固液两相叶片圆盘泵蜗壳内流动数值模拟

为研究叶片圆盘泵蜗壳内固液两相流动规律,应用计算流体力学软件Fluent对模型泵内部的固液两相湍流进行数值模拟。通过对叶轮无叶区和叶片区所对应蜗壳截面速度、压力和颗粒体积分数分布的比较分析。得到了能够反映叶片圆盘泵工作特点的蜗壳内固液两相流动特征。     

离心三相分离过程数值模拟研究

悬浮液的沉降过程主要由固相颗粒浓度和凝聚状态等决定,为了定量描述油渣水在离心力场中的分离过程,以含油渣水三相的罐底油为研究对象,提出固-液-液三相离心分离的概念,进行模型分析,采用计算流体力学软件FLUENT对其分离过程进行数值模拟研究,分析了其影响因素。研究表明:数值模拟与实验结果基本一致,利用FLUENT软件模拟三相离心分离过程符合实际状况,能够很好的指导实践。     

液固环流反应器流动状况的数值模拟

利用计算流体力学方法对液固环流反应器内的液固流动行为进行了数值模拟. 由Euler法的双流体模型和颗粒动力学理论建立了数学模型，对液固环流反应器内液固两相流动状况进行模拟，模拟结果很好地解释了液固环流反应器内的流动行为，固体颗粒速度模拟计算值与实验值的吻合说明了模型的可信性.     

溶气气浮池气液两相流二维数值模拟

采用计算流体力学软件FLUENT对溶气气浮池进行了二维数值模拟,分别对液相单相流动和气液两相流动进行了研究。模拟采用了RNG k-ε湍流模型,气液两相流的模拟采用了欧拉模型。计算得到了溶气气浮池内液相流场情况和气相在溶气气浮池内的体积分数分布,模拟结果与实验结果符合。     

固液两相离心泵内颗粒流动特性的研究进展

渣浆泵和泥沙泵等输送固液两相混合物的水泵是泵类中的耗能大户,在工农业各部门中应用广泛。固液两相离心泵的性能和效率受控于泵内的两相流动规律,理解泵内的两相流动规律,对于合理设计和延长泵的使用寿命有重要意义。本文重点阐述了固液两相流泵的研究现状及其进展。在内部流动特性方面介绍了固体颗拉在叶轮和蜗壳内部的流动规律,研究了泵内部过流部件的磨损规律及抗磨措施。并对低比转速固液两相流离心泵研究热点和发展趋势进行了讨论。     

卧螺离心机内盐析流场的CFD-PBM耦合计算

目前对卧螺离心机内部流场的数值模拟大多采用传统欧拉模型,考虑其内部伴有盐析等固相粒子微观行为过程的研究少有报道。本文应用计算流体力学软件Fluent,基于群体平衡模型与多相流Eulerian模型、RNG k-ε模型耦合方法,对卧螺离心机内部盐析两相流场进行三维数值模拟,通过仿真与实验相结合的方式,得到卧螺离心机内盐析流场的晶体颗粒粒径分布、组分数分布和浓度分布及其变化规律,初步揭示了卧螺离心机内伴有盐析的流场晶体颗粒分布特性。研究结果表明：卧螺离心机内盐析晶体粒径的分布随液环半径的增大而增大,螺旋叶片正壁面粒径明显较背面大,从排液端至排渣端的晶体粒径分布有整体逐渐变大的轴向粒径梯度;流道内晶体粒径随转鼓转速的增大而减小,随进口固相体积分数的增大而增大;大粒径晶体的组分数在液环外侧及螺旋叶片正面附近相对较大,而中、小粒径晶体组分数的分布规律则与之相反;盐析颗粒浓度在液环外侧较高且分布均匀,且随转鼓转速的提高而提高,PBM模型与Euler模型计算结果有一定的相似与差异。     

前混合磨料水射流的数值模拟

磨料水射流是高速水射流与磨料颗粒相混合形成的液固两相流,它利用高速水射流带动磨料颗粒,通过磨料颗粒的冲击和水蚀冲击进行破岩。本文基于液固两相流的基本理论,通过计算流体力学的计算方法,对淹没条件下前混合磨料水射流的流场进行了数值模拟。     

新型减温器的结构设计与仿真分析

为提高减温器在工作过程中的减温效果，以文丘里式减温器为研究对象，在新型减温器入口处设计一个螺旋节流结构，为了验证该结构能否增强减温水的雾化效果，采用计算流体力学CFD进行仿真模拟分析，利用流体力学软件Fluent内置的k-ε湍流模型和离散相模型，模拟原始结构减温器和新型减温器的内部流体状态，对流体的温度、水蒸气含量和颗粒直径分布云图进行比较分析，结果表明：有螺旋结构的减温器内部流体气液混合均匀、减温水雾化程度高、减温效果好，具有一定的应用价值。     

旋流分离器在乙二醇脱盐过程中的模拟研究

应用计算流体力学(CFD)模拟研究了旋流分离器内液固(乙二醇-NaCl)两相分离过程.应用RSS雷诺应力湍流模型、DPM离散相颗粒模型,建立液固两相分离模型,研究了旋流器结构、固相颗粒粒径、操作条件对颗粒分离效率、压降的影响.结果表明:采用优化的旋流分离器,粒径大于35μm的NaCl颗粒分离效率可以达到99.6％以上.     

一种新型浮选柱的数值模拟及性能研究

自主研制了一种新型多级规整填料浮选柱,应用计算流体力学软件FLUENT6.3.26进行数值模拟计算,对其内部的气液两相流动进行了考察,采用了欧拉-欧拉多相流模型,对气相的模拟采用单一气泡尺寸,液相湍流采用了标准k-ε模型,两相之间的动量传输仅考虑曳力作用。通过模拟,获得了不同实验条件下浮选柱内部的气液速度场分布、气含率分布等,对部分模拟结果进行了定量比较。结果表明随着气相流量的增大,浮选柱内部气含率增大,液体循环速度增大,从而气液之间混合更加充分,这对于提高浮选柱的分选效率和设备的放大有重要意义。在唐山钱家营开滦煤矿选煤厂进行了以其煤浆为原料的浮选性能的测试,在气体1.25 m³/h,进料0.05 L/h条件下20 min停留时间获得了精煤灰分10.28%,尾煤灰分43.39%,精煤产率52.53%的指标,与该厂浮选精煤灰分10.58%相接近。     

双螺杆挤出机液体进料工艺在改性塑料中的应用

采用双螺杆液体进料接枝法合成聚丙烯接枝丙烯酸共聚物,研究双螺杆液体进料接枝共聚方法对接枝物接枝率大小及性能的影响,采用红外光谱对接枝物结构进行分析。结果表明：用恒流泵在液体加料口匀速进料,当调节恒流泵转速8．0时,接枝率最高：6．254％。     

环状流液滴夹带率测量方法及分析

针对气液两相环状流液膜参数溯源问题,设计了一种液膜在线提取装置和基于液膜质量流量测量的夹带率测量方法。该装置利用超声波测距传感器对储液箱液位进行实时监测并反馈至控制系统,利用单片机控制抽气泵开关实现对环状流多孔渗水介质管段内外差压调节控制液膜析出速率,使用换向器实现计量和废液管路切换并记录两次切换之间的时间间隔。利用精密电子天平对取出液膜进行称重测量,结合记录时间和液相质量流量计测量结果实现液膜质量流量和液滴夹带率等参数的测量。在小口径高精度气液两相流模拟装置进行了75组实流验证实验,并结合两种典型夹带率模型预测结果对测量系统进行了科学评价。研究结果表明,液膜质量流量和液滴夹带率测量结果可溯源,测量准确度高,为研究气液两相环状流液膜流动特性提供了一种可靠的实验测试方法。     

Mass transfer at the confining wall of helically coiled circular tubes with gas–liquid flow and fluidized beds

Experiments were conducted to investigate the effect of various dynamic and geometric parameters on mass transfer coefficients in two-phase helically coiled flow systems. Computation of mass transfer coefficients was facilitated by the measurement of limiting current at the electrodes fixed flush with the inner surface of the tube wall. Two flow systems were chosen: a two-phase liquid solid fluidized bed and a two-phase gas–liquid up flow. An equimolar potassium ferrocyanide and potassium ferricyanide solution in the presence of sodium hydroxide was used as the liquid phase. In the fluidized bed, glass spheres and sand of different sizes were employed as fluidizing solids. In two-phase flow system nitrogen was employed as inert gas. The pressure drop in the presence of fluidizing solids in helical coils was found to increase with increase in the pitch of the coil and was maximum for straight tube. The mass transfer coefficients were found to increase with increase in liquid velocity. The mass transfer coefficients in case of gas–liquid flow were found to be independent of liquid velocity and the pitch of the coil, and were largely influenced by gas velocity only. The data were correlated using j_D factor, Helical number, Froude number and Stanton number.     

Measurement of real-time flow structures in gas–liquid and gas–liquid–solid flow systems using electrical capacitance tomography (ECT)

The real-time cross-sectional distributions of the gas holdups in gas–liquid and gas–liquid–solid systems are measured using electrical capacitance tomography. For the gas–liquid system, air as the gas phase and both Norpar 15 (paraffin) and Paratherm as the liquid phases are used. Polystyrene beads whose permittivity is similar to that of Paratherm are used as the solid phase in the gas–liquid–solid system. The three-phase system is essentially a dielectrically two-phase system enabling measurement of the gas holdup in the gas–liquid–solid system independent of the other two phases. A new reconstruction algorithm based on a modified Hopfield dynamic neural network optimization technique developed by the authors is used to reconstruct the tomographic data to obtain the cross-sectional distribution of the gas holdup. The real-time flow structure and bubbles flow behavior in the two- and three-phase systems are discussed along with the effects of the gas velocity and the solid particles.     

基于CFD的液环真空泵两相流动性能分析

运用CFX流动软件中的多相流欧拉分析方法,模拟计算一单级单作用液环真空泵在4种转速下的三维稳态气液两相流分布问题,计算区域包括液环泵进出气段、叶轮、进水管及泵体。计算结果表明,该分析方法和手段可以较好地模拟分析、计算液环真空泵气液两相流动问题。     

冷却水流量对ORC系统性能影响的实验研究

采用自主研发的单螺杆膨胀机作为机械动力,实验研究了冷却水流量对ORC余热发电测试系统及单螺杆膨胀机性能的影响。实验结果表明：当冷却水流量从8 m³·h^-1升至19 m³·h^-1时,单螺杆膨胀机输出功和轴效率分别从4.31 kW、36.38%增至5.15 kW、41.1%,分别增加了19.5%、13%。针对本实验系统,在考虑润滑油泵、工质泵、冷却水泵和冷却塔风扇等所有系统辅机功耗之后,当冷却水流量为12 m³·h^-1时,系统净输出功和系统净效率达到最大值,分别为2.44 kW和2.47%。通过研究冷却水流量对ORC系统性能的影响,为ORC冷却系统的设计和优化系统性能提供重要的实验依据。     

测定两相流动体系中局部相体积分率用阻抗探针仪的研制和应用

研制了应用于气/液和液/液两相流动体系中测定局部相体积分率的阻抗探针仪。该仪由方形波发生器、同轴电缆探头、数据采集卡和电脑信号处理系统组成。利用煤油/水两相流动体系进行实际测定,结果表明此项技术对分辨两相敏感,测试结果在非乳液体系中可靠,可用于气液、液液两相流的局部相体积分率的在线测量。     

Green crop fractionation by twin-screw extrusion: Influence of the screw profile on alfalfa (Medicago sativa) dehydration and protein extraction

Alfalfa was studied to define a new approach for green plant fractionation using twin-screw extrusion, leading to the production of a green filtrate, rich in proteins and a solid fibrous residue, rich in cellulose. The influence of the screw profile on protein recovery in the liquid extract and on plant dehydration was characterised. Three screw profiles were tested, at different liquid/solid ratios and plant inlet flow rates. A significant difference was determined, at a confidence level of 95%, between the influence of the three profiles on alfalfa dehydration and protein extraction in the raw filtrate. When mechanical action on the plant is stronger, both protein recovery and solid dehydration are better with more than half of the initial proteins (50.8%) recovered in the liquid extract in the best screw configuration (profile 3). However, extrusion is not efficient for the plant dehydration but the interest of adding a second filtration zone was demonstrated; after the first pressing and liquid expression in a first stage, water is added to the residual matter, which leads to a better protein extraction in the second filtration stage.     

Identification of rheological parameters by the squeezing test

Ceramic paste extrusion is investigated using a squeezing test, which compresses a disk of paste between two parallel plates, one of which is moving at a constant speed. From this test, the two-phase nature of ceramic paste can be evidenced. Liquid migration is observed at low compression speed, resulting in very dry paste at the end of the test.

The use of this squeezing test for discriminating paste formulation is illustrated with titanium and aluminium oxide pastes. This test is also a good tool for constructing a two-phase model for paste flow modelling. The paste is composed of a pseudoplastic saturated solid and a Newtonian liquid phase.

Model parameters K and m, characterising the saturated solid rheology, and k, filtration coefficient characterising the two-phase interaction, can be identified from runs at low and high compression speeds.     

Isothermal flow of viscous liquids in corotating twin screw devices

A mathematical model is derived for isothermal flow of a Newtonian liquid through corotating twin screw equipment. Two different flow regimes are studied. In the first, channels of twin screw equipment are completely filled with liquid, generate a pressure gradient, and provide a discharge pressure at the end of the pump. Equations are given for drag flow rate, pressure backflow rate, and flow rate through the nip zone. It is shown how the analysis of single screw pumps can be modified for twin-screw pumps. In the second regime channels are partly full, which is the case with extraction equipment. Equations show how the degree of fill in the equipment changes with flow rate, speed, and dimensions.