Apparatus for supplying a fuel cell with a gas

Abstract

The invention relates to an apparatus (100, 200, 300) for supplying a fuel cell (125) with a gas, comprising: a compression device (115), which is designed to intake and compress the gas and supply it to a cathode (K) of the fuel cell (125); an expansion device (120), which is designed to expand an exhaust gas of the cathode (K); wherein the compression device (115) has an electric motor (110) with a shaft (130) which can rotate about its longitudinal axis, wherein the shaft (130) has, along the longitudinal axis, a cavity (140); a pump device (150, 310), which is designed to pump a portion of the expanded exhaust gas (185) through the cavity (140) of the shaft (130) toward the compression device (115).

Description

[0001] DEVICE FOR SUPPLYING A FUEL CELL WITH A GAS

[0002] The present invention relates to a device for supplying a fuel cell with gas, a fuel cell system and an electrically driven system.

[0003] Energy conversion systems are known in which electrical energy can be generated through an electrochemical reaction using an oxidizing agent and a fuel. These systems include fuel cell systems.

[0004] A fuel cell system can be used, for example, to generate electrical energy to operate an electric motor for an electrically powered vehicle. The fuel cell system can comprise a fuel cell stack with a plurality of fuel cells arranged side by side. In a fuel cell, an electrolyte layer, in particular a proton-conducting polymer electrolyte membrane, is arranged between two electrodes, a cathode and an anode. Electrical energy can be generated in the fuel cell by reacting a fuel with an oxidizing agent, in particular oxygen.

[0005] To provide the oxidant, ambient air can first be drawn in using a compressor, which may include an electric motor. This ambient air is then compressed by the air compressor and fed to a cathode of the fuel cell. Exhaust gas from the cathode then expands, cooling the exhaust gas. During operation, the electric motor heats up, requiring cooling. Separate cooling devices can be provided for this purpose, for example, fans that draw in air from outside the electric motor and use it to cool the electric motor.

[0006] Cooling systems are also known in which an electric motor shaft is directly cooled with a cooling medium. With a hollow shaft, the cooling medium can also be passed directly through the hollow shaft for cooling. In each of these solutions, a separate cooling circuit is provided, in which the cooling medium flows past or through the shaft via a pump.

[0007] The present invention is based on the object of providing a device that enables efficient cooling of an electric motor of a compressor.

[0008] This object is achieved according to the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the dependent claims.

[0009] A first aspect of the solution relates to a device for supplying a fuel cell with a gas, comprising: (i) a compression device, in particular a compressor, which is configured to suck in the gas, in particular air, compress it and supply it to a cathode of the fuel cell; (ii) an expansion device, in particular a gas turbine, which is configured to expand an exhaust gas from the cathode; (iii) wherein the compression device comprises an electric motor with a shaft rotatable about its longitudinal axis, wherein the shaft has a cavity along the longitudinal axis; (iv) a pumping device which is configured to pump a portion of the expanded exhaust gas through the cavity of the shaft in the direction of the compression device.

[0010] The terms "comprises," "includes," "includes," "has," "has," "with," or any other variation thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or that are inherent in such a method or apparatus.

[0011] Furthermore, unless explicitly stated to the contrary, "or" refers to an inclusive "or" rather than an exclusive "or." For example, a condition A or B is satisfied by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).

[0012] The terms "a" or "an" as used herein are defined as "one or more." The terms "another" and "another," and any other variations thereof, are defined as "at least one other."

[0013] The term "plurality" as used here is to be understood as meaning "two or more".

[0014] The term “configured” or “set up” to fulfil a specific function (and respective variations thereof) as used here is to be understood to mean that the corresponding device is already in a design or setting in which it can carry out the function or is at least adjustable - i.e. configurable - so that it can carry out the function after being set accordingly. The configuration can be carried out, for example, by appropriately setting parameters of a process sequence or of switches or similar for activating or deactivating functionalities or settings. In particular, the device can have a plurality of predetermined configurations or operating modes, so that the configuration can be carried out by selecting one of these configurations or operating modes.

[0015] The term "fuel cell" as used here refers in particular to a device in which chemical energy is directly converted into electrical energy through an electrochemical reaction of a fuel with an oxidizing agent. For this purpose, an electrolyte layer can be provided in the fuel cell between two layers designed as electrodes. The electrolyte layer is designed, for example, as a polymer electrolyte membrane (PEM), which must be moist during operation in order to conduct protons. A fuel, for example hydrogen, is dissociated at an electrode designed as the anode. The resulting protons can diffuse through the membrane to the electrode used as the cathode, where they react with an oxygen atom of the oxidizing agent reduced by the cathode, forming water (formally: 2H+ + O2 - H2O).The term "Archimedean screw" or "screw pump" as used here refers in particular to a screw arrangement comprising an elongated body around which spiral blades extend, forming a cylinder as an enveloping shape. When the screw arrangement is arranged in a cylindrical cavity, chambers are formed between the spiral blades and an inner wall of the cavity, so that a medium located in the chambers can be conveyed along this longitudinal axis by a rotational movement of the screw arrangement about its longitudinal axis.

[0016] The term "compression device" or "compressor" as used here refers in particular to a device for compressing a fluid, in particular a gas, in particular air. Compressing the gas increases its pressure and temperature. In particular, the compressor can be designed as a turbocompressor, in particular as a radial or axial compressor. In an axial compressor, the gas to be compressed flows through the compressor parallel to the axis of the compressor. In a radial compressor, the gas flows axially into an impeller of a compressor stage and is subsequently deflected radially outward.

[0017] The term "expansion device" as used here refers, in particular, to a device by which a gas can be expanded, thereby increasing the volume of the gas, decreasing the pressure of the gas, and thereby reducing the temperature of the gas. Such a device can be designed, in particular, as a gas turbine. In particular, such a gas turbine has turbine blades that can rotate around a shaft. A gas flowing around these turbine blades transfers heat energy to these turbine blades, which can cause the shaft to rotate, and the gas cools.

[0018] The term "jet pump" or "jet pump," as used here, refers specifically to a pump that uses a propellant to generate a pumping action for a suction medium. The propellant exits a nozzle at high velocity. This creates a static pressure drop, resulting in a negative pressure. This negative pressure allows the suction medium to be sucked in and transported.

[0019] The device according to the first aspect makes it possible to use a portion of the exhaust gas expanded by the expansion device, which has been cooled by the expansion, for cooling the electric motor. This portion of the exhaust gas is pumped by means of a pumping device through a cavity in the shaft of the electric motor toward the compression device.

[0020] By cooling the shaft and thus the electric motor from within the shaft, i.e., from within the hollow space, effective cooling can be achieved. By utilizing a portion of the exhaust gas already present in the device and expanded or cooled, the overall efficiency of the device can be increased. In particular, a cooling device located outside the shaft or electric motor can be dispensed with. This saves installation space.

[0021] Furthermore, cheaper magnets with lower requirements regarding their heat dependence or temperature resistance, in particular neodymium-iron-boron (NeFe) magnets, can be used for the electric motor instead of, for example, samarian-cobalt (SmCo) magnets.

[0022] Preferred embodiments of the device are described below, which can be combined with each other as well as with the other aspects described, unless this is expressly excluded or is technically impossible.

[0023] In some embodiments, the pumping device comprises an Archimedean screw arranged in the cavity such that rotation of the rotatable shaft causes the Archimedean screw to rotate, allowing the expanded exhaust gas to be pumped through the cavity toward the compression device. This advantageously allows the rotation of the shaft to be used to rotate the Archimedean screw. The rotation of the motor and thus of the shaft can thereby initiate cooling of the motor. Furthermore, by using the Archimedean screw in the cavity, no additional installation space is required for cooling.

[0024] In some embodiments, the pumping device comprises a jet pump, and the device comprises a first connecting line through which a portion of the gas compressed by the compression device can be supplied to the jet pump. The compressed gas from the compression device can thereby act as a driving medium for the jet pump, allowing the expanded exhaust gas to be sucked in and pumped into the cavity. This allows for effective cooling with improved efficiency.

[0025] In some embodiments, the device comprises a heat pipe, in particular a so-called heat pipe, arranged in the cavity of the rotatable shaft. The heat pipe can provide improved cooling of the shaft and thus of the electric motor. Furthermore, the heat pipe can be easily installed in the cavity.

[0026] In some embodiments, the device comprises a second connecting line through which an opening in the cavity, through which the expanded exhaust gas pumped through the cavity can exit, is fluidically connected to an intake region for the gas to be sucked in by the compression device. This allows the expanded exhaust gas, which has been pumped through the cavity toward the compression device, to be sucked in by the compression device. This can be particularly advantageous if the gas sucked in by the compression device has previously been filtered through a filter, since the gas from the cavity has already been filtered. Overall, the compression device can be operated more effectively by reusing the gas pumped through the cavity.

[0027] In some embodiments, the compression device and the expansion device have a common rotatable shaft, which is identical to the rotatable shaft of the electric motor. This allows the shaft to have multiple functions. On the one hand, for use as the compression device and expansion device, which are used to process the gas for the fuel cell. On the other hand, for use as the motor that drives the compression device. And finally, for use as cooling, which is achieved by passing the cooled exhaust gas through the hollow space of the shaft.

[0028] A second aspect of the solution relates to a fuel cell system comprising a fuel cell and a device according to the first aspect.

[0029] A third aspect of the solution relates to an electrically driven system comprising a fuel cell system according to the second aspect.

[0030] In some embodiments, the electrically powered system comprises a motor vehicle or an emergency power generator for a power system.

[0031] The features and advantages explained with regard to the first aspect of the solution also apply accordingly to the other aspects described.

[0032] Further advantages, features and possible applications emerge from the following description of preferred embodiments in conjunction with the figures.

[0033] This shows

[0034] Fig. 1 schematically shows a device for supplying a fuel cell with air according to an embodiment;

[0035] Fig. 2 schematically shows a device according to a further embodiment;

[0036] Fig. 3 schematically shows a device according to a further embodiment; and

[0037] Fig. 4 schematically shows a fuel cell system according to an embodiment.

[0038] Throughout the figures, the same reference numerals are used for the same or corresponding elements. Figure 1 schematically shows a device 100 for supplying a fuel cell 125 with air according to one embodiment, as well as a fuel cell 125. The device 100 has a housing 105. A compressor 115 with an electric motor 110 and a gas turbine 120 are arranged in the housing 105. The compressor 115, the electric motor 110, and the gas turbine 120 have a common rotatable shaft 130.

[0039] Compressor 115 draws in ambient air 180, which typically has a pressure of approximately 100 kPa (approximately 1 bar) at room temperature, i.e., approximately 20°C. This drawn-in air can be filtered by an air filter (not shown here) upstream of compressor 115. Compressor 115 increases the pressure of the drawn-in ambient air. This increased pressure can reach pressure values ​​of 280 kPa to 320 kPa and temperature values ​​of 150°C to 200°C.

[0040] This compressed air is fed to a cathode K of the fuel cell 125 to conduct an electrochemical reaction with a fuel from the anode A via an electrolyte layer (not shown here). The resulting exhaust gas from the cathode, which has a pressure in the range of 230 kPa to 270 kPa and a temperature between 70°C and 90°C, is then passed through the gas turbine 120, which is driven by the thermal energy of the exhaust gas. The gas turbine 120 converts the thermal energy of the exhaust gas into mechanical kinetic energy, and the exhaust gas expands and is consequently cooled. The gas turbine reduces the pressure of the exhaust gas to approximately 100 kPa at a temperature of 50°C to 70°C.

[0041] A cavity 140 is formed in the shaft 130 along its longitudinal axis, which runs parallel to the x-axis. An Archimedean screw 150 is arranged in the cavity 140. A pipe section 160 is connected to the cavity 140 and extends into an area into which the exhaust gas 185 expanded or cooled by the gas turbine flows. When the shaft 130 rotates about its longitudinal axis due to a rotation of the electric motor 110, the Archimedean screw 150 also rotates about this longitudinal axis. The Archimedean screw 150 is oriented such that the rotation of the shaft 130 by the electric motor 110 creates a vacuum, whereby a portion of the expanded exhaust gas 185 flows into the pipe section 160 and through the cavity 140 towards the compressor 115. The expanded exhaust gas 185 can then be led out of the housing 105 via a pipe 170 connected to the cavity 140.In particular, the pipeline 170 can be fluidically connected to an intake area of ​​the ambient air 180 to be sucked in by the compressor 115, so that this exhaust gas is fed back to the compressor 115.

[0042] By passing the expanded and cooled exhaust gas 185 through the cavity 140, the shaft 130 and ultimately the electric motor 110 are cooled. The rotation of the electric motor 110 itself is utilized to rotate the shaft 130 and thus the Archimedean screw 150 arranged in the cavity 140.

[0043] Likewise, by pumping the expanded or cooled exhaust gas 185, moisture can also be brought to an intake area of ​​the compressor 115. This can reduce the size of a humidifier used in a fuel cell system.

[0044] Figure 2 schematically shows a device 200 according to a further embodiment. The device 200 according to Figure 2 differs from the device 100 according to Figure 1 in that a so-called heat pipe 210 is additionally arranged in the cavity 140. The heat pipe 210 can achieve improved cooling of the shaft 130 and thus of the electric motor 110. Furthermore, the heat pipe 210 can be easily installed in the cavity 140.

[0045] Figure 3 schematically shows a device 300 according to a further embodiment. In contrast to the exemplary embodiment according to Figure 1, the device 300 according to Figure 3 does not have an Archimedean screw 150. Instead, the device 300 according to Figure 3 has a jet pump 310, also known as a jet pump. Furthermore, a further pipeline 320 is provided, through which a portion of the air compressed by the compressor 115 can be fed to the jet pump 310. As a result, the air compressed by the compressor 115 can act as a driving medium for the jet pump 310, whereby the cooled exhaust gas 185 can be sucked in by the jet pump 310 and pumped into the cavity 140 in the direction of the compressor 115. As a result, cooling can take place effectively and with improved efficiency.

[0046] Likewise, in the embodiment according to Figure 3, it is also conceivable that a heat pipe 210 is arranged in the cavity 140.

[0047] Figure 4 schematically shows a fuel cell system 400 according to one embodiment. The fuel cell system 400 comprises a device 100, 200, 300 and a fuel cell 125 or a fuel cell stack with a plurality of fuel cells 125. Compressed air is supplied to the cathode K of the fuel cell 125 by the device 100, 200, 300, and an exhaust gas from the cathode K is expanded and cooled by a turbine 120 of the device 100, 200, 300.

[0048] While at least one exemplary embodiment has been described above, it should be appreciated that a large number of variations exist. It should also be noted that the described exemplary embodiments are only non-limiting examples and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description will provide a guide to implementing at least one exemplary embodiment, with the understanding that various changes in the operation and arrangement of the elements described in an exemplary embodiment may be made without departing from the subject matter defined in the appended claims, as well as their legal equivalents.

[0049] 100, 200, 300 device

[0050] 105 housings

[0051] 110 electric motor

[0052] 115 Compressor

[0053] 120 gas turbines

[0054] 125 fuel cell

[0055] 130 Wave

[0056] 140 cavity

[0057] 150 Archimedes screw

[0058] 160 pipe section

[0059] 170 pipeline

[0060] 180 ambient air

[0061] 185 Expanded exhaust gas

[0062] 210 heat pipe

[0063] 310 jet pump

[0064] 320 pipeline

[0065] 400 fuel cell system

[0066] A Anode

[0067] K cathode

Claims

CLAIMS 1. Device (100, 200, 300) for supplying a fuel cell (125) with a gas, comprising: A compression device (115) which is configured to suck in the gas, compress it and feed it to a cathode (K) of the fuel cell (125); an expansion device (120) which is configured to expand an exhaust gas from the cathode (K); wherein the compression device (115) comprises an electric motor (110) with a shaft (130) rotatable about its longitudinal axis, wherein the shaft (130) has a cavity (140) along the longitudinal axis; a pump device (150, 310) which is configured to pump a portion of the expanded exhaust gas (185) through the cavity (140) of the shaft (130) in the direction of the compression device (115).

2. Device (100, 200) according to claim 1, wherein the pumping device comprises an Archimedean screw (150) arranged in the cavity (140) such that rotation of the rotatable shaft (130) causes rotation of the Archimedean screw (150), whereby the expanded exhaust gas can be pumped through the cavity (140) in the direction of the compression device (115).

3. Device (300) according to claim 1 or 2, wherein the pumping device comprises a jet pump (310), and wherein the device (300) comprises a first connecting line (320) through which a part of the gas compressed by the compression device (115) can be supplied to the jet pump (310).

4. Device (100, 200, 300) according to one of the preceding claims, comprising a heat pipe (210) arranged in the cavity (140) of the rotatable shaft (130).

5. Device (100, 200, 300) according to one of the preceding claims, comprising a second connecting line (170) through which an opening of the cavity (140) at which the fluid pumped through the cavity (140) expanded exhaust gas (185) can escape, is fluidly connected to an intake area for the gas to be sucked in by the compression device (115).

6. Device (100, 200, 300) according to one of the preceding claims, wherein the compression device (115) and the expansion device (120) have a common rotatable shaft which is identical to the rotatable shaft (140) of the electric motor (110).

7. A fuel cell system (400) comprising a fuel cell (125) and a device (100, 200, 300) according to any one of the preceding claims.

8. An electrically driven system comprising a fuel cell system (400) according to claim 7.

9. Electrically powered system according to claim 8, comprising a motor vehicle or an emergency power generator for a power supply system.

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