Gas Turbine Engine Blades Research Articles

Overview of technical solutions for improving of magnetron sputtering devices

The paper provides a brief overview of technical solutions that allow expanding the capabilities of magnetron sputtering systems using different options for organizing an external source of charges. Among them, the following are considered in detail: electron emission in the magnetron discharge track; argon ionization in the space above the target; argon ionization in the vacuum chamber volume; the use of an uncooled "hot" target; bombardment of the target surface with a beam of argon ions. Among the solutions considered, a combination of a magnetron with an ion source or an incandescent cathode is noted, which in principle can provide equal-dimensional reactive sputtering on "long" (more than 1 m) magnetrons and flexible control of the properties of coatings intended for dimensional elements of equipment of the fuel and energy and oil and gas complexes, as well as solutions based on spraying a "hot" target, which can find industrial application for the formation of thermal barrier coatings on the blades of modern power gas turbines and aviation gas turbine engines.

CAMERA: A method for cost-aware, adaptive, multifidelity, efficient reliability analysis

Estimating probability of failure in aerospace systems is a critical requirement for flight certification and qualification. Failure probability estimation involves resolving tails of probability distributions, and Monte Carlo sampling methods are intractable when expensive high-fidelity simulations have to be queried. We propose a method to use models of multiple fidelities that trade accuracy for computational efficiency. Specifically, we propose the use of multifidelity Gaussian process models to efficiently fuse models at multiple fidelity, thereby offering a cheap surrogate model that emulates the original model at all fidelities. Furthermore, we propose a novel sequential acquisition function based experiment design framework that can automatically select samples from appropriate fidelity models to make predictions about quantities of interest at the highest fidelity. We use our proposed approach in an importance sampling setting and demonstrate our method on the failure level set and probability estimation on synthetic test functions and two real-world applications, namely, the reliability analysis of a gas turbine engine blade using a finite element method and a transonic aerodynamic wing test case using Reynolds-averaged Navier-Stokes equations. We show that our method predicts the failure boundary and probability more accurately and at a fraction of the computational cost compared with using just a single expensive high-fidelity model. Finally, we show that our sequential approach is guaranteed to asymptotically converge to the true failure boundary with high probability.

Mathematical Modeling of Loading for Remanufactured Compressor Blades of Gas Turbine Engines

Mathematical Modeling of Loading for Remanufactured Compressor Blades of Gas Turbine Engines

A Review of Laser Peening Methods for Single Crystal Ni-Based Superalloys

Single crystal Ni-based superalloys are often used to create gas turbine engine blades for their high strength under intense thermo-mechanical loading. Though they are remarkably capable under these conditions, a particular class of premature failure mechanisms known as surface-initiated damage mechanisms can lead to the early fracture of an otherwise healthy blade. This review paper discusses the current progress of post-processing techniques that can greatly mitigate the potency of surface-initiated damage mechanisms. In particular, laser peening (LP) is of significant interest due to the relatively low amount of cold work it induces, greater depth of compressive residual stresses than other cold working methods, ability to accommodate complex part geometries, and the minuscule effect it has on surface roughness. The residual stresses imparted by LP can greatly hinder crack growth and consequently allow for enhanced fatigue life. Given that turbine blades (constructed with single crystal Ni-based superalloys) are prone to fail by these mechanisms, LP could be a worthy choice for increasing their service lives. For this reason, initiative has been taken to better understand the mechanical and microstructural modifications imparted by LP on single crystal Ni-based superalloys and a summary of these investigations are presented in this review. Results from several works show that this class of alloy responds well to LP treatment with improvements such as ~30–50% increase in microhardness, 72% increase in low cycle fatigue life, and elevated resistance to hot corrosion. The primary objective of this review is to provide insight into current state-of-the-art LP techniques and summarize the findings of numerous works which have utilized LP for increasing the service lives of single crystal Ni-based superalloy components.

Experimental and Computational Study of Mechanical and Thermal Characteristics of h-BN and GNP Infused Polymer Composites for Elevated Temperature Applications

Polymer-based nanocomposites are being considered as replacements for conventional materials in medium to high-temperature applications. This article aims to discover the synergistic effects of reinforcements on the developed polymer-based nanocomposite. An epoxy-based polymer composite was manufactured by reinforcing graphene nanoplatelets (GNP) and h-boron nitride (h-BN) nanofillers. The composites were prepared by varying the reinforcements with the step of 0.1 from 0.1 to 0.6%. Ultrasonication was carried out to ensure the homogenous dispersion of reinforcements. Mechanical, thermal, functional, and scanning electron microscopy (SEM) analysis was carried out on the novel manufactured composites. The evaluation revealed that the polymer composite with GNP 0.2 by wt % has shown an increase in load-bearing capacity by 265% and flexural strength by 165% compared with the pristine form, and the polymer composite with GNP and h-BN 0.6 by wt % showed an increase in load-bearing capacity by 219% and flexural strength by 114% when compared with the pristine form. Furthermore, the evaluation showed that the novel prepared nanocomposite reinforced with GNP and h-BN withstands a higher temperature, around 340 °C, which is validated by thermogravimetric analysis (TGA) trials. The numerical simulation model is implemented to gather the synthesised nanocomposite’s best composition and mechanical properties. The minor error between the simulation and experimental data endorses the model’s validity. To demonstrate the industrial applicability of the presented material, a case study is proposed to predict the temperature range for compressor blades of gas turbine engines containing nanocomposite material as the substrate and graphene/h-BN as reinforcement particles.

Theoretical and experimental evaluations of pre-swirl rotor-stator system with inner seal bypass configuration for turbine performance improvement

Pre-swirl system has strong potential to improve the cooling performance and service life of high-pressure turbine rotor blades in gas turbine engines. This study is to evaluate and improve the temperature drop and power consumption characteristics of the pre-swirl system with multi-in and multi-out seal flow by theoretical and experimental analysis. Then, a high-speed rotating test rig of the pre-swirl rotor-stator system is established, considering the inner seal by-pass configuration to prevent the flow of hot gas into the pre-swirl cavity. In addition, the rotor-stator domain parameters in the pre-swirl system test rig are accurately measured at high-speed operating conditions. Three experimental schemes of pre-swirl systems are proposed for comparison under different operating conditions. The experimental results show that the temperature drop of the prototype pre-swirl system is in the range of 9.28–20.78 K, with the power consumption of the system ranging between −0.23 and −6.67 kW and the system pressure ratios being around 1.3–1.9. Because of the inner seal inflow ratio ranging within 0–15%, the system temperature drops for the improved pre-swirl system built-in inner seal by-pass passages notably reach a value between 12.12 K and 25.54 K with an average system power consumption within −0.41 to −8.21 kW. Thus, the improved pre-swirl system arrangement has dual advantages of a higher cooling effect and lower power consumption.

A Review on Failure Analysis of Turbine Blades of Aero Gas Turbine Engine

Almost all commercial electrical power on earth is generated with a turbine, driven either by wind, water, steam or burning gas. Turbine blades are subjected to very strenuous environments inside a gas turbine. They face high temperatures, high stresses, and a potentially high vibration environment. All these factors can lead to blade failure, resulting in catastrophic failure of turbine. In the event of turbine blade failure, turbine does not work and this leads to shutdown of power plant from one to four weeks or longer, depending on the extent of the damage and the procedure used to make the machine operational again, which results in economic loss and service to mankind also stops. For each day of a forced outage, a utility could lose hundreds of thousands of rupees in electrical power. The external and internal surface damages include corrosion, oxidation, crack formation, erosion, foreign object damage and fretting. The internal damage of microstructure include γ’ phase, CoNi3 [(Al, Ti)] phase aging (rafting), grain growth, brittle phases formation, carbides precipitation, creep and grain boundary void formation. These damages produce dimensional change which results in increase in operational stress that leads to deterioration in turbine efficiency. The deterioration of blade material is related to the high gas temperature, high steady state load levels (centrifugal load) and high thermal transient load (trips, start-ups, start downs). In this research, a review of common failures due to metallurgical defects found in gas turbine discussed is presented.

The microstructure and thermal properties of Yb2SiO5 coating deposited using APS and PS-PVD methods

The new ceramic material for Enviromental Barrier Coatings (EBC) on ceramic material was developed. The ytterbium monosilicate was deposited using two methods: atmospheric plasma spray (APS) and plasma spray physical vapour deposition (PS-PVD). Obtained coating was characterized by dense structure and columns typically formed in PS-PVD process were not observed. In comparison with APS-deposited coating, in this method, both elements segregation and formation of ytterbium oxide occurred. The further research for production of columnar coatings will be necessary. Developed coatings migh be used for next generations of ceramic materials used for gas turbine and jet engine blades and vanes as a high temperature and corrosion protection. The first time the ytterbium monosilicate was produced bot by APS and LPPS methods.

Structural and Mechanical Properties of the Nickel Alloy of Gas-Turbine Engine Blades

Structural and Mechanical Properties of the Nickel Alloy of Gas-Turbine Engine Blades

Improving the efficiency of finishing-hardening treatment of gas turbine engine blades

This paper considers the influence of the technology to finish and strengthen compressor blade tips made of EP718-ID alloy on the characteristics of the surface quality, surface layer, and bearing capacity. Taking into consideration the special role of the finishing-strengthening treatment in the formation of the quality of the surface layer, various options for blade tip processing were investigated. The blade tips were shaped by high-speed line milling. The finishing-strengthening stage of tip machining included manual polishing and ultrasonic hardening operations with steel balls in various combinations. The basic regularities have been established in the formation of the roughness of tip surfaces, the maximum height of micro-irregularities, the surface microhardness, and the propagation depth of the hardened layer, depending on the combination of finishing-strengthening machining techniques. The results of tests are given for multi-cycle fatigue of blade batches treated according to various variants of the technological process. The efficiency of polishing the surface of the tip after strengthening treatment has been established. To restore the quality characteristics of the surface layer after polishing, it is proposed to perform repeated strengthening treatment. It is shown that the use of double deformation hardening technology with intermediate polishing at the finishing-strengthening stage of blade manufacturing makes it possible to increase the endurance limit from 320 MPa to 400 MPa while increasing durability. Technology for the finishing-strengthening stage of machining blades made from nickel alloys, characterized by significant viscosity, has been devised. It is shown that based on the criteria of minimum labor intensity of machining and maximum endurance of blades, it is effective to use double deformation hardening with steel balls in an ultrasonic field with intermediate polishing.

The Method of Calculating the Optimal Shape of the Electrode-Tool for Electrochemical Treatment of Gas Turbine Engine Blades

The article outlines the method of digital simulation of electrochemical processing, which allows calculating the shape of the electrode-tool in conjunction with the mode, taking into account the real conditions of processing. The technique allows you to ensure the maximum possible performance with specified processing accuracy and limitations that exclude critical phenomena in the channel between electrodes during intensification of modes. Mathematically, the task is presented in the form of minimax problem with application of penalty functions.

Моделирование процесса формообразования лопаток газотурбинных двигателей с внутриоперационной корректировкой параметров резания

The blades of gas turbine engines have a complex shape of the profiled part and low rigidity. In blade manufacture, there occur feather geometry errors, exceeding the tolerances of feather’s shape and dimensions. To minimize these errors, we propose a technological chain of mechanical processing of a blade on adaptively controlled machine tools, in which various cutting parameters and the trajectory of the cutting tool are adjusted to obtain the required geometry of the part. The use of intraoperative control allows calculating the correction value depending on the deviations of the actual parameters from the nominal ones. We built an ideal mathematical model, which will serve as the basis for the nominal shape of the blade, as well as a corrected geometric model of the blade for the subsequent operation. To calculate the correcting values ??of the parameters, we propose to use the mirror and secant methods. The mirror method consists in adding the error caused by the previous machining process to the current nominal depth of cut. The secant method is to express the nominal depth of cut of the next process as the sum of the nominal depth of cut of the previous process and the correction value. These methods make it possible to take into account the errors arising from previous operations.

Effect of Types of Grinding Fluid on Grinding Characteristics of CMSX4

Nickel-based heat-resistant alloys are widely used for fabricating the turbine blades in gas turbine engines. An increase in the number of such engines operated by air carriers will increase the demand for high-efficiency machining of nickel-based heat-resistant alloys. However, the high-efficiency grinding of nickel-based heat-resistant alloys is challenging because of their low thermal conductivity and thermal diffusivity, high chemical activity, large work-hardening properties, and high-temperature strength. In this work, the authors propose a high-efficiency grinding technique that uses speed-stroke grinding of nickel-based heat-resistant alloys, and aim to clarify the optimum grinding conditions for the proposed grinding method. The workpiece material is CMSX4 used for the turbine blades. A Cubitron + WA grinding wheel and WA grinding wheel mounted on a linear motor-driven surface grind machines are used for grinding, and the grinding force, surface roughness, and grinding ratio are investigated with the removal rate maintained constant. Two types of grinding fluid are prepared: solution and soluble. From the experiments, it is found that wet grinding features a lower grinding force, smaller surface roughness, and higher grinding ratio when compared to dry-cut grinding. The improvement in the grinding ratio at high table speeds is significant, and it is found to be greater for the soluble-type fluid than for the solution-type fluid.

Development of methods for eliminating of surface defects of forgings of titanium blades of gas turbine engines

The methods for eliminating of defects on the surface of forgings of titanium blades by studying the temperature field on the surface of the workpiece in the QForm3D software package are considered.

Effect of microstructure on thermal cycle fatigue resistance in a SPS-TBC

The turbine blades of gas turbine engines used in thermal power plants are coated with a thermal barrier coating (TBC) made of ceramics to provide heat resistance. In recent years, gas turbines for power generation have been utilized as a regulating power source for engines, which are subject to frequent start-up and shutdown and output fluctuations. In this context, the suspension plasma spraying (SPS) method, which has been developed recently, has been studied intensively because it has a porous columnar structure and superior thermal cycle properties compared with the conventional atmospheric plasma spraying method. In this study, we evaluated the thermal cycle properties of TBCs with different microstructures prepared by varying the deposition conditions of the SPS method, and investigated the effect of microstructures on the thermal cycle properties. The experimental results indicated that the thermal cycle fatigue life of SPS-TBC increased with decreasing column diameter. The effect of microstructure on the thermal cycle fatigue life was discussed based on the thermal stress in top-coating evaluated by the FE analysis.

ПРИМЕНЕНИЕ МАШИННОГО ЗРЕНИЯ ДЛЯ ВЫЧИСЛЕНИЯ РАЗМЕРОВ ДЕФЕКТОВ ПРИ ЛЮМИНЕСЦЕНТНОМ ПРОНИКАЮЩЕМ КОНТРОЛЕ ЛОПАТОК ГТД

The authors consider development of a method to automatically determine the size of defects on the surface of a gas turbine engine (GTE) blade during fluorescent penetrant inspection applying computer vision. The article discusses the main approaches to scanning the surface of a GTE blade, a method to search luminescence on the surface of a GTE blade, as well as a method to calculate the size and position of a defect on the surface of a GTE blade.

Highly sensitive methods for vibration diagnostics of fatigue damage in structural elements of aircraft gas turbine engines

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. The 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. The second 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.

Исследование высокотемпературной гомогенизации монокристаллического никелевого жаропрочного сплава 3-го поколения

High-alloyed nickel-based superalloys used for casting of single crystal blades of aircraft gas-turbine engines have to be subjected to a long-term high-temperature homogenization annealing for dissolution of nonequilibrium γ′-eutectics and smoothing of dendritic segregation of alloying elements. Single crystal nickel-based superalloy of the 3-rd generation CMSX-10 developed by Cannon-Muskegon corporation for casting highly loaded uncooled single crystal blades of the first stage of a high pressure turbine of an aviation gas turbine engine Trent 800 belongs to such alloys. In the present work, the processes occurring during high-temperature homogenization annealing of this alloy have been investigated. It is shown that the kinetics of dissolution of nonequilibrium γ′-eutectics strongly depends on temperature: in the range of 1340 – 1360 °C the dissolution rate increases by about an order of magnitude with increasing temperature by 10 °C. Two types of homogenization annealing with a stepwise increase of temperature proposed for CMSX-10 by Cannon-Muskegon have been investigated: a long 45-hour annealing with 10 steps of temperature increase and a shortened 20-hour annealing with 6 temperature steps. The change in the solidus temperature of the alloy during the homogenization was studied by the method of measurement of the specific electrical resistance. It is shown, that during homogenization annealing of the both types the nonequilibrium eutectics is completely dissolved, and a longer 45-hour annealing provides a deeper chemical homogenization of the alloy. This is especially important for such alloying element as rhenium, which has a high segregation coefficient and very slow diffusion mobility in nickel. Deeper homogenization provides better thermal stability of the alloy microstructure and consequently higher long-term creep strength. A negative effect of high-temperature homogenization is increased porosity resulting from the dissolution of γ′-eutectics. Homogenization porosity can be reduced by optimizing the alloy composition and reducing the fraction of nonequilibrium γ′-eutectics.

The Fabrication Method and Tribological Properties of Co-TiC Sintered High-Temperature Alloy

Turbine blades of aircraft gas-turbine engines were always the place to apply novel materials and technologies. Special attention was paid to strength, corrosion-oxidation, and tribological performance. The blade top-shrouds are one of the most vulnerable places from the point of wear resistance. This problem was usually solved by applying coatings (weld-deposition, electro-spark coating, gas-spray coatings). The new method proposed here is to use soldering technology: the to-size plate manufactured of wear-resistant material is bonded to the friction surface by the solder with the composition close to the composition of the turbine blade. In this work, we propose the method and the material for improving the wear resistance of the turbine blade’s top shrouds. The cobalt-based materials (Co-15Cr-2.5Fe-2.5Al-36TiC) seem very promising for this. In the present work, the manufacturing technology of the alloy by HIP method, microstructure, and high-temperature fretting-wear characteristics (1050?C) are discussed.

Verification of numerical methods for modeling of investment casting for gas turbine engines castings in program LVMFlow

Experimental casting of gas turbine engine blade type castings is carried out. A comparative analysis of the numerical method for calculating of the filling of the mould with melt and solidification of the casting with full-scale experiments is performed. The main factors affecting on the accuracy of simulation are identified.