An investigation into the deformation, movement and coalescence characteristics of water-in-oil droplets in an AC electric field

Drop-drop coalescence is important in electric dehydrators used for oil-water separation in the oil industry.The deformation degree,angle between the electric field and the center line of two drops,effects of intensities and frequencies of the electric field have been studied by analyzing droplet images.However,seldom have people investigated the movement and the relative velocity in the process of dropdrop coalescence.In this paper forces acting on a single droplet and horizontal water droplets in an AC electric field were analyzed,and experiments were carried out to investigate the deformation,movement and coalescence characteristics of droplets with white oil and water.With a micro high-speed camera system and image processing technology,the droplet images were collected and analyzed.The results indicate that the deformation is mainly affected by the electric field intensity,frequency,droplet diameter and the oil viscosity.High field strength and large diameter facilitate deformation of drops in the electric field.The effect of frequency and oil viscosity is not obvious.Higher frequency and higher oil viscosity will lead to smaller oscillation amplitude.The effect of electric field intensity and droplet diameter on oscillation amplitude is not obvious.When the center-to-center distance between droplets is large,the forces acting on droplets in the horizontal direction are mainly dipole-dipole attraction and drag forces.There is also the film-thinning force when droplets get closer.The forces are simplified and derived.Based on force analysis and Newton’s second law,the relative movement is analyzed in different parts,and the relationship of center-to-center distance and time is in accordance with an explinear function at different stages.According to experimental data,the movement of 145 μm double droplets before coalescence can be fitted well with an explinear function at two stages.In addition,the whole movement process is investigated and can be estimated with a fourth order polynomial curve,from which the relative velocity of droplet movement can also be obtained.With an increases in electric field intensity and droplet diameter and a decrease in oil viscosity,the relative velocity increases.Only when the oil-water interfacial tension is obviously high,can it influence the relative movement significantly.The coalescence is mainly dipole coalescence and chain coalescence under influence of the AC electric field.     

超级电容器集流体用铝箔交流腐蚀研究

对48微米铝箔集流体在50 Hz交流电腐蚀下进行正交试验的研究,包括因子盐酸、铝离子、硫酸及温度等条件,发现了取得比容的最佳条件是各个因素的相互作用.讨论了在低电量时,高浓度的盐酸更趋向于形成发孔密度大、孔洞大小均一的腐蚀孔,而失重效率反而低于2N盐酸,可能是因为高浓度盐酸在交流电解负半周的沉积膜保护作用而导致.SEM分析显示备我们所制备的样品表面形貌抛光图与日本进口集流体形貌极为相似.     

High-quality output PWM AC voltage regulator based on Cuk converter

This paper describes the design of an AC–AC converter capable of generating a high-quality output. It is based on the Cuk configuration, with the transistors replaced by bidirectional switches. Since there are no transformers in the configuration, the converter lends itself to a compact and lightweight implementation. The design process is aimed at using, as much as possible, the tools and devices already developed for DC–DC applications. This approach greatly simplifies the design and implementation of the converter. An integrated circuit, developed for DC–DC applications, is used to control the converter. Both the set-point and the feedback signal are rectified in order to fit the input range of the controller. Tests performed show that the output exhibits a maximum total harmonic distortion of 3% (resistive load). The efficiency is slightly higher than 89%, and the average output regulation is 0.3%. The converter is capable of correcting voltage sags down to 60% and voltage swells up to 30%, with the output returning to its nominal value within one mains cycle. The results show that the converter is suitable for energizing information-processing equipment.     

FPGA solution for matrix converter double sided space vector modulation algorithm

Matrix Converters (MCs) present several advantages, but yet several barriers must be overcome, such as MC modulation and control technique complexity. This article proposes a multiplatform environment that allows the implementation of the Double Sided Space Vector Modulation (DS-SVM) algorithm in a last-generation Field Programmable Gate Array (FPGA) device. The traditional digital control architecture, based on a SP and some additional devices, is improved by means of a last generation FPGA where the main processor (PowerPC), internal memory, communication interfaces, I/O capabilities and a hardware core that executes the DS-SVM have been connected using on-chip buses. The methodology begins by defining the DS-SVM in a Matlab-Simulink environment. The PowerPC delivers 680 MIPS, but it is not a good candidate to execute the DS-SVM algorithm because it is not possible to achieve the modulation frequency that is necessary for an MC. A new configurable hardware circuit that implements the whole DS-SVM algorithm is proposed. This solution achieves modulation frequencies over 100 kHz. This hardware core is connected to one of the PowerPC buses and the processor can configure it or get feedback information at any time. As the processor is liberated from the very time-consuming DS-SVM computation, it can execute many higher level tasks.     

低压端采用阻抗变换器的电力电子变压器的仿真分析

鉴于电力电子相关技术和智能电网技术的发展,配电用电力电子变压器技术得到了广泛的研究.提出了两类单相交流电源输入、三相交流低压输出、低压端增加阻抗变换器的电力电子变压器拓扑:第一类可以实现单向能量传输,由交流推挽变换器、阻抗变换器(PFC)和电压源逆变器构成;第二类可以实现双向能量传输,由交流推挽变换器、矩阵变换器、阻抗变换器(VSR)和电压源逆变器构成.在理论分析的基础上,利用MATLAB/Simulink进行了仿真分析,所得结果验证了所提方案的正确性.     

BPA向PSS/E的数据转换及暂态稳定比较研究

BPA和PSS/E均为机电暂态仿真软件,两者潮流数据和暂态模型具有较好的相似性,在对BPA和PSS/E两种仿真软件的暂稳态数学模型分析和比较的基础上,提出了BPA向PSS/E数据转换的详细方法,并通过某交直流系统进行仿真测试,对潮流计算结果和稳定计算结果进行了对比分析,仿真结果表明两者潮流基本一致,暂态仿真结果相似,暂稳态过程基本吻合,表明BPA数据可以准确的转换为PSS/E数据,实现数据共享.     

AC800F系统与智能仪表通信的实现

介绍AC800F系统与智能仪表通信的实现方案.     

软件测频方法及其在交流电参数采集中的应用

在傅里叶交流采样算法的基础上提出一种软件测频方法,该方法既保留了傅式算法滤波能力强的优点,又简化了系统的硬件测频电路。阐述了软件测频的原理,推导交流电各个参数的计算公式,并结合单片机技术给出了一种基于STM32F103ZE处理器和AD7606模数转换芯片的交流电参数采集实现方案,论述了软件设计的流程,通过测试验证了该方案的适用性。     

南方电网火电快速调整能力测试与分析

南方电网的电源以火电为主,火电机组的快速调整性能在电网事故处理中有重要作用,直接影响到事故后电网的安全稳定运行。根据南方电网运行要求,对广东、云南和广西三省的火电机组快速调整性能进行了实测分析并给出了改进建议,对交直流并联运行的电网有借鉴意义。     

交流变频同步电动机的研制

目前大型无缝钢管轧机和大型厚板轧机使用的主拖动电机大多采用可无级调速的大型直流电动机,其最大的缺点是结构复杂、制造难度大、检修维护不便。通过对4000kW交流变频同步电动机的设计进行分析与直流电动机调速性能对比,发现交流变频同步电动机具备结构简单、运行可靠的特点,实验证明完全可以取代直流电动机的工作。