Analysis of the nutation and precession of the vortex core and the influence of operating parameters in a cyclone separator

Vortices motion in the anisotropic turbulent flow of cyclones makes a vital impact on flow stability and collection performance.Nevertheless,there remains a lack of clarity in the overall feature of vortices motion.In this work,a numerical analysis was conducted to clarify the complex motion of the vortex core in a cyclone separator.The validity of the numerical model was demonstrated by comparing the computational results with experimental data in the literature.As revealed by the results,the vortex core not only has a precession motion about the geometrical center axis but also does a nutation motion in the axial direction.The frequencies of the precession motions show two main peaks.And the magnitudes of the precession and nutation motions have non-uniform distributions in the cyclone.Moreover,the precession-nutation motions of the vortex cores exhibit a similar fluctuant pattern to the dust ring on the separator wall.The inlet gas velocity and the inlet solid loading show vital effects on the magnitudes and frequencies of precession and nutation motion.

Research on High-Efficiency Cyclone Separators and Their Optimum Design

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Effect of inlet area on the performance of a two-stage cyclone separator

The cyclone separator is an important separation device.This paper presents a new type of embedded two-stage cyclone,which includes a 2 nd-stage cyclone(internal traditional cyclone)with multiple inlets and a 1 st-stage cyclone(outer cylinder)that unifies the 2 nd-stage cyclone inlets into one inlet.The Taguchi experimental method was used to study the two-stage cyclone separator’s inlet area on its performance.Studies have shown that the increase of the 1 st-stage cyclone inlet area and the increase in the number of 2 nd-stage cyclone inlets(N)positively affect reducing the pressure drop and a negative effect on efficiency.It is recommended to use 2 S(the original 1 st-stage cyclone inlet area)of the 1 st-stage cyclone inlet area and 2 N of the 2 nd-stage cyclone inlets when separating fine particles.Compared with a traditional cyclone,the pressure drop is reduced by 1303 Pa,the mass separation efficiency(Eq)is increased by 0.56%,and the number separation efficiency(En)is increased by 2.05%.When separating larger particles,it is recommended to use 2 S of the 1 st-stage cyclone inlet area and 4 N of the 2 nd-stage cyclone inlets.Compared with a traditional cyclone,although Endecreases slightly,the pressure drop is reduced by 3055 Pa,and the Eqis increased by 0.56%.The research results provide new insight into the design of the cyclone.

Performance analysis of gas-liquid cylindrical cyclone (GLCC) separator with an inclined and perforated wall

As primary separators in pressurized water reactors (PWRs), cyclone separators separate most of the water from vapor-water two-phase mixture, which is important to the safety and economics of nuclear power plants. To improve the performance of cyclone separators, we tested new structures in this study, e.g. porosity and inclined angle of the separator wall. Under different structures, separation efficiency and pressure drop were studied theoretically and experimentally. Results show that each of the structural parameters has an effect on separator performance, but none of the trends is monotonically in experimental ranges. Besides separator structures, the comprehensive performance is also determined by flow patterns. From segregated to homogeneous flow, the separation ability decreases. The separation efficiency is about 5% higher at 20° inclined angle when the superficial velocities are 0.012 and 16 m·s-1 for the liquid and gas, respectively. The separation efficiency is only 91% without an impeller, while it is up to 100% at the same superficial velocities of air and water, 16 and 0.015 m·s-1 , respectively. Based on the study, it is promising to understand deeply the separation mechanism and further to provide data for designing large-scaled separators for advanced pressurized water reactors.

Improving advantages and reducing risks in increasing cyclone height via an apex cone to grasp vortex end

For a cyclone, it is possible to improve separation efficiency and reduce pressure drop by increasing the cyclone height. However, an exceeded height increase could result in a dramatical drop in separation efficiency. In this study, experimental and computational fluid dynamics simulation results exhibit that the introduction of an apex cone at the dust outlet could avoid the risk of separation efficiency drop but lead to a continuous reducing of the pressure drop. Generally, the optimal cyclone height should be closely related to the natural vortex length. While, when the vortex end contracts into the separation space in the cyclone with an exceeded height, severe back-mixing of particles always occurs, which will result in the decrease of separation efficiency. Herein, it is found that when an apex cone is installed at the dust outlet, the vortex end can be grasped by the cone so as to weaken the back-mixing of particles.Meanwhile, the introduction of this apex cone can enhance the secondary separation to capture the back-mixed particles again so as to protect the efficiency. In addition, it is found that the enhanced secondary separation could come from either the stagnant current of axial velocity in the center or the improved tangential velocity of inner vortex whereas the forcibly extending the length of vortex to exceed its natural length will not significantly increase efficiency.

Structural Optimization of a Novel Up-run Gas-solid Separator

A new gas-solid separator dedicated to heavy-oil fast pyrolysis process incorporating inertial and centrifugal separation was designed. Gas and typical fluid catalytic cracking （FCC） catalyst particles （with a density of 1500 kg/m3, and a mean diameter of 45.81 p.m） were used in the study. The inlet gas velocity was kept constant at 13.36 m/s, while the solid loading at the inlet ranged from 0 to 700 g/m3. When the exhaust pipe opening was provided with two narrow-width slots near the inlet without baffles, the solid collection efficiency increased with an increasing solid loading at the inlet and was close to 95% along with a decreasing pressure drop. After increasing the secondary separation structure, the separation efficiency greatly improved. By adjusting the diameter of the secondary exhaust pipe, the separation efficiency and pressure drop could be balanced. Under the experimental conditions, when the diameter of the second exhaust pipe was equal to d=100 mm, the pressure drop was lower than 1400 Pa while the separation efficiency could exceed 99.50%; and when the diameter was equal to d=120 mm, the pressure drop was less than 700 Pa, with the separation efficiency reaching over 99.00%.

Determination of design parameter for three-product heavy-medium cyclone

Analyzed the selected raw coal nature and forecasted the number quality of its separated product. Considering each product＇s density, volume, and suspending liquid assignment, combining the separating mechanism of the cyclone and the rela- tive formulas obtained from scientific experimentation and practice, the structure parameter was determined by calculation. This provides a more scientific reasonable method for determining the structure parameter of the unpressurized feeding three-product heavy-medium cyclone.

出口结构对轴流式旋风分离器性能影响的数值模拟

为探究出口结构对轴流式旋风分离器性能的影响,通过大涡模拟与离散相模型耦合的数值方法,对4种不同出口结构轴流式旋风分离器进行数值模拟研究,同时,引入Omega准则识别内部空间涡结构。结果显示,在轴流式旋风分离器内部,叶片吸力面与导流锥底部形成了叶间通道涡与导流锥尾迹涡,且涡旋速度梯度大,并会将颗粒卷吸到涡核中心,使分离效率降低;楔形与弧形出口结构加剧了涡结构在出口管内破碎的现象,且较直筒型出口的压力损失更低。在弧形出口前设计直线段可减缓型面扩张,即混合型出口可进一步改善弧形出口的流阻与分离性能。总体来看,楔形出口和混合型出口的性能较好,可为轴流式旋风分离器的结构改进提供一定参考。

基于响应面法的过轴式旋流器分离性能优化

为解决旋流器在井下狭小空间内的适用性问题,提出一种新型过轴式旋流器,通过响应面法对构建的旋流器结构参数与分离效率间的数学关系模型进行结构优化。采用数值模拟方法,对优化前后旋流器在不同处理量与含水率条件下旋流器内流场特性及分离效率的对比情况开展研究。结果表明:优化后模型效率均优于优化前,优化后模型处理量在2—6.5 m^(3)/h变化,处理量为6.5 m^(3)/h时分离性能最佳,分离效率由60.30%增至97.10%;含水率在92%—99%变化,含水率99%时分离性能最佳,分离效率由93.15%增至99.72%。采用数值模拟与实验相结合的方法,对优化后旋流器在不同分流比条件下分离效率开展研究,数值模拟与实验结果呈现出较好的一致性,验证结构优化的可行性及数值模拟结果的准确性。

旋风分离器内置导流叶片结构参数优化研究

为研究旋风分离器内置导流叶片各个结构参数之间的相互作用,基于CFD数值模拟方法和BBD试验设计,采用二阶多项式基函数建立了Stairmand旋风分离器的叶片轴向位置、叶片长度及叶片偏转角度与分离效率及压降间的数学模型。拟合结果表明:响应目标的决定系数均在0.99以上,表明相关性和回归模型效果较好。使用Design Expert软件处理数据后选择了最佳推荐点,对分离器结构进行了优化。优化后的模型与原结构对比结果如下:优化模型的压降略有上升;颗粒直径在1~20μm范围内时,优化前后分离器的分离效率变化明显,尤其在1~15μm范围内时,优化前分离效率为6.8%~31.0%,优化后则达到了17.0%~54.0%,提升约20个百分点;而当粒径在15~40μm区间时,优化前后的分离效率变化不明显,尤其是在粒径20~40μm时,优化前的分离效率为71.0%~98.0%,而优化后的分离效率只有77%~99%,提升约10个百分点;优化后的模型性能符合“高效低阻”的设计目标。所得结论可为旋风分离器内置叶片的改进提供设计指导。

外筒结构对轴流导叶式气液分离器分离性能的影响研究

气离心分离器因体积小、效率高而受到广泛的应用,提出了一种结合重力分离和离心分离的可处理复杂、不稳定两相流动的新型气液分离器。通过数值模拟对外筒结构进行优化并设计了气液分离试验以验证该分离器的分离性能。研究表明,随着分离器内外筒高度比的增大,分离效率会缓慢增大,压降也会随之增大。随着内外筒直径比的增大,分离效率会显著增大,压降会随之减小。

井下多级并联微旋流器流量均布性分析及优化

采用多级并联微旋流器的方式实现井下油水分离,不仅可以提高采出液含油体积分数,同时能够满足高处理量要求。在井下工作时,若油水分离设备与套管间形成的油套环空流场结构不合理,会导致每级微旋流器组得到的流量不均匀,影响多级并联微旋流器分离装置的整体分离性能。基于数值模拟和响应面Box-Behnken试验设计方法,构建了分离装置和套管形成的油套环空流体域的结构参数与流量不均匀系数、最大压力损失间的数学模型,并对模型的有效性进行了验证。分析结果表明:当每级入口间距为400 mm、每级入口角度为90°、总级数为3级、出入口面积比为0.5时,优化后的流量不均匀系数从0.02653减小到0.01289,降幅达51.41%;与初始结构对比,当雷诺数在3000~8000范围内变化时,优化结构的流量不均匀系数在各种工况下比较稳定,最大可减小0.04708,最小为0.01125;优化后的结构呈现了较好的流量均匀分配性能及适应性。所得结果可为井下多级并联微旋流器的设计及应用提供参考。

倒锥参数对气举式水力旋流器分离性能的影响

利用单因素试验设计方法,针对气举式水力旋流器倒锥参数,开展不同参数下的性能优化研究。利用数值模拟方法,对不同倒锥高度、注气直径和注气速度下的流场特性及分布规律进行分析。结果表明,当倒锥高度为130 mm、注气直径为1.8 mm、注气速度为3.5 m/s时,分离效率达到最佳,较优化前提高了0.98%。对比倒锥参数优化前后的气举式水力旋流器油核分布形态,优化后油核均在倒锥结构上方形成,促进了旋流器分离性能的提升,验证了倒锥参数优化对气举式水力旋流器的重要性。

旋风分离器流固耦合分析与裂纹产生机理探究

高压旋风分离器是压气站天然气出站前的重要净化分离设备,其入口压力高,波动大,内部动力学响应复杂。目前,国内运行中的分离器壳体入口区域多出现微裂纹。为探究旋风分离器内部流场分布情况,研究分离器壳体的动态响应,准确认识分离器入口区域裂纹产生机理,基于有限元法分别计算了稳定和非稳定压力入口边界条件下分离器内部流场分布规律,将流场压力结果通过流固耦合面传递至分离器壳体作为固体域的载荷边界条件,计算分离器壳体的应力和变形。再制作标准试件,以分离器入口区域的应力值作为载荷条件,进行了拉伸和疲劳试验,探寻其入口区域微裂纹产生机理。该研究可为旋风分离器的裂纹预防和工程维护提供理论指导。

CFD numerical simulation of flow velocity characteristics of hydrocyclone

A CFD based numerical simulation of flow velocity of hydrocyclone was conducted with different structural and operational parameters to investigate its distribution characteristics and influencing mechanism. The results show there exist several unsymmetrical envelopes of equal vertical velocities in both upward inner flows and downward outer flows in the hydrocyclone, and the cone angle and apex diameter have remarkable influence on the vertical location of the cone bottom of the envelope of zero vertical velocity. It is also found that the tangential velocity isolines exist in the horizontal planes located in the effective separation region of hydrocyclone. The increase of feed pressure has almost no effect on the distribution characteristics of both vertical velocity and tangential velocity in hydrocyclone, but the magnitude and gradient of tangential velocity are increased obviously to make the motion velocity of high density particles to the wall increased and to make the cyclonic separation effect improved.

基于CPFD方法的生物质燃气旋风分离陶瓷膜一体化除尘器仿真

为缩短高温燃气除尘工艺,提高除尘效率,提出了一种耦合复合陶瓷膜组的一体化旋风除尘器。在温度为573 K的条件下对陶瓷膜的流动阻力进行了实验研究,考察了流量和压力对单个陶瓷膜过膜压降的影响,得到过膜压降与流速之间的关系式,基于计算颗粒流体力学(CPFD)方法模拟了除尘器内部的气固两相流动特性,探讨了生物质燃气除尘过程中内部颗粒的分布规律、速度和停留时间,探究了复合陶瓷膜组对除尘器压降和效率的影响。结果表明:在入口温度为573 K、压力为111325 Pa、进口气体积流量为7909 m^(3)/h的条件下,较之无陶瓷膜组的除尘器,一体化除尘器内部粉尘颗粒的停留时间更长,其对粉尘颗粒捕集效率更高,颗粒聚集性能更好,除尘效率从91.2%提升至99.7%,然而总体压降增大了78 Pa。

高含气井低速叶轮动态气液分离设备参数优化

针对目前高含气井电潜螺杆泵举升效率低的问题,提出一种低速叶轮动态气液分离方法。综合高气油比、低转速、低液量等因素的影响,建立低速叶轮气液分离场气泡运移数学模型和动态气液分离RNG k-ε模型,依据SIMPLE压力-速度耦合算法求解结果,揭示叶片数目、叶片螺距和叶片长度等参数对动态气液分离效率的影响规律,并依据叶轮结构优化正交试验结果,探究转速和含气量等操作参数的敏感性及其对分离效率的影响。研究结果表明:增加叶片数目、叶片螺距和叶片长度时,低速叶轮动态分离效率先增大后减小;叶片数目为15片,叶片螺距为250 mm,叶片长度为420 mm时,分离效率达到最大值81%;增大转速可有效提升低速叶轮动态分离效率,转速由150 r/min提至300 r/min,分离效率由38%显著升至81%;同时低速叶轮动态分离效率随含气量的增加而不断减小,入口含气量由35%增至50%,分离效率则由87%降至63%。所得结论可为适用于电潜螺杆泵的低速叶轮动态气液分离设备的参数优化提供指导。

叶片式气液分离器结构优化

为了研究结构参数对叶片式气液分离器分离性能的影响,采用Realizable k-ε湍流模型和DPM模型,对叶片结构参数进行优化,对叶片式分离器内的气液两相流动进行模拟研究,得到了分离器内速度分布、压力分布以及结构参数对分离效率和压降的影响规律,并通过气液分离试验验证了模拟的可靠性。结果表明:对于本文设计的DN450型叶片式气液分离器,叶片弯曲角度为100°时可有效分离粒径为40μm及以上的液滴,继续增大该参数并无明显效果,且对压降无明显影响;叶片数目为12、叶片倾角为5°、叶片分布锥角为9°时,分离器的分离效率最高且压降最低,处理气量为150 m3/h时,压降低于50 Pa;对于30μm以上的液滴,分离效率可达到90%以上。优化后结构相比于优化前,对于30μm粒径液滴,当处理气量大于90 m^(3)/h时,分离效率可提升最高达到60%,40μm液滴分离效率提升了29%;优化前、后结构压降基本一致。研究成果可为叶片式气液分离器的进一步改进和实际工程应用提供理论依据。

基于相关性分析和响应面法的复合旋流器结构参数优化

为了提高旋流器优化参数的准确性,得到其在结构优化中的最优解,以一种新型复合旋流器为研究对象,基于相关性的单因素分析寻优法,以相关性分析的结果来指导优化范围的选取,提高其结构参数优化范围的准确性。结合响应面优化方法,以分离效率为优化目标,确定旋流器的最优结构参数,建立了分离效率和结构参数之间的回归模型。结果表明:不同的结构参数和各性能指标之间的显著关系并不相同,根据相关性分析的结果确定各结构的优化范围为:上锥角为0°~4°,下锥角为8°~12°,底流口直径为12~16 mm;响应面优化得到旋流器最优结构为:上锥角为2.565°,下锥角为11.719°,底流口直径为12.889 mm,在本组参数下旋流器固体分离效率达到了99.945%,气体分离效率达到了93.807%。为旋流器的结构优化提供了一种新方法。

柴油机复式油气分离器设计与试验验证

设计了一款新型复式油气分离器,采用迷宫式结构作为粗滤组件、滤网作为精滤组件。设计开发了油气分离器部件性能试验台,通过正交试验设计方法设计多方案油气分离器,并基于部件试验台进行多方案性能试验测试。最终设计出满足要求的复式油气分离器,并通过整机试验验证其性能。结果表明,油气分离器综合性能影响因素由强到弱依次为滤网层数、滤网目数、过滤孔孔径、孔数、孔板间距。整机试验发现在300 L/min窜气量下分离效率达到了92.6%,压力损失小于3 kPa,满足发动机使用要求。