3kA钕电解槽流场中颗粒受力分析

近年来随着NdFeB永磁的应用发展,对金属Nd质量的要求越来越高,而电解过程碳颗粒运动及溶解对金属质量的影响至关重要。通过理论与数值模拟相结合的方式对流场中不溶于电解液的碳固体颗粒的主要受力类型进行梳理,对其运动轨迹进行数值模拟研究,针对稀土电解槽进行了颗粒-流场的计算及模拟,研究发现曳力及重力是颗粒在电解槽中起主要作用的力。曳力是改变颗粒运动轨迹的影响因素,且曳力随粒径的增大而增大。0.07 mm颗粒粒径是区分主要作用力是重力还是曳力的临界值,颗粒粒径越大,越不利于电解槽得到纯净的Nd单质。对进一步改进电解槽槽型,从而得到质量更好、杂质更少的稀土金属,并对后续各物理场对颗粒的影响提供参考意义。     

纳米金杂化酶研究进展

随着纳米技术和生物技术的发展,将纳米颗粒材料与天然酶结合起来构建纳米杂化酶,可以解决酶的负载量低、活性和稳定性不好等问题.目前,新型纳米颗粒材料-纳米金被广泛应用于构建杂化酶体系.我们将从纳米金杂化酶的种类、制备方法、优势以及应用等方面对纳米金杂化酶的研究进展进行概述.     

Effective scrap iron particles (SIP) pre-treatment for complete mineralization of benzidine based azo dye effluent

This study proposed that hybrid scrap cast iron particles (SIP)-aerobic biodegradation technology could enhance the biodegradability of toxic wastewater. SIP cleaved the azo linkages of Direct Green1 dye to form benzidine, 4-aminophenol, aniline and 1,2,7-triamino-8-hydroxynapthalene-3,6-disulfonic acid. SIP-mediated dye reduction was effective at wide pH range; however, kinetic analysis revealed fastest pseudo-first order dye reduction rate at acidic pH 3 (k_d = 0.549 min⁻¹) followed by pH 9 (k_d = 0.383 min⁻¹) and pH 7 (k_d = 0.318 min⁻¹). The daughter aromatic amines produced were partially adsorbed onto the SIP surface and maximally at neutral pH. The adsorption process followed pseudo-second order adsorption kinetics and Langmuir isotherm. Benzidine was adsorbed more than 4-aminophenol and aniline. BOD₅ of the SIP-treated effluent increased from 0.93 to 12 mg/L showing improved biodegradability. The daughter amines were rapidly mineralized in the aerobic bioreactor within 6 h. Cost-effective SIP pre-treatment could accelerate mineralization and detoxification of recalcitrant wastewater.     

Preparation of monodispersed polymer-modified colloidal silica particles of less than 50 nm diameter

The preparation of monodisperse, ultrafine polymermodified colloidal silica, 11 or 42 nm in diameter, were studied. The reaction of the colloidal silica with polymeric silane coupler in 1,2-dimethoxyethane and removal of the unreacted polymer with granular silica gel (10–20 mesh) in acetone gave a suspension of monodisperse composite particles.     

Structured latex particles as impact modifiers for poly(styrene–co-acrylonitrile) blends

This work was focused on the influence of the morphology of composite natural rubber (NR)-based particles on the toughness of poly(styrene–co-acrylonitrile) (PSAN) blends. In order to be suitable for the reinforcement of PSAN blends, the NR-based particles were coated with a shell of crosslinked poly(methylmethacrylate) (PMMA). Furthermore, polystyrene (PS) subinclusions were introduced into the NR rubber core. PSAN blends were prepared by adding the wet latex directly into a twin screw-extruder. This new method allowed even tacky pure rubber particles to be dispersed as shown by transmission electron photomicrographs which confirmed the integrity of the soft particles after mixing. Solid NR particles or NR-based latex particles containing rigid PS subinclusions and no hard shell did not offer any impact improvement to PSAN. Only NR-based core–shell particles containing at least 25% PMMA in the shell toughened the brittle matrix. Prevulcanized NR-based latex particles which do not cavitate easily were less effective. Core–shell particles containing PS subinclusions within a natural rubber core allowed more effective use of the rubber phase. From the fracture surface morphology the failure mechanisms of PSAN blends containing the different composite NR particles could be deduced. Monodisperse poly(n-butylacrylate)-based core–shell particles were too small to toughen PSAN. However, a similar dependence of the fracture mechanisms on the morphology of the incorporated toughening agent could be established by scanning electron microscopy.     

The controlled flocculation of submicron emulsion particles. I. A three-step synthetic route to supermicron polymer particles

The basic features of a three-step experimental process to produce supermicron polymer particles are described. First, a submicron emulsifier-free latex is prepared by a well-known technique. Second, the latex is aggregated by destabilizing with cetyl pyridinium chloride under constant stirring conditions, to yield roughly spherical clusters of 6-12 μ diameter. Third, the aggregates are stabilized with poly(vinyl alcohol) and internally coalesced by heating at or above the glass transition temperature. The final product particles have relatively smooth surfaces. Results are qualitatively interpreted in terms of a dynamic equilibrium where the aggregate size is determined by a balance between attractive interparticle potentials and stirring shear forces. Bimodal aggregate size distributions suggest the aggregate break-up mechanism may involve the erosion of individual latex particles and small fragments from the surface of aggregates. © 1996 John Wiley & Sons, Inc.     

燃烧管内悬浮铝粉燃烧爆炸过程的研究

 铝粉的燃烧与加速机理一直是相关部门研究的热点。为了深入研究其在受限空间内的燃烧与传播特性,基于双流体模型、湍流k-ε模型以及铝粉燃烧等模型,选用SIMPLE格式,对大型卧式燃烧管内铝粉颗粒与空气的两相悬浮流湍流燃烧加速转爆炸现象进行了数值研究,得到了铝粉火焰在管内的燃烧传播过程中管内各相关参数的详细变化情况,并与相关的实验结果吻合。     

LES-DSMC方法研究超细颗粒气固两相流动过程

采用考虑颗粒脉动流动对气相湍流流动影响的大涡模拟(LES)研究气相湍流,采用直接模拟蒙特卡罗方法(DSMC)模拟颗粒间的碰撞。单颗粒运动满足牛顿第二定律,颗粒相和气相相间作用的双向耦合由牛顿第三定律确定,考虑超细颗粒间的van der Waals作用力。数值模拟垂直管内超细颗粒气固两相流动,对颗粒相速度、浓度以及团聚物流动过程进行分析。     

驻波声场中单分散细颗粒的相互作用特性

利用外加声场促进悬浮在气相中的细颗粒发生相互作用,进而引起颗粒的碰撞和凝并,使得颗粒平均粒径增大、数目浓度降低,是控制细颗粒排放的重要技术途径.为探究驻波声场中单分散细颗粒的相互作用,建立包含曳力、重力、声尾流效应的颗粒相互作用模型,采用四阶经典龙格-库塔算法和二阶隐式亚当斯插值算法对模型进行求解.将数值模拟得到的颗粒声波夹带速度和相互作用过程与相应的解析解和实验结果进行对比,验证模型的准确性.进而研究颗粒初始条件和直径对相互作用特性的影响.结果表明,初始时刻颗粒中心连线越接近声波波动方向、颗粒位置越接近波腹点,颗粒间的声尾流效应就越强,颗粒发生碰撞所需要的时间就越短.研究还发现,颗粒直径对颗粒相互作用的影响取决于初始时刻颗粒中心连线偏离声波波动方向的程度.当偏离较小时,颗粒直径越大,颗粒发生碰撞所需要的时间越短;当偏离很大时,直径较小的颗粒能够发生碰撞,而直径较大的颗粒则无法发生碰撞.     

燃气透平叶片表面颗粒沉积特性数值研究进展

污染物颗粒在燃气透平叶片表面及冷却通道内的沉积将影响透平叶片的冷却特性和安全服役寿命。国外许多研究机构对燃气透平叶片表面污染物颗粒沉积特性及其与叶片气膜冷却的相互作用机制进行了持续研究。本文首次系统总结了近年来燃气透平叶片表面污染物颗粒沉积特性数值研究进展,重点介绍了燃气透平叶栅流道内污染物颗粒的沉积机制、颗粒沉积和脱离物理模型以及颗粒沉积与透平叶片冷却特性相互作用的数值模拟方法和研究成果。基于当前研究热点和发展趋势,结合作者的研究经历,指出了国内在研发先进燃气轮机透平冷却结构时应注意的问题和方向,为高效、燃料适应性更广的燃气轮机技术自主开发奠定基础。