煤粉水平管道气力输送模拟研究

以气力输送欧拉双流体模型为基础,根据颗粒运动的动力学理论建立了煤粉气力输送的动力学模型和SIMPLE算法。并利用FLUENT流体分析计算软件进行煤粉气力输送管道输送特性研究,参照煤粉颗粒特性参数得到了煤粉悬浮输送过程气固两相速度和浓度分布情况,并分析了形成原因,为煤粉管道输送研究提供了一定的理论分析依据。     

表观气速对密相气力输送流型影响的模拟研究

针对目前密相气力输送数值模拟关于流型演变方面所存在的问题,提出了一种基于颗粒所在局部空间的固相浓度及颗粒群运动特征来描述颗粒间相互作用的数学模型。该模型能够对气力输送,甚至是颗粒发生大量堆积情况下的密相输送进行数值模拟,使得长期以来缺乏有效模型对密相输送流型进行数值模拟研究的问题得到一定解决。利用该模型,对水平管中煤粉高压密相气力输送的颗粒流动过程进行了数值模拟,获得了输送过程中管道内所发生的气固两相之间的分离、沉积现象,展现了沙丘流及栓塞流等流型的演变特征,模拟结果与实验观察到的现象吻合较好,从而进一步验证了新数学模型的有效性。此外,通过对不同表观气速下固相流态分布的定量分析,揭示了输送流型变化的一些内在规律。     

炭黑在气力输送系统中的压力损失试验研究

炭黑在气力输送过程中的输送参数的确定大多以经验为主,极易造成输送效率的降低以及输送过程的不稳定对炭黑在输送管道中进行气力输送试验,分析了其在水平管、垂直管和弯管中的输送压力损失,分别得到了在这三种输送管道中的压力损失计算公式：该公式可作为工程上分析炭黑与气体混合流在输送管道中压力损失的经验公式。     

炭黑在气力输送管道中的压力损失研究

对以炭黑为输送对象的气力输送管道中水平管、垂直管和弯管的输送压力损失分别进行了分析,得到了炭黑在这3种输送管道中的压力损失计算公式.该公式可作为工程上分析炭黑与气体混合流在输送管道中压力损失的经验公式.     

炭黑气力输送流动特性研究

对气力输送过程中炭黑的流动特性进行了试验研究.依据试验结果,分析了炭黑的粒径大小与输送管道阻力、输送压力与输送管道压力损失、气体流量与炭黑的质量流量、输送压力与炭黑粒子破碎率之间的关系,为炭黑气力输送系统的设计及其工艺参数的确定提供参考.     

散状物料在气力输送管道中的密相流动数值模拟与分析

基于计算流体力学理论,采用CDF软件包中的Fluent软件建立了气固两相流在气力输送管道中的密相输送模型,对散状物料在气力输送水平管和竖直管内的流动过程进行模拟,得出了散状物料分别在水平管和竖直管的密相流动状态,可为气力输送系统的研究和设计提供参考依据。     

密相气力输送水泥粉体流动特性研究

论文建立了工业级别1∶1正压旋转供料器气力输送实验系统。在本实验系统上以两种不同水泥粉体为输送物料进行气力输送研究,通过改变输送管道内的气体速度得出了固体输送能力、平均固气质量比、固体平均速度及单位长度压力损失等参数的变化规律,为该类型气力输送水泥粉体提供依据。     

粉煤灰中浓度气力输送管道压降研究

对于粉体气力输送流动区域划出中等浓度区，使浓相输送与稀相输送的区分变得清楚、分析了粉体气力输送管道压降的主要影响因素，在量纲分析基础上，对中浓度气力输送提出一个比较简洁的管道压降关联式，与文献的实验数据进行拟合，结果表明该式可以很好地描述粉煤灰中浓度气力输送管道的总压降。对于给定的一个相图，该式的系数k、有一固定的数值；此值与物料质量流率（或气体质量流率）、料气比无关。     

气力输送过程中物料破碎率的研究

气力输送过程中影响物料破碎率的因素很多,包括气力输送的形式、物料的物性、输送管道的布置、输送系统的工艺参数等.本文以炭黑气力输送系统为例,研究了减少炭黑破碎率的方法及炭黑破碎率的测量方法.并利用MATLAB神经网络对炭黑的破碎率进行预测.     

炭黑在气力输送过程中破碎率的影响因素分析

介绍了在气力输送系统中炭黑的破碎机理,分析了炭黑破碎率的影响因素,指出炭黑品种,炭黑的堆积密度、压碎强度和不同粒径质量分布等物性,输送管道长度及其布置、输送压力和炭黑输送速度等工艺参数是影响炭黑破碎率的主要因素,并通过实验结果进行了论证.     

Modeling of sequence length distribution for olefin copolymerization with vanadium-based catalyst

Some thermodynamic and mechanical properties of a polyolefin, such as the melting temperature and the rigidity, are dependent on the nature of its sequence distribution. Accurate modeling of sequence length distribution (SLD) is important in precisely tuning and optimizing the properties of polymers produced. In this article, we proposed a model to predict the molecular weight distribution (MWD) and SLD for olefin copolymerization with vanadium-based catalyst. Due to the 2,1-insertion of α-olefin with vanadium-based catalyst, the SLD is expressed by uninterrupted methylene sequence distribution instead of conventional triad sequence distribution. To obtain a reliable model, parameter estimation with experimental data is first conducted. The SLD model along with the estimated kinetic parameters can be used to predict unmeasurable sequence length fraction. For the experimental conditions studied, the average methylene sequence length is predicted to change from 10 to 4 units as the propylene/ethylene mole feed ratio increases from 1.1 to 3.4.     

基于Galton板的固定床内示踪剂浓度分布

从概率论角度出发，利用传统的Galton板模型，以催化剂捆扎包内的一个小布袋为研究对象，建立了固定床内示踪剂浓度分布模型，得到了固定床内示踪剂浓度分布模型的具体表达式。同时，以KCl溶液为示踪剂，建立了实验装置，将模型计算值与实验结果比较，结果吻合良好，说明所建模型是可靠的。考察不同参数对示踪剂浓度分布的影响，结果表明：在固定床内，随着催化剂粒径的增大、液体喷淋量的减小、固定床高度的增加，示踪剂浓度分布曲线逐渐变得平缓。     

Full copolymer characterization by SEC-NMR combined with SEC-MALDI

Measurements on a series of random copolymers with units of methylmethacrylate, butylacrylate, styrene and maleic-anhydride are performed. A method is used which consists in fractionating the copolymer by size exclusion chromatography (SEC), collecting 30-40 fractions and then recording both the NMR and MALDI spectra of the fractions. In a successive step, bivariate distribution of chain sizes and composition maps are derived from knowledge of the molar mass, weight and composition of the copolymer fractions. The compositional distribution is obtained by summation of the sections of the bivariate distribution which belong to a narrow compositional range.A model for SEC fractionation of copolymers is developed. It allows to predict the composition and D(x) of the SEC fraction (D(x) is the ratio between the number-average and the weight-average molar mass, x is the fraction number).Offline SEC-MALDI measurements are performed, in order to measure experimentally D(x) for the random copolymer. The agreement between theoretical and experimental values for D(x) and for the composition of the SEC fraction (as derived from SEC-NMR measurements) is good. The predictions of the model were also compared with literature data for SEC fractionation of a copolyester with units of butileneadipate and butilenesebacate. The agreement between theoretical and experimental values is more than satisfactory.     

逆体积排阻层析法测定层析介质的孔径分布

针对层析介质的孔径分析,基于刚性球状分子进入柱状孔的假设,分别采用高斯正态分布和对数正态分布描述孔径分布,利用简化的单孔分配因子模型,建立了孔径分布函数和分配因子Kd的关联,通过体积排阻层析实验测定系列标准物的Kd,从而拟合得到孔径分布信息,建立了逆体积排阻层析法。以葡聚糖作为分子大小的标准物,测定了5种典型层析介质(SP Sepharose FAST FLOW、Q Sepharose FAST FLOW、ToyopearlDEAE-650M、Streamline DEAE和Sephadex G-150)的Kd,计算和比较了不同介质的孔径分布,分析了介质的可吸附孔表面积等结构参数,证实了逆体积排阻层析法分析层析介质孔径分布的可行性和实用性。     

Axisymmetric radiation intensity model for annular reactors

Cylindrical lamps are usually equipped in the tubular UV reactor to offer UV radiation. This paper describes the axisymmetric characteristics of UV radiation from the cylindrical UV lamp. Axisymmetric lamp emission models are developed in a two-dimensional axisymmetric space for the line source, the superficial source and the volumetric source. The present axisymmetric lamp emission models are easy to understand and of simple mathematical expressions. The experimental data in literature is used to validate the present axisymmetric lamp emission models. Good agreements have been obtained between the experimental data and the computations. A comparison show that the present models obtain the identical results as previous models.     

气升式内环流反应器中油滴的分散特性

本文研究了气升式内环流反应器中油滴的分散特性。以对数正态分布密度函数为油滴尺寸的分散模型,导出了油滴的Sauter平均直径解析式。对模型作了实验验证,关联了模型参数。提出了油滴的尺寸分布密度函数和Sauter平均直径的半经验式。结果表明计算值与实验值吻合良好。     

Rushton搅拌釜内的气含率分布及其流动特性的模拟

利用雷诺应力模型结合多参考系法模拟了Rushton气液搅拌釜内的气液流动特性,得到了不同截面处气含率大小分布规律,并与γ射线CT实验所测得的结果做了比较,发现除排出流区CFD模拟值与实验值相差较大外,上循环区与下循环区都吻合得较好;结果表明排出流区的气含率最高,在搅拌桨高速旋转下,流体沿叶片端面急速排出,湍动也十分强烈...     

DYNAMICS OF BUBBLE SIZE DISTRIBUTION IN TURBULENT GAS-LIQUID DISPERSIONS

The population balance equation coupled with the proposed breakage kernel and the previously developed breakage model is applied to the analysts of bubble size distribution for non-coalescing systems in a bench-scale airlift column. Good agreement obtained between the theoretical results and the experimental data is encouraging and indicates that the model is suitable for predicting dispersion properties such as bubble size and interfacial area in turbulent gas-liquid dispersions.     

Effect of Surfactant Concentration on the Dispersion Coefficient for the Comparison of Model and Experimental Results in Emulsion Polymerization of Butadiene

In this work, a mechanistic model was developed on the basis of population balance equations for butadiene emulsion polymerization and validated with experimental data in a batch reactor. A combination of finite difference and weighted essentially nonconciliatory (WENO) schemes was used as a precise technique for the discretization of the population balance equations. The obtained values during the evolution of conversion and the average particle diameter values were in good agreement with the measured results for different surfactant concentrations. However, the simulated particle-size distributions (PSDs) were much narrower than the experimental PSDs. Therefore, to match the experimental PSDs, a stochastic term was included in the zero–one model. The effect of surfactant concentration, which is an important factor with a direct impact on the dispersion coefficient, was also investigated and confirmed with experimental results.     

A mixed Weibull model for size reduction of particulate and fibrous materials

This paper describes a simple alternative to the classical population balance breakage model, which characterizes and controls the size distribution of particles submitted to a reduction process. The new approach is based on cumulative distribution functions of mixed random variables. Results indicate that a Weibull mixture distribution function adequately models the size of particles submitted to various breakage processes. The model was further applied to experimental reduction processes with apparently random breakage probability and yielded good estimates of the unbroken particle and fragment distributions. Use of these results for direct and indirect prediction of the size alteration under dimensional reduction processes is discussed.