Muffler for an exhaust gas section of a fuel cell system

Abstract

The invention relates to a muffler (1) for an exhaust gas section of a fuel cell system (2), comprising a cavity (10), a muffler device (20) arranged within the cavity (10) for reducing the noise of the exhaust gas flow (S), and a water separating device (30) arranged within the cavity (10) upstream of the muffler device (20) for separating water from the exhaust gas flow (S), wherein the water separating device (30) has an impact element (32) arranged in the water separating chamber (31) for radially expanding the exhaust gas flow (S) flowing in through the inlet opening (11) and a funnel-shaped conducting element (33) downstream of the impact element (32) for radially tapering the exhaust gas flow (S) expanded by the impact element (32).

Description

[0001] Description

[0002] Silencer for an exhaust system of a fuel cell system

[0003] 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 15.

[0004] A fuel cell converts the chemical reaction energy of a continuously supplied fuel, e.g. hydrogen, and an oxidizing agent, e.g.

[0005] 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.

[0006] To supply the fuel and oxidizer, a fuel cell system uses several mechanical devices, which, during operation, generate noise that can be perceived as disturbing. To reduce the noise generated in the fuel cell system, silencers are installed within the fuel cell system, for example, in an exhaust system.

[0007] 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.

[0008] The exhaust gas produced during the power 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 muffler's surfaces, which negatively impacts the muffler's function - regardless of whether it is based on the reflection or absorption principle. In unfavorable cases, the moisture that accumulates in the muffler causes additional noise, which is perceived as unpleasant.

[0009] 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.

[0010] The object of the present invention is therefore to provide a silencer for an exhaust system of a fuel cell system, with which a reliable reduction of the noise associated with the operation of the fuel cell system can be achieved while at least partially avoiding the disadvantages of the prior art. At the very least, an alternative to existing solutions is to be created. 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 15. 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 for an exhaust system of a fuel cell system has a cavity through which an exhaust gas stream of the fuel cell system can flow along a flow path from an inlet opening of the cavity to an outlet opening of the cavity. Furthermore, the silencer has a sound-damping device arranged within the cavity for reducing noise from the exhaust gas stream, wherein the sound-damping device has at least one sound-damping chamber. The silencer also has a water separation device for separating water from the exhaust gas stream.The water separation device has at least one water separation chamber and is also arranged within the cavity and upstream of the silencer device, such that the exhaust gas flow flowing in through the inlet opening must first pass through the water separation device, in particular the entire water separation device, before the exhaust gas flow flows into the silencer device. The water separation device has a baffle element arranged in the water separation chamber for radially expanding an exhaust gas flow flowing in through the inlet opening, and downstream of the baffle element, a funnel-shaped guide element for radially tapering the exhaust gas flow expanded by the baffle element.

[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 cavity's inlet opening into the water separation chamber. In particular, the cavity's inlet opening simultaneously forms the inlet opening of the water separation chamber. In the water separation chamber, the exhaust gas stream is first widened by the impact element and then narrowed again by the funnel-shaped guide element arranged downstream before the exhaust gas stream is fed to the silencer. In this way, the exhaust gas stream in the water separation chamber is guided along the largest possible surface area, on which the water contained in the exhaust gas can condense.The water can condense on the impact element, on the funnel-shaped guide element, and on a wall bordering the water separation chamber, in particular a wall of a silencer housing. This achieves a high degree of dehumidification, so that impairment of the function of the downstream silencer device due to excessively humid exhaust gas is reduced or completely prevented.

[0014] The design of the water separation chamber eliminates the need for water-absorbing material, simplifying the silencer's construction. Depending on the silencer's installation position, the condensed water collects due to gravity in a predetermined area of ​​the water separation chamber, from where it can be easily removed actively or passively.

[0015] A “water separation device” is a device that primarily serves to separate water (and / or another liquid) from the exhaust gas. A silencer device is therefore not to be regarded as a water separation device, even if a certain amount of condensation and removal of moisture also occurs in the silencer chamber. The impact element preferably has a cross-section that increases continuously from its upstream end to its downstream end. This results in a gradual radial expansion of the exhaust gas flow at the outer surfaces of the impact element. To promote uniform and quiet flow, the impact element can be at least partially rotationally symmetrical. The impact element can have a conical, truncated cone-shaped, or paraboloid-shaped flow body.The upstream end of the impact element can be designed as a particularly rounded tip. Preferably, the impact element is hollow—e.g., in the form of a cap with its tip oriented toward the inlet opening—which reduces the material costs and weight of the silencer.

[0016] The funnel-shaped guide element defines a flow channel from its upstream end to its downstream end, with a continuously decreasing flow cross-section. In this way, the exhaust gas flow expanded by the impact element is recaptured, with the funnel shape reducing or even preventing the formation of turbulence - which often occurs around sharp corners. This reduces pressure loss in the silencer. Furthermore, water condensed on the funnel-shaped guide element can slide along the surface of the guide element due to gravity and thus be discharged, for example, to a drain opening in the water separation chamber. To promote laminar and quiet flow, the funnel-shaped guide element can be rotationally symmetrical.In particular, the funnel-shaped guide element has a concave surface along which the exhaust gas stream can flow. This promotes a laminar and quiet flow and increases the available condensation surface. In particular, the impact element and the funnel-shaped guide element are spaced apart from one another in the longitudinal direction of the silencer or in the main flow direction of the exhaust gas stream. The silencer device preferably has a perforated tube extending through the silencer chamber. In particular, an upstream tube end is connected to the funnel-shaped guide element such that the tube interior is in fluid communication with the water separation chamber. Preferably, a downstream tube end is connected to the outlet opening. The perforation of the tube establishes a fluid communication with the rest of the silencer chamber.The silencer device can generally be designed as a reflection silencer or an absorption silencer. Preferably, the silencer device is a reflection silencer. This allows for simple additional dehumidification within the silencer device through condensation of 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 perforation pattern in the pipe can be adapted to a specific frequency range to be attenuated.

[0017] In a preferred embodiment of the silencer according to the invention, the cross-section of the impact element at its downstream end is larger than the flow cross-section of the inlet opening. In this way, the exhaust gas flow is expanded into a large volume and can be guided along a large condensation surface.

[0018] In a further preferred embodiment of the silencer according to the invention, the impact element is designed to generate a swirl in the exhaust gas flow. For this purpose, the impact element preferably has one or more guide elements, e.g. in the form of guide vanes, which, due to their shape, set the exhaust gas flow flowing along the impact element into a swirling movement about an axis of rotation running parallel to the longitudinal direction of the silencer or to the main flow direction of the exhaust gas flow. Due to the swirling movement, the flow path of the exhaust gas flow is curved and thus lengthened, which further promotes dehumidification. Alternatively or additionally, the impact element can also have one or more depressions as guide elements. Preferably, the funnel-shaped guide element is designed to feed the tapered exhaust gas flow to the silencer device.In this way, a particularly compact design of the silencer can be realized, which eliminates the need for additional structures for supplying the exhaust gas flow.

[0019] In a further preferred embodiment of the silencer according to the invention, the silencer has a condensation screen that separates the water separation chamber into two sub-chambers. In this way, the exhaust gas stream is forced to pass through the condensation screen arranged in the water separation chamber. The water contained in the exhaust gas stream can condense on the screen lining, thereby further increasing the degree of dehumidification of the water separation device. In particular, a mesh, wire cloth, wire grid and / or perforated sheet forms the screen lining. The condensation screen preferably has a mesh size of at least 160 pm, preferably at least 300 pm, particularly preferably at least 500 pm, and a maximum of 1000 pm, preferably a maximum of 900 pm. It has surprisingly been found that good dehumidification results can be achieved with such mesh sizes.The condensation screen is preferably arranged downstream of the impact element so that the exhaust gas flow is already expanded and guided along the largest possible condensation surface before it impacts the condensation screen. Particularly preferably, the condensation screen is arranged at least partially within the funnel-shaped guide element. In this way, the exhaust gas flow is directed by the funnel-shaped guide element onto the condensation screen and compressed before passing through the condensation screen, so that pressure loss due to the flow resistance of the condensation screen is reduced. The condensation screen is preferably designed in the shape of a cylinder jacket. This simple structural design allows the condensation screen to be optimally positioned in the water separation chamber between the impact element and the funnel-shaped guide element.The condensation screen is preferably mounted on a support structure that spaced the impact element from the funnel-shaped guide element. The support structure can have one or more support elements (e.g., in the form of support struts) extending in the longitudinal direction of the silencer or in the main flow direction of the exhaust gas stream. The silencer preferably has at least one heating element for heating the condensation screen. This ensures that the close-meshed condensation screen does not freeze at low outside temperatures. To provide favorable heating performance, the at least one heating element for heating the condensation screen is preferably arranged on or in the support structure on which the condensation screen is mounted.

[0020] In a further preferred embodiment of the silencer according to the invention, the funnel-shaped guide element forms a partition wall between the water separation chamber and the sound-damping chamber. In this way, the two chambers are separated at least partially, preferably completely, by one and the same structure, thereby enabling a particularly compact silencer design, particularly with a direct transition from the water separation chamber to the sound-damping chamber.

[0021] In a further preferred embodiment of the silencer according to the invention, the silencer device has at least one further silencer chamber downstream of the silencer chamber. Due to its structural design, the silencer according to the invention is ideally suited for a simple, implementable extension of the silencer device by one or more silencer chambers. 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 hole pattern of the perforation in the tube. In particular, a perforated tube extends through the silencer chambers, with the silencer chambers being separated from one another outside the tube by partition walls. For optimal damping, the silencer device preferably has two, particularly preferably four silencer chambers.

[0022] In a further preferred embodiment of the silencer according to the invention, the cavity 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 to the longitudinal central axis. Thus, the exhaust gas flow only needs to change its flow direction slightly when transitioning from the water separation device to the silencer device, thereby promoting a uniform and quiet flow of the exhaust gas flow. Furthermore, a compact design of the silencer can be realized in this way. In particular, the inlet opening and the outlet opening are arranged centered to the longitudinal central axis. Preferably, the cavity is at least partially, preferably completely, cylindrical or formed from a plurality of coaxially aligned cylindrical partial cavities.

[0023] In a further preferred embodiment of the silencer according to the invention, the silencer has a housing that at least partially defines the cavity, wherein the housing defines at least the outer surface(s) of the cavity, wherein the silencer has a structure that can be assembled from modules or formed in one piece and that can be inserted into the housing as a whole, wherein the structure, together with the housing, forms the water separation device and the sound damping device. The housing can expose at least one insertion opening through which the structure can be inserted into the housing. The insertion opening can be closable by means of a separate cover. Alternatively, a part of the structure can form the cover and, when the structure is inserted into the housing, close the insertion opening.In particular, the structure comprises the impact element, the funnel-shaped guide element, the perforated tube, and, if there are multiple sound-damping chambers, one or more partition walls for separating the sound-damping chambers. The structure can, for example, comprise a support structure that attaches the impact element to the funnel-shaped guide element at a distance from the funnel-shaped guide element.

[0024] Preferably, the housing and / or the structure consists predominantly of a material comprising a thermoplastic.

[0025] In a further preferred embodiment of the silencer according to the invention, the silencer has a water collection chamber that at least partially surrounds the water separation chamber and is in fluid communication with the water separation chamber via a drain opening such 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. In this way, the separated water is drained 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, accumulated water is prevented from being transported by the exhaust gas flow toward the silencer device and impairing its function.Reliable drainage of water from the water separation chamber is crucial for the function of the silencer. For example, when a 100 kW fuel cell is running at full load, around 0.5 L of water can be separated from the exhaust gas. The water collected in the water collection chamber can be easily drained from the water collection chamber, for example via a drainage opening, either actively - e.g. using a pump - or passively - e.g. automatically due to gravity. The water collection chamber only has to surround a small area of ​​the water separation chamber - e.g. an area located at the bottom with respect to the direction of gravity. The water collection chamber can therefore have a much smaller internal volume than the water separation chamber. The cavity and the water collection chamber are preferably separated by a wall of the cavity, which results in a compact silencer design.

[0026] In a further preferred embodiment of the silencer according to the invention, the water collection chamber further at least partially surrounds the silencer chamber and is fluidly connected to the silencer chamber via an opening such that water condensed from the exhaust stream can flow out of the silencer chamber into the water collection chamber, in particular independently due to gravity. In this way, the separated water is removed from the silencer chamber, thereby preventing water from accumulating in the silencer device, which could otherwise have a negative impact on noise reduction. To avoid impairing its function, the opening for the condensed water is preferably located in a corner of the silencer chamber.Preferably, in the case of a plurality of 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.

[0027] Preferably, the water collection chamber extends along at least half the total length, preferably at least two-thirds of the total length of the cavity. This increases the absorption capacity of the water collection chamber. Furthermore, a compact design of the silencer can be realized.

[0028] In a further preferred embodiment of the silencer according to the invention, the silencer has a heating element for heating at least part of a wall defining the water collection chamber. This ensures water drainage even at low outside temperatures, where freezing of the condensate is to be expected. The heating element can extend along at least half the total length, preferably at least two-thirds of the total length of the water collection chamber. The heating element is preferably embedded in a region of the wall defining the water collection chamber surrounding the drainage opening.

[0029] The silencer can be provided with a nozzle in the area of ​​the inlet opening and in the area of ​​the outlet opening, to which a section of the exhaust line can be attached.

[0030] According to what has already been described above and what has been described further below, the object set out at the outset is also achieved by a fuel cell system having the features of claim 15.

[0031] 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.

[0032] In laboratory tests, by comparing the relative humidity and the temperature at the inlet and outlet openings, it was found that the silencer according to the invention is capable of removing approximately 75% to 80% of the moisture from the exhaust gas stream.

[0033] 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.

[0034] 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:

[0035] Fig. 1 shows an embodiment of a fuel cell system according to the invention;

[0036] Fig. 2 shows a first embodiment of a silencer according to the invention in a sectional view;

[0037] Fig. 3 shows a second embodiment of an inventive

[0038] Silencer in a sectional view; and

[0039] Fig. 4 is a front view of an impact element as it can be used in one of the embodiments according to Fig. 1 or 2.

[0040] Parts with the same or similar effects are provided with identical reference numerals where appropriate. 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.

[0041] Fig. 1 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.

[0042] Fig. 2 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. The silencer 1 has a cavity 10 through which an exhaust gas flow S of the fuel cell system can flow from an inlet opening 11 to an outlet opening 12. The position of the inlet opening 11 and the outlet opening define a main flow direction R, which in the present case runs parallel to the longitudinal center axis A of the silencer 1. A silencer device 20 for reducing noise of the exhaust gas flow S is arranged within the cavity 10. Furthermore, a water separator device 30 for separating water from the exhaust gas flow S is arranged within the cavity 10 upstream of the silencer device 20, wherein the water separator device 30 has a water separation chamber 31.Within the water separation chamber 31, a baffle element 32 is arranged for radially expanding the exhaust gas flow S flowing in through the inlet opening 11. Downstream of the baffle element 32, a funnel-shaped guide element 33 is arranged for radially tapering the exhaust gas flow S expanded by the baffle element 32. The exhaust gas flow S can be guided from the fuel cell 3 into the cavity 10 via an exhaust gas feed line 4a (Fig. 1) of the exhaust system 4, which can be attached to the inlet nozzle 16 of the silencer 1. In the water separation chamber 31, the exhaust gas flow S is expanded by the 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 stream S is thus guided along as large an area as possible, where water contained in the exhaust gas can condense.The exhaust gas stream S is dehumidified to a high degree before being 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 guided away from the silencer 1 via an exhaust gas discharge line 4b (Fig. 1) of the exhaust system 3, which can be attached to the outlet connection 17 of the silencer 1.

[0043] Due to the shape of the impact element 32, i.e., due to the cross-section that steadily increases from its upstream end 321 to its downstream end 322, a gradual radial expansion of the exhaust gas flow S occurs at the outer surfaces of the impact element 32. In order to achieve sufficient radial expansion of the exhaust gas flow S, the cross-section of the impact element 32 at its downstream end 322 is larger than the flow cross-section of the inlet opening 11. To promote a uniform and quiet flow, the impact element 32 is essentially rotationally symmetrical and has a conical flow body with a rounded tip. To reduce weight, the impact element 32 is hollow.

[0044] The funnel-shaped guide element 33 defines a flow channel with a continuously decreasing flow cross-section from its upstream end 331 to its downstream end 332. In this way, the exhaust gas flow S expanded by the impact element 32 is recaptured, whereby the funnel shape reduces or even prevents the formation of turbulence and the associated pressure loss. For example, condensed water can slide along the surface of the guide element 33 due to gravity, e.g. in the direction of the discharge opening 41, and can thus be more effectively discharged. To promote laminar and quiet flow, the funnel-shaped guide element 33 is designed to be rotationally symmetrical about the longitudinal central axis A. The funnel-shaped guide element 33 has a concave surface along which the exhaust gas flow S can flow.This promotes a laminar and quiet flow and increases the available condensation surface. In order to achieve the most compact design possible for the silencer 1, the funnel-shaped guide element 33 forms a partition wall between the water separation chamber 31 and the silencer chamber 21a. The impact element 32 and the funnel-shaped guide element 33 are spaced apart from one another in the longitudinal direction of the silencer 1 and in the main flow direction R of the exhaust gas flow S. The funnel-shaped guide element 33 is designed to feed the tapered exhaust gas flow S to the silencer device 20, i.e. the downstream end 332 of the funnel-shaped guide element 33 directly adjoins the upstream end of the perforated tube 22. In the present case, the funnel-shaped guide element 32 and the perforated tube 22 are formed as a single piece.

[0045] In the present case, the silencer device 20 forms a reflection silencer with four silencer chambers 21 a, 21 b, 21 c, 21 d, through which a perforated tube 22 extends and which are further separated from one another by three partition walls 23 a, 23 b, 23 c.

[0046] The cavity 10 extends along the longitudinal center axis A of the silencer 1 and is rotationally symmetrical about the longitudinal center axis A. In the present case, the cavity 10 is cylindrical. The water separation device 30 and the silencer device 20 are arranged centered on the longitudinal center axis A. This promotes a uniform and quiet flow of the exhaust gas stream, since, in particular, a change in the main flow direction R (flow reversal) is avoided. The advantageous flow behavior is also promoted by the fact that the inlet opening 11 and the outlet opening 12 are arranged centered on the longitudinal center axis A.

[0047] The silencer 1 has a housing 13 that defines the outer surface of the cylindrical cavity 10. In the present case, the housing 13 additionally defines an inlet-side end face of the cavity 10, while an outlet-side end face is defined by a separate cover 15. Due to the structural design of the silencer 1, in particular due to the rotational symmetry of the individual components of the silencer 1 about the longitudinal central axis A, particularly simple production is possible. The silencer 1 can have a structure 14 that can be assembled from modules or formed in one piece and can be inserted as a whole into the housing 13, wherein the structure 14, together with the housing 13, forms the water separation device 30 and the sound damping device 20. In the present case, the housing 13 for this purpose provides an insertion opening for the structure 14 on the outlet side, which can be closed with the cover 15.The cover 15 can also be attached to the structure 14 or formed integrally therewith. The structure 14 can, for example, have the impact element 32, the funnel-shaped guide element 33, the perforated tube 22, and the partition walls 23a, 23b, 23c for separating the sound-damping chambers 21a, 21b, 21c, 21d. The structure 14 can, for example, have a support structure 50 that attaches the impact element 32 to the funnel-shaped guide element 33 at a distance from the funnel-shaped guide element 33. In the present case, the structure has a further support structure 51 that spaces the impact element 32 from the housing 13 in the region of the inlet-side end face of the cavity 10. In some applications, it can also be advantageous to divide the structure 14 into individual modules at at least one cross-sectional plane.

[0048] The silencer 1 has a water collection chamber 40 partially surrounding the water separation chamber 31, which is in fluid communication with the water separation chamber via a discharge opening 41 such that water separated from the exhaust gas flow S can flow out of the water separation chamber 31 independently 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 as well as the

[0049] The shape of the funnel-shaped guide element 33 promotes a directed flow of the separated water towards the discharge opening 41.

[0050] The water collected in the water collection chamber 40 can be easily discharged from the water collection chamber or from the silencer, e.g., via a discharge opening 42, either actively—e.g., by a pump—or passively—e.g., automatically due to gravity. The water collection chamber 40 only has to 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 area can be located approximately between a “5 o’clock position” and a “7 o’clock position” when viewed parallel to the longitudinal center axis A. The water collection chamber 40 can therefore have a significantly smaller internal volume than the water separation chamber 31. The cavity 10 and the water collection chamber 40 are separated by a wall of the cavity 10, thereby achieving a compact design of the silencer 1.A wall defining the water collection chamber 40 can also be part of the housing 13 and, in particular, be formed integrally therewith. In this case, a partition wall that can be inserted into the housing 13 can be provided, separating the water separation chamber 31 from the water collection chamber 40.

[0051] 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 independently due to gravity into the water collection chamber 40. This prevents water from accumulating in the silencer device 20, which could otherwise have a negative impact on noise attenuation. In order not to impair the function of the sound damping device 20, the openings 41 a, 41 b, 41 c for the condensed water are preferably arranged in the corners of the sound damping chambers 21 a, 21 b, 21 c, 21 d, wherein adjacent sound damping chambers 21 a, 21 b, 21 c, 21 d have a common opening 41 a, 41 b, 41 c in the region of an end face of the respective partition wall 23 a, 23 b, 23 c.To provide sufficient absorption capacity, the water collection chamber 40 extends substantially along the total length L of the cavity 10.

[0052] The silencer 1 has a heating element 43 for heating at least part of a wall defining the water collection chamber 40. In this way, water drainage can be ensured even at low outside temperatures, where freezing of the condensate is to be expected. The heating element 43 is embedded in the wall and extends along at least half of the total length L of the water collection chamber 40. Alternatively, the heating element 43 can be embedded in a region of the wall defining the water collection chamber 40 surrounding the drainage opening 42. Multiple heating elements 43 can also be provided.

[0053] Fig. 3 shows a second embodiment of a silencer 1 according to the invention for an exhaust system 4 of a fuel cell system 2 in a sectional view. The silencer 1 of the second embodiment differs from the silencer 1 of the first embodiment only in that the silencer 1 has a condensation screen 34 that separates the water separation chamber 31 into two sub-chambers 311, 312. In order to pass from the first sub-chamber 311 into the second sub-chamber, the exhaust gas flow must pass through the condensation screen 34, whereby the water contained in the exhaust gas flow S can condense on the screen lining. The screen lining can be formed from a mesh, wire mesh, wire grid and / or perforated sheet.The condensation screen 34 is arranged downstream of the impact element 32, so that the exhaust gas flow S is already expanded and guided along the largest possible condensation surface before it impinges on the condensation screen 34. In addition, the condensation screen 34 is partially arranged within the funnel-shaped guide element 33. In other words, the condensation screen 34 and the funnel-shaped guide element 33 overlap in a longitudinal section. In this way, the exhaust gas flow S is directed by the funnel-shaped guide element 33 onto the condensation screen 34 and compressed before passing through the condensation screen 34, so that a pressure loss due to the flow resistance of the condensation screen 34 is reduced. The condensation screen 34 is designed in the shape of a cylinder jacket and is mounted on the support structure 50 that spaced the impact element 32 from the funnel-shaped guide element 33.

[0054] In the second embodiment, it is advantageous to divide the structure 14 into individual modules at least at one cross-sectional plane between the impact element 32 and the funnel-shaped guide element 33, so that the condensation sieve 34 can be easily attached to the structure 14. For example, a first module of the structure 14 can comprise the impact element 32 and the further support structure 51, and a second module of the structure 14 can comprise the support structure 50, the condensation sieve 43, the funnel-shaped guide element 33, and optionally the components belonging to the silencer device 20 (perforated tube 22, partition walls 23a, 23b, 23c). The first module of the structure 14 can also comprise a cover that at least partially delimits the inlet-side end face of the cavity 10. The second module of the structure 14 can also comprise a cover that at least partially delimits the outlet-side end face of the cavity 10.

[0055] Fig. 4 shows a baffle element 32 in a front view (viewing in the main flow direction R), as can also be used in the first or second exemplary embodiment. The baffle element 32 is designed to generate a swirl in the exhaust gas flow S. For this purpose, the baffle element 32, in addition to its conical flow body shown in Figs. 2 and 3, further comprises a plurality of guide elements in the form of guide vanes 323, which, due to their shape, impart a swirling movement around the longitudinal center axis of the silencer to the exhaust gas flow S flowing along the baffle element 32. The swirling movement curves and thus lengthens the flow path of the exhaust gas flow S, which further promotes dehumidification.

[0056] Additionally, it should be noted that "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. The scope of the present invention is defined by the claims and is not limited by the features explained in the description or shown in the figures.

[0057]

[0058] 1 silencer

[0059] 2 Fuel cell system

[0060] 3 Fuel cell

[0061] 4 exhaust system

[0062] 4a Exhaust gas supply line of the exhaust system

[0063] 4b Exhaust gas discharge of the exhaust system

[0064] 5 Hydrogen

[0065] 6 Air

[0066] 10 Cavity of the silencer

[0067] 11 Inlet opening of the cavity

[0068] 12 Outlet opening of the cavity

[0069] 13 Silencer housing

[0070] 14 Structure of the silencer

[0071] 15 Silencer cover

[0072] 16 Silencer inlet port

[0073] 17 Exhaust port of the silencer

[0074] 20 Silencer silencer device

[0075] 21a-d Silencing chambers of the silencer device

[0076] 22 perforated pipe of the silencer device

[0077] 23a-c Partition walls of the silencer device

[0078] 30 Water separator

[0079] 31 Water separation chamber of the water separation device

[0080] 311 first sub-chamber of the water separation chamber

[0081] 312 second sub-chamber of the water separation chamber

[0082] 32 Impact element of the water separation device

[0083] 321 upstream end of the impact element

[0084] 322 downstream end of the impact element

[0085] 323 Guide elements of the impact element

[0086] 33 funnel-shaped guide element of the water separator

[0087] 331 upstream end of the funnel-shaped guide element

[0088] 332 downstream end of the funnel-shaped guide element

[0089] 34 Condensation sieve of the water separator

[0090] 35 wall defining the water separation chamber

[0091] 40 Water collection chamber of the silencer

[0092] 41 Drain opening of the water collection chamber

[0093] 41 ac Openings of the water collection chamber 42 Drain opening of the water collection chamber

[0094] 43 Heating element of the silencer

[0095] 50 Support structure

[0096] 51 further support structure A Longitudinal center axis of the silencer

[0097] G Direction of gravity

[0098] L Total length of the cavity

[0099] R Main flow direction of the exhaust gas flow

[0100] S exhaust gas flow

Claims

Patent claims 1. A silencer (1) for an exhaust system of a fuel cell system (2), comprising a cavity (10) through which an exhaust gas stream (S) of the fuel cell system can flow from an inlet opening (11) to an outlet opening (12), a silencer device (20) arranged within the cavity (10) for reducing noise of the exhaust gas stream (S), wherein the silencer device (20) has at least one silencer chamber (21a, 21b, 21c, 21d), a water separator device (30) arranged within the cavity (10) upstream of the silencer device (20) for separating water from the exhaust gas stream (S), wherein the water separator device (30) has at least one water separator chamber (31),wherein the water separation device (30) has a baffle element (32) arranged in the water separation chamber (31) for radially expanding the exhaust gas flow (S) flowing in through the inlet opening (11) and, downstream of the baffle element (32), a funnel-shaped guide element (33) for radially tapering the exhaust gas flow (S) expanded by the baffle element (32).

2. Silencer (1) according to claim 1, wherein the impact element (32) has a cross-section that increases in particular continuously from its upstream end (321) to its downstream end (322).

3. Silencer (1 ) according to claim 1 or 2, wherein the cross section of the impact element (32) at its downstream end (322) is larger than the flow cross section of the inlet opening (11 ).

4. Silencer (1) according to one of the preceding claims, wherein the impact element (32) is designed to generate a swirl in the exhaust gas flow (S).

5. Silencer (1) according to one of the preceding claims with a condensation sieve (34) separating the water separation chamber (31) into two sub-chambers (311, 312).

6. Silencer (1) according to claim 5, wherein the condensation sieve (34) is arranged between the impact element (32) and the funnel-shaped guide element (33).

7. Silencer (1) according to claim 6, wherein the condensation sieve (34) is cylindrical in shape.

8. Silencer (1) according to one of the preceding claims, wherein the funnel-shaped guide element (33) forms a partition wall between the water separation chamber (31) and the sound damping chamber (21a).

9. Silencer (1) according to one of the preceding claims, wherein the silencer device (20) has at least one further silencer chamber (21b, 21c, 21d) downstream of the silencer chamber (21a).

10. Silencer (1) according to one of the preceding claims, wherein the cavity (10) extends along a longitudinal central axis (A) and in particular rotationally symmetrical about the longitudinal central axis (A), wherein the water separation device (30) and the sound damping device (20) are arranged centered to the longitudinal central axis (A).

11. Silencer (1) according to claim 10, wherein the cavity (10) is cylindrical or is formed from a plurality of coaxially aligned cylindrical partial cavities, wherein the silencer (1) is a the cavity (10) has a housing (13) at least partially delimiting, wherein the housing (13) delimits at least the lateral surface(s) of the cavity (10), wherein the silencer (1) has a structure (14) which can be assembled from modules or is formed in one piece and which can be inserted as a whole into the housing (13), wherein the structure (14) together with the housing (13) forms the water separation device (30) and the sound damping device (20).

12. Silencer (1 ) with a water collection chamber (40) which at least partially surrounds the water separation chamber (31 ) and 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.

13. Silencer (1) according to claim 12, wherein the water collecting chamber (40) further at least partially surrounds the silencer chamber(s) (21a, 21b, 21c, 21d) and is in fluid-conducting connection with the silencer chamber(s) (21a, 21b, 21c, 21d) via an opening (41a, 41b, 41c) in such a way that water condensed from the exhaust gas flow (S) can flow out of the silencer chamber(s) (21a, 21b, 21c, 21d), in particular independently due to gravity, into the water collecting chamber (40).

14. Silencer (1) according to claim 12 or 13 with a heating element (43) for heating at least part of a wall delimiting the water collecting chamber (40).

15. Fuel cell system (2) with a fuel cell (3), an exhaust line (4) leading from the fuel cell (3) and a silencer (1) installed in the exhaust system (4) according to one of the preceding claims.

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