Aviation and spacecraft engineering. Рубрика в журнале - Siberian Aerospace Journal
Статья научная
Many developers of new high-thrust solid-propellant rocket engines are faced with the problem of acoustic instability of combustion. The phenomenon of resonant combustion of solid fuel is associated with a number of specific features. The cavities of the combustion chambers of such engines have complex geo-metric shapes. The gas channel is long enough. Its length usually exceeds five or more calibers. The thick-ness of the flame front is measured in micrometers and the combustion zone is localized over the open fuel surface. The flame front often turns out to be capable of amplifying pressure perturbations at the frequency of one of the acoustic eigenmodes if the wave antinode falls on a thin combustion zone. The oscillatory process can be regular or sporadic. Resonances of the longitudinal acoustic mode are most often observed. However, there were cases of simultaneous oscillation of two modes. In some cases, during the operation of the engine, the amplitude of the resulting oscillations began to decrease and the combustion process be-came almost quasi-stationary. Self-oscillatory processes in the combustion chambers of solid propellants have a threshold sensitivity to pressure overshoots. The vibration amplitudes can be several tens of percent, sometimes reaching the nominal working pressure in the chamber. The amplitude-frequency characteristics of the oscillations are sensitive to the composition of the fuel, responding to changes in the chemical com-position, as well as to the mechanical properties of the fuel. The regions of unstable regimes are definitely related to the geometry of the gas cavity. Together with pressure fluctuations, the combustion process is influenced by gas-dynamic factors, significant non-uniformity of the gas flow parameters along the length of the channel, its turbulence, and other factors. When designing solid-propellant rocket engines, it is nec-essary to estimate the frequencies of the natural acoustic resonances of the combustion chambers. The article discusses a technique for determining the frequencies of natural resonances of the first and second tone of the longitudinal mode of acoustic vibrations in the combustion chambers of solid propellant rocket engines. The gas path of the combustion chamber is divided into homogeneous sections, for which the solutions of the wave equation are presented. To determine the natural frequencies and distribution of vibrational pressures and velocities, the method of “stitching” acoustic fields at the boundaries of the cavi-ties was used.
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Actuator made of a material with a shape memory effect for transformable space structures
Статья научная
Transformable structures represent a special class of large space systems. They are delivered into orbit in a tightly packed state. When the required parameters of the orbit are reached, their deployment or trans-formation is carried out. The shape of the transformed structure is rigidly fixed upon completion of the transformation process. At the same time, shock loads occur on its constituent elements. The complication of design schemes and the increase in the dimensions of modern transformable space systems due to the increase in their operational functionality leads to the necessity of improving their mass characteristics. At present, many variants of transformable structures of space antennas have been developed abroad and in our country, the ratio of the mass of mirrors to their areas has decreased to 0.5.–1.5 kg/m2. Further im-provement of transformable space structures is possible with the use of materials with the shape memory effect to create actuators that ensure controlled shock-free deployment of these structures from the transport state to the working position Experimental and theoretical studies of the actuator model made of titanium nickelide material have confirmed the fundamental possibility of its use for the deployment of promising transformable space structures. During the tests, the main characteristics of the actuator model were determined, namely: the actuation force, the working stroke and the actuation time.
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Additional screening tests at the testing technical center for ground power equipment
Статья научная
When testing a spacecraft in a thermal vacuum chamber, special attention is paid to ensuring guaranteed continuous power supply to the spacecraft for a long time (up to several months). The de-energization of the spacecraft can lead to the failure of thermal control systems, up to the complete failure of the spacecraft worth several billion rubles. During the operation of ground power equipment, the necessary data on the intensity and types of failures in the operation of this ground power equipment were obtained, the result of which led to an increase in the test time and the risks of failure of the spacecraft at this stage. As a result of collaborative work of JSC “Academician M. F. Reshetnev Information Satellite Systems” and Research Institute of Automation and Electromechanics of Tomsk State University of Control Systems and Radioelectronics on the analysis of failure statistics obtained during operation, a technical task was worked out to develop methods for increasing the uptime of ground power equipment manufactured. One of the key requirements for the new generation of ground power equipment being manufactured is to ensure a high reliability indicator – “uptime”. Experience in the field of additional screening tests of electro-radio parts before their installation in a spacecraft allows us to propose a method for determining the quantitative value of the decreasing coefficient of screening tests using a method for evaluating the coefficients characterizing the degree of difference between radio-electronic products that have successfully passed additional screening tests and received ones from the factory manufacturer. As a result of the calculations of the decreasing coefficient and the mathematical calculations of the uptime, it is possible to determine the effect of the decreasing coefficient of screening tests on improving the reliability of ground power equipment. High requirements for uptime of ground power equipment for electrical tests of the spacecraft have led to the need for additional screening tests in special testing technical centers, where the verification of indicators of the number of failures by confidence probabilities should be carried out. The introduction of additional screening tests in the technological process of ground equipment manufacturing is the next step in the methods of increasing reliability.
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Alternative method of solar simulation for thermal vacuum tests of spacecraft
Статья научная
Solar simulators based on gas-discharge xenon lamps, used to obtain the thermal state of objects for thermal vacuum testing of spacecraft, are one of the key, most complex and energy-consuming elements of test equipment. Complexity of the optical system, the large number of optical elements, the need for constant monitoring of their condition, tuning and adjustment by highly qualified personnel significantly complicate obtaining of required luminous characteristics, mainly spatial uniformity of irradiance. Another common drawback is their low energy efficiency, which does not exceed 10 %. We proposed an alternative method of solar simulation using solid-state luminous sources – high-efficiency LEDs, with their placement without a bulky and complex optical system directly in a thermal vacuum chamber. At the same time, one of the most difficult problems of adapting to the conditions of thermal vacuum tests is to provide the necessary luminous characteristics. The required wavelength range, spectral match is obtained by combining assemblies of high-efficiency LEDs of six different wavelengths and halogen lamps. We carried out a number of experiments, including measuring the luminous characteristics of alternative luminous sources and mathematical modeling of the matrix emitter. As a result, the possibility of using the proposed method for thermal vacuum tests of spacecraft was confirmed; the luminous characteristics of the model meet the requirements, and in terms of uniformity of irradiance and energy efficiency, they significantly exceed those of traditional solar simulators.
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Статья
The authors propose an approach to research tests of copra-spring stand, designed for testing rockets and spacecraft on inertial forces of a pulse character. The authors present the design of the stand, consisting of two main parts: mobile and stationary. The authors present a method for calculating the magnitude of the load factors and the oscillation frequency of the test object, and calculate the parameters for adjusting the spring stiffness. They describe the possibility of carrying out dynamic tests for imitating transient loads that hermetic structures such as modules of habitable orbital stations, loaded by internal pneumatic pressure, withstand during their lifecycle. The authors present the results of research tests when the stand without any additional weight was falling from the height of 20, 35 and 50 mm. They determine the levels of axial and transverse accelerations on the envelope of the stand and the lower ring. A comparison of the original and filtered signal from the load factor sensors obtained in each test case was made. The authors present the results of calculating accelerations of the moving part of the stand using the video processing of the experiment. To determine the position of the stand envelope they developed special software. The essence of the software was to determine the coordinate of the border of the color change from the frame height from a light color to a darker one using averaging in rows. The authors show that the results of a comparison of manual frame-by-frame measurement and data obtained by the software method indicate a sufficient convergence of the results using a drop from the height of 20 mm experiment. The comparison of axial loads obtained by various methods is given, when the moving part of the stand is thrown from the height of 20, 35 and 50 mm, respectively. The zero time points for the video and accelerometers were determined so that the first maximum is reached simultaneously. According to the results of research tests, the authors describe the development and validation of the finite element model of the stand. The calculations were carried out in a nonlinear formulation, which makes it possible to correctly take into account the loading of the stand at all stages, using the method of direct solution of the equations of motion. The authors show the results if calculating the time dependences of displacements and load factors at the sensor installation places and a comparison with the experimental results, which shows a good convergence.
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Analysis of the ADS-B airspace monitoring system
Статья научная
One of the most important aspects of flight safety is awareness of AC air position (AC is the short for aircraft). The leading method of stating AC airspace location is the use of radar systems – primary, secondary, combined primary – secondary surveillance radars-though radar systems have significant drawbacks. However, at present, more advanced technologies are also in use, for example, ADS-B and multilateration. This article is focused on ADS-B broadcasting. Global coverage, low cost, great amount of obtainable information makes Automatic Dependent Surveillance – Broadcast a highly efficient system. Application of the method for AC air positioning is equally effective for helicopters, especially for those operated by special emergency services. As for the infrastructure of air navigation, the research in this sphere is focused on surveillance systems necessary for reliable control of increasing air traffic. The problem of better awareness of AC air position is still acute and has always been the object of extensive research. At present, homemanufactured civil aviation helicopters are practically never equipped with ADS-B transponders, and hardly ever use the available resources of transceiver-based surveillance systems. The objective of the analysis presented is to demonstrate the applicability of Flightradar system options, as well as implementation of ADS – B transponders for helicopter fleet. Operating surveillance systems like Flightradar may considerably increase flight safety by improving the awareness of helicopters current air position.
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Статья научная
The force measuring device is a part of the bench force measurement system required for direct meas-urement of the rocket engine thrust during the test. One of the common types of force-measuring device calibration systems is a lever-type calibration device. The simplicity of the kinematic scheme is one of the main advantages of its use as a calibration system. Along with this, the disadvantages of this scheme are concentrated in the supporting elements of the lever system, since it is the wear of the supports that leads to the accumulation of a systematic error of the entire system with a proportional deterioration in the accura-cy of the force measurement process. The aim of the work was to analyze the features of prismatic supports used as part of a lever-based calibration device of a force-measuring device, as well as to simulate the stress-strain state of a model of a real prismatic support used in an existing force-measuring system. The work considers the closest theoretical information associated with calculating the stress distribution in the wedge and half-plane in accordance with the plane problem of the theory of elasticity. The selection of the mechanical properties of materials was carried out depending on the specified hardness indicators, as well as the modeling of the contact problem in a given prismatic support, depending on the angle of inclination of the prism in relation to the pad, using the static analysis of the Solidworks Simulation software package. In this work the calculation results are given and also conclusions are drawn.
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Approximation of beam support coefficient val-ues at vibrations and buckling
Статья научная
The problem of calculating the first natural frequency of vibration and the first critical force for a beam with elastic supports is considered. An analytical review of the literature on solving such problems showed that in the theory of vibrations and the theory of stability of beams, consideration of the support conditions is based on the use of support coefficients, the values of which were obtained after solving the corresponding differential equation. The reviewed literature contains only a limited set of values of these coefficients, mainly for ideal supports of simple types: hinges, embedding, etc. Consideration of the stiffness of supports can only be found in individual editions and only for a limited number of values. In this work, the calculation of the support coefficients depending on the stiffness of the beam supports for the first natural frequency of vibrations and the first critical force is made. The obtained values were divided into three zones and approximated within each zone by quadratic functions. The use of quadratic approximation made it possible to obtain simple analytical dependencies suitable for engineering applied calculations, and the division of stiffness into zones provided an acceptable error of the obtained values. Also, quadratic dependencies made it possible to solve inverse problems for determining the stiffness of supports for a given value of the first natural frequency of vibrations or the first critical force. A detailed study of the error of the obtained approximating functions over the entire considered range of stiffness was carried out, which showed that the error in determining the coefficient of supports during fluctuations is not more than 2 %, and in case of loss of stability – 6 %. The error depends on the combination of stiffness of the supports, and can increase if the stiffnesses differ by more than an order of magnitude. The high sensitivity of the solution of the inverse problem to the input data was also established, which is the result of the high nonlinearity of the dependence of the coefficients of the supports on the stiffness. The obtained results can be used in engineering calculations of the first natural frequency of vibrations and the first critical force of a beam with elastic supports.
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Статья научная
Lithium-ion batteries (LIB) are widely used as energy accumulators in the electrical power systems (EPS) of spacecraft. The article considers the automated bench SIA 12/24 for electrical tests and diagnostics of the resource characteristics of lithium-ion cells (LIC), on the basis of which the EPS LIB of spacecraft is developed and manufactured. LIC resource tests are the most time-consuming and lengthy, they are carried out in ground conditions for several months with repeated cycling of charge/discharge and cell temperatures until the conditions for completion of the tests are reached with periodic monitoring, measurement and registration of LIC parameters. The use of the automated bench, which makes it possible to carry out resource testing of LIC based on dynamic stress testing (DST), makes it possible to shorten the resource testing of LIC and thereby significantly accelerate the design and development of EPS LIB of spacecraft. The structure, the description of the component parts and the technical characteristics of the bench SIA 12/24 allowing to perform electrical tests simultaneously of twelve LIC are given. The principle of operation and technical characteristics of the original charging-discharge device with a load converter (CDD-LC) forming the basis of the bench are considered. The proposed original CDD-LC and load converter (LC) topologies with two-stage power conversion and stabilized bridge transformer converter (BTC) input voltage make it possible to automate the process of lithium-ion cells electric testing by automatically reproducing functionally necessary test modes and by ensuring energy saving in cells charging-discharge modes. For a two-stage power conversion CDD-LC, it is shown that the use of BTC input voltage stabilization gives the following benefits: – extension of the LIC attribute control ranges: current, voltage, power; – low dependency of static error of stabilization of LIC attributes and transition quality indicators on the type of LC load.
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Beam support stiffness analytic solution for the first eigenfrequency and critical force
Статья научная
The problem of providing the required first natural frequency of bending vibrations of the beam under the action of a longitudinal force by introducing the necessary stiffness of the supports is discussed in the article. Considering and combining the equations of free vibrations of the beam and the equations describing the loss of its stability helped to obtain the operability condition based on providing a minimum given value of the first natural frequency of vibrations considering the action of the axial force. In this case, the achievement of the zero frequency of natural vibration corresponds to the loss of stability, which allows solving both problems. This task is mathematically complicated, and in the known scientific literature its solution is usually given only in graphical or tabular forms. The problem is in the nonlinear dependence of the coefficients of supports on the stiffness during vibrations and loss of stability. To solve this problem, the approximation of the nonlinear coefficients of the supports by the least squares method and the obtaining of quadratic approximating functions was used. As a result, the problem of determining the required stiffness of the supports brought to a fourth-degree resolving algebraic equation, for which an analytic solution exists. The obtained solution allows the stiffness of the beam supports, which provides the required value of the first natural frequency of vibrations of the beam and its first critical load in the form of external compressive force or temperature effects. Replacing the nonlinear dependencies of the support coefficients with the stiffness of the supports with simpler quadratic functions led to relatively simple analytic dependencies that allow the resolution equation to be transformed according to the particular problem being solved. At the same time, quadratic functions influenced the calculation error, to reduce which, the range of the support stiffness under consideration was limited and divided into three zones. The results of calculations using the proposed analytical solution were compared with numerical calculations using finite element method. The comparison of the calculation results showed an error of not more than 5 % for the considered range of stiffness of the supports, which is quite enough for engineering calculations of beam structures. To limit the error of the result, it is recommended that the stiffnesses of both supports be equal or of the same order.
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CFD methods for cavitation modeling in centrifugal and axial pumps of LRE
Статья научная
Currently, design and manufacture of liquid-propellant rocket engines (LRE) are imposed with ever greater reliability requirements. Accordingly, the standards for the design and manufacture of rocket engine units are raising. One of these units is a turbopump unit (TNA), which provides continuous supply of liquid components from combustion reaction to the combustion chamber of a rocket engine to create traction or other engine units. TNA is also the main source of pressure increase for these liquid components in front of the LRE combustion chamber. Important requirements are imposed on a turbopump unit (TNA): ensuring work performance and basic parameters for a given resource with the necessary possible pauses of a specified duration; providing all engine operating modes, supplying the fuel components of the required flow rate and pressure, guarantying a high degree of reliability with acceptable entire unit efficiency; providing high anti-cavitation characteristics of the pump in all modes. In the article, the authors summarize the latest results of the study on cavitation in turbopump units of liquid propellant rocket engines alongside with the relevant research in the field of hydraulics. The problems of cavitation in cryogenic liquids, simulation of stall characteristics, and usability of various models to simulate cavitation flow are observed. A solution to the problems of flow modeling was considered with respect to applicability to the following structural elements of LRE units: interscapular space of the screw centrifugal main and booster pumps, axial pre-pump. Particular attention is paid to the implementation of various numerical methods based on the use of various cavitation models, computational fluid dynamics in various CFD packages, and also comparison of results with the model. In summary, the authors draw conclusions about the possibility of applying these methods to solve the problems of the cavitation phenomenon research in LRE.
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Статья научная
The thermal control system (TCS) is one of the most important systems, which largely determines the design of the spacecraft. At the present stage of development of methods and tools for spacecraft design, a promising direction is the creation of thermal mathematical models of the TCS, calculation algorithms, which allow to create effective design solutions at various design stages. The purpose of this work is to bring the system of equations of heat balances of the liquid circuit (LC) of TCS to a form that allows programmatic numerical integration in the solution search algorithm along the length of the middle line of the heat and mass exchange fluid circuit taking into account certain complex thermal resistances. In fact, this means that the terms of the temperature of the contour and the linear coordinate, the integration variable, should remain as variables in the equation record, everything else should be numerically determined from the properties of the real object. For the boundary conditions of the LC TCS of the spacecraft, the coefficients of complex heat transfer were calculated taking into account the actual topology of the circuit and the thermal properties of the coolant. Using these values, the system of thermal balances of the spacecraft of the spacecraft on the characteristic surfaces of constant temperatures was reduced to a form that allows a numerical solution: the number of equations corresponds to the number of detected temperatures along the north and south panels and is closed through the temperature of the liquid circuit refrigerant. The resulting system of equations allows us to investigate the thermal state of nonhermetic formation spacecraft at the stage of preliminary design with varying operational and design parameters in order to determine the area of efficiency and the area of optimal operation under certain performance criteria.
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Calculation of heat transfer characteristics of a finned wall
Статья научная
The reliability and resource of the radio-electronic equipment of the spacecraft is increased by ensuring op-timal temperature conditions. Thermal control systems maintain the set temperature mode and heat removal from the onboard equipment to the surrounding space. Finned heat exchangers are an important element of the de-sign of thermal control systems, which allows intensifying the heat transfer process. The calculation of the char-acteristics of finned heat exchangers must be carried out taking into account their parameters and the physical properties of the heat transfer agent. The organic liquid LZ-TK-2, which has a very low freezing point and other useful performance characteristics, is considered as a heat transfer agent. The dependences of the local heat transfer coefficient of the LZ-TK-2 heat transfer agent on the wall temperature are calculated using criteria equations. Based on the numerical solution of the two-dimensional problem of thermal conductivity, the tempera-ture fields in finned walls of various configurations are determined. Calculations of the heat transfer coefficient of the finned wall of the heat exchanger were made in two model approximations, the error of using a simplified approximation that does not take into account the temperature dependence of the local heat transfer coefficient was determined.
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Calculation of the parameters and characteristics of a rotating lunar jet penetrator
Статья научная
The purpose of the work is to determine the parameters of the internal ballistics of a solid propellant jet engine mounted on a jet penetrator entering the ground at a high rotation speed around its own axis. Research methods: to determine the pressure in the chamber of a rotating engine, the known equations for the balance of gas inflow and consumption are usually used, as in the case of a non-rotating solid propellant jet engine. The difference between the internal ballistics of a rotating solid propellant jet engine is that the effect of rotation on the operating process is taken into account by the coefficient of gas flow from the chamber of the rotating engine; a change in the rate of erosive combustion of solid propellant during rotation of a solid propellant jet engine; heat loss coefficient. Results: it was found that the parameters of the internal ballistics of rotating jet engines of solid propellant are mainly influenced by the coefficient of gas flow from the chamber of the rotating engine; effect of erosive combustion of solid propellant and change in heat loss coefficient. The main calculated dependencies for determining the pressure in the combustion chamber of a rotating solid propellant engine are presented for periods when the pressure reaches a stationary mode of operation of the engine, operation of the engine in a stationary mode and during the period of free flow of gases from the chamber of a solid propellant jet engine. A method for selecting the linear and angular dimensions of a rotating engine nozzle is presented. An estimate of the thrust force for a single nozzle rotating solid propellant jet engine is given. It has been established that the magnitude of the thrust force of rotating engines (under other identical conditions in the combustion chamber) is 1.1–1.36 times less than that of non-rotating solid propellant jet engines. The experiments carried out showed a decrease in the degree of swirl of the gas flow of rotating solid propellant engines with an increase in the number of propellant pellets in the engine charge. Conclusion: the results presented in the article can be useful for scientists, graduate students and engineers involved in the creation and operation of aviation and rocket and space technology, and can also be useful for students of technical universities studying in relevant specialties.
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Characteristics of low thrust liquid-propellant rocket engines testing process
Статья научная
Low thrust liquid-propellant rocket engines (LTLPRE) are the main type of rocket engines for control systems of space aircrafts. The thrusters are able to work either in continuous or impulse regime, which is one of their main characteristics. The suggestion about engines` reliability should come from the results of tests which create real or greatly approximated to the real conditions. The development process of thrusters takes into a great account the problems of bench testing methodic, technical equipment of test benches for creating the closest possible to space conditions and the use of diagnostic methods and instruments for various types of physical research and dimensions. The ground test effectiveness depends on the level of real conditions imitation and the level of attention to all operational factors that influence the credibility of reliability parameter estimation during the development. One of the most important questions in terms of testing effectiveness is the question of testing result accuracy and credibility. The testing process of thrusters mainly goes under the requested conditions of vacuum, created in pressure chambers. To increase the effectiveness of space conditions imitation the paper suggests using the pressure chamber, equipped with the tube shield with the circulating liquid nitrogen under required mass flow rate. The impulse working regime creates instability of propellant moving in pipelines. The paper considers the methods of providing dynamically similar characteristics of supply systems in propulsion systems as well as conformity of hydraulic, inert and wave characteristics of supply pipelines.
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Characteristics research of a low thrust rocket engine manufactured using additive SLM technology
Статья научная
The development and improvement of rocket and space technology are largely determined by the application of manufacturing technologies that enable the production of high-reliability products with energy efficiency, while simultaneously reducing material intensity and shortening the production cycle. Among these progressive technologies, additive technologies should be mentioned. The essence of these technologies lies in obtaining parts through layer-by-layer melting of material based on a computer 3D model of the product in a chamber of a specialized 3D printer equipped with a laser device. The application of additive technologies in rocket engine construction requires extensive scientific research and experimental work to confirm compliance with industry standards, rules, and mandatory certification at the state level. In accordance with the program of priority research at SibSU, in collaboration with the industrial partner “Polychrome” LLC a complex of experimental work is being carried out to test and refine the 3D printing modes of a demonstrator model of a low thrust rocket engine (LTRE). The design of the LTRE, operating on environmentally friendly gaseous fuel components, has been developed and adapted for 3D printing on the ASTRA 420 printer. The parameters and characteristics of the printer are considered, and the sequence of experimental work on selecting printing modes for the engine chamber housing and mixing head is outlined. The fundamental possibility of adjusting the modes of laser material melting and forming of the part has been established. The main technological stages of post-printing processing of LTRE chamber parts are presented. A description of the equipment for heat treatment and electrochemical polishing of parts is provided. The sequence of material structure research is outlined, and the results of metallographic and X-ray analysis of the internal state of the metal are presented. The importance of stand tests of rocket engines in the development of innovative design solutions and the implementation of innovative production technologies is demonstrated. A description and composition of the testing stand system at SibSU are presented. The results of stand firing tests indicate the fundamental possibility of manufacturing LTRE using selective laser melting of heat-resistant alloy.
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Статья научная
A turbopump unit (TPU) is one of the main units of a liquid propellant rocket engine. Ensuring the op-erability and the possibility of continuous supply of fuel and oxidizer components with a given flow rate and pressure throughout the entire operation cycle of a liquid-propellant rocket engine is one of the main tasks in the design of a heat pump. A negative effect that manifests itself in the case of a local decrease in pressure to the pressure of saturated steam is cavitation. Currently, in connection with the growth of the computing power of modern computer systems, the methods of computational fluid dynamics (Сomputational Fluid Dynamics, CFD) are increasingly being used to test the anti-cavitation parameters of the pump in various areas of general mechanical engineering. For the rocket and space industry, which has special requirements for reliability, more statistical data is needed. At the moment, there is no cavitation model capable of fully simulating the entire process of nucle-ation, growth and collapse of a cavitation bubble. However, there are a number of simplified models of this process, among which we can single out the numerical model Zwart – Gerber – Belamri, designed to simu-late the cavitation flow in pumps. The mentioned model is the most suitable and is applied in all the works discussed below. This paper analyzes the experimental data and the results of numerical simulation of pumps with vari-ous parameters of flow, pressure and geometry. In the course of work with the model, calculations were performed in the ANSYS environment. In the final part, a conclusion was made about the relationship be-tween the characteristics and applicability of the Zwart – Gerber – Belamri model to the design of the cavi-tation flow in the TPU of an LRE taking into account the peculiarities of the pump operation.
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Статья научная
One of the main systems of a spacecraft (SC) is a power supply system (PSS). The basis of a PSS are secondary power sources (SPSs), which use various methods of controlling and converting electricity, which leads to significant differences in their dynamic properties. On the onboard consumer side, the dynamics of the PSS is determined by the total internal resistance (impedance) of the SPSs. When conducting ground electrical tests of spacecraft EES (electrical engineering systems), due to the complexity of using power supply systems, test complexes are used, the basis of which is simulators of electrical characteristics of the PSS (PSSS). Modern PSSSs use a modular configuration principle, which makes it possible to produce PSSSs of different powers, but energy modules have fixed or adjustable impedance frequency response over a narrow frequency range, which leads to the limitation of the types of PSS being simulated. Equipping the PSSS with the property of regulating frequency response in a wide frequency range expands the functionality of the PSSS, as it allows simulating the dynamic properties of the PSS containing different types of SPSs. The purpose of the work is to study and carry out the comparative analysis of three methods for regulating the impedance frequency response (IFR) of the PSSS module. The methods for regulating the frequency response of a PSSS are being considered on the basis of its generalized functional diagram containing mathematical models: adder amplifier (AA), feedforward compensator (FC), power amplifier (PA), voltage divider (VD) and load (L). The article analyzes options for regulating the impedance frequency response of PSSS, and considers three methods for regulating the IFR: two with a passive FC and one with an active FC. The paper presents a simulation model in the MicroCap package of the electrical circuit of the PSSS module, and computational experiments have been carried out on each method of regulating the IFR of the PSSS. Based on the results of the study, a method for correcting and regulating the IFR of the PSSS is recommended, which makes it possible to separately regulate the low-frequency and mid-frequency regions of the IFR, which allows us to significantly simplify the configuration and provision of the IFR of the PSSS in accordance with the specified requirements.
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Concentration of carbon dioxide in products of combustion of GTE NK-16ST and NK-16-18ST
Статья научная
This paper considers the design of two combustion chambers of a gas turbine engine running on natural gas. One combustion chamber has 32 burners, and the other has 136 nozzles located in two rows in the flame tube head. A major contributor to global warming is considered to be the significant emissions of greenhouse gases, primarily CO2, including those emitted by gas turbine engines and power plants. The reduction of carbon dioxide levels by developing a set of structural measures in the combustion chamber is one of the urgent tasks of engine construction which requires a solution in order to meet modern environmental requirements for gas turbine engines serving as blower drives for gas compressor units. The presented research is dedicated to the analysis of influence of changes in combustion chamber design on reduction of CO2 level in exhaust gases of gas turbine engine NK-16ST. Two modifications of the combustion chamber are considered. The first one was a serial combustion chamber with diffusion combustion; the second one was a modernized combustion chamber with a modified front device. Each of the chambers considered was tested as part of the engine. During the study, combustion products were sampled directly in the exhaust tower and their concentrations, including the CO2 content, were determined. As a result of this work, it was confirmed that there is a possibility to reduce the concentration of CO2 in the engine combustion products up to 20 % without affecting the engine parameters. This reduction in carbon dioxide content was made possible by reducing the completeness of fuel combustion in the combustion chamber. The obtained data on changes in CO2 concentration can be useful in selecting the most suitable mode of engine operation, and the presented approaches to combustion processes organization can be used by developers in designing combustion chambers of natural gas-fired gas turbine engines.
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Control and regulation equipment of electric power system for a prospective piloted transport system
Статья научная
The aim of this work is to consider solving complex of tasks focused on fulfilling the complicated tactical and technical requirements for regulation and monitoring equipment (RME) of electric power supply system (EPS) for a prospective spacecraft. These requirements are imposed due to the need to ensure high reliability of the equipment during operation under the influence of external factors (vacuum, vibro-impact loads, radiation, absence of convective cooling), as well as to achieve high mass-dimensional parameters of the equipment and its high functionality The complexity of problem solving lies in the need to ensure conflicting requirements – high levels of energy density, weight and size characteristics, reliability and durability. These problems fully apply to the RME of the EPS for a prospective piloted transport system (PPTS) which design example shows ways of solving abovementioned problems. The most rational way of solving these contradictions is to increase the specific energy indicators of the main components of the RME devices – power converters, which can be achieved by using modern power electronic elements, using new materials and semi-finished products, for example, printed circuit boards with a metal heat sink, as well as increasing the layout density design. Determining solution is to select an optimal structure of the power converter, which provides the best efficiency. An additional way to reduce the mass-dimensional indicators of the RME is the use of a digital control method, the collection of telemetric information, and the receiving and processing of commands. At the same time, on the contrary, to ensure the specified reliability of the equipment, it is necessary to use excess reservation at the element level – for power components, and the principles of majority reservation at the functional block level – for control and telemetry schemes. Using the example of RME, developed by CJSC “Orbita”, the main EPS parameters of a new generation spacecraft are shown and most important power supply subsystems are considered in the article: the solar energy control subsystem and the power storage subsystem, ways to build them for meeting specified requirements, taking into account the proposed solutions. As a result of this work, the optimal structures of power converters – the current regulator of the solar battery and the current regulator of the battery – were selected, the basic principles of power components reservation ensuring the operability of the equipment in case of a single failure of any component without loss of performance and deterioration of RME parameters as a whole are shown. Block-modular construction method is used for optimal layout and high reliability of the RME, it ensures uniform heat removal from electronic components, which is especially important in vacuum conditions, minimum dimensions and mass optimization of the RME, as well as high mechanical strength of the structure. The implemented principles of building the RME for PPTS using this approach will allow to increase the active lifetime (ALT) and reliability of the spacecraft with a simultaneous decrease in mass and dimension parameters.
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