计算多轴拌器的轴功率

对三种搅拌器：锚式、螺旋式、锯齿式，在不同的转速配比下进行了轴功率测试，搅拌雷诺数为０．８～３０００００，液体的粘度为０．００１～８４Ｐａ．ｓ。液体的性质属牛顿型流体，试验过程用计算机控制．通过测量轴的扭矩来确定搅拌器的轴功率。实验测定了不同情况下搅拌器相互之间的影响。实验数据由马跨特计算方法确定模型参数并给出层流至湍流范围内三种搅拌器轴功率的计算公式．     

Circulation and power consumption in helical ribbon powder agitators

In an earlier paper we presented a theory for predicting the circulation rate and torque in a helical ribbon agitator filled with a granular material. In this paper, we give the results of experiments on a small-scale model agitator and show that these are in good agreement with the predictions of the theory.     

搅拌槽内多层组合桨对液-液分散特性的影响

以水-煤油及水-环己烷为体系,研究Rushton涡轮桨(RT),半椭圆管涡轮(HEDT)及翼形轴流式桨(CBY)的6种不同组合桨的液-液分散特性。测定了不同输入功率时分散相体积分率沿轴向及径向的分布。结果表明:当搅拌槽内液位与槽径之比达1.5,在相同输入功率时,三层桨的液液分散性能优于两层桨,功率准数较低的CBY组合桨在输入功率0.8kW/m~3时,槽内的轴向及径向分散相体积分率达到稳定的均匀分布。而功率准数较大的RT组合桨需要在输入功率1.8kW/m~3才能达到槽内分散相的均匀分布。     

Measurement of gas and liquid flows in stirred tank reactors with multiple agitators

The gas flow in a 3:1 aspect ratio vessel agitated by triple Rushton turbines has been measured by an ultrasound Doppler probe and by means of residence time studies. Strong recirculation around each impeller is found which fits in well with the compartmentalisation found in earlier liquid mixing studies. Surprisingly, when two axial A315 impellers above a Rushton turbine were used, gas recirculation around each impeller was still found. Study of the liquid phase mixing by a decolourisation technique confirmed that the gas flow essentially destroyed the strong axial liquid flow expected. Indeed, even under unaerated conditions, compartmentalisation was found between each impeller.     

三种新型桨搅拌特性比较

在直径为２４０ｍｍ的搅拌釜内,考察了最大叶片式桨、泛能式桨和叶片组合式桨的功率消耗、传热及混合特性,并与螺带桨及三叶后掠式桨进行了比较,实验表明,在中低粘度范围内,３种新型桨的传热和混合性能优于螺带桨及三叶后掠式桨。     

Suspension by side entering agitators

Most of the processes for desulphurization of flue gases are wet methods based on lime. Thus, in nearly all process stages suspension of solids has to     

Turbulent blend times with off-centre v-mounted agitators

Experimental measurements in a flat-bottom tank with narrow-blade hydrofoil and pitched-blade impellers are used to develop guidelines for off-centre, or eccentric, placement of vertical agitators in unbaffled tanks. The guidelines are based on providing a turbulent blend time that is no more than 20% longer than that of the same impeller operating at the same rotational speed on the centreline of a baffled tank. In addition to investigating the effect of impeller type, impeller diameter and off-bottom clearance are also considered. The results support the commonly noted rule of thumb that as off-centre distance is increased, performance in an unbaffled vessel approaches that in a baffled tank. A notable exception to this axiom occurs when a large impeller is located close to the tank base (specifically, D/T = 0.40, C/T = 0.10, and O/T = 0.25). In this case, a stable impeller tip vortex forms with both impeller types, with slow exchange of material between the vortex and bulk liquid leading to long blend times. Besides blend time decreasing with increasing off-centre distance, the uncertainty or run-to-run variation in blend time also decreases dramatically. In most cases, the pitched-blade turbine requires a smaller off-centre distance than the hydrofoil impeller to approximate the blending performance provided during baffled operation.     

组合式搅拌器对疏水缔合聚合物溶解特性的影响

机械搅拌是目前加速疏水缔合聚合物溶解熟化所广泛采用的一种方法。然而,聚合物溶解是一个从多相到单相、从低黏到高黏的变化过程,单一搅拌器用于聚合物的溶解过程存在诸多的问题。本文采用适用中低黏度的翼型搅拌器（KCX）和适用高黏度的锚框式搅拌器（MS）的组合,通过实验研究了翼型搅拌器不同操作方式（上翻或下压）和锚框式搅拌器不同转速等操作工况对聚合物溶解熟化过程中的作用,并将翼型搅拌器功率的实验数据与数值模拟的结果进行了比较。研究结果表明：翼型和锚框式搅拌器在聚合物不同的溶解熟化过程中其作用是不一样的;双搅拌器的同向运行可以促进罐内的流动和整体循环,加速聚合物的溶解和熟化;采用翼型搅拌器下压操作（KCXD）与MS搅拌器同向运转操作方式最利于聚合物的溶解和熟化。     

Measurement of pumping characteristics of agitators in tubes

The Pumping characteristic of an agitator in a tube is necessary of the calculation of its pumping capacity in configuration in the vessel with a draught tube. The general dimensionless equation of the pumping characteristic suitable for the higher Reynolds number region was derived by inspection analysis of basic equations. The new dynamic experimental method for determination of pumping characteristics is put forward. The application of this method is illustrated on a special three-blade axial-flow impeller.     

Determination of operating characteristics of agitators in tubes

Operating characteristics of an agitator in a tube are necessary for the calculation of its pumping capacity and power consumption in a given configuration. General dimensionless equations for pumping and power characteristics are presented which were derived by inspection analysis of basic equations. Experimental procedure for the determination of these characteristics is put forward. This procedure is based on the measurement of flow rate or pressure rise and power consumption for an agitator in a draft tube, calandria or closed tube. The measurements and their evaluation are illustrated on the example of a three-blade screw agitator.     

过程工业双轴组合式搅拌器的开发及研究进展

鉴于传统的单一桨型搅拌器和单轴组合式搅拌器都具有一定的局限性,分析了开发双轴组合式搅拌器的必要性,并介绍了国内外该类型搅拌器的研究进展,概述了卧式和立式双轴组合式搅拌器的适用范围,最后对双轴组合式搅拌器的发展与应用前景进行了展望。     

Power consumption of partially filled twin-screw extruders

Twin-screw extruders are used very effectively, when partially filled, for mixing and surface renewal of high-viscosity fluids. The rate of energy input, often sufficiently high to be a major design consideration, determines the drive power, the heat input to the fluid, and the cooling requirements. Operating limitations may be fixed by thermal degradation of the material being processed. A simple model for the rate of energy dissipation in twin-screw extruders predicts that the power input is proportional to the square of the screw speed. Measurements were made of shaft torque and screw speed for polyisobutylene passing through a large twin-screw extruder having co-rotating shafts. The experimental procedure avoids the problems of changes in holdup and temperature that accompany changes in screw speed under steady state conditions. The power input was found to be proportional to the screw speed raised to the exponent 1.90. This result was attributed to slightly pseudoplastic behavior of the fluid in the radial clearances.     

The trailing vortex system produced by Rushton turbine agitators

Further studies of the discharge from a six blade Rushton turbine are reported. Photographic velocity measurements have been used to examine the trailing vortex system in water and aqueous glycerol. An analysis of the vortex field in terms of a solution to the simplified Navier-Stokes equations shows reasonable agreement with the measured velocity profiles.Pressure field determinations at two different scales prove that Reynolds number alone is a sufficient scale-up parameter. The centrifugal accelerations and shear rates associated with the trailing vortices are shown to be much greater than previous literature has implied. Although restricted to single phase flow the results presented are of importance to most applications of disc turbines to dispersion operations.     

组合桨聚合釜内非牛顿流体的混合特性

在φ476mm的椭圆底有机玻璃聚合釜中,以羧甲基纤维素-甘油水溶液(前者质量分数为1.3％)为实验物系。利用酸碱中和法测定了9种不同的搅拌桨直径与聚合釜直径比接近于1的组合搅拌桨沿聚合釜轴向及径向的混合特性。结果表明：内外螺带-锚式组合桨的轴向混合最强,但径向混合较差。框板式搅拌桨的轴向混合较内外螺带-锚式组合桨弱,但比改进偏框式桨强,其径向混合较后者弱。改进偏框桨的7种不同组合方式沿径向的混合良好,多数组合桨沿轴向的混合较前2种组合桨弱,更接近于平推流。     

海上油田聚合物熟化过程双搅拌器的优化

自渤海油田实施聚合物驱油以来,海上油田注聚配注系统为适应海上作业条件和聚合物性质在持续优化。由于搅拌设备对聚合物的溶解熟化起着至关重要的作用,因此,熟化过程搅拌系统的优化一直是配注系统优化设计的一个重要方向和一项重要工作。文中在聚合物溶解熟化过程内外组合搅拌器流场特性数值模拟基础上,开展了室内优化实验,实验结果表明:采用同向运转翼型搅拌器KCX和较低转速锚式搅拌器MS的内外组合双搅拌,可显著提升聚合物溶解熟化速度,与数值模拟结果基本一致。     

Power consumption scale-up in agitating non-newtonian fluids

A method for the determination of power consumption of industrial agitators in non-Newtonian fluids on the basis of measurements on a model device is presented. The applicability of this method for purely viscous, time dependent and viscoelastic fluids is discussed. The method was tested experimentally using agitators of two different sizes and results of measurements confirmed the applicability of the present method for engineering calculations.     

A new expression of the Ks factor for helical ribbon agitators

The purpose of this note is to present a new model that is able to predict an effective shear rate in a vessel equipped with helical ribbon agitators, when mixing shear‐thinning fluids. This model is based on well established results obtained for non‐Newtonian flow in cylindrical ducts.