WO2017102445A1

WO2017102445A1 - Method for diagnosing leakage, and fuel cell system

Info

Publication number: WO2017102445A1
Application number: PCT/EP2016/079909
Authority: WO
Inventors: Johannes Schild
Original assignee: Robert Bosch Gmbh
Priority date: 2015-12-17
Filing date: 2016-12-06
Publication date: 2017-06-22
Also published as: JP2019500725A; DE102015225600A1; CN108475797A; CN108475797B; JP6781757B2

Abstract

Disclosed is a method (100) for diagnosing the leakage of at least one first fluid (10) in a fluidic system (1), in particular in a fuel cell system (1), said method comprising the following steps: a) provision of a first reference gradient (210) of an operating pressure (200) of the first fluid (10), b) determination of an operating gradient (201) of the operating pressure (200) at a first operating point (202), c) defining a second reference gradient (211) of the operating pressure (200) by means of a model (220), the model (220) taking into consideration the first reference gradient (210) and at least one other operating parameter (221) at the first operating point (202), d) comparison of the operating gradient (201) and the second reference gradient (211).

Description

description

title

The present invention relates to a method for diagnosing a leak in a fuel cell system and to a fuel cell system itself.

PRIOR ART Various different systems are known from the prior art, which contain a fluid or in which a fluid is conducted. In order to hold the fluid in such a fluid system, such a system is normally at least partially sealed. Due to manufacturing tolerances and due to operational wear, for example. Of seals, it may happen that the system has a leak and that the fluid exits the system.

In particular, in security-relevant systems, such as a

Fuel cell system, it may therefore be useful to a leak

monitor. For this purpose, a permissible, maximum leakage value is often defined at a certain operating point under certain conditions. Over the service life of the fluid system, this is therefore in particular the operating environment taken several times and produced under laboratory conditions, the previously defined operating point with the specific conditions, so that the leakage can be detected under these conditions and tested against the maximum permissible leakage value.

Disclosure of the invention

The present invention relates to a method according to the independent method claim and a device according to the independent

Apparatus claim. Further features and details of the invention will become apparent from the

Subclaims, the description and the drawings. In this case apply

Features and details which have been described in connection with the method according to the invention, of course, also in connection with the fuel cell system according to the invention and in each case vice versa, so that with respect to the disclosure of the individual aspects of the invention always reciprocal reference is or can be.

The measures listed in the dependent claims are advantageous developments and improvements of the independent

Claim specified method possible.

The method according to the invention for diagnosing a leakage (in particular a critical leakage) of at least one first fluid of a fluid system comprises the steps a) to d). According to step a), a first reference gradient of an operating pressure of the first fluid is provided. Step b) includes determining an operating gradient of the operating pressure at a first operating point. According to step c), a second reference gradient of the operating pressure is determined by a model. The model takes into account the first reference gradient and at least one further operating parameter at the first operating point. A comparison of the operating gradient of the second reference gradient takes place in accordance with step d).

In this case, a leakage can be understood in particular as a volume loss of the first fluid from the fluid system per unit of time. A critical leak may also be a leak that can be hazardous to the fluid system or the environment. However, leakage may be critical even if it appears interesting for some other reason, such as the effect on the consumption of the first fluid. An indicator of the

Leakage of the first fluid of the fluid system may in particular be the gradient of the operating pressure. For the purposes of the invention, a gradient may be understood to mean the change with time of a pressure, in particular a pressure drop over time. In other words, for example, a high pressure loss within a short time, and thus in particular a high gradient of the pressure, may be caused by a leak. The first reference gradient of the Operating pressure can therefore also be understood as the limit of the pressure change per unit time under fixed conditions, up to which an operating gradient under these conditions can be classified as non-critical or critical. For example. For example, the first reference gradient may represent a maximum allowable pressure gradient under the specified conditions. In order to determine a gradient of the operating pressure, it is preferably possible to measure a pressure over a period of at least two points in time, so that the quotient of the difference of the measuring points and the time period results in the gradient. The model, which may be, for example, a mathematical, in particular analytical or numerical function, determines the second reference gradient in particular from the first reference gradient and at least one ambient condition in the form of a further operating parameter at the first operating point. In particular, an operating point may comprise a period during the determination of the operating gradient. In this case, the second reference gradient represents in particular a limit of the pressure change per time under real

Conditions up to which an operating gradient can be classified as non-critical or critical. In particular, therefore, an outweighing of the environmental conditions from the set limit of the reference value of the critical leakage. This results for the inventive method the advantage that the diagnosis of leakage at least within certain limits, for example. Within a temperature range in which the model is valid in all operating points is feasible. As a result, creeping leaks can be detected early, in particular so that the maintenance of the

Fluid system is reduced. For example, an extension of

Maintenance intervals may be provided so that a malfunction of the operation is reduced by the method. By virtue of the mathematical basis, the method can, for example, also run automatically in a computer program or can be controlled by a computer program. In particular, the operating gradient of the operating pressure is further easily measurable, so that a precise localization of a leakage point for the diagnosis of the particular critical

Leakage may not be necessary. Advantageously, the first

Reference gradient of the operating pressure also be defined for the fluid system once in a reference operating point. Such a one-time test can, for. B. already be performed under laboratory conditions prior to delivery of the fluid system to the end customer, in particular so that a Tolerance determination individually for each manufactured product is possible. As a result, the accuracy of the method can be increased because in the first

Reference gradients already corresponding real manufacturing deviations are taken into account.

Furthermore, the fluid system may be a fuel cell system, so that the method according to the invention may advantageously be designed to diagnose a leak (in particular a critical leakage) in a fuel cell system. Furthermore, the operating pressure may preferably be an anode pressure of the fuel cell system. This can increase safety in the fuel cell system

be significantly increased in particular. For example, the first fluid may be hydrogen, which is under high pressure in the fuel cell system, and a particularly strong outlet from the fuel

Fuel cell system may pose a potential source of danger. Therefore, early detection of leaks in a fuel cell system is particularly desirable.

It is furthermore conceivable that the method is used in a fluid system in a vehicle or the fluid system is installed in a vehicle while a method according to the invention is being carried out. This correspondingly increases the safety during operation of the vehicle, in particular since the method is carried out under real conditions and thus the real ambient conditions can also be taken into account. Thus, the method z. B. automatically during operation of the vehicle, eg permanent or at regular intervals or fixed triggering functions (eg. Before starting or after stopping) or manually triggered by the driver. Alternatively or additionally, however, it can also be provided that the method is carried out in a workshop, for example during an inspection of the vehicle.

Preferably, the method can be performed when starting the vehicle, so that a malfunction of the operation is reduced and previously formed leaks, especially before a possible hazard, are detected. It is also conceivable that a method according to the invention is carried out under steady-state operating conditions. Thus, for example, it may be provided that a section of the fluid system is at least partially closed by closing at least one valve. This allows the determined

Operating gradient of the operating pressure in the first operating point with increased safety associated with a leakage. This allows an increase in the accuracy of the process and thus increased safety of

Fluid Systems. Under stationary operating conditions can therefore, for example.

be understood that the flow of the first fluid in one

Flow equilibrium is or that no additional pressure of the first fluid, for example, is generated by a pump in the portion of the fluid system.

In the context of the invention, it can furthermore be provided that the model takes into account a secondary pressure of a second fluid based on a further operating parameter in the first operating point. The secondary pressure may preferably be the cathode pressure of a fuel cell.

Preferably, the second fluid can be understood to mean a gas or a liquid, the second fluid particularly preferably a

Can have oxygen. Thus, it may be at the second fluid z. B. to act air. With regard to the consideration of the secondary pressure by the model, the secondary pressure itself, a pressure difference between an anode and a cathode in the fuel cell system or a further quantity dependent on the secondary pressure can represent the further operating parameter. By taking into account the secondary pressure of the second fluid, an environmental parameter can thus be taken into account by the model, which is easy to measure. In particular, the cathode pressure has a great influence on the accuracy of the result, so that consideration of the cathode pressure in a fuel cell system results in a high accuracy of the method and thus an increased safety of the fuel cell system.

Advantageously, it can be provided in a method according to the invention that in the event of exceeding or falling below the second reference gradient by the operating gradient, an error reaction takes place. So z. B. a warning message that another, in particular more accurate test is required or the system can be shut down. This can increase the safety of the fluid system.

In a method according to the invention, the model can advantageously be based on a further operating parameter in the first operating point

Consider condensation of water in the fluid system. For this, the condensation of water may preferably be represented by a partial pressure of the water. In particular, the condensation of water itself, the partial pressure of the water as a function of the condensation of water or a further quantity dependent on the condensation of water can be the further operating parameter. Depending on the outside temperature or cooling of the first fluid, water vapor may condense in the fluid system during the measurement of the operating gradient or during the execution of the method, the percentage of the condensed water in particular depending on the dew point of the water. A condensation of

Water, in turn, may result in a change in the operating gradient, such that consideration by the model approximates the second reference gradient to the real conditions. As a result, a more accurate method and thus increased safety of the fluid system can be achieved.

It is furthermore conceivable that in a method according to the invention the first fluid is cooled by a coolant, the model taking into account the change in the temperature of the coolant based on a further operating parameter at the first operating point and / or the cooling before carrying out at least step b). of the method is turned off. Also the

Cooling as such may have an impact on the operating gradient during performance of the process, particularly during the establishment of the operating gradient, so that a corresponding pressure drop or pressure increase is not entirely due to leakage. Preferably, the change in the temperature of the coolant itself or a dependent on the temperature of the coolant size represent the other operating parameters. By taking into account the change in the temperature through the model or by switching off the cooling can thus increased accuracy of the method, in particular the second Reference gradients can be achieved so that the safety of the fluid system is increased. Thus, for example, the frequency of a misjudgment of a critical leak can be reduced.

It is furthermore conceivable that in a method according to the invention the model has a reaction term which takes into account the influence of a chemical reaction within the fluid system on the second reference gradient on the basis of at least one further operating parameter in the first operating point. Under the reaction term z. As the, in particular mathematical, modeling of the chemical reaction at the membrane of a fuel cell can be understood. This results in possible

Dependencies of the reaction term the temperature, the oxygen partial pressure, the hydrogen partial pressure and / or similar operating parameters. Of the

Reaction term may preferably be provided as an analytical, mathematical function or as a characteristic map generally intended for a series or a single product of the fluid system. This can be an influence of a

Residual reaction of at least the first fluid to the operating gradient of the operating pressure are taken into account and therefore a more accurate result can be achieved. This, in turn, leads to increased security. The reaction term can in particular itself represent the further operating parameter.

Within the scope of the invention, it can furthermore be provided that at least steps b) to d) of the method are repeated cyclically. As a result, a leak can be checked regularly, so that the sample size of the measured values and thus the accuracy of the method is increased. Under a cyclic repetition in the context of the present invention, a

Be understood repetition, the z. B. takes place after a certain period. Preferably, however, a cyclic repetition may also be understood to mean that the steps of the method are per cycle of operation of the fluid system, for. B. when starting and / or switching off the fluid system can be performed. Thus, an interruption of the operation can be reduced and a reliable detection of a critical leakage can be given. Advantageously, in the context of the invention, the method steps in the order a) to d) can take place. In particular, however, it is also conceivable that the method steps, if technically expedient, are carried out in a changed order and / or individual steps of the method are repeated.

According to a further aspect of the invention, a fuel cell system is claimed which has at least one first fluid and at least one sensor for detecting at least one operating pressure. In this case, the fuel line system for carrying out a method according to one of claims 1 to

9 suitable. The sensor may preferably be a pressure sensor, so that a pressure gradient can be determined in a simple and cost-effective manner. Preferably, the fuel cell system may be a fuel cell system of a vehicle, so that the safety of the vehicle is increased by the method. Thus, a fuel cell system according to the invention brings the same advantages as have been described in detail with reference to a method according to the invention. Further, measures improving the invention will become apparent from the following description of some embodiments of the invention, which are shown schematically in the figures. All from the

Claims, the description or the drawings

Features and / or advantages, including design details, spatial arrangements and method steps, can be essential to the invention, both individually and in the most diverse combinations. It should be noted that the figures have only descriptive character and are not intended to limit the invention in any way. Show it:

Figure 1 is a schematic representation of the individual steps

inventive method in a first embodiment, 2a and 2b each show a diagram of a pressure gradient over time in a further exemplary embodiment, each with different operating gradients,

FIG. 3a-d a modeling of a second reference gradient in one

Diagram in each case a further embodiment,

Figure 4 is a schematic representation of a model of a

inventive method in a further embodiment,

Figure 5 shows an inventive fuel cell system in one

another embodiment and

Figure 6 shows a vehicle with an inventive

Fuel cell system in another embodiment.

In the following figures, the identical for the same technical features of different embodiments

Reference numeral used.

FIG. 1 shows steps a) to d) of a method 100 according to the invention in a first exemplary embodiment, wherein according to a step a) a first reference gradient 210 of an operating pressure 200 of a first fluid is provided. The provision may, for example, by a measurement of the first

Reference gradients 210 of the operating pressure 200 in one

Reference operating point 203. In step b) becomes

Operating gradient 201 of the operating pressure 200 in a first operating point 202 determined. By means of a model 220, which takes into account the first reference gradient 210 according to step a) and at least one further operating parameter 221, a second reference gradient 211 is determined according to step c). The model 220 is predefined as a mathematical function, so that the further operating parameter 221 and the first reference gradient 210 can be used to determine the second reference gradient 211. According to step d), the operating gradient 201 is compared and the second reference gradient 211. Specifically, at a time pressure loss represented by the operation gradient 201, which is higher than the second reference gradient 211, an error response 212 is triggered. This may warn a user of critical leakage. Furthermore, in particular at least steps b) to d) can be repeated, for example by more

Check operating points.

FIG. 2 a shows a diagram of a pressure gradient with respect to at least one further operating parameter 221. The curve which marks the

Model 220 represents the respective reference gradients depending on the particular operating point. Thus, the illustrated diagram is a simple, two-dimensional representation, with a dependence of the model 220 of additional operating parameters next to the other

Operating parameters 221 at this point, a multi-dimensional diagram is conceivable. The curve of the model 220 also passes through a point formed by the combination of a reference operating point 203 and a first reference gradient 210. This will be the particular

Laboratory conditions marked, under which the first reference gradient 210 is determined. Furthermore, an operating gradient 201 is in a first

Operating point 202 plotted, wherein the operating gradient 201 below the

Curve of the model 220 and thus below a second

Reference gradient 211 in the first operating point 202 is located. As a result, the operating gradient 201 is to be classified such that an existing leakage is not critical. In particular, the pressure gradient may be the amount of the pressure gradient. FIG. 2b shows a

Operating gradient 201 at the first operating point 202, wherein the operating gradient 201 is above the curve of the model 220, so that the operating gradient 201 represents a critical leakage of a first fluid 10. FIGS. 3 a to d each show different embodiments of the invention

Dependence of a model 220 on different factors. For this purpose, the diagrams each show a pressure gradient compared to a further operating parameter 221. The curve of the model 220 contains both a first reference gradient 210 which is assigned to a reference operating point 203 and a second reference gradient 211 which corresponds to a first operating point 202 assigned. Between the reference operating point 203 and the first operating point 202, the further one respectively differs

Operating Parameters 221. The curve of the model 220 therefore arises due to a mathematical function that takes into account the reference gradient 210 and respective other operating parameters 221. In particular, the first reference gradient 210 is a constant in the mathematical modeling of the model 220. In FIG. 3a the other one is involved

Operating parameter 221 by a pressure difference between the anode and cathode, which pressure difference is correspondingly dependent on a secondary pressure 221.1, which corresponds to the cathode pressure in a fuel line system 1. FIG. 3b shows a diagram of a pressure gradient with respect to FIG

Partial pressure of water, which depends on the condensation of water 221.2. Accordingly, the mathematical modeling of the curve of the model 220 is based on the first reference gradient 210 and the condensation of water 221.2. Since the condensation of water 221.2 is easy to measure, in particular via the partial pressure of the water, the dependence of the model 220 on the condensation of water 221.2 is realized by taking into account the partial pressure. Similarly, in the embodiment according to FIG. 3c, consideration of the change in the temperature 221.3 in the model 220 takes place in that the, in particular theoretical, physical change of an operating pressure 200 mathematically enters the model 220 due to the temperature change 221.3. Accordingly, e.g. also a

Reference operating point 203 defined by the change in the temperature 221.3, so that a first reference gradient 210 the

Reference operating point 203 is assigned. FIG. 3d shows, in a further exemplary embodiment, a curve of the model 220, which has a first

Reference gradients 210 and a reaction term 221.4 considered. The reaction term 221.4 is to be understood in particular as a further mathematical function which, for example, at least the influence of the temperature and the

Partial pressure of a first fluid 10 and a second fluid 11 taken into account. As a result, the chemical reaction of a fuel cell 1 during the execution of a method 100 can be taken into account by the reaction term 221.4. FIG. 4 schematically shows a model 220 with different input variables. Thus, the model 220 is dependent on a first reference gradient 210, a secondary pressure 221.1, which may be represented for example by a pressure difference between an anode and a cathode in a designed as a fuel cell system 1 fluid system 1, a condensation of

Water 221.2, which may be represented, for example, by the partial pressure of water, a change in the temperature 221.3, which may be represented, for example. By a theoretical pressure difference, through this

Temperature change 221.3 can be caused and a

Reaction term 221.4, which represents the change in pressure due to a residual chemical reaction, in particular mathematically. By taking into account such relevant variables, it is possible, in particular, to take into account the influence of the ambient conditions on an operating gradient 201 by adapting a second reference gradient 211. The second reference gradient 211 thus represents a comparison quantity, which is a

Limit the critical leakage of a

Reference operating point 203 is converted to a real operating point 202 converted. FIG. 5 shows a fuel cell system 1 according to the invention in another

Embodiment in a schematic representation. This shows that

Fuel cell system 1, a cathode 3, which is supplied with a second fluid 11 and an anode 2, which is supplied with a first fluid 10. A reaction of the first fluid 10 with the second fluid 11 in

In particular, fuel cell system 1 can generate an electrical voltage. The flow path of the first fluid 10 further comprises two valves 5 and a sensor 6. In order to produce stationary operating conditions, in particular the valves 5 can be closed so that the sensor determines an operating gradient 201 by measuring the pressure over a period of time, in particular at least two times. By closing the

Valves 5, the operating gradient 201 is in particular independent of

Pressure conditions of the first fluid 10 outside the corresponding

Section on the anode 2. Furthermore, it is shown that the

Fuel cell system 1 is cooled by a cooling 4 by means of a coolant 12, wherein this cooling can be switched off and / or the temperature change of the coolant 12 can be measurable, so that the influence of the coolant 12 on a method 100 for diagnosing a leakage, in particular a critical leakage, of the fuel cell system 1 can be reduced.

Figure 6 shows a vehicle 300, which is an inventive

Fuel cell system 1 has. For the fuel cell system 1, in particular a method 100 for diagnosing a critical leakage can be carried out, wherein the method 100 can be initiated and in particular controlled by a control unit 301 of the vehicle 300.

The above explanation of the embodiments describes the present invention solely by way of example.

Of course, individual features of the embodiments, if technically feasible, can be combined freely with one another, without departing from the scope of the present invention.

Claims

claims

A method (100) for diagnosing leakage of at least a first fluid

(10) of a fluid system (1), in particular of a fuel cell system (1), comprising the following steps:

a) providing a first reference gradient (210) of a

Operating pressure (200) of the first fluid (10),

b) determining an operating gradient (201) of the operating pressure (200) at a first operating point (202),

c) determining a second reference gradient (211) of the operating pressure (200) by a model (220), wherein the model (220) the first reference gradient (210) and at least one further

Operating parameter (221) in the first operating point (202) taken into account, d) comparing the operating gradient (201) and the second

Reference gradients (211).

Method (100) according to claim 1,

characterized,

the method (100) is used in a fluid system (1) in a vehicle (300).

Method (100) according to claim 1 or 2,

characterized,

the method (100) is carried out under steady-state operating conditions.

4. Method (100) according to one of the preceding claims,

characterized,

that the model (220) based on a further operating parameter (221) in the first operating point (202), a secondary pressure (221.1) of a second fluid

(11).

5. Method (100) according to one of the preceding claims,

characterized,

in the event of the operating gradient (201) exceeding or falling below the second reference gradient (211), an error reaction takes place.

6. Method (100) according to one of the preceding claims,

characterized,

the model (220) takes into account a condensation (221.2) of water in the fluid system on the basis of a further operating parameter (221) in the first operating point (202).

7. Method (100) according to one of the preceding claims,

characterized,

that the first fluid (10) is cooled by a coolant (12), the model (220) based on a further operating parameter (221) in the first operating point (202) the change in temperature (221.3) of

Coolant (12) taken into account and / or the cooling is switched off before performing at least step b) of the method (100).

8. Method (100) according to one of the preceding claims,

characterized,

in that the model (220) has a reaction term (221.4) which takes into account the influence of a chemical reaction within the fluid system (1) on the second reference gradient (211) on the basis of at least one further operating parameter (221) in the first operating point (202).

9. Method (100) according to claim one of the preceding claims, characterized in that

that at least steps b) to d) of the method (100) are repeated cyclically.

10. Fuel cell system (1), in particular of a vehicle (300), the at least one first fluid (10) and at least one sensor (6) for Detecting at least one operating pressure (200), for carrying out a method (100) according to one of claims 1 to 9.