Numerical Simulation of Particle Concentration in a Gas Cyclone Separator

The particle concentration inside a cyclone separator at different operation parameters was simulated with the FLUENT software. The Advanced Reynolds Stress Model （ARSM） was used in gas phase turbulence modeling. Stochastic Particle Tracking Model （SPTM） and the Particle-Source-In-Cell （PSIC） method were adopted for particles computing. The interaction between particles and the gas phase was also taken into account. The numerical simulation results were in agreement with the experimental data. The simulation revealed that an unsteady spiral dust strand appeared near the cyclone wall and a non-axi-symmetrical dust ring appeared in the annular space and under the cover plate of the cyclone. There were two regions in the radial particle concentration distribution, in which particle concentration was low in the inner region （r/R≤0.75） and increased greatly in the outer region （r/R〉0.75）. Large particles generally had higher concentration in the near-wall region and small particles had higher concentration in the inner swirling flow region. The axial distribution of particle concentration in the inner swirling flow （r/R≤0.3） region showed that there existed serious fine particle entrainment within the height of 0.SD above the dust discharge port and a short-cut flow at a distance of about 0.25D below the entrance of the vortex finder. The dimensionless concentration in the high-concentration region increased obviously in the upper part of the cyclone separation space when inlet particle loading was large. With increasing gas temperature, the particle separation ability of the cyclone was obviously weakened.

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.

Numerical analysis on the influence of vortex motion in a reverse Stairmand cyclone separator by using LES model

This study aims to analyze the influence of vortex motion in a reverse Stairmand cyclone separator by using LES model.The mathematical analysis indicated that the energy dissipation and the flow characteristics of incompressible fluid are directly related to on the vortex motion.The results of the Q criterion-based iso-vortex surface could well reflect the tendency of the vortex structure,in which the iso-vortex surface exhibited a distorted distribution rather than around the center axis.At the turning point of velocity vector,vortices were formed and developed,and the point was the center of the local vortex core.In addition,the vortex formed an irregular annular region around the wall at the bottom of vortex finder.The vortex structure near the dust hopper presented a strong distortion.Moreover,there were two rotating flow in the opposite direction within the dust hopper.These phenomena would affect the separation performance,which was significance to cyclone separator.

Numerical investigation on dynamic characteristics of flow field in cyclone separators with different dust hopper structures

The dynamic characteristics of flow field in cyclone separators with different dust hopper structures were studied by coupling Reynolds Stress Model(RSM)and Lagrangian Particle Tracking(LPT)methods.The characteristic frequencies of cylinder section,cone section and dust hopper were calculated as f_(1)=53 Hz,f_(2)=65 Hz,and f_(3)=8 Hz by using Fast Fourier Transform(FFT)method,respectively.Based on the effects of f3 on the motion of vortex,the separated space was divided into none affected region,weakly affected region,and strongly affected region.The characteristic frequency of dust hopper increased with the decrease of dust hopper diameter,while it was independent of the height.The dust hopper with d=1.5D(model D3)and h=1.5D(model H3)can significantly decrease the effect of back-mixing on the motion of inner vortex,which is beneficial to improve the efficiency of cyclone separator.

Effects of working parameters on the performance of cyclone separator for rapeseed combine harvester based on CFD

Existing development for cyclone separation cleaning components of the rapeseed combine harvester,which employs the suspending airflow to separate the rapeseeds from the materials other than grain(MOG),has the challenge to figure out the optimal working parameters,highlighting a need for exploration of the invisible airflow based on Computational Fluid Dynamics(CFD).The airflow status was mainly affected by the air velocities of the inlet,and the outlet for the MOG.The single factor and response surface experiments were carried out.It could be found that the inlet and MOG outlet velocities affected the air velocities through the change in the air quantity.Furthermore,the mathematical model of the relationship between the air velocities inside the cyclone and the working parameters was built,and the optimal combination of working parameters was obtained by multi-objective optimization.The inlet and outlet velocities of the optimal combination were 4.25 m/s and 29.87 m/s,respectively.Under this condition,the cleaning ratio and loss ratio of the cleaning device was 94.62%and 5.39%,respectively,as validated by the field experiment.The findings provide references for the improvement of cleaning systems for rapeseed combine harvesters.

Experimental investigation on separation characteristics of axial cyclone separator

Axial cyclone separator has been widely applied in chemical production as an efficient gas-liquid separation device.In this study,a new axial cyclone separator with integrated swirler and exhaust pipe is designed to achieve the development goal of compact structure for advanced engine,and the distribution characteristics of swirling flow patterns as well as the variation in separation characteristics are investigated under slug flow pattern.Based on flow visualizations and fluctuation characteristics of pressure signals,three typical flow patterns,namely,slug flow,swirling intermittent flow,and swirling annular flow,in the horizontal swirling separation flow are characterized.It is investigated how the inlet conditions affect the separation characteristic parameters.The separation purity and extreme points of the air separation efficiency are independent of the inlet liquid flow rate.The separation pressure drop is quadratically related to the inlet air flow rate.Based on the drift-flux model and other methods,the prediction methods for the air separation efficiency and pressure drop are proposed,and the prediction accuracy is within±20%,which may provide instructions for the practical application of axial cyclone separator.

A PARTITIONING PARALLEL PROCEDURE FOR NUMERICAL SIMULATION OF GAS FLOW IN A CYCLONE SEPARATOR

Based on the SIMPLE-C algori thm and the non-overlapping Domain Decomposition Method (DDM), in which the Dirichlet-N eumann alternative algorithm is employed, a partitioning parallel procedure was developed to numerically simulate fluid flow in complex 3-D domains. It can well remove the limitation of speed and capacity of personal computer on large-scale numerical simulation of complex 3-D domains. In this paper, the 3-D turbulent swirling gas flow in cyclone separator was simulated. In view of the physica l reality, the computational results are bascally reasonable.

Numerical simulation of a dense solid particle flow inside a cyclone separator using the hybrid Euler-Lagrange approach

This paper presents a numerical simulation of the flow inside a cyclone separator at high particle loads. The gas and gas–particle flows were analyzed using a commercial computational fluid dynamics code. The turbulence effects inside the separator were modeled using the Reynolds stress model. The two phase gas–solid particles flow was modeled using a hybrid Euler–Lagrange approach, which accounts for the four-way coupling between phases. The simulations were performed for three inlet velocities of the gaseous phase and several cyclone mass particle loadings. Moreover, the influences of several submodel parameters on the calculated results were investigated. The obtained results were compared against experimental data collected at the in-house experimental rig. The cyclone pressure drop evaluated numerically underpredicts the measured values. The possible reason of this discrepancies was disused.

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.

Modeling the gas flow in a cyclone separator at different temperature and pressure

The gas flow field in a cyclone separator,operated within a temperature range of 293 K-1373 K and a pressure range of 0.1-6.5 MPa,has been simulated using a modified Reynolds-stress model(RSM)on commercial software platform FLUENT 6.1.The computational results show that the temperature and pressure significantly influence the gas velocity vectors,especially on their tangential component,in the cyclone.The tangential velocity decreases with an increase in temperature and increases with an increase in pressure.This tendency of the decrease or increase,however,reduces gradually when the temperature is above 1000 K or the pressure goes beyond 1.0 MPa.The temperature and pressure have a relatively weak influence on the axial velocity profiles.The outer downward flow rate increases with a temperature increase,whereas it decreases with a pressure increase.The centripetal radial velocity is strong in the region of 0-0.25D below the vortex finder entrance,which is named as a short-cut flow zone in this study.Based on the simulation results,a set of correlations was developed to calculate the combined effects of temperature and pressure on the tangential velocity,the downward flow rate in the cyclone and the centripetal radial velocity in the short-cut flow region underneath the vortex finder.

STUDY ON THE CHARACTERISTICS OF AGGLOMERATION AND CYCLONE SEPARATION OF DIESEL PARTICULATE

A particulate separation system that can be used to study the characteristics of the diesel particulate agglomeration and cyclone separation is developed It includes a diesel particulate agglomerator and a cyclone separator mainly A preliminary investigation on the cyclone separation tech nology for controlling the exhaust particulate from a diesel engine is conducted The experimental results show that the diameter distribution of the diesel particulate is changed after they pass through the agglomerator,almost 30%～40% o f the particulate agglomerated from less than 1.0μm to larger than 1.0μm ,this change contributes to trap diesel particulate With this system installed on the exhaust pipe of a single cylinder engine,the particulate separation efficiency is around 40%～60% under typical engine running condition The back pressure of this system is less than 5 kPa on full load condition,much less than that of other methods of particulate filtration This technology has the possibility to open a new prospect for particulate reduction because of its simplicity,reliability and low resistance.

Parameter matching and experiment of the combined cyclone separation and cylinder sieve cleaning system for rape combine harvester

Existing rape combine harvester with a cyclone separation cleaning device has the challenge that the loss rate and the cleaning rate increase and decrease simultaneously.A cleaning process route was proposed,which involves the cyclone separation cleaning device removing light and tiny impurities,and the cylinder sieve device removing coarse and long impurities such as pod shells and short stems.A novel cleaning system combining the cyclone separation cleaning device and cylinder sieve cleaning devices was designed.The ranges of the structure and operation parameters for each component were analyzed based on kinematics and dynamic analysis.A four-factor five-level quadratic orthogonal test was carried out,in which the loss rate and cleaning rate were taken as the evaluation indexes.The velocity at the suction port,the rotation speed of the cylinder sieve,the screw pitch of the spiral blade and the diameter of the sieve hole were taken as the influencing factors.The orthogonal test results showed that the cleaning system performed best at a rotation speed of the winnower is 600 r/min,an airflow velocity at the suction port is 18.25 m/s,a rotation speed of the cylinder sieve is 87 r/min,a screw pitch of the spiral blade is 440 mm and a diameter of the sieve hole is 4.48 mm.At this time,the loss rate of the cleaning system is 3.22%,and the cleaning rate is 95.67%.Compared to the conventional cyclone separation cleaning device,the loss rate is reduced by 2.17%and the cleaning rate is increased by 1.05%.This study can provide a reference for the optimal cleaning system design for rape combine harvesters.

Effect of inlet volute wrap angle on the flow field and performance of double inlet gas cyclones

In response to the divergent understanding of double inlet cyclone performance in the literature,the effect of inlet volute wrap angle on the performance and flow field of double inlet cyclone separator was studied by Computational Fluid Dynamic(CFD)method.The results showed that the inlet volute wrap angle can affect the comparison results of the single and double inlet gas cyclones with the same total inlet cross-sectional area and velocity.0°and 90°volute double inlet improved the efficiency mainly by separating particles below 10μm,while 180°volute double inlet had no separation advantage for any particles,so the symmetrical double inlet does not always improve the efficiency,and the appropriate inlet volute wrap angle should be selected according to the actual situation,otherwise,the expected performance requirements of the symmetrical double inlet cyclone cannot be achieved.Compared with the flow field,it is found that the inlet volute wrap angle changed the tangential velocity of the sym-metrical double inlet cyclone separator,thus changing the performance.

Experimental study on sand particles accumulation,migration and separation efficiency in slug catcher

Sand production often leads to the failure of production equipment on offshore platform.Therefore,a new idea has been put forward,which is installing cyclone or baffle in the internal of the slug catcher for better sand control.In this paper,an experimental study is presented,which mainly includes sand particles accumulation shape,migration law and separation performance.The results suggest that the accumulation area is mainly divided into two zones:the crowded settlement zone and the free settlement zone.The crowded settlement zone has a special shape,which can be characterized by two parameters:accumulation length and accumulation angle.Axial sampling analysis shows obvious particle classification.Median particle size decreases with the increase of the axial distance,and the range of particle size distribution narrows gradually.The separation experiment shows that the gas velocity has the greatest influence on the separation efficiency.When the gas velocity is 14 m·s^ 1,the separation efficiency drops sharply,which can be abated by installing cyclone separator.In addition,the separation efficiency tends to be a constant under different gas velocities by installing baffle with appropriate height.Then the effectiveness and rationality of installing internal components can be strongly proved.All these provide important guidance for maximizing the sand control function of the slug catcher.

Cyclonic separation process intensification oil removal based on microbubble flotation

The cyclonic-static microbubble flotation column has dual effects including the cyclonic separation and floatation separation with the characteristics of the small lower limit of the effective separation size, short separation time, large handling capacity, and low operation cost. It shows significant advantages in the oily wastewater treatment field, especially the polymer flooding oily wastewater treatment aspect. In this paper, the cyclonic separation function mechanism of the cyclonic-static microbubble flotation column was studied, the impact of the parameters including the feeding rate, aeration rate, circulating pressure, and underflow split ratio on the cyclonic separation efficiency was investigated, and the cyclonic separation efficiency model was established as well. In addition, by applying the Doppler Laser Velocimeter (LDV) and Fluent simulation software, the test and simulation to the single-phase flow velocity field of the cyclonic separation section of the cyclonic-static microbubble flotation column were carried out, and the velocity distribution rule of the cyclonic separation section was analyzed under the singlephase flow conditions.

Experiment on Vaporization of Jet into Cross-Flow

The injection characteristics of the main fuel nozzle,which is widely applied in advanced lean-premixed-prevaporized(LPP)low-emission combustors,can be simplified as the atomization and vaporization processes of a jet into cross-flow.In this study,a nozzle with a diameter of 0.4 mm is designed and processed through the heating of the inlet air,and the vaporization characteristics are investigated.The optical measurement and cyclone separation methods are separately used to investigate the evaporation rate of a jet into cross-flow.Experimental results show that the fuel evaporation rate in cross-flow is mainly affected by the Weber number(We),equivalent ratio(φ),momentum rate of fuel to air(q),and air temperature.In addition,the inlet temperature is a crucial factor for the evaporation ratio of a jet into cross-flow.The evaporation results measured by two different methods in the same cross-flow are very close to each other with a deviation within 10%.

ANALYSIS ON CYCLONE COLLECTION EFFICIENCIES AT HIGH TEMPERATURES

In order to predict the influence of operating temperature on cyclone performance, an experimental investigation on particle separation was conducted in a 300 mm diameter, tangential volute-inlet and reverse flow cy-clone separator with air heated up to 973 K. The test powder silica has a mean mass diameter of 10 microns and the inlet velocity ranges from 12 m.s-1 to 36 m-s-1. Both the overall efficiency and fractionai efficiency of the cyclone were measured as a function of the inlet velocity and operating temperature. It is shown that at the same inlet velocity both the overall efficiency and fractionai efficiency decrease with an increase of temperature. An analysis of our own data and published results has shown that the fractionai efficiency of a cyclone is a defmite function of such dimensioniess numbers as Stokes number, Reynolds number, Froude number and dimensioniess cyclone inlet area and dimensioniess outlet diameter. A nondimensionai experimental correlation of the cyclone performance, including the influence of the temperature, was obtained on the basis of our own previous work. The prediction of the influence of temperature on separation efficiencies is in fairly good agreement with experimental results.

STUDY OF AXIAL VELOCITY IN GAS CYCLONES BY 2D-PIV,3D-PIV,AND SIMULATION

The axial velocity distribution in a gas cyclone has been examined with two-dimensional particle image velocimetry （2D-PIV） and three-dimensional particle image velocimetry （3D-PIV） experiments in this study. Due to the limitation of 2D-PIV configuration, the contamination generated by the strong tangential velocity in the cyclone can be registered in the axial velocity detected by 2D-PIV. Efficient methods are proposed in this work to remove this contamination. The contamination-removed 2D-PIV data agree well with 3D-PIV results. The distributions of the axial velocity are also computed by the Reynolds stress model （RSM） and verified using the PIV experimental results. Reasonable agreements are obtained.

Numerical analysis of non-Newtonian rheology effect on hydrocyclone flow field

In view of the limitations of the existing Newton fluid effects on the vortex flow mechanism study,numerical analysis of non Newton fluid effects was presented.Using Reynolds stress turbulence model(RSM)and mixed multiphase flow model(Mixture)of FLUENT(fluid calculation software)and combined with the constitutive equation of apparent viscosity of non-Newtonian fluid,the typical non-Newtonian fluid(drilling fluid,polymer flooding sewage and crude oil as medium)and Newton flow field(water as medium)were compared by quantitative analysis.Based on the research results of water,the effects of non-Newtonian rheology on the key parameters including the combined vortex motion index n and tangential velocity were analyzed.The study shows that:non-Newtonian rheology has a great effect on tangential velocity and n value,and tangential velocity decreases with non-Newtonian increasing.The three kinds of n values(constant segment)are:0.564(water),0.769(polymer flooding sewage),0.708(drilling fluid)and their variation amplitudes are larger than Newtonian fluid.The same time,non-Newtonian rheology will lead to the phenomenon of turbulent drag reduction in the vortex flow field.Compared with the existing formula calculation results shown,the calculation result of non-Newtonian rheology is most consistent with the simulation result,and the original theory has large deviations.The study provides reference for theory research of non-Newtonian cyclone separation flow field.

OIL/WATER SEPARATION IN A LIQUID-LIQUID CYLINDRICAL CYC-LONE

The oil/water separation in a liquid-liquid cylindrical cyclone is experimentally studied in this article.The effects of the flow split-ratio and the flow rate on the oil/water separation performance are determined.From the experimental results,it is shown that with the increase of the flow split-ratio,the oil/water separation efficiency is enhanced at first,and an optimal flow split-ratio exists,beyond that optimal split-ratio,the watercut in the underflow keeps constant,while the oil content in the overflow begins to decrease.The process of the oil core structure formation and the phase distribution in the cyclone are determined by numerical simulations.Furthermore,the dependence of the separation efficiency on the Reynolds number and the flow split-ratio is investigated based on a dimensional analysis.A comparison between the predicted values and the experimental data shows a good agreement.