Gas Turbine Engine Components Research Articles

Synthesis and Characterization of Lanthanum Zinc Aluminate.

Thermal barrier coating materials (TBC) are temperature resistance material which is applied to components in gas turbine or rocker engine in order to improve the life of the component. In this work, the lanthanum Zinc Aluminate are extracted in the form of powder and synthesized using the sol gel process. For sol gel process, Sample of different weight are taken and mixed with distilled water and these are prepared with a controlled stoichiometry by mixing of components. The powder which is obtained from the sol-gel process is to be characterized and the reported.

Low Cycle Fatigue Behavior of Superalloy GH4169 in High Temperature Gas Environment

Turbine components (blades, guides and casing) of gas turbine engine usually suffer from fatigue load in company with a HTG environment in service. The corrosive substances in HTG can deposit on the surface of turbine components and induce accelerated damage known as hot corrosion. In this study, an experimental system is designed and built up to conduct LCF tests of superalloy in HTG environment. The influence of HTG on the LCF behavior of the nickel-base superalloy GH4169 at 650°C is studied. According to the test results, the average fatigue life of the specimens in HTG environment (22270 cycles) is about 31.5% less than that in air (32496 cycles). The protective oxide film on the surface of the specimen can be destroyed by the electrochemical reaction between HTG and oxide film. Compared with the specimen tested in air, there are more fatigue sources in the specimen tested in HTG environment, and the transgranular–intergranular transition occurs in the crack growth area.

Effect of Laser Shock Peening on Fatigue Life at Stress Raiser Regions of a High-Speed Micro Gas Turbine Shaft: A Simulation Based Study

Fatigue failure due to stress raiser regions on critical rotating components in gas turbine engines, such as the shaft, is a crucial aspect. Methods to reduce these stresses and improve fatigue life are a source of ongoing research. Laser shock peening is a method where compressive residual stresses are imparted on the stress raisers of such components. However, numerical based studies on multiple laser shock peening applied to stress raisers is under-researched. Hence, this study will attempt to predict the fatigue life at fillet radii step induced stress raiser regions on a high-speed gas turbine engine shaft by utilization of laser shock peening. The objective of this study was achieved by developing a more computational efficient finite element model to mimic the laser shock peening process on the fillet radii step induced stress raiser regions of a shaft. A modified laser shock peening simulation method for effective prediction of the residual stress field was introduced. Furthermore, the fatigue life improvement due to laser shock peening was predicted by employing Fe-safe fatigue software. From the results, the modified laser shock peening simulation method provided accurate prediction of the residual stress field with a reduced computational time of over 68% compared to conventional methods. The fatigue life revealed an improvement of 553% due to laser shock peening, which is comparable to similar findings in the literature. Hence, from the findings and results achieved, the developed finite element model can be an appropriate tool to assist in the fatigue life estimation of laser shock peening applied to stress raisers.

Prospects of application of additive technologies to develop parts and components of gas turbine engines and ramjets

The possibility of reducing the weight, simplifying the design, reducing the time and cost of development, production and operation are important advantages in the implementation of additive technologies (AT). The use of AT can significantly improve fuel efficiency, environmental and other characteristics of aircraft engines. The possibility of using AT in the production of various parts and components of engines is being currently investigated at CIAM. Examples of these developments, advantages of the use of AT and problems arising in the implementation of these technologies are presented in this article. Models of turbine blades with a highly efficient cooling system, in particular, with penetration cooling were designed and manufactured using optimization methods and taking into account the capabilities of AT. The possibilities of using AT for the manufacture of elements of molds for precision casting of gas turbine engine (GTE) blades of heat-resistant alloys and ceramic rods are shown. Elements of a two-zone front module of the low-emission combustion chamber of an advanced GTE are designed and manufactured using the AT method. Research of prospective branched tree channels of heat exchangers with mutually porous bodies that can be made only by AT methods and the use of which will make it possible to increase the efficiency of heat exchange in the case of lower weight, than that of the structures made by traditional technologies, is being carried out. The AT was used to manufacture complex elements of a ramjet engine. Fire tests of printed sections of the combustion chamber were carried out successfully. Cellular structures to be used in gas turbine engine parts with the aim of reducing their weight were developed. A hollow blade model with cellular-type core was made using AT. Tests of the designed cellular prototypes were carried out. The possibilities of reducing the mass of structural elements using cellular structures obtained by AT methods are shown. Research of hollow disks of turbines and other engine components produced with the aid of AT are carried out. Despite the fact that experimental studies of structural elements obtained by additive technologies have not been completed yet, these works show the prospects for the use of AT in the development of a wide range of engine parts and components.

Life of gas turbine engine components under corrosive exposure

Currently, operation of gas turbine engines takes place in the aggressive medium of the atmosphere of some climatic regions. As a consequence, this may cause fast degradation of the strength properties of parts of gas turbine equipment and their subsequent premature failure. The problem of determining the life of gas turbine engine components under corrosive exposure is vital. We present an analysis of the state of the art in the field of assessment of gas turbine engine component life under the influence of corrosive environment in Russia and abroad. UEC-Aviadvigatel, FSUE VIAM and NPO TSKTI JSC formulated approaches to the development of the lifing process for engine parts operating in corrosive environment.

Segmented Thermal Barrier Coatings for ID and OD Components Using the SinplexPro Plasma Torch

Thermal barrier coatings (TBCs) with high thermal strain tolerance and erosion resistance are commonly applied onto the inner and outer diameters of hot sections of gas-turbine engine components. In this work, strain-tolerant, segmented TBCs were developed using the SinplexPro-cascaded torch. Design of experiments were carried out to study the effect of process variables such as plasma power, powder feeding rate, spraying distance and surface speed on the coating microstructure and properties. Optimized process parameters for the segmented coating microstructures at shorter spray distance ( 114mm) are achieved, which are targeted for spraying inner diameter (ID) and outer diameter (OD) engine components, respectively. The plasma torch hardware life was evaluated by torch cycle duration runs. Examples of highly strain-tolerant TBCs onto the ID and OD engine components were demonstrated, highlighting the wide versatility and process range of the SinplexPro.

Measurement of Hysteresis Energy Using Digital Image Correlation With Application to Energy-Based Fatigue Life Prediction

A modified experimental method using digital image correlation (DIC), a noncontact optical method for measuring full-field displacements and strains, is used to interrogate accumulated fatigue damage for low and high cycle fatigue at continuum scales. Previous energy-based fatigue life prediction methods have shown that cyclic strain energy dissipated during fatigue acts as a key damage parameter for accurate determination of total and remaining fatigue life. DIC enables the collection of accurate strain energy measurements or damaging energy of complex geometries that would otherwise be exceedingly difficult and time consuming using traditional strain measurement techniques. Thus, the use of DIC to obtain strain energy measurements of gas turbine engine (GTE) components is highly advantageous for energy-based fatigue life prediction methods. Presented in this study is the experimental characterization of the cyclic strain energy dissipation as a means of predicting fatigue performance and assessment of damage progression of Aluminum 6061 subjected to fully reversed axial fatigue loading utilizing DIC. Validation of total and cyclic strain energy dissipation DIC measurements is accomplished with the simultaneous use of axial extensometery for direct comparison and implementation to strain energy-based life prediction methods.

Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions.

Higher durability in thermal barrier coatings (TBCs) is constantly sought to enhance the service life of gas turbine engine components such as blades and vanes. In this study, three double layered gadolinium zirconate (GZ)-on-yttria stabilized zirconia (YSZ) TBC variants with varying individual layer thickness but identical total thickness produced by suspension plasma spray (SPS) process were evaluated. The objective was to investigate the role of YSZ layer thickness on the durability of GZ/YSZ double-layered TBCs under different thermal cyclic test conditions i.e., thermal cyclic fatigue (TCF) at 1100 °C and a burner rig test (BRT) at a surface temperature of 1400 °C, respectively. Microstructural characterization was performed using SEM (Scanning Electron Microscopy) and porosity content was measured using image analysis technique. Results reveal that the durability of double-layered TBCs decreased with YSZ thickness under both TCF and BRT test conditions. The TBCs were analyzed by SEM to investigate microstructural evolution as well as failure modes during TCF and BRT test conditions. It was observed that the failure modes varied with test conditions, with all the three double-layered TBC variants showing failure in the TGO (thermally grown oxide) during the TCF test and in the ceramic GZ top coat close to the GZ/YSZ interface during BRT. Furthermore, porosity analysis of the as-sprayed and TCF failed TBCs revealed differences in sintering behavior for GZ and YSZ. The findings from this work provide new insights into the mechanisms responsible for failure of SPS processed double-layered TBCs under different thermal cyclic test conditions.

Control of the Deep Grinding of Gas-Turbine Components

The efficiency of deep grinding may be increased by regulating the longitudinal supply of the table. The selection of the control algorithm is considered in machining the components of gas-turbine engines.

Impedance measurements of acoustically nonlinear engine components

Currently, the acoustic analysis of combustion systems generally consists of simplified impedance networks. For effective simulation, the impedance of these components must be known, for which there is a large gap in the current knowledge. This study examines the acoustic impedance for various different types of gas-turbine engine components, including acoustically nonlinear components such as swirlers and orifice plates. Experimental results are obtained using a specially designed impedance tube. Acoustic pressure and velocity measurements are made using a multiple microphone method. The impedance is then calculated using the reflection coefficient, and impedance subtraction used to isolate the test article. This method obtains accurate results within a relatively wide range of frequency values, 100–1500 Hz for this study. Amplitude sweeps conducted for each test article demonstrate the nonlinear aspects, if any, for each test article. These results are then compared to acoustic simulations conducted in COMSOL to assess the capabilities and shortcoming of COMSOL’s linear acoustic package to provide predictions of the acoustic impedance of these components. The results for this are intended to provide valuable data for modeling the acoustics of combustion systems, as well as demonstrate an effective method for obtaining impedance data for various acoustic components.

Size- and Temperature-Dependent Collision and Deposition Model for Micron-Sized Sand Particles

Sand ingestion and deposition in gas turbine engine components can lead to several operational hazards. This paper discusses a physics-based model for modeling the impact, deposition, and sticking of sand particles to surfaces. The collision model includes both normal and tangential components of impact. The normal collision model divides the impact process into three stages, the elastic stage, the elastic–plastic stage, and full plastic stage, and the recovery process is assumed to be fully elastic. The adhesion loss in the recovery stage is described using Timoshenko's model and Tsai's model, and shows that the two models are consistent under certain conditions. Plastic deformation losses of surface asperities are also considered for particle–wall collisions. The normal impact model is supplemented by an impulse-based tangential model, which includes both sliding and rolling frictions. Sand properties are characterized by size and temperature dependencies. The predicted coefficient of restitution (COR) of micron-sized sand particles is in very good agreement with experimental data at room temperature and at higher temperatures from 1073 K to 1340 K. The predicted COR decreases rapidly at temperatures above 1340 K. There is a strong interplay between the size-dependent properties of micron sand particles and the temperature dependency of yield stress on the collision and deposition characteristics. This is the first physics-based high temperature model including translation and rotation of micron-sized sand particles with sliding and rolling modes in the gas turbine literature.

Micro Structural Characterization of CF 8C Alloy and Its Effect on Tensile Properties at Various Temperatures

CF 8C alloy is an Iron-Chromium-Nickel austenitic stainless steel. It is a cast grade of AISI 347 stainless steel. CF 8C is niobium stabilized alloy and is extensively used in various components of Gas Turbine Engine and Turbocharger. It has good strength and ductility up to 550°C.Corrosion resistance is better than other austenitic stainless steel due to the presence of Niobium. Microstructure of this alloy consists of carbides and delta (δ) ferrite within austenitic matrix. The distribution, size and amount of delta ferrite are dependent on material processing condition. This paper is an attempt to understand the effect of delta ferrite on uniaxial tension testing at a constant strain rate over a range of temperatures. Detailed microstructral study and elemental analysis using optical and SEM has been carried out to understand delta (δ) ferrite distribution.

Microstructure and microhardness of nickel-base heat-resistant alloys obtained by directional and equilibrium crystallization

In order to determine the safe operational life of the components of gas turbine engines (GTE), introductory tests of nickel-base heat-resistant alloys (NHRA) have been performed. X-ray fluorescence and X-ray diffraction analyzes, optical microscopy and Vickers hardness measurements provided data on the phase-structural state and mechanical properties of the pristine ZhS6K-VI and ZhS32-VI alloys obtained by equilibrium and high-speed directional crystallization, respectively. Almost complete compliance of the investigated materials with the certified alloys in chemical and phase composition has been found. A significant difference in the parameters of the fragments of the microstructure of the investigated alloys, which is naturally consistent with the conditions of equilibrium and high-speed directional crystallizations, was revealed. A slightly lower anisotropy of microhardness (2.8 %), measured in transverse and longitudinal sections, was found in the ZhS6K-VI alloy as compared to the anisotropy (5.1 %) in the ZhS32-VI alloy. The obtained results will be used to test a non-destructive method for determining the safe operational life of gas turbine engine components.

Failure of Gadolinium Zirconate and Yttria Stabilized Zirconia Thermal Barrier Coatings Subjected to High Temperature Calcia-Magnesia-Alumino-Silicate Attack

Nowadays, the contribution of rare-earth oxide compounds is extensively investigated with the aim to improve the service life of gas turbine engine components protected by thermal barrier coatings (TBCs) against the environmental Calcia-Magnesia-Alumino-Silicate (CMAS) attack. Therefore, the TBCs consisting of a NiCrAlY bond coat, Yttria Stabilized Zirconia (YSZ) and/or mixture of YSZ and Gadolinium Zirconate (YSZ+GZ) interlayers, and a GZ top coat, which were all deposited by atmospheric plasma spraying onto the nickel-based superalloy substrates, are introduced in this contribution. The CMAS-attack resistance was evaluated using an indirect method. Firstly, the thin layer of CMAS prepared from colloidal solutions was deposited onto the top coat surface and, after drying, the samples were heat treated with the aim to glassified the CMAS. Secondly, the coated samples containing CMAS glass debris were subjected to rapid heating (up to 1200 °C) and enforced cooling cycles at the burner-rig test device and the failure of TBC was investigated. In all cases, the failure mechanism due to the CMAS attack was the top coat spallation. The functional graded TBC was found to be the most resistant system.

Digital shadow identification from feed drive structures for virtual process planning

A requirement for Industry 4.0 style manufacturing is the ability to identify, update, and utilize ‘digital shadow’ type reduced order mathematical models of machine tools and processes, in a non-intrusive and effective manner. This paper presents two new approaches for building such CNC feed drive – structure models from in-process data, typically without interrupting the production. These models can be used to simulate and optimize multi-axis manufacturing trajectories, so that quality and cycle time reduction objectives can be met. The proposed methodology has been demonstrated experimentally on machine tools, and in the context of gas turbine engine component manufacture.

Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties.

Alloy 718 finds application in gas turbine engine components, such as turbine disks, compressor blades and so forth, due to its excellent mechanical and corrosion properties at elevated temperatures. Electron beam melting (EBM) is a recent addition to the list of additive manufacturing processes and has shown the capability to produce components with unique microstructural features. In this work, Alloy 718 specimens were manufactured using the EBM process with a single batch of virgin plasma atomized powder. One set of as-built specimens was subjected to solution treatment and ageing (STA); another set of as-built specimens was subjected to hot isostatic pressing (HIP), followed by STA (and referred to as HIP+STA). Microstructural analysis of as-built specimens, STA specimens and HIP+STA specimens was carried out using optical microscopy and scanning electron microscopy. Typical columnar microstructure, which is a characteristic of the EBM manufactured alloy, was observed. Hardness evaluation of the as-built, STA and HIP+STA specimens showed that the post-treatments led to an increase in hardness in the range of ~50 HV1. Tensile properties of the three material conditions (as-built, STA and HIP+STA) were evaluated. Post-treatments lead to an increase in the yield strength (YS) and the ultimate tensile strength (UTS). HIP+STA led to improved elongation compared to STA due to the closure of defects but YS and UTS were comparable for the two post-treatment conditions. Fractographic analysis of the tensile tested specimens showed that the closure of shrinkage porosity and the partial healing of lack of fusion (LoF) defects were responsible for improved properties. Fatigue properties were evaluated in both STA and HIP+STA conditions. In addition, three surface conditions were also investigated, namely the ‘raw’ as-built surface, the machined surface with the contour region and the machined surface without the contour region. Machining off the contour region completely together with HIP+STA led to significant improvement in fatigue performance.

Оptimization of gas turbine aircraft engine control throughout the engine service life

The task of optimizing control methods in order to maintain key performance parameters of a gas turbine engine throughout the engine service life is considered. Variations in the performance characteristics of engine components in the process of operation are analyzed. To study the effect of deterioration on the engine parameters, a mathematical model of a turbofan engine was modified. The influence of degradation of the gas turbine engine components on its key performance parameters with traditional control methods is assessed. An engine control method using the value of thrust calculated in the on-board engine mathematical model is proposed. This method makes it possible to compensate for the negative effect of the components performance degradation due to their wear. The results of mathematical modeling of the operation of a turbofan engine in steady-state and transient modes are given. The results confirm the effectiveness of the proposed control method: despite the engine deterioration the original thrust value is maintained due to the available gas temperature margin in the combustion chamber

Technique of increasing the accuracy of GTE parts manufactured by selective laser melting

Among the complex profile components of modern gas turbine engines, special attention is paid to the impellers and its blades, and their surfaces have the most strict requirements for geometric precision. At the present time, additive technologies are becoming increasingly widespread, through which it is possible to obtain complex shape parts in a short time with minimal post-processing. However, the process of selective laser melting (SLM) is accompanied by a constantly changing redistribution of temperature stresses in the fusion zone and in the entire part, which can lead to significant deflections of geometry. The authors propose a technique that allows reducing the drawbacks that occurs during the printing process. The technique is based on the use of computer simulation of the selective laser process for predicting deflections and subsequent pre-correction of the input triangulation model by moving the nodes of its surfaces. Based on the results of the approbation, control and analysis of the batch parts obtained by SLM, an additional algorithm for compensating for discrepancies that exist due to instability of the process was implemented with MATLAB.

Thermal-mechanical behavior of a SiC/SiC CMC subjected to laser heating

With ceramic matrix composites (CMCs) being targeted for use as hot section components in gas turbine engines, it is important to understand the thermal-mechanical behavior of these materials within extreme application environments. This work focused on characterization of the in-situ response of a melt-infiltrated (MI) composite (i.e., a laminated Hi-Nicalon™, BN-interphase, melt-infiltrated (MI) SiC matrix composite) subjected to combined thermal-mechanical loads representative of intended operational environments. Laboratory scale test specimens were loaded in uniaxial tension at room temperature and at elevated temperature under both isothermal and non-isothermal conditions. During laser heating experiments, a number of in-situ techniques enabled monitoring of damage formation, strain evolution, and temperature up to failure at 1150 °C. Results indicate that applying mechanical loads axially in the presence of thermal gradients may induce interply delamination cracks not observed after CMC test specimens are loaded axially under isothermal conditions.

Simulation of Volcanic Ash Ingestion Into a Large Aero Engine: Particle–Fan Interactions

Volcanic ash (VA) clouds in flight corridors present a significant threat to aircraft operations as VA particles can cause damage to gas turbine engine components that lead to a reduction of engine performance and compromise flight safety. In the last decade, research has mainly focused on processes such as erosion of compressor blades and static components caused by impinging ash particles as well as clogging and/or corrosion effects of soft or molten ash particles on hot section turbine airfoils and components. However, there is a lack of information on how the fan separates ingested VA particles from the core stream flow into the bypass flow and therefore influences the mass concentration inside the engine core section, which is most vulnerable and critical for safety. In this numerical simulation study, we investigated the VA particle–fan interactions and resulting reductions in particle mass concentrations entering the engine core section as a function of particle size, fan rotation rate, and for two different flight altitudes. For this, we used a high-bypass gas-turbine engine design, with representative intake, fan, spinner, and splitter geometries for numerical computational fluid dynamics (CFD) simulations including a Lagrangian particle-tracking algorithm. Our results reveal that particle–fan interactions redirect particles from the core stream flow into the bypass stream tube, which leads to a significant particle mass concentration reduction inside the engine core section. The results also show that the particle–fan interactions increase with increasing fan rotation rates and VA particle size. Depending on ingested VA size distributions, the particle mass inside the engine core flow can be up to 30% reduced compared to the incoming particle mass flow. The presented results enable future calculations of effective core flow exposure or dosages based on simulated or observed atmospheric VA particle size distribution, which is required to quantify engine failure mechanisms after exposure to VA. As an example, we applied our methodology to a recent aircraft encounter during the Mt. Kelud 2014 eruption. Based on ambient VA concentrations simulated with an atmospheric particle dispersion model (FLEXPART), we calculated the effective particle mass concentration inside the core stream flow along the actual flight track and compared it with the whole engine exposure.