Distinctive flow properties of liquid jet generated by EHD pump and conical nozzle

The electrohydrodynamic liquid jets induced by the mechanism which is referred to as pure conduction pumping were investigated in isothermal weakly conducting liquids, HFC43‐10 and HCFC123. The properties of the liquid jets (flow velocity, pumping pressure, and flow pattern) were examined by using grounded electrodes of four different types opposite a pseudo‐doughnut electrode under an applied DC voltage. These electrode systems gave rise to a powerful liquid jet, but in the working liquids used here, there was an effect of the voltage polarity on the flow direction. In order to create a more effective liquid jet with high directivity, a special nozzle (referred to as a conical nozzle in this paper) was used together with the electrode system. This nozzle can produce a distinctive pattern (spiral structure) of jets emerging from the outlet of the nozzle. In this paper, the spiral structure of the liquid jets has been analyzed using the basic equations of fluid mechanics. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(1): 9–19, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20133     

Electrohydrodynamically induced dielectric liquid flow through pure conduction in point/plane geometry

Mildly polar liquids generally exhibit an ohmic behavior when subjected to electric fields of limited values. The resulting conduction is then associated with heterocharge layers of finite thickness in the vicinity of the electrodes. In the absence of charge injection or induction, a simple conduction model based on the processes of dissociation of a neutral electrolytic species and recombination of the generated ions is presented. This model is first applied to parallel plane electrode geometry to describe the build-up of the heterocharge. Then, the case of point/plane configuration is considered where the effect of Coulomb force is different in the two layers next to the electrodes. A net motion toward the point electrode is predicted to occur. With a rough approximation for the harmonic field, an analysis is presented which leads to an expression for the axial component of the net force exerted on the liquid. A simple static pump is designed and built to experimentally investigate the pressure head generated through pure conduction. Two working fluids (refrigerant R-123 and n-hexane) and two different electrode designs are considered in this study. The experimental results are qualitatively compared to the theoretical predictions.     

Theoretical/numerical study of electrohydrodynamic pumping through conduction phenomenon

In an isothermal liquid, only the Coulomb force which is the force acting on the free charges, can contribute to the net electrohydrodynamic (EHD) motion. In the absence of a direct charge injection or induction, the charges can be generated through the dissociation process of the fluid. The generated charges by dissociation are redistributed by the applied electric field, resulting in the heterocharge layers around the electrodes. The pumping of an isothermal liquid without ion injection is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes. This type of pumping is referred to as the conduction pumping. This paper investigates the pressure head generated by the conduction pumping mechanism theoretically through the numerical solutions. For this purpose, a theoretical model for the static case (i.e., without a fluid motion) is established and a numerical code using finite volume method is developed. Electric potential, electric field, charge density, and electric body force distributions for the selected electrode configuration are presented. The generated pressure as a function of the applied voltage is also presented. The numerical results confirm the EHD conduction pumping concept theoretically.     

Modeling the distribution of liquid between the flow core and film in adiabatic annular two-phase flows

The numerical simulation of adiabatic steam-water flow performed using the droplet entrainment model developed by the authors reflects the experimentally observed regularities of liquid flow rate variation in the film over the channel length. A procedure of calculating the fraction of entrained liquid is proposed for the conditions of dynamic equilibrium between the droplet entrainment and deposition processes. The results from application of the proposed procedure are consistent with the available experimental data.     

Burnout and distribution of liquid between the flow core and wall films in narrow slot channels

Previous works on studying distribution of liquid between the flow core and wall films in narrow slot channels are briefly reviewed. Interrelation between mass transfer processes and burnout is shown. A procedure for calculating burnout on convex and concave heat-transfer surfaces in narrow slot channels is presented.     

Optical investigation of high-field conduction and prebreakdown ina dielectric liquid

Light emission studies of the high-field conduction and prebreakdown phenomena in a mixture of mono and dibenzyl-toluene (M/DBT), used as polypropylene impregnant in the all-film capacitor technology, have been undertaken to gain insight into the underlying physical mechanisms responsible for these processes. The absorption spectrum of this fluid, in the UV region, shows the appearance of structured bands at 348, 366 and 386 nm indicating a luminescence process via anthracene and 9-methylanthracene impurities at a concentration of 3×10^-3 mol/l. Optical and electrical measurements were performed simultaneously on the electrically stressed fluid. Electroluminescence of the impurities contained in M/DBT has been investigated using a new uniform field electrode arrangement. The light inception stress was determined to be ~ 20 μm^-1 for ac excitation (50 Hz). Configurations with different interfacial situations were studied and we have evidenced a correlation between charge injection and electroluminescence activity. Spectral analysis of the light radiated by streamers in M/DBT in a needle-plane electrode geometry, under step voltage (1 to 50 μs, 30 kV) revealed, for both polarities, the presence of H₂ and C₂ characteristic bands emerging from a continuum corresponding to the dissociation and recombination of molecular fragments     

Stability of electrohydrodynamic induction pumping of liquid film in vertical annular configuration

Instability of electrohydrodynamic (EHD) induction pumps can manifest itself in a sudden drop/jump in pump output. The instability can also result in alternating/bidirectional flow. To understand and avoid this erratic behavior of the pump operation, a nondimensional stability analysis of EHD induction pumping of liquid film in a vertical annular configuration in the presence of an external load (i.e., pressure gradient and gravitational force) for repulsion mode is carried out. A general nondimensional stability criterion is presented, indicating that the stability of the pump depends on the nondimensional geometric parameters of the pump as well as the nondimensional electric properties of the liquid film. A stability map based on dimensionless electric conductivity and liquid-film thickness is presented. The effect of the dimensionless angular velocity on the nondimensional interfacial velocity under the influence of a pressure gradient and gravitational force is investigated. It is also shown that the erratic behavior of the unstable pump can be eliminated by a proper selection of geometric and liquid-film parameters, as well as the traveling electric-wave frequency.     

建立具有竞争力的分配机制满足企业发展战略的需要

要有效实施发展战略,其中一项十分重要的工作就是要制定具有竞争力的分配制度。黑龙江省火电第三工程公司结合电力施工企业的特点,在分配制度改革方面做了一些积极的探索,使企业的分配机制起到了调动员工积极性,提高劳动效率,确保企业竞争优势的作用,促进了公司的稳步发展,推进了公司发展战略的实施。     

电解液流动分配研究

锌银集中贮液式贮备电池组的电解液分配管道决定着电解液分配的均匀性,是影响大型贮备电池组性能的关键问题之一。目前通用的等截面分配管道,分配到各单体的电液量存在着明显差异,而且单体数量越多流量相差越大,浪费电解液,影响电池性能。文章提出了一种新的变截面管道,改善了各个单体间的流量分配均匀性,为工程中类似问题的解决提供了新的思路。     

大型立式泵站簸箕型进水流道三维紊流数值模拟

针对典型的簸箕型进水流道 ,应用紊流模型对流道内部流态及水泵吸水管各断面流速分布进行了数值模拟 ,计算结果符合实际情况。数值计算揭示了簸箕型进水流道内流动规律 ,进水流道吸水管下方存在奇点 ,如相关设计参数不当易产生漩涡。根据计算分析 ,提出大型泵道簸箕型控制参数 ,对于工程设计有重要参考价值     

Experiments and modeling of conduction and charge accumulation in liquid crystal cells

A combination of different electrical measurement techniques is applied to liquid crystal (display) cells; voltage drop, current-voltage, dc stress measurements and impedance spectroscopy. It is found that at small timescale (seconds) conduction is dominated by transport of mobile ions, but at long timescale (hours) by (bulk) generation of extremely low mobility ions. These slow ions accumulate at ionic double layers at the liquid crystal-polyimid interface, giving rise to electric fields over the polyimid alignment layers. These processes of charge transport and accumulation are represented in consistent and insightful electrical network models.     

交流谐波经MMC的传导机理及叠加特性研究

连接大量交流源、荷是基于模块化多电平换流器(MMC)的中压柔性直流配电网的未来应用场景之一。然而,非理想交流源、荷产生的谐波扰动会使MMC桥臂出现电压波动并激发环流,进而使桥臂电流畸变,导致直流侧出现纹波。为研究交流谐波经MMC的传导机理,通过平均开关函数和桥臂瞬时功率方程,推导了交流负荷谐波电流和交流系统背景谐波电压在MMC内部激发的桥臂电压波动及环流表达式,分析了其传导机理和规律。同时,分析了不同次交流谐波经MMC的传递叠加特性及其对直流侧纹波含量的影响。仿真结果验证了理论分析的正确性。     

Impedance spectroscopy and conduction mechanism of NaYP2O7 ceramic compound

Journal of Electroceramics - In the present study, NaYP2O7 compound was prepared by solid-state method and was characterized by powder X-ray diffraction and Raman spectroscopy. The X-ray...     

A mathematical model for the fluidelastic mechanism exciting vibrations in a system of blunt bodies placed in cross flow of liquid

A model of numerical experiment involving the use of the modernized method of discrete vortices is proposed for fully simulating the main mechanisms through which vibrations of tube bundles are excited: periodic vortex separation and fluidelastic excitation. A mathematical model simulating fluidelastic excitation of tube bundle vibrations by an external cross flow and intended for calculating the stability curve for a concrete row of tubes is developed on the basis of available experimental data.     

消除带有防跳的断路器控制电路寄生回路的方法

分析了具有防跳装置的断路器操动机与保护装配配合时产生的寄生回路。比较了保护装置TBJ的防跳与机构内防跳作用的差异，指出了目前常采用的2种取消寄生回路措施所存在的问题，提出了一种较为合理的改进方案。     

Analyzing the effect on heat transfer due to nonuniform distribution of liquid flow among the tubes of a shell-and-tube heat exchanger

A method is proposed using which nonuniform distribution of liquid flow among the tubes of a shell-and-tube apparatus can be taken into account by means of a statistical distribution function. A formula showing interrelation of this function with the indicator of heat transfer intensity in the apparatus tube space is given.     

Numerical analysis of transit conduction current in an insulating liquid with added ionic electrolyte

We simulated the phenomena of transit conduction in an insulating liquid with added ionic molecules such as surfactant, by using the charge‐injection model with dissociation‐recombination. When the parameters of C_i (density of injected charge) and C₀ (density of created charge in the liquid) are C_i>C₀ in this simulation, the waveform of current density showed an injection type with a peak, and when C_i<C₀, it showed a dissociation‐recombination type. A decreasing characteristic appeared in the low electric field, maximum one in the middle field, and saturating one in the high field. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 10– 16, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20327     

Structure and operation mechanism of a friction-type piezoelectric motor utilizing the principle of strain-wave gearing

This paper proposes a new type of motor which utilizes multilayer piezoelectric devices for electromechanical power conversion and the mechanism of the strain-wave gearing to generate traveling waves and motive force. The construction and basic operation of the motor are described. The motor can be operated in variable frequency because piezodevices are operated in the nonresonant mode. Approximate analysis is performed to clarify the operating mechanism of the motor and to obtain characteristics on the rotational speed in the case of no-load. Experimental results on rotational speed of the prototype motor made of metals except for the piezoelectric devices also are presented, which verifies the feasibility of the proposed motor.     

Analysis of flow electrification in fuel distribution systems

The authors examine flow electrification in typical automotive fuel distribution systems consisting of a fuel tank, pump, insulating fuel lines, and filter. Factors influencing the degree of electrification and the failure mechanisms of these fuel systems are discussed. Various experimental techniques that may be used to characterize flow electrification in any fuel distribution system are reviewed. An analysis methodology that allows use of charge density data to quantitatively assess the probability of an external electrical discharge or dielectric breakdown of the pipe wall is presented