Vol 13, No 5-1 (2014): Special Issue

Full Issue

Conception of cycle life additivity and its application for determining the resource of aero engine disks
Tumanov N.V., Lavrentyeva M.A.
Abstract

Taking into account the universal character and high energy intensity of the mechanism of low cycle fatigue (LCF) crack stable growth which ensures a long safety period for the growth of such cracks a conception of cycle life additivity is proposed. According to the conception the cycle life of an aero engine disk is determined up to the limiting state connected with the transition of a LCF crack to unstable growth in the critical area of a disk. The cycle life prior to the first overhaul is calculated by adding the life cycle before the crack origination and that of stable crack growth (survivability resource); the overhaul period is determined by the survivability resource. The latter is also the lower bound of the disk life at the design stage. To estimate the overhaul period we suggest using survivability diagrams representing the dependence of LCF crack stable growth in the critical area of the disk on the size of the crack. Methods of constructing survivability diagrams have been developed for simple and complex loading cycles. Examples of applying the conception for the estimation of cycle life of aero engine disks made of wrought and powder alloys are presented.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):9-17
views
Kinetic equation of stable growth for low cycle fatigue cracks
Tumanov N.V.
Abstract

Based on the analysis of the literature data on the correlation of parameters of the empirical Paris equation that links the fatigue crack growth rate (FCGR) with the stress intensity factor (SIF) range by power dependence it is established that the equation contains a latent parameter normalizing the magnitude of the SIF range, while both the parameter itself and the coefficient of proportionality between FCGR and some power of normalized SIF range are constant or slightly changing magnitudes for alloys of different types on the same basis. For reasons of dimension and symmetry analysis the nature of this parameter as well as the magnitudes of the proportionality coefficient and the index of power are determined. As a result a kinetic equation is obtained coinciding with the kinetic equation for low cycle fatigue (LCF) crack stable growth deduced earlier using a physically justified mathematical model. The same equation is obtained on the basis of experimental data that describe the LCF crack kinetics in standard specimens at the stage of crack stable growth with the use of fatigue striations as a FCGR measure. Examples of application of the kinetic equation for LCF crack stable growth modeling in aero engine disks are presented.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):18-26
views
Dynamic elastic and damping models development and research for technical objects vibration safety providing
Shakirov F.M.
Abstract

This article considers single-mass elastic-damper model of oscillating system; simplified classic versions with pendants in the form of rheological models of Poynting-Thomson, Kelvin, Maxwell, Hooke can be derived from this model. The difference between this model and other classic versions is that the components of researched model suspension system are based on different foundations; one of foundations can be vibro-active. Model has two modifications, the difference between these modifications is that in one case elastic part of suspension system is based on vibro potentially active foundation and in other case elastic – damper part of suspension system is based on vibro potentially active foundation. The article also contains mathematical models of these modifications with allowance for damping of nonlinear type. Dynamical functions of variation are researched. In this variation vibrations can be transmitted from foundation to protected mass through elastic component. Article shows the cases of force and kinematic vibro-loading of mass with appliance of frequency functions on absolute and relative parameters. Dynamics of researched model is identical to dynamics of classic model in case of force vibro-loading of researched model. New properties (two invariant points) appear on amplitudefrequency characteristic of relative parameter in case of kinematic vibro-loading. This fact is used for optimization of damping level in order to minimize the resonance amplitude. The range of low-frequency vibration isolation is not less than the range of conservative oscillating system. Its size depends on damping and stiffness of elastic elements, so the choice of these values is associated with the achievement of compromise between
limitation of the range of resonance oscillations and providing of the low-frequency vibration isolation of the required quality.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):27-36
views
Analysis of the thermal state of aircraft engine supports
Vinogradov A.S., Badykov R.R., Fedorchenko D.G.
Abstract

The paper discusses the main sources of heat that enters the aircraft engine support. It explores the ways of determining them and provides their quantitative comparison for certain operating conditions of the compressor support. On the basis of determining the amount of heat coming from each of the sources and the results of the previously performed thermogasdynamic design hydraulic analysis of the engine support air cooling is carried out and the distribution of convection coefficients and temperature on the walls of the support is calculated. Then the structural heat calculation is performed. On the basis of the structural analysis the temperature distribution in the support elements is determined. Examples of estimating the impact of the amount of heat from different sources as well as the impact of changing the amount of heat from an individual source on the level of oil circulation in the engine are given. The rates of heat transfer for various sources depending on the engine operating condition are compared. On the basis of the proposed sequence of calculations a methodology of determining the thermal state of aircraft engine supports was compiled that will make it possible to choose the required cooling system and adjust the basic parameters of the engine oil system.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):37-44
views
Cycle parameters of an internal combustion spark-ignition gas piston engine with an electronic control system
Shishkov V.A.
Abstract

The purpose of the work is to develop methods of managing the cycle of bifuel and single-fuel vehicles with engines running both on petrol and gas fuel as well as physically and mathematically reasonable algorithms for an electronic control system. On the basis of full-scale tests of an internal combustion spark-ignition piston engine and a technique developed for designing an ejeсtor with non-stationary physical parameters of working bodies a method of compensating power losses by ejecting a portion of air with the help of pressure difference on the valve of a gas electromagnetic injector is proposed. On the basis of the theoretical analysis and experimental data an algorithm of determining the fuel injection rate taking into account the subcritical or critical fuel discharge from the injector nozzle, the change in the speed of sound, the gas fuel pressure undershoot in the process of fuel feeding and the power supply voltage on the electromagnetic coil of the gas injector is developed. A method of determining the ignition advance angle when switching from petrol to gas fuel is developed for an electronic control system of an internal combustion spark-ignition engine which serves as the basis for calculating
the adjusting factors for liquefied petroleum gas and compressed natural gas.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):45-53
views
Elastic damping and dynamic characteristics of vibration isolators made of wire materials of different types
Yermakov A.I., Lazutkin G.V., Parovay F.V., Boyarov K.V., Bondarchuk P.V., Davydov D.P.
Abstract

A technology of manufacturing all-metal vibration insulation elastic-damping elements made of different wire materials (Metal Rubber, MR – Russia, Spring Cushion – Germany) is presented in the paper. Elasticdamping, amplitude-frequency and mass-overall characteristics of three types of Russian and German vibration insulators are obtained and compared. On the basis of these results the main conclusions on different types of vibration insulators are formulated and recommendations for the application of MR vibration insulators in the world practice of vibration protection are given. The results of research and comparison of static, dynamic and mass-overall characteristics of three different types of vibration insulators are presented in the paper.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):54-61
views
Research of the influence of the diamond burnishing process parameters on the surface roughness of a steel 15CR12NI2MOVWANB-S workpiece when using an indenter made of natural diamond
Shvetsov A.N., Skuratov D.L.
Abstract

The paper presents the results of analyzing the process of diamond burnishing of a sample made of heat-resistant wrought steel 15Cr12Ni2MoVWANb-S using an indenter made of natural diamond OST2 I77-5-75. Burnishing of the sample was carried out after previous turning. The process of turning was carried out by a carbide cutting tool with a mark T15K6 plate with the test sample fixed in a holder with the snap-action tailstock center. Burnishing was performed using two different methods of fixing the sample (in the centers and in a three- jaw chuck with a snap-action tailstock center). The roughness parameters were measured using the automated profilograph-profilometer of the BV-7669 model. The studies have shown the possibility of macrorelief formation on the burnished surface if the sample was machined in the centers and its absence if the sample was machined in the holder with a snap-action tailstock center. In order to obtain the empirical relationships linking the surface roughness with the diamond burnishing process parameters (pressing force, speed, feed, the initial peak-to-trough height and the radius of the diamond burnishing tool) a series of single-factor experiments treated with the use of the method of least squares was carried out. The results obtained correlate well with the experimental results previously obtained in studying the process of diamond burnishing with the use of a diamond burnishing tool made of synthetic diamond ASB-1.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):62-67
views
Calculation method for determining the characteristics of elastic-damping suspension made of metal analoque of rubber for plain bearings
Parovay Y.F., Parovay F.V.
Abstract

The paper is devoted to creating a comprehensive methodology for calculating the characteristics of hydrodynamic bearings of a new type. The design of these bearings has several advantages in comparison with rolling bearings and traditional hydrodynamic bearings. However, the creation of effective bearings requires the development of their design methodology based on accurate mathematical apparatus and the use of the capabilities of modern CAE-programs. One of the most important stages of the design is to determine the required parameters of the elastic suspension material. The paper discusses developed mathematical models of the "working gap - bearing - elastic suspension" system behavior. The model is created with the aim of determining the characteristics of the elastic suspension material to ensure the best operation of the bearing. The mathematical apparatus developed is based on the model of V.N. Buzitskiy and A.A. Troynikov for the MR material and takes into account the peculiarities of the lubrication flow in the gap of the bearing. The paper presents a method of calculating the basic characteristics of the MR material, such as wire diameter, deformation and material density. The required parameters are determined on the basis of the results of CFD calculations of lubricant flow characteristics (pressure distribution in the working gap, the amount of deformation etc.)

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):68-74
views
Method of gas turbine malfunction diagnostics using hybrid intellectual systems
Antropov P.G., Dolinina O.N., Shvarts A.Y.
Abstract

Methods of improving the safety and efficiency of gas turbines are analyzed. The existing diagnostic methodologies and software for compression stations are reviewed. Lists of significant diagnostics parameters, typical faults and their causes are compiled. A model of a hybrid intellectual system of gas turbine fault diagnosis based on artificial neural network and fuzzy inference is introduced. The fuzzy inference method which allows processing an arbitrary number of intermediate variables and transitive relations is described. Moreover, the method makes it possible to take into account the inaccuracies in expert knowledge not only in describing the facts of an application domain but also in cause-and-effect relations between them. The implementation of the proposed model and the method in the system of taking decisions that makes it possible to reveal both the presence and character of the faults and their possible causes is described. The proposed system makes it possible to improve the accuracy and completeness of gas turbine diagnostics, which, in its turn, will increase the labor safety for the compression station staff as well as the promptness of repair and maintenance. Thus, the application of the system may have a positive effect on the service life and economic feasibility of gas turbines.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):75-84
views
Experimental verification of the possibility of improving the liquid propelant rocket engine performance for the “Vega” launcher upper stage
Kovalenko A.N., Pereverzev V.G., Marchan R.A., Blishun Y.V.
Abstract

Successful flight missions demonstrated the high level of reliability and performance of the 4th stage liquid engine developed by the” Yuzhnoye” design bureau for the “Vega” launcher. The obtained specific impulse is 3104.8 m/s which is higher than it was demanded at the initial stage of the development (3094 m/s). Meanwhile, the engine characteristics like mass or specific impulse can be further improved, which was confirmed by experimental investigations. These experimental results and further possible thrust chamber improvements such as implementation of a new radiation-cooling nozzle extension, cooling system redesign and injectors optimization
are discussed and analyzed in the article.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):85-95
views
Non-destructive testing of aircraft engine parts made of composite materials. Identifying the limits of acceptable defects
Karimbayev T.D., Palchikov D.S.
Abstract

An important engineering challenge of providing the reliability of products made of composite materials (CM) is the identification of dangerous types of defects, their permissible values and developing techniques for their detection. A set of techniques of non-destructive testing (NDT) is presented as applied to the problem of monitoring and identification of the acceptable limits of technological defects of aircraft engine parts made of composite materials. The paper also includes experimental tests aimed at determining the effect of a fiber defect on the mechanical characteristics of a polymer composite material. Joint use of different NDT techniques is necessary for the detection of multiple types of technological defects typical for CMs. Defect detection is an integral part of the processing of composite materials into products. Test samples with artificially damaged fibers show their significant influence on tensile strength characteristics and shear modulus in the plane of the layer. The effect of possible defects on the mechanical characteristics of fiber should be considered when designing CM products.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):96-105
views
Parametric instability of the dynamics of gear wheels
Kurushin M.I., Balyakin V.B., Kurushin S.A.
Abstract

Analytical research was carried out with the aim of finding the cause of dynamic processes of vibration excitation of gear wheels. This paper presents an elastic model of gearing without regard for compliance of supports. It is shown that parametric oscillations are caused by a periodic change of mesh force gearing in passing from one tooth mesh to double pair meshing and vice versa. The dynamics of an elastic system can be controlled by using the contact ratio e in the gear mesh which does not depend on the transmitted power. The size of instability zones depends both on the gear wheel rotation frequency and on the degree of overlap in teeth mesh. There are several zones of instability and stable operation of elastic systems at all gear wheel rotation frequencies except those equal to doubled first frequencies. All zones of instability and resonances are located in the zones of phase vibration changes, with maximum efforts taking place in the areas of one tooth mesh before passing the zone of instability or resonance, while after passing these zones the maximum mesh force, on the contrary, will take place in the areas of double pair meshing.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):106-111
views
50 n thrust correction engine for the "Luna-resurs" lunar module descent engine
Ageenko Y.I., Pegin I.V., Chesnokov D.V.
Abstract

Research to develop a 50 N thrust correction low-thrust liquid rocket engine with a deflector-centrifugal scheme of mixing nitrogen tetroxide and unsymmetrical dimethylhydrazine propellants on the inner wall of the combustion chamber has been conducted at the Chemical Machinery Design Bureau named after A.M. Isaev. In the deflector-centrifugal mixing scheme developed at the Chemical Machinery Design Bureau the oxidizer gets to the conical deflector via the jet nozzle and is transformed into a primary film running off the edge of the deflector onto the inner wall of the combustion chamber where it is transformed into a secondary film that flows along the wall of the chamber to the point of meeting the film from the centrifugal fuel spray nozzle coaxial with the combustion chamber. Upon meeting the films of oxidizer and fuel continue flowing along the wall of the combustion chamber at the same time penetrating each other and carrying out the liquid-phase mixing with the formation of transformation products of hypergolic fuel. Thus, practically all the fuel gets to the inner wall of the combustion chamber, participating in its cooling and removal of a considerable part of the heat flow directed along the wall of the combustion chamber from its critical section in the direction of the nozzle head. The engine has the highest (in its class) geometric nozzle expansion ratio ( Fа =200) among analogues of domestic production, meanwhile preserving acceptable dimensions and weight characteristics. The combustion chamber in the engine designed is made of a niobium alloy with a protective heat resistant coating - molybdenum disilicide MoSi2 deposited on the inner surface while niobium disilicide NbSi2 formed by silicon impregnation of a niobium alloy is used on the outer surface. During the firing tests the jet centrifugal scheme of organizing the work process in the combustion chamber designed at the Chemical Machinery Design Bureau confirmed its efficiency in a 50 N-thrust engine. The adopted design and technological solutions in creating a 50N thrust engine ensured high power and energy-mass characteristics, as well as stable engine performance in a wide range of pressures of fuel entering the engine: up to 70.3 N in power augmentation and up to 45.9 N in throttling

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):112-117
views
Numerical research of the static stability of honeycomb composite materials
Pershin А.M.
Abstract

The article presents a numerical research of static stability of honeycomb-filled sandwich panels used in jet engine casing. The application of honeycomb-filled panels in aircraft manufacture has a number of advantages over one-piece constructions. For the assessment of the stability of the whole structure the static-state analysis of a full-scale model was performed at the initial stage of the research and the radial and axial displacements as well as tensile and compressive stresses were evaluated. A model of the periodic cell of a honeycomb sandwich panel was developed at the next stage. The use of such a model in the stability analysis is justified by the absence of boundary effects. To account for the initial shape deformation and the plastic material behavior a non-linear boundary-value problem was incorporated in the analysis. The influence of the honeycomb material (aluminum alloy and fiberglass), the time step, and the finite element size on the stability parameter was evaluated. The analysis of the results obtained was carried out, graphs were constructed. Further research of the honeycomb sandwich panel behavior demands more in-depth analysis of structurally similar elements and full-scale structures.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):118-123
views
Research of the influence of design parameters of a 400 N-thrust low-thrust liquid rocket engine on its energy efficiency
Ageenko Y.I., Ilyin R.V., Pegin I.V.
Abstract

Computational and experimental work to select optimal design parameters of a fuel injector in order to obtain high-energy characteristics of low-thrust liquid rocket engines (LTLRE) with a deflector-centrifugal mixing scheme with 400 N thrust was carried out. A centrifugal atomizer is installed coaxially with the combustion chamber in the deflector-centrifugal mixing scheme. The engine thrust increases with the diameter of the combustion chamber and, consequently, the length of the free span of the fuel film in the cone of the fuel spray of the centrifugal injector also increases before hitting the inner wall of the combustion chamber. Thus, it is necessary to determine the parameters of the injector which provide the stability of the fuel film (absence of the film decay) along the span before it gets to the wall of the combustion chamber. For efficient organization of liquid-phase mixing of fuel components on the inner wall of the combustion chamber the design parameters of the centrifugal nozzle (the diameter of tangential holes, the length and diameter of the vortex chamber, the length and diameter of the injector nozzle) that would ensure the stability of the fuel film all along the free span up to the inner wall of the combustion chamber, as well as the speed, the film thickness and the angle of the atomization cone were calculated. In case of the optimal choice of parameters the films of oxidizer and fuel interpenetrate each other through their thickness. Thus, complete conversion of the fuel components takes place, which ultimately provides higher power characteristics of the engine. The article presents the results of firing tests of a 400 N LTLRE with different design parameters of an injector with the deflector-centrifugal mixing scheme. It follows from the test results that as the nominal pressure drop across the centrifugal nozzle decreases to a certain limit the value of the specific impulse increases. If the inlet pressure is considerably reduced and, as a consequence, there is a significant reduction in the pressure drop across the centrifugal nozzle, the amplitude of the pressure oscillations in the engine’s combustion chamber is increased. The analysis of the test results made it possible to optimize the design parameters of the fuel swirler for a regular 400N LTLRE.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):124-131
views
Assessing reduction gear mass in the problem of optimizing parameters of the working process of a turboprop engine at the initial design stage
Grigoryev V.A., Zagrebelnyi A.O., Prokaev A.S., Kuznetsov S.P.
Abstract

The paper analyzes mathematical models of the mass of the reduction gear as part of a turboprop engine power plant in the problem of optimizing the parameters of the working process of the gas turbine engine at the initial design stage. The necessity of optimal matching of the main parameters of the power plant and the aircraft based on their system performance criteria is the main feature of the initial design of turboprop engines. To solve the problem of optimizing the parameters of the engine work process, under certain design constraints, it is important to know the take-off weight of the aircraft in the formation of which the weight of the power plant with a turboprop engine is one of important components that actually determine the coordination of the aircraft and engine parameters. The mass of the reduction gear of a turboprop engine makes up a significant part of the power plant mass. The existing models of the mass of the power plant with a turboprop engine do not separate the weight of the gear from the weight of the power plant. Thereby, the reduction gear weight is erroneously associated with gear parameters used in the model of the mass of the engine. This does not include the obvious dependence of the gear mass on the transmitted power which is closely linked to the distribution of the free energy of the turboprop engine.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):132-138
views
Development of methods of designing modern gas turbines
Inozemtsev A.A., Khairulin V.T., Tikhonov A.S., Samokhvalov N.Y.
Abstract

The paper is focused on the evaluation of integral and local parameters of advanced aero engine highpressure and low-pressure turbines using the method of 3D numeric simulation in ANSYS CFX. The models used were very detailed high-pressure and low-pressure turbine models with adjoined cavities and a transition duct consisting of 577 million finite elements. Numerical analysis was conducted both in stationary and nonstationary setup using BSL and SST models of turbulence. The resulted design data were verified against the turbine test results. Deviations between design and test data, both local and integral, are insignificant (local deviation is not more than 5%). The results of numerical analysis show high level of turbines’ efficiency. The current configuration was optimized based on the results of verification, which allowed increasing HPT design efficiency by 0.4%. The model was taken as a basis for a series of works aimed at improving the key parameters of both individual turbine components and the module on the whole.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):139-147
views
CFD-modeling of processes in a high-pressure oxidizer pump for the turbopump assembly of a liquid rocket engine
Zubanov V.M., Shabliy L.S.
Abstract

The article presents CFD modeling of the work process in the oxidizer pump of a turbopump assembly using the ANSYS CFX software, as well as the comparison of numerical and theoretical calculations of the analytical relations based on geometric data. Problems were encountered when modeling the flow of the pump due to inaccuracies in the drawing. The spherical radius in the area of the volute chamber throat had to be reduced, otherwise the model would not be topologically consistent with the original. The data on the vane angles at the inlet and outlet of the centrifugal impeller were absent in the drawings. The blade angles were determined by the previously constructed geometric model. Negative pressure at the entrance of the impeller vanes was found in the analysis of the first results of CFD-calculation. Increasing the number of elements in this part of the calculation model made it possible to reduce the area of the negative pressure. CFD-modeling error with respect to the analytical solution does not exceed 11% by the parameters of total and static pressure. The results of the work can provide a visual representation of the processes taking place during the operation of the high-pressure pump of a turbopump assembly. The CFD-model can also be used for further research of work processes in liquid oxygen pumps to reduce the number of development tests.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):148-153
views
The influence of the shuttle effect on the intensification of heat losses in a Stirling engine
Savchenko V.A., Stolyarov S.P.
Abstract

The paper presents a methodology of calculating negative heat flows in the cylinder-piston group of the Stirling engine. Some of the most important of them are the shuttle effect and the pumping losses. The introductory part of the article describes the physical side of the phenomena under investigation. The main relationships recommended by the researchers for the calculation of the shuttle effect and pumping losses are presented in the paper. A mathematical model is developed for the purpose of calculating the heat losses mentioned. The model is based on representing the phenomenon as quasistationary radial heat transfer by means of convection and radiation. A system of algebraic differential equations of heat exchange between single elements of arrays is presented. The system of the main equations is solved by a numerical method of integration (a variety of Euler method - the method of limiting overrelaxation). Algorithms of controlling the accuracy of the calculations performed are incorporated in the program of calculation. The algorithm is used for defining the level of shuttle conduction and pumping loss in the1R30/6 Stirling engine designed at Saint-Petersburg State Marine Technical University. In addition a methodology of finding the heat dissipation factor in the gap between the displacer and the cylinder wall was developed. The extent of influence of the engine design data on the phenomena under consideration is analyzed. Rank diagrams are constructed that visualize the results obtained.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):154-162
views
Validation of CFD-models of gas turbine engine uncooled turbines
Matveev V.N., Popov G.M., Goryachkin E.S., Smirnova Y.D.
Abstract

In the course of the work presented in the paper the agreement between the parameters obtained by methods of computational fluid dynamics and the values used in the JSC "Kuznetsov" in the mathematical model of a gas-turbine unit NK-36ST was verified. A lowpressure turbine and a free turbine of a stationary gas turbine plant were the object of research. During the research three computational models of turbines with different numbers of finite-element computational grids were devised that do not take into account the presence of the turbine cavities. The models of the first level contained approximately 450,000 items in one blade row, the models of the second level - approximately one million elements in one blade row, while those of the third level - about 2 000 000 items per one blade row. A model that includes turbine cavities was also constructed. Diagrams of pressure profiles, total temperature, flow angle and turbulent viscosity throughout the height of the flow section
derived from the preliminary CFD calculations were set as boundary conditions at the inlet of the turbines. The calculation was performed in the Numeca Fine/Turbo software package and resulted in obtaining the basic parameters of the flow in turbines. The dependences of the flow capacity of the turbine А, turbine efficiency, turbine pressure ratio, the outlet flow angle in absolute frame on the parameter n/C*эф were found on their basis. The influence of the calculated mesh dimensions on the results of turbine characteristics simulation was investigated. The effect of taking into account the turbine cavities on the design characteristics of the turbine in the process of simulation was also investigated. Recommendations for constructing computational models of uncooled axial turbines of gas turbine engines are developed, the possibility of optimization and preliminary calculations using models that do not take into account the turbine cavities is justified.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):163-172
views
Peculiarities of modeling the work process in a low-pressure compressor of a gas turbine plant
Matveev V.N., Popov G.M., Goryachkin E.S., Smirnova Y.D.
Abstract

The problem of weight decrease is crucial for modern gas turbine engines. Application of supersonic and transonic compressors is one of the ways of solving this problem. This allows reaching a higher pressure ratio at each stage than while using subsonic compressors and thus reducing the number of stages required to produce the desired value of pressure ratio. In compressors of this kind the flow is slowed down due to a system of shockwaves in the supersonic part and due to the flow deflection in the diffuser channels formed by the rotor blades and guide vanes in the subsonic part. The design of new compressors and modernization of old ones is inextricably connected with the usage of computational fluid dynamics methods at the present stage of engine construction development. The necessity of simulating a shockwave system imposes high demands on the construction of a computational mesh. In particular, the choice of the method of parameter passing between the domains of rotating blades and those of fixed guide vanes is an urgent task. It is shown in the paper that the use of different methods of averaging and parameter passing between domains can make a significant difference in compressor design characteristics (for example, a three-stage low-pressure compressor). Three methods of passing parameters between the domains that are used in the software package NUMECA/Fine Turbo are analyzed. The calculated compressor characteristics are compared with the experimental data at different rotation frequencies
of the rotor. The data obtained show the adequacy of the numerical model of the work process in the compressor under investigation. Typically, air bleeding for various needs takes place in compressors. Compressor performance changes when the air enters it, which should be considered in the calculations. It is shown in the example of the compressor tested that the inclusion of air bleeding results in quantitative and qualitative changes in the compressor performance. Among other things, parameters like pressure ratio and dynamic stability margin are changed, which may lead to inconsistent operation of the compressor as part of the engine. Thus, a conclusion about the necessity of taking into account the simulation of air bleeding in the calculation of supersonic compressors is made. The results obtained make it possible to expand the understanding of the working process of supersonic and transonic compressors and can be used later in the creation of numerical computational models of compressors of this type.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):173-179
views
Dependence of the endurance limit on the character of residual stresses distribution in the surface layer of hardened parts
Kirpichyov V.A., Vakulyuk V.S., Bukaty A.S., Lunin V.V., Mikhalkina S.A.
Abstract

The influence of the character of compressive residual stress distribution on the endurance limit of surfacehardened specimens made of various steels and alloys under bending has been examined. Specimens made of ВНС40 and 38Х2МЮА steels with V-shaped notches were hardened by nitriding, foundation specimens made of ВКС-5 alloy – by cementation and ionic cementation, flat specimens made of ЭИ698ВД alloy – by airshot-blasting. The influence of surface hardening on the endurance limit was assessed using two criterions, namely: residual stresses on the dangerous section surface and the average integral residual stresses. It was established that the endurance limit of surface-hardened specimens (parts) is determined not by the value of compressive residual stresses on the surface but by the completeness of the diagram of the residual stress over the part surface layer thickness on condition that the surface layer thickness is equal to the critical depth of the nonpropagating fatigue crack. The average integral residual stress criterion calculated over the thickness of a surface layer of the dangerous section equal to the critical depth of the non-propagating fatigue crack gives a rather accurate estimation of the influence the character of compressive residual stress distribution has on the endurance limit of hardened specimens (parts). In practice the estimation of the increment of surface- hardened specimens (parts) endurance limit by the criterion of residual stresses on the dangerous section surface may lead to a significant error.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):180-187
views
Modeling of stall cavitation sensitivity of a booster turbopump assembly and comparison between experimental and numerical results
Kazyonnov I.S., Kanalin U.I., Poletaev N.P., Chernisheva I.A.
Abstract

Nowadays, screw booster pumps (BP) are used in engines of large and small thrust both of Russian and foreign designs to reduce the pressure in the tanks. Cavitation may occur in BPs like in any hydraulic systems. To determine the cavitation characteristics of screw and centrifugal pumps a number of empirical formulas were obtained which do not fully take into account all the geometrical features of variable-step screws. Various models of cavitation are used in CFD programs; cavitation properties of any geometry can be obtained on the basis of these models. The paper presents the results of numerical analysis of the cavitating flow in a booster pump and their comparison with the experimental ones. Modeling was performed by ANSYS CFX. The cavitation phenomena were simulated in a stationary approach using the Rayleigh-Plesset model. The geometrical model included an axial-radial wheel and straightening vanes. The analysis was performed with and without a shroud ring, a clearance gap and roughness. On this basis, a method of calculating the stall cavitation characteristics is developed using ANSYS CFX.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):188-198
views
Design of the gas turbine engine rotor wheel with ceramic blades
Sapronov D.V., Reznik S.V.
Abstract

The use of ceramic parts in the hot section of a gas turbine engine will make it possible to increase the engine efficiency due to the increased operating gas temperature at the combustion chamber outlet and reduced air consumption for blade cooling, as well as significantly reduce the weight of the parts due to the low density of ceramics. The main disadvantage of ceramic parts is the brittleness of the material. Mechanical properties of
advanced ceramic materials are insufficient for making a whole wheel, however, they are sufficient for making blades. The main problem in making a structure of this kind is ensuring the strength of the interlock between a metal disk and ceramic blades. Previous works of the authors presented analysis of various types of interlocks between ceramic blades and a metal disk. This paper is devoted to the design of an aero engine gas turbine rotor wheel using a high-strength silicon nitride ceramic material. A software code in the APDL Ansys environment is created that makes three-dimensional design definition possible. A rotor wheel with ceramic blades is designed on the basis of a typical aircraft high-pressure gas turbine engine. A commercial heat-resistant nickel alloy is considered as the disk material, while silicon nitride is used for the production of blades. Evaluation of the stress-strain state and strength analysis are conducted, the properties of the ceramic material are analyzed. The results of the research show that it is necessary to make a special cooling system for a metal disk and that the properties of the ceramics presented are to be improved. It is reasonable to apply similar constructions on stationary gas turbine plants.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):199-206
views
Research of shaft seals made of porous wire «metal rubber» material
Zhizhkin A.M., Zrelov V.A., Zrelov V.V., Ardakov A.Y., Osipov A.A.
Abstract

The possibility of using elastic porous elements made of "metallic rubber" (MR) as rotor seals is discussed in the paper. The technology of manufacturing of such elements is developed for the mechanical damping of vibration in mechanical systems where they are widely used. Comparative analysis of rating curves of labyrinth, honeycomb, brush seals and seals made of MR material has shown that seals made of MR material have better rating curves than labyrinth and honeycomb seals, but slightly worse ones than those of the brush design. Therefore, the use of porous MR material shows promise for making parts of the seals for gas or oil cavities of rotors. Seals made of MR material are designed for optimum performance in the most demanding aerospace sealing applications where high speed and vibration are the norm, and where axial shaft movement takes place. An installation imitating conditions of using rotor seals is designed for the purpose of analyzing seals made with the use of MR material.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):207-214
views
Latest investigations on underplatform damper inner mechanics
Gola M.M., Gastaldi C.
Abstract

Underplatform dampers (UPDs) are widely used as a source of friction damping and are frequently incorporated into compressors and turbines for both aircraft and power-plant applications to mitigate the effects of resonant vibrations on fatigue failure. Due to the nonlinear nature of dry friction, in general dynamic analysis of structures constrained through frictional contacts is difficult, direct time integration with commercial finite element codes may not be a suitable choice given the large computation times. For this reason, ad hoc numerical
codes have been developed in the frequency domain. Some authors prefer a separate routine in order to compute contact forces as a function of input displacements, others include the damper in the FE model of the bladed array. All numerical models, however, require knowledge or information of contact -friction parameters, which are established either through direct frictional measurements, done with the help of single contact test arrangements, or by fine tuning the parameters in the numerical model and comparing the experimental response
of damped blade against its computed response. The standard approach is to fine-tune and experimentally validate the UPDs models by comparing measured and calculated vibration response of blade pairs. To our knowledge, nobody has ever attempted to directly measure the forces transmitted between the platforms through the damper and the relative damper-platform movement. In the light of recent results from direct measurements on dampers it is evident that a dedicated routine for the damper mechanics is an effective tool to capture those finer details which are essential to an appropriate description of damper behaviour. This was made possible by the successful effort of the present authors to accurately measure the forces transmitted between the platforms through the damper, to connect them with the relative platforms movement and to use the findings for the validation of the numerical model. The crosscomparison between numerical and experimental results allows to gain a clear understanding of all contact events (stick, slip, lift) which take place during the cycle, and on how they influence the damping performance.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):215-226
views
Life cycle assessment of the production chain of oil-rich biomass to generate BtL aviation fuel derived from micraoalgae
Gehrer M., Seyfried H., Staudacher S.
Abstract

Considerable efforts are made to generate drop-in aviation fuels from microalgae to avoid competition with food production. Synthetic biofuel from oil-rich biomass is produced along four process lines: cultivation, harvest, extraction of raw material and conversion to fuel. This study deals with the life cycle assessment of fuel obtained from cultivation of the fresh water alga Auxenochlorella protothecoides and concentrates on the cultivation in open ponds as well as the harvesting steps preconcentration, electroporation and dewatering. Energy balance and environmental impact is analysed using GaBi software and data base. The main goal is to identify those factors or processes exerting the strongest impact, either environmentally or from the point of view of the energy balance. Production of one kilogram of dry oil-rich algal biomass (kg DM) consumes 118.56 MJ of primary energy. The primary energy demand is apportioned as follows: 71.7 % during proliferation in Erlenmeyer flags and bubble columns, 15.5 % by cultivation in raceway ponds and 12.8 % in preconcentration, electroporation and dewatering. This converts into a net energy ratio (NER) of 0.266 and a CO2-equivalent of 6.45 kg CO2 per kg DM. These values are disadvantageous when compared to kerosene (NER=0.867, 0.384 kg CO2 per kg kerosene). Production can be optimized using process energy from regenerative sources such as hydroelectric power (NER = 0.545, 1.27 CO2 per kg DM). In this case total primary energy input must be corrected for the portion of renewable sources resulting in a NERcorr of 3.04. CO2-equivalents per kg DM remain unfavourably high as compared to kerosene; the main driver responsible for this discrepancy is the usage of freshwater and fertilizer.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2014;13(5-1):227-235
views

This website uses cookies

You consent to our cookies if you continue to use our website.

About Cookies