Different Speeds Of Rotation Research Articles

Application of computational fluid dynamics for simulation of stirred bioreactors in Ansys Fluent

Stirred bioreactors are widely used in the pharmaceutical industry to produce various active substances for the treatment of cancer, heart and vascular diseases, viral and bacterial infections. Despite the widespread use of bioreactors with a stirrer, the optimization of mixing conditions remains an urgent task. In bioreactors of this type, continuous mixing of cells in a medium with a high rotation speed should be carried out. The manuscript considers an example of the use of computational fluid dynamics to study and model the process of cultivation Escherichia coli bacterial cells in a batch bioreactor (NLF, 30 l.). Computational fluid dynamics was used to analyze the hydrodynamic conditions in a bioreactor with a double Rushton turbine stirrer. To describe the movement of flows and evaluate turbulence in a batch bioreactor, the multiphase Euler model and the k-𝜀 turbulence model, respectively, were used, the built-in Ansys Fluent software package. A geometric model was built with the original dimensions of the bioreactor with an NLF 30 stirrer. Based on the geometric model, a computational grid was created for the working volume of the bioreactor and the optimal parameters for constructing the computational grid were selected. As a result of modeling the hydrodynamic regime, the distribution profiles of the turbulence kinetic energy over the volume of the bioreactor were obtained and the velocities of cell movement were found at different speeds of rotation of the stirrer. The obtained results show the possibility and applicability of the Ansys Fluent software package for calculating the hydrodynamic situation in a bioreactor with a stirrer at different stirring rates and at different cell volume fractions.

Modeling of mixing process of the polymer composition in the dynamic mixer of the worm extruder

Mixing processes play an important role in the processing of polymer materials, because the quality of the mixing of the polymer material depends on its level of homogeneity, which in turn affects the quality of the final product. It is another matter when the polymer material consists of two or more components, in this case, the issue of the process of obtaining a homogeneous polymer composition becomes extremely acute. In order to improve the quality of the final product and justify the design and technological parameters of the mixing zone, it is necessary to investigate the regularity of the quality of mixing in a dynamic mixer of the CTM worm extruder type.
 According to existing works on determining the quality of mixing of polymeric material, the difference in concentrations of one of the components in different cross-sections along the length of the channel can be used as a criterion for homogeneity of mixing.
 Numerical modeling of the process of mixing the polymer composition in the dynamic mixer installed in the dosing zone of the worm extruder, which is equipped with an additional injection device that supplies the additional component to the dynamic mixing zone through the injection channel located in the body of the worm extruder, was carried out. Calculations were carried out on the basis of the finite element method (FEM) using the ANSYS software complex.
 A mathematical model of the process of mixing the polymer composition in a dynamic mixer of the CTM type of a worm extruder with the addition of an additional component, which is identical in density and viscosity to the main polymer material and can differ only in a certain feature that does not affect the properties of the components, such as color, has been developed. Moreover, the properties were set in such a way that the temperature distribution of the mixture was completely determined by the convective component, that is, it resulted only from the conditions of the mechanical movement of the volumes of the components.
 The dependence of the homogeneity of the polymer composition as a result of mixing on the technological and design parameters of the dynamic mixer of the CTM type was obtained. The research was carried out at different speeds of rotation of the mixer rotor and at different speeds of supplying the additional component. The movement of the components of the mixture was determined by their flow rate at the entrance to the main channel and at the entrance to the additional injection channel.
 The most optimal technical characteristics were selected in order to achieve the best level of uniformity.

Optimization Model of the Shell Capsules Geometry for a System for Diagnosing Damage to Gas Turbine Blades in Non-stationary

Scientific research is devoted to the problem of diagnosing damage in the blades of gas turbine engines in non-stationary conditions. The paper proposes a model for a more accurate calculation of the parameters of the crack detection system using a system of capsules, inside of which, under the influence of pressure, there is a substance exhibiting ionizing properties. In the study, the relations for determining the uneven pressure due to the action of centrifugal tensile forces during the rotation of the turbine blade are obtained. The relations for calculating the minimum required diameter of the capsule to ensure the rupture of the capsule when cracks are opened for the effective operation of the crack detection system are obtained. Calculations of the pressure inside the capsule and the geometry of the capsule at different speeds of rotation of the turbine blade are carried out. An estimate of the error in calculating the pressure inside the capsule is given in the case of not taking into account the action of centrifugal forces. The obtained dependences will significantly optimize the system for detecting damage to turbine blades, and increase the efficiency and safety of the operation of gas turbine engines.

Designing a voltage control system of the magnetoelectric generator with magnetic flux shunting for electric power systems

The object of research in this work is a three-phase magnetoelectric generator with magnetic flux shunting based on industrial induction electric motors. The presence of a magnetic shunt makes it possible to control the voltage of the generator by changing the excitation current in the non-contact electrical winding of the magnetic shunt, which is powered by direct current. Thus, the problem of stabilization of the output voltage of the generator with permanent magnets is solved when the speed of rotation and load change. This paper reports the construction of a three-dimensional field mathematical model of the generator, which allows for electromagnetic calculations of the generator with specified parameters, taking into consideration the influence of final effects, magnetic scattering fields, as well as their radial-axial nature. The results of the calculation of the electromagnetic field are the initial parameters for building a simulation model in the MATLAB-Simulink environment. A simulation model of a magnetoelectric generator with magnetic flux shunting under conditions of changing rotational speed and load has been constructed in the MATLAB-Simulink environment. On the basis of the built models, the performance characteristics of a magnetoelectric generator with magnetic flux shunting were established, which show the limits of control of the output voltage. Adjusting characteristics were determined at zero and rated shunt current for different types of load. The adjusting characteristics of the generator are presented at the rated voltage of the generator for different types of load and with an increase to 150 % of the rated value. The study's results show the high efficiency of the voltage control system of a magnetoelectric generator with a magnetic shunt at different speeds of rotation and load

Natural Frequency Evaluation of Low-Pressure Stage Blade of a 210 MW Steam Turbine

Steam turbines rely heavily on the performance and reliability of their rotor blades. When a steam turbine blade fails, it can pose a risk to workers' life, need expensive repairs, and cause income losses. The failure mechanism differs from case to case and is typically quite complex. The last stage turbine blades are very long and rotate at high speed. In extreme dynamic loads, these big blades are the most susceptible to failure. So, the dynamic behaviour of the last stage steam turbine blade is of great importance and analysed by numerical simulation in this work. Mode shapes at natural frequencies of the blade at stationary condition and at different speeds of rotation are determined. A Campbell diagram is used to forecast the expected operational conditions that may result in blade resonant vibration.

Analysis of the causes of undesirable curvature of the workpiece during longitudinal rolling using numerical simulation

Undesirable additional deformation was observed during the experimental cold rolling of steel. A simulation was performed in Deform software to clarify the causes. The influence of the unequal coefficient of friction, geometric inaccuracies of the rolls and the conveyor, and the situation when the rolls did not have the same diameter or rotated at different speeds were investigated. Simulations with different roll speeds corresponded best to reality. The simulation of the undesired curvature of the workpiece at different speeds of rotation of the rolls and 30% reduction was subsequently performed as an elastoplastic problem in order to determine the amount of springback and residual stress. Furthermore, the press straightening of the workpiece was simulated. Inhomogeneous and accidental deformation and residual stresses must be taken into account, especially when researching the effect of cold rolling on the mechanical properties and structure of the material.

Optimization of the main parameters of a mixing box in a periodic mode of operation in the preparation of liquid lumps in animal husbandry

The article discusses the problem of developing means that can increase the efficiency of mechanization of the process of preparing liquid feed in animal husbandry. Design bureaus, research and technological institutes for mechanization and electrification of agriculture have developed new progressive technologies, as well as kits, units, machines and apparatus for animal husbandry and fodder production. On the basis of this technique, complex mechanization of farms is being introduced and livestock complexes with industrial production technology are being created. But recently, the widespread use of domestic machines for the preparation of liquid feed mixtures has not been presented. Therefore, an experimental setup is proposed that combines three functions: a batcher, a pump and a mixer, which ultimately allows to obtain a mixture of good quality. The article provides a program and research methodology for the installation. For this, a special stand has been developed, which makes it possible to determine the parameters of the mixture quality. As a search for the optimal combination of factors for the optimization criteria: the degree of homogeneity and, plan 33 was chosen. Experimental studies have shown the range of the installation feed at different speeds of rotation of the impeller shaft. Mixing studies have confirmed the effectiveness of the design of the plant and its components: dispenser, pump and mixer. With the help of experimental planning methods, the main factors influencing the mixing process are identified, and the optimal parameters of the mixture quality are determined.

SORPTION OF OIL BY MECHANOCHEMICALY ACTIVATED SHUNGITE

In the paper the sorption capacity of shungite rocks of the Koksu field (Kazakhstan) in relation to the oil from the Karazhanbas and Tengiz fields (Kazakhstan) were studied. Oil spills occurring during production, gathering, transportation, storage and refining, and repair work on wells are an urgent environmental problem. There are effective methods of soil purification, including particular interests addressed to sorption process. The aim of this research is to study oil sorption by shungite rocks of the Koksu deposit after mechanochemical activation. The mechanochemical activation of shungite rock samples was carried out in a planetary ball mill at different speeds of rotation and ratios of ball mass to the sample. The developed sorbents based on shungite rocks of the Koksu deposit were tested for cleaning samples of oil-contaminated soils and their sorption capacities under dynamic and static conditions were determined. For the sorption of oil, the sorbent based on shungite of shale grade (TS) after mechanochemical activation is recommended, which sorption capacity under dynamic conditions is 2.57-2.85 g/g. Sorption of oil from 10 % of oil contaminated soil samples with the sorbents based on shungite after mechanochemical activation showed sorption capacity of 0.44-0.45 g/g in 60 days under static conditions. The practical significance of the research lies in the prospects of using shungite rocks to clean up oil spills.

Experimental investigation of the generator mode for a brushless dc motor at an increased rotational speed

This article deals with a commercially available direct drive brushless DC motor that was investigated in the generator mode at an increased speed above the rated one. During the conducted experiments the increase of the generator rotational speed was carried out due to a three-phase asynchronous motor with 5.5 kW rated power and 2920 rpm rated speed, which was further increased by a two-stage belt gearbox with a reduction ratio from 0.16 to 1.6. However, with an increase in the rotational speed, the magnetic losses also increase, which in turn increase the required value of the input mechanical power and lead to thermal overload of the brushless DC machine. An increase the generator rotational speed leads to an increase of the EMF value and, at the same value, of the stator current, leads to an increase the generated power. Throughout the experiment, the voltage was rectified using a diode bridge and bulk capacitor, after that it was connected to a load resistance. The presented calculations of the magnetic power losses for different electrical steel grades clearly demonstrate the nonlinear dependence between the magnetic field frequency and its magnitude. Experimental studies were carried out at different speeds of rotation of a brushless DC machine in a very wide range from 140 rpm to 5228 rpm, moreover, the values of the output power were obtained depending on the rotational speed. It is concluded, that in the generator mode of the brushless DC machine, it is necessary to take into account the feature of the operation at wind power plants, autonomous power supply such as hybrid power plants. In the first case, it is worth limiting the rotational speed from the driven mechanism, and in the second case, this mode of operation may be necessary for partial boosting of output power for short-term use.

Methodology for Calculating Heat Loss in the Study of Friction Stir Welding

Currently, the most promising high-tech and productive process is friction stir welding. An important element of this technology is the determination of the material temperature in the stir zone, which can be determined by calculation based on the amount of heat input introduced into the welding zone. To determine this value, experimental of the dependence of heat input on the tool rotation speed and welding speed were carried out. For this, a scheme of experiments has been selected in which the material to be welded (aluminum alloy AMg5) is modeled as an experimental tube with a diameter of 20 mm, and the tool (made of tool steel R6M5) is modeled as a working plate. On the designed and manufactured stand, studies of the dependence of the heat-liberation value for the speeds of rotation of the experimental tube 42-105 rad/s were carried out. In this case, due to the pressing force of the experimental tube and the working plate, a constant temperature of the place of friction was maintained. The obtained experimental data were used to calculate the heat-liberation value and heat power on each concentric ring 2 mm wide at the end of the working tool with a diameter of 20 mm, as well as the total heat power for different speeds of rotation and welding.When carrying out experiments on the bench, heat losses were determined by thermal conductivity along the rod on which the experimental tube is fixed, as well as from the working plate made of tool steel through the gasket onto the working table and by convection from the surface of the rotating experimental tube into the environment. The calculation results showed that each of these losses does not exceed 3-10%. These losses are taken into account in the heat supply calculations.

РАЗРАБОТКА ЭКСПЕРИМЕНТАЛЬНОГО СТЕНДА ОСЕВОГО КОМПРЕССОРА С ИСПОЛЬЗОВАНИЕМ АДДИТИВНЫХ ТЕХНОЛОГИЙ

In practice, the creation of compressor units is impossible without a large amount of experimental work. A lot of money is being invested in solving this problem, and many people participate in testing. Almost all calculation methods that are used in design are experimental and theoretical. In this regard, the modernization of calculation methods is inextricably linked with the development of experimental research, improvement of means and methods of measurements. In this paper, the created miniature experimental stand of a two-stage axial compressor is described, the general scheme of the stand is shown, the systems are described in detail. Several experiments were carried out at different speeds of rotation with different loads, the results were analyzed. Methods for obtaining characteristics of axial compressors using a software package for numerical three-dimensional thermodynamics modeling are presented. The described compressor unit has a set of sensors for collecting flow parameters in different planes. The signals from the sensors are processed by an eight-bit microcontroller. The stand is made of plastic using fused deposition modeling (FDM) on a 3D printer. Preliminary calculations of the strength of the rotor structure elements were carried out, the materials recommended for the manufacture of the installation were determined. The stand is proposed to be used for the design and optimization of two-stage compressor, as well as in the educational process. Also, in this article describes a constructed numerical model for studying the flow parameters of a compressor, presents the results of comparing some experimental and calculated data, constructs a flow characteristic, estimates the measurement uncertainty, and formulates several recommendations.

Study of the continuous mode of mixing feed components in a mixing plant

The article discusses the problem of developing means that can increase the efficiency of mechanization of the process of preparing liquid feed in animal husbandry. Design bureaus, research and technological institutes for mechanization and electrification of agriculture have developed new progressive technologies, as well as kits, units, machines and apparatus for animal husbandry and fodder production. On the basis of this technique, complex mechanization of farms is being introduced and livestock complexes with industrial production technology are being created. But recently, the widespread use of domestic machines for the preparation of liquid feed mixtures has not been presented. Therefore, an experimental setup is proposed that combines three functions: a batcher, a pump and a mixer, which ultimately allows to obtain a mixture of good quality.
 The article provides a program and research methodology for the installation. For this, a special stand has been developed, which makes it possible to determine the parameters of the mixture quality and the specific consumption of electrical energy. As a search for the optimal combination of factors for the optimization criteria: the degree of homogeneity and the specific consumption of electrical energy, plan 32 was chosen. Experimental studies have shown the range of supply of the installation at different speeds of rotation of the impeller shaft. Mixing studies have confirmed the effectiveness of the design of the plant and its components: dispenser, pump and mixer. With the help of experimental planning methods, the main factors influencing the mixing process are identified, and the optimal parameters of the mixture quality are determined. According to the studies carried out on the continuous introduction of components in an experimental installation for the preparation of liquid feed mixtures, we obtained that the optimal combinations of factors would be the water temperature t = 26...38 C and the rotation frequency n = 1500...1650 min1, while the degree of homogeneity reaches = 94,6 % and unit costs of electric energy Eel = 0,198 kWh/t.u. st.un.

THE GRINDING MECHANISM ON A KNIFE CENTRIFUGAL GRINDING MACHINE

The article presents a methodology for calculating the force effect on a fibrous suspension of working bodies in a centrifugal grinding apparatus. The aim of the research is to calculate the force per tooth of an inertial body at different speeds of rotation of the rotor, to determine the effect of the circumferential speed of movement of inertial bodies on the grinding process of fibrous semi-finished products. The article discusses the mechanism of grinding on a centrifugal knife grinding apparatus, determines the tangential shear forces at the contact of the grinding satellite knives with the grinding bowl knives, determines the effect on the fiber of rolling friction forces and sliding friction forces when the grinding satellite knives come into contact with the grinding bowl knives, as well as the effect of specific pressure at the point of contact of the satellite knives with the grinding bowl knives under the influence of inertial forces. Based on the research results, it is scientifically substantiated that the forces arising at the minimum of the considered values of the rotation speed of inertial bodies are sufficient to break the fiber when using this installation for grinding fibrous semi-finished products. An increase in the speed of rotation of the satellites causes a positive change in the physical and mechanical characteristics of the finished castings.

Моделювання аеромеханіки процесу подрібнення у відцентровому млині

The article discusses aeromechanical processes in a centrifugal mill at different speeds of rotation in order to establish the regularities of the kinematics of the flow of a heterogeneous medium in the grinding chamber of the mill, its interaction with the working body and the classification of the crushed material when removed from the grinding chamber. The study of gas dynamics of processes in the flow path of a centrifugal mill has been carried out. The trajectories of streams, velocity and pressure fields were investigated. The influence of various factors on the efficiency of the classification and the maximum diameter of particles removed from the grinding chamber was revealed. The regularities of the movement of a heterogeneous medium, its interaction with the working body and the classification of the crushed material when removed from the grinding chamber were established, the gas dynamics of processes in the flow path of a centrifugal mill was studied. The main way to increase the speed of air flows is to increase the flow of transport air, which in turn affects the aerodynamics of the processes in the grinding chamber of the mill, productivity and grinding time of the material. Processes of gas dynamics in a compressed medium of the flow path of a centrifugal mill were described by a system of non-stationary Navier-Stokes equations of continuity, energy and equation of state in approximation of the turbulence model. Analysis of the results of mathematical modeling of processes in the working chamber showed that the air flow carries out a complex rotational movement in the transverse and longitudinal sections with the formation of local zones of increased turbulence. As a result of numerical modeling and analysis of the results, factors have been identified that make it possible to intensify the process of material grinding. The flows have a pronounced ballistic trajectory. They start their movement from the center of the bottom of the grinding chamber and move along the walls of the chamber while rotating in a spiral and moving down the wall of the hollow shaft. It is observed that the point of separation of the flows rotating in the lower part of the grinding chamber and the flows moving in the upper part is on 60% of the height of the chamber. Keywords: modeling, centrifugal mill, finite element method, Navier-Stokes equation.

Экспериментальное определение механического КПД некоторых судовых дизелей

The article summarizes the results of heat engineering tests of diesels used in the educational process of Volga State University of Water Transport and its branches. Although the test goals were different in each case, the indicator diagrams of the working process in each cylinder were recorded in the course of the tests. Analysis of indicator diagrams helped to determine the indicator power of the engine in each case. By comparing the indicator parameters with the corresponding effective ones there was performed the estimation of the mechanical efficiency of each engine at different speeds of rotation of the crankshaft. The studies were carried out on engines of brands 6NVD48AU, 6L275RrII/PN, 8NVD36U, 6L160PNS. It was found that in almost all cases, mechanical losses included fan losses in load devices and friction losses in their bearings. The concept of a screw characteristic is considered. A graph of the propeller characteristics in relative units for various types of engines is built. It is noted that it is very difficult to set a specific value of the crankshaft speed required for testing, the actual points will be close to the theoretical ones, shifting along the helical characteristic. An algorithm for testing and processing the results is presented. There have been analyzed the dependences covered in literature (analytical and statistical) for determining the mechanical efficiency.

Optimisation for enhancing sludge dewaterability using different conditioners

Dewatering of alum sludge from drinking-water plants is proving to be a major challenge because of the large amounts of residual sludges produced annually. In the last few years, most studies have focused on improving the dewatering process to reduce costs of alum sludge management and transport. In the present study, three different types of conditioners were tested. Lime was used as an example of an inorganic conditioner, ferric chloride (FeCl3) was used as an example of a chemical conditioner and chitosan was used as an example of a biopolymer. The performance of a conditioner was evaluated with respect to its effect in reducing the resistance of the conditioned sludge to filtration, namely the specific resistance to filtration (SRF). Tests are run using different concentrations of the conditioners, different speeds of rotation and different pH values to investigate the maximum value of percentage reduction in SRF. The response surface methodology was chosen from the Design-Expert program (version 12), and the Box–Behnken design was employed to find factor settings that optimise the output response – that was, percentage reduction in SRF (Red. %). The model obtained proved to be significant enough but with varying degrees. Chitosan showed to be the most favourable conditioner with a maximum percentage reduction in SRF of 98.57%. This was followed by ferric chloride, which gave a value of 89.2% for percentage reduction in SRF, and lastly came lime with a percentage reduction of 79.81%. Besides, a lower concentration of the conditioner and a lower speed of rotation are required when using chitosan as a conditioner.

Investigation of influence of plate rolling parameters on the product quality

During plate rolling in most cases a breakdown of symmetry conditions of the strip deformation relative to the upper and lower rolls takes place. The rolling process becomes an asymmetric one. This phenomenon causes an adverse bending of the strip towards the lower or upper roll. Subsequent finishing operations do not ensure the exclusion of the deformed (wavy) shape, since the strip has a high rigidity. With this production, large technological waste, associated with the undulation of the front end of the strip arises. In addition, the work rolls of the rolling mill and auxiliary equipment are subject to increased wear. The introduction of controlled asymmetry into the rolling process by differentiating speed of rotation of the work rolls can be one of the ways to prevent this phenomenon. Using of asymmetry allows to change the stress and strain state in the deformation zone. This method does not increase the load on the rolling stand and the gear of the rolling mill. The paper presents results of investigation of plate rolling parameters (billet feeding angle, degree of deformation, value of the asymmetry coefficient of rolls rotation speed) on the strip curvature. The work was carried out according to conditions of hot rolling of steel grade S355J2+N. For numerical simulation of the rolling process the coefficients of the Hensel–Spittel function were refined. The authors conducted a study of rolling of plates using two types of asymmetry, a geometric (as a result of feeding the workpiece at an angle) and a kinetic (by changing the speed of rotation of individual rolls). The analysis of the results was carried out using numerical simulation based on the modern Forge soft- ware package. According to the results of the work, an analysis of the influence of the parameters of plates hot rolling on the metal flow in the deformation zone is presented. The conditions for reducing the curvature of the end of the strip are determined. The expediency of introducing a controlled asymmetric rolling process by application of different speeds of rotation of the work rolls is shown.

Systematic Characterization of Near-Index-Matched Optics Based Atmospheric Turbulence Simulator

In the present communication, a systematic characterization of atmospheric turbulence simulator (ATS) based on near-index-matched optics is reported. Characteristics of the propagating laser beam in actual turbulence can be realized in the laboratory by employing such types of turbulence simulators. Such simulators are necessarily required to evaluate the performance of an adaptive optics sensor and compensator modules in the laboratory. Various strengths of atmospheric turbulence can be generated by selecting the different speeds of rotation and the diameters of the beam-interacting area of ATS. A MATLAB-based high-speed video processing method is developed and used for estimating the various turbulence parameters such as angle-of-arrival fluctuations, Fried parameter, Hurst exponent, turbulence frequencies and the scintillation index from the generated turbulence. Also, the maximum transmitted wavefront error produced by this turbulence simulator is measured by an in-house developed Shack–Hartmann wavefront sensor.

ВІБРАЦІЙНА НАВАНТАЖЕНІСТЬ ТА РУЙНУВАННЯ ЗУБЧАСТИХ ПЕРЕДАЧ ВЕРТОЛІТНИХ РЕДУКТОРІВ

Роглянута вібраційна навантаженість високошвидкісних зубчастих передач вертолітних редукторів на злітному і крейсерському режимах експлуатації, розподіл навантаження між зубцями в зоні багатопарного зачеплення, динамічні навантаження в зачепленні зубчастих коліс та їх пошкоджуваність і руйнування.

Detection and classification of bearing faults in industrial geared motors using temporal features and adaptive neuro-fuzzy inference system

This paper concerns the automatic diagnosis of ball bearing defects in industrial geared motor based on statistical indicators and the Adaptive Neuro-Fuzzy Inference System (ANFIS). The approach consists of three essential steps: the first is the extraction of statistical indicators from the root mean square (RMS) of the raw vibration signals measured experimentally for different states of the bearing (healthy and in the presence of defects). The second step consists of the selection of the more relevant indicators, and finally the introduction of these indicators to the ANFIS network in order to classify the various defects in the bearing (inner and outer race faults, and combined fault). A test campaign was conducted on an industrial installation (Wheeled Conveyor) to collect data as the RMS trend of the raw vibrations using adequate instrumentation in order to verify the validity of the method in real test conditions. The obtained results show that the proposed approach can reliably detect and classify various faults at different speeds of rotation of the electric motor. The effectiveness of the proposed method was also approved by using additional test data.