DE102022132052A1 - Method for operating a fuel cell device, fuel cell device and fuel cell vehicle - Google Patents

Abstract

The invention relates to a method for operating a fuel cell device (1) with a fuel tank (5), a fuel cell stack (2) and a fuel line (8) connecting the fuel tank (5) to the fuel cell stack (2), to which a plurality of injectors (13) is assigned, for the control of which a 2-point hysteresis controller (19) is provided, comprising the steps:
a) Check whether the fuel cell stack (2) is operated in a lower load range for which the supply from only one of the injectors (13) is sufficient,
b) in the event that the fuel cell stack (2) is operated in the lower load range, rolling control of the injectors (13),
c) temporal recording of the pressure increase for each injector (13) when it is put into use as a quality criterion for the flow of the fuel,
d) Comparison of the pressure increases of the injectors (13),
e) issuing a warning message if a difference between the pressure increases exceeds a predetermined or predeterminable threshold.
The invention further relates to a fuel cell device (1) and a fuel cell vehicle.

Description

1. a) Überprüfen, ob der Brennstoffzellenstapel in einem unteren Lastbereich, für den die Versorgung mit nur einem der Injektoren ausreichend ist, betrieben wird,
2. b) für den Fall, dass der Brennstoffzellenstapel in dem unteren Lastbereich betrieben wird, rollierende Ansteuerung der Injektoren, also Nutzung des ersten Injektors für die erste Hysterese und sukzessive Nutzung eines der weiteren Injektoren für die weiteren Hysterese, bis nach der Nutzung sämtlicher Injektoren erneut der erste Injektor genutzt wird,
3. c) zeitliche Erfassung des Druckanstieges für jeden Injektor bei dessen Nutzungsaufnahme als Gütekriterium für den Durchfluss des Brennstoffes,
4. d) Vergleich der Druckanstiege der Injektoren,
5. e) Ausgabe einer Warnmeldung, sofern eine Differenz zwischen den Druckanstiegen einen vorgegebenen oder vorgebbaren Schwellenwert überschreitet.

The invention relates to a method for operating a fuel cell device with a fuel tank, a fuel cell stack and a fuel line connecting the fuel tank to the fuel cell stack, to which a plurality of injectors is assigned, for the control of which a 2-point hysteresis controller is provided, comprising the steps:

1. a) Check whether the fuel cell stack is operated in a lower load range for which the supply from only one of the injectors is sufficient,
2. b) in the event that the fuel cell stack is operated in the lower load range, rolling control of the injectors, i.e. use of the first injector for the first hysteresis and successive use of one of the other injectors for the further hysteresis until the first injector is used again after all injectors have been used,
3. c) temporal recording of the pressure increase for each injector when it is put into use as a quality criterion for the flow of the fuel,
4. d) Comparison of the pressure increases of the injectors,
5. (e) issuing a warning message if a difference between the pressure increases exceeds a predetermined or predeterminable threshold.

The invention further relates to a fuel cell device and a fuel cell vehicle.

Fuel cell devices are used for the chemical conversion of a fuel with oxygen to water in order to generate electrical energy. For this purpose, fuel cells contain the so-called membrane electron unit as a core component, which is a composite of a proton-conducting membrane and an electrode arranged on both sides of the membrane, namely an anode and a cathode. In order to supply the majority of fuel cells combined in a fuel cell stack with sufficient fuel, in particular hydrogen, injectors are used between a hydrogen tank and the anode side of the fuel cell stack to regulate the hydrogen pressure. The hydrogen target pressure results from a power requirement and the associated current, which is then determined using the Faraday constant and a lambda factor. In order to control the injectors and regulate the required pressure, a 2-point hysteresis controller is used, which regulates the degree of opening of the injectors. To determine the hydrogen consumption more precisely, the injectors can also be released depending on the load point and, for example, in the lower load range the pressure is regulated with only one injector, at partial load with two injectors and at full load with three injectors.

The EN 10 2005 047 972 A1 shows an anode inlet unit for a fuel cell system that uses multiple injectors to control the hydrogen flow rate. At a low flow rate, the duty cycle of one of the injectors is controlled and the other injectors are kept closed. As the flow rate increases, the duty cycle of the injector is increased until it is fully open and then other injectors are controlled in the same way one after the other. In the EN 10 2008 010 305 A1 A method is disclosed which detects and reduces the pressure increase caused by a defective open injector. AT 522100 A1 A method for creating an injection strategy for a fuel cell system is known in which a control error is determined as a difference value between the desired anode pressure and a current anode pressure in order to then determine a desired injection frequency.

The problem is that the injectors can drift during production, i.e. they can inject a different amount of hydrogen at the same load point and the same pre-pressure, or they can be open for different lengths of time, meaning that the injectors are not the same and have different characteristics. In the worst case, not enough hydrogen can be injected, which leads to an undersupply with insufficient power and possible damage to the fuel cells.

It is therefore an object of the present invention to provide an improved method for operating a fuel cell device and an improved fuel cell device as well as an improved fuel cell vehicle.

This object is achieved by a method having the features of claim 1, by a fuel cell device having the features of claim 6 and by a fuel cell vehicle having the features of claim 7. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

The method mentioned above offers the advantages that the operating state of the fuel cell device can be better determined without costly additional sensors, namely by taking advantage of the fact that only one injector is required in the lower load range, which does not always have to be identical but can also be replaced, so that in the end all injectors can be recorded and compared individually.

It is particularly preferred if at least three of the injectors are intended for rolling operation and if the injector causing the difference is identified in the warning message.

This also makes it possible for the injector causing the difference to be excluded from use during operation in the partial load range and/or in the lower load range. As a result, uninterrupted operation of the fuel cell device can be guaranteed in these load ranges.

Even if a warning message is issued in step e), the power that can be delivered by the fuel cell stack can be limited to a value below the maximum power, i.e. if the third injector is also required to be used for the full load range, the detected fault can be taken into account by reducing the power, which also prevents "fuel starvation".

If there is no serious fault but only an impairment affecting consumption, if a difference below the threshold is detected, the calculated fuel consumption can be corrected on the basis of that difference.

The above-mentioned advantages and effects also apply mutatis mutandis to a fuel cell device with a control unit that is set up to carry out the above-mentioned method, and to a fuel cell vehicle with such a fuel cell device, wherein with regard to the fuel cell vehicle in particular the consumption and thus the remaining range can be determined more precisely and it is also possible to advise the user to visit a workshop to replace the injectors in order to prevent damage.

The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and/or shown alone in the figures can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also to be regarded as being included and disclosed by the invention that are not explicitly shown or explained in the figures, but which emerge and can be produced from the explained embodiments using separate combinations of features.

• 1 eine schematische Darstellung einer Brennstoffzellenvorrichtung.

Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and the drawing.

• 1 a schematic representation of a fuel cell device.

In the 1 1 schematically shows a fuel cell device 1 which has a fuel cell or a plurality of fuel cells combined to form a fuel cell stack 2.

Each of the fuel cells comprises a membrane electrode assembly consisting of an anode and a cathode and a proton-conductive membrane separating the anode from the cathode.

Fuel (for example hydrogen) is supplied to the anodes via anode spaces within the fuel cell stack 2. In a polymer electrolyte membrane fuel cell (PEM fuel cell), fuel or fuel molecules are split into protons and electrons at the anode. The membrane allows the protons (for example H ⁺ ) to pass through, but is impermeable to the electrons (e ^- ). The following reaction takes place at the anode: 2H ₂ → 4H ⁺ + 4e ^- (oxidation/electron release). While the protons pass through the membrane to the cathode, the electrons are conducted to the cathode or to an energy storage device via an external circuit. Cathode gas (for example oxygen or oxygen-containing air) can be supplied to the cathodes via cathode spaces within the fuel cell stack 2, so that the following reaction takes place on the cathode side: O ₂ + 4H ⁺ + 4e ^- → 2H ₂ O (reduction/electron absorption).

Compressed air is supplied to the fuel cell stack 2 via a cathode fresh gas line 3 by a compressor 4. In addition, the fuel cell is connected to a cathode exhaust gas line 6. On the anode side, hydrogen in particular is supplied to the fuel cell stack 2 via a fuel line 8 from a fuel tank 5.

In the 1 a plurality of injectors 13 is shown, in the embodiment shown three injectors 13, which act as pressure regulators in order to achieve the desired par for the given power requirement with the associated load point. tial pressure of fresh fuel, whereby at full load all three injectors 13 are used, at partial load two of the three injectors 13 and in the lower load range the use of one of the injectors 13 is sufficient. The desired partial pressure can also be present within an anode circuit, which is created by the anode recirculation line 7. With the anode recirculation line 7, the fuel not used in the fuel cell stack 2 can be fed again to the anode spaces upstream of the fuel cell, so that the anode recirculation line 7 flows back into the fuel line 8. Used fuel is removed from the fuel cell via the anode exhaust line 9. To bring about recirculation, alternatively or additionally a 1 The recirculation fan also shown can be used. In the anode recirculation line 7 there is also a water separator 14 with a water separator valve 15.

To provide the fresh hydrogen, the injectors 13 can be repeatedly opened and closed in order to provide the hydrogen target pressure. After the injectors 13 and upstream of the fuel cell stack 2, the prevailing pressure can be detected by means of a hydrogen pressure sensor 16 and, in addition to the hydrogen target pressure 17, the measured value of the hydrogen pressure sensor 16 can also be fed to a 2-point hysteresis controller 19 as a control signal 18, whereby a sawtooth curve of the fuel pressure results due to the hysteresis pressure control carried out by the control unit with a hysteresis maximum and a hysteresis minimum. Each injector 13 not only has an open or closed position, but can also assume any intermediate position between the open and closed positions.

1. a) Überprüfen, ob der Brennstoffzellenstapel 2 in einem unteren Lastbereich, für den die Versorgung mit nur einem der Injektoren 13 ausreichend ist, betrieben wird,
2. b) für den Fall, dass der Brennstoffzellenstapel 2 in dem unteren Lastbereich betrieben wird, rollierende Ansteuerung der Injektoren 13, also Nutzung des ersten Injektors 13 für die erste Hysterese und sukzessive Nutzung einen der weiteren Injektoren 13 für die weiteren Hysterese, bis nach der Nutzung sämtlicher Injektoren 13 erneut der erste Injektor 13 genutzt wird,
3. c) zeitliche Erfassung des Druckanstieges für jeden Injektor 13 bei dessen Nutzungsaufnahme als Gütekriterium für den Durchfluss des Brennstoffes,
4. d) Vergleich der Druckanstiege der Injektoren 13,
5. e) Ausgabe einer Warnmeldung, sofern eine Differenz zwischen den Druckanstiegen einen vorgegebenen oder vorgebbaren Schwellenwert überschreitet.

To control the state of the injectors 13, a method for operating a fuel cell device 1 with a fuel tank 5, a fuel cell stack 2 and a fuel line 8 connecting the fuel cell tank 5 to the fuel cell stack 2, to which a plurality of injectors 13 is assigned, for the control of which a 2-point hysteresis controller 19 is provided, can be used, which comprises the steps:

1. a) Check whether the fuel cell stack 2 is operated in a lower load range for which the supply from only one of the injectors 13 is sufficient,
2. b) in the event that the fuel cell stack 2 is operated in the lower load range, rolling control of the injectors 13, i.e. use of the first injector 13 for the first hysteresis and successive use of one of the other injectors 13 for the further hysteresis, until after all injectors 13 have been used the first injector 13 is used again,
3. c) temporal recording of the pressure increase for each injector 13 when it is put into use as a quality criterion for the flow of the fuel,
4. d) Comparison of the pressure increases of the injectors 13,
5. (e) issuing a warning message if a difference between the pressure increases exceeds a predetermined or predeterminable threshold.

This takes advantage of the fact that only one injector 13 is required in the lower load range, the characteristics of which can thus be observed in isolation from the behavior of the other injectors 13.

In the exemplary embodiment, at least three of the injectors 13 are provided for rolling operation, so that the injector 13 causing the difference can be identified in the warning message. This then also gives rise to the possibility that the injector 13 causing the difference is excluded from use during operation in the partial load range.

In order to avoid “fuel starvation”, in particular in the event of a warning message being issued in step e), the power that can be delivered by the fuel cell stack 2 can be limited to a value below the maximum power.

However, the method also offers advantages if the difference is below the threshold value, since the calculated fuel consumption can be corrected based on this difference.

The advantages of the invention are particularly evident when a fuel cell device 1 with a control unit that is set up to carry out the above-mentioned method is assigned to a fuel cell vehicle, since its reliability and utility value are increased and the consumption and thus also the remaining range can be determined more precisely.

LIST OF REFERENCE SYMBOLS:

1

Fuel cell device

2

Fuel cell stack

3

Cathode fresh gas line

4

compressor

5

Fuel tank

6

Cathode exhaust line

7

Anode recirculation line

8th

Fuel line

9

Anode exhaust line

10

Fresh gas supply line

11

Cathode exhaust line

13

Injector

14

Water separator

15

Water separator valve

16

Hydrogen pressure sensor

17

Hydrogen target pressure

18

Control signal

19

2-point hysteresis controller

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102005047972 A1 [0004]
• DE 102008010305 A1 [0004]
• AT 522100 A1 [0004]

Claims (7)

Method for operating a fuel cell device (1) with a fuel tank (5), a fuel cell stack (2) and a fuel line (8) connecting the fuel tank (5) to the fuel cell stack (2), to which a plurality of injectors (13) is assigned, for the control of which a 2-point hysteresis controller (19) is provided, comprising the steps: a) checking whether the fuel cell stack (2) is operated in a lower load range for which the supply with only one of the injectors (13) is sufficient, b) in the event that the fuel cell stack (2) is operated in the lower load range, rolling control of the injectors, i.e. use of the first injector for the first hysteresis and successive use of one of the further injectors (13) for the further hysteresis until the first injector (13) is used again after all injectors (13) have been used, c) temporal recording of the pressure increase for each injector (13) at its Use as a quality criterion for the flow of fuel, d) comparison of the pressure increases of the injectors (13), e) issuing a warning message if a difference between the pressure increases exceeds a specified or specifiable threshold value. Procedure according to Claim 1 , characterized in that at least three of the injectors (13) are provided for rolling operation, and that the injector (13) causing the difference is identified in the warning message. Procedure according to Claim 2 , characterized in that the injector (13) causing the difference is excluded from use during operation in the partial load range. Method according to one of the Claims 1 until 3 , characterized in that in the event of a warning message being issued in step e), the power that can be delivered by the fuel cell stack (2) is limited to a value below the maximum power. Method according to one of the Claims 1 until 4 , characterized in that if a difference below the threshold value is detected, the calculated fuel consumption is corrected on the basis of this difference. Fuel cell device (1) with a control device which is configured to carry out the method according to one of the Claims 1 until 5 to carry out. Fuel cell vehicle with a fuel cell device (1) according to Claim 6 .

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