Patent Application
20230378494
This application claims priority of German patent application no. 10 2022 112 680.3, filed May 20, 2022, the entire content of which is incorporated herein by reference.
The present disclosure relates to a fuel-cell exhaust system via which the process gas discharged from a fuel cell can be discharged to the environment as fuel-cell exhaust gas.
In order, in particular in the case of vehicles powered by electric motors, to enable the provision of the energy to operate the electric drive motors and also the other electrical energy loads in such vehicles, it is known to use fuel cells. In the operation of such a fuel cell, hydrogen, or an anode gas highly enriched with hydrogen, is supplied to an anode region. Oxygen, or air containing oxygen, is supplied as cathode gas to a cathode region. Electric current is generated, with hydrogen and oxygen being converted into water. The hydrogen-depleted anode exhaust gas and the water-enriched cathode exhaust gas leave the fuel cell as fuel-cell exhaust gas, or process gas. During operation of the fuel cell, at least the cathode exhaust gas is discharged to the environment. In various operating phases such as, for example, during purging, in particular of the anode region before the start of operation of the fuel cell, the anode exhaust gas, or the gas conducted through the anode region in such an operating phase, can also be discharged to the environment.
It is an object of the present disclosure to provide a fuel-cell exhaust system for a fuel-cell arrangement, in particular in a vehicle, by which liquid, in particular water, entrained in the fuel-cell exhaust gas can be efficiently extracted from the fuel-cell exhaust gas.
This object is achieved, according to the disclosure, by a fuel-cell exhaust system for a fuel-cell arrangement, in particular in a vehicle, including a fuel-cell exhaust line through which fuel-cell exhaust gas can flow and a condenser unit having a condenser-unit body through which the fuel-cell exhaust gas can flow.
With the condenser unit, liquid is condensed out of the fuel-cell exhaust gas. This prevents fuel-cell exhaust gas, which in particular is enriched with water vapor, from being discharged to the environment, such that in particular the formation of a mist in the region of a tailpipe of a fuel-cell exhaust system can be avoided. The liquid extracted from the fuel-cell exhaust gas can be fed back into the fuel-cell process if required. It is also possible to use the condensed-out liquid, for example, as windshield washer water, for cleaning sensors in particular in vehicles for autonomous driving, for air humidification in air conditioning systems and the like.
There may be a liquid separating unit arranged downstream of the condenser unit. As a result of the condenser unit being arranged upstream of a liquid separating unit, it is ensured that condensed-out liquid, that is, droplets, can be efficiently separated from the fuel-cell exhaust gas in the liquid separating unit arranged further downstream and, if necessary, can be reused for various processes, for example in a vehicle, or can be discharged to the environment in liquid form.
For particularly efficient separation of liquid from the fuel-cell exhaust gas, it is proposed that the condenser-unit body be constructed substantially entirely with metal material or/and include at least one condenser-unit line element, preferably having a flattened flow cross-section, through which the fuel-cell exhaust gas can flow and around which a cooling medium can flow on an outer side.
In order to obtain the largest possible surface area for thermal interaction between the condenser unit and a cooling medium, the condenser-unit body may include a plurality of mutually parallel condenser-unit line elements through which the fuel-cell exhaust gas can flow.
For enhanced heat dissipation in this case, there may be a plurality of heat transfer fins provided on the outside of at least one, preferably each, condenser-unit line element.
For the purpose of integrating the condenser unit into the fuel-cell exhaust line, it is proposed that the condenser unit include an upstream condenser-unit connection element, connected to the condenser-unit body, for connecting the condenser unit to the fuel-cell exhaust line, or/and that the condenser unit include a downstream condenser-unit connection element, connected to the condenser-unit body, for connecting the condenser unit to the fuel-cell exhaust line.
For a structure that is lightweight, inexpensive to manufacture and in particular corrosion-resistant, the upstream condenser-unit connection element may be constructed with plastic material, or/and the downstream condenser-unit connection element may be constructed with plastic material.
The fuel-cell exhaust line may include an upstream line portion leading to the liquid separating unit, and a downstream line portion leading away from the liquid separating unit. The condenser unit in this case may be arranged in the upstream line portion.
For the purpose discharging liquid from the fuel-cell exhaust stream downstream of the condenser unit, the liquid separating unit may include an upstream separating line part, a downstream separating line part and an opening region in the region of the downstream separating line part adjacent to the upstream separating line part.
In order to ensure defined flow conditions for the fuel-cell exhaust gas also in the region of the liquid separating unit, it is proposed that an upstream end portion of the downstream separating line part be positioned to engage in a downstream end portion of the upstream separating line part, in such a manner that a liquid separating opening of the opening region is formed between the upstream end portion of the downstream separating line part and the downstream end portion of the upstream separating line part.
The opening region may be open to a liquid collecting chamber, via which the liquid collected therein can then either be discharged to the environment or fed back into the fuel cell process if required.
There may be a swirl flow generation unit provided upstream of the opening region. The generation of a swirl flow in the fuel-cell exhaust flow creates a centrifugal force that acts upon the condensed liquid, forces the liquid radially outward and thus has the effect that it is primarily the liquid conveyed radially outward, or a portion of the fuel-cell exhaust flow highly enriched with such liquid, that is drawn off in the opening region.
The swirl flow generation unit may include a plurality of flow deflector elements that succeed one another in the circumferential direction with respect to a flow center axis and are pitched with respect to the exhaust-gas main flow direction. In order to provide a very lightweight structure, the swirl flow generation unit may also be constructed substantially entirely with plastic material.
In order to muffle noise produced in the region of a fuel cell, a muffler unit may be provided, including:
The muffler unit also may be constructed substantially entirely with plastic material, in order to obtain a lightweight and corrosion-resistant structure that can be realized inexpensively.
Likewise, the fuel-cell exhaust line and/or the liquid separating unit may be constructed substantially entirely with plastic material.
The invention will now be described with reference to the drawings wherein:
The fuel-cell exhaust system 10 includes a fuel-cell exhaust line 12, denoted in general by 12, through which fuel-cell exhaust gas B can flow, and a muffler unit 14 integrated into the fuel-cell exhaust line 12. An upstream line portion 16 of the fuel-cell exhaust line 12 connects to the muffler unit 14 in a fuel-cell exhaust inlet region 18 of a muffler housing 20. In a fuel-cell exhaust outlet region 22 of the muffler housing 20, a downstream line portion 24 of the fuel-cell exhaust line 12 connects to the muffler unit 14. For example, the fuel-cell exhaust gas B discharged from one or more fuel cells of a fuel-cell system can be discharged to the environment via the downstream line portion 24 of the fuel-cell exhaust line 12. An upstream end region 26 of the upstream line portion 16 of the fuel-cell exhaust line 12 may be configured to be connected to different system regions of one or more fuel cells, or fuel cell stacks, discharging fuel-cell exhaust gas as process gas.
For example, the anode region and/or the cathode region of the fuel cell, or of each fuel cell, may be connected to the upstream end region in order to introduce the process gas leaving the anode region and/or the process gas leaving the cathode region, as fuel-cell exhaust gas B, into the fuel-cell exhaust system 10 in a defined manner. Furthermore, ambient air may be introduced into the fuel-cell exhaust system 10, for example via a line region that is open to the environment.
To set the back-pressure generated in the fuel-cell exhaust system 10, or also the gas flows introduced into it, a gas flow regulating valve 28 may be arranged, for example, near the upstream end region 26 of the upstream line portion 16 of the fuel-cell exhaust system 12. A hydrogen sensor 30 may be provided in the downstream line portion 24 to provide information about the hydrogen concentration of the fuel-cell exhaust stream flowing through the downstream line portion 24. This stream can contain hydrogen, in particular if the anode region is purged at the beginning, or before the beginning, of the operation of fuel-cell and the process gas discharged from the anode region is discharged to the environment via the fuel-cell exhaust system 10. If the signal generated by the hydrogen sensor 30 indicates an excessively hydrogen concentration, a proportion of air, or an increased proportion of air, may be added to the fuel-cell exhaust gas B conducted through the fuel-cell exhaust system 10, for example by controlling the gas flow regulating valve 28 accordingly, in order thus to achieve a lower hydrogen concentration.
Upstream of the muffler unit 14, a condenser unit, denoted in general by 31, may be provided, which supports the condensing-out of liquid, or vapor, generally water vapor, transported in the fuel-cell exhaust gas B. In the muffler unit 14, as described below, such condensed liquid can be extracted from the fuel-cell exhaust gas B, collected and fed back into the fuel-cell process.
The structure, or function, of the muffler unit 14 is explained in detail below with reference to
The muffler housing 20 is elongate in the direction of a muffler-housing longitudinal axis L, and is configured, in an upstream end region 32, for connection of the upstream line portion 16 of the fuel-cell exhaust line 12. In a downstream end region 34, the muffler housing 20 is configured for connection of the downstream line portion 24 of the fuel-cell exhaust line. For example, the line portions 16, 24 may be interfaced to corresponding connection pieces of the muffler housing 20 by the use of pipe clamps or the like.
Formed inside the muffler housing 20 are two muffler chambers 36, 38, as well as a liquid separating chamber 40. The upstream muffler chamber 36 is separated from the liquid separating chamber 40 by a dividing wall 42, and the downstream muffler chamber 38 is separated from the upstream muffler chamber 36 by a dividing wall 44. The downstream line portion 24 of the fuel-cell exhaust line 12 is open to the downstream muffler chamber 38. The upstream line portion 16 of the fuel-cell exhaust line 12 is open to the two muffler chambers 36, 38 via a liquid separating line portion 46 of a liquid separating unit, denoted in general by 45, arranged in the liquid separating chamber 40. The separating line portion 46 of the liquid separating unit 45 includes a tubular upstream separating line part 48 connecting to the upstream line portion 16 of the fuel-cell exhaust line 12 in the upstream end region 32 of the muffler housing 20, as well as a downstream separating line part 50 connecting to, or passing through, the dividing wall 42. The downstream separating line part 50 of the separating line portion 46 may connect to, or be realized integrally with, a single-piece or multi-piece fuel-cell exhaust pipe 52 extending inside the muffler housing 12. The fuel-cell exhaust pipe 52 is open to the upstream muffler chamber 36 via a plurality of openings 56 realized in a pipe wall 54 of the fuel-cell exhaust pipe 52. The fuel-cell exhaust pipe 52 is open to the downstream muffler chamber 38 via a plurality of openings 58 realized in the pipe wall 54. The fuel-cell exhaust pipe 52 extends through the dividing wall 44 that separates the two muffler chambers 36, 38 from each other, or it may be realized integrally with it, at least partially, and connect, in the downstream end region 34 of the muffler housing 20, to the downstream line portion 24 of the fuel-cell exhaust line 12.
It can be seen in this structure that the fuel-cell exhaust gas B conducted through the muffler unit 14 can flow through the muffler housing 20, substantially without flow deflection, in a straight line along the longitudinal axis L of the muffler housing, such that no significant flow resistance is generated by the muffler unit 14. Nevertheless, it is possible to muffle sound by reflection and absorption as a result of the communication with the various muffler chambers 36, 38. For this purpose, for example additional sound-muffling material such as, for example, porous fibrous or foamed material, may be arranged in one or both muffler chambers 36, 38. It is to be noted that more than two successive muffler chambers may also be provided, or also that only a single such muffler chamber may be provided in the interior of the muffler housing 20. Furthermore, at least one of the muffler chambers may act as a resonator chamber of a Helmholtz resonator, and different ones of the muffler chambers may communicate with each other via additional fuel-cell exhaust pipes.
The upstream separating line part 48 has a downstream end portion 60 that widens, for example, substantially conically in the direction of an exhaust-gas main flow direction H along a flow center axis S. At the same time, the downstream separating line part has an upstream end portion 62, which widens, for example, conically in the exhaust-gas main flow direction H in this region, and is positioned to engage in the downstream end portion 60 of the upstream separating line part 48. A substantially annular liquid separating opening 66 is formed in an opening region 64 of the separation line section 46, between the end portions 60, 62 that widen radially in the exhaust-gas main flow direction H along the flow center axis S.
Upstream of the opening region 64, a swirl flow generating unit 68 is arranged, for example, in the upstream separating line part 48, which is realized integrally with a housing cover that provides an upstream end wall of the muffler housing 20, or in the upstream line portion 16 of the fuel-cell exhaust line 12. This unit may include a plurality of substantially radially extending flow deflector elements 69 that succeed one another in the circumferential direction about the flow center axis S and are pitched with respect to the exhaust-gas main flow direction H. The swirl flow generation unit 68 generates a swirl flow in the fuel-cell exhaust gas B conducted in the exhaust-gas main flow direction H. Due to this swirl flow and the centrifugal forces created therein, liquid components transported in the fuel-cell exhaust gas B, for example water droplets or the like, are forced radially outward and accumulate at a concentration in the radially outer region of the fuel-cell exhaust-gas flow. This radially outer part of the fuel-cell exhaust-gas flow can be drained at least partially through the liquid separating opening 66 into the liquid separating chamber 40, such that liquid extracted from the fuel-cell exhaust-gas flow can accumulate in the liquid separating chamber 40.
A liquid collecting chamber 70 is formed in what is a lower region of the muffler housing 20 in a vertical direction V when the fuel-cell exhaust system 10 has been mounted in a vehicle. This chamber can preferably extend along the entire length of the muffler housing 20, from the upstream end region 32 to the downstream end region 34 thereof, and is separated from the two muffler chambers 36, 38 and also from the liquid separating chamber 40 by a housing base 72. In association with each of these chambers, there is respectively at least one liquid passage opening 74, 76 and 78, respectively realized in the housing base 72. Liquid accumulating in each of the muffler chambers 36, 38 and also the liquid separating chamber 40 can pass through the associated liquid passage openings 74, 76, 78 into the liquid collecting chamber 40 and accumulate there.
At least one liquid drain opening 80 having a liquid discharge valve 82 is provided in association with the liquid collecting chamber 70. It can be seen in
A liquid level sensor 84, represented schematically in
If this quantity is sufficiently large to allow the liquid, that is, water, to be used in fuel cell operation or in other systems of a vehicle, the liquid discharge valve 82 can be opened. Also, if a threshold level is exceeded and there is a risk that fluid can no longer flow into the fluid collecting chamber 70 from at least the lowest region of the downstream muffler chamber 38, the fluid discharge drain 82 can be opened to discharge fluid from the fluid collection chamber 70.
Furthermore, a heating unit 86 represented schematically in
Furthermore, at least one hydrogen discharge opening 89, constituted by a hydrogen discharge nozzle 88, may be provided in association with the liquid collecting chamber 70. This hydrogen discharge opening 89 may be positioned in such a way that it is higher in the vertical direction V than the highest region of the liquid collecting chamber 70. Hydrogen introduced into the fuel-cell exhaust system 10 during fuel-cell operation, or during purging of the anode region, can thus, when it enters the liquid collecting chamber 70 via the liquid passage openings 74, 76, 78, accumulate in the highest region of the liquid collecting chamber 70, in which the liquid collecting chamber 70 is open to the environment via the hydrogen discharge opening 89. Thus, hydrogen entering the liquid collecting chamber 70 can be substantially permanently discharged to the environment without the risk of a critical hydrogen concentration being formed in the liquid collecting chamber 70.
The condenser unit 31 includes a condenser-unit body 90, represented in longitudinal section in
The surface available for heat transfer to a medium M, for example air, flowing around the condenser-unit body 90 may be further increased by providing heat transfer fins 98 on an outer side of the condenser-unit line elements 92, 94, 96, which can preferably be oriented substantially parallel to a flow direction of the medium M flowing around the condenser-unit body 90, in order to ensure the fastest possible flow-around, and thus efficient heat removal. For example, the heat transfer fins 98 may be constituted by fin elements 91, 93, 97, 99, realized on the flat outer sides of the condenser-unit line elements 92, 94, 96, for example in the form of corrugations, which are in heat transfer contact with at least one of the condenser-unit line elements 92, 94, 96. Alternatively, the heat transfer ribs 98 may be formed by moldings in the body material of the condenser-unit line elements 92, 94, 96, which are also formed on the inside, that is, on the surface over which the fuel-cell exhaust gas B flows, in order to provide an enlarged surface for heat transfer there as well.
If air, that is, ambient air, is used as the medium M used for cooling, the fuel-cell exhaust system 10 is installed in a vehicle in such a way that, similar to the case with a vehicle radiator, the air transported by the vehicle airstream can flow efficiently around the condenser unit 31.
It is to be noted that, as an alternative to air flowing around the condenser-unit body, it is also possible, for example, for a liquid to flow around it, in order to absorb heat in this liquid and to enable it to be transferred, for example in a further heat exchanger, to the air to be introduced in a vehicle interior.
For the purpose of integrating the condenser unit 31 into the upstream line portion 16 of the fuel-cell exhaust line 12, the condenser unit 31 has an upstream condenser-unit connection element 100 and a downstream condenser-unit connection element 102. Via respective plate-type coupling regions 104 and 106, these can be interfaced in a gas-tight and liquid-tight manner to respective plate-type coupling regions 108, 110 of the condenser-unit body 90, for example, by screw connection.
Whereas, for the most efficient heat transfer, the condenser-unit body 90 is produced from metal material such as, for example, high-grade steel or copper, substantially all other functional regions of the fuel-cell exhaust system may be constructed with inexpensive and also lightweight plastic material. This applies in particular to the line portions 16, 24, the muffler housing 20, or the system regions arranged inside it, such as, for example, the dividing walls 42, 44, all functional parts of the liquid separating unit 45 and the swirl flow generating unit 68. The use of plastic material for these components results in a structure of low weight which, moreover, can be produced at low cost and with a large degree of freedom in shaping. Due to the fact that the fuel-cell exhaust gas B contains a comparatively high proportion of liquid, in particular water, corrosion problems in the region of the fuel-cell exhaust system 10 are thus substantially completely eliminated.
A fuel-cell exhaust system according to the disclosure combines functions that are advantageous, or relevant, for its operation, or for the operation of a fuel-cell system in a vehicle. On the one hand, the muffling function of the muffler unit ensures that noise on the flow path of the fuel-cell exhaust gas caused, for example, by the compressors guiding the process gas through the fuel cell, is reduced or almost completely excluded. On the other hand, it is possible to extract a portion of the liquid entrained in the fuel-cell exhaust gas, that is, in particular water, from the fuel-cell exhaust gas, such that the extracted portion of the liquid is not expelled as liquid vapor into the environment with the fuel-cell exhaust gas, but can either be discharged into the environment in liquid form or, if required, fed back into the operating cycle of a fuel-cell system or other systems. The occurrence of a critical hydrogen concentration, in particular in the region of the muffler unit, is avoided by the permanent possibility of discharging hydrogen to the environment. Also contributing to this functionality, in particular, is the fact that the fuel-cell exhaust gas can flow through the muffler unit substantially in a straight line. This avoids pronounced bends in pipe portions carrying the fuel-cell exhaust gas, in particular inside the muffler unit, and the resulting flow deflections.
Since water, or water vapor, and hydrogen can be drained from the fuel-cell exhaust gas during operation of a fuel-cell system and, if necessary, fed back into the fuel-cell process, for example, excessive loading of the environment of a vehicle with such substances is avoided as far as possible.
It is to be noted that such a fuel-cell exhaust system may also be used in stationary fuel-cell systems or, for example, in fuel-cell systems provided in ships or the like.
It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 112 680.3 | May 2022 | DE | national |
