Modelling of electrical breakdown in supercritical CO2 with molecular clusters formation
Modelling of electrical breakdown in supercritical CO2 with molecular clusters formation
复制标题
超临界 CO2 中电击穿与分子簇形成的建模
DOI：
10.1109/icpadm.2018.8401205
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
L. Graber
中科院分区：
文献类型：
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作者：
Yunbo Tian;Jia Wei;Chanyeop Park;Zhenxing Wang;L. Graber
建立了一个理论模型来描述分子团簇形成的超临界流体中的电击穿机理。该模型首先考虑了团簇内电子的能量损失，计算了超临界团簇的碰撞截面。然后，通过玻尔兹曼分析得到了超临界二氧化碳的电子能量分布函数，并通过电离系数(α)和附着系数(η)估算了超临界二氧化碳的介电击穿特性。结果表明，超临界流体中的团簇效应对碰撞截面和介电性质都有显著的影响。形成团簇的超临界气体的密度折合临界电场低于相应气体的临界电场。此外，随着密度的增加，团簇的平均尺寸变大，截面受团簇效应的影响更大。因此，击穿电压在超临界区域趋于饱和。在311K和8.4 Mpa下，超临界CO2的密度约化临界电场为66TD，而CO2气体的密度约化临界电场为97TD。本文的结果与我们的实验结果吻合较好。
A theoretical model is developed to describe the mechanism of electrical breakdown in supercritical fluids (SCFs) with molecular cluster formation. The model first calculates the collisional cross sections of supercritical clusters by taking into consideration of energy losses of electrons inside clusters. Then, Boltzmann analyses are performed to obtain the electron energy distribution function (EEDF) and estimate the dielectric breakdown characteristics of supercritical CO2 by the ionization (α) and attachment (η) coefficients. The results show that the clustering effect in SCFs has a significant effect on both collisional cross sections and dielectric properties. The density-reduced critical electric field of SCFs with clusters formation is lower than that of the corresponding gas. Moreover, as the density increases, the average size of clusters gets bigger, the cross sections are more affected by the clustering effect. As a result, the breakdown voltage tends to saturate in the supercritical region. For supercritical CO2 at 311 K and 8.4 MPa, the density-reduced critical electric field is 66 Td, while for CO2 gas, it is 97 Td. The results in this paper are in good agreement with our experimental results.