进口结构对方形旋风分离器性能影响的数值研究

利用CFD模拟研究了一种具有双矩形进口的方形截面的旋风分离器内部的流动特点,其中气相模型采用了雷诺应力湍流模型（Reynolds stress model,RSM）,颗粒相采用随机轨道模型。计算结果与文献实验数据的对比表明模型具有可靠性。模拟结果表明：在分离器内部的排气管和分离器壁面间的区域为强旋湍流区,靠近分离器壁面和排气管壁面的区域旋流强度较弱;排气管下的分离器内出现了回流;进口结构影响分离器内的旋流分布特点和回流开始位置及湍动能的分布,从而影响了分离效率和阻力,其中倾斜双进口的方形分离器内旋转向下的气流运动区域更大,回流开始位置更低,因此其分离效果更好;进口结构影响分离器内局部湍动能的分布特点和大小,从而决定了分离器的阻力大小;倾斜双进口的方形分离器内的局部湍动能小于对应的垂直单、双进口分离器,因此其阻力系数最小。     

旋风分离器中气相流动特性及颗粒分离效率的数值研究

采用Fluent软件对一切向进口旋风分离器内的气相流场和颗粒分离效率进行了三维数值研究。用RNG(重整化群)k-ε模型模拟气相紊流特性。研究表明，分离器内气流的切向速度分布呈复合双层结构；轴向速度方向在内外层分布不同，外层向下，内层向上，但部分断面轴心处的轴向速度出现了下降流动特征。流场的计算结果与实验结果进行了对比，表明RNGk-ε模型能较好地模拟分离器内的强旋流场。采用拉格朗日模型对固相颗粒的轨迹进行了模拟，研究了颗粒的进口位置、进口速度以及分离器排气管直径对分离效率的影响，表明颗粒进口位置和进口速度对颗粒的分离效率有较大影响；排气管直径越小，颗粒相分离效率越大，但当排气管直径减小到一定幅度时，效率提高的幅度减小。图10参9     

端盖与旋流子对轴流旋风分离器的性能影响

为了研究轴流旋风分离器性能的结构影响因素,采用Fluent软件对装有不同内径端盖和不同种类旋流子的旋风分离器的流场进行了数值模拟,同时用Fluent中的DPM模型分析了不同尺寸及种类的旋风分离器对水颗粒的分离效果。结果表明：较小的端盖内径可以提高旋风分离器的分离效率,但是带来更大的阻力;旋流子叶片的螺旋角度是影响分离效率的主要因素,螺旋角度越大则分离效率越高,但是阻力也会随之增加;叶片数量不是影响阻力的主要因素。     

惯性分离器内气固两相流雷诺应力数值模拟

对循环流化床中气田惯性分离过程进行了详细的数值研究。湍流模型采用雷诺应力模型,研究对象为U型分离器内的气一固两相流动。为了真实描述固体颗粒与分离器壁面之间的碰撞过程,固体颗粒模拟采用颗粒轨道模型,引入壁面粗糙度的影响,同时考虑了固体颗粒在湍流中的扩散作用和颗粒之间的相互碰撞。模拟计算了不同入口速度、分离器挡板数目对颗粒分离效率和流体压降的影响,计算结果不仅给出了分离器内的气-固两相流动结构特性,而且给出了分离器效率、压降与入口主流速度和分离器结构参数的关系。     

不同入口高宽比旋风分离器内气固流动的数值模拟

采用雷诺应力模型(Reynolds stress model,RSM)对两种不同入口高宽比分离器的气相流场进行了数值模拟,同时用拉格朗日法模拟了分离器内颗粒的运动轨迹.结果表明:数值计算得到的分离器效率和气相流场分布与试验结果基本吻合;在相同入口面积下,入口高宽比大的分离器B的分离效率比分离器A约高2%～8%,但分离器B的压降也更大;分离器B内气相的切向速度大、颗粒平均进入位置低以及颗粒运动至壁面的距离短,有利于提高其分离效率,但是分离器B的短路流及排尘口附近偏心的纵向环流更大,不利于分离效率的提高.     

方形卧式分离器两相流场的数值模拟

方形卧式分离器是一种结构简单、布置方便、效率高的新型分离器，为掌握其内部流动特性，对该分离器内部紊流气固两相流动进行了数值模拟，采用雷诺应力模型(RSM)模拟气相流动，采用离散相模型(DPM)的非耦合法追踪颗粒运动轨迹，揭示了该分离器的流动与分离机理。计算结果表明：气固两相流在离心力作用下绕排气管流动，进入排气管时由内旋流转为外旋流，在排气管处形成强旋涡，同时计算并显示了入口速度为20m／s时1μm、50μm和500μm颗粒的运动轨迹。图10参7     

工业油水分离器湍流两相流场的数值模拟

本文应用双流体模型及ｋ－ε－ｋｐ两相湍流模型，研究了水力旋流器内油水两相湍流流场。建立了适用于旋流分离器中两种液体混合物的有旋湍流流动的ｋ－ε－ｋｐ模型。并针对影响旋流器分离效率的不同影响因素，进行了变更入口流动参数及分离器几何参数的数值实验，为工业用油水旋流分离器的优化设计提供了一个有效的数值模拟工具。     

新型旋风分离器的阻力特性与节能效果研究

一、前言工业上广泛应用旋风分离器作为分离设备。旋风分离器发展至今,人们对其进行了大量的理论与实验研究工作。据前人对其流场和阻力特性的测定可知,压力损失主要起因于半径方向的离心力作用,而离心力主要由切向速度和旋转半径决定。旋风分离器内气流主要由向下的外旋流及向上的内旋流组成,内外旋流均造成旋涡流场损失。但外流能量对颗粒的捕集分离起决定性作用,是有效能量。而内旋流能量则纯属消耗性能量。     

卧式热交换式方形分离器分离性能的试验研究

对卧式热交换式方形分离器在不同风速和不同入口浓度下分离效率和阻力进行试验研究,并分析了运行工况分离性能。为了进行优化设计,对不同的结构方案进行了优化试验。结果表明,排气管直径和仲入长度分别为分离器特征尺寸的1／3和1／15的分离器具有高效、低阻等优点;对于粒径大于100μm的固体颗粒,其分离效率在90％以上,阻力小于1500Pa。     

循环流化床锅炉旋风分离器入口烟道内气固流动特性的试验研究

在循环流化床(CFB)锅炉冷模试验台上,对高温旋风分离器入口烟道内的气固流动特性进行了试验研究.应用高速摄影机拍摄了示踪粒子在2种结构入口烟道中的运动轨迹并对其进行了分析,得到了不同结构的分离器入口烟道对固体颗粒的加速性能.结果表明:长烟道内颗粒的加速性能比短烟道内颗粒的加速性能好,但长烟道内压降比短烟道内的大.同时,对长、短烟道分别与分离器相连时分离器的分离效率和压降进行了对比,结果表明:在相同工况下,配长烟道分离器的分离效率高于配短烟道分离器的分离效率,但前者的分离器压降大于后者.     

带加速段的卧式旋风分离器的数值模拟及工业应用

带加速段的卧式旋风分离器具有体积小、结构简单、造价低、分离效率高等优点,为了解其工作机理,应用Fluent软件,采用雷诺应力模型模拟气相流动、离散相模型模拟颗粒运动轨迹,同时计算并给出了加速段出口速度为25.46 m/s时,粒径为1μm、5μm、10μm和30μm的颗粒运动轨迹,结果表明该分离器对细小颗粒具有一定的分离效率,与实验吻合良好。最后应用Fluent软件对实际应用的卧式旋风分离器进行了数值模拟,在不考虑物料循环的条件下,该分离器分离效率为85.8%,分离效率较高。     

Experimental and CFD study of wall effects on orderly stacked cylindrical particles heat transfer in a tube channel

In this study, the flow and heat transfer characteristics of regularly arranged cylindrical particles in a bed with bed-to-particle diameter ratio of 2.65 (The particle and bed diameter are 25 and 66 mm respectively and the bed height is 200 mm) have been studied in two different arrangements of particles. The first layout is coaxial particles which embrace 8 layers and 3 equilateral cylindrical particles in each layer); the second arrangement is similar to the first one but the intermittent layers have been rotated 60^o. Three dimensional CFD simulation of air flow through these arrangements of particles in bed have been carried out by the standard κ-ε turbulence model with using of FEMLAB (Multiphysics in MATLAB) software version 2.3. For two configurations, comparisons between CFD results and experimental data have been drawn. Our results have been compared with prediction of empirical correlations for pressure drop of flow through the bed. The heat transfer CFD results were validated by naphthalene sublimation mass transfer experiments. The particle Nusselt number was obtained by using analogy between mass and heat transfer. A good quantitative and qualitative agreement between hydrodynamic of CFD simulation and experimental results was gained for both arrangements. The model predicts pressure drop of channel with two arrangements, coaxial and non-coaxial particles with an average error of 10% and 15%, respectively. Moreover, the CFD simulation has predicted the average particle Nusselt numbers of these two arrangements with an average quantitative error of 7% and 14%. Furthermore, the influence of wider range of Reynolds number (2500–6800) on particle Nusselt number has been investigated.     

数值研究生物质焦油在旋风分离器中分离特性

借助CFD软件FLUENT对该工况下旋风分离器内部的气液两相流进行了数值模拟,其中连续相采用雷诺应力湍流模型(RSM),离散焦油液滴采用DPM模型,通过数值模拟得出了旋风分离器内部的静压场、轴向速度场与径向速度场的分布云图、液滴相的轨迹图和焦油液滴的分离与分级效率。数值计算结果表明,对于此结构的旋风分离器,分离器内部整体形成双层流动结构,近壁处径向速度与轴向速度相比较小,同时壁面对焦油液滴具有良好的捕集效果,适合用于生物质燃气焦油液滴的脱除。     

一种新型液包气雾化喷嘴流场特性的研究

基于CFD技术对一种新型液包气雾化喷嘴内部的气液两相流流场进行了数值模拟,分析了该喷嘴内部气液两相流的流动特性,得到气相和液相入口压力对气液两相流流动特性的影响,并结合试验数据对模拟结果进行了验证.结果表明:当气相和液相入口压力在0.1～0.5 MPa变化时,喷嘴的出口湍流强度随气相和液相入口压力的提高而增大;提高气相入口压力有利于减小雾化粒径;提高液相入口压力有利于提高雾化粒径的均匀性.     

3D CFD simulation and experimental validation of particle-to-fluid heat transfer in a randomly packed bed of cylindrical particles

The heat transfer characteristics of solid cylinders in a bed with tube-to-particle diameter ratio equal to 2, by the presence of contact points between the cylinders were investigated numerically. Three-dimensional CFD simulation of air flow through two different arrangements of particles in this randomly packed bed have been carried out by the standard κ–ε turbulence model with the use of FEMLAB (Multiphysics in MATLAB) software version 2.3. The simulation results were validated by naphthalene sublimation mass transfer experiments. From mass and heat transfer analogy, the Nusselt numbers for each cylindrical particle in bed were found from the corresponding Sherwood numbers. It is shown that the CFD simulation results can predict the heat transfer characteristics, with an acceptable average error compared to experimental values.     

Numerical Study on Particle Motions in Swirling Flows in a Cyclone Separator

The purpose of this study is to establish the high-accurate prediction method of particle separation in a cyclone separator. Numerical simulation of the swirling flows in a cyclone separator is performed by using a large eddy simulation (LES) based on a Smagorinsky model. The validity of the simulation and the complicated flow characteristics are discussed by comparison with experimental results. Moreover, particle motions are treated by a Lagrangian method and are calculated with a one-way method. A performance for particle separation is predicted from the results of the particle tracing. As results of our investigation, the influences of the inserted height of the outlet pipe on the performance for particle separation of cyclone separator are shown.     

Selection of the Relevant Turbulence Model in a CFD Simulation of a Flow Disturbed by Hydraulic Elbow——Comparative Analysis of the Simulation with Measurements Results Obtained by the Ultrasonic Flowmeter

The article is an attempt to compile the results of CFD liquid flow simulation through pipeline section containing hydraulic elbow with the results of ultrasonic flow measurements. To carry out the measurements behind the flow disturbing element (hydraulic elbow), an ultrasonic flowmeter with applied head set in accordance with the Z-type system was used. For comparative purposes, a flow simulation for 3 different turbulence models (k-epsilon, SST and SSG) was performed. It was found that with a proper ultrasonic flowmeter heads configurations, it is possible to measure the flow rate disturbed by the hydraulic elbow at any distance from the source of the disturbance. It has to use appropriate correction factor that can be determined by knowing the flow velocity profile equation. Based on comparison of CFD simulation results with experimental data, the accuracy/ purposefulness of using individual turbulence models in the case of discussed hydraulic installation was evaluated.     

旋风除尘器内三维流场的数值模拟

文中建立了用于旋风除尘器模拟的计算模型,并数值模拟了旋风除尘器内部的流场运动情况,预测了复杂流场中影响颗粒分离效率的因素,为旋风除尘器流动机制的研究和进一步结构优化设计提供了参考依据.     

Characteristics Of Vertical Mantle Heat Exchangers For Solar Water Heaters

The flow structure in vertical mantle heat exchangers was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the mantle were measured using a particle Image Velocimetry (PIV) system. A CFD simulation model of vertical mantle heat exchangers was also developed for detailed evaluation of the heat flux distribution over the mantle surface. Both the experimental and simulation results indicate that distribution of the flow around the mantle gap is governed by buoyancy driven recirculation in the mantle. The operation of the mantle was evaluated for both high and low temperature input flows.