Device for determining and / or measuring the composition of a gaseous medium

Abstract

The present invention relates to an apparatus (1) for determining and / or measuring the composition of a gaseous medium in the anode circuit (2) of a fuel cell system (31), wherein the apparatus (1) has a sensor element (18), wherein the sensor element (18) determines, in particular by means of the surface hot film method (OHF), the measurement parameter wall shear stress T of the gaseous medium. w The sensor element (18) is located in the housing (36) of the device (1) and is at least indirectly fluidly connected to the anode circuit (2). According to the invention, the device (1) has at least one Prandtl probe assembly (7) in addition to at least one sensor element (18), wherein both elements (7, 18) are arranged in the housing (36) of the device (1), wherein the sensor element (18) can be supplied and / or loaded with a sub-mass flow (8) of the gaseous medium via an inlet funnel (5) and the Prandtl probe assembly (7) via an inlet channel (20). The invention further relates to a fuel cell system (31) and a method for operating the device (1) and / or the fuel cell system (31).

Description

Technical Field

[0001] This invention relates to an apparatus for determining and / or measuring the composition, particularly hydrogen, of a gaseous medium in the anode circuit of a fuel cell system, especially a fuel cell system configured for use in a vehicle with a fuel cell drive. Furthermore, this invention relates to a fuel cell system and a method for operating the apparatus and / or the fuel cell system. Background Technology

[0002] In the automotive field, gaseous fuels will play an increasingly important role in the future, in addition to liquid fuels. This is especially true in vehicles with fuel cell drives, where hydrogen gas flow needs to be controlled. Instead of the discontinuous control of the gas flow as in liquid fuel injection, the gas is drawn from at least one high-pressure storage tank and guided to the injector unit via an inflow line of a medium-pressure line system. The injector unit then guides the gas to the fuel cell via a connection line of a low-pressure line system. After flowing through the fuel cell, the gas is returned to the injector unit via a return line.

[0003] An apparatus for determining and / or measuring the composition of a gaseous medium in the anode circuit of a fuel cell system is known from the previously undisclosed DE 10 2022 213 712. This apparatus includes a sensor element that determines, particularly by means of the hot-film surface method (OHF), the measuring parameter wall shear stress of the gaseous medium, and wherein the sensor element is located within the housing of the apparatus and is at least indirectly fluidly connected to the anode circuit. This apparatus is arranged in a side-channel compressor for a fuel cell system.

[0004] The device known from DE 10 2022 213 712 may have certain drawbacks.

[0005] To maintain a high hydrogen concentration in the gaseous medium, a nitrogen- and / or water-rich gas mixture needs to be purged and replaced with fresh hydrogen. This control output (Absteuerung), especially the "purge," is performed on a time-grid basis because determining the nitrogen content is not easily achieved technically (e.g., using a mass spectrometer). Consequently, a significant amount of valuable hydrogen is lost during purging and / or "purge." Therefore, more hydrogen must be introduced into the anode circuit, for example from a high-pressure storage tank, to maintain a correspondingly high hydrogen concentration in the gaseous medium. The device known from DE 10 2022 213 712 has the disadvantage that it does not detect the velocity of the gaseous medium, especially the flow velocity, thus allowing only inaccurate calculations of the composition and viscosity of the gaseous medium. Therefore, the purging (so-called "purge") of the gaseous medium can only be conditionally and accurately initiated for components that are not hydrogen. This reduces the efficiency of the fuel cell system. Summary of the Invention

[0006] Advantages of the invention According to the present invention, an apparatus is provided for determining and / or measuring the composition of a gaseous medium in the anode circuit of a fuel cell system, wherein the apparatus has a sensor element that determines the wall shear stress τ of the gaseous medium by means of the surface hot film method (OHF). w Furthermore, the sensor element is located within the housing of the device and is at least indirectly fluidly connected to the anode circuit. Additionally, a fuel cell system, a method for operating the device, and / or the fuel cell system are proposed and provided.

[0007] Referring to claim 1, a device is proposed that, in addition to at least one sensor element, also has at least one Prandtl probe assembly, wherein both elements are arranged within the housing of the device. Here, the sensor element can be supplied and / or loaded with a sub-mass flow of a gaseous medium via an inlet funnel and the Prandtl probe assembly via an inlet channel. This approach achieves the advantage that the wall shear stress τ of the gaseous medium can be detected. w The wall shear stress is related to the viscosity of the gaseous medium. Viscosity varies with the composition of the gaseous medium. By additionally using a Prandtl probe assembly integrated into the device, in addition to the sensor element, a more accurate calculation of viscosity can be achieved because the measured parameter, wall shear stress τ... wThe velocity of the gaseous medium is related to its viscosity and velocity. By arranging the Prandtl probe assembly in close proximity to the sensor element, the velocity of the gaseous medium, especially the submass flow, can be determined with high accuracy, and / or, due to the spatial proximity of the Prandtl probe assembly to the sensor element, more accurate conclusions about the velocity of the gaseous medium on the sensor element can be derived. Therefore, by arranging and using the Prandtl probe assembly, the parametric wall shear stress τ can be obtained. w By controlling the flow velocity of the gaseous medium, more accurate calculations of viscosity can be achieved, thereby enabling precise derivation of the characteristics and composition of the gaseous medium. This allows for more targeted and time-efficient "sweeping" of the heavier components of the gaseous medium, improving the efficiency of the fuel cell system. Furthermore, the arrangement of sensor elements and Prandtl probe assemblies allows for a compact and flat design of the device. This enables a compact design for the entire side-channel compressor, minimizing the structural space required within the vehicle.

[0008] The dependent claims relate to preferred extensions of the invention.

[0009] According to an advantageous configuration of the equipment, at least one device is arranged at least indirectly in the main flow channel of the anode circuit. This allows for the following advantages: the device is located directly in a region where the gaseous medium flowing through the equipment for measurement purposes has representative composition and / or representative viscosity and / or representative velocity and / or representative temperature. Furthermore, multiple devices can be used to improve the accuracy of the measurement results, wherein the devices are arranged in at least almost all of the flow regions of the anode circuit. Therefore, the wall shear stress τ of the gaseous medium can be measured by means of the device. w And / or velocity measurements can be performed more accurately, thereby improving the precision of one or more measurement results. This enables better prediction of the composition of the gaseous medium, thereby improving the efficiency of subsequent conditioning processes. Furthermore, cost-effective integration of the equipment in the anode circuit is possible.

[0010] According to a particularly advantageous extension, the device is constructed such that the sensor element is arranged in a secondary flow channel, particularly a measurement channel, within the housing. The measurement channel is enclosed by a cover, which at least partially defines the measurement channel geometrically. Here, a gaseous medium is guided through the channel, where laminar flow can be formed, particularly in the measurement channel, by means of the pressure difference Δp between the channel inlet and outlet and the small diameter of the channel. Therefore, the maximum effect of viscosity can be achieved. Here, the sensor element measures, particularly by means of a surface thermal film, the wall shear stress τ. wThe viscosity of the anode gas is calculated from the known Δp and the known flow geometry of the channel. Here, the measuring channel can have a maximum diameter of 2.5 mm, and more specifically 1 mm. Since the gas composition only changes at the operating point during normal operation, it can be determined from the wall shear stress τ. w The change in the gas mixture is inferred from the change in the flow path. Here, in this configuration of the device according to the invention, the device is protected from flow vortices by the geometric representation of the main flow channel, thereby reducing the wall shear stress τ. w The accuracy of measurements of flow velocity and / or other parameters can be improved. Furthermore, a compact design for both the sensor elements and the entire device can be achieved, minimizing the structural space required throughout the vehicle.

[0011] According to an advantageous configuration of the device, the main flow channel extends along a first axis, the measurement channel of the sensor element extends along a second axis, the inlet channel of the Prandtl probe assembly extends along a third axis, and the outlet channel extends along a fourth axis. Here, the first three axes extend at least almost parallel to each other, and the fourth axis extends at least almost orthogonal to the first three axes. In this way, the following advantages can be achieved: with the help of the Prandtl probe assembly, when using absolute pressure P... abs and / or static pressure P Stat In this case, the pressure difference Δp can be measured more accurately. Furthermore, since the first three axes of the corresponding channels extend at least almost parallel, the discharge of submass flow can be achieved with minimal frictional and / or flow and / or velocity losses of the gaseous medium. Therefore, this device improves measurement results and enables more sustainable laminar flow within the device. Additionally, it reduces flow resistance in the anode loop, thereby improving the efficiency of the fuel cell system.

[0012] According to a particularly advantageous configuration of the device, it has at least one temperature sensor located on the side wall of the main flow channel facing the anode circuit of the device housing. This configuration offers the advantage of reliably measuring the temperature of the gaseous medium using the temperature sensor. By placing the temperature sensor on the side wall of the main flow channel facing the anode circuit of the device housing, temperature measurement can be performed as close as possible to the main flow area of ​​the gas mass flow and / or within the main flow of the gas mass flow, thus minimizing deviations in the measured temperature of the gaseous medium. Therefore, by incorporating the temperature measurement using the appropriately positioned temperature sensor into the measurements of other sensors, a more accurate determination of the viscosity of the gaseous medium can be achieved. This further improves measurement accuracy and minimizes the impact of viscosity. Consequently, a precise derivation of the properties and composition of the gaseous medium can be obtained. Therefore, the efficiency of the fuel cell system can be improved.

[0013] According to a particularly advantageous configuration of the device, the temperature sensor is located downstream of the outlet channel of the Prandtl probe assembly in the main flow channel of the anode circuit. This arrangement offers the advantage that, since the temperature sensor is positioned downstream of the outlet channel of the Prandtl probe assembly in the main flow channel of the anode circuit, the flow influence of the temperature sensor can at least almost eliminate or reduce the distortion in velocity measurement and / or static pressure loading on the outlet-facing end of the Prandtl probe assembly. Therefore, the velocity of the gaseous medium, especially the sub-mass flow and / or gas mass flow, can be measured sufficiently accurately with the help of the Prandtl probe assembly without the influence of the temperature sensor, particularly on the inflow via the inlet and / or the outflow via the outlet channel of the Prandtl probe assembly. Thus, accurate derivation of the characteristics and composition of the gaseous medium can be obtained. Therefore, the efficiency of the fuel cell system can be improved. Furthermore, the arrangement of the temperature sensor according to the invention enables a compact construction of the device.

[0014] According to an advantageous configuration of the device, the measuring channel has a surface roughness k and / or a length L2 and / or a diameter D, such that laminar flow is always formed in the flow channel under different operating conditions and / or different flow velocities of the gas mass flow. In this way, the following advantages can be achieved: the wall shear stress τ can be determined using sensor elements. wThe measurements can be obtained, and if necessary, additional measurements, such as pressure difference, can be obtained using a Prandtl probe assembly, and the temperature of the gaseous medium can be obtained, for example, using a temperature sensor. From these measurements, the viscosity and / or composition of the gaseous medium, particularly the proportions of hydrogen and / or nitrogen and / or water, can be determined. Water in the gaseous medium can be more effectively removed using a purge valve located in the anode circuit. Therefore, the efficiency of the side-channel compressor and the entire fuel cell system can be improved because less hydrogen is lost.

[0015] According to an advantageous extension of the side-channel compressor, the sensor element and cover device are constructed as a combined measuring channel-cover assembly, which can be pre-assembled and / or implemented as a structural unit. This approach offers the following advantages: the measuring channel-cover assembly can be quickly constructed as a single, integrated solution during the assembly of the side-channel compressor, reducing assembly and processing time. Therefore, the assembly and processing costs for each manufactured side-channel compressor can be reduced. Furthermore, in the event of maintenance or repair due to malfunction (e.g., due to contaminated or blocked channels or defective sensor elements), the combined measuring channel-cover assembly can be completely removed and replaced with a new unit in a single work step. This further reduces maintenance and repair costs.

[0016] In addition, to address the aforementioned tasks, a fuel cell system with a side-channel compressor is proposed. According to an advantageous configuration of the fuel cell system, the equipment is arranged in the anode loop of the fuel cell system, particularly in the area of ​​the return line and / or tank line and / or connection line. Furthermore, the fuel cell system includes a controller and / or a purge valve. Therefore, a compact construction and arrangement of components can be achieved. Moreover, within the framework of the fuel cell system design, particularly the anode loop, this arrangement of at least one or more components in the anode loop enables the most accurate measurement possible of the viscosity and / or composition of the gaseous medium in the anode loop, and allows for the most efficient removal of heavy components, such as water, nitrogen, or other substances, from the anode loop, for example, by means of a purge valve.

[0017] Furthermore, a method for operating equipment and / or fuel cell systems is proposed. Here, in the first step, the wall shear stress τ is measured using sensor elements. w In the second step, the absolute pressure P is detected using a Prandtl probe assembly. abs static pressure P Stat In the third step, when using absolute pressure P... abs and / or static pressure P StatIn this case, the flow velocity of the gaseous medium is calculated, particularly with the aid of a controller, using the pressure difference Δp. Here, known flow geometry of the inlet channel, such as its length L2 and / or its diameter, can be used, so that these values ​​can be used in the algorithm stored in the controller for calculation. In an optional fourth step, the temperature is detected using a temperature sensor. In a fifth step, the viscosity of the gaseous medium at a given time point T1 is determined.

[0018] Furthermore, a method for operating equipment and / or fuel cell systems is proposed, the method having the following additional steps: calculating the change in composition of the gaseous medium by means of a controller through differential calculation of multiple measurement points Tn, and controlling a purge valve.

[0019] The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, various modifications that are within the scope of the claims and are of skill to those skilled in the art are possible. Attached Figure Description

[0020] The invention will now be described in more detail with reference to the accompanying drawings.

[0021] The attached diagram shows: Figure 1 A schematic diagram of a fuel cell system according to the invention is shown, the fuel cell system having an anode circuit and at least one device according to the invention located in the anode circuit. Figure 2 A schematic longitudinal sectional view of a device according to the invention is shown, the device having sensor elements and Prandtl probe assembly. Figure 3 A cross-sectional view shows the Prandtl probe assembly according to the invention. Figure 2 An enlarged diagram of the segment marked II in the diagram. Figure 4 The sensor element according to the invention is shown in Figure 2 The top view marked AA in the middle. Figure 5 This illustrates one possible configuration of the operating method according to the invention. Figure 6 The following components are shown in schematic diagram: sensor, controller, speed sensor, pressure sensor, and purge valve. Detailed Implementation

[0022] according to Figure 1The schematic diagram illustrates a fuel cell system 31 according to the invention, having an anode circuit 2 and at least one device 1 according to the invention located in the anode circuit 2. Here, a conveyor unit 13 is shown connected to a fuel cell 32 via a connecting line 29, the fuel cell including an anode region 42 and a cathode region 40. Furthermore, a return line 23 is provided, connecting the anode region 42 of the fuel cell 32 to a first inlet 28 and thus, in particular, to the intake region 7 of the conveyor unit 13. By means of the return line 23, a first gaseous medium unused in the anode region 42 during operation of the fuel cell 32 can be returned to the first inlet 28. This first gaseous medium is, in particular, a recirculation medium.

[0023] As from Figure 1 As can be further seen, the second gaseous medium stored in tank 34 is supplied to the second inlet 30 of conveyor unit 13 via tank line 27. This second gaseous medium is, in particular, the driving medium. Here, device 1 is arranged in the anode circuit 2 of fuel cell system 31, particularly in the area of ​​return line 23 and / or tank line 27 and / or connecting line 29, and wherein fuel cell system 31 has controller 47 and / or purge valve 44. Here, the measurements of the corresponding device 1 can be transmitted to controller 47 for analysis, for example, by means of a stored algorithm, wherein controller 47, based on the results of the algorithm, causes control of purge valve 44 to efficiently and in relation to the operating conditions discharge the heavier components of the gaseous medium (e.g., water or nitrogen) from anode circuit 2 into environment 46.

[0024] Figure 2 A schematic longitudinal sectional view of a device 1 according to the invention is shown, the device having a sensor element 18 and a Prandtl probe assembly 7. Here, upstream of device 1, a total mass flow 4 of the gaseous medium flows into a main flow channel 15. At the upstream end of device 1, the total mass flow 4 branches into a gaseous mass flow 6, which flows as a main flow 12 alongside device 1 through the main flow channel 15 without flowing through device 1. Furthermore, the total mass flow 4 branches into a sub-mass flow 8 of the gaseous medium, which flows through openings in the end of device 1, particularly the inlet channel 20 of the Prandtl probe assembly 7 and / or the inlet funnel 5 of the sensor element 18. Thus, the sub-mass flow 8 re-branches before flowing through channel 25 and into inlet 20.

[0025] like Figure 2As shown, the sensor element 18 is arranged in a channel 25, particularly a measurement channel 25, within the housing 36, particularly the substrate 36. Here, the channel 25 is enclosed by a covering device 22, which defines the channel 25. Here, the sensor element 18 and the covering device 22 are implemented as a combined measurement channel-cover assembly 33, which can be pre-assembled and / or implemented as a structural unit 33. Here, a gaseous medium flows through the channel 25 alongside the sensor element 18 in the flow direction 10, wherein the flow 10 exists as laminar flow 38a and / or as turbulent flow with a viscous underlayer 38b due to the geometric manifestations, particularly the diameter of the channel 25. Here, the sensor 18 has at least one surface heating element (OHF element) 26, which is passed through by the flow 38a, b and / or measures are performed at this location in the channel 25 by means of a surface heating film method. In one exemplary embodiment, sensor element 18 and / or device 1 may be supplemented by additional (not shown) resistive elements that can be used for temperature compensation of the bridge measurement circuit. To minimize pressure drop in the measuring device, the accelerated flow in channel 25 is slowed again by diffuser 11, which is in particular a Venturi nozzle 11.

[0026] like Figure 2 As shown, device 1 is arranged at least indirectly in the main flow channel 15 of anode circuit 2. Here, the main flow channel 15 extends along a first axis 37, the measurement channel 25 of sensor element 18 extends along a second axis 39, the inlet channel 20 of Prandtl probe assembly 7 extends along a third axis 41, and the outlet channel 24 of Prandtl probe assembly 7 extends along a fourth axis 43. In one exemplary embodiment of device 1 and / or anode circuit 2 and / or fuel cell system 31, the first three axes 37, 39, and 41 extend at least substantially parallel to each other, wherein the fourth axis 43 extends at least substantially orthogonal to the first three axes 37, 39, and 41.

[0027] Furthermore, the device 1 is shown to have at least one temperature sensor 9, which is disposed on the side wall 21 of the housing 36 of the device 1 facing the main flow channel 15. The temperature of the gaseous medium can be determined by means of the temperature sensor 9. Here, the temperature sensor 9 is located downstream of the outlet channel 24 of the Prandtl probe assembly 7 in the main flow channel 15 of the anode circuit 2, wherein this arrangement at least almost completely prevents interference with measurements, such as measurements of the flow velocity of the gaseous medium. Furthermore, the temperature sensor 9 is oriented towards the main flow 12 so as not to be distorted due to heating of the OHF element 26.

[0028] In addition, Figure 2As shown, device 1 is a combined sensor assembly 1 having at least one sensor element 18 and a Prandtl probe assembly 7. Here, the sensor element 18, the Prandtl probe assembly 7, and the covering device 22 are implemented as a combined measurement channel-cover assembly 33, which can be pre-assembled and / or installed and / or constructed as a structural unit 33 in or on the main flow channel 15. The sensor element 18 can be determined, in particular, by means of the surface hot film method (OHF) and the wall shear stress τ obtained from the gaseous medium. w And, if necessary, additional parameters are used to derive the viscosity and / or composition of the gaseous medium. Here, the wall shear stress τ can be determined using at least one OHF element 26 of sensor element 18. w Among them, the wall shear stress τ w This describes the momentum flux through a volume of gaseous medium adjacent to a wall, caused by friction between fluid elements on the wall and among themselves. Wall shear stress τ w Velocity is measured via dynamic pressure. By understanding the geometry and velocity curve, the derivative of velocity perpendicular to the OHF can be calculated. The only unknown is the viscosity associated with the mixture.

[0029] To determine the wall shear stress τ w The following formula is used here: Figure 2 Furthermore, a sub-mass flow 8 branches off from the total mass flow 4, and this sub-mass flow is supplied to and flows through the device 1. Here, the remaining gas mass flow 6 flows alongside the device 1 in the main flow direction 12 through the main flow channel 15, which is located, for example, in the return line 23 and / or tank line 27 and / or connecting line 29 of the anode circuit 2. Here, the branched sub-mass flow 8 is supplied, on the one hand, to the measuring channel 25 of the sensor element 18 via the inlet funnel 5, particularly the nozzle 5. On the other hand, the sub-mass flow 8 is supplied to the sensor and / or measuring section of the Prandtl probe assembly 7 via the inlet channel 20. Here, the Prandtl probe assembly 7 is specifically implemented as a Prandtl total pressure pipe 7 and is used to determine the velocity of the gaseous medium, particularly the flow velocity. Using the Prandtl probe assembly 7 and the sensors therein, the total pressure 17 is measured upstream of the Prandtl probe assembly 7, particularly in the initial region of the inlet channel 20, and the static pressure 19 is measured using laterally arranged sensors, particularly in the outlet 24 of the Prandtl probe assembly 7. This static pressure is also used, for example, to determine material data. Here, the difference between the two pressures is proportional to the inflow velocity. Here, in an exemplary embodiment of device 1, the Prandtl total pressure tube 7 can be a combination of a pressure probe and a Pitot tube. The measured parameter is the wall shear stress τ. wIts value is related to the viscosity and velocity of the medium. Viscosity varies with the gas composition. Velocity is obtained through the integrated Prandtl total pressure tube 7, or derived from the measurement signal. Here, the total pressure 17 can correspond to the absolute pressure P. abs The static pressure 19 can correspond to the static pressure P. Stat .

[0030] Here, in Figure 2 The measurement channel 25 shown may have a surface roughness k and / or length L2 and / or diameter D such that laminar flow 38 is always formed in the measurement channel 25 under different operating conditions and / or different flow velocities of the gas mass flow 6. The measurement position in the measurement channel 25 is defined by known parameters k, L1, and D, which in particular has a prescribed geometry, wherein the measurement position is loaded with sub-mass flow 8. The ratio of sub-mass flow 8 to gas mass flow 6 is related to the installation position and must be considered accordingly, particularly the corresponding ratio of cross-sectional areas.

[0031] Figure 3 A cross-sectional view of the Prandtl probe assembly 7 according to the present invention is shown. Figure 2 Enlarged schematic diagram of the segment indicated by II. This shows a stagnation pressure measurement being performed in the region of the upstream inlet 20, wherein the total pressure 17 is determined, which corresponds in particular to the stagnation pressure 17 and / or the total pressure 17. Here, inlet 20 ideally mimics the head of a Prandtl probe, such that the static pressure P after length L2... Stat Corresponding to the actual static pressure P of the flow Stat2 Here, the difference between the two pressures 17 and 19 is proportional to the inflow velocity, particularly the velocity of the submass flow 8. In one exemplary embodiment, the Prandtl probe assembly 7 is not subjected to flow penetration; instead, it is loaded with total pressure 17 on its end face facing the inlet channel 20 and with static pressure 19 on its end face facing the outlet 24. The Prandtl probe assembly 7 obtains the pressure difference Δp from these two pressures 17 and 19, and thus obtains the dynamic pressure ~v.

[0032] Figure 4 The sensor element 18 according to the present invention is shown in Figure 2The top view is indicated by AA. Here, sensor element 18 is shown to have at least one surface hot film element (OHF element) 26. In this exemplary embodiment, sensor element 18 has three OHF elements 26, which are elongated and rod-shaped, extending in an extension direction 51, which is at least almost orthogonal to the flow direction 10 of the gaseous medium. Here, the gaseous medium passes sequentially through a corresponding first OHF element 26a, then a corresponding second OHF element 26b, and then a corresponding third OHF element 26c in the flow direction 10 as it flows through the measurement channel 25.

[0033] exist Figure 5 The diagram illustrates a possible configuration of the operating method according to the invention. Here, the multi-stage method for operating device 1 is shown in a highly simplified manner by rectangles 51 to 56 and the arrows between them. In the first method step 51, the wall shear stress τ is measured using sensor element 18. w In step 52 of the second method, the absolute pressure P is detected using the Prandtl probe assembly 7. abs static pressure P Stat In step 53 of the third method, when using absolute pressure P... abs and / or static pressure P Stat In this case, the flow velocity of the gaseous medium is calculated, particularly by means of the controller 47, using the pressure difference Δp. Here, known flow geometry of the inlet channel 20, such as its length L2 and / or its diameter, can be used, so that these values ​​can be used in the algorithm stored in the controller 47 for calculation 53. In an optional fourth method step 54, the temperature is detected using the temperature sensor 9. In a fifth method step 55, the viscosity of the gaseous medium at a determined time point T is determined using the controller 47. In an optional sixth method step 56, the change in the composition of the gaseous medium is calculated by performing a difference calculation (Delta-Berechnung) on ​​multiple measurement points Tn using the controller 47, and the purge valve 44 is actuated.

[0034] Figure 6The arrangement of different components of device 1 and / or fuel cell system 31 is shown. This arrangement is illustrated here as follows: sensor element 18, controller 47, Prandtl probe assembly 7, optional temperature sensor 9, and purge valve 44. Here, controller 47 and purge valve 44 are not necessarily required to be located in or on device 1; instead, they can be located in other areas of fuel cell system 31, particularly in anode circuit 2. Here, sensor element 18 and / or Prandtl probe assembly 7 and / or optional temperature sensor 9 provide measured values ​​and data to controller 47, which controls purge valve 44 according to a stored algorithm for analyzing and processing the data. Here, purge valve 44 is opened by the control of controller 47 only when the gaseous medium has a high concentration of water and / or nitrogen and / or other components (the other components are not hydrogen).

[0035] Here, raw data is recorded and / or analyzed by means of sensors and controller 47, and meaningful opening of purge valve 44 (so-called "purge") can be achieved, for example by means of an algorithm stored in controller 47, to discharge water and / or nitrogen and / or other components in a manner that meets the requirements, with only a small amount of hydrogen or at least almost no loss of hydrogen.

Claims

1. An apparatus (1) for determining and / or measuring the composition of a gaseous medium in the anode circuit (2) of a fuel cell system (31), wherein, The device (1) has a sensor element (18), wherein the sensor element (18) determines, in particular by means of the oil flow method (OHF), a measurement variable wall shear stress τ w of the gaseous medium, and wherein the sensor element (18) is located in a housing (36) of the device (1) and is at least indirectly fluidically connected to the anode circuit (2), characterized in that the device (1) has, in addition to the at least one sensor element (18), at least one Prandtl probe assembly (7), wherein both elements (7, 18) are arranged in the housing (36) of the device (1), wherein the sensor element (18) can be supplied and / or loaded with a sub-mass flow (8) of the gaseous medium by means of an inlet funnel (5) and the Prandtl probe assembly (7) can be supplied and / or loaded with a sub-mass flow (8) of the gaseous medium by means of an inlet channel (20).

2. The device (1) according to claim 1, characterized in that, At least one device (1) is arranged at least indirectly in the main flow channel (15) of the anode circuit (2), particularly in the area of ​​the return line (23) and / or the tank line (27) and / or the connecting line (29).

3. The device (1) according to claim 1 or 2, characterized in that, The sensor element (18) is arranged in the secondary flow channel (25), particularly the measurement channel (25), in the housing (36), wherein the measurement channel (25) is closed by means of a cover (22), and wherein the cover (22) at least partially defines the measurement channel (25) geometrically.

4. The device (1) according to claim 2 or 3, characterized in that, The main flow channel (15) extends along the first axis (37), the measurement channel (25) of the sensor element (18) extends along the second axis (39), the inlet channel (20) of the Prandtl probe assembly (7) extends along the third axis (41), and the outlet channel (24) of the Prandtl probe assembly (7) extends along the fourth axis (43), wherein the first three axes (37, 39, 41) extend at least almost parallel to each other, and wherein the fourth axis (43) extends at least almost orthogonally to the first three axes (37, 39, 41).

5. The device (1) according to any one of the preceding claims, characterized in that, The device (1) has at least one temperature sensor (9), wherein the temperature sensor (9) is arranged on the side wall (21) of the housing (36) of the device (1) facing the main flow channel (15).

6. The device (1) according to claim 5, characterized in that, The temperature sensor (9) is located downstream of the outlet channel (24) of the Prandtl probe assembly (7) in the main flow channel (15) of the anode circuit (2).

7. The device (1) according to any one of claims 3 to 6, characterized in that, The measuring channel (25) has a surface roughness k and / or a length L2 and / or a diameter D, such that laminar flow (38) is always formed in the measuring channel (25) under different operating conditions and / or different flow velocities of the gas mass flow (6).

8. The device (1) according to any one of claims 2 to 7, characterized in that, The sensor element (18), the Prandtl probe assembly (7), and the cover device (22) are implemented as a combined measurement channel-cover assembly (33), which can be pre-assembled and / or installed as a structural unit (33) in or on the main flow channel (15).

9. A fuel cell system (31) comprising the device (1) according to any one of claims 1 to 8, wherein, The device (1) is arranged in the anode circuit (2) of the fuel cell system (31), particularly in the area of ​​the return line (23) and / or the tank line (27) and / or the connection line (29), and wherein the fuel cell system (31) has a controller (47) and / or a purge valve (44).

10. A method for operating the device (1), particularly the measuring device (1) and / or fuel cell system (31) according to any one of the preceding claims, the method comprising the steps of: - The wall shear stress τ is measured (51) by means of the sensor element (18). w ; - The absolute pressure P is detected (52) by means of the Prandtl probe assembly (7). abs static pressure P Stat ; - Using the absolute pressure P abs And / or the static pressure P Stat In the case of pressure difference Δp, the flow velocity of the gaseous medium is calculated (53), especially by means of the controller (47). Here, the known flow geometry of the inlet channel (20), such as its length L2 and / or its diameter, can be used in the algorithm stored in the controller (47) for calculation (53). - Temperature can be optionally detected (54) using the temperature sensor (9); - The viscosity of the gaseous medium at a determined time point T1 is determined by means of the controller (47).

11. The method for controlling a device (1), particularly a measuring device (1), and / or a fuel cell system (31) according to claim 10, the method comprising the following additional steps: - The controller (47) calculates (56) the change in the composition of the gaseous medium by performing difference calculation on multiple measurement points Tn, and controls the purge valve (44).

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