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The microstructure and surface morphology of (Ba0.8,Sr0.2)TiO3 based glass-ceramics with different amounts of La and Ce were studied. It was shown that the addition of the 1.5% La and >2%Ce led to formation of dendrite-like structures. The isolated clusters of ferroelectric phase were found in all investigated samples. Fraction of ferroelectric phase was about 0.75% for La addition and 0.25% for Ce addition.

The paper presents the main ideas of the virtual test bench concept for rapid obtaining of the reliable characteristics of compressors based on a multi-level mathematical model with a two-step identification using data obtained from mathematical models with a high order of accuracy. One of the possible identification algorithms and the results of its successful testing are given on the example of a centrifugal compressor stage developed and tested at NASA.

The paper presents the results of numerical simulation of the effect of flow nonuniformities at the engine inlet on the working process of the engine fan. Flow nonuniformities is created by pushing the interceptor into the flow part of inlet device like as it is often done during field tests. The authors have created a numerical model capable of considering non-stationary pro-cesses in the fan using nonlinear harmonic analysis. As a re-sult, qualitative and quantitative estimates were obtained of the influence of overlapping of the inlet duct by the interceptor on the main parameters of the fan workflow. It is shown that the more the duct is blocked, the more its parameters are deteriorated. Moreover, the deterioration is not linear, but according to.

The paper provides a description of the algorithm, an example of a specific task, and the results of the optimization of a 15-stage three-spool compressor for a ground-based GTU by the efficiency criteria of the engine. It can be performed by using the proposed algorithm to find such a compressor configuration that will be not just the optimum compressor, but the best option for working as part of the engine under the specified operating conditions and with various types of required restrictions. Using the proposed algorithm, varying only the stagger angles of the profiles, the authors managed to find a way to increase the overall efficiency of the NK-36ST engine by 0.43%. Obviously, it is possible to achieve a more impressive result and at the same time to increase reliability, reduce the weight and cost of the engine by applying more complex models by changing the shape of the blade profiles.

The paper presents the main ideas of the virtual test bench concept for rapid obtaining of the reliable characteristics of compressors based on a multi-level mathematical model with a two-step identification using data obtained from mathematical models with a high order of accuracy. One of the possible identification algorithms and the results of its successful testing are given on the example of a centrifugal compressor stage developed and tested at NASA.

We studied microstructure, surface morphology, and domain structure of (Ba0.75,Sr0.25)TiO3 based glass-ceramics with different amount of Mn additive (from 0 to 0.5%) prepared from melted and quenched mixed powders using several microscopic methods. The as-quenched sample was annealed and subjected to a controlled crystallization in air for 2h at temperatures 850 and 950degC. It was shown that the addition of the Mn up to 0.5% had no impact on morphology and domain structure. The dendrite structure was revealed in the samples crystallized at 850degC. The geometry of the clusters was analysed in terms of fractal approach. The faceted grains with size about 150 nm were found in ceramics annealed at 950degC. Individual grains demonstrated non-uniform piezoresponse, which could be attributed to existence of domain structure.

The goal of the research was to improve efficiency of four-stage low-pressure turbine with outlet guide vane (LPT) at the design point by optimization the shape of all turbine stator vanes and the stagger angles of all rotor blades. The LPT mathematical model was created by using NUMECA FineTurbo software. Several constraints were imposed the mass flow rate through the LPT and the total pressure ratio at the design point may vary within +-0.5% from the original. Parameters of the stator blade shape and rotor blades stagger angles were obtained. This new geometry of the LPT blades produce a 0.8% increase in efficiency at the design point.

Based on the previous investigations, regression equation for calculating the profile losses was found by the least squares based on the analysis of the profile losses nature and using mathematical optimization techniques. This equation makes possible to define the profile loss of axial turbine more accurate than the existing models and equations. It allows the calculation of profile loss values in the axial turbine that differ from the actual value by 10+-61% with a probability of 95%. The obtained equation is not only superior to other loss models in statistical criteria, but it also considers the increasing number of factors affecting the profile losses.

Here we present the results of the study of electromechanical performance of the Ce0.8Gd0.2O1.95 (CGO) self-supported thin circular membranes with aluminum and titanium as contact electrode materials. The electromechanical performance of both membranes was investigated using highly sensitive interferometric technique and showed two principal excitations mechanisms: common electrostriction and thermal contribution due to the Joule heating. Operating the membranes at frequencies about MHz results in significant contribution of the thermal excitation due to a large power dissipation for every electrode. The excitation of the membrane with aluminum electrodes at the frequencies about 1 Hz leads to the formation of the Schottky barrier at the interface with CGO. That is why the electromechanical response was almost independent on frequency and electric field. Membrane with titanium electrodes showed a prevalence of electrostriction effect with weak frequency dispersion and significant enhancement of the response with temperature.

The article presents one optimization method for improving of the working process of an axial compressor of gas turbine engine. Developed method allows to perform search for the best geometry of compressor blades automatically by using optimization software IOSO and CFD software NUMECA Fine/Turbo. Optimization was performed by changing the form of the middle line in the three sections of each blade and shifts of three sections of the guide vanes in the circumferential and axial directions. The calculation of the compressor parameters was performed for work and stall point of its performance map on each optimization step. Study was carried out for seven-stage high-pressure compressor and three-stage low-pressure compressors. As a result of optimization, improvement of efficiency was achieved for all investigated compressors.

Gas flow nonuniformity is one of the main sources of rotor blade vibrations in the gas turbine engines. Usually, the flow circumferential nonuniformity occurs near the annular frames, located in the flow channel of the engine. This leads to the increased dynamic stresses in blades and as a consequence to the blade damage. The goal of the research was to find an acceptable method of reducing the level of gas flow nonuniformity as the source of dynamic stresses in the rotor blades. Two different methods were investigated during this research. Thus, this study gives the ideas about methods of improving the flow structure in gas turbine engine. On the basis of existing conditions (under development or existing engine) it allows the selection of the most suitable method for reducing gas flow nonuniformity.

The article presents the results of work on the design of the air brake for testing of industrial gas turbine engines with free turbine. Designing of the air brake was performed on the basis of existing units using the program CFD - simulation Numeca FineTurbo. During the design the air brake arrangement was determined, which allows to utilize the required power to the shaft of the free turbine, increases stall margin of the air brake by waisting of the meridional flow channel. It was also made designing of the outlet guide vane to remove the residual twist. Unified nozzle also was designed to provide the air brake work at necessary points on the characteristic.