电场作用下双液滴聚合特性

doi:10.11949/0438-1157.20201130

摘要/Abstract

摘要：

乳状液破乳分离是目前高含水期油田开采过程中难以解决的技术问题，电场破乳方法具有高效清洁等优点，是解决该问题的有效手段。采用数值模拟与试验验证相结合的方法研究电脱水过程中阶跃、斜坡电场诱导下双液滴的聚合与分离特性。结果表明，在斜坡电场作用下，界面张力引起的泵吸作用大于电场力引起的颈缩作用，有利于液滴聚并，且液滴发生二次乳化现象的概率降低。而施加阶跃电场时，一定范围内能够达到液滴破乳的目的，但液滴在聚并过程中易发生二次乳化现象。从电场对连续相影响的角度分析发现，阶跃电场不仅对液滴具有驱动作用，对连续相的影响也较为明显，阶跃电场会增大连续相内湍流作用，不利于电脱水过程。因此，采用斜坡信号诱导液滴聚合能够降低二次乳化现象发生的概率。

关键词: 液滴, 相场方法, 电脱水, 聚结, 分离, 数值模拟

Abstract:

Demulsification of emulsion is a difficult technical problem to be solved in the process of oilfield production in high water cut period. Electric field demulsification is an effective ways to solve this problem because of its advantages of clean and high efficiency. In this paper, numerical simulation and experimental verification were applied to study the coalescence and separation characteristics of double droplets induced by the step and ramp signal electric field in the process of electric dehydration. The results show that under the action of ramp signal electric field, the pumping suction effect caused by interfacial tension is far greater than the necking effect caused by electric field, which is conducive to the coalescence of droplets, and reduces the probability of secondary emulsification of droplets. While applying the step signal electric field, the demulsification of the droplet can be achieved within a certain range, but the droplet is prone to secondary emulsification during coalescence. From the perspective of the effect of electric field on the continuous phase, it is found that the step signal electric field not only drives the droplet deformation and coalescence, but also has an obvious effect on the continuous phase. The step signal electric field increases the turbulence effect in the continuous phase, which is unfavorable to the electric dehydration process. Therefore, applying ramp signal to induce droplet coalescence could reduce the probability of secondary emulsification in the electric dehydration process.

Key words: droplet, phase field method, electric dehydration, coalescence, separation, numerical simulation

中图分类号:

TQ 028

宋粉红, 王伟, 陈奇成, 范晶. 电场作用下双液滴聚合特性[J]. 化工学报, 2021, 72(S1): 371-381.

SONG Fenhong, WANG Wei, CHEN Qicheng, FAN Jing. Coalescence characteristics of the double droplets under electric field[J]. CIESC Journal, 2021, 72(S1): 371-381.

图/表 15

图1 数值模拟模型

Fig.1 Diagram of numerical simulation model

图2 电场作用下液滴聚并试验系统

Fig.2 Experimental system of droplet coalescence under electric field

图3 系统施加阶跃信号电压时设置的激励信号

Fig.3 Excitation signal set to apply step signal voltage to the system

图4 阶跃信号电场作用下液滴的变形与聚并过程（E=4 kV）

Fig.4 Deformation and coalescence process of droplets under step signal electric field (E=4 kV)

图5 电场力沿Y方向的分布（E=4 kV）

Fig.5 Distribution of electric field force in Y direction (E=4 kV)

图6 两个液滴在水平阶跃电场作用下聚并失败的过程图（E=2 kV）

Fig.6 Failed coalescence process of two droplets under step signal electric field (E=2 kV)

图7 阶跃信号作用下液滴间距离随时间的变化（E=2 kV）

Fig.7 Time evolution of the distance between two droplets under step signal electric field (E=2 kV)

图8 液滴在水平阶跃电场作用下的破乳过程（E=21 kV）

Fig.8 Demulsification process of droplets under step signal electric field E=21 kV

图9 系统施加斜坡信号电压时设置的激励信号

Fig.9 Excitation signal set to apply ramp signal voltage to system

图10 双液滴在水平斜坡信号作用下的聚并过程（E=4 kV）

Fig.10 Coalescence process of droplets under ramp signal electric field (E=4 kV)

图11 液滴所受沿Y方向的电场力分布（E=4 kV）

Fig.11 Distribution of electric field force in Y direction (E=4 kV)

图12 两液滴在斜坡电场作用下的逐渐靠近过程（E=21 kV）

Fig.12 Approaching process of two droplets under ramp signal electric field (E=21 kV)

图13 液滴在斜坡电场作用下的聚并过程（E=21 kV）

Fig.13 Coalescence process of droplets under ramp signal electric field (E=21 kV)

图14 聚并液滴在斜坡电场持续作用下的后续移动过程（E=21 kV）

Fig.14 Subsequent moving process of coalesced droplet under ramp signal electric field (E=21 kV)

图15 斜坡电场作用下的液滴距离变化曲线（E=21 kV）

Fig.15 Time evolution of distance between two droplets under ramp signal electric field (E=21 kV)

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