Inside Cyclone Research Articles

Numerical Investigation of Cyclone Separators: Physical Mechanisms and Theoretical Algorithms

AbstractGas‐particle aero‐type cyclones have revolutionized biochemical processes, engineering industries, and environmental pollution protection by effectively separating particles from gas. These devices rely on gravitational energy and centrifugal force to dissipate particle phase energy, but achieving optimal energy efficiency while minimizing pressure drop remains challenging. This has led to the development of various cyclone designs in commercial industries, each with unique energy efficiency characteristics. The intricate gas‐particle flow inside cyclones is a critical issue impacted by cyclone geometry, operating conditions, and media parameters. Advanced numerical simulations have been employed to understand this complex flow pattern better, offering researchers valuable insights into the mechanisms of different cyclone separators. This comprehensive review explores the available numerical methods in the literature on cyclones and their corresponding validations. Computational numerical modeling is a promising technique for predicting cyclone energy efficiency, gas‐particle behavior, and overall performance. This investigation delves into the progress and numerical forms of gas‐particle flow cyclones, examining how different parameters impact cyclone performance and flow patterns within the two‐phase flow. The future developments and challenges that may further promote the development of aero‐type cyclone separators, providing theory and engineering support for future cyclone designs, are also covered. As a result, it can confidently be reported that aero‐type cyclone separators remain a critical component in various industrial sectors, offering energy‐efficient solutions for mitigating environmental pollutants and gas‐particle separation systems. With continued development and research, these devices will undoubtedly shape the future of energy processes and engineering industries, ushering in a new era of sustainability and efficiency.

Relationship between global ocean mixing and coherent mesoscale eddies

Numerous studies have indicated that mesoscale eddies play an important role in diapycnal mixing and drive global water circulation. Although the relationships between eddy surface features and turbulent mixing have been discussed for individual cases of typical eddies, global studies cannot rely on ship-based microstructural measurements. Fine-scale methods have been developed, wherein either the vertical shear of velocity or density strain is used to estimate turbulent mixing. In this study, the turbulent dissipation rate was estimated using strain information from Argo floats trapped in eddies. Spatially averaged estimates revealed the global distribution patterns of the dissipation rates inside the eddies. In addition, the relationships between eddy features (polarity, radius, vertical extent, and aspect ratio) and turbulent dissipation rates were analyzed. Three main conclusions were made from this study. First, turbulent dissipation rates inside anticyclones were generally larger than those inside cyclones. Second, turbulent dissipation rates inside eddies are related to their vertical extent but not to their horizontal scale. For shallow eddies (with a vertical extent less than 250 m for cyclones and 1000 m for anticyclones), the deeper the vertical extent, the larger the turbulent dissipation rate. Finally, the relationship between the eddy aspect ratio and turbulent dissipation rate was characterized by skewness. The average turbulent dissipation rate reached a maximum value when the cyclone aspect ratio was approximately 0.007; conversely, no maximum value was reached for anticyclones. This work establishes a correlation between eddy features and turbulent dissipation rates, which will help guide numerical simulations of mesoscale eddies.

A Numerical Approach to Characterize the Efficiency of Cyclone Separator

Cyclone separators are active filtering devices suitable for a variety of industrial applications from conventional cutting oil pumps to recycling liquids. Since the vortex flow inside cyclones is highly complicated, the performance and flow patterns of these filters should be thoroughly researched. Liquid–solid cyclones mostly use water. Numerical studies on cyclones using higher-viscosity oils are limited. In this study, a liquid–solid cyclone injected with medium-viscosity cutting oil containing various sized-particles was comprehensively investigated. The reliability of computational fluid dynamics (CFD) methods was verified through a comparison with the experimental results. Three models with different geometries were considered for the analysis. One model was used for CFD verification. The other two models involved adding sockets for hopper length extension and changing the shape of the bottom of the hopper. The models that changed the shape of the hopper, thus directly affecting the cyclone performance, were investigated, and each model was qualitatively compared using a validated method. In addition, particle separation efficiency was evaluated by focusing on the velocity distribution to quantitatively confirm the influence of changing the shape of the hopper. The tangential velocity was determined to be similar across all three models, while the axial velocity was different and the change in the velocity of transport of the particles affected the filter function.

Numerical investigations of the flow-field inside cyclone separators with different cylinder-to-cone ratios using large-eddy simulation

The present study aims at investigating numerically the effect of changing height ratios of cylinder and cone on the cyclone performance. Ratios of the cylindrical and conical segments are changed in a way that the total cyclone height remains the same. Eight different models with increasing barrel height viz. H/D = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 (wherein H/D = 4.0 corresponds to the cyclone model without a conical segment) are evaluated. All the cyclones operate at a Reynolds number (based on a body diameter of 0.205 m) of 2.71 · 105. The fluid domain is discretized with Cartesian mesh using Ansys workbench 16.2. The velocity and pressure fields, collection efficiency, and pressure drop in each model are predicted using large-eddy simulation (LES) with standard Smagorinsky model (Cs = 0.1) for sub-grid scales. Conclusive results indicate that increasing the length of the cylindrical segment significantly reduces the pressure drop with a marginal decrease in the collection efficiency. Furthermore, the cylinder-to-cone ratio affects the fluctuating field much more than the mean flow field. The frequency with which the vortex core precesses is also presented for each model.

Turbulence Modelling of a Single-Phase Flow Cyclone Gasifier

The current work aims to make a foundation for an engineering design of a cyclone gasifier to be able not only to predict its flow field with a suitable accuracy but also to investigate a large number of design alternatives with limited computer resources. A good single-phase flow model that can form the basis in an Euler-Lagrange model for multi-phase flow is also necessary for modelling the reacting flow inside a cyclone gasifier. The present paper provides an objective comparison between several popular turbulence modelling options including standard k-e and SST with curvature corrections, SSG-RSM and LES Smagorinsky models, for the single-phase flow inside cyclone separators/gasifiers that can serve as a guide for further work on the reacting multi-phase flow inside cyclone gasifiers and similar devices. A detailed comparison between the models and experimental data for the mean velocity and fluctuating parts of the velocity profiles are presented. Furthermore, the capabilities of the turbulence models to capture the physical phenomena present in a cyclone gasifier that affects the design process are investigated.

South-Eastern Bay of Biscay eddy-induced anomalies and their effect on chlorophyll distribution

The analysis of deep-water glider hydrographic and fluorescence data, together with satellite measurements provides a new insight into eddy-induced anomalies within the South-Eastern Bay of Biscay, during summer. Two cyclonic eddies and a SWODDY have been observed in different glider transects and by means of different sources of satellite data. Vertical profiles reveal complex structures (characteristic of the second baroclinic mode): upward/downward displacement of the seasonal/permanent thermocline in the case of X13 and the opposite thermocline displacements in the case of the cyclones. This is a typical behaviour of mode-water and “cyclonic thinny” eddies. A qualitative analysis of the vertical velocities in the anticyclone indicates that though geostrophy dominates the main water column, depressing the isopycnals, near the sea-surface the eddy-wind interaction affects the vertical currents, favouring Ekman pumping and upwelling. The analysis of the Θ-S properties corroborates that inside cyclones and between the 26 and 27 isopycnals, net downwelling occurs. These two types of intra-thermocline lenses appear to deeply impact the Chl-a fluorescence profiles, since the maximum Chl-a fluorescence is located just below the seasonal thermocline. The mean Chl-a fluorescence was higher in the anticyclone than within the cyclones and the mean for the entire study period; the highest values were observed in the centre of the anticyclone. These results are in agreement with previous findings concerning the SWODDY F90 and surrounding cyclones, located in the South-Western Bay of Biscay. Significant differences in the Θ-S properties of the two cyclonic mesoscale structures have been observed: higher temperatures and lower salinity in the easternmost cyclone. Finally, time variation of the salinity content of the shallowest water masses of the anticyclone (salinity decreasing over time), probably indicates advective mixing processes occurred during the mission.

The Numerical Simulation of the Flow Field in the Underground Hydrocyclone

For preventing sand in underground oil, this paper structures a model of hydrocyclone with the inside cyclone and the outside one seriesing and describes how it works. By the TGrid procedures, the all of the hydrocyclone is meshed with the tetrahedral and the boundary conditions are determined. The methods of Three-dimensional numerical simulation in FLUENT are used to simulate the velocity field distribution, the pressure field distribution, the path lines of the separated medition characteristics of the separated medium and the phase distribution of the medium. The affect of the internal separated medition characteristics to the separated performance is analysed. Through the simulation, it is found that the spiral fin in the hydrocyclone can guide the fluid to produce a vortex flow to meet the purpose of separating the solid-liquid. There is no formation of the air column comparing with the conventional cyclone, so the internal flow field is more stable to conductive to the separation of the media. It provides a basis for the improvement of the cyclone.

Research on Characteristics of Flow Field Inside Tangential Inlet Cyclone Separator by Orthogonal Design Method

The flow field inside cyclone separator is a kind of complex three-dimensional rotation turbulent flow with two-phase separation phenomenon. In order to optimize the structure and shorten the cycle of research and development, it is very essential to find the appropriate calculation method for the flow field inside cyclone separator. In this article, the internal flow field of tangential inlet cyclone separator was simulated and calculated by adopting different calculation model and different numerical simulation scheme by orthogonal design method. And the result was compared with that of existing experiment to find a reasonable method for the simulation of the flow field inside the cyclone. On the basis of standard k-ε model, the numerical simulation scheme was formulated by the orthogonal test method, through the comparison of results, the best combinations are gained; This research result has certain reference value for cyclone separator design and performance optimization.

A CFD study of the effect of cyclone size on its performance parameters

A three-dimensional Eulerian–Lagrangian fluid dynamics (CFD) model was developed to simulate the gas particulate flow inside cyclones with different sizes. Cyclones of different sizes, were used which named as cyclones I, II, and III. Cyclone I was considered as the biggest and cyclone III was considered as the smallest cyclone. The effects of cyclone size and inlet velocity on hydrodynamics behavior and performance parameters including cut-off diameter and pressure drop were investigated. The renormalization group (RNG) k– ɛ model and Reynolds stress model (RSM) were used to study the effect of turbulent modeling. Particle trajectories were calculated via discrete phase model (DPM). The velocity fluctuations were simulated with discrete random walk (DRW) model to study the turbulent dispersion of particles. The cut-off size and pressure drop were increased with increasing the cyclone size. The RSM predicted the cut-off diameter very well with the deviations of 2.3%, 3.4%, and 3.6% of the experimental data, for cyclones I, II, and III, respectively. CFD model was developed using Fluent code to simulate the gas particulate flow inside cyclone. The simulation results also confirmed the applicability of CFD modeling with RSM as a promising tool to study the cyclone size effect on performance parameters.

Gas-particle flow inside cyclone diplegs with pneumatic extraction

This paper presents a detailed flow analysis inside cyclone diplegs equipped with bottom gas extraction. Up to now, little experimental work has been done related with these devices, specially used for hot gas cleaning applications, such as pressurized fluidized bed combustion (PFBC). Tests varying inlet solid loading and gas extraction flow rate were carried out in a one-fifth cold-flow model of a PFBC cyclone. Velocity and pressure measurements along cyclone dipleg have been carried out. Results from experimental measurements reveal that the swirling flow penetrates inside the dipleg, deeper than can be anticipated by literature predictions on conventional cyclone designs. This effect is caused by the high inlet velocities of this kind of cyclones and the gas suction at dipleg bottom. Dipleg pressure coefficient is shown to be a function of the inlet solid loading and the tangential to axial velocity ratio. Although for standard cyclone designs it has been claimed that underneath the vortex end there is a stagnant region where solid recirculation and reentrainment can occur, it has been experimentally verified that even with a small percent of gas extracted at the bottom a substantial tangential velocity component is induced at dipleg bottom. This velocity assures solids conveyance to the extraction device. As solid loading is increased, an upward movement of the vortex end is detected from wall pressure measurements. The solid loading causes an important decrease of the vortex energy and, consequently, a weakening of the dipleg tangential velocity. A new method for measuring the vortex penetration in dipleg is presented.