Silencer for an exhaust tract of a fuel-cell system

Abstract

The invention relates to a silencer having a cavity (10) which is at least partially delimited by a housing (13), and a silencing device (20) which is arranged inside the cavity (10) for reducing the noise of the exhaust-gas flow (S). According to the invention, a heat-accumulator body (50, 50a, 50b, 50c, 50d) containing a phase-change material is arranged inside the cavity (10) in order to delay or prevent the freezing of condensate.

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 with the features of claim 1. The invention further relates to a fuel cell system with the features of claim 13.

[0004] A fuel cell converts the chemical reaction energy of a continuously supplied fuel, such as hydrogen, and an oxidant, such as oxygen, into electrical energy. Fuel cells are used, for example, in fuel cell vehicles to directly convert the generated electrical energy into motion via an electric drive or to temporarily store it in a traction battery. Besides hydrogen, fuel cells can also use other fuels, particularly methanol, butane, or natural gas.

[0005] Several mechanical devices are used in a fuel cell system to supply the fuel and oxidizer. These devices generate noise during operation, which can be perceived as disturbing. To reduce the noise generated in the fuel cell system, silencers are installed within the system, for example, in the exhaust system.

[0006] The silencers used in this context can be based on the reflection principle or the absorption principle. A reflection silencer consists of one or more chambers in which the sound can propagate. The sound waves can be reflected at changes in cross-section and at open pipe or duct ends, resulting in a loss of some sound energy. One type of reflection silencer, for example, can have several chambers of different sizes connected to each other, e.g., by a perforated pipe running through the chambers. The sound waves are reflected within the chambers. The coupling of the individual chambers creates so-called resonators, in which the sound waves are reflected, partially cancel each other out according to the interference principle, and are thus attenuated.Individual chambers can be adapted to a specific frequency range to be attenuated by their size and / or the perforation pattern in the pipe. Generally, the greater the number of chambers, the more efficient the attenuation. Another type of reflection silencer can consist of several pipes nested within each other, with the annular gaps between the pipes forming a labyrinthine propagation path for the sound waves, along which some of the sound energy is dissipated. An absorption silencer typically has only one chamber containing a perforated pipe. The chamber is filled with a sound-absorbing material, such as long-fiber mineral wool. The sound waves penetrate the perforated pipe and enter the sound-absorbing material, where they are converted into heat through friction.The achieved damping depends on the material used, the packing density, the length and layer thickness of the chamber.

[0007] The exhaust gas produced during the power generation reaction in a hydrogen-oxygen fuel cell, which is primarily discharged from the fuel cell's cathode, contains water (mostly in the form of water vapor and water droplets) and has an exhaust gas temperature of around 80 °C. Because the exhaust gas temperature is below the boiling point of water, the water is difficult to evaporate and remove. However, if excessively moist exhaust gas enters the silencer, the water vapor condenses, particularly on the silencer's surfaces, negatively impacting its function—regardless of whether it operates on the reflection or absorption principle. In unfavorable cases, the moisture accumulated in the silencer can generate additional noise, which is perceived as unpleasant.

[0008] To counteract this problem, US Patent 2013 175114 A1 proposes a hybrid silencer in which a dehumidification chamber, essentially completely filled with a water-absorbing material, is placed upstream of a sound-absorbing device based on the reflection principle. However, to ensure adequate dehumidification, 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 the condensate that continues to form in the silencer device must be absorbed by a portion of the water-absorbing material that extends into the silencer device. Furthermore, the water absorbed by the water-absorbing material cannot be easily discharged but usually has to be pumped out.Overall, this results in a relatively complex design for the hybrid silencer, which takes up a relatively large amount of installation space and is expensive to manufacture and operate.

[0009] At ambient temperatures below freezing, condensation from the moist exhaust gas can freeze, reducing the flow cross-section of certain sections of the silencer. Furthermore, particularly small openings in the silencer, such as those intended for drainage, can freeze completely. All of this negatively impacts the silencer's functionality and, in the worst-case scenario, can lead to damage in upstream components such as the fuel cell. For this reason, heating elements are often integrated into such silencers; these elements require an electrical power supply and temperature control.

[0010] The object of the present invention is therefore to provide a silencer for the 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 even at ambient temperatures below freezing, while at least partially avoiding the disadvantages of the prior art. At the very least, an alternative to existing solutions should be provided. Furthermore, it is an object of the present invention to provide a fuel cell system with such a silencer.

[0011] This task is accomplished by a silencer with the features of the claim.

[0012] 1 and a fuel cell system with the features of claim 13. Preferred features are the subject of the dependent claims. Further advantages and features can be found in the general description and the exemplary embodiments.

[0013] The silencer according to the invention for an exhaust stream of a fuel cell system has a cavity at least partially bounded by a housing, through which an exhaust gas flow of the fuel cell system can flow along a main flow direction from an inlet opening to an outlet opening of the cavity. The silencer further comprises a sound-absorbing device arranged within the cavity for reducing noise of the exhaust gas flow, wherein the sound-absorbing device has a sound-absorbing chamber extending along a longitudinal direction and radially bounded by an inner wall of the housing, through which the exhaust gas flow can flow from an inlet opening to an outlet opening of the sound-absorbing chamber. The silencer is characterized by at least one heat storage element arranged within the cavity, containing a phase change material (PCM).

[0014] The heat storage element containing the phase change material forms a latent heat storage system. The phase change material, which can be an inorganic material containing salt or an organic material containing paraffin, undergoes a phase change, for example, between a solid and a liquid phase, at its specific phase change temperature. During operation of the silencer, the warm exhaust gas can transfer heat to the phase change material, thus increasing its temperature. Upon reaching the phase change temperature, the additional heat energy extracted from the exhaust gas is used to change the material's phase and is stored as latent heat. This latent heat is stored at the storage temperature and can be accessed at that temperature.Once a contiguous portion of the material has completely transitioned into the liquid phase, any further supplied heat energy is stored as a temperature increase of the liquid material. Due to its arrangement within the silencer cavity, the phase-change material can efficiently extract excess heat from the system and, in the absence of warm exhaust gas, release the stored heat inside the silencer. This allows the silencer to be maintained at operating temperature for a longer period, thus at least delaying the freezing of condensate at particularly low temperatures. The risk of freezing during short periods of inactivity, such as breaks or refueling, can therefore be effectively reduced. The advantages of the invention can be realized for silencers operating on the reflection principle, the absorption principle, or a combination thereof.

[0015] Preferably, the phase change material is an encapsulated phase change material, i.e., the phase change material is arranged in a capsule or chamber with a membrane or wall that is impermeable to the material. Preferably, the phase change material contains paraffin.

[0016] The terms upstream and downstream always refer to the main flow direction.

[0017] In a preferred embodiment of the silencer according to the invention, the at least one heat storage body has a plurality of sealed chambers, each filled with the phase change material. Preferably, the at least one heat storage body has a planar support made of a polymeric material in which and / or on which the plurality of chambers are arranged. The chambers can be distributed at regular intervals on the surface of the body. The polymeric support can be rigid or flexible. A rigid support has the advantage that the heat storage body is dimensionally stable and can be easily assembled as a whole. A flexible support has the advantage that the heat storage body can be adapted to various surfaces, particularly curved ones, and attached to them, for example, by means of adhesives or other joining techniques.In this way, the heat storage element can be processed like a flat structure and excellently integrated into various silencer geometries. Preferably, the carrier has a first side and a second side facing away from the first, the second side being essentially flat. In this way, the second side forms a substantially flat surface that can be easily conformed to various surfaces, especially curved ones. In other words, the second side has no protrusions.

[0018] In a further preferred embodiment of the silencer according to the invention, the inner wall of the sound-absorbing chamber is lined with a heat storage element for temperature control. This allows the heat storage element to interact effectively with the exhaust gas flowing through the sound-absorbing chamber. Furthermore, the heat storage element forms a thermal barrier against the external environment of the silencer. In particular, at least 50%, and preferably at least 80%, of the surface of the inner wall of the sound-absorbing chamber is lined with the heat storage element. The heat storage element preferably extends along the entire length of the sound-absorbing chamber and, in particular, completely around a longitudinal central axis of the sound-absorbing chamber. The planar support can be a tubular body with a round, square, or polygonal cross-section.The planar support can be arranged with its particularly flat second side abutting the inner wall.

[0019] In a further preferred embodiment of the silencer according to the invention, the heat storage element for temperature control of the sound-absorbing chamber is covered on its side facing away from the inner wall with a layer of sound-absorbing material. The sound-absorbing material is preferably at least partially fluid-permeable. The sound-absorbing material can, for example, be long-fiber mineral wool. The heat storage element and / or the layer of sound-absorbing material can be held in the immediate vicinity of the inner wall by a fluid-permeable support structure comprising one or more support elements. In one embodiment, the support structure can be a perforated or recessed tube arranged radially inside the sound-absorbing material.In an alternative embodiment, the layer of sound-absorbing material can be held in place by a grid structure or wire mesh as a retaining structure in the immediate vicinity of the heat storage body lining the inner wall. The layer of sound-absorbing material preferably extends along the entire length of the sound-absorbing chamber, completely surrounding the flow guide device.

[0020] In a further preferred embodiment of the silencer according to the invention, it has a water separator arranged within the cavity upstream of the silencer for separating water from the exhaust gas stream. The water separator has at least one water separation chamber through which the exhaust gas stream can flow along the main flow direction from an inlet opening to an outlet opening of the water separation chamber. At least one (further) heat storage element is arranged within the water separation chamber.

[0021] The water separator device is arranged upstream of the soundproofing device, so that the exhaust gas flow entering through the inlet opening must first pass the water separator device, in particular the entire water separator device, before the exhaust gas flow enters the soundproofing device.

[0022] The exhaust gas stream, which is drawn off, for example, from the cathode of a fuel cell in the fuel cell system and fed directly or indirectly to the silencer, can flow into the water separation chamber through the inlet opening of the cavity. Specifically, the inlet opening of the cavity simultaneously forms the inlet opening of the water separation chamber. The exhaust gas stream is dehumidified in the water separation chamber, thus reducing or completely preventing any impairment of the function of the downstream silencer device by excessively moist exhaust gas. Depending on the installation position of the silencer, the condensed water collects due to gravity in a known area of ​​the water separation chamber and can be easily discharged from there, either actively or passively. A "water separation device" is understood to be a device primarily used for separating water (and / or another liquid) from the exhaust gas.A sound-absorbing device is therefore not to be regarded as a water separation device, even if some condensation and removal of moisture also occurs in the sound-absorbing chamber.

[0023] In a further preferred embodiment of the silencer according to the invention, an inner wall radially bounding the water separation chamber is lined with a heat storage element for temperature control. This allows the heat storage element to interact effectively with the exhaust gas flowing through the water separation chamber. Furthermore, the heat storage element forms a thermal barrier against the external environment of the silencer. In particular, the surface of the inner wall of the water separation chamber is lined with the heat storage element to at least 50%, preferably at least 80%. The heat storage element preferably extends along the entire length of the water separation chamber and, in particular, completely around a longitudinal central axis of the water separation chamber.The planar support can form a tubular body with a round, square, or polygonal cross-section. The planar support can be arranged with its second, particularly flat, side abutting the inner wall.

[0024] The water separation chamber and the sound absorption chamber are preferably radially bounded by the same inner wall.

[0025] In a further preferred embodiment of the silencer according to the invention, the water separator has a baffle element arranged in the water separation chamber for radially expanding the exhaust gas flow entering through the inlet opening, wherein a heat storage element for temperature control of the baffle element is arranged on the baffle element. In this way, heat can be effectively extracted from the exhaust gas flow impacting the baffle element. The baffle element can be equipped with a heat storage element on its side or surface facing the inlet opening of the water separation chamber. To keep the flow path as unobstructed as possible, the baffle element is preferably provided with a heat storage element on its side or surface facing away from the inlet opening.

[0026] Preferably, the cross-section of the baffle element at its downstream end is larger than the flow cross-section of the inlet opening. This expands the exhaust gas flow into a large volume and allows it to be guided along a large condensation surface. Preferably, the baffle element has a cross-section that increases, particularly 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 baffle element. To promote a uniform and quiet flow, the baffle element can be at least partially rotationally symmetrical. The baffle element can have a conical, frustoconical, or paraboloid flow body. The upstream end of the baffle element can be designed as a particularly rounded tip. Preferably, the baffle element is hollow – e.g.,in the form of a cap with its tip aligned towards the inlet opening, which reduces the material costs and weight of the silencer.

[0027] In a further preferred embodiment of the silencer according to the invention, the water separator has a funnel-shaped guide element arranged in the water separation chamber, which is designed to radially narrow the exhaust gas flow, which has been widened in particular by the baffle element, and in particular to direct it to the outlet opening. A heat storage element for temperature control of the funnel-shaped guide element is arranged on the funnel-shaped guide element. In this way, heat can be effectively extracted from the exhaust gas flow that is channeled through the funnel-shaped guide element. The funnel-shaped guide element can be equipped with a heat storage element on its side or surface facing the inlet opening of the water separation chamber. To keep the flow path as clear as possible, the funnel-shaped guide element is preferably equipped with a heat storage element on its side facing away from the inlet opening.Surface equipped with a heat storage element.

[0028] The funnel-shaped guide element defines a flow channel from its upstream end to its downstream end, with a flow cross-section that decreases continuously. In this way, the exhaust gas flow, which has been widened by the baffle element, is recaptured, and the funnel shape reduces or even prevents the formation of turbulence, such as that which often occurs in the vicinity of sharp corners. This reduces pressure loss in the silencer. Furthermore, water that condenses on the funnel-shaped guide element can slide along its surface due to gravity and thus be discharged, for example, to a drain opening in the water separation chamber. To promote laminar and low-noise 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 flow can pass. This promotes a laminar and low-noise flow and increases the available condensation surface. Specifically, the baffle element and the funnel-shaped guide element are spaced apart from each other in the longitudinal direction of the silencer, i.e., in the main flow direction of the exhaust gas stream.

[0029] In a further preferred embodiment of the silencer according to the invention, the silencer includes a condensation screen that divides or separates the water separation chamber into two sub-chambers. In this way, the exhaust gas flow is forced to pass through the condensation screen arranged in the water separation chamber. The water contained in the exhaust gas flow can condense on the screen material, thereby further increasing the dehumidification efficiency of the water separation device. In particular, the screen material consists of a mesh, wire mesh, wire grid, and / or perforated sheet metal. Preferably, the condensation screen has a mesh size of at least 160 µm, more preferably at least 300 µm, particularly preferably at least 500 µm, and a maximum of 1000 µm, preferably a maximum of 900 µm. Surprisingly, it has been found that good dehumidification results can be achieved with such mesh sizes.Preferably, the condensation screen is arranged downstream of the baffle element, so that the exhaust gas flow is already expanded and guided along the largest possible condensation surface before it encounters 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 it, thus reducing pressure loss due to the flow resistance of the condensation screen. Preferably, the condensation screen has a cylindrical shape. This simple design allows the condensation screen to be optimally positioned in the water separation chamber between the baffle element and the funnel-shaped guide element.Preferably, the condensation screen is mounted on a support structure that separates the impact element from the funnel-shaped guide element. The support structure can include one or more support elements (e.g., in the form of support struts) extending longitudinally along the silencer or in the main flow direction of the exhaust gas stream. Due to its particularly small openings, the condensation screen is susceptible to condensate freezing at low ambient temperatures, so its functionality is particularly enhanced by one or more heat storage elements arranged in the water separation chamber.

[0030] As a further measure, the funnel-shaped guide element can have a bypass that provides a flow path from the water separation chamber to the soundproofing chamber, bypassing the condensation screen. The bypass is preferably dimensioned such that it offers an alternative channel for the exhaust gas flow if the condensation screen becomes clogged (e.g., by frozen condensate). Freezing of the bypass can be prevented or at least delayed by one or more heat storage elements within the soundproofing chamber, particularly in the area of ​​the funnel-shaped guide element.

[0031] In a further preferred embodiment of the silencer according to the invention, it has a water collection chamber that at least partially surrounds the cavity. This chamber is connected to the cavity via a drain opening in such a way that water separated from the exhaust gas stream can flow out of the cavity, particularly by gravity, into the water collection chamber and be collected there. At least one heat storage element is arranged within the water collection chamber to maintain its temperature. In this way, the separated water is, for example, drained from the water separation chamber, thus preventing water accumulation in the water separation device, which could otherwise negatively affect dehumidification. Furthermore, this prevents the accumulated water from being transported by the exhaust gas stream towards the silencer and impairing its function.Reliable water drainage from the water separation chamber is crucial for the silencer's function, as approximately 0.5 liters of water can be separated from the exhaust gas during full-load operation of a 100 kW fuel cell. The water collected in the water collection chamber can be easily drained, either actively (e.g., via a pump) or passively (e.g., by gravity) through a discharge opening. The water collection chamber only needs to surround a small portion of the water separation chamber—for example, a section located at the bottom relative to gravity. Therefore, the water collection chamber can have a significantly smaller internal volume than the water separation chamber. Preferably, the cavity and the water collection chamber are separated by a cavity wall, resulting in a compact silencer design.The heat storage element can prevent or at least delay the freezing of the condensate in the water collection chamber. The heat storage element can extend along at least half, preferably at least two-thirds, of the total length of the water collection chamber.

[0032] Preferably, the cavity extends along a longitudinal central axis and, in particular, is rotationally symmetrical about this axis, with the sound-absorbing device and / or the water separator being arranged centered on the longitudinal central axis. Thus, the exhaust gas flow only needs to change its direction slightly when transitioning from the water separator to the sound-absorbing device, which promotes a uniform and quiet exhaust gas flow. Furthermore, this design allows for a compact silencer construction. In particular, the inlet and outlet openings are arranged centered on the longitudinal central axis. Preferably, the cavity is at least partially, and more preferably completely, cylindrical or composed of several coaxially aligned cylindrical sub-cavities.

[0033] Preferably, the housing and / or structure consists predominantly of a material that is a thermoplastic.

[0034] 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 an exhaust pipe section of the exhaust system can be attached.

[0035] As described above and below, the problem set out at the beginning is also solved by a fuel cell system with the features of claim 13.

[0036] The fuel cell system according to the invention comprises a fuel cell, an exhaust stream leading from the fuel cell, and a silencer according to the invention installed in the exhaust stream. The advantages of the silencer described above and below are thus realized for the fuel cell system.

[0037] It is expressly pointed out that the embodiments of the invention described above can each be combined individually or in any technically meaningful combination with each other with the subject matter of the independent claims.

[0038] Variations and embodiments of the invention as well as further advantages and

[0039] Details of the invention can be found in the following description and drawings. The schematic figures show:

[0040] Fig. 1 shows an embodiment of a fuel cell system according to the invention;

[0041] Fig. 2 shows an embodiment of a silencer according to the invention in a sectional view; and

[0042] Fig. 3 shows a detail of the silencer according to the invention from Fig. 2 in a perspective view.

[0043] Parts that have the same or similar effects are provided with identical reference numerals, if applicable.

[0044] Individual technical features of the embodiments described below can also be combined with previously described embodiments as well as the features of the independent claims and any further claims to create objects according to the invention.

[0045] 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. A silencer 1 according to the invention is arranged in the exhaust system 4 of the fuel cell system 2. An exhaust gas inlet 4a conveys an exhaust gas flow S from the fuel cell 1 to the silencer 1, while an exhaust outlet 4a conveys the dehumidified and noise-reduced exhaust gas flow S away from the silencer 1 – e.g., to an end pipe of the exhaust system 4.

[0046] Fig. 2 shows a cross-sectional view of an embodiment of a silencer 1 according to the invention for an exhaust stream 4 of a fuel cell system 2. 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 this case runs parallel to the longitudinal center axis A and to the longitudinal direction L of the silencer 1. A sound-absorbing device 20 is arranged within the cavity 10 to reduce the noise of the exhaust gas flow S. The sound-absorbing device 20 has a sound-absorbing chamber 21 extending along the longitudinal direction L and radially bounded by an inner wall 130 of the housing 13, through which the exhaust gas flow S can flow from an inlet opening 211 to an outlet opening 212 of the sound-absorbing chamber 21.Within cavity 10, several heat storage elements 50, 50a, 50b, 50c, 50d containing a phase-change material are arranged. During operation, heat from the exhaust gas stream S is stored in the heat storage elements 50, 50a, 50b, 50c, 50d, primarily as latent heat, and released again when the outside temperature or operating temperature drops (e.g., due to a reduction or cessation of the exhaust gas stream S). In this way, the cooling of the silencer 1 can be delayed, which counteracts the freezing of condensate originating from the moist exhaust gas.

[0047] In the soundproof chamber 21, the inner wall 130 is lined with a heat storage element 50 for temperature control of the soundproof chamber 21. The heat storage element 50 extends along the entire length L2 of the soundproof chamber 21 and completely around the longitudinal central axis A. In this way, the heat storage element 50 can interact effectively with the exhaust gas S flowing through the soundproof chamber 21. Furthermore, the heat storage element 50 forms a thermal barrier against the external environment of the silencer 1.

[0048] In this case, the sound attenuation device 20 forms a combination of a reflection silencer and an absorption silencer. However, the sound attenuation device 20 can also be a purely reflection silencer or an absorption silencer. The heat storage elements 50, 50a, 50b, 50c, 50d shown here can also be combined with these types of silencers.

[0049] In the sound attenuation device 20 shown here as an example, a direct flow path between the inlet opening 211 and the outlet opening 212 is blocked by a flow guide device 23 arranged within the sound attenuation chamber 21. The flow guide device 23 has a widening element 231 arranged downstream of the inlet opening 211 for radially widening at least a portion of the exhaust gas flow S through the inlet opening 211 in the direction of the inner wall 130. Downstream of the widening element 231, the flow guide device 23 forms a backflow channel 230 by means of its two partially overlapping pipe sections 232, 233, within which a flow path is provided for the exhaust gas flow S, the flow direction SR of which is opposite to the main flow direction R.The flow guide device 23 thus forms a labyrinthine propagation path for the exhaust gas flow S, along which the exhaust gas flow S is deflected at least twice, thereby extracting some of its sound energy. The expansion element 231 has a perforated area 231a which is aligned with the inlet opening 211.

[0050] The flow guide 23 directs the expanded portion Sa of the exhaust gas stream S close to the inner wall 130, where the heat storage element 50 for temperature control of the sound-absorbing chamber 21 is located. The heat storage element 50 is covered on its side facing away from the inner wall 130 with a layer 22 of a sound-absorbing material. The sound-absorbing material is at least partially fluid-permeable, so that the expanded portion Sa of the exhaust gas stream S can interact with both the sound-absorbing material and the heat storage element 50. The heat storage element 50 and / or the layer 22 of sound-absorbing material can be held in the vicinity of the inner wall 130 by a fluid-permeable support structure (not shown here) comprising one or more support elements.The layer 22 of sound-absorbing material extends along the length L2 of the sound-absorbing chamber completely around the flow guide device 23. Furthermore, a water separator 30 for separating water from the exhaust gas stream S is arranged within the cavity 10 upstream of the sound-absorbing device 20. The water separator 30 has a water separation chamber 31 through which the exhaust gas stream S can flow along the main flow direction R from an inlet opening 38 to an outlet opening 39 of the water separation chamber 31. Several heat storage elements 50a, 50b are arranged within the water separation chamber.

[0051] In the water separation chamber 31, an inner wall 130a, radially bounding the water separation chamber 31, is lined with a heat storage element 50a for temperature control of the water separation chamber 31. The heat storage element 50a extends along the entire length of the water separation chamber 31 and completely around the longitudinal central axis A. In this way, the heat storage element 50a can interact effectively with the exhaust gas S flowing through the water separation chamber 31. Furthermore, the heat storage element 50a forms a thermal barrier against the external environment of the silencer 1.

[0052] 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 this case, the cavity 10 is cylindrical. The water separator 30 and the silencer 20 are arranged centered on the longitudinal center axis A. This promotes a uniform and quiet exhaust gas flow, as it avoids a change in the main flow direction R (flow reversal). The advantageous flow characteristics are further enhanced by the fact that the inlet opening 11 and the outlet opening 12 are arranged centered on the longitudinal center axis A.

[0053] The silencer 1 has a housing 13 that defines the outer surface of the cylindrical cavity 10. In this case, the housing 13 also 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 design of the silencer 1, in particular the rotational symmetry of the individual components of the silencer 1 about the longitudinal center axis A, particularly simple manufacturing is possible.

[0054] Within the water separation chamber 31, a baffle element 32 is arranged to radially expand the exhaust gas flow S entering through the inlet opening 11. The exhaust gas flow S can be directed from the fuel cell 3 into the cavity 10 via an exhaust gas supply line 4a (Fig. 1) of the exhaust system 4, which can be attached to the inlet nozzle 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 bounding the water separation chamber 31. A heat storage element 50b is arranged on the baffle element 32 for temperature control. In this way, heat can be effectively extracted from the exhaust gas flow (S) impacting the baffle element 32. In order to avoid influencing the flow path as much as possible, the heat storage body 50b is arranged on one side of the impact element 32 facing away from the inlet opening 11.

[0055] The shape of the baffle element 32, i.e., its cross-section which increases continuously from its upstream end 321 to its downstream end 322, causes a gradual radial widening of the exhaust gas flow S at the outer surfaces of the baffle element 32. To achieve sufficient radial widening of the exhaust gas flow S, the cross-section of the baffle 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 baffle element 32 is essentially rotationally symmetric and has a conical flow body with a rounded tip. The baffle element 32 is hollow to reduce its weight.

[0056] Downstream of the baffle element 32, a funnel-shaped guide element 33 is arranged to radially narrow the exhaust gas flow S, which has been widened by the baffle element 32. This ensures that the exhaust gas flow S is guided along the largest possible surface area, allowing any water contained in the exhaust gas to condense. The exhaust gas flow S is thus largely dehumidified before it is fed to the sound-absorbing device 20. A heat storage element 50c for tempering the funnel-shaped guide element 33 is arranged on the funnel-shaped guide element. In this way, heat can be effectively extracted from the exhaust gas flow S, which is channeled through the funnel-shaped guide element 33. To minimize any influence on the flow path, the heat storage element 50c is arranged on the side of the baffle element 33 facing away from the inlet opening 11, i.e., in this case, within the sound-absorbing chamber 21.

[0057] The funnel-shaped guide element 33 defines a flow channel with a continuously decreasing cross-sectional area from its upstream end 331 to its downstream end 332. In this way, the exhaust gas flow S, which has been widened by the baffle element 32, is recaptured, with the funnel shape reducing or even preventing the formation of turbulence and the associated pressure loss. Furthermore, condensed water can, due to gravity, slide along the surface of the guide element 33, for example, towards the outlet opening 41, and thus be more efficiently discharged. To promote laminar and low-noise flow, the funnel-shaped guide element 33 is rotationally symmetrical about its 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 low-noise flow and increases the available condensation surface. To achieve the most compact possible design of the silencer 1, the funnel-shaped guide element 33 forms a partition between the water separation chamber 31 and a sound-absorbing chamber 21 of the silencer 30. The baffle element 32 and the funnel-shaped guide element 33 are spaced apart from each other in the longitudinal direction of the silencer 1 and in the main flow direction R of the exhaust gas stream S, respectively. The funnel-shaped guide element 33 is designed to direct the narrowed exhaust gas stream S to the silencer 20; that is, the downstream end 332 of the funnel-shaped guide element 33 connects directly to the sound-absorbing chamber 21.

[0058] The silencer 1 has a condensation screen 34 that separates the water separation chamber 31 into two sub-chambers 311 and 312. To pass from the first sub-chamber 311 to the second sub-chamber, the exhaust gas stream S must pass through the condensation screen 34, allowing the water contained in the exhaust gas stream S to condense on the screen material. The screen material can be made of a mesh, wire mesh, wire grid, and / or perforated sheet metal.

[0059] The condensation screen 34 is arranged downstream of the baffle element 32, so that the exhaust gas flow S is already expanded and guided along the largest possible condensation surface before it encounters the condensation screen 34. Furthermore, the condensation screen 34 is partially located 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 from the funnel-shaped guide element 33 onto the condensation screen 34 and compressed before passing through it, thus reducing pressure loss due to the flow resistance of the condensation screen 34. The condensation screen 34 has a cylindrical shape. The condensation screen 34 can be supported by a support structure (not shown) that separates the baffle element 32 from the funnel-shaped guide element 33.Due to its particularly small openings, the condensation screen 34 is susceptible to condensate freezing at low outside temperatures, so its functionality is particularly enhanced by the heat storage elements 50a, 50b, which are arranged in the water separation chamber 31.

[0060] The funnel-shaped guide element 33 has a bypass 33a in the form of a through-hole, which bypasses the condensation screen 34 and provides a flow path from the water separation chamber 31 to the sound attenuation chamber 21. The bypass 33a is dimensioned such that, in the event that the condensation screen 34 is blocked, e.g., by frozen condensate, it provides an alternative channel for the exhaust gas flow S.

[0061] The silencer 1 has a water collection chamber 40 that partially surrounds the cavity and is connected to the cavity 10 via several drain openings 41, 41a, 41b, 41c in such a way that water separated from the exhaust gas stream S in the water separation chamber 31 and also in the sound attenuation chamber 21 can flow into the water collection chamber 40 under its own weight due to gravity and be collected there. The separated water can thus drain optimally from the cavity. The shape of the baffle element 32 and the shape of the funnel-shaped guide element 33 promote a directed flow of the separated water towards the drain opening 41. A heat storage element 50d is arranged inside the water collection chamber 40 for temperature control, which prevents or at least delays the freezing of the condensate in the water collection chamber 40.The heat storage body 50d extends along the entire length of the water collection chamber 40.

[0062] The water collected in the water collection chamber 40 can be easily discharged from the water collection chamber or the silencer 1, either actively – e.g., by a pump – or passively – e.g., by gravity – via a discharge opening 42. The water collection chamber 40 only needs 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, viewed from a direction parallel to the longitudinal center axis A, can be situated approximately between a "5 o'clock position" and a "7 o'clock position". 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, resulting in a compact design for the silencer 1.A wall delimiting the water collection chamber 40 can also be part of the housing 13 and, in particular, can be formed integrally with it. 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.

[0063] The water collection chamber 40 further surrounds the sound-absorbing chamber 21 and is in fluid-conducting communication with the sound-absorbing chamber 21 via openings 41a, 41b, 41c such that water condensed from the exhaust gas stream S can flow from the sound-absorbing chamber 21 into the water collection chamber 40 by gravity. In this way, water accumulation in the sound-absorbing device 20 is avoided, which could otherwise negatively affect the noise reduction.

[0064] To provide sufficient intake capacity, the water collection chamber 40 extends essentially along the entire length of the cavity 10.

[0065] Fig. 3 shows the heat storage element 50 for temperature control of the sound-absorbing chamber 21 in detail. The heat storage element 50 has a plurality of sealed chambers 52, each filled with the phase-change material. The heat storage element 50 has a planar support 51 made of a polymeric material, on which the plurality of chambers 52 are arranged. The chambers are arranged at regular intervals on a first side 511 of the support 41. The support 51 has a thickness that is less than the height of the individual chambers 52 and is flexible. In this case, the chambers 52 have a circular base, so that the planar support 51 can be bent in all directions and thus adapted to various curved surfaces. In this case, the support 51 is cylindrically bent.The cylindrical shape can be produced, for example, from a flat, rectangular heat storage body by joining two opposite edges of the heat storage body together at a joint 513. Alternatively, the chambers 52 could also have a strip-shaped base extending in the longitudinal direction L. A second side 512, or rear side, of the support 51, facing away from the first side 511, is essentially flat, i.e., it has no protrusions. In this way, the heat storage body 50 can be particularly well attached to various surfaces.

[0066] The spatial and physical features of the heat storage body 50 shown in Fig. 3 for temperature control of the sound-absorbing chamber 21 described above can be transferred analogously, individually or in any combination, to the other heat storage bodies 50a, 50b, 50c, 50d. It should be further noted that "having" does not exclude any other elements or steps, and "a" or "an" does not exclude a plurality.

[0067] The scope of protection 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.

[0068]

[0069] 1 silencer

[0070] 2 Fuel cell system

[0071] 3 Fuel cell

[0072] 4 Exhaust system

[0073] 4a Exhaust gas supply line of the exhaust system

[0074] 4b Exhaust gas discharge of the exhaust system

[0075] 5 Hydrogen

[0076] 6 air

[0077] 10 Cavity of the silencer

[0078] 11 Inlet opening of the cavity

[0079] 12 Cavity outlet opening

[0080] 13 Silencer housing

[0081] 130 Inner wall of the housing

[0082] 14 Structure of the silencer

[0083] 15. Silencer cover

[0084] 20. Silencing device of the silencer

[0085] 21 Sound damping chamber of the sound damping device

[0086] 210 Longitudinal section of the sound-absorbing chamber

[0087] 211 Inlet opening of the soundproof chamber

[0088] 212 Outlet opening of the sound attenuation chamber

[0089] 22 layers of sound-absorbing material

[0090] 23 Flow guide device of the sound damping device

[0091] 231 Expansion element

[0092] 231 a perforated area of ​​the expansion element

[0093] 232 first pipe section

[0094] 233 second pipe section

[0095] 30 Water separator device

[0096] 31 Water separation chamber of the water separation device

[0097] 311 first sub-chamber of the water separation chamber

[0098] 312 second sub-chamber of the water separation chamber

[0099] 32 Impact element of the water separator device

[0100] 321 upstream end of the impact element

[0101] 322 downstream end of the impact element

[0102] 33 funnel-shaped guide element of the water separator device

[0103] 33a Bypass in the funnel-shaped guide element

[0104] 331 Upstream end of the funnel-shaped guide element 332 Downstream end of the funnel-shaped guide element

[0105] 34 Condensation screen of the water separator

[0106] 38 Inlet opening of the water separation chamber

[0107] 39 Outlet opening water separator chamber

[0108] 40 Water collection chamber of the silencer

[0109] 41 Drainage opening of the water collection chamber

[0110] 41 openings of the water collection chamber

[0111] 42 Drainage opening of the water collection chamber

[0112] 50 heat storage elements for temperature control of the soundproof chamber

[0113] 50a Heat storage body for temperature control of the water separation chamber

[0114] 50b Heat storage body for tempering the impact element

[0115] 50c heat storage body for tempering the funnel-shaped guide element

[0116] 50d heat storage body for temperature control of the water collection chamber

[0117] A Longitudinal center axis of the silencer

[0118] G Direction of gravity

[0119] L Longitudinal direction of the silencer

[0120] R Main flow direction of the exhaust gas stream

[0121] S Exhaust gas flow

[0122] Sa widened part of the exhaust stream

[0123] SR Flow direction

Claims

Patent claims 1. Silencer (1), in particular for an exhaust system (4) of a fuel cell system (2), with - a cavity at least partially bounded by a housing (13) (10), through which an exhaust gas flow (S) of the fuel cell system (2) passes along a main flow direction (R) from an inlet opening (11 ) can flow to an outlet opening (12) of the cavity (10), - a sound-absorbing device (20) arranged within the cavity (10) for reducing noise of the exhaust gas flow (S), wherein the sound-absorbing device (20) has a sound-absorbing chamber (21) extending along a longitudinal direction (L) and radially bounded by an inner wall (130) of the housing (13), through which the exhaust gas flow (S) can flow from an inlet opening (211) to an outlet opening (212) of the sound-absorbing chamber (21), - containing at least one heat storage body (50, 50a, 50b, 50c, 50d) arranged within the cavity (10) containing a phase change material.

2. Silencer (1) according to claim 1, wherein the at least one heat storage body (50, 50a, 50b, 50c, 50d) has a plurality of enclosed chambers (52) each filled with the phase change material.

3. Silencer (1 ) according to claim 2, wherein the at least one heat storage body (50, 50a, 50b, 50c, 50d) has a planar support (51 ) made of a polymeric material in which and / or on which the plurality of chambers (52) is arranged.

4. Silencer (1) according to one of the preceding claims, wherein the carrier (51) has a first side (511) and a second side (512) facing away from the first side (511), wherein the second side (512) is planar.

5. Silencer (1 ) according to one of the preceding claims, wherein in the soundproofing chamber (21 ) the inner wall (130) is lined with a heat storage body (50) for temperature control of the soundproofing chamber (21 ).

6. Silencer (1 ) according to claim 5, wherein one of the preceding claims, wherein the heat storage body (50) for tempering the sound absorption chamber (21 ) is covered on its side facing away from the inner wall (130) with a layer (22) of a sound-absorbing material.

7. Silencer (1) according to one of the preceding claims with a water separator (30) arranged within the cavity (10) upstream of the silencer (20) for separating water from the exhaust gas stream (S), wherein the water separator (30) has at least one water separation chamber (31) through which the exhaust gas stream (S) can flow along the main flow direction (R) from an inlet opening (38) to an outlet opening (39) of the water separation chamber (31), within which at least one heat storage element (50a, 50b) is arranged.

8. Silencer (1 ) according to claim 7, wherein in the water separation chamber (31 ) an inner wall (130a) radially limiting the water separation chamber (31 ) is lined with a heat storage body (50a) for tempering the water separation chamber (31 ).

9. Silencer (1 ) according to claim 7 or 8, wherein the water separator device (30) has a baffle element (32) arranged in the water separator chamber (31 ) for radially widening the exhaust gas flow (S) entering through the inlet opening (38), wherein a heat storage body (50b) for tempering the baffle element (32) is arranged on the baffle element (32).

10. Silencer (1 ) according to one of claims 7 to 9, wherein the water separator device (30) has a funnel-shaped guide element (33) arranged in the water separator chamber (31 ), which is designed to radially narrow the exhaust gas flow (S) and in particular to direct it to the outlet opening (38), wherein a heat storage body (50c) for tempering the funnel-shaped guide element (33) is arranged on the funnel-shaped guide element (33).

11. Silencer (1) according to one of claims 7 to 10 with a condensation screen (34) separating the water separation chamber (31) into two sub-chambers (311, 312).

12. Silencer (1) according to one of the preceding claims with a water collection chamber (40) at least partially surrounding the cavity (10), which is in fluid-conducting communication with the cavity (10) via a drain opening (41) such that water separated from the exhaust gas stream (S) can flow out of the cavity (10), in particular due to gravity, into the water collection chamber (40) and be collected there, wherein at least one heat storage element (50d) is arranged within the water collection chamber (40) for temperature control of the water collection chamber (40).

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

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