to remove ions from the cooling water.

[0044] Figure 5 Yes Figure 2 The diagram shows the structure of each air path. Figure 6 yes Figure 5 The cross-sectional view of the VI-VI line is shown. Figure 5 and Figure 6 In FIG. 1 , black arrows indicate the flow of air compressed by the air compressor 22 , and hollow arrows indicate the flow of exhaust gas discharged from the fuel cell stack 11 .

[0045] like Figure 5 As shown, the air bypass path 25 has a branch portion 26 that branches from the air supply path 21 between the fuel cell stack 11 and the air compressor 22. Figure 5 and Figure 6 As shown, the air bypass path 25 has a connection portion 27 connected to the air discharge path 24 for merging with an outlet 24 a of the air discharge path 24 for discharging exhaust gas to the atmosphere and the air discharge path 24 between the fuel cell stack 11 .

[0046] like Figure 6 As shown, a flow hole 31 is formed in the connection portion 27. The flow hole 31 is an opening formed in the connection portion 27. The flow hole 31 has a shape that creates a flow path cross-sectional area smaller than the flow path cross-sectional area of the air bypass path 25 upstream of the connection portion 27. In other words, the flow path cross-sectional area of the connection portion 27 in which the flow hole 31 is formed is smaller than the flow path cross-sectional area of the air bypass path 25 upstream of the connection portion 27. The flow hole 31 can also be formed by providing a plate-shaped member 31a extending along the air exhaust path 24 near the connection portion 27 to the connection portion 27.

[0047] The flow rate of air passing through the connection portion 27, where the flow holes 31 are formed, is faster than the flow rate of air flowing through the air bypass path 25 upstream of the connection portion 27. The pressure of air passing through the connection portion 27, where the flow holes 31 are formed, is lower than the pressure of air flowing through the air bypass path 25 upstream of the connection portion 27. The air, whose pressure has been reduced by passing through the connection portion 27, merges with the exhaust gas flowing through the air exhaust path 24. As a result, the pressure of the air exhaust path 24 near the connection portion 27 is lower than when the flow holes 31 are not formed. Therefore, when the flow holes 31 are formed in the connection portion 27, the exhaust gas flowing through the air exhaust path 24 upstream of the connection portion 27 is more easily drawn toward the vicinity of the connection portion 27.

[0048] This increases the flow rate of air flowing through the fuel cell stack 11 connected to the air exhaust path 24. In other words, in this case, the flow rate of air supplied to the fuel cell stack 11 can be increased even without increasing the output of the air compressor 22. By forming the flow holes 31 in the connection portion 27, the fuel cell system 10 can supply a desired flow rate of air to the fuel cell stack 11 even if the output of the air compressor 22 is reduced compared to conventional methods. Consequently, the fuel cell system 10 can reduce the power consumption of the air compressor 22.

[0049] If the power consumption of the air compressor 22 can be reduced, the amount of power supplied from the fuel cell stack 11 to the air compressor 22 can be reduced, thereby increasing the amount of power supplied from the fuel cell stack 11 to the propeller device 5. Therefore, the fuel cell system 10 can improve the fuel efficiency of the unmanned aerial vehicle 1 equipped with the fuel cell system 10, for example, extending the cruising range and cruising time.

[0050] And, as Figure 6 As shown, the air discharge path 24 has a throttle portion 32 upstream of the connection portion 27. The flow path cross-sectional area in the throttle portion 32 is smaller than the flow path cross-sectional area of the air discharge path 24 upstream of the throttle portion 32.

[0051] The flow rate of the exhaust gas passing through the throttle portion 32 is faster than the flow rate of the exhaust gas flowing in the air exhaust path 24 on the upstream side of the throttle portion 32. The difference in flow rate between the exhaust gas passing through the throttle portion 32 and flowing in the air exhaust path 24 near the connection portion 27 and the air passing through the connection portion 27 and flowing into the air exhaust path 24 can be reduced. The confluence loss between the exhaust gas flowing in the air exhaust path 24 near the connection portion 27 and the air passing through the connection portion 27 can be reduced. As a result, the fuel cell system 10 can further suppress the output of the air compressor 22 required to supply the desired flow of air to the fuel cell stack 11. The fuel cell system 10 can further suppress the power consumption of the air compressor 22. The fuel cell system 10 can further improve the fuel efficiency of the unmanned aerial vehicle 1 equipped with the fuel cell system 10.

[0052] And, as Figure 6As shown, the air bypass path 25 merges with the air exhaust path 24 at an angle of an acute angle θ relative to the flow direction of the exhaust gas flowing in the air exhaust path 24. The merging loss of the exhaust gas flowing in the air exhaust path 24 near the connection portion 27 and the air passing through the connection portion 27 can be reduced. As a result, the fuel cell system 10 can further suppress the output of the air compressor 22 required to supply the desired flow rate of air to the fuel cell stack 11. The fuel cell system 10 can further suppress the power consumption of the air compressor 22. The fuel cell system 10 can further improve the fuel efficiency of the unmanned aerial vehicle 1 equipped with the fuel cell system 10.

[0053] Furthermore, the air supply path 21 described in the above embodiment is an example of a "supply path" as described in the claims. The air compressor 22 is an example of a "compressor" as described in the claims. The air exhaust path 24 is an example of a "exhaust path" as described in the claims. The air bypass path 25 is an example of a "bypass path" as described in the claims.

[0054] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the aforementioned embodiments and various modifications may be made without departing from the spirit of the present invention as set forth in the claims. The present invention may include adding the structure of one embodiment to the structure of another embodiment, replacing the structure of one embodiment with that of another embodiment, or deleting a portion of the structure of one embodiment.

Claims

1. An unmanned aerial vehicle equipped with a fuel cell system, characterized in that: The fuel cell system comprises: A fuel cell stack, which is the power source of the unmanned aerial vehicle; a supply path for supplying air to the fuel cell stack; a compressor, disposed in the supply path and configured to pressurize air to the fuel cell stack; an exhaust path for discharging exhaust gas including air exhausted from the fuel cell stack to the atmosphere; a bypass path branching from the supply path between the fuel cell stack and the compressor and merging with the exhaust path; as well as a flow hole formed at a connection portion between the bypass path and the discharge path, The flow hole is formed by providing a plate-shaped member extending along the discharge path near the connection portion at the connection portion, so that the flow path cross-sectional area of the connection portion is smaller than the flow path cross-sectional area of the bypass path on the upstream side of the connection portion. The discharge path includes a throttle portion at a position upstream of the orifice formed in the connection portion. The flow path cross-sectional area of the throttle portion is smaller than the flow path cross-sectional area of the air exhaust path upstream of the throttle portion, thereby reducing the flow velocity difference between the exhaust gas passing through the throttle portion and flowing in the exhaust path near the connecting portion and the air passing through the flow hole and flowing into the exhaust path.

2. The unmanned aerial vehicle according to claim 1, wherein: The bypass path is inclined at an acute angle with respect to the flow direction of the exhaust gas flowing in the exhaust path and merges with the exhaust path.

3. The unmanned aerial vehicle according to claim 1 or 2, characterized in that: The supply path directly supplies the air compressed by the compressor to the fuel cell stack.

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