喷动床内气固二相流动行为的计算模拟

采用双流体模型结合颗粒动理学理论对喷动床内气固二相流体流动行为进行了计算模拟研究。模型中运用颗粒动理学理论描述颗粒相应力封闭流体控制方程,使用Gidaspow曳力模型描述气固相间作用。喷动床内颗粒在浓相区的体积分数很大,采用Schaeffer′s模型描述颗粒间的摩擦应力。模拟计算结果表明,喷动床内分喷射区、喷泉区、环隙区3个区域,在射流入口处形成一个瓶颈。模拟计算得到的颗粒速度和空隙度分布与实验数据进行比较,计算结果与实验结果吻合较好。     

喷动床内气固二相流体动力行为颗粒动理学

应用气固二相双流体模型数值模拟了喷动床内流体动力行为,模型中采用稠密固相动力-摩擦应力模型。模型中同时考虑了动理学理论和摩擦应力理论。应用贴体坐标系使得网格与喷动床的倒锥体边界符合良好。模拟得到的喷动床内颗粒速度和浓度实验数据吻合较好。     

导向管液固喷动床的数值模拟研究

本文以液-固两相流理论为基础,用颗粒动力学理论描述颗粒与颗粒间的碰撞,用标准湍流方程模拟液相和颗粒相的湍动,并且考虑液-固两相的相互作用,旨在探索一种工程设计和放大的新方法。对比颗粒循环速率和密相区真实液相流速的模拟结果与实验值,结果吻合较好。     

不同固相黏度模型对鼓泡床气泡行为的数值模拟

基于双流体模型,应用Fluent软件包对带有单喷嘴的二维鼓泡床中气泡行为进行数值模拟。采用常固相黏度模型(CPV)和基于颗粒动理学的固相黏度模型(KTGF),通过计算气泡的形成、气体泄漏率、气泡直径及气泡上升速度对不同模型进行比较研究,其中编程实现了KTGF模型中的Lun等模型与Hrenya和Sinclair模型模块。通过与文献中的实验数据进行对比发现KTGF模型普遍优于CPV模型,其中Lun等模型与Hrenya和Sinclair模型的模拟值最接近实验数据。     

大涡模拟方法模拟鼓泡床内气固两相流动

采用大涡模拟（LES）方法模拟气相湍流,颗粒动理学方法考虑颗粒相碰撞产生的动量和能量传递和耗散,采用颗粒相大涡模拟方法（LESp）模拟颗粒脉动导致的能量耗散,同时考虑介观尺度对颗粒相压力的影响,建立了气体-颗粒LES-θ-LESp双流体模型,研究鼓泡流化床内气固两相流动的特性。数值模拟与文献实测颗粒速度和实测颗粒浓度结果具有相同的变化趋势。     

摩擦-动力应力模型研究喷动床内气固两相流动过程

考虑颗粒滑动的半持续性接触应力和颗粒碰撞瞬时接触应力对颗粒相应力的贡献,建立了喷动床内气体颗粒两相流动计算模型。采用颗粒动理学和Johnson 等的摩擦应力模型,数值模拟喷动床颗粒流动过程,获得了喷动床喷射区、环隙区和喷泉区内颗粒流动特性。模拟计算与He等的实验结果进行了对比。同时分析了摩擦应力模型对颗粒相黏度变化的影响,表明中速颗粒流的颗粒相摩擦应力模型将直接影响喷动床气体颗粒两相流动的预测。     

带导流管液固喷动床的最小喷动速度研究

在截面为矩形有机玻璃喷动床内，使用四种粒径的窄筛分球形玻璃珠，以常温水作为喷动和辅助液体。综合考虑床体的几何尺寸、操作参数以及液体和颗粒的物性特征，系统研究带导流管喷动床的最小喷动速度，得出最小喷动速度的经验公式，为设计和操作提供参考。     

循环流化床气固两相流动数值模拟的研究进展

对循环流化床气固两相流动数值模拟的研究进展进行介绍,包括传统的欧拉双流体模型、基于颗粒动力学理论的双流体模型、基于拉格朗日坐标系下的颗粒轨道模型、能量最小多尺度模型和小室模型,并对上述模型的原理、发展和优缺点进行了描述。     

喷动床反应器气固流动模型的研究进展

首先对喷动床流动特征参数关联式进行了扼要介绍,继而着重总结了近年来喷动床内气固流动模型(喷射区气固稀相流模式、环隙区气体渗流模式以及固体颗粒流模式)、以及喷动床放大规律等基础理论研究的进展。最后,提出了未来喷动床流动模型工作的突破点和相应思路。     

锥底喷动床内气固两相流的数值模拟

为了得到喷动床内流场分布的详细信息,给进一步的实验研究和工业放大提供理论依据,对锥底喷动床内气固两相流的流动状况进行数值模拟.使用欧拉模型进行计算,得到稳定的喷动区、环隙区和喷泉区等喷动床典型流动特征.考察喷动床内颗粒相在喷动区、环隙区和喷泉区的速度分布以及空隙率和颗粒体积分率的分布.计算结果同实验观察得到的结果相符.     

MODELING AND SIMULATION OF AIRFLOW IN SPOUTED BED DRYERS

ABSTRACT

This paper presents an axisymmetric three-dimensional semi-empirical model that describes the airflow in both the spout and annular regions. Both the pressure and air velocity distributions can be calculated at any point inside the dryer. Thus, the effect of the fluid dynamics on the heat and mass transfer coefficients and, consequently, on the drying process, can be evaluated. The finite element method was used to solve the model. Pressure distributions were measured for several conditions in which stable spouted bed flow regime was attained. Simulated pressure distributions agreed well with experimental data.     

喷动床反应模型的研究进展

喷动床是一种可实现热量重复循环的高效反应器 .介绍了目前喷动床研究中出现的各种反应模型 ,从等温和非等温两个方面讨论了一维轴向、流管、半分割和流动反应耦合等各类模型的基本思想和理论及各自的特点 ,并提出了进一步发展的方向 .     

液固磁稳定床流体力学特性

The hydrodynamic characteristics of liquid-fluidized magnetically stabilized beds (MSB) with commercial amorphous nickel alloy catalyst (SRNA- 4) as solid phase and water as liquid phase in a cold model experimental apparatus of Φ140 mm were investigated. The influence of magnetic field intensity on bed structure, pressure drop, minimum fluidization velocity, transition velocity, and liquid holdup were investigated. Mathematical models for minimum fluidization velocity, transition velocity, liquid holdup were established respectively. The operating phase diagrams of liquid-fluidized MSB with SRNA-4 catalyst of two different sizes were obtained.     

狭缝式矩形喷动床中多粒度颗粒体系的最大喷动压降

在 15 0 mm× 5 0 mm× 110 0 mm的矩形喷动床中 ,研究了单一粒径体系和二组分及三组分混合粒径颗粒体系的最大喷动压降受颗粒粒径及粒度组成、静止床高和气体入口狭缝宽度的影响情况。实验采用宽度为2、4、6 mm三种宽度的狭缝式气体分布板 ,实验物料为单一粒径分别为 1、1.5、2 mm的玻璃珠。实验表明矩形喷动床的最大喷动压降与上述三种影响因素都有关系。本文还给出了最大喷动压降随这三种因素变化的实验关联式     

CONVECTIVE HEAT TRANSFER DURING COATING OF PARTICLES IN TWO-DIMENSIONAL SPOUTED BEDS

ABSTRACT

This work deals with the evaluation of gas-to-particle convective heat transfer in a process of coating of particles in two-dimensional spouted beds. A detailed calculus routine is presented and two correlations of heat transfer coefficient, for the spout and annular regions are derived. The study is performed with two, two-dimensional spouted beds with different sizes and with two different particles, placebo and soybean.     

NUMERICAL SIMULATION OF THE GAS-PARTICLE FLOW IN RISERS I: THE MACRO FLOW BEHAVIOR

The steady gas-particle flow in risers under variant operating conditions was predicted based on a k-?-k_p-?_p-Θ two-fluid model, which describes the dense turbulent gas-particle flow by the Eulerian method, considering the turbulence of both gas and particles as well as the particles' collisional effects. Much information on the macro flow behavior in risers, such as the profiles of local particle axial velocity, solids volume fraction, and solids mass flux in different operating regimes was obtained, and the predicted results show satisfactory agreement with experimental data. Further analysis of the predictions gives the comprehension of flow characteristics on the macro scale.     

NUMERICAL SIMULATION OF THE GAS-PARTICLE FLOW IN RISERS I: THE MACRO FLOW BEHAVIOR

The steady gas-particle flow in risers under variant operating conditions was predicted based on a k-ε-k_p-ε_p-Θ two-fluid model, which describes the dense turbulent gas-particle flow by the Eulerian method, considering the turbulence of both gas and particles as well as the particles' collisional effects. Much information on the macro flow behavior in risers, such as the profiles of local particle axial velocity, solids volume fraction, and solids mass flux in different operating regimes was obtained, and the predicted results show satisfactory agreement with experimental data. Further analysis of the predictions gives the comprehension of flow characteristics on the macro scale.     

旋转填充床内微观混合的数值模拟

旋转填充床作为新型的高效反应传质设备,广泛应用于快速反应过程,如制备纳米粉体材料.对旋转填充床内微观混合进行研究,有助于进一步认识旋转填充床内高度分散液体微元在填料丝网中的流动行为和分散混合机制,为旋转填充床内液液反应混合制备纳米材料提供理论基础.基于公开文献报道的实验观测结果,通过合理假设,建立了旋转填充床内微元流动的物理模型.在该物理模型的基础上,结合此前提出的湍流混合与反应模型,模拟计算了液体微元经过实验条件下50层丝网填料最终流出填料空间的浓度分布.由浓度分布得到的微观混合特征指数与实验值进行了对比,吻合良好.     

SLC-S分解炉增加物料进口时气固两相流场的数值模拟

以SLC-S分解炉为基准模型,新增一个物料进口,分别对两物料进口在不同的相对位置时的气固两相流场进行了数值模拟.对连续相、颗粒相的计算分别采用k-ε双方程湍流模型和离散相模型,对离散相与湍流之间的相互作用采用随机跟踪模型.模拟所得的气流场分布规律与模型实测结果吻合较好,而且所预测的固、气停留时间以及固气停留时间比值与模型实验预测值相一致.对结构进行优化的模拟结果表明:当两物料进口之间的水平投影夹角大于或等于135°时,尤其是在157.5°时,物料在分解炉内的分散状况皆良好,物料停留时间的绝对值和固气停留时间比值皆很高,为适宜的夹角范围.     

DRYING OF HIGH MOISTURE CONTENT PADDY IN A PILOT SCALE TRIANGULAR SPOUTED BED DRYER

From the successful drying of paddy in a lab-scale triangular spouted bed (TSB), a pilot scale unit with a capacity of 500kg/batch was constructed and used to dry paddy of high moisture contents. The drying tests showed that air temperatures of up to 160°C in the first stage, followed by a lower temperature of 80-100°C in the second stage, can be used to dry paddy from more than 25% down to around 15% (w.b.) without significantly changing grain quality in terms of head rice recovery. Moisture distribution in the pilot-scale TSB was observed to be satisfactorily uniform.