不同光学模型对颗粒测量结果的影响

通过试验得出在颗粒粒度测量中，采用Mie散射模型或Fraunhofer衍射模型对检测结果有一定的影响，从理论上对产生差异的原因进行了分析。     

不同光学模型对颗粒测量结果的影响

通过试验得出在颗粒粒度测量中,采用Mie散射模型或Fraunhofer衍射模型对检测结果有一定的影响,从理论上对产生差异的原因进行了分析。     

激光散射法中折射率对粒度结果的影响

用激光散射法测量粒度时,要考虑引入折射率,本文讨论了它对粒度结果的影响。     

旋风分离器内颗粒质量浓度分布数值模拟

采用颗粒随机轨道模型和单元内颗粒源法,对旋风分离器内不同粒径颗粒质量浓度分布进行了数值模拟。结果表明,粒径较小的颗粒(dp≤4μm)大部分在旋风分离器分离空间锥段进行分离,而较大颗粒(dp>4μm)大部分在环形空间与分离空间筒段即被分离。随着颗粒粒径增加,分离器外壁的颗粒质量浓度逐渐呈螺旋灰带分布,内旋流夹带减小,环形空间顶板下方出现顶灰环。升气管入口0.25D(筒体直径)附近的短路流对小颗粒的影响较大。在分离空间下部排尘口附近0.5D有明显的颗粒返混,返混量随着颗粒粒径增大而减少。     

气固两相流中局部颗粒质量流率的测量新方法

Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is presented. The measurement of upward, downward and net solid fluxes was carried out in a cold model circulating fluidized bed (CFB) unit. The result shows that the profile of the net solid flux is in good agreement with the previous experimental data measured with a suction probe. The comparison between the average solid flux determined with the optical measuring system and the external solid flux was made, and the maximum deviationturned out to be 22%, with the average error being about 6.9%. These confirm that the optical fiber system can be successfully used to measure the upward, downward and net solid fluxes simultaneously by correctly processing the sampling signals obtained from the optical measuring system.     

光纤后向动态光散射测量纳米颗粒的浓度适用范围研究

常用的动态光散射法在测量高浓度纳米颗粒时需要充分稀释样品,避免多次散射效应,以得到准确的测量结果。基于单模光纤后向动态光散射原理发展了一套光纤后向动态光散射测量装置,利用单根单模光纤同时发射激光与接收散射光来抑制多次散射,无须稀释样品,实现了高浓度纳米颗粒粒度的直接测量。为确定该测量方法的浓度适用范围,开展了理论与实验研究。首先,理论分析了不同粒径的颗粒散射平均自由程与体积浓度的关系,并根据该装置的散射区域特性计算了理论测量浓度上限。其次,利用该装置对不同粒径纳米颗粒多种体积浓度的样品进行了颗粒粒度测量。理论与实验结果表明,随着粒径的增加,测量浓度的上限降低,二者趋势一致,但在颗粒大于300 nm后实验结果与理论分析结果的偏差逐渐增大,实验浓度略低于理论浓度1%～2%(体积)。     

g射线衰减技术在提升管内颗粒浓度测量上的应用

在实验室流化床装置上用g射线衰减技术对f186 mm′12 m提升管内的FCC催化剂颗粒浓度进行了测量. 通过对测量数据的处理，获得了横截面上的浓度等值线图. 测量结果表明，应用g射线技术测量的提升管内颗粒浓度分布与已往文献的测量结果一致，颗粒浓度分布是一种环核结构，中心区域浓度低，边壁区域浓度高. 但g射线技术的测量结果表明，在提升管横截面上催化剂颗粒浓度分布不是严格的轴对称分布，存在着一定程度的偏流现象. g射线技术的测量结果与光纤法的测量结果对比表明，两者在浓度分布的形态和数值上基本吻合，但在提升管的中心区域光纤测量的浓度比g射线测量的浓度高约20%. g射线技术测量不干扰流场，可以获得整个横截面上的浓度分布图，整体反映提升管内气固两相流的复杂特征.     

气力输送粉料流量测量的差压—浓度法

本文基于物料稀相气力输送压损比与混和比的比例关系式：ΔＰｔ／ΔＰｑ＝１＋Ｋ．ｍ，提出了一种以气固两相管程总压降和粉料浓度为测量参数的在线测量气力输送粉料流量的新方法，建立了差压－浓度法粉料流量测量数学模型及相应的测量系统。经实验验证，精度为５％，满足工业应用要求。     

A new method to determine monomer concentration in the polymer particles of emulsion polymerization systems by dynamic light scattering

Emulsifier‐free emulsion polymerization of styrene was performed in the presence of small amount of methacrylic and itaconic acids as carboxylic acid monomers and potassium persulfate as an initiator at 70°C to prepare monodisperse polymer particles. Diameter of monomer swollen polymer particles (d_pswol) was measured by dynamic light scattering for samples taken from the reaction mixture during the Intervals II and III of the emulsion polymerization. Graphically treatment of d_pswol versus conversion data allowed us for the first time to directly determine the critical monomer conversion (x_c), from which constant monomer concentration in the polymer particles (C_MP) during the Interval II was then calculated. x_c and C_MP were obtained to be 0.379 and 5.68, respectively. C_MP value is in good agreement with that obtained by centrifugation method and those reported in the literature for the similar system. Attempts were also made to evaluate the average number of growing chain per particle ( ) during the Interval II of emulsion polymerization of styrene. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Experimental equation on intensity of transmitted light through particle suspension of higher concentration

For a given medium and wave and path lengths of incident light, the relationship was experimentally investigated among the intensity of transmitted light, the suspension concentration of particles and the median size on particle volume basis. The numerical correlations were examined and an approximate equation was proposed over a wider range of concentrations up to about 3 vol.%. This expression was found to be valid not only for uniformly sized particles but also for mixtures of different particle sizes as compared with the previous equations for low concentration of particles of uniform size.     

Effect of apex cone shape on fine particle classification of gas-cyclone

The purpose of this paper is to study the effects of apex cone shape on particle separation performance of gas-cyclones by experiment and CFD studies. It is found that the optimum apex cone angle is 70°. The minimum 50% cut size was obtained by use of this special apex cone. From the flow visualization method by use of soap foam, the upward flow and downward flow coexisted on the surface of this special apex cone. The clear interface between upward flow and downward flow was detected on the apex cone angle of 70°. The effect of the apex cone angle on particle separation performance decreases under high inlet velocity conditions, because most particles are moving in the area away from the apex cone.The particle separation performance and flow visualization results qualitatively supported the 3-dimensional CFD simulation based on the direct method.     

Effect of particle concentration and turbidity on particle characterization using digital holography

In this paper, the effect of particle concentration and turbidity on the performance of inline transmission based digital holography (DH) for particle characterization is studied. The results are analyzed based on the two metrics, i.e., detection efficiency and mean size of the particle population. Two sample depths are analyzed to quantify the effect of particle concentration. Considering 50% detection efficiency as a threshold, it is concluded that DH works well up to 0.1% (v/v) and 0.2% (v/v) particle concentrations for 10 mm and 5 mm sample depths, respectively. From the turbidity tests, it is found that DH works well up to 150 nephelometric turbidity unit (NTU) turbidity level for 10 mm sample depth.     

基于浓度/速度场测量的吸收过程液相传质系数

针对矩形流道内气、液流体的并流吸收传质过程,分别应用实时激光全息干涉术和激光多普勒速度仪对不同气、液流速下液相内近界面浓度分布与速度分布进行了实验观测.结果表明,边界层内浓度分布呈指数下降,流速越大梯度越陡,且速度边界层厚度要大于浓度边界层厚度.建立了通过物料衡算求算液相传质系数的方法.得到了不同条件下平均液相传质系数,并与Whiteman’s双膜理论的计算结果进行了比较.     

Measurement of large gas-liquid interfacial areas by the light transmission method

Theoretical formulations previously put forward to account for the effect of multiple scattering in the measurement of gas-liquid interfacial areas, at high AL values, are critically assessed. It is shown that inconsistencies arising from these can be satisfactorily resolved on the basis of the theory of Al Taweel et al. (1984) and experimental data available in the literature for the evaluation of the different parameters associated with the theory. An equation is proposed for the calculation of large gas-liquid interfacial areas for AL ≤ 280 and excellent agreement between predicted and experimental values is demonstrated.     

散射法粒度分布测试中无约束反演的误差分析

激光散射法测量粒度分布技术近年来发展很快,其测量误差涉及散射理论及其反演计算,有关的理论研究还不充分。通过数值模拟,利用Chahine算法研究包含反演计算在内的系统误差。计算结果表明,光散射测量粒径不能通过简单的增加离散级数来提高测量精度,必须通过反演算法的改进来提高。     

PX氧化反应催化剂、促进剂质量浓度控制系统特性分析及优化

对三井专利技术的精对苯二甲酸装置PX氧化反应单元催化剂、促进剂浓度控制系统进行了详细的研究,通过对给料冲程泵冲程特性的校核,以及控制系统原理的分析,完全掌握了三井专利技术PX氧化反应单元催化剂、促进剂浓度控制系统的机理。根据现有冲程泵冲程特性和当前催化剂、促进剂浓度配比,对控制系统的参数进行了优化,使得催化剂、促进剂浓度的波动范围大为减小,平稳了PX氧化反应过程。     

筛孔塔板浓度场的测量与模拟

通过测量被纯氧饱和的水在塔板上发生氧解吸时液相氧浓度,得到了伴有传质的浓度场,并发现在速度返流区会出现浓度旋涡.使用计算传质学的方法对塔板浓度场进行了数值模拟,计算值与实验值符合得较好.通过模拟,同时得到了湍流传质扩散系数的分布.