Plasma breakdown in bubbles passing between two pin electrodes
Plasma breakdown in bubbles passing between two pin electrodes
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DOI：
10.1088/1361-6463/ac9538
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
N. Pillai;N. Sponsel;J. T. Mast;M. Kushner;I. Bolotnov;K. Stapelmann
中科院分区：
文献类型：
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作者：
N. Pillai;N. Sponsel;J. T. Mast;M. Kushner;I. Bolotnov;K. Stapelmann
液体中等离子体的点燃具有从医疗仪器到液体化学操纵的应用。直接在液体中形成等离子体通常需要极高的电压才能引发击穿。在浸没在具有较高介电常数的液体中的气泡中产生等离子体流可以通过减少产生击穿所需的电场来显着降低启动放电所需的电压。气泡与电极的接近程度以及气泡的形状对于等离子体在气泡中产生和传播的方式起着关键作用。在本文中，我们讨论了三维直接数值模拟 (DNS) 的结果，该模拟用于研究将空气注入水中形成的气泡的形状。与配套实验的结果进行比较。然后，使用 DNS 生成的静态气泡几何形状，使用二维等离子体流体动力学模型来捕获气泡中的等离子体流光传播。模拟显示了取决于气泡形状的两种不同的流光形成模式。在椭圆形气泡中，短时间的电子雪崩触发了表面电离波 (SIW)，导致等离子体沿着气泡表面传播。在圆形气泡中，电子雪崩首先穿过气泡的中间，然后两个 SIW 开始从最接近接地电极的点传播，其中体积流光与表面相交。在接近针对针配置的通电电极的椭圆形气泡中，我们通过实验观察到与计算结果定性对应的流光行为。在流光曲线的生命周期中沿着变形气泡的路径捕获的光发射，表明流光沿着液体/气体边界界面传播。由变形气泡表面边界的局部场增强支持的等离子体生成是可能导致流注形成的机制。
The ignition of plasmas in liquids has applications from medical instrumentation to manipulation of liquid chemistry. Formation of plasmas directly in a liquid often requires prohibitively large voltages to initiate breakdown. Producing plasma streamers in bubbles submerged in a liquid with higher permittivity can significantly lower the voltage needed to initiate a discharge by reducing the electric field required to produce breakdown. The proximity of the bubble to the electrodes and the shape of the bubbles play critical roles in the manner in which the plasma is produced in, and propagates through, the bubble. In this paper, we discuss results from a three-dimensional direct numerical simulation (DNS) used to investigate the shapes of bubbles formed by injection of air into water. Comparisons are made to results from a companion experiment. A two-dimensional plasma hydrodynamics model was then used to capture the plasma streamer propagation in the bubble using a static bubble geometry generated by the DNS The simulations showed two different modes for streamer formation depending on the bubble shape. In an elliptical bubble, a short electron avalanche triggered a surface ionization wave (SIWs) resulting in plasma propagating along the surface of the bubble. In a circular bubble, an electron avalanche first traveled through the middle of the bubble before two SIWs began to propagate from the point closest to the grounded electrode where a volumetric streamer intersected the surface. In an elliptical bubble approaching a powered electrode in a pin-to-pin configuration, we experimentally observed streamer behavior that qualitatively corresponds with computational results. Optical emission captured over the lifetime of the streamer curve along the path of deformed bubbles, suggesting propagation of the streamer along the liquid/gas boundary interface. Plasma generation supported by the local field enhancement of the deformed bubble surface boundaries is a mechanism that is likely responsible for initiating streamer formation.