How to Calibrate a Fuel Sensor

Abstract

The present invention relates to a method for calibrating a fuel sensor (S) of a fuel cell system (100), the method comprising the steps of: 1) opening a bypass valve (BV) provided in the bypass line (13) to operate the bypass line (13) open; 2) closing shutoff valves (SV1, SV2) provided in the supply air line (11) and in the exhaust air line (12) to direct all supply air from the supply air line (11) around the at least one fuel cell (101) and into the exhaust air line (12); and 3) performing a zero-point calibration of the fuel sensor (S).

Description

[Technical field]

[0001] The present invention relates to a method for calibrating a fuel sensor as described in the independent method claim, a corresponding fuel cell system with a correspondingly calibrated fuel sensor as described in the independent apparatus claim, and a vehicle with a corresponding fuel cell system as described in the parallel independent apparatus claim. [Background technology]

[0002] Fuel cell systems are basically known and are also known as suppliers of energy in vehicles. In fuel cell systems, oxygen from the ambient air is typically used as oxidant and hydrogen as reductant or fuel, which reacts in the fuel cell stack of the system to produce water (or water vapor) and provide electrical power by electrochemical conversion. The ambient air is provided to the fuel cell stack by a cathode system, which usually has an air compression system. Hydrogen is typically stored in a high-pressure tank (e.g. 700 bar), fed to the fuel cell stack via lines and valves and recirculated in the looped anode system of the anode system. The anode loop must be periodically purged and drained during operation to reduce the increased nitrogen content (due to diffusion through the membrane) and concentrated water in the anode. Part of the purge gas is then also hydrogen. The purge gas is therefore led into the air system-offgas passage, where it is diluted by the air mass flow to such an extent that no explosive mixtures can form.

[0003] A fuel cell stack usually comprises several fuel cells, which are sealed from each other by a number of seals. These seals are, however, exposed to temperature fluctuations, pressure fluctuations, etc., and age accordingly. Therefore, a fuel cell stack is usually not tight in the absolute sense either. On the other hand, the high pressure tank that stores the hydrogen or its armature, actuators, sensors and / or piping may be tight.

[0004] Since hydrogen is highly volatile and can form explosive mixtures with air, especially in partitioned or enclosed spaces, reliable detection of hydrogen leaks is sometimes important for safety. For hydrogen leak detection, several hydrogen sensors are usually installed. These sensors are associated with significant costs. Furthermore, the sensors must be calibrated in a time-consuming manner in order to be able to meet the high safety demands. Summary of the Invention Effect of the Invention

[0005] According to a first aspect, the present invention provides a method for calibrating a fuel sensor comprising the features of the independent method claim, according to a second aspect, a corresponding fuel cell system comprising a correspondingly calibrated fuel sensor comprising the features of the independent device claim, and according to a third aspect, a vehicle comprising a corresponding fuel cell system comprising the features of the parallel independent device claim. Further advantages, features and details of the invention can be found in the dependent claims, the description and the drawings, whereby it is self-evident that the features and details described in relation to the individual inventive aspects also apply in relation to the other inventive aspects and vice versa, so that reference is or can always be made to each other in relation to the disclosure of the individual inventive aspects.

[0006] According to a first aspect, the present invention provides a method for calibrating a fuel sensor of a fuel cell system, the fuel cell system being designed for a vehicle. The fuel cell system comprises the following elements: at least one fuel cell, at least one fuel cell per fuel cell stack, preferably a plurality of fuel cell stacks may be provided, the fuel cell stacks possibly being configured with a stack-ambient-ventilation system, a cathode system for providing reactants comprising oxygen to at least one fuel cell, the cathode system having a supply air line providing supply air to the at least one fuel cell and an exhaust air line conducting exhaust air from the at least one fuel cell; and the cathode system has a bypass line, the bypass line connecting the supply air line and the exhaust air line, whereby the supply air can be guided at least partially from the supply air line, bypassing the at least one fuel cell, and introduced into the exhaust air line. A cathode system; an anode system providing reactants including a fuel, for example hydrogen, to at least one fuel cell, optionally comprising an anode system-ambient-ventilation system; the anode system having a purge system and / or a drain system for purging the anode system and / or conducting product water away from the anode system; an anode system; a tank system for reactants, including fuel, preferably constructed in a modular manner, with at least one tank or several tanks per module, possibly with a tank system-ambient-ventilation system, The tank system, The fuel sensor in the sense of the present invention is arranged in the exhaust air line of the fuel cell system. Advantageously, the fuel sensor is arranged to sense fuel leaks and / or fuel mass flow from all possible fuel sources inside and outside the fuel cell system. Preferably, the fuel sensor in the sense of the present invention is arranged to sense fuel leaks and / or fuel mass flow of all subsystems of the fuel cell system that may be direct and / or indirect sources for fuel leaks and / or fuel mass flow. Counted among the subsystems are, insofar as they exist, for example the purge and / or drain systems, the stack-ambient-ventilation system, the anode system-ambient-ventilation system and / or the tank system-ambient-ventilation system. As an indirect source, the cathode path itself can be mentioned, which may contain fuel due to various effects, for example membrane impermeability or the so-called "proton pumping".

[0007] A method in the sense of the present invention comprises the following steps: 1) To operate the system with the bypass line open, a bypass valve provided in the bypass line is opened; 2) closing shutoff valves in the supply air line and the exhaust air line to direct the supply air, preferably all of the supply air, from the supply air line through the bypass line, around the at least one fuel cell, and into the exhaust air line; 3) Calibrate the fuel sensor, especially the zero point calibration; It has steps.

[0008] A fuel sensor in the sense of the present invention can preferably be used as a single fuel sensor in the entire fuel cell system and the entire vehicle. When a secondary ventilation system for fuel-guiding components is used in the vehicle, such as the ventilation system of the anode system, the vehicle interior, the trunk space system, etc., a separate fuel sensor is not required for this purpose. All direct and / or indirect sources for fuel leakage and / or fuel mass flow can thus be detected by only one fuel sensor. The fuel sensor can then be configured, for example, in the form of a hydrogen sensor.

[0009] The purge system and / or the drain system may then have at least one purge line and / or drain line. The at least one purge line and / or drain line may form a combined purge discharge line and / or drain discharge line. The at least one purge line and / or drain line may, however, have two separate discharge lines, i.e. a purge discharge line for the purge process and a drain discharge line for the drain process.

[0010] The stack-ambient ventilation system may have at least one stack-ambient air vent line, which may then have one stack-ambient air vent line per fuel cell or stack or may be configured as one common stack-ambient air vent line, so that gases or gas mixtures used for ventilation of the vicinity or immediate surroundings of the fuel cells or stacks can be drawn off from the stack surroundings.

[0011] The anode system-ambient ventilation system may have at least one anode system-ambient air vent line by means of which a gas or gas mixture used for ventilation of the immediate or immediate surroundings of the components of the anode system can be led away from the surroundings of the anode system.

[0012] The tank system-ambient ventilation system may have at least one tank-air vent line, which may be configured as one tank-air vent line per tank or per module having several tanks or as one common tank-air vent line, so that a gas or gas mixture used for ventilation of the adjacent or immediate surroundings of the tank system can be led away from the surroundings of the tank system.

[0013] Furthermore, at least one purge line and / or drain line, at least one stack-ambient-air vent line and / or at least one tank-air vent line, preferably all air vent lines, may open into or be fluidly connected to the exhaust air line, in particular immediately before the fuel sensor.

[0014] The fuel sensor may preferably be arranged downstream in the exhaust air line of the cathode system. The fuel sensor may advantageously be arranged in the exhaust air line by a media merging device. The media merging device may then be configured with or without a water storage function. The media merging device may provide that the exhaust air of the at least one fuel cell, possibly together with another media flow from the fuel cell system, is flowed through the media merging device and mixed there before being discharged preferably to the environment.

[0015] Downstream in the exhaust air line can be approximately the end of the exhaust air line, and after the fuel sensor according to the invention, only a silencer can still be arranged in the exhaust air line.

[0016] Fuel cell systems can be used in mobile applications, for example in automobiles, but also in stationary applications, for example in power generation installations.

[0017] At a minimum, the following sources count as fuel: - at least one purge and / or drain line (a source of intentional fuel mass flow); Possibly at least one stack-ambient-air vent line (a source of unintended fuel leakage), The at least one stack-ambient-air vent line may include a plurality of stack-ambient-air vent lines; at least one fuel cell or at least one fuel cell stack is arranged without an additional housing or at least partially or completely within an additional housing, A stack-ambient-air vent line; Optionally, at least one tank-ambient-air vent line, The at least one tank-ambient-air vent line may include a plurality of tank-air vent lines; Regardless of whether the tank system is arranged without an additional housing or whether it is arranged at least partially or completely within an additional housing, A tank-ambient-air vent line; Optionally, at least one anode system-ambient-air vent line, whether the anode system is arranged without an additional housing or at least partially or completely within an additional housing, an anode system-ambient-air vent line; an indirect source of fuel leakage, which may also be referred to as the cathode pathway, which may contain fuel based on fuel migration through the membrane or other effects; and an additional ventilation system and / or source for possible fuel leaks and fuel mass flow rates may be fluidly connected to the exhaust air line just prior to the fuel sensor, similar to the air bleed line listed.

[0018] Advantageously, detection and dilution for all possible (unintentional) fuel leaks and / or all possible (intentional) fuel mass flow rates can be performed in one place and with only one fuel sensor.

[0019] Advantageously, the fuel headroom can be diluted at least by exhaust air of the cathode system and possibly by bypass air of the cathode system.

[0020] Advantageously, diagnostic and / or monitoring methods may be implemented which involve pin-pointing, i.e. detection of from which source a fuel leak and / or fuel mass flow rate originates.

[0021] One further advantage is that the exhaust air line can be used to exhaust the water to the environment or to direct the water to another functional system and / or vessel of the fuel cell system for further utilization.

[0022] Furthermore, it may be advantageous that dilution of the possibly fuel-containing exhaust air can be performed by a secondary air mass flow, for example by the air mass flow of a fresh air blower in the vehicle interior and / or an own ventilation blower, thus providing decoupling from and / or redundancy for the air compressor operation in the supply air line.

[0023] The idea of ​​the invention is that such a fuel sensor can be calibrated simply and with little effort. For the zero-point calibration, the bypass valve is opened and the shut-off valve for the stack is closed, so that it can be ensured that all the supply air is guided around the stack and reaches the exhaust air line. The invention is based on the idea that in this case only fresh or fuel-free air flows past the fuel sensor. The sensor can be calibrated to zero in this way.

[0024] All further subsystems present in the system that may be sources of fuel, such as the purge system and / or drain system, as well as all ventilation systems, such as the anode system-ambient-ventilation system, the stack-ambient-ventilation system and the tank system-ambient-ventilation system, may be closed to perform a zero point calibration of the fuel sensor, thereby ensuring with increased probability that only fresh air flows past the fuel sensor.

[0025] Further, in the method of calibrating a fuel sensor, the method further comprises at least one of the following steps: 2a) operating a compressor provided in the supply air line at at least one speed; 2b) determining, e.g., calculating or estimating, a predicted mass flow rate of the oxygen-containing reactant that should arrive at the fuel sensor; 2c) checking, for example by measurement and calculation, the mass flow rate of the reactants, including oxygen, that should be at the sensor using the measurements of a mass flow sensor in the cathode system, for example in the supply air line; 2d) checking or measuring the pressure in the cathode system by means of a pressure sensor, for example a pressure sensor in the exhaust air line of the cathode system; 2e) Changing the compressor speed, 3a) monitoring the fuel sensor measurements, and / or 3b) determining that the fuel sensor is functioning properly when the fuel sensor measurement does not change when the compressor speed is changed, when the mass flow rate of the oxygen-containing reactant at the sensor is changed, and / or when the pressure in the cathode system is changed; The step may include steps.

[0026] The measurement result of the fuel sensor should be independent of the mass flow rate at the sensor or the pressure of the exhaust air. The compressor speed should also not affect the measurement result of the fuel sensor. If the fuel sensor is in good working order, the measurement result of the fuel sensor will not change substantially when the compressor speed is changed, when the mass flow rate of the reactants, including oxygen, and / or when the pressure in the cathode system is changed (a certain amount of noise is not counted in this substantial change). In this way, the good working order of the fuel sensor can be easily and comfortably ensured.

[0027] Furthermore, the mass flow, for example the mass flow in the exhaust air line, can be measured by a mass flow sensor, so that it can be checked whether the expected mass flow actually arrives at the mass flow sensor at a given compressor speed.

[0028] The pressure, for example in the discharge air line, can also be measured by a pressure sensor, so that it can be checked whether the expected pressure actually prevails in the discharge air line at a given compressor speed. The measured pressure in the discharge air line can also be used to check and / or validate the nominal mass flow rate.

[0029] Further, in the method of calibrating a fuel sensor, the method further comprises at least one of the following steps: 4) introducing or injecting a mass flow of reactants, including fuel, into the exhaust air line (suitably) before the fuel sensor; 5) performing a quantitative calibration of the fuel sensor, in particular a quantitative calibration with respect to the expected concentration of reactants, including the fuel, in the fuel sensor; The step may include steps.

[0030] In this way, in addition to the zero-point calibration, a quantity calibration of the fuel sensor can be carried out. It can be advantageously ensured that the concentration of fuel in the exhaust air does not exceed a critical limit, the so-called explosion limit. For the quantity calibration of the fuel sensor, when the anode path is guided in as defined a manner as possible, for example by purging with fresh fuel, fuel can be appropriately fed into the exhaust air line via the purge line and / or the drain line when the concentration of fuel is high and approximately known.

[0031] Further, in the method of calibrating a fuel sensor, the method further comprises at least one of the following steps: 4a) operating a compressor provided in the supply air line at at least one speed; 4b) determining, e.g., detecting and calculating or estimating, a target mass flow rate of a reactant, including oxygen, at the fuel sensor; 4c) checking (detecting and calculating) the mass flow rate of reactants, including oxygen, that should be present in the fuel sensor using the measurement results of a mass flow sensor provided in the cathode system; 4d) Check the pressure in the cathode system using a pressure sensor; 4e) Changing the compressor speed, 4f) varying the mass flow rate of reactants, including fuel, introduced into the exhaust air line upstream of the fuel sensor; and / or 5a) calibrating the fuel sensor for a measuring point corresponding to a given concentration of the fuel-containing reactant, in particular as a function of the mass flow rate of the fuel-containing reactant introduced upstream of the fuel sensor in the exhaust air line, the compressor speed, the mass flow rate of the oxygen-containing reactant and / or the pressure in the cathode system; The step may include steps.

[0032] By varying the compressor speed and / or the mass flow rate of the reactants, including the fuel, introduced into the exhaust air line upstream of the fuel sensor, the concentration of the fuel in the exhaust air can be adapted to provide different measurement points for flexible calibration of the fuel sensor at the different measurement points.

[0033] In addition, in the method for calibrating a fuel sensor, the method further comprises at least one of the following steps: 4g) increasing, decreasing or turning off the mass flow rate of reactants, including fuel, introduced into the exhaust air line before the fuel sensor; 5b) Checking if and / or how quickly the fuel sensor responds to increasing, decreasing or turning off the mass flow rate; The step may include steps.

[0034] Thus, one or more reaction tests can be provided to check how quickly the fuel sensor reacts to changes in the concentration of fuel in the exhaust air, thus further improving the reliability of the operation of the fuel cell system.

[0035] Further, in the method of calibrating a fuel sensor, the method further comprises at least one of the following steps: 6) carrying out the anode system purge process; 7) Evaluation of purge gas using fuel sensor measurement results, 8) adapting the anode system purge process until the fuel sensor detects an expected concentration of reactants, including fuel, in the purge gas mass flow; The above formula may be used.

[0036] Thus, the purge gas can preferably be investigated to determine its proportion compared to the fuel, for example nitrogen, which can provide improved control of the purge process.

[0037] It is possible within the scope of this disclosure that steps of the methods of the present invention may be performed simultaneously, at least partially simultaneously and / or in tandem.

[0038] Advantageously, the method may be performed periodically, in particular after a predefined time and / or periodically, in particular after a predefined consumption, for example of an oxygen-containing reactant and / or of a fuel-containing reactant, and / or depending on a load profile, so that it can be ensured that the fuel sensor is repeatedly calibrated to ensure reliable functioning of the fuel sensor over its lifetime.

[0039] For example, the method may be integrated into the operation of a fuel cell system, particularly when power from the fuel cell system is not required, and thus may be integrated into the operation of the fuel cell system without unintended interruptions.

[0040] In addition, the fuel cell system can be brought into a power-free state in order to carry out the method, which can be understood as a state in which the fuel cell system does not provide electrical energy and the shut-off valves in the supply air line and the exhaust air line of the cathode system are closed, thereby ensuring that the method can be carried out whenever this is necessary, for example whenever it is found that the fuel sensor does not provide reliable results.

[0041] According to a second aspect, the present invention provides a fuel cell system comprising a fuel sensor calibrated by a method that may proceed as described above, the fuel sensor being arranged in an exhaust air line and configured to sense fuel leaks and / or fuel mass flow in all subsystems of the fuel cell system that are present in the system and that may be sources for fuel leaks and / or fuel mass flow. The fuel cell system according to the invention allows achieving the same advantages as described above in connection with the method according to the invention, which advantages are referred to generically here.

[0042] According to a third aspect, the present invention provides a vehicle comprising a fuel cell system, which may be configured as described above. With the vehicle according to the invention the same advantages can be achieved as explained above in relation to the method according to the invention, which advantages are referred to here in general terms.

[0043] The invention as well as its developments and its advantages are explained in more detail below on the basis of the drawings, each of which is schematic. [Brief description of the drawings]

[0044] [Figure 1] 1 is a schematic diagram of a fuel cell system in the sense of the present invention; [Diagram 2] 2 is a schematic diagram of a diagnostic method for possible fuel leaks and / or fuel mass flow in a fuel cell system. [Diagram 3] 2 is a schematic diagram of a method for calibrating a fuel sensor in the sense of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] In the different figures, identical elements of the invention are always given the same reference numerals and therefore these elements are usually only described once.

[0046] FIG. 1 shows a fuel cell system 100 in the sense of the present invention, which can be used, for example as a source of electrical energy, in a vehicle 1, preferably an electric vehicle and / or a highly automated or even autonomous vehicle.

[0047] The fuel cell system 100 comprises at least one fuel cell 101, or even a stack or stack of several fuel cells 101, joined together to form a fuel cell stack, the fuel cell 101 or stack or stack being configured with a stack-ambient-ventilation system Q2. The fuel cell 101 or the fuel cell stack or stack may exhibit fuel leakage towards the outside, since many fuel cells 101 are configured with many seals, which are exposed to various ageing mechanisms due to media, mechanical stress, temperature fluctuations, pressure fluctuations, etc. The fuel cell 101 or the fuel cell stack or stack may be at least partially accommodated (at least in the upper region) in a housing 102, so that ambient ventilation may be appropriately performed. The escaping fuel, in particular hydrogen, may remain in the upper region, from which the stack-ambient-air vent line L2 of the stack-ambient-ventilation system Q2 may be led out. The stack-ambient-air vent line L2 of the stack-ambient-ventilation system Q2 is introduced into the exhaust air line 12 of the cathode system 10 prior to a fuel sensor S, in particular in the form of a hydrogen sensor. The exhaust air from the exhaust air line 12 of the cathode system 10 may dilute the possibly stagnant fuel H2.

[0048] For ventilation of the fuel cell 101 or fuel cell stack, the supply air from the supply air line 11 of the cathode system 10 or the supply air of another supplier A2, A3, for example the fresh air blower IN of the vehicle interior and / or the own ventilation blower BG, can be used as the first supplier A1. The supply air can in this case be introduced into the housing 102 of the fuel cell 101 or fuel cell stack, preferably in the lower area, for example via a connecting line, which may optionally but advantageously include throttles VQ2, VQ3 and / or adjustable valves VSQ2, VSQ3. To provide an air mass flow, different suppliers for the ventilation lines A1, A2, A3 (for example the supply air line 11, the fresh air blower IN of the vehicle interior and / or the own ventilation blower BG) can be possible, which will be explained in more detail below.

[0049] As already mentioned above, the fuel cell system 100 comprises a cathode system 10 which provides reactants including oxygen to at least one fuel cell 101 or fuel cell stack, the cathode system 10 having a supply air line 11 which provides supply air to the at least one fuel cell 101 and an exhaust air line 12 which leads exhaust air from the at least one fuel cell 101. The system topology according to the invention provides only one fuel sensor S for the entire fuel cell system 101 and the vehicle 1. The various sources for direct and / or indirect (unintentional) fuel leakage and / or (intentional) fuel mass flow rates provided in the system 100 are led into the exhaust air line 12 of the cathode system 10 by the corresponding subsystems Q1, Q2, Q3, Q4, Q5 present in the fuel cell system 100.

[0050] A cathode system 10 is exemplarily shown in Fig. 1. Supply air is in this case drawn in, for example, from the surroundings U and can be filtered by an air filter AF, depending on the needs of the fuel cell 101. Various system topologies are possible, such as with or without a supply air cooler IC, with or without a turbine in the exhaust air line 12, with or without a humidifier H, single or multi-stage compression, single-flow or multi-flow compressor V, single-shaft or twin-shaft system, with or without water injection, etc.

[0051] The fuel cell system 100 further comprises an anode system 20 which provides reactants, including a fuel, to at least one fuel cell 101 or fuel cell stack, the anode system 20 comprising a purge and / or drain system Q1 for purging the anode system 20 and / or for drawing off product water from the anode system 20. The purge and / or drain lines L1 are advantageously introduced into the exhaust air line 12 of the cathode system 10 before the fuel sensor S and are diluted there. The anode system 20 may also comprise an anode system-ambient ventilation system Q4, by means of which the surroundings of the components of the anode system 20 can be ventilated. The anode system-ambient ventilation system Q4 may then comprise at least one anode system-ambient air vent line (not shown) by means of which a gas or gas mixture used for ventilation of the surroundings adjacent or directly surrounding the components of the anode system 20 can be drawn off from the surroundings of the anode system.

[0052] The purge process can advantageously be carried out not only when a sufficient air mass flow / air volume flow is provided to the cathode system 10, but also when this is not the case. For this purpose, the fuel cell system 100 can use, in addition to the supply air from the supply air line 11, further suppliers A2, A3, for example a fresh air blower IN of the vehicle interior and / or its own ventilation blower BG.

[0053] The cathode system 10 further comprises a bypass line 13, which fluidly connects the supply air line 11 and the exhaust air line 12, so that the supply air can be guided at least partially from the supply air line 11 around the at least one fuel cell 101 and into the exhaust air line 12. A bypass valve BV is preferably provided in the supply air line 13, so that the amount of supply air that is guided around the at least one fuel cell 101 can be controlled. The bypass valve BV is open, so that the bypass line 13 can be operated open.

[0054] In addition, the cathode system 10 has a shutoff valve SV1 in the supply air line 11 immediately before the inlet of the supply air line 11 into the at least one fuel cell 101, and a shutoff valve SV2 in the exhaust air line 12 immediately after the outlet of the exhaust air line 12 from the at least one fuel cell 101. The shutoff valves SV1, SV2 are closed to guide the supply air completely through the bypass line 13, bypassing the at least one fuel cell 101, so that a calibration of the fuel sensor S can be performed (see FIG. 3). The method according to the invention for calibrating the fuel sensor S will be discussed in more detail below in connection with FIG. 3.

[0055] The fuel cell system 100 further comprises a tank system 30, preferably a modular tank system 30, which comprises at least one tank T for reactants including fuel (preferably several tanks T or cylinders per module) and a tank system-ambient-ventilation system Q3. The tank system 30 can be arranged, for example, in the rear area of ​​the vehicle 1 (for example in the trunk space), but also in the underfloor of the vehicle (for example under the fuel cell stack or under the passenger compartment). The modular structure of the tank system 20 allows for small spacing between the tank system 30 and the stack and / or the cathode path 10 and for simple connections between these systems. Advantageously, the individual tanks T in a module in the tank system 30, for example in one of the modules, can be surrounded by a (respective) tank housing 31, which can form part of the tank system-ambient-ventilation system Q3. The tank housing 31 can, on the other hand, comprise a tank-air vent line L3.

[0056] For ventilation of the tank system 30, the supply air from the supply air line 11 of the cathode path 10 and / or fresh air from another supplier A2, A3, for example a fresh air blower IN in the vehicle interior and / or a separate ventilation blower BG, can be used as a first supplier A1.

[0057] The supply air for ventilation is provided by a first supplier A1 via a ventilation line A1 which branches off from the supply air line 11 of the cathode system 10, for example before the humidifier H (ventilation line A1.1), after the humidifier H (ventilation line A1.2) or before the supply air cooler IC (ventilation line A1.3).

[0058] The purge and / or drain system Q1 may have a (combined or double) purge and / or drain line L1. The stack-ambient-ventilation system Q2 may have at least one (or several) stack-ambient-air vent line L2. The tank system-ambient-ventilation system Q3 may also have at least one (or several) tank-air vent line L3. The anode system-ambient-ventilation system Q4 may also have an air vent line, not shown. At the end of the exhaust air line 12 of the cathode system 10 or downstream in the exhaust air line 12, a fuel sensor S, for example in the form of a hydrogen sensor, is arranged, in particular only one for the entire fuel cell system 100 and the entire vehicle 1. According to the invention, the purge line and / or drain line L1, at least one stack-ambient-air vent line L2, at least one tank-air vent line L3 and / or anode system-ambient-air vent line, insofar as they exist, open into the exhaust air line 12 of the cathode system 10 (preferably all three lines L1, L2, L3) before the fuel sensor S1, as shown in FIG. 1.

[0059] Within the scope of the present invention, only one fuel sensor S can be used for the complete fuel cell system 100 and the entire vehicle 1. In this case, all lines L1, L2, L3 which can be a source of fuel, in particular hydrogen, can be merged in the exhaust air line 12 of the cathode system 10. FIG. 1 exemplarily shows the purge and / or drain line L1, the stack-ambient-air vent line L2, regardless of whether the at least one fuel cell 101 or the at least one fuel cell stack is open or is at least partially arranged in a housing 102, and the tank-air vent line L3, regardless of whether the tank system 30 is open or is at least partially arranged in a housing 31. Within the scope of the present invention, however, other sources for possible fuel leakage are also conceivable, which can be fluidly connected to the exhaust air line 12 of the cathode system 10, preferably upstream of the fuel sensor S, similarly to the mentioned air vent lines L1, L2, L3.

[0060] This allows detection of all possible direct and / or indirect fuel leaks anywhere in the fuel cell system 100. Advantageously, the fuel headroom can be diluted with at least the exhaust air of the cathode system 10.

[0061] The described fuel cell system 100 further allows for a diagnostic or checking method involving pin-pointing, i.e., detection of the source from which a hydrogen leak or hydrogen mass flow is coming, as shown in FIG. 2.

[0062] Insofar as they exist, the anode system-ambient-ventilation system Q4, the tank system-ambient-ventilation system Q3 and / or the stack-ambient-ventilation system Q2 are connected to the exhaust air line 12 so that the fuel H2 trapped in the respective systems can be reliably diverted and diluted.

[0063] Advantageously, in the described fuel cell system 100, the dilution of the purge gas can be performed by a secondary air mass flow A2, A3, for example the air mass flow A2, A3 of the fresh air blower IN of the vehicle interior and / or of an own ventilation blower BG, thereby providing decoupling from the air compressor operation in the supply air line 11 and redundancy.

[0064] However, the ventilation systems Q2, Q3, Q4 of the tank system 30, stack and / or anode system 20 provided in the system 100 may also be provided with decoupling from the cathode path 10 and with redundancy for ventilation of the respective systems.

[0065] FIG. 2 illustrates generally one possible method for diagnosing fuel leaks and / or fuel mass flow in a fuel cell system 100, which may be configured as described above.

[0066] The diagnostic method may have at least one of the following steps: D4) During ongoing operation of the fuel cell system 100 ("normal operation"), the readings of the fuel sensor S are monitored.

[0067] During the diagnosis in step D4), the measured value or values ​​or the measurement signal of the fuel sensor S can be compared with a threshold value or values. This measured value or values ​​or the measurement signal of the fuel sensor S can advantageously be evaluated over time so that an increase in the fuel content and fuel leaks can be detected at an early stage. If this measured value or values ​​or the measurement signal of the fuel sensor are sufficiently low, no further diagnosis is necessary or, depending on the threshold value, no further diagnosis is necessary for the time being. However, if the values ​​exceed the applicable limits, further diagnosis D1), D2), D3) can be carried out.

[0068] A lower limit or a first threshold value that is not exceeded in step D4) may be a sign of "all is well". Exceeding this lower limit may for example introduce a handling check, for example a more frequent reading of the fuel cell sensor S in step D4), observing an increase in the fuel content and / or introducing further diagnostics D1), D2), D3), etc. A higher limit or a second threshold value may for example result in a handling warning, for example a request to the driver to stop the vehicle 1, a request to the vehicle occupants to move the vehicle 1 out of the way, a warning to other road users, etc.

[0069] From a certain threshold, the following steps can be introduced: D1) Operate the purge and / or drain system Q1 while the stack-ventilation system Q2, the tank-ventilation system Q3 and the anode system-ambient-ventilation system Q4, to the extent present, are inactive (i.e., deactivated or not operational and the purge valve PDV is closed); D2) operating the stack-ventilation system Q2 while the purge and / or drain system Q1, the anode system-ambient-ventilation system Q4 and the tank-ventilation system Q3 are inactive; and / or D3) Operate the tank-ventilation system Q3 while the purge and / or drain system Q1, the anode system-ambient-ventilation system Q4 and the stack-ventilation system Q2 are inactive.

[0070] Additionally, another step may be performed, not shown in FIG. 2, in which the anode system-ambient-ventilation system Q4 is operated while the purge and / or drain system Q1, the stack-ventilation system Q2 and the tank-ventilation system Q3 are inactive.

[0071] Steps D1), D2) and / or D3) may also be performed periodically, which may make it possible to detect from which source a fuel leak or a fuel mass flow rate originates.

[0072] To this end, the paths Q1, Q2, Q3, Q4, Q5 of each possible source present in the system 100 are switched so that only one possible source for a fuel leak or fuel mass flow is detected for a short period of time.

[0073] Between steps D1), D2) and D3) there may be provided predefined waiting times and / or notifications, recommendations to the user of the vehicle 1. Step D4) may be performed, for example, when the vehicle 1 is stopped or immediately before the start of the vehicle 1, for example to quickly check whether the ventilation system Q2, Q3, Q4 is abnormal and / or if additional diagnostics D2) and / or D3) are required and / or to obtain reference measurements for steps D2) and / or D3).

[0074] In addition, to validate the results of the diagnostic method, the measured values ​​in steps D1) to D4) can be compared with each other or in combination with each other (e.g., does the value in D4 = the value in D2 + the value in D3?).

[0075] In addition, the diagnostic method may comprise at least one of the following steps: D5) The fuel sensor S readings are monitored during unvented operation ("all closed") of the fuel cell system 100, with the purge and / or drain system Q1, stack-ventilation system Q2, tank-ventilation system Q3, and anode system-ambient-ventilation system Q4 all turned off, to the extent present. This allows the fuel sensor S1 to be qualified or calibrated. This also allows for open / close diagnostics of the purge valve PVD to be performed.

[0076] The diagnostic method may further comprise at least one of the following steps: D6) Monitor the measurements of the fuel sensor S during full ventilated operation of the fuel cell system 100 ("all open"), when the purge and / or drain system Q1, the stack-ambient-ventilation system Q2, the tank-ambient-ventilation system Q3 and the anode system-ambient-ventilation system Q4 are all active, to the extent that they are present. This step D6) can be performed, for example, when the vehicle 1 is stopped or just before the start of the vehicle 1, for example, to quickly check if all is well and / or to know if additional diagnostics D1), D2) and / or D3) are necessary and / or to obtain reference measurements for steps D1), D2) and / or D3).

[0077] In addition, to validate the results of the diagnostic method, the measured values ​​in steps D1) to D6) can be compared with each other or in combination with each other (e.g., is the value in D1≦the value in D6?).

[0078] FIG. 3 is used to explain a method according to the present invention (or calibration method for short) for calibrating a fuel sensor S used as a single fuel sensor S for sensing and / or monitoring all fuel leaks and / or fuel mass flow rates within the fuel cell system 100 shown in FIG. 1.

[0079] The calibration method shown in FIG. 3 can be implemented, for example, in step D5) of the diagnostic method shown in FIG.

[0080] However, it is contemplated that the calibration method illustrated in FIG. 3 may be performed as a separate method, separate or independent from the diagnostic method illustrated in FIG.

[0081] A calibration method in the sense of the present invention comprises the following steps: 1) To operate the system with the bypass line 13 open, the bypass valve BV provided in the bypass line 13 is opened. 2) closing the shutoff valves SV1, SV2 in the supply air line 11 and in the exhaust air line 12 to guide the supply air, preferably all of the supply air, from the supply air line 11 through the bypass line 13, around the at least one fuel cell 101, and into the exhaust air line 12; 3) Calibrate the fuel sensor S, especially the zero point calibration.

[0082] In this way, it can be ensured that the supply air from the supply air line 11 reaches the fuel sensor S.

[0083] In step 2), preferably, all further subsystems Q1, Q2, Q3, Q4, Q5 present in the system 100 and which may be sources of fuel H2, for example, the purge system and / or drain system Q1, insofar as they exist, as well as all ventilation systems Q2, Q3, Q4, for example the stack-ambient-ventilation system Q2, the tank system-ambient-ventilation system Q3 and the anode system-ambient-ventilation system Q4, as well as the cathode path as an indirect source Q5 for fuel, may be closed and / or blocked and / or disconnected.

[0084] In this way it can be ensured that no fuel H2 arrives at the fuel sensor S in order to carry out a calibration, in particular a zero point calibration, of the fuel sensor 3) in step 3).

[0085] The current measuring point of the fuel sensor S can therefore be set to zero.

[0086] After or during step 2), at least one further (sub) step may further be provided: 2a) The compressor V provided in the supply air line 11 is operated at least at one speed.

[0087] Thus, a mass flow of supply air can be pumped through the supply air line 11 , the bypass line 13 and the exhaust air line 12 .

[0088] If desired or necessary, a planned mass flow rate approximately estimated to arrive at the fuel sensor S may be calculated. For this purpose, after or during step 2), at least one further (sub) step may furthermore be provided: 2b) A predicted mass flow rate of the reactant, including oxygen, that should arrive at the fuel sensor S is determined, e.g., measured and calculated or estimated.

[0089] This makes it possible to check whether the calculated nominal mass flow actually arrives at the fuel sensor S. For this purpose, after or during step 2), at least one further (sub) step may also be provided: 2c) The mass flow rate of the oxygen-containing reactants that should arrive at the fuel sensor S is checked, for example measured and calculated, using the measurements of a mass flow sensor provided in the cathode system.

[0090] Furthermore, the pressure in the exhaust air line 12 may be measured in order to determine or verify the nominal mass flow rate with increased accuracy. For this purpose, after or during step 2), at least one further (sub) step may furthermore be provided: 2d) The pressure in the cathode passage 10 is checked or measured by a pressure sensor.

[0091] The determined nominal mass flow rate, the measured mass flow rate and the pressure can be used to check whether the compressor V is functioning properly and / or whether there are leaks in the lines 11, 12, 13.

[0092] Normally, fuel H2 should not be detected at fuel sensor S. Zero point calibration can be performed with improved reliability in this case.

[0093] Furthermore, it is envisaged that at least one further (sub) step may be provided: 2e) Change the speed at which compressor V operates.

[0094] In this way, multiple operating points in the operation of the compressor V can be covered.

[0095] After or during step 3), at least one further (sub) step may further be provided: 3a) Monitoring the measurement result of the fuel sensor S; 3b) When the measurement result of the fuel sensor S does not change when the rotation speed of the compressor V is changed, when the mass flow rate of the reactant containing oxygen is changed, and / or when the pressure in the cathode path 10 is changed, the fuel sensor S is determined to be functioning normally.

[0096] The measurement result of the fuel sensor S should be independent of the mass flow rate or pressure of the exhaust air. The compressor speed should also not influence the measurement result of the fuel sensor S. If the fuel sensor S is in good working order, the measurement result of the fuel sensor S will not change when the speed of the compressor V is changed, when the mass flow rate of the reactants including oxygen is changed and / or when the pressure in the cathode path 10 is changed. In this way, the good working order of the fuel sensor S can be ensured simply and conveniently.

[0097] The calibration method may further comprise at least one further step of the following steps: 4) introducing a mass flow rate of reactants including fuel into the exhaust air line 12 before the fuel sensor S; 5) Perform quantitative calibration of the fuel sensor S.

[0098] In this way, if desired, a calibration of the fuel sensor S can be carried out at different quantity points. For the quantity point calibration of the fuel sensor, fuel can be appropriately fed into the exhaust air line 12 via the purge line and / or the drain line L1 when the anode path is preferably guided in as defined a manner as possible, for example by purging with fresh fuel, and the fuel concentration is high and approximately known. It can then be advantageously ensured that the concentration of fuel in the exhaust air does not exceed a critical limit, the so-called explosion limit.

[0099] During point calibration, the method may also have at least one further step: 4a) The compressor V provided in the supply air line 11 is operated at least at one speed.

[0100] Thus, the injected mass flow rate of the reactant including fuel in step 4) can be diluted as desired, for example to obtain a predetermined concentration of the reactant including fuel at the fuel sensor S.

[0101] The method may further comprise at least one of the following steps: 4b) calculating or estimating a target mass flow rate of reactants including oxygen arriving at the fuel sensor S; 4c) checking the mass flow rate of the oxygen-containing reactants arriving at the fuel sensor S using the measurements of a mass flow sensor in the cathode path, for example in the supply air line 11, and / or 4d) Check the pressure in the cathode passage 10 with the pressure sensor.

[0102] The method may further comprise at least one of the following steps: 4e) Changing the speed at which compressor V operates; 4f) varying the mass flow rate of the reactants, including the fuel, introduced into the exhaust air line 12 upstream of the fuel sensor S; and / or 5a) Calibrating the fuel sensor S for a measuring point corresponding to a given concentration of the fuel-containing reactant, in particular as a function of the mass flow rate of the fuel-containing reactant introduced upstream of the fuel sensor S in the exhaust air line 12, the speed of the compressor V, the mass flow rate of the oxygen-containing reactant at the fuel sensor S and / or the pressure in the cathode path 10.

[0103] In this way, additional calibration of the fuel sensor S can be carried out at different quantity points. Here too, it can be advantageously ensured that the concentration of fuel in the exhaust air does not exceed a critical limit, the so-called explosion limit.

[0104] Advantageously, additional steps may be carried out for testing the response of the fuel sensor S: 4g) increasing, decreasing or turning off the mass flow rate of reactants, including fuel, introduced into the exhaust air line 12 before the fuel sensor S; 5b) Check if and / or how quickly the fuel sensor S reacts to mass flow being increased, decreased or turned off.

[0105] Further in accordance with the present invention, the calibrated fuel sensor S: 6) performing a purge process for the anode system 20; 7) Evaluation of purge gas using the measurement results of fuel sensor S, 8) adapting the purge process of the anode system 20 until the fuel sensor S detects an expected concentration of reactants, including fuel, in the purge gas mass flow; It may be possible to use the same in the above-mentioned cases.

[0106] In this way the purge gas can be preferably monitored with respect to its proportion of fuel, for example compared to nitrogen, which can provide improved control of the purge process.

[0107] Advantageously, the results of the diagnostic method shown in FIG. 2 and / or the calibration method shown in FIG. 3 can be recorded in storage of the fuel cell system 101 or in online storage.

[0108] Furthermore, the diagnostic method shown in Figure 2 and / or the calibration method shown in Figure 3 can be performed periodically, e.g. after a predefined time, periodically, e.g. after a tank change, tank refill, after a pressure fluctuation, after each long-term parking of the vehicle 1, e.g. overnight or in an airport parking lot, etc., and / or depending on the load profile, e.g. after a predefined number of starts / stops and / or after a predefined provided power (total mileage of the vehicle 1, power (kilowatts) of the fuel cell system 100, a predefined compressor discharge rate, etc.). The diagnostic method shown in Figure 2 and / or the calibration method shown in Figure 3 can be evaluated, for example, in a control device of the fuel cell system 100 or in an online server.

[0109] It may also be advantageous to provide a user of vehicle 1 with information about the results of the diagnostic method shown in FIG. 2 and / or the calibration method shown in FIG. 3, for example via a display unit, for example provided in the dashboard of vehicle 1, in a head-up display or the like.

[0110] In addition, the fuel cell system 100 can be brought into a power-free state to carry out the method. The power-free state of the fuel cell system 100 can be understood as a state when the fuel cell system does not provide electrical energy and the shut-off valves in the supply air line and the exhaust air line of the cathode system are closed. This can ensure that the method can be carried out whenever this is necessary, for example whenever it is found that the fuel sensor does not provide reliable results.

[0111] According to a second aspect, the present invention provides a fuel cell system 100 including a fuel sensor S calibrated by a method that may proceed as described above.

[0112] A vehicle 1 equipped with a corresponding fuel cell system 100 also forms an aspect of the present invention.

[0113] The above description of the drawings has only explained the invention within the scope of examples, and it is self-evident that the individual features of the embodiments can be freely combined with one another, in so far as this is technically meaningful, without departing from the scope of the invention. [Explanation of symbols]

[0114] 1 vehicle 10. Cathode System 11 Air supply line 12 Exhaust air line 13 Bypass pipeline 20 Anode System 30 Tank System 31 Tank housing 100 Fuel Cell System 101 Fuel Cell 102 Housing AF Air Filter A1, A1.1, A1.2, A1.3, A2, A3 Supplier, Ventilation Pipeline BG Ventilation Blower BV Bypass valve D1, D2, D3, D4, D5, D6 steps H humidifier H2 fuel IC Supply Air Cooler IN Fresh air blower L1 Purge line and / or drain line L2 Stack-ambient-air vent line L3 Tank-Air Vent Pipe PDV Purge Valve Q1 Subsystem, purge system and / or drain system Q2 Subsystem, Stack-Ambient-Ventilation System Q3 Subsystem, Tank System-Ambient-Ventilation System Q4 Subsystem, Anode System-Ambient-Ventilation System Q5 Subsystems, indirect sources S Fuel Sensor SV1, SV2 shutoff valve T Tank U Periphery V Compressor VQ2, VQ3 aperture VSQ2, VSQ3 valves

Claims

1. A method for calibrating a fuel sensor (S) of a fuel cell system (100), comprising the steps of: The fuel cell system (100) comprises: at least one fuel cell (101), a cathode pathway (10) for providing reactants including oxygen to at least one of said fuel cells (101), The cathode system (10) comprises a supply air line (11) for providing a supply air to the at least one fuel cell (101) and a discharge air line (12) for conducting discharge air from the at least one fuel cell (101); and the cathode system (10) has a bypass line (13) connecting the supply air line (11) and the exhaust air line (12), whereby the supply air can be guided at least partially from the supply air line (11) around at least one of the fuel cells (101) and introduced into the exhaust air line (12). A cathode path (10); an anode system (20) providing reactants, including a fuel, to at least one of said fuel cells (101); Equipped with the fuel sensor (S) is disposed in the exhaust air line (12) and is configured to sense fuel leaks and / or fuel mass flow in all subsystems (Q1, Q2, Q3, Q4, Q5) of the fuel cell system (100) that may be sources for fuel leaks and / or fuel mass flow; The method comprises the steps of: 1) To operate the system with the bypass line (13) open, a bypass valve (BV) provided in the bypass line (13) is opened; 2) closing shut-off valves (SV1, SV2) in the supply air line (11) and in the exhaust air line (12) to guide all of the supply air from the supply air line (11) around the at least one fuel cell (101) and into the exhaust air line (12); 3) performing zero point calibration of the fuel sensor (S); having the steps of: A method for calibrating a fuel sensor (S) in a fuel cell system (100).

2. 2. The method according to claim 1, characterized in that in step 2) all subsystems (Q1, Q2, Q3, Q4, Q5) of the fuel cell system (100) that may be sources for fuel leakage and / or fuel mass flow are switched off and / or blocked, including at least one purge and / or drain system (Q1) as well as the stack-ambient-ventilation system (Q2), the tank system-ambient-ventilation system (Q3) and / or the anode path-ventilation system (Q4) as direct sources, and the cathode path as an indirect source (Q5).

3. The method may further comprise at least one of the following steps: 2a) operating a compressor (V) provided in the supply air line (11) at at least one speed, 2b) determining a predicted mass flow rate of the oxygen-containing reactant that should arrive at the fuel sensor (S); 2c) checking the mass flow rate of the oxygen-containing reactant arriving at the fuel sensor (S) using measurements from a mass flow sensor provided in the cathode system (10); 2d) checking the pressure in the cathode passage (10) by a pressure sensor; 2e) changing the rotation speed at which the compressor (V) is operated; 3a) monitoring the measurement results of the fuel sensor (S); and / or 3b) determining that the fuel sensor (S) is in working order when the measurement result of the fuel sensor (S) does not change substantially when the rotation speed of the compressor (V), the mass flow rate of the oxygen-containing reactant, and / or the pressure in the cathode path (10) are changed; 3. The method according to claim 1, further comprising the steps of:

4. The method may further comprise at least one of the following steps: 4) introducing a mass flow rate of the fuel-containing reactant into the exhaust air line (12) before the fuel sensor (S); 5) performing a quantitative calibration of the fuel sensor (S); 4. The method according to claim 1, further comprising the steps of:

5. The method may further comprise at least one of the following steps: 4a) operating a compressor (V) provided in the supply air line (11) at at least one speed, 4b) determining a target mass flow rate of the oxygen-containing reactant at the fuel sensor (S); 4c) checking the mass flow rate of the oxygen-containing reactant present at the fuel sensor (S) using the measurements of a mass flow sensor provided in the cathode system (10); 4d) checking the pressure in the cathode passage (10) by a pressure sensor; 4e) changing the rotation speed at which the compressor (V) is operated; 4f) modifying the mass flow rate of the reactants, including the fuel, introduced into the exhaust air line (12) upstream of the fuel sensor (S); and / or 5a) calibrating the fuel sensor (S) for a measuring point corresponding to a given concentration of the fuel-containing reactant, in particular as a function of the mass flow rate of the fuel-containing reactant introduced upstream of the fuel sensor (S) in the exhaust air line (12), the speed of the compressor (V), the mass flow rate of the oxygen-containing reactant at the sensor (S) and / or the pressure in the cathode path (10), 5. The method of claim 4, comprising the steps of:

6. The method may further comprise at least one of the following steps: 4g) increasing, decreasing or turning off the mass flow rate of reactants including the fuel introduced into the exhaust air line (12) before the fuel sensor (S); 5b) checking if and / or how quickly the fuel sensor (S) reacts to increasing or decreasing or switching off the mass flow rate; 6. The method according to claim 1, further comprising the steps of:

7. The method may further comprise at least one of the following steps: 6) carrying out a purging process of the anode system (20); 7) Evaluation of purge gas using the measurement results of the fuel sensor (S); 8) adapting the purge process of the anode system (20) until the fuel sensor (S) detects an expected concentration of reactants, including the fuel, in the mass flow of the purge gas; 7. The method according to claim 1, further comprising:

8. carrying out said steps of the method according to the invention simultaneously, at least partially simultaneously and / or sequentially, and / or carrying out the method periodically, in particular after a predefined time and / or periodically, in particular after a predefined consumption, for example of the oxygen-containing reactant and / or the fuel-containing reactant, and / or depending on a load profile, and / or incorporating the method into the operation of the fuel cell system (100), particularly when power of the fuel cell system (100) is not required; and / or transitioning the fuel cell system (100) to a power-free state to carry out the method.

8. The method according to claim 1, characterized in that

9. A fuel cell system (100), comprising: A fuel sensor (S) calibrated by the method according to any one of claims 1 to 8, the fuel sensor (S) is disposed in the exhaust air line (12) and is configured to sense fuel leaks and / or fuel mass flow in all subsystems (Q1, Q2, Q3, Q4, Q5) of the fuel cell system (100) that may be sources for fuel leaks and / or fuel mass flow; A fuel cell system (100).

10. A vehicle (1) comprising a fuel cell system (100) according to claim 9.

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