Jet Engine Turbine Blades Research Articles

Investigation of microstructural and thermal stability of Ni-Y-Zr ternary nanocrystalline alloy

This investigation focused on the thermal stability of nanocrystalline (NC) binary and ternary Ni-Y-Zr alloys synthesized through ball-milling. The microstructural changes following annealing, conducted up to 1200 °C, were studied using various techniques, including X-ray-line-broadening, micro-hardness, and transmission electron microscopy. The results revealed that the rate of grain growth observed in the Ni-Y-Zr ternary alloy at 600 °C resembled that in pure NC-Ni at 100 °C. Moreover, the Ni-1.4Y-1.1Zr ternary system exhibited a maximum hardness of 753 HV (average) at 600 °C, which was approximately 60 HV higher than the Ni-1.2Y/1.9Y and Ni-1.5Zr/2.7Zr binary alloys and more than double that of pure NC-Ni for similar grain sizes. These characteristics were linked to the formation of nano-sized oxides and nitrides of Y and Zr within the microstructure. In summary, this study emphasizes the notable high-temperature microstructure stability of Ni-based ternary alloys, attributed to the additive effects of Y and Zr. Due to this extended stability, this ternary system could find potential applications at elevated temperatures in areas such as jet engine turbine blades and power plants.

Analysis of the aerothermal performance of modern commercial high-pressure turbine rotors using different levels of fidelity

In the field of design and optimization of sophisticated geometries such as film-cooled turbine blades of modern jet engines, Computational Fluid Dynamics (CFD) simulation is commonly employed. As the pursuit for higher turbine entry temperatures intensifies, it becomes crucial for computational analyses to offer accurate predictions of metal temperatures and heat transfer coefficients on these critical components. This study investigates the impact of key physical factors that characterize the operation of these components on the accuracy of the computational model. In particular, the effects of including the exchange of thermal energy between the fluid and solid domains, as well as modelling the unsteady interaction between the rotor and stator are studied. The research focuses on a fully featured one-and-a-half stage high-pressure turbine of a commercial jet engine, utilizing proprietary software for conducting 3D Reynolds-Averaged Navier-Stokes flow simulations. To model the fluid-solid thermal interaction, steady-state Conjugate Heat Transfer (CHT) simulations are performed. The CHT results are then compared with experimental data obtained from a thermal paint test, achieving good levels of agreement. Additionally, phase-lag simulations are executed under adiabatic-wall conditions to evaluate the influence of stator-rotor interaction on near-wall gas temperatures. This work shows that, by modelling the periodic unsteadiness at the stator-rotor interface with a phase-lag technique, the maximum near-wall gas temperature prediction is significantly increased, sometimes more than 100K, with respect to the steady-state model one. Findings from this work also suggest that simplified “strip” source terms used to model the presence of film cooling hole rows on the surface of a blade can be used with satisfactory accuracy only for nominal conditions. The mass flows delivered by each source strip should not be linearly scaled based on mainstream quantities for use in different conditions, but they should be recalculated from scratch for the new conditions.

Enhancing thermal stability and corrosion resistance of carbon-carbon composites with iridium coatings deposited by electron beam physical vapor deposition

Abstract Carbon–carbon (C−C) composites are extensively used in high-temperature environments such as Combustor Liners and Turbine Blades in jet engines and Throat Inserts, Nozzle Extensions and Exit Cones in rocket engines due to their excellent thermal stability and mechanical properties. However, at temperatures exceeding 800 °C, these composites require additional protection to prevent degradation. This study aims to investigate the behavior of C−C composites when coated with high-purity metallic iridium using Electron Beam Physical Vapor Deposition (EBPVD). The research problem focuses on enhancing the high-temperature performance and corrosion resistance of C−C composites for aerospace applications. The methodology involves depositing a uniform 5.6 microns thick iridium coating on C−C substrates and characterizing the coating’s microstructure, hardness, and corrosion resistance. FESEM micrographs reveal that the iridium coating adheres uniformly to the substrate without any seepage, and XRD analysis confirms an FCC crystal structure with a densely packed grainy surface. Corrosion tests were conducted using a BIOLOGIC electrochemical workstation in a sodium chloride environment indicate a corrosion rate of 0.00307 mm year−1. The Nyquist, Bodo plots, and Taffel plots were constructed for the better understanding of the corrosion mechanism. While the OCP was constructed to understand the stability and the corrosion resistance of the C−C samples. Microhardness of the coating, measured under a normal applied load of 0.20 N, is 702 HV. The coated samples also could withstand thermal shocks between −40 °C and 1500 °C for 40 h without observable damage or color change. These findings demonstrate the potential of iridium-coated C−C composites to maintain structural integrity and performance in extreme aerospace environments, significantly impacting the field by providing a reliable protective solution for high-temperature applications.

A simulation based analysis for enhancement of performances of turbine blades in turbo jet engines with thermal barrier coatings (TBCs)

The enhancement of turbine blade performance within turbo jet engines is crucial for prolonged engine life. Amidst various cooling strategies for turbine blades, thermal barrier coatings (TBCs) emerge as a highly effective method. Just as the choice of material for the turbine blade holds importance, so too do the materials comprising TBCs. The current research work aims to pursue finite element-based analyses of turbine blades with TBCs, an almost real complex-shaped geometric model comprising the blade body with a rabbet is essential, the stress generated during TGO growth which is crucial for analysis, to select the substrate from both a thermo-structural and cost perspective. In this research endeavor, TBCs were structured with a substrate, a bond coat (NiCoCrAlY), and a top coat of lanthanum cerate (La2Ce2O7) ceramic layers. A thermally grown oxide (TGO), namely α-Al2O3, forms between the bond coat and the top coat due to the elevated temperatures experienced. Two distinct substrates, Inconel 625 and Titanium-T6 alloy, were meticulously chosen as turbine blade materials. Commencing with NACA 4412 airfoil data, the turbine blade was meticulously designed using CATIA, followed by simulations conducted on ANSYS software through a static thermal structural model. The simulation aimed to determine the optimal top coat/thermally grown oxide (TC/TGO) and TGO/bond coat (TGO/BC) layer thicknesses to achieve minimal equivalent stress and total deformation in the turbine blade. The simulated results revealed that a combination of 400 µm TC/10 µm TGO and 10 µm TGO/100 µm BC provided the lowest equivalent stress and total deformation, thereby offering valuable insights for the current research.

Automatic Defect Detection of Jet Engine Turbine and Compressor Blade Surface Coatings Using a Deep Learning-Based Algorithm

The application of additive manufacturing (AM) in the aerospace industry has led to the production of very complex parts like jet engine components, including turbine and compressor blades, that are difficult to manufacture using any other conventional manufacturing process but can be manufactured using the AM process. However, defects like nicks, surface irregularities, and edge imperfections can arise during the production process, potentivally affecting the operational integrity and safety of jet engines. Aiming at the problems of poor accuracy and below-standard efficiency in existing methodologies, this study introduces a deep learning approach using the You Only Look Once version 8 (YOLOv8) algorithm to detect surface, nick, and edge defects on jet engine turbine and compressor blades. The proposed method achieves high accuracy and speed, making it a practical solution for detecting surface defects in AM turbine and compressor blade specimens, particularly in the context of quality control and surface treatment processes in AM. The experimental findings confirmed that, in comparison to earlier automatic defect recognition procedures, the YOLOv8 model effectively detected nicks, edge defects, and surface defects in the turbine and compressor blade dataset, attaining an elevated level of accuracy in defect detection, reaching up to 99.5% in just 280 s.

Identifying low-cost, machinable, impact-resistant TiAl alloys suitable for last-stage turbine blades of jet engines

Existing TiAl alloys used for fabricating last-stage turbine blades of jet engines are relatively cost-prohibitive and unreliable, particularly for use in next-generation engines. The present study was conducted to address these issues by uncovering new TiAl alloy compositions with a focus on improving machinability and impact resistance. Ternary alloys integrated with V or Cr were examined and compared with two commercial TiAl alloys (TiAl4822 and TNM alloy). V and Cr were selected because they are significantly cheaper than the Nb added to existing commercial TiAl alloys and can improve impact resistance (results of previous research). A comparison of the commercial alloys revealed no significant differences in impact resistance; however, TiAl4822 was notably superior to TNM alloy in terms of machinability. Moreover, the V-containing ternary alloys demonstrated significantly higher impact resistance than that of TiAl4822, yet they exhibited inferior machinability. Notably, numerous Cr-doped ternary alloys (such as 48.0Al-2.0Cr/2.5Cr) were superior to TiAl4822 in both machinability and impact resistance. Overall, the study findings indicate that a new TiAl alloy for fabricating jet engine turbine blades with significantly reduced cost and improved reliability can be obtained simply by removing Nb from the existing TiAl4822.

Review: Rhenium and its smelting and recycling technologies

Rhenium is utilized as an additive to improve the high-temperature strength and stability of materials, such as nickel-based superalloys, which are employed in jet engine turbine blades, alloys for ultrahigh-temperature thermocouples, and platinum catalysts, which are used in oil refining. Currently, around 80% of rhenium demand is for superalloy production, and this demand has been increasing with the increase in demand for aircrafts. The abundance of rhenium in the earth's crust is only 1 ppb (10−9), which is less than those of platinum and gold. Owing to the rare and unevenly distributed nature of rhenium, there is the risk of supply disruption and rapid increases in its price. In this article, the recent situation of rhenium and its compounds are reviewed, especially with respect to their demand, distribution characteristics, smelting, and recycling. Some of the technologies recently developed for smelting and recycling rhenium are also introduced.

A novel method for the natural frequency estimation of the jet engine turbine blades based on its dimensions

This study provides a novel methodology for the natural frequency estimation of the jet engine turbine blade by using the dimension check. This paper presents a summarization of the ongoing research devoted to the method for the turbine blade natural frequency estimation. The main target of the research presented in the paper is to develop a novel method that can calculate the natural frequency of a particular turbine blade by using the dimensions of investigated turbine blade from a dimension check. This goal is achieved by the combination and interaction of several methods as for instance computed aided design (CAD) finite element modelling (FEM), artificial neural network (ANN) and others. As it is mentioned in the following chapters of the article a unique novel method is developed that can predict natural frequency according to the dimensions. The results confirmed the correctness of the new methodology, which can predict natural frequency by the dimensions of a turbine blade immediately with a relatively high level of accuracy (maximal errors are under 1.5%). Every jet engine manufacturer (GE aviation, Rolls Royce, Prat and Whitney, etc.) has to test jet engine parts for the natural frequencies in order to avoid the resonance at early stage of the manufacturing process in order to mount the blades into the engine. The experimental tests of every single turbine blade are time-consuming, a novel method can predict natural frequency according to the dimensions by using data from dimension check in 0.0051 s. The presented method is under patent pending.

Evaluation of Forged TiAl Alloy Usefulness Based on Their Impact Resistance

The purpose of this study is to determine if forged TiAl alloys are worth using for small parts such as jet engine turbine blades. As part of this goal, this study investigated ways to improve the impact resistance of forged TiAl alloys and compared them to cast TiAl alloys. The effects of additive elements and microstructure on the impact resistance of forged ternary TiAl alloys of 43.5 at. % Al were evaluated using the Charpy impact test on specimens heated to 500 °C prior to testing. The impact resistance of the forged alloys improved with the addition of Cr, V, and Mn and deteriorated with the addition of Nb. The impact resistance of the microstructure containing a β-phase, a common microstructure in forged TiAl alloys, was significantly lower. The fully lamellar structure obtained at the expense of forgeability showed much higher impact resistance than this. However, even the best impact resistance of the forged alloys was significantly inferior to that of cast ternary alloys of 46.5 at. % Al prepared with the same additive content. Combined with the high cost and low high-temperature strength of the forged TiAl alloys, it is concluded that it is pointless to use forged TiAl alloys for small parts that can be made via casting.

Model-based systems engineering examination of failures ontology in aircraft turbine blades

The concept of Systems Engineering (SE) is widely used in modern times, with approaches based on analyzing the levels and processes of a system. SE approaches are elaborate based on the interpretation of the system's levels and analyzing the whole process. Although such methods are usually used in the analysis of organizations or enormous systems, this effort attempts to show that the same SE analytical tools can be useable in the deepest level of a system. The study focuses on investigating the failure process of a turbine blade, which is considered a system component. The first essential issue in analyzing a system is its interactions with the environment and its effects on the system's internal cybernetics. The study identifies failure processes that cause structural damage as well-defined and tangible processes of microsystem interactions. The research provides a comprehensive architecture of possible failures in an aircraft's jet engine's hot section turbine blades, utilizing a systemic approach and SE tools such as SysML-based models and Domain Mapping Matrices (DMM) to allocate causes of these failures. This research aims to propose an allocated SE-oriented architecture of Failure-Causes in jet engine turbine blades that is more suitable for use in programming.

The Wuliping ion-adsorption deposit, Guizhou Province, South China: A new type of rhenium (Re) deposit

Rhenium (Re) is an extremely rare element and was also the last stable (non-radioactive) element discovered. Owing to the extremely high melting point, Re is ideal for high-temperature applications, for example, as an alloying metal for jet engine turbine blades. This, in turn, leads to an increasing demand for Re resources. Previous studies show that the most common host minerals for Re in the Re-bearing deposits are sulfides (especially molybdenite), and to a lesser extent, U minerals and organic matter. In this study, we report high Re grades and the corresponding host minerals in the weathered Shangsi Formation (dominated by mudstone) of the Wuliping Pb-Zn-Mo polymetallic deposit, based on whole-rock major and trace element geochemical, TOC, XRD, SEM-EDS, and LA-ICP-MS analyses. We find that all weathered samples from the Shangsi Formation display noticeable enrichment of Re (and also Mo), with Re concentrations ranging from 12.61 to 93.13 ppm (averaging 28.23 ppm versus <0.1 ppb in the upper continental crust). However, the high Re concentrations are not found in either sulfides (e.g., molybdenite) or organic matter; rather, our results reveal that Re is mainly adsorbed by kaolinite. We propose that the Wuliping ion-adsorption deposit should be a new type of ion-adsorption Re deposit, which is noticeably different from known Re deposit types. We suggest that ion-adsorption deposits, such as the one explored in this study, may become one of important sources of critical metals in this era of ever increasing demand.

The High Pressure Gas Turbine Blades of Jet Engines

The modern turbo-engine is one of the finest examples of engineering ingenuity, complexity and usefulness. The turbo-engine, whether used in land-based power generating equipment or in aircraft propulsion, has had a profound impact on our lives. Increasing air-travel, rising fuel prices, and environmental concerns have all combined to increase the need for more fuel-efficient engines. The blades of the high-pressure turbine are the most severely loaded members in the turbo-engine. The various aspects of these blades are described. First, the major components of a turbo-engine as well as the different types of turbo-engines are briefly described. Then the development of the turbo-engine is placed in its historical perspective. Next, the severity of the blade loading conditions, such as high temperatures, high centrifugal stresses, corrosion, oxidation, sulphidation, foreign object damage, etc., and the resulting failure modes are summarized. Super alloys are the materials of choice for these blades. The incremental improvements in the alloy chemistry are briefly traced. Important developments in the blade manufacture, the different types of blade cooling channels and their machining, thermal barrier coatings to decrease the blade temperature while increasing the Turbine Inlet Temperature (TIT), and future trends are discussed. The future belongs inevitably to advanced ceramics and their composites, with coatings for environmental protection.

Effect of Microstructure on Impact Resistance and Machinability of TiAl Alloys for Jet Engine Turbine Blade Applications

The impact resistance and machinability of TiAl alloys, which are used for jet engine turbine blades, are critical for ensuring reliability and reducing manufacturing costs. This study investigated the effects of the microstructure on these properties using Ti–Al–Cr ternary alloys via Charpy impact tests at room temperature and 700 °C and performing cutting tests using a face mill with cemented carbide tools. As a result, it was confirmed that six types of typical microstructures of TiAl alloys, namely, fine FL, coarse FL, L + γ, γ, γ + β, and L + γ + β, could be formed by varying the Al and Cr concentrations and heat-treatment conditions. Impact resistance and machinability are each the exact opposite trends to the other, with coarse FL having the best impact resistance but poor machinability. Meanwhile, γ has the best machinability but the weakest impact resistance. L + γ has no major drawbacks, including creep strength. As the microstructure of TiAl4822, currently used in LEAP (leading edge aviation propulsion) engine blades, is almost a γ single-phase microstructure, we assumed that manufacturers chose this microstructure to improve machinability and thus reduce the cost. However, because the γ microstructure has the lowest impact resistance, caution should be exercised when applying it to other engines with different operating environment. On the other hand, the microstructure containing the β phase is inferior in all aspects, including creep strength. Thus, it is questionable to use TiAl-forged materials with a residual β phase in small-sized products that can be manufactured by casting.

Net-HDMR Metamodeling Method for High-Dimensional Problems

Abstract Metamodel technology provides an efficient method to approximate complex engineering design problems. However, the approximation for high-dimensional problems usually requires a large number of samples for most traditional metamodeling methods, which leads to the difficulty of “curse of dimensionality.” To address the aforementioned issue, this paper presents the Net-high dimension model representation (HDMR) method based on the Cut-HDMR framework. Compared with traditional HDMR modeling, the Net-HDMR method incorporates two novel modeling approaches that improve the modeling efficiency of high-dimensional problems. The first approach enhances the modeling accuracy of HDMR by using the net function interpolation method to decompose the component functions into a series of one-dimensional net functions. The second approach adopts the CV-Voronoi sequence sampling method to effectively represent one-dimensional net functions with limited samples. Overall, the proposed method transforms complex high-dimensional problems into fitting finite one-dimensional splines, thereby increasing the modeling efficiency while ensuring approximate accuracy. Six numerical benchmark examples with different dimensions are examined to demonstrate the accuracy and efficiency of the proposed Net-HDMR. An engineering problem of thermal stress and deformation analysis for a jet engine turbine blade was introduced to verify the engineering feasibility of the proposed Net-HDMR.

A small‐scale creep test for calibrating an efficient lifetime model for high pressure turbine blades

AbstractJet engines of airplanes are designed such that in some components damage occurs and accumulates in service without being critical up to a certain level of damage. Since maintenance, repair, and component exchange are very cost‐intensive, it is necessary to predict efficiently the component lifetime with high accuracy. A former developed lifetime model, based on interpolated results of aerodynamic and structural mechanics simulations, uses material parameters estimated from literature values of standard creep experiments. For improved accuracy, an experimental procedure is developed for the characterization of the short‐time creep behavior, which is relevant for the operation of turbine blades of jet engines. To consider microstructural influences resulting from the manufacturing of thin‐walled single crystal turbine blades, small‐scale specimens from used turbine blades are extracted and tested in short‐ and medium‐time creep experiments. Based on experimental results and literature values, a creep model, which describes the fracture behavior for a wide range of creep loads, is calibrated and is now used for the lifetime prediction of turbine blades under real loading conditions.

Characterization of a Newly Designed Test Bench for Investigations of Flame–Wall Interaction

Abstract For the thermal design of combustion chambers and turbine blades in jet engines, a detailed knowledge of the combustion and of the heat loads to the walls is necessary. In general, high operating temperatures and reduced combustor size are striven for in order to increase engine efficiency and reduce weight. Consequently, the components are exposed to temperatures above the melting point of the materials and there is a growing risk of incomplete combustion within the combustion chambers. To study these effects, we setup a new test bench for fundamental investigation of chemical near-wall reactions at atmospheric pressure. First results of gaseous, nonpremixed near-wall CH4/air and H2/air flames are presented. Optical methods such as two-line laser-induced fluorescence thermometry and OH* chemiluminescence were applied. Further, the heat release to the wall was determined by means of inverse heat conduction calculation using the data of implemented thermocouples.

Comportamiento a fatiga de baja frecuencia del compuesto Rene®80 recubierto de aluminuro de platino cerca y por encima del DBTT

La superaleación Rene®80 a base de Ni se utiliza para fabricar álabes de turbinas de gas en motores a reacción. La vida útil de algunas palas de turbina de motores a reacción está limitada por la fatiga de baja frecuencia y esta propiedad se ha visto fuertemente afectada por los revestimientos. La temperatura de transición de dúctil a frágil (DBTT) es el factor más importante que afecta las propiedades mecánicas de las aleaciones recubiertas. En este estudio, se evaluó el comportamiento de fatiga a alta temperatura y baja frecuencia del compuesto Rene®80 sin recubrimiento y recubierto con aluminuro de platino (Pt-Al) a temperaturas de 871 °C (cerca del DBTT) y 982 °C (por encima del DBTT). Los resultados de las pruebas de fatiga, en condiciones de deformación controlada a 871 °C para R = 0 y una tasa de deformación de 2×10-3 s-1, en un intervalo de deformación total de 0,8%, mostraron una disminución de la resistencia a la fatiga de las muestras recubiertas de aproximadamente un 14%, en comparación con las no recubiertas. Sin embargo, el aumento de la temperatura de prueba de 871 °C a 982 °C, condujo a un aumento en el comportamiento a fatiga de baja frecuencia del compuesto Rene®80 recubierto en aproximadamente un 10% en comparación con las muestras sin recubrir.

Electron backscattered diffraction analysis of cold work in a shot peened single crystal nickel superalloy

Shot peening has traditionally been thought to improve the fatigue performance of polycrystalline nickel-based superalloys by inducing a compressive residual stress at the surface of the material. Jet engine turbine blades, manufactured from single crystal superalloys, are routinely exposed to high temperatures. This high temperature exposure can cause relaxation of residual stress arising from shot peening, while a surface layer of cold work is retained. The cold work layer therefore appears to be responsible for improved fatigue damage resistance in such components. The work reported in this study has built up a systematic understanding of how varying shot peening intensity, coverage and shot size affects the amount and depth of cold work by examining samples of a common superalloy, CMSX-4Ⓡ, peened under eighteen different conditions. Local misorientation analysis in electron backscattered diffraction was used to investigate cold work structure. Intensity was seen to increase cold work depth, with a diminishing gradient, in µm/Almen, at higher intensity. Coverage increased the amount of cold work at a given depth, the severity of slip bands and the regularity of cold work. Shot size had a weak effect on cold work, slightly increasing its depth with increasing shot size, but concurrently decreasing its magnitude. In addition, the orientation of the crystal matrix relative to the sample was found to influence the resultant cold work. Samples with shot peened face normals closer to a <110> orientation displayed lower cold work than those with normals closer to <100>.

Fourth-generation single crystal nickel base superalloy for jet engine turbine blades application. 3D imaging and metrology of microstructure elements

Fourth-generation single crystal nickel base superalloy for jet engine turbine blades application. 3D imaging and metrology of microstructure elements

Thermal Barrier Coatings—A State of the Art Review

Thermal barrier coatings (TBCs) have seen considerable advancement since the initial testing and development of thermal spray coating. Thermal barrier coatings are currently been utilized in various engineering areas which include internal combustion engines, gas turbine blades of jet engines, pyrochemical reprocessing units and many more. The development of new materials, deposition techniques is targeted at improving the life of the underlying substrate. Hence, the performance of the coating plays a vital role in improving the life of substrate. The scope for advancement in thermal barrier coatings is very high and continuous efforts are being made to produce improved and durable coatings. Thermal barrier coatings have the potential to address long term and short-term problems in gas turbine, internal combustion and power generation industry. The study of thermal barrier coating material, performance and life estimation is a critical factor that should be understood to introduce any advancement. The present review gives an overview of the thermal spraying techniques and current advancements in materials, mechanical properties, understanding the high temperature performance, residual stress in the coating, understanding the failure mechanisms and life prediction models for coatings.