BIPOLAR PLATE WITH INCLINATIONALLY ARRANGED INFLOW CHANNEL SECTIONS FOR A FUEL CELL STACK, FUEL CELL SYSTEM AND MOTOR VEHICLE

Description

[0001] The invention relates to a bipolar plate for a fuel cell stack of a fuel cell system with at least one main channel section which is configured for the supply of a fluid; several inlet channel sections branching off from the main channel section; and with several distribution channel sections in fluid communication with the inlet channel sections.

[0002] From DE 10 2019 001 337 A1, a separator plate for a fuel cell stack is known, in which outlet-side outflow channel sections, which are connected to a main channel for the removal of a fluid, are arranged such that flow-induced liquid separation can occur in the main removal channel. From CN 105839136 A, a circular bipolar plate is known with spirally arranged distribution channels.

[0003] US 2017 / 0 033 373 A1 describes a bipolar plate for a fuel cell stack of a fuel cell system, in which inclined inflow channel sections are present.

[0004] EP 2 299 527 A1 describes a bipolar plate in which the inflow channel sections are aligned at an angle of attack to generate a swirling flow.

[0005] EP 1 942 546 A1 describes a bipolar plate with an internal distribution structure for generating a swirling flow.

[0006] DE 10 2019 001 337 A1 describes a separator plate for a fuel cell stack, wherein, according to the Figure 2Inflow channel sections are inclined at least part of the circumferential contour of the main channel section to a collecting channel section perpendicular to the path. The collecting channel section is aligned parallel to one side of the main channel section and extends almost across the entire width of the separator plate to ensure uniform filling of the appropriately dimensioned flow field.

[0007] In fuel cells, bipolar plates are used to supply the electrochemically active surfaces with the necessary media. The bipolar plates and electrochemically active membrane units are alternately assembled into fuel cell stacks to achieve the highest possible voltage by connecting the individual cells in series. The distribution of the reaction media (reactants) to the typically several hundred individual cells occurs via an opening (main channel section) that penetrates all the individual cells, forming a main channel for the respective medium or reactant. From these main channels, the three media or fluids (two reactants and a coolant) are introduced through radially oriented openings towards the active area.

[0008] Due to the individual cells being manufactured with identical geometry for economic reasons, the main channel must have a constant cross-section along its entire length. Therefore, the inflow of fluid, especially reactants, into the first individual cells of the stack is usually very poor due to the high flow velocities in the main channel (at the beginning of the main channel, where the full mass flow of the fluid is present). The constant cross-section of the main channel makes it difficult to optimize the uniform distribution of fluid to the various individual cells.

[0009] The object underlying the invention is seen as being to provide a bipolar plate in which the media or fluids, in particular the reactants, can be better distributed when flowing into or being supplied to the fuel cell or fuel cell stack.

[0010] This problem is solved by a bipolar plate, a fuel cell system, and a motor vehicle with the features of the respective independent patent claims. Advantageous embodiments with expedient further developments are specified in the dependent patent claims.

[0011] A bipolar plate is proposed for a fuel cell stack of a fuel cell system with at least one main channel section designed for the supply of a fluid; several inflow channel sections branching off from the main channel section; and several distribution channel sections in fluid communication with the inflow channel sections.It is provided that the inlet channel sections are arranged along at least a part of the circumferential contour of the main channel section in such a way that each inlet channel section is inclined to the circumferential contour present in a respective connection area between the inlet channel section and the main channel section, such that an angle of attack is formed between the orthogonal and an inlet channel axis, whereby a swirling flow for the inflowing fluid can be generated based on the inclined arrangement of the inlet channel sections in the main channel section.

[0012] By angling the inlet channel sections, a quasi-tangential orientation can be used to impart a slight swirl to the fluid flow in the main channel, which is formed by several main channel sections. This deflection towards a swirl flow improves fluid inflow into the first cells. The degree of swirl can be varied depending on the angle of the inlet channel sections, thereby optimizing the uniform distribution into the individual cells and the pressure drop across the main channel. Thus, the optimized design of the media inlet (inclined inlet channel sections) into the bipolar plate (distribution channel sections) forces a swirl flow in the main channel, improving the media / fluid flow and uniform distribution throughout the fuel cell stack.

[0013] In the bipolar plate, the inflow channel sections are distributed along the entire circumferential contour of the main channel section, according to the invention. This allows the swirl flow generated in the main channel to be fully utilized to improve the distribution of fluid into the inflow channels and thus into the individual cells.

[0014] In a bipolar plate, the inlet channel sections can lead into at least one collecting channel section, which is connected to the distribution channel sections. By means of such a collecting channel section, the fluid flowing in from the main channel can be distributed evenly to the distribution channel sections. The at least one collecting channel section can extend along part of the circumferential contour of the main channel section or along the entire circumferential contour of the main channel section.

[0015] With the bipolar plate, the angle of attack can be in a range of 10° to 80°, particularly 20° to 70°. The angles of attack of individual inlet channel sections and / or groups of inlet channel sections can be set or selected depending on their position relative to the circumferential contour. This allows the desired swirl flow in the main channel to be generated and controlled.

[0016] A fuel cell stack with several bipolar plates as described above and with several membrane units arranged between each pair of adjacent bipolar plates is also proposed, wherein the respective main channel sections of the bipolar plates form a continuous main channel for a fluid of the fuel cell stack.

[0017] In such a fuel cell stack, the main channel can be connected to a fluid supply element arranged at the inlet, wherein the fluid supply element is designed such that the fluid flow before or at the entry into the main channel is at least partially induced to form a swirling flow. For example, the fluid supply element can have a corresponding geometry and / or include at least one flow guide element. The flow guide element can be inclined and / or curved with respect to a main fluid flow direction, so that the fluid flow is deflected or can be deflected with respect to generating a swirling flow.

[0018] In the fuel cell stack, at least the main channel sections or the respective main channel for supplying the reactants, in particular hydrogen and air or oxygen, can be designed with inclined inlet channel sections, so that, based on the inclined arrangement of the inlet channel sections in the respective main channel for the reactant in question, a swirl flow can be generated for the inflowing reactant.

[0019] A fuel cell system can have at least one fuel cell stack described above.

[0020] A motor vehicle, in particular a motor vehicle that is at least partially electrically powered, may be equipped with or have such a fuel cell system.

[0021] Further advantages and details of the invention will become apparent from the following description of embodiments with reference to the figures. These show: Fig. 1 a simplified and schematic representation of a fuel cell stack; Fig. 2 a simplified and schematic representation of a bipolar plate with main channel section and inlet channel sections; Fig. 3 a simplified and schematic representation of a bipolar plate with main channel section, inlet channel sections and collector channel section; Fig. 4 a simplified and schematic, slightly enlarged representation of the main channel section to illustrate the angle of attack of the inlet channel sections; Fig. 5 simplified and schematic representations of the arrangement of inlet channel sections in one and / or two adjacent bipolar plates; Fig. 6 a simplified and schematic representation of a fuel cell stack in a housing with a fluid supply element.

[0022] In Fig. 1A simplified and schematic representation of a fuel cell stack 10 with several bipolar plates 12 is shown. Only some bipolar plates 12 are depicted; it should be noted that a typical fuel cell stack 10 has many more than the number of bipolar plates 12 indicated here.

[0023] Each bipolar plate 12 has a main channel section 14. By arranging the bipolar plates 12 in series, a main channel 16 is formed in the fuel cell stack by a multitude of main channel sections 14.

[0024] For example, in Fig. 1 a fuel cell stack 10 shown, with input-side main channels 16 for two reactants R1, R2 and a coolant K, which is illustrated by the respective arrows.

[0025] As is generally known, bipolar plates 12 are used in fuel cells to supply the electrochemically active areas with media. The bipolar plates 12 and electrochemically active membrane units, which are not shown in detail, are alternately assembled to form the fuel cell stack 10 in order to achieve the highest possible voltage by connecting the individual cells in series. The distribution of the reaction media R1, R2 (reactants) to the typically several hundred individual cells is effected via an opening (main channel section 14) that penetrates all the individual cells, forming the main channel 16 for the respective medium or reactant R1, R2. From these main channels 16, the typically three media or fluids (two reactants R1, R2 and a coolant K) are introduced through radially oriented openings towards the active area.

[0026] Fig. 2Figure 1 shows a simplified and schematic representation of an enlarged partial view of a bipolar plate 12 and an inlet-side main channel section 14. The main channel section 14 serves to supply a fluid or reactant to the fuel cell or fuel cell stack 10. This main channel section 14 may be used to form the main channel 16 for reactant R1. The following descriptions relating to the main channel section 14 of the bipolar plate 12 shown here also apply to other main channel sections 14 of the same bipolar plate 12 or of other bipolar plates 12 of the fuel cell stack 10. It should be noted that the following explanations refer to the inlet side or the supply side of the fuel cell stack 10 or the bipolar plates 12.

[0027] Starting from the main channel section 14, several inlet channel sections 18 extend. By means of the inlet channel sections 18, medium or fluid flowing through the main channel section 14, in particular a reactant R1, R2, is supplied to the active area of ​​the fuel cell, which is not shown further.

[0028] The inflow channel sections 18 are arranged along at least a part of the circumferential contour 20 of the main channel section 14 such that each inflow channel section 18 is inclined to the circumferential contour present in a respective connection area 22 of inflow channel section 18 and main channel section 14.

[0029] This is an example of a single inlet channel section 18 in the Fig. 4The image is shown slightly enlarged. The inlet channel section 18, or all inlet channel sections 18, are configured such that an angle of attack α is formed between the orthogonal OT and an inlet channel axis EA. Based on the inclined arrangement of the inlet channel sections 18 in the main channel section 14, a swirling flow can be generated for the incoming fluid, in particular the reactants R1 and R2. The orthogonal OT in the connection area can also be understood as the radial direction if the circumferential contour 20 is curved. The angle of attack can, for example, be in a range of approximately 10° to 80°, preferably approximately 20° to 70°.

[0030] The design of the circumferential contour 20 of the main channel section 18 is shown here in the Figures 1 to 5The example shown is a rectangle with rounded corners. However, it should be noted that this is only one possible configuration. The arrangement of the inlet channel sections 18 at an angle of attack can also be implemented, for example, with a circular circumferential contour. In this case, the aforementioned orthogonal line in each connection area is the radial direction of the circular main channel section 14. Of course, other geometric shapes for the circumferential contour are also conceivable.

[0031] The generation of the swirl flow DS is in the Figures 2 and 3This is illustrated by the curved arrow. The swirl flow DS is achieved by the non-orthogonal or non-radial alignment of the inlet channel sections 18. In other words, arranging the inlet channel sections 14 at a specific angle of attack promotes the generation of a swirl flow DS throughout the entire main channel 16. The generated swirl flow DS improves the distribution of the medium or fluid, particularly reactants R1 and R2, so that the fluid can be distributed evenly along the entire length of the main channel 16 to the respective active areas of the individual fuel cells.

[0032] In Fig. 2Figure 1 shows an example where the inlet channel sections 18 transition directly into distribution channel sections 24. In this example, the distribution channel sections 24 are essentially parallel to each other, at least where they connect to the respective inlet channel sections 18. The further course of the distribution channel sections 24, not shown here, can be configured according to common bipolar plate designs.

[0033] In Fig. 3 Figure 1 shows an example where the inlet channel sections 18 initially flow into a collecting channel section 26. The collecting channel section 26 is connected to the distribution channel sections 24. As can be seen from the Fig. 3As can be seen, the collecting channel section 26 extends along part of the circumferential contour 20 of the main channel section 14. Alternatively, a collecting channel section 26 can also be designed to extend along the entire circumferential contour 20 of the main channel section 14, which is additionally shown with dashed lines in the figure. By means of a collecting channel section 26, the incoming fluid can be distributed more homogeneously and evenly to the several distribution channel sections 24 and thus supplied to the active areas of the fuel cells.

[0034] Fig. 5 Figures A) to C) show examples of bipolar plates 12 with different arrangements of the inflow channel sections 18 in the respective bipolar plate halves 12-1, 12-2. According to the example in Fig. 5A All inflow channel sections 18 are formed in the same bipolar plate half 12-1. According to the example of the Fig. 5BThe inflow channel sections 18 are formed alternately in the two bipolar plate halves 12-1, 12-2. According to the example of the Fig. 5C The inflow channel sections 18 are formed one above the other in both bipolar plate halves 12-1, 12-2, which allows a larger cross-section of the inflow channel sections 18 to be formed.

[0035] The one in Fig. 5 The trapezoidal shape of the inlet channel sections 18 shown is purely exemplary. The inlet channel sections 18 and / or the distribution channel sections 24 and / or a collecting channel section 26 can also have a different cross-sectional shape, for example semicircular or rectangular or the like.

[0036] Fig. 6 The figure shows a simplified and schematic representation of a fuel cell stack not visible, which is housed in a fuel cell casing 28. This is an example relating to the Figure 6On the left side of the fuel cell housing, a fluid supply element 30 is shown, which is connected to a main channel (not visible) for a fluid or reactant R1, R2. The fluid supply element 30 is designed such that the flow of the fluid or reactant is at least partially induced to form a swirling flow before or upon entering the main channel (not visible). For example, the fluid supply element 30 can have a corresponding geometry and / or include at least one flow guide element 32. The flow guide element 32 can be inclined and / or curved with respect to a main flow direction HS of the fluid, so that the fluid flow is deflected or can be deflected with respect to generating a swirling flow.For example, it is conceivable that rib-like structures are arranged along an inner circumference of the fluid supply element 30 to generate a swirling flow. It is also conceivable to arrange a centrally or concentrically positioned flow guide element 32 in the fluid supply element 30, which, for example, has essentially radially extending profile elements to generate a desired swirling flow.

[0037] By arranging the inlet channel sections 18 at an angle, which can also be described as a quasi-tangential orientation of the inlet channel sections 18, a slight swirl can be imposed on the flow of the fluid or reactants R1, R2 in the main channel 16, which is formed from several main channel sections 14. This deflection towards a swirl flow improves the inflow of fluid into the first fuel cells. Depending on the angle of attack α of the inlet channel sections 18, the degree of swirl can be varied, thereby optimizing the uniform distribution into the individual cells and the pressure drop across the main channel 16. Thus, the optimized design of the media inlet (inclined inlet channel sections 18) into the bipolar plate (distribution channel sections 24) forces a swirl flow in the main channel 16, which improves the media / fluid flow and the uniform distribution through the fuel cell stack 10.

[0038] One above, referring to the Figs. 1 to 6 The described fuel cell stack 10 can be used or installed in a motor vehicle that is at least partially electrically powered, in particular as part of a fuel cell system of the motor vehicle.

Claims

1. Bipolar plate (12) for a fuel cell stack (10) of a fuel cell system having at least one main channel portion (14) which is configured for the supply of a fluid (R1, R2, K); multiple inflow channel portions (18) which branch off from the main channel portion (14); multiple distributor channel portions (24) which are fluidically connected to the inflow channel portions (18); wherein the inflow channel portions (18) are arranged along at least a portion of the circumferential contour (20) of the main channel portion (14) in such a manner that each inflow channel portion (18) with respect to a notional orthogonal (OT) to the circumferential contour (20) provided at that location in a respective connection region of the inflow channel portion (18) and main channel portion (14) is constructed to be inclined with respect to this orthogonal (OT) such that between the orthogonal (OT) and an inflow channel axis (EA) an angle of attack (α) is formed, wherein based on the inclined arrangement of the inflow channel portions (18) a twisted flow (DS) can be produced in the main channel portion (14) for the incoming fluid (R1, R2, K), characterized in that the inflow channel portions (18) are distributed along the entire circumferential contour (20) of the main channel portion (14).

2. Bipolar plate (12) according to claim 1, characterized in that the inflow channel portions (18) open in at least one collection channel portion (26) which is connected to the distributor channel portions (24).

3. Bipolar plate (12) according to claim 2, characterized in that the at least one collection channel portion (26) extends along a portion of the circumferential contour (20) of the main channel portion (18) or along the entire circumferential contour (20) of the main channel portion (18).

4. Bipolar plate (12) according to any one of the preceding claims, characterized in that the angle of attack (α) is in a range from 10° to 80°5. Fuel cell stack (10) having multiple bipolar plates (12) according to any one of the preceding claims and having multiple membrane units which are arranged between two adjacent bipolar plates (12) in each case, wherein the respective main channel portions (14) of the bipolar plates (12) form a continuous main channel (16) for a fluid (R1, R2, K) of the fuel cell stack (10).

6. Fuel cell stack (10) according to claim 5, characterized in that the main channel (16) is connected to a fluid supply element (30) which is arranged at the input side, wherein the fluid supply element (30) is constructed in such a manner that the flow of the fluid (R1, R2, K) before or upon entry into the main channel (16) is at least proportionally caused to form a twisted flow (DS).

7. Fuel cell stack (10) according to claim 5 or 6, characterized in that at least the main channel portions (14) or the respective main channel (16) are constructed for the supply of the reagents (R1, R2), in particular hydrogen and air or oxygen, with inclined inflow channel portions (18) so that based on the inclined arrangement of the inflow channel portions (18) in the respective main channel (16) for the relevant reagents (R1, R2) a twisted flow (DS) for the incoming reagents (R1, R2) can be produced.

8. Fuel cell system having at least one fuel cell stack (10) according to any one of claims 5 to 7.

9. Motor vehicle, in particular an at least partially electrically driven motor vehicle, having a fuel cell system according to claim 8.