Authors:Pavlo Lukianov, Lin Song Pages: 4 - 20 Abstract: The subject of this work is the development of compact analogs of vortex flows models, which are used in the modeling of vortex structures observed during the flight of an aircraft and the motion of a body in a fluid. In particular, two significant misunderstandings prevailing in this area of science are highlighted. The first misunderstanding is that the stationary motion of fluid parcels in a circle is treated as an inviscid vortex. Therefore, any vortex flow model that does not explicitly contain viscosity is considered to describe inviscid vortex motion. It has been proven that this is not so: the stationary viscous motion of fluid parcels in circular orbits corresponds to the self-balance of one force - the force of viscosity. This conclusion, in an explicit form, was made for the first time. This is very important because it changes our ideas about force balance, where two or more forces of different natures must necessarily be present. Overcoming this misunderstanding opens the way for creating compact analogs of existing models of vortex motions. Along the way, one more - the second general misunderstanding in the field of vortex dynamics was eliminated. Wherever we read it, we can see that the compactness of the vortex flow is associated with the compactness of the vorticity field. This is facilitated by the fact that the equations for vorticity and not for velocity are considered. As a result, except for one or two models of vortices, which correspond to the rotation of the entire space, up to infinity, this violates the fundamental law of physics - the law of conservation and transformation of energy. It is about the fact that, as a second misunderstanding, an error is assumed when calculating the kinetic energy of the vortex flows: the Jacobian in cylindrical (polar) coordinates is not considered. As a result, all the mentioned models of vortex flows, which correspond to the hyperbolic law as their asymptotics in the periphery, have infinite kinetic energy. Certainly, this does not correspond to the formation and evolution of compact vortex structures. Therefore, in this work, based on overcoming the aforementioned misunderstandings, many previously obtained models of compact vortex flows, as well as those obtained for the first time, are presented. In particular, this applies to the turbulent vortex flow during the formation of a vortex sheet, which is a compact analog of the Burgers-Rott vortex - both the classical one corresponding to laminar motion and the one consisting of a laminar flow in the core and a turbulent flow on the periphery of the vortex. Research methods are entirely theoretical. Well-known theorems of theoretical mechanics, mathematical theory of field, and calculus of variations, etc. are used. The obtained solutions are compared with the existing corresponding analogs of non-compact flows. Conclusions. Using the methods of calculus of variation, it was possible to show the possibility of the formation of quasi-solid-like rotational motion in a boundary layer of an incompressible fluid. The very presence of viscosity, or rather its taking into account (boundary layer), indicates a possible transition of the flow from plane-parallel motion to the just-mentioned rotational one due to the Kelvin-Helmholtz instability. In addition, two new models of the Burgers-Rott vortex flow were obtained in this study. The first model uses the general solution obtained by Burgers, but this model corresponds to a combined vortex: although the velocity field is continuous, the vorticity field has a discontinuity - at the point of maximum velocity. It is proved that such an approach is quite possible: the equation of motion is satisfied everywhere, i.e., at every point in space, and the tangential stresses are continuous functions. Since the periphery of the Burgers-Rott vortex is an unstable flow, another model is proposed - with a laminar core and a turbulent periphery. Certainly, the motion of fluid parcels in the peripheral region is described by a velocity distribution other than that of Burgers. Finally, the possible use of known models of compact vortex flows to simulate the von Karman vortex street is considered, with an indication of the advantages of these models. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.01
Authors:Tetiana Labutkina, Ruslan Ananko Pages: 21 - 49 Abstract: Promising approaches to updating multi-faceted information about space vehicles and objects of space debris involve the addition of networks of ground-based surveillance tools using satellite systems for observing near-Earth space, built on several orbital groups (segments). The purpose of the research is to develop the task of building a satellite system that provides total coverage of a given area of heights above the Earth's surface by the application zones of orbital-based devices that carry out "horizontal observations" (the axis of symmetry of the instantaneous zone of possible application of the "horizontal" observation device lies in the plane of the instantaneous local horizon space vehicle-device carrier). Results: 1) two "symmetrical" methods of solving the problem of choosing the parameters of the grouping of one of the segments of the satellite observation system, which has a well-known, often used structure based on the "rings" of spacecraft in symmetrically spaced orbital planes, have been developed (the grouping should ensure total coverage of the spherical layer in the altitude area of near-Earth space in its environment with the given parameters of the instantaneous cone-shaped zone of application of the observation device; the "width" of the covered spherical layer is chosen as a part of the layer that would be covered using observation devices with the given characteristics with an infinite number of spacecraft based on them); 2) the proposed approach to the construction of a satellite system of "horizontal" observations on several orbital groups of different heights, quasi-optimal according to the criterion of minimizing the number of spacecraft; 3) calculated examples of the application of the developed methods are given, and several approximate estimates are made regarding the implementation of systems based on "horizontal" observations. Conclusions: satellite systems for observing orbital objects based on "vertical" (in the radial direction) observations can be supplemented with the implementation of "horizontal" observations. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.02
Authors:Taras Mykhailenko, Oleksandr Goridko, Illia Petukhov Pages: 50 - 56 Abstract: The modern gas turbine engines (GTEs) development is associated with an increase in the compressor pressure ratio and the gas temperature at the turbine inlet with a simultaneous reduction in the size and weight of the engine. The reliable operation of the GTE largely depends on the oil system excellence. In circulating oil systems, to ensure the lubrication and cooling of engine friction units, a high multiplicity of oil circulation is necessary. The preparation of oil for the next lubrication cycle is related to its cooling, cleaning of mechanical impurities formed during operation, and air separation. Oil coolers are used to cool the oil in GTEs. Air or fuel can be used as the cooling medium. Regardless of the cooling medium choice, a two-phase mixture (oil-air) and not a single-phase oil, as is considered when designing oil coolers, affects the course of thermo-hydraulic processes. Therefore, the subject of this paper is thermohydraulic processes in two-phase media. The goal of this study is to determine the specific aspects of thermohydraulic processes during the oil-air mixture cooling in an aviation gas turbine engine to further improve oil cooler design approaches. This paper aims to show the differences in the course of thermohydraulic processes in two-phase media from single-phase media and to emphasize the importance of considering them when designing oil coolers. The main results are as follows. For a two-phase flow, changes in temperature and pressure change not only the thermophysical properties of the phases but also the gas content, density, and speed of the mixture, which affects the course of thermohydraulic processes in the oil cooler. Under certain combinations of parameters, the structure of the two-phase flow may change. A low value of the equilibrium speed of sound can lead to unpredictable operation of the oil cooler and the oil system as a whole. In addition, the presence of an oil-air mixture reduces the heat transfer capacity of the oil cooler compared with the results of calculations using standard methods. In conclusion, it can be stated that to increase the efficiency of the oil system, it is extremely important to establish the regularities of thermo-hydraulic processes for the two-phase flow of the oil-air mixture and consider this during the design of oil coolers. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.03
Authors:Olena Zolotko, Oleksandr Zolotko, Oleksandr Aksonov Pages: 57 - 63 Abstract: The subject of study in this article is the processes that occur during the disposal of solid fuel rockets, methods of disposal, and criteria for choosing an effective method of disposal. This study identified the most significant criteria that determine the choice of an effective method for the disposal of decommissioned solid-fuel rocket charges. The task: to consider the risks of the man-made impact of the process of disposal of solid-fuel intercontinental ballistic missiles on the environment, associated with the emission of harmful substances into the atmosphere, the scattering of fragments, the occurrence of shock air, and seismic and soliton waves; analyze the advantages and disadvantages of existing methods of destruction and use of solid propellant charges of rocket engines; expertly evaluate the criteria for the selection of disposal methods; and a priori ranking of criteria. The method of a priori ranking was chosen as the method of solving the given problem. The following results were obtained. The degree of consistency of the experts’ conclusions was assessed using the concordance coefficient. The hypothesis regarding the significance of the concordance coefficient was tested on the basis of a comparison of the calculated value of the concordance coefficient with the tabulated value at the given values of the significance level and the number of degrees of freedom. The most significant factors that should be taken into account when choosing a disposal method are identified (economic efficiency; the possibility of reusing the fuel that is removed; manufacturability; the probability of emergency situations during the implementation of the method; environmental safety; energy intensity), and factors that can be excluded from further analysis (the need for additional special systems, the degree of mastery of the method). Conclusions. The scientific novelty of the obtained results is as follows: the formalization and mathematical processing of a priori data on the subject of research was conducted, and a comparative assessment of the degree of influence of various criteria on known and promising methods of disposal of solid rocket fuel charges is given. According to the preliminary evaluation, the set of significant selection criteria is most fully met by the cryogenic washing method, the application of which allows the use of solid fuel and crushed substances extracted from solid fuel charges to improve the characteristics of modern detonation engines, to improve the characteristics of the technological processes of applying special refractory coatings, and to organize highly efficient combustion processes in the detonation mode of fuel with the production of thermal and electrical energy. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.04
Authors:Yurii Shashko, Oleksiy Kulyk Pages: 64 - 77 Abstract: The correct choice of technological modes can guarantee the results of inkjet processing. However, the need to consider a significant amount of input data, namely the parameters of the equipment, the abrasive jet, the physical and mechanical properties of the material, and the shape of the processed product surfaces, as well as the lack of clear recommendations and technological data, significantly complicates the process. The subject of this study is the process of processing the surface of closed-type blades with an abrasive-air jet made in one piece with a disk of the "monowheel" type, using the SLM technology of Inconel 718 alloy. The goal of this task is to model the jet processing of closed-type monowheel blades using the ANSYS CFX finite element analysis software system. This article presents the results of numerical modeling of the surface treatment of closed turbine blades and the identification of technological factors that affect the roughness and quality of the surface of the compressed air environment on samples of closed turbine blades made of Inconel 718 alloy. The task: to develop a research plan and study the processing process and accompanying phenomena occurring during processing using the finite element method using the ANSYS CFX software complex, considering the physical and mechanical properties of the abrasive often, the environment, and the processed material. The following results were obtained: during mathematical modeling using the finite element method, data were obtained for sixteen calculation variants of blade surface treatment, from which the most optimal one was chosen, which provides the largest contact area of abrasive particles and their uniform interaction with the processing surface. In addition, during the research, the impact of "unevenness of erosion" and the graininess of abrasive materials on the quality of the treated surface was studied. Further analysis of the data of the research results made it possible to find ways to solve these tasks, which was confirmed by the control and verification results. Conclusions. The scientific novelty of the obtained results is as follows: for the first time, the processing of closed turbine blades made in one piece with a "monowheel" type disk and obtained by the additive method with an abrasive air jet was investigated. The obtained research data were used as a basis for developing a real route technological process for processing closed-type turbine blades manufactured using the additive method. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.05
Authors:Aleksey Losev, Valeriy Sikulskyi, Hanna Seleznova, Igor Bychkov, Iurii Vorobiov Pages: 78 - 86 Abstract: The subject of study in this article is theoretical and experimental studies of the process of removing burrs in the details obtained by metalworking using the thermopulse method of combustion of detonating gas mixtures. The purpose of this article is to substantiate the use of the thermopulse method for finishing parts, which was developed at Kharkiv Aviation Institute in the early 70s of the 20th century for the flexible automation of cleaning the surfaces and edges of parts of hydraulic and fuel units of aviation and rocket-space equipment from burrs and technological contamination. The task was to determine the features of the thermal pulse method, the parameters of the technological process from the viewpoint of its application for processing the edges of parts with complex internal and external surfaces, and to reveal its potential for use in precision engineering. The research methods used are the modeling of processes using the finite element method and an experimental method for checking the adequacy of the proposed numerical models. The following results were obtained: processing of parts made of materials with different thermal conductivities, cleaning of rubber products, and rounding of the edges of threaded holes of aluminum alloy parts by melting. The scientific and practical novelty of the obtained results is as follows: the technological possibilities of thermopulse processing, justified control parameters, and optimization of processing modes are given; to consider the processes of heating the elements of the part and the combustion of detonating mixtures in the working chamber of the equipment; obtained regularities of changes in the temperature fields of liquids and structural elements of parts during pulsed, constant, and mixed heating, which make it possible to form regimes of thermopulse processing of parts considering their structural features in several thermophysical properties of materials; developed processes of thermal pulse removal of burrs, microparticles, and dimensional rounding of edges using the results of modeling and experimental refinement on T-15 installations. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.06
Authors:Vitaliy Kulanov, Artem Perepelitsyn Pages: 87 - 97 Abstract: The subject of study in this article is the modern technologies of programmable logic devices, the history of product changes of leading manufacturers, including development environments, and project optimization processes. The goal is to improve modern methods, technologies, and software tools for the development and integration of FPGA-as-a-Service in the form of services in cloud infrastructures, data centers, and on-board high-performance systems, with taking into account the ever-changing conditions and requirements, and the constraints of platforms. Task: to analyze the history of product changes of the leading vendors and manufacturers of programmable logic devices; analyze the dynamics of changes in the functionality of project development environments for FPGA-based systems, with taking into account the existing requirements and restrictions from vendors of software and hardware platforms and components; perform a comparative analysis of modern development boards and accelerator cards for the prototyping and testing of projects based on the chips of programmable logic; analyze the use of an existing services and solutions based on FPGA technologies as part of cloud services from modern cloud providers; propose practical steps for the development of systems based on FPGA resistant to project requirements change; propose the sequence for the development and optimization of high-performance systems with their implementation based on FPGA; and to provide practical example of the use of the proposed method. According to the tasks, the following results were obtained. The history of changes in the leading companies of programmable logic manufacturers, as well as changes in versions of the development environments and the products of one of the largest companies, is analyzed. The use of existing FPGA-based solutions as part of cloud services is analyzed in detail. Two sequences for optimizing projects and increasing their productivity with reducing of the prototyping efforts during their creation and porting to new versions of software and hardware platforms are provided. Based on the results of the research, a prototype was developed and tested, which allowed the application of the proposed method in practice for adapting and porting the FPGA as a service project during the transfer to another version of the accelerator card. Conclusions. The main contribution and scientific novelty of the obtained results is that an experimental study of the paradigm of runtime reprogramming of programmable logic was performed, which made it possible to formulate the elements of a new method of creation projects as a service for cloud infrastructures, data centers, and artificial intelligence systems. A set of practical steps for the development of systems that are tolerant to changes in conditions and requirements is proposed. The application of the proposed method allows to avoid costs of project support in the case of changes in requirements. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.07
Authors:Artem Tetskyi, Artem Perepelitsyn, Olexander Zheltukhin Pages: 98 - 108 Abstract: The subject of study in this article and research is the process of reuse and recovery of power elements and batteries of modern digital electronics and laptop batteries, as well as controller diagnostic and repairing processes. The goal is to increase the duration of the lifetime and improve the maintainability and efficiency of reusing batteries of laptops and portable electronic devices. The task is to analyze existing types of laptop batteries; analyze different models of battery controllers; analyze options for repairing Li-ion batteries from secondary good market; propose a sequence of repairing of laptop batteries and portable electronics with use of Li-ion cells; and perform practical application of the research results. According to the tasks, the following results were obtained. The possibilities and existing options for repairing laptop batteries are analyzed. The possible mechanisms of protection of Li-ion batteries with different principles of action are analyzed. An analysis of the possibility of repairing of batteries with diagnostics of the elements in the laptop accumulator is performed. The process of repairing of the operation of laptop Li-ion batteries is proposed. A sequence for resetting error flags using additional equipment is proposed. The process of mechanical disassembling of the plastic housing of the laptop battery for the replacement of elements is described. The necessary equipment and tools for performing advanced diagnostics of laptop batteries are provided. A comparison of the results of the analysis of battery controllers and the practical experience of their recovery is performed. The description of the utility package for working with battery controllers is provided. Conclusions. The scientific novelty of the obtained results is in the fact that the comparative analysis of recovery methods of different models of batteries from different manufacturers allows to assess in advance the possibility of successful repairing of a laptop battery with a given controller. The proposed method of repairing of laptop batteries makes the recovery process predictable and reproducible for a wide range of battery models. The provided practical example of using the method demonstrates the possibility of obtaining additional information about batteries, even if the manufacturer does not provide documentation. The practical use of the research results allows to perform the process of repairing of a part of laptop battery models without additional knowledge and tools. It allows to reduce costs for the processes of maintaining the workability of electronics with extending of efficient device lifitime. PubDate: 2023-10-03 DOI: 10.32620/aktt.2023.5.08
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