Hydrodynamic analysis of a Banbury mixer

A fluid dynamics analysis package—FIDAP—using a finite element method was employed to simulate the flow patterns in a Banbury mixer. The flow simulations were carried out only for the intensive mixing region, and they were limited to a two-dimensional analysis. A Lagrangean point of view was adopted and 18 different geometries were selected to represent one revolution of the rotor. A power-law model with time and temperature dependent parameters was used to characterize the rheological behavior of the mixture. Steady-state, isothermal flow simulations as well as a transient, non-isothermal flow analysis were performed for a Banbury B mixer. The results of the analysis show good agreement with experimental observations regarding the development of vortices, the pressure, and the temperature profiles.     

密炼机转子的优化设计

以单位体积胶料的能耗最小及强化胶料在密炼室内轴向循环流动为优化目标,对本伯里型密炼机转子的主要几何结构参数进行了优化设计。转子的优化设计属于多维有约束的非线性规划问题。根据数学模型的特点,选择复合形法进行寻优。结果表明,与国类型机台相比;优化效果明显,几何参数的最传真取值合理。     

不同转子构型的部分充满密炼机胶料流场数值模拟

使用软件Fluent对Banbury和Roller转子部分充满状态下的密炼机胶料流场进行二维等温数值模拟.研究结果表明:Roller密炼机流场更加频繁地经历最大剪切应力,两转子间的交换更加剧烈,胶料流动更复杂;Banbury 密炼机流场的平均混合指数略大于Roller密炼机,但所需要的扭矩输入较大.     

Internal mixing: A practical investigation of the influence of intermeshing rotor configuration and operating variables on mixing characteristics and flow dynamics

This paper deals with the measurement and interpretation of pressures and temperatures produced by the mixing of a rubber compound in the chamber of an internal mixer equipped with interlocking rotors. Pressure transducers and infrared/fiber optic temperature sensors were sited flush with the inner surface of the mixing chamber of a Francis Shaw KO Intermix of 2 L chamber volume. The variation of pressure with transducer position In the chamber wall and with rotor position was measured for selected fill factors and rotor speeds at “equilibrium” conditions (quasi-static power requirement for the mixer) and at intervals during a complete mixing cycle. Two rotor designs were studied. Interpretation of the results was carried out with reference to biconical rotor rheometer measurements on the mixed rubber compounds and by reference to four regimes of viscoelastic behavior identified for two-roll mill mixing. A basic flow analysis was carried out by use of the lubrication approximation in conjunction with an isothermal power-law model.     

Experiments and modeling of flow of elastomers in an internal mixer with intermeshing rotors

The direct observation of flow in the internal mixer with various rotor geometries is described. With decreasing distance between two rotors, additional transfer flow was observed in the inter-rotor area. The FAN (Flow Analysis Network) method with assumption of fully filled, Newtonian fluid and isothermal condition was employed to simulate the flow patterns in the mixer with non-intermeshing and intermeshing rotors. The distributive mixing capability was considered in terms of the fractional flow in the mixer calculated for various rotor geometries.     

转子速率正弦变化对流体混合的影响

建立了圆形转子混合设备的二维流动有限元模型,采用网格重叠技术,利用粒子跟踪法对瞬态混炼流场进行了数值模拟,对不同相位差下的的分散混合性能、分布混合性能、线拉伸以及混合效率进行了统计和比较;分析了相位角对流体混沌混合对效率的影响,为密炼机驱动系统的新的优化方向提供了一定的理论参考。     

生胶摩擦性能对密炼机工作的影响

由微观和唯象分析建立了橡胶粘附摩擦的理论模型。通过对模型的分析和试验验证,提出了提高密炼机混炼效果的新途径;（１）密炼机温度控制采用温水冷却,使密炼机处于最佳工作状态;（２）通过合理选择密炼室和转子表面材料以改变材料表面能来增大胶料与它们之间的摩擦力;（３）在压砣压力较大的条件下,在密炼室内壁沿与转子轴线同方向加工浅的光滑槽,可明显改善混炼效果。     

Analysis of the effect of mixing vane geometry on the flow in an annular centrifugal contactor

The annular centrifugal contactor is a compact mixer/centrifuge developed for solvent extraction processes for recycling used nuclear fuel. This research effort couples computational fluid dynamics (CFD) modeling with a variety of experimental observations to provide a valid detailed analysis of the flow within the centrifugal contactor. CFD modeling of the free surface flow in the annular mixing zone using the volume-of-fluid method combined with large eddy simulation of turbulence was found to have very good agreement with the experimental measurements. A detailed comparative analysis of the flow and mixing with different housing vane geometries (four straight vanes, eight straight vanes, and curved vanes) was performed. Two additional variations on the eight straight vane geometry were also simulated. This analysis determined that at the simulated moderate flow rate the four straight mixing vane geometry has greater mixing and fluid residence time as compared to the other mixing vane configurations. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

啮合式转子密炼机中转子的模拟和设计

对聚合物在啮合式转子密炼机中的流动进行了模拟分析,并分析了4种不同类型啮合式转子的混炼作用,还将模拟分析结果与分离式转子密炼机的实验结果进行了比较,结果表明,啮合式转子密炼机的填充因数比分离式转子密炼机大。     

Flow field analysis of a cavity transfer mixer

The cavity transfer mixer (CTM) was primarily designed as a distributive mixing device to be used as an add-on unit to existing extruders. In determining the CTM overall mixing efficiency as well as its potential use for various applications, the flow patterns/characteristics within this mixer must be well understood. In this work, a fluid dynamics analysis package, FIDAP, based on the finite element method was employed to simulate the flow patterns in a CTM with 6 rows and 4 cavities per row. A 3D, isothermal flow analysis was carried out and the fluid of choice was a flexible polyvinylchloride whose rheological behavior is described by a power-law model fluid. The flow field was characterized in terms of velocity profiles, pressure distributions, shear rates/shear stresses generated and a parameter λ quantifying the elongational flow components. The results of the flow simulations were compared with experimental data. The CTM potential use for dispersive mixing was discussed.     

Numerical simulation of flow of rubber compounds in partially filled internal mixer

Most numerical simulations of the flow in an internal mixer are based on the assumption that the internal mixer is totally filled with rubber compounds. However, in fact, the internal mixers are only partially filled with rubber compounds, thus posing many challenges for researchers in simulating the flow in the internal mixer. In this study, the volume of fluid method and the dynamic mesh technology of commercial CFD software FLUENT were used to simulate the flow of rubber compound in a partially filled internal mixer. To improve simulation accuracy, every 18 degrees in circumferential direction, we manually re‐meshed the calculated transient location of the rubber compound. Thus, we obtained the transient distribution of the rubber compound in the internal mixer as the rotors rotated. The simulation results showed that voids were mainly located behind the rotor blades, and there were material exchanges in the bridge regions between the two chambers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42496.     

风粉混合器内气固两相流动的模拟及试验研究

煤粉工业锅炉系统中风粉混合器是实现煤粉与一次风快速均匀混合的关键设备,测量及计算风粉混合器内煤粉、一次风气固两相流流场,对于优化风粉混合器结构,强化风粉混合效率及提高一次风粉的均匀稳定供给具有重要意义。笔者针对竖直结构及倾斜结构的2种风粉混合器,开展了数值计算及现场工程试验研究。基于几何拓扑学知识,采用ICEM软件针对2种风粉混合器划分了合适的三维网格;多相流理论模型中,多相连续介质模型中的双流体模型各相视为相互渗透、耦合但又保持各自运动特征的连续介质,相比于单流体模型,双流体模型考虑了固相的湍流输运以及气固两相间相互滑移引起的阻力,使得计算结果更接近实际情况;冷态双流体模型基本方程由守恒方程、相间耦合方程以及封闭方程构成,其中相间耦合方程用于表征气固相动量之间的耦合;为了探究不同停留时间下风粉混合器内气固两相的流场特征,采用非稳态数值计算方法,利用Fluent软件开展数值计算。基于两相流模型及Schilller-Naumann曵力系数模型研究了不同结构下风粉混合器内煤粉浓度分布随停留时间变化特征,采用德图testo425热敏风速仪测量了不同煤粉落料量下风粉混合器内负压变化规律。结果表明,竖直结构的风粉混合器内停留时间由0.25 s增至1 s时,混合器底部颗粒沉积的现象一直存在,即存在较长时间的颗粒流动死角区域;而对于倾斜结构的风粉混合器,当停留时间大于0.3 s,混合器内颗粒浓度基本降为0,较好避免了颗粒在混合器底部的沉积,该结构对于强化混合器内风粉混合及降低供料波动具有重要意义。不同落料量下的现场工程试验结果表明,高落料量下竖直结构的风粉混合器内平均负压偏小,几乎接近正压,且存在间断正压喷粉的现象,故该风粉混合器在高落料量下负压不足,易造成供料波动较大;高落料量下倾斜风粉混合器负压平均值仍大于-1 000 Pa,且无喷粉现象。相比于竖直结构,倾斜风粉混合器具有稳定且较宽的负压变化范围,能较好地克服供料波动大的现象。     

串联密炼机组的研发和应用概况

介绍串联密炼机组的研发和应用概况。串联密炼机组由带压砣的上位机与不带压砣的大容量下位机组成,上位机采用低温转子,下位机采用啮合型转子。串联密炼机组可以实现从原材料投入到终炼胶产出连续一步完成,尤其适用于白炭黑用量大的胶料混炼,可提高混炼质量和生产效率,降低混炼能耗。大连橡胶塑料机械股份有限公司串联密炼机组的结构设计重点:密炼室和转子、传动系统、液压式压砣、冷却系统和过渡翻板门等;系统控制要点:密炼室温度和冷却效果、转子无级调速和压砣位置无级调整等。     

管型混合澄清槽内的液-液两相流的数值模拟

管型混合澄清槽在工业生产中具有广阔的应用前景。通过计算流体力学分别对管型混合澄清槽内的混合室和澄清室进行数值模拟,系统地探究了分散相液滴尺寸（d₃₂₌ 100~500 μm）、进料油水比（O∶A = 1∶1~1∶5）、入口挡板及入口位置对混合澄清效果的影响,并将模拟结果与传统方型混合澄清槽进行对比。结果表明,管型混合室内的流场分布更合理,不易形成流动死区。管型混合室内搅拌桨上方和下方形成压力更小的低压区,流体的湍动能更大,搅拌性能更好。在混合室中,降低分散相d₃₂和进料油水比能够提高混合性能。在澄清室中,提高分散相d₃₂和降低进料油水比能够提高澄清性能,入口挡板能够有效提高澄清性能。     

静态混合器气液两相流压降的数值模拟及实验研究

气泡流经过静态混合器的压降问题涉及到舰船动力系统性能的好坏。在分析了气泡平均驰豫时间的基础上,结合k ε湍流模型,利用平衡流模型模拟静态混合器内形成的稀疏湍流气泡流,得到了混合器内两相流流场。空气—水系统的压力降实验表明,计算流体力学模拟能够很好地预测SMV型静态混合器内气泡流的压降,是静态混合器设计的有效手段。     

Performance of Kenics static mixer over a wide range of Reynolds number

The present study deals with the numerical simulation of flow patterns and mixing behaviour in Kenics static mixer over a wide range of Reynolds number. Three different sets of Kenics mixer (aspect ratio = 1.5) comprised of 3, 9 and 25 elements each have been characterized. The Reynolds number was varied in the range of 1 to 25,000 (i.e., from laminar to turbulent flow regime). The numerical approach takes into account the aspects of the fluid flow at higher Reynolds number values including circumferential velocity profiles at different cross-sections within the Kenics mixer, which were neglected in previous studies. It was observed that cross-sectional mixing in the turbulent flow regime takes place up to 30% of each element length at element-to-element transition; beyond that velocity profiles were uniform. The experiments were also carried out to measure the circumferential and axial velocity profiles and pressure drop in three different Kenics Mixers using air as fluid. The pressure drop per unit element (ΔP/η) was found to be independent of the number of Kenics mixing elements used in the system. The total pressure drop across Kenics mixer obtained by CFD simulations were compared with the experimental pressure drop values and correlations available in the literature. The numerical results were found in good agreement with the experimental as well as the results reported in the literature. A new pressure drop correlation in the Kenics static mixer has been developed.     

SK型静态混合器流体湍流阻力的研究

为了获得流体在SK型静态混合器中湍流流动时的流动阻力规律,提出一种新的流体阻力的计算模型。在流体不可压缩的假设前提下,将流体在SK型静态混合器中的螺旋形运动分解成轴向直线运动和环向旋转运动。在流体作湍流流动时,运用流体力学理论,分别求解出流体作2种运动时所产生的流体阻力的计算式,然后进行叠加得到SK型静态混合器湍流时流体阻力理论计算式。以水为实验介质,对SK型静态混合器流体湍流阻力进行了实验测量,回归出实验公式。与理论结论进行比较分析,得出流动摩擦系数与雷诺数的负0.25次幂呈线性关系的结论。     

Experiment and lattice Boltzmann simulation of two-phase gas-liquid flows in microchannels

The two-phase flows in microchannels have many advantages in heat and mass transfer compared to single-phase flows. In particular, segmented flows such as bubbly and slug flows are often used in microfluidic devices. In the present study, experiments and Lattice Boltzmann simulations were carried out to study the gas-liquid flow in microchannels under various conditions. Two types of mixer geometries were used, including the cross-shape and the converging shape channels. The bubble shape, bubble size, and formation mechanism were investigated for different flow rates and different mixer geometries. The simulation results and the experimental results were compared based on dimensionless numbers, and good agreement was found in general. Different flow regimes with different bubble shapes were found depending on the Capillary number of the flow. The simulation data confirmed that the breakup was induced by the pressure difference in the two phases for small Capillary numbers. The geometry of the mixing section was also observed to have an impact on the size of the gas and liquid slugs.     

双转子连续混炼机混沌型转子混合性能的研究

在提出一种新型混沌型转子结构的基础上,运用Polyflow软件对其混炼过程进行三维非牛顿等温模拟,并借助于粒子示踪法对物料所经历的流场特性进行统计学分析;分析了转子结构和工艺参数对转子混合性能的影响,同时通过共混改性实验,对转子的混合效果进行了评估和表征。结果表明,高混沌型转子的分布混合能力有较大的提高,同时保持着良好的分散混合能力;混沌型转子制备的复合材料力学性能优于经典转子;转子转速的提高可以增强混沌转子的分散及分布混合能力,适当的加料速率是保证取得较好混合效果的关键因素。     

Effects of geometry and operating conditions on the mixing behavior of an in-line impinging stream mixer

The present study investigated experimentally the effects of various geometric and operating parameters on the mixing characteristics of model liquids undergoing mixing in a novel in-line mixer, viz. an in-line impinging stream (IS) mixer. First, the mixer with one set of three inlet jets was used. Later two sets of inlet jets were used in order to increase the number of impingement zones and hence the mixing capability of the mixer. A statistical analysis was performed to indicate the best geometry of the mixer based on the data of both the mixing effectiveness and the pressure loss due to impingement of liquid streams.