灰斗对旋风分离器气相流场的影响

本文采用fluent数值模拟的方法研究了中国石油辽河石化分公司聚丙烯装置在用旋风分离器内气相流场,将改造前和改造后两种结构旋风分离器内部流场进行了对比,研究发现,旋风分离器不设计灰斗时分离空间内最大切向速度减小,轴向速度中心上行流速度增大,旋转气流延伸到收料罐,大大降低了分离旋风分离器效率。     

直切单双进口旋风分离器流场及颗粒分离特性的数值模拟

采用计算流体力学(CFD)方法对Stairmand高效旋风分离器气相流场进行数值模拟,获取旋风分离器不同截面上的切向和轴向速度分布,与试验结果进行比较,两者能够较好吻合;采用此方法对直切单双进口旋风分离器颗粒分离的过程进行数值模拟。结果表明:双进口型改善了单进口型流场的不对称性,在进气量相同的条件下,双进口型的切向速度增大,径向速度明显减小,粒径分离效率提高了6%~30%。     

高效、低阻分离器入口结构改进及测试分析

为了改进旋风分离器的分级除尘效率和压力损失等性能指标,通过对SLK型高效低阻分离器的分级过程和不同入口形式的旋风分离的颗粒切向速度和沉降速度的分析计算,重点研究SLK型分离器入口形式对旋风分离器内气流速度的影响及其对分级除尘效率和压力损失的影响,通过试制SLK样机并利用粉煤灰进行测试分析,定性验证SLK型分离器高效低阻的性能特点。结果表明:该分离器能获得较高的分离效率,并且压力损失比同型号分离器减小100～400Pa。     

稳涡器提升旋风分离器性能的流场分析

为了提高旋风分离器分离效率,采用实验和CFD模拟相结合的方法,研究稳涡器的轴向位置对旋风分离器气固两相流动特性和分离性能的影响,探讨稳涡器抑制颗粒返混逃逸机制的形成。结果表明:稳涡器的设置降低轴线附近气流的轴向速度,加深气流的滞流程度,抑制颗粒的返混和逃逸,强化返混颗粒的二次分离作用,提高颗粒的分离效率;稳涡器轴向位置较高时,排尘口截面的通流面积小,下行气流阻力大,运行压降大;当稳涡器顶部与排尘口等高时,轴线附近的轴向速度降幅最大,返混逃逸颗粒数量减少25%～50%,分离效率最高。     

旋风分离器在冷镦机油雾处理中的应用探讨

借助计算流体力学软件Fluent,探讨旋风分离器分离冷镦机产生的油雾的可行性。运用雷诺应力二次压力应变模型和离散相随机轨道模型对旋风分离器进行数值仿真,分析了流场、颗粒轨迹、油雾内PM2.5分离效率。结果表明:旋风分离器可作为冷镦机油雾处理的初级分离设备。     

旋风分离器内气相数值模拟研究

旋风分离器内部进行的是两相流运动,是气相和固体颗粒相的分离过程,而固体颗粒的运动在很大程度上取决于分离器内湍流的运动.对湍流及其模型的研究具有十分重要的意义.在综述旋风分离器内湍流模型和数值模拟相关理论研究进展的基础上,着重分析了k-ε双方程模型和雷诺应力模型在旋风分离器流场预测方面的进步和不足,并展望今后湍流模型的发展趋势.     

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.     

新型旋风分离器的试验研究与流场分析

文章针对高温高压的条件对传统旋风分离器入口结构进行改进,提出了圆柱形径向插入、端面加导流板结构的新型旋风分离器结构。由冷态模型下对超细滑石粉和FCC催化剂颗粒的分离效率-压降对比试验结果表明,新型旋风分离器入口结构强度性能优良,虽然对超细粉料分离性能略有不足,但对大颗粒粉料的分离性能接近传统直切入口旋风分离器,可以满足要求。并且数值流场模拟结果表明,分离器压降与实验结果相一致。     

旋风分离器内颗粒藏量的实验测量

根据旋风分离器的气固分离特点,定义用于描述旋风分离器气固分离过程的颗粒藏量参数为操作中旋风分离器有效分离空间内全部颗粒的质量,选用流化催化裂化平衡催化剂粉料,通过实验测量旋风分离器内颗粒藏量与入口速度和入口浓度的关系。结果表明:颗粒藏量随着入口浓度和入口速度的增大而增大;旋风分离器的颗粒藏量主要来源于旋风分离器环形空间顶灰环,其余部分是旋风分离器的器壁表面颗粒层。     

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％。     

Effects of the prolonged vertical tube on the separation performance of a cyclone

This article aims at the gas flow into the dustbin of conventional cyclones, the prolonged cyclone (attaching a vertical tube at the bottom of the dust outlet) is proposed by some researchers, which can make flow with dust enter into the tube and separate further. The Reynolds stress transport model (RSTM) has been employed to predict the gas flow fields of the conventional and prolonged cyclones. The tangential velocity, axial velocity profiles and turbulent kinetic energy profiles are presented, and the downward flow rates into the dustbin of the three cyclones are compared. The separation performances of these three cyclones are tested. The result indicates that the tangential velocity, axial velocity and turbulent kinetic energy in the dustbin reduce greatly when the prolonged vertical tube attaching into the dust outlet, which can avoid the re-entrainment of already separated dust effectively. Furthermore, the prolonged vertical tube increases the separation space of dusts. The downward flow rate into the dustbin of the prolonged cyclone decreases compared with the conventional cyclone. The experimental results show that the prolonged vertical tube can improve the separation efficiency by a slightly increased pressure drop. However, for an even longer tube, the separation efficiency is slightly reduced. Thus, there is an optimal tube length for a given cyclone.     

Experimental and CFD study on effects of spiral guide vanes on cyclone performance

This paper presents an experimental and numerical study on a tangential inlet cyclone separator with a spiral guide vane which is not often researched. Numerical pressure drop results were in close agreement with the experimental data. The spiral guide vane was also found to considerably influence the velocity distribution, turbulence intensity, pressure drop and collection efficiency in the cyclone. A critical value of spiral guide vane turns appeared below or above which there was a marked increase in collection efficiency, pressure drop, and tangential velocity. Compared to a cyclone with zero spiral guide vane turn, the maximal decrease in collection efficiency in the cyclone with the critical spiral guide vane turns (one turn) was 2% approximately. The maximum-efficiency inlet velocity appeared to exist independent of spiral guide vane turns, as inlet velocity affected the radial distance traveled by the rebounded particles from the inner wall. The analysis of flow field in cyclones indicated that the flow field was improved with the spiral guide vanes employed to some extent. The results presented here may provide a workable reference for the effects of spiral guide vanes on the flow field and corresponding performance in cyclone separators.     

Influences of inlet height and velocity on main performances in the cyclone separator

Aiming at improving collection efficiency in the cyclone separator, the effects of inlet height and velocity on tangential velocity, static pressure and collection efficiency were studied. A three-dimensional model including gas-flow, and particle-dynamics fields was built by the Reynolds stress turbulence model, and the numerical simulation was achieved using the FLUENT software. The static pressure distribution, tangential velocity distribution, and particle trajectory of the cyclone were obtained, and the variation law of the collection efficiency with inlet height and velocity as well as particle diameter was analyzed. Numerical results indicate that both the static pressure and the tangential velocity in the cyclone basically present the axial symmetrical distribution, the static pressure shows a nonlinear increasing trend in the radius direction and the distribution of the tangential velocity is in the shape of a “hump.” The increase of inlet height in a certain range reduces the rotation numbers of particles in the cyclone and shortens the residence time, which results in the improvement of trapping performance. Furthermore, the appropriately increasing inlet velocity in a reasonable range can make the collection efficiency increased.     

Modeling and numerical simulation of flow field in three types of standard new design cyclone separators

In this paper, numerical simulation of flow field in three types of standard new design cyclone separators namely 1D2Dn, 1D3Dn and 2D2Dn are investigated. In these standard cyclones, the length of cylindrical top part of the body is equal to 1, 1 and 2 times of the body diameter, respectively; and the length of the cylindrical bottom part is 2, 3 and 2 times of the body diameter. The new design cyclone is based on the idea of improving cyclone collection efficiency and pressure drop by increasing the vortex length. The Eulerian-Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). Results show that among the three standard new design cyclones, cyclone 2D2Dn has the highest efficiency followed by 1D3Dn one with about only 2% lower efficiency. Cyclone 1D2Dn possesses the lowest efficiency among all. Similarly, the highest pressure drop occurs in cyclone 2D2Dn. Cyclones 1D3Dn and 1D2Dn followed 2D2Dn one with a marked difference of about 20%. In result section, the details of the flow field including velocity, pressure contours, turbulence, velocity vectors and particle trajectory will be presented.     

高温高压旋风分离器流场模拟及性能试验

提出一种圆形径向进口、筒体段扩径的拱顶旋风分离器新结构;并与PV型分离器进行了流场和分离性能对比。结果表明:在相同处理气量下,新型分离器外旋流区切向速度显著大于PV型,中心涡核区轴向速度小于PV型;用中位粒径为9μm的滑石粉进行冷模试验,新型旋风分离器分离效率比PV型高约1%;新型旋风分离器结构强度和分离性能优良,适合高温、高压的工况下应用。     

Evaluation of numerical schemes using different simulation methods for the continuous phase modeling of cyclone separators

The steady and unsteady state simulations of Stairmand cyclone separator were carried out to investigate the performance of different interpolation schemes for discretization of pressure gradient and advection terms. The RSM turbulence model was revisited to explore its simulation capability of PVC phenomenon and fluctuating velocity profiles of cyclone separators. The combination of Presto, SO, standard and BFW schemes for discretization of pressure gradient and FOU, power law, SOU, QUICK and MUSCL schemes for discretization of advection terms were studied. The double precision solver of Fluent 6.3.26 and modified RSM turbulence model constants of Jiao et al. (Chem. Eng. Technol. 30 (2007) 15–20) were also verified for simulation of cyclone separators. The predicted mean and fluctuating velocity profiles and pressure drop inside the cyclone separator with steady and unsteady simulations have been compared to experimental results available in literature.The steady state simulation failed to predict velocity profiles and pressure drop inside cyclone separator accurately, whereas the unsteady state simulation predicted velocity profiles, pressure drop and PVC phenomenon close to experimental values. The prediction of fluctuating velocity profile was better than previously reported work in the core region compared to the off core region. The present study revealed that the SOU scheme for discretization of advection terms of momentum, kinetic energy and its dissipation rate equations and the FOU scheme for Reynolds stresses together with the Presto scheme for discretization of pressure gradient with unsteady simulation are the optimum choice for simulation of cyclone separators.     

多效旋风分离器压降的实验研究

为了有效提高新型多效旋风分离器对粒径为0.1~3μm颗粒的分离效率,获取该设备的阻力性能,采用实验方法研究该新型多效旋风分离器压降与进口气速的关系,并与Lapple型旋风分离器进行比较。结果表明:进口风速为5~30m/s时,主体直径为0.25m的多效旋风分离器总阻力系数为7.29,其中,一级和二级预分离螺旋管的阻力系数分别为1.04和1.73;主体的阻力系数为4.52。直径为0.25m的Lapple型旋风分离器的阻力系数为7.21。     

三维旋转流场特征与压力损失关系的研究

本文以Stairmand高效旋风分离器为实验模型，利用五孔球形探针测试了典型三维旋转流动的速度和压力分布。并结合减阻杆的研究发现，测试了安装不同类型减阻杆后速度和压力分布的变化，从而在分析减阻杆减阻机理的同时，认识了三维旋转流场特征与压力损失的关系。     

倾斜蜗舌对多翼离心风机流场及噪声的影响

利用Fluent软件对常规直蜗舌多翼离心风机与倾斜蜗舌多翼离心风机进行流场和噪声的数值模拟研究。研究结果表明：倾斜蜗舌对多翼离心风机速度场的影响主要集中在蜗舌区域,对其它区域影响较小。倾斜蜗舌减小蜗舌区域的速度,同时改变蜗舌表面的流体速度矢量,减小蜗舌区域的局部旋流。在相同转速下,多翼离心式风机采用倾斜蜗舌结构虽然流量降低5.67 %,但是叶轮的功率降低9.13 %,噪声也降低12.2 dB,降低能耗和噪声效果都比较显著。     

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.