车载燃料电池电堆中膜电极水含量实时测量和动态工况中不同位置水含量规律分析：膜电极水含量测试的三种方法

Real－time Measurement of Water Content ofCCM in On－board Fuel Cell Stack System

Toru IWANARI

Kazuyoshi MIYAJIMA

Koichiro FURUSAWA

Masajiro INOUE

In order to increase the durability of fuelcell stacks， the in－plane water content of the catalyst－coated membranes （CCM）in the cells is controlled within the proper range using stack impedance． Settingout to elucidate the status of the in－plane water content of the CCM， theresearch discussed in this paper employed a water content distributionmeasurement system to conduct real－time measurements of the in－plane watercontent of the cells in a fuel cell stack forming part of an on－boardgeneration system． The use of the system makes it possible to determine the in－plane water content of the CCMduring both constant current generation and transient current generation．The results of this study verified the effectiveness of the in－plane CCM watercontent control employed in the 2016 model FCV． In addition， optimization ofthe control of in－plane water content of the CCM has also had an effect infurther increasing the durability of the fuel cell stacks．

Fig． 1 Schematic image of fuel cell

The in－plane distribution of water contentof the CCM in the cells displays a range of variation due to instantaneous changesin operating conditions， including the flow rate and pressure of the gasessupplied to the stack， the temperature of the stack， and the current being generated．

图2和图3是核心逻辑。再好的逻辑也需要有实验支持要有数据库。

Fig． 2 Upper and lower limits for water  content to maintain PEM thickness and Pt surface area

Fig． 3 Relationship between stack  impedance and water content

Fig． 4 Schematic image of humidity  control of supplied air

虽然加增湿和旁路后系统变得有些复杂，但是在后文图15你会发现这个系统控制后效果不错。

Fig． 5 Dry weight method for measurement  of water content of CCM

Conventionally，

膜电极水含量测试的三种方法：

方法一：the dry weight method  （Fig． 5） or

方法二：the nuclear magnetic resonance （NMR） method have been used to  measure the in－plane distribution of water content of the CCM．

方法三：

impedance distribution measurement system  （IDMS）

如果这三种都看不上或者都无法实施，只能花钱找别人做第三种。

Fig． 6 Fuel cell system with IDMS for  bench use

impedance distribution measurement system  （IDMS）

Fig． 7 Water content distribution under  conditions of constant current generation

Fig． 8 Schematic image of movement of  water in CCM

Fig． 9 Results for water content under  conditions of constant current generation

Fig． 10 Schematic image of evaluation  running mode for fuel cell vehicle

Fig． 11 Time－series results for water  content in acceleration mode and deceleration mode

Fig． 12 Results for water content  distribution in acceleration mode and deceleration mode

Fig． 13 Time－series results for water  content in idling mode

Fig． 14 Results for water content  distribution in idling mode

Fig． 15 Effect of change in control on  water content at cathode inlet

Conclusion

Verification of the control of the  in－plane water content of the CCM in cells employed in the 2016 model FCV generation  system produced the following results：

（1）      It was verified that during  constant current generation， stack impedance control maintained the in－plane  water content of the CCM within the upper and lower limit values．

（2）      It was verified that the  in－plane water content of th CCM was maintained within the upper and lower  limit values during acceleration and deceleration， when transient current  generation is occurring． The causes of a reduction in the in－plane water  content of the CCM below the lower limit value during idling were identified，  and measures introduced in response were verified to be effective．

（3）      These results demonstrate the  effectiveness of control of the in－plane water content of the CCM in cells  using stack impedance． In addition， the optimization of control has also had  an effect in increasing the durability of the fuel cell stack．