CN102170002A

CN102170002A - Fuel cell flow field structure with depth gradually-diminished flow channels

Info

Publication number: CN102170002A
Application number: CN2011100863290A
Authority: CN
Inventors: 金正南; 孙红; 高晓佳; 吴玉厚; 唐玉兰; 王逊
Original assignee: Shenyang Jianzhu University
Current assignee: Shenyang Jianzhu University
Priority date: 2011-04-07
Filing date: 2011-04-07
Publication date: 2011-08-31

Abstract

The invention relates to the technical field of fuel cells, in particular to a fuel cell flow field structure with depth gradually-diminished flow channels. The advantages are adopted and the defects of the snakelike flow field are abandoned in the invention. The gas flow speed and pressure drop are well adjusted by using different depths of the flow channels so as to ensure that the electrochemical reaction inside the battery cell is carried out well. The width of each flow channel and the width of the bank keep constant and the depths of the flow channels are gradually diminished from a gas inlet hole to a gas outlet hole of a single snakelike flow channel. The depths of the flow channels are smoothly transited at a certain gradient at the corner connecting part of the flow channels with different depths. The flow field with gradually-diminished depths ensures that the gas pressure drop and the flow speed keep constant along the direction of the flow channels so as to effectively prevent from water logging.

Description

The fuel cell flow field structure that flow channel depth successively decreases step by step

Technical field

The present invention relates to the fuel cell technology field, the fuel cell flow field structure that specifically a kind of flow channel depth successively decreases step by step.

Background technology

Fuel cell is a kind ofly can be converted into the electrochemical appliance of electric energy by electrochemical reaction with being stored in chemical energy in the fuel.It is not subjected to the restriction of Carnot cycle without the overheated machine process, energy conversion efficiency height (40～60%); Environmentally friendly, discharge nitride and sulfide hardly; Emission amount of carbon dioxide is low, reduces more than 40% than the power plant.In addition, it also has, and noise is low, and startup is fast, does not have corrosion, prepares the advantage of easy and long service life.Because have these outstanding advantages, countries in the world government and large enterprise have dropped into great amount of manpower and material resources are researched and developed fuel cell technology.

Proton Exchange Membrane Fuel Cells is to belong to low-temperature fuel cell, working temperature is generally at 40～80 ℃, operation principle is: hydrogen and oxygen arrive the anode and the negative electrode of battery respectively by the air guide channel on the bipolar plates, reacting gas arrives proton exchange membrane by the diffusion layer on the electrode, anode one side at film, hydrogen is dissociated into hydrogen ion (proton) and electronegative electronics under the effect of anode catalyst, hydrogen ion is with proton hydrate H ⁺(xH ₂O) form shifts in proton exchange membrane, arrives negative electrode at last, realizes proton conductive.This transfer of proton causes anode electronegative electron accumulation to occur, thereby becomes an electronegative terminal (negative pole).Meanwhile, the oxygen molecule of negative electrode and catalyst excite the electronics of generation to react, become oxonium ion, make negative electrode become the terminal of positively charged (positive pole), its result has produced a voltage between the positively charged terminal of the electronegative terminal of anode and negative electrode.If link to each other the two poles of the earth by external circuit this moment, electronics will flow to negative electrode from anode by the loop, thereby produces electric energy.Simultaneously, hydrogen ion and the cation generation water that reacts.Electrode reaction is:

Anode (negative pole): H ₂→ 2H ⁺+ 2e ^-

Negative electrode (positive pole): 1/2O ₂+ 2H ⁺+ 2e ^-→ H ₂O

Cell reaction: H ₂+ 1/2O ₂→ H ₂O

Fuel cell is made up of a plurality of Proton Exchange Membrane Fuel Cells battery cells, and the core of Proton Exchange Membrane Fuel Cells is membrane electrode and bipolar plates.Bipolar plates provides the jog of gas distribution and collected current, and negative area is the flow field, and the flow field is the chief component of bipolar plates.The flow field mainly is divided into following several types: point-like, netted, porous body, parallel, snakelike, interdigitated and new flow field.The point-like flow field structure is simple, is specially adapted to pure hydrogen, pure oxygen, the fuel cell of steam state draining.To the Proton Exchange Membrane Fuel Cells of mainly discharging,, be unfavorable for discharging aqueous water because reaction gas flow is difficult to reach very high linear speed through this flow field with aqueous water.Mesh flow field is a kind of way of abandoning runner, because the rate of flow of fluid in this runner is lower, so drainability is relatively poor, but moisture-retaining capacity is stronger relatively, the fluid flow uniformity is generally not ideal enough, flowing of line zone is fast importing and exporting, and has delay on the corner, problems such as concentration polarization or water logging occur.The outstanding advantage of porous body runner is that it is low to the electrode diffusion layer requirement of strength, and when reaction gas when this flow field, easily form local turbulence and help the mass transfer of diffusion layer, reduce concentration polarization.Parallel flow field has the little advantage of flow resistance, this can reduce the pressure loss to a certain extent, improve the whole efficiency of battery, yet the minute differences of gas flow and response situation can cause disturbance to the overall performance of battery in each runner, occurs the situation of unstable properties easily.Serpentine flow is a kind of runner form that early proposes, its outstanding advantage is to get rid of the aqueous water of generation rapidly, be not prone to the situation in choked flow road, yet for the bigger flow-field plate of area, serpentine flow path can cause the reaction gas pressure drop to cause impeded drainage and electric current distribution inhomogeneous greatly because of runner is long.The design in interdigitated flow field can make reactant more fully by runner, and has good drainability, still, because the resistance of diffusion layer is bigger, can make the pressure in flow field fall increase simultaneously, and is short-circuited easily or the situation of channel.Chinese patent publication number CN1622377A discloses the patent of invention that a kind of name is called " a proton exchanging film fuel battery flow field structure ", it is exactly a kind of exchange film fuel battery of mesh flow field structure, Chinese patent publication number CN2893939Y discloses the utility model patent that a kind of name is called " a proton exchanging film fuel battery flow field structure ", its essence is a kind of serpentine flow.

Summary of the invention

In order to solve the shortcoming of above-mentioned middle serpentine flow, promptly owing to falling, air pressure causes impeded drainage generation water logging phenomenon greatly easily.The fuel cell flow field structure that provides flow channel depth to successively decrease step by step.

The present invention has drawn the advantage of serpentine flow, eliminates its shortcoming, has regulated gas flow rates and pressure drop well with different flow channel depths, guarantees good the carrying out of inside battery electrochemical reaction.At runner air inlet nose end, the reactant abundance, it is less to generate water, gas flow rate is very fast, and flow channel depth maximum herein is along the gas flow direction, along with the carrying out of reaction, the loss gradually of reactant, gas pressure intensity reduces, electrochemical reaction generates water content and increases, flow velocity reduces, and at this moment, the flow field that the degree of depth is successively decreased guarantees the downstream of gas in the flow field, especially end has certain pressure and flow velocity, thereby has prevented the water logging phenomenon effectively.

For achieving the above object, the technical solution used in the present invention is:

In Proton Exchange Membrane Fuel Cells single snake-like flow field, to the venthole direction, the degree of depth of runner is successively decreased step by step along the serpentine flow path air admission hole, forms the gradient of a runner integral body.

Specific as follows: to venthole 2 directions, the width of every width of flow path and bank keeps constant from the gas air admission hole 1 of single snake-like runner, and flow channel depth successively decreases step by step, and in the corner junction in deep stream not at the same level road, flow channel depth becomes certain slope to seamlessly transit.

The width of width of flow path and ridge is 1mm, 2 directions from gas air admission hole 1 to venthole, and per two flow channel depths are identical, are decided to be one-level, and the last item runner is an one-level.The 1st grade of flow channel depth is 1.5mm, and downward successively every grade of degree of depth is successively decreased, and the afterbody flow channel depth is 0.5mm.

Description of drawings

Figure 1 shows that the fuel cell flow field structure vertical view that the degree of depth is successively decreased step by step;

Figure 2 shows that the fuel cell flow field structure A-A profile that the degree of depth is successively decreased step by step;

Figure 3 shows that the fuel cell flow field structure B-B profile that the degree of depth is successively decreased step by step.

1 is air admission hole among the figure, and 2 is venthole.

Embodiment

The present invention is the improvement of carrying out on existing serpentine flow, and other aspects of fuel cell are not had to change substantially.Adopt the flow-field plate shown in the accompanying drawing to be elaborated, flow-field plate adopts the graphite cake (size only is used for illustrating) of 75mm * 75mm * 10mm, and the flow field effective area is 4 * 4=16mm ², totally 21 runners, every width of flow path is 1mm, the width of ridge (shoulder) is 1mm.There are one group of air admission hole (3) and one group of venthole (3) in whole flow field, and air admission hole is on the degree of depth top of dark runner, and venthole is at the degree of depth end of shallow runner.

Flow field of the present invention has 21 runners, and to the venthole direction, per two runners are one-level along serpentine flow path from air admission hole, and the degree of depth of every grade of runner is identical, and the last item runner is an one-level, totally 11 grades.The runner of air inlet nose end is the 1st grade, and the runner of the nose end of giving vent to anger is the 11st grade.The 1st grade of flow channel depth is 1.5mm, and the 2nd grade of flow channel depth is 1.4mm, and the degree of depth at different levels afterwards 0.1mm that successively decreases step by step successively is 0.5mm until the 11st grade of flow channel depth.The corner becomes gradient continuous transition between the two-stage runner.

Claims

1. the fuel cell flow field structure that successively decreases step by step of flow channel depth, it is characterized in that: from the gas air admission hole (1) of single snake-like runner to venthole (2) direction, it is constant that the width of every width of flow path and bank keeps, flow channel depth successively decreases step by step, in the corner junction in deep stream not at the same level road, flow channel depth becomes certain slope to seamlessly transit.

2. the fuel cell flow field structure that flow channel depth according to claim 1 successively decreases step by step, it is characterized in that: the width of width of flow path and ridge is 1mm, from gas air admission hole (1) to venthole (2) direction, per two flow channel depths are identical, be decided to be one-level, the last item runner is an one-level, and the 1st grade of flow channel depth is 1.5mm, downward successively every grade of degree of depth is successively decreased, and the afterbody flow channel depth is 0.5mm.