Gas Turbine Engine Blades Research Articles

Application of the vacuum casting technology in the production of small-size gas turbine engine blade machines

The application of casting technologies in the production of parts and assemblies of small-size gas turbine engines is justified in the paper. The technology of vacuum casting in gypsum molds was tested during the production of an experimental centrifugal compressor of a small-size gas turbine engine. On the basis of a 3D model of the designed centrifugal compressor, computational studies of vacuum casting were carried out and rational parameters of the technological process were determined. Prototypes of the developed centrifugal compressor of a small-size gas turbine engine were made. The results of calculations and the performed technological experiment confirmed the fill rate of the gating form and the absence of short pour. The distribution of shrinkage porosity and cavities corresponds to the design values and is concentrated in the central part of the casting that is subjected to subsequent machining. The area of the blades, disc and sleeve is formed without defects. The use of casting technologies in the production of parts and assemblies of small-size gas turbine engines assures the required quality with a comparatively low price of the finished product, making it possible to achieve the balance between the cost of the technology and the quality of the product made according to this technology.

Increase in productivity and quality based on the control of thermodynamic processes during deep profile grinding of the gas-turbine engine blade

The article provides the system of interaction of dynamic processes during deep profile grinding of complex profiles on a multiaxis machine, the influence of dynamic processes on the quality of the surface layer, the endurance limit of the gas-turbine engine blade. The method presented allows to assign corresponding grinding modes based on the forecast of the dynamics of elastic, thermal and working processes in a thermomechanical system. This technique allows to control the process of deep profile grinding to achieve the specified parameters of surface quality, the endurance limit of the blade and increase process efficiency.

The numerical optimization methods usage for choosing blisk trajectory during PVD coating deposition

PVD coating deposition is a considerable way to prevent the gas turbine engine blade from erosive wear. However, the process for blisks is complicated by the part complex shape which leads to uneven film thickness. The research considers an approach for optimizing the blisk trajectory in a vacuum chamber. This approach reduced the calculated non-uniformity of the coating thickness from 4.3-10.8 to 6.2-10.4 μm.

Numerical research of flame propagation conditions in narrow channels using the technology of thermal impulse treatment of turbine blades

The analysis of the main modern trends in the development of views on the issue of cleaning of the cooling channels of turbine blades in gas turbine engines in the process of manufacture and repair at military repair enterprises has been carried out; the usage of the method of thermo impulse treatment with detonating gas mixtures for cleaning of the cooling channels of turbine blades in gas turbine engines is proposed.
 Cleaning the cooling channels of turbine blades of modern gas turbine engines is one of the most complex processes in their manufacture and repair. At the manufacturing stage, the cleaning process is necessary to remove microparticles of ceramics and cutting chip that are produced during the formation of the output edges of the cooling.

Dependence of thermogasodynamic parameters of operation of a helicopter gas turbine engine on its operation and dust in the atmosphere

By scanning the blades of the impeller and the guide devices of the full-scale compressor of the helicopter gas turbine engine, a solid-state design model of the compressor with a tunable geometry in the height of the blades was developed. The empirical dependencies of the values of nonlinear wear of the blade of the 1st stage of the compressor on the operating time and the concentration of dust in the air are presented. A block diagram of the procedure for calculating the characteristics and parameters of a helicopter gas turbine compressor is presented. When calculating the flow in the gas–air path of the compressor, the numerical solution of the Navier–Stokes equations averaged by Reynolds, the finite element method in combination with the establishment of patterns of erosive wear of the blades depending on the operating conditions of the engine is used. Mathematical dependencies of the thermogasodynamic parameters of the helicopter gas turbine compressor operation on its operating time and the dustiness of the atmosphere are obtained using modeling. The obtained results can be used in the development of a methodology for automated monitoring of the wear condition of the compressor blades of a helicopter gas turbine engine according to its thermogasodynamic parameters, applied to various climatic operating conditions.

VIBRATION DIAGNOSTICS OF FATIFUE DAMAGE IN STRUCTURAL ELEMENTS OF GAS TURBINE ENGINES AT THE REPAIR STAGE

Vibration diagnostics of damage belongs to the class of non-destructive methods, which usually do not take long time. However, the main problem of vibration diagnostics is relatively low sensitivity to the critical damage of fatigue crack type, which arises because of long time accumulation of plastic deformation. To improve the sensitivity and reliability of vibration diagnostics of damage two methods were considered. First method was based on the fact, that a characteristic feature of vibrations of structural elements with fatigue crack is the occurrence of non-linear resonances (sub- and super-harmonic) and significant non-linearity of vibration response at these resonances. Secon one – on the fact, that quite noticeable in certain cases increase of damping characteristic caused by a crack can be observed. Analytical and experimental studies of these methods were carried out as applied to the blades of aircraft gas turbine engines. As a result of the studies, the intensity of change in parameter of super-harmonic resonance and in damping characteristics at different parameters of crack was determined. Besides, the experimental techniques for vibration testing of turbine blades were developed. There was demonstrated, that the sensitivity of both considered methods of vibration diagnostics is several orders of magnitude higher than the sensitivity of conventional methods based on the change in natural frequencies and mode shapes, and they can be effectively used for the diagnostics of blades on the stage of engine repair. All the other conditions being equal, second-order superharmonic resonance demonstrates a higher sensitivity to the presence of cracks than the damping characteristic. The smallest crack with an area of 0.2% considered in the work causes a reliably recorded non-linearity of vibration response at superharmonic resonance of order of 2/1. At this the change of damping characteristic slightly exceeds the error of experiment.

Экспериментальное определение вибрационных характеристик рабочих лопаток турбин помехоустойчивым цифровым спекл-интерферометром

The paper notes the wide possibilities and high efficiency of vibration diagnostics of parts and assemblies of power units by the method of electronic speckle interferometry (ESI), shows the feasibility of developing and improving methods for obtaining speckle interferograms of vibrating objects. A patented by the authors' scheme of a digital speckle interferometer (DSI) for determining the dynamic parameters of products is presented. The diffuse reference wave greatly simplifies its alignment, mainly the aligned channels of propagation of interfering beams determine the resistance to mechanical and thermal disturbances, and the separate beam splitter and diffuser make it easy to optimize the optical scheme for the object under study. Speckle interferograms are obtained by speckle correlation methods and a developed method for determining the contrast of the dynamic speckle pattern. It does not impose special requirements on the parameters of the video system, does not require the use of a specialized video camera, and allows, by using a rotary platform, to organize a panoramic view of the oscillatory forms of asymmetric structures. The use of this method in combination with the proposed optical scheme provides an express analysis of products in off-bench conditions. The increased noise immunity of the installation allows the determination of the spectrum of frequencies and vibration modes (SFVM) of samples under free boundary conditions, which is rarely realized in interferometry. The paper presents examples of such speckle interferograms, the expediency of obtaining which is important in the resonance study of the elastic properties of the material and vibration resonance flaw detection. The implemented software and hardware solutions increase the resolution and visibility of the band patterns; facilitate their quantitative interpretation and the extraction of numerical information on the distribution of vibration amplitudes. The area of scientific interests and the specificity of the author's developments have determined the preferential adaptation of the proposed device with a complex of software and methodological developments for vibration testing of gas turbine engine (GTE) blades.

Production of single-crystal seeds [001] from nickeltungsten alloys by directional crystallization

The problem of obtaining priming materials from Ni-W alloys arose in connection with the development of technology for casting single-crystal turbine blades of gas turbine engines (GTE) from hightemperature alloys. This technology uses a seed method for producing single-crystal castings with a crystallographic orientation [001] using seedings from alloys of the Ni-W system with a melting point 120–140°C higher than the casting alloy. The use of such primers greatly simplifies the casting process of turbine blades with a single-crystal structure, increases its reliability both in pass-through furnaces of the PMP-2 type and in high-gradient furnaces of the UVNK-9A type. The article presents the results of the study of the influence of temperature-velocity parameters of directional crystallization, namely, the temperature gradient GZ on the structure of the obtained single-crystal seed blanks, as well as the study of effects of tungsten and carbon on the structure of single-crystal seed blanks, and makes recommendations for optimizing the technological process of single-crystal casting of Ni–W seed blanks adjusting the alloy composition for the seed blanks.

Vibration damping of aircraft propeller blades using shunted piezoelectric transducers

Gas turbine engine blades experience vibrations due to the flow disturbances, these vibrations are critical to the engine durability and performance. Piezoelectric transducers (sensors and actuators) have been used for engine blade vibrations damping either through a passive or active vibration control. The propeller blades are part of turboprop engine and considered as one of the main source of turboprop engine vibrations. Piezoelectric blade damping ideas have been studied by other researchers for fan blades and compressor blades. In this research a vibration damping procedure using piezoelectric transducers applied to an unmanned aerial vehicle (UAV) composite propeller. Experimental investigation introduces an approach for the propeller vibration damping using piezoelectric transducers in conjunction with appropriate shunt circuit. Three thin piezoelectric transducers macro fiber composite (MFC) type PZT-5A are surface-mounted on the propeller, one at each blade. These transducers are placed at locations of high modal strain areas for the propeller first mode at each blade, where these locations are identified by finite element numerical simulation. Electronic resonance shunt circuit, resistor-inductor-capacitor type, for the piezoelectric transducers is designed and experimentally developed such that effective vibration suppression of the propeller is achieved. The experimental and numerical investigations in this research illustrate that piezoelectric transducers with appropriate shunt circuit reduces the aircraft propeller vibrations.

ɤ-TiAl alloy: revisiting tensile creep deformation behaviour and creep life at 832 °C

ABSTRACT Creep deformation in single-phase ɤ-TiAl alloys manufactured using different processing techniques has been an extensively studied topic owing to the high specific strength and excellent creep properties of these alloys at temperatures between 760 and 1000°C. In addition, these lightweight and creep-resistant alloys are being presently considered as replacements to the comparatively heavier Ni-based superalloys for application in the low-pressure turbine blades of the next-generation gas turbine engines. However, there is limited information on the tensile creep deformation behaviour and creep life of ɤ-TiAl alloys at 832°C where these alloys have been reported not to exhibit steady-state creep. To this end, the present work revisits the work on understanding the tensile creep deformation behaviour of wrought single-phase ɤ-TiAl alloy by Saha [1] and is aimed to develop an understanding of the tensile creep deformation behaviour at 832°C and the influence of creep activation energy on the creep life of wrought single-phase ɤ-TiAl alloy for stress levels of 69.4 and 103.4 MPa at 832°C using Monkman–Grant [2] approach.

Determining High-Temperature Oxidation Resistance of (TI-Al-X-N) Based Coatings for Titanium Alloys

Basic titanium alloys are successfully used in modern aviation GTE (gas turbine engine). They are used for parts of a compressor and partly in low pressure part of turbine (intermetallic Ti-Al alloys) due to their high specific strength and at the same time low density, high corrosion resistance but can be used only up to 700 °C. The paper deals with the results of heat resistance testing at 750 °C of Ti-Al-(X)+N based thin ion-plasm multilayers coatings, with different priority of monolayers- intermetallic, conglomerate or nitride for gas turbine engine (GTE) blades from titanium alloys. All coatings showed high resistance during the test, with a maximum efficiency 42.8 of coating with a priority of conglomerate after 30 hours of testing.

High Strain Rate Behavior of GTM-900 Titanium Alloy

Abstract GTM-900 is an α + β alloy of titanium used in low-pressure (LP) compressor blades of gas turbine (GT) engines. The maximum allowable operating temperature of this alloy is 500°C. Silicon is added to enhance the creep resistance at elevated temperatures. The aim of this work is to establish the microstructural stability of this alloy and determine the high strain rate Johnson-Cook (J-C) material parameters such as A, B, and n. The material parameters are subsequently used by designers to simulate the “blade-off” and “casing containment” capability of the LP compressor blade. Split Hopkinson tensile bar was used to conduct high strain rate tests at about 2,000 s−1, and at three different temperatures, viz., 25°C, 300°C, and 500°C, to simulate critical conditions. Data obtained from these testing were used to construct a J-C model. Flow stress increased with an increase in strain rate and decreased with an increase in temperature because of thermal softening. Characterization, using optical and electron microscopes, indicated that the microstructure was stable even after the deformation at 500°C. The presence of needle-like silicide phase was observed under transmission electron microscopy and the composition was verified with X-ray diffraction results. A high strain hardening rate was observed even at elevated temperatures in this alloy (n ≈ 0.54 at 2,000 s−1 and 500°C) compared to Ti-6Al-4V titanium alloy (n ≈ 0.28). Considering good strength and microstructural stability up to 500°C, the present material offers to be an attractive alternate to other contemporary titanium alloys currently used in GT engine applications.

Predicting the composition of primary carbides of the multicomponent system Ni-5Cr-9Co-6Al-8.3W-4Re-4Ta-1Mo-1.5Nb-0.15C

Abstract. Problem. Development of new and optimization of existing casting alloys for the manufacture of blades of gas turbine engines for various purposes is an important scientific and technical problem. Given the sensitivity of the structural components to the concentration of alloying elements, there are difficulties in assessing the expected set of properties of the blades from the optimization of the chemical composition or structural state of alloys. Goal. The aim of this work is to study the specifics of the influence of alloying elements on the distribution of primary carbides in the structure, their topology, morphology and their composition for a multicomponent system such as Ni-5Cr-9Co-6Al-8,3W-4Re-4Ta -1Mo-1 , 5Nb-0.15C using the calculation method of CALPHAD prediction (passive experiment) in comparison with the data obtained by electron microscopy (active experiment). Methodology. Modeling of thermodynamic processes occurring during crystallization (cooling) or heating in the structure of alloys was carried out by the CALPHAD method. Results. The results of thermodynamic calculations of the chemical composition of carbides are presented in comparison with experimental data obtained by electron microscopy on a microscope REM-106I with a system of energy-dispersion X-ray spectral microanalysis. Originality. It is shown that when the total concentration of carbide-forming elements increases, the chemical composition of carbides also becomes more complicated. At a concentration of more than 2% of the mass. But in the alloy, in the carbide of MS, the content of tantalum prevails over the content of niobium, it also leads to a decrease in the concentration of tungsten and molybdenum in the carbide. It was found that when the concentration of niobium is more than 3 wt%. in the alloy, its content in the primary carbide exceeds the content of tantalum and the carbide becomes based on Ta. Practical value. On the basis of an integrated approach, computational and experimental, for multicomponent heat-resistant alloys, new regression models are obtained that allow to adequately predict the chemical composition of carbides by the chemical composition of the alloy. which is confirmed by the obtained experimental data.

Test technique for turbine cooled blades of gas turbine engines

Test technique for turbine cooled blades of gas turbine engines is developed. The new approaches during development of inductor structures, induction heating devices, cooling systems, hydraulic force loading system and methods for their design to provide the prescribed nonuniform heating the turbine cooled blades and to carry out more effective the thermocyclic tests are presented taking into account the developed test technique. Study of effect of the clearances between inductor and blade surface and change of inductor efficiency on the thermal state of blade is presented. The test rig and improved systems of induction heating and mechanical loading are used to improve accuracy and simulate more complete the operating thermomechanical loading the full-scale cooled and uncooled blades at the thermocyclic tests. The results of rig testing the turbine cooled monocrystalline blades of gas turbine engine are received according to the developed test technique.

Influence of operating conditions on the protective polyurethane coating for carbon fiber reinforced plastic blades of gas turbine engines

The article presents research results of protective coating, which is a two-component composition based on polyurethane, developed in Bauman Moscow State Technical University, in operating conditions. The influence of sea water and negative temperature on the properties of carbon fiber reinforced plastic with protective coatings, as well as resistance to erosion wear, was determined. It is shown that the developed coating has high performance properties and resistance to erosion wear compared to existing commercial coatings certified by Boeing, Pratt & Whitney and Airbus.

Development of a method for manufacturing ceramic tooling for precision casting of blades made of heat-resistant alloys using additive technologies

The technology traditionally used to produce castings of gas turbine engine (GTE) blades involves a large number of alterations, high labor costs due to the large amount of manual labor required, and complex and expensive equipment and tooling. This technology is only suited for large-scale production due to its use of expensive reusable metal molds.The ceramic shell mold for turbine cooled and uncooled blades can be manufactured more quickly and cheaply. This is especially important for fast hardware redesign and reconfiguration.This proposal describes an approach for producing a shell mold including with an internal rod using three-dimensional (3D) printing with refractory ceramic pastes that does not involve a lengthy and time-consuming process of designing and manufacturing forming equipment for the production of castings based on smelted models.

Finishing surface treatment of GTE parts with dry electropolishing

One of the major problems in GTE production is ensuring high performance of compressor blades. Existing methods of surface polishing have a number of disadvantages and, cannot ensure a high-quality surface of gas turbine engine blades. The most advanced method of polishing parts is the technology of dry electropolishing in the medium of granules (DEPG). However, the use of the DEPG method during polishing leads to defects. The study of the defect causes during DEPG allowed the authors of this paper to develop a brand new technology of dry tape electropolishing. This method made it possible to eliminate the disadvantages of DEPG and to ensure the specified geometric parameters of the blade airfoil.

Verification of a Mathematical Model of a Dry Friction Damper for a GTE Blade

This paper presents the verification of the mathematical model utilized to calculate the damping capacity of a dry friction damper. The mathematical model is based on determining natural frequencies and mode shapes, as well as relative characteristics of the friction energy losses. To estimate the applicability of the mathematical model to full-scale assemblies of a gas-turbine engine, the model was verified by the results of the experiment. The experiment was carried out in a laboratory where the damping capacity of the gas-turbine engine blade with a model under-platform damper was examined at constrained and damped oscillations. During the experiment multiple materials of contact pair were examined to determine how microslip affects the damping capacity. Based on the results of comparing calculations with the experiment, by selecting the dry friction coefficient, a good convergence on the oscillation decrement and natural frequency was achieved. The conducted research has shown that the mathematical model provides reliable results with Coulomb friction and can consider microslip effects on the damper capacity.

Development and Testing of Polyurethane Coating for Protection of Gas Turbine Engine Blades

The article presents testing of polymer protective coating based on polyurethane developed in Bauman Moscow State Technical University. It is shown that the developed coating has an increased resistance to erosive wear, an increased level of adhesion and temperature resistance, compared with the existing coatings, certified by aviation.

Effect Of Technological Parameters Of Production Of Tfp Preforms Of Gas Turbine Engine Blades On Their Physical And Mechanical Properties

The article discusses the features of the destruction of carbon fiber reinforced plastics on the basis of tfp-preforms produced using various stitching mode parameters, and provides for studies of their physical and mechanical properties and structure. The effect of the carbon fiber laying density and the piercing step of the aramid yarn on the elastic-strength properties of composites is shown. The optimal technological parameters for creating tfp-preforms of gas turbine engine blades were chosen.