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Khairy Elsayed - One of the best experts on this subject based on the ideXlab platform.
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Studying the effect of Vortex Finder eccentricity on the gas cyclone performance
Engineering Research Journal, 2019Co-Authors: Shimaa Helmy, Khairy Elsayed, Momtaz SedrakAbstract:In this study, cyclone separator, with nine different Vortex Finder eccentricities are simulated computationally (CFD). The numerical technique is based upon solving three dimensional, incompressible, turbulent flow governing equations using the Reynolds stress turbulent model. The results show that moving the Vortex Finder eccentricities in two directions is more effective than moving it in one direction only. Case 5 achieves the lowest pressure drop where the Vortex Finder eccentricity is moved in the positive x and y directions toward the cyclone inlet. It is found that moving the eccentricities in both x, y directions towards the cyclone inlet reduces the pressure drops by 31% and decreases the collection efficiency by 17.4% compared to case 0 (where the Vortex Finder is concentric in the cyclone centerline).
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Impacts of the Vortex Finder eccentricity on the flow pattern and performance of a gas cyclone
Separation and Purification Technology, 2017Co-Authors: Farzad Parvaz, Seyyed Hossein Hosseini, Goodarz Ahmadi, Khairy ElsayedAbstract:Abstract The impact of eccentricity of the Vortex Finder with deviations in the range of 4–10% on the flow pattern and performance of gas cyclone was studied. The Eulerian-Lagrangian approach in conjunction with the Reynolds stress turbulence model (RSM) of the ANSYS-FLUENT 15 code was used in these simulations. It was found that with increasing deviation of Vortex Finder up to 10%, the tangential velocity was increased. The maximum tangential velocity obtained for the radial profiles was 1.8 times that of the inlet velocity and the lowest tangential velocity was 1.58 times that of the inlet velocity. The maximum periodic variation in axial and tangential velocities was in the free Vortex (central portion of the cyclone). It was shown that increasing the eccentricity of the Vortex Finder led to an increase in the intensity of oscillation of the axial velocity. For 6% eccentricity, the axial velocity was reduced due to a decrease in the oscillation rate downstream of the cyclone, which is a major factor affecting the cyclone performance. The pressure drop was also increased with increasing eccentricity of the Vortex Finder. It was found that the gas cyclone with an eccentricity of 8% was more efficient for droplets larger than 1 µm. In this case, also the liquid film flow does not occur on the cyclone wall.
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Design of a novel gas cyclone Vortex Finder using the adjoint method
Separation and Purification Technology, 2015Co-Authors: Khairy ElsayedAbstract:Abstract Gas cyclones have many industrial applications in solid–gas separation. The Vortex Finder is an essential part in gas cyclones where the shape and diameter highly affect the cyclone performance. Many optimization studies have been conducted to optimize the cylindrical Vortex Finder diameter. This study introduces a new Vortex Finder shape optimized for minimum pressure drop using the discrete adjoint method. The new optimum cyclone will save 66% from the driving power needed for the Stairmand cyclone. To efficiently perform the grid independence study for the new cyclone, a new framework using the adjoint solver and the grid convergence index is proposed and tested. The proposed framework relies on local mesh adaptation instead of the global mesh refinement approach. A comparison of numerical simulation of the new cyclone and the Stairmand cyclone confirms the superior performance of the new Vortex Finder shape for the pressure drop and the cut-off diameter. The results of this study open a new era gas cyclones geometry optimization by using the adjoint method instead of the traditional surrogate based optimization technique. Moreover, the computational costs for the grid independence studies will be reduced via the application of the adjoint methods.
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The effect of cyclone Vortex Finder dimensions on the flow pattern and performance using LES
Computers & Fluids, 2013Co-Authors: Khairy Elsayed, Chris LacorAbstract:Abstract The effect of the Vortex Finder dimensions (both the diameter and length) on the performance and flow field pattern in nine cyclone separators has been investigated computationally using the large eddy simulation (LES). The Vortex Finder diameter varies from 0.3 to 0.5 times the cyclone diameter. The Vortex Finder length varies from 0.5 to unity times the cyclone diameter. Decreasing the Vortex Finder diameter by 40% results in 175% increase in the dimensionless pressure drop (Euler number) and 50% decrease in the Stokes number. Doubling the Vortex Finder length increases both the Euler number and the Stokes number by 25%. Decreasing the Vortex Finder diameter causes a gradual change in the axial velocity profile from the inverted W to the inverted V profile accompanied with 73% increase in the maximum axial velocity. The maximum tangential velocity approaches asymptotically 1.6 times the inlet velocity (25% increase) when decreasing the Vortex Finder diameter by 40%.
Jin You-hai - One of the best experts on this subject based on the ideXlab platform.
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Effects of Slotted Vortex Finder on Cyclone Tube's Separation Performance
Chemical Engineering & Machinery, 2011Co-Authors: Jin You-haiAbstract:Effects of slotted area ratio and position of Vortex Finder on pressure drop and separation efficiency of cyclone tube were analyzed.The results show that the slotted Vortex Finder can reduce cyclone tube pressure drop while separation efficiency rises;and the slotted area ratio increase can lower this pressure drop.Separation efficiency of over 5μm particles is the highest while slotted area ratio reaches 3.0.The slotted Vortex Finder with slots at its lower part can improve operational flexibility of the cyclone tube.
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The Optimization of Slotted Vortex Finder in PSC Cyclone Tube Based on Flow Field Control
Journal of Chemical Engineering of Chinese Universities, 2010Co-Authors: Jin You-haiAbstract:Experimental and computational fluid dynamics were conducted to evaluate the effects of the slots area on the cyclone performance and flow field of the cyclone with slotted Vortex Finder. The results show that the flow ratio of gas running into the exhaust pipe through the slots on the Vortex Finder increases with the increase of the slots area, while the flow ratio changes to keep constant when the slots area ratio is more than 2.9. The short circuit flow ratio is reduced by the slotted Vortex Finder and keeps to be less than 5% of the inlet flow when the slots area ratio is more than 1.94. The tangential velocity, axial velocity and centripetal radial velocity in separation region decrease as the slots area increases. The cyclone separator pressure drop decreases with the increase of the slots area, and the slots area has greater influence on the pressure drop in the internal swirl region and in the exhaust tube. It was found that the optimal range of the slots area ratio is 1.94~2.9. The experimental results show that, when the inlet gas flow rate is 2380 m3·s-1 and the inlet SiO2 particle concentration is 1 g ·m3, the separator with slotted Vortex Finder has about 3% higher collection efficiency; and about 73% energy cost can be reduced by using the slotted Vortex Finder with the inlet gas flow rate of 1000~2500 m3·s-1.
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CFD Analysis on Collection Performance of Swirl Tube with Different Vortex Finder Geometries
Computer Simulation, 2009Co-Authors: Jin You-haiAbstract:The pressure drop and collection efficiency of a swirl tube with different Vortex Finder geometries were studied numerically. The gas flow fields were simulated by means of Reynolds Stress Model (RSM). The effect of instantaneous turbulence on particle tracking was taken into account with the stochastic tracking approach in discrete phase model (DPM). The flow behavior near Vortex Finder in swirl tube was proposed,and the changes of flow field and pressure distribution in swirl tube caused by different Vortex Finders also could be predicted by CFD simulation. The results indicate that the decrease of Vortex Finder diameter leads to higher tangential velocity,which helps to improve the separation efficiency. The back flow can be observed in converging coned-shaped Vortex Finder,which causes the energy loss through swirl tubes,meanwhile the diverging coned-shape Vortex Finder can make the flow move smoothly to reduce pressure drop. Results obtained from the computer modeling have demonstrated the CFD is suitable for modeling an effect of Vortex Finder dimension in swirl tube on its performance.
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Numerical simulation of the gas phase flow field in inlet annular space of a guide vane cyclone tube
Petro-chemical Equipment, 2006Co-Authors: Jin You-haiAbstract:With the help of Fluent software and Reynolds Stress Model,numerical simulation was performed on three-dimension strong swirling turbulent flow within a guide vane cyclone tube with slotted Vortex Finder.Specially,numerical results for the gas phase flow field in the inlet annular space and the Vortex Finder were compared with available experimental data,good agreement was obtained between the predictions and the experiments.Part of gas enters the Vortex Finder through lathy gaps to realize the gas shunt.Interaction between two tubulent flow in different directions make rolling velocity of gas flow decline in Vortex Finder.
Youhai Jin - One of the best experts on this subject based on the ideXlab platform.
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Performance evaluation of a new cyclone separator – Part II simulation results☆
Separation and Purification Technology, 2016Co-Authors: Jianjun Wang, Youhai JinAbstract:Abstract A novel Vortex Finder (slotted Vortex Finder) was designed to improve cyclone separator performance. The gas flow in axial-inlet cyclone separator with the novel Vortex Finder is simulated by means of Reynolds Stress Model (RSM). The computational results of the flow patterns in cyclone separator are compared with the experimental ones, and the results show that RSM offers a robust, reliable modeling option for such flows. Three dimensional gas flow simulation results indicate that the gas flow exits the separator through two pathways. One part of the gas spirals down from outer annular space to outer separation space and dust hopper, then spirals upward in the inner part of separator, and finally exits the separator. The other gas flow enters the vent pipe through the slots in Vortex Finder rather than entering the separation space. The simulation results show that the latter part flow accounts for 54% of the total gas flow. Diversion of gas pathways has three advantages. Firstly, the 54% of the gas–solid flows can be separated by slots due to the novel Vortex Finder. Secondly, the results also indicate that there are almost no short circuit flows under the inlet of the slotted Vortex Finder. Thirdly, the slotted Vortex Finder reduces the flow swirling intensity and undesired instabilities, and thus the slotted Vortex Finder can reduce pressure drop.
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Performance evaluation of a new cyclone separator – Part I experimental results
Separation and Purification Technology, 2015Co-Authors: Jianjun Wang, Youhai JinAbstract:Abstract This paper presents the gas flow characteristics of a guide-vane-inlet cyclone separator with a novel Vortex Finder. The new design is based on the idea of increasing cyclone efficiency and reducing pressure drop by improving Vortex Finder structure. Instead of traditional vent pipe, the Vortex Finder is slotted on side wall. A model of cyclone with this novel Vortex Finder has been manufactured and tested. Total collection efficiency, grade collection efficiency and pressure drop were measured at various flow rates. Experimental results show that the novel Vortex Finder can increase particle collection efficiency and reduce pressure drop.
Jianjun Wang - One of the best experts on this subject based on the ideXlab platform.
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Performance evaluation of a new cyclone separator – Part II simulation results☆
Separation and Purification Technology, 2016Co-Authors: Jianjun Wang, Youhai JinAbstract:Abstract A novel Vortex Finder (slotted Vortex Finder) was designed to improve cyclone separator performance. The gas flow in axial-inlet cyclone separator with the novel Vortex Finder is simulated by means of Reynolds Stress Model (RSM). The computational results of the flow patterns in cyclone separator are compared with the experimental ones, and the results show that RSM offers a robust, reliable modeling option for such flows. Three dimensional gas flow simulation results indicate that the gas flow exits the separator through two pathways. One part of the gas spirals down from outer annular space to outer separation space and dust hopper, then spirals upward in the inner part of separator, and finally exits the separator. The other gas flow enters the vent pipe through the slots in Vortex Finder rather than entering the separation space. The simulation results show that the latter part flow accounts for 54% of the total gas flow. Diversion of gas pathways has three advantages. Firstly, the 54% of the gas–solid flows can be separated by slots due to the novel Vortex Finder. Secondly, the results also indicate that there are almost no short circuit flows under the inlet of the slotted Vortex Finder. Thirdly, the slotted Vortex Finder reduces the flow swirling intensity and undesired instabilities, and thus the slotted Vortex Finder can reduce pressure drop.
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Performance evaluation of a new cyclone separator – Part I experimental results
Separation and Purification Technology, 2015Co-Authors: Jianjun Wang, Youhai JinAbstract:Abstract This paper presents the gas flow characteristics of a guide-vane-inlet cyclone separator with a novel Vortex Finder. The new design is based on the idea of increasing cyclone efficiency and reducing pressure drop by improving Vortex Finder structure. Instead of traditional vent pipe, the Vortex Finder is slotted on side wall. A model of cyclone with this novel Vortex Finder has been manufactured and tested. Total collection efficiency, grade collection efficiency and pressure drop were measured at various flow rates. Experimental results show that the novel Vortex Finder can increase particle collection efficiency and reduce pressure drop.
Tao Song - One of the best experts on this subject based on the ideXlab platform.
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CFD simulation of hydrocyclone-separation performance influenced by reflux device and different Vortex-Finder lengths
Separation and Purification Technology, 2020Co-Authors: Jinyi Tian, Tao Song, Jianing ZhaoAbstract:Abstract Hydrocyclone has a history of approximately 129 years, and its separation performance is closely related to its Vortex-Finder length. To date, however, most studies have been limited to the range of from 0 to cylindrical-section length, and almost all researchers argue that the optimum Vortex Finder is shorter than the cylindrical-section length. To comprehensively study the effect of Vortex-Finder length and understand its mechanism, a hydrocyclone with reflux device and Vortex-Finder length of from 0 to twice cylindrical-section length was studied with FLUENT. Reynolds Stress Model and Discrete Phase Model were used. Results showed that, when the Vortex-Finder length was not longer than the cylindrical-section length, both the separation efficiency and split ratio were proportional to the Vortex-Finder length in general. This was consistent with the sandy-water experimental results obtained by Ni et al. in 2017. When it was just a little longer than the cylindrical-section length, they first decreased and then increased slightly with increase of the Vortex-Finder length due to effect of the cylindrical-conical interface. When the Vortex-Finder length was long enough, the separation efficiency was always close to 100%, whereas the split ratio was inversely proportional to the Vortex-Finder length. Because at this time, the axial distance between two minimum-pressure positions in the centric-axial direction was inversely proportional to the Vortex-Finder length, and it was so small that the fluids on the two positions could attract each other. Even at the Vortex-Finder length of 475–535 mm, they were combined into one. Consequently, some “circulation eddies” appeared near bottom of the Vortex Finders with length of 415–535 mm and near top of the underflow pipe at the Vortex-Finder length of 535 mm. Besides, the high separation efficiency (99.87–100%) and low split ratio (29.13–32.54%) were simultaneously obtained when the Vortex-Finder length was 1.68–2.02 of cylindrical-section length.
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Response surface method to study the effect of conical surface and Vortex-Finder lengths on de-foulant hydrocyclone with reflux ejector
Separation and Purification Technology, 2020Co-Authors: Tao Song, Yang YaoAbstract:Abstract The structure of the hydrocyclone always changes with the application scene due to its excellent separation performance. A de-foulant hydrocyclone with a reflux ejector (DFHRE) has a completely different flow field structure from that of a conventional one. Under the effect of the reflux ejector, DFHRE has the function of overflow-suck-underflow to achieve continuous discharge and high separation performance. To further improve its separation performance, an inner conical surface was added to control the turbulence intensity, and the suction angle and Vortex-Finder insertion depth were adjusted to control the intensity of the overflow-suck-underflow. The single factor method and response surface method (RSM) were used to conduct experiments through general-purpose polystyrene particles (GPPS) water and sewage. The results show that the separation performance of DFHRE first increased and then decreased as the lengths of conical surface Lc and Vortex-Finder Lv increase, whereas the separation efficiency and the energy consumption changed monotonically with the increase of suction angle α. For the results of RSM, these three factors (Lc, α, Lv) had significant effects on maximizing separation efficiency and minimizing split ratio, whereas their combined effects were not significant. Finally, the maximum separation efficiency and minimum total pressure drop optimized by the RSM model are 94.62% and 1.09 kPa, respectively. The optimal values of Lc, α, and Lv was 0.29 (height ratio of inner conical surface to that of the outer cone), 30°, and 0.50 (length ratio of the Vortex-Finder insertion to the total of cylinder-cone), respectively. Therefore, these three factors must be fully considered for designing DFHRE, and the insertion depth of the Vortex-Finder can exceed the interface of the cylinder and cone but not too much, which is different from that of the traditional hydrocyclone.
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Numerical analysis of the flow field and separation performance in hydrocyclones with different Vortex Finder wall thickness
Powder Technology, 2019Co-Authors: Qiang Zhao, Tao Song, Baoyu Cui, Dezhou Wei, Yuqing FengAbstract:Abstract High separation sharpness of hydrocyclones is an ultimate goal for the classification process and has attracted considerable attention. The existence of some special flow patterns, such as short-circuit flow and circulation flow, play an important role in the separation process and have not been clearly understood. This paper presents a numerical study of the effects of Vortex Finder wall thickness on the flow field and separation performance. More importantly, the formations and effects of short-circuit flow, circulation flow, and axial velocity wave zone (AVWZ) were investigated and understood. The simulation results were analyzed in terms of pressure drop, water velocity, separation efficiency, and particle distribution. The results indicate that a thicker Vortex Finder wall could reduce pressure drop, tangential velocity magnitudes, and the flow rates of both short-circuit flow and circulation flow but increase the fluctuations of axial and radial velocities especially beneath the Vortex Finder where the AVWZ is formed. The leakage effect of short-circuit flow on sub-coarse particles is less significant than the fluctuation effect of AVWZ. The circulation flow in pre-separation space is beneficial to re-separate the sub-fine and sub-coarse particles to improve the separation sharpness. Consequently, the hydrocyclone with a thin-walled Vortex Finder is more beneficial for efficient classification.
