CN104713689A - Gas leakage detection method of permeable bipolar plate in proton exchange membrane fuel cell stack - Google Patents

Abstract

The water-permeable bipolar plate in the proton exchange membrane fuel cell stack has the functions of water permeability and gas barrier, which can ensure that the gas in the oxidant chamber does not enter the water chamber while discharging the water generated by the fuel cell; however, during the operation of the fuel cell, if the operating conditions When the control is improper or the bipolar plate is damaged, the seal fails and other faults, the permeable bipolar plate may leak air, that is, lose the original gas barrier function. The invention relates to a method for detecting the water-permeable bipolar plate that has lost the gas-blocking function in a multi-section water-permeable-plate fuel cell stack, and can quickly find out the bipolar plate that has lost the gas-blocking function without completely disassembling the stack The plate is used to process it, ensuring high utilization of the oxidant gas, and avoiding unnecessary impact on other components during the complete disassembly of the stack and improving work efficiency.

Description

Gas leakage detection method of permeable bipolar plate in proton exchange membrane fuel cell stack

technical field

The invention relates to a method for detecting air leakage of a fuel cell, and is particularly suitable for the method for detecting air leakage of a water-permeable bipolar plate in a proton exchange membrane fuel cell stack.

Background technique

A proton exchange membrane fuel cell is a power generation device that directly and efficiently converts the chemical energy in fuel and oxidant into electrical energy through the electrocatalytic reaction on the membrane electrode. The bipolar plate is an important component in the proton exchange membrane fuel cell stack, which has functions such as fluid distribution, conduction, cooling, and separation of fuel and oxidant. Common bipolar plates (traditional bipolar plates) have a total of three chambers: fuel chamber, oxidant chamber, and coolant chamber. The three chambers are kept separated, and the fluids do not flow through each other in the three chambers. The electrochemistry of the membrane electrode assembly (MEA) After the produced water enters the oxidant chamber, it is carried out of the cell directly by the air flow or by gravity.

In recent years, a new type of water-permeable bipolar plate (CN 1179428C, CN101501909A) has appeared. The fuel chamber and the oxidant chamber are kept isolated, but there is a water-permeable plate (or "porous water transfer plate") between the oxidant chamber and the coolant chamber. . In addition to the functions of the above-mentioned traditional bipolar plates, the water-permeable bipolar plate also has the function of water-permeable and gas-blocking. The so-called water-permeable gas barrier means that during the operation of the fuel cell, the generated water in the oxidant chamber can directly pass through the water-permeable plate of the bipolar plate and enter the coolant chamber by means of the pressure difference between the oxidant chamber and the coolant chamber. The coolant exits the cell, but the gas in the oxidant chamber does not pass through the permeable plate into the coolant chamber. The unique water-permeable and gas-blocking function of the water-permeable bipolar plate greatly reduces the flow rate requirements of the gas in the oxidant chamber, improves the water management capability of the battery, and ensures a high utilization rate of the oxidant.

However, during the operation of the water-permeable bipolar plate fuel cell, it is necessary to keep the pressure difference between the two chambers (oxidant chamber and coolant chamber) before and after the water-permeable plate within a certain range. If the air leaks, the original air-blocking function will be lost; in addition, if the permeable plate is damaged or there is a problem with the sealing, it will also cause the permeable plate to leak air. At this time, it is necessary to find out the bipolar plate that has lost the gas barrier function in order to deal with it. The usual practice is to completely disassemble the battery and conduct a separate leak test on each bipolar plate until the faulty bipolar plate is found. This method is time-consuming and labor-intensive, and in the process of battery disassembly, it is inevitable to touch other components, such as MEA, glue lines, etc., which may cause damage to these components.

Contents of the invention

The present invention aims to overcome the shortcomings and deficiencies of the above-mentioned prior art, and provides a detection method for the water-permeable bipolar plate that loses the gas barrier function in the multi-section water-permeable plate proton exchange membrane fuel cell stack, which is used in the fuel cell stack After the assembly is completed, without completely disassembling the stack, quickly find the bipolar plate that has lost the gas barrier function. The detailed method is as follows:

(1) Ensure that in the initial state, each cell in the stack has no voltage value or the voltage value is significantly lower than the open circuit level (for example, use nitrogen to purge the fuel chamber and oxidant chamber, or discharge).

(2) The fuel chamber and oxidant chamber of the battery to be tested are respectively fed with fuel (such as hydrogen) and inert gas (such as nitrogen) at a certain pressure. The purpose of feeding inert gas is to prevent external air from entering the oxidant chamber and disturbing the test results.

(3) Let the coolant cavity of the battery under test flow into the oxidizer (such as air) at a certain pressure for a period of time.

(4) Observe and record the time when the voltage value of each single cell in the battery appears or reaches the normal open circuit time: for the permeable plate with air leakage, the air enters the coolant chamber and quickly leaks into the oxidant chamber, and generates electricity with the catalyst in the oxidizer chamber. The chemical reaction causes the open circuit of this battery to rise rapidly; for the air-tight permeable plate, although the air cannot directly enter the oxidant chamber from the coolant chamber, because the oxidant chambers of each single cell are connected, the oxidant of the air-leakage permeable plate The air in the cavity will also gradually diffuse into the oxidant cavity of the normal permeable plate, causing the corresponding open circuit voltage to gradually increase, but the time it takes to start rising and reach the open circuit voltage is lower than that of the battery corresponding to the leaky permeable plate. Therefore, by detecting the starting time when the voltage of each battery starts to rise and the time when the voltage reaches the open circuit voltage, the specific position of the bipolar plate that loses the gas barrier function can be determined.

In the detection method of the water-permeable bipolar plate that has lost the gas barrier function of the present invention, fuel, inert gas and oxidant with a certain pressure need to be introduced. The certain pressure refers to keeping the pressure of fuel and inert gas as consistent as possible to prevent the battery MEA from being damaged due to excessive pressure difference on both sides; The maximum pressure difference that can be tolerated exceeds this maximum pressure difference, and the normal permeable plate will also leak air. In severe cases, the plate will be completely damaged due to excessive pressure difference.

The advantages of the present invention: the application of the present invention to detect the gas leaking bipolar plates in the multi-section permeable plate fuel cell stack can quickly find out the bipolar plates that have lost the gas barrier function without completely disassembling the stack Plate, in order to process it, ensure high utilization of oxidant or fuel, and avoid unnecessary impact on other components during the complete disassembly of the stack and improve work efficiency.

Description of drawings:

In the embodiment of Fig. 1, the stack voltage distribution situation when the coolant cavity is fed into the air for 5s;

In the embodiment of Fig. 2, the voltage distribution of the stack when the coolant cavity is filled with air for 20s.

Detailed ways

In order to make those skilled in the art understand the purpose, features and effects of the present invention, the present invention will be described in detail by the following specific examples.

Example:

In this embodiment, the permeable bipolar plate proton exchange membrane fuel cell stack is composed of 6 single cells connected in series, and the water generated in the oxidant chamber needs to be introduced into the coolant chamber through the water permeable plate. The water-permeable plate has a pressure resistance of 1.0 bar, that is, when the fluid pressure difference between the oxidant chamber and the coolant chamber is higher than 1.0 bar, the water-permeable plate loses its gas-blocking function. Under normal circumstances, when the air pressure difference between the oxidant chamber and the water chamber of the permeable plate is within 1.0 bar, the oxidant will not leak into the water chamber, but now there is an obvious air leakage phenomenon, and it is necessary to determine which bipolar plate is leaking, and then take corresponding measures. repair strategy.

In view of the above situation, the following detection method is applied:

Connect the voltage inspection circuit of each cell of the stack to be tested. At this time, each cell in the stack has no voltage value; feed 0.5bar nitrogen into the oxidant chamber of the stack, and at the same time, inject nitrogen into the fuel chamber Introduce 0.5 bar of hydrogen; then introduce 0.5 bar of air into the coolant cavity, and observe the voltage value change of each cell in the stack. Figure 1 and Figure 2 show the voltage distribution of each cell after 5s and 20s of air flow respectively. It can be seen from Figure 1 that when the air is fed for 5 seconds, the voltage value of the fifth single cell reaches 0.75V, and the other nodes have no voltage for the time being, indicating that there is air leakage in the bipolar plate on the side of the oxidant chamber used in this single cell; from Figure 2 It can be seen that as the air continues to flow in, the voltage of section 5 continues to rise, and reaches 0.91V in 20s, basically reaching the open circuit voltage level. At the same time, voltages appear in sections 4 and 6, and the voltage values are 0.22V respectively. , 0.15V, this is not due to air leakage from the water-permeable panels used in Sections 4 and 6, but due to the gradual diffusion of air from the oxidant chamber in Section 5 to the oxidant chamber in Section 4 and 6, because the voltage in Section 4 and 6 occurs when the Significantly later than v5. Therefore, according to the above results, it can be known that the bipolar plate on the side of the oxidant chamber used in the fifth battery is the bipolar plate that has lost the gas barrier function.

If you need to confirm again, you can stop feeding air into the coolant chamber, and use a resistor to discharge the battery while maintaining the nitrogen gas in the oxidant chamber until the open circuit voltage of each single cell returns to 0V (or ≤0.6V). Then repeat the above detection process.

Claims (8)

1. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling, is characterized in that: concrete detecting step is as follows:

In guarantee battery, respectively save the equal no-voltage in single pond or when being starkly lower than open-voltage level (≤0.6V), mesuring battary fuel cavity, oxidant cavity are passed into fuel and inert gas respectively; Then mesuring battary coolant cavity is passed into oxygenant; Observe and record each time saved unit voltage value time of occurrence or reach normal open circuit in battery: for the porous disc that gas leakage occurs, air leaks to oxidant cavity rapidly after entering coolant cavity, with oxidant cavity inner catalyst generation electrochemical reaction, this batteries open-circuit is caused to rise rapidly; The bipolar plates of the used in battery oxidant cavity side occurring voltage at first or reach normal open circuit is the bipolar plates losing choke function.

2. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling according to claim 1, is characterized in that: fuel used is hydrogen-containing gas.

3. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling according to claim 2, is characterized in that: described hydrogen-containing gas comprises pure hydrogen, general hydrogen.

4. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling according to claim 1, is characterized in that: described inert gas refer to not with the gas of fuel-cell catalyst generation electrochemical reaction.

5. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling according to claim 4, is characterized in that: described inert gas comprises nitrogen, argon gas, helium.

6. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling according to claim 1, is characterized in that: described oxygenant is oxygen-containing gas.

7. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling according to claim 6, is characterized in that: described oxygenant comprises pure oxygen, air.

8. permeable double-polar plate gas leakage detection method in proton exchange film fuel cell electric piling according to claim 1, it is characterized in that: in testing process, fuel, inert gas, oxygenant need be passed into, describedly pass into fuel, inert gas, oxygenant have certain pressure, certain pressure refers to fuel, inert gas pressure is consistent as far as possible; Should ensure that between inert gas, oxygenant, pressure differential (absolute value) is not higher than the maximum differential pressure that porous disc can bear under normal circumstances simultaneously.