车用燃料电池停机耗氧补氢控制策略：为什么补氢，怎么补氢，补到什么程度

Investigation on a parking control strategy for automotive proton exchange membrane fuel cell

Tiancai Ma 马天才

Dong Zhu 朱东

Jialin Xie

Weikang Lin

Yanbo Yang

Abstract

In the proton exchange membrane fuel cell （PEMFC） for vehicles， the changes in gas composition and oxygen accumulation may exist during the parking process even by using a shut－down strategy of oxygen consumption， which can lead to the hydrogen／air interface． However， this process of oxygen accumulation is often ignored． Thus， in this work， the diffusion rate of the gas， the gas composition changes， and the starting voltage of the PEMFC stack are discussed． According to the experiment， it is proved that the poor gas tightness of the stack results in the formation of the oxygen inside the stack during the parking process and the threshold parking time of no hydrogen inside the stack is above 1 h． Then， a parking control strategy is proposed by injecting hydrogen into the anode， and the hydrogen injection cycle is set as 1 h by the anodic hydrogen concentration． Based on the strategy， the starting voltage of the fuel cell is declined from 18 V to 3 V． That means the hydrogen／air interface is declined． Therefore， the durability of the PEMFC for vehicles can be enhanced．

TABLE 1 Parameters of the PEMFC Stack

The experiments were implemented by using a largescaled PEMFC stack manufactured by Sinosynergy Co．， Ltd．国鸿氢能的9SSL应该可以看做是Ballard的拳头产品。

FIGURE 1 Schematic diagram of the fuel cell engine testbench

TABLE 2 Parameters of the fuel cell engine testbench

TABLE 3 Test condition setting of pressure－maintaining test

TABLE 4 Test condition setting of parking

FIGURE 2 The starting voltage of the PEMFC stack during the first 3 s at different parking times

通过浓度检测和停机启动初始状态总电压证明了停机2hr后空腔存在氧分压。

这个实验也可以用于检测空腔内的氧分压，系统避免氢氧界面的措施是否充分。3hr 3s时电压值5．4V，40mV／cell

real－time detection of oxygen concentration in the anode chamber and CO2 concentration in the cathode chamber during start－up．

FIGURE 3 The curves of pressure change under pressure－maintaining test． （a） Nitrogen diffusion of valves，（b） nitrogen diffusion of PEMFC stack

停机关闭阀门压力下降实验，停机2hr后空腔存在氧分压的原因是因为密封件的泄露。

FIGURE 4 The curves of pressure change under pressure－maintaining test． （a） Nitrogen diffusion of valves， （b） nitrogen diffusion of PEMFC stack

这个图像说明估计直接拷贝图3，弄错了，做的是表3的实验。

From Figure 4a，b， the pressure drop time of anode nitrogen crossover and anode hydrogen crossover were， respectively， 200 s and 40 s from 50 kPa to 40 kPa．Anode hydrogen crossover rate was above five times faster than that of the nitrogen crossover．

不知道文中的解释数据是从哪里来的，从图上测量分别是260s和30s。（空腔是385s）

这里有个问题，图3中的实验1和实验5，气体除了外漏，还会向膜电极的另一侧泄露，泄露路径不唯一。

the hydrogen crossover rate given in the general literature is three times that of the nitrogen crossover rate ［24］．

24． T． R． Ralph， S． Hudson， D． P． Wilkinson， ECS Trans． 2019， 1， 67．

不存在这篇文献，

T． R． Ralph， S． Hudson， D． P． Wilkinson， ECS Trans． 2006， 1， 67．这篇文献也没有关于保压侧漏的数据，此次存疑。

通过压力下降方法计算泄露速率并不是可以用于任何压力段的，因为deltaP决定了某一时刻的泄露量，作为工程计算可以作为一定的参考。运算中需要使用假设：如不考虑水分压，氢渗透速率和氮渗透速率比对每种材料都是一样的，如果不是这样，方程解不出来。

TABLE 5 Diffuse rate of different system components under
pressure－maintaining test

根据公式和气压下降的数据计算得到的数据和表格中的数据相当。

the anode chamber volume is 3 L， the cathode chamber volume is about 4 L

我计算的结果是这样的：

N2  氢外漏＋串漏68．3ml／minN2 空外漏＋串漏61．5ml／minN2 氢外漏＋空外漏10．4ml／minH2 氢外漏＋串漏592．2

ml／min

再基于一定假设，可以得到：

N2 氢外漏8．6ml／minN2 串漏59．7ml／minN2 空外漏1．8ml／minH2 氢外漏74．4ml／minH2 串漏517．8ml／min

FIGURE 5 The curves of pressure change of the anode and cathode and the hydrogen concentration change of the outlet of the cathode during the parking process

这个图是全文的核心数据。作者把渗透分成三个区，氢快速扩散，氮中速扩散，环境氧慢速扩散。

氢腔压力最低值84kPa abs＠5170s，空腔压力最低值87kPa＠5000s

a hydrogen concentration sensor （Toan TA300） was added to measure the hydrogen concentration at the cathode outlet of the PEMFC stack

结论是：

it can be concluded that it is not an effective control strategy to use the shut－down strategy of oxygen consumption to mitigate the carbon corrosion during the start－up in a long parking time．

每天都开车的话，至少停机策略要满足晚6到早6这12hr，至少早8到晚5这9hr的问题。

FIGURE 6 The curves of pressure changes during parking 6 h and the starting voltages of the PEMFC stack． （a） Pressure with parking
control strategy， （b） starting voltage with parking control strategy， （c） pressure without parking control strategy， （d） starting voltage without
parking control strategy

耗氧后补氢的策略

氢腔压力最低值68kPa abs＠8000s（2．25hr）补氢瞬时电压4V，对比实验22000s 补（6．1hr）氢瞬时电压21．7V

FIGURE 7 The starting voltage of PEMFC stack at parking 6 h with and without a parking control strategy

CONCLUSIONS

In this work， the formation mechanism of the hydrogen／air interface after the parking process is investigated． In detail， the diffusion rate of the gas inside the PEMFC stack， the gas composition changes of the PEMFC stack， and the starting voltage of the PEMFC stack are discussed to explore the air source in the anode of the stack and prove the existence of hydrogen／air interface after the parking process． Based on the experimental results， a high starting voltage is displayed which means the oxygen is accumulated in the anode after a long parking time， and the hydrogen／air interface is formed during start－up． Meanwhile， it is proved that the formation of the hydrogen／air interface is occurred by the poor gas tightness of the stack． Then， a parking control strategy is proposed by injecting hydrogen into the anode， and the hydrogen injection cycle is set as 1 h by the anodic hydrogen concentration．

这件事情在文章中没有提，没有必要这么频繁。

Based on the strategy， the starting voltage of the fuel cell is declined， and the formed hydrogen／air interface is suppressed． Therefore，the durability of the PEMFC can be enhanced by using the parking control strategy which can promote the application of fuel cell technology in the automotive field．