Centrifugal Force Field Research Articles

A method for the approximate determination of microparticle amount and mass in biological mixtures using a fractionation process in a centrifugal force field

The paper presents a simplified method of estimating the amount and specific mass of microparticles in complex biological mixtures using the fractionation process in the field of centrifugal forces. In the presented method, using the heaviest blood cells – erythrocytes – as an example, a geometric model of a binary fraction in a borderline equilibrium state formed in the process of blood fractionation was used. In this model, an approximated shape of the erythrocyte and a sample normal distribution of the size and number of microparticles in the examined model fraction filled with erythrocytes were used. Based on publicly available blood data, it has been shown that it is possible to estimate the amount and specific weight of microparticles. The accuracy of such estimation generally depends on the precision of representation of shapes, the degree of filling the fraction with microparticles and on the individual quantitative and dimensional distribution of these particles in the examined fraction. The above conclusions, which determine the accuracy of the method presented, were verified in the paper with the use of rheological blood data, commonly available in literature for various types of measuring containers, which affect the level of filling of a given fraction with microparticles. Keywords: fractionation of biological mixtures, fractionation of blood components, erythrocyte model, erythrocyte shape, blood components

Estimation of the Fluid Velocity Profile in the Stratification Zone of a Falcon Concentrator

The Falcon concentrator is capable of separating minerals in fine size classes based on their differential density. Separation of mineral particles depends upon the fluid flow characteristics and relative movement of particles in a fluid. In the present study, a fluid flow characteristic inside the Falcon concentrator was established through experimentation and modeling. The Falcon concentrator has two fluid entry points: (a) Fluid entering through gravity assisted feeding system and (b) Fluid entering through the fluidized hole on the concentrator wall. In order to identify the role of fluid entering the concentrator, a tracer was injected into the system. As per the tracer based experimentation, it was established that fluid entering through the gravity based feeding system is responsible for thin flowing film formation in the stratification zone where particles are stratified based on their relative density. The momentum balance and continuity equations were simplified for a high centrifugal force field, and the fluid velocity profile was estimated inside the thin flowing film. Estimated fluid flow profiles will help to simulate the particle trajectories inside the Falcon concentrator. The influence of rotational speed, fluid flow rate, and cone angle on the fluid velocity profile were investigated. Fluid thickness over the concentrator wall is also estimated, and it is typically of the order of ~150–200 μm.

Development of a methodology for predicting particle attrition in a cyclone by CFD-DEM

Cyclones are commonly used in the process industry to separate entrained particles from gas streams. Particles entering a cyclone are subjected to a centrifugal force field, driving them to the cyclone walls, where they experience collisional and rapid shearing stresses. Consequently, particle attrition and erosion of the cyclone walls occur, depending on the mechanical properties of the particles and cyclone walls.In this work, the attrition of manganese oxide particles, intended for use in the Chemical Looping Combustion (CLC) process, flowing through a standard design cyclone (Stairmand design) is analysed as an example by considering surface damage processes of chipping and wear. A new methodology is developed, whereby Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations are used to analyse the particle motion and interactions with the cyclone walls. The approach is then coupled with breakage models of chipping and wear to predict the extent of attrition.The impact breakage due to chipping is evaluated experimentally first as a function of particle size and impact angle and velocity. The data are fitted to the chipping model of Ghadiri and Zhang. The model is then coupled with the frequency of collisions and impact velocity, obtained from the CFD-DEM simulation, to work out the particle attrition by chipping. For surface wear the model of Archard is used to account for particle wear by shearing against the walls. The outcome of the work provides a methodology for describing the extent of attrition in different regions of the cyclone.

Numerical Investigation of Stress-Strain State of Composite Compressor Blades in the Field of Centrifugal Forces

In this paper, based on the technical theory developed by the article contributors and the theory designed for twisting of a composite laminated rod of any cross section, a computer program for numerical stress-strain analysis of laminated composite blades in the centrifugal forces field is presented. The naturally twisted laminated composite blade is considered to be under the combined action of the tensile stresses, bending and twisting moments or under the influence of centrifugal forces. In the program, the technological problem of blade unfolding into petals is solved. These petals lie in planes which are parallel to the rod axis and appear due to the varying cross-section along the length of the blade. The investigated blade is represented with eight sections. The results of research on stress-strain behaviour of boron aluminium laminated compressor blades which operate in the fields of centrifugal forces are analysed.

Effect of centrifugal casting process on mold filling and grain structure of K418B turbine guide

Due to the complicated geometry and thin wall of the turbine guide, some casting defects such as misrun and coarse columnar grains are usually produced during the gravity investment casting process, which have a close relationship with the mold filling and melt solidification processes. In this study, the filling and solidification processes of K418B nickel-based superalloy turbine guide under centrifugal casting condition were studied by numerical simulation with ProCAST software, and the actual pouring experiment was carried out to verify the filling integrity and grain structure of the castings. The results show that the pouring temperature of 1540 °C and centrifugal velocity of 150 rpm were beneficial to the complete mold filling of the guide castings, and the misrun defects at the exhaust sides of the guide were completely eliminated. At the same time, under the action of centrifugal force field, the coarse columnar grains perpendicular to the exhaust sides of the guide vanes were replaced by the fine equiaxed grains, which might help for improving the comprehensive mechanical properties of K418B turbine guide.

VORTEX GAS SEPARATORS DESIGN OPTIMIZATION

Currently, one of the ways to intensify oil production is to increase the depression to the reservoir by reducing the bottomhole pressure, usually to values below the saturation pressure. Therefore, a gas-liquid mixture is formed in the well, and gas separators are included in the composition of the electric centrifugal pump installations. However, with an increase in flow rate, firstly, the time spent by the gas-liquid mixture in the field of centrifugal separator forces decreases and the separation efficiency decreases. Secondly, the removal of rock particles increases, especially in wells after hydraulic fracturing, which, under the action of centrifugal forces, accumulate at the walls of the gas separator housing, which leads to their hydroabrasive destruction. A possible solution of this problem is the use of vortex gas separators, which use a shortened separation unit (screw), after which, downstream, there is a vortex chamber, where the liquid continues to rotate by inertia. Initially, vortex separators were designed to reduce the hydroabrasive effect of rock particles on the hull through the use of shorter screws. The purpose of this work is to solve the problem of optimizing the design of vortex gas separators. We have proposed a dimensionless criterion that determines the value of the separation ratio of gas separators depending on the geometrical dimensions of the vortex chamber, the operating conditions: gas concentration and shaft rotation frequency. Bench tests of three new designs of vortex gas separators in 5, 5A and 6 dimensions were carried out, showing that the dependence has a relatively narrow maximum which allows choosing the optimal dimensions of the vortex chamber for the given operating conditions.

Process Intensification in a Gas–Solid Vortex Unit: Computational Fluid Dynamics Model Based Analysis and Design

The process intensification abilities of gas–solid vortex units (GSVU) are very promising for gas–solid processes. By working in a centrifugal force field, much higher gas–solid slip velocities can...

Investigation on fabrication and property of graded composites obtained via centrifugal casting in the magnetic field

The development of a modern technique allowing to gain the gradient composites is of both practical and scientifically importance. The one presented in this paper is based on combines three operations: magnetic fields, centrifugal acceleration, and slip casting. The paper presents the production of gradient composites from the ceramic-metal system by an innovative method. The focus was on investigating the influence of the solid phase content in the composite slurry on their rheological properties and, consequently, their influence on the structure of the obtained composite material. It was observed that simultaneous action of centrifugal force and strong magnetic field results in obtaining a characteristic material structure with nickel particle chains. The content of the solid phase in the slurry affects its viscosity, which, along with its increase, changes the character of the distribution of the metallic chains in the volume of the material. The article proposes a model for the formation of such a structure. These studies are a great basis for further attempts to create the gradient structures desired for given properties.

Separation performance of mechanical flotation cell and cyclonic microbubble flotation column: in terms of the beneficiation of high-ash coal fines

ABSTRACT Separation performance of mechanical flotation cell and cyclonic microbubble flotation column (FCMC) was compared in terms of the beneficiation of high-ash coal fines that has the characteristics of the content of <0.045 mm accounting for more than 50% of the flotation feed and the ash content of <0.045 mm being more than 50%. The optimal experimental results of the mechanical flotation were determined as the flotation perfection index η of 47.37%, the clean coal yield of 39.19% and the clean coal ash content of 10.78% at the feed pulp concentration of 40 g/L through twice explorative flotation experiments and the orthogonal experiment. It was found that the ash content of the clean coal had a strong dependence on the feed concentration. In contrast, the yield of the concentrate of the column flotation was increased to 43.26% with the lower ash content of 9.47% and the higher η of 54.51% even at higher feed concentration of 60 g/L. The remarkable separation efficient of the FCMC flotation column for the difficult-to-float coal slime that has the characteristics of high content of fine particles with high ash was attributed to the presence of the centrifugal force field, more microbubbles generated by hydrodynamic cavitation, the form of countercurrent mineralization, and thicker froth layer.

The Vacancy Cluster Tubes Formation and Metal Properties Changes After Dynamic Centrifugal Casting

Presents experimental results of Al and Pb metals crystallization carried out under high intensity plastic deformation (HIPD) [e′ = (102–104) sec-1] reaching the level of so called «solid-liquid» state in the new type of centrifugal casting device at rotor speeds of up to 2000 rpm. Using the method of atomic force microscopy (AFM), vacancy cluster tubes (VCT) with average diameters of 39 nm for Al and 25 nm for Pb have been detected in the crystallized volume of Al and Pb metals. Physical model of the formation of a new substructure within the metals in the form of vacancy cluster tubes, received in the process of high-intensive plastic deformation (HIPD) during the process of mass crystallization of Al and Pb melts, and, also the changes in the mechanical, magnetic and superconducting properties of the above metals, which followed this process. When crystallizing Al and Pb under high-intensive plastic deformation (HIPD) of e′ = (102–104) per second type, in high-speed centrifugal casting devices, specially selected modes of metal crystallization are being chosen and special conditions are being created to achieve the dimensional effect of dynamic (shift) re-crystallization. Shift deformation during centrifugal crystallization is caused primarily by a large incline of the temperature field from the periphery (relative to the cold wall of the rotor) to the molten central part of the rotor. The difference in the angular movement velocities of the already-frozen part of the metal (adjacent to the outer surface of the rotor wall) and the central part, where the metal still remains in the molten state, leads to a high-intensity deformation [e′ = (102–104) sec-1] of the crystallized metal melt solidified phase. Since the grain sizes at the crystallized phase initially comprise around tens of nano-meters (approximately crystal nucleation size), it becomes possible to achieve the dimensional effect of the dynamic re-crystallization of a «nanocrystalline» solidified metal at high shift of strain velocities. The «non-equilibrium vacancies» formed this way condense into vacancy clusters, which are formed in the centrifugal force field in the form of vacancy-shaped cluster tubes stretched out to the center of rotation of the rotor. The process undergoes conditions that are considerably different from the «equilibrium» conditions as compared to the ordinary metal crystallization from the melt. Such processes can lead to the formation of highly ordered non-equilibrium states characteristic of non-equilibrium open systems.

1D finite element for modelling of turbine blade vibration in the field of centrifugal forces

The paper deals with the modelling of turbine blade vibrations by means of a novel 1D finite element that has only 16 degrees of freedom. Assuming linear elastic behaviour of the blade material and considering small displacements and strains, the derived blade finite element takes into account the effects of tension, torsion and bending in accordance with the Bernoulli’s hypothesis. Additionally, the finite element interlinks bending and torsion, and respects membrane forces acting on the blade. The derivation of matrices and vectors describing the blade finite element is provided in detail by using the Lagrange’s equations while the effect of membrane forces is included via the virtual work principle. For modelling purposes, the mathematical model of a turbine blade requires only the knowledge of cross-section contour points at several selected sections along the turbine blade axis. On the basis of these points, cross section characteristics including the warping function ar e approximated along the blade axis by means of cubic splines. The advantage of this approach lies in the fact that all the blade cross section parameters are identified before running numerical simulations. The warping function introduced in this paper and derived by variational principle describes cross section warping caused just by torsion of a prismatic rod. For the verification of the proposed 1D finite element, an analysis of modal properties of the turbine blade M6 L-1 manufactured by SKODA-Doosan Pilsen is performed. This is achieved by comparing the lowest natural frequencies and corresponding mode shapes computed by the 1D and 3D models for a standing blade. The results revealed good agreement between both models despite the significant difference in their degrees of freedom. The applicability of the 1D finite element is further demonstrated by analyzing the dependence of natural frequencies on rotor speed.

Metals Property Changes Under Effect of Vacancy-Cluster Structures

The experimental results analysis of a metals property changes under vacancy-cluster structure effects are shown. Two technological approaches of such structures obtaining are considered. The first is a nanopowders compaction under high (up to 5GPa) hydrostatic compression, on example of a Ni nanopowder (70nm). The second is the Al and Pb crystallization under the high-intensity plastic deformation [e¢ = (102-104) sec-1] (НIPD) conditions on the solid-liquid boundary in the centrifugal casting machine with rotary speed up to 2000 rpm. Using the method of atomic force microscopy (AFM), vacancy cluster tubes (VCT) with average diameters of 39 nm for Al and 25 nm for Pb have been detected in the crystallized volume of Al and Pb metals. Discussed the physical model of a new substructure formation within the metals in the form of vacancy cluster tubes, obtained in the process of high-intensive plastic deformation (HIPD) during the process of mass crystallization of Al and Pb and the changes in the mechanical, magnetic and superconducting properties of the above metals, which followed this process. During Al and Pb crystallization under high-intensive plastic deformation (HIPD) range about [e′ = (102–104) sec-1] with specially selected modes of metals crystallization in high-speed centrifugal casting machine the special conditions are being created to achieve the dimensional effect of dynamic (shifting) re-crystallization. Shifting deformation during centrifugal crystallization caused primarily by a large incline of the temperature field from the periphery (relative to the cold wall of the rotor) to the molten central part of the rotor. The difference in the angular velocities of the already-frozen part of the metal (adjacent to the outer surface of the rotor wall) and the central part, where the metal still remains in the molten state, leads to a high-intensity deformation [e′ = (102–104) sec-1] of the crystallized metal melt solidified phase. Since the grain sizes at the crystallized phase initially comprise around tens of nano-meters (approximately crystal nucleation size), it becomes possible to achieve the dimensional effect of the dynamic re-crystallization of a «nanocrystalline» solidified metal at high shift of strain velocities. The ≪non-equilibrium vacancies≫ formed this way condense into vacancy clusters, which are formed in the centrifugal force field in the form of vacancy-shaped cluster tubes stretched out to the center of rotation of the rotor. The process proceeds under conditions far from the equilibrium in comparison with the usual crystallization of the metal from the melt. Such processes can lead to the formation of highly ordered non-equilibrium statescharacteristic of non-equilibrium open systems. Discussed the physical model of a metals vacancy-cluster structures formation at high hydrostatic nanopowders compression (up to 5 GPa) and high-intensity plastic deformation (HIPD) at the stage of Al and Pb alloys mass crystallization during centrifugation. Conclusion of the article is that the high-intensity plastic deformation (НIPD) at the melt crystallization stage against a background of high stationary nonequilibrium vacancies concentration brings to the new type of the elements structure formation - vacancy cluster tubes (VCT). A comparative analysis of mechanical, magnetic and superconducting properties changes for structured metals introduced.

Completely New Gravitational Physics: The Ingenious Outside-Inside Centrifuge Mechanism of Gravity Clarified

The present work implements the idea that gravity is not a fundamental force and that the observed gravitational dynamics is the result of inertial motions within a Keplerian velocity field of the Higgs Quantum Space (HQS), giving mass and ruling the inertial motions of matter-energy. The Higgs theory introduces profound changes in the current view about the nature of empty space. It introduces the idea that a real quantum fluid medium, filling up the whole of space, gives mass to the elementary particles by the Higgs mechanism, an effect analogous to the Meissner effect, giving mass to the photons within superconductors. This HQS necessarily governs the inertial motion of matter-energy and is the locally ultimate reference for rest and for motions. The HQS materializes the local Lorentz frames (LFs), turning them into local proper LFs, intrinsically stationary with respect to the local moving HQS. This HQS also necessarily is responsible for the gravitational dynamics; because it is mass that creates the gravitational fields. The observed absence of the gravitational slowing of the GPS clocks by the solar field and the absence of light anisotropy with respect to the moving earth are both obvious signatures of the true physical mechanism of gravity. These observations demonstrate that the HQS is circulating round the sun and round earth according to Keplerian velocity fields (GM/r)1/2, closely consistent respectively with the planetary motions and the orbital motion of the Moon. In this Keplerian velocity field the planets are closely stationary with respect to the local HQS and carried by the moving HQS round the sun without the need of a central force field. The Keplerian velocity field of the HQS is the only possible imaginable mechanism able to give rise to the ingenious outside-inside centrifuge mechanism of gravity that creates a central field of centrifugal forces toward the gravitational center on all matter bodies not moving strictly along direct circular equatorial orbits. The Keplerian velocity field of the HQS is shown to appropriately create all the observed effects of the gravitational fields on matter, on light and on clocks.

A review on nanofiber fabrication with the effect of high-speed centrifugal force field

Among the traditional methods for nanofiber fabrication, their inherent defects limit their application in industry. This work presents a simple and novel spinning technology to fabricate nanofiber, which uses a high-speed rotary spinneret called high-speed centrifugal spinning. Unlike electrospinning, the electric field is not required, and it could fabricate nanofiber in bulk from melt or solution materials. This work introduces the mechanism principle and development of high-speed centrifugal spinning. Besides, the high-speed centrifugal spinning is compared with the traditional spinning methods. The jet movement and nanofiber formation process under the action of centrifugal force are explained in detail. The effects of equipment parameters and spinning solution parameters on final nanofiber morphology are presented. These parameters are controllable, they include rotational speed of spinneret, length and diameter of nozzle, spinning solution concentration, spinning solution viscosity and surface tension, and collection distance.

Mathematical Modelling of Shafts in Drives

Propeller shafts of the vehicle's drive transmit a torque to relatively large distances. The shafts are basically long and slender and must be dimensioned not only in terms of torsional stress, but it is also necessary to monitor their resistance to lateral vibration.In the paper, a simple model (of the solved problem) is constructed by the method of physical discretization, which is evident from the nature of the centrifugal force fields' influence on the spectral properties of the shaft. An analytical solving of speed resonances prop shafts test model (whose aim is to obtain values for verification subsequently processed models based on the transfer-matrix method and the finite element method) is performed.

Convection of a heat-generating fluid in a rotating cylindrical cavity subject to transverse vibrations

abstract The goal of this research is to study experimentally and theoretically the influence of transversal vibrations on the average convection of a non-isothermal fluid in a rotating cavity when the rotational frequency and vibration frequency approach each other. The research involves experimental studies of the convection of a heat-generating fluid in a rotating horizontal cylinder with isothermal boundaries subject to translational vibrations, perpendicular to the rotation axis. In the absence of vibrations, at fast cavity rotation the fluid is in an equilibrium state in the centrifugal force field with the temperature maximum at the cavity axis. The excitation of average convection and increase of heat transport is discovered when the vibration frequency is near to the rotation frequency. At some discrepancy between the frequencies, the resonance excitation of azimuthal two-dimensional inertial oscillations of the non-isothermal fluid column takes place. This results in significant decrease of the temperature at the cavity axis. When the frequencies coincide, the vibrations break the axial symmetry of the centrifugal force field. The resulting force field is stationary in the cavity frame and results in an intensive thermal convection; the theoretical analysis of this phenomenon is presented. The dependence of heat transport on the parameters of vibrations is determined both in the case of resonance liquid oscillations and in the case of equal frequencies. The vibrational and the centrifugal mechanisms play the key role in the convection. The transverse vibrations are demonstrated to be an efficient tool for the control of thermal convection in rotating systems.

Innovative design and study of an oil-water coupling separation magnetic hydrocyclone

Traditional oil-water separation hydrocyclone mainly uses different centrifugal force between oil and water to achieve rapid separation. However, with gradual expansion of oilfield polymer flooding, ASP (alkali-surfactant-polymer) flooding, and other oil displacement technologies, viscosity of produced fluid is increasing, and emulsification is serious, then the efficiency of separation is greatly affected. Therefore, it is intended to add another field on the basis of centrifugal force field to realize oil-water separation under a stronger coupling field. Subsequently, concept of magnetic field is introduced into hydrocyclone. High efficient separation of hydrocyclone under the coupling of a centrifugal force field and magnetic field could be achieved, and a kind of magnetic hydrocyclone (MHC) is designed. Structure and separation principle of the MHC are introduced. During the separation process, magnetic particles are subjected to centrifugal force and magnetic force simultaneously, so they could “carry” or “push” part of the oil droplets towards the center of the hydrocyclone through contact and collision between magnetic particles and oil droplets, and ultimately achieve more efficient separation of oil and water. Firstly, the PIV (Particle Image Velocimetry) experiment was carried out. Then numerical simulation of coupling between a centrifugal force field and a magnetic field was conducted on the basis of theoretical calculation. Simulation results indicates that the magnetic force on particles for hydrocyclone having an optimum separation performance is 7.5 × 10−8 N. Initial efficiency was 74.9%, and the efficiency was increased to 98.1% after applying a magnetic field. Through PIV test and numerical simulation analysis, it is found that the MHC has an obvious improvement on oil-water separation effect. It also provides a new idea for separation methods and structure designs of hydrocyclones.

Calculation of the Process of Separation of Insoluble Fluid Systems

In technology and practice, it is often necessary to separate liquid homogeneous mixtures consisting of two phases — solvent and solute. When the densities of the substances differ, gravitational, centrifugal or other type clarifiers can be used for the separation of phases. In the work done based on the example of a water + oil solution, a physico-mathematical model was formulated describing separation of liquid mixtures of this kind in a field of gravity (gravity settler) and in a centrifugal force field (in a liquid centrifuge). Based on the proposed mode of separation of solutions on the considered types of equipment, a numerical simulation is proposed to describe the process of separating the oil phase from the aqueous phase.

The effect of increasing centrifugal acceleration/force and flow rate for varying column aspect ratios on separation efficiency in Counter-Current Chromatography

Increasing column/tubing aspect ratio has been shown in a feasibility study to improve column efficiency when operating in reversed phase mode. This paper contains a thorough investigation on how increases in mobile phase flow and centrifugal force field affect stationary phase retention and column efficiency (as measured by the resolution between adjacent peaks) for columns wound with rectilinear tubing of different aspect ratio. The study uses a Mini CCC instrument operating from 1500 to 2100 rpm (126–246 g) to compare three columns with the same cross-sectional area but different aspect ratio – rectangular horizontal (force field perpendicular to the flat side – aspect ratio 3.125); square (aspect ratio 1.0) and rectangular vertical (flat side parallel with force field – aspect ratio 0.32). Columns are compared by measuring stationary phase retention, resolution and normalized resolution for 3 different mobile phase flow rates 2, 4 and 8 ml/min in both normal phase and reversed phase modes. The results with rectilinear tubing are compared to conventional circular tubing with the same cross-sectional area. The results show that resolution increases with aspect ratio and that at the highest aspect ratio the highest flow rate can maintain a high efficiency only if the highest g-field of 246 g is used. When comparing the rectangular horizontal tubing which gave the best results with conventional circular tubing with the same cross-sectional area a 45% improvement was found in reversed phase mode and a 51% improvement in normal phase mode over the conventional circular cross-section tubing. In other words, a rectangular horizontally wound bobbin with half the length of tubing can achieve the same result as a circular one. These are very significant results for halving separation times analytically or enabling designers to produce new instruments of the same capacity with a much-reduced size.

A new methodology of floatability tests on Polish copper ores based on grain size-density fractions

Ores difficult to enrich require the appropriate methodology of tests on enrichment for the preparation of ore for flotation tests and precise mineralogical analytics. A feature which should differentiate the separated ore samples for flotation tests is not only the size of grains, but also their density. These features reflect the characteristics of real industrial streams directed for flotation. The methodology for separating narrow grain classes by means of sieves applied to date did not guarantee meeting these separation conditions. The article presents a new methodology for examining the copper ore enrichment based on, instead of testing samples in grain classes, testing grain size-density fractions. To conduct these tests, the hydraulic classification in the field of centrifugal force which ensures the separation of grain size-density fractions varied in terms of granulation and density was used. Samples prepared in this way were subjected to flotation tests.