不同旋流数下湍流气粒两相流动特性的PDPA实验研究

利用相位多普勒仪 (PDPA)系统研究了不同旋流数下突扩旋风筒内气粒两相湍流特性的变化规律 .在相同的进口形状和总风量的条件下 ,分别测量了旋流数为 0、 0 .5和 1.0时气相和颗粒相的轴向、切向的平均速度和脉动速度 .结果表明 :旋流数的变化对轴向速度的分布和切向速度的似固核 -位涡结构 ,以及两相脉动速度和两相湍流各向异性都有比较明显的规律性影响 ;总体上 ,旋流对两相湍流起抑制作用 ,但随旋流数的增大 ,两相湍流脉动及其各向异性都有先减弱 ,后来又有所增大的趋势     

旋流数为0.1的强旋湍流两相流动的PDPA实验

采用相位多普勒颗粒测速仪（ＰＤＰＡ）对旋流数为１．０的轴向和切向进风的圆柱形旋风筒内强旋湍流气粒两相流动进行了测量研究，并与旋流数为０．４７、１．５和２．０８的实验结果进行了对比分析，指出了旋流数变化夺两相流场及两相湍流特性的影响。     

辊道窑烧嘴喷射角度对窑内湍流气流影响的研究

应用k -ε两方程湍流模型 ,对辊道窑烧成带的湍流旋流流动进行了理论分析 ,并用计算流体力学软件Fluent进行数值模拟 ,研究了烧嘴的喷射角度对烧成带内的湍流旋流流动的影响及其对制品烧成的作用     

旋流燃烧室内气体-颗粒两相湍流流动的数值模拟

综合应用代数Reynolds应力模型和流体相脉动速度大小和方向均具有随机性的颗粒相随机轨道模型,对旋流燃烧室内有直流射流与旋转射流相互作用的气-固两相湍流流动进行了数值模拟.得到的气相轴向与切向速度和轴向脉动速度均方根值分布以及颗粒相轴向总质量流通量和轴向与切向速度分布与实验基本相符合,并比对气相湍流采用k-ε模型的相应计算结果有较明显的改进.     

油水旋流分离器研究方法分析

从流动机理模型理论和计算流体动力学(CFD)模拟等方面综述了油水旋流分离器的研究进展状况.应用计算流体力学软FLUENT得到模拟结论,建立模型时运用RSM湍流模型和基于欧拉法的MIXTUER两相流模型.数值模拟得到的结论对油水旋流分离器的设计具有指导意义,为进一步研究油水旋流分离性能提供了参考依据,并且通过对用于油水旋...     

聚结器浓度场的数值模拟

为优化聚结器结构,应用计算流体力学（CFD）方法,选用RNG k-ε模型,以SIMPLE算法为基础,对旋流式和蛇形管式聚结器在湍流状态下的流体流动场进行数值模拟,得出该两种结构聚结器的油相浓度分布云图。数值模拟结果表明,蛇形管式聚结器对油滴的兼并和聚结效果优于旋流式聚结器。     

旋流片强化传热的数值模拟和场协同分析

基于壳程周期性单元流道模型;采用数值模拟方法分析了一种新型的传热强化元件——旋流片作为管间支撑物的湍流流动与传热特性。数值模拟采用重整化（RNG）κ ε双方程湍流模型;SIMPLEC算法进行压力和速度的耦合;壁面处理采用强化壁面处理法。分析了单元流道横截面流场和湍流强度的周期性变化;以及截面上流场和温度场的协同关系。比较了截面平均Nusselt数和平均协同角的对应变化趋势。结果表明;旋流片使流体在管束间做三维螺旋运动;破坏了流体流动的连续性和稳定性;增强湍流强度从而强化传热;同时改变了管束间流体的速度场与温度场分布;旋流片强化传热的根本机理是改善了两场的协同关系。     

万吨片碱分离装置性能研究

分离器是万吨质量分数72%片碱生产系统中重要设备之一,采用数值模拟方法研究分离器的压力分布,分析了旋流板式分离器内部的三维二相流场,气相采用RNG湍流模型,液相采用离散相模型,选择SIMPLE算法进行计算,讨论了不同入口气速对旋流板式分离器性能的影响.计算结果表明:在入口气速为3-13 m/s时,旋流板式分离器的分离压...     

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.     

水力旋流器流动特性的数值模拟研究

本文采用双流体模型以及RSM雷诺应力湍流模型,以油水混合液为介质,对水力旋流器的油水分离过程进行模拟。研究结果表明:旋流腔为预分离段,使油水两相粒子达到径向上的规律性分布,起到主要分离作用的是锥段,使油水两相分别从不同的出口排出。通过改变水力旋流器的入口段角度,分析入口角度变化为旋流器分离效率的影响,结果表明:旋流器的入口角度对分离性能的影响不可忽略,当β=0°和β=45°时分离效率较高,当β=60°时分离效率最低。     

分级进风燃烧室内旋流反应流的湍流特性

This paper presents an experimental investigation of the turbulent reacting flow in a swirl combustor with staged air injection. The air injected into the combustor is composed of the primary swirling jet and the secondary non-swirling jet. A three dimension-laser particle dynamic analyzer （PDA） was employed to measure the instantaneous gas velocity. The probability density functions （PDF） for the instantaneous gas axial and tangential velocities at each measuring location, as well as the radial profiles of the root mean square of fluctuating gas axial and tangential velocities and the second-order moment for the fluctuating gas axial and tangential velocities are obtained. The measured results delineate the turbulence properties of the swirling reacting flow under the conditions of staged combustion.     

Simulation of swirling gas–particle flows using USM and k–ε–kp two-phase turbulence models

The turbulent swirling gas–particle flows with swirl numbers 0.47 and 1.5 are simulated using a unified second-order moment (USM) (two-phase Reynolds stress equations) and a k–ε–kp two-phase turbulence models. The results are compared with experiments. Both two models can well predict the axial time-averaged two-phase velocities in case of s=0.47, but the USM model is better than the k–ε–kp model in predicting the tangential time-averaged two-phase velocities of strongly swirling flows (S=1.5). The anisotropic two-phase turbulence can well be described only using the USM model. The results give the difference in flow behavior between weakly swirling and strongly swirling gas–particle flows.     

A second-order-moment–Monte-Carlo model for simulating swirling gas–particle flows

A second-order moment (SOM) gas-phase turbulence model, combined with a Monte-Carlo (MC) simulation of stochastic particle motion using Langevin equation to simulate the gas velocity seen by particles, is called an SOM–MC two-phase turbulence model. The SOM–MC model was applied to simulate swirling gas–particle flows with a swirl number of 0.47. The prediction results are compared with the PDPA measurement data and those predicted using the Langevin-closed unified second-order moment (LUSM) model. The comparison shows that both models give the predicted time-averaged flow field of particle phase in general agreement with those measured, and there is only slight difference between the prediction results using these two models. In the near-inlet region, the SOM-MC model gives a more reasonable distribution of particle axial velocity with reverse flows due to free of particle numerical diffusion, but it needs much longer computation time. Both models underpredict the gas and particle fluctuation velocities, compared with those measured. This is possibly caused by the particle–wall and particle–particle interaction in the near-wall region, and the effect of particles on dissipation of gas turbulence, which is not taken into account in both models.     

Experimental study of gas swirling flow instability characteristics in a cyclone using the hot-wire anemometry technique

The instability characteristics of gas swirling flow in a cyclone were investigated experimentally by measuring the instantaneous tangential velocity with the hot-wire anemometry. The results showed that the instantaneous tangential velocity fluctuated continuously with time at both low and high frequencies. Further analysis of measured data regarding time and frequency domain by probability density and spectral methods revealed that the velocity fluctuation was affected not only by the turbulence flow itself but also by gas swirling flow instability. Also, the distributions of dominant frequency and amplitude indicated that low-frequency velocity fluctuation caused by the instability had the transfer behavior and attenuation character, which could be characterized by the dominant frequency that varied little along the radial position and decreased gradually along the axial direction, while the amplitude increased significantly with decreased radial position. Due to the gas swirling instability, the turbulence intensity and the fine particle diffusion were enhanced, which would degrade the separation efficiency of cyclone.     

Stereoscopic PIV studies on the swirling flow structure in a gas cyclone

Understanding the swirling flow in a gas cyclone is of great importance in improving the cyclone design. Once the three-dimensional strong swirling flow is fully understood, cyclone performance such as pressure drop and separation efficiency can be improved by optimizing the cyclone design. The swirling flow was investigated by the stereoscopic particle image velocimetry (Stereo-PIV) in this work. The instantaneous whole-field tangential, axial, and radial velocities were measured simultaneously in the cylindrical and conical separation zone, and in the dust hopper area of the cyclone with gas inlet velocity of .The time-averaged flow pattern in the cylindrical and conical sections of the cyclone showed: a typical Rankine vortex with inner quasi-forced vortex and outer quasi-free vortex which is generated by tangential gas velocity; inner upward flow and outer downward flow of axial gas velocity; and centripetal flow in the region close to the wall due to the presence of radial gas velocity. In the dust hopper, a secondary longitudinal circular flow is formed in the annulus area between the conical body and the cylindrical wall. Experimental results indicate that the separated particles may be re-entrained into the cyclone from the bin to degrade the separation efficiency of the cyclone.     

旋风分离器内气相旋转流动态特性分析与表征

旋风分离器内的气相旋转流具有很强的动态特性,表现为流场瞬时参数随时间波动变化。为了对旋风分离器内气相旋转流动态特性进行表征,本文基于热线/热膜风速仪（HWFA）和动态压力传感器测量的旋风分离器内瞬时切向速度和瞬时压力,从时域和频域两个方面进行了分析。结果表明,旋风分离器内瞬时切向速度信号时域上的波形分布与旋转流的摆动存在联系,时域上的标准偏差可以直观地表征旋风分离器内旋转流的波动强度;频域的主频和功率谱密度（PSD）可以表征旋转流动态参数波动的准周期行为、传递行为和强度衰减特征,也是旋转流摆动行为及其影响范围的反映。基于瞬时切向速度和瞬时压力的时域和频域分析能较好地反映旋转流流场的波动特点,均可用于表征旋风分离器内气相旋转流的动态特性。     

旋风分离器内旋转流的不稳定性

<正>引言旋风分离器内的流场是一个复杂的旋转流流场,以往的流场研究主要集中在稳态流场的时均特性上,重点关注流场的时均速度分布和湍流特性方面,从实验测量和模拟两方面进行,而对瞬态速度的分析不够,对流场的不稳定性尚缺乏分     

Gas and particle flow patterns in cyclones at room and elevated temperatures

Experimental results are presented for a study of gas and particle flows in a 102 mm diameter conventional cyclone operated at temperatures between 300 and 2000 K. Inlet gas velocities ranged from 3 to 42 m/s. Particle deposition patterns and the measurements of local pressures were used to determine the flow patterns and velocity profiles within the cyclone. A “Reynolds Number” has been defined based on the mean inlet velocity and the hydraulic diameter of the annulus between the cyclone wall and the gas outlet duct. An empirical equation was derived to correlate the ratio of the wall tangential velocity to the mean inlet velocity with this Reynolds Number.