Hong-Bo Liu

The structural design of the flow channel of a redox flow battery directly affects ion transport efficiency, electrode overpotential, and stack performance during charge-discharge cycles. A tapered hierarchical interdigitated flow field design that has independent flow channel structures for different levels of flow was developed in this work. Especially, the secondary branch channels are the tapered type and the corresponding cross-sections are gradually reduced along the flow direction, which is beneficial for improving the flow rate at the end of channels and enhancing mass transfer. The performances of a vanadium redox flow battery with interdigitated flow field, hierarchical interdigitated flow field, and tapered hierarchical interdigitated flow field were evaluated through 3D numerical model. The results showed that at 240 mA cm⁻² and 6 ml s⁻¹, the pump-based efficiency of the hierarchical interdigitated flow field increased by 4%-7% compared with the interdigitated flow field. Furthermore, the pump-based efficiency with tapered hierarchical interdigitated flow field increased by 1.6%-3% compared with the hierarchical interdigitated flow field. This indicates that the tapered hierarchical interdigitated flow field shows further advantages in redox flow battery applications.

Space charge is accumulated in the DC voltage transmission line when corona discharge happening. The generation of space charge can make the air gap insulation degrade and lead to breakdown. In order to accurately obtain the charge distribution, this paper presents a set of test systems using coaxial cylinder measurement model based on acoustic pulse method to gauge one-dimensional charge distribution, including acoustic emission system, space charge generation system and signal reception system. This paper focuses on the parameters of the structure and the main com-opponents of each part. It can simulate DC negative voltage transmission line corona discharge and obtain the information of space charge, so the one-dimensional space charge distribution and the influencing factors would be studied. Preliminary experimental studies have shown that: Charge density has a maximum value near the wire and a minimum value near the cylinder. This distribution is consistent with the effectiveness of the actual circumstances of charge, verifying the effectiveness of the system. This research finally provides a comprehensive means to measure distribution of space charge in two-dimensional and three-dimensional perspectives and study the mechanism of corona discharge.