Propagation of positive discharges in an air bubble having an embedded water droplet
Propagation of positive discharges in an air bubble having an embedded water droplet
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DOI：
10.1088/1361-6595/abc830
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发表时间：
2020-11
影响因子：
3.8
通讯作者：
W. Ning;Janis Lai;Juliusz Kruszelnicki;J. Foster;D. Dai;M. Kushner
中科院分区：
文献类型：
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作者：
W. Ning;Janis Lai;Juliusz Kruszelnicki;J. Foster;D. Dai;M. Kushner
浸泡在水中的气泡内产生低温等离子体是将等离子体产生的反应物质快速转移到水中的一种有效方法，在生物医药、农业和环境等领域有广泛的应用。反应性物质通常在气相等离子体中产生，然后溶化成液体。气泡的大表面体积比（SVR）加速了这一过程。在水中产生气泡时，气溶胶和液滴也包含在气泡中。这些液滴也有很大的SVR，因此可以迅速被等离子体激活。然而，液滴的存在也会影响等离子体在气泡中的传播。本文讨论了浸没在水中有水滴的气泡中排放物的形成和演化的计算和实验研究结果。计算采用二维等离子体流体力学模型进行。实验采用准二维气泡仪进行。在具有液滴的气泡中，等离子丝通常从通电电极桥接到液滴，然后从液滴桥接到气泡表面。在气泡的内表面和液滴的表面上也出现表面拥抱飘带。这两种表面飘带部分是由于表面电荷积累造成的，并且可以控制运输到液滴中的反应物质的形成。液滴电导率的增加抑制了表面放电的传播，导致水反应物质的密度降低。增加周围水的导电性不会改变排放的整体结构，但会略微提高排放强度。嵌入液滴的大小和形状对流光的形成和传播有显著影响。
Low temperature plasmas generated inside gas bubbles immersed in water is an effective method of rapidly transferring plasma generated reactive species to the water for applications in biomedicine, agriculture and environment. Reactive species are generally produced in the gas phase plasma and then solvate into the liquid. The large surface-to-volume ratio (SVR) of the bubble accelerates this process. In generating bubbles in water, aerosols and droplets are also contained within the bubble. These droplets also have a large SVR and so can be rapidly plasma activated. However, the presence of the droplets can also impact the propagation of the plasma in the bubble. In this paper, results are discussed from computational and experimental investigations of the formation and evolution of discharges in an air bubble immersed in water with an embedded water droplet. The computations were performed with a two-dimensional plasma hydrodynamics model. Experiments were performed with a quasi-2D bubble apparatus. In bubbles having a droplet, a plasma filament typically bridges from the powered electrode to the droplet, and then from the droplet to the bubble surface. A surface-hugging streamer also occurs on the inner bubble surface and on the surface of the droplet. Both surface streamers result in part from surface charge accumulation and can dominate the formation of reactive species that transport into the droplet. Increasing droplet conductivity suppresses propagation of the surface discharge and leads to a lower density of aqueous reactive species. Increasing conductivity of the surrounding water does not change the overall structure of the discharge but does slightly elevate the discharge intensity. The size and shape of the embedded droplet can significantly affect the formation and propagation of the streamer.