Vol 18, No 1 (2019)
- Year: 2019
- Articles: 17
- URL: https://journals.ssau.ru/vestnik/issue/view/318
Full Issue
AIRCRAFT AND SPACE ROCKET ENGINEERING
Convective current experiments using Dakon-P equipment onboard “Progress” cargo spacecraft
Abstract
In order to conduct experiments to study convection under microgravity it is proposed to use the “Progress” cargo transportation spacecraft. This is due to the fact that the microgravity environment onboard the Russian Segment (RS) of the ISS is not favorable, since the ISS center of mass is in the US segment, while many onboard systems generating micro-accelerations are installed in the ISS RS. There is no crew and no life support systems onboard the cargo spacecraft and micro-accelerations in it are significantly lower than those in the ISS RS. Passive modes of the cargo spacecraft attitude control are particularly favorable for carrying out microgravity experiments in space. In the course of a series of experiments conducted onboard a cargo spacecraft to find the minimal level of residual micro-accelerations, the gravity orientation mode turned out to be the most suitable one. It is planned to conduct an experiment to study convective isothermal currents using the Dakon-P scientific gear specifically developed for this purpose onboard “Progress” spacecraft in free flight in the gravity orientation mode.
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Analysis of control programs and climb paths of the hypersonic first stage of an aerospace system
Abstract
Control programs and flight paths of the hypersonic first stage of an aerospace system in climb with acceleration to hypersonic velocity are analyzed. Two approaches to determining the control programs and flight paths are identified: the "traditional" approach and the "optimization" one. The "traditional" approach implies specifying a typical mission profile with max-q and peak heat flux. In the case of the "optimization" approach the problem of propellant mass minimum is stated and solved using the method of Pontryagin’s maximum principle. It concerns the mass of propellant consumed in hypersonic acceleration for various terminal flight path angles. Optimal control programs and optimal flight paths are determined. Those meeting the max-q and peak heat flux requirements are selected. The results of modeling the motion of a hypersonic booster with typical and optimal angle-of-attack schedules corresponding to the "traditional" and "optimization" approaches are presented and discussed. It is established that less propellant is consumed in the case of optimal control, which is accounted for by more efficient use of the hypersonic booster's aerodynamic performance due to direct control of the angle of attack.
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Imitation models of aircraft hydraulic units with account for typical faults
Abstract
А method based on comparing oscilloscope patterns of operational parameters with reference curves is one of the most promising methods of diagnosing hydraulic systems among the existing ones. Its implementation does not allow accurate localization of the faulty unit in the system and quantitative estimation of the magnitude of the fault. To eliminate these shortcomings, it is advisable to use simulation models of hydraulic units, taking into account typical faults of a hydraulic system. Their use makes it possible to evaluate the effect of a particular malfunction on the change of dynamic parameters at the stage of mathematical modeling. As a result of the analysis of statistical information and literary sources, characteristic faults of hydraulic systems are identified. Their causes and the impact on the operation of hydraulic units are examined. Simulation models of units taking into account typical faults are described in the Matlab / Simscape software package. They are implemented using a typical hydraulic system as an example. Dynamic characteristics of a hydraulic system in a healthy condition and those of a system with one of the characteristic faults are compared.
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Gas dynamic calculation of detonation in variable cross-section ducts
Abstract
Formulas of gas dynamic calculation of detonation parameters in variable cross-section ducts are presented and a design detonation diagram is given. The diagram shows the detonation characteristics of super-compressed detonation and under-compressed detonation as the function of shock wave specific speed depending on the intensity of temperature of the ideal gas in a subsonic one-dimensional flow behind the shock wave propagating in a chemically active air-fuel mixture and on the ratio of geometrical expansion (convergence) of the duct. The propagation of a stationary shock-wave the static pressure of which in the output cross-section of the expanded duct is equal to atmospheric pressure is referred to as design detonation. This means that all the energy of the shock wave at the output of the duct can be converted into polytropic work function of gas expansion in a detonation engine. Otherwise, if the flow takes place in the mode of overexpansion due to the separation of the compressive shock wave inside the duct or in the case of insufficient expansion part of the shock wave energy will be lost. The total impulse equation for a geometrically expanding duct is solved by replacing the integral describing the thrust force with the average integral value of the curve of the static pressure acting on the side wall of the expanding duct. The frictional force is neglected due to its insignificant value. It is shown that the presence of an insufficiently compressed shock wave is not possible as the shock wave moving at the supersonic speed in the convergent duct will be decelerated to the sonic speed. To stabilize it additional heat should be supplied to transform the convergent duct behind the compressive shock wave into a semi-permanent cross-section duct wherein thermal crisis stabilizing the shock wave can be achieved. The minimum value of the detonation pipe diameter of 50 mm is substantiated. Below that value sharp reduction of combustion efficiency takes place. The results of the work can be used for the computation of detonation engine thermodynamic cycle parameters.
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Research of the operability of an air-fuel lubrication and cooling system of gas turbine engine rotor bearings
Abstract
The article is devoted to the problem of ensuring the operability of air-fuel lubrication and cooling systems for gas turbine engine (GTE) rotor bearings. The paper considers one of the advanced designs of a GTE in which an air-fuel mixture obtained in a special mixer is fed to a bearing installed in the turbine support and then through a hollow shaft to the bearing of the compressor support and then directed to the engine input. It is difficult to implement such a GTE scheme because of the necessity to ensure the operability of bearings lubricated with an air-fuel mixture for a predetermined period of time. It is impossible to determine the thermal state of the bearings and the friction regime in them with sufficient accuracy. The solution of the problems requires carrying out experimental work to determine the coefficients of friction and convective heat transfer in the bearings, as well as their full service life under various operating conditions and parameters of the air-fuel mixture blown through the bearings. The paper presents the results of testing a 45-126205РЯ radial thrust bearing lubricated with an air-fuel mixture, МС-8П oil and a non-lubricated bearing of the same kind. The operability of the GTE rotor bearings lubricated with the air-fuel mixture is analyzed, the area of efficient application of the gas turbine engine with an air-fuel lubrication system is determined.
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Influence of the geometry fidelity of resonant sound-absorbing liner samples on their acoustic characteristics
Abstract
Samples of sound-absorbing Helmholtz resonator-type liners of circular shape were manufactured from two types of ABS plastic and nylon on the basis of 3D modeling and 3D printing technology. Check samples were made of metal on a numerically controlled machine. Deviations of geometric parameters of the manufactured samples from the design values were determined by visual and dimensional inspection using high-precision equipment. The minimum deviations were obtained for check samples made of metal. The acoustic characteristics of the samples were experimentally determined using an interferometer with normal wave incidence at high sound pressure levels. Numerical simulation of the acoustic processes in the interferometer for the given samples was carried out on the basis of solving full Navier-Stokes equations with account for compressibility. The obtained values of the resonant frequency, impedance and sound absorption coefficient were compared with the experimental ones. It was noted that the impedance values are most sensitive to the deviations of the geometric parameters of the samples from the design values, while the deviations in the sound absorption coefficient and resonance frequency are not so sensitive to them.
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Development of blend composition of aviation kerosene surrogate for the simulation of workflow of gas turbine engine combustion chamber
Abstract
In this paper, the criteria for determining the composition and physicochemical properties of aviation kerosene were formulated. The data on the physicochemical properties of known kerosene surrogates were systematized and classified. The main classes of individual chemical components of aviation kerosene were determined, and the main representatives of these classes which were used in the preparation of surrogates, were investigated. Four- and six-component kerosene substitutes are proposed. The physical properties of the developed surrogates were validated according to the flow characteristics and the spray angle of the flame of a centrifugal fuel nozzle. The dependence of the flame speed on the composition of the mixture of developed kerosene surrogates was determined. The results of determining the composition of combustion products during the combustion of TS-1 brand aviation kerosene and its surrogates in a model combustion chamber were compared.
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Investigation of the technology of mutual navigation and orientation of small space vehicles flying in formation
Abstract
The paper presents the problem of ensuring support of the flight of a group of small spacecraft (microsatellites) taking into account the small mutual distances between them. The purpose of using the orbital constellation specified is to create a radio communication system to control remote objects like unmanned aerial vehicles and ground robots located in hard-to-reach areas of the Earth from the Central ground station. To reduce the cost of microsatellite design, it was decided to rigidly fix the receiving and transmitting antennas on their housings and use the spatial orientation of the entire apparatus for antenna guidance. This seriously complicated the tasks of navigation and orientation of microsatellites in a formation and required the development of a new method for determining the orientation of a single microsatellite. The essence of the method is to process the image obtained by means of a video camera mounted on a nearby microsatellite. We used methods of computer vision. The results of mathematical modeling simulation, as well as the results of full-scale bench experiment confirming the efficiency of the proposed method are presented.
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Multi-satellite Universat-SOCRAT mission for monitoring technogenic and natural hazards
Abstract
The natural and “man-made” space environment generates serious risks for the implementation of space missions, both automatic and human. The main natural and technogenic risk factors that limit or pose a threat to the implementation of space-based automatic and manned space missions in the near-Earth space are cosmic radiation and space debris. In the upper layers of the atmosphere, natural transient electromagnetic phenomena associated with significant energy release are also risk factors for suborbital flights. It is planned to create a system of spacecraft in the proposed “Universat-SOCRAT” project that makes it possible, in a mode close to real-time, to determine the radiation conditions in a significant part of the area of trapped radiation, up to the orbits of global navigation satellite systems or the geostationary orbit. It is also planned to create a space segment of monitoring space debris and electromagnetic transients in the upper atmosphere. Monitoring of space debris will allow all-weather and global tracking of near-Earth objects and, thereby, increase the efficiency of analyzing data and making necessary decisions. In some cases it will improve the accuracy of determining the coordinates of objects for their subsequent cataloging. Successful realization of the project will make it possible to create a space system for monitoring and preventing space hazards for both ongoing and planned space missions for the first time in the world.
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Influence of the stressed state of the surface layer on the endurance of gas turbine engine compressor blades
Abstract
Different types of final strengthening treatment of gas turbine engine (GTD) compressor blades are considered. The influence of each type of treatment on the formation of roughness of the surface with favorable microrelief, as well as on the level and depth of distribution of residual compressive stresses in the compressor blade airfoil is analyzed. The causes of blade fatigue failure are described and methods of controlling this kind of failure are presented. The results of testing special specimens made of VT9 titanic alloy are presented to establish the influence of final strengthening treatment modes on the compressor blade resistance to fatigue stress. The results of testing residual stress distribution along the thickness of compressor blade airfoil are presented. A method of improving dynamic strengthening of specimens due to the protection of compressor blade edges is discussed. The results of semi-graphical analysis of the stressed state of low-pressure and medium-pressure compressor blades made of VT9 alloy are presented. They take into account residual stresses, as well as operating load stresses in the process of operation. We show that it is possible to increase the limit of the blade endurance due to the optimization of residual stress diagrams by improving the final strengthening technology with the use of dust blasting.
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Development of the active gas generator for high altitude firing test benches
Abstract
The results of research on increasing the efficiency of a firing test facility for testing thrusters under high-altitude conditions are presented. The increase in efficiency consists in reducing the expansion pressure generated by the ejector and the flow of the active gas (air) consumed by it. Experimental studies were carried out using three versions of gas generators developed by the author which ensure an increase in the energy of the active gas before it is supplied to the ejector. When using the GG-1 gas generator with working media such as air, kerosene and water, the vacuum of less than 1 mm Hg was achieved with the air mass flow rate of 1.1 kg/s (the ejector provides a vacuum of 13 mm Hg with the cool air flow rate of 2 kg/s). However, the design features of the gas generator led to a cumbersome system of supplying working fluids and a complicated start-up sequence. The GG-2 gas generator with air and kerosene as working media failed to provide the temperature of the active gas below 600°C, therefore, to prevent ejector malfunctioning, GG-2 was turned off when the rarefaction reached 13 mm Hg. The air mass flow rate was 1.1 kg/s. The working media of the GG-3 gas generator are air and kerosene or air and natural gas. The design of the GG-3 makes it possible to regulate the temperature of the produced active gas. When working on kerosene, a vacuum of 4 mmHg was reached with the air mass flow rate of 1.5 kg/s. The studies of GG-3 using natural gas as a fuel are going on.
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Russian-Azerbaijani space project of a small satellite for science and technology experiments
Abstract
The paper presents a project of a satellite experiment on the observation of intense flashes (transients) of electromagnetic emission from the Earth's atmosphere in different spectral ranges, as well as the measurement of medium- and long-term dynamics of spatial distribution of fluxes of energetic charged particles in the near-Earth space. To implement the experiment, it is planned to develop a Russian-Azerbaijani small spacecraft capable of carrying a payload of up to 25-30 kg. The satellite is also expected to realize a number of technology experiments, in particular, to study the effect of space flight factors on the matrices of silicon photomultipliers. We also consider the possibility of installing a telescope for photometric observations of binary stars. The requirements to the orbit and spacecraft attitude modes, as well as to its on-board systems, are considered in accordance with the goals and objectives of the experiment. The measurement data which are planned to be obtained during this experiment will subsequently be used for various scientific and applied problems including validation of existing and development of new dynamic models of radiation in the near-Earth space, ensuring the safety of the functioning of spacecraft.
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Optimization of space vehicle combined orbital plane change maneuver on the basis of pontryagin’s maximum principle
Abstract
The task of optimizing the space vehicle combined orbital plane change maneuver with the aim of maximizing its final mass is considered in the paper. Burst of power is used for the vehicle’s exit from the initial low earth orbit and subsequent re-entry. Starting from atmospheric entry till the end of the orbital plane change with the entry in the final orbit the angle of attack, the air-path bank angle and the fuel-flow rate are used as controls. Limitations for the angle of attack, fuel-flow rate, adiabatic recovery temperature, longitudinal and vertical load factor are introduced. The successive linearization method is used to determine the optimal control programs. Solving the optimization task is exemplified by a hypothetical space vehicle. The results of modeling space vehicle motion are presented. The changes in the determined “aerodynamic” (angle of attack and air-path bank angle) and “motion” (fuel-flow rate) controls with increasing the angle of orbital plane change are discussed with and without account of the key limitation on the modes of motion – maximum adiabatic recovery heating temperature.
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Use of ultra-small space vehicles for studying near-Earth plasma by radiophysical methods
Abstract
The paper shows the possibility to measure plasma density and its fluctuations in the ionosphere on ultra-small space spacecraft using radiophysical methods that allow determining the characteristics of the medium through which radiation is transmitted. It is assumed that each spacecraft will have a navigational satellite receiver, as well as a device for emitting and detecting a signal at two multiple frequencies in the radio band. With this approach, information on plasma density is contained in the received phase difference. Radio receivers and radio transmitters on satellites constantly exchange radio signals and then it is possible to determine the electron concentration and its fluctuations from the phase shift. The authors obtained numerical estimates of the resulting phase difference for different frequencies from 10 MHz to 10 GHz with typical ionospheric parameters depending on the distance between the satellites. Calculations were also made to determine the maximum distance between satellites at which it is possible to receive a signal, provided that the transmitter power is 2 watts.
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MECHANICAL ENGINEERING
Theoretical and experimental studies of a gas stamping device with a piston pressure multiplier
Abstract
In many industries, the share of small-scale production plants is significant. In these conditions, compared with traditional methods of pressure treatment, pulse pressure treatment methods, one of the varieties of which is gas stamping, are more efficient. However, the known devices of gas stamping provide mainly stamping of thin-walled parts. To expand the technological capabilities of gas stamping, the authors developed a gas stamping device with a piston pressure multiplier, in which heating and deformation of the stamping workpiece is carried out using the energy of combustion of fuel mixtures in the combustion chamber, in the working cylinder and in the cavity of the matrix. This article is devoted to the study of the workflow of this device. Theoretical analysis of the workflow was carried out, and, as a result, a pattern was determined for the variation of the pressure that performs the stamping process in the working cylinder. In particular, it was found that at the final stage of the stamping process, due to the energy of combustion of the fuel mixture, the pressure in the working cylinder increases 1.5...2 times, which allows a significant increase in the thickness of the parts to be stamped. An experimental gas stamping device with a piston pressure multiplier was developed, and experimental studies were carried out. The studies confirmed the main results of the theoretical analysis: the discrepancy between the theoretical and experimental values of the degree of pressure multiplication in the working cylinder does not exceed 11%.
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Application of additive technology of selective laser melting (SLM) in designing a low emission combustion chamber of a gas turbine plant
Abstract
The paper deals with the questions of introducing the additive technology of selective laser melting (SLM) into the production of the main structural elements of a combustion chamber for ground-based gas pumping, power and transport gas turbines. A fundamentally new design of a low-emission two-circuit burner was developed, adapted for the manufacture of products with a complex geometry through the use of selective laser melting (SLM) of metal powders according to mathematical CAD-models with the help of an advanced production technology. Technical difficulties associated with the implementation of additive manufacturing technology were overcome. The process chain was tried out from design to manufacturing and quality control of finished structural elements under conditions of mass production. The deficiencies of the parts manufactured by the additive technology were revealed and ultimately eliminated. Successful development of burners for a low-emission combustion chamber using a new technology significantly reduces labor intensity and time of production while maintaining high quality.
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Mechanism of failure of working faces of big bearings in the process of operation
Abstract
The article presents the results of analyzing the mechanism of failure of working faces of big roller bearings made of 0,2C2Cr4Ni (E3316 AISI) structural steel. The microstructure was investigated with the help of a METAM LV-31 metallographic microscope. The surface of the bearing rings and rollers was tested for various kinds of defects using a TESCAN Vega SB scanning microscope. The PMT-3 micro-hardness tester was used to measure micro-hardness. Studies show that the microstructure of steel is a fine-needled tempered martensite with chromium carbide inclusions observed near the surface. The depth of the cementation zone was determined on the basis of the measurement results. The value of the depth exceeds the standard established by the manufacturer. The destruction of the bearing roller assembly is characterized by spalling, stratification and cratering. The destruction of the bearing ring is characterized by scouring and indentation caused by metal particles caught up in the ring-roller contact in the process of operation. These defects result in the formation of micro-cracks and, as a result, further spalling and peeling. It is possible to prevent the defects by reducing the depth of the carbonization zone, as well as reducing the surface maximum hardness by changing the mode of final heat treatment.
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