Chargeability of ethanol–petrol biofuels

Chargeability of ethanol–petrol biofuels during refuelling has been studied in real dispenser environment in order to assess safety risks due to fuel charging at fuel filling stations. Two biofuel blends were studied: E10 containing 10 vol-% of ethanol and 90 vol-% of petrol, and E85 containing about 85 vol-% of ethanol and 15 vol-% of petrol. Charging of standard 95 Octane petrol was studied as a reference. The results show that the charging of E85 is negligible and no charge will be accumulated as long as the fuel dispenser system is properly grounded. In the case of refuelling with E10, charge is accumulated but the level of total charge is still so low that no real electrostatic ignition hazards exist due to fuel charging at filling stations as long as the system is properly grounded. Electrostatic ignition hazards due to fuel charging are real only for standard petrol fuel.     

An assessment of electrostatic ignition hazards associated with fuel flow through plastic pipes at roadside filling stations

The use of electrically insulating synthetic materials, such as high-density polyethylene (HDPE), for fuel pipelines and other fuel handling components is now widespread. It is well reported however that the flow of fuel under certain conditions in plastic pipes can produce measurable levels of electrostatic charge.This paper describes in detail a full-scale experimental test rig simulating a filling station layout – in particular the conditions existing during road tanker delivery of high-charging fuels. It presents data from a series of electrostatic measurements, discusses results and draws conclusions with regard to existing safety margins and precautions for safe operation.     

Induction charging risk assessment: Charged board alike discharges to metal and human body

Charge can easily be induced on electronics or on other conducting parts if they are exposed to external electrical fields. In production facilities where sensitive electronics are handled, strong electrostatic fields should be avoided due to the risk of causing electrostatic discharges (ESDs) that could damage components. In electronics manufacturing this is usually achieved by grounding all conductors and removing all insulators from an ESD Protected Area (EPA) in the facility. However, it is not always possible to remove all insulators from the EPA as they are sometimes an essential part of the production processes. In this case, a method of risk assessment is necessary to evaluate safe operation. We have studied induction charging of a dummy PWB (Printed Wiring Board) through a grounded MOSFET transistor, by grounding it directly to metal or through the human body, when the PWB is exposed to a static electric field. The experimental setup can easily be turned into an induction charging probe by changing the MOSFET transistor to a low leakage current, high voltage capacitor of suitable size and measuring the voltage over this capacitor.     

界面极化注极聚丙烯薄膜驻极体的电荷存储特性研究

本文报道一种基于双层介质界面极化机理的新型驻极体注极技术: 借助辅助层对PP薄膜进行注极. 采用表面电位测试方法考察了注极温度、注极电压对所获PP薄膜驻极体电荷存储性能的影响, 并利用热刺激放电技术研究了其高温电荷存储性能, 同时测试了PP薄膜驻极体在X和Y方向的静电场分布. 结果表明: 界面极化注极是一种比电晕注极更为优异的驻极体形成方法. 在一定温度下, 驻极体表面电位随注极电压的增加而增加, 而且两者呈线性关系, 这一结果与注极过程的电荷积聚方程的分析完全一致. 注极温度的影响研究表明, 在保持注极电压不变(注极电压范围为0.5–3.0 kV)的情况下, 温度低于75 ℃时, 温度的变化对于注极效果的影响不明显; 当注极温度大于75 ℃ 时, PP薄膜驻极体的表面电位随注极温度的增加而增加. 表面电位随时间的变化研究表明, PP薄膜驻极体具有良好的电荷存储稳定性. 对其表面电位分布的测试表明, 界面极化注极所形成的PP薄膜驻极体呈现均匀的静电场分布.     

Gasoline electrification: moisture and temperature influence

In the last decades, car manufacturers have introduced plastic materials into the vehicle fuel circuit. Do these modifications have an influence on electrostatic hazards? Several accidents were listed in Japan and the United States while filling the tank. Flow electrification was suspected to be responsible for some of these accidents. In this context, our laboratory studies flow electrification of fuels on the surface of dielectric and conducting materials on different conditions (fuels, moisture, temperature, Reynolds number, etc.).This paper is interested in flow electrification variation depending on atmospheric conditions (moisture and temperature) and on Reynolds number. We propose to evaluate the electrostatic hazards according to these parameters for a commercial gasoline/stainless steel interface.An experimental setup was developed in our laboratory. It consists of a loop representing fuel flowing through a pipe under a specific gas environment (controlled air moisture and gasoline temperature). The current generated by fuel flow is measured. This study allows to determine the main experimental parameters that modify flow electrification phenomenon in fuel.     

等离子体环境下孤立导体表面充电时域特性研究

航天器在等离子体环境下的表面充放电受到多种因素影响, 其中充电时间是影响静电放电频次的一个重要因素. 本文从等离子体的微观结构出发, 同时考虑材料参数特性, 在对每个粒子运用力学原理的基础上, 以统计方法 推导出孤立导体球表面充电电位时域表达式. 利用电位时域表达式推导出孤立导体球净电荷量时域表达式及静电场能量时域表达式. 以较低非极地地球轨道和较高地球同步轨道为例对孤立导体球电位、 净电荷量及静电场能量的时域特性进行了讨论, 分析了空间环境参数和导体球半径大小对表面充电的影响, 总结出等离子体环境下孤立导体表面充电时域特性规律. 关键词： 等离子体 孤立导体 表面带电 时域     

Electrostatic charging of the NH90 helicopter

This article discusses electrostatic charging of the NH90 medium transport/utility helicopter and assesses the safety of transported products against electrostatic discharges originated from the helicopter. Key questions were to determine charging characteristics of the composite material body NH90 compared to metal body helicopters as well as the charging levels in typical operating situations and climate conditions in Northern Europe. Most attention was paid to a situation where a load was winched to ground from a levitating helicopter at 40–80 feet altitudes. The measurements were supported with a simplified numeric simulation model and calculations of the charging of the helicopter.According to the study, there is no significant difference in electrostatic charging characteristics between composite body NH90 helicopter and metal body helicopters. The tight grounding net of the NH90 helicopter enables the charge currents to discharge in the same manner as in metal body helicopters. In all measured situations, the electrostatic charging of the NH90 or a person moving inside the helicopter is under the transport requirements depicted in the standard STANAG 4235.     

Medium velocity impact triboelectrification experiments with JSC Mars-1 regolith simulant

As land-based robotic missions to Mars have increased in scope and mobility, NASA has intensified its research efforts involving the mechanisms of electrostatic charging on the surface of Mars. The primary concern is that electrostatic adhesion and discharge might interfere with the operation of sensitive components, or interfere with communications and control systems. A secondary effect might be the electrostatic build-up of dust on solar panels, reducing mission effectiveness. One goal of this research is to assist in the development of electrostatic mitigation, including the selection of materials that resist excessive charging when placed in frictional contact with the Martian regolith.¹ However, most information related to frictional charging, or triboelectrification, is of an empirical nature. Based on experimentation, some materials have historically been arranged into triboelectric series in which the magnitude and sign of charge acquired through frictional contact can be predicted with reasonable accuracy. However, Martian regolith is not a homogeneous substance, so the approach of the traditional triboelectic series cannot be easily applied. Furthermore, an adequate theory that fully explains triboelectrification does not yet exist. For these reasons, it is necessary to empirically determine the materials and environmental conditions in which frictional charging on Mars becomes significant.Therefore, an experimental procedure has been developed for determining some triboelectric charging characteristics of JSC MARS-1 regolith simulant, based on a shaker box concept suggested by Dr. Carlos Calle of the Materials Research Laboratory at Kennedy Space Center. Over 300 trials under specific test conditions have been performed using this test procedure, with materials common to NASA project equipment used in space exploration. Test results indicate that moderately successful control over test conditions has been achieved, but the acquired electrostatic charge of the regolith simulant did not follow expected trends for all test materials. An analysis of time dependence trials conducted during this study indicates that at least two distinct, identifiable charging mechanisms affected magnitude and sign of the cumulative charge. The first is triboelectrification between the simulant and the test material. The second is inter-particle charging of the regolith simulant, with subsequent transfer between the test material and simulant. With some test materials these differing mechanisms yielded opposing charge polarities, in that the resulting magnitude of the acquired charge appears to be the difference, not the sum of the charging processes.     

毫米级栅型电场分布FEP薄膜驻极体的制备及其电荷存储性能研究

采用电晕注极和热注极技术, 在厚度为25 μm的氟化乙丙烯共聚物(FEP)表面制备了宽度为2 mm和3 mm的具有栅型电场分布的驻极体, 研究了注极温度和电极宽度对其电荷存储性能的影响. 样品注极后经150天的存储, 栅型电场分布变得清晰而有规律, 覆盖铝电极区电位已衰减至接近零, 未覆盖铝电极区仍保持高电位; 对电极宽度为2 mm和3 mm的样品, 覆盖铝电极区与未覆盖铝电极区的表面电位差分别为110 V和130 V(电场强度差分别为44 kV/cm和52 kV/cm). 表面电位跟踪测试结果表明: 电晕注极样品初始表面电位高于热注极样品; 在相同的注极方法下, 注极温度越高初始表面电位越高, 电极宽度越小初始表面电位越低. 依据电晕注极和热注极原理对实验结果的分析表明, FEP和金属铝在电荷存储性能上的差异是FEP表面蒸镀铝电极后能获得栅型电场分布的原因所在.     

Spacecraft charging potential during electron-beam injections intospace plasmas

Injections of nonrelativistic electron beams from an infinite conductor have been simulated by using a two-dimensional electrostatic particle code to study the spacecraft charging potential. The simulations show that the conductor charging potential at the end of simulations does not vary with the beam density when the beam density exceeds four times the ambient density. The reflection coefficient, which determines a percentage of incident electrons reflected by the conductor, increases the charging potential. To charge the conductor to the beam energy, the reflection coefficient needs to be about 0.5. The results are applied to explain the spacecraft charging potential measured during the SEPAC (Space Experiments with Particle Accelerators) experiments from Spacelab 1     

Risks of damage to electronics with reference to charged clothing

Risks of damage to electronic devices with reference to charged clothing have been identified and quantified. The key parameters to control, in order to minimise the device failures due to electrostatic discharge (ESD), are peak ESD current and charge transfer in a direct discharge and device charging by induction and rubbing. An extensive experimental program was carried out to gain experience on threshold levels of these parameters. Use of ESD protective garments over normal clothes of operators is highly recommended in order to minimise ESD failures of devices. The ESD protective garments must be properly used and designed, otherwise they themselves form an ESD risk to electronics.     

航天器内部孤立导体表面带电面积效应研究

航天器内部孤立导体充放电对航天器的影响更为隐蔽, 造成直接和潜在的伤害更加严重. 综合考虑航天器内部环境中粒子参数及材料二次电子特性等因素, 基于气体动理论, 结合粒子的麦克斯韦速度分布函数, 得出孤立导体球充电电位一般表达式. 利用电位表达式推导得出孤立导体球净电荷量及静电场能量与导体面积关系表达式. 讨论了特殊情况下孤立导体静电场能量与面积及空间环境的关系, 与地面电子元器件电磁脉冲放电损伤值进行了对比, 总结出孤立导体表面带电面积效应规律. 关键词： 孤立导体 表面带电 静电场能量 面积效应     

The measurement of charging efficiencies and losses of aerosol nanoparticles in a corona charger

A methodology is proposed for the measurement of a number of parameters relevant to the performance evaluation of aerosol corona chargers. These parameters are intrinsic and extrinsic charging efficiencies, and diffusion and electrostatic particle losses. The methodology is essentially the same as that used in earlier works, except that free ions are removed just after the charger outlet in order to minimize the extent of possible after-charging effects which might lead to measurement errors. However, the experimental results show that after-charging is negligible and that, consequently, practically all the effective ion–particle collisions take place before the aerosol leaves the charger. Formation of new particles during corona discharge, which could in principle be an additional cause of measurement error, has not been observed in the working voltage range of the charger. Particle diffusion and electrostatic losses have been measured at varying values of the voltage applied to the charger: for a given particle size, diffusion loss decreases and electrostatic loss increases as the charger voltage is increased. The intrinsic charging efficiency increases with particle size and charger voltage. In contrast, the extrinsic charging efficiency, which is the parameter of importance in practice, attains a maximum value for a given charger voltage in such a manner that this optimum voltage depends on particle size.     

Enhancement of charging and discharging rates in a latent heat storage system by use of PCM with different melting temperatures

A latent heat storage module with rapid charging and discharging rates has been developed. The heat storage module consisted of horizontal cylindrical capsules filled with three types of PCM with different melting temperatures. A numerical model has been developed to predict the transient behavior of the heat storage module. Both the experimental and numerical results showed some improvements in charging and discharging rates by use of a “three-type” PCM     

Particle charging characteristics with the low-speed mixed fluid under high electric field

Air pollution caused by particles with small size has been a global concern because of threats to human health. A feasible way to remove these super fine suspended particles is using electrostatic precipitation technology. Herein, the PIV was used to measure the particle velocity distribution. By analyzing the particle motion trend in high electric field, a process of particle charging loss was observed. This phenomenon cannot be explained by current particle charging theories. Our conclusions may improve the understanding of particle charging processes.     

Charge distribution and stability of charged carbon nanotubes

Density-functional calculations of charge distribution on negatively and positively charged nanotubes result in charge density profiles characterized by a significant increase of charge density at the tube ends. These results are in quantitative agreement with classical electrostatic analysis, which assumes constant electrostatic potential on the conductive tube surface. At high charging levels, the tube ends are observed to be unstable due to Coulomb repulsion. By combining ab initio calculations with classical electrostatics, we determine, as a function of tube length and geometry of the tube end, the critical voltage beyond which nanotubes are unstable.     

Charged spray generation for gas cleaning applications

The paper presents results of experimental investigation of properties of charged sprays generated by two types of pressure atomizers with charging by induction. Among other possible methods of charged spray generation, the induction charging has been considered due to its most practical importance. The goal of this research is to optimise the charging process with respect to obtain droplets of required size and charge for their application for exhaust gas cleaning from submicron particles in electrostatic scrubber used for the removal of PM from Diesel engine exhausts. Electrostatic scrubbers use electrostatic forces in order to deposit fine charged particles onto oppositely charged droplets.     

Performance of a sonic jet-type charger in high dust load

Sonic jet chargers have originally been used in aerosol measurement devices for particle charging and neutralization. Here, our goal was to study if this charger type could be used in particle control devices in which particle concentrations and gas volumes are much higher. The study includes charging efficiency tests in a laboratory and with a commercial 20 kW wood pellet burner. Actual particle removal efficiency was tested with a laboratory scale parallel plate electrostatic collector. The results show that sonic jet-type chargers also have potential in filtering applications.     

Corona charging of granular layers of insulating particles at the surface of a grounded electrode

The aim of the present paper is to introduce a simple experimental technique for estimating the corona charging conditions of insulating granules that form a layer at the surface of the grounded electrode of roll-type electrostatic separators. The basic idea consists in measuring the potential at any point on the surface of this layer by means of an electrostatic probe. The capacity of the probe–layer system being constant, the measured potential is proportional to the charge. The results clearly show that the charges imparted to the particles in the corona discharge depend on their positions at the surface of the electrode and on the inter-electrode spacing. This observation could be of use, for instance, to particle charging simulations performed as a preliminary step of any feasibility study of new electrostatic separation applications.     

A life of its own: The tenuous connection between Thales of Miletus and the study of electrostatic charging

Thales of Miletus, a Presocratic Greek Philosopher, is often credited with discovering electrostatic charging and carrying out the first experiments or systematic observations of this phenomenon. We examine the original sources from antiquity to uncover Thales' true contributions. Thales is likely to have commented on electrostatics in connection to his philosophical idea that even lifeless things have a share or piece of soul in them, but there is no basis to believe that he discovered, carried out experiments on, or systematically observed electrostatic charging.