不同类型黏土对煤泥水中颗粒分散行为的影响

测定了蒙脱石、高岭石和煤颗粒的表面接触角和ζ电位,根据扩展的Derjaguin-Landau-Verwey-Overbeek(DLVO)理论,计算了含两种黏土煤泥水中颗粒间的相互作用势能,并分析了颗粒分散行为.在沉降试验基础上讨论了颗粒之间的沉降模式.结果表明:试验中高岭石颗粒之间总作用势能为正,煤颗粒之间及其与高岭石颗粒之间总作用势能均为负,含高岭石的煤泥水上清液中仅含少量剩余分散的高岭石颗粒,其余凝聚后沉降.含蒙脱石的煤泥水中,蒙脱石颗粒之间及其与煤颗粒之间总作用势能均为正,蒙脱石颗粒形成网架结构,煤颗粒被"包裹"其中,所以呈整体沉降.     

直吸式太阳能热化学反应器内工质流动特性的数值模拟

采用CFD软件,选用离散相追踪模型对直吸式太阳能热化学反应器内悬浮粒子系的运动轨迹进行三维数值模拟,从而得到反应器内离散颗粒相的运动轨迹.对比不同进口速度下反应器内的粒子轨迹可知,反应器存在一个最佳进口速度,使悬浮粒子系在反应器内达到较好的悬浮流动状态.通过分析模拟结果,在采用粒径为0.5μm,密度为550 g/m3的炭黑颗粒的情况下,理论研究所采用的反应器的最佳进口速度为2 m/s.     

Monte Carlo simulation for simultaneous particle coagulation and deposition

The phenomena of simultaneous particle coagulation and deposition are of great ubiq- uity and of key importance in nature and various engineering applications, including the precipitation and downfall of rain, ice, snowflakes, fog and hail, the scavenging of fly ashin electrostatic precipitator of power plant, the transplantation of fume in smoke flue of pulverized coal-fired plant, nuclear reactor analysis modeling aerosol’s diffusion and deposition when blasting, the suspension and sedimenta…     

化学混凝与活性炭吸附联用处理水源水研究

化学混凝法和活性炭吸附是水处理的常用工艺,其中化学混凝法效率较低,活性炭吸附成本较高,然而这两种工艺联用是否经济有效并不清楚.本研究探讨了粒状/粉末活性炭吸附、化学混凝法、混凝-活性炭吸附3种工艺处理大明山水源水的效率和成本.结果表明：在各工艺的最优条件下,混凝-粉末活性炭工艺的效率最高,其最优条件是不调节原水pH （pH=6.35～6.69）,三氯化铁（40 mg/L）混凝,0.2 mg/mL粉末活性炭吸附.经此工艺处理后原水的色度（35度～37度）降为1.5度, 浊度（4NTU～6 NTU）降为0.5 NTU,COD（19 mg/L～22 mg/L）降为4.5 mg/L,去除率分别达到95.7％,91.6％,79.4％,已达到生活饮用水标准,并且此工艺成本仅相当于单纯粉末活性炭工艺的37.2％.综上,选择混凝-粉末活性炭工艺处理南宁大明山水源水在技术和经济上具有可行性.     

The event-driven constant volume method for particle coagulation dynamics

Monte Carlo (MC) method, which tracks small numbers of the dispersed simulation particles and then describes the dynamic evolution of large numbers of real particles, constitutes an important class of methods for the numerical solution of population balance modeling. Particle coagulation dynamics is a complex task for MC. Event-driven MC exhibits higher accuracy and efficiency than time-driven MC on the whole. However, these available event-driven MCs track the “equally weighted simulation particle population” and maintain the number of simulated particles within bounds at the cost of “regulating” computational domain, which results in some constraints and drawbacks. This study designed the procedure of “differently weighted fictitious particle population” and the corresponding coagulation rule for differently weighted fictitious particles. And then, a new event-driven MC method was promoted to describe the coagulation dynamics between differently weighted fictitious particles, where “constant number scheme” and “stepwise constant number scheme” were developed to maintain the number of fictitious particles within bounds as well as the constant computational domain. The MC is named event-driven constant volume (EDCV) method. The quantitative comparison among several popular MCs shows that the EDCV method has the advantages of computational precision and computational efficiency over other available MCs. Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2006CB705800), the National Natural Science Foundation of China (Grant No. 20606015) and the Fok Ying Tong Education Foundation (Grant No. 114017)     

A modified TEMOM model for Brownian coagulation of nanoparticles based on the asymptotic solution of the sectional method

The Taylor-series expansion method of moments(TEMOM)is modified to match the behavior of real self-preserved aerosols by taking advantage of the numerical results obtained by the sectional method for Brownian coagulation in both continuum and free molecular regimes.The newly proposed model is able to predict the evolution of the zeroth and second moments more accurately than the original TEMOM when the aerosol size distribution approaches self-preserving or the coagulation time is sufficiently long.A special kind of coordinate diagram,which describes the relationship between the moment equations and one non-dimensional moment is first used to investigate different methods of moments that only involve the first three moments.The errors produced by different methods of moments can be qualitatively explained by these diagrams.By polynomial fitting,a new set of moment equations for Brownian coagulation in the free molecular regime is proposed in the framework of the log-normal preserving theory.     

丙烯酰胺在炭黑表面接枝聚合研究

利用Ｃ_ｅ~（４＋）和羟甲基组成的氧化还原体系，探讨丙烯酰胺在炭黑表面的水溶液接枝聚合机理。经接枝聚合改性的炭黑，在水分散体系中具有优异的分散稳定性。     

真空离子渗碳的试验和计算机数字仿真

本文研究了离子渗碳的工艺参数和试验结果,讨论了离子渗碳过程的动力学,提出了用于计算离子渗碳工件的表面碳浓度分布的数学模型,并在TP—803微型计算机上进行了数字仿真。     

提高喷泉水流动态模拟效果的改进方法

For the purpose of improving the dynamic simulation effect of the particle system, this paper focuses on studying the dynamic simulation of the fountain flow based on particle system theory. A fountain particle motion model is constructed by applying the physical dynamic principle. The bead particle is structured by using OpenGL “short line” as the basic particle voxel, which performs better in real-time processing compared with other bead particles, such as sphere, cube and square. To avoid the invisibility of partial particles in 3D scene, the technique of the “△” line combination unit is adopted to implement the dynamic simulation of water beads. In order to agglutinate lots of particles to form water beads with different sizes and show the intermittent cylinder shape of the fountain, the fake particle viscosimetry and the blend operation in OpenGL are also adopted, making the fountain flow more realistic. Experiment indicates that the proposed method can effectively improve the reality and real-time performance of the fountain flow.     

冬季黄河水强化混凝方式的优化选择

通过生产性实验，比较了活性炭与聚合硫酸铁、活性炭与聚合氯化铝铁、活性炭与聚合硫酸铁和聚合氯化铝铁三种强化混凝方式的混凝效果。结果证明，对于冬季黄河水的处理，利用活性炭与聚合硫酸铁和聚合氯化铝铁的强化混凝方式效果最优。     

一种评价煤泥颗粒凝聚效果的激光粒度分析方法

为了实现对煤泥颗粒凝聚效果的量化评价,使用了一种激光粒度分析的方法.通过激光粒度分析仪,测试煤泥颗粒在不同转速和不用浓度的Ca2+或Na+溶液中的粒度分布.结果表明:Ca2+比Na+更容易使煤泥颗粒凝聚,Ca2+浓度越高,煤泥颗粒越容易凝聚.在转速为1 000rpm和Ca2+浓度大于5mmol/L时,颗粒的凝聚效果最好,d90可达到700μm以上.根据煤泥颗粒粒度分布的d10,d50和d90的大小,可实现对颗粒凝聚效果的量化分析.     

颗粒凝并过程中需要考虑的几个因素

凝并是气溶胶颗粒的基本的现象之一,目前主要通过颗粒的凝并方程来描述这一物理过程。在颗粒凝并方程中,认为只要发生颗粒的碰撞便会发生颗粒的凝并,这种假设具有一定的局限性。针对这种不足,作者主要介绍了需要进一步考虑的影响因素,包括:颗粒间彼此存在作用力情况下的凝并;颗粒的回弹;颗粒自身属性的影响。     

在飞行模拟器中实现雪的实时模拟

基于粒子系统和空气动力学效应对下雪这一自然现象进行了实时仿真,建立了一个风的模型,把雪的运动看作风的运动和雪的自由落体的综合运动。根据雪粒子的自然属性和飞行模拟实际的视景需求,简化了数学计算,模拟了下雪这一特殊气象。最后对粒子间的碰撞做了简要介绍。     

凝并区放电类型对电凝并装置去除亚微米粉尘效果的影响

通过改变电凝并装置凝并区的放电类型,提出了粉尘在正负脉冲电场中的异极性荷电新方法.并将其与交变电场放电条件下粉尘的除尘效率进行了对比研究,结果表明,当集尘区板间平均场强为5kV/cm、凝并区为脉冲电场且脉冲电压峰值10kV时,除尘效率达到了97％,比凝并区为交变电场且交变电压为10kV时提高了1％.     

凝固浴中加入碳纳米管对ＰＡＮ碳纤维原丝结构性能的影响

在凝固浴中加入经酸处理的多壁碳纳米管（MWNTs）,制得多壁碳纳米管-聚丙烯腈纤维,并对其进行了表征．结果表明：在凝固浴中加入酸处理MWNTs,对填补PAN碳纤维原丝内部的微孔有明显的作用;对PAN原丝的结晶结构几乎没有影响;降低了原丝的晶区取向;提高了原丝的断裂强度、断裂伸长率及拉伸韧度．     

均匀堆积碳黑颗粒氧化特性实验研究

采用固定床反应器对均匀堆积碳黑颗粒层进行氧化,并对不同氧化阶段的碳黑颗粒进行取样,离线开展热重分析获得碳黑颗粒的氧化特性,同时利用电镜分析碳黑颗粒的纳观结构及参数,探索均匀堆积颗粒的氧化过程及氧化特性。实验结果表明:增加氧化温度对均匀堆积碳黑颗粒层的排放特性和氧化效率有促进作用;均匀堆积时,颗粒氧化时主要以CO排放为主;在氧化末期,碳黑颗粒起燃温度和活化能会随氧化温度增加而增加。随着氧化温度增加,碳黑基本粒子的纳观结构先从外层崩解和剥离,然后又逐渐形成更有序和稳定的“壳–核”结构,且趋于短微晶小间距的结构。     

大涡模拟气固两相三维湍流射流

为了研究三维矩形射流中拟序结构的空间演化和颗粒扩散特征，建立了气固两相矩形射流流场内气体、颗粒两相运动的大涡模拟数学模型，并在此基础上完成了对流动雷诺数等于11 500的气固两相射流的数值模拟.采用亚网格应力模型模拟气相场,并用Lagrangian方法跟踪了颗粒相运动.模拟结果显示了流场流向涡拟序结构随时间发展的演变过程，同时给出了气流相三维拟序结构作用下微细颗粒在整个流场空间中的运动扩散特性.     

煅烧对微硅粉性能的影响

采用同步热分析法、X射线衍射、扫描电镜、比表面积和白度等测试手段对煅烧前后的微硅粉样品进行了分析.实验结果表明:在600℃、4 h煅烧时微硅粉的除碳效果最佳,煅烧后样品中碳的质量分数由1.96%下降到0.65%;样品主要成分二氧化硅晶体结构并未变化,仍旧为非晶态,煅烧后仍出现了碳化硅的特征峰,表明煅烧去除的主要为游离碳;微观形貌分析表明,煅烧后样品微观颗粒粒径在长大,片状物质的含量却明显减少,但是组成颗粒的一次粒子长大并不明显;比表面积测试表明煅烧前后比表面积变化不大,但白度由31.04提高到70.14.     

The Nucleation Process in the Preparation of Graphene Films by Pulsed Laser Deposition

The nucleation process of graphene films prepared by pulsed laser deposition has been investigated in detail. It is found that graphene nucleates at the steps on the substrate surface firstly, from aggregation of nuclei into particles. High pulsed laser energy offers large incident energy for carbon particles deposited on the surface of the substrate, which is beneficial to the nucleation of graphene. A lot of steps are formed on the copper substrate due to the high temperature, so that the high incident energetic carbon species are able to form a stable nucleus at the steps. As the incident particles increases, the graphene nuclei are combined to grow together. Further, it is found that graphene tends to form few layer graphene particles instead of large graphene sheets.     

河道水流三维流速场的数值模拟研究

为了寻求一种先进的数值模拟方法来研究河段水流的流场特性,采用VOF紊流数学模型对大渡河安顺场堤防工程兴建河段建堤前后的水流流速场进行了三维数值模拟研究,模拟计算了该河段堤防兴建前后流速场内流速大小、方向、水位等的变化情况。计算表明,VOF紊流数学模型是一种处理复杂自由表面的有效方法。该法不仅具有稳定性好,灵活性强和精度高的优点,而且网格划分灵活,因此能较好地模拟不规则河道边界,很适合于天然河道三维水流流速场问题的数值模拟研究。