150hr强化道路振动工况实验下燃料电池电堆的气密性和电绝缘特性的变化

Experimental investigation of gas－tightnessand electrical insulation of fuel cell stack under strengthened road vibratingconditions

Yongping Hou

Wei Zhou

Caoyuan Shen

Abstract

Gas－tightness and electrical insulation aretwo important evaluation indexes of fuel cell vehicle safety． In this paper，the variation of gas－tightness and electrical insulation of fuel cell stackunder long－term vibrating conditions are experimentally investigated through a 150 h strengthened vibration test． Theload spectra applied in the test are simulated by the acceleration signals ofthe fuel cell stack， which are previously measured in a vehicle vibration test．The load signals of the vehicle vibration test are iterated through a roadsimulator from vehicle acceleration signals which are originally sampled in thestrengthened road of the ground prove． The test results show that the hydrogen leak rate of the stack increases1．5 times during the test． Additionally， the insulation resistance of the stack experiences a rapid decline atfirst， and then a steady linear decrease to 17．55％ of the original value． It isobserved that the decrease rate at the first stage is 25 times higher than theone at the second stage．

Fig． 1 e The road simulation test bench

通用接口总线（General－Purpose Interface Bus，GPIB）是一种设备和计算机连接的总线。

The labtronic 8800数字模拟结构测试控制系统

文中未提到车辆和电堆信息，从图上看是超越3号。

The 50 kW FC power module used here are consists of a stack with

560 cells assembled in series．

The effective membrane area per cell is 280 cm 2 ．

2004年，上海弘枫实业有限公司参与中国国家863项目，为超越3号50KW乘用车提供石墨双极板；随后，公司又为北京奥运会及中国世博会的燃料电池示范车辆提供石墨双极板。

Fig． 2 e Location of the accelerometers  on the FC stack．

Fig． 3 e The vibration test of FC stack  on the six－channel MAST．

Six－channel Multi Axial Simulation Table  （MAST）

Fig． 4 e Comparison of hydrogen intake  pressure between beginning and end of the vibration test．

During the test， the gas－tightness and  electrical insulation of the stack were measured six times at regular  intervals， respectively at 0， 26， 62， 72， 123．5 and150．

Fig． 5 e Hydrogen intake pressure varied  with time of vibration test．

Fig． 6 e The change of FC stack  insulation resistance with vibration time．

During the test， the electrical  insulation of the stack was evaluated by separately measuring  ground－resistances between cathode and anode with a megger under the hot conditions，  where the FC system load was disconnected and the coolant and humidification water circulated．

Conclusion

In summary， following conclusions can be  made from the investigation：

1． The impact of strengthened road  vibration conditions on the gas－tightness of FC stacks is divided into two  stages． At the beginning， no significant affect on the gas－tightness is found  during the test． However， the impact  becomes more distinct after 70 h of vibration． It can be inferred that  the real roads vibration does not have a significant influence on the  gas－tightness of the FC stack until the mileage reaches a certain extent．

2． The hydrogen leak rate of the FC stack  increases 50％ after a 150 h strengthened vibration test． It is obvious that  the long－term vibration leads to the damage of internal sealing structure of  the FC stack and makes the gas－tightness decline．

3． The decrease of insulation resistance  is divided into two phases． In the first phase the insulation resistance decreases  dramatically with a rate of 17．85 Ω／（V＊h）． In the second stage， it decreases  on a more steady and lineal path with a rate of 0．7016 Ω／（V＊h）． The decrease  rate of the first phase is 25 times higher than of the second phase．

4． After the 150 h strengthened road  vibration test， the insulation resistance of the FC stack decreases to 17．55％  of the original value．

The  insulation resistance at the end of test is 115 Ω／V， which is lower than the  standard value specified by SAE J2578， 4．3 （125 Ω／V） and may endanger the  safety of passengers．

很遗憾，对这个问题对于燃料电池电堆没有进一步的失效分析的结果。

It can be concluded that the long－term  strengthened road vibration has a great influence on the gas－tightness and  the electrical insulation of FC stacks． Such an effect cannot and should not  be ignored during the investigation．