Diagnostic method for detecting a blockage or leakage of an anode recirculation portion

Abstract

The present invention relates to a diagnostic method for detecting a blockage or a leakage of an anode recirculation portion (112) of a fuel cell stack (110) of a fuel cell system (100), comprising the steps of: - measuring an anode recirculation pressure (PRZ) in the anode recirculation portion (112) of the fuel cell stack (110); - measuring an anode supply pressure (PAZ) in an anode supply portion (122) downstream of a mixing portion (114) with the anode recirculation portion (112) of the fuel cell stack (110); - calculating a difference (Dif) of the anode supply pressure (PAZ) and the anode recirculation pressure (PRZ); and - comparing the difference (Dif) with a reference value (R) in order to detect a blockage or a leakage in the anode recirculation portion (112).

Description

[0001] Diagnostic method for detecting a blockage or leakage of an anode recirculation section

[0002] The present invention relates to a diagnostic method for detecting a blockage or a leakage of an anode recirculation section, a computer program product for carrying out such a diagnostic method and a diagnostic device for detecting a blockage or a leakage of an anode recirculation section.

[0003] It is known in the prior art that a portion of the anode exhaust gas coming from the anode section of a fuel cell stack is guided from the anode exhaust section via the anode recirculation section to the anode supply section. The anode exhaust gas is mixed with the anode supply section via a mixing section. If a blockage or leak occurs in the anode recirculation section, this portion of the anode exhaust gas cannot be mixed with the anode supply section as desired.

[0004] Against this background, one object of the present invention is to at least partially remedy the disadvantages described above. In particular, the object of the present invention is to be able to diagnose whether a blockage or leakage has occurred in the anode recirculation section.

[0005] The above object is achieved by a diagnostic method having the features of claim 1, a computer program product having the features of claim 14, and a diagnostic device having the features of claim 15. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the diagnostic method according to the invention naturally also apply in connection with the computer program product according to the invention and the diagnostic device according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0006] Accordingly, a diagnostic method for detecting a blockage or leakage of an anode recirculation section of a fuel cell stack of a fuel cell system is described. The diagnostic method comprises the following steps:

[0007] Measuring an anode recirculation pressure in the anode recirculation section of the fuel cell stack,

[0008] Measuring an anode feed pressure in an anode feed section downstream of a mixing section with the anode recirculation section of the fuel cell stack,

[0009] Calculating a difference between the anode feed pressure and the anode recirculation pressure, and

[0010] Comparing the difference with a reference value to detect a blockage or leak in the anode recirculation section.

[0011] By comparing the difference between the anode supply pressure and the anode recirculation pressure with the reference value, it can be determined whether there is a problem in the anode recirculation section, i.e., whether there is a blockage or a leak in the anode recirculation section. In the event of a blockage, the anode exhaust gas flowing in the anode recirculation section is blocked, resulting in no or reduced flow of anode exhaust gas. In the event of a leak, anode exhaust gas can escape from the anode recirculation section. In both cases, this leads to a problem because less anode exhaust gas reaches the mixing section than intended. In the event of such a problem in the anode recirculation section, the entire fuel supply to the anode section can be stopped.

[0012] Essentially, the anode supply pressure and the anode recirculation pressure can be the same. During normal operation, i.e., operation without malfunctions, only minor fluctuations occur. Excessive fluctuations in the anode recirculation pressure can be diagnosed as a fault.

[0013] In particular, the difference between the anode supply pressure and the anode recirculation pressure is considered and compared with the reference value. Accordingly, it is not important that the lower pressure be subtracted from the higher pressure or vice versa.

[0014] The anode recirculation section connects the anode discharge section for discharging anode exhaust gas from the anode section with the anode supply section for supplying anode supply gas to the anode section. The portion of the anode exhaust gas supplied to the anode recirculation section is supplied to the anode supply section via the mixing section.

[0015] Recirculation can, in particular, be passive recirculation. The difference between the anode supply pressure and the anode recirculation pressure can be measured using a Venturi nozzle. The diagnostic procedure can therefore be applied particularly to a passive anode recirculation section with a Venturi nozzle.

[0016] The reference value is determined, in particular, before measuring the anode supply pressure and the anode recirculation pressure. However, the reference value may depend on the anode supply pressure and / or the anode recirculation pressure.

[0017] In the mixing section, the newly supplied fuel (e.g. hydrogen) is mixed with the anode exhaust gas from the anode recirculation section and passed to the anode section via the anode supply section.

[0018] The fuel cell stack may comprise multiple fuel cells. The fuel cell system may in turn comprise multiple fuel cell stacks.

[0019] According to one embodiment of the diagnostic method, the reference value depends on the anode supply pressure. In particular, the reference value can be a function of the anode supply pressure. According to another embodiment of the diagnostic method, the reference value depends on the anode recirculation pressure. In particular, the reference value can be a function of the anode recirculation pressure.

[0020] According to a further embodiment of the diagnostic method, a corridor is determined with an upper corridor limit and a lower corridor limit, the corridor having a diameter from the upper corridor limit to the lower corridor limit that is twice the reference value. The corridor is a range of pairs of an anode supply pressure and an anode recirculation pressure, each of which does not result in an error message. For these pairs, the condition applies that the difference between the anode supply pressure and the anode recirculation pressure is smaller than the reference value. In particular, the magnitude of the anode supply pressure and the anode recirculation pressure is smaller than the reference value.

[0021] According to a further embodiment of the diagnostic method, a point at which the anode supply pressure is equal to the anode recirculation pressure is defined as a corridor center. The corridor upper limit and the corridor lower limit are each spaced from the corridor center by the reference value. The point is a pair of an anode supply pressure and an anode recirculation pressure. The corridor upper limit minus the corridor center equals the reference value. Furthermore, the corridor center minus the corridor lower limit also equals the reference value.

[0022] According to a further embodiment of the diagnostic method, the corridor upper limit and the corridor lower limit form a straight line as a function of the anode supply pressure or the anode recirculation pressure. In particular, for the corridor upper limit and / or the corridor lower limit, the anode recirculation pressure is equal to the anode supply pressure times a constant, or the anode supply pressure is equal to the anode recirculation pressure times a constant.

[0023] According to a further embodiment of the diagnostic method, the reference value is determined by measurements. Alternatively, the reference value is calculated. The reference value can be or be determined by measurements in which many measurements are or are carried out during normal operation, i.e. operation without faults. Furthermore, it is also possible for measurements to be carried out on a test bench, and the reference value to be determined in this way. In these cases, the reference value is set such that the difference between the anode supply pressure and the anode recirculation pressure is smaller than the reference value. In particular, the absolute value of this difference is smaller than the reference value. This means that the measuring points are then within the corridor during normal operation. Alternatively, theoretical considerations and calculations can also be used to define the reference value and thus the corridor.

[0024] According to a further embodiment of the diagnostic method, a recirculation rate lies between 0% and 100%, between 20% and 80%, or between 40% and 60%, with the reference value depending on the recirculation rate. Alternatively, the recirculation rate lies between 0% and 40%, between 5% and 30%, or between 10% and 20%, with the reference value depending on the recirculation rate. In a further alternative, the recirculation rate lies between 60% and 100%, between 70% and 95%, or between 80% and 90%, with the reference value depending on the recirculation rate. The recirculation rate is the proportion of the anode exhaust gas that is returned to the anode feed section.

[0025] According to a further embodiment of the diagnostic method, the reference value depends on influencing parameters. Such influencing parameters include, for example, a start-up of the fuel cell system, a cold start of the fuel cell system, or a shutdown of the fuel cell system. Environmental parameters, such as the ambient temperature or ambient pressure, also belong to the influencing parameters. The diagnostic method can be stopped if influencing parameters are present and cannot or should not be taken into account.

[0026] According to a further embodiment of the diagnostic method, the reference value is a previously determined absolute value. The absolute value is a specific differential pressure value. The difference between the anode supply pressure and the anode recirculation pressure, or the magnitude of this difference, is then compared with this differential pressure value. "Previously determined" means that the absolute value is determined before the anode supply pressure and the anode recirculation pressure are measured. The absolute value can be determined by measurements or calculated based on theoretical considerations. According to a further embodiment of the diagnostic method, the diagnostic method is stopped during a special situation. Advantageously, the diagnostic method can be stopped if it would not deliver reliable or even incorrect results. A special situation could be, for example, the separation of water accumulations in the anode recirculation section.For this purpose, the accumulated water is drained into depressions, for example. Another special situation could be, for example, flushing the anode recirculation section. In principle, a special situation could be any situation in which the otherwise closed anode recirculation section needs to be opened.

[0027] According to a further embodiment of the diagnostic method, the diagnostic method is stopped, and a fault signal is output if the difference is greater than the reference value. In particular, the diagnostic method is stopped, and a fault signal is output if the difference between the anode supply pressure and the anode recirculation pressure is greater than the reference value. The fuel supply to the anode section can also be stopped. The fuel can be hydrogen.

[0028] According to a further embodiment of the diagnostic method, an output is provided indicating that the anode recirculation pressure is unproblematic if the difference is smaller than the reference value. In particular, such an output is provided if the absolute value of the difference between the anode supply pressure and the anode recirculation pressure is smaller than the reference value. "Unproblematic" means, in particular, that when measuring one anode supply pressure and one anode recirculation pressure, this pair is within the corridor described above, which indicates no malfunctions. The output can, for example, indicate visually or acoustically that the anode recirculation pressure is unproblematic and that no maintenance or the like is required.

[0029] Furthermore, the present invention relates to a computer program product comprising instructions which, when executed by a computer, cause the computer to perform the steps of a diagnostic method according to the invention. Thus, a computer program product according to the invention also provides the same advantages as those explained in detail with reference to a diagnostic method according to the invention.

[0030] Furthermore, a diagnostic device for detecting a blockage or leakage of an anode recirculation section of a fuel cell stack of a fuel cell system is provided. The diagnostic device comprises an anode recirculation pressure measuring module for measuring an anode recirculation pressure in the anode recirculation section of the fuel cell stack, an anode supply pressure measuring module for measuring an anode supply pressure in an anode supply section downstream of a mixing section with the anode recirculation section of the fuel cell stack, a calculation module for calculating a difference between the anode supply pressure and the anode recirculation pressure, and a comparison module for comparing the difference with a reference value to detect a blockage or leakage in the anode recirculation section.

[0031] The anode recirculation pressure measuring module, the anode supply pressure measuring module, the calculation module and / or the comparison module are designed in particular for carrying out the diagnostic method according to the invention.

[0032] Further possible implementations of the invention also include combinations of features described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0033] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments are described in detail with reference to the drawings. They show:

[0034] Fig. 1 is a schematic view of a fuel cell system with a fuel cell stack and a diagnostic device;

[0035] Fig. 2 is a diagram showing the process steps of a diagnostic procedure;

[0036] Fig. 3 is a diagram in which the anode recirculation pressure is plotted against the anode supply pressure; and Fig. 4 is a diagram in which the anode supply pressure is plotted against the anode recirculation pressure.

[0037] Fig. 1 shows a schematic view of a fuel cell system 100 with a fuel cell stack 110 and a diagnostic device 10. The fuel cell stack 110 has an anode section 120, a cathode section 130, an anode supply section 122, an anode discharge section 124, and an anode recirculation section 112. The anode supply section 122 serves to supply anode supply gas AZG to the anode section 120. Furthermore, the anode discharge section 124 serves to discharge anode exhaust gas AAG from the anode section 120. By means of the anode recirculation section 112, a portion of the anode exhaust gas AAG can be conducted from the anode discharge section 124 to the anode supply section 122. The part of the anode exhaust gas AAG is fed to the anode feed section 122 via a mixing section 114.

[0038] The diagnostic device 10 comprises an anode recirculation pressure measuring module 20, an anode supply pressure measuring module 30, a calculation module 40, and a comparison module 50. The diagnostic device 10 serves to detect a blockage or leakage of the anode recirculation section 112 of the fuel cell stack 110. Using the anode recirculation pressure measuring module 20, an anode recirculation pressure PRZ in the anode recirculation section 112 can be measured. Furthermore, using the anode supply pressure measuring module 30, an anode supply pressure PAZ in the anode supply section 122 downstream of the mixing section 114 with the anode recirculation section 112 can be measured. The calculation module 40 is used to calculate a difference Dif of the anode supply pressure PAZ and the anode recirculation pressure P Z. The comparison module 50 is used to compare the difference Dif with a reference value R in order to detect a blockage or a leak in the anode recirculation section 112.

[0039] Fig. 2 shows a diagram with the process steps of a diagnostic method. The diagnostic method is used to detect a blockage or leak in the anode recirculation section 112 of the fuel cell stack 110.

[0040] In a first step S1, an anode recirculation pressure PRZ is measured in the anode recirculation section 112 of the fuel cell stack 110. In a second step S2, an anode supply pressure PAZ is measured in the anode supply section 122 downstream of the mixing section 114 with the anode recirculation section 112.

[0041] Steps S1 and S2 can be reversed in their sequence. Furthermore, steps S1 and S2 can also be performed simultaneously.

[0042] In a third step S3, a difference Dif between the anode supply pressure PAZ and the anode recirculation pressure PRZ is measured.

[0043] In a fourth step S4, the difference Dif is compared with a reference value R to detect a blockage or leak in the anode recirculation section 112. By comparing with the reference value R, it can be determined whether there are problems in the anode recirculation section 112 that impede the supply of anode exhaust gas AAG to the anode supply section 122.

[0044] Fig. 3 shows a diagram in which the anode recirculation pressure PZ is plotted against the anode supply pressure PAZ. Each point 60 in the diagram corresponds to a pair of an anode supply pressure PAZ and an anode recirculation pressure PRZ. The diagram shows a corridor K with a corridor upper limit Ko and a corridor lower limit Ku. The corridor K has a diameter D from the corridor upper limit Ko to the corridor lower limit Ku, which is twice as large as the reference value R. The points at which the anode supply pressure PAZ is equal to the anode recirculation pressure PRZ form the corridor center KM. The corridor upper limit Ko and the corridor lower limit Ku are each spaced from the corridor center K by the reference value R.

[0045] Since the anode supply pressure PAZ is equal to the anode recirculation pressure PRZ at the corridor center KM, the distance of point 60 shown in Fig. 3 from the corridor center KM represents the difference Dif between the anode supply pressure PAZ and the anode recirculation pressure PRZ. In particular, the absolute value of the difference Dif between the anode supply pressure PAZ and the anode recirculation pressure PRZ can be considered. Then, when comparing with the reference value R, it is not necessary to subtract the smaller pressure value from the larger pressure value. Small fluctuations in the anode supply pressure PAZ and the anode recirculation pressure PRZ are normal. If the difference Dif between the anode supply pressure PAZ and the anode recirculation pressure PZ is large, this is an indicator that a problem has occurred in the anode recirculation section 112, e.g. a blockage or leakage.At all points 60 located within the corridor K, the condition that the difference Dif is smaller than the reference value R applies. In this case, an output can be generated indicating that the anode recirculation pressure PRZ is unproblematic. Otherwise, if the difference Dif is greater than the reference value R, the diagnostic procedure can be stopped and a fault signal can be output. Furthermore, the fuel supply to the anode section 120 of the fuel cell stack 110 can be completely stopped.

[0046] As shown in Figure 3, the reference value R depends on the anode supply pressure PAZ. Furthermore, the upper limit of the corridor Ko and the lower limit of the corridor Ku can form a straight line as a function of the anode supply pressure PAZ. The condition PRZ = k * PAZ can then apply, where k is a different constant for the upper limit of the corridor Ko and the lower limit of the corridor Ku.

[0047] Alternatively, the reference value R can be a previously determined absolute value.

[0048] Fig. 4 shows a diagram in which the anode supply pressure PAZ is plotted against the anode recirculation pressure PRZ. The difference between which pressure is plotted against which pressure distinguishes the otherwise identical Figures 3 and 4. Accordingly, only the fact that the reference value R can depend on the anode recirculation pressure PRZ will be discussed.

[0049] The reference value R can be determined by measurements, e.g., on a test bench. Alternatively, the reference value R can be calculated using theoretical considerations. Furthermore, the reference value R can depend on an influencing parameter. Such an influencing parameter is, for example, the ambient temperature or the ambient pressure.

[0050] The recirculation rate, i.e., the proportion of the anode exhaust gas AAG that is directed to the anode feed section 122, can be between 0% and 100%, between 20% and 80%, or between 40% and 60%. The reference value R can depend on this recirculation rate.

[0051] Furthermore, it is possible to stop the diagnostic procedure during a special situation. A special situation is, for example, a situation in which the otherwise closed anode recirculation section 112 is opened. In such a situation, the diagnostic procedure would not provide correct values.

[0052] List of reference symbols

[0053] 10 Diagnostic device

[0054] 20 Anode recirculation pressure measuring module

[0055] 30 Anode feed pressure measuring module

[0056] 40 Calculation module

[0057] 50 Comparison module

[0058] 60 positions

[0059] 100 fuel cell system

[0060] 1 10 fuel cell stacks

[0061] 1 12 Anode recirculation section

[0062] 1 14 Mixing section

[0063] 120 anode section

[0064] 122 Anode feed section

[0065] 124 Anode discharge section

[0066] 130 Cathode section

[0067] AZG anode feed gas

[0068] AAG anode exhaust gas

[0069] R reference value

[0070] PZ anode recirculation pressure

[0071] PAZ anode feed pressure

[0072] Dif Difference

[0073] K Corridor

[0074] D Diameter

[0075] Ko corridor ceiling

[0076] Ku corridor lower limit KM corridor middle

[0077] 51 Step 1

[0078] 52 Step 2

[0079] 53 Step 3

[0080] 54 Step 4

Claims

Patent claims 1 . Diagnostic method for detecting a blockage or a leakage of an anode recirculation section (112) of a fuel cell stack (110) of a fuel cell system (100), characterized by the steps: - measuring an anode recirculation pressure (PRZ) in the anode recirculation section (112) of the fuel cell stack (110), - measuring an anode feed pressure (PAZ) in an anode feed section (122) downstream of a mixing section (114) with the anode recirculation section (112) of the fuel cell stack (110), - Calculating a difference (Dif) of the anode feed pressure (PAZ) and the anode recirculation pressure (PRZ), and - comparing the difference (Dif) with a reference value (R) to detect a blockage or a leak in the anode recirculation section (112).

2. Diagnostic method according to claim 1, characterized in that the reference value (R) is dependent on the anode supply pressure (PAZ).

3. Diagnostic method according to claim 1 or 2, characterized in that the reference value (R) is dependent on the anode recirculation pressure (PZ).

4. Diagnostic method according to one of the preceding claims, characterized in that a corridor (K) with a corridor upper limit (Ko) and a corridor lower limit (Ku) is determined, wherein the corridor (K) has a diameter (D) from the corridor upper limit (Ko) to the corridor lower limit (Ku) which is twice as large as the reference value (R).

5. Diagnostic method according to claim 4, characterized in that a point at which the anode supply pressure (PAZ) is equal to the anode recirculation pressure (PRZ) is defined as a corridor center (KM), and the corridor upper limit (Ko) and the corridor lower limit (Ku) are each spaced from the corridor center (K ​​) by the reference value (R).

6. Diagnostic method according to claim 4 or 5, characterized in that the corridor upper limit (Ko) and the corridor lower limit (Ku) form a straight line as a function of the anode supply pressure (PAZ) or the anode recirculation pressure (PRZ).

7. Diagnostic method according to one of the preceding claims, characterized in that the reference value (R) is determined by measurements, or that the reference value (R) is calculated.

8. Diagnostic method according to one of the preceding claims, characterized in that a recirculation rate is between 0% and 100%, between 20% and 80%, or between 40% and 60%, and the reference value (R) is dependent on the recirculation rate.

9. Diagnostic method according to one of the preceding claims, characterized in that the reference value (R) is dependent on influencing parameters.

10. Diagnostic method according to claim 1, characterized in that the reference value (R) is a previously determined absolute value. 1 1. Diagnostic method according to one of the preceding claims, characterized in that the diagnostic method is stopped during a special situation.

12. Diagnostic method according to one of the preceding claims, characterized in that the diagnostic method is stopped and an interference signal is output if the difference (Dif) is greater than the reference value (R).

13. Diagnostic method according to one of the preceding claims, characterized in that an output is provided which indicates that the anode recirculation pressure (PRZ) is unproblematic if the difference (Dif) is smaller than the reference value (R).

14. A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the steps of a diagnostic method having features of any one of claims 1 to 13.

5. Diagnostic device (10) for detecting a blockage or a leakage of an anode recirculation section (112) of a fuel cell stack (110) of a fuel cell system (100), characterized by an anode recirculation pressure measuring module (20) for measuring an anode recirculation pressure (PRZ) in the anode recirculation section (112) of the fuel cell stack (110), an anode supply pressure measuring module (30) for measuring an anode supply pressure (PAZ) in an anode supply section (122) downstream of a mixing section (114) with the anode recirculation section (112) of the fuel cell stack (110), a calculation module (40) for calculating a difference (Dif) between the anode supply pressure (PAZ) and the anode recirculation pressure (PRZ), and a Comparison module (50) for comparing the difference (Dif) with a reference value (R) in order to detect a blockage or a leak in the anode recirculation section (112).

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