Vol 14, No 2 (2015)

Full Issue

AIRCRAFT AND SPACE ROCKET ENGINEERING
Computational algorithm of forming program motion in a scheduled turn of small spacecraft
Salmin V.V., Filatov A.V., Tkachenko I.S., Tyugashev A.A., Sopchenko E.V.
Abstract

A mathematical model and software implementation of a computational algorithm of forming program motion in a scheduled turn of small spacecraft are described in the article. The algorithm is intended to calculate the key parameters of the path of a scheduled turn of small spacecraft, to specify the time moments when spacecraft motion has to be changed, and motion parameters at these points to determine the intervals characterized by the constancy of object motion laws and the positions of the object rotation axes during these intervals. Information on the equipment used (sensors, mechanisms, flywheels), the basic modes of operation, the principles of organizing the motion control system and flight control software is presented in the article. The AIST-2D Experimental Small Spacecraft has a mass of less than 500 kilograms and can operate on a near-circular orbit of 600 kilometers. The Spacecraft Orientation System comprises sensors and actuator mechanisms as well as its own computer. The Flight Control Software is organized as software incorporated in the technical system and implements full support of spacecraft motion control logic both in normal and abnormal situations. The software is subjected to a multiphase debugging process that ensures the achievement of the required indicators of quality and robustness.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):9-19
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MECHANICAL ENGINEERING AND POWER ENGINEERING
Research of a sleeve connection of the aircraft pipeline under the influence of dynamic loading
Agafonov V.M., Pykhalov A.A.
Abstract

The article presents the results of analyzing the dynamic behavior of a prefabricated single-span pipeline with a tube connection on external cone under the influence of kinematic excitation. Five models of pipelines with different conjugation conditions in tube connection on external cone are described. The results have been obtained by using the finite element method and solving a contact problem of deformable body mechanics. At the first stage amplitude-frequency characteristics for the models of pipeline under consideration are constructed. The result shows the dependence of amplitude-frequency characteristics of the pipeline vibrations on the conjugation conditions in the collecting pipe connection.  It was found in the process of research that the resonant frequency of the pipeline varies with introducing admissible gaps in the tube connection on external cone. This change may lead to a shift of the resonance frequency of the pipeline in the range of operating frequencies of the structure that may lead to the destruction of the pipeline. The article also reflects the influence of the external dynamic load on the distribution of contact pressure in the prefabricated tube connection on external cone while passing the resonance frequency. This distribution determines the tightness of connections.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):20-28
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Characteristic of energy efficiency index and drawing intermediate conclusions on the reduction of consumption of energy resources at SSAU
Anishchenkova E.I., Biryuk V.V., Anisimov M.Y.
Abstract

The main directions of improving energy efficiency at state institutions are discussed. The area of using the energy efficiency index depending on the purpose of analysis and further application is specified. The specific character of SSAU activities is shown. In this connection the expedience of taking into account the specific energy costs not only for the students but for the teaching staff, the research force and the personnel is indicated. The necessity of calculating the indices of heat energy consumption on the basis of the area and volume of the heated space is determined. Development and implementation of energy-saving and energy-efficiency measures are essential mechanisms of reaching the target of creating economic and organizational conditions for efficient use of energy resources. Specific indicators of heat energy consumption over time, before and after taking energy-saving measures are calculated. The energy survey revealed a number of problems, in which the energy saving potential of SSAU is hidden.  The energy-saving measures taken are presented. Intermediate conclusions on reducing energy consumption and improving the energy efficiency of SSAU are drawn, in the long run it leads to tangible energy savings and reduction of costs.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):29-34
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Strength analysis of internal combustion engine elements by using ANSYS with taking into account heat processes in the combustion chamber
Biryuk V.V., Gorshkalev A.A., Kayukov S.S., Saigakov E.A.
Abstract

A procedure of modeling working processes of internal combustion engines (ICE) by using CAD/CAE software is presented. Issues of modeling gas- dynamic and heat process in 4-stroke internal combustion engines by using ANSYS Fluent and ANSYS Steady-State Thermal software which allows obtaining the fields of distribution of the principal thermodynamic parameters are discussed. Special attention is paid to developing a method of strength analysis and the peculiarities of adjusting it to solving of the tasks connected with internal combustion engine designing.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):35-43
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Experimental investigation of heat transfer in energy separation chambers of the vortex tube
Veretennikov S.V., Barinov S.N.
Abstract

One of the ways of improving the efficiency of gas turbines is to increase the efficiency of the cooling system of the blades using swirling flows. However, to date there is insufficient research on heat transfer in confined swirling flows, in particular in non-adiabatical vortex tubes. This paper presents the results of experimental studies of heat transfer of swirling flows in the energy separation chambers of non-adiabatical vortex tubes. Experimental study of unsteady heat transfer in a counter-flow vortex tube in the case of changing the flow pattern has been carried out. The temperature distribution over the surface of the energy separation chamber and the duct of the cooled flow at different times as well as the dependences of the absolute effect of heating and cooling on time are presented.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):44-51
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Simulation of the profile of a sample’s X-ray diffraction line in diffusion metal saturation
Volkov V.V., Pokoev A.V.
Abstract

This article deals with methods of non-destructive control of diffusion-saturated layers of polycrystalline alloys, and in particular, in steel hardening. There exist simple and reliable X-ray techniques of studying diffusion processes. Their main advantages are the safety, availability and absence of necessity to destroy the sample. Diffraction scattering of characteristic X-ray character radiation on a crystal lattice of a polycrystalline alloy contains information on the interior structure and concentration distribution of the diffusing material (carbon used as the diffusant impurity) in the solvent lattice (iron alloy) after isothermal annealing. Application of numerical methods makes it possible to simulate the shape of the line profile by varying the parameter of the alloy lattice, caused, for example, by diffusion penetration of carbon in steel. This approach is used for choosing the best conditions of saturating the surface of a metal alloy for the case of steady- source diffusion. With some assumption, the application of the calculation algorithm shows good approximation for the carbonization of polycrystalline alloys, which makes it possible to determine the degree of the diffusion saturation depending on the process parameters and to control them. The curve variations are related to the gradient of concentration of the diffusant and the depth of X-ray penetration. An algorithm of simulation has been developed and tested allowing prediction of diffusion area parameters in carbonization. It is shown that the depth of investigation using X-rays makes it possible, under certain conditions, to obtain information on the dimensions of the diffusion area in layers considerably in excess of half thickness values. The experimental data obtained in carbonization of a sample are compared with the results of simulation of a diffractive profile. 

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):52-58
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Investigation of the seizing mechanism of aviation hydraulic drive spool–and–sleeves
Gareyev A.M., Popelniuk I.A.
Abstract

The paper is devoted to the study of the process of seizure of spool-and-sleeve pairs of aviation hydraulic drives under the influence of contamination particles contained in working fluids of aircraft hydraulic systems. The mechanism of the particles’ action on the hydraulic drive is discussed. The process of seizure development is analysed in detail. Two techniques based on the analysis of the results are proposed that make it possible to estimate the state of the spool-and-sleeve. The first one is based on direct measurement of the gap in the spool-and-sleeve of the hydraulic drive during repair. To implement the technique it is necessary to analytically determine the minimal allowed size of the gap that would provide stable functioning of the unit over the whole pressure range of the hydraulic system. The second technique is less labour-intensive (but also less precise) in comparison to the first one and is based on the measurement of the hydraulic drive macroparameter the variation of which depends on the change of the gap size in the spool-and-sleeve during maintenance. It is necessary to determine the dependence of the macroparameter chosen on the size of the spool-and-sleeve  gap. Implementation of the described techniques will improve economic efficiency of aircraft usage by reducing the costs and the idle time in repair.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):59-69
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Determining the boundaries of ignition of aluminum particle aerosuspension in a high-velocity airflow
Egorov A.G., Tizilov A.S.
Abstract

The results of determining the boundaries of ignition of a turbulent flow of aluminum-air mixture as well as the influence of parameters such as the flow rate, turbulence and particle size on the boundaries of ignition are presented in the paper. It has been found that as the initial turbulence increases the nucleation site for ignition splits under the influence of pulsation and flame tails are carried into the main stream and die out there, thus increasing the time of ignition of the main flow of the mixture; as the initial  turbulence increases the boundaries of aluminum-air mixture ignition expand and the flow rate of the aluminum-air mixture increases; the boundary of ignition of a powdered aluminum-magnesium alloy corresponds to the boundary of ignition for combustion chambers of aircraft gas turbine engines; presence of fine aluminum powder particles in the area of ignition contributes greatly to the expansion of the boundaries of  ignition of the flow of aluminum-air mixture. It has also been established that the maximum velocity of flame propagation and heat generation for aluminum-air mixture is observed when the mixture composition is close to stoichiometric, just as for gas-air mixtures. However, a distinguishing feature of aluminum-air mixture is the presence of the second maximum speed of flame propagation and heat generation for mixture compositions with α<0.3. The resulting boundaries of ignition of aluminum-air mixture lie within the area of flame stabilization.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):70-77
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Experimental research of internal heat transfer in the vortex heat generator
Zhornik M.N., Piralishvili S.A., Mogileva K.A.
Abstract

The results of the experimental study of internal heat transfer in a vortex heat generator incorporated in a deicing system of a ground gas turbine engine are presented in article. The essence of the experimental methods based on the theory of steady-state heating conditions is outlined. The method is implemented in an experimental installation that makes it possible to analyze internal heat transfer in axisymmetric channels quickly and effectively. The experimental model presents a counterflow vortex tube with a heat- isolated chamber of energy separation. The results of the experimental studies are used for the calculation of the thermal state of the inlet guide vane unit of the GTD-110engine equipped with a vortex heat generator when functioning in the conditions of icing.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):78-87
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Calculation of displacements in a viscoelastic square plate with a round cut
Ivanov E.Y.
Abstract

Calculation of the strained state of structures made of anisotropic viscoelastic materials under the influence of temperatures is reduced to the calculation of the strained state of structures made of elastic materials on the basis of the conformity principle developed earlier.  A method of calculating the strained state of non-uniform anisotropic structures of an arbitrary shape in the case of their static loading under the influence of temperatures has been developed on the basis of this principle. Displacements caused by the influence of external variable pressure and variable temperature field inside a steel square plate with a round cut are calculated. The problem of linear incoherent thermoviscoelasticity selected as a model provides a strict analytical solution, convenient for the analysis of steel parts in different operation modes. 

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):88-92
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Analysis of the possibility of improving performance characteristics of a solenoid injector for the CommonRail system
Kayukov S.S., Gallyamov R.E., Belousov A.V.
Abstract

The paper analyzes the possibility of improving the performance of a solenoid injector by switching to constant high-pressure operation. The structure of a solenoid injector design model is presented in the LMS Imagine. Lab AMESim package. Variation of the injector flow rate in the case of varying spring and magnet parameters is discussed. The data are compared relative to the value of the phase dose for the same control signal. Preconditions for the necessity of continuing the investigations in the direction of analyzing the influence of other factors and optimizing their values with the aim of obtaining maximum speed are outlined

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):93-96
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The effect of the way of setting boundary conditions on the results of modeling a flow at the flameholder outlet
Kolomzarov O.V., Anisimov V.M., Zubrilin I.A.
Abstract

The influence of different algorithms of generating inlet turbulent fluctuations on the results of calculating the flow parameters downstream the flameholder is discussed in the paper. Large eddy simulation is used on a turbulence model with a subgrid Smagorinsky-Lilli model. Propane-air mixture with a temperature of 300 K in a square-section channel is investigated. A bluff body with a base of an equilateral triangle with the side length equal to 25 mm is placed inside the channel. The mass-averaged inlet velocity is 10 m/s. Several ways of setting inlet boundary conditions are considered. Two cases without turbulence at the inlet (uniform velocity distribution across the inlet section and pipe velocity profile) and two cases with artificially modeled turbulence (vortex method and spectral turbulence synthesizer) are analyzed. The values of flow intensity upstream the stabilizer, the distribution of flow velocity and kinetic energy in longitudinal and cross sections downstream the stabilizer have been obtained. The graphs of the velocity fluctuation power density spectrum are also presented.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):97-105
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Numerical and experimental study of the strength of fabric carbon-epoxy composite structures
Komarov V.A., Kishov E.A., Charkviani R.V., Pavlov A.A.
Abstract

The problem of adequate modeling of thin-walled laminate composite structures reinforced by woven fabrics is discussed in the paper. The conformity of numerical and experimental values of ultimate load is investigated. Standard-dimension strip-like specimens and lugs with quasi-isotropic layup of three standard sizes are used for the investigation. Static strength of the specimens has been tested. Finite-element models of the described structures are developed using the NASTRAN software. The accuracy of ultimate load prediction by several failure criteria (maximum stress, maximum strain, Tsai-Wu, Tsai-Hill, etc.) is analyzed. Recommendations for choosing failure criteria for laminate composite materials are given. The soundness of simplified modeling of contact interaction of the lug axis and hole surface by transferring the load from the hole surface to peripheral nodes using rod finite elements is discussed. 

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):106-112
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Numerical method for determining the parameters of a creep curve on the basis of Soderberg law
Makarov R.Y.
Abstract

The article discusses the development of a new numerical method for determining the parameters of a creep model.  A discrete linear parametric model describing the relationship between successive values of creep strain in the form of a difference equation is proposed. Formulas for describing the relationship between the coefficients of the linear parametric discrete model and the creep model parameters have been obtained. An iterative procedure of mean-square estimation of coefficients of the linear parametric discrete model is described. A technique of estimating the error of calculating the model parameters of creep is shown, numerical and analytical studies of reliability and correctness of the described procedure have been carried out. Experimental verification of the results with good agreement between theoretical and experimental data is presented. The developed numerical method of determining the creep curve parameters can be applied at the stages of stationary and non-stationary creep.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):113-118
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Determination of thermal state and modification of the flame tube cooling system with the help of three-dimensional modeling methods
Matveev S.G., Anisimov V.M., Zubrilin I.A., Kolomzarov O.V., Mironov N.S.
Abstract

The results of calculating the thermal state of the flame tube walls are presented, a gas turbine engine annular combustor taken as an example. The three-dimensional Ansys Fluent simulation package is used. A finite element conjugate model is created. The conformal (node-to-node) interface «gas-to-metal» is a characteristic feature of the grid. The number of elements over the thickness of the wall is taken to be not less than 5. The total number of elements is 8.6 million. The HN50VMTYUB-VI heat-resistant alloy is used as the material of the flame tube. A thermal barrier coating (TBC) is deposited on the hot side of the flame tube. The thickness of the ceramic coating is assumed to be equal to 0.4 mm. The thermal barrier coating consists of an intermetallic bonding layer that contains elements of the wall material of the flame tube and ceramics, as well as a ceramic protective layer with low thermal conductivity. The shell surface of the flame tube walls is assigned to take into account the thermal barrier coating. The density of the ceramic coating is 6 t/m3, and the dependence of the isobaric heat capacity of the thermal barrier coating on the temperature in the range of 473 K to 1473 K is specified.  The distribution of the heat flux in the thermal barrier coating is taken into account only in the direction perpendicular to the surface of the flame tube. The influence of the thermal barrier coating on the flame tube thermal condition is analyzed. Measures have been taken to improve the cooling system of the flame tube. Variations of the temperature of the flame tube along its length are analyzed.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):119-128
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Statistical physics and cycles of operation of heat engines
Mikheenkov E.L.
Abstract

Products of fuel combustion are the working body in the process of expansion cycles of heat engines. The composition of all combustibles is their common property – all of them are hydrocarbons, i.e., their molecules consist of carbon and hydrogen atoms. The article deals only with the properties of the products of fuel stoichiometric combustion in atmospheric air. The combustion products are a mixture of oxides of constituent elements of CO2, H2O and the main element of air – nitrogen N2. It is the products of combustion that determine the expansion processes in the most widespread operation cycle of power plants – the Brayton cycle. This article is an attempt to use the methods of statistical physics to describe the properties of combustion products

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):129-136
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ASMTurbC method of autonomous statistical modeling of diffusion turbulent combustion and the results of its testing
Nuzhnov Y.V.
Abstract

A new principle of constructing mathematical models for the processes of diffusion turbulent combustion is formulated and a method of autonomous statistical modeling of hydrodynamic characteristics of such processes (ASMTurbC method) is proposed. Consideration of the intermittence effects of dynamic and scalar fields combined with the known method of «reduced concentration of fuel» is the distinctive feature of the method. The fundamental distinction of the ASMTurbC method is the possibility of constructing mathematical models for calculating statistical characteristics (one-point ordinary and central moments) of dynamic and scalar fields of the flow only of turbulent fluid of the turbulent flow. The models constructed by the ASMTurbC method make it possible to find the conditional statistical characteristics of the inhomogeneous field of reduced fuel concentration (with the fuel used as a passive admixture) and, as a result, to obtain concentrations of the major chemical reagents of fuel and oxidizer. The method is tested using the construction of a mathematical model of a turbulent flame of a submerged axisymmetric fuel jet (propane). The results of testing are presented in the form of calculations of the main statistical characteristics of dynamic and scalar fields of the flame. It is shown that the results of calculations are in good agreement with the known experimental data and that the calculations are not time-consuming.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):137-150
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Numerical study of the characteristics of a double-circuit vortex tube in a stationary and a nonstationary settings
Piralishvili S.A., Sokolova O.A.
Abstract

The results of numerical modeling of thermodynamics of a swirled flow in an energy separation chamber of vortex devices in stationary and non-stationary settings are presented in the paper. The results of investigation confirmed the presence of precession motion of the paraxial vortex core, velocity, pressure and temperature pulsations in the energy separation chamber. The processing of these made it possible to design a reverse cycle produced by large-scale vortex structures in a p, v-diagram. The cycle is responsible for the major portion of energy transfer from the periphery to the near-axial layers. It was found that the heated masses of gas are added to the cooled flow near the end surface of the diaphragm due to the angle vortex produced. We propose making the nozzle inlet inclined in the form of a slope using the Bernoulli lemniscate, which results in the improvement of energy separation characteristics by 1.5-2.0 per cent. Different areas of the flow such as the recirculation zone, the vortex core, the open jet at the outlet of the slot diffuser are the components of a single vibration system. Numerical simulation of flow in a vortex energy separator and analysis of non-stationary phenomena taking place in a DCVT show that vortex core precession is the source of large-scale periodic vibrations in a vortex tube.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):151-158
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Experimental research of the possibility of heat transfer enhancement in gas dynamic energy separation process
Popovich S.S., Vinogradov Y.A., Strongin M.M.
Abstract

Analysis of the mechanism of heat transfer enhancement in a device of machineless energy separation of flows (Leontiev tube) is presented in the paper. The main parameters that define the device's efficiency are the temperature recovery factor and heat transfer in the supersonic channel of the device. Changes in the shape and relief of the flow surface, the use of working fluids with a low Prandtl number, low-intensity shock waves and local separation areas in the supersonic channel are among the methods of heat transfer enhancement in an energy separation device. The results of experimental investigation of the influence of a supersonic separation flow on the adiabatic wall temperature and the temperature recovery factor are presented. The range of the Mach numbers analyzed is between 2 and 3.5. The Reynolds criterion along the length of the dynamic boundary layer amounts to at least 6·106. Field distributions of the adiabatic wall temperature and temperature recovery factors along the plate are presented for different Mach numbers. The results indicate that local separation boundary layer regions will probably intensify heat transfer in the supersonic channel of a gas dynamic energy separation device. The research has been conducted using the experimental facilities of the Institute of Mechanics of Lomonosov Moscow State University.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):159-169
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Fuel spraying and mixing in a simulated combustion chamber in the presence of air flow precession
Sviridenkov A.A., Tretyakov V.V.
Abstract

Numerical calculations of the flow downstream the flame tube of the combustion chamber in the conditions of nonstable flow are presented in the paper. The obtained velocity fields were used for the modeling of non-stationary nature of the flow. The comparison of the results of calculations carried out using this model with the results of calculations based on the fluent commercial packages showed their good agreement. It was found that the flow under consideration is essentially nonstationary, with signs of precession. Numerical calculations of liquid fuel droplet distributions in the area stimulating the configuration of the combustor liner were carried out. It was found that a significant portion of the fuel hits the walls of the chamber. The processes of atomization of fuel in a non-stationary precession jet flowing out of the chamber are investigated experimentally. It has been shown that the interaction of fuel jet with precession air flow gives a sufficiently homogeneous air-fuel mixture with an average droplet diameter of about 50 microns or less. Data on the dependence of the concentration distribution and droplet size on flow regimes of air and fuel have been obtained. It is shown that the base of the jet fuel in a swirling air flow under the influence of the vortex precession performs rotational - oscillatory movement. This process is visually observed only in conditions of pulsed illumination of the flow.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):170-178
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Experimental study of hydrocarbon fuel combustion in the air
Sergeev S.M., Petrukhin N.V., Masyukov M.V.
Abstract

An improved constant- volume bypass arrangement intended for measuring visible and normal velocities of flame propagation in gas and droplet gas mixtures and the ignition delay period for the mixtures mentioned above in the millisecond range is described in the paper.  Unlike the other available installations the one under consideration is developed for operating with liquid hydrocarbons. It has an additional device for injecting liquid reagents and nanoparticles as well as a fiber-optic sensor to specify the instance of ignition. The temperature range of conducting the experiments is extended up to 850 K. A method of operating the experimental installation is presented.  The values of visible combustion velocities are obtained for various hydrocarbon fuels depending on the temperature at the pressure ≈ 50 kPa. The effective activation energies and pre-exponential multipliers of temperature dependences of the visible velocity of hydrocarbon fuel combustion in the air are specified by the experimental data. The results obtained are in good agreement with the modern concepts of the mechanism of hydrocarbon fuel combustion in the air.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):179-183
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Identifying the causes of excessive vibration in gas turbine engines in the course of their rig tests
Sundukov A.Y., Sundukov Y.V., Plotnikov S.M.
Abstract

Examples of identifying the causes of high vibration of engines during rig tests based on many years of experience in evaluating the vibration behavior of gas turbine engines are presented in the paper. Defects such as slippage of the outer bearing support, failure to comply with the geometric parameters of the hydrodynamic damper with elastic rings and the conditions of oil feeding, unsatisfactory laying of the engine on the engine frame, rubbing of individual elements of the rotors, their wedging and rotational stall are diagnozed. The practice of using  modern methods of processing and analysis of vibration processes that makes it possible to optimize the amount of subsequent work with the engine is shown, with the above-mentioned defects taken as an example. A standard technique for diagnosing the causes of excessive vibration in gas turbine engines using the most efficient methods of signal processing is proposed on the basis of the experience gained. In case of detecting high vibration by bench vibration measuring apparatus we propose to install additional vibration sensors with the registration of vibration in the frequency range of up to 30 kHz parallel to the standard vibration sensors. This is  followed by sequential data processing with obtaining autospectrums in speed and acceleration, calculation of the cospectrum, the spectrum of highs, the envelope spectrum, cascade demodulation on the basis of highs, multiple iterations of the cascade demodulation procedure. The effectiveness of the proposed method has been confirmed by many years of its practical use and can be applied both in the conditions of the test bench and in operation for the evaluation of the  engines’s health. 

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):184-192
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Vibrodiagnostics of turboprop engine gearbox wear
Sundukov A.Y., Sundukov Y.V., Plotnikov S.M.
Abstract

The peculiarities of the structure of the vibration spectrum of the turboprop engine differential gear in the case of wear of the central gear teeth are discussed and a technique of vibration diagnostics of the defect is proposed in the paper. It is found that the wear leads to multiple harmonics, including tooth harmonics, in the broadband vibration maxima spectrum. The frequency of the first harmonic of the series is determined by multiplying the speed of rotation of the outer central gear by the number of the worn teeth. It has been shown that increased intensity of one of the components of this series is the cause of the fatigue failure of a rotor blade of one of the compressor stages. Comparative analysis of the autospectra, the spectrum peaks of the spectrum envelope and the data of cascade demodulation show that in this case the autospectra is most informative. On the basis of the statistics of reworked gearboxes and a gearbox with the level of wear twice the norm threshold values were obtained for two of the most informative spectral components. These values make it possible to identify the gear unit with inadmissible degree of wear of its teeth. Statistical analysis of gear vibration of the repaired items revealed the presence of a component that characterizes relative beating of the outer central gear and satellites. It was found that its intensity differs from engine to engine by more than an order of magnitude. The impact of this beating is considered to be one of the main causes of increased wear. The investigation of the effect of this factor on the development of the defect is determined as the line of further research.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):193-201
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Experience of operational development of starting characteristics of the APU combustion chamber
Chechulin A.Y.
Abstract

The working process of a combustion chamber of the evaporative type used on most types of modern APUs is described in the paper. The combustion chamber discussed is characterized by a highly efficient working process with high combustion, low emissions of CO and NOx and low fuel-injection pressure in steady-state operation. However, the starting characteristics of the evaporative combustion chamber need to be improved. Ways of improving the starting characteristics of the auxiliary GTE with an evaporative type combustion chamber by optimizing the number and location of starting centrifugal injectors, the adjustment of the fuel feed law are discussed. Comparative computational and experimental data on the variations in combustion efficiency, partial operation of the turbine, gas temperature fields at the turbine inlet are given. Modeling of the startup process is performed by the developed nonlinear dynamic model of starting in which the combustion efficiency is represented as the product of two components: a known criterion of forcing Kv and a component approximated according to the thermal condition of the chamber evaporating pipe. Checking the engine starting with the activities for developing the combustion chamber at the high altitude-climatic test bench at the Central Institute of Aviation Motors has shown the necessity of adjusting the characteristics of fuel supply for high-altitude conditions N ≥ 4000m. It is shown that the maximum local gas temperature at the turbine inlet can be reduced by 50-60 ° C andthe range of reliable engine starting by fuel supply  can be increased by the factor of 1.5-2.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):202-210
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ELECTRONICS, MEASURING EQUIPMENT, RADIO ENGINEERING AND COMMUNICATION
Functional chart of a multichannel hydrologic-optical-chemical measuring complex and new measuring channels of hydrophysical parameters
Smirnov G.V., Olenin A.L.
Abstract

The results of the analysis of design and development of data measuring systems of oceanographic parameters in the 60-70s and 80-90s are presented in the paper. Data measuring systems based on the CAMAC standard (created under the leadership of academician Nesterikhin Y.E.) had a great influence on the design of instrumentation. However, their direct use in oceanographic measurements proved impossible. It so happened because of the need for in situ measurement of parameters at a considerable distance from the control devices. A basic structural arangement of a measurement system was developed by the end of the 80s and oceanographic sounding towed autonomous measuring systems were created, certified and put into practice. They were used for experimental studies in the ocean in the range from seconds to tens of days in time and from centimeters to hundreds or thousands of kilometers in distance. Measuring channels are being developed on the basis of  high-speed data receivers (television cameras, acoustic devices). A structural arrangement of a multi-channel hydrological- optical-  and chemical measuring complex that makes it possible to assimilate in its composition measuring channels of oceanographic parameters at different information rates has been developed. A process platform for the development, testing and certification of new measurement channels for the parameters of the marine environment has been designed and built on the basis of this scheme. The results of full-scale tests of the process platform carried out on the Black Sea near Gelendzhik are presented.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):211-222
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CONTROL, COMPUTER SCIENCE AND INFORMATION SCIENCE
Modeling of dynamic processes in micromechanical inertial sensors and their components using specialized software
Barulina M.A., Pankratov V.M.
Abstract

Software packages which can be used for the creation of specialized software to investigate the dynamics of micromechanical inertial sensors have been developed. These software packages take full account of the Timoshenko theory and the influence of the gyroscopic effect. The possibility of using the developed software is shown using modeling of a superminiature micromechanical gyro and a micromechanical gyro with a gimbal sensing element as an example. The use of specialized software guarantees the possibility of implementing the required functionality as well as full control of the implementation of the algorithms and visualization of the results at every stage of the investigation. The development and using of specialized software can help to achieve significant reduction of requirements imposed upon the computing resources and calculation time in comparison with universal software of finite-element modeling.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):223-233
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ECONOMICS AND HUMANITIES
Analysis of various aspects and state of the distance education system in Russia
Belousov A.I., Gromova T.V.
Abstract

The article presents the results of the analysis of various aspects and status of distance learning to identify the positive aspects and disadvantages, problems, and possible solutions to improve the efficiency of the educational process. Distance learning as an educational problem and at the same time as a new form of getting education calls for teachers of a new breed. This is a teacher who constantly supports the distance learner, has a command of distance learning technologies and a pool of techniques and methods, first of all, computer skills. To solve the problem it is necessary to determine the essence of a number of key concepts of distance learning, to reveal the multidimensionality of the problem of its organization, to analyze the foreign and domestic experience of training teachers for distance learning and plan the ways of preserving and upscaling the human, scientific, educational and material potential accumulated by the domestic system of education, to apply the existing and prospective means of new information technologies.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):234-247
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Functional components of the model of pedagogical activity of a distance learning teacher
Belousov A.I., Gromova T.V.
Abstract

The paper presents a functional-role model of the distance learning (DL) teacher working in the system of distance education technologies (DET). A teacher is regarded as a person possessing multidimensional qualities as this person is to organize, implement, motivate and control intensive purposeful independent cognitive, research and professional practical activity of the students online, i.e. in conditions of practically complete absence of direct communication and personal contact. From the point of view of the role concept, the DL teacher performs a set of roles, from the operator of didactic means to the author of a course. The essence of the major functional components of the teaching activities (functions of the design process of training, support and development of learners, management, control, diagnostic, informative, motivational, organizational, consultative, communicative, reflective) is defined and discussed in the paper.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):248-260
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System of indicators for assessing operational and commercial activities of an enterprise
Morozov V.V., Demidenko E.V.
Abstract

The article presents indicators characterizing the efficiency of operational and commercial activities of a company in market conditions. The coefficient of economic, social, organizational and technical capacity of the enterprise, economic performance of the company management, the share  of management costs, the ratio of the number of administrative staff to the number of staff personnel of the enterprise, the ratio of line and functional personnel management staff, the cost-effectiveness ratio of administrative activity; the level of organization of production, the impact of production management and sale of products, the level of product profitability; the level of remuneration of staff; the profitability of equity capital, the level of profitability of production and sales, return on assets, the ratio of real equity value, the coefficient of effective use of current assets; the coefficient of effective use of working capital, the coefficient of the utilization of all assets, the cost of one share; earnings per share, dividend per share, the price of one share of income; total assets; profit margin, gross margin ratio, sales gross profit margin; the complex integrated factor of the company’s management efficiency are among the most important of them. Calculation and analysis of the indicators described in the article for a particular company should help to solve the tasks of engineering and reengineering.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(2):261-265
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