Статьи журнала - Siberian Aerospace Journal
Все статьи: 352
Статья научная
This article presents a detailed description of an experimental setup for testing two-phase thermal control systems of spacecraft. The setup is a climatic chamber for simulating real operating conditions of elements in the subzero temperature range and includes three circuits: a coolant pumping circuit corresponding in parameters to the thermal control system under study, a cooling system circuit, and a thermal load simulator circuit. Electric heating elements are used as a thermal load simulator. Transparent inserts provide the ability to visually monitor the structure of a two-phase flow during boiling and estimate the volume content of the vapor phase. A testing methodology was developed for the installation under consideration, including a testing algorithm and a description of the software and hardware testing tools. The software and hardware testing tools include electronic measuring tools for the main parameters of the operating modes of the two-phase thermal control system and an automated testing process control system. The developed automated testing process control system provides the ability to monitor a wide range of thermal and physical parameters of the coolant at various points in the circuit. The control system is based on the use of programmable logic controllers. To automate the operation of the installation, the OWEN PLC200 controller is used in the stand – a monoblock controller with discrete and analog inputs/outputs, designed to control and manage the operating modes of small systems. The software part of the algorithm is based on the CODESYS environment. The results obtained in the work can be used in planning and implementing programs for ground-based experimental testing of two-phase thermal control systems, in developing test stands for conducting research on spacecraft systems.
Бесплатно
Статья научная
Aluminum-based alloys are widely used in many branches of modern industry (aviation, mechanical engineering, shipbuilding, instrument-making, energy and medicine, etc.). The promising method for further expanding the scope of these alloys is surface treatment based on the use of concentrated energy fluxes (laser beams, plasma flows, powerful ion beams, continuous and pulsed electron beams). The purpose of this paper is to establish the possibilities of integrated electron-ion-plasma modification of the structure and properties of the surface layer of technically pure aluminum A7. The surface alloy was formed in a single vacuum cycle using the “KOMPLEX” facility (ISE SB RAS) by spraying a titanium film with a thickness of 0.5 μm and the subsequent irradiation with an intense pulsed electron beam in the aluminum melting mode. After 20 “spraying/irradiation” cycles, nitriding (540 °C, 8 h) of the formed surface alloy was performed in a low-pressure gas discharge plasma using the plasma generator “PINK”. Surface alloy studies were carried out applying the modern materials science methods (scanning and transmission electron diffraction microscopy, X-ray phase analysis, determination of hardness and wear resistance). The choice of elements alloying the surface layer of aluminum was based on the analysis of binary state diagrams of Al-N, Al-Ti, Ti-N systems and the isotermal section of the ternary system Al-Ti-N. It has been shown that formation of an entire series of binary and ternary compounds, including MAX-phases of the composition Ti2AlN and Ti4AlN3, is observed under equilibrium conditions in the Al-Ti-N system. The carried out research has allowed to state that an integrated method of electron-ion-plasma modification of technically pure A7 aluminum by nitriding (540 °C, 8 h) of the surface alloy formed by pulsed melting in vacuum of the Al-Ti system (20 “spraying/irradiation” cycles with an electron beam with parameters 10 J/cm2; 50 μs; 10 pulses; the titanium film thickness in each cycle 0.5 μm) leads to formation of a multiphase multielement submicro-nanocrystalline surface layer up to 20 μm thick. It is shown that the mechanical (microhardness) and tribological (wear resistance and friction coefficient) properties of the formed surface layer exceed manifold the properties of the original commercially pure aluminum A7.
Бесплатно
Статья научная
Exploring the Solar system by humans implies the development of long-term habitable bases on several planets: the Moon, Mars, and others. Maintaining an environment favorable for a crew on such bases is possible due to life support systems (LSS), where a closed mass transfer of products and waste is imple-mented among the crew, the higher plants and other links. Closure increases the reliability and autonomy of the system, and reduces the cost of its supply.Controlling such mass transfer appears to be a difficult technical task requiring many man-hours, which is a valuable resource in the implementation of manned space missions. In the general case, this problem is solved by means of automation, however, it is neces-sary to take into account the features of the processes that support mass transfer, since this will allow find-ing ways to simplify the hardware and logical components, increase their versatility and reliability. This article presents an analysis of the technological processes of the experimental unit for extracting NaCl from solutions of mineralized human metabolites and proposes a simple control algorithm to be used for all processes of the unit without fundamental changes. Without developing a NaCl transformation cycle, it becomes almost impossible to develop a long-term functioning biological and technical life support sys-tem – the optimal LSS option for alien bases. In such systems, mass transfer occurs between the crew and the higher plants and there is a danger of NaCl accumulation in irrigation solutions and subsequent poi-soning of the plant link. Therefore, the problem of controlling the NaCl transformation cycle in mass trans-fer processes of a high degree of closure is relevant, and the universal principles of automated control can be used not only in space, but also in terrestrial applications: in closed agrotechnical cycles and scientific, and educational stands.
Бесплатно
Development of interface module emulator architecture for spacecraft life support systems
Статья научная
The article gives an analysis of special characteristics of ground-based experimental evaluation of on-board radioelectronic equipment, taking the control unit of up-to date spacecraft on-board control complex as the test objective. The focus is the problem of providing testing procedures of the specific software employed in design and manufacture process. A solution of the problem is worked out on the basis of performance of a hardware-software complex which emulates interface modules for the computing module of control unit. According to the general operation algorithm of the control unit, the developed complex is regarded as a multi-user system. The main functional requirements for hardware-software emulator, regarded as the corresponding queuing system, are also defined. The results of the experiments with the computer module operation prompted the requirements for the emulator response time from the point of view of its operation stability in real strict-time mode. In order to ensure the required efficiency of operation, the emulated functions of the interface modules are classified according to the severity level of their execution determinacy. The results of experimental evaluation оf the service channel hardware design variants when applying multi-functional reconfigurable input-output digital devices allowed to develop a hardware-software emulator structural circuit based on operation parallelism of programmable integrated logic circuits and flexibility of software reconfiguration. The realization of emulated functions of selected classes within the available architecture was carried out using the corresponding hardware blocks and software module. The presented analysis of the emulator response limits was performed with the application of National Instruments technologies. The results of the developed hardwaresoftware emulator evaluation and practical application, as well as other possible ways of applying the proposed approach for tests of spacecraft on-board radio-electronic equipment and space system components were also analyzed.
Бесплатно
Статья научная
The original method for encoding binary data streams based on QPSK quadrature phase shift keying in a wireless optical communication channel in the visible range is suggested. The algorithm for analyzing signals in the receiving tract is presented. It allows to analyze the presence of two or three pulses of different colors at the input, which will signal the presence of interference or the occurrence of "illumination". In addition, the algorithm provides a possibility of dynamic compensation of external "illumination" by changing the gain of the photodetectors and adjusting the brightness of emitting LEDs. The functional scheme of the device for realization of the offered coding method in the wireless channel on the basis of optical radiation has been developed. Given that most photodiodes are sufficiently wide-band in the visible range of light waves, to increase sensitivity of each color channel and selectivity of the receiving tract it is necessary to apply optical filters for each color channel. The most effective are interference filters made of optically transparent materials with different physical characteristics. The approach for calculating optical filters has been presented.
Бесплатно
Development of the CYCLOPS CubeSat payload
Статья научная
The number of CubeSat satellites launched has been increasing over the past decades. These satellites have a number of advantages: short development time, low cost, possibility of modifications for certain scientific tasks and testing of technical solutions and new developments. This article describes payloads of a small spacecraft: CubeSat 3U CYCLOPS designed by D.F.Ustinov Baltic State Technical University "Voenmeh" within grant under Space-Pi program. The purpose of the study is to create, test and study the performance of payload modules of the vehicle, built using commercially available components, under space flight conditions. The text describes the structure of interaction between the payload and the OrbCraft-Pro 3U platform from Sputnix LLC. The process of development of payload control board is con-sidered. The control system software for mechatronic and multiaxis actuator modules with logging and error correction is described. In addition to the above-mentioned modules, the payload control system was also developed to carry out a series of experiments in the presence of a small spacecraft in orbit. The paper explains how the spacecraft communicates with the ground via special software Houston control applica-tion and Houston Telnet. The results describe tests performed on the mechanical components of the space-craft. Examples of telemetry packets received from on-board the spacecraft are given. The article also re-flects further plans for the project and the prospects of using the developed hardware for implementation in large-scale space systems and complexes. Also as part of the project students were able to gain engineering experience in the development of devices designed to work in space conditions.
Бесплатно
Development of the concept of a reusable liquid rocket engine with three-component fuel
Статья научная
The article considers a promising direction for the development of liquid-propellant rocket engines (LPRE) – the use of three-component propulsion systems. The interest in this topic is based on a number of advantages that can be obtained by using this LPRE concept, namely: saving the mass of the launch vehicle (LV) by using a denser hydrocarbon fuel at the initial launch site; high specific impulse values at high-altitude launch sites due to the use of a more efficient pair of fuel components (FC): liquid oxygen + liquid hydrogen; reducing the cost of removing the payload, due to the use of a single propulsion system for both launch sites. An analytical review of implemented three-component LPRE schemes developed in Russia and abroad has been conducted, and their main advantages and disadvantages have been highlighted. Based on a detailed study of a number of circuit solutions for liquid-propellant rocket engines running on three-component fuel, the concept of a two-mode single-chamber three-component engine made according to a closed circuit with afterburning of generator gas is proposed. The oxidizer is liquid oxygen, the fuel is RG-1 kerosene and liquid hydrogen. In the first mode, the engine runs on three components, the share of liquid hydrogen in the fuel mixture is 4% of the total consumption of components. In the second mode, the engine runs on FC liquid oxygen + liquid hydrogen. The results of a computational and analytical study of the optimal design parameters of the engine are presented. The aim of the study was to understand the qualitative picture of the influence of various fuel parameters on the thermodynamic properties of the combustion products of the fuel mixture and the engine efficiency. Based on the results of the study, the optimal percentage of fuel components was determined. A mathematical model for calculating a three-component LPRE has been developed. The results of calculation of energy coupling are presented. A comparative analysis of the mass characteristics of the designed propulsion system is carried out.
Бесплатно
Development of the heat panel of the small space apparatus for navigation support
Статья научная
To clarify the trajectory of the spacecraft in a given orbit, the parameter of unmodeled acceleration is taken into account. Today, in the design and manufacture of a spacecraft to meet the requirements of the technical specifications for the maximum allowable values of unmodeled accelerations during the operation of on-board equipment, it is necessary to take into account the effects of asymmetric heat fluxes from the panels of the spacecraft on the deviation of its center of mass from a given orbit. This article discusses the problem of the influence of asymmetric heat fluxes from the surfaces of the spacecraft emanating from the panels ± Z, + Y (deterministic and non-deterministic component) on the level of unmodeled accelerations, which significantly affects the trajectory of the spacecraft. In order to meet the requirements for the temperature control system in terms of ensuring efficient heat removal from the on-board equipment devices and its distribution over the surface of the instrument installation panel, it is necessary to significantly improve the technical characteristics of heat transfer and heat conduction processes in the spacecraft. The analysis of the current thermal control system in modern satellites is carried out and its shortcomings are revealed. A constructive option is proposed for creating an energy-intensive thermal panel, which allows more efficient heat removal from devices and distribution over the panel. The designed thermal panel is a flat sealed panel of a single complex design of aluminum alloy, made by the additive technology method. The dimensions of the thermal panel are limited by the structural dimensions of the working area of 3D printers. At the moment, the main dimensions reach 600-800 mm. An increase in the working area in the future will enable the installation of large-sized electronic equipment. A two-dimensional mathematical model for calculating heat transfer processes in the designed thermal panel is presented. For the calculation, specific average values are introduced that characterize the effective cross sections for the vapor channels and the wick in the longitudinal and transverse directions, physical parameters (porosity of the wick and its degree of liquid saturation).
Бесплатно
Статья научная
The article provides a brief description of the flight scheme of a prospective automatic spacecraft intended for the study of Mars and its satellites by remote and contact methods. At the near-Martian expedition site, it is planned to first bring the vehicle into orbit of the artificial satellite Deimos, and then landing on Phobos with the subsequent delivery of its soil to Earth. The main ballistic characteristics of the spacecraft flight conditions at all stages of the flight at launch after 2025 are given. The time frames for the five starting periods are considered - in 2026, 2028, 2030, 2033 and 2035. The launch of the spacecraft on the flight path to Mars is performed by a heavy class launcher. The article describes the design of the vehicle, propulsion systems of its modules and flight scheme at all stages – from launch from the Earth to landing on Phobos, and returning back to Earth. The article describes the propulsion systems of the main spacecraft units proposed for the mission implementation – the propulsion module, the flight landing platform and the return vehicle. The designs of these units are provided in the work. Flight schemes have been developed in accordance with their characteristics, which allows conducting remote study of Deimos, making a soft landing on the surface of Phobos, and then delivering samples of its soil to Earth. The project should be developed on the basis of the spacecraft launch from the Vostochny launch site by the Angara- A5 launch vehicle and the KVTK upper stage. An alternative variant of the construction of a spacecraft involves the use of a vehicle of a lighter class - perspective Soyuz-5 launch vehicle and Fregat-SBU upper stage. In this case, the engine module is excluded, and the flight and landing module is replaced by a heavier version with larger tanks. Both proposed options for constructing a spacecraft make it possible to implement the developed trajectory, while ensuring full-time operation of the target equipment and conducting a set of experiments during a given period of active spacecraft existence.
Бесплатно
Статья научная
In this material development stages of the two-fuel combustion chamber for the HK-16-18CT engine are presented. Calculation of processes on the basis of the theory of turbulent burning is made. One of competitive advantages of stationary gas-turbine installation is the possibility of work on two types of fuel: on diesel and on gaseous. Therefore creation of the two-fuel combustion chamber is relevant. The designing process of the two-fuel combustion chamber consists of several stages. At the first stage the nozzle is developed. It is equipped with two internal fuel channels. Then the front device is designed. in it nozzles are placed in two ranks. This device is equipped with two separate fuel collectors. It contains cavities for a fuel supply to two channels of nozzles. Such constructive decision allows to carry out switching of one type of fuel to another without stopping operation of the engine. As a prototype for distribution of air on length of a spherical pipe the combustion chamber of the NK-8-2U engine is taken. Calculation of processes in the combustion chamber was carried out on the basis of the theory of turbulent burning. During calculation such parameters as the normal speed of burning, the pulsation speed, coefficient of turbulent exchange, scale of turbulence and intensity of turbulence are determined. The equation of thermal balance for determination of temperature in the considered area at combustion of natural gas and diesel fuel is created. It is considered what in one case is spent warmly going for evaporation of liquid fuel, in other case it is not necessary. For calculation of formation of nitrogen oxides Ya. B. Zeldovich's theory of thermal oxidation of nitrogen is used by oxygen. Emissions of carbon monoxide are determined by an empirical formula From gasdynamic calculation of the HK-16-18CT engine parameters on an entrance to the combustion chamber on various operating modes at combustion of natural gas are known. Calculation for definition of a necessary consumption of diesel fuel for power setting at preservation of temperature at the exit is executed from the combustion chamber. By results of calculation the schedule of emission of harmful substances from power setting on gas and diesel fuels is constructed. The comparative schedule of dependence of completeness of combustion of fuel on power setting is constructed. Settlement emissions of harmful substances of the developed combustion chamber in the range of operation of the engine on power from 0,7Ne to 1 Ne for liquid fuel: NOx15%O2 does not exceed 250 mg/m3, СO15%О2 does not exceed 300 mg/m3; for gaseous NOx15%O2 fuel does not exceed 120 mg/m3, СO15%О2 does not exceed 150 mg/m3.
Бесплатно
Development of tunable band noise genera-tors
Статья научная
The aim of the work is to develop and study the principle of operation of tunable band noise generators (TBNG) and their characteristics, a noise signal conditioner of a modular type, which provides controlling the bandwidth of a noise signal for using it as a means set-ting radio noise. It is possible to do it through the formation and radiation in the surrounding space of electromagnetic fields of the energy spectrum in specified frequency ranges, with the possibility of changing the amplitude and bandwidth of the signal. To improve performance and make them more widely used in order to provide high-quality counteraction to unauthor-ized removal (by intruders) of information on emission channels of spurious electromagnetic radiation (SER), it is necessary to create multichannel adaptive TBNGs. In the developed generators in each noisy channel, it is possible to provide power adjustment, generated noise signal and noise bandwidth control, which will improve the electromagnetic compatibility of such devices. To ensure this, it is proposed to use a design concept based on the use of con-trolled modules of noise sources with band-pass filters, which also allows you to get a noise signal uniform in amplitude.
Бесплатно
Development of workspace and algorithms for testing SpaceWire onboard equipment
Статья научная
For a long time, the foreign space industry has been using one of the most advanced and actively devel-oping technologies for transmitting information on board a spacecraft – SpaceWire. This technology pro-vides high-speed transmission of large amounts of information, the creation of a single high-speed data processing infrastructure for connecting sensors, data processing system elements and mass memory blocks. In Russia, SpaceWire is gradually being introduced and used on promising spacecraft. To verify the compliance of the onboard equipment of such vehicles with the requirements of the SpaceWire ECSS-E-ST-50-12C Rev standard.1 there is a need to develop the workplace described in this article. The workplace is designed so that SpaceWire onboard equipment can be connected to it and tests can be run that check cer-tain parameters of information exchange regulated by the standard. The article presents the general struc-ture of the workplace, as well as a description of each of its elements separately, together with a descrip-tion of their functionality. The article also describes the developed testing algorithms. Among them, we can single out a check for compliance with the bit error coefficient to the required value, a check for support for the header removal method by SpaceWire switches, as well as a check for compliance with the require-ments for the RMAP and STP-ISS transport protocols. The algorithms of these tests are presented in the form of flowcharts and a detailed text description. The tests themselves are implemented in the form of pro-gram code in the C language. As a confirmation of the correctness of the developed tests, practical testing of SpaceWire devices was carried out, among which two payload boards for the NORBY spacecraft can be distinguished, as well as an ultra-large integrated circuit 1931KH014 of a programmable switch for SpaceWire networks. A brief description of the testing devices used in the work is given in the form of a presentation of their functionality applicable to the testing workplace being developed.
Бесплатно
Differential evolution in the decision tree learning algorithm
Статья научная
Decision trees (DT) belong to the most effective classification methods. The main advantage of decision trees is a simple and user-friendly interpretation of the results obtained. But despite its well-known advantages the method has some disadvantages as well. One of them is that DT training on high-dimensional data is very time-consuming. The paper considers the way to reduce the DT learning process duration without losses of classification accuracy. There are different algorithms of DT training; the main of them being ID3 and CART algorithms. The paper proposes a modification of DT learning algorithms by means of the information criterion optimization for some selected attribute. The use of this modification allows avoiding optimization by means of enumeration search over the entire data set. The Separation Measure method is used to select the attribute. The method selects the attribute whose class-based averages are most distant from each other. Optimization of the selected attribute is carried out using the method of differential evolution, which is one of the evolutionary modeling methods designed to solve problems of multidimensional optimization. Self-configuring at the population level based on the probabilities of using mutation operator’s variants was applied for differential evolution. The classification problems were solved to compare standard DT learning algorithms with the modified ones. Algorithm efficiency refers to the percentage of correctly classified test sample objects. Statistical analysis based on Student's t-test was carried out to compare the efficiency of the algorithms. The analysis showed that the use of the proposed modification of the DT learning algorithm makes it possible to significantly speed up the training process without losses in the classification effectiveness.
Бесплатно
Статья научная
The power supply system (PSS) of a spacecraft (SC) is one of its most critical systems. The generation of electrical energy in modern SC PSS is typically carried out by solar panels (SP). In the absence of energy generation from the SP or during periods of low energy output, the necessary electrical energy is supplied to the load from battery packs (BP) through a charge-discharge device (CDD). Usually, the CDD is connected in parallel to the output buses of the PSS and, in battery discharge mode, provides stable voltage to the load. The replenishment of energy in the BP — its charging — occurs during time inter-vals when the energy generated by the SP exceeds the energy consumed by the load. Additionally, the CDD can provide voltage stabilization at the load. The article presents the power circuit of a pulse converter capable of reversing the flow of energy and operating in a buck-boost mode with high efficiency. It is shown that using the power circuit of this pulse converter in the CDD of SC power supply systems can improve several of their characteristics, namely, energy-mass and reliability metrics, enhance efficiency, and improve the quality of the output voltage of the PSS while reducing the level of generated electromagnetic interference. The article includes research results on the CDD, with the power section designed according to a prom-ising scheme obtained using a simulation model and a physical prototype. It is demonstrated that the synthesized control law allows for maintaining the astatism of the output voltage and a short duration of tran-sient processes. However, it was found that the simulation model of the CDD provides a shorter duration of transient processes compared to the physical prototype. This is explained by the fact that due to the short time interval during which the controlling microcontroller must perform calculations for switching mo-ments of the power transistors, the mathematical expressions used for calculations had to be simplified. The aim of the work is to find a technical solution for generating control signals that allows for the elimination of complex mathematical calculations of the switching moments of the power transistors in realtime. To achieve this, it is proposed to precalculate the switching moments of the power transistors for the entire range of power transmitted through the CDD and for the entire range of possible voltages on the BP. The obtained values of the switching moments of the power transistors in the form of tables should be recorded in the memory of the microcontroller controlling the power circuit of the CDD and used for control purposes. The article discusses the methodology for obtaining tables of switching moments for the power transis-tors of the CDD, which essentially serve as a digital twin of the CDD, and provides an example of such tables.
Бесплатно
Digital twin for combined casting and rolling line control
Статья научная
Aluminum alloys of all kinds are widely used in rocket and other space vehicles construction and operation - in structural elements, communication lines and power supply units. The parameters of alloys processing operations must be strictly maintained in order to exclude de-fects and obtain products of the required quality. Technologies of metal processing in space engineer-ing include such operations as casting, rolling and forming; continuous melt-crystallization-forming lines can also be used, which imposes additional requirements on the integrated control of such a line. The article is focused on the design of a digital twin to be used for controlling a combined casting and rolling complex. Basing on the previously worked-out mathematical models of the units and com-ponents of the complex (furnace, tray, mold, forming unit, rectifying and cooling assembly, spools), a special program has been designed in the TIA Portal software environment using the S7-1200 micro-processor controller, which simulates the parameter changes of both rolled metal and casting and rolling line units. The article also presents the structure and the user interface of the specified pro-gram. There are calculations of the technological cycle parameters for processing of three alloys - that gives an understanding of temperatures and speeds distribution in the rolled metal at each unit of the line. The program can be used for production lines and complexes both in preliminary processing calcu-lations for various alloys (to select the necessary control options) and during the process itself as part of the applied process control system (to confirm the cooling parameters and casting speed).
Бесплатно
Dynamic flow parameters in natural curvilinear coordinates for a current line in a rotating channel
Статья научная
A special interest in the topic of mathematical analysis of the flow of heat transfer processes is determined by the scientific significance and practical application in the development, design and production of rocket and space vehicles and installations. Substantiation of the developed techniques and modeling of the data obtained during the experiment using 3D process technologies gives an advantage. The accuracy and reliability of the calculation results play a key role in ensuring the safety and reliability of rocket and space systems. Regular verification and verification of the results are also necessary to ensure a high degree of reliability and safety. The comprehensive analysis of the fluid flow in the inter-vane channel of the impeller of a low-flow centrifugal pump presented in the article, with the construction of the energy characteristics of the impeller, can be used to clarify the number of vanes. The developed calculation method consists of four parts: firstly, an expression is obtained to determine the projection of the pressure gradient on the longitudinal axis φ, secondly, an expression is obtained to determine the projection of the pressure gradient on the transverse axis ψ, thirdly, the derivative of the longitudinal velocity in the transverse direction is determined, and fourthly, the results are presented numerical and experimental visualization: the power balance, the dependence of the pressure and the coefficient of influence of a finite number of vanes on the flow rate of a low-flow centrifugal pump. Based on the results of theoretical research, an algorithm and a calculation program were developed that allows calculating local values. The considered approach is confirmed by verification of the results of mathematical modeling by graphical visualization of the flow and measurement of the power balance of a low-flow centrifugal pump. The obtained expressions for pressure gradient projections, determination of the derivative of the longitudinal velocity and experimental visualization play an important role in the calculation and analysis of the operation of centrifugal pumps. However, there is a need for further elaboration of the method to bring it to a form that allows calculating the three-dimensional flow of the working fluid in an arbitrary channel.
Бесплатно
Статья научная
The paper investigates areas of dynamically unstabilized flows characteristic of the elements of the flowing parts of turbopump units of liquid propellant rocket engines; studies of rectangular variable cross-section, cylindrical variable cross-section, rotational currents in cavities with fixed walls, fixed and rotat-ing walls. The specific elements include: delivery and discharge units, side cavities between the rotor and the stator, cavities of hydrodynamic seals and elements of the interblade channel of centrifugal pumps and gas turbines. Due to the specific features of the operating and design parameters, the initial components of dynami-cally unstabilized flows are predominant in the flow parts of the delivery units. These areas have a signifi-cant impact on the energy parameters of the assembly and affect the heat exchange processes and, as a result, the reliability of structural elements. In the specific elements of the feed systems, both laminar and turbulent modes of the flow of the working medium are realized. Using the methods of three-dimensional boundary layer theory, specific thicknesses of boundary layer such as thickness of dynamic boundary layer, displacement thickness and momentum loss thickness are determined. Dependences for determination of flow core velocities, necessary for evaluation of losses due to the length of specific sections, are obtained. Proper selection of friction laws and velocities profiles in the boundary layer and consideration of initial section is necessary for the purposes of reliable determina-tion of energy parameters. Obtained dependences consider velocity distribution profile in the boundary layer on specific sections of laminar and turbulent regimes cases.
Бесплатно
Статья научная
The article contains the results of research on the effect of abrasive flow machining on the roughness and microhardness of the surface of small channels (holes) in samples of workpieces made of 12X18H10T steel. Empirical dependencies of the change in roughness and microhardness of the surface of a small channel on the degree of filling of the working medium with a plasticizer and the shear pressure of the hydraulic system with the extreme of these functions in the studied area are obtained. Based on these dependencies, the composition of the working environment was selected: the degree of filling of the work-ing media base (with a constant content of white electro corundum – 30 %) with a plasticizer in the form of diamond paste (ACN 60/40 BOM Г) Ka 40 % and CKT rubber 30 %, respectively. As a result of abrasive flow machining, it was possible to reduce the roughness of the surface layer from Ra = 0.49…0.62 µm to Ra = 0.047…0.06 µm, and also to increase the microhardness of the surface from h = 188…192 HV to h = 213…220 HV. The thickness of the hardened layer is ≈ 7.24 µm. Analysis of surface profilograms shows that as a result of abrasive flow machining, both the height roughness parameters (average – Ra, Rz, Rp; maximum – Rmax) and the depth roughness parameters (Rk) were significantly reduced. Using electron microscopy (SEM MAG), a qualitative assessment of the structure of the surface layer of the small channel was carried out. The obtained results show good machinability by abrasive flow of austenitic steel blanks, in particular 12X18H10T steel.
Бесплатно
Effect of electron-phonon interaction on transport properties in TmxMn1-xS
Статья научная
In solid solutions TmxMn1-xS, based on measurements of IR spectra and thermal expansion coefficient in the temperature range 80–500 K, the temperatures of sample deformation and disappearance of the absorption intensity of IR spectra at some frequencies are established. Anomalies in the temperature behavior of the electrical resistance are found, the sign of the current carriers and the mobility are determined from the Hall coefficient. The correlation between the temperatures of coefficient of electrical resistance and lattice deformation has been determined. A model of lattice polarons is proposed. The spectrum of electronic excitations and the density of electronic states in the interaction of electrons with flexural and tensile modes of the octahedron are calculated in the random phase approximation.
Бесплатно
Efficiency improving of emergency monitoring and forecasting based on the information system
Статья научная
The article is devoted to the automated information system modification to solve monitoring and forecasting problems of natural and man-made emergencies in order to increase the efficiency of its functioning, namely, to increase the execution speed of the main operations, to reduce the error probability. Monitoring and forecasting of emergencies are among the priorities in the field of population from emergencies protection, as the prevention and elimination of their consequences are carried out on the basis of these tasks. At the same time, the data collection speed, processing and analysis largely determine the efficiency of the obtained results. The existing system of monitoring and forecasting of natural and man-made emergencies, its functional model in IDEF0 notation, characteristic features, advantages and disadvantages are considered. The existing system can be improved by automating a number of tasks related to the processing, transmission and storage of large data amounts, including real time data, as well as the generation of consolidated reports on the results of monitoring and forecasting of various objects. The information architecture of the solution reviewed and the corresponding database model form the basis of the proposed solution. The IDEF0 model of emergency monitoring and forecasting has been introduced taking into account the proposed modification of the automated information system. The main operation execution time comparative analysis based on the initial and modified automated information system (AIS) using the existing hardware confirms the effectiveness of the proposed solution. Data exchange and generation automation of consolidated reports on multiple monitoring objects will simplify analysis of the obtained results and solutions development based on them aimed at prevention of natural and man-made emergencies, as well as elimination of their consequences.
Бесплатно
