导叶式旋风管入口颗粒粒度分布对分离效率的影响

为深入研究导叶式旋风管的分离机理,用不同粒度分布的SiO2颗粒对分离总效率与粒级效率进行了对比研究。实验结果表明:入口颗粒的粒度分布不但对旋风管的分离总效率有影响,而且对粒级效率也有较大影响;不同粒径大小的颗粒在旋风管中的分离机理不同。     

旋风分离器减阻杆对流场的影响

在研究发现旋风分离器减阻杆的基础上，研究了减阻杆对流场的影响，发现了减阻杆使切向速度分布趋于平缓、轴向速度上升峰值内移、径向上压力梯度减小、轴向上中心区从逆压梯度变为顺压梯度等重要规律，从而为分析旋风分离器减阻杆的减阻机理提供了依据。同时本文还首次发现旋风分离器入口附近有近２４％的短路流量，提出设法减小这部分短路流量是提高分离效率的一个研究方向。     

旋风分离器两相流研究综述

综述了旋风分离器内部流场、颗粒运动和数值计算模型的理论研究发展历程。     

卧式旋风筒流场性能分析与优化

采用冷模实验方法,用五孔探针对卧式旋风筒的流场分布与阻力性能进行了实验研究,对设备的性能与技术特点做出了客观评价。通过研究看出,卧式旋风筒内气流流动主要是切向流动,径向流动最小,并且切向速度有较好的分布规律,主要是以强制涡区为主,自由涡区很小;卧式旋风筒内压损较小,仅为立式旋风筒的一半。最后对所研究的设备提出了优化改进建议。     

热端管直径对涡流管内部场分布的影响

本文以理想二氧化碳气体为工质,采用Standard k-ε湍流模型,对涡流管能量分离效应进行数值模拟,分析了管内流体速度、温度、压力的分布。在此基础上,探究了进口温度为298.15 K、进口压力为6.5 MPa、冷流率为0.1时,热端管直径对涡流管内速度场、温度场、压力场分布以及能量分离性能的影响。模拟结果表明:热端管直径D在4.0~6.0 mm范围内变化时,随着热端管直径的增大内旋流的轴向、径向空间增大、切向速度逐渐减小、冷热流分界的轴向距离逐渐增大、径向上的压降逐渐减小,并且热端管直径在D=5.0 mm时达到最佳的冷热平衡。     

流动参数对导叶式旋风管内固相颗粒运动影响的数值模拟

对导叶式旋风管内气、固两相进行数值模拟,从颗粒在排尘锥内不同位置的碰撞概率、返混情况、停留时间分布3个方面对颗粒的运动情况进行描述,研究不同流动参数下颗粒的运动变化。结果表明,在排尘锥两侧缝环面的重叠处,颗粒的碰撞概率达到最大值,此处结垢和磨损的可能性较大;随着颗粒粒径的增大,直接捕集的比例增大,排尘锥返混和灰斗返混的比例减小,并且排尘锥返混多于灰斗返混;在一定的流量范围内,随着流量的减小,颗粒返混现象加重,并且随着粒径的减小,相同粒径的颗粒在分离空间内和排尘锥内停留时间延长的幅度变大,返混现象更加明显。     

Effects of Exit Tube Diameter on the Flow Field in Cyclones

A number of cyclones with different exit tube diameters have been simulated with CFD in this study. Results show that the exit tube diameter influences not only the velocity magnitude, but also the shape of the velocity profiles within cyclones. Depending on the diameter of the exit tube, the axial velocity profiles can exhibit a either maximum or a minimum on the axis. If the exit tube diameter is small, the central flow has a jet-like appearance. On the other hand, axial velocity dip in the profile can be observed near the center in a cyclone with a large gas exit tube. In addition, the well-known double vortexes, which commonly are present in a cyclone of practical design, do not exist in a cyclone with an excessively large exit tube. Quantitative comparison of velocity distribution shows that the tangential velocity increases as the exit tube diameter is reduced, giving rise to higher particle collection efficiency. Usually, the pressure drop decreases with increasing exit tube diameter. However, if the exit tube size is excessively large, the pressure drop may start to increase. Practically, cyclone with an excessively large exit tube should be avoided.     

空调用高效旋流油分离器仿真优化与实验

为了提高空调系统中旋流油分离器的分离效率、降低压力损失,本文对其结构参数进行了优化设计,通过流体仿真研究了油分离器内部各参数对分离效率和压力损失的影响,得到最佳的参数尺寸比例,并据此制作了一款新型油分离器,安装在空调系统中进行实验测试。实验结果表明:新型油分离器在回油工况(最低制冷剂流速)下分离效率由95.5%提高到99.0%,名义制冷工况下分离效率由97.3%提高到99.6%;名义制冷工况下压力损失由55.2 k Pa降低至23.1 k Pa;同时获得了油滴颗粒的分布函数。     

烟道凝聚器流场及细颗粒凝聚特性研究

为研究烟道凝聚器的凝聚机制及颗粒物减排特性,通过商业计算流体力学（computational fluid dynamics,CFD）软件,模拟并得到了凝聚器湍流区定常/非定常工况条件下的流场特性;理论计算了凝聚器内颗粒的凝聚过程,并通过扫描电镜进行了验证;实验室中凝聚器对PM2.5的减排幅度为20.8%,实际工程中,300 MW和660 MW机组PM2.5的减排幅度分别为30.1%和37%。研究结果可为颗粒凝聚技术的大规模工程应用提供参考。     

出口结构对双蜗壳式旋风分离器内流场的影响

用智能七孔球探针测试仪对不同出口结构的双蜗壳式旋风分离器内不同位置的三维速度及压力进行测量,从而获得不同结构参数对流场的影响。实验结果表明,排尘锥结构具有一定的稳流作用,有利于分离器的分离;分流型芯管的开缝有分流的作用,降低了芯管内的气流旋转强度,使上下行流都有所减少,旋风管中心附近以及边壁附近的切向速度都有所减小;分流型芯管的特有的缩口结构使不同截面上的切向速度的最大值都有所增加,距离缩口越近增加越强烈。     

Effect of crystallization parameters and presence of aqueous extract of Nigella Sativa on growth inhibition of calcium oxalate monohydrate particles

For the first time, nucleation kinetics, crystal growth and agglomeration of calcium oxalate monohydrate (COM) are studied as a crystal growth inhibitor with and without Nigella Sativa(NS) extract. The induction period was determined under different supersaturation ratios ranging from 1.63 to 4.51 at 37°C using the conductivity method. Based on the classical homogeneous nucleation theory; the critical nucleation parameters were evaluated at higher supersaturation ratio. The calculated surface energy was increased from 7.97?mJ/m² without additive to 10.31?mJ/m² with NS extract. However, the nucleation rate at a supersaturation ratio of 3.26 corresponding to 5.44 with the NS extract was decreased from 3.9?×?10²⁹ nuclei/cm³.s (without additive) to 1.3?×?10²⁹ nuclei/cm³.s with NS extract addition. The number of molecules required for the formation of a stable nucleus was calculated with and without NS extract at different supersaturation ratios. The crystallite sizes of the formed crystals without and with the additive are 93 and 51?nm, respectively. Scanning electron microscopy (SEM) photomicrographs show the formation of small crystals and less aggregated with the NS inhibitor compared with the baseline (without the inhibitor). This study can help us with a clear understanding of the inhibition mechanism of an aqueous NS extract on COM crystals.     

旋转直流内循环式旋风分离器流场测定与分析(Ⅱ)

在流场测定的基础上，着重分析了旋转直流内循环式旋风分离器内三维速度分布和压力分布随入口气速的变化规律，回归了分离段切向速度计算的无因次经验方程，探求了压降性能的放大效应。结果表明该新型旋风分离器的流场规整，放大效应小，阻力系数比常用的反转式旋风分离器降低约30％。     

旋转直流内循环式旋风分离器流场测定与分析(Ⅰ)

采用五孔探针测试技术及相应的计算机数据采集与处理系统，测定了旋转直流内循环式旋风分离器的三维流场分布。对所测流场分4个区域进行了分析讨论，并对内循环气量进行了衡算。结果表明该新型旋风分离器设计合理，结构有利于气流中颗粒的分离。     

页岩灰与催化裂化催化剂细粉旋风分离性能的对比试验研究

试验测定和对比页岩灰和流化催化裂化三旋灰(FCC三旋灰)的旋风分离器性能,考察入口气速、入口浓度对分离效率和分离器压降的影响.结果表明,在相同操作条件下,同一台旋风分离器上,粒度小于75 μm的页岩灰与FCC三旋灰的分离效率和分离器压降曲线差别显著;页岩灰的分离效率与分离器压降都明显低于FCC三旋灰,且入口浓度增大,页岩灰分离器压降的下降幅度高于FCC三旋灰;页岩灰分离效率最高的入口气流速度也低于FCC三旋灰.颗粒特性对旋风分离器的分离性能有明显影响,页岩灰和三旋灰的颗粒特性与形状差别是导致其旋风分离特性不同的一个基本原因;油页岩旋风分离器的设计应当考虑油页岩颗粒特性的影响.     

粉尘对空气滤清器原始过滤效率测试结果的影响

为了比较国内外不同试验粉尘对空气滤清器原始过滤效率测试结果的影响,说明试验粉尘对于过滤效率测试的重要性,对国内外标准所规定的试验粉尘的粒径分布和形貌特征进行测试分析。结果表明:在相同实验条件下,以石英砂作为试验粉尘测得的原始过滤效率为99.35%,以A2细灰作为试验粉尘测得结果为99.10%;从粉尘粒径分布和形貌特征两方面讨论造成原始过滤效率测试结果不一致的原因。     

Theory of the Cut-Size,The Fractional Collection Efficiency,and the Vortex Breakdown in the Axial Flow Hydro-Cyclone

From a practical point of view, it is important to be able to predict the collection efficiency of the axial flow hydro-cyclone. In order to perform such estimation, it is necessary to predict the cut-size for the various operating conditions. Up to this time, there were many papers that derived the cut-sizes theoretically based upon the effect of the centrifugal force on the suspended solid particles, and experimentally based upon the effect of the geometrical construction of the hydro-cyclone on particle size. However, there have been few, if any, papers that included the effects of gravitational settling on the suspended solid particles when estimating the cut-size for the hydro-cyclone. Therefore, this paper presents the theoretical equation of the cut-size, which includes the gravitational and centrifugal forces acting on the suspended solid particles in the axial flow hydro-cyclone. The equation is derived based on the mass balance. The characteristics of the predicted cut-size are divided into two regions, one of which is dominated by the gravitational force effect while the other is dominated by the centrifugal force effect. Therefore the maximum value of the cut-size will be located between these two regions. Comparison of the predicted cut-size with the cut-size that was determined experimentally using glass beads reveals that the cut-sizes agree well. The vortex breakdown phenomena that occur in the exit pipe are also presented in detail in this paper. The phenomena are predicted with the simplified flow model (Hallett), and experimentally confirmed through experimentation, the results of which are presented photographically.     

Theory of the Cut-Size, The Fractional Collection Efficiency, and the Vortex Breakdown in the Axial Flow Hydro-Cyclone

From a practical point of view, it is important to be able to predict the collection efficiency of the axial flow hydro-cyclone. In order to perform such estimation, it is necessary to predict the cut-size for the various operating conditions. Up to this time, there were many papers that derived the cut-sizes theoretically based upon the effect of the centrifugal force on the suspended solid particles, and experimentally based upon the effect of the geometrical construction of the hydro-cyclone on particle size. However, there have been few, if any, papers that included the effects of gravitational settling on the suspended solid particles when estimating the cut-size for the hydro-cyclone. Therefore, this paper presents the theoretical equation of the cut-size, which includes the gravitational and centrifugal forces acting on the suspended solid particles in the axial flow hydro-cyclone. The equation is derived based on the mass balance. The characteristics of the predicted cut-size are divided into two regions, one of which is dominated by the gravitational force effect while the other is dominated by the centrifugal force effect. Therefore the maximum value of the cut-size will be located between these two regions. Comparison of the predicted cut-size with the cut-size that was determined experimentally using glass beads reveals that the cut-sizes agree well. The vortex breakdown phenomena that occur in the exit pipe are also presented in detail in this paper. The phenomena are predicted with the simplified flow model (Hallett), and experimentally confirmed through experimentation, the results of which are presented photographically.     

Validation of CFD model of multiphase flow through pipeline and annular geometries

Accuracy of prediction of pressure losses plays a vital role in the design of multiphase flow systems. The present study focused on the development of a computational fluid dynamics model to predict these parameters conveniently and accurately. The main objective was to validate the developed model through comparison of its simulation results with existing experimental data and empirical correlations. Both pipeline and annular geometries were considered for validation. Several data sets that involved a significant variation in process conditions were used for the validation. All three phases—liquid (water), gas (air), and solid (sand)—were taken into account. The simulations were conducted using the workbench platform of ANSYS Fluent 16.2. The Eulerian model of multiphase flow and the Reynolds stress model of turbulence closure available in Fluent were used for the present study. The average velocities and volumetric concentrations of involved phases were specified as the inlet boundary conditions. The stationary surfaces of the flow channels were hydrodynamically considered as either smooth or rough walls, and the outlets were regarded as being open to the atmosphere. The simulation results of pressure loss showed a good agreement with the corresponding measured values as well as with the predictions of well-established correlations.     

A Model for the Prediction of Concentration and Particle Size Distribution for the Flow of Multisized Particulate Suspensions through Closed Ducts and Open Channels

The model proposed by Karabelas has been modified for the prediction of solid concentration and particle size distributions for the flow of multi size particulate slurries through pipe, 2-D duct, and open channel. The experimental data reported in the literature have been used to establish the limitations of the Karabelas model. Based on extensive analysis of the experimental data, modifications have been proposed in the model to overcome the deficiencies. In particular, the effect of solid concentration on particle settling and turbulent diffusivity has been incorporated into the modified model. The modified model predicts the solid concentration and particle size distribution with reasonable accuracy for all the geometries considered.