粉末喷涂技术及其选择

粉末喷涂技术粉末喷涂技术可分为三大类,高压静电法(电晕充电),摩擦静电法以及接触充电法.正确地选择合适的粉末喷涂技术,首先要明白他们的工作原理.高压静电喷涂(Corona)     

粉末静电涂覆机理的探讨

文章指出用“电晕充电”理论难以解释粉末静电涂覆实践中出现的一些现象，提出了“极化充电”的观点，并按此观点提出等场强静电喷涂的概念，用其分析了三种静电喷涂技术。     

总能量充电技术

本文介绍的是英国依路达（EUROTEC）公司所发明的“总能量粉末充电技术”－Total Energy Control(TEC)及其投放市场后的一些经验和影响。TEC技术已投放市场，并逐渐被用户认识和接受，为了帮助分辨各种不同的静电充电方式，在此将各种静电充电方式的基本原理及性能作出简单的介绍和对比。     

第4讲 烟火药安全性测试技术基础知识讲座 静电感度试验(续)

1.4JGY-50Ⅲ静电感度测试仪1.4.1 JGY-50III静电感度测试仪原理静电引起火工药剂或电火工品的意外起爆,是由于火工药剂或电火工品受到一定能量的静电火花作用产生。因此,火工药剂和电火工品的静电感度,可用充电至一定电压的电容器,对试样放电的模拟方法测试和评定。药剂静电感度试验时,将试样放在放电回路的针一板电极     

高压静电场中水煤浆射流雾化的雾滴特性

为探讨水煤浆在高压静电场中雾化的雾滴特性,采用针管-环电极配制的静电雾化系统,通过测量在不同的雾化操作参数下,雾滴的荷质比大小以及直径的大小和分布规律,深入分析了不同的射流雾化模式下,充电电压以及射流流量对水煤浆雾滴特性的影响。研究表明,充电电压在5—15 kV时,荷电射流呈稳定多股射流雾化模式,随充电电压的不断增加,雾滴的粒径有规律地减小,不同粒径的雾滴频数逐渐趋于均匀,粒径分布谱略有拓宽,该特性对于提高水煤浆燃烧稳定性及燃烧效率具有重要的工程应用价值。     

静电除盐技术的研究进展

静电除盐是一种以直流电为驱动力,利用电化学双电层充电原理脱盐的方法.介绍了静电除盐技术的基本原理和特点,对该技术中关键组件所采用的各种电极材料的研究进展进行了综述,同时对其发展趋势、应用开发及所存在的主要问题等作了介绍.     

水煤浆气力式静电雾化喷嘴设计及雾化流场形貌

借鉴已有的常规水煤浆气力式雾化喷嘴的研究与应用成果,设计了新型的气力式静电雾化喷嘴。在此基础上搭建了以环电极感应充电方式的水煤浆静电雾化实验台,利用激光粒子成像速度仪(PIV)上的CCD相机对其静电雾化流场的形貌进行实验观察,获取其荷电射流雾化角度随外加电场增加的变化情况;并利用激光粒子动态分析仪(PDA)系统分别获得流场轴线上以及轴线150 mm处横截面的透浆率随环电极电压的变化情况。实验结果表明:在感应电场的作用下,荷电喷雾流场随外加电场的增加而扩展,射流雾化角在42°—65°变化,且随充电电压的上升略呈一定的指数规律增加;水煤浆雾滴在射流轴线附近聚集的现象得以改善,浆滴在雾炬空间的弥散愈加均匀,可在一定程度上解决水煤浆雾炬核心区贫氧燃烧的难题。     

新能源充电装置用砂纹粉末涂料的制备和应用研究

对新能源汽车配套充电装置上应用的砂纹粉末涂料进行了制备和应用研究,重点考察了在厚涂的要求下,通过电荷调整剂加量、磨粉粒径分布、喷涂参数控制3个方面的分析和讨论,得到了稳定的涂装砂纹效果,克服了工件边角静电花、堆积坑的弊病问题,在客户处成功应用。     

以1—（2，4，7—三硝基）芴基—2，6—二甲基苯胺为电子传输材料的单层结构有机光导体的研究

系统地研究了在由1－（2，4，7－三硝基）芴基－2，6－二甲基苯胺（DMT－NF），4－（二乙氨基）－苯甲醛－1，1－二苯基腙（DEH）和Y晶型氧肽酞菁（Y－TiOPc)或非金属酞菁（H2Pc)构成的单层结构有机光导体的性能，考查了电荷产生材料（CGM）浓度、电场强度和CGM的种类对光导体静电照相性能的影响。研究结果表明，光导体的量子收率和感光度与CGM浓度有很大关系，正充电时随CGM的浓度的增加而增加，负充电时随CGM的浓度增加而降低。两种光导体在近红外光谱区表现出良好的光敏性，适合LD扫描成像。Y－TiOPc光导体的最高峰在780nm处，半衰曝光量为0.588μJ/cm^2（正充电），0.828μJ/cm^2(负充电）；H2Pc光导体正充电最高峰在800nm处，半衰曝光量为1.50μJ/cm^2，负充电最高峰在820nm处，半衰曝光量为1.97μJ/cm^2。     

光电导高聚物

1958年首次报道了聚(N-乙烯基咔唑)(PVK)具有光电导性,并立即进行实用性开发,70年代起有了进一步发展。目前世界上约有10种光电导高聚物静电复印机用商品,预计90年代可能完全取代目前广泛使用的硒静电复印机。光电导高聚物具有透明性好、价格低、加工方便、可以加工成大面积材料等优点,但在光耐久性和感度等方面尚需提高。除了静电复印之外,它还用于排字、印刷制版、测绘地图、电子计算机激光脉冲高速印出书、传真通讯、医用x-射线照像和激光全息记录等方面,是一种信息功能材料。目前大多按电子照像原理应用,一般是先用电晕充电,使材料两面均匀分布异号电荷,光照后电阻率按光强分布下降,发     

荷电器内煤粉荷电颗粒运动轨迹仿真

从单个荷电颗粒的受力分析入手,建立了线筒型荷电器内适合FLUENT软件求解的单个煤粉颗粒运动轨迹的数学模型.模型涉及的方程包括:颗粒荷电方程、电场与电荷守恒方程、气体质量与动量守恒方程、颗粒质量与动量方程等.根据模型,利用FLUENT软件对荷电器中荷电颗粒的运动轨迹进行模拟,通过用户自定义函数-UDF编程引入电场力,最终得到不同颗粒粒径、荷电电压、射流流速下的运动轨迹仿真,并得出规律性结论.     

Evaluation of various particle charging models for simulating particle dynamics in electrostatic precipitators

Many numerical models have been developed to model the particle dynamics in the electrostatic precipitators in recent years. These models employ various particle charging models including field charging theory, diffusion charging theory and combined field-diffusion theory. These various charging models have different accuracy and require different amount of computational time. This work constructed a numerical model of the electrostatic precipitator and nine particle charging models were evaluated based on the existing experimental results. The results show that predictions of the constant charging models are higher than that of the non-constant models but differ little for the sub-micrometer particles. In the field-diffusion combining models, the one developed by Lawless (1996) should be the first choice relatively for numerical models of the particle dynamics in electrostatic precipitators.     

静电危害及防止措施

日常生活生产中,静电问题和危害普遍存在。本文简单分析了静电产生的原因,重点阐述了流体静电、粉体静电和聚合过程静电带来的的危害,从而提出防止静电危害的一些措施。     

Numerical analysis of frictional charging and electrostatic interaction of particles

Triboelectrification due to frictional contacts between particles and surfaces is prevalent in many powder handling processes. Aiming to explore the friction-induced electrostatic charging behavior, a discrete element method (DEM) is developed for the first time in the current article, in which a frictional charging model and electrostatic interaction models are implemented. The charge accumulation on both the particles and the surface in a rotational container is then analyzed numerically and experimentally to evaluate the developed DEM. The numerical results for the frictional electrification between insulant particles and an insulant wall agree well with the experimental measurement. It is also shown that both the net charge on the particles and the degree of the particle dispersion are a function of the charging time. Moreover, it is revealed that the friction-induced particle charge enhances particle dispersion, and increases the granular temperature due to the electrostatic interactions.     

The effect of vibrating conditions on the electrostatic charge in a vertical vibrating granular bed

In this study, we carried out experiments to measure the electrostatic charge of a granular matter in a vertical shaker device. The purpose was to quantify the effect of the vibrating conditions on electrostatic charging in the granular matter. In each experimental run, 3 mm glass beads were first discharged to remove any residual charge prior to subsequently studying their electrostatic charging. The accumulative electrostatic charges of the granular materials were measured using a Faraday cage. The findings show that the vibrating conditions play an important role in the saturated electrostatic charge and time constant. The electrostatic charges of granular materials are mainly generated by the contact potential difference mechanism in the vibrating granular system. The results show that the saturated accumulation charge increases as the dimensionless vibrating acceleration increases, and decreases with increasing vibrating frequency. The time constant is small when a higher vibrating frequency is applied in the vibrating granular system. Finally, we demonstrate that the saturated accumulation charge increases linearly with the increase of the dimensionless vibrating velocity regardless of the vibrating frequency.     

Modeling of Gravitational Wet Scrubbers with Electrostatic Enhancement

Conventional gravitational wet scrubbers, which generally perform removal of fine particles with low efficiency, cannot meet new standards for pollution emissions. One way of improving the collection efficiency of fine particles is to impose additional electrostatic forces upon particles by means of particle‐charging, or droplet‐charging, or even opposite‐charging of particles and droplets. A Monte Carlo method for population balance modeling is presented to describe the particle removal processes of gravitational wet scrubbers with electrostatic enhancement, in such a way that the grade collection efficiency and particle size distribution are calculated quantitatively. Numerical results show that, the grade collection efficiency of submicron particles is only ca. 5 % in conventional wet scrubbers. However, it reaches ca. 25 % in particle‐charging wet scrubbers, ca. 70 % in droplet‐charging wet scrubbers, and even above 99 % in opposite‐charging wet scrubbers. Furthermore, population balance modeling is used to optimize the operational parameters of the droplet‐charging wet scrubbers by means of the quantitative comparison of the grade collection efficiency. It is found that the operational parameters that are beneficial to the high‐efficiency removal of fine particles are faster gas velocity, slower droplet velocity, larger liquid‐to‐gas flow ratio, larger charge‐to‐mass ratio of droplets, smaller geometric mean diameter and smaller geometric standard deviation of droplets.     

Electrostatic performance of various lubricant powders in P/M electrostatic die wall lubrication

Electrostatic die wall lubrication is an advanced lubrication technique in the production of machinery parts of powder metallurgy. Electrostatic performance of lubricants is one of key factors for successful operation. Among electrostatic parameters, the charge-to-mass ratio of dry lubricant powders has been considered to be the most critical factor to make good adhesion between the dry lubricant powders and the inner die wall. This paper investigates electrostatic performances and potential dependences of the charge-to-mass ratios of various single lubricants and lubricant mixtures, such as zinc stearate, W-special wax, EBS wax, graphite and h-boron nitride, and some combinations of these single lubricants. The experimental results indicate that not all of the single lubricants can properly be charged by electrostatic charging. Zinc stearate, h-BN and EBS wax can easily be charged and the charge-to-mass ratios can be obtained up to the proper value (0.2 μC/g) high enough for die wall lubrication practice. For lubricant mixtures, wax combinations show satisfactory electrostatic response and both conducting and insulating lubricant powder additions influence the electrostatic performance of the mixtures significantly. Mechanism of charging is discussed and a quantitative estimation of the ratio is given. Processing variables influencing the charge-to-mass ratios are also discussed.     

电晕放电喷雾荷电特性

静电喷雾广泛应用于工业各个领域,如静电喷涂、静电雾化燃烧、静电雾化除尘等,其应用效果与喷雾荷电特性密切相关。为获得更佳荷电效果,本文探究了电晕荷电过程中感应电流对液滴真实荷电电流的影响,通过改变荷电电压、电极间距、电极环直径及液体流量等,实验研究了各因素变化对喷雾荷质比、电荷衰减及液滴粒径的影响。结果表明：相比于感应荷电,电晕荷电过程不稳定但能获得更佳的荷电效果,液滴荷质比随荷电电压的增加而先减小后增大,随电极环直径的增加而先增大后减小,随电极间距的增大而增大,电极环直径80mm,电极间距40mm能获得最佳荷电效果;荷电液滴带电量会随输运距离增加而泄漏衰减,相同距离下液滴通过电晕放电带有电荷后衰减更快;液滴带电后能够降低液体表面张力,随着液滴荷电量的增加,雾化液滴粒径有所降低。     

Charging of unfunctionalized graphene in organic solvents

Unfunctionalized graphene is positively or negatively charged when it is dispersed in organic solvents. The charging is negative in solvents with high electron donor numbers and positive in those with low donor numbers. We suggest that the charging originates from electron transfer between graphene surfaces and solvent molecules, and the stable dispersion of unfunctionalized graphene in organic solvents is mainly controlled by electrostatic repulsion between the charged graphene surfaces.     

Testing the application of Free Flapping Foils (FFF) as a method to improve adhesion in an electrostatic wall-climbing robot

In this paper, extensive testing on an electrostatic wall-climbing robot is carried out to examine the electrostatic adhesion force when using the Free Flapping Foils (FFF) method. This method is successfully applied to an electrostatic robot to enable it to stick more firmly, by about three times, on walls with different materials, including wood, plaster, granite, glass and climb wall with a continuous movement. The innovation in this paper is that successful tests were carried out, when using thin flexible electrodes made from aluminium foil and free movement of those electrodes. The FFF electrodes are flexible enough to get the shape and roughness of the wall and increases the contact surface. Thus, they increase the adhesion force and would also improve performance of the robot in rough surfaces. The experimental parameters including charging voltage, charging time, number of electrodes, area of electrodes, wall material (permittivity) and surface finishing of wall that affect the electrostatic carrying force were investigated. The robot could cross obstacles with different heights. The final robot was 1.27?Kg and able to convey 14?N extra load when sticking and climbing vertical walls.