错流旋转填料床气相压降特性

旋转填料床的气相压降是旋转填料床应用和设计的一项重要指标。在气液两相错流流动条件下，利用空气-水系统对错流旋转填充床的气相压降进行分段模型化和实验研究。按照错流旋转填料床气体流动的路径将气相压降分为进口压降、填料层压降、集气段旋转动能转化压降和出气段压降。推导出压降与操作工况的关联式，其计算值与实测值吻合较好。实验表明错流旋转填料床的气相总压降与气体流量、旋转床转速、液体流量有关。在高转速和小气量的条件下，气相压降随气量增大先下降后上升；其他情况随气量增大而上升。错流旋转填料床气相压降随转速上升而下降，在小气量情况下转速对气相压降有明显影响。气相压降随进液量的增大而增大，当旋转填料床在低转速时进液量对气相压降有明显影响。     

分层填料旋转床气相流场的CFD模拟研究

分层填料旋转床(SP-RPB)是一种新型高效的化工过程强化设备,对气相阻力控制的吸收、精馏等传质过程有明显的强化作用。文中采用计算流体力学方法(CFD)对该结构旋转床内的气相流场进行了模拟研究,分析了流体流速、转子转速及填料转动形式对SP-RPB内部压力场、速度场和湍动能分布的影响规律。计算使用RNG k-ε湍流模型和SIMPLE算法,填料层用多孔介质(Porous Media)模型,模拟结果与实验数据吻合良好。结果表明:SP-RPB内气相压降主要产生在填料区,切向速度远大于径向速度,流场以旋转场为主,湍动程度高于普通的旋转填料床,且湍动能沿径向的分布更为均匀,表明分层填料旋转床在强化气相传质方面比普通旋转填料床更具优势。     

错流旋转填料床气相压降特性研究

旋转床的气相压降是旋转床工程设计的一项重要指标。笔者利用空气,水系统对错流旋转填料床的气相压降进行实验研究。结果表明：在实验范围内,错流旋转床压降是逆流旋转床的十分之一;对错流旋转床压降影响较大的是转速和气量,与液流量几乎无关。     

动-静填料旋转床内部气相流场CFD模拟研究

通过对动-静填料旋转床进行简化,建立了二维物理模型,采用计算流体力学软件Fluent中多孔介质模型对旋转填料床内部流场进行了模拟研究。通过对旋转填料床进口结构形式、填料层厚度、动填料转速及进气速度对气相压降和速度分布影响的模拟研究,得出切向进口旋转填料床内气体分布更均匀;保持填料外径不变,增大填料层厚度,气相压降随之降低;气相压降随动填料转速和进气速度的增加而增大,这与常规的整体填料旋转床保持一致。     

新型径向叶片式旋转床压降分析及气相流场模拟

针对折流式旋转床压降高、能耗大的问题,提出了一种新型超重力旋转床设备--径向叶片式旋转床。首先,对该旋转床的压降进行了理论分析和建模,并利用水-空气体系进行了实验研究。通过改变气量、转速和液量探究了新型径向叶片式旋转床压降的变化规律,结果表明压降随气量、转速和液量的增加而增加,且随着气量和转速的增加,液量对压降的贡献逐渐减小。压降模型的预测值与实验数据的相对偏差基本在10%以内,表明模型可以较好地预测新型径向叶片式旋转床的压降。另外,通过计算流体力学（CFD）软件的模拟获得了旋转床内气相流场和压力分布的结果,发现转子内压降是总压降的主要部分;气体进入转子后会因叶片作用使得周向速度变大,并在转子外缘处达到最大值;气体的进口流速将会影响旋转床内的气相分布。利用实验数据对CFD模拟结果进行了验证,两者的相对偏差在10%左右。     

错流同心圆环旋转床的气相压降

在转速为865～1 300 r/min、液体体积流量为0～1600 L/h的情况下,以空气-水为体系,在直径为400 mm的错流同心圆环旋转床内,对其气相压降进行分段模型化和实验研究,并得到了压力降与操作工况的关联式.该关联式的计算值与实测值比较吻合.实验结果表明,错流同心圆环旋转床的湿床压降比干床压降大,气相总压降随气量和转速增大而明显增加,但随液量增大而缓慢增加.     

错流旋转填料床气相压降的研究

利用空气-水系统对错流旋转填料床的气相压降进行了实验研究。采用因次分析的方法推导出错流旋转填料床气相压降的无因次关联式。结果表明,错流旋转填料床欧拉准数在旋转填料床转速与气速之比(旋流比)小于30时,欧拉准数随旋流比的增大反而减小;当旋流比大于30时,欧拉准数随旋流比的增大而增大。旋流比小于30时欧拉准数与填料层轴向厚度的0.9次方成正比,旋流比大于30时欧拉准数与填料层轴向厚度的0.5次方成正比。湿床旋流比小于30时,欧拉准数随进液量的增大而上升;旋流比大于30时,欧拉准数随进液量的增大而下降。     

折流式旋转床气相流场数值模拟研究

采用CFD方法对折流式旋转床气液两相流动及压降进行数值模拟,建立了二维物理模型,研究了折流式旋转床转速、动静圈对数、进气量对气相压降和气相流场的影响,并用实验数据对模型进行验证. 结果表明,计算与实验相对误差在15%以内. 气相压降随进气量和动静圈对数增加而显著增大;转速增加,压降增大,但不明显,压降主要集中在转子内部,占总压降的88%~97%,其中转子压降的55%~73%由拐弯处的摩擦阻力引起;气体在静圈下隙存在回流,在动圈上隙气体流动缓慢,存在流动死区,气速主要以切向速度为主(占80%以上),峰值位于转子外缘,并与气体入口存在较大速度梯度,径向和轴向速度所占比例较小,且因位置不同而不同. 速度变化和压降的变化是转速、进气量和动静圈数等共同作用的结果.     

旋转填料床气液两相流场的仿真分析

通过合理简化旋转填料床(RPB)结构,建立了三维物理模型,利用商用软件Fluent的计算平台,采用欧拉两相流模型和多孔介质模型对旋转填料床内的气液两相流场进行了仿真分析,深入分析了其压力场分布和速度场分布,并在此基础上对比了气相压降随旋转床转速变化的仿真结果与实验结果,两者变化趋势一致,表明所建立模型能近似地模拟旋转填料床的流场分布,并指导理论研究和实验研究进一步深入。     

折流式旋转床出口气相流场研究

采用实验的方法对折流式旋转床气体出口流场进行研究。实验在旋转床壳体直径为724mm,气体出口直径为152mm的折流式旋转床中进行,在常温常压空气单相的情况下采用5孔探针测量了不同转速和气量下旋转床出口位置的气相流场。实验得到了不同转速不同气量下气相切向、径向和轴向速度随无因次半径变化的流场分布情况,从而为折流式旋转床的设计提供理论基础。     

物质流、能量流与信息流协同的初探

任何一个系统（生态的、自然的、生产过程、社会的、市场的）在其内部各个环节之间及与外部环境之间都在不断地进行着物质、能量和信息的交换,在时间和空间上形成物质流、能量流和信息流.本文主要根据协同学原理,描述物质流、能量流和信息流是如何相互影响和相互依存的,并进一步指出通过对物质流、能量流与信息流协同的研究,可以实现三者之间的协调配合,以在时间和空间上形成一种最佳的有序结构.     

基于框架设计的液流电池流场优化模拟研究

液流电池通常采用对角平推流流场,会形成电解液滞留区,造成电池局部浓差极化大,影响综合性能。鉴于此,提出了一种基于框架设计的流场优化方法,通过设计电极框架,可以得到“蛇形流道”和“平行流道”两类流场。以全钒液流电池为例,通过数学建模,研究了不同流场结构和参数对于多孔电极内电解液流动特性、电化学反应和温度变化特性的影响规律。计算结果与实验结果一致性良好,结果表明：电解液在“平行流场”内的流动均匀性比在“蛇形流场”内好,且不存在滞留区,同时在“平行流场”内浓差极化也较“蛇形流场”低;此外,对于同样的电极面积,在电极内部的“平行流道”越多,电解液的流速分布越均匀,反应特性越好。     

全混流反应器内流动规律模拟研究

研究了一种接近全混流的小型气固相反应器,可以用于在实验室研究时需要实现全混流接触状态的气固相反应的研究.采用计算流体力学软件(CFD)进行模拟得到最优结构,其结构包括1个圆锥形反应器主体,4个连接在反应器主体底部的进料口,1个连接在反应器主体上部的出料口.气体从4个进料口进入,催化剂在流动过程中从中部掉落,形成气体水平...     

Prediction of flow patterns in horizontal two-phase pipe flow

A new concept of a sequence of plots is used for the separation of flow regimes in two-phase flow. The empirical correlations themselves are based on extensive tabulations of flow-type data from the AGA-API Data Bank. Provided these data and the tabulations are accurate, the accuracy of the proposed method is better than 5%. The accuracy for any separation can easily be obtained from the information given. The probability of being able to separate flow types by the various correlations was determined and used to select the best correlations. In actual use, there will be times when a complete separation cannot be made. However, one will know this and be able to say that the flow is one of two or, rarely, more types.     

Heat transfer and flow pattern in vertical liquid-solids flow

Wall-to-bed heat transfer in hydraulic transport of spherical glass particles of diameter 1.20, 1.94 and 2.98 mm and in single-phase flow regime was studied. Experiments were performed by transporting the spherical glass particles with water in a 25.4 mm I.D. copper tube equipped with a steam jacket.In the runs without particles, the tube Reynolds number varied between 2280 and 21,300, while in hydraulic transport runs, the tube Reynolds number varied between 3300 and 20,150. The loading ratio (G_p/G_f) was between 0.07 and 0.328, and the fluid superficial velocity was between 0.29·U_t and 2.86·U_t, where U_t represents the single particle terminal velocity. For these ratios, the voidage ranged from 0.715 to 0.895.The data for the heat transfer factor (j_H) in single-phase flow are correlated using a general form j_H=f(Re). The data for wall-to-bed heat transfer in the hydraulic transport of particles show that an analogy between heat and momentum transfer exists. The data were correlated by treating the flowing fluid-particle suspension as a pseudofluid, by introducing a modified suspension-wall friction coefficient (f_w) and a modified Reynolds number (Re_m).     

Film flow down a fibre at moderate flow rates

We consider axisymmetric fluid flow down the exterior of a rigid straight vertical cylinder and model the emergence and propagation of the finite-amplitude waves that are created at the free surface. A system of evolution equations for the film thickness and volumetric flow rate, that was first derived by Trifonov [1992. Steady-state travelling waves on the surface of a viscous liquid film falling down on vertical wires and tubes. A.I.Ch.E. Journal 38, 821-834] has been re-formulated as an extension of the classical falling film problem. To inspire confidence in the predictions of this model, its linear stability characteristics versus those of the full Navier-Stokes equations are examined yielding very good agreement. Travelling wave solutions are determined and analysed in detail over a wide range of system parameters. The solutions resemble those associated with film for sufficiently small film thickness to fibre radius ratios, and beads when these ratios are relatively large. Transient computations are also performed for comparison with the travelling wave solutions and demonstrate the selection mechanism leading to the development of so-called ‘dominating’ waves for comparison with experimental observations.     

旋流在气流床气化炉中的应用

在气流床气化炉内高温高压的环境下,气固混合是影响气化炉效率的重要因素,而旋流在强化气固混合方面已在燃烧中得到广泛使用,文中综述了旋流在气流床气化炉中的应用。首先介绍了旋流的数学描述,包括旋流的概念,旋流N-S方程的表示方法以及其解析解,旋流的解析解均是在一定假设前提下得到的,具有一定的局限性;其次,介绍了旋流的特性和生成方式,主要通过切向入口、旋流叶片和机械旋转引入旋流;然后介绍了旋流在气化炉中的应用,包括喷嘴旋流和炉膛旋流2种,并结合具体结构展示了旋流的作用,主要有增强混合和便于排渣;最后对旋流在气化炉中的应用进行了总结和展望。     

Modeling of flow dynamics in laminar aerosol flow tubes

Flow behaviour in laminar aerosol flow tubes was investigated using a Computational Fluid Dynamics (CFD) model. Since these flow tubes are typically operated at low gas velocity, even small temperature gradients produce convection currents strong enough to interfere with laminar flow. This results in recirculation, causing the residence times of aerosol particles to be poorly defined. The situation is exacerbated when temperature inversions are present, or when the flow direction and temperature are changed simultaneously. We analyzed several characteristic flow tube configurations to define the range of experimental conditions that will ensure a laminar flow profile with minimal recirculation. For a laminar flow situation, we evaluated the extent of diffusion-controlled exchange between aerosol and the flow tube wall.     

Measurements of flow characteristics in a confined vortex flow

A study of air flow patterns by hot-wire anemometry is reported for a vortex chamber consisting of an upper cylindrical section 122 cm in diameter and 61 cm high and a conical bottom section 122 cm high. Quantitative data are presented for flow angles, profiles of mean tangential and axial velocities, and radial distributions of tangential and axial intensities of turbulence as a function of air entrance velocities of 1.6, 2.4 and 3.2 m/s, and axial distance from the top of the chamber. In general, the quantitative results confirm the theoretical predictions and the experimental trends reported in the literature. In particular, they fully support the conclusion that the flow pattern is relatively insensitive to the entrance volumetric flow rate. A generalized correlation is presented for the axial velocity distribution. Preliminary correlations are also presented for the tangential velocity distributions in the core and in the annular region of the vortex near the wall. These were found to be functions of the axial location and of the air entrance velocity.     

脉动条件下旋流场内气液两相流流型及其转变机理

运用高速摄像技术对流量脉动条件下旋流分离器内气泡动力学行为及气液两相流流型展开研究。研究发现,在完整脉动周期内,流量在3.62~4.18 m³/h范围内波动,流量增大段的气核整体向溢流口方向运移,流量减小段的气核整体向底流口方向运移,气核大小及形态变化呈现周期往复性。通过脉动周期内特殊帧的分析,得出流量脉动条件下旋流场内气液两相流流型主要包括：气泡流、塞状流、弹状流、丝状流及波状流等五种形式。根据实验得出的气液两相折算速度,确定了脉动条件下气液两相流流型转换界限图,而气泡间的聚并破碎行为是产生气液两相流型的主要原因,最终构建了表征截面含气量和分离效率之间关系的评价模型。