Vol 13, No 5-2 (2014): Special Issue

Laser microstructuring of the surface can be used for improving tribological properties of materials. This trend suggests a laser treatment to create on the material’s surface microstructures with spatial selectivity of physical-mechanical properties, such as microhardness, friction factor, etc. The microstructuring of the external surface of gas-dynamic compactions is perspective. To increase the capacity of the practical use of it is expedient to enhanced functionality through the use of laser microstructuring of the more common laser systems with pulse durations in the millisecond range. A method of surface’s modification of silicon carbide details by laser treatment for improving their tribological properties has been developed. A material structure in the heat-affected zone after laser microstructuring has been studied. Evaluated the morphological changes of the treated surface after a repetitively pulsed laser exposure. It was established that the pulse-periodic laser exposure leads to the formation on the polished surface of the silicon carbide parts recesses are round to oval. Along with the formation of acyclic microrelief occurs modifying surface structure details. Under laser exposure on the surface of the ceramic material is a decomposition of silicon carbide and graphite to form a solid solution of carbon in silicon. Supposed to carry out the study of the tribological properties of the resulting structures.

The verbal and mathematical formulations of the problem of multicriterion ranging of the pulse detonation  engine design variants were carried out. Using the method of morphological box the morphological table was composed, on the basis of which many possible design variants of the pulse detonation engines were generated. When compiling the morphological table a conception of pulse detonation engines in the form of the following subsystems was considered: detonation chamber, components supply system, initiation system, control system. Eventually as valid options, which were subjected to a study on the firing test bench, we selected twenty variants. The system of criteria for the assessment of the pulse detonation engines design variants (specific thrust, frontal thrust, specific consumption, unit weight, length) was proposed. Criteria values were determined during firing tests. The peculiarities of solving problems by using the methods of "hard" ranging, hierarchies analysis, Borda`s method were discovered. The criterion formation of the true Pareto tuples was formulated. Using the methods of "hard" ranging, hierarchies analysis, Borda`s method, the criterion of the true Pareto tuples formation the applied problems of choosing the best pulse detonation engine variant for three important cases were resolved: - the atmosphere is taken into account, pulse detonation engine suffers the influence of the frontal resistance; - the atmosphere is taken into account, pulse detonation engine is located inside the aircraft and does not suffer the immediate impact of the frontal resistance; - the influence of the atmosphere is not taken into account, only pulse detonation engines without ejector are subject to the analysis. The best pulse detonation engine design variants for different values of the criteria priorities were revealed.

An experimental characterization of small-size centrifugal compressor for turbine-driven generator-compressor unit of a closed-Brayton Cycle gas turbine power plant is presented. Operating fluid is a mixture of inert gases. Bench equipment (replacement of pressure sensors and systems for collecting and processing signals) was upgraded for characterization to complete control of research. The paper describes the test facility, the equipment used and the method of research performance. Test runs were carried out in air compressor, with a cover of the throttle before the surge. Comparison with the calculated point restated at the speed of the experiments (30 000 rev / min) is presented. The influence of the physical properties of the working fluid on the performance of a centrifugal compressor at the calculated pressure ratio (1.75) is evaluated. Experimental research on Xenon and helium mixture (molar mass of argon) and argon at full throttle and varying speeds from 23700 to 30300 rpm is presented.

The results of an experimental study of the conversion of intermediate (liquid-phase and gasified) product exothermic liquid-phase interaction of hypergolic propellant components in the initial stage of combustion are presented. To investigate the present step conversion of intermediates experimental method for the flow reactor is used. In the process of the experiment the centrifugal and wedge mixing elements is used as propellants mixing systems for flowing reactor. This mixing elements allowed interaction of components in the liquid phase and subsequent flow of the liquid-phase intermediates on the wall of the reactor. Thereby dividing the flow of liquid and gasified intermediates in cross-section is achieved. During the experiment the effect of the following basic parameters of the processes of transformation of intermediates is revealed: the effectiveness of liquid-phase mixing of the fuel components, the residence time of intermediate products in the channel and the pressure of gasified products. Results of the study of converting liquid-phase intermediates in the combustion stage confirm the assumption about the prospects of using of liquid-phase products for internal cooling of rocket engine chamber wall provided efficient organization of the chamber working process, because of the temperature of liquid-phase products, washing the inner surface of the channel changes slightly along the entire length of the channel. Exothermic processes of liquid-phase interaction between fuel components at this stage is substantially complete. Heat removal of energy from previously gasified intermediates is required for subsequent gasification of liquidphase intermediates. Unlike the liquid-phase conversion of intermediates, converting process of the gasified intermediates occurs quite rapidly in the initial stage of combustion. The temperature of gasified intermediates depending on the boundary conditions in preflame zone was ~ 900 ... 1100 K, and in the output section of the channel of the reactor reached ~ 1400 ... 2000 K.

In this paper, constructions’ peculiarities and an action mechanism are described as well as a design process of low demand sliding bearings. The analysis of the existing design methodologies shows their imperfections and impossibility adequately applying for characterization of low-flow sliding bearings. These bearings is operated under low lubrication supply (no oil bath). Efficiency of the proposed design of the sliding bearing is based on availability of the elastic suspension, bushings' bore in the radius of the shaft, which minimizes the time of boundary friction and increases the bearing life. Described hydrodynamic model of the working gap allows to determine the characteristics of the oil-flow. As a result of computational research has been established a generalized designing method for new type of bearing, comprising stages: geometry choice, 3D-design, finite element models of the narrow gaps creation, the calculation of the oil-flow characteristics, calculating the characteristics of the elastic suspension, polycriterial optimization. Also shows the results of computational research of bearing's characteristics (diagram of pressure, depending the characteristics of the flow of lubricant on the angle of bushings, etc.). Recommendations are given for optimizing the design and choice of materials.

This article contains materials about defect of two-stage combustion chamber gas turbine engine occurring by high temperatures. The design of basic burner with blade swirler is shown. Improvement of burner by using of the minimum of design changes is required. Ways by absence overheating of elements homogeneous burners combustion chambers is developed. Six variants of burners were selected for their studying. They were made by machining bush of basic burner. This machining bush consists of increasing diameter of inner center hole. It is having variant complete deleting bush and his changing on groove nozzle. Data of experimental works to determine capacity eight types of burners as function of air pressure and formatting field of pressure on edge of burner is presented. The research result of two types burner with groove nozzle for search new ways to solve task of increasing reliability burners is shown. Optimal method tweaking burners for absence overheating swirler was selected.

The paper brings forward the method of determining nonsynchronous vibrations of turbomachinery bladed discs, based on the hypothesis of mechanical generator. Turbomachinery stages represented as a mechanical generator open up new opportunities for test results interpretation for the purpose of gas-turbine engine mounts development and make it possible to improve the reliability of diagnostics of nonsynchronous vibrations and their occurrence and development mechanism. Turbomachinery bladed discs represented as a mechanical generator component part revealed that nonsynchronous vibrations of turbomachinery bladed disc are determined by design features of bladed disc and vane. The paper contains some examples of spectra for fan strain-gauging results, on the basis of which the analysis of nonsynchronous vibrations of turbomachinery bladed discs was carried out. Vibrations of bladed disc with forward and backward strain waves having coefficients k1 and k2, respectively, are considered as a mode of bladed disc being a part of the mechanical generator, which vibration mode is presented by the algebraic sum of broken coefficients. The algebraic sum of these coefficients equals with a ratio of vibration frequency of bladed disc as a mechanical generator part to rotation frequency. The introduced generator of mechanical vibrations model can be applied to the analysis of nonsynchronous vibrations when processing results of turbomachinery bladed discs rig tests.

The results of the experimental study of heat exchange in flat channel, executed by method lazer stereolithography, is presented. The studied heatexchange surface represents the thin metal plate forming one of channel sidewalls. Researches were performed under different criterion Bi in broad range criterion Re. For determination of heat-transfer coefficient is used infrared heat diagnostics, in base which prescribed method of the regular heat mode of the first sort. At first the metal plate was heated, after through an internal channel turned on blowing cold air. Temperature of plate was measured by infrared thermography. In processing the results were based on graphics logarithm excess temperature from time. Slope ratio of the curves is the rate of cooling of the plate. The borders of application of this method are experimentally determined from criterion Bi. The experimental results coincide well with the known criterion dependence Nu=0,018Re0,8. Developed experimental setup and methodology of transitional experiment allow to determine the heat transfer coefficient in forced for restricted flow, when the regular warm mode of 1 type is realized.

The design of a combined case with wound non-impregnation aramid fibers is presented. The main purpose of winding non-impregnation aramid fibers is to prevent the departure of the blade beyond the design of the engine. Wound non-impregnation aramid fibers - a new trend in security systems for aircraft gas turbine engines. Such systems are very cost-effective (value for money) to solve, for example, the problem of localization of the fragments of the engine when the blade is broken, since the threads have high specific strength per unit of weight. In this regard, the introduction of engine design combined body is a very promising solution. The principle of operation of a combined case is as follows: compressor blade breaks into contact with the adjacent blades and the housing. Metal case partially destroyed. Fragment blade engages through a metal casing with a thread wound to absorb the main part of the impact energy and keep the blade fragment to the drawing and friction with each other. For the proposed options to protect the body from Flight of the blade turbine engine developed a mathematical model based on the design of the complex LS-DYNA. The created model is verified by the results of field experiments and used to calculate the retention case cut short blades of a gas turbine engine.

The article presents the results of the searching and experimental research in the field of treatment of discontinuous surfaces in parts of cooling systems. The existing methods and means of technological equipment for providing of quality surface treatment of slot channels are described. Slot channels are especially technologically complex for treatment. A new method of combined treatment was proposed based on an analysis of existing treatment methods. The method allows to achieve the specified operational characteristics of .slot channels. Basic technological principles to design a new method of finishing of small-flow parts, which combines finishing and control operations, are developed. In article the mechanism of combined finishing for slotted channels are described. The results of experimental verification of the technological capabilities of the combined treatment are presented.

This paper presents the results of comparative fire test investigations of the bipropellant thruster 11Д428А-22 with both plate and bellows flow stabilizers. The direct-acting bellows flow stabilizer 11Д428А.410.00/-01 presented in this paper meets all current requirements and progress trends of such type of hardware. In the developed stabilizer the bellows is used as a sensitive element, which excludes any uncontrollable leakages of a working medium and improves the reliability by eliminating cramping and varying frictional forces typical for pistons and plungers. The use of bellows-expanding spring at an initial state of the stabilizer extends the regulation range of the latter and increases the maintenance accuracy of specified flow over the entire control range. The flow stabilizer provides the starting propellant flow at the expense of added mass; hence the negative regulator effect becomes the favorable one in respect of a feed pipeline of liquid propellant thruster to improve thruster operation dynamics. Novelty of the flow stabilizer configuration is combining functions of a regulator and a starting device and broadening a regulation range and accuracy due to the spring expands the bellows at the initial state. The development construction is easy to fabricate and it provides the agreement of calculated regulator parameters and those resulted at the tests.

There is no manufacture of aviation engines in power range of 100-300 hp. One of the most perspective decisions of the domestic low-sized aviation engines developing is creation of engines on the basis of modularity principle. This principle consists in designing of the unified power part and creation on the basis of it multisection or multicylinder engines for maintenance necessary performance. Most simply given problem dares at creation of rotary engines. The paper presents modern design procedure of single rotary engine. This procedure includes statement of target engineering performance, calculation of the basic dimensions of rotary engine, engine performance assessment subject to gas dynamics and mechanical losses, simulation of working process subject to basic dimensions of rotary engine and heat transfer into combustion chamber wall. 3D-model of rotary engines is created on the basis of calculations mentioned above. Calculation of engine geometry is carried out by analytical methods. Performance of rotary engine is calculated by using modern software. The 100 hp single rotary engine project was developed on the basis of this design procedure. In future this design procedure will be applied for developing 200 hp and 300 hp aviation rotary engines.

Ultralow power turbine drives (ULPTD) are used in the aerospace industry and in other sectors of the economy as source of energy for ancillary systems. At present, the actual task is improvement of their efficiency. One of the most promising areas for its increase is to optimize the parameters of turbine drive already in the early stages of design.The article discusses the design of optimalultralow power turbine (ULPT), which is the main hub of ultralow power turbine drive. The basic problems of ultralow power turbine drive system optimization through a systemic approach to design. The problem of optimization is tasked as a problem of the conventional vector structural-parametric optimization. Methods and algorithms for its solution, justified criteria for ULPTD effectiveness evaluating, selected optimized parameters of axial and centrifugal turbines types are described. As the performance criteria is selected coefficient of performance (COP) of the turbine, its mass, the specific consumption of the working fluid, the cost of operating turbine drive. Expediency calculation mode selection in the optimization process of regime parameters evaluation criteria for generalized on ULPTD modes efficiency is grounded. Results on the effect of uncertainty on the value of project information criteria are given.

The problem of structural and parametric optimization of ultralow power turbine (ULPT) in the system of turbine drive (ULPTD) on the initial design stage is formulated. It is described a method and algorithm for selection of rational value sand schemes of ULPT during optimization. Optimization problem involves the use of par ametric minimax principle of optimality in the choice of a rational variant of the turbine, which ensures the reliability of selected solutions. The estimation of the reliability and method effectiveness developed by its validation with the method of designing multimode ULPTD аnd results of computational experiments. The examples of energy and mass efficiency improving of aerospace turbine drive special purpose using the developed method are given. Validation was carried out by the example of the initial design of multi-mode centripetal turbine drive for special purposes. It has been shown that the efficiency by mass turbine drive special purpose can be enhanced with minimal loss in efficiency, if the two-criteria optimization problem solving. Its decision at a loss in terms of efficiency and weight of 1.8% and 11% with respect to the results of a one-criterion optimization possible to increase the efficiency of turbine drive initial version by 6.5% and reduce its weight by 25%. Also it is formed a look of turbine drive switching device. The use of axial turbine instead of centripetal at worst case of original data has allowed to reduce the specific consumption of working fluid and the specific drive mass on the 24 and 48%, respectively.