Characterization of chargeability of biological particulates bytriboelectrification

Triboelectric chargeability of pecan pollen and lycopodium spores, using commercial Teflon and nylon chargers, has been investigated as reported in this paper. The charge-to-mass ratio of lycopodium, measured at different powder feed rates, i.e., 50-500 mg/s, indicated that both Teflon and nylon chargers increased particle charge by approximately elevenfold over background with Teflon charging particles positively to +11.06 mC/kg and nylon negatively to -11.52 mC/kg. Pecan pollen charge increased by approximately 11 times for Teflon charging positively to +7.59 mC/kg, and five times for nylon charging negatively to a value of -3.72 mC/kg. Pollen charging was not affected by carrier-air humidity in the range of 18.1%-47.6% relative humidity (RH) and at a temperature of 22.5°C. Pollen chargeability by Teflon measured as a function of the duration of air flow over the charger surface indicated that triboelectric charging was not degraded, even by 3.5 h continuous flow of humid air (44.2% RH at 19.2°C). Results indicate that tribocharging is a feasible method for imparting charge to pollen in electrostatic pollination technology currently under development     

Characterization of tribocharging properties of powder paint

The charge-to-mass ratio (q/m) of individual particles plays a vital role in the powder coating process. Simultaneous measurements of particle size and electrostatic charge were performed on triboelectrically charged powder paint and other powders in the particle size range 1.0 to 65.0 μm in diameter. An electrical single particle aerodynamic relaxation time (ESPART) analyzer was used to measure electrostatic charge (q) and aerodynamic size (d_a) distributions on a single particle basis and in a noninvasive manner. The powders were triboelectrically charged against nonconducting surfaces. Experimental data show that (1) the magnitude of the charge increases linearly with the surface area of the particle and consequently, the charge-to-mass ratio of the particles decreases inversely with respect to d_a in the entire size range, and (2) twenty to sixty percent of the particles were charged with opposite polarity. The average charge attained by particles larger than 4.0 μm in diameter was less than the Gaussian limit of saturation charge. The charge-to-mass ratio of the bulk powder sample depends upon the range of particle size in the sample. The mass median aerodynamic diameter of the sample studied was 30.0 μm with the geometric standard deviation of 2.0     

Measurement of particle size and electrostatic charge distributionson toners using E-SPART analyzer

Performance characteristics of a laser-based instrument called the electrical-single particle aerodynamic relaxation time (E-SPART) analyzer for measuring aerodynamic size and electrostatic charge distribution of particles in real time and on a single-particle basis are described. Applications of this analyzer along with experimental data of the characterization of different toners for their size and charge distributions are presented, including operational principles and methods of data acquisition. Size distribution ranged from 2.0 to 20.0 μm in aerodynamic diameter, and the charge-to-mass distribution ranged from 0 to ±20 μC/g. The method is noncontact and provides both magnitude and polarity of electrostatic charge on an individual particle basis. The aerodynamic diameter and charge are measured simultaneously at an average count rate of approximately 100 particles/s     

The Use of Tribocharging in the Electrostatic Beneficiation of Lunar Simulant

The use of tribocharging as a potential method to provide sufficient charge to several different lunar simulants for electrostatic beneficiation was investigated. The objective was to determine whether specific minerals of interest (e.g., ilmenite) that are present in lunar regolith could be enriched in concentration by beneficiation that would therefore allow for more efficient extraction for in situ resource utilization use. The production of oxygen, water, and other resources on the Moon from raw materials is vital for future missions to the Moon. Successful separation of ilmenite was achieved for a prepared simulant (KSC-1), which is a mixture of pure commercially supplied pyroxene, olivine, feldspar, and ilmenite, in a 4 : 4 : 1 : 1 ratio, showing proof of concept when tribocharged against three different charging materials, namely, Al, Cu, and PTFE. Separation by chemical composition was also observed for existing lunar simulants JSC-1 and JSC-1A; however, the interpretation of the separation was difficult due to the complex mineralogy of the simulants compared to the simple prepared mixture.      

Effects of surface properties on the tribocharging characteristics of polymer powder as applied to industrial processes

Experiments performed on different powders of different size distributions tribocharged with stainless-steel (SS) beads showed the charge acquired by the powder could be correlated with the actual work function difference between the powder and SS. Ultraviolet and X-ray photoelectron spectroscopy were performed on various materials involved, and showed the work function increased with surface contamination and oxidation, and the difference narrowed for metals and polymers. Such a small difference in work function may contribute to bipolar charging. Experiment data showed that while charge acquired increased with particle size, the charge distribution was generally bipolar. Both surface analysis and charge distribution studies suggest that for tribocharging, minimization of oxidation and surface contamination are needed. It also appears that the relative humidity must also be controlled to obtain reliable tribocharging. Semiempirical molecular modeling calculations of the work function of several polymers showed good agreement with experiment. Surface plasma treatment is presented as a viable method for modifying the work function.     

Experimental Evaluation and Analysis of Electrodynamic Screen as Dust Mitigation Technology for Future Mars Missions

The electrodynamic screen (EDS) is considered to be one of the feasible dust mitigation technologies for future Mars missions. In this paper, the performance of EDS for surface cleaning was characterized with respect to the following operational parameters: 1) the efficiency of screens under both continuous and intermittent operations with different rates of dust deposition; 2) electrical power requirements for the screen operation with respect to dust removal efficiency (DRE), frequency, and excitation frequency; and 3) the optical transmission efficiency of the transparent EDSs and the corresponding power loss, when these screens were placed on solar panels. The average DRE of EDS during continuous dust loading was over 95%, whereas it was 90% when the screen was activated intermittently. Power consumption by EDS, as well as the size and weight of the power supply, is one of the critical factors for its applicability for dust removal from solar panels during future Mars mission. The power consumption by EDS was measured under several dust loadings and using different frequencies and electrical field intensities for the safe operation of power supplies without Paschen breakdown. Experiments were conducted under simulated Martian atmosphere (5.0 mb $hbox{CO}_{2}$ atmosphere) using a screen with an active surface area of 59 $hbox{cm}^{2}$. The average power consumption of screen varied between 1.02 and 2.87 mW. The optical transmission efficiency for a transparent EDS (PET substrate with indium tin oxide electrodes) was measured for a PET screen with ITO electrodes. It was found that placing the transparent EDS on a typical space-type solar panel resulted in a significant obscuration. The power output of the solar panel decreased by 15%.      

Triboelectric charging of polymer powders in fluidization andtransport processes

In this paper, we investigated the role of tribocharging in fluidization, flowability, and q/m distribution as functions of particle size distribution (PSD), fluidization time, and transport tubes of different materials. A charge separator was used to determine mass fractions of powder that had positive, zero, and negative charges. For the two acrylic powders tested, one (Sample A) had volume median diameter d₅₀ 18.73 μm while the other (Sample B) had d₅₀ 24.17-μm diameter. During fluidization for 1 h at a relative humidity of 57%, powder B acquired positive charge with charge-to-mass ratio Q/M=0.3 μC/g, and 25% of the powder mass had negative charge with Q/M=-0.36 μC/g. About 35% of the powder mass had particles with nearly zero net charge. Tribocharging during fluidization and transport processes was attributed to particle-particle and particle-wall collisions. Of the total charged particles, about 60% were positively charged while 40% were negatively charged. Each particle may have had patches of charges on its surface, some positive and some negative. The sum total of all patches of charges may yield positive, negative, or essentially neutral polarities on a given particle. For a relatively narrow size distribution of powder, the PSD is often assumed to be conserved during fluidization. A shift in PSD toward larger diameter particles was anticipated because of the possible elutriation of the fine fraction of the powder, but the actual shift was only about 1 μm after 1 h of fluidization. Under identical operational conditions using a fluidized bed, powder pump, transport hose, and corona gun, powder B had nearly twice the mass flow rate of Powder A. Such differences in flowability of powders influence charging and deposition efficiencies in powder coating applications     

Fault‐tolerant control allocation for Mars entry vehicle using adaptive control

Accurate and reliable control of planetary entry is a major challenge for planetary exploration vehicles. For Mars entry, uncertainties in atmospheric properties such as winds aloft and density pose a major problem for meeting precision landing requirements. Anticipated manned missions to Mars will also require levels of safety and fault tolerance not required during earlier robotic missions. This paper develops a nonlinear fault‐tolerant controller specifically tailored for addressing the unique environmental and mission demands of future Mars entry vehicles. The controller tracks a desired trajectory from entry interface to parachute deployment, and has an adaptation mechanism that reduces tracking errors in the presence of uncertain parameters such as atmospheric density, and vehicle properties such as aerodynamic coefficients and inertias. This nonlinear control law generates the commanded moments for a discrete control allocation algorithm, which then generates the optimal controls required to follow the desired trajectory. The reaction control system acts as a non‐uniform quantizer, which generates applied moments that approximate the desired moments generated by a continuous adaptive control law. If a fault is detected in the control jets, it reconfigures the controls and minimizes the impact of control failures or damage on trajectory tracking. It is assumed that a fault identification and isolation scheme already exists to identify failures. A stability analysis is presented, and fault tolerance performance is evaluated with non real‐time simulation for a complete Mars entry trajectory tracking scenario using various scenarios of control effector failures. The results presented in the paper demonstrate that the control algorithm has a satisfactory performance for tracking a pre‐defined trajectory in the presence of control failures, in addition to plant and environment uncertainties. Copyright © 2010 John Wiley & Sons, Ltd.     

Corona Discharge and Electrostatic Precipitation in Carbon Dioxide Under Reduced Pressure Simulating Mars Atmosphere

In this paper, the possibility of using electrostatic precipitation (ESP) to clean the gas above solar panels of modules on the surface of planet Mars is investigated. Results are presented on corona discharge in carbon dioxide gas under reduced pressure ranging from 5 to 10 mbar with different electrode configurations. The corona-discharge inception voltage and the threshold of back discharge have been measured for three electrode configurations. The charging of suspended particles of micrometer size in the gas by unipolar ions is examined. Under the considered reduced pressure, diffusion charging very likely dominates over field charging. The drift velocity of charged particles is then estimated and is found to be not drastically lower than in industrial precipitators for fine particles despite the much lower electric field which can be applied under reduced pressure. Finally, the results of a laboratory experiment examining the dust deposit onto photovoltaic cells are presented. It appears that ESP reduces the rate of a Mars analog dust deposit and might be used in order to increase the lifetime of solar panels during Mars missions.     

Comparison of two particle charging experiments for testing the JSC Mars-1 Martian regolith simulant against man-made materials

NASA has great interest in testing the electrostatic charging of various materials due to the saltation process near the surface of Mars. As wind blows over the Martian regolith, particles are picked up, travel over a distance, and then fall back to the surface. These moving particles collide with each other and with any other materials present giving rise to a triboelectric charge transfer. Variables involved in this charge transfer include the number of particles, the frequency of collisions, and the particle velocities. It is necessary to know the extent of charging of man-made materials in this process in order to better plan future Mars missions. Two different methods for creating frictional charging between the regolith simulant and the materials in question are described. The first method utilizes a deflection board apparatus. The second uses a shaker box apparatus. The benefits and drawbacks of each experimental approach are listed. Some experimental data obtained through each method is provided but further study is required to fully characterize these charging processes.     

碱性固态Zn/MnO2电池研究

为解决碱性锌锰电池体系存在的电解液易泄露、加工封闭难等问题,利用溶剂浇铸法制备了PVA-KOH-H2O碱性固态聚合物电解质(ASPE),通过XRD、循环伏安及交流阻抗测试对ASPE样品进行表征.结果表明:ASPE具有良好的导电性(室温电导率达10-2S/cm)及较宽的电化学稳定窗口(相对于不锈钢电极,其电压稳定窗口为2.0 V).Zn|ASPE|MnO2模拟电池以1 mA恒电流放电至0.9 V,放电容量达210 mAh/g.     

核电给水加热器不锈钢换热管的选用

不锈钢管具有优良的使用性能,核电厂给水加热器常采用不锈钢管作为换热管.不锈钢管的材质包括有奥氏体不锈钢管和铁素体不锈钢管.分析了不锈钢换热管的失效机理,并对采用不锈钢管给水加热器的运行经验进行了总结.在选择换热管材质时,需综合考虑耐腐蚀和耐冲蚀性能、力学性能、最高运行温度、潜在振动等方面的要求.     

E-SPART Analyzer for Mars Mission: A New Approach in Signal Processing and Sampling

This paper introduces a novel electrical single particle aerodynamic relaxation time (E-SPART) analyzer for dust particle analysis in the Mars mission. The new E-SPART analyzer is based on a stationary-fringe laser Doppler velocimeter that can simplify the system hardware and reduce its physical size and weight. This paper presents the new operational principle and the signal processing methods. The requirement of the size of sensing volume is discussed by considering pedestal removal and the required time duration of a Doppler signal burst. Experimental results are given to confirm the effectiveness of the principle.     

Modeling of electrostatic-based pesticide spray systems

A microscopic model for the electrostatic spraying system is presented to investigate the effect of the voltage applied to the induction nozzle on the droplet's charge, mobility, and charge-to-mass ratio. The variation of these parameters along the jet was also included. The model also lays particular emphasis on the effect of the applied voltage on the spray current and the charge density at the nozzle. A macroscopic model for the electrostatic spraying system is also presented. The objective of the model was to study the spatial distribution of the droplet charge density, transit time, and trajectory in the region between the nozzle and the target in terms of the flow velocity of the spray and the space-charge-produced electric field. On the macroscopic scale, both the droplet charge density and the spray current increase with the voltage applied to the charging electrode. With the decrease of the spray flow velocity, the space-charge-produced electric field becomes dominant and tends to: contract the droplet trajectories toward the axis of the spray system, and hence enhance the droplet deposition efficiency; and decrease the charge density at the target with the possibility of minimizing back-ionization. On the microscopic scale, induction charging eliminates the ion current from the current to the target and the associated back-ionization. The calculated droplet charge and charge-to-mass ratio which increase with the voltage applied to the charging electrode, agreed with the values reported previously     

Mathematical modeling of powder paint particle trajectories inelectrostatic painting

The trajectories of charged powder particles in an electrostatic powder coating system were modeled considering electrical and fluid forces. The mathematical model employed an iterative technique wherein the charge simulation method was used to compute the electric field strength and the method of characteristics was used to compute the charge density in the gun-to-target region. The fluid flow between the electrostatic gun and the target was modeled using interpolated experimental data assuming stagnation point flow. Particle trajectories were simulated for size range 10-40 μm and charge-to-mass ratios of -0.1 to -1 μC/g. The simulation results showed good agreement with experimental data (charge and mass measurements) at several collection points on the painting target and provided valuable information concerning particle deposition     

大型汽轮发电机风扇静叶改型分析

采用轴向-径向通风的大型汽轮发电机多级轴流风扇静动叶片皆采用不锈钢材料,为进一步优化发电机结构,将静叶材料改为锻铝。受锻铝材料刚度和叶片生产工艺的影响,按原叶型生产的静叶容易发生变形,需对静叶叶型进行改型。采用NUMECA软件对叶片加厚和宽度减小两种静叶叶型的4级风扇气动性能进行了数值模拟,并与原风扇性能进行了比较。计算表明:叶片加厚方案气动性能更优,与原风扇相比,静压升只降低0.95%,对风扇在设计工作点的气动性能影响很小,改型方案可行。     

聚苯胺改性钢在模拟PEMFC环境下的电化学行为

利用电化学方法沉积纳米导电聚苯胺膜对质子交换膜燃料电池(PEMFC)用薄层金属双极板改性,并对改性双极板在模拟PEMFC阳极环境下的电化学性能进行了测试.结果表明,纳米聚苯胺膜层能使1Cr18Ni9Ti不锈钢在模拟腐蚀液中的腐蚀电位由-350mV提高到250mV.在模拟阳极操作电位下,经10h恒电位极化没有观察到膜层的降解和脱落.纳米导电聚苯胺膜层能显著提高不锈钢在模拟电池环境下的耐蚀性而不影响其导电性,进一步提高导电聚合物涂层性能和评价其长期效果还需进行深入的研究.     

不锈钢设备酸洗钝化及其质量控制技术

对不锈钢材料的酸洗钝化原理和工艺控制过程进行了阐述,用浸渍法和膏剂法进行酸洗钝化过程中的关键要素,是钝化膜的形成及如何对形成钝化膜的保护.对所形成钝化膜优劣的判断,提出四种质量控制检验方法,即目视法、蓝点法试验、耐蚀性试验和酸洗钝化液中金属离子浓度的控制.其中,对酸洗钝化液中金属离子浓度的控制,进行了详细量化的电感耦合...     

旋转雾化蒸发技术对脱硫废水和烟气的适应性研究

开展了脱硫废水旋转雾化蒸发实验,研究了该技术对废水水质和烟气参数的适应性,分析了优化废水蒸发效果的方法。结果表明,旋转雾化蒸发技术对废水盐含量（TDS）、悬浮物含量（SS）、烟气温度和烟气粉尘含量等有很强的适应性。在适当的实验条件下,当废水含盐量高达200000 mg/L,悬浮物含量高达6%,烟气温度≥300 ℃,或烟气粉尘含量高达30 g/m³时,蒸发塔出口和底部灰分的含水率均低于2%,废水蒸发效果良好。此外,增加气液比或提高雾化器转速可有效降低蒸发塔出口和底部灰分的含水率,可用于对废水蒸发进行优化。     

The nondestructive measurement of the charge-to-mass ratio of aninsulating tone layer present on a photoconductor

Nondestructively measuring the charge present in a toner layer based upon a noncontacting measurement of the potential across the layer and the solution of Poisson's equation for the toner layer is addressed. The former is easily accomplished using commercially available electrostatic voltmeters. The latter requires detailed knowledge of the toner layer morphology. Solid-area continuous-tone images of various densities have been studied microscopically to determine toner stack height and volume-mass density. From these data, the toner charge-to-mass ratio is determined. An adjustment of the data for stack height to account for the surface-layer topology (roughness) yields a final accuracy of about 6%