Technical mechanics最新文献

{"title":"System of fuzzy automatic control of coal massif cutting by a shearer drum","authors":"A. Bublikov, N. Pryadko, Y. Papaika","doi":"10.15407/itm2021.03.099","DOIUrl":"https://doi.org/10.15407/itm2021.03.099","url":null,"abstract":"Up to now, automatic control of the shearer speed has been performed to keep the actual speed at an operator-specified level or to keep the actual power at a stable level without overheating or overturning. However, the problem of control of coal seam cutting by the upper drum of a shearer in the case of a variable angle of drum – coal seam contact has yet to be studied. The aim of this work is to develop a method for synthesizing a system of fuzzy automatic control of coal massif cutting by a shearer drum based on an information criterion for the power efficiency of coal cutting with cutters. In this work, based on an information criterion for the power efficiency of coal cutting with cutters, a fuzzy inference algorithm is constructed for a system of automatic control of coal massif cutting by a shearer drum. In doing so, the parameters of the output linguistic variable term membership functions of the system and fuzzy operations are determined according to the recommendations of the classical Mamdani fuzzy inference algorithm using substantiated fuzzy production rules. The fuzzy inference algorithm constructed in this work is tested for efficiency based on the fraction of effective control actions generated by the fuzzy automatic control system. Using simulation, the efficiency of drum rotation speed control with the use of the proposed fuzzy inference algorithm is compared with that with the use of an uncontrolled shearer cutting drive. The study of the generation of control actions involving the upper shearer drum rotation speed showed that effective control actions were generated in the overwhelming majority of cases (about 93%). The proposed method forms a theoretical basis for the solution of the important scientific and practical problem of upper shearer drum rotation speed control automation with the aim to reduce specific power consumption and the amount of chips.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130671288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Minimax model of transport operations of emergency on-orbit servicing in heliosynchronous orbits","authors":"Yu.M. Holdshtein","doi":"10.15407/itm2021.03.048","DOIUrl":"https://doi.org/10.15407/itm2021.03.048","url":null,"abstract":"Heliosynchronous orbits are attractive for space system construction. As a result, the number of spacecraft operating therein is constantly increasing. To increase their efficiency, timely on-orbit servicing (both scheduled and emergency) is needed. Emergency on-orbit servicing of spacecraft is needed in the case of unforeseen, emergency situations with them. According to available statistical estimates, emergency situations with serviced spacecraft are not frequent. Because of this, serviced spacecraft must be within the reach of a service spacecraft for a long time. In planning emergency on-orbit servicing, the following limitations must be met: the time it takes the service spacecraft to approach any of the serviced spacecraft must not exceed its allowable value, and the service spacecraft’s allowable energy consumption must not be exceeded. This paper addresses the problem of searching for emergency on-orbit servicing that would be allowable in terms of time and energy limitations and would meet technical and economical constraints. The aim of this work is to develop a mathematical constrained optimization model for phasing orbit parameter choice, whose use would allow one to minimize the maximum time of transport operations in emergency on-orbit servicing of a spacecraft group in the region of heliosynchronous orbits. The problem is solved by constrained minimax optimization. What is new is the formulation of a minimax (guaranteeing) criterion for choosing phasing orbit parameters that minimize the maximum time of emergency on-orbit servicing transport operations. In the minimax approach, the problem is formulated as the problem of searching for the best solution such that the result is certain to be attained for any allowable sets of indeterminate factors. The proposed mathematical model may be used in planning emergency on-orbit service operations to minimize the maximum duration of emergency on-orbit servicing transport operations due to a special choice of the service spacecraft phasing and parking orbit parameters.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130224805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Current problems in the low-frequency dynamics of liquid-propellant rocket propulsion systems","authors":"O. Pylypenko, O.N. Nikolayev, N. Khoriak, S. Dolgopolov, I. D. Bashliy","doi":"10.15407/itm2021.03.009","DOIUrl":"https://doi.org/10.15407/itm2021.03.009","url":null,"abstract":"One of the key problems in liquid-propellant rocket engine (LPRE) design is to provide the stability of LPRE working processes, in particular low-frequency stability. In LPRE experimental tryout, every so often there occur situations where the development of divergent oscillations set up in some of the LPRE loops or units results in contingencies: exceeding the engine ultimate strength, pump stall, chamber ignition, etc. Such contingencies may lead to grave consequences, including engine and bench equipment failure. Because of this, mathematical simulation is one of the main tools that allow one to predict he dynamic performance of an LPRE both in its steady operation and in transients and its startup operation features at the design and tryout stage. This paper overviews and analyzes scientific publications for the past 15 years concerned with the study of the dynamics and low-frequency stability of advanced LPREs and units thereof along different lines. This analysis made it possible to identify problems in low-frequency stability prediction and assurance for liquid-propellant rocket propulsion systems (LPRPSs) under design, to cover new research results (experimental and theoretical) on the origination and development of all-engine low-frequency oscillations and low-frequency oscillations in LPRPS systems and units and to identify new approaches to the mathematical simulation and study of low-frequency processes in LPRPSs and promising lines of investigation. The man lineы of the analysis are as follows: the low-frequency dynamics of cavitating inducer-equipped centrifugal pumps and LPRE gas paths, LPRE thrust control problems, the interaction of launch vehicle airframe longitudinal oscillations with low-frequency processes in the sustainer LPRPS, dynamic processes during an LPRE startup/shutdown, and low-frequency in-chamber oscillations.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121343218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimation of probe measurements reliability in a supersonic flow of a four-component collisionless plasma","authors":"D. Lazuchenkov, N. Lazuchenkov","doi":"10.15407/itm2021.03.057","DOIUrl":"https://doi.org/10.15407/itm2021.03.057","url":null,"abstract":"The aim of this work is to estimate the reliability of extracting the plasma electron density and temperature and ionic composition from the current-voltage (I-V) characteristic of an isolated probe system with cylindrical electrodes. An earlier proposed mathematical model of current collection by the probe system at positive bias potentials and an arbitrary ratio of the electrode areas is analyzed. The model is supplemented with a formula that determines, with an accuracy of several percent, the value of the bias potential at which the probe is under the plasma potential and the I-V characteristic splits into a transition and an electronic region. The analytical dependence of the bias potential on the plasma parameters and the ratio of the electrode areas made it possible to formalize the procedures for determining and assessing the reliability of the extracted plasma parameters using the regions of their strongest effect on the collected probe current. Parametric studies of the effect of the plasma parameters on the probe current were carried out for conditions close to measurements in the ionosphere. The paper demonstrates the feasibility of partitioning the sought-for plasma parameters into the regions of their strongest and weakest effect on the probe current in the range of the bias potentials considered. The problem of plasma parameter identification is formulated on the basis of a comparison of the probe current and the measured I-V characteristic in the L2 theoretical approximation. To each parameter there corresponds an objective function of its own, which differs in the domain of definition and the ratio of the electrode areas used in I-V characteristic measurements. Based on this formulation of the inverse problem in L2, estimates of the reliability of identification of the parameters of a plasma with two ion species are obtained depending on the errors of the model and probe measurements. The results obtained may be used in ionospheric plasma diagnostics.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122384379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of the efficiency of a multiple launch rocket system","authors":"E. Hladkyi, O. Zavoloka","doi":"10.15407/itm2021.03.037","DOIUrl":"https://doi.org/10.15407/itm2021.03.037","url":null,"abstract":"Up-to-date multiple launch rocket systems (MLRSs) are adopted by many countries of the world, and they are an effective weapon against dispersed multiple targets. Developing and upgrading MLRSs calls for estimating their efficiency with the aim to select an optimum alternative. For an MLRS, the basic measure of area target destruction efficiency is the relative damage area. This measure depends on the damage area of the MLRS itself (extent of damage by one salvo). The paper suggests a relative criterion that allow one to estimate and optimize the salvo damage area. The criterion is based on the ratio of the salvo damage area to the maximum damage area and that of the undamaged area to the coverage area. The coverage area is defined as the area of the enveloping convex polygon for all points of missile impact in a salvo. It is shown that the domain of variation of the suggested criterion is the interval [0, 1]. Using the suggested criterion for 4 points of missile impact with a circular damage area, two basic structures are studied: a rhomb (two regular triangles) and a square. For them, optimum distances between the missile impact points that maximize the destruction level are determined. It is shown that the obtained optimum arrangement of missile impact points allows one to bring the extent of damage for the square structure to the more optimum rhomb layout (represents a part of the hexagonal structure, which is the most efficient from the standpoint of the packing problem). For a 16-missile salvo, it is shown that from the standpoint of the suggested criterion there exists an optimum relation between the missile damage area (radius) and the technical scattering parameters. The maximum value of the criterion for a missile salvo with account for the technical spread does not exceed 0.33 and is much lower than the value that can be obtained for the optimum structures (rhomb and square). The paper shows possibilities of using the criterion in deciding on optimum missile impact points with account for various typical targets within a multiple target and missile damage area configurations other than a circle.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128041473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Verification of a mathematical model for the solution of the Stefan problem using the mushy layer method","authors":"R.S. Yurkov, L. Knysh","doi":"10.15407/itm2021.03.119","DOIUrl":"https://doi.org/10.15407/itm2021.03.119","url":null,"abstract":"The use of solar energy has limitations due to its periodic availability: solar plants do not operate at night and are ineffective in dull weather. The solution of this problem involves the introduction of energy storage and duplication systems into the conversion loop. Among the energy storage systems, solid–liquid phase transition modules have significant energy, ecologic, and cost advantages. Physical processes in modules of this type are described by a system of non-stationary nonlinear partial differential equations with specific boundary conditions at the phase interface. The verification of a method for solving the Stefan problem for a heat-storage material is presented in this paper. The use of the mushy layer method made it possible to simplify the classical mathematical model of the Stefan problem by reducing it to a nonstationary heat conduction problem with an implicit heat source that takes into account the latent heat of transition. The phase transition is considered to occur in an intermediate zone determined by the solidus and liquidus temperatures rather than in in infinite region. To develop a Python code, use was made of an implicit computational scheme in which the solidus and liquidus temperatures remain constant and are determined in the course of numerical experiments. The physical model chosen for computer simulation and algorithm verification is the process of ice layer formation on a water surface at a constant ambient temperature. The numerical results obtained allow one to determine the temperature fields in the solid and the liquid phase and the position of the phase interface and calculate its advance speed. The algorithm developed was verified by analyzing the classical analytical solution of the Stefan problem for the one-dimensional case at a constant advance speed of the phase interface. The value of the verification coefficient was determined from a numerical solution of a nonlinear equation with the use of special built-in Python functions. Substituting the data for the physical model under consideration into the analytical solution and comparing them with the numerical simulation data obtained with the use of the mushy layer method shows that the results are in close agreement, thus demonstrating the correctness of the computer algorithm developed. These studies will allow one to adapt the Python code developed on the basis of the mushy layer method to the calculation of heat storage systems with a solid-liquid phase transition with account for the features of their geometry, the temperature level, and actual boundary conditions.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"58 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120916194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aerodynamic improvement of an aircraft gas-turbine engine fan","authors":"Y. Kvasha, N. Zinevych","doi":"10.15407/itm2021.03.023","DOIUrl":"https://doi.org/10.15407/itm2021.03.023","url":null,"abstract":"This work is concerned with the development of approaches to the aerodynamic improvement of axial-flow compressors for gas-turbine engines. The aim of this work is the aerodynamic improvement of an aircraft gas-turbine engine two-stage fan by numerical simulation of 3D turbulent gas flows. The approach used in this study features: varying the spatial shape of the fan blades for the first- and the second-stage impeller by varying the profile angle along the blade height; formulating quality criteria as the mean integral values of the power characteristics of each impeller of the fan over the operating range of the air flow rate through the impeller; and searching for advisable values of the impeller blade parameters by scanning the independent variable range at points that form a uniformly distributed sequence of small length. The basic tool is a numerical method developed at the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, which simulates 3D turbulent gas flows using the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. It is shown that varying the profile angle along the blade height for the fan second-stage impeller allows one to increase the air compression ratio in the fan by about 2 percent throughout the operating range of the fan air flow rate without affecting the adiabatic efficiency of the fan. On the whole, by the example of the fan under study, the paper considers the assumption that the aerodynamic improvement of compressors at the initial stage can be made on an impeller by impeller basis. It is shown that in further analysis providing the gas-dynamic stability of the compressor should be accounted for. The results obtained are intended to be used in the aerodynamic improvement of multistage compressors for aircraft gas-turbine engines and various power plant.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128083064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"State of the art in the development of orbital industrial platforms","authors":"O. Palii","doi":"10.15407/itm2021.03.070","DOIUrl":"https://doi.org/10.15407/itm2021.03.070","url":null,"abstract":"The goal of this article is to analyze the state of the art in the development of orbital industrial platforms and their components. The article proposes the general arrangement of a base orbital industrial platform, which consists of main supporting structures, onboard systems, an onboard control system, onboard service devices, receiving docks, a primary processing module, a secondary processing module, an industrial module, and an assembly module. The state of the art in the development of the key component modules of an orbital industrial platform is analyzed, and it is concluded that space conditions make it possible to produce new materials and substances whose characteristics are improved in comparison with their earth counterparts. The most interest in the development of production processes in vacuum and zero gravity conditions is shown by the USA, Russia, and the EU countries. It is shown that at the initial stage of development of orbital industrial platforms raw materials for the production of unique materials can be supplied from the Earth. With further technological development, it will be possible to use space resources. Orbital industrial platforms are a new class of engineering systems. To develop a mathematical model of an orbital platform and components thereof, its functional diagram with the key functional links between the platform components is presented. The problem of orbital industrial platform development is complex, and thus it has a wide range of different aspects of its solution. The need to develop a scientific methodology for the process of orbital industrial platform development has given rise to a package of scientific and technological problems generated by the features of this problem. This package includes the development of new classifiers, construction arrangements, mathematical models, and design methods for a base platform and components thereof.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114653458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of a cathode resistant to vacuum chamber operation conditions","authors":"S.M. Kulahin, M.I. Pysmennyi, D.K. Voronovskyi, B.V. Yurkov","doi":"10.15407/itm2021.03.030","DOIUrl":"https://doi.org/10.15407/itm2021.03.030","url":null,"abstract":"The aim of this work is to develop a thermoemission cathode that would ensure the required operating parameters and remain operable after long, several-day, exposure to the air without any additional ampulization. Cathode thrmoemitter degradation (“poisoning”) processes are overviewed. The problem of degradation of tungsten-barium cathodes is caused by the penetration of chemically active substances (for example, oxygen) into the interior space of a cathode. The “poisoning” process is so complex that it can hardly be simulated by simple theoretical methods. Because of this, the cathode “poisoning” degree under exposure to the atmosphere is usually assessed using experimental data. The analysis of publications on the resistance of cathode emitters to atmospheric exposure showed that one of the most promising solutions to the cathode “poisoning’ problem is the use of an emitter based on barium scandate. A cathode construction diagram was chosen, and a laboratory prototype cathode was made. The current dependence of the discharge voltage at different xenon flow rates and the xenon flow rate dependence of the discharge voltage at different currents were studied experimentally (xenon was the plasma-forming gas). During the trests, the cathode was periodically removed from the vacuuum chamber to inspect it for further use, the maximum duration of continuous exposure to the air was 14 days, and the resets did not reveal any significant change in the performance. The use of barium scandate as an emission-active substance for the thermoemission cathode improved its resistance to atmospheric exposure. The practical use of the cathode developed in experimental studies, for example, in the vacuum chamber of the plasmaelectrodynamic setup of the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, will eliminate frequent cathode replacements, thus significantly speeding up research activities.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131552313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Model of Е-polarized wave propagation in a multilayer dielectric structure","authors":"P. Zabolotnyi","doi":"10.15407/itm2021.03.111","DOIUrl":"https://doi.org/10.15407/itm2021.03.111","url":null,"abstract":"This paper addresses the determination of the dielectric constant of multilayer dielectric structures by radiowave interferometry. In the general case, in interferometry measurements to one measured value of the reflection coefficient there may correspond an infinity of dielectric constants. This ambiguity may be resolved by first determining the effect of different parameters of the probing electromagnetic wave on the reflection coefficient. In particular, it is important to have a preliminary estimate of the effect of the incidence angle and the polarization on the range of variation of the reflection coefficient with the variation of one of the structure parameters. This paper considers the case where a plane E-polarized electromagnetic wave, i.e. a wave whose magnetic field is perpendicular to the incidence plane, is incident on a multilayer dielectric structure. The aim of this work is to develop a model of the propagation of an E-polarized electromagnetic wave through a multilayer dielectric structure at an arbitrary incidence angle and to determine the range of variation of the reflection coefficient with the variation of the dielectric constants of the layers. The paper presents a model of the propagation of an E-polarized electromagnetic wave in a two-layer dielectric structure. A metal base, which is an ideal conductor, underlies the structure. The electromagnetic wave is incident from the air at an arbitrary incidence angle. Based on the model, a method is proposed for measuring the relative dielectric constant and the dielectric loss tangent. It is shown that at a normal incidence the reflection coefficient magnitude is the same both for H- and E-polarization. Because of this, determining the relative dielectric constant and the loss tangent from the measured reflection coefficient magnitude calls for measurements not only at a normal incidence, but also at an oblique incidence, at which the reflection coefficient magnitudes will be different for H- and E-polarization.","PeriodicalId":287730,"journal":{"name":"Technical mechanics","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128974803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}