Centrifugal Force Field Research Articles

Optimization of Performance Characteristics of Magnetofluidic Seals for Wind Power Plants

The use of magnetofluidic seals are a promising direction in sealing rotating shafts of wind power plants. Magnetofluidic seals are characterized by high tightness, simplicity of the design, low losses by friction. Magnetic fluid seal of the rotating shaft consists of a ring magnet and two concentrators of magnetic field, forming with the shaft a narrow ring gap in which the magnetic fluid retained by magnetic field is a hermetic seal. Magnetic forces provide balance of volume of magnetic fluid under the impact of pressure drop and centrifugal forces. With an increase in the speed of rotation of the shaft up to 10 m/s, deformation of the free surface of the magnetic fluid at the surface of the shaft in the form of a funnel is visually observed, which causes a decrease in the retained pressure drop. As the rotation speed increases, the funnel increases, part of the magnetic fluid is ejected from the working area, the retained pressure drop decreases, and at 50 m/s there is a complete release of the magnetic fluid and depressurization of the seal. In order to increase the stability of the free surface of the magnetic fluid in the field of centrifugal forces, multilayer carbon nanotubes were introduced into it. They are characterized by a high specific surface area and, accordingly, a strong Van der Waals attraction. In a magnetic fluid, multilayer carbon nanotubes form structures which are oriented along the magnetic field lines. The following increase in the static load retained by a layer of magnetic fluid has been experimentally determined with the introduction of nanocarbon structures: when coinciding with the axis of the structures the increase was by 100 %, for the normal direction of the load to the axis of the structure – by 50 %. In the seal, with an increase in the shaft rotation speed, deformation of the free surface of a magnetic fluid with nanocarbon structures was observed at 18 m/s at a distance of 3 mm from the shaft surface. The pressure drop retained by the seal increased in the speed range of 10–40 m/s, the maximum effect of 50 % was obtained at a speed of 40 m/s. Thus, the introduction of nanocarbon structures into the magnetic fluid made it possible to reduce the influence of centrifugal forces on the retained pressure drop and increase the efficiency of the magnetofluidic seal at high speeds of rotation of the shaft of wind power plants.

Determination of the maximum droplet diameter during centrifugal extraction, soil analysis, contamination and waste disposal

The prospects of the research are determined by the high potential for solving current problems related to environmental problems. Extraction allows not only the purification of chemical production waste, but also the analysis of elements distributed in the soil, which is especially important for migrating contaminants, and contaminants obtained from chemical, paint and varnish and agricultural waste. Examples of such waste are metals and their compounds, fertilizers and pesticides, and radioactive waste. These contaminants enter the human body through food chains, producing toxic, carcinogenic, and mutagenic effects. This approach has several directions that allow us to solve the problem comprehensively. In the first direction of our research, we will consider how this mathematical model can be applied in waste treatment technologies. In the second direction, we will pay attention to soil analysis. In the third research direction, we will focus on optimizing extraction and waste disposal technologies. This paper considers a mathematical model that describes the formation of the shape of droplets when moving in a field of centrifugal forces. When liquid droplets move within liquid or gaseous media, the surface of these droplets undergoes deformation, which can lead to their destruction and the formation of smaller droplets.

Конструкция экстрактора для реализации процесса экстрагирования из твердых веществ из измельченного растительного сырья

The article highlights a rational design of the extractor for extracting from solids from crushed vegetable raw materials. In the process of developing the extractor the results of numerous experimental and analytical studies, including the analysis of scientific, technical and patent literature, were taken into account. A distinctive feature of the proposed solution is the possibility to extract efficiently during the development of the interfacial surface due to the energy of compressed air, when the air flows are organized in such a way that a field of centrifugal forces is created inside the apparatus. The design of the apparatus also provides unloading of waste crushed raw materials and producing the dehydrated waste raw materials without using mechanically rotating parts (rotor), thereby simplifying the manufacturing process and operation of the device

Determining the rational operating parameters for granite crushing to obtain cubiform crushed stone

Purpose. Determining the rational operating parameters for granite crushing under impact in the field of centrifugal forces to obtain cubiform crushed stone. In order to achieve the purpose set, the task is to determine the operating parameters for obtaining the main grain-size classes: -50.0 + 20.0; -40.0 + 20.0; -20.0 + 10.0; -10.0 + 5.0 and 5.0 mm. Methods. The crushing process of granite crushed stone is studied in the conditions of the Kolomoievskyi Granite Quarry, Dnipropetrovsk region. Granite crushed stone with an initial grain-size of 100.0-0.0 mm and strength grade of M1400 is subjected to crushing. The accelerating rotor rotation frequency is the design value n = 200-1200 min-1. Fine crushing of granite is performed in a centrifugal-impact crusher by a free impact in the field of centrifugal forces. Findings. The optimal speed modes of centrifugal crusher operation, which provide the production of high-quality crushed stone with a maximum content of 90-95% cubiform fractions, have been substantiated. Originality. The yield dependences have been obtained of the grain-size classes: -50.0 + 20.0; -40.0 + 20.0; -20.0 + 10.0; -10.0 + 5.0 and 5.0 mm depending on the speed mode of the centrifugal crusher operation. Practical implications. The operating parameters for obtaining the main grain-size classes of cubiform crushed stone from granite have been determined: -50.0 + 20.0; -40.0 + 20.0; -20.0 + 10.0; -10.0 + 5.0 and 5.0 mm. In particular, it has been determined that for the production of cubiform crushed stone with -50.0 + 20.0 mm grain-size, the rotor rotation reasonable speed is 400-500 min-1 (the speed of material departure from the accelerating rotor is 45-50 m/sec); for cubiform crushed stone of -40.0 + 20.0 mm grain-size, the speed mode is 200 min-1 (25 m/sec); for cubiform crushed stone of -20.0 + 10.0 mm grain-size – 600-650 min-1 (70-80 m/sec), respectively. The maximum content of cubiform fractions in the -20.0 + 10.0 mm grain-size class is 95%, which is achieved at a rotor speed of 650-700 min-1 (departure speed is 75-80 m/sec). The maximum content of cubiform fractions in the -10.0 mm grain-size class is 94-95%, which is achieved at the accelerating rotor speed within 700-800 min-1 (departure speed is 70-80 m/sec). The obtained data make it possible to practically choose a rational speed mode of the centri-fugal-impact crusher operation to obtain the maximum yield of cubiform crushed stone.

Heat release and transfer of premixed propane/air flames in high g-load centrifugal force fields

Rapid combustion and propagation are crucial for energy conversion and utilization equipment, such as power plants and thrust engines. High g-load in centrifugal flow fields has been demonstrated to be able to elevate turbulent flame speed. However, more details of flame behaviors in strong centrifugal force fields still need to be investigated. This paper focuses on flame bubble behaviors and related aspects by conducting Large Eddy Simulations (LES) of high g-load centrifugal flames stabilized by a backward step in an annual combustor. A centrifugal force was produced by setting different circumference inlet velocities (0 ms/, 4 m/s, 8 m/s, 12 m/s and 16 m/s) while axial velocity was constant (12 m/s). Wall-adapting Local Eddy-viscosity (WALE) model was used as the subgrid-scale model. Flamelet Generated Manifold (FGM) model and a 31-species and 107-step propane/air reaction mechanism were used for combustion modeling. The centrifugal body force exerted on flame bubbles and cold gas parcels is found to be able to make them move oppositely in the radial direction, and thus makes the flame surface more wrinkled. This effect leads to reinforced heat exchange between hot burned gas and cold fresh mixture. The consequent results are not only that the flame propagation speed is increased and the flame zone is broadened, but also that the local heat loss is enhanced, which leads to a weaker local heat release rate and might even lead to flame extinction. Additionally, the time-averaged flame front consists of a preheating zone and a reaction zone, along with a centrifugal-force-induced heat transfer from the post-flame zone to the cold fresh mixture.

Competitive effects of centrifugal force and electric field force on centrifugal electrospinning

Competitive effects of centrifugal force and electric field force on centrifugal electrospinning

Free vibrations of rotating pre-twisted blades including geometrically nonlinear pre-stressed analysis

The steady-state equilibrium deformations (SSEDs) caused by centrifugal force field in rotating blades are not necessarily perturbed disturbances. These deformations can be considered as large amplitude deformations, especially for high values of the rotating speed. Accordingly, in the current study, geometrically nonlinear terms are included in the static analysis under centrifugal forces (SACF) to accurately model the stiffening/softening effects in the vibrations of rotating pre-twisted blades. To this end, by developing a shell model based on first-order shear deformation theory (FSDT), nonlinear and linear integral boundary value problems (IBVPs) governing the SSEDs and vibrations of the blade are obtained, respectively. Multi-mode discretization of these IBVPs is carried out by the spectral Chebyshev technique. The discretization of the nonlinear IBVP results in nonlinear algebraic equations. By solving these equations, nonlinear pre-stressed analysis (NPA) is performed to achieve the SACF. Then, the free vibrations of the rotating pre-twisted blade about the determined equilibrium position is investigated. The numerical results show that the natural frequencies obtained in the presence of the nonlinear terms are extremely lower than those of the linear pre-stressed analysis.

Orthogonal Optimization Research on Various Nozzles of High-Speed Centrifugal Spinning.

High-speed centrifugal spinning is a burgeoning method of fabricating nanofibers by use of the centrifugal force field. This article studied four different spinning nozzles, which were called stepped nozzle, conical-straight nozzle, conical nozzle, and curved-tube nozzle, to explore the optimal nozzle structures for fabricating nanofibers. According to the principle of centrifugal spinning, the spinning solution flow states within the four nozzles were analyzed, and the solution outlet velocity model was established. Then, the structural parameters of the four kinds of nozzles were optimized with the spinning solution outlet velocity as the test index by combining the orthogonal test and numerical simulation. Based on the orthogonal test results, the influence of nozzle structure parameters on the solution outlet velocity was analyzed, and the best combination of parameters of the centrifugal spinning nozzle structure was obtained. Subsequently, the four kinds of nozzles were used to fabricate nanofibers in the laboratory, under different solution concentration, motor rotation speed, and outlet diameters. Finally, the scanning electron microscope (SEM) was applied to observe the morphology and surface quality of nanofibers. It was found that the surface of nanofibers manufactured by the conical-straight nozzle and curved-tube nozzle was smoother than that by stepped and conical nozzles, and the fiber diameter by the conical-straight nozzle was minimal, followed by curved-tube nozzles, stepped nozzles, and conical nozzles in the diameter distribution of nanofibers.

CFD analysis on hydrodynamics and residence time distribution in a gas-liquid vortex unit

A gas-liquid vortex unit (GLVU) operates in a centrifugal force field which significantly intensifies the gas–liquid mixing and interphase mass transfer. Experimentally obtaining detailed hydrodynamic information on the flow behavior and mixing process in a GLVU is difficult due to the presence of a highly turbulent liquid layer. In this study, a 3D computational fluid dynamics (CFD) Euler–Euler model is developed to study hydrodynamics and residence time distribution in a GLVU. The numerical results are validated using experimentally obtained pressure drop measurements and liquid velocity data. The liquid layer is found to rotate in the vortex chamber and suppress the gas phase vortex flow. Near the gas injection slots, the flow behavior is similar as in a continuous stirred tank reactor (CSTR), improving mixing and mass transfer efficiency. Finally, our CFD results show that the use of multiple liquid inlets results in an even more uniform liquid velocity distribution in the vortex unit, which further improves the performance of the GLVU.

Response of centrifugal pendulum vibration absorber considering gravity at low engine speed

This study examined the performance of the centrifugal pendulum vibration absorber’s (CPVA) under the influence of centrifugal force and gravity fields. The focus was on identifying the factor that influenced noise, vibration, and harshness (NVH) problems that originate owing to the centrifugal pendulum absorber being at low engine speed such as engine start-stop or idle. Consequently, mathematical models were established employing Lagrange equation of the second kind, analytical solutions were obtained using the method of multiple scales, and several simple elementary mathematical equations describing the movement of the absorber were derived. Further, the analytical solutions were compared with the numerical simulation results of the complete non-linear equation of motion, which indicated that the former were suitable for studying the performance of CPVA. The theoretical analysis of the application with four absorbers and two absorbers under gravity field was conducted. The absorbers were found to be not always synchronized in the gravity field in certain special conditions such as lower engine speed range or small viscous damping. It was concluded that larger viscous damping coefficient can result in an improvement in the synchronization or reduce the range of nonlinear jumps caused by changes in excitation torque. Further, super-harmonic resonance of CPVA under the gravity field was determined and exact response was calculated, wherein the term “2nd order response gravity impact factor” was defined. In addition, the effects of CPVA installation angle relative to engine ignition angle were analyzed, and a set of tautochronic epicycloid CPVA was tested to verify the findings. The analytical solutions were consistent with the test results, thereby proving the applicability of the research method and results in a vehicle.

Сравнение современных моделей турбулентности для течения Тейлора-Куэтта

Swirling flows of fluids and gases are an integral part of many complex flows which are widely encountered in nature and technology. The working process of numerous technical devices (cyclones, vortex combustion chambers, air separators, gas and steam turbines, electric machines and generators, etc.) is generally determined by the laws of hydrodynamics and heat exchange of rotating flows. The problem of deriving general laws for a turbulent flow in the field of centrifugal forces provokes considerable scientific interest since it belongs to an underdeveloped field of hydromechanics. Therefore, mathematical modeling of swirling turbulent flows is still an urgent problem. In this paper, a comparative analysis of the advanced turbulence models for the Taylor -Couette flow is carried out. For this purpose, the linear turbulence models (SARC and SST-RC), the Reynolds stress method SSG/LRR-RSM-w2012, and a two-fluid model are used. The results obtained using these models are compared with each other and with known experimental data and direct numerical simulation results. The numerical results calculated with the use of turbulence models for the Taylor-Couette flow confirm that almost all the models adequately describe velocity profiles. However, they yield different turbulent viscosity values and, as a result, different friction coefficients. A comparison of the numerical results shows that the friction coefficient calculated using a two-fluid turbulence model is the closest to that obtained experimentally.

Heat Release and Transfer of Premixed Propane/Air Flames in High G-Load Centrifugal Force Fields

Heat Release and Transfer of Premixed Propane/Air Flames in High G-Load Centrifugal Force Fields

Convective Heat Transfer Motivated by Liquid-to-Vapor Density Difference in Centrifugal Force Field of Axially Rotating Loop Thermosyphons

The innovative rotating looped thermosyphons (RLTs) with and without a coil insert were proposed with cooling applications in rotating machinery. The spatial gradients of body forces among the vapor–liquid mixture of the distilled water in a strong centrifugal acceleration field motivated the flow circulation in a RLT to facilitate the latent heat transmissions. The effective thermal conductivity (Keff), the thermal resistance (Rth), the Nusselt numbers in the condenser (Nucon) and evaporator (Nueva), and the Nusselt number of the airflow induced by the rotating bend of the condenser (Nuext,con) of each RLT were measured at various rotating speeds and heat powers with two filling ratios of 0.5 and 0.8. The increase of filling ratio from 0.5 to 0.8 to maintain a thin liquid film along the rotating inner leg of each RLT substantially improved the heat transfer performances. The Keff, Nucon, Nueva, and Nuext,con were increased with rotating speed, leading to the corresponding reduction of Rth. On the basis of the experimental data, the empirical correlations that were used to calculate Rth, Keff, Nucon, Nueva, and Nuext,con of the RLTs at the two filling ratios with and without coil were proposed to assist the relevant design applications.

Liquid-Phase Separation Of Oil Sludges In The Field Of Centrifugal Forces Using A Deemulgator

The process of separation of oil sludge, which is obtained after cleaning the oil refining units of the Bukhara oil refinery, is presented. Methods of obtaining petroleum liquid rafinate using several experimental laboratory installations for liquid-phase separation of oil sludge in a centrifugal force field with the use of a deemulgator "Disolvan-4411" and sawdust from the processing of old furniture of local raw materials are used. The composition and amount of heavy sediment and clarified oil products from oil sludge were obtained

A micro study on centrifuge model test of dynamic compaction using discrete-element method

Using the discrete-element method (DEM), a numerical simulation of dynamic compaction (DC) under an acceleration field of 50g was used to study the microscopic behaviours and macroscopic responses of soils under DC on the basis of a centrifuge model test of DC. The crater depth of the numerical simulation was compared with that of the centrifuge model test and field test. The results showed that the crater depth of the numerical simulation was in reasonable agreement with that of the centrifuge model test and a field test. Microscopic behaviours and macroscopic responses of soils under DC can thus be simulated using DEM by applying a centrifugal force field. Variations of dynamic stress, porosity and coordination number under DC were analysed. The effect of local damping on crater depth was also assessed. This study sheds light on the microscopic mechanism of DC, which should be helpful for improving the effect of DC.

DEVELOPMENT OF AN EVAPORATING TYPE AIR COOLER FOR VENTILATION SYSTEMS

Statement of the problem. The air supplied to the premises during the hot season must be cooled to comfortable temperatures. Due to the fact that additional energy consumption for this cooling is not provided, it is possible to use an evaporative-type air cooler. However, the currently known results of experimental and theoretical studies of such devices do not allow their design, which prevents their spread. The structure of such an apparatus is considered and its theoretical and experimental studies are carried out, the results of which can be used for engineering calculation and design of such apparatus.Results. An evaporative-type air cooler designed by the authors for ventilation systems is described. A theoretical and experimental study of the air cooler has been carried out. Analytical relationships were obtained for determining the time of movement of the material checker in the "wet" chamber of the apparatus, the temperature of the cooled air and the temperature of the checker in any section of the circulation loop. Empirical relationships have been obtained for the efficiency coefficient of the cooler and its hydraulic resistance. Conclusions. The obtained dependencies will serve as the basis for the development of a methodology for the design calculation of indirect-evaporative air coolers with a moving fluidized bed in the field of centrifugal forces.

DETERMINATION OF HYDRODYNAMIC PARAMETERS OF THE SEALED PRESSURE EXTRACTOR

The subject matter of the article: Sealed extractor with pressure. The goal of the work: Determination of hydrodynamic parameters of the sealed extractor with pressure. The following tasks were solved in the article: Theoretical research on the creation of a sealed extractor with pressure. It is need to development of ways of implementation and practical recommendations for the given technical solutions in the experimental sample. The following methods are used: Mathematical modeling, differential and integral calculus, experimental research methods. The following results were obtained: The processes occurring in sealed extractors are described mathematically. Parameters that affect the performance of aggregates are determined. Conclusions: As a result of the analysis of the technological process and equipment used in the factories for primary processing of wool, shortcomings and problems are identified and means for their elimination are proposed. It is proposed to use small-sized equipment to work on waste-free technology based on a hydrodynamic pressure extractor. Extraction as an efficient mass transfer process for removing organic components from aqueous solutions has the advantages of low operating temperatures and efficiency. The design features of the sealed pressure extractor are as follows: high angular velocities, the moment of inertia of rotating details, powerful pressure, the presence of nodes that provide a supply and discharge of liquids, tightness. The kinematic and geometric parameters of the rotor affect the sealed extractors’ performance). In sealed extractors, the heavy fraction in the field of centrifugal forces will accumulate on a large radius of the inner side of the rotor and for its movement it is necessary to create an excess pressure at the extractor inlet.

Development of Virus Sterilization Device Applying Filtered Vent Technology

We have developed a demonstration machine of a large-capacity air purification system that purifies a large amount of polluted air using a gas-liquid mixing nozzle and a multi-layer metal fiber filter. A gas-liquid mixing nozzle, driven by the air blower, sucks and accelerates water to form a high-speed two-phase flow. In the centrifugal force field, all the fine particles and aerosols in the bubbles are transferred to the liquid phase water, and the hypochlorite water whose disinfecting effect has been confirmed by the Product Evaluation Technology Infrastructure Organization (NITE). The demo machine can remove fine particles and viruses in the air at 100 m3 per hour with a single nozzle. We have also developed a large-capacity air purification system that can purify 2400 m3 of air per hour with 24 nozzles. In the virus removal evaluation test conducted by The Japan Textile Products Quality and Technology Center (QTEC), the sterilization performance of 99.975% or more was confirmed. We aim to put this technology to practical use at an early stage to purify the air in hospitals, schools, office buildings, etc.

Experimental Study of Thermal Convection in a Cylindrical Layer with a Longitudinal Partition at Modulated Rotation

Thermal convection of a liquid in a simply connected horizontal cylindrical layer rotating at a variable velocity is investigated experimentally. The inner boundary of the layer has a higher temperature. The cavity rotates rapidly and the liquid is stably stratified in a centrifugal force field. The parameters of the experiment correspond to the conditions when inertial waves are not excited (the modulation frequency is more than twice the cavity rotation frequency). The excitation thresholds of thermal convection and the structure of convective flows are studied depending on the rotation velocity and the parameters of the rotational vibrations of the cavity. It is found that the thermal convection is excited in a threshold way and its excitation is not associated with the manifestation of the mechanism of pendulum vibrational convection. A system of toroidal rolls with a spatial period commensurate with the layer thickness is observed in the cavity.

Evaluation and application of advanced CFD models for rotating disc flows

This paper addresses limitations of widely used Reynolds-averaged turbulence models (RANS) for prediction of gas turbine internal air systems. Results from direct numerical simulation (DNS), wall-resolved large-eddy simulation (LES), wall-modelled large-eddy simulation (WMLES), and RANS for benchmark test cases are compared. For rotor-stator disc cavity flows results for mean velocities, velocity fluctuations, rotor torque and laminar-turbulent transition are considered and compared with published data. For cavities between co-rotating discs attention is focused on buoyancy-driven convection in the centrifugal force field. It is concluded that WMLES is suitable for application in engine conditions, offering better accuracy than RANS in some critical applications. This confirms recently published results for turbine rim sealing and is further illustrated by application to convection in a sealed cavity at higher Rayleigh number than is practical with DNS or wall-resolved LES. The results show that the approximate near-wall treatment gives reasonable results for complex flows and extend previous studies to higher speed rig conditions where Eckert number effects become significant.