Internal heating strategy for avoiding ice bridges for hydrogen recirculating blowers in fuel cell systems
By providing heat on the recirculation blower to evaporate residual water, the problem of ice bridge formation is solved, and the rapid start of fuel cells is achieved and the complexity of the deicing process is reduced.
Patent Information
- Application Number
- CN202380072526.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-10-13
- Filing Date
- 2023-10-12
- Publication Date
- 2025-06-10
AI Technical Summary
The remaining process water in the recirculation blower may freeze under low temperature conditions, resulting in the formation of ice bridges and hindering the start and operation of the blower.
By providing heat on the recirculation blower, the residual water is evaporated and the heat supply is terminated when the predefined evaporation criteria are met.
The degree of icing on the recirculation blower is significantly reduced, the formation of ice bridges is avoided, the rapid start of the fuel cell is ensured, and the complexity of the deicing process is reduced.
Smart Images
Figure CN120129970A_ABST
Abstract
Description
Background Art
[0001] Fuel cells are known in which a recirculation blower is used to improve the return of unconsumed hydrogen from the exhaust gas outlet of the fuel cell back to the fuel inlet of the fuel cell. The recirculation blower is also referred to as an anode recirculation blower or simply ARB. The recirculation blower is a component of an anode subsystem of the fuel cell, and the anode subsystem typically has a water separator upstream of the recirculation blower for separating process water of the fuel cell.
[0002] To improve the separation of process water, the recirculation blower can also additionally have an integrated water separator. By combining the two water separators, the share of separated process water should be further increased so that as little water as possible is conveyed to the fuel cell inlet by the recirculation blower.
[0003] Even if most of the process water can be separated in this way, a small share of process water may still remain in the anode subsystem, for example in the pipelines or within the recirculation blower. The remaining process water can freeze when the motor vehicle stops and the temperature is below 0 °C and may block movable components or small channels of the fuel cell. In particular, there is such a risk for the recirculation blower: the remaining process water forms an ice bridge.
[0004] An ice bridge is an ice connection formed by freezing between two components. For components that must move relative to each other during operation, an ice bridge is a particularly troublesome problem. Thus, an ice bridge may cause the recirculation blower to be uncontrollable or non-rotatable at startup. A common and well-known location where ice bridges often form is the gap between the magnetic can of the recirculation blower and the gap can of the recirculation blower. Due to the formation of an ice bridge at this location, the rotational startup of the impeller of the recirculation blower can be blocked. If the torque of the recirculation blower is not sufficient to break the ice bridge, the recirculation blower is not operable in this state.
[0005] To ensure the proper operation of the fuel cell, hitherto, devices and methods for melting ice by supplying heat have been used. Heat can be provided, for example, by an additional heating cylinder that can be installed in the impeller housing of the recirculation blower. Alternatively, heat can be provided by generating eddy current losses in the recirculation blower in a targeted manner. In addition, it is known that the recirculation blower can be manipulated in a targeted manner to break the ice bridge, for example, by oscillatory manipulation. The purpose of all these devices and methods is to remove the existing ice within the framework of the startup process of the fuel cell. Summary of the Invention
[0006] According to a first aspect of the present invention, there is provided a method for operating a fuel cell having a recirculation blower. The method has:
[0007] - Provide heat for evaporating water on the recirculation blower through a heating device.
[0008] - Evaporate the water on the recirculation blower through a heating device.
[0009] - Terminate the heat supply when a predefined evaporation criterion is met.
[0010] Preferably, the method is carried out before the ambient temperature of the vehicle reaches or falls below the freezing point.
[0011] Provide heat for evaporating water through a heating device. Providing heat on the recirculation blower can include, within the framework of the present invention, providing heat outside and / or inside the recirculation blower. Preferably, the heat supply is carried out such that the heat is directed to the process water accumulation site where process water accumulates, in order to specifically evaporate the process water. Preferably, heat is provided such that the recirculation blower or at least some parts of the recirculation blower, especially the parts in contact with the process water, are heated to a temperature of at least 100 °C.
[0012] By providing heat over a certain period of time, the water on the recirculation blower is evaporated. Thus, the heat is transferred to the water in such a way that the water evaporates. When a predefined evaporation criterion is met, the heat supply for evaporating water is terminated. The evaporation criterion determines when the heat supply should be terminated. The evaporation criterion can determine, for example, how much water should be reliably evaporated or what share of the total remaining water before evaporation the evaporated water should account for. The evaporation criterion can determine, for example, that at least 95% of the remaining water must be evaporated. The satisfaction of the evaporation criterion can be checked, for example, by means of a characteristic curve field, empirical values or similar methods.
[0013] After the heat supply is terminated, at most only so much water remains in or on the recirculation blower that there is no longer a threat of blocking the channels or rotating parts on the recirculation blower due to frozen water or only to such an extent that the ice that may form can be removed without problems and without necessary delay during the operation of the recirculation blower.
[0014] Compared with traditional methods, the method according to the present invention for operating a fuel cell with a recirculation blower has the advantage that, by simple means and at low cost, the degree of icing on the recirculation blower is significantly reduced. In a corresponding embodiment of the method according to the present invention, the formation of ice in the area of the recirculation blower can be completely prevented. Thus, during the start-up process of the vehicle, the fuel cell can start running again without delay. No complex de-icing process is required anymore. Evaporating the water has the additional advantage that the combustible gas, such as hydrogen, transported to the fuel inlet via the recirculation blower has no or only a minimal amount of water.
[0015] According to a preferred extension of the present invention, it can be provided in a method that heat is provided during the inactive period of the fuel cell. Preferably, the method is carried out directly after the fuel cell is shut down. Shutting down the fuel cell is understood within the framework of the present invention as placing the fuel cell in an inactive state. In the inactive state, the fuel cell is not supplied with hydrogen for combustion, so that neither current is generated nor process water is formed. Preferably, in the inactive state, the fuel cell is also not supplied with oxygen. This has the advantage that by simple means and at low cost, it is ensured that after carrying out the method according to the present invention, no or only very little process water remains on the recirculation blower, because no new process water is generated during the execution of the method. Therefore, the risk of icing is further reduced.
[0016] Preferably according to the present invention, the motor of the recirculation blower is operated as a heating device for providing heat for evaporating water by targeted control of the motor. Preferably, the motor is controlled such that the iron losses are particularly high. This can be achieved, for example, by voltage vectors that are equal in amplitude and have a phase difference of 180°, where the voltage is provided at a pre-given frequency, so that a continuous change in the magnetic flux direction of the motor magnetic field is caused thereby. Preferably, the control is carried out such that no rotating field for rotating the rotor is generated. By targeted control of the motor, the stator and / or rotor of the motor is heated up, preferably to a temperature exceeding 100 °C, so that the remaining process water is evaporated thereby. This has the advantage that heat for evaporating water can be provided by simple means and at low cost. Additional heating devices can be dispensed with, so that the cost and weight of the fuel cell can be reduced.
[0017] Furthermore, preferably, a heating device that can be separately controlled from the recirculation blower is used to provide heat for evaporating water. The heating device is preferably arranged directly on the recirculation blower to specifically heat the recirculation blower. For this purpose, the heating device can have, for example, a heat exchanger and / or a resistance heating element and / or a combustion device or the like. Preferably, the heating device is constructed such that the control of the heating device can be carried out independently of the control of the recirculation blower. Thus, in the case where the heating device is active, the rotor of the recirculation blower can still operate, for example. Preferably, a heating device that can be separately controlled from the recirculation blower and the recirculation blower are used as heating devices to provide the required thermal energy, so that the size design of the separately controllable heating device can be particularly low-cost, space-saving and lightweight. This has the advantage that particularly effective water evaporation is caused by simple means and at low cost.
[0018] In a particularly preferred configuration of the present invention, it can be provided in a method that the recirculation blower operates in the manner of a blower in order to discharge the evaporated water. Due to the evaporation of water, at least a part of the evaporated water is discharged from the fuel cell. In order to prevent the water from re-condensing on the recirculation blower after the heat supply is terminated, that is, the water remains on the recirculation blower and forms an ice bridge when frozen, the recirculation blower is operated to convey the water out of the recirculation blower. This has the advantage that a particularly large proportion of the water can be discharged from the fuel cell by simple means and at low cost, and thus the risk of ice bridge formation is significantly reduced.
[0019] Preferably, a determined duration for providing heat for evaporating water is used as the evaporation criterion. In the case where the heating power of the heating device is known, it can be easily determined based on empirical values, simulations, algorithms, characteristic curve fields or similar methods how much water volume is evaporated after a limited duration at a limited heating power. By estimating the existing water volume before providing heat for evaporating water, the duration can thus be obtained after which the water volume is evaporated. A safety factor can be used here, such that for example, a higher water volume is based on when determining the duration. Thus, it can be ensured that the recirculation blower is also dry after a limited duration after the heat supply. Preferably, the external temperature and / or the temperature of the recirculation blower are taken into account here. The lower this temperature, the greater the heat required to evaporate the same water volume. This has the advantage that reliable drying of the recirculation blower is achieved by simple means and at low cost. In addition, over-supply of heat can be avoided, such that the method can be carried out particularly energy-efficiently.
[0020] According to a preferred embodiment of the present invention, the determined duration is obtained based on the water volume obtained on the recirculation blower and / or based on the evaporation power of the heating device. The water volume can be obtained, for example, by sensors, empirical values, operating data of the fuel cell, simulations, algorithms, characteristic curve fields or similar methods. The evaporation power of the heating device can be obtained, for example, via empirical values, simulations, algorithms, characteristic curve fields or similar methods. Preferably, the determined duration is determined by obtaining the water volume and the evaporation power. This has the advantage that reliable drying of the recirculation blower is achieved by simple means and at low cost. In addition, over-supply of heat can be avoided, such that the method can be carried out particularly energy-efficiently.
[0021] Particularly preferably, the heating device is controlled by the blower control device of the recirculation blower and / or the central control device of the fuel cell to provide heat for evaporating water. Within this framework, for example, it can be provided that the heating device, which is configured to be controllable separately from the recirculation blower, is controlled by the blower control device or by the central control device. Similarly, the recirculation blower can be controlled by the blower control device or by the central control device as a heating device. Within the framework of the present method, it can be provided that the recirculation blower and / or the separately configured heating device are controlled in parallel by the blower control device and the central control device respectively. This has the advantage that reliable control of the heating device for providing heat can be ensured by simple means and at low cost.
[0022] Preferably according to the invention, the external temperature in the fuel cell area is determined, and when the external temperature is below the temperature threshold, heat for evaporating water is provided purposefully. The temperature threshold can be, for example, between 3 °C and 5 °C. When the external temperature is above the ambient threshold, no heat for evaporating water is provided. For the external temperature, the real-time external temperature and / or the predicted external temperature, i.e., the externally expected temperature in the future, can be used. The value of the external temperature can be determined, for example, via the temperature sensor of the vehicle. This has the advantage that the temperature actually endured by the fuel cell can be determined in this way. Thus, for example, it can be prevented that heat is provided when the motor vehicle is parked in a garage with a positive temperature while the surrounding environment of the garage already has a negative temperature. Alternatively, the value of the external temperature can be obtained from a server and, for example, be based on the meteorological data of a weather station. Similarly, the external temperature can be determined from a temperature prediction based on meteorological data or empirical values. For example, it can be that the real-time external temperature is greater than 5 °C, while the externally predicted temperature estimated for several hours later is below 0 °C. The temperature prediction can also be carried out, for example, taking into account empirical values. When the temperature is approximately 6 °C at 16:00 in winter, it can be considered that the external temperature may drop below 0 °C by 24:00. In this case, it is preferable to provide heat at a time point when the recirculation blower is expected to have the maximum temperature, so that the heat to be provided for evaporating water has the minimum value, because at this time the waste heat of the recirculation blower can be fully utilized. This has the advantage that the economy in implementing the method according to the invention can be improved by simple means and at low cost.
[0023] According to a second aspect of the present invention, a fuel cell for directly generating electric energy from hydrogen is provided. The fuel cell has an anode, a cathode, an electrolyte membrane arranged between the anode and the cathode, an electrolyte, a fuel inlet, an oxygen inlet, an exhaust gas outlet, a recirculation blower for returning the unconsumed fuel from the exhaust gas outlet back, a water outlet for discharging water from the fuel cell, and a central control device for controlling the fuel cell. According to the invention, the fuel cell is configured to perform the method according to the invention.
[0024] Preferably, the recirculation blower mechanism of the fuel cell is configured to provide a heating device for providing heat for evaporating water on the recirculation blower. Alternatively or additionally, the fuel cell may have an additional heating device for providing heat for evaporating water. The central control device is configured to control the fuel cell. Preferably, the central control device is configured to control the recirculation blower. According to the present invention, it may be provided that the fuel cell has an additional blower control device for controlling the recirculation blower. The fuel cell preferably has one or more water separators for separating process water during the operation of the fuel cell. The outlet of the water separator is preferably coupled in fluid communication with the water outlet. Via the water outlet, water such as process water can be led out from the fuel cell. The fuel cell is configured to evaporate the remaining water or at least most of the remaining water during the inactive state of the fuel cell by providing heat through the heating device, and discharge the water vapor thus generated or at least most of the water vapor from the fuel cell.
[0025] In the fuel cell according to the present invention, all the advantages described in the method for operating a fuel cell having a recirculation blower according to the first aspect of the present invention are obtained. Therefore, compared with traditional fuel cells, the fuel cell according to the present invention has the advantage that the degree of icing on the recirculation blower can be significantly reduced by simple means and at low cost. When the fuel cell according to the present invention is operated accordingly, the formation of ice in the area of the recirculation blower can be completely prevented. Therefore, during the start-up process of the vehicle, the fuel cell starts running again without delay. No complex de-icing process is required. The evaporation of water has other advantages, that is, the combustible gas, such as hydrogen, delivered to the fuel inlet via the recirculation blower has no or only a minimal amount of water. Description of the Drawings
[0026] The fuel cell according to the present invention and the method for operating the fuel cell according to the present invention will be further explained below with reference to the drawings. The drawings schematically show respectively:
[0027] Figure 1 : A perspective view of the anode subsystem of a fuel cell for performing the method according to the present invention,
[0028] Figure 2 : Figure 1 A cross-sectional view of the recirculation blower of the anode subsystem of
[0029] Figure 3 : A cross-sectional view of a fuel cell according to a preferred embodiment of the present invention,
[0030] Figure 4 : A flowchart of a preferred embodiment of the method according to the present invention.
[0031] Elements having the same function and mode of operation are respectively provided with the same reference signs in Figures 1 to 4 . Detailed Description of the Invention
[0032] In Figure 1 , the anode subsystem 14 of a fuel cell 1 for carrying out the method according to the invention is schematically shown in a perspective view (see Figure 3 ). The anode subsystem 14 has a main water separator 15 and a recirculation blower 2 arranged thereon with an integrated secondary water separator 16.
[0033] Figure 2 The recirculation blower 2 of the anode subsystem 14 is schematically shown in a sectional view Figure 1 . The recirculation blower 2 has an electric motor 4 which is configured to provide a heating device 3 for the heat for evaporating water on or in the recirculation blower 2. The electric motor 4 has a stator 17 which is arranged in a gap tank 18 of the electric motor 4. The stator 17 and the gap tank 18 are together surrounded by a stator housing 19 of the electric motor 4, wherein the stator housing 19 is open on one end face of the gap tank 18.
[0034] An impeller 20 of the electric motor 4 is arranged on a hub 21 of the electric motor 4. A magnetic tank 22 of the electric motor 4 is arranged on the hub 21. The magnetic tank 22 has a plurality of permanent magnets not described in the figures. The impeller 20, the hub 21 and the magnetic tank 22 are arranged in an impeller housing 23 which is open towards the stator 17 of the electric motor 4. The hub 21 is rotatably supported on the impeller housing 23.
[0035] The magnetic tank 22 is arranged adjacent to and directly facing the gap tank 18 such that a gap is formed between the magnetic tank 22 and the gap tank 18, and water W is arranged in the gap. By carrying out the method according to the invention, the water W can be evaporated such that an ice bridge cannot be formed between the magnetic tank 22 and the gap tank 18.
[0036] In Figure 3 , a fuel cell 1 according to a preferred embodiment of the invention is schematically shown in a sectional view. The fuel cell 1 has an anode 7 and a cathode 8 arranged in an electrolyte E. An electrolyte membrane 9 is arranged between the anode 7 and the cathode 8. For supplying hydrogen, the fuel cell 1 has a fuel inlet 10 on the anode side. For discharging anode gas, the fuel cell 1 has an exhaust gas outlet 12 on the anode side. For supplying oxygen, the fuel cell 1 has an oxygen inlet 11 on the cathode side. For discharging water W, the fuel cell 1 has a water outlet 13 on the cathode side. For controlling the fuel cell 1, the fuel cell 1 has a central control device 6.
[0037] Furthermore, the fuel cell has an anode subsystem 14, which has a recirculation blower 2 that can operate as a heating device 3, an additional optional heating device 3, and a blower control device 5 for controlling the recirculation blower 2. To discharge the separated water W, the anode subsystem 14 and the water outlet 13 are coupled in fluid communication. To return the unconsumed hydrogen, the anode subsystem 14 is coupled in fluid communication via a return line 24 and the fuel inlet 10.
[0038] Figure 4 Schematically, a preferred embodiment of the method according to the invention is shown in a flow chart. In a first method step 100, the operating state of the fuel cell 1 is monitored, for example by means of a central control device 6 of the fuel cell 1. If the central control device 6 determines an inactive state of the fuel cell 1, for example when the vehicle is parked, then in a second method step 200 the external temperature in the region of the fuel cell 1 is monitored. Here, for example, the real-time external temperature or the predicted external temperature can be monitored. The monitoring of the external temperature can also be carried out already when the fuel cell 1 is still active.
[0039] If the external temperature is below a determined temperature threshold and the fuel cell is in an inactive state, then in a third method step 300 the heating device 3 of the fuel cell 1 is controlled by means of the blower control device 5 and / or the central control device 6 such that heat is provided for evaporating the water W on the recirculation blower 2. This can be done, for example, by purposefully controlling the recirculation blower 2 to generate high iron losses and thus high heat losses and / or by controlling the optional additional heating device 3. In a fourth method step 400, if a predefined evaporation criterion is met, such as a predefined length of time, a predefined amount of heat or a similar criterion, then the supply of heat is terminated. The evaporation criterion is determined such that after the execution of the method no water W remains in the recirculation blower 2 or only a very small amount of water W remains in the recirculation blower 2, so that even when the recirculation blower 2 cools below 0 °C, an ice bridge is avoided between the moving parts of the recirculation blower 2 or the lines of the recirculation blower 2 are not blocked by ice. In this way, a rapid start of the fuel cell 1 can be ensured without a melting process.
Claims
1. A method for operating a fuel cell (1) with a recirculation blower (2), comprising: providing heat for evaporating water (W) on the recirculation blower (2) by means of a heating device (3), evaporating the water (W) on the recirculation blower (2) by means of the heating device (3), and terminating the heat supply when a predefined evaporation criterion is met.
2. The method according to claim 1, characterized in that the heat supply is carried out during periods when the fuel cell (1) is inactive.
3. The method according to claim 1 or 2, characterized in that the electric motor (4) of the recirculation blower (2) operates as a heating device (3) for providing heat for evaporating water (W) by targeted control of the electric motor (4).
4. The method according to any one of the preceding claims, characterized in that a heating device (3) that can be separately controlled from the recirculation blower (2) is used to provide heat for evaporating water (W).
5. The method according to any one of the preceding claims, characterized in that the recirculation blower (2) operates in a blower mode to discharge the evaporated water (W).
6. The method according to any one of the preceding claims, characterized in that a determined duration for providing heat for evaporating water (W) is used as the evaporation criterion.
7. The method according to claim 6, characterized in that the determined duration is determined based on the amount of water determined on the recirculation blower (2) and / or based on the evaporation power of the heating device (3).
8. The method according to any one of the preceding claims, characterized in that the heating device (3) is controlled by the blower control device (5) of the recirculation blower (2) and / or by the central control device (6) of the fuel cell (1) to provide heat for evaporating water (W).
9. The method according to any one of the preceding claims, characterized in that the external temperature in the region of the fuel cell (1) is determined, and when the external temperature is below a temperature threshold, heat for evaporating water (W) is provided in a targeted manner.
10. A fuel cell (1) for directly generating electrical energy from hydrogen, having an anode (7), a cathode (8), an electrolyte membrane (9) arranged between the anode (7) and the cathode (8), an electrolyte (E), a fuel inlet (10), an oxygen inlet (11), an exhaust gas outlet (12), a recirculation blower (2) for returning unconsumed fuel from the exhaust gas outlet (12), a water outlet (13) for discharging water (W) from the fuel cell (1), and a central control device (6) for controlling the fuel cell (1), characterized in that the fuel cell (1) is configured to perform the method according to any one of the preceding claims.