Physicomathematical Modeling of Explosive Dispersion of Liquid and Powders

Studies have been conducted with respect to the generation of fine‐disperse aerosols with the use of an explosive disperser model based on hydrodynamic shock tube. The physicomathematical model for the process of explosive dispersion with the aforesaid design is described [1]. The use of elements in the model design to produce cavitation bubbles under the action of shock wave and ensurance of slower outflow process of a water‐steam mixture makes it possible to obtain liquid disperse aerosols. The experimental results for aerosol disperse parameters and the processes of initiation and propagation of an aerosol cloud produced upon explosive dispersion of a variety of liquids and condensed powders are presented. Pressure values in the combustion chamber of the disperser, velocity of aerosol particles, and aerosol disperse parameters were obtained. The design of the explosive disperser with a nozzle, which provides favorable conditions for cavitation processes inside the dispersed liquid, is shown to allow the generation of a high dispersity aerosol (about 1–100 nm), which is essential for many practical problems. The function of distribution of such particles by size cannot be measured reliably and directly by methods available; however, indirect experiments (measurement of humidity when dispersing water) permit estimating the existence of particles in the aerosol with sizes below 1 μm in quantity of approx. 90 %.     

新型扇形雾化喷嘴的实验研究

在对Y型喷嘴结构和雾化机理研究分析的基础上,设计了一种新型的扇形雾化喷嘴,并对该喷嘴进行了实验研究. 实验测量了不同气、液压力下扇形雾化喷嘴的流量、雾化角和索特尔平均粒径及其在空间上的横向和纵向分布. 通过对液流量用Y型喷嘴设计公式进行拟合,得到了公式中适合扇形雾化喷嘴设计的系数取值：m=0.39, b=0.98. 喷雾雾化角a大约在90o~98o之间,变化不大. 喷雾的索特尔平均粒径在空间横向呈类似"W"的分布,在空间纵向呈逐渐降低并趋于稳定的分布.     

离心光散射法测定乳液液珠大小与分布

用日本 Shimadzu SA-CP3型粒度分布仪测定由低分子量挥发性有机物构成的 O/W型和 W/O型乳液中液珠大小与分布。讨论了稀释液种类、稀释倍数和离心速度对测试结果的影响     

Predicting Droplet Size Distribution by Image Processing Technique for an Air Blast Atomizer

An image processing technique was used to predict the size distribution of the high speed, fine droplets at downstream of an air blast atomizer. The spray visualization setup consisted of UV lamps as light source, a stroboscope for slowing down the droplet motion, and a digital camera to capture the droplet images. The experiments were carried out at different liquid flow rates with various nozzle diameters. Two key unknown parameters (spray half angle and dispersion angle) of the air blast atomizer model in Fluent were obtained from these experiments. Using the obtained parameters and other structural parameters, the spray modeling was performed, and the Rosin–Rammler distribution was obtained and compared with those obtained from image processing technique through a diagnostic matrix. Regarding the kappa value, the agreement between predictions of the Fluent model and the image processing technique was moderate.     

Droplet Size Distributions of Liquid-Liquid Dispersions in Centrifugal Pumps

The generation of liquid-liquid dispersions with defined droplet size distributions is an important aspect for process equipment design. In this work, two centrifugal pumps with different impeller diameters were used to generate dispersions at selected operating points for a paraffin oil-water system. The droplet break-up phenomena within the centrifugal pumps were analyzed using a transparent pump design in combination with high-speed imaging. Droplet size distributions at centrifugal pump discharge nozzle were recorded with optical probe measurement technologies and evaluated by means of image processing using a neural network. The influence of impeller diameter, rotational speed, volumetric flow rate and dispersed phase fraction are discussed. Experimental data is correlated using fluid properties, operating data as well as centrifugal pump dimensions. The correlations developed from results of this work serve as a basis for the equipment design of centrifugal pumps.     

影响火炸药吸湿性因素的研究

火炸药在国防军事和工业生产中有着较为广泛的使用范围,研究火炸药的吸湿性对于火炸药的生产、储存有着极大的军事经济价值。分析火炸药的物理化学性质,进而探索其吸湿的原因,分析影响火炸药吸湿性的各种因素,并以此改善火炸药的生产、存储环境。     

液体燃料爆炸抛撒和云雾形成全过程的数值研究

对燃料空气云雾形成过程进行数值模拟。因过程的复杂性分近场与远场两个阶段处理。对近场阶段,利用运动边界处理方法,建立一维气相流动模型和液相运动模型。对远场阶段,采用多相流模型描述云雾膨胀运动过程。将两过程耦合,对抛撒全过程编制程序。数值预测给出了云雾区内的重要物理参数变化,计算的云雾外形变化曲线与实验结果具有较好的一致性。     

Dimensional Analysis of Particle and Liquid Dispersion in Draining Foam

A dimensionless correlation for the axial dispersion of particles and liquid tracer in draining foam has been developed that expresses the dimensionless dispersion as a function of Peclet and Stokes numbers. The correlation is fitted to the data of Lee et al., Coll. and Surf. A. 263 , 320‐329 (2005). The value of the axial dispersion coefficient is independent of the self‐dispersivity. It is seen that Saffman, J. Fluid. Mech. 6 , 321‐349 (1959) model for the dispersion coefficient in solid porous media only provides order of magnitude prediction of the axial dispersion coefficient but it can inform about the dominant mechanisms of dispersion.     

多层组合桨搅拌槽内气-液分散特性的研究

在直径为0,476m的椭圆底搅拌槽中,采用由六叶半椭圆管叶盘式涡轮桨(HEDT)及四叶宽叶翼型桨的上提(WHU)及下压(WHD)操作组合的六种不同的三层桨,研究了气-液两相体系中的通气功率变化及气含率特性,获得不同桨型的通气搅拌功率及气含率的关联式;结果表明,底桨为HEDT的组合桨通气功率下降幅度最小,相同输入功率时气含率最高,其次为WHD,WHU为底桨时气液分散性能最差。因此,适用于气液两相操作的优化组合桨应以HEDT为底桨。此研究结果可为工业用多层组合桨气液搅拌反应器的设计提供参考。     

充填式浮选柱二维返混特性的实验研究

以二维扩散模型为基础，采用点源脉冲示踪法对开式浮选柱和装有不同类型规整填料的充填式浮选柱内液相的轴向与径向返混进行了实验研究，得到了各种填料内轴向和径向彼克列准数与气相、液相表观雷诺数的关联式。通过比较发现，在所用填料中，装有250Y或350Y型填料的浮选柱不仅轴向返混最小，而且径向返混最大，最有利于提高回收率。另外，对起泡剂的影响进行了实验研究，发现起泡剂可以减小返混，但当起泡剂浓度大于一定值时反而会增大径向返混。     

扁平绕带爆炸容器的力学研究进展评述

评述了扁平绕带爆炸容器力学行为的理论和实验研究成果 ,对今后的研究方向和内容等做了展望并提出了一些建议     

电动潜油离心泵单级高扬程叶导轮的设计与应用

通过对潜油电动离心泵的叶导轮内的液体质点的运动研究,建立其运动方式的速度三角形,同时研究影响叶导轮抽液性能的结构尺寸和性能参数,主要包括：①铸件表面光洁度的影响;②叶导轮的流道开口尺寸和叶片出口角。在上述研究的基础上,对目前使用的叶导轮进行优化,开发研制出单级高扬程的叶导轮。此项研究的成功,可以减少离心泵的级数,从而节约其组装成本,创造良好的经济效益。     

Experimental and Theoretical Investigation of Droplet Dispersion in Venturi Scrubbers with Axial Liquid Injection

Droplet dispersion in a Venturi scrubber with axial liquid injection was investigated both experimentally and theoretically. The main objective of this study was to develop a mathematical model to predict droplet dispersion in a Venturi scrubber with axial liquid injection. The effects of the Peclet number and droplet size distribution on droplet dispersion were studied using the developed model. Sampling of the droplets was carried out, isokinetically, in 16 positions at the end of the throat section. The experimental data were used to find the parameters of the developed model, such as the Peclet number. From the results of this study, it was found that the Peclet number was not constant across the cross section of the scrubber channel. In order to achieve a better agreement between the results of the model and the experimental data, it was required to consider Peclet number variations across the Venturi channel. It was also revealed that the parameter representing the width of the Rosin‐Rammler distribution of droplet size could not be considered constant and it was influenced significantly by the operating parameters such as liquid flow rate and gas velocity.     

Radial Liquid Dispersion and Bubble Distribution in Three‐Phase Circulating Fluidized Beds

The liquid dispersion and bubble distribution in the radial direction have been investigated in the riser of a three‐phase circulating fluidized bed whose diameter is 0.102m and 3.5m in height. Effects of gas and liquid velocities and solid circulation rate have been determined. It has been found that the radial distribution of bubbles is related closely to the liquid dispersion in the radial direction. The size and rising velocity of bubbles tend to increase as the radial position approaches to the center of the riser. The bubble size increases with increasing U_G, but it decreases with increasing U_L or G_S in all radial positions. The radial dispersion coefficient of the liquid phase increases with increasing U_G or G_S, however, it tends to decrease with increasing U_L. The value of Dr has been well correlated in terms of dimensionless groups based on the isotropic turbulence model.     

液滴在高压静电场中分散现象的实验研究

液滴在高压电场的作用下将分散成粒径细小的均匀雾滴。用涂有硅油的玻璃板对分散后的雾滴进行收集,通过统计学的方法即可测出雾滴平均粒径的大小。实验测量了不同液体的雾滴在不同电压下的平均粒径以及丙三醇在不同流量下雾滴平均粒径随电压升高的变化趋势,意在考察电压和流量这两大因素对液滴分散的影响。实验发现每种液体都存在一个临界电压,只有当电压超过临界值时,液滴才会发生大面积的分散。而在其它条件不变的情况下,流量的升高将导致临界电压的升高及平均粒径的增大。     

A Numerical Study of Both Internal and External Two-Phase Flows of a Rotating Disk Atomizer

In this paper, a numerical study has been carried out to model and simulate the air-liquid two-phase flows both inside and around a rotating disk atomizer, which is fitted with multiple spray nozzles. The physical problem was simulated with an Eulerian multiphase model in a single computational domain. The realizable two-equation turbulence model was used for the turbulent flow. The governing equations were solved with a finite-volume-based numerical method. The rotary frame method was used for the spinning disk. Numerical simulation was conducted in a rotational disk speed range of 1000 to 10000 rpm and a liquid feed flow rate range of 100 to 175 gpm for the liquid feeder. Both uniform and non-uniform liquid distribution conditions were considered. Detailed results about flow velocity and volume fraction fields inside and outside of the atomizer are presented and discussed. It was found that when liquid is nonuniformly distributed through the distributors, some of the nozzles could reach flooding conditions at lower rotational disk speeds and liquid feed volume flow rates, as compared to uniform distribution cases.     

The Effect of Rotary Disk Atomizer RPM on Particle Size Distribution in a Semi-Industrial Spray Dryer

Spray drying is the most commonly used method in industry to produce powders on a large scale. One of the major problems in spray drying is control of the product particle size distribution since it is very important for most industries; e.g., catalyst, chemicals, foods, pharmaceuticals, ceramics, etc. The objective of this work is to study the effect of the atomizer rotational speed on the product size distribution. In order to obtain the typical particle size distribution of the required product, a specially designed atomizer disk is used in the study. The particle size distributions under atomizer rotating speeds in the 9,000–10,000 rpm range were measured and discussed.     

Microbubble Generation with the Aid of a Centrifugal Pump

For saturation of water treated with atmospheric air in a dissolved air flotation (DAF) system and the production of microbubbles, air was introduced through the suction pipe of a centrifugal pump. The operating conditions of the centrifugal pump were adjusted to avoid the occurrence of cavitation phenomena. The novel technique was applied for the treatment of oily water in a DAF pilot prototype. A central composite rotational design (CCRD) was used to determine the high efficiency of the separation process. In addition to this high degree of oil‐water separation, the technique reduces space and energy costs in comparison to conventional processes of saturation of the effluent treated with compressed air.     

分散聚合法制备彩粉的粒径调控

采用分散聚合的方法制备出一种粒径在2～5μm之间,表面光滑、窄分布的彩粉.研究了引发剂、分散剂用量、分散介质中乙醇/水的比例、初始单体比及石蜡用量对彩粉粒径及粒径分布的影响.     

Fractal Characterization of Liquid Dispersion in Trickle Bed Reactor

INTRODUCTIONDispersionisveryimportanttothedesignoftricklebedreactorforbothchemicalandbiochemicalprocesses Thedegreeofdispersionofteninfluencesreactor　　performanceandscale up Thetraditionalmethodformodelingdispersionprocessesintricklebedreactorsisbasedontheconvective diffusionequation (CDE) Themostcommonlyusedisthelongitudinal dispersionmodel[1,2 ] Themagnitudeofliquiddispersionisusuallyconsideredindependentofpositionalongthelongitudinaldirectionofthereactor Themainassumptionofthelongitudinal dispersionmod...