Статьи журнала - Siberian Aerospace Journal
Все статьи: 330
Статья научная
The burning of fuel in the combustion chamber of a gas turbine engine (GTE) is accompanied by formation of toxic substances. The most dangerous among them are carbon oxides that have a detrimental effect on humans and environment. In this regard the article is solving the urgent problem of determining the optimal method of gaseous fuel supplying in GTE combustion chamber to ensure low carbon-oxide emissions. The paper presents the design features of injectors that work with a separate supply of air and fuel. Natural gas is used as fuel. One of the considered injectors provides jet fuel supply by means of a perforated spray, and another one provides twisted fuel supply by means of a swirler built into the fuel channel. The main geometric parameters of the injectors are given as well, such as the size of the swirler, the number of blades, and the diameter of the output nozzle. In this regard the quality of air-fuel mixture preparation in a swirl jet in the outlet of the burner with two types of injector is defined. It is found that the best quality of mixing is ensured by the injector with jet spray. The design of a heat pipe simulator, in which the tested nozzle is placed, is considered. The design of a stand installation designed for testing injectors in a heat pipe simulator, as well as the modes under which these tests were carried out, are presented. The results were obtained in a heat pipe simulator with installed jet injectors and injectors with a swirling fuel jet. An analysis was conducted, which resulted in conclusions about the effectiveness of using jet injectors. According to the conducted research, the parameters of the injector with a swirling fuel jet are characterized by the presence of high values of CO levels in the combustion products, which is explained by the extremely low quality of mixing fuel with air and, consequently, low efficiency of fuel combustion. Jet fuel injection has low CO values, which indicates good quality of mixing fuel with air and high efficiency of a combustion process. As a result, we have received recommendations on setting the selected type of injectors in a full-size combustion chamber.
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The magnetic anisotropy comparison of polycrystalline and single-crystal Fe3Si films
Статья научная
High-tech devices improvement requires development of technology and search for new materials from science. Currently, the development of the magnetism research field has reached a very broad knowledge, making it possible to create and study a variety of artificial ferromagnetic materials, which are already actively used in science and technology. The latest scientific knowledge shows that the same material in different states can exhibit different electrical and magnetic properties. Thus, thin magnetic films are actively used in modern devices. Physical processes in thin films proceed differently than in bulk materials. As a result, the film elements have characteristics that differ from those of bulk samples and make it possible to observe effects that are not characteristic of bulk samples. A film is a thin layer of a bound condensed substance, the thickness of which is compared with the distance of surface forces action; it is a thermodynamically stable or metastable part of a heterogeneous film-substrate system. Further researsh of film structures led to the creation and study of multilayer magnetic systems. In such structures, the presence of both various ferromagnetic materials layers and non-ferromagnetic interlayers is possible, and the multilayer systems properties can differ significantly from the properties of any system components. These materials also have many practical applications, including radio communications and geological exploration. In our experiment, ferromagnetic thin films of Fe3Si silicide were synthesized by molecular beam epitaxy with co-deposition of Fe and Si. A polycrystalline silicide film was obtained on a SiO2/Si(111) substrate, and a single-crystal film - on Si(111)7×7. The structure was investigated using the diffraction of reflected fast electrons directly during the growth process. The magnetic anisotropy of the obtained samples was studied applying the method of ferromagnetic resonance. It was found that the polycrystalline film is characterized by uniaxial magnetic anisotropy, which is 13.42 Oe and is formed as a result of “oblique” deposition, whereas the magnetic anisotropy for a single-crystal Fe3Si film is formed to a greater extent by internal magnetocrystalline forces.
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Статья научная
In this paper, the issues of ensuring the resistance of the onboard equipment of spacecraft to the effects of ionizing radiation from outer space, which significantly limits the period of active existence of the space-craft, are considered. The paper describes the methodology for ensuring radiation resistance, developed by the specialists of JSC “ISS”. The result of the work done is to ensure the guaranteed performance of the target function by spacecraft with long period of active lifetime of 15 or more years. Among the outer space factors affecting the spacecraft, ionizing radiation of outer space is the main factor limiting the period of active existence. Exposure to energetic particles of ionizing radiation from outer space causes degradation of the electronic component base, which leads to failures and malfunctions of on-board equipment and degradation of its functional surfaces. Ensuring the radiation resistance of a spacecraft (SC) is a complex task, one of the stages of which is to determine the radiation resistance of components that complete the on-board equipment. As a result of accumulated experience in conducting radiation tests and analysis of the results, specialists of JSC “ISS” developed a methodology that allows to guarantee the radiation resistance of the spacecraft under conditions of tight production deadlines and optimized costs.
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Статья научная
The paper proposes the method for the numerical solution of Poisson kinematic equations system determining the evolution of the spacecraft position. The system of Poisson kinematic equations is used to designate the transition matrix from the coordinate system associated with the spacecraft at the selected time t1 to the coordinate system associated with the spacecraft at the current time t2. This matrix is used in the process of solving problems of determining a three-axis orientation of the spacecraft from the readings of the magnetometer using information about its angular velocities. The proposed method is based on replacing the derivatives of the desired functions in the Poisson kinematic equations by partial sums of series in the scaled Haar system. The partial sums of these series are generalized polynomials in the scaled Haar system. Hence, these sums are step (piecewise constant) functions. The estimates of the proposed method error are derived, which reveal that in the case of the coefficients of the equations which are functions matching the Lipschitz condition, the absolute error in calculating each of the elements of the transition matrix from one coordinate system to another is the value O(N–1) at N , where N is the number of partitions of the segment [t1, t2] when constructing a grid of nodes involved in this method. It is proved that the complexity of constructing an algorithm for approximating the system of Poisson kinematic properties insignificantly exceeds the complexity of solving this system by Euler method, which has the first order of accuracy. The research presents the results of numerical experiments, showing that in certain cases the Haar sums method gives an error that is much smaller than the Euler method, and is almost identical to the errors of the Euler – Cauchy and Runge – Kutta methods of the 2nd order, the complexity of which is approximately two times greater than the complexity of the Haar sums method.
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Статья научная
Plates, beams and shells with non-uniform and micro-inhomogeneities regular structure are widely used in aviation and rocket and space technology. At the preliminary design stage, it is initially important to know whether the design safety factor meets the specified strength conditions. To determine the margin factor, it is necessary to solve the elasticity problem for the designed structure by the finite element method (FEM), taking into account its inhomogeneous structure, which requires large computer resources. In this paper, we propose a method of equivalent strength conditions (MESC) for calculating the static strength of elastic structures with a inhomogeneous regular structure. The proposed method is reduced to the calculation of the strength of isotropic homogeneous bodies using equivalent strength conditions. The MESC is based on the following statement. For any composite body V0 , there exists such an isotropic homogeneous body Vb and such a number p (equivalence coefficient) that if the body Vb stock coefficient satisfies 0 nb the equivalent strength conditions 0 pn1 nb pn2 , then the body V0 stock coefficient satisfies n0 the given strength conditions n1 n0 n2 , and Vice versa, n1 , n2 – given, the coefficients 0 nb , n0 , meet the exact solutions of elasticity problems constructed for bodies V0 , Vb . The method under consideration is reduced to FEM strength calculation of isotropic homogeneous bodies, which is the easiest to implement and requires less computer memory than a similar calculation of composite bodies taking into account their inhomogeneous structure. The procedure for determining the equivalence coefficients for a number of composite plates, beams and shells of rotation is described. High-precision multigrid finite elements generating discrete models of small dimension and solutions with small error are used in the construction of elastic solutions according to FEM for isotropic homogeneous bodies. The adjusted equivalent strength conditions are of the form pn1(11) nb pn2 (12 ) , where nb is the body Vb reserve coefficient and the values 1 , 2 correspond to the approximate solution constructed for the body Vb . Implementation of FEM for multigrid discrete models requires several 103-106 times less computer memory than for basic models. The calculation of the strength of a beam with a micro-homogeneous regular structure with the help of MESC is given.
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Статья научная
When the strength of elastic composite structures (plates, beams, shells) widely used in aviation, rocket and space technology is calculated with the finite element method (FEM), it is important to know the solu-tion error. To analyze the solution error, it is necessary to use a sequence of approximate solutions con-structed according to the FEM using the grinding procedure for basic discrete models (BMs), which take into account an inhomogeneous microheterogeneous structure of bodies within the microapproach. Dis-crete models obtained by grinding BMs have a high dimension, which makes it difficult to use the FEM for them. In addition, there are BMs of composite solids (CSs), for example, BMs of bodies with a microhet-erogeneous structure, which have such a high dimension that the implementation of the FEM for such BMs is practically impossible due to limited computer resources. To solve these problems, it is proposed to use fictitious discrete models in the calculations of CSs according to the FEM. In this paper we propose a method of fictitious discrete models (MFDM) for calculating the strength of elastic bodies with an inhomogeneous microheterogeneous regular structure. The MFDM is implemented with the help of the FEM using corrected strength conditions, which take into account the error of ap-proximate solutions. The method is based on the following provision. We believe that BMs of CSs generate solutions that slightly differ from the exact ones. Such BMs always exist for CSs due to the convergence of the FEM. The calculation of CSs according to the MFDM is reduced to the construction and calculation of the strength of fictitious discrete models (FMs), the dimensions of which are smaller than the dimension of the BMs. FMs reflect: the shape, characteristic dimensions, fastening, loading and the type of the inhomogeneous structure of CSs and the distribution of the elastic moduli corresponding to the BM of the CS. The sequence consisting of the FM converges to the BM, i.e., the limiting FM coincides with the BM. The convergence of such a sequence ensures uniform convergence of the FM stresses to the corresponding BM stresses. The implementation of the FEM for FMs with the use of multigrid finite elements leads to a large saving of computer resources, which makes it possible to use the MFDM for strength calculations of bodies with a microheterogeneous regular structure. Calculation of the CS strength according to the MFDM requires times less computer memory volume than a similar calculation using the BM of the CS, and does not contain the procedure for grinding the BM. The given example of calculating the strength of a beam with an inhomogeneous regular fibrous structure according to the MFDM shows its high efficiency. Applying the adjusted strength conditions allows using approximate solutions with larger errors in CS strength calculations, which leads to improving the efficiency of the MFDM.
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Статья научная
A method of synthesizing a digital controller for a solar energy conversion channel in a power supply system of a spacecraft is presented. The method is based on the initial functional diagram of the pulse converter and the method of switching discontinuous functions. In accordance with the technique, which is formally presented in the form of eight consecutively executed items, a block diagram of the shunt converter has been developed in the basis of switching functions, which is taken as an example for testing the technique. The shunt converter is one of the three energy conversion channels in modern power supply systems of a spacecraft. The block diagram showed that all nonlinearity of the system can be reduced to nonlinearities of two multiplication links and nonlinearity of a pulse-width modulator. The possibility and acceptability of joint linearization of each of the specified nonlinear multipliers with a pulse-width modulator at the selected operating point is shown. A linearized block diagram of the control object was obtained, after which the transformation and simplification of the block diagram to a convenient form for calculation was carried out. Using the transfer functions of the linearized block diagram, the logarithmic frequency characteristics were calculated analytically and the results of their comparison with the frequency characteristics obtained experimentally on a simulation model, which confirmed their identity in the working frequency domain, were presented. At the same time, the specified simulation model of a shunt pulse converter, built in the Simulink package of the Matlab design environment, took into account all the mentioned nonlinearities of the real converter. According to the obtained logarithmic characteristics, a classical synthesis of the analogue prototype correcting section was produced. The transition from the analog correcting section of the prototype to the implementation of the digital correcting section is shown. Simulation modeling of a closed-loop power supply system with a synthesized analog controller, in its mode of operation from a solar battery, confirmed the correctness of the methodology and the achievement of the goals. The results of the work are intended to create a new onboard energy conversion equipment for power supply systems of high-potential spacecrafts. The scope of application of the project results is space instrumentation.
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The method of the automation of the plasmotron movement by six-axis robotic manipulator
Статья научная
The article presents a method for automating the creation of trajectories of the plasmotron movement by a six-axis robotic manipulator. The automation system was created on the basis of an industrial robot from KUKA. The automation of the creation of trajectories of the plasmatron over the surface of the part is implemented as follows: the trajectory of the plasmatron is created in a graphic editor in the .dwg format. The created file is loaded into the CAM program for CNC machines. A CAM program converts a vector or an area specified by vectors into a control command in g-code format, which is then converted to KRL by a program written in the Python programming language. The development of the program consisted of two stages: the creation of rectilinear movements and the creation of curvilinear movements. The result of the method is presented.
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The method of the disk friction determining of low mass flow centrifugal pumps
Статья научная
Low mass flow centrifugal pumps are currently widely used in the energy supply system of liquid rocket engines, the engines of correction, docks, consisting of on-Board power sources on-Board sources power supply system of fuel components in the in gas generator systems for inflating fuel tanks, and in temperature control systems of aircraft and spacecraft. When designing low mass flow centrifugal pumps for aerospace purposes, methods for calculating and optimizing the flow rate are often used corresponding to the design methods of full-size centrifugal pumps, which limits the mode and design potential of pumps and affects their energy characteristics and reliability. Reliability requirements often lead to the need to reserve units and fuel-supply systems. Despite the large amount of research works, the issues of reliable design of low mass flow centrifugal pumps with high energy and operational parameters for spacecraft and aircraft remains an urgent task. The article analyses the operational parameters of low mass flow centrifugal pumps used in aircraft and spacecraft power systems. Taking into account working fluid used and the temperature range, it was found that a laminar rotational flow with Reynolds number characteristic Re 103 3105 is realized in the lateral cavity between the impeller and the pump housing. The determination of power losses on disk friction of the impeller technique is developed taking into account design features and the applied schemes. Equations for determining the disk friction coefficients are consistent with the dependencies obtained by other authors. The obtained equations for the laminar rotational flow made it possible to determine the dependences for the resistance moment and the disk friction power of the impeller determining of a low mass flow centrifugal pump.
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The possibility of using methane-hydrogen fuel in converted gas turbine engines for power plants
Статья научная
Taking into account the fact that recently the topic of using methane-hydrogen mixtures as a fuel for gas turbine engines used in power plants has been actively developed, it is necessary to have engineering methods for calculating the fuel system and combustion chamber of engines operating on such fuel. The paper proposes the methodology that allows performing such calculations. A gas turbine unit (GTU) based on a converted aircraft engine NK-16ST was taken for the calculation. The calculation according to this method is carried out in three stages. At the first stage the composition is selected and the thermophysical characteristics of the gas under consideration are determined. At the second stage the fuel system is calculated, the consumption characteristics of the engine fuel system and the combustion chamber system are built. The consumption characteristics built for natural gas and for methane-hydrogen mixture are compared. The analysis makes it possible to develop recommendations for optimizing the design of the fuel supply equipment and fuel nozzles in terms of changing the volume of internal channels. At the third stage the combustion chamber is calculated and recommendations about the need to change the flame tube head or redistribute air along the flame tube length are made. The volumetric heat intensity parameter is used to estimate the sufficiency of the available volume of the flame tube for operation on methane-hydrogen mixture and to determine the gas average temperature in the combustion zone of the combustion chamber. The possibility of operation of the NK-16ST gas turbine unit on a methane-hydrogen mixture was confirmed on the basis of the results of the work performed. It was also concluded that in order to supply large volumes of methane-hydrogen mixture in comparison with natural gas, it is required to increase the size of fuel pipelines, metering and control units and fuel nozzles.
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The process of nanomodifying cast aluminum alloy ingots for components of aerospace vehicles
Статья научная
Currently, increasing attention has been paid to such a class of materials as nanopowders (NP) of chemical compounds, which are ultra-thin formations of not more than 100 nm in size. Such attitude to these materials is explained by the fact that they have unique physical, chemical and mechanical properties significantly different from the properties of materials of the same chemical composition in a massive state, and these properties can be transferred to some extent from them or with their participation to the products. The existing methods of introducing NP into metal melts could not be used due to their special properties in comparison with coarse powders, and therefore a new method of their introduction into the melt was developed, excluding direct contact of NP particles with oxygen and unhindered penetration of particles into the melt through the oxide layer. The essence of the method was as follows. In the aluminum container filled up with aluminum particles or deformable aluminum alloys D1 or D16 and various NP (nitrides, carbides, oxides, etc.), and this composition was pressed into the rod, with its help NP was introduced into the melt during casting of aluminum ingots and deformable aluminum alloys. The results of the study showed that this excludes the appearance of cracks in the ingots, as well as improves their technological and mechanical properties.
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Статья научная
Today, protective coatings are applied to almost all parts and components of engineering products in order to ensure high performance properties of machines, with the lowest economic cost. The method of plasma spraying allows to apply heat-resistant coatings on a different kind of basis, in addition to a wide variety of materials. Therefore, rocket and space engineering is primarily interested in the method. In modern conditions of high rate of mechanical engineering development engineers must develop and put into operation products within the shortest possible period of time. As a rule, engineers select the modes of plasma spraying using the method of selecting the empirical relationship between the properties of the coatings and the values of the specified parameters of plasma spraying, which suggests conducting a huge number of experiments. That is why we see the need to find new methods for selecting the plasma spraying parameters, which are based on mathematical and analytical apparatus. We set the task to study and show the applicability and prospects of the proposed method. In the work we carried out the operations of spraying nichrome coating, at different values of the arc current. We studied the adhesive strength of the coatings obtained and their microstructure. We showed the relationship between the arc current and the adhesion of the coatings using their microstructure. These studies have made it possible to exclude a large number of experiments, which usually establish an empirical relationship between the values of the input parameters of the deposition process and the values of the characteristics of the coatings obtained. In the future, we assume that the database of such relationships will make it possible to fully use this method in engineering industries.
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Статья научная
The most important resource for improving the performance of parts is the reduction of the surface roughness. One of the promising ways to reduce the surface roughness is the abrasive extrusion processing. When developing the AEP technology, it is necessary to know the flow rate (pressure) of the WE, which depends on the viscosity of the latter. In turn, the viscosity of the WE is determined by its temperature. The temperature of the working environment at AEP can be calculated if the coefficients of thermal conductivity and thermal diffusivity of the WE are known. The working environment for AEP consists of two components, therefore, the coefficient of thermal conductivity can be calculated by known formulas. However, the calculation error is significant, therefore, the experimental determination of the abovementioned coefficients is required. The installations for the coefficients research have been presented, the methods of conducting experiments have been developed. After mathematical processing of the experiments results by means of the AdvanceGrapher v. 2.11, the dependences of the thermal conductivity and thermal diffusivity on the abrasive concentration have been obtained. The studies of the thermophysical properties of the working environment have shown that the values of thermal conductivity and thermal diffusivity of the WE are mainly determined by the concentration of abrasive grains in the working environment. The direct dependence of these coefficients on the degree of filling the working environment with abrasive grains has been established.
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Статья научная
Electrical discharge machining and electrochemical machining of metals are used in the production of parts for aircraft and rocket technology, especially electrical discharge machining. A type of electrical discharge machining, electrical contact machining, is used in metallurgy. The paper investigates a combined method of metal machining, including electrical contact and electrochemical methods using vibration of the electrode tool. This method is used for copying and piercing operations in the manufacture of parts from metals that are difficult to machine mechanically. The peculiarity of the above-mentioned method of electrical machining is the formation of surface roughness of the metal being machined due to anodic dissolution and the electrical discharge machining process. The side surface of the workpiece is formed due to electrochemical processes. The end surface is formed due to electrical contact machining. Based on literature data for pulsed electrochemical machining and experiments, expressions for calculating the roughness parameter of the side surface are obtained. The formula takes into account the time of anodic dissolution for one period of oscillation of the cathode tool, the voltage on the electrodes and the concentration of the electrolyte. The calculation of the roughness parameter of the end surface is carried out similarly to the expression for electrical discharge machining, but instead of the duration of the electric pulse, the duration of contact of the electrodes is used. The experiments carried out confirmed the correctness of the expressions used and made it possible to obtain the dependence of the coefficient on the vibration frequency of the cathode-tool.
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Статья научная
Today, the scope of application of electric propulsion systems for orbit correction and spacecraft’s attitude control is rapidly expanding due to their high efficiency compared to liquid jet systems. The main elements of electric jet systems are plasma or ion thrusters. To ensure power supply of such thrusters, complex electronic power processing systems – power processing units (PPU) – are used. These units are capable to operate for a long time (up to 15 years or more) in a high vacuum environment and generate sufficiently high accelerating voltages – from 300 V and higher. PPU’s comprise various EEE-parts, mainly in the case design. As a rule, the technology of their production is such that air or nitrogen is initially located inside the housing at atmospheric pressure. During the operation of the unit, the non-absolute hermeticity causes pressure decrease inside EEE housings. Due to high voltages applied, this can lead to electrical breakdowns between current-carrying ele-ments inside the parts, their failure with the subsequent failure of the functional blocks of the unit. The paper considers the physical principles of the breakdown occurrence inside EEE-parts cases. The results of non-hermiticity measurements of several types of HV EEE-parts are presented. The dynamics of the pressure drop to the values dangerous from the point of view of breakdown event and the relevant occurrence duration are esti-mated. It is shown that duration of being exposed to the pressure-dangerous conditions can be as long as space-craft service lifetime. It can make difficult to use packaged gas-filled EEE-parts at the level of units intended to operate in non-pressurized compartments of spacecraft. Recommendations are provided for selecting the design of EEE parts with an operating voltage of about 300 V or more, as well as circuit solutions used to develop high-voltage equipment intended to operate in vacuum environment.
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The use of the inverse transformation method for time series analysis
Статья научная
In modern conditions of technology development, signs of systemacity are manifested to one degree or another in all areas, so the use of system analysis is an urgent task. In this case, the main factors in this situation are data processing and prediction of the state of a system. Mathematical modeling is used as a prediction method for a given subject area. A mathematical model is a universal tool for describing complex systems representing the approximate description of the class of phenomena of the external world expressed by mathematical concepts and language. The mathematical model can be represented as a set of systematic components and a random component. In this article, the object of prediction is the irregular random component of a model, which reflects the impact of numerous random factors. The origin, nature and laws of variation of the random variable are known, therefore, to simulate its behavior or predict its future value, one needs high degree of certainty to establish the form of continuous distribution function of the random variable. The empirical distribution function is calculated using the sample of random variable values. This empirical function is close to the values of the desired unknown function of distribution. The resulting empirical function is discrete, therefore it is necessary to apply piecewise linear interpolation to obtain a continuous distribution function. The predicted random component of time series has been included in the initial regression model. In order to compare augmented and initial regression models, several values were excluded from the time series and new prediction was built. The value of the average approximation error for assessing the quality of the model is calculated. The augmented regression model proved to be more effective than the original one.
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Thermal emission and pyroelectric current in manganese chalcogenides
Статья научная
Manganese chalcogenides, which are promising for the manufacture of thermoelements, are being studied. The current is measured in the temperature range of 80–500 K, in the absence of external voltage, which can be caused by a temperature gradient (thermopower), a change in electrical polarization (pyroelectric current), piezoelectric current (when the sample is deformed, a potential difference arises) or thermionic emission (thermal emission current) . Temperatures of current anomalies and their relationship with thermionic current and polarization current are found. A change in electrical polarization with temperature will cause a pyroelectric current. Compensation for excess electrical charge will result in local electrical polarization. Partial decompensation will cause the formation of an electric field in the sample. The critical temperatures for the disappearance of electric polarization were determined for different concentrations. In the region of concentration of thulium ions flowing through the lattice, the activation nature of the thermionic current was established and the activation energy was found. The pyroelectric current has a smaller value compared to the thermionic current. The current mechanism is determined by the emission of electrons from deep traps and the temperatures of the maximum thermionic current correlate with the temperatures at which IR absorption disappears. The electric current density and its value depend on the type of substituted rare earth element are calculated.
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Three-component aerodynamic load cells
Статья научная
The article examines the effect of flow on models studied in wind tunnels. To determine the force effect of the flow on the model under study, a more accurate and reliable method of directly measuring forces and moments using aerodynamic strain gauge balances is proposed. When solving a plane problem for a symmetrical model at zero slip angle, a design of three-component scales is proposed that measures the lift force, the drag force and the pitching moment. To eliminate the interaction between the supporting devices and the model, which causes disturbances in the flow near the model, the scales are located outside the model and the working part of the wind tunnel. The components of the aerodynamic force and moment acting on the model are measured using resistance strain gauges, which convert the deformation of the elastic element into a change in electrical resistance, which is measured by an instrument connected to an appropriate measuring circuit. The choice of strain gauges as weight elements is due to their very small size and weight, the ability to measure very small relative deformations of elastic elements, low inertia, which makes it possible to measure not only static but also dynamic loads, and the possibility of remote measurements. To compensate for the influence of various sources of errors, increase sensitivity and ensure greater measurement accuracy, the strain gauges are connected via a bridge circuit and included in all four arms of the bridge. Deformation of the horizontal measuring beam causes a change in resistance not only in the strain gauges that measure the pitching moment, but also in the strain gauges designed to measure the lift force. Since the design of the scales does not allow for electrical separation of these components, the influence of the pitching moment on the magnitude of the lift force is determined during the calibration process and is assessed using a special influence graph constructed from the results of calibration data. In strain gauge measurements, the output values of forces and moments acting on the model under test are obtained in the form of corresponding readings from a device that measures electrical signals proportional to the applied forces. To convert instrument data into values of forces and moments, a joint calibration of scales and instruments is carried out in order to obtain calibration coefficients. Additional components of aerodynamic forces and moments created by the holder are determined by purging it in the presence of the model. Calculated dependencies for determining the components of the aerodynamic impact are given. The values of the coefficients of aerodynamic forces and moments are given in the flow coordinate system. The pledge has been given.
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Статья научная
Ensuring high reliability of unique high-critical products at the design stage is an actual task that the aerospace industry faces. For high reliability indicators, at the design stage, it is necessary to ensure the basic property of the product – its strength, with a high probability of non-destruction. It is provided by introducing the corresponding coefficients – «safety coefficient» and «margin of safety» into the strength calculations. The necessity in these coefficients is based on the spread of values of external loading factors: magnitude of forces, combination of forces, kind of actions, place of connection, etc. In this case, the safety coefficient is related to external factors. The margin of safety refers to internal factors: the spread of the mechanical characteristics of the product material, the spread of the geometric dimensions of the product, etc. To determine, with a given probability, the safety coefficient and margin of safety, it is necessary to know their dependence on the combination of spread of external and internal factors. The purpose of this work is to determine the mathematical connection between the internal factors of the spread and the safety coefficient, external factors of the spread and the margin of safety, the combination of these factors and the probability of non-destruction of structures. In this work the values of internal and external factors, which affect the strength and probability of non-destruction of the product and have the boundaries of the spread of their values, using the tools of probability theories, were characterized as random variables, the values of which are determined by the distribution density, expected value and variance. I this work there was found a high dependence of the product strength on the spread of its geometric characteristics and tools were defined to determine the total spread of the values of the main strength characteristics of the product with a given probability of non-destruction. The practical significance of the results of this work can be achieved in the aerospace industry, in particular, at the design stage of unique high-critical products.
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To the question of forecasting the technical condition of low-thrust liquid rocket engines
Статья научная
In the rapidly developing space and rocket industry, spacecrafts are being equipped with low-thrust liquid rocket engines. Нigh requirements are imposed on the reliability, efficiency and economy of fuel use for this type of rocket engine. To ensure monitoring of the characteristics of spacecrafts, a functional diagnostic system is used, which includes telemetry and analytical data processing. Telemetry performs the functions of receiving and transmitting information. Information processing is carried out in computer centers located on the spacecraft and the Earth. The most promising computing tool capable of predicting time series and classifying a large amount of interconnected data is considered an artificial neural network. In this regard, the subject of research in the work is data processing methods based on an artificial neural network. The purpose of the work is to develop a method for forecasting the technical condition of low-thrust liquid rocket engines using an artificial neural network. The relevance of research on the use of a neural network in the system of functional diagnostics of low-thrust liquid rocket engines for spacecraft is explained in the introduction. In the main part, an analysis of many telemetric data of the rocket engine is carried out and their strength in the forecast of the main diagnostic parameters is determined. It is proposed to use traction, specific impulse, and temperature of the structure as diagnostic parameters. The prognostic capabilities of the neural network were investigated and a schematic diagram of a method for predicting the technical condition of a low-thrust liquid rocket engine was developed. In the developed method, at the first stage, the neural network performs the approximation of the function and extrapolates the time series of telemetric data; the second stage determines the probable class of the technical condition of the engine. The conclusion outlines a plan for further experimental research in the study area and provides recommendations on the development and improvement of algorithms for functioning of artificial neural networks as part of the functional diagnostics system of the spacecraft. Due to the generalized nature of the methodological schemes, the results of the work can be applied to any type of rocket engines and used at all enterprises of the rocket and space industry of the corresponding profile.
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