Silencer for an exhaust system of a fuel cell system

Abstract

The invention relates to a hybrid silencer (1) for an exhaust system of a fuel cell system (2), comprising a silencer device (20) for reducing noise from an exhaust gas stream (S) of the system (2), a water separation device (30) for separating water from the exhaust gas stream (S), and a water collection chamber (40) which is in fluid communication with the water separation chamber (31) via an outlet opening (41) such that water separated from the exhaust gas stream (S) can flow into the water collection chamber (40) and be collected there. An improved sensor device (50) for detecting the water level in the water collection chamber (40) is proposed.

Description

[0001] The present invention relates to a silencer for an exhaust system of a fuel cell system having the features of claim 1. Furthermore, the invention relates to a fuel cell system having the features of claim 8.

[0002] A fuel cell converts the chemical reaction energy of a continuously supplied fuel, e.g., hydrogen, and an oxidizing agent, e.g., oxygen, into electrical energy. Fuel cells are used, for example, in fuel cell vehicles to convert the generated electrical energy directly into motion using an electric drive or to temporarily store it in a traction battery. Fuel cells can also use other fuels besides hydrogen, particularly methanol, butane, or natural gas.

[0003] A fuel cell system uses several mechanical devices to supply the fuel and oxidizer, which, during operation, generate noise that can be perceived as disturbing. To reduce the noise generated in the fuel cell system, silencers are installed in the fuel cell system, for example, in an exhaust system.

[0004] The silencers used in this context can be based on the reflection principle or the absorption principle. A reflection silencer consists of chambers of different sizes that are connected to one another, for example, by a perforated tube extending through the chambers. The sound waves are reflected in the chambers. The coupling of the individual chambers creates so-called resonators in which the sound waves are reflected, partially canceling each other out according to the interference principle and thus being dampened. Individual chambers can be adapted to a specific frequency range to be dampened by their size and / or the hole pattern of the perforation in the tube. The greater the number of chambers present, the more efficient the damping is. An absorption silencer usually has only one chamber, through which a perforated tube runs. The chamber is lined with a sound-absorbing material, e.g.long-fiber mineral wool. The sound waves penetrate the perforated tube into the sound-absorbing material and are converted into heat through friction. The attenuation achieved depends on the material used, the packing density, the length, and the layer thickness of the chamber.

[0005] The exhaust gas produced during the electricity generation reaction in a hydrogen-oxygen fuel cell, which is primarily discharged from the fuel cell cathode, contains water (mostly in the form of water vapor and water droplets) and has an exhaust gas temperature in the range of 80 °C. Because the exhaust gas temperature is below the boiling point of water, the water is difficult to evaporate and discharge. However, if excessively humid exhaust gas penetrates the muffler, the water vapor condenses, particularly on the surfaces of the muffler, which negatively impacts the function of the muffler - regardless of whether it is based on the reflection principle or the absorption principle. In unfavorable cases, the moisture that accumulates in the muffler causes additional noise, which is perceived as unpleasant.

[0006] To counteract this problem, US 2013 175114 A1 proposes a hybrid silencer in which a dehumidification chamber, which is essentially completely filled with a water-absorbing material, is arranged upstream of a silencer device based on the reflection principle. However, to ensure a suitable dehumidification function, the dehumidification chamber must have a significantly larger volume than the silencer device. Nevertheless, the exhaust gas can only be dehumidified to a certain extent in the dehumidification chamber, so that the condensate that continues to form in the silencer device must be absorbed by a part of the water-absorbing material that projects into the silencer device. Furthermore, the water absorbed by the water-absorbing material cannot be easily drained away, but must usually be sucked out using a pump.Overall, this results in a relatively complex structure of the hybrid silencer, which takes up a relatively large amount of space and is complex to manufacture and operate.

[0007] The patent application (application no. DE 10 2022 212 595), which was not yet published at the time of filing, describes a hybrid silencer with a water separation chamber in which the exhaust gas flow is first expanded by an impact element and then narrowed again by a funnel-shaped guide element. In this way, the exhaust gas flow is guided along the largest possible surface area, where the water contained in the exhaust gas can condense. Due to gravity, the condensed water collects in the lower area of ​​the water separation chamber or in a water collection chamber located below it.

[0008] More effective dehumidification now results in significant amounts of water being generated. For example, when operating hydrogen-oxygen fuel cells, consuming 10 kg of hydrogen, which roughly corresponds to a full tank of a car, can result in up to 9 liters of water being emitted with the exhaust. Depending on the installation position, driving conditions, and weather, excessive water may accumulate in the muffler under certain circumstances. These large amounts of water must be reliably removed to maintain the muffler's functionality.

[0009] For controlled water drainage, it is helpful to know the amount of water currently separated and collected in the silencer. CN 212113902 U describes a water collection chamber that can be connected to a silencer, with a fill level measurement carried out by a level sensor located in the upper area of ​​the chamber. When the water level approaches the upper limit of the storage capacity of the water collection chamber, this can be detected by the level sensor, allowing water drainage to be initiated. However, the concept described here only provides limited information about the collected amount of water, namely whether the upper limit of the storage capacity has been reached or not. In addition, the level sensor must be in direct contact with the water, which makes installation of the level sensor complex and can compromise the watertightness of the water collection chamber.

[0010] The object of the present invention is therefore to provide a hybrid silencer of the type mentioned above for an exhaust system of a fuel cell system, in which the water level can be determined precisely and easily. Furthermore, the object of the present invention is to provide a fuel cell system with such a silencer.

[0011] This object is achieved by a silencer having the features of claim 1 and a fuel cell system having the features of claim 8. Preferred features are the subject of the dependent claims. Further advantages and features can be found in the general description and the exemplary embodiments.

[0012] The silencer according to the invention, through which an exhaust gas stream of the fuel cell system can flow from an inlet opening to an outlet opening, has the following: - A silencer device to reduce the noise of the exhaust gas flow, - a water separation device arranged upstream of the silencer device for separating water from the exhaust gas stream, wherein the water separation device has at least one water separation chamber, - a water collection chamber which is in fluid communication with the water separation chamber via a discharge opening in such a way that water separated from the exhaust gas flow can flow out of the water separation chamber, in particular independently due to gravity, into the water collection chamber and be collected there, - a sensor device for detecting the water level in the water collecting chamber, wherein the sensor device has two electrodes and is designed and arranged to detect an electrical capacitance at least in sections within an internal volume of the water collecting chamber, so that a conclusion about the water level can be drawn from the detected electrical capacitance.

[0013] The exhaust gas stream, which is, for example, discharged from the cathode of a fuel cell in the fuel cell system and fed directly or indirectly to the silencer, can flow through the inlet opening into the water separation chamber. In the water separation chamber, the exhaust gas stream is guided along as large a surface as possible, on which any water contained in the exhaust gas can condense. This dehumidifies the exhaust gas, reducing or completely preventing any impairment of the function of the downstream silencer device due to excessively humid exhaust gas. Depending on the installation position of the silencer, the condensed water collects due to gravity in a predetermined area of ​​the water separation chamber and can then be easily discharged actively or passively into the water collection chamber.

[0014] A "water separation device" is a device primarily used to separate water (and / or another liquid) from the exhaust gas. A silencer device is therefore not considered a water separation device, even if some condensation and removal of moisture also occurs in the silencer chamber.

[0015] The silencer device preferably comprises a perforated tube extending through the silencer chamber. In particular, a downstream tube end is connected to the outlet opening. The perforation of the tube establishes a fluid-conducting connection with the rest of the silencer chamber. The silencer device can generally be designed as a reflection silencer or as an absorption silencer. Preferably, the silencer device forms a reflection silencer. This allows additional dehumidification in the silencer device to be carried out in a simple manner by condensing the water contained in the exhaust gas on the surfaces of the walls of the silencer chamber. The size of the silencer chamber and / or the hole pattern of the perforation in the tube can be adapted to a specific frequency range to be attenuated.

[0016] The silencer device can have multiple silencer chambers and at least one additional silencer chamber. This promotes both damping and additional dehumidification. Each of the silencer chambers can be adapted to a different frequency range to be dampened by its size and / or the corresponding perforation pattern in the pipe. In particular, a perforated pipe extends through the silencer chambers, with the silencer chambers separated from each other by partition walls outside the pipe. For optimal damping, the silencer device preferably has two, particularly preferably four, silencer chambers.

[0017] The silencer preferably extends along a longitudinal central axis and in particular rotationally symmetrically around the longitudinal central axis, wherein the water separation device and the silencer device are arranged centered on the longitudinal central axis. This means that the exhaust gas flow only has to change its flow direction slightly when transitioning from the water separation device to the silencer device, which promotes a uniform and quiet flow of the exhaust gas flow. Furthermore, a compact design of the silencer can be achieved in this way. In particular, the inlet opening and the outlet opening are arranged centered on the longitudinal central axis. Preferably, a cavity of the silencer containing the water separation device and silencer device is at least partially, preferably completely, cylindrical or formed from a plurality of coaxially aligned cylindrical partial cavities.

[0018] Preferably, the housing of the silencer consists of at least 50 vol.% of a material comprising a thermoplastic.

[0019] The silencer has a water collection chamber. The water collection chamber is preferably arranged such that it at least partially surrounds the water separation chamber. In particular, at least a portion of the water collection chamber surrounds at least a portion of that region of the water separation chamber in which the condensed water collects due to gravity in the water separation chamber, depending on the installation position of the silencer. Separating water from the water separation chamber can flow through a drain opening, in particular independently due to gravity, into the water collection chamber and be collected there. In this way, the separated water is removed from the water separation chamber, thereby preventing water from accumulating in the water separation device, which could otherwise have a negative impact on dehumidification.Furthermore, it prevents accumulated water from being transported by the exhaust stream toward the silencer, thereby impairing its function. The water collected in the water collection chamber can be easily drained from the water collection chamber, e.g., via a drain opening, either actively—e.g., by a pump—or passively—e.g., automatically due to gravity. In particular, the drain opening can be closed, partially closed, or opened by a controllable valve (e.g., a solenoid valve).

[0020] The water collection chamber can have a significantly smaller internal volume than the water separation chamber. Preferably, the water separation chamber and the water collection chamber are separated by a wall, thus achieving a compact silencer design.

[0021] Preferably, the water collection chamber further at least partially surrounds the one or more sound-damping chambers and is in fluid communication with the sound-damping chamber(s) via an opening such that water condensed from the exhaust gas stream can flow out of the sound-damping chamber(s) into the water collection chamber, in particular independently due to gravity. In this way, the separated water is removed from the sound-damping chamber, thereby preventing water from accumulating in the sound-damping device, which could otherwise have a negative impact on noise dampening. To avoid impairing function, the opening for the condensed water is preferably located in a corner of the sound-damping chamber.Preferably, if there are several adjacent sound-damping chambers separated by a partition wall, a common opening is arranged in the region of one end face of the partition wall, whereby condensed water from both sound-damping chambers can flow through the opening into the water collection chamber.

[0022] Preferably, the water collection chamber extends along at least half the total length, preferably at least two-thirds of the total length of the silencer. This increases the absorption capacity of the water collection chamber. Furthermore, a compact design of the silencer can be realized.

[0023] The silencer also has a sensor device for detecting the water level in the water collection chamber. The electrical capacitance between the electrodes depends on the dielectric constant of a medium located in the area of ​​the electrodes. A change in the electrical capacitance therefore allows conclusions to be drawn about a change in the distribution of the media in the area of ​​the electrodes. For example, a change in the media distribution in the water collection chamber from, for example, 70% water and 30% air to a distribution of 50% water and 50% air can be measured as a change in the electrical capacitance between the electrodes. In this way, not only the exceeding of a predetermined fill level, but also an absolute measurement of the fill level can be realized.

[0024] Such a sensor device can be used to set up a fill level monitor, which can be used to determine when water needs to be drained, for example, by controlling a valve that opens a drain opening in the water collection chamber. It can also be continuously monitored to determine whether the system is functioning properly and whether the water has been drained from the water collection chamber. For this purpose, the sensor device can be connected to a correspondingly configured control unit of the fuel cell system for signal transmission or can itself comprise a control unit configured to control the actuators required for the drain.

[0025] In a preferred embodiment of the silencer according to the invention, the sensor device is arranged on an outer wall of a wall defining the internal volume of the water collection chamber. This allows for a non-invasive measurement of the water level in the water collection chamber, thus maintaining the integrity and tightness of the silencer. Such a sensor device is ideally suited as a retrofit solution.

[0026] In a preferred embodiment of the silencer according to the invention, the outer wall is curved along a direction of curvature, and the electrodes are strip-shaped and extend parallel to each other transversely to the direction of curvature. This creates a compact sensor arrangement in which a portion of the field lines of the electric field that builds up between the electrodes during the measurement penetrates a portion of the internal volume of the water collection chamber in an arc shape, which promotes the dependence of the measured capacitance on the water level.

[0027] In a further preferred embodiment of the silencer according to the invention, the sensor device has a flexible printed circuit board with a first side on which the two electrodes are arranged, in particular printed. In this way, a sensor device is created which can be easily attached from the outside, even to a curved outer wall of the water collection chamber. Flexible printed circuit boards or printed circuit foils, e.g. based on polyimide foils, are used as an alternative to rigid printed circuit boards in the field of entertainment electronics. In particular, the flexible printed circuit board is arranged on the outer wall of the water separation chamber such that its first side, on which the electrodes are arranged, faces the outer wall. In other words, the flexible printed circuit board is preferably arranged and / or fastened with the first side, on which the electrodes are arranged, adjacent to the outer wall.In this way, the circuit board, made of a non-conductive material, can form a protective layer for the electrodes against external influences. The flexible circuit board can be glued or otherwise attached to the outer wall.

[0028] In a further preferred embodiment of the silencer according to the invention, the sensor device has a shielding layer made of conductive material, which is arranged on a second side of the flexible circuit board opposite the first side of the flexible circuit board. The shielding layer can, for example, be a metal foil or a second conductive layer inside or outside the flexible circuit board. In this way, the sensor device is protected against external electronic or electromagnetic interference, which promotes the accuracy of the water level measurement.

[0029] In a further preferred embodiment of the silencer according to the invention, the sensor device has a temperature sensor. In this way, a temperature in the region of the sensor device can be determined and taken into account when determining the water level based on the measured electrical capacitance. For example, the influence of temperature on the electrical capacitance can be calculated out. For this purpose, the temperature sensor can be connected to a corresponding control unit of the fuel cell system in a signal-transmitting manner. Alternatively, the temperature can also be evaluated by a control unit of the sensor device itself. The temperature sensor is preferably arranged on the first side of the flexible printed circuit board.

[0030] In a further preferred embodiment of the silencer according to the invention, the sensor device has a heating wire arrangement for heating at least part of the water collection chamber, in particular for heating at least part of the outer wall of the water collection chamber. In this way, water drainage can be ensured even at low outside temperatures, at which freezing of the condensate is to be expected. The heating wire arrangement is preferably arranged and / or printed on the first side of the flexible printed circuit board. The heating wire arrangement can advantageously interact with the remaining sensor device. For example, if the temperature monitored by the temperature sensor in the region of the sensor arrangement falls below a predetermined threshold value, the heating wire arrangement can be used to heat part of the water collection chamber, preventing the water collected in the water collection chamber from freezing.On the other hand, heating may be unnecessary, for example, if the capacitance measurement shows that there is no or very little water in the water collection chamber. The heating wire arrangement can extend along at least half the total length, preferably at least two-thirds of the total length, of the water collection chamber.

[0031] Overall, the present invention describes a sensor device with extensive functionality that is easy to manufacture and can be easily mounted on a hybrid silencer.

[0032] According to what has already been described above and further below, the object set out at the outset is also achieved by a fuel cell system having the features of claim 8.

[0033] The fuel cell system according to the invention comprises a fuel cell, an exhaust system leading from the fuel cell, and a silencer according to the invention installed in the exhaust system. The advantages of the silencer described above and below are thus realized for the fuel cell system.

[0034] In a preferred embodiment of the fuel cell system according to the invention, the fuel cell system has a control unit which is designed and configured to control an outlet valve, with which the discharge opening or a discharge line of the water collection chamber leading from the discharge opening can be closed or opened, depending on the water fill level determined by means of the sensor device.

[0035] It is expressly pointed out that the embodiments of the invention explained above can be combined individually or in any technically reasonable combination with each other with the subject matter of the independent claims.

[0036] Modifications and embodiments of the invention, as well as further advantages and details of the invention, can be found in the following description and the drawings. The schematic figures show: Fig. 1 shows an embodiment of a silencer according to the invention in a sectional view; Fig. 2 the silencer Fig. 1 in a view from below; Fig. 3 remove the silencer Fig. 1 in a cross-sectional view; and Fig. 4 an embodiment of a fuel cell system according to the invention.

[0037] Parts with the same or similar function are provided with identical reference numbers where appropriate.

[0038] Individual technical features of the exemplary embodiments described below can also be combined with previously described exemplary embodiments as well as the features of the independent claims and any further claims to form subject matter according to the invention.

[0039] Fig. Figure 1 shows a first embodiment of a silencer 1 according to the invention for an exhaust system 4 of a fuel cell system 2 in a sectional view. An exhaust gas flow S of the fuel cell system can flow through the silencer 1 from an inlet opening 11 to an outlet opening 12. The position of the inlet opening 11 and the outlet opening 12 defines a main flow direction R, which in the present case runs parallel to the longitudinal center axis A of the silencer 1.

[0040] A silencer device 20 is arranged within the silencer 1 for reducing noise from the exhaust gas stream S. Furthermore, a water separator device 30 for separating water from the exhaust gas stream S is arranged within the silencer 1 upstream of the silencer device 20, the water separator device 30 having a water separation chamber 31.

[0041] In the water separation chamber 31, the exhaust gas flow S is expanded by a baffle element 32 and can thus be guided along an inner surface of a wall 35 delimiting the water separation chamber 31, before the exhaust gas flow S is tapered again by the funnel-shaped guide element 33 arranged downstream. The exhaust gas flow S is thus guided along the largest possible surface on which water contained in the exhaust gas can condense. The exhaust gas flow S is dehumidified to a high degree before the exhaust gas flow S is fed to the silencer device 20. The function of the silencer device 20 is thus not impaired by excessive amounts of moisture. Furthermore, noise generation due to moisture accumulating in the silencer device 20 is avoided. The dehumidified and noise-free exhaust gas can be discharged via an exhaust gas discharge line 4b ( Fig. 4) of the exhaust system 4, which can be attached to the outlet nozzle 17 of the silencer 1, can be led away from the silencer 1.

[0042] In the present case, the silencer device 20 forms a reflection silencer with four silencer chambers 21a, 21b, 21c, 21d, through which a perforated tube 22 extends and which are further separated from one another by three partition walls 23a, 23b, 23c.

[0043] The main part of the silencer 1, namely the water separation device 30 and the silencer device 20, extends substantially along the longitudinal center axis A of the silencer 1 and rotationally symmetrically about the longitudinal center axis A. In the present case, the water separation device 30 and the silencer device 20 are arranged in a cylindrical cavity 10 of the silencer.

[0044] The silencer 1 has a water collection chamber 40 partially surrounding the water separation chamber 31, which is fluidly connected to the water separation chamber via a drain opening 41 such that water separated from the exhaust gas flow S can flow out of the water separation chamber 31, due to gravity, into the water collection chamber 40 and be collected there. Separating water can thus flow optimally out of the water separation chamber 31. The shape of the impact element 32 and the shape of the funnel-shaped guide element 33 promote a directed flow of the separated water toward the drain opening 41.

[0045] The water collection chamber 40 further partially surrounds the silencer chambers 21a, 21b, 21c, 21d and is in fluid communication with the silencer chambers 21a, 21b, 21c, 21d via openings 41a, 41b, 41c such that water condensed from the exhaust gas stream S can flow out of the silencer chambers 21a, 21b, 21c, 21d into the water collection chamber 40 independently due to gravity. This prevents water from accumulating in the silencer device 20, which could otherwise have a negative impact on noise reduction. In order not to impair the function of the sound damping device 20, the openings 41a, 41b, 41c for the condensed water are preferably arranged in the corners of the sound damping chambers 21a, 21b, 21c, 21d, wherein adjacent sound damping chambers 21a, 21b, 21c, 21d have a common opening 41a, 41b, 41c in the region of an end face of the respective partition wall 23a, 23b, 23c.To provide sufficient absorption capacity, the water collection chamber 40 extends substantially along the total length L of the silencer 1.

[0046] The water collected in the water collection chamber 40 can be easily discharged from the water collection chamber 40 or from the silencer 1, e.g., via a discharge opening 42, actively—e.g., by a pump—or passively—e.g., automatically due to gravity. The water collection chamber 40 need only surround a small area of ​​the water separation chamber 31—e.g., an area located at the bottom with respect to the direction of gravity G, which, viewed parallel to the longitudinal center axis A, can be located approximately between a "5 o'clock position" and a "7 / 7 o'clock position." The water collection chamber 40 can thus have a significantly smaller internal volume than the water separation chamber 31.

[0047] In principle, the water separation device 30 and / or the sound damping device 20 shown here can be constructed differently.

[0048] The silencer 1 further comprises a sensor device 50 for detecting the water level in the water collection chamber 40. The sensor device 50 is arranged on an outer wall 45 of a wall 44 delimiting the internal volume 43 of the water collection chamber 40. The sensor device 50 is designed and arranged to detect an electrical capacitance at least in sections within the internal volume 43 of the water collection chamber 40, so that a conclusion about the water level can be drawn from the detected electrical capacitance.

[0049] The detailed structure of the sensor device 50 is shown in the Fig. 2 and Fig. 3 shown. Fig. 2 shows the silencer 1 from Fig. 1 from below, i.e. from a viewing direction opposite to the direction of gravity G. The sensor device 50 has two electrodes 51a, 51b. The electrodes 51a, 51b are strip-shaped and extend along the longitudinal center axis A of the silencer. The sensor device 50 has a flexible printed circuit board 52. Both electrodes 51a, 51b are arranged on a first side 521 (see Fig. 3) of the circuit board 52, which faces the outer wall 45 of the water collection chamber 40. The electrodes 51a, 51b are thus protected from external influences by the circuit board 52. The electrodes 51a, 51b can be connected, for example, to a control unit 7 of the fuel cell system 2 via their respective connection contacts 510a, 510b in a signal-transmitting manner. Also arranged on the first side 521 of the circuit board 52 are a temperature sensor 53 and a heating wire arrangement 54 for heating at least part of the water collection chamber 40. These components can also be connected, for example, to a control unit 7 of the fuel cell system 2 in a signal-transmitting manner. The sensor device 50 can also have its own control unit. The control unit of the sensor device 50 can be arranged on the first side 521 of the circuit board 52.

[0050] Fig. 3 shows the silencer 1 from Fig. 1 in the area of ​​the water collection chamber 40 filled with water W in a cross-sectional view. The outer wall 45 of the water collection chamber 40 is curved along a direction of curvature U – which in this case can also be referred to as the circumferential direction. The strip-shaped electrodes 51a, 51b extend transversely to the direction of curvature U and parallel to one another. Due to this arrangement, a portion of the field lines E of the electric field that builds up between the electrodes 51a, 51b during the measurement penetrates a portion of the internal volume 43 of the water collection chamber 40 in an arc shape, which favors the dependence of the measured capacitance on the water level. The electrical capacitance between the electrodes 51a, 51b depends on the dielectric constant of a medium located in the area of ​​the electrodes. If the proportion of water W in the internal volume 43 changes, the measured capacitance changes.In this way, not only the exceeding of a predetermined fill level, but also an absolute measurement of the fill level can be realized.

[0051] The sensor device 50 has a shielding layer 55 made of conductive material, which is arranged on a second side 522 of the flexible printed circuit board 52 opposite the first side 521 and, in this case, completely covers the latter. In this way, the sensor device 40 is protected against external electronic interference, which promotes the accuracy of the water level measurement. The shielding layer 55 can, for example, be a metal foil or a metal mesh, or be made of another electrically conductive material.

[0052] Fig.4 shows an embodiment of a fuel cell system 2 according to the invention. Hydrogen 5 and oxygen-containing air 6 are supplied to a fuel cell 3, in this case a hydrogen-oxygen fuel cell. A compressor is often used to supply the air 6, the operation of which is accompanied by considerable noise generation. A silencer 1 according to the invention is arranged in the exhaust system 4 of the fuel cell system 2. An exhaust gas supply line 4a conveys an exhaust gas stream S from the fuel cell 1 to the silencer 1, while an exhaust gas discharge line 4a conveys the dehumidified and noise-reduced exhaust gas stream S away from the silencer 1—e.g., toward a tailpipe of the exhaust system 4.

[0053] The fuel cell system 2 has a control unit 7, which is designed and configured to control an outlet valve 60, with which the discharge opening 42 or a discharge line 46 of the water collection chamber 40 can be closed or opened, depending on the water level in the water collection chamber 40 determined by the sensor device 50. For this purpose, the control unit 7 is connected to the sensor device 50 and to the outlet valve 60 in a signal-transmitting manner.

[0054] It should also be noted that “having” does not exclude other elements or steps and “a” or “an” does not exclude a plurality.

[0055] The scope of protection of the present invention is given by the claims and is not limited by the features explained in the description or shown in the figures. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2013 175114 A1

[0006] DE 10 2022 212 595

[0007] CN 212113902 U

[0009]

Claims

[1] Silencer (1) for an exhaust system of a fuel cell system (2), through which an exhaust gas flow (S) of the fuel cell system (2) can flow from an inlet opening (11) to an outlet opening (12), the silencer (1) comprising: - a silencer device (20) for reducing noise from the exhaust gas flow (S), - a water separation device (30) arranged upstream of the silencer device (20) for separating water from the exhaust gas stream (S), wherein the water separation device (30) has at least one water separation chamber (31), - a water collection chamber (40) which is in fluid communication with the water separation chamber (31) via a discharge opening (41) in such a way that water separated from the exhaust gas flow (S) can flow out of the water separation chamber (31), in particular independently due to gravity, into the water collection chamber (40) and be collected there, - a sensor device (50) for detecting the water level in the water collecting chamber (40), wherein the sensor device (50) has two electrodes (51a, 51b) and is designed and arranged to detect an electrical capacitance at least in sections within an internal volume (43) of the water collecting chamber (40), so that a conclusion about the water level can be drawn from the detected electrical capacitance. [2] Silencer (1) according to claim 1, the sensor device (50) is arranged on an outer wall (45) of a wall (44) delimiting the inner volume (43) of the water collecting chamber (40). [3] Silencer (1) according to claim 2, wherein the outer wall (45) is curved along a direction of curvature (U) and the electrodes (51a, 51b) are strip-shaped and extend parallel to one another transversely to the direction of curvature (U). [4] Silencer (1) according to one of the preceding claims, wherein the sensor device (50) comprises a flexible printed circuit board (52) with a first side (521) on which the two electrodes (51a, 51b) are arranged, in particular printed. [5] Silencer (1) according to claim 4, wherein the sensor device (50) comprises a shielding layer (55) made of conductive material, which is arranged on a second side (522) of the flexible printed circuit board (52) opposite the first side (521). [6] Silencer (1) according to one of the preceding claims, wherein the sensor device (50) comprises a temperature sensor (53). [7] Silencer (1) according to one of the preceding claims, wherein the sensor device (50) comprises a heating wire arrangement (54) for heating at least part of the water collecting chamber (40). [8] Fuel cell system (2) with a fuel cell (3), an exhaust gas line (4) leading from the fuel cell (3), and a silencer (1) according to one of the preceding claims installed in the exhaust system (4). [9] Fuel cell system (2) according to claim 8, comprising a control unit (7) which is designed and configured to control an outlet valve (60) with which the discharge opening (42) or a discharge line (46) of the water collection chamber (40) can be closed or opened as a function of the water level determined by means of the sensor device (50).

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