FUEL CELL SYSTEM WITH A FUEL CELL STACK AND A FLOW ARRANGEMENT FOR SUPPLYING A MEDIUM FLOW TO THE FUEL CELL STACK

Description

[0001] The present invention relates to a fuel cell system with a fuel cell stack and with a flow arrangement for supplying a media flow to the fuel cell stack, wherein the flow arrangement has a flow section connected to the fuel cell stack in terms of flow technology.

[0002] With such a fuel cell stack and the corresponding flow arrangement, the problem is known that the outer fuel cells in the stack are exposed to the fluid flow supplied by the flow arrangement only minimally or at varying temperatures. Consequently, it is desirable to supply all fuel cells with the available fluid flow as uniformly as possible.

[0003] Fuel cell systems with a fuel cell stack and with a flow arrangement for supplying a media flow to the fuel cell stack are known, for example, from EP 3331080 A1 and WO 2010056231 A1.

[0004] It is an object of the present invention to at least partially overcome the disadvantages described above. In particular, it is an object of the present invention to provide, in a cost-effective and simple manner, a media flow with the greatest possible uniform distribution to the individual fuel cells of the fuel cell stack.

[0005] The foregoing problem is solved by a fuel cell system having the features of claim 1. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings.

[0006] According to the invention, a fuel cell system is provided with a fuel cell stack and a flow arrangement for supplying a media flow to the fuel cell stack, wherein the flow arrangement has a flow section connected to the fuel cell stack in terms of fluid dynamics. The flow arrangement further comprises a flow insert arranged in the flow section, which extends along the flow section with its main direction of extension, has a flow inlet for admitting the media flow, and has at least one flow recess, which is formed on a flow insert side of the flow insert facing away from the fuel cell stack.

[0007] According to the invention, the problem is solved by using a flow insert in the flow section of the flow arrangement. This flow insert is designed to supply the media flow evenly to the individual fuel cells of the fuel cell stack. The even distribution of the media flow is provided via the at least one flow recess, since the media flow is discharged in a controlled manner through the at least one flow recess, rebounds off an inner wall of the flow section, which faces the side of the flow insert facing away from the fuel cell stack, and is deflected in the opposite direction onto the fuel cell stack, whereby the flow insert is particularly affected by the flow.By guiding the media flow within the flow insert, it is prevented that the media flow flows unevenly within the flow section to individual fuel cells of the fuel cell stack, while reaching other fuel cells not at all or only to a limited extent, particularly with reduced mass, velocity, and / or temperature. The use of the flow arrangement according to the invention thus makes it possible to distribute the media flow entering the flow insert through the inlet opening more evenly, particularly with regard to the mass, temperature, and / or velocity of the media flow, to the individual fuel cells of the fuel cell stack. Where the term "uniform distribution" is used here, it does not necessarily refer to a mathematically perfect distribution, as such a distribution is practically impossible to achieve.Rather, the intention is to achieve the maximum or best possible uniform distribution of the media flow to the fuel cells of the fuel cell stack. A further advantage achieved by the invention is that the media flow is guided with the greatest possible uniformity simply by adding flow-guiding elements to the individual fuel cells of the fuel cell stack, without requiring individual adjustment of each identical fuel cell.

[0008] In addition to a fuel cell stack and a flow arrangement, the fuel cell system can, of course, include further peripherals and devices for operating the individual fuel cell stacks. These can include, for example, valves, pumps, recirculation fans, etc., for instance, to supply the fluid flow to the flow arrangement. Furthermore, more than one fuel cell stack and / or more than one flow arrangement can be provided in the fuel cell system.

[0009] Furthermore, the flow insert and the flow section can optionally be separate components, particularly one-piece components, or an integrally manufactured flow assembly. The first option has the advantage of allowing for easy retrofitting of existing flow sections by equipping them with the flow insert, which can be attached to the flow section. The second option offers the advantage of simple manufacturing, for example, through the use of a 3D printing process. The flow section can also be advantageously designed as a housing.

[0010] The principal direction of extension of the flow inlet can, in particular, be a longitudinal direction along which the flow inlet extends lengthwise and perpendicularly thereto in widthwise. Furthermore, the principal direction of extension, in particular the longitudinal direction, of the flow inlet can coincide with that of the flow section.

[0011] It may be preferable for the at least one flow recess to be oriented towards an inner wall of the flow section. This ensures that the media flow exiting the at least one flow recess bounces off the flow section and reverses its direction towards the fuel cell stack. It has been shown that this provides a flow-enclosed flow insert, which enables a more uniform distribution of the media flow around the fuel cell stack and thus a more uniform media supply to all fuel cells in the fuel cell stack.

[0012] Furthermore, it may be preferred that at least one flow recess extends along the main direction of the flow insert. This allows the media flow to be distributed as uniformly as possible along the length of the flow insert, thus ensuring the desired uniform media supply to the individual fuel cells, which may be stacked on top of each other along the main direction of extension.

[0013] Furthermore, it may be preferred that several flow recesses are formed in the flow insert, spaced apart from one another along the main direction of extension of the flow insert. By providing several flow recesses, for example two, three, four or more, the uniform distribution of the media flow at the fuel cell stack can be further improved. The spacing between the recesses, which can be uniform in particular, largely prevents or minimizes any mutual interference between the individual partial media flows into which the media flow in the flow insert can be divided by the flow recesses and which exit from the flow recesses, so that these can be supplied to the individual fuel cells in a flow-optimized manner.Alternatively, a single flow recess extending lengthwise in the main direction of extension can be provided, as will be explained in more detail later with reference to further advantageous features.

[0014] Furthermore, it may be preferred that at least one first flow-guiding element is arranged on the flow insert, extending from the at least one flow recess into the flow insert. The flow-guiding element can thus advantageously impose a flow direction on the media flow. The flow rate, in turn, can be determined by the dimensioning of the flow recess or recesses.

[0015] In addition to the first flow-guiding element, this text also refers to a second flow-guiding element, which will be explained in more detail later and may differ, in particular, with regard to its position or arrangement within the flow arrangement. The designation as first or second flow-guiding element serves only to distinguish between the two elements and does not represent a restriction. For example, the presence of a first flow-guiding element is not a requirement when referring to a second flow-guiding element.

[0016] It is preferable for the first flow guide element to form a flow slot leading from within the flow insert to the at least one flow recess. This gives the flow recess not only an extension around the flow insert but also an extension into the flow insert. The fluid flow must pass through the flow slot to exit the flow insert. The flow slot can be formed by two opposing, and especially parallel, first flow guide elements. The advantage of the flow slot is that it can form a narrow gap between them, which can break the axial flow moment of the fluid flow through the flow insert and thus limit the radial flow of the fluid outwards through the flow recesses.

[0017] It may be preferred that the flow slot extends substantially continuously within the flow section along the main direction of extension of the flow insert. In other words, the flow slot can extend substantially along the entire length of the flow insert that runs within the flow section. This allows the fluid flow to exit uniformly along the entire length of the flow section and flow to the fuel cell stack. The flow section can be configured, particularly in terms of length, to correspond to the fuel cell stack arranged therein.

[0018] Furthermore, it may be preferred that the flow slot has outwardly inclined inner edges along the main direction of extension of the flow insert towards the flow section, or in other words, that are inclined outwards. This allows for a simple throttling of the media flow through the flow slot.

[0019] According to the invention, the side of the flow insert facing away from the fuel cell stack is inclined towards the fuel cell stack along the main direction of extension of the flow insert. This inclination can be formed, in particular, relative to a substantially straight inner edge of the flow slot or its at least one flow guide element. This also allows for a simple throttling of the media flow through the flow slot.

[0020] Furthermore, it may be preferred that at least one second flow guide element is formed at the at least one flow recess to generate a flow vortex of the medium flow that leads around at least a part of the flow insert and to the fuel cell stack. The second flow guide element can optionally be straight, inclined (relative to the main axis of extension of the flow insert), and / or curved (in particular, in the direction away from the fuel cell stack). Furthermore, the flow guide element can be arranged on the aforementioned side of the flow insert facing away from the fuel cell stack, or alternatively, on a side of the flow insert facing the fuel cell stack. Of course, intermediate positions are also possible.The inclusion of at least one second flow guide element enables controlled flow guidance, preventing unwanted turbulence or mixing of partial media flows emerging from the at least one flow recess. The length and swirl of the generated and desired flow vortex are adjustable via the position of the at least one flow guide element on the one hand, and its shape, as previously described (e.g., inclined and / or curved), on the other. The momentum of the media flow is thereby redirected. This creates 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 the media flow to the fuel cell stack.

[0021] It can also be advantageous if the second flow guide element is arranged or attached to the flow insert or the flow section.

[0022] Furthermore, it may also be preferred that the flow insert has several flow recesses transversely, and in particular perpendicularly, to the main direction of extension of the flow insert. Consequently, alternatively or in addition to flow recesses along the main direction of extension, flow recesses, for example two, three, four or more, may be provided transversely. This can also improve the uniform distribution of the media flow at the fuel cell stack, although a greater pressure drop at the flow recesses may be expected in this case.

[0023] It may also be preferred that at least one flow opening is designed as a slot and / or a perforation in the flow insert. The slot can, for example, have a rectangular, round, oval, or similar shape. A slot can have a greater longitudinal extent than a greater width. It is particularly easy to manufacture in the flow insert and can have a limited flow cross-section in order to prevent the entire flow of media from escaping the flow insert, allowing only a controlled and limited flow rate.

[0024] It is further preferred that the at least one intermediate flow recess is designed as a slot in the flow insert. The slot can, for example, have a rectangular, oval, or similar elongated cross-section. A slot has a greater longitudinal extent than a lateral extent. It is particularly easy to manufacture in the flow insert and can have a limited flow cross-section in order to prevent the entire flow of media from escaping the flow insert, but rather only a controlled and limited flow rate. A perforation can, for example, have a round or oval cross-section.

[0025] It is also preferable for the flow section and / or the flow insert to be a tube. Designing it as a tube is relatively straightforward and particularly cost-effective. Various cross-sections of the flow section and / or the flow insert are conceivable, for example, round, square, oval, heart-shaped, a combination of the above, or similar.

[0026] In particular, the flow insert is spaced apart from the flow section, especially on all sides or radially. It is particularly preferred that the flow insert is arranged concentrically, and especially coaxially, to the flow section. This allows a uniform distance to be achieved between the flow section, especially its inner wall, and the flow insert, through which the media flow can pass to reach the fuel cell stack.

[0027] Finally, it may be preferred that the flow section is arranged on an air side or on a fuel side of the fuel cell stack.

[0028] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments are described in detail with reference to the drawings. The drawings schematically show: Fig. 1a a vertical cross-sectional view through a fuel cell system according to a first embodiment of the invention, Fig. 1b a horizontal cross-sectional view through the fuel cell system of the Fig. 1aFig. 2 a vertical cross-sectional view through a fuel cell system according to a second embodiment of the invention, Fig. 3 a vertical cross-sectional view through a fuel cell system according to a third embodiment of the invention, Fig. 4a a vertical cross-sectional view through a fuel cell system according to a fourth embodiment of the invention, Fig. 4a a horizontal cross-sectional view through the fuel cell system of the Fig. 4a , Fig. 5 a vertical cross-sectional view of a flow arrangement according to a fifth embodiment of the invention, and Fig. 6 a perspective view of the fuel cell system.

[0029] Identical or functionally equivalent elements are in the Figures 1 to 6 each designated with the same reference symbol.

[0030] Figure 1aFigure 1 shows an embodiment of a fuel cell system 50 according to the invention, comprising a fuel cell stack 40 and a flow arrangement 30 into which a media flow 1 is introduced via an inlet opening 24 and is fed or conveyed directly to the fuel cell stack 40 over the stack height of the fuel cells. The fuel cell stack 40 can, for example, be a polymer electrolyte membrane or solid oxide fuel cell stack.

[0031] The fuel cell system 50 is in the Fig. 1a in this context, as well as its exemplary implementations in the Fig. 2, 3 4a and 5, shown in a vertical cross-section along the main extension direction of a flow insert 20, which is arranged in a flow section 10 of the flow arrangement 30. The main extension direction of the flow insert 20 is also a longitudinal extension direction and also coincides with the flow direction of the supplied media flow 1 within the flow insert 20.

[0032] The flow insert 20 is arranged at a distance from the inner wall 12 of the flow section 10. In particular, the flow insert 20 is arranged concentrically within the flow section 10.

[0033] The flow section 10 and / or the flow insert 20 can be tubular in shape, as shown in the Figure 1b in a situation opposite the Fig. 1aA horizontal cross-section through the fuel cell system 50 for the flow section 10 and the flow insert 20 is shown. The tubular cross-sections of the flow section 10 and the flow insert 20 are shown here as rounds for illustrative purposes only; alternatively, one or both of them could also be rectangular, elliptical, or heart-shaped, for example.

[0034] As in the Fig. 1a As indicated, the flow insert 20 includes a flow inlet 24 on its underside, through which the media flow 1 is admitted into the flow insert 20 and thus into the flow section 10. In this way, the media flow 1, which may contain, for example, air or fuel for the fuel cell stack 40, can be introduced into the flow insert 20 and flow along the flow section 10 within it.

[0035] The flow insert 20 of this embodiment of the fuel cell system 50 has a flow recess 22 on a flow insert side 21 facing away from the fuel cell stack 40, wherein the flow recess 22 extends essentially continuously along the length of the flow insert 20. Alternatively, flow recesses 22 spaced apart from one another can be provided along the flow insert 20, as for example in the Fig. 4a shown.

[0036] In Fig. 1bThe figure shows how two first flow-guiding elements 26 extend from the flow recess 22 into the flow insert 20, thereby forming a flow slot 27 from the center of the flow insert 20 to the flow recess 22. The media flow 1 entering through the flow inlet 24 can flow out in a controlled and continuous manner along the entire longitudinal extent of the flow insert 20 through this slot. The media flow 1 exiting the flow recess 22 or the flow slot 27 rebounds off the inner wall 12 of the flow section 10, as indicated by the corresponding arrows representing partial flow directions of the media flow 1, and is deflected towards the fuel cell stack 40. It then flows radially out of the flow insert 20 and along its outer surface.

[0037] Figure 2 shows a modification of the flow insert 20 of the flow arrangement 30 of the Fig. 1a and 1b, in which the side edges 28 of the first flow-guiding elements 26 or of the flow slot 27 are inclined towards the flow section 10.

[0038] Figure 3 shows a modification of the flow insert 20 of the flow arrangement 30 of the Fig. 1a and 1b , in which the side of the flow insert 21 facing away from the fuel cell stack 40 is inclined towards the fuel cell stack 40. Both design variants of the flow inserts 20 of the Fig. 2 and Fig. 3 Different throttling of the media flow is provided by the different lengths of the flow slot 27 along the longitudinal extent of the flow insert 20.

[0039] Figures 4a and 4bshow alternative embodiments of the flow arrangement 30 in a fuel cell system 50, in which several flow recesses 22 (for clarity, only some are shown here) are spaced apart from one another in the main direction of extension of the flow insert 20. How Fig. 4b As can be seen particularly well, several flow recesses 22 are also provided transversely to the main direction of extension of the flow insert 20, whereby these are designed here as perforations in the flow insert 20, whereas they are designed as slots in the Figs. 1a to 3 are trained.

[0040] Instead of or in addition to the first flow guide elements 26 (see lowest flow guide element 26 in the Fig. 4a ), which are arranged in the flow insert 20 and can in particular be part, especially an integral part, of the flow insert 20, are in the Figs. 4a and 4bSecond flow-guiding elements 14 are provided outside the flow insert 20. These second flow-guiding elements 14 are each assigned to the flow recesses 22 extending perpendicular to the main direction of extension of the flow insert 20. They can connect the flow insert 20 to the flow section 10 and be formed integrally with one or both. They allow for optimized flow guidance outside the flow insert 20 in the gap between the flow insert 20 and the inner wall 12 of the flow section 10 towards the fuel cell stack 40. The flow-guiding elements can advantageously be attached to the flow insert 20 or to the flow section 10, for example, by force-fit or material bonding. It is advantageous if the flow-guiding elements are always significantly more dominant than the remaining gap, thereby promoting flow guidance.Advantageously, the size of the gap is only about 5% to 20% of the size of the flow insert 20.

[0041] Figure 5 shows a modification of the flow arrangement 30 of the Figs. 4a and 4b , in which the first flow-guiding elements 26 (for clarity, only some are shown here) are provided, but no second flow-guiding elements 14 are provided. Furthermore, the flow insert 20 does not extend to the upper side of the flow section 10, so that a flow opening (not shown here) may be provided on the upper side of the flow insert 20 opposite the flow inlet 24. The flow insert 20 can therefore be open on its upper side, allowing the media flow 1 to escape.

[0042] Figure 6Figure 1 shows in a perspective view the principle of the flow of medium 1 to a very wide fuel cell stack 40 explained here by means of a flow insert 20 with circumferential flow recesses 22, whereby the flow section 10 is not explicitly shown here.

[0043] The preceding descriptions of the embodiments describe the present invention solely by way of example. Combinations of the individual embodiments are possible. Reference symbol list

[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 Inner edge 30 Flow arrangement 40 Fuel cell stack

Claims

1. A fuel cell system (50) comprising a fuel cell stack (40) and a flow arrangement (30) for supplying a media flow (1) to the fuel cell stack (40), wherein the flow arrangement (30) comprises a flow section (10) fluidically connected to the fuel cell stack (40), the flow arrangement (30) further comprises a flow insert (20) arranged in the flow section (10), which extends with its main direction of extension along the flow section (10), has a flow inlet (24) for admitting the media flow (1), and has at least one flow recess (22) formed on a flow insert side (21) of the flow insert (20) facing away from the fuel cell stack (40), characterized in that the flow insert side (21) facing away from the fuel cell stack (40) is inclined along the main extension direction of the flow insert (20) towards the fuel cell stack (40).

2. Fuel cell system (50) according to claim 1, characterized in that the at least one flow recess (22) is aligned with an inner wall (12) of the flow section (10).

3. Fuel cell system (50) according to claim 1 or 2, characterized in that the at least one flow recess (22) extends lengthwise along the main extension direction of the flow insert (20).

4. Fuel cell system (50) according to one of the preceding claims, characterized in that a plurality of flow recesses (22) are formed in the flow insert (20), which are spaced apart from one another along the main extension direction of the flow insert (20).

5. Fuel cell system (50) according to one of the preceding claims, characterized in that at least one first flow guide element (26) is arranged on the flow insert (20), which extends from the at least one flow recess (22) to within the flow insert (20).

6. Fuel cell system (50) according to claim 5, characterized in that the at least one first flow guide element (26) forms a flow slot (27) leading from within the flow insert (20) to the at least one flow recess (22).

7. Fuel cell system (50) according to claim 6, characterized in that the flow slot (27) is formed substantially continuously within the flow section (10) along the main extension direction of the flow insert (20).

8. Fuel cell system (50) according to claim 6 or 7, characterized in that the flow slot (27) has inner edges (28) inclined along the main extension direction of the flow insert (20) in the direction of the flow section (10).

9. Fuel cell system (50) according to one of the preceding claims, characterized in that at least one second flow guide element (14) is formed on the at least one flow recess (22) for generating a flow vortex of the media flow (1) around at least a portion of the flow insert (20) and leading to the fuel cell stack (40).

10. Fuel cell system (50) according to one of the preceding claims, characterized in that a plurality of flow recesses (22) are formed in the flow insert (20) transversely to the main extension direction of the flow insert (20).

11. Fuel cell system (50) according to one of the preceding claims, characterized in that the at least one flow recess (22) is formed as a slot and / or a perforation in the flow insert (20).

12. Fuel cell system (50) according to one of the preceding claims, characterized in that the flow section (10) and / or the flow insert (20) is a tube.

13. Fuel cell system (50) according to one of the preceding claims, characterized in that the flow insert (20) is arranged concentrically to the flow section (10).

14. Fuel cell system (50) according to one of the preceding claims, characterized in that the flow section (30) is arranged on an air side or on a fuel side of the fuel cell stack (40).