Fuel cell air flow guide polar plate suitable for normal pressure or low pressure operation
Technical Field
The invention relates to a fuel cell, in particular to an air guide polar plate of the fuel cell suitable for normal pressure or low pressure operation.
Background
An electrochemical fuel cell is a device that is capable of converting hydrogen fuel and an oxidant into electrical energy and reaction products. The inner core component of the device is a Membrane Electrode (MEA), which is composed of a proton exchange Membrane and two porous conductive materials sandwiched between two surfaces of the Membrane, such as carbon paper. The membrane contains a uniform and finely dispersed catalyst, such as a platinum metal catalyst, for initiating an electrochemical reaction at the interface between the membrane and the carbon paper. The electrons generated in the electrochemical reaction process can be led out by conductive objects at two sides of the membrane electrode through an external circuit to form a current loop.
At the anode end of the membrane electrode, fuel can permeate through a porous diffusion material (carbon paper) and undergo electrochemical reaction on the surface of a catalyst to lose electrons to form positive ions, and the positive ions can pass through a proton exchange membrane through migration to reach the cathode end at the other end of the membrane electrode. At the cathode end of the membrane electrode, a gas containing an oxidant (e.g., oxygen), such as air, forms negative ions by permeating through a porous diffusion material (carbon paper) and electrochemically reacting on the surface of the catalyst to give electrons. The anions formed at the cathode end react with the positive ions transferred from the anode end to form reaction products.
In a pem fuel cell using hydrogen as the fuel and oxygen-containing air as the oxidant (or pure oxygen as the oxidant), the catalytic electrochemical reaction of the fuel hydrogen in the anode region produces hydrogen cations (or protons). The proton exchange membrane assists the migration of positive hydrogen ions from the anode region to the cathode region. In addition, the proton exchange membrane separates the hydrogen-containing fuel gas stream from the oxygen-containing gas stream so that they do not mix with each other to cause explosive reactions.
In the cathode region, oxygen gains electrons on the catalyst surface, forming negative ions, which react with the hydrogen positive ions transported from the anode region to produce water as a reaction product. In a proton exchange membrane fuel cell using hydrogen, air (oxygen), the anode reaction and the cathode reaction can be expressed by the following equations:
and (3) cathode reaction:
in a typical pem fuel cell, a Membrane Electrode (MEA) is generally placed between two conductive plates, and the surface of each guiding plate in contact with the MEA is die-cast, stamped, or mechanically milled to form at least one or more guiding grooves. The guide electrode plates can be plates made of metal materials or plates made of graphite materials. The diversion pore canals and the diversion grooves on the diversion electrode plates respectively guide the fuel and the oxidant into the anode area and the cathode area on two sides of the membrane electrode. In the structure of a single proton exchange membrane fuel cell, only one membrane electrode is arranged, and a flow guide polar plate of anode fuel and a flow guide polar plate of cathode oxidant are respectively arranged on two sides of the membrane electrode. The flow guide polar plates are used as a current flow collection mother plate and mechanical supports at two sides of the membrane electrode, and flow guide grooves on the flow guide polar plates are also used as channels for fuel and oxidant to enter the surfaces of the anode and the cathode and as channels for taking away water generated in the operation process of the fuel cell.
In order to increase the total power of the whole proton exchange membrane fuel cell, two or more single cells can be connected in series to form a battery pack in a straight-stacked manner or connected in a flat-laid manner to form a battery pack. In the direct-stacking and serial-type battery pack, two surfaces of one polar plate can be provided with flow guide grooves, wherein one surface can be used as an anode flow guide surface of one membrane electrode, and the other surface can be used as a cathode flow guide surface of another adjacent membrane electrode, and the polar plate is called a bipolar plate. A series of cells are connected together in a manner to form a battery pack. The battery pack is generally fastened together into one body by a front end plate, a rear end plate and a tie rod.
A typical battery pack generally includes: (1) the fuel (such as hydrogen, methanol or hydrogen-rich gas obtained by reforming methanol, natural gas and gasoline) and the oxidant (mainly oxygen or air) are uniformly distributed in the diversion trenches of the anode surface and the cathode surface; (2) cooling fluid (such as water) is uniformly distributed into cooling channels in each battery pack through an inlet and an outlet of the cooling fluid and a flow guide channel, and heat generated by electrochemical exothermic reaction of hydrogen and oxygen in the fuel cell is absorbed and taken out of the battery pack for heat dissipation; (3) the outlets of the fuel gas and the oxidant gas and the corresponding flow guide channels can carry out liquid and vapor water generated in the fuel cell when the fuel gas and the oxidant gas are discharged. Typically, all fuel, oxidant, and cooling fluid inlets and outlets are provided in one or both end plates of the fuel cell stack.
The proton exchange membrane fuel cell can be used as a power system of all vehicles, ships and other vehicles, and can also be used as a portable, movable and fixed power generation device. The pem fuel cell power generation system must include fuel cell stack, hydrogen supply, air supply, cooling, automatic control, and power output. The stability and reliability of operation of pem fuel cells are very important for applications as vehicle, marine power systems or mobile power plants. Wherein improving the operational stability and reliability of the fuel cell stack is critical.
At present, in the design of an air guide polar plate of a proton exchange membrane fuel cell stack, in order to reduce air resistance, the size of a single cross section of an air flow groove is large, and the number of the air flow grooves is small; in addition, in order to increase the rapid diffusion of the oxidant air to the electrode reaction zone, the air flow channels on the air guide flow plate are often designed to have a serpentine or bent shape, so as to form a turbulent flow for the fluid to pass through, thereby facilitating the diffusion of the oxidant air to the electrode reaction zone. For example, US patent US5,773,160, as shown in fig. 1.
The design of the air flow-guiding polar plate in the fuel cell stack has the following technical defects:
since the number of air flow channels is small and the flexibility is large, and the length of the air flow channels is long, the product water produced by the fuel cell is easily generated on the cathode side of the electrode to block the air flow channels, and the product water produced by the fuel cell is also easily generated on the anode side of the electrode by reverse osmosis to block the hydrogen flow channels. Especially when the fuel cell is used as a vehicle or ship power system or a movable power generation device, the working condition of the power system is greatly changed, the output power of the fuel cell is also greatly changed, and thus the air and hydrogen flow channels are easily blocked by water generated by the fuel cell.
In addition, in order to prevent the water generated by the fuel cell from blocking the diversion trench, the air-hydrogen metering ratio of the operation of the fuel cell is often increased, that is, the air and hydrogen flow rates are increased, and the product water is taken out of the fuel cell by using excessive air and hydrogen.
And thirdly, when the air flow groove or the hydrogen flow groove of the guide plate of the fuel cell is blocked in operation, the voltage of a certain blocked cell is very low or even has a negative value, so that the operation of the fuel cell is unstable, and the electrode is punctured in serious conditions, so that the whole cell stack is damaged.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the fuel cell air guide polar plate which is not easy to block a guide groove, runs stably and is suitable for normal-pressure or low-pressure operation.
The purpose of the invention can be realized by the following technical scheme: the utility model provides a fuel cell air water conservancy diversion polar plate that is fit for ordinary pressure or low pressure operation, its characterized in that, this air water conservancy diversion polar plate is air conservancy diversion flow plate and cooling water board back of the body group go back to the body square water conservancy diversion bipolar plate of an organic whole, and this water conservancy diversion bipolar plate includes air inlet mainstream hole, air outlet mainstream hole, hydrogen inlet mainstream hole, hydrogen outlet mainstream hole, cooling water inlet mainstream hole, cooling water outlet mainstream hole, and each fluid is advanced, is gone out mainstream pore diagonal setting, air inlet, the outlet mainstream hole of air flow plate between be equipped with many root air flow grooves,cooling water inlet, the outlet mainstream hole of cooling water board between be equipped with many cooling water launders.
Sealing grooves are arranged among the fluid main flow holes, between the fluid main flow holes and the air flow groove or the cooling water flow groove, and at the periphery of the air guide flow plate or the cooling water plate.
The air flow grooves are divided by the air inlet main flow holes, distributed in an S-shaped trend and converged by the air outlet main flow holes.
The connecting part of the air flow groove and the air inlet and outlet main flow hole is provided with a metal bridge seal, and air flows through the metal bridge seal.
The air flow grooves divided from the main air inlet flow holes are subdivided into at least two parts after passing through the temporary flow field, and are combined into at least two parts after passing through the S-shaped flow field to form a plurality of air flow grooves again, and then the air flow grooves are converged at the main air outlet flow holes.
The cooling water flow grooves are divided from the cooling water inlet main flow holes, distributed in an S-shaped trend and collected in the cooling water outlet main flow holes; the cooling water flow grooves divided from the cooling water inlet main flow hole are subdivided into two parts after passing through the transient flow field, and are combined into one part after passing through the S-shaped flow field, so that the cooling water flow grooves are formed again and are collected to the cooling water outlet main flow hole.
And the opposite corners of the cooling water plate are respectively provided with a voltage detection tank.
And a positioning hole pin is respectively arranged at the opposite angles of the air guide flow plate corresponding to thecooling water plate.
The depth of the air flow groove is multiplied by the width of the groove, which is 0.1-1.0 multiplied by 0.1-2.0 mm, and the number of the grooves is 10-60.
The depth of the cooling water flow groove is multiplied by the width of the groove, which is 0.1-1.0 multiplied by 0.1-2.0 mm, and the number of the grooves is 10-40.
Compared with the prior art, the invention has the following advantages:
1. the air guide grooves are in an S-shaped trend on the guide flow field, so that the defect that the pressure difference between air inlet and air outlet is increased due to the fact that the air guide grooves with a small number are bent back and forth repeatedly on the guide flow field in the prior art is overcome, and the air guide groove is suitable for normal-pressure air operation.
2. The cooling water channels are subdivided on the flow guide field to form an S-shaped trend, the water flow resistance is small, the temperature difference between the inlet and the outlet of the cooling water is small, and the operation temperature of the fuel cell is uniform.
3. Even if a few grooves of the plurality of air diversion grooves are blocked, most other grooves are still smooth, and the operation influence of the fuel cell is small.
4. A plurality of air diversion grooves are arranged on the diversion plate in an S-shaped trend, so that the trend of the air diversion grooves is prevented from being repeatedly bent, and the generated water is easily taken out of the fuel cell.
Drawings
FIG. 1 is a schematic view of an air-guiding flow field structure of a conventional air-guiding plate;
FIG. 2 is a schematic structural view of the air guide plate of the present invention;
fig. 3 is a schematic structural view of another air guide plate according to the present invention;
FIG. 4 is a schematic structural diagram of a cooling water plate on the reverse side of the air guide plate according to the present invention.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
As shown in fig. 2 and 4, the fuel cell air flow guiding polar plate suitable for normal pressure air operation used in 1 to 100KW fuel cell is 200 × 200 × 1.5mm in size, the air flow guiding polar plate is a square flow guiding bipolar plate with an air flow guiding plate 1 and a cooling water plate 2 combined into a whole in a reverse direction, the flow guiding bipolar plate includes an air inlet main flow hole 3, an air outlet main flow hole 4, a hydrogen inlet main flow hole 5, a hydrogen outlet main flow hole 6, a cooling water inlet main flow hole 7, and a cooling water outlet main flow hole 8, each of the fluid inlet and outlet main flow holes is diagonally arranged, a plurality of air flow grooves 9 are arranged between the air inlet and outlet main flow holes of the air flow guiding plate, the groove depth × the groove width of the air flow grooves is 0.8 × 0.8mm, the number of the grooves is 30, a plurality of cooling water flow grooves 10 are arranged between the cooling water inlet and outlet main flow holes of the cooling water plate, the groove depth × the cooling water groove width is 0.5 × 0.8mm, the number of the grooves is 20, and sealing grooves 11 are arranged among the fluid main flow holes, between the fluid main flowholes and the air flow grooves or the cooling water flow grooves, and on the periphery of the air guide flow plates or the cooling water plates.
The air flow grooves 9 are divided from the air inlet main flow holes 3, distributed in an S-shaped trend and then converged in the air outlet main flow holes 4.
The connecting part of the air flow groove 9 and the air inlet and outlet main flow hole is provided with a metal titanium plate bridge seal 12, and air flows through the metal bridge seal.
The cooling water grooves 10 are divided by the cooling water inlet main flow hole 7, distributed in an S-shaped trend and collected by the cooling water outlet main flow hole 8; wherein, many cooling water flowing grooves which are divided from the cooling water inlet main flow hole 7 are divided into two parts after passing through the transient flow field, and are combined into one after passing through the S-shaped flow field, and many cooling water flowing grooves are formed again and are collected to the cooling water outlet main flow hole 8.
And a voltage detection groove 13 is respectively arranged at the opposite corners of the cooling water plate 2.
And the opposite angles of the air flow guide plate 1 and the cooling water plate 2 are respectively provided with a positioning hole pin 14, and the hole pins 14 are used for being matched and positioned with the positioning hole pins of the hydrogen flow guide plate.
Example 2
As shown in fig. 3 and 4, the fuel cell air flow guiding polar plate suitable for normal pressure air operation used in 1 to 100KW fuel cell is 200 × 200 × 1.5mm in size, the air flow guiding polar plate is a square flow guiding bipolar plate with an air flow guiding plate 1 and a cooling water plate 2 combined into a whole in a reverse direction, the flow guiding bipolar plate includes an air inlet main flow hole 3, an air outlet main flow hole 4, a hydrogen inlet main flow hole 5, a hydrogen outlet main flow hole 6, a cooling water inlet main flow hole 7, and a cooling water outlet main flow hole 8, each of the fluid inlet and outlet main flow holes is diagonally arranged, a plurality of air flow grooves 9 are arranged between the air inlet and outlet main flow holes of the air flow guiding plate, the groove depth × the groove width of the air flow grooves is 0.8 × 0.8mm, the number of the grooves is 30, a plurality of cooling water flow grooves 10 are arranged between the cooling water inlet and outlet main flow holes of the cooling water plate, the groove depth × the cooling water groove width is 0.5 × 0.8mm, the number of the grooves is 20, and sealing grooves 11 are arranged among the fluid main flow holes, between the fluid main flow holes and the air flow grooves or the cooling water flow grooves, and on the periphery of the air guide flow plates or the cooling water plates.
In this embodiment 2, the plurality of air flow grooves 9 branched from the air inlet main flow hole 3 are subdivided into two parts (forming branch air flow grooves) after passing through the transient flow field, and are combined into one after passing through the S-shaped flow field to form a plurality of air flow grooves 9 again, and then are collected in the air outlet main flow hole. The rest of the structure is the same as in example 1.
Example 3
The fuel cell stack of example 1 is a fuel cell air guide plate with dimensions of 200 × 200 × 1.5mm suitable for normal pressure air operation, and example 3 is a fuel cell air guide plate with dimensions of 200 × 200 × 1.5mm suitable for low pressure air operation, and the other designs are the same as those of example 1, except that: the air flow groove has a groove depth × a groove width of 0.3 × 0.8mm, the number of grooves is 25, and the flow resistance of air entering from the inlet of the guide plate is greater than that in example 1, so that the air operation pressure is about 0.5 atm (relative pressure).
Example 4
This example 4 is an air guide plate used in a fuel cell suitable for medium and low pressure air operation, the depth and width of the grooves are the same as those of example 1, but the number of the grooves is reduced to 20, and the air operation pressure is about 1 atmosphere (relative pressure).