Dynamic model for estimation of hydrogen flow rate in hydrogen recirculation system for the PEM fuel cell stack

IF 17 1区工程技术 Q1 ENERGY & FUELS

Etransportation Pub Date : 2025-06-18 DOI:10.1016/j.etran.2025.100438

Po Hong, Pingwen Ming, Cunman Zhang

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Abstract

Hydrogen utilization rate is critical for hydrogen-electricity conversion efficiency of the PEM fuel cell system. Significant part of hydrogen is inevitably wasted as a result of essential periodical vent of accumulated gaseous and liquid impurities, which degrades hydrogen flow rate and hydrogen concentration, in hydrogen recirculation system (HRS) for anode reaction chamber of the stack. Estimation of hydrogen flow rate is the key to improving hydrogen utilization rate, because impurities can be vented only when actual flow rate is lower than acceptable range. This paper investigates dynamic model of the HRS to construct connection between hydrogen flow rate and obtainable parameters. Firstly, lumped-parameter dynamic model is established for the recirculation pump-driven and ejector-driven HRS. Coupling mechanism between hydrogen flow rate and pressure of each recirculation apparatus is introduced to dynamic model, and then transfer function between pressure at inlet and outlet of anode chamber is derived for estimation of hydrogen flow rate in comparison. According to Nyquist plot, the recirculation pump-driven HRS behaves as a common first-order or second-order inertial system while the ejector-driven HRS behaves as a novel shifted first-order system. Secondly, effect of purge valve action on flow rate of the ejector-driven HRS is analyzed in analogical way based on transition between operating points on ejector characteristic curve. It shows that opening purge valve contributes to larger flow rate, even if pressure at backflow inlet is decreased. Thirdly, experiment on plant of an ejector-driven HRS shows that Nyquist plot of transfer function in complex coordinate is a circle with origin included and it's in consistent with that by dynamic model. Besides, relation is found between circle radius and flow rate at ejector outlet. Finally, experiment result on a 120 kW fuel cell system validates explanation to effect of opening purge valve on hydrogen flow rate of the ejector-driven HRS.

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PEM燃料电池堆氢循环系统中氢流量估算的动态模型

氢的利用率对PEM燃料电池系统的氢-电转换效率至关重要。在堆阳极反应室氢气循环系统中，由于积累的气液杂质必须周期性排出，导致氢气流速和氢气浓度降低，不可避免地浪费了相当一部分氢气。氢气流量的估算是提高氢气利用率的关键，因为只有当实际流量低于可接受范围时，杂质才能排出。本文研究了HRS的动态模型，建立了氢气流速与可得参数之间的联系。首先，建立了循环泵驱动和喷射器驱动两种HRS的总参数动力学模型。在动力学模型中引入各循环装置氢气流量与压力的耦合机理，推导出阳极室进出口压力之间的传递函数，用于比较估算氢气流量。根据Nyquist图，再循环泵驱动的HRS表现为普通的一阶或二阶惯性系统，而喷射器驱动的HRS表现为一种新型的移位一阶系统。其次，基于喷射器特性曲线上工作点间的转换，类比分析了吹扫阀作用对喷射器驱动式高压水射流流量的影响。结果表明，在降低回流口压力的情况下，开启吹扫阀可以提高流量。第三，在喷射器驱动HRS装置上的实验表明，在复坐标下传递函数的Nyquist图是一个包含原点的圆，与动力学模型的传递函数Nyquist图一致。此外，还发现了圆半径与喷射器出口流量之间的关系。最后，在120kw燃料电池系统上进行了实验，验证了开启吹扫阀对喷射器驱动HRS氢气流量影响的解释。

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来源期刊

Etransportation Engineering-Automotive Engineering

CiteScore

19.80

自引率

12.60%

发文量

审稿时长

39 days

期刊介绍： eTransportation is a scholarly journal that aims to advance knowledge in the field of electric transportation. It focuses on all modes of transportation that utilize electricity as their primary source of energy, including electric vehicles, trains, ships, and aircraft. The journal covers all stages of research, development, and testing of new technologies, systems, and devices related to electrical transportation. The journal welcomes the use of simulation and analysis tools at the system, transport, or device level. Its primary emphasis is on the study of the electrical and electronic aspects of transportation systems. However, it also considers research on mechanical parts or subsystems of vehicles if there is a clear interaction with electrical or electronic equipment. Please note that this journal excludes other aspects such as sociological, political, regulatory, or environmental factors from its scope.