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

Abstract

The invention also relates to a device (1) for determining and / or measuring the composition of a gaseous medium in an anode circuit (2) of a fuel cell system (31), wherein the device has a sensor element (18), wherein the sensor element (18) determines the measured variable of wall shear stress Tw, in particular by means of a surface hot-film method, 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). According to the invention, the device (1) has at least one Prandtl probe arrangement (7) in addition to the at least one sensor element (18), wherein both elements (7, 18) are located in the housing (36) of the device (1), wherein a partial mass flow (8) of the gaseous medium can be supplied and / or applied to the sensor element (18) by means of an inlet funnel (5) and to the Prandtl probe arrangement (7) by means of a feed channel (20). The invention also relates to a fuel cell system (31) and to a method for operating a device (1) and / or a fuel cell system (31).

Description

[0001] Description

[0002] title

[0003] Device for determining and / or measuring the composition of a gaseous medium

[0004] State of the art

[0005] The present invention relates to a device for determining and / or measuring the composition of a gaseous medium, in particular hydrogen, in an anode circuit of a fuel cell system, which is intended in particular for use in vehicles with a fuel cell drive. Furthermore, the present invention relates to a fuel cell system and a method for operating a device and / or a fuel cell system.

[0006] In the future, gaseous fuels will play an increasingly important role in the automotive sector, alongside liquid fuels. Hydrogen gas flows must be controlled, particularly in fuel cell-powered vehicles. The gas flows are no longer controlled discontinuously, as with liquid fuel injection; instead, the gas is drawn from at least one high-pressure tank and fed to an ejector unit via an inlet line of a medium-pressure line system. This ejector unit feeds the gas to a fuel cell via a connecting line of a low-pressure line system. After the gas has flowed through a fuel cell, it is fed back to the ejector unit via a return line.

[0007] From the unpublished DE 10 2022 213 712, a device for determining and / or measuring the composition of a gaseous medium in an anode circuit of a fuel cell system is known. The device comprises a sensor element, wherein the sensor element determines the measured value of wall shear stress of the gaseous medium, in particular by means of a surface hot film (OHF) method. The sensor element is located in a housing of the device and is at least indirectly fluidically connected to the anode circuit. The device is arranged in a side channel compressor for a fuel cell system. The device known from DE 10 2022 213 712 can have certain disadvantages.

[0008] In order to keep the hydrogen concentration in the gaseous medium high, the nitrogen-rich and / or water-rich gas mixture must be vented and replaced with fresh hydrogen. This control, in particular "purging", takes place according to a time grid, since the determination of the nitrogen content is not easy to implement metrologically (e.g. with a mass spectrometer). As a result, a lot of valuable hydrogen is lost during venting and / or "purging". Therefore, more hydrogen must be added, for example from a high-pressure tank into the anode circuit, so that the hydrogen concentration in the gaseous medium can be kept correspondingly high. The device known from DE 10 2022 213 712 has the disadvantage that the velocity, in particular the flow velocity, of the gaseous medium is not recorded, which means that the composition of the gaseous medium and its viscosity can only be calculated imprecisely.This means that purging of non-hydrogen components of the gaseous medium can only be carried out with limited precision. This reduces the efficiency of the fuel cell system.

[0009] Disclosure of the invention

[0010] Advantages of the invention

[0011] According to the invention, a device for determining and / or measuring the composition of a gaseous medium in an anode circuit of a fuel cell system is provided, the device comprising a sensor element, the sensor element measuring the measured value wall shear stress T w, in particular by means of a surface hot film method (OHF), of the gaseous medium, and wherein the sensor element is located in a housing of the device and is at least indirectly fluidically connected to the anode circuit. Furthermore, a fuel cell system, a method for operating the device and / or a fuel cell system are proposed and provided. With reference to claim 1, a device is proposed which, in addition to the at least one sensor element, has at least one Prantl probe arrangement, wherein both elements are arranged in the housing of the device. The sensor element can be supplied with and / or acted upon by a partial mass flow of the gaseous medium by means of an inlet funnel, and the Prantl probe arrangement by means of an inlet channel. In this way, the advantage can be achieved that a wall shear stress T wof the gaseous medium can be measured, whereby this depends on the viscosity of the gaseous medium. Viscosity varies with the composition of the gaseous medium. By additionally using the Prantl probe arrangement, which is integrated in the device in addition to the sensor element, a more accurate calculation of the viscosity can be achieved, since the measured value wall shear stress T wdepends on the viscosity and the velocity of the medium. By arranging the Prantl probe arrangement in the immediate vicinity of the sensor element, the velocity of the gaseous medium, in particular the partial mass flow, can be measured with high accuracy and / or more precise conclusions can be drawn about the velocity of the gaseous medium at the sensor element due to the spatial proximity of the Prantl probe arrangement to the sensor element. Thus, the arrangement and use of the Prantl probe arrangement allows for a more precise calculation of the viscosity from the parameters wall shear stress T wand flow velocity of the gaseous medium, allowing for a precise derivation of the properties and composition of the gaseous medium. This allows for more targeted and time-optimized purging of the heavy components of the gaseous medium, thus improving the efficiency of the fuel cell system. Furthermore, the arrangement of the sensor element and the Prantl probe arrangement allows for a compact and flat design of the device. This allows for a compact design of the entire side channel compressor, keeping the required installation space in the overall vehicle to a minimum.

[0012] The subclaims relate to preferred developments of the invention.

[0013] According to an advantageous embodiment of the device, at least one device is arranged at least indirectly in a main flow channel of the anode circuit. In this way, the advantage can be achieved that the device is located directly in the region in which the gaseous medium, which is to flow through the device for measurement purposes, has a representative composition and / or a representative viscosity and / or a representative velocity and / or a representative temperature. In addition, the use of several devices can be carried out in order to improve the accuracy of the measurement results, wherein the device is arranged in at least almost all flow regions of the anode circuit. Thus, the measurement of the wall shear stress T wThe device allows for much more precise measurement of the gaseous medium's velocity and / or flow rate, thereby improving the accuracy of the measurement result(s). This allows for a better prediction of the gaseous medium's composition, improving the efficiency of a downstream control process. Furthermore, cost-effective integration of the device into the anode circuit is possible.

[0014] According to a particularly advantageous development, the device is designed such that the sensor element is arranged in a secondary flow channel, in particular a measuring channel, in the housing, wherein the measuring channel is closed by means of a cover, and wherein the cover geometrically defines the measuring channel at least partially. The gaseous medium is guided through the channel, wherein a laminar flow can be formed, in particular in the measuring channel, by means of the pressure difference Ap between the channel inlet and the channel outlet and the small diameter of the channel. Thus, a maximum influence of the viscosity can be achieved. The sensor element measures the wall shear stress T, in particular by means of a surface hot film. wand calculates the viscosity of the anode gas from the known Ap and the known flow geometry of the channel. The measuring channel can have a maximum diameter of 2.5 mm, in particular 1 mm. Since during normal operation only the gas composition changes at one operating point, a change in the wall shear stress T w The sensor element in this inventive design of the device is protected from flow turbulence caused by geometric features of the main flow channel, which increases the accuracy of the measurement result wall shear stress T wand / or flow velocity can be improved. In addition, a compact design of the sensor element and the entire device can be achieved, so that the required installation space in the overall vehicle remains low. According to an advantageous embodiment of the device, the main flow channel runs along a first axis, the measuring channel of the sensor element runs along a second axis, the inlet channel of the Prantl probe arrangement runs along a third axis, and an outlet channel runs along a fourth axis. The first three axes run at least almost parallel to one another, the fourth axis running at least almost orthogonal to the first three axes. In this way, the advantage can be achieved that a more precise measurement of the pressure difference Ap by using an absolute pressure p abs and / or a static pressure p stat is possible using the Prantl probe arrangement. Furthermore, the partial mass flow can be diverted with the lowest possible friction losses and / or flow losses and / or velocity losses of the gaseous medium, since the first three axes of the respective channels run at least nearly parallel. Thus, the device improves the measurement results and allows for more sustainable laminar flow within the device. Furthermore, the flow resistance of the device in the anode circuit can be reduced, thereby improving the efficiency of the fuel cell system.

[0015] According to a particularly advantageous embodiment of the device, it has at least one temperature sensor, wherein the temperature sensor is located on a side wall of the device housing facing the main flow channel of the anode circuit. This provides the advantage that a reliable measurement of the temperature of the gaseous medium can be carried out using the temperature sensor. By placing the temperature sensor on the side wall of the device housing facing the main flow channel of the anode circuit, a temperature measurement can be carried out as close as possible to and / or in a main flow of a gas mass flow, so that a deviation in the measurement result of the temperature of the gaseous medium can at least be reduced.Thus, by incorporating the temperature measurement using the appropriately positioned temperature sensor into the other parameters of the measurements of the other sensors, a more precise determination of the viscosity of the gaseous medium can be achieved. This allows the measurement accuracy to be further increased and a maximum influence of the viscosity of the gaseous medium is achieved. In this way, an exact derivation of the properties and composition of the gaseous medium can be determined. This can increase the efficiency of the fuel cell system. According to a particularly advantageous embodiment of the device, the temperature sensor is located downstream of the outlet channel of the Prantl probe arrangement in the main flow channel of the anode circuit.In this way, the advantage can be achieved that any falsification of the measurement of the velocity and / or the application of the static pressure on the end face of the Prantl probe arrangement facing the outlet due to a flow influence of the temperature sensor can be at least almost excluded or reduced, since the temperature sensor is arranged downstream of the outlet channel of the Prantl probe arrangement in the main flow channel of the anode circuit. Thus, a sufficiently precise measurement of the velocity of the gaseous medium, in particular of the partial mass flow and / or the gas mass flow, can be carried out by means of the Prantl probe arrangement, without the inflow via the inlet and / or outflow via the outlet channel of the Prantl probe arrangement being influenced by the temperature sensor, in particular in terms of flow technology. In this way, an exact derivation of the properties and composition of the gaseous medium can be determined.This allows the efficiency of the fuel cell system to be increased. Furthermore, a compact design of the device is possible thanks to the inventive arrangement of the temperature sensor.

[0016] According to an advantageous embodiment of the device, the measuring channel has a surface roughness k and / or a length L2 and / or a diameter D such that, under different operating conditions and / or flow velocities of the gas mass flow, laminar flow always develops in the flow channel. This provides the advantage that the measured values ​​for determining the wall shear stress T wDetermined by means of the sensor element and, if necessary, further measured values, such as the pressure difference, which can be determined using the Prantl probe arrangement, and, for example, the temperature of the gaseous medium, which can be determined using the temperature sensor, and from which the viscosity of the gaseous medium and / or the composition of the gaseous medium can be determined, in particular the proportions of hydrogen and / or nitrogen and / or water. In this way, a more targeted removal of the water in the gaseous medium can be achieved using a purge valve in the anode circuit. This improves the efficiency of the side channel compressor and the entire fuel cell system, since less hydrogen is lost.

[0017] According to an advantageous development of the side channel blower, the sensor element and the cover are designed as a combined measuring channel-cover arrangement that can be pre-assembled and / or designed as a structural unit. This has the advantage that the measuring channel-cover arrangement can be quickly installed as a one-piece solution during assembly of the side channel blower, so that the assembly and processing time of the side channel blower can be reduced. This also reduces the assembly and processing costs per manufactured side channel blower. In addition, in the event of maintenance or repair due to a failure, for example due to a dirty or blocked channel or a defective sensor element, the combined measuring channel-cover arrangement can be completely removed in a single step and replaced with a new unit. This reduces maintenance and repair costs.

[0018] To achieve the stated object, a fuel cell system with a side-channel compressor is also proposed. According to an advantageous embodiment of the fuel cell system, the device is arranged in the anode circuit of the fuel cell system, in particular in the region of a return line and / or a tank line and / or a connecting line. Furthermore, the fuel cell system has a control unit and / or the purge valve. This allows for a compact design and arrangement of the components.Furthermore, within the scope of a design of the fuel cell system, in particular of the anode circuit, such an arrangement of at least one arrangement or several arrangements in the anode circuit can be made so that the viscosity and / or the composition of the gaseous medium in the anode circuit can be measured as accurately as possible, so that the most efficient removal of heavy components, such as water or nitrogen or other substances, from the anode circuit can be brought about, for example by means of the purge valve.

[0019] A method for operating a device and / or a fuel cell system is also proposed. In a first step, the wall shear stress T w by means of the sensor element. In a second step, the absolute pressure p abs and the static pressure p S t at using the Prantl probe arrangement. In a third step, the flow velocity of the gaseous medium is calculated using the pressure difference Ap by using the absolute pressure p abs and / or the static pressure p stat , in particular by means of the control unit. In particular, a known flow geometry of the inlet channel, for example its length L2 and / or its diameter, can be used to calculate these values ​​in an algorithm stored in the control unit. In a fourth optional step, the temperature is recorded using the temperature sensor. In a fifth step, the viscosity of the gaseous medium is determined at a specific time T1.

[0020] Also proposed is a method for operating a device and / or a fuel cell system, comprising the following additional step: calculating a change in the composition of the gaseous medium by delta calculation of several measuring points Tn by means of the control unit and controlling the purge valve.

[0021] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

[0022] Short description of the drawing

[0023] The invention is described in more detail below with reference to the drawing.

[0024] It shows:

[0025] Figure 1 is a schematic representation of a fuel cell system according to the invention with an anode circuit and at least one device according to the invention located in the anode circuit, Figure 2 is a schematic longitudinal section through the device according to the invention with the sensor element and a Prantl probe arrangement

[0026] Figure 3 shows a sectional view of a section of the Prantl probe arrangement according to the invention, designated II in Fig. 2, in an enlarged view,

[0027] Figure 4 is a plan view of the sensor element according to the invention, designated AA in Figure 2,

[0028] Figure 5 shows a possible embodiment of the operating method according to the invention,

[0029] Figure 6 is a schematic diagram of the elements sensor, control unit, speed sensor, pressure sensor and purge valve.

[0030] Description of the embodiment

[0031] The illustration in Fig. 1 shows a schematic representation of a fuel cell system 31 according to the invention with an anode circuit 2 and at least one device 1 according to the invention located in the anode circuit 2. It is shown that a delivery unit 13 is connected via a connecting line 29 to a fuel cell 32, which comprises an anode region 42 and a cathode region 40. In addition, a return line 23 is provided, which connects the anode region 42 of the fuel cell 32 to a first inlet 28, and thus in particular to an intake region of the delivery unit 13. By means of the return line 23, the first gaseous medium not used 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. As can be seen from Fig.As can also be seen in Figure 1, the second gaseous medium stored in a tank 34 is fed via a tank line 27 to a second inlet 30 of the delivery unit 13. This second gaseous medium is, in particular, a propellant medium. It is shown that the device 1 is arranged in the anode circuit 2 of the fuel cell system 31, in particular in the region of the return line 23 and / or the tank line 27 and / or the connecting line 29, and wherein the fuel cell system 31 has a control unit 47 and / or the purge valve 44.The measured values ​​of the respective device 1 can be transmitted to the control unit 47 in order to be evaluated, for example, by means of a stored algorithm, wherein the control unit 47, on the basis of the results of the algorithm, triggers a control of the purge valve 44 in order to achieve an efficient and operating state-dependent discharge of heavy components of the gaseous medium, such as water or nitrogen, from the anode circuit 2 into an environment 46.

[0032] Fig. 2 shows a schematic longitudinal section through the device 1 according to the invention with the sensor element 18 and a Prantl probe arrangement 7. It shows that upstream of the device 1, a total mass flow 4 of the gaseous medium flows in the main flow channel 15. On the upstream end face of the device 1, the total mass flow 4 branches into a gas mass flow 6, which flows past the device 1 as the main flow 12 through the main flow channel 15 without flowing through the device 1. In addition, the total mass flow 4 branches into a partial mass flow 8 of the gaseous medium, which flows through openings in the front side of the device 1, in particular an inlet channel 20 of the Prantl probe arrangement 7 and / or an inlet funnel 5 of the sensor element 18. Thus, the partial mass flow 8 branches again twice before flowing through a channel 25 and into an inlet 20.

[0033] As shown in Fig. 2, the sensor element 18 is arranged in the channel 25, in particular a measuring channel 25, in a housing 36, in particular a base body 36. The channel 25 is closed by means of a cover 22, wherein the cover 22 defines the channel 25. The sensor element 18 and the cover 22 are designed as a combined measuring channel-cover arrangement 33, which can be pre-assembled and / or designed as a structural unit 33. The gaseous medium flows through the channel 25 in a flow direction 10 past the sensor element 18, wherein the flow 10 is present as a laminar flow 38a and / or as a turbulent flow with a viscous underlayer 38b due to the geometric shape, in particular the diameter of the channel 25.The sensor 18 has at least one surface hot film element (OHF element) 26, over which the flow 38a, b flows and / or carries out a measurement at this point in the channel 25 by means of a surface heating film method. In an exemplary embodiment, the sensor element 18 and / or the device 1 can be supplemented by further resistance elements (not shown) that can be used for temperature compensation of the measuring bridge circuit. To ensure that only a minimal pressure drop occurs in the measuring device, the flow accelerated in the channel 25 is decelerated again via a diffuser 11, which is in particular a Venturi nozzle 11.

[0034] As shown in Fig. 2, the device 1 is arranged at least indirectly in the main flow channel 15 of the anode circuit 2. The main flow channel 15 runs along a first axis 37, the measuring channel 25 of the sensor element 18 runs along a second axis 39, the inlet channel 20 of the Prantl probe arrangement 7 runs along a third axis 41, and the outlet channel 24 of the Prantl probe arrangement 7 runs along a fourth axis 43. In an exemplary embodiment of the device 1 and / or the anode circuit 2 and / or the fuel cell system 31, the first three axes 37, 39, 41 run at least almost parallel to one another, with the fourth axis 43 running at least almost orthogonal to the first three axes 37, 39, 41.Furthermore, it is shown that the device 1 has at least one temperature sensor 9, wherein the temperature sensor 9 is arranged on a 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. The temperature sensor 9 is located downstream of the outlet channel 24 of the Prantl probe arrangement 7 in the main flow channel 15 of the anode circuit 2, wherein such an arrangement at least almost prevents any influence on the measurement, for example the flow velocity of the gaseous medium. In addition, the temperature sensor 9 is directed towards the main flow 12 so as not to be distorted by the heating of the OHF element 26. Furthermore, Fig.2 shows that the device 1 is a combined sensor arrangement 1 comprising at least one sensor element 18 and the Prantl probe arrangement 7. The sensor element 18, the Prantl probe arrangement 7, and the cover 22 are designed as the combined measuring channel cover arrangement 33, which can be preassembled and / or mounted and / or installed as a structural unit 33 in or on the main flow channel 15. The sensor element 18 can be measured, among other things, using a surface hot film method (OHF) and the wall shear stress T determined therefrom. w of the gaseous medium and, if necessary, other parameters, a determination of the viscosity and / or composition of the gaseous medium can be derived. The wall shear stress T w can be determined by means of at least one OHF element 26 of the sensor element 18, wherein the wall shear stress T wdescribes the momentum flow through the volume of the gaseous medium adjacent to the wall and results from the friction of the fluid elements against the wall and among themselves. The wall shear stress T is measured. w and the velocity via the dynamic pressure. Knowing the geometry and the velocity profile, the derivative of the velocity perpendicular to the OHFs can be calculated. The only unknown factor remains the mixture-dependent viscosity.

[0035] To determine the wall shear stress T w The following formula is used:

[0036] Fig. 2 also shows that the partial mass flow 8 is branched off from this total mass flow 4, which is fed to the device 1 and flows through it. The remaining gas mass flow 6 flows in a main flow direction 12 past the device 1 through the main flow channel 15, which is located, for example, in the return line 23 and / or the tank line 27 and / or the connecting line 29 of the anode circuit 2. The branched partial mass flow 8 is fed, on the one hand, via the inlet funnel 5, in particular a nozzle 5, to the measuring channel 25 of the sensor element 18. On the other hand, the partial mass flow 8 is fed via the inlet channel 20 to a sensor and / or a measuring section of the Prantl probe arrangement 7. The Prantl probe arrangement 7 is designed in particular as a Prantl pitot tube 7 and serves to determine the velocity, in particular the flow velocity of the gaseous medium.By means of the Prantl probe arrangement 7 and the sensors present therein, a total pressure 17 is measured upstream of the Prantl probe arrangement 7, in particular in the initial region of the inlet channel 20. A static pressure 19 is measured by means of a laterally arranged sensor, in particular in the outlet 24 of the Prantl probe arrangement 7, which is also used, for example, to determine the material data. The difference between the two pressures is proportional to the velocity of the inflow. In an exemplary embodiment of the device 1, the Prantl Pitot tube 7 can represent a combination of a pressure probe and a Pitot tube. The measured variable is the wall shear stress T. w, which depends on the viscosity and the velocity of the medium. The viscosity varies with the gas composition. The velocity is determined via the integrated Prantl's Pitot tube 7 or derived from this measurement signal. The total pressure 17 can be equal to an absolute pressure p abs and the static pressure 19 corresponds to the static pressure p sta t correspond.

[0037] The measuring channel 25 shown in Fig. 2 can have a surface roughness k and / or a length L2 and / or a diameter D such that a laminar flow 38 always develops in the measuring channel 25 under different operating conditions and / or flow velocities of the gas mass flow 6. The parameters k, Li and D, which are known, define the measuring location in the measuring channel 25, in particular with a fixed geometry, wherein the partial mass flow 8 is applied to it. The ratio of partial mass flow 8 and gas mass flow 6 depends on the installation location and must be taken into account accordingly, in particular the respective ratio of the cross-sectional areas.

[0038] Fig. 3 shows a sectional view of a section of the Prantl probe arrangement 7 according to the invention, designated II in Fig. 2, in an enlarged view. It is shown that a dynamic pressure measurement is carried out in the area of ​​the upstream inlet 20, during which the total pressure 17, which corresponds in particular to the dynamic pressure 17 and / or the total pressure 17, is determined. The inlet 20 is ideally modeled after the head of a Prantl probe, so that the static pressure p sta t according to the length L2 the actual static pressure P stat2 of the flow. In this case, in the region of the The difference between the two pressures 17, 19 is proportional to the velocity of the inflow, in particular of the partial mass flow 8. In an exemplary embodiment, the Prantl probe arrangement 7 is not flowed through, but the Prantl probe arrangement 7 can be subjected to a total pressure 17 on its end face facing the inlet channel 20 and a static pressure 19 on its end face facing the outlet 24. From these two pressures 17, 19, the Prantl probe arrangement 7 determines a pressure difference Ap and thus the dynamic pressure ~v.

[0039] Fig. 4 shows a plan view of the sensor element 18 according to the invention, designated AA in Fig. 2. It is shown that the sensor element 18 has at least one surface hot film element (OHF element) 26, wherein the sensor element 18 in this exemplary embodiment has three OHF elements 26 which are elongated and which extend in a rod-like manner in a direction 51, wherein the direction 51 runs at least almost orthogonal to the flow direction 10 of the gaseous medium. As it flows through the measuring channel 25 in the flow direction 10, the gaseous medium successively passes a respective first OHF element 26a, then a respective second OHF element 26b, and then a respective third OHF element 26c.

[0040] Fig. 5 shows a possible embodiment of the operating method according to the invention. Rectangles 51 to 56 and arrows arranged therebetween illustrate in a highly simplified manner how the multi-stage method for operating the device 1 can proceed. In a first method step 51, a wall shear stress T w measured by the sensor element 18. In a second method step 52, the absolute pressure p abs and the static pressure p sta t by means of the Prantl probe arrangement 7. In a third method step 53, the flow velocity of the gaseous medium is calculated using the pressure difference Ap by using the absolute pressure p abs and / or the static pressure p stat, in particular by means of a control unit 47. In particular, a known flow geometry of the inlet channel 20 can be used, for example its length L2 and / or its diameter, in order to use these values ​​in an algorithm stored in the control unit 47 for calculation 53. In an optional fourth method step 54, the temperature is detected by means of the temperature sensor 9. In a fifth method step 55, the viscosity of the gaseous medium at a specific time T is determined by means of the control unit 47. In an optional sixth method step 56, a change in the composition of the gaseous medium is calculated by delta calculation of several measuring points Tn by means of the control unit 47 and actuation of the purge valve 44.

[0041] Fig. 6 shows an arrangement of various components of the device 1 and / or the fuel cell system 31. The arrangement is a schematic diagram of the elements sensor element 18, control unit 47, Prantl probe arrangement 7, optional temperature sensor 9 and purge valve 44. The control unit 47 and the purge valve 44 do not necessarily have to be arranged in or on the device 1, but can alternatively be located in a further area of ​​the fuel cell system 31, in particular in the anode circuit 2. The components sensor element 18 and / or Prantl probe arrangement 7 and / or optional temperature sensor 9 can supply measured values ​​and data to the control unit 47, wherein the control unit 47 controls the purge valve 44 depending on a stored algorithm for evaluating the data.The purge valve 44 is only opened by means of a control of the control unit 47 when the gaseous medium has a high concentration of water and / or nitrogen and / or other components that are not hydrogen.

[0042] The raw data is recorded and / or evaluated by means of the sensors and the control unit 47 and, for example, by means of an algorithm stored in the control unit 47, a sensible opening of the purge valve 44, a so-called purging, can be achieved to drain water and / or nitrogen and / or other components as required, while only a small amount or at least almost no hydrogen is lost.

Claims

Claims 1. Device (1) for determining and / or measuring the composition of a gaseous medium in an anode circuit (2) of a fuel cell system (31), wherein the device (1) has a sensor element (18), wherein the sensor element (18) determines the measured value wall shear stress Tw, in particular by means of a surface hot film method (OHF), 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 Prantl probe arrangement (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 acted upon by a partial mass flow (8) of the gaseous medium by means of an inlet funnel (5) and the Prantl probe arrangement (7) by means of an inlet channel (20).

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

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

4. Device (1) according to claim 2 or 3, characterized in that the main flow channel (15) runs along a first axis (37) and the measuring channel (25) of the sensor element (18) runs along a second axis (39) and the inlet channel (20) of the Prantl probe arrangement (7) runs along a third axis (41) and an outlet channel (24) of the Prantl probe arrangement (7) runs along a fourth axis (43), wherein the first three axes (37, 39, 41) run at least almost parallel to one another and wherein the fourth axis (43) runs at least almost orthogonal to the first three axes (37, 39, 41).

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

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

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

8. Device (1) according to one of claims 2 to 7, characterized in that the sensor element (18), the Prantl probe arrangement (7) and the cover (22) are designed as a combined measuring channel-cover arrangement (33) which can be pre-assembled and / or attached and / or installed as a structural unit (33) in or on the main flow channel (15).

9. Fuel cell system (31) with a device (1) according to one of claims 1 to 8, wherein the device (1) is arranged in an anode circuit (2) of the fuel cell system (31), in particular in the region of the return line (23) and / or the tank line (27) and / or the connecting line (29), and wherein the fuel cell system (31) has a control unit (47) and / or the purge valve (44).

10. Method for controlling a device (1), in particular a measuring device (1), and / or a fuel cell system (31) according to one of the preceding claims, comprising the following steps: Measuring the wall shear stress T w (51) by means of the sensor element (18), Detecting (52) the absolute pressure p abs and the static pressure p S t at by means of the Prantl probe arrangement (7), calculation (53) of the flow velocity of the gaseous medium by means of the pressure difference Ap by using the absolute pressure p abs and / or the static pressure p stat , in particular by means of the control unit (47). In particular, a known flow geometry of the inlet channel (20) can be used, for example its length L2 and / or its diameter, in order to use these values in an algorithm stored in the control unit (47) for the calculation (53). Optional detection (54) of the temperature by means of the temperature sensor (9), Determination (55) of the viscosity of the gaseous medium at a specific time T1 by means of the control device (47).

11. A method for controlling a device (1), in particular a measuring device (1), and / or a fuel cell system (31) according to claim 10, with the following additional step: Calculation (56) of a change in the composition of the gaseous medium by delta calculation of several measuring points Tn by means of the control unit (47) and control of the purge valve (44).

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