US-12620607-B2 - Bipolar plate with insertable diaphragm and fuel cell stack

US12620607B2US 12620607 B2US12620607 B2US 12620607B2US-12620607-B2

Abstract

A bipolar plate for a fuel cell comprises an active region and an edge region surrounding the active region, the edge region being associated to a first media guide fluidically connected to a first passage and a second media guide fluidically connected to a second passage, as well as having a media duct which runs through the active region and fluidically connects the first passage to the second passage. At least one of the media guides comprises a first partial chamber and a second partial chamber having the passage. A flow cross-section of the media guide is tapered between the first partial chamber and the second partial chamber, and a diaphragm can be inserted or is inserted into the second partial chamber.

Inventors

Markus Gretzer
Norbert Kluy

Assignees

AUDI AG

Dates

Publication Date: 20260505
Application Date: 20211025
Priority Date: 20201030

Claims (10)

1 . A bipolar plate for a fuel cell, comprising: an active region; an edge region surrounding the active region, the edge region being associated to a first media guide fluidically connected to a first passage and a second media guide fluidically connected to a second passage; a media duct which runs through the active region and fluidically connects the first passage to the second passage, wherein at least one of the first and second media guides comprises a first partial chamber and a second partial chamber having the first passage or the second passage, respectively, wherein a media guide channel is provided between the first partial chamber and the second partial chamber, wherein a flow cross-section of the media guide is reduced at the media guide channel provided between the first partial chamber and the second partial chamber such that a flow cross-section of the media guide channel is smaller than a flow cross-section of the first partial chamber adjacent to the media guide channel and smaller than a flow cross-section of the second partial chamber adjacent to the media guide channel, and wherein the second partial chamber is configured to receive a diaphragm or the diaphragm is inserted into the second partial chamber.
2 . The bipolar plate according to claim 1 , wherein the diaphragm is inserted into the second partial chamber, and wherein the diaphragm is adjustably mounted by an actuator within the second partial chamber for adjustment of a flow cross-section of the first passage or the second passage.
3 . The bipolar plate according to claim 1 , wherein the diaphragm is inserted into the second partial chamber, and wherein the diaphragm is displaceably mounted by an actuator within the second partial chamber for adjustment of a flow cross-section of the first passage or the second passage.
4 . The bipolar plate according to claim 1 , wherein the reduced flow cross-section of the media guide at the media guide channel between the first partial chamber and the second partial chamber is formed by at least one protruding projection.
5 . The bipolar plate according to claim 1 , wherein the reduced flow cross-section of the media guide at the media guide channel between the first partial chamber and the second partial chamber is formed by two opposing protruding projections.
6 . The bipolar plate according to claim 4 , wherein the at least one protruding projection forms a guide rail for the diaphragm.
7 . The bipolar plate according to claim 1 , wherein the other one of the first and second media guides also comprises a first partial chamber and a second partial chamber having the first passage or the second passage, respectively, wherein a media guide channel is provided between the first partial chamber and the second partial chamber, wherein a flow cross-section of the media guide is reduced at the media guide channel provided between the first partial chamber and the second partial chamber such that a flow cross-section of the media guide channel is smaller than a flow cross-section of the first partial chamber adjacent to the media guide channel and smaller than a flow cross-section of the second partial chamber adjacent to the media guide channel, and wherein the second partial chamber is configured to receive a second diaphragm or the second diaphragm is inserted into the second partial chamber.
8 . The bipolar plate according to claim 7 , wherein the second diaphragm is inserted into the second partial chamber of the other one of the first and second media guides, and wherein the second diaphragm is adjustably mounted by an actuator within the second partial chamber for the purpose of adjustment of a flow cross-section of the first passage or the second passage.
9 . The bipolar plate according to claim 7 , wherein a cross-sectional area of the second partial chamber of the first media guide is different from a cross-sectional area of the second partial chamber of the second media guide.
10 . A fuel cell stack formed of a plurality of fuel cells stacked on top of each other in a stacking direction, comprising at least one bipolar plate according to claim 1 and a membrane electrode assembly.

Description

BACKGROUND Technical Field Embodiments of the invention relate to a bipolar plate for a fuel cell having an active region and an edge region surrounding the active region, the edge region being associated to a first media guide comprising a first passage and a second media guide comprising a second passage. Further, a media channel extending through the active region and fluidically connecting the first passage to the second passage is provided. Embodiments of the invention further relate to a fuel cell stack having at least one bipolar plate. Description of the Related Art Fuel cell devices are used for the chemical conversion of a fuel with oxygen to water in order to generate electrical energy. For this purpose, fuel cells contain a so-called membrane electrode assembly (MEA) as a core component, which membrane electrode assembly is a composite of a proton-conducting membrane and an electrode (anode and cathode) arranged on both sides of the membrane. In addition, gas diffusion layers (GDL) can be arranged on both sides of the membrane electrode assembly on the sides of the electrodes facing away from the membrane. During operation of the fuel cell device with a plurality of fuel cells combined to form a fuel cell stack, the fuel, in particular hydrogen H2 or a hydrogen-containing gas mixture, is supplied to the anode, where an electrochemical oxidation from H2 to H+ takes place with the release of electrons. A transport of the protons H+ from the anode compartment to the cathode compartment takes place via the electrolyte or the membrane, which separates the reaction compartments in a gas-tight manner and electrically insulates them. The electrons provided at the anode are fed to the cathode by means of an electrical line. Oxygen or an oxygen-containing gas mixture is fed to the cathode so that a reduction from O2 to O2− takes place with absorption of the electrons. At the same time, these oxygen anions react in the cathode compartment with the protons transported across the membrane forming water. The reactant gases are fed to the electrodes of the fuel cells by means of bipolar plates. In addition to the reactant gases, a cooling medium is also passed through the bipolar plates, so that three different media are passed through the bipolar plates in the smallest of spaces. In order to fulfill high performance requirements, a plurality of fuel cells are combined or alternatively stacked on top of each other to form a fuel cell stack. In this, the media guide can be designed as media ports formed as recesses in the edge region, which give rise to a plurality of three-dimensional spaces when the individual layers of the fuel cell stack are stacked on top of each other. Alternatively, the media guide can also be formed as a functional component associated with the edge region of the bipolar plates and the fuel cells, and formed separately therefrom, in which a three-dimensional space is formed. In other words, an external heater may be associated with the fuel cells and bipolar plates stacked on top of each another. In this manner, a plurality of three-dimensional spaces are formed along the stacking direction for the supply of the reactants and the cooling medium into the active region of the fuel cells, and a plurality of three-dimensional spaces are formed along the stacking direction for the discharge of the reactants and the products as well as the cooling medium. Typically, a channel structure of media channels is formed by means of the active region of the bipolar plate, which channel structure fluidically connects one of the media guides, such as a media port, to another of the media guides. At least one passage is realized in the bipolar plate body of the bipolar plate, which passage fluidically connects the media guide, for example the media port, with the media channel(s). In this, the efficiency of the fuel cell is significantly influenced by the media mass flow that flows through the media channels. This is determined to a considerable extent by the choice of the flow cross-section, which is to say, the diameter of the passage, which is defined when the bipolar plate is manufactured. The choice of diameter represents a compromise between different requirements for humidification and power output of the fuel cell. This makes it difficult to quickly adjust the power profile of the fuel cell stack during operation. Moreover, a uniform distribution of reactants within a fuel cell stack is desired in order to optimally supply all fuel cells with humidity and fuel. For this purpose, in DE 10 2014 22 06 82 A1 a bipolar plate with a plurality of media ports, which form a manifold, is described, wherein an insert element can be deployed in the manifold. This insert element changes the cross-section of the manifold in sections in order to supply each of the fuel cells within the fuel cell stack with the same volume flow of media. DE 10 2016 225 444 A1 moreover describes a separator plate with a pluralit