Stationary Mode Of Operation Research Articles

Определение усилий натяжения канатов при эксплуатации мобильных транспортно-перегрузочных канатных комплексов

During the operation of aerial ropeways, the system of carrying and carrying-traction ropes, which provides the possibility of moving passengers or transported goods between the terminal points of the route, experiences a high level of loading from a variety of operational loads and environmental influences. These loads and influences form the tension of the ropeway system variable along the length of the ropeway route, which has a decisive impact on the main technical and economic indicators of mobile ropeways, and thereby determines specific areas of their effective and inappropriate or unacceptable use. This article presents an engineering technique for constructing tension diagrams of carrying-traction ropes in stationary and non-stationary modes of operation of a mobile ropeway. Calculated dependences are given to determine the tension forces of ropes at characteristic points along their length, as well as calculated dependences for determining the resistance forces to the movement of ropes on characteristic sections of the mobile ropeway route. This technique can be used both for calculating the loading of the rope system based on taking into account a large number of factors characterizing operational loads, terrain parameters and transported cargo, and for analyzing the direction and significance of the variation of these factors and the main design parameters of the main technological equipment of mobile transport and reloading rope complexes. The results of the analysis of the influence of the variation of a number of significant quantitative parameters on the change in the tension forces of the carrying-traction ropes are also presented.

The Methods of Three-Dimensional Modeling of the Hydrogenerator Thrust Bearing

In the presented scientific work, the basic design versions of the thrust bearings of Hydrogenerators are considered. The main causes of emergencies in the thrust bearing unit of a high-power Hydrogenerator are considered. The main requirements for the operation of thrust bearings are submitted. Cause-and-effect relationships of emerging and development of defects are established. Existing methods for calculating the stressed state of a thrust bearing in the classical formulation for a stationary mode of operation are considered. The main features of the operation of the thrust bearing unit are investigated in relation to the features of the sliding bearings. The calculation of the elastic chambers of the hydraulic thrust bearing in a three-dimensional formulation is carried out, taking into account the physical properties of the oil, the material of the chambers and distribution of the acting loads. It is shown that the applied designs of Join Stock Company “Ukrainian Energy Machines” can be used in high-power Hydrogenerators.

Conductor Design for Toroidal Field Coils of a High Magnetic Field Tokamak TRT20

Recently, the developmentof the concept project of the high magnetic field (HMF) tokamak continues in the Russian Federation. The value of the magnetic field on the plasma axis in the device is about 8 T. The maximum field on the winding of the toroidal field coils is about 15 T. The creation of a high magnetic field in a limited space of tokamak-type device with a given aspect ratio-R/a≈3.77 (R = 2.15 m-the big radius of the tokamak, and a = 0.57-the “radius” of the plasma) leads to a significant increase in the engineering current density in the toroidal field coils. The mechanical stresses in the magnet increase accordingly. Acceptable from a technical point of view for protective energy output are the values of the maximum electrical voltage relative to the ground-U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ≤+/−5 kV and the temperature in the “hot spot” - T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ∼200 K. In addition, it is necessary to minimize heat losses in the stationary mode of operation of the tokamak, which significantly depend on the number of current leads used in the toroidal magnet. In this paper, we propose original possible solutions of the problems listed above. A “cable-in-conduit” type of conductor (CICC) is used in the TRT toroidal magnetic system. The cable portion of the conductor is manufactured from parallel non-transposed tapes of HTS REBCO coated conductor, which are oriented mainly parallel to the vector of the toroidal magnetic field. We call this design PaST (Parallel Stacked Tapes) conductors. The design of the conductor is developed to the requirements for a real device and differs from the previously proposed by more compact dimensions.

Аналіз роботи гідростатичного підшипника на перехідних режимах

The design of reliable rotor supports for modern high-speed machines is associated with the solution of many complex problems, both theoretical and experimental. Experimental studies play an important role in the system of scientific research and allow improvement and refine mathematical models and the application of numerical methods for their implementation. Experimental studies are usually selective and therefore require careful preparation. The task was set to investigate the characteristics of a hydrostatic bearing in the starting and braking modes. A program of experimental studies of the behavior of a shaft on hydrostatic bearings for the most difficult operating conditions has been developed. The advantages of hydrostatic bearings are given compared with other types of plain bearings, as well as compared with rolling bearings. The effectiveness of hydrostatic bearings is shown, compared with other types of bearings, for modern high-speed machines, in which there is an increase in vibration overloads and vibration displacements. Hydrostatic bearings have proven themselves in all operating modes, including transient ones. A description of the experimental setup for the study of transient modes of operation of the shaft on hydrostatic bearings is given. Studies of the transient modes of operation of the shaft on hydrostatic bearings were conducted at various values of the pressure of the working fluid supply, residual unbalance, as well as various values of the diameter of the hydrostatic bearing. To identify the movement of the rotor on hydrostatic bearings, the values of the amplitudes of oscillations during stationary (steady) movement of the rotor are also presented. It is shown that the comparison of the oscillation amplitudes of the rotor on hydrostatic bearings with a diameter of 0.06 m for the cases of non-stationary and stationary modes of its operation during the acceleration of the amplitude of oscillations in the entire range of rotational speeds is slightly lower (by about 15…20 %) than in the case of a stationary mode of operation of the rotor. When the rotor slows down, the amplitude of the rotor oscillations at high speeds is somewhat larger (by about 7…9 %), and at low speeds it is less by 8…10 % than in the case of a stationary rotor operation. The small influence of the non-stationary nature of the rotor movement on the dynamic characteristics can be explained by its large mass.

Synchro-Drive-Based Underwater Climbing Adsorption Robot

This article proposes an underwater climbing adsorption robot. The robot avoids coming into contact with adsorbates by using a mechanism of negative pressure adsorption based on Bernoulli's theorem, which allows it to generate a maneuverable force. A synchro-drive locomotion mechanism is developed to boost the maneuverability of the robot such that it can carry out omnidirectional motion using the least mechanical parts. Discrete and continuous modes of locomotion are proposed and verified to enable the robot to follow a complex path, and a switch strategy to balance its adsorption and locomotion is developed. In stationary operation mode, the adsorption force can be increased by reducing the gap to maintain the stability of the robot when carrying loads. In the motion mode, the size of the gap is increased to lend the robot a powerful obstacle-surmounting capacity when it moves on rough and curved surfaces. The results show that the proposed robot has the advantages of being non-contact, and having high adsorption and mobility that are suitable for challenging operations on a variety of underwater structural surfaces.

MATHEMATICAL MODEL OF GRAIN RAW MOVEMENT IN INTERACTION WITH DISPERSER AND SCREW FEEDER

Bioactivated dispersed grain, which is obtained by soaking followed by grinding on a dispersant is a promising raw material for expanding the range of bakery products and providing the population with products of high biological value. Bioactivation is understood as the process of grain saturation with moisture, during which the transformation of macromolecular substances into easily accessible forms takes place, which makes it a source of bioactive substances. However, the implementation of the process of dispersing bioactivated grain material remains relevant, the process of grinding which is mainly influenced by such factors as moving the grain with the help of a screw feeder and pushing it through the cutting mechanism. To obtain dispersed grain, there are a large number of crushing machines, the main working bodies of which are the screw feeder, knives and lattice. Many scientific papers are devoted to improving the helical transport mechanism of the disperser, by changing its design, which allows to increase the homogeneity of the grain mass at the outlet, its dispersion, reduce energy consumption and increase productivity. However, the use of screw feeders for grain dispersion raises a number of issues that require further research. Namely, the study of the influence of the additional pressure required to work when loading the material on the process of its movement, and determining the speed of movement of the grain material through the cutting mechanism for grinding in the dispersant. To address the above issues, a mathematical model for the movement of grain raw materials during grinding is proposed. Mathematical dependences for determining the speed of the dispersing process have been obtained, which can be applied taking into account the physical properties of the material in the stationary mode of operation of the dispersant.

PREVENTION OF HYDRODYNAMIC INSTABILITY CONDITIONS IN SAFETY SYSTEMS WITH PUMPS OF NUCLEAR POWER PLANTS

The study of hydrodynamic instability in the safety systems of nuclear power plants is relevant. In the deterministic analysis of the safety of nuclear power plants based on accident simulation, it is necessary to take into account the possibility of hydrodynamic instability in the operational and transient modes of safety systems. The consequences of the emergence of hydrodynamic instability in safety systems can be following: a significant deterioration of the heat and mass exchange conditions in the reactor and steam generators during the heating process, an increased power of thermo-hydro-shock on the equipment of the nuclear installation and other negative effects. The negative consequences of the hydrodynamic instability in the safety systems of nuclear power plants can be a significant deterioration in the conditions of heat-mass exchange and the thermal water hammers with increased power. The main reasons for the hydrodynamic instability in safety systems are inertial lag in the response of control valves and head-flow characteristic of pumps to “fast” changes in hydrodynamic parameters in nuclear power plant systems. The purpose of this work is to determine methods for minimizing the impact of the causes of hydrodynamic instability in security systems. The methods of substantiating effective structural and technical parameters of damping devices to prevent conditions of hydrodynamic instability in stationary working and transient modes of safety systems with pumps are given. A method for substantiating effective design and technical parameters of damping devices to prevent conditions of hydrodynamic instability in transient modes of starting pumps of safety systems is presented. Stability conditions in stationary operating modes of the initial steam-gas volume of damping devices are determined. The minimum permissible dimensions of damping devices that meet the conditions of hydrodynamic stability in the transient modes of SB pumps are determined.

Strength and Service Life of a Steam Turbine Stop and Control Valve Body

The stability of operation of steam turbines depends (along with other factors) on the reliable operation of their steam distribution systems, which are based on stop and control valves. This paper considers the strength of the elements of the K-325-23.5 steam turbine valves, in whose bodies, after 30 thousand hours of operation, cracks came to be observed. Previously determined were the nature of gas-dynamic processes in the flow paths of the valves and the temperature state of the valve body in the main stationary modes of operation. To do this, a combined problem of steam flow and thermal conductivity in stop and control valves was solved in a three-dimensional formulation by the finite element method. Different positions of the valve elements were considered taking into account the filter sieve. The assessment of the thermal stress state of the valve body showed that the maximum stresses in different operating modes do not exceed the yield strength. Therefore, the assessment of the creep of the valve body material is important to determine the valve body damage and service life. Modeling the creep of the stop and control valves of the turbine was performed on the basis of three-dimensional models, using the theory of hardening, with the components of unstable and steady creep strains taken into account. The creep was determined at the maximum power of the turbine for all the stationary operating modes. The maximum calculated values of creep strains are concentrated in the valve body branch pipes before the control valves and in the steam inlet chamber, where in practice fatigue defects are observed. However, even for 300 thousand hours of operation of the turbine (with a conditional maximum power) in stationary modes, creep strains do not exceed admissible values. The damage and service life of the valve bodies were assessed by two methods developed at A. Pidhornyi Institute of Mechanical Engineering Problems of the NAS of Ukraine (2011), and I. Polzunov Scientific and Design Association on Research and Design of Power Equipment. (NPO CKTI) – 1986. The results of assessing the damage and the turbine valve body wear from the effects of cyclic loading and creep of the turbine in stationary modes for 40, 200 and 300 thousand hours show that the thermal conditions of the body in the steam inlet chamber are not violated (without taking into account possible body defects after manufacture). The damage in valve body branch pipes after 300 thousand hours of operation exceeds the admissible value, with account taken of the safety margin. At the same time, the damage from creep in stationary operating modes is about 70% of the total damage. The maximum values of damage are observed in the areas of the body where there are defects during the operation of the turbine steam distribution system. The difference between the results of both methods in relation to their average value is ~20%.

Methodology improvements to simulate performance and emissions of engine transient cycles from stationary operating modes: A case study applied to biofuels

In the present study engine/vehicle responses from a standardized transient test cycle are estimated using 13 stationary operating regimes following a previously developed methodology. The main advantage of the methodology tested is that allows obtaining an estimation of transient parameters in a stationary test bench, which requirements are much less demanding than those of the transient test bench. The objectives are: in one hand, to demonstrate that the methodology correctly estimates engine responses regardless of the fuel tested, as it is proposed in a previous paper and, on the other hand, to improve the methodology and the accuracy of the estimated parameters. The fuels tested are renewable fuels from different raw materials (biodiesel from rapeseed, sunflower, and soybean), and diesel fuel as the reference. Biodiesels were tested neat and blended (30% v/v) with diesel fuel. The engine is a common-rail light-duty one, and the standardized testing procedure used to illustrate the implementation of the methodology is the New European Driving Cycle (NEDC). Two design of experiments (DoE) of 13 runs each were analyzed. One of the DoE tested was proposed for characterizing the NEDC, referred as to CTDoE design, while the other one is a five-level fractional factorial design (FFDoE) that adequately matches the optimality criteria of orthogonality, D-optimal criterion, rotatability, and space-filling. The original methodology was improved by the implementation of a new fitting function that simulates the cold start effect over the engine parameters and by an new definition of the boundary in the [n,M] domain. These improvements showed significantly higher accuracy of the estimated engine parameters obtained, both instantaneous and accumulated, respect to the original methodology. The results obtained based on the application of the FFDoE design support the feasibility of the methodology tested. Engine performance and regulated emissions responses, such as intake air and fuel mass flow rate, thermomechanical exergy rate, exhaust gas residual heat rate, total hydrocarbons (THC), nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter (PM) emissions from a transient test were instantaneously and cumulatively predicted with high accuracy using the engine responses from 13 steady-state operating modes.

Method for increasing the dynamic characteristics of thermoelectric coolers

The influence of the efficiency of the initial thermoelectric materials on the dynamics of the functioning of the thermoelectric cooling device for various characteristic current modes of operation in the range of operating temperature drops and heat load at a given geometry of thermoelement legs is considered. The parameters of thermoelectric materials of thermoelements are conventionally divided into three groups: used for batch production, laboratory research and maximum values.The criterion for choosing the operating mode of the thermoelectric cooler takes into account the mutual influence and weight of each of the limiting factors. Since the design conditions can be very diverse, simultaneously varying several limiting factors (constructive, energy and reliability), you can choose the most rational mode of operation.The analysis was carried out for typical current modes of operation of thermoelectric coolers: maximum cooling capacity, maximum cooling capacity at a given current, maximum coefficient of performance, minimum failure rate. It is shown that with an increase in the efficiency of the initial thermoelectric materials, the time for reaching the stationary operating mode of the thermoelectric cooler, the required number of thermoelements, and the maximum temperature difference increase.A method is proposed for reducing the time constant of thermoelectric coolers due to the revealed relationship between the efficiency of thermoelectric materials and the dynamic characteristics of thermoelements. It is shown that an increase in the dynamic characteristics of thermoelectric coolers is achieved without changing the design documentation, manufacturing technology and additional climatic and mechanical testing of products.

Study of the dependences of coal-wood composition, identification of combustion features of the obtained composite materials

In the study of the combustion of samples, it was found that, other things being equal, under the experimental conditions and with the fixed technical characteristics of the fuel, different parameters of the flame are observed, namely, the speed of reaching a stationary mode, the completeness of fuel combustion, the size and distribution of temperature zones strongly depend on the methods used to carry out the mechanical fuel processing. Comparison of the results showed that under the same experimental conditions, the temperature distribution along the length of the experimental stand, in a stationary mode of operation, is higher for the composite fuel. In the case of composite fuel, 70 percent of the fuel burned up was observed at a 1 m section, which is indicative of these fuel consumption and kindling processes at industrial thermal power plants.

Theoretical Disquisition on the Static and Dynamic Characteristics of an Adaptive Stepped Hydrostatic Thrust Bearing with a Displacement Compensator

Stepped hydrostatic thrust bearings used in metal-cutting machines are characterized by high load capacity and damping, which ensure the stable operation of structures. However, in comparison with throttle thrust bearings, they have a high compliance. It is preferable that, in addition to the main bearing function, a modern hydrostatic bearing has the ability to provide low (including negative) compliance for the implementation of an adaptive function in order to actively compensate for the deformation of the machine resilient system, thereby increasing the accuracy of metalworking. This paper considers the design of a stepped hydrostatic thrust bearing, which, in order to reduce the compliance to negative values, features a technical improvement consisting of the use of an active displacement compensator on an elastic suspension. In this paper, the results of mathematical modeling and theoretical research of stationary and non-stationary modes of operation of the adaptive thrust bearing are presented. The possibility of a significant reduction in the static compliance of the structure, including the negative compliance values, is shown. It was found that negative compliance is provided in a wide range of loads, which can be up to 80% of the range of permissible bearing loads. The study of the dynamic characteristics showed that with a targeted selection of parameters that ensure optimal performance, the adaptive thrust bearing is able to operate stably in the entire range of permissible loads. It has been established that an adaptive stepped hydrostatic thrust bearing with a displacement compensator has a high stability margin, sufficient to ensure its operability when implementing the adaptive function.

Method of Switching on and Off a Power Transformer with a Capacitor Bank in an Electrothermal Installation

The article is devoted to issues related to increasing the energy efficiency of industrial electrothermal installations, both in starting and stationary operating modes due to the use of capacitors and thyristor starters with special control. The results of a significant reduction in the duration of the transient process, elimination of surges and asymmetry of starting currents and voltage drawdowns are presented. The results of full compensation of the reactive power of the network in the steady-state mode are also presented. It is shown that the starting currents do not exceed their steady-state values and that the shutdown of the electrothermal installation is performed without the occurrence of an arc and switching losses at the contacts of the switches. Researches of an electrothermal installation with a capacity of 750 kV⋅A and a voltage of 380 / 80 V are made on the model in the Matlab environment.

Calculating the sequence of stationary modes in power distribution networks of Russia for wide-scale integration of renewable energy based installations

The global trend of the past decades on the development of the decentralized power generation concept is associated with the growing number of power plants integrated into power distribution networks including those employing renewable energy sources. In recent years, high-capacity wind power and solar PV stations have been put into operation, in Russia, and wide-scale construction of micro-generation sites is at the stage of planning and design. Under these conditions, power distribution networks will be permanently affected by the deviation of operational status that can be indicated in the temporary change of stationary mode parameters. Currently it is not technically possible to equip all network control and supervision Centers with hardware and software complexes designed to calculate automatically transients in operation modes in order to work out decisions on prompt actions for controlling network operational status and maintaining its operation modes within the range of permissible values of their rated parameters. In this article, the principles have been analyzed that enable to apply the existing software complexes for calculating the sequences of stationary operating modes (SSOP). Results of calculating SSOP make it possible to perform the analysis of changes that may occur in power distribution, in transient conditions, and to work up reasonable control actions in order to stabilize operation modes of power network equipment. Properly estimated amount of available reactive capacity of generating installations helps to prevent critical voltage drop in load nods, as well as occurrence of voltage avalanche, in installations, particularly in industrial power consuming areas. In power distribution networks, operating mode characteristics essentially depend on parameters of loads due to their comparability with the aggregate capacity of generating installations and low interaction impedance. The issues of accurate load modeling and those of possible assumptions have been considered. The principles of application of the results of SSOP calculations for the analysis of the effect of voltage control devices, in live conditions, automatic voltage control equipment and quick-response shunt compensation devices that make their contribution in VAR flow and distribution power network operation have been demonstrated.

Comparative analysis of means to control the thermal regime of a cooling thermoelement while minimizing the set of basic parameters

This paper reports a comparative analysis of the thermal regime control means while minimizing a set of basic parameters in various combinations with the indicators of reliability and dynamics of the functioning of a single-stage thermoelectric cooler. The connection has been established between the optimal relative operating current corresponding to the minimum of the set on the relative temperature difference and heat sink capacity of the radiator. The results of calculating the main parameters, reliability indicators, time of entering the stationary mode of operation for various current modes of operation at a fixed temperature difference, thermal load at different geometry of the branches of thermoelements are given. A comparative analysis of the main parameters, indicators of the reliability and operational dynamics of a single-stage cooler under various characteristic current modes of operation has been carried out. Minimizing the set of basic parameters in conjunction with the reliability indicators and operational dynamics of the cooling thermoelement provides a decrease in the refrigeration coefficient up to 40 % compared to the maximum cooling capacity mode, as well as the optimal heat sink capacity of the radiator, the amount of energy expended, the time of entering the stationary mode, the relative intensity of failures. The analysis of the influence of the temperature difference at a predefined thermal load on the relative operating current, the time it takes for the cooler to enter the stationary thermal regime, the heat sink capacity of the radiator, the relative intensity of failures has been performed. The devised method of optimal control over the thermal regime of a single-stage thermoelectric cooler based on minimizing the set of basic parameters makes it possible to search for and select compromise solutions, taking into consideration the weight of each of the limiting factors

Dynamics and Strength of Housings and Supporting Elements of Hydrogenerator Design

The basic designs of Hydrogenerators are considered in the presented scientific work. It is shown that one of the most loaded units of Hydrogenerator is the thrust bearing. The analysis of the causes of emergencies in the thrust bearing unit of the high power Hydrogenerator is performed based on the experience of operation. Cause-and-effect relations of origin and development of defects are determined. Existing methods of calculation of the stressed state of the chambers of the thrust bearing unit in the classical formulation for the stationary mode of operation are considered. The main features of the thrust bearing unit operation with respect to the features of the sliding supports were studied. An updated Diagram of the sliding supports loading is presented. For the first time, the calculation of the elastic chambers of the thrust bearing was performed in three-dimensional formulation taking into account the physical properties of the oil, the material of the chambers and the unevenness of the existing loads. It is shown that the applied designs of SE “Рlant “Electrotyazhmash” can be used in high power Hydrogenerators in the entire range of operational loads without restrictions.

MATHEMATICAL MODELING OF TECHNOLOGICAL MODES OF HEAT-PUMPING SYSTEMS FOR TECHNOLOGICAL PROCESSES

One of the ways to increase the energy efficiency of the process of heat supply of technological facilities and production facilities of the agro-industrial complex is the use of heat pumps. Their use allows to increase the energy potential of heat carriers. To optimize the mode parameters and create systems for automatic control of the heat pump installation, it is necessary to establish a relationship between the parameters of the processes occurring in the elements of the installation by creating a mathematical model of non-stationary thermal modes. In the analysis of recent studies and publications, it is established that the calculations of processes in heat pumps are presented mainly for stationary modes of operation without taking into account the dynamics of the condenser. If the dynamic modes of individual elements are given, then they are described by mathematical models of considerable complexity, which greatly complicates their practical implementation. In the article, the heat pump installation, as an object of modeling, is considered as a physical system, which consists of four series-connected elements: evaporator, condenser, compressor, throttle valve forming a closed circuit. The principle of operation of a simple heat pump installation is explained by the scheme and schedule of the theoretical cycle of the steam compressor heat pump. To simplify the mathematical model, certain assumptions were made: the change in the parameters of liquid, vapor and air varies in a straight line, the thermophysical characteristics of the material of heat exchangers, air and vapor flows, heat transfer coefficients do not depend on temperature and are average for the cycle. On the basis of thermal and material balance the corresponding differential equations which make mathematical model of dynamics of change of parameters of the heat exchanger have been made. The mathematical model is supplemented by a simulation model in the MatLAB / Simulink computer environment, as well as graphical interpretations of dynamic characteristics. The developed mathematical model of dynamics of thermal processes in the heat pump installation can be used for calculation of parameters of heating and cooling of streams of heat carriers and creation of system of automatic control of them.

THERMAL PHYSICAL ASPECTS OF DETERMINATION OF LOAD CAPACITY MEDIUM VOLTAGE POWER CABLES WITH CROSS-POLYETHYLENE INSULATION IN STATIONARY OPERATING MODES

Currently, the development trends of global medium voltage cable networks are aimed at the introduction of cables with cross-linked polyethylene insulation. Such cables have a higher operating temperature, which allows to increase their throughput, and increased stability when working in conditions of overload and short circuits. It is possible to determine the allowable heat and electrical loads only if the heat balance is observed. Fundamentally important for solving the problems of heat balance is the significant dependence of thermal conductivity and heat capacity of polyethylene insulation on temperature. It is established that the capacity of the cable, determined by regulatory models and average environmental parameters, provides only preliminary information about its heating. For certain requirements and for innovative cable designs, a necessary condition for determining the load capacity in real stationary modes of operation is the use of the heat balance model. A system of mathematical equations is proposed, which due to the combination of structural and thermophysical parameters of the cable with the conditions of the external environment allows to determine the parameters of the stationary thermal regime of the cable at any load current.

Model and Results of a Study of the Synthesis of Finely Dispersed Silicon Carbide in an Electro-Thermal Reactor

The high-temperature synthesis of silicon carbide (SiC) in an electro-thermal fluidized bed reactor (EFB) has advantages, in comparison with the production in resistance furnaces, in terms of specific energy consumption, productivity and the level of automation of the technological process. The basic equations of the fluidized-bed carbide formation process model are presented in the paper. The results of calculating the synthesis parameters of finely dispersed SiC in the stationary operation mode of the EFB reactor are also presented. The correspondence between the calculated and available experimental results on the output of the final product is shown.

Theoretical Investigation on Performance Characteristics of Aerostatic Journal Bearings with Active Displacement Compensator

Active aerostatic bearings are capable of providing negative compliance, which can be successfully used to automatically compensate for deformation of the machine tool system in order to reduce the time and improve the quality of metalworking. The article considers an aerostatic radial bearing with external combined throttling systems and an elastic displacement compensator, which is an alternative to aerostatic bearings with air flow rate compensators. The results of the mathematical modeling and theoretical research of stationary and nonstationary modes of operation of bearings with slotted and diaphragm throttling systems are presented. A counter-matrix sweep method has been developed for solving linear and nonlinear boundary value problems in partial derivatives with respect to the function of the square of the pressure in the bearing gap and inter-throttling bearing cavities for any values of the relative shaft eccentricity. A numerical method is proposed for calculating the dynamic quality criteria, and the transfer function of the dynamic compliance of a bearing with small displacements is considered as a linear automatic control system with distributed parameters. An experimental verification of the theoretical characteristics of the bearing was carried out, which showed a satisfactory correspondence among the compared data. It is shown that bearings with a throttle system have the best quantitative and qualitative load characteristics. The possibility of optimal determination of the values of a number of important parameters that provide the bearing with optimal performance and a high stability margin is established. It is shown that bearings with an elastic suspension of the movable sleeve allow one to compensate for significant movements, which can be larger than the size of the air gap by an order of magnitude or more. In these conditions, similar bearings with air flow compensators would be obviously inoperative.