Physical Properties Important to Electrostatic and Non electrostatic Powder Transfer Efficiency in a Tumble Drum

ABSTRACT: Popcorn was oiled and coated in a tumble drum nonelectrostatically and electrostatically with sugar, cornstarch, salt, cellulose, maltodextrin, all-purpose flour, whole-wheat flour, or soy flour. Particle size, density, flowability, and chargeability were correlated to transfer efficiency using regression analysis. Of the various methods to measure chargeability, charge-to-mass and adhesion improvement were the most significant. For nonelectrostatic coating, small, dense, free-flowing powders were most efficient. Small, free-flowing highly charging powders were most efficient for electrostatic coating. Percent improvement was the highest for the least efficient powders. The greatest benefit with electrostatic coating was for low density, highly charging powders with no effect of size.     

External and internal electrostatic potentials of cholinesterase models

The electrostatic potentials for the three-dimensional structures of cholinesterases from various species were calculated, using the Delphi algorithm, on the basis of the Poisson–Boltzmann equation. We used structures for Torpedo californica and mouse acetylcholinesterase, and built homology models of the human, Bungarus fasciatus, and Drosophila melanogaster acetylcholinesterases and human butyrylcholinesterase. All these structures reveal a negative external surface potential, in the area around the entrance to the active-site gorge, that becomes more negative as the rim of the gorge is approached. Moreover, in all cases, the potential becomes increasingly more negative along the central axis running down the gorge, and is largest at the base of the gorge, near the active site. Ten key acidic residues conserved in the sequence alignments of AChE from various species, both in the surface area near the entrance of the active-site gorge and at its base, appear to be primarily responsible for these potentials. The potentials are highly correlated among the structures examined, down to sequence identities as low as 35%. This indicates that they are a conserved property of the cholinesterase family, could serve to attract the positively charged substrate into and down the gorge to the active site, and may play other roles important for cholinesterase function.     

Effect of electrode geometry and charge on the production of polymer microbeads by electrostatics

Experimental parameters which are critical for producing small diameter (i.e. 100-300 μm) polymer microbeads, using electrostatic droplet generation, were investigated with three types of electrodes; a parallel plate, a positively charged needle and a grounded needle with alginate as the polymer. Electrode spacing was a critical factor controlling microbead size, but only for the parallel plate set-up. While the applied potential affected droplet size in all three set-ups, the smallest droplet size was produced with the positively charged needle. In some experiments needle oscillation was observed resulting in even smaller microbeads (i.e. < 100 μm). Calculated microbead diameters agreed well with experimental values.     

Dynamics of electrically charged transient evaporating sprays

The evolution of an evaporating spray plume typical of those under consideration for use in direct injection spark ignition (DISI) engines, for early and late fuel injection strategies is investigated. Here the effect of electric charge, present on individual drops, upon the spray dispersal and evaporation rate is investigated with the aim of optimizing these parameters with respect to typical engine timescales and injection strategy. The predictions suggest that applying electric charge to drops in sprays injected early into the intake stroke does not have a beneficial effect. The spray evaporation rate is not significantly enhanced, and the long time interval between fuel injection and ignition actually promotes spray wall deposition. Conversely, applying electric charge to sprays injected late encourages secondary atomization and the increase in surface area greatly improves the evaporation rate. This is also true at higher engine speeds, corresponding to a much reduced time between fuel injection and ignition. Therefore it is suggested that the selective use of electric charge is viable way of tuning the spray character without effecting fuel metering when moving from an early to a late injection strategy in DISI engines when variable loads are required. Copyright © 2006 John Wiley & Sons, Ltd.     

A fast boundary cloud method for 3D exterior electrostatic analysis

An accelerated boundary cloud method (BCM) for boundary‐only analysis of 3D electrostatic problems is presented here. BCM uses scattered points unlike the classical boundary element method (BEM) which uses boundary elements to discretize the surface of the conductors. BCM combines the weighted least‐squares approach for the construction of approximation functions with a boundary integral formulation for the governing equations. A linear base interpolating polynomial that can vary from cloud to cloud is employed. The boundary integrals are computed by using a cell structure and different schemes have been used to evaluate the weakly singular and non‐singular integrals. A singular value decomposition (SVD) based acceleration technique is employed to solve the dense linear system of equations arising in BCM. The performance of BCM is compared with BEM for several 3D examples. Copyright © 2004 John Wiley & Sons, Ltd.     

反胶束萃取大豆蛋白前萃过程的动力学研究

系统研究了影响总传质系数的各个主要因素(缓冲溶液pH、反胶束含水量W0、表面活性剂浓度、KCl浓度、振荡速度操作温度),探讨了以丁二酸二异辛酯磺酸钠(AOT)/异辛烷反胶束体系萃取大豆蛋白前萃过程的动力学。结果表明,大豆蛋白前萃过程中总传质系数随缓冲溶液pH和KCl浓度的升高先增大后减小,分别在pH7.0和KCl浓度0.1mol/L附近出现最大值;随W0和AOT浓度的增加而增大,当W0大于12时,总传质系数基本不变;随温度的变化总传质系数变化不大。由此可以推断出蛋白质的加溶过程,不仅与蛋白质分子和表面活性剂之间的静电相互作用力和疏水力有关,而且与界面阻力有关。     

DEM‐CFD modeling of particle systems with long‐range electrostatic interactions

To investigate dynamic behaviors of monocharged particle systems, a direct truncation (DT) method and a hybrid particle‐cell (HPC) method are implemented into the discrete element method coupled with computational fluid dynamics (DEM‐CFD) with defined cutoff distances. The DT method only considers electrostatic interactions between particles within the cutoff distance while the HPC method computes electrostatic interactions in the entire computational domain. The deposition process of monocharged particles in a container in air was simulated using the developed DEM‐CFD. It was found that using the DT method, the macrostructure, evolution of granular temperature, and radial distribution function of the particle system were sensitive to the specified cutoff distance. In contrast, using the HPC method, these results were independent of the specified cutoff distance, as expected. This implies that, although electrostatic interactions between particles with large separation distances are weak, they should be considered in DEM‐CFD for accurate modeling of charged particle systems. © 2015 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 61: 1792–1803, 2015     

A hybrid approach to computing electrostatic forces in fluidized beds of charged particles

In particulate flow devices particles acquire electric charge through triboelectric charging, and resulting electrostatic forces can alter hydrodynamics. To capture this effect, the electrostatic force acting on individual particles in the device should be computed accurately. Electrostatic force is calculated using a hybrid approach consisting of: (1) long‐range contributions from an Eulerian electric field solved using the Poisson equation (2) short‐range contributions calculated using a truncated pairwise sum and (3) a correction to avoid double counting. Euler‐Lagrange simulation of flows incorporating this hybrid approach reveals that bed height oscillations in small fluidized beds of particles with monopolar charge decreases with increasing charge level, which is related to lateral segregation of particles. A ring‐like layer of particles, reported in experimental studies, forms at modestly high charge levels. Beds with equal amounts of positively and negatively charged particles are fluidized in a manner similar to uncharged particles. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2282–2295, 2016