scholarly journals Technological features of production of copper-based composites reinforced with cast iron granules by means of casting

2019 ◽  
pp. 114-118
Author(s):  
A. S. Kalinichenko ◽  
V. A. Sheinert ◽  
V. A. Kalinichenko ◽  
A. G. Slutsky
Keyword(s):  
Cast Iron ◽  
Composite Materials ◽  
Low Cost ◽  
Experimental Studies ◽  
Operational Reliability ◽  
Operating Conditions ◽  
High Wear Resistance ◽  
Friction Units ◽  
Wide Range ◽  
Methods Of Synthesis

Increasing the operational reliability of friction units is one of the priorities for mechanical engineering, which requires the creation of effective tribotechnical materials. First of all, this applies to sliding bearings, which are used in various friction units in a wide range of operating conditions and must meet a number of requirements: low coefficient of friction, high wear resistance and fatigue resistance, as well as good thermal conductivity, workability, corrosion resistance and machinability, low coefficient of linear expansion and low cost. It is problematic to satisfy these requirements in real conditions; therefore, different friction materials that are best suited to specific conditions have been developed. In particular, cast composite materials (LCM) have been developed, which have found application in various friction units operating in severe operating conditions. Currently, the theoretical foundations of the mechanics of reinforced composite materials are well developed, and a significant progress has been achieved in their material science. However, there are still many problems associated with the choice of optimal technology ensuring the achievement in practice of the predicted composites properties by theory, control of interfacial interaction to improve the stability of the structure and properties of CM, with the development of new types of reinforcing elements that can raise the level of composite performance.In the present work results of scientific and experimental studies on the development of casting technology (solid-liquid synthesis) for obtaining composite materials with macroheterogeneous structure have been summarized. The structures of composites are studied for different methods of synthesis, as well as for different chemical composition of cast iron granules. The prospects of using white vanadium cast iron granules as a reinforcing phase are shown.

scholarly journals Pressure losses and oscillations in a compact valve of a steam turbine

2021 ◽  
Vol 345 ◽  
pp. 00027
Author(s):  
Václav Sláma ◽  
David Šimurda ◽  
Lukáš Mrózek ◽  
Ladislav Tajč ◽  
Jindřich Hála ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Pressure Oscillation ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Steam Turbines ◽  
Valve Seat ◽  
Pressure Losses ◽  
Oscillation Analysis ◽  
Seat Angle ◽  
Wide Range

Characteristics of a new compact valve design for steam turbines are analysed by measuring pressure losses and oscillations on the valve model. It is the model of an intercept valve of the intermediate-pressure turbine part. This valve is relatively smaller hence cheaper than usual control and intercept valves. Besides, four different valve seat angles were tested in order to investigate the valve seat angle influence. In order to further clarify measured phenomena, the wide range of numerical simulations were also carried out. Measurements were performed in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences in an air test rig installed in a modular aerodynamic tunnel. Numerical simulations were performed in the Doosan Skoda Power Company using a package of ANSYS software tools. Measurement results are compared with numerical and generalized in the form of valve characteristics and pressure oscillation maps. As a result of the pressure loss analysis, pressure losses in similar valve assemblies can be predicted with required accuracy for each new turbine where modern compact valves are used. As a result of the pressure oscillation analysis, operating conditions at which dangerous flow instabilities can occur were identified. Thanks to this, the areas of safe and dangerous operating conditions can be predicted so that the operational reliability of the valve can be guaranteed.

scholarly journals Hydrothermal Energy Systems Development in the USA

1997 ◽  
Author(s):  
Radon Tolman ◽  
Ronald C. Timpe
Keyword(s):  
Activated Carbon ◽  
Steam Generator ◽  
Low Cost ◽  
Energy Systems ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Federal State ◽  
Supercritical Conditions ◽  
Wide Range ◽  
The Usa

A revolutionary hydrothermal steam generator is being developed by a federal, state university and industry partnership in the US to enhance economic growth and trade. The new generator is designed to accept solutions and slurries without corrosion and deposition on heat transfer surfaces up to the supercritical conditions of water, above 221 bar (3205 psia) and 374 C (705 F). The generator will produce steam from low quality water, such as from geothermal sources, for increased electric power generation. Water treatment costs and effluents will be eliminated for “zero discharge.” To improve efficiency and limit carbon dioxide and other emissions, the new steam generator will be tested for converting wastewater slurries of low-cost fuels and “negative value” wastes such as hazardous wastes, composted municipal wastes and sludges, to clean gas turbine fuel, hydrocarbon liquids, and activated carbon. Bench-scale results at sub- and supercritical conditions for lignite, refuse derived fuel, tire rubber and activated carbon are presented. An advanced continuous-flow pilot plant is being designed to test the generator over a wide range of operating conditions, including slurry feed up to 30 percent solids. Demonstration of the hydrothermal steam generator will be followed by design and construction of combined-cycle energy systems.

A New Analytical Model of a Centrifugal Compressor and Validation by Experiments

2010 ◽  
Vol 26 (1) ◽  
pp. 37-45 ◽  
Author(s):  
H. Pourfarzaneh ◽  
A. Hajilouy-Benisi ◽  
M. Farshchi
Keyword(s):  
Conceptual Design ◽  
Centrifugal Compressor ◽  
Experimental Studies ◽  
Design Tool ◽  
Operating Conditions ◽  
Experimental Results ◽  
Design Phase ◽  
Robust Model ◽  
Conceptual Design Phase ◽  
Wide Range

AbstractIn the conceptual design phase of a turbocharger, where emphasis is mainly on parametric studies, before manufacturing and tests, a generalized and robust model that implies over a wide range properly, is unavoidable. The critical inputs such as compressor maps are not available during the conceptual design phase. Hence, generalized compressor models use alternate methods that work without any supplementary tests and can operate on wide range. One of the common and applicable modeling methods in design process is the ‘Dimensionless Modeling’ using the constant coefficient scaling (CCS). This method almost can predict the compressor characteristics at design point. However, at off design conditions, error goes up as mass flow and speed parameters increase. Therefore, the results are not reliable at these points. In this paper, a variable coefficient scaling (VCS) method is described. Then, a centrifugal compressor is modeled using the VCS method. To evaluate the model and compare it with the experimental results, some supplementary experiments are performed. Experimental studies are carried out on the compressor of a S2B model of the Schwitzer turbocharger in the turbocharger Lab., at Sharif University of Technology. The comparison between the experimental results and those obtained by the VCS method indicates a good agreement. It also suggests that the present model can be used as an effective design tool for all operating conditions.

scholarly journals RESEARCH OF TECHNICAL CHARACTERISTICS OF NEW TYPES OF COUPLINGS

2020 ◽  
pp. 113-121
Author(s):  
Oleksii Tokarchuk ◽  
Yurii Polievoda
Keyword(s):  
Elastic Element ◽  
Rational Design ◽  
Experimental Studies ◽  
Bending Moment ◽  
Operational Reliability ◽  
Modern Technology ◽  
Operating Conditions ◽  
The Moment ◽  
Working Bodies ◽  
Moment Of Resistance

Dynamic loads that occur during the operation of existing couplings cause significant shock loads, which leads to rapid wear of the surfaces of the couplings and shortens the service life. Modern technology faces the task of improving the operational reliability of the working bodies and drives of machines. One way to solve this problem is to develop and use high-precision and low-dynamic safety couplings. In this regard, the question of developing new designs of safety couplings that reduce impact loads and increase the reliability and durability of machinery is relevant. The synthesis of structural and kinematic schemes of ball, cam and planetary safety couplings, the method of their calculation in combination with the nature of the change in the moment of resistance on the working body of the equipment. The article conducts a set of theoretical and experimental studies to determine their rational design, kinematic and dynamic parameters that will satisfy the operating conditions of machines and mechanisms. A force analysis of the elastic element (ring spring) was performed. The scheme of loading of an elastic element by two forces and other settlement schemes are constructed, namely: equivalent system; force diagrams for determining the load torque; force schemes for determining the unit moment; schemes of total bending moment; force schemes to determine the total unit moment. During static experimental studies of the developed ball safety couplings, the nature of their operation was established, the maximum torque at the two stages of operation of the couplings was determined and a comparative analysis between the results of theoretical and experimental studies was performed. The positive results of experimental researches of the developed coupling and theoretical positions which can be applied to a substantiation and a choice of rational parameters of the developed designs of couplings and their engineering designing were confirmed.

scholarly journals IMPROVING THE OPERATIONAL RELIABILITY OF HYDRAULIC FACILITIES WHEN USING POLYMER AND POLYMER-CEMENT COMPOSITES

2019 ◽  
pp. 217-230
Author(s):  
O. V. Kovalenko
Keyword(s):  
Composite Materials ◽  
Environmental Factors ◽  
Concrete Structures ◽  
High Strength ◽  
Cement Composite ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Hydraulic Structures ◽  
Water Reclamation ◽  
Technical Solutions

Actualuty of the problem. The effective functioning of water-reclamation systems depends to a large extent on the operational reliability and durability of hydraulic structures. The structural elements of hydraulic structures of water management and reclamation complex from the moment of commissioning are subject to aggressive environmental influences. Aggressive factors (hydrostatic water pressure, alternating freezing and thawing, wetting and drying, corrosive action of salts dissolved in water, dynamic action of ice, etc.) constantly affect concrete structures, gradually destroying them. Therefore, the development of measures aimed at ensuring high resistance of structures to the aggressive environmental factors is relevant. Effective operation of structures with long-term aggressive environmental factors is only possible if they are protected (reinforced) with effective insulating, anticorrosive, high-strength, wear-resistant and cavitation-resistant composite materials. Specific characteristics of polymer and polymer-cement composite materials (high strength, corrosion resistance, frost resistance, adhesion to different coatings) enable to create effective technologies for restoring the functional capacity of hydraulic structures and increasing their stability. The need of reinforcing concrete structures of hydraulic facilities by combining or partially replacing them with modern composite materials and structures made of polymers and polymer cement is determined in view of increasing coolness, reliability and durability of the structures. These materials should be standardized at the stage of design, construction, repair and reconstruction of structures that will ensure their operational reliability and durability in aggressive environment. The development and implementation of technical solutions increasing the operational reliability and durability of hydraulic facilities for water-reclamation purposes while reducing their material and metal intensity are ones of the main areas of scientific research in the field of construction, repair and reconstruction of water-reclamation systems. Achieving high technical and economic performance of hydraulic facilities, taking into account the significant effect of aggressive environmental factors on them is possible using a scientifically sound combination of concrete and reinforced concrete structures with polymer and polymer cement composite materials. The highest level of reliability will be ensured by the structures providing the protection against damage, corrosion and filtration using the latest high performance composite materials. Optimization of technical solutions to increase the operational reliability and durability of hydraulic facilities is only possible provided that modern composite materials properties are comprehensively studied, their compliance with the requirements of water and reclamation construction, taking into account extreme operating conditions, is determined and new efficient technologies for future performance of the facilities are created. Along with expanding the use of polyme and polymer-cement composite materials, finding new varieties of polymer additives and obtaining reliable data on the durability of these materials in different operating conditions will be extended. Results. The Institute of Water Problems and Land Reclamation of NAAS has developed the main technological areas of polymer and polymer-cement composite materials application for increasing the operational reliability of hydraulic structures of water management and reclamation complex: polymeric film screens and geomembranes for increasing the anti-filtration properties; polymer and bitumen-polymer sealants for the arrangement and restoration of deformation joints; polymer and polymer-cement mixtures for structural repairs, restoration of bearing capacity, waterproofing protection, protection against filtration, accidental damage, corrosion, cavitation and actuation of hydraulic structures; concrete polymers, polymer concrete and polymer cement with high physical and mechanical properties for construction, repair and reconstruction of hydraulic structures.

scholarly journals Estimation peculiarities of external polymer insulation reliability of gas-filled instrument transformers

2021 ◽  
pp. 3-9
Author(s):  
Liudmyla Zhorniak ◽  
Alexej Afanasiev ◽  
Vitaliy Schus ◽  
Olexij Morozov ◽  
Julia Rudenko
Keyword(s):  
High Voltage ◽  
Accurate Determination ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Operational Reliability ◽  
Current Transformer ◽  
Operating Conditions ◽  
Distribution Law ◽  
Instrument Transformers ◽  
And Performance

In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of operational reliability. In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of the operational reliability of a solid insulating structure of high-voltage devices, which is a supporting insulating cover for high voltage instrument transformers filled with gas as an insulating liquid. This technique makes it possible to estimate the parameters of a new distribution law, which is chosen on the condition that it does not contradict the existing distribution law with its known parameters. The developed technique makes it possible to obtain the values of the indicators of the operational reliability of high-voltage equipment by determining the parameters of theoretical distributions, if the developer is the data of experimental studies or statistical information as a result of monitoring the operation of insulating structures, taking into account the actual operating conditions of such high-voltage devices.  This makes it possible to take into account the influence of external factors and performance characteristics inherent in instrument transformers, both current and voltage. In the proposed methodology, as an example, a supporting insulating casing is considered, which is during operation in the most unfavorable conditions, such as external pollution, humidification, overvoltage, etc. The theoretical conclusions are confirmed by the results of calculations using the example of the design of a current transformer of the ТОГ-362 series. A more accurate determination of the effectiveness of the proposed method for predicting the parameters of theoretical distribution laws can be achieved by performing an additional series of calculations and experimental tests of specific insulating structures. Thus, it was concluded that it is possible to use the results obtained to assess the operational reliability of both gas-filled instrument transformers and similar high-voltage equipment.

scholarly journals Program for determination of zones of gold concentration on sluices of washing devices

2021 ◽  
Vol 895 (1) ◽  
pp. 012002
Author(s):  
V S Alekseev ◽  
R S Seryi
Keyword(s):  
High Performance ◽  
Two Phase Flow ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Phase Flow ◽  
Technological Parameters ◽  
Two Phase ◽  
Alluvial Gold ◽  
Wide Range ◽  
Host Rocks

Abstract Currently sluice washing devices are the most common in alluvial gold mining. Their use provides a sufficiently high performance, relatively low power consumption, and acceptable recovery of valuable components. The theoretical provisions of traditional hydraulics make it possible to determine all the main parameters of the movement of particles of rocks and gold in the pulp, however, in real operating conditions of the sluice box, their actual values will differ greatly from the calculated ones, especially if there are solid fractions in the pulp with a particle size of more than 20 mm. This is explained by significant fluctuations in the values of the surface, average and bottom velocities of the two-phase flow, vertical pulsation velocity in conditions of constrained movement of the different fractional composition of rocks. The article presents the results of experimental studies to identify the dependence of the distance traveled by an individual gold particle and host rocks in a two-phase flow through a sluice, the bottom of which is lined with trapping coatings, on the design and technological parameters of the flushing device. The mathematical model for determining this distance formed the basis of the Gold Enriching program. The program allows, in a wide range of initial data, to determine the zones of concentration of gold of a certain size at the sluice boxes.

Elastohydrodynamic Film Thickness in Concentrated Contacts: Part 2: Correlation of Experimental Results with Elastohydrodynamic Theory

1986 ◽  
Vol 200 (3) ◽  
pp. 219-226 ◽  
Author(s):  
R J Chittenden ◽  
D Dowson ◽  
C M Taylor
Keyword(s):  
Film Thickness ◽  
Experimental Studies ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Experimental Results ◽  
Experimental Techniques ◽  
Dimensionless Parameters ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Computational Procedures

The existence of a coherent film of lubricant between highly loaded machine elements has been recognized for many years. Over this period of time measurements of film thickness have gone hand in hand with theoretical analyses in the field now known as elastohydrodynamic lubrication. The experimental techniques of capacitance, electrical resistance and X-ray measurement have been supplemented by the use of optical interferometry while the analytical expressions obtained with the use of elegant simplifications have been superseded by those developed from extensive and comprehensive computational procedures. These developments in experimental techniques have yielded a substantial number of measurements of both minimum and central film thickness. Likewise, the advent of the digital computer has allowed the derivation of a large number of solutions to the problem of elastohydrodynamic lubrication of concentrated contacts. All these results, covering a wide range of geometrical conditions, are to be found in the literature, yet little attempt appears to have been made to assemble a representative set of experimental data to permit a detailed evaluation of the theoretical formulae for elliptical contacts. The second part of this paper therefore considers the correlation between a number of experimental studies covering a wide range of operating conditions and geometries, and the predictions of recent elastohydrodynamic theory. Some of the important aspects of each set of experimental results are then considered and examples are provided which illustrate the following points: 1. Good estimates of lubricant film thickness may be obtained from the theoretical expressions recently derived, even when the dimensionless parameters involved are outside the ranges considered in the derivation of the formulae. 2. The discrepancies which exist between theoretical predictions and some of the measured film thicknesses are nevertheless quite large, even when the dimensionless parameters are within their usual limits. On the whole there is good agreement between experiment and theory, while the general trend of the results indicates that theoretical predictions may underestimate the minimum film thickness by about 10 per cent and the central film thickness by about 25 per cent. This measure of agreement is quite remarkable when the extreme difficulty of interpreting the magnitudes of effective and very thin mean film thicknesses between machined components in various forms of experimental equipment is considered.

Restoration of Agricultural Machines Surfaces by White Cast Iron with the Formation of Technological Repair Units

2018 ◽  
Vol 927 ◽  
pp. 43-47
Author(s):  
V.K. Afanasyev ◽  
A.P. Chernysh ◽  
S.V. Dolgova
Keyword(s):  
Surface Layer ◽  
Cast Iron ◽  
White Cast Iron ◽  
Low Cost ◽  
Operating Conditions ◽  
Technological Environment ◽  
New Approach ◽  
Selection Of ◽  
Agricultural Machines

This article develops a fundamentally new approach in the selection of optimal methods for restoring of worn surfaces of agricultural machines’ tools with the formation and application of technological repair units. Based on the systematization and linkage of modular worn-out surfaces, their operating conditions, technological environment and the choice of their optimal combinations, it found a low-cost method of restoring details with white cast iron to gain a necessary quality of a new surface layer.

scholarly journals ANALYSIS OF THE CONDITIONS OF OCCURRENCE AND SUPPRESSION OF LATERAL VIBRATIONS IN MICROWAVE POWER FETS

2020 ◽  
Vol 258 (3) ◽  
pp. 4-21
Author(s):  
V. L. Aronov ◽  
E. M. Savchenko ◽  
D. M. Moseykin ◽  
A. D. Pershin ◽  
D. G. Drozdov
Keyword(s):  
Experimental Studies ◽  
Element Model ◽  
Excitation Power ◽  
Point Of View ◽  
Operating Conditions ◽  
Stability Factor ◽  
Lateral Instability ◽  
Wide Range ◽  
Amplifier Stage ◽  
The Stability

Lateral instability is inherent in power transistors structures, consisting of several simple transistors connected in parallel. The large number of transistor elements complicates the analysis of such instability. The introduction of suppressing resistors makes it possible to prevent the occurrence of lateral oscillations, however there are no unambiguous criteria for achieving stability this way. The matter is further complicated by the fact that transistor exhibits nonlinear operation in a typical amplifier stage, and the operating conditions in many cases correspond to a relatively wide range of frequencies. In this paper, we present an analysis of lateral instability of a power amplifier stage, created on a basis of modern GaN field-effect transistor (FET). We had designed all dies and circuits for this FET. The main feature of the analysis is that we carried it out in the time domain, which made possible to estimate the stability of the stage not only under the excitation power pulse, but also after the end of the pulse. Our approach makes it possible to assess the stability of the amplifier between the excitation pulses, which is very important from the operational point of view. We calculated the estimates of operational stability and stability factor using a simplified transistor model, with the multi-element model reduced to a two-element model. Nevertheless, the results of the estimates retain their significance in real conditions, when the introduction of suppressing resistors creates a significant margin of stability, including the actual operating frequency band of the stage. To date, the data we have obtained after the manufacture of the samples only partially confirms the calculated estimates, due to the complexity of managing the experimental studies. However, there are no recorded results, which deny our estimates for the model.

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