Aviation and spacecraft engineering. Рубрика в журнале - Siberian Aerospace Journal
Статья научная
High complexity and cost of developing flying models necessitate the use of such design and production techniques that would ensure the best flight technical and technological characteristics of the model also would raise of it operation effectiveness. These techniques include the experimental control method of flying model’s mass-inertia asymmetry parameters during final assembly of the model. Solution of the problem of optimization the process of bringing parameters of mass-inertia asymmetry of the conical flying model to specified standards is considered in the article. The only correction plane is designed to be positioned close to cone face, away from the center mass of the flying model. The flying model as a component of prefabricated rotor is being balanced in dynamic mode on a low-frequency dynamic vertical stand, which based on gas bearings. Before balancing experiment the weigh, longitudinal center of mass and inertia moments of the flying model have to be controlled with use of another measurement equipment. As a criterion of optimization is sorted the reaching of minimum of the angle of deviation of principal longitudinal centroidal axis of inertia from geometrical axis of the flying model. But simultaneously the pre-set standard of center-mass shift from the geometrical axis must be ensured. Balancing algorithm, easy-to-realized by modern computers, is presented. Numerical illustration of balancing is given. The algorithm enables omitting intermediate steps of balancing, reducing them to one step (as a rule), and shortening the balancing time, as well. In one step of balancing the engineering model permits either bringing parameters of mass-inertia asymmetry of the flying model to specified standards, or diagnosing impossibility of attaining the specified standards with available design of flying model. The algorithm and balancing method are experimentally tested at newly-designed vertical dynamic stand on conical gas bearings. It’s high precision and efficiency are corroborated.
Бесплатно
Energy saving simulation test complex for spacecraft power supplies full-scale electrical tests
Статья научная
The aim of this paper is to describe an energy saving automatized simulation test complex used for spacecraft power supplies full-scale electrical ground-based tests. The complex allows you to simulate the operation of solar array, lithium- ion-battery and spacecraft payload. The distinctive features of the test complex are a continuous and impulse control methods combination with an improved dynamic accuracy, and recuperation of consumed energy into its internal DC network for the better energy efficiency. Test complex operational time from uninterruptible power supply accumulator batteries is significantly increased due to the recuperation of excess power into the test complex internal DC network. The results are experimentally proved. The authors of the paper analyzed dynamic accuracy improvement and energy saving during ground-based spacecraft power system electrical tests. The process of ground-based spacecraft electrical testing includs the following tasks: – the accurate simulation of static and dynamic characteristics of spacecraft power system energy sources and loads; – the utilization of energy produced by power system under load and during spacecraft battery charge simulation. The paper deals with the description of energy saving automatized simulation test complex (ESAST) including complex subsystems structure and experimental study of the test complex characteristics. Commercially available simulation test complexes usually use continuous or impulse control methods. The continuous control methods decrease energy efficiency, as the most part of energy is dissipated on the regulator, which requires massive heat sink, increasing weight and size. It makes difficult to produce high-power test complexes. The impulse control methods provide better energy efficiency, but limit dynamics and real devices fast response reproduction accuracy. The paper describes the combination of continuous and impulse control methods with the aim of taking the advantages of both. The energy consumed by the test complex can be utilized either by the heat dissipation in the environment or by the recuperation into industrial AC grid. The heat dissipation reduces the energy efficiency, increases the testing room temperature (in case of high-power spacecraft power system) and an air conditioning system. The recuperation into AC grid is free of specified disadvantages, but it requires the recuperated excess energy parameters matching with AC grid requirements through the network of grid-tied inverters, which leads to the increase of weight and size of the test complex. Moreover, the recuperation into AC grid is difficult during grid emergency shutdown, which can result in long test failure. The paper describes the method of excess energy recuperation into the complex internal DC network. The method significantly reduced test complex energy consumption, which in case of powering test complex from uninterruptible power supply (UPS) notably increase operating time from UPS accumulator batteries during AC grid emergency shutdown. In conclusion the main advantages of ESAST are given: – more than twice wattage reduction of test complex main power supply; – the ability to work during AC grid emergency shutdown with increased operating time from UPS; – the significant reducing of ESAST main parts weight and size.
Бесплатно
Статья научная
Currently, in the field of engine building, development of three-component propulsion systems (PS) is a very promising task. Liquid-propellant rocket engines (LPRE) operating at the initial stage of launching a launch vehicle (LV) on liquid oxygen + kerosene fuel and at high-altitude launch sites using cryogenic fuel (liquid oxygen + liquid hydrogen) are in particular interest. LPRE that use three-component fuel have a high pressure level in a combustion chamber (CC) (up to 30 MPa) and temperatures (up to 4000 K). In this regard, arise questions related to reliable cooling of such engines, as well as ensuring minimal hydraulic fluid losses in a cooling passage in order to further use re-frigerant as a working fluid for driving the turbine of a booster turbo pump unit (BTP). The object of research is a two-mode single-chamber three-component liquid-propellant rocket engine, made in a closed circuit with generator gas afterburning. Oxidizing agent is liquid oxygen, fuel is RG-1 kerosene and liquid hydrogen. Cooling of the chamber is combined: it consists of regenerative and internal. Regenerative cooling passage is formed by longitudinal integral-machined fins. Hipercritical hydrogen is used as an engine coolant. Internal cooling includes a tantalum coating applied to a fire wall of the chamber in a critical section. The article examines the problems of organizing cooling system (CS) and implementation of effective heat removal from a firing wall of a three-component rocket engine. Basing on existing liquid-propellant engine cooling systems, optimal circuit solutions and measures to remove thermal load in the most stressed places are proposed. A mathematical model has been developed for calculating a CS of a three-component LPRE. The results of the design calculation of cooling using several calculation methods are presented.
Бесплатно
Статья научная
The reliability of ring current-collecting devices during a given service life plays a decisive role in the operation of power supply systems of various equipment and largely depends on the strength and reliability of all its components, in particular, contact rings. One of the most important characteristics of ring current collectors is the contact resistance, which is reduced by using non-ferrous and precious materials with low resistance, while increasing the downforce between the rings of the current collector. With an increase in the compression force F of the contact ring, the resistance of the contacts decreases to a certain minimum value and practically does not decrease with further growth of the force. The dependence of the contact resistance on the compression force has the form of a power function, the coefficients of which are determined experimentally. However, the operability of the contact rings in such severe conditions can be ensured in the case of low speeds and a small number of loading cycles by using the low-cycle fatigue area on the Weller curve. Having determined the coefficients of the equation of the inclined section on the Weller curve in the area of low-cycle fatigue, it is possible to determine the number of permissible loading cycles at a given stress level or solve the inverse problem of determining the permissible stress level if the number of loading cycles is known. To substantiate the correctness of the selected compressive force and the corresponding stresses, methods for calculating the fatigue margin coefficient, as well as a method for calculating the reliability of the ring material, are proposed. Reliability is estimated by the Gauss curve and is numerically expressed in the form of the probability of failure-free operation and the probability of failure, for which the corresponding theoretical dependencies are obtained. According to the proposed methods, calculations of the rings of the current-collection device used in EXPRESS-type spacecraft were performed, which showed the operability of the methods and allowed to ensure the required service life of the contact rings and their reliability. A very simple analytical formulation of the methods allows us to solve both verification and design calculations of rings, depending on the task at hand.
Бесплатно
Статья научная
Heterogeneous energy sources and homogeneous energy sources with different characteristics are frequently used in autonomous power supply systems. Solar batteries are widely used as primary energy sources for on-board power supply systems of spacecrafts, unmanned and manned aircrafts. Renewable energy sources such as solar, wind, geothermal and hydro energy, serve as primary energy sources of terrestrial autonomous power supply systems. Matching primary energy sources with different characteristics and operating conditions within a unified power supply system leads to problems connected with the power control of energy sources, which determines the relevance of the considered problems. The main aim of the study is to develop a combination of primary energy sources and control techniques which allow using primary energy sources with different characteristics and operating conditions in unified autonomous power supply system. The objectives of the study are to create the simulation model of a power supply system using MATLAB/Simulink software; to develop and test control algorithms for primary energy source controllers that would allow to maintain the needed battery charging current; to develop and test control algorithms for primary energy source controllers that would allow the primary energy sources to operate in the maximum power point tracking mode and to minimize the maximum power point search time. Methods used in the study: the simulation of a power supply system using MATLAB 7.9 Simulink software. Results: the simulation model of a power supply system including two primary energy sources with different characteristics is designed. In the case of excess power generating by the primary energy source, its controller operates in the battery charging mode. When the primary source power shortage occurs, its controller operates in the maximum power point tracking mode. The proposed power supply system structure allows controlling two energy sources independently, thus the primary energy source controllers can operate in different modes. This provides flexibility of the power supply system. The use of fuzzy logic control algorithm increases the accuracy and search speed of the maximum power point tracking algorithm. Simulation results confirmed the efficiency of the proposed solar controller operation algorithms in all modes stated above. The efficiency of controller operation modes selection algorithm was confirmed in different operating conditions. The proposed algorithms allow implementing the effective control of primary power sources depending on power supply system operating conditions.
Бесплатно
Ensuring the thermal regime of spacecraft structures
Статья научная
The main requirement for the smooth operation of the spacecraft is its stable thermal regime. A particularly difficult task is to ensure a stable temperature control system of the device, taking into account strict restrictions on energy and mass costs for temperature control devices. These tasks need to be solved at every stage of the creation of satellites. At each stage, thermal calculations are carried out with the choice of optimal thermophysical parameters. This amount of work is about a tenth of all work with the satellite. The need for theoretical and experimental refinement of calculation methods is an urgent task that will significantly reduce the material and time costs of designing, testing and fine-tuning the device. Therefore, the calculation and analysis of the thermal regimes of spacecraft is an important stage in the design of satellites. Ground thermal vacuum tests are very costly, both in time and financially. The essence of the concept is to conduct only stationary thermal modes under conditions of maximum and minimum thermal loads on the satellite as a whole and its individual external elements, followed by ensuring convergence of test results with calculated results. And the confirmation of intermediate requirements to ensure the specified thermal conditions is carried out by calculation. The article considers the tasks of ensuring the thermal regime of spacecraft structures. Classification of devices used to ensure the thermal regime. Ground-based testing of the thermal regime of communication satellites during thermal vacuum tests. Ensuring the thermal regime of the communication spacecraft during ground-based electrical tests. Thermal regime of spacecraft structures during transportation from the manufacturer to the technical position.
Бесплатно
Estimation of measurement errors of navigation and landing parameters using pseudosatellites
Статья научная
At the moment, a significant number of regional airfields do not have sufficient space for ground navigation equipment, this can lead to undesirable consequences when landing an aircraft with a weak visual contact of the crew with the runwaу. The pseudo-satellite system is able to improve flight safety at the landing stage in difficult meteorological conditions at regional airfields without using ILS (indicator on the windshield), after evaluating errors in navigation and landing parameters. The pseudo-satellite system can be used to improve flight safety at the landing stage in difficult meteorological conditions at regional airfields. This system consists of a control and correction station and pseudo satellites that operate in certain frequency ranges. When using this system, the PNP-72 scheduled navigation device is installed on the aircraft, which provides basic navigation information with a given accuracy. This allows pilots to use more accurate information and perform a safe approach and landing of the aircraft on the runway, even with weak visual contact with it. Thus, the use of a pseudo-satellite system at regional airfields can significantly improve flight safety at the landing stage, especially in difficult meteorological conditions when the use of ILS is impossible. The use of a pseudo-satellite system can also help solve the problem of an insufficient number of ground navigation aids at regional airfields. This will allow for a more accurate determination of the aircraft's location and improve the quality of navigation information provided to the crew. The use of pseudo-satellites could be an alternative to expensive and complex ILS systems, especially at small airfields where the installation of such systems may be impractical or not economically viable. However, for the successful implementation and operation of the pseudo-satellite system, additional research and testing is necessary to determine the optimal parameters of the system, as well as to develop appropriate regulatory documents and procedures to ensure flight safety.
Бесплатно
Статья научная
Transport operations that ensure the change of the orbit of a spacecraft or its transfer to the departure trajectory are an integral part of almost all space missions. Increasing requirements for the efficiency of transporting spacecraft form the need to search for possible ways to increase this efficiency and assess the characteristics associated with the proposed methods. Current boosters and interorbital tugs, as a rule, use a chemically powered cruise engine, although solutions with the use of an electric jet engine are becoming more common. Due to the high rate of the outflow of working fluid which is much higher than that of combustion products in a chemical engine, the efficiency of use of the substance mass by an electric jet engine significantly exceeds this indicator for a chemical engine. However, the low thrust provided by the electric jet engine leads to high duration of the transport operation and, as a result, to considerable time of exposure to the outer space factors, in particular, radiation. Therefore, the use of the electric jet engine only does not always meet the requirements for the mission. One of the promising ways to increase the efficiency of transport operations is the combination of the traditional chemical and electric jet engines in the propulsion system. Various aspects of the use of such an integrated propulsion system (IPS) consisting of a solar electric jet system and “Fregat” booster were considered, for example, in the framework of “Dvina TM” research project. Unlike a chemical engine, in which energy is released from chemical bonds, the energy for accelerating the working fluid by an electric jet engine is supplied from outside. Solar batteries are the most widespread energy source in nearearth orbits, where the amount of solar radiation is sufficient to meet the energy needs of a spacecraft. Solar batteries are sensitive to radiation, damage accumulates in their internal structure and their characteristics degrade. Therefore, there is a need to account for the radiation dose accumulated during the execution of the transport operation and to evaluate the reduction in the efficiency of solar batteries. Uneven irradiation intensity in the radiation belts formed by the Earth’s magnetic field (Van Allen belts) can be taken into account if the assessment of the radiation intensity at the trajectory points of the maneuver is made using the Earth radiation belt model. The paper proposes a method that allows taking into account the effect of ionizing radiation on the degradation of solar batteries when performing a transport operation using an integrated propulsion system based on a liquidpropellant rocket engine and an electric jet engine, taking into account the chosen trajectory and the model of the Earth’s radiation belt.
Бесплатно
Статья научная
The article discusses the prospects of utilization of aerodynamic control to maintain the formation of nanosatellites of the CubeSat class. The purpose of this work is to estimate the limits of the application of active aerodynamic control to stabilize the relative motion of two CubeSat 3U satellites in a sunsynchronous orbit with a height of 570 km. A review of theoretical information about aerodynamic forces acting on artificial Earth satellites is carried out, within the framework of which models of the Earth's upper atmosphere are considered. Aspects of creating a differential drag force for nanosatellites as an active control actuating mechanism are considered. To study the orbital motion of satellites under the action of aerodynamic control using the General Mission Analysis Tool program, a group flight of two spacecraft was simulated taking into account the factors causing orbital disturbances. Based on the results of experiments, the dynamics of the inter-satellite distance was studied, and a conclusion was made about the possibility of using an aerodynamic differential force to achieve a stable relative motion.
Бесплатно
Статья научная
The prospects for the development of space technology are currently closely connected with the creation of fundamentally new large-sized space structures. When designing large-sized systems, the scheme of which allows for automatic configuration change of the structure, it is necessary to take into account shock loads. They inevitably arise when fixing the working state of the structure in orbit upon completion of the process of its opening. To ensure smooth, reliable and shock-free opening of large-sized space structures, it is proposed to use force drives with active elements made of titanium nickelide material with a shape memory effect. The proposed shape memory force actuator uses an active element in the form of a wire made of titanium nickelide material which is heated during opera-tion by passing an electric current through it. One of the main parameters for the opening drive of large-sized structures is its deformation-force characteristic. Experimental studies aimed at studying this characteristic of the active element of the actuator were carried out in the work. The study of the force-deformation characteristics was carried out under two types of loading: in one, the force changed during the test, and in the other it remained constant. It is worth noting that the amount of deformation that an active element can produce is directly related to the magnitude and nature of the resistance force applied to it. In the experiment, the active element demonstrated sufficient displacement under significant load. The experimental data obtained show the fundamental possibility of using active elements made of a material with a shape memory effect in the opening drives of large-sized space structures. The obtained characteristic will play an important role in the development of a mathematical model of the functioning of an active element made of a material with a shape memory effect for the opening of a space structure with transformable configuration.
Бесплатно
Evaluation of the main parameters of ReshUCube-1 telemetry over a period of 10 months in orbit
Статья научная
With the increase in the number of launched spacecraft, such a direction as automation of spacecraft control processes is gaining popularity. One of these most important processes is the analysis of telemetry data during the operation of a spacecraft. Scientific and educational satellite of the Reshetnev Siberian State University of Science and Technology has been successfully exploitated in orbit and has been performing its scientific tasks for more than six months. The article considers a list of the main parameters analyzed by the operators of the Mission Control Center to assess the state of the ReshUCube-1 satellite. The composition and main functional characteristics of the equipment on the spacecraft are described. Qualitative indicators and quantitative limits for all described parameters are given, as well as their significance and impact on the functioning of devices and the entire spacecraft as a whole.
Бесплатно
Статья научная
The development of new ballistic-type aircraft is characterized primarily by improved aerodynamic characteristics and higher speed limits. Ground track testing of aviation and rocket technology is a stage whose task is to confirm the efficiency and effectiveness of new developments. Track tests make it possible to simulate real loads, they are simpler and much cheaper than flight tests. Experimental installation "Rocket rail track 3500" of Scientific Test Range of Aviation Systems named after L. K. Safronov is constantly being upgraded in order to conduct track tests of products at a speed greater than 3M. The experimental setup includes a two-rail track, made on a special foundation, which excludes unacceptable rail deflection with a mass of up to 3000 kg. The rail track has an acceleration section with an angle of attack 2500 m long and a deceleration section. A tray filled with water is made on the braking section between the track rails. It is designed for hydrodynamic braking to a complete stop of the rocket sled with stored equipment. The movable rocket track sled is made of a massive steel plate to which three cross beams are welded. The front and rear beams end with axles on which sliding supports are pivotally mounted. On the rear and middle beams there are lodgements for fastening rocket engines of solid fuel. Depending on the required test speed, from one to five motors can be placed on the cradles. The test object is usually mounted on the front and middle beams along the axis of the sled and fixed in a cantilever, with the head part extended forward. The design of the supports – shoes is made to encircle the rail head in such a way that it provides sliding contact along the upper plane of the rail head, and in the event of a lifting force exceeding the weight of the sled at high speeds, it keeps the structure from free flight by contacting the lower surface of the rail head. Track high-speed tests of special equipment objects are always accompanied by intense vibration and shock effects of structural elements. Due to the desire to conduct track testing of products at a faster rate, it becomes necessary to reduce the level of dynamic loads and eliminate resonant interactions. The article presents an algorithm and methodology for statistical processing of random signals of three-axis vibration acceleration sensors installed on the shoes of the rocket track sled and on the fairing of the test object. Due to the placement of registration data storage devices on the sled, experimental vibration data were stored when testing the product at a speed of more than 1M. The autocorrelation functions of the signals of vibration accelerations of sensors placed on various elements of the rocket sled, the functions of mutual correlation of the corresponding signals, the density of the amplitude spectra, the density of the power spectra and the transfer functions that characterize the dynamic conductivity of vibrations from the shoes sliding along the rail guides to the test object were determined.
Бесплатно
Статья научная
Electro-jet (plasma or ion) thrusters are becoming increasingly common to correct a satellite orbit and perform orbit raising maneuvers to achieve the geostationary orbit. This is due to the greater efficiency of plasma thrusters compared to chemical ones. When developing a satellite platform, an important place is the matching up of the electrical character-istics of the electric power subsystem (EPS) and on-board consumers. Intrinsically, this issue is an intersys-tem problem. The lack of proper attention paid to find the timely and correct solution of this problem can complicate the operation of the satellite electric power subsystem. The most important subsystem, which has a significant impact on the operation of the satellite EPS, is the electric-jet propulsion subsystem, since among on-board consumers, this one is the most powerful consumer being switched simultaneously. Tran-sients occurred in the power supply circuits following thruster firing and shut down processes can reach significant values. An electric jet thruster only runs in conjunction with a complex electronic unit – a power processing unit (PPU), which converts the voltage of the on-board power supply into a set of voltages nec-essary for thruster components to run. Therefore, in the preliminary design of the propulsion subsystem, it is necessary to know the electrical characteristics of transients and ripples in the power supply circuits of the thruster / PPU combination being an electrical load of the Electric power subsystem. It is difficult to obtain the characteristics of such processes by the calculation method. Therefore, an experimental method is the most common and objective method to obtain this information. JSC ISS carried out tests allowing to measure characteristics of transients and ripples under firing, running and shut down of plasma thrusters of different types powered by corresponding PPU’s. These tests were conducted using a vacuum chamber GVU-60. A test power supply was used to simulate EPS operation. This paper presents the results of meas-urements and analysis of parameters of transients and ripples on PPU power buses used for thrusters and devices of three types. These results are considered to be preliminary. It is shown that the greatest difficul-ties can arise when operating high-power thrusters. It is concluded that for each new type of thrusters and PPU’s it is advisable to conduct interface tests of the propulsion subsystem and the satellite electric power subsystem.
Бесплатно
Статья научная
During the liquid rocket engines (LRE) testing, direct thrust measurement is carried out using thrust measurement devices. The aim of the work was, on the basis of existing data from the theory of tests and test stands devices, to highlight the design features of the thrust measurement devices and propose an option to improve the performance of this stand system. The work considers the basic circuit power schemes of thrust measurement devices by the example of power measuring systems of existing fire test stands and the features of work on preparing systems for testing. The types of calibration systems worked out in practice, their advantages and disadvantages, which constitute calibration errors, are considered. An option is proposed to modernize thrust measurement devices, in particular, through implementing of an electromechanical drive based on a planetary roller-screw mechanism as a force setting element into the calibration system. A possible general conceptual diagram of the power drive operation as a part of the calibration system of the thrust measurement devices is given. The advantages and disadvantages, the predicted effects of implementation are considered. A more detailed analysis of this proposal may serve as an occasion for the modernization of the specific operational thrust measurement devices design at the fire test stand for LREs or may be a working option when designing a new thrust measurement device.
Бесплатно
Features of reaching limiting speed values of track tests of ballistic type aircraft
Статья научная
The development of high-speed ballistic aircraft with speeds exceeding 1000 m/s is currently a priority abroad and in Russia. The effectiveness of new such products is confirmed by track tests at the speed of their use. Test sites with rail tracks exist in almost all countries, for example in the USA there are more than 15 of them. Double-rail, monorail and various combinations thereof, differing in length, width of the rail pair, rails and the design of the track itself, including a sealed shell over the rail track to fill it with a lighter one environment. The longest track in the USA is Holloman AFB, located in New Mexico with a length of 15536 m. They have track ranges with different lengths and their own special design in England, France, Germany, Canada, Italy, Japan, India, China, Korea, Turkey and other countries, including African continent. Highspeed range tests in Russia are carried out on the experimental installation “Rocket Rail Track 2500”, located on the territory of the FSE “Scientific test range of aviation systems named after L.K. Safronov”. The experimental installation consists of a rail track placed on a special base, providing the necessary vertical profile of the track with sections of ascent and straight horizontal movement, as well as a technological descent section for braking moving technological equipment. The product under test is placed on a rocket track sled moving along rails on sliding supports. To accelerate the track carriage, solid fuel rocket engines are used, the thrust of which is selected based on ballistic calculations to achieve the required test speed. The length of the track plays an important role in achieving the maximum acceleration speeds of moving track equipment. The enormous aerodynamic drag, proportional to the square of the speed of movement of the carriage, when tested at high speeds, leads to the need to reduce the midsection and mass of the mobile unit. An increase in engine thrust leads to an increase in the weight and cost of track equipment, as well as to the need to increase the safety margin of sliding supports. However, an increase in test speed can be achieved by replacing the air medium with gases that have a significantly lower density, for example, helium. Track testing of new aircraft or their elements, although cheaper than flight testing, is quite expensive. In this regard, work on the theoretical assessment of replacing the medium from ambient air with helium, as well as with a mixture of helium and air at different concentrations in an indoor gallery on a track rail track, is a new, relevant and practically useful task. The work performed a numerical simulation of the problem of supersonic flow around a helium-air mixture at different volumetric ratios. Numerical values of aerodynamic resistance were obtained at a sled speed of 830 m/s. The results of numerical calculations of the motion dynamics of a 3D model of monorail track equipment, which are planned for use in conducting full-scale fire experiments, are presented.
Бесплатно
Flow dynamics in the radial-annular cavity of turbomachines
Статья научная
This paper considers the problem of modeling a rotational flow in the radial-annular cavity of turbo machines with fixed walls. This case corresponds to the boundary conditions of the supply channel for a radial centripetal turbine. In the presented model, the flow is conventionally divided into radial and circumferential movement. The radial component of the velocity is determined by the mass flow rate from the continuity equation, the circumferential component is formed by the tangential channel supply. The main equation in the integration is the equation of the change in the momentum for the flow in the form of the Euler equation. In the case of the circumferential component of the velocity, the angular momentum law is used, assuming the potentiality of the flow and the constancy of the angular momentum within the integration step. As a result of the transformations of the motion equations, differential equations for the radial, circumferential component of velocity and static pressure are obtained, which represent a certain system of three equations in three unknowns. The system of equations allows integration under known boundary conditions at the inlet; as a result of integration, it is possible to obtain the field of distributions of velocities and pressures along the radius of the radial-annular cavity. The results of the study can be used in modeling the circumferential and radial forces on the rotor (impeller) of turbo machines.
Бесплатно
Flow model in the impeller of a centrifugal pump
Статья научная
In accordance with the results of the features analysis of foreign design technology and the creation of aerospace technology products, the certification orientation of all types of work can be traced, starting from the preliminary design stage, which imposes particularly high requirements on the quality of calcula-tion methods, algorithms and software used in the design development of the project. Without the advanced level of domestic developments in the field of modeling hydrodynamic processes in aircraft systems, in the next decade it will become impossible to compete with foreign developers of aviation and rocket-space sys-tems. In accordance with modern theoretical and experimental studies, the flow pattern in the flow path of a vane machine is a complex superposition of the main and secondary flows. The article discusses the method for calculating the fluid flow in the interscapular channel of a centrifugal impeller with a finite number of vanes, the construction of the energy characteristics of the impeller and its optimization by the number of vanes. The calculation consists of two parts: firstly, the determination of the theoretical head taking into account the influence of the finite number of vanes based on analysis of force interaction, and, secondly, determination of hydraulic losses in the impeller by integrating friction stresses along the limit-ing surfaces. The results from both parts are used to optimize the number of vanes in the pump impeller. Analytically, an equation for the pressure at a point and the coefficient of influence of a finite number of vanes are obtained. Taking into account the law of friction, an expression was obtained for the pressure loss. The described method for calculating the spatial boundary layer is quite simple and intuitive, and gives approximate results that make it possible to estimate the required quantities. However, there is a need for further elaboration of the method to bring it to a form that makes it possible to calculate the three-dimensional flow of the working fluid in a channel of arbitrary shape. Based on the results of theoretical studies, an algorithm and a calculation program were developed that allow calculating local values. The results of the calculation of the theoretical head in the impeller can be used for a more accurate calcula-tion of a centrifugal pump.
Бесплатно
Статья научная
The aim of the study is to form an approach to modeling the operations of the orbital assembly of a reconfigurable spacecraft (RS) in geostationary orbit. Reconfigurable spacecraft are a set of modular spacecraft (MS), where, in a particular case, one MS can be assigned the functions of the service systems module (MSS), and the second - the functions of the payload module (MPN). To ensure the assembly of the RC, or the replacement of some MC, for example, in case of its failure with a new one, it is necessary to provide a solution to the problem of bringing the MS with the RS. The article analyzes and studies the operation of the motion control system of the MS during the convergence of the MS with the RS. A list of necessary mathematical models for performing operations in solving the problem of convergence of the MS with the RS is formed, and a block diagram of the interaction of mathematical models is presented. The paper presents a brief description of the mathematical apparatus that allows modeling the operations of convergence of the MS with the RS. This mathematical apparatus includes: a model of the orbital motion of the MS and the RS, models of the angular motion of the MS and the RS, sensitive elements and executive bodies. In this paper, the mathematical modeling of the MS with the RS convergence operations is considered as the subject of research. The object of the study is the motion control system of the MS, which ensures the implementation of the approach of the RS in geostationary orbit.
Бесплатно
Ground control system for distant space vehicle
Статья научная
The demand for research of a promising ground-based long-range spacecraft control complex, which has great capabilities not only in the control of deep space vehicles, but also in carrying out fundamental and applied radio astronomical research. Much attention is paid to the analysis of the requirements to the radio complex, which must be fulfilled to realize the possibility of several directions of scientific research and, first of all: planetary radiolocation; interferometry with ultra-long baselines; radio-reflecting; radi-oastronomy. Based on the analysis of the state of the ground control system of deep spacecraft, the direc-tions of its development on the basis of modernization of existing facilities are revealed, and the prospects for the use of new technologies for the development of deep space on flight paths to the Moon, Mars, other celestial bodies of the solar system, the objects of alien and interplanetary infrastructure are shown.
Бесплатно
Heat transfer in the centrifugal force field for gas turbines elements
Статья научная
The study of heat transfer from combustion products (CP) to the impeller and the casing of gas turbines of liquid rocket engines (LRE) is an urgent task. The solution of the flow problem, taking into account heat transfer, in rotational flows, in the flowing parts of the turbopump units (TPU) of the rocket engine, is carried out by the following methods: numerical methods; analytical approach, when solving the equations of dynamic and temperature boundary layers; as well as using empirical dependencies. The temperature parameter of the gaseous combustion products and, as a consequence, the heat exchange between the combustion products and the structural elements of the flow part, significantly affects the working and energy characteristics of the TPU LRE. When designing gas turbines of LRE, it is necessary to take into account the presence of heat exchange processes, the working fluid temperature distribution and the structural element temperatures in the cavities of the TPU LRE (since energy losses and viscosity depend on the temperatures of the working fluid, and also determine the flow parameters). The temperature distribution in the structural elements determines the performance and reliability of the unit. In the case of the use of cryogenic fuel components in the TPU LRE units the heating of the component leads to the implementation of cavitation modes and a drop in operating and energy characteristics. On the other hand, a lowered temperature of the working fluid leads to an increased viscosity of the components and, as a consequence, a decrease in the efficiency of the unit (especially when using gel-like components). When studying heat transfer in the field of centrifugal forces for elements of rocket engine gas turbines it is necessary to obtain a joint solution of the equations of dynamic and temperature boundary layers in the boundary conditions of the flow parts. This article offers a model of the distribution of dynamic and temperature boundary layers taking into account the convective component (for the case of a gaseous working fluid, i. e. Pr < 1), which is necessary for the analytical solution and determination of the heat transfer coefficient in the boundary conditions of the flow cavities of the LRE turbine. The energy equation has been analytically obtained for the boundary conditions of the temperature boundary layer, which allows integration over the surface of any shape, which is necessary in determining the thickness of the energy loss. Taking into account the integral relation, the heat transfer law of the turbulent boundary layer for the rotation cavities is written. The equations for determining the heat transfer coefficient in the form of the Stanton criterion for rectilinear uniform and rotational flows for cases of turbulent flow regimes were obtained analytically. The obtained equations for heat transfer coefficients are in good agreement with experimental data and dependences of other authors.
Бесплатно
