Grounding resistance for control of static electricity ignition hazards

The flow of hydrocarbon product in pipes generates static electricity at density levels that may be sufficient to cause sparks and ignition when product is delivered to a tank. This paper describes the formulation of a method that can be used to control such electrostatic ignition hazards during tank filling operations. The grounding current for a grounded metallic tank being filled with charged liquid was found. The grounding current found was used to find the grounding resistance limit that ensures that dischargeable energy is always below the ignition level. The analysis presented in this paper was focused on cylindrical tanks; however, the method can be extended to any shape charged liquid container whose electric potential is known.     

Simulation test on charge density and surface potential in an oil tank during filling operation

Explosion accidents in oil tanks took place twice in the last three years in China. The simulation test on charge density and surface potential during filling gasoline into a tank has been conducted. The volume-averaged charge density was found to rise to a maximum about 20 min after the pump was started and then began to decrease. The surface potential rose steadily for about 30 min and then decreased during filling operation. The maximum of surface potential sharply increased when the filling rate rose.     

On the electrostatic potential distribution in a screened Corbino disk carrying a transport current under conditions of the quantum Hall effect

It is shown that the characteristic features of the chemical potential for 2D electrons in a magnetic field, which lead to sharp dips in the magnetic field dependence of the capacitance of a 2D system, also affect the electrostatic potential distribution in the direction of the transport current flowing through a 2D Corbino disk under conditions of integral magnetic filling factor. The associated details of the temperature dependence of the electrostatic potential distribution, the distances to the screening electron, and the transport potential difference at the Corbino edges are investigated. The possibilities of experimentally observing these features of the electrostatic potential distribution along a Corbino disk with a transport current under conditions of the quantum Hall effect are discussed. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 8, 545–550 (25 October 1997)     

汽油储罐火灾燃烧特性的实验研究

本文通过对直径为1 m、 1.5 m和2.7 m的汽油储罐进行火灾实验,分析了汽油罐燃烧时不同阶段的燃烧特 性。本文重点讨论了描述燃烧特性的几个重要参数的变化规律,包括火焰脉动频率、火焰高度、倾斜角度以及火焰的温度 分布等,并将结果拟合为相应的实验关联式,以揭示油罐火灾的内在规律和预测其发展趋势。     

‘Operational health’ monitoring for confidence in long term electric field measurements

The paper describes practical aspects of electrostatic fieldmeter instrumentation for long term monitoring of electric fields in adverse environmental conditions. Examples of applications have been in studies of tank washing on large crude oil tankers and measurement of atmospheric electric fields. Particular attention is drawn to the technique developed for continuous monitoring of operational health to justify confidence in observations.     

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.     

离子型表面活性剂对双重乳粒分散性能的影响

为了改善臭氧处理PS单层球与PVA溶液生成的双重乳粒在油相中的分散性,采用了低分子量阴离子型表面活性剂十二烷基硫酸钠(SDS)和十二烷基苯磺酸钠(SDBS)及高分子量混合型表面活性剂十八烷基胺聚氧乙烯醚双季铵盐(PAVDA)来改性该种PS单层球,测试并分析了不同表面活性剂对相应薄膜亲水接触角及其对PVA吸附速率的影响,同时也考察并对比了静电排斥作用和空间位阻作用对双重乳粒分散性的影响。实验结果表明这三种表面活性剂均能不同程度的改善双重乳粒在油相中的分散性。其中,经SDS和SDBS处理后,双重乳粒在油相中固化时会发生絮凝作用而无法以较高成活率制得大尺寸双层球;经PAVDA处理PS单层球后,实现了以较高的成活率制得700~900μm的PS-PVA双层空心微球。同时,也表明在改善PS单层球的分散性方面,空间位阻稳定作用较静电排斥作用更为有效。     

Effects of electrode and filter element shapes on characteristics of charge injection type of electrostatic oil filter

This paper reports on an improvement of the filtration speed of charge injection type of electrostatic oil filter. Numerical simulations of the ion drag flow field and electric field are performed to compare the charge density distribution, ion drag flow pattern, and electric field strength distribution for different electrode and filter element shapes. Filtration experiments are conducted and the experimental results are discussed in relation to the simulation results. It is shown that the numerical simulations used in this study can contribute in predicting a better structure for electrostatic oil filters.     

高真空多层绝热低温容器真空丧失后的传热研究

高真空多层绝热低温容器的绝热夹层发生完全的真空丧失事故后,由于自然对流换热的原因,其绝热夹层的漏热量会急剧增加.在搭建了高真空多层绝热低温容器完全真空丧失后的传热研究实验台的基础上,使用于燥氮气为破空介质、液氮为低温介质,进行了多次高真空多层绝热低温容器的完全真空丧失实验.重点研究了低温容器液位及绝热材料层数的变化对其...     

着火油罐燃烧特性的理论分析

本文利用自行建立的油罐火灾燃烧特性通用模型,计算得到了燃烧速度、火焰高度,火焰跳动频率和平均温度等油罐燃烧特性的变化规律,并深入探讨了油品燃烧速度在油罐直径、风速、环境温度和油位等因素影响下的变化趋势。为了验证理论计算的准确性,将计算结果与汽油和柴油储罐的燃烧实验数据进行了对比,获得了较为满意的结果。     

粉末颗粒气力加注特性实验研究

粉末发动机是以粉末颗粒为燃料的新型发动机,具有多次起动和推力调节的功能.粉末加注是粉末发动机实验组织过程中的重要环节.本研究通过搭建粉末供应系统开展粉末气力加注实验,研究对比了集粉箱加注位置、流化气量对粉末气力加注特性的影响.考虑了供粉过程中储箱内粉末堆积密度的动态变化,并建立了相应的计算方法,同时还采用控制系统理论揭示了储箱内粉末堆积密度的变化规律.结果表明:在相同条件下,较大的流化气量有利于加注过程稳定,但集粉箱加注率较低;气力加注方式下集粉箱内的粉末堆积密度大于储箱内初始堆积密度;采用较小的流化气量与集粉箱壁面切向加注方式有利于提高粉末粒径分布均匀性;集粉箱壁面切向加注方式下,流化气量较小时储箱内粉末的堆积密度是先增大后减小,且堆积密度最终值小于初始值,而流化气量较大时,储箱内粉末的堆积密度是先增大后减小再增大后减小,且堆积密度最终值大于初始值;储箱内粉末堆积密度的动态变化过程类似于欠阻尼二阶系统,流化气量较小时系统阻尼系数较小,而流化气量较大时系统阻尼系数较大,且是一个变阻尼过程.     

Correlations between the electric charging properties and the optically determined structure of non-woven fabrics

The aim of this paper is to determine the degree of correlation between the electrostatic potential distribution on the surface of non-woven fabrics and the material structure as obtained by optical means. The potential distribution on the material surface was monitored for several samples of two types of fabrics that were electrically charged using corona discharge. The results show that the charge distribution on the samples surface significantly correlates with the spreading and the third centered moment of the gray-scale pictures of the samples.     

球罐BLEVE碎片抛射的危害性研究

 多米诺效应是造成重大事故损失加剧、灾难升级的一个重要原因。爆炸碎片是化工区多米诺事故的重要诱因之一。以球罐液体沸腾进而扩展为蒸气云爆炸（BLEVE）为例,从爆炸碎片飞行过程的规律性及碎片产生抛射的不确定性出发,采用蒙特卡罗方法进行模拟,利用相关数据和资料确定爆炸碎片产生和飞行中的不确定性参数,计算出碎片的抛射范围。并在此基础上,计算得到了不同充装水平下的球罐爆炸后产生碎片碰撞两种目标容器的概率。研究发现：当目标容器不同时,储罐爆炸产生碎片的碰撞概率差别较大;当目标容器一定时,不同充装水平的储罐可造成的多米诺效应虽有不同,但差别不大。研究结果对于定量评价储罐爆炸碎片的危害性,减缓和控制碎片产生的风险,确定罐区之间防护碎片危害所需的安全距离等提供了指导和借鉴。     

低温容器夹层真空度对内罐压升率的影响研究

针对低温容器夹层真空失效工况,建立了低温容器夹层真空度与通过内罐壁面热流密度的理论模型,结合ANSYS-FLUENT软件对某立式低温容器内的液氮蒸发过程进行了仿真模拟,研究了初始充满率为50%时,低温容器内罐空间温度及压力随夹层真空度变化的规律。结果表明,随着夹层真空度降低,通过低温容器内罐壁面的平均热流密度增大,内罐中液体温度升高速率增大;当夹层真空完全失效时,内罐压升率分别是夹层真空度为10-3 Pa、1 Pa和10 Pa时的10.4倍、5倍和1.2倍。     

着火油罐燃烧过程预测的通用模型

本文根据油罐火灾的燃烧特点,从基本的传热规律和燃烧机理出发,以油品表面热反馈的能量平衡为前提,并利用化工热力学方法计算了火焰的平均温度,通过迭代方法,并结合相关的实验数据和结果,提出了油罐火灾燃烧过程的通用模型,该模型可适用于多种碳氢类燃料。本文以汽油为例,通过计算可以得到着火油罐的多项燃烧特性,包括燃烧速度、平均火焰温度等,是获取油罐周围热辐射规律的基础和前提,计算结果可为火灾现场战术的决策以及预案的制订提供依据。     

在柱坐标系中求解轴对称的静电场

提出了求解轴对称静电场的柱函数展开法,推导出用对称轴上的电势分布表示空间电势分布的级数展开式,并给出了求解轴对称静电场的例子.     

复合式反应破片对柴油油箱的毁伤效应试验研究

 设计并制备了两种不同配方的新型复合式反应破片,并进行了该反应破片对装有柴油油箱的毁伤试验。复合式反应破片由壳体、裸反应破片、顶盖组成。裸反应破片采用铝粉和聚四氟乙烯、钛粉和聚四氟乙烯两种材料配方真空高温烧结制成。试验利用12.7 mm弹道枪发射复合式反应破片,并用高速摄影仪记录破片对油箱的毁伤过程。两种配方的复合式反应破片均能穿透6 mm厚油箱壁,并具有明显的引燃效果。试验结果表明,与惰性破片相比,复合式反应破片兼有侵彻能力和引燃纵火能力。     

自仿集的势论和分析性质

研究了关于自仿集上电荷分布的势论及有关分析性质。指出电荷分布、势及其Fourier变换的构造性质;明确给出了三分Cantor集上二项分布及其矩、Fourier变换、势的具体表达式;并给出一些数值结果。     

Contribution to static electrification of mineral oils and natural esters

A failure of an insulation system of a power transformer can result into an interruption of a power supply and subsequently to a large economic damage. In some cases, the malfunction is so serious that a transformer may explode and catch fire resulting in a direct threat to the life of the device operator. These devices rely on a combined insulation system oil-paper. The oil in a transformer not only impregnates the pressboard paper insulation, hence increases its electric breakdown strength, but also acts as a coolant of active parts of the device. During the cooling, the oil flows in the transformer tank around the core, windings and isolation barriers from hardened paper. At the interface of two dielectrics, the oil and the cellulose in the transformer, electrostatic charges appear. The charges of one polarity are carried in the oil, and the charges of the opposite polarity remain captured in the barrier that is formed by the internal structure of the transformer. The accruing of a certain amount of charge leads to discharges along the surface of the solid insulation and therefore to its partial damage. Ultimately, this can lead to the damage of the whole insulation system of the transformer by its breakdown. At present, the mineral oils are used as the main liquid insulating medium because of their good electrical insulating and cooling properties. On the other side, there is a high environmental burden for their operation and maintenance as well as the subsequent disposal of the discarded oil. The natural esters may be used as a replacement for the mineral oil. They go well with the environment, they are biodegradable and in case of the transformer malfunction, its disposal costs less money.This paper presents the results of the experiments of electrostatic charging of the mineral oils and natural esters and their comparison. The charging process in the transformer is modelled using a metal cylindrical container with a forced flow of oil using a controlled rotating circular disc from a hardened paper. The results indicate that increasing intensity of friction, increases the electrical charge, which is generated at the interface of the solid phase and the liquid. In these experiments two types of mineral oils were studied. For comparison, two types of natural esters (sunflower and colza oils) were selected and used in the same experiments. The charging of the oils was examined at various temperatures ranging from 25 °C up to 70 °C.