A study of thermal bubble behavior in the simulated electrode system of HT superconducting coils
A study of thermal bubble behavior in the simulated electrode system of HT superconducting coils
复制标题
高温超导线圈模拟电极系统中的热气泡行为研究
DOI：
10.1109/94.752018
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发表时间：
1999
影响因子：
3.1
通讯作者：
M. Hara
中科院分区：
文献类型：
--
作者：
B. Seok;N. Tamuro;M. Hara
采用具有绝缘屏障和间隔片的同心圆层-圆柱电极系统浸泡在液氮中，模拟高温超导线圈在淬火状态下的绝缘环境，对气泡行为进行了理论和实验研究。结果表明：60 Hz电场和压力对气泡行为影响较大；根据线圈层与圆柱形电极之间冷却通道的宽度l/sub / c/分为两种。当l/sub / c/大于线圈电极释放的气泡直径时，在低电压下，气泡通过浮力上升，但在高电压下，它们被困在线圈匝间的凹槽中。如果没有障碍物，困住的气泡沿槽移动，否则则向槽外移动。当l/sub / c/小于气泡直径时，由于表面张力，气泡被困在凹槽中，即使在没有施加电压的情况下，气泡也会沿着凹槽移动。在较高的施加电压下，气泡被紧紧捕获，如果存在间隔，气泡表面就会激发出电流体动力学（EHD）不稳定性。由于EHD不稳定性和浮力的影响，气泡从槽中流出。
Bubble behavior is studied theoretically and experimentally with an electrode system which consists of concentric coil layer-to-cylindrical electrodes with insulation barrier and spacers immersed in liquid nitrogen for the simulation of the insulation environment in high temperature superconducting coils at the quenching state. The results show that bubble behavior is affected severely by 60 Hz electric field and pressure; it is categorized into two types according to the width l/sub c/ of the cooling channel between coil layer and cylindrical electrode. When l/sub c/ is larger than the diameter of bubble released from the coil electrode, bubbles rise by buoyancy at a low applied voltage, but they are trapped in grooves between coil-turns at higher applied voltages. Trapped bubbles move along the groove if there is no obstruction, but otherwise move out of the groove. When l/sub c/ is smaller than the bubble diameter, the bubbles are trapped in the groove due to surface tension, and now along the groove even at no applied voltage. At higher applied voltages, the bubbles are trapped tightly and an electrohydrodynamic (EHD) instability is excited on the bubble surface if the spacer exists. Bubbles stream from the groove due to the effects of EHD instability and buoyancy.