Fuel cell system comprising a fuel cell stack and a flow assembly for supplying a medium flow to the fuel cell stack - Patents.com

Abstract

The present invention relates to a fuel cell system (50) comprising a fuel cell stack (40) and a flow assembly (30) for supplying a medium flow (1) to the fuel cell stack (40), the flow assembly (30) having a flow section (10) fluidically connected to the fuel cell stack (40), the flow assembly (30) further comprising a flow insert (20) arranged in the flow section (10) and extending with a main direction of extension along the flow section (10), a flow inlet (24) for admitting the medium flow (1), and at least one flow recess (22) formed in a side (21) of the flow insert (20) facing away from the fuel cell stack (40).

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system comprising a fuel cell stack and a flow assembly for supplying a medium flow to the fuel cell stack, the flow assembly having a flow section fluidically connected to the fuel cell stack. [Background technology]

[0002] In such fuel cell stacks with corresponding flow assemblies, there is a known problem that the outer fuel cells in the fuel cell stack receive only a small amount of the medium flow provided by the flow assembly or at different temperatures, and it is therefore desirable to distribute the provided medium flow as uniformly as possible to all fuel cells. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to at least partially eliminate the above-mentioned disadvantages, in particular to provide a medium flow to the individual fuel cells of a fuel cell stack in as uniform a distribution as possible in a cost-effective and simple manner. [Means for solving the problem]

[0004] The above problem is solved by a fuel cell system having the features of claim 1. Further features and details of the invention emerge from the dependent claims, the following description and the drawings.

[0005] According to the present invention, there is provided a fuel cell system comprising a fuel cell stack and a flow assembly for supplying a medium flow to the fuel cell stack, the flow assembly having a flow section fluidly connected to the fuel cell stack, the flow assembly further comprising a flow insert disposed in the flow section with its main extension direction extending along the flow section, a flow inlet for admitting the medium flow, and at least one flow recess formed in a side of the flow insert opposite the fuel cell stack.

[0006] According to the present invention, this problem is solved by using a flow insert in the flow section of the flow assembly. The flow insert is configured to supply a uniform distribution of the medium flow to the individual fuel cells of the fuel cell stack. The uniform distribution of the medium flow is provided via at least one flow recess, whereby the medium flow exits in a controlled manner through the at least one flow recess, bounces off the inner wall of the flow section facing the side of the flow insert opposite the fuel cell stack, and is redirected back toward the fuel cell stack, particularly around the flow insert. By guiding the medium flow within the flow insert, uneven flow of the medium flow within the flow section to the individual fuel cells of the fuel cell stack is prevented, while the medium flow does not reach other fuel cells or reaches only a small amount of them, particularly with a reduced mass, velocity, and / or temperature. That is, by using the flow assembly according to the present invention, it is possible to more uniformly distribute the medium flow entering the flow insert through the inlet opening to the individual fuel cells of the fuel cell stack, particularly with regard to the mass, temperature, and / or velocity of the medium flow. To the extent that equal distribution is mentioned herein, it should not necessarily be understood as mathematically perfect equal distribution, since such distribution is not practically achievable. Rather, an attempt is made to achieve the maximum or best possible equal distribution of the medium flows to the fuel cells of the fuel cell stack. A further advantage achieved by the present invention is that by simply adding flow guide elements to the individual fuel cells of the fuel cell stack, the medium flows are guided as evenly as possible, without the need to individually adapt each identical fuel cell.

[0007] In addition to the fuel cell stacks and flow assemblies, the fuel cell system may of course include further peripherals and devices for operating the individual fuel cell stacks, which may include, for example, valves, pumps, recirculation fans, etc. for supplying the medium flow to the flow assemblies. Furthermore, a fuel cell system may include multiple fuel cell stacks and / or multiple flow assemblies.

[0008] Furthermore, the flow insert and the flow section can optionally be separate, in particular integral parts, or an integrally manufactured flow assembly. The first variant has the advantage that existing flow sections can be easily retrofitted by equipping them with flow inserts that can be attached to the flow section. The second variant has the advantage of easy manufacturing, for example by means of 3D printing. The flow section can also be advantageously designed as a housing.

[0009] The main direction of extension of the flow insert may in particular be a longitudinal direction along which the length of the flow insert extends and a width thereof extends perpendicularly thereto. Furthermore, the main direction of extension, in particular the longitudinal direction of the flow insert, may coincide with the main direction of extension of the flow section.

[0010] It may be preferable for the at least one flow recess to be aligned with an inner wall of the flow section, thereby ensuring that the medium flow exiting the at least one flow recess bounces back in the flow section and reverses its direction towards the fuel cell stack. It has been found that this provides a flow-encircling flow insert that allows for a more uniform distribution of the medium flow to the fuel cell stack and therefore a more uniform medium supply to all fuel cells in the fuel cell stack.

[0011] Furthermore, it may be preferable for the length of the at least one flow recess to extend along the main extension direction of the flow insert, in this way allowing the medium flow to flow as uniformly as possible over the length of the flow insert, which also allows for the desired uniform medium supply to the individual fuel cells which may be stacked along the main extension direction.

[0012] Furthermore, it may be preferable for the flow insert to be formed with several flow recesses that are spaced apart from one another along the main extension direction of the flow insert. By providing several flow recesses, for example two, three, four or more, the uniform distribution of the medium flow to the fuel cell stack can be further improved. In this case, the spacing, which may be particularly uniform, allows the medium flow in the flow insert to be divided by the flow recesses, and mutual influence of the individual partial medium flows emerging from the flow recesses can be largely avoided or minimized, resulting in an optimized flow and supply of the partial medium flows to the individual fuel cells. However, as will be explained in more detail below based on another advantageous feature, a single flow recess can alternatively be provided, the length of which extends in the main extension direction.

[0013] Furthermore, it may be preferable that at least one first flow guide element is arranged in the flow insert, extending from the at least one flow recess into the flow insert. The flow guide element can thereby advantageously impart a flow direction to the medium flow. The flow rate can also be determined by the dimensioning of the flow recess or recesses.

[0014] In addition to the first flow guide element, reference is made herein to a second flow guide element, which will be described in more detail below and which may differ, particularly with respect to its location or arrangement in the flow assembly. The designations first or second flow guide element are used herein only to distinguish between the two flow guide elements and are not limiting. For example, when referring to a second flow guide element, the first flow guide element need not be present.

[0015] In that case, it may be preferable for the at least one first flow guide element to form a flow slot leading from within the flow insert to the at least one flow recess. The flow recess thereby extends into the flow insert in addition to extending around the periphery of the flow insert. The medium flow must flow through the flow slot to leave the flow insert. In that case, the flow slot can be formed, in particular, by two first flow guide elements standing opposite each other, in particular parallel to each other. The advantage of the flow slot is that it can form a narrow gap between them, which can break the axial flow momentum of the medium flow through the flow insert and thus limit the radial flow of the medium flow outward through the flow recess.

[0016] In that case, it may be preferable for the flow slots to be formed substantially continuously in the flow section along the main direction of extension of the flow insert. In other words, the flow slots can extend along substantially the entire length of the flow insert extending into the flow section. This allows the medium flow to flow uniformly over the entire length of the flow section and to the fuel cell stack. In that case, the flow section can be designed so that its extension, in particular its length, corresponds to the fuel cell stack arranged therein.

[0017] Furthermore, in this case it may be preferred if the flow slots have inner edges that slope along the main extension direction of the flow insert in the direction towards the flow section, or in other words outwards, whereby a simple throttling of the medium flow through the flow slots can be achieved.

[0018] Alternatively or additionally, it may be preferred that the side of the flow insert facing away from the fuel cell stack is inclined towards the fuel cell stack along the main extension direction of the flow insert. This inclination can be formed in particular relative to a substantially straight inner edge of the flow slot or of its at least one flow guide element. This also makes it possible to achieve a simple throttling of the medium flow through the flow slot.

[0019] Furthermore, it may be preferable to form at least one second flow guide element in at least one flow recess for generating flow vortices around at least a portion of the flow insert and for the medium flow reaching the fuel cell stack. The second flow guide element can be selectively straight, inclined (with respect to the main extension axis of the flow insert), and / or curved (especially in the direction away from the fuel cell stack). Furthermore, the flow guide element can be arranged on the aforementioned opposite side of the flow insert, or alternatively on the side of the flow insert facing the fuel cell stack. Naturally, positions in between are also possible. The at least one second flow guide element allows for controlled flow guidance and prevents undesired turbulence or mixing of the partial medium flows from the at least one flow recess. The length and swirl of the desired generated flow vortices can be adjusted, on the one hand, by the position of the at least one flow guide element and, on the other hand, by its shape, e.g., inclined and / or curved as described above. In that case, the impulse of the medium flow is redirected. This provides a desired and controlled flow vortex around the flow insert between the inner wall of the flow section and the flow insert, further improving the uniform distribution of media flow to the fuel cell stack.

[0020] It may also be advantageous if a second flow guide element is arranged or fixed on the flow insert or flow section.

[0021] Furthermore, it may be advantageous if the flow insert is provided with a plurality of flow recesses formed transversely, in particular perpendicularly, to the main direction of extension of the flow insert. Thus, instead of or in addition to the flow recesses along the main direction of extension, for example, two, three, four or more flow recesses can be provided transversely thereto. This can also improve the uniform distribution of the medium flow to the fuel cell stack, although in some cases a larger pressure drop across the flow recesses is expected.

[0022] It may also be preferred that at least one flow recess is formed in the flow insert as a slot and / or perforation. The slot may have, for example, a rectangular, circular, oval, or similar shape. The slot may have a greater extension in the longitudinal direction than in the width direction. The slot is particularly easy to make in the flow insert and may have a restricted flow cross-sectional area to allow only a controlled and limited flow rate to escape rather than all the medium flow within the flow insert.

[0023] Furthermore, it may be preferable for at least one intermediate flow recess to be formed as a slot in the flow insert. The slot may have, for example, a rectangular, elliptical, or similar elongated cross section. The slot has a greater extension in the longitudinal direction than in the width direction. The slot can be particularly easy to make in the flow insert and may have a restricted flow cross-sectional area in order to allow only a controlled and limited flow rate to escape, rather than all the medium flow within the flow insert. The perforations may have, for example, a circular or elliptical cross section.

[0024] It may also be preferred that the flow sections and / or flow inserts are tubes, which are less complex to design and are particularly cost-effective. Various cross sections of the flow sections and / or flow inserts are then possible, such as circular, square, oval, heart-shaped, mixtures thereof, or the like.

[0025] In particular, the flow inserts are spaced apart from the flow section, in particular on all sides or radially. In particular, it may be preferred for the flow inserts to be arranged concentrically, in particular coaxially, with respect to the flow section. In this way, a uniform distance can be achieved between the flow section, in particular its inner wall, and the flow inserts, through which the medium stream can flow to reach the fuel cell stack.

[0026] Finally, it may be preferable for the flow section to be located on the air side or the fuel side of the fuel cell stack.

[0027] Other advantages, features and details of the invention will become apparent from the following description in which exemplary embodiments are explained in detail with reference to the drawings. [Brief explanation of the drawings]

[0028] [Figure 1a] 1 is a vertical cross-sectional view of a fuel cell system according to a first embodiment of the present invention. [Figure 1b] FIG. 1b is a horizontal cross-sectional view of the fuel cell system of FIG. 1a. [Figure 2] FIG. 2 is a vertical cross-sectional view of a fuel cell system according to a second exemplary embodiment of the present invention. [Figure 3] FIG. 10 is a vertical cross-sectional view of a fuel cell system according to a third exemplary embodiment of the present invention. [Figure 4a] FIG. 10 is a vertical cross-sectional view of a fuel cell system according to a fourth exemplary embodiment of the present invention. [Figure 4b] FIG. 4b is a horizontal cross-sectional view of the fuel cell system of FIG. 4a. [Figure 5] FIG. 10 is a vertical cross-sectional view of a flow assembly according to a fifth exemplary embodiment of the present invention. [Figure 6] FIG. 1 is a perspective view of a fuel cell system. DETAILED DESCRIPTION OF THE INVENTION

[0029] Identical or functionally similar elements are given the same reference numerals in each of FIGS. 1a to 6.

[0030] 1a shows an exemplary embodiment of a fuel cell system 50 according to the invention, comprising a fuel cell stack 40 and a flow assembly 30, in which a medium stream 1 enters the flow assembly via an inlet opening 24 and is fed or routed directly to the fuel cell stack 40 across the stack height of the fuel cells of the fuel cell stack 40. The fuel cell stack 40 can be, for example, a polymer electrolyte membrane or solid oxide fuel cell stack.

[0031] In that case, the fuel cell system 50 is shown in Figure 1a in a vertical cross section along the main extension direction of the flow insert 20 arranged in the flow section 10 of the flow assembly 30, as in the exemplary embodiments in Figures 2, 3, 4a and 5. In that case, the main extension direction of the flow insert 20 is also the longitudinal extension direction, which further coincides with the flow direction of the medium stream 1 fed into the flow insert 20.

[0032] In this case, the flow insert 20 is spaced apart from the inner wall 12 of the flow section 10. In particular, the flow insert 20 is concentrically disposed within the flow section 10.

[0033] The flow section 10 and / or the flow insert 20 may be tubular in shape, and in contrast to Figure 1a, Figure 1b shows a horizontal cross section of the fuel cell system 50 for the flow section 10 and the flow insert 20. The tubular cross sections of the flow section 10 and the flow insert 20 are shown here as circular, by way of example only, although alternatively, one or both of them may be rectangular, oval, or heart-shaped, for example.

[0034] 1a, the flow insert 20 includes a flow inlet 24 on its underside through which the media stream 1 enters the flow insert 20 and thus the flow section 10. The media stream 1, which may include, for example, air or fuel for the fuel cell stack 40, is introduced into the flow insert 20 and can flow therethrough along the flow section 10.

[0035] The flow insert 20 of this exemplary embodiment of fuel cell system 50 has flow recesses 22 on a side 21 of the flow insert opposite the fuel cell stack 40, which here illustratively extend substantially continuously along the length of the flow insert 20. Alternatively, spaced-apart flow recesses 22 can be provided along the flow insert 20, as shown, for example, in FIG.

[0036] 1b shows how two first flow guide elements 26 extend from the flow recesses 22 into the flow insert 20, thereby forming flow slots 27 from the center of the flow insert 20 to the flow recesses 22, so that the medium stream 1 entering through the flow inlets 24 is controlled by the flow recesses and can exit continuously throughout the entire longitudinal extension of the flow insert 20. The medium stream 1 exiting the flow recesses 22 or the flow slots 27 then bounces off the inner wall 12 of the flow section 10 and is redirected towards the fuel cell stack 40, as shown by the corresponding arrows representing the partial flow directions of the medium stream 1, where the medium stream exits the flow insert 20 radially and flows along its outer surface.

[0037] FIG. 2 shows a variant of the flow insert 20 of the flow assembly 30 of FIGS. 1a and 1b, in which the side edges 28 of the first flow guide element 26 or flow slot 27 are inclined with their inlet edges towards the flow section 10.

[0038] 3 shows a variation of the flow insert 20 of the flow assembly 30 of FIGS. 1 a and 1 b in which the side 21 of the flow insert opposite the fuel cell stack 40 is angled towards the fuel cell stack 40. Both embodiment variations of the flow insert 20 of FIGS. 2 and 3 provide different throttling of the media flow due to different lengths of the flow slots 27 along the longitudinal extension of the flow insert 20.

[0039] Figures 4a and 4b show an alternative embodiment of a flow assembly 30 in a fuel cell system 50, in which a plurality of flow recesses 22 (only a few of which are shown here for clarity) are spaced apart from one another in the main direction of extension of the flow insert 20. As can be particularly well seen in Figure 4b, a plurality of flow recesses 22 are also provided transversely to the main direction of extension of the flow insert 20, which here are exemplarily formed as perforations in the flow insert 20, whereas in Figures 1a to 3 they are formed as slots.

[0040] Instead of or in addition to the first flow guide elements 26 (see the bottom flow guide element 26 in FIG. 4 a ), which are arranged on the flow insert 20 and may in particular be part of, in particular an integral part of, the flow insert 20, in FIGS. 4 a and 4 b second flow guide elements 14 are provided on the outside of the flow insert 20. The second flow guide elements 14 are each assigned to a flow recess 22 extending perpendicularly to the main extension direction of the flow insert 20. They connect the flow insert 20 to the flow sections 10 and may be formed integrally with one or both. They enable optimized flow guidance towards the fuel cell stack 40 outside the flow insert 20 in the gap between the flow insert 20 and the inner wall 12 of the flow section 10. The flow guide elements can then advantageously be attached to the flow insert 20 or to the flow section 10, for example by force or material bonding. It is advantageous if the flow guide elements always dominate the remaining gap significantly, which facilitates flow guidance. Advantageously, the size of the gap is only about 5% to 20% of the size of the flow insert 20 .

[0041] 4a and 4b, in which first flow guide elements 26 (only some of which are shown here for clarity) are provided, but no second flow guide elements 14 are provided. Furthermore, since the flow insert 20 does not extend to the upper side of the flow section 10 here, flow openings (not shown here) can be provided on the upper side of the flow insert 20 opposite the flow inlet 24. That is, the flow insert 20 can be open on the upper side, so that the medium stream 1 can exit there.

[0042] FIG. 6 shows in a perspective view the principle described here, where a medium stream 1 flows into a very wide fuel cell stack 40 by means of a flow insert 20 having a circumferential flow recess 22, where the flow section 10 is not explicitly shown.

[0043] The above description of the embodiments only explains the invention to the extent that it is an example, and a combination of the individual embodiments may be provided. (Other possible items) (Item 1) 1. A fuel cell system (50) comprising a fuel cell stack (40) and a flow assembly (30) for supplying a medium flow (1) to the fuel cell stack (40), the flow assembly (30) having a flow section (10) fluidically connected to the fuel cell stack (40), wherein the flow assembly (30) further comprises a flow insert (20) arranged in the flow section (10) and extending with a main direction of extension along the flow section (10), a flow inlet (24) for admitting the medium flow (1), and at least one flow recess (22) formed in a flow insert side (21) of the flow insert facing away from the fuel cell stack (40). (Item 2) 2. The fuel cell system (50) of claim 1, wherein the at least one flow recess (22) is aligned with an inner wall (12) of the flow section (10). (Item 3) 3. The fuel cell system (50) according to item 1 or 2, wherein the at least one flow recess (22) has a length extending along the main extension direction of the flow insert (20). (Item 4) 4. A fuel cell system (50) according to any one of items 1 to 3, wherein the flow insert (20) is formed with a plurality of flow recesses (22) spaced apart from one another along the main extension direction of the flow insert (20). (Item 5) 5. The fuel cell system (50) of any one of items 1 to 4, wherein at least one first flow guide element (26) is disposed on the flow insert (20) and extends from the at least one flow recess (22) into the flow insert (20). (Item 6) Item 5. A fuel cell system (50) as described in item 5, wherein the at least one first flow guide element (26) forms a flow slot (27) that leads from within the flow insert (20) to the at least one flow recess (22). (Item 7) 7. The fuel cell system (50) of claim 6, wherein the flow slot (27) is formed substantially continuously within the flow section (10) along the main extension direction of the flow insert (20). (Item 8) 8. The fuel cell system (50) of claim 6 or 7, wherein the flow slot (27) has an inner edge (28) that is inclined toward the flow section (10) along the main extension direction of the flow insert (20). (Item 9) 9. The fuel cell system (50) of any one of items 1 to 8, wherein the side of the flow insert (21) opposite the fuel cell stack (40) is inclined toward the fuel cell stack (40) along the main extension direction of the flow insert (20). (Item 10) 10. The fuel cell system (50) according to any one of items 1 to 9, wherein at least one second flow guide element (14) is formed in the at least one flow recess (22) around at least a portion of the flow insert (20) and for generating flow vortices of the medium flow (1) reaching the fuel cell stack (40). (Item 11) 11. The fuel cell system (50) of any one of items 1 to 10, wherein the flow insert (20) has a plurality of flow recesses (22) formed transversely to the main extension direction of the flow insert (20). (Item 12) Item 12. The fuel cell system (50) of any one of items 1 to 11, wherein the at least one flow recess (22) is formed as a slot and / or a perforation in the flow insert (20). (Item 13) 13. The fuel cell system (50) of any one of items 1 to 12, wherein the flow section (10) and / or the flow insert (20) are tubes. (Item 14) 14. The fuel cell system (50) of any one of items 1 to 13, wherein the flow insert (20) is arranged concentrically with respect to the flow section (10). (Item 15) 15. The fuel cell system (50) of any one of items 1 to 14, wherein the flow section (30) is disposed on the air side or the fuel side of the fuel cell stack (40). [Explanation of symbols]

[0044] 1 Media flow 10 Flow Section 12 Inner wall 14 Second flow guide element 20 Flow Insert 21 Flow insert side 22 Flow recess 24 Flow Inlet 26 First flow guide element 27 Flow Slot 28 Side edge 30 Flow Assembly 40 Fuel Cell Stack

Claims

1. 1. A fuel cell system comprising a fuel cell stack and a flow assembly for supplying a medium flow to the fuel cell stack, the flow assembly having a flow section fluidically connected to the fuel cell stack, the flow assembly further comprising a flow insert arranged in the flow section, the flow insert having a main direction of extension along the flow section, a flow inlet for admitting the medium flow, and at least one flow recess formed in a side of the flow insert opposite the fuel cell stack.

2. The fuel cell system of claim 1 , wherein the at least one flow recess is aligned with an inner wall of the flow section.

3. 2. The fuel cell system of claim 1, wherein the at least one flow recess has a length extending along the primary extension direction of the flow insert.

4. 10. The fuel cell system of claim 1, wherein said flow insert defines a plurality of flow recesses spaced apart from one another along said primary extension direction of said flow insert.

5. 10. The fuel cell system of claim 1, wherein the flow insert comprises at least one first flow guide element disposed thereon, the first flow guide element extending from the at least one flow recess into the flow insert.

6. 6. The fuel cell system of claim 5, wherein the at least one first flow guide element defines a flow slot leading from within the flow insert to the at least one flow recess.

7. 7. The fuel cell system of claim 6, wherein the flow slot is substantially continuously formed within the flow section along the primary extension direction of the flow insert.

8. 7. The fuel cell system of claim 6, wherein the flow slots have inner edges that are angled along the primary extension direction of the flow insert toward the flow section.

9. 10. The fuel cell system of claim 1, wherein the side of the flow insert opposite the fuel cell stack is angled toward the fuel cell stack along the main direction of extension of the flow insert.

10. 2. The fuel cell system of claim 1, wherein at least one second flow guide element is formed in the at least one flow recess around at least a portion of the flow insert and for generating a flow vortex of the medium flow reaching the fuel cell stack.

11. 10. The fuel cell system of claim 1, wherein said flow insert defines a plurality of flow recesses transverse to said primary extension direction of said flow insert.

12. 10. The fuel cell system of claim 1, wherein the at least one flow recess is formed as a slot and / or a perforation in the flow insert.

13. 10. The fuel cell system of claim 1, wherein the flow section and / or the flow insert is a tube.

14. The fuel cell system of claim 1 , wherein the flow insert is concentrically positioned relative to the flow section.

15. 15. The fuel cell system of claim 1, wherein the flow section is located on the air side or the fuel side of the fuel cell stack.

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