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With the rising demands of industry to increase the working temperature of gas turbine blades and internal combustion engines, thermal barrier coatings (TBC) were found to be an effective way to further enhance the lifetime of aero components through the improvement of mechanical properties and oxidation-resistance. Thus, this paper aims to review coating technologies with special emphasis on plasma-sprayed thermal barrier coatings (PS), and those produced by physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods. Each technology was assessed in terms of its effectiveness to enhance the mechanical response and oxidation resistance of nickel-based parts working at high temperature. The effect of coating technology on mechanical strength, hardness, fatigue and creep of nickel alloys was discussed to reveal the potential candidates for future applications in aggressive environments. [ABSTRACT FROM AUTHOR]

The heat transfer simulations of turbine blades with internal cooling are faced with so many uncertainties, of which some originate from the secondary air system, including the inlet hot gas temperature and pressure and the cooling side boundary conditions, and the blade material. The main objective of this work is to carry out a suitable sensitivity analysis on a specific novel turbine vane to improve the thermal performance of its internal cooling system and to quantify how the uncertainties on the designed/calculated values can desirably/undesirably affect the maximum blade surface temperature, which can consequently affect the gas turbine engine efficiency. Furthermore, the sensitivity analysis is carried out to find the effects of uncertainties of a number of key parameters on the resulting blade temperature distribution. To arrive at trustworthy conclusions, the conjugate heat transfer (CHT) method is used to analyze the heat and fluid flow behavior. This work suitably develops a CHT-based method/solver to perform the proposed study. This method/solver uses a segregated iterative procedure, in which the outer hot gas region is simulated using the computational fluid dynamics (CFD) solver, the flow passing through the connected internal cooling passages is calculated using a 1D correlated-based solver, and the vane conduction is predicted using a 3D finite-element solver, which are fully coupled. The results show that the cooling channel wall temperature has a direct impact on the convective coefficient magnitude; especially in lower temperature regions. As a novel contribution, this work takes into account the cooling wall temperature influence on the 1D code calculations. To implement this, an artificial neural network is suitably trained to predict better convective coefficient. The results of this developed CFD-CHT code are validated against experimental data available for a benchmark vane. Eventually, the sensitivity analysis is carried on the present specific novel turbine vane. [ABSTRACT FROM AUTHOR]

Manually preparing the data for the analysis of the calculation of a pipe network of air-cooled turbine blades is inefficient. In this paper, a method to adaptively divide the blade model and extract data of the flow units is proposed. In this method, the topological lines of the flow channels for the calculations of the pipe network were extracted based on the simulatedfluid flow. The abstracted lines of the fluid flow area were used to replace the manual interpretation of expertsto realize the adaptive division of the flow units and to understand the connection relationship of the units and the layout of the spatial network. In addition, by establishing a basic flow unit library and constructing a specific algorithm, we quickly extracted the data from the typical flow units. Finally, the proposed method and algorithm were verified with a representative case study. The results illustrated that our method could cut down the pre-processing in the calculation of the pipe network of air-cooled turbine blades to several minutes from the several hours required for the manual method while providing reliable quality. [ABSTRACT FROM AUTHOR]

The corrosion fatigue behavior of a martensitic stainless steel AISI 410 with 12% Cr, used in the fabrication of steam turbine blades at low pressure (L-P), was studied using the electrochemical noise technique (EN) under mechanical fatigue (immersion and aired) conditions. The tests were done in a simulated environment using four levels of mechanical stress (Δσ) in a 3 wt.% NaCl solution at 90 °C. The specimens underwent pitting corrosion when exposed to the corrosive environment; afterwards, such pits generated mechanical strength sites over the metallic surface, facilitating the initiation and propagation of cracks, which was already enhanced by the applied cyclic loads. From scanning electron microscope (SEM) images, it was possible to observe localized plastic deformation. In such instances, the fatigue damage was caused by the microplasticity (μ), i.e., the shear strength, resulting from the breakdown of the passive layer that was subjected to mechanical load, which led to a significant increment of the velocity of crack propagation, and therefore, a decrement of the useful life of the material. The obtained results show that the fatigue resistance limit in the corrosive medium was lower than that observed in aerated conditions due to the sum of the effects of mechanical fatigue and corrosion. [ABSTRACT FROM AUTHOR]

The jet always sweeps to the leftmost and rightmost points in the sweeping jet and film composite cooling (SJF) process, resulting in a different coolant flow in each film hole. The film can not easily cover the outer surface evenly under the scouring of the mainstream. This work presents a case study to analyze the effects of two mainstream variables on the film areodynamic and cooling performance of the SJF. Three different mainstream velocities (Vm= 10 m/s, 50 m/s, 90 m/s) and three different mainstream turbulence intensities (Tu = 1%, 10%, 20%) are discussed. Results indicate that the increase of mainstream velocity yields to better film attachment. When the mainstream velocity increases from 10 m/s to 50 m/s, the overall cooling effectiveness and total pressure loss coefficient are reduced by 17.68% and 98.60%, respectively. When the mainstream velocity increases from 50 m/s to 90 m/s, the overall cooling effectiveness and total pressure loss coefficient are almost unchanged. The effect of turbulence intensity on the overall cooling effectiveness and total pressure loss coefficient are relatively small. The increase of mainstream turbulence intensity enhances the disturbance of the mainstream to the coolant from the middle film holes, and the distribution of adiabatic film cooling effectiveness is more uneven when the mainstream turbulence intensity is raised to 10% and 20%. In the research scope of present work, the flow structure, total pressure loss coefficient and overall cooling effectiveness are the most expected under the conditions of lower turbulence intensity and higher mainstream velocity (Tu = 1%, Vm= 90 m/s). [ABSTRACT FROM AUTHOR]

One of the most important factors for increasing the durability of turbine engines is the use of turbine blades characterized by the best possible convergence of the thermophysical properties of the protective coating and the base material of the blade. The aim of the research was to evaluate the heat resistance of prototype two-layer protective coatings applied to turbine blades. The inner layer of the coating enables shaping the thermophysical convergence of the coating and the base material of the blade. The outer layer is used for thermal protection of the blade material. The inner layer was applied to the blade by plasma spraying, and the outer layer was diffusion aluminized for the first type by a non-contact gas method, for the second type by a slurry method, and for the third type, the ceramics were plasma sprayed. Turbine blades with prototype coatings were subjected to an engine test, and after the test, macro- and microstructure tests were performed. The tests showed that the prototype protective coating with an inner layer of the MCrAlY type applied to the blade by plasma spraying and an outer layer aluminized by diffusion by a non-contact gas method protects the blade material against oxidation and ensures its thermal insulation. [ABSTRACT FROM AUTHOR]

The squealer tip with rail crown holes is a novel design that offers superior overall performance, effectively enhancing tip cooling and controlling leakage flow in turbine blades. In this study, the transverse divider wall is added to the squealer cavity further to explore the potential advantages of this novel blade tip structure. This study aims to investigate the influence of the position and number of the divider walls on the blade tip performance. Numerical results show that the hindrance effect of the divider wall significantly enlarges the range of the cavity coolant, which enhances the coolant reattachment on the cavity floor and reduces the leading-edge high heat transfer coefficient (h). After cavity flow strides over the divider wall, it inclinedly impacts the rear cavity floor, forming a reattachment line (RL), which increases both the film cooling efficiency (η) and h behind the divider wall. As the divider wall shifts backward, the h near the leading-edge RL gradually increases, and the low- η region of the suction-side corner is expanded. As the divider wall number increases, the second utilization of the coolant within the cavity is improved, compared with Baseline, the η ‾ in case with three divider walls is improved by about 59.13 %. The flow structure near each divider wall is similar, simultaneously, the downstream divider wall can promote coolant attachment near the adjacent upstream divider wall. In aerodynamic aspect, the position and number of the divider walls minimally influence the total leakage flow rate (LFR), but they exert a notable effect on the LFR distribution along streamwise. In general, upstream of the divider wall, the LFR is significantly diminished, but the reduced leakage is compensated downstream of the divider wall, resulting in an overall constant total leakage. • A novel tip cooling protection scheme with rail crown holes and cavity transverse divider walls is introduced and developed. • The influence of the position and number of the divider walls on the blade tip performance is investigated. • The flow structures near the novel tip are illustrated. [ABSTRACT FROM AUTHOR]

This study addresses the diverse application requirements of turbine blades by utilizing a composite anti-seepage masking layer to protect the Ni-based superalloy from Al deposition during aluminizing. Simultaneously, the unmasked areas simulate blade airfoils for aluminized coating formation. Ethylene-based and glass-ceramic coatings were evaluated for anti-seepage effectiveness after aluminizing at 800 ∼ 1000 ℃. The results reveal that ethylene-based coatings prevent Al diffusion into the substrate at 800 ℃, and degradation occurs at higher temperatures. However, adding a glass-ceramic coating significantly enhances high-temperature stability and suppresses ethylene-based coating fluidity. The composited anti-seepage masking layer, with the ethylene-based and glass-ceramic coating applied twice, exhibits excellent anti-seepage masking performance on GH4169, DZ22B, and K477 superalloys, providing protection and easy removal without affecting unmasked areas. This approach improves the comprehensive performance of turbine blades, meeting the requirements of both dovetail and airfoil sections. [Display omitted] [ABSTRACT FROM AUTHOR]

• In this paper, an accurate point cloud reconstruction and multi-point cloud registration method based on structured light is proposed. • In this paper, the rotational measurement under the clamping state of the turbine blade is realized. • A phase-matching method based on epipolar constraint is proposed, achieving precise mapping of phase information in stereoscopic views. • An iterative closest point method with weighted mark points is proposed to optimize the stability of the ICP algorithm. In recent years, the industry has increasingly adopted vision-guided laser processing techniques to machine cooling holes in turbine blades, placing higher demands on the accuracy of visual measurement. Therefore, to meet the need for high-precision measurement of the three-dimensional shape of turbine blades in the context of laser processing of film cooling holes, this paper proposes a structured light-based method for precise reconstruction of turbine blade point clouds and multi-point cloud registration. Specifically, to improve the accuracy of point cloud reconstruction, an improved phase matching and reconstruction method based on epipolar constraints is proposed. To enhance the accuracy and stability of multi-point cloud registration, a weighted iterative closest point (ICP) method combined with a mark point registration strategy is proposed, optimizing the stability of the ICP algorithm and achieving high-quality multiple point cloud stitching. Experimental results validate the effectiveness and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

• Droplet growth period reduces by 79.4% as rotation speed rises from 10 to 40 r/min. • Droplet frozen period rises by 114.1% as rotation speed rises from 10 to 40 r/min. • Most droplets in inner region exhibit equivalent diameters ranging from 40 to 60 μm. • Rotation speed promotes frosting but adversely affects the final droplet diameter. • Frost layer surface roughness exhibits more fluctuations at lower rotation speeds. Frosting is a prevalent issue across various industries, negatively impacting the functionality of equipment operating at low surface temperatures. Despite extensive research that has been conducted on frosting, investigations specifically addressing frosting progress on rotating surfaces remain limited. Therefore, this study aims to experimentally investigate the characteristics of condensation frosting on a horizontal cold plate at varying rotation speeds. The results reveal that an increase in rotation speed promotes frosting, as evidenced by the notably reduced duration of the droplet condensation and growth (DCG) stage, which decreases from 786 to 162 s as the rotation speed increases from 10 to 40 r/min. Accordingly, the rotation speed adversely affects the average droplet diameter at the end of the DCG stage, although the droplet growth rate increases with the rotation speed. Specifically, the average equivalent droplet diameter at the end of the DCG stage in the edge region varies from 181.1 to 230.9 μm, while in the inner region, it varies from 50.4 to 76.9 μm as the rotation speed decreases from 40 to 10 r/min. Notably, the frost layer surface roughness exhibits greater fluctuations at lower rotation speeds. The results of this study are anticipated to help the understanding, prediction, and mitigation of frosting on rotating surfaces. [ABSTRACT FROM AUTHOR]

• Early and current film cooling loss models are reviewed. • Trend of future film cooling loss models are predicted. • Combination of loss analysis and algorithm optimization is evaluated. The development of turbine loss models, especially the loss models under the influence of film cooling were reviewed. From early loss models with only aerodynamic analysis to film cooling loss models, a series of experimental and numerical simulation validation, application of film cooling loss models at present were summarized and limitations of the current film cooling loss models were exposed. Development of film cooling loss models was found to have a delay in experimental application, though the mixing process had three-dimensional assumption. The feasibility of loss models needed to be improved. Some recent models with targeted optimization algorithms were gathered and analyzed. It can be predicted that the newly proposed film cooling loss model will be more closely related to optimization algorithms with more realistic assumptions and more detailed analyses. and will have more practical application value such as being able to be validated in experiments under extreme conditions. [ABSTRACT FROM AUTHOR]

To optimize the inclined rim design, multi-objective optimization was numerically conducted on the suction-side rim of the squealer tip in the GE-E3 rotor blade. The RANS equations, incorporating with the standard k-ω model, were numerically solved. Through the implementation of a Kriging surrogate model coupled with the NSGA-II evolutionary optimization technique, six geometric parameters on the suction-side rim went through iterative optimization. This process yielded three optimized squealer tip geometries on the Pareto front: Structure 1 with minimum total pressure loss, Structure 2 with optimal comprehensive aerothermal performance, and Structure 3 with minimum tip heat load. Comparative analysis revealed that with the inner and external wall inclined toward the cavity and passage respectively, the optimization results in a 3 %–11 % reduction in tip heat load, accompanied by an 8.5 %–10.2 % reduction in aerodynamic loss, facilitated by an attenuated upper passage vortex (UPV) and strengthened tip leakage vortex (TLV). The critical inclined region of the external rim wall, spanning 7 %–80 %, influences the exit total pressure loss distribution. The inclined inner wall upstream of 50 % C ax obstructs coolant jets from exiting the cavity, reducing the heat load on the cavity bottom. However, the inclined external wall from 66 % to 90 % C ax amplifies the impingement of the scraping vortex (SV), increasing local heat transfer. The thermal behavior of Structure 1 is sensitive to changes in tip clearance, whereas Structure 2 and 3 show more robust advantages. As the clearance increased, the aerodynamic losses associated with the TLV rise for all three optimized tips, but losses from the UPV remain similar. This study provides a novel approach for designing efficient squealer tip geometries incorporating an inclined rim. [ABSTRACT FROM AUTHOR]

This study examined how various plasma actuator (PA) configurations affect the passage vortex (PV) reduction in a linear turbine cascade (LTC) utilizing dielectric barrier discharge PAs. The experiments were carried out under three specific layout conditions: axial placement of the PA, slanted placement at the blade inlet, and slanted placement inside the blade. Particle image velocimetry was employed to measure the velocity distribution of the secondary flow at the LTC exit, followed by an analysis of the streamline patterns, turbulence intensity distribution, and vorticity distribution. At a Reynolds number of 3.7 × 104, the PA with an oblique orientation at the blade inlet provided the most effective PV suppression. The average value of the secondary flow velocity and the peak vorticity value at the LTC exit decreased by 59.0% and 68.8%, respectively, compared to the no-control case. Furthermore, the wind tunnel blower’s rotation speed was modified, adjustments were made to the LTC’s mainstream velocity, and the Reynolds number transitioned from 1.0 × 104 to 9.9 × 104, approximately 10 times. When the slanted PA was used at the blade inlet, the PV suppression effect was the highest. The peak vorticity value owing to the PV at the LTC exit decreased by 62.9% at the lowest Reynolds number of 1.0 × 104. The Reynolds number increased with a higher mainstream velocity and decreased flow induced by the PA, consequently reducing the PV suppression effect. However, the drive of the PA was effective even under the most severe conditions (9.9 × 104), and the peak vorticity value was reduced by 20.2%.

Rapid advances in 3D printing enable the construction of complex metal structures. However, sensor embedding within 3D printed metal structures has been challenging due to its extremely high-temperature condition. Here, we embedded an optical fibre sensor for temperature monitoring within a Ni-alloy miniature turbine blade by directed energy deposition (DED) printing. To endure the high-temperature condition, a fibre Bragg grating (FBG) sensor was electroplated with a Ni layer, and various 3D printing parameters were optimised. In particular, to minimise the accumulation of thermal energy in the FBG sensor, ‘line-by-line printing and stop’ process was applied around the sensor. The embedded sensor accurately measured temperature cycling up to 500°C with the sensitivities of 28.3 and 27.2 pm/K in heating and cooling cycles, respectively. Finally, an FBG sensor was successfully embedded in a miniature turbine blade by our DED process, demonstrating its feasibility for high-temperature monitoring.

Macroscopic examination, chemical composition analysis, metallographic structure, fracture scanning and element composition energy dispersive spectrum analysis were carried out on the cracked blade of the last stage of No.2 steam turbine unit in a thermal power plant. Results showed that the crack formation of turbine blades belonged to corrosion fatigue. The electrochemical corrosion of the blade was caused by corrosive media such as chlorine and sulfur in steam, and then intergranular stress corrosion cracking occurred under the centrifugal tensile stress, forming the crack source. Under the combined effect of corrosive medium, tensile stress and exciting force, the corrosion fatigue crack accelerated to expand and finally broke instantaneously.

In this study, the structural and thermal analysis of the final stage compressor rotor blades, which are currently used on-site, is performed by using the ANSYS program. For that reason, a 3D model of the existing compressor blade has been done. Later on, this model was transferred to the ANSYS program and analyzed. In the analysis, the parameters formed in the blade geometry were determined. By creating a design geometry with the selected parameters, the stress of the existing blade under operating conditions was examined. All external parameters in this study were taken from an F-class gas turbine operating under real field conditions. The stresses of the obtained values in different regions on the blade were examined. This study is also a reverse engineering study and the effects of real field conditions on the compressor blades have been analyzed.

The turbine blades were directionally solidified by a high-rate solidification process by the Bridgman technique using directional solidified Ni-based master superalloy DZ125 and operated on the engine bench with a high-temperature gas environment of more than 1500 °C from combustor and high-speed rotation of more than 13500 rpm for 400 h. A service-environment-based model was put forward to simulate the distribution of temperature and stress on the DZ125 blade in service. It was found that the distribution of temperature and stress on the serviced DZ125 blade was closely related to its geometric structure. The microstructural evolution of the serviced DZ125 blade was analyzed and the variations of microstructures with temperature and stress were investigated by using a scanning electron microscope. The results revealed that the evolution process of microstructures on the serviced DZ125 blade was different from that of the standard sample tested at constant temperature and uniaxial tensile stress. The reason for this discrepancy was explored using a combination of finite-element calculation and diffusion coefficient calculation.

The features of aero-engine hollow turbine blades show a complicated inner air tract, which have a significant influence on the engine's performance. Inspection of the internal structure and flaws of the blades become indispensable. Non-destructive testing, such as computed tomography (CT), is an effective method for detecting internal problems. The purpose of this study is to demonstrate how an iterative excitation can be used to recover an incomplete projection in CT for a turbine blade. Firstly, the variance of the background was gathered as previous information. Then, to make up for the missed sample at the ill-angle position, a noise map was added and filtered as prep work for the forward projection. The original projections were retained, and the revised projections were used to extract additional characteristics from the damaged data. Finally, both simulation and actual tests were studied. The Normalised Mean Square Distance (NMSD) of the reconstructed image was reduced by over 20%. The Structural Similarity Index Measure (SSIM) and the Universal Quality Index (UQI) were both enhanced by at least 60% and 41%, respectively. It was demonstrated that the technique can increase the accuracy of reconstruction for a hollow turbine blade. [ABSTRACT FROM AUTHOR]

Surface scale is usually formed in the aerofoil part of as-cast nickel-based single crystal turbine blades by the strong interaction between the mould wall and the melt, and the subsequent oxidation of the fresh metallic surface of the casting. For better understanding of the scaling, the scaled region was investigated, and an interesting region containing hafnium oxides and a rhenium-rich particle was found. Generally, a continuous aluminium oxide layer was detected on the outer surface of the base material and covered the surface of an unscaled region. In contrast, there was no oxide on the surface of a scaled region, but it was replaced by several tiny particles remaining locally on the outer surface of the base material. SEM-EDX and TEM-EDX point analysis of these particles indicated not only the existence of high amounts of hafnium, but also several particles such as hafnium oxide, aluminium oxide, and even tiny metallic particles. Most of all, STEM-EDX point analysis clearly detected zirconium in the hafnium oxide. Furthermore, a rhenium-rich particle was also detected towards the outer surface of the base material, which suggested that the surface of the scaled region might be exposed to high enough temperatures to allow the diffusion of heavy alloying elements. Based on the observation, the formation mechanism of hafnium oxide containing zirconium and its meaning was discussed. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies of a linear high-loaded turbine cascade with a dual−cavity tip structure are presented in this paper. The experimental conditions contained an increase in the outlet Mach number from 0.42 to 0.92, a change in the incidence angle from −15° to 15° and an increase in the relative clearance size from 0.36% to 1.4%. The ability of the dual−cavity tip to control leakage losses and vortices is assessed using the total pressure coefficient and the Q-criterion. This research indicates that the leakage vortex interacts strongly with the passage vortex, and the change in working conditions affects the balance between the two vortices and thus the flow field structure. The experimental and numerical results prove that the dual−cavity tip can reduce losses in all operating conditions, with the best control effect reduced by 0.025 in a large clearance size condition. In addition, the leakage control effect of the blade tip structure is more influenced by the incoming flow angle and clearance size than the Mach number. [ABSTRACT FROM AUTHOR]

A numerical turbine-blade fatigue-life analysis method is suggested. This method comprises a stationary thermal 3D finite element (FE) analysis of the hot run for the combined high-cycle fatigue (HCF) and creep analysis, and a follow-on (one-way coupled) quasi-stationary structural 3D FE analysis (including six load steps) of a single and two half turbine blades and the related disk and rotor section and a (modified Goodman equation based) post-processing fatigue life analysis for the highest HCF-loaded point of the turbine blade. For the low-cycle fatigue (LCF) analysis, this includes a transient thermal 3D FE analysis of two full loading cycles, a follow-on (one-way coupled) quasi-stationary structural 3D finite element analysis of a single and two half turbine blades and the related disk and rotor section and a (modified-Langer-equation-based) post-processing fatigue life analysis approach for the highest LCF-loaded point of the turbine blade. Finally, this approach is demonstrated by the numerical HCF, LCF and creep analysis of a generic turbine blade of the first rotor row of a full admission hydrogen turbo pump of a 1 MN thrust class gas generator LOX-LH2 liquid rocket engine (LRE). For this numerical example, the LCF loading turned out to be dominant. Creep turned out to be negligible. [ABSTRACT FROM AUTHOR]

The paper investigated numerically the heat transfer and pressure loss characteristics of the converging matrix cooling channels for turbine trailing edges with response surface method. The three selected design factors are scale factor (SF), rib inclination angle (α) and channel wedge angle (β). The discussed range for the design factors, SF, α and β, are 2.5–10; 30°–60° and 1.5°–2.5°. And the investigated Reynolds number range is from 15,000 to 40,000. The turbulence model selected was SST k - ω model. It is newly found that the heat transfer and pressure loss characteristics of the converging matrix cooling channels depend heavily on the scaling effect. The matrix cooling channels with larger scale factor generally present higher heat transfer enhancement, higher pressure loss and lower overall thermal performance. In addition, the converging matrix cooling channels with smaller rib inclination angle and larger channel wedge angle present higher heat transfer enhancement and larger pressure loss. Among all the 13 cases, Case 9 with SF = 2.5, α = 45° and β = 1.5° has the highest averaged thermal performance factor under 6 Reynolds numbers. [ABSTRACT FROM AUTHOR]

Bend-twist coupling (BTC), a method of passive load alleviation for turbine blade, has a significant influence on blade mechanical properties. The coupling behavior between bending and twisting motions stems from the material anisotropy in blade laminate or from the unique blade geometry such as sweep, deflection, and pre-bending. The material-based approach is employed in this research to determine influence regularity of BTC design on blade mechanical properties. To begin with, the blade property analysis tool PreComp that integrates a shear flow method with the classical laminate theory is adopted to compute the cross-sectional stiffnesses of the blades with different degree of BTC effect. Next, the bend-twist coupling coefficients for the BTC blades with different fiber orientation are calculated. Finally, the remaining mechanical properties including static performance, modal characteristics and buckling limits for different BTC blades are determined by the finite element method and the influence of changes in the degree of BTC effect on all these mechanical properties is further evaluated. The results show that the BTC effect markedly influences the different mechanical properties of the blade in different patterns. The 20° BTC blade has the highest BTC coefficient and the edgewise BTC coefficient at 100 m is 2.5 times higher than the flapwise BTC coefficient, while the maximum value of the torsional modal frequency of 3.8429 Hz and the greatest critical buckling load of 4328.1 kN corresponds to the 10° BTC blade and the 15° BTC blade respectively. [ABSTRACT FROM AUTHOR]

Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings (TBCs), to simplify the modeling process and improve the calculation efficiency. The results show that the virtualwall thickness method can improve themesh quality by 20%, reduce the number ofmeshes by 76.7% and save the calculation time by 35.5%, compared with the traditional real wall thickness method. The average calculation error of the two methods is between 0.21% and 0.93%. Furthermore, the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition. The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant. The thermal insulation effect of TBCs is the worst near the air film hole, and the best at the blade leading edge. According to the calculated temperature field of the substrate-coating system, the highest thermal insulation temperature of the TC layer is 172.01 K, and the thermal insulation proportions of TC, TGO and BC are 93.55%, 1.54% and 4.91%, respectively. [ABSTRACT FROM AUTHOR]

In order to enhance the cooling performance of turbine blades, novel cooling channels filled with X-shaped truss array were investigated in this study. The flow mechanism and heat transfer characteristic of the cooling channel filled with X-shaped truss array were analyzed numerically. The empirical correlations of friction coefficient and Nusselt number related to the inlet Reynolds number (10000-60000) and truss rod inclination angle (30-45°) were fitted. The results show that the secondary flow vortex in the channel and the Nusselt number on the channel wall both show periodic distributions along the streamwise direction. The row-averaged Nusselt number and friction coefficient of the channel first decrease quickly and then decrease slowly along the streamwise direction. When truss rod inclination angle increases from 30-60°, the whole-averaged Nusselt number and the whole friction coefficient of the channel increase by 25.4-52.3% and 1.19-1.33 times, respectively under different Reynolds number. The channel with truss rod inclination angle of 45° has the best comprehensive thermal performance. In all cases, the ratio of heat transfer quantity of the truss rod surface to the total heat transfer quantity of the channel ranges from 22.9-42.3%. The increase of Reynolds number improves the heat transfer quantity of the channel wall and the increase of truss rod inclination angle reduces the heat transfer quantity of the channel wall. [ABSTRACT FROM AUTHOR]

Artifacts are divergent strip artifacts or dark stripe artifacts in Industrial Computed Tomography (ICT) images due to large differences in density among the components of scanned objects, which can significantly distort the actual structure of scanned objects in ICT images. The presence of artifacts can seriously affect the practical application effectiveness of ICT in defect detection and dimensional measurement. In this paper, a series of convolution neural network models are designed and implemented based on preparing the ICT image artifact removal datasets. Our findings indicate that the RF (receptive field) and the spatial resolution of network can significantly impact the effectiveness of artifact removal. Therefore, we propose a dilated residual network for turbine blade ICT image artifact removal (DRAR), which enhances the RF of the network while maintaining spatial resolution with only a slight increase in computational load. Extensive experiments demonstrate that the DRAR achieves exceptional performance in artifact removal. [ABSTRACT FROM AUTHOR]

The present paper investigates a three‐dimensional simulation of film cooling on a C3X turbine blade with a single hole at a suction surface. The Reynolds averaged Navier–Stokes approach with k–ε realizable turbulence model and enhanced wall function are used for the numerical simulation. To simulate the jet flows, the length of the jet input approximately 4.5 times the diameter of the hole is added to the geometry so that the jet outlet flow is closer to the actual condition. The density ratio of the cooling flow to the mainstream flow is assumed about 2. The numerical results in four blowing ratios of 0.5, 0.7, 1.0, and 1.4, and at the low turbulence intensity (0.02%), and high turbulence intensity (12%) are extracted and compared for the turbine blade with a single hole. The results show that the turbulence intensity has a dual effect on the film cooling effectiveness and a higher blowing ratio increases the strength of the jet against the cross‐flow. Moreover, it is illustrated that the distribution of the film cooling effectiveness in higher blowing ratios and high turbulence intensity is more uniform than the low blowing ratios and low turbulence intensity. [ABSTRACT FROM AUTHOR]

With the increasing size of wind turbines in terms of their dimensions and capacity, structural design optimization for their blades is becoming all the more important. This study suggests an improved optimization framework. Blade optimization is performed in two stages: the ply lay-up pattern of the spar cap in the initial blade configuration based on the existing configuration, followed by the cross-sectional design optimization at several spanwise locations. The genetic algorithm is adopted and, in terms of the structural integrity evaluation, the final configuration results are found to be safe; in addition, the number of plies in the spar cap rapidly decreases through the two-stage design optimization procedure. As a result, the blade is lighter, and the lighter blade also reduces the applied load on the wind turbine. This will have an excellent effect that leads to a reduction in the weight of the entire turbine system. [ABSTRACT FROM AUTHOR]

Photovoltaics and wind power are expected to account for a large share of power generation in the carbon-neutral era. A gas turbine combined cycle (GTCC) with an industrial gas turbine as the main engine has the ability to rapidly start up and can follow up to load fluctuations to smooth out fluctuations in power generation from renewable energy sources. Simultaneously, the system must be more efficient than today's state-of-the-art GTCCs because it will use either Carbon dioxide Capture and Storage (CCS) when burning natural gas or hydrogen/ammonia as fuel, which is more expensive than natural gas. This paper describes the trend of cooled turbine rotor blades used in large industrial gas turbines that are carbon neutral. First, the evolution of cooled turbine stationary vanes and rotor blades is traced. Then, the current status of heat transfer technology, blade material technology, and thermal barrier coating technology that will lead to the realization of future ultra-high-temperature industrial gas turbines is surveyed. Based on these technologies, this paper introduces turbine vane and blade cooling technologies applicable to ultra-high-temperature industrial gas turbines for GTCC in the carbon-neutral era. [ABSTRACT FROM AUTHOR]

For currently used TiAl alloys, the impact resistance is a critically important property that determines their suitability for use, especially in settings when continuous use under harsh conditions is necessary. However, there are almost no examples of the investigation of the impact resistance of these alloys at realistic temperatures. Therefore, in this study, the impact resistance from room temperature to 1000 °C of various cast and forged TiAl alloys proposed to date or still in commercial use, as well as simple composition TiAl alloys and Inconel 713C—a commonly used material—were evaluated using the Charpy impact test, which is the simplest and most realistic way to evaluate industrial impact resistance. It was found that the TiAl alloys underwent brittle fracturing, even at high temperatures, and had significantly lower impact resistances than Inconel 713C. In addition, the impact resistances of all commercial TiAl alloys were inferior to those of the binary alloys, and those of the TiAl4822 and TNM alloy were not significantly different. Crucially, it was found that ternary alloys containing Cr or V had much better impact resistance than the commercial and binary TiAl alloys. [ABSTRACT FROM AUTHOR]

In view of the problem that the gas turbine blades rely more on the long-term test of the whole machine in the later stage to expose the insufficient design, this paper takes the gas turbine blades of an engine as an example to study the low cycle fatigue life of gas turbine blades. Firstly, the stress-strain analysis of gas turbine blade is carried out under typical cycles. It is determined that the main failure mode of gas turbine blade is low cycle fatigue failure controlled by strain fatigue. According to the principle of linear damage accumulation, the low cycle fatigue life of gas turbine blade is predicted. Then, a design method of low cycle fatigue test of turbine blade on rotating test-bed is innovatively proposed. The method uses open-loop electromagnetic induction coil to heat the blade, realizes the temperature field of gas turbine rotor with temperature gradient through heat conduction, and determines the test speed of gas turbine rotor according to the principle of strain equivalence. The test results show that the predicted service life of gas turbine blade is within 5 times of service life dispersion zone, and the crack position of component test blade is consistent with the test results of the whole machine.

The grain selector method is a prevailing technique in the manufacturing process of Ni-based single crystal superalloy, however, it cannot control the orientation of single crystal within an appropriate scope. In this study, a novel technique named substrate stimulating method was proposed and DD32 Ni-based single crystal superalloy was prepared. The microstructure evolution was characterized by EBSD and OM, and the temperature field and temperature gradient distribution were predicted by the finite volume method. With a substrate height of 18 mm, the proportion of grains with deviation angles less than 12° and 8° account for 100 % and 99 % at the entrance of spiral selector, compared with 80 % and 51 % by grain selector method, which makes significance sense for optimizing the orientation of single crystal casting and improving the yield of single crystal casting. The morphology and the orientation of the substrate stimulated grains, which are mainly determined by temperature gradient and melt undercooling, could be optimized by adjusting the substrate height and melt pouring temperature.

The quality of the blade material and specimens cast from a ZhS3DK-VI heat-resistant nickel alloy with 50% returns in the charge (after preliminary remelting), subject to hot isostatic pressing (HIP) and standard heat treatment, was evaluated. It is established that the chemical composition, macroand microstructure, mechanical and heat-resistant properties of the casting material meet the requirements of standard specifications and engineering documentation. The bending angle on the blades was found to be within 88–126° (according to the OST 1.90.126-85 requirements, it should be no less than 20°). Hot isostatic pressing of the blades at 1210°C and 160 MPa brings about the healing of microporosity and looseness that do not come out at the surface of the componenti (located in the bulk of the metal). The structure of the turbine blades after HIP is practically free of micropores, which contributes to the stabilization of the structure and properties of the material. Single micropores detected after HIP are more than 40 times smaller compared to those revealed in the cast blades before HIP. Thus, it supports the feasibility of fabricating the turbine blades with 50% returns in the charge. Hot isostatic pressing before standard heat treatment is shown to positively influence the complex of physical, mechanical, and service properties of critical cast products from heatresistant nickel alloys for aviation and power plants. [ABSTRACT FROM AUTHOR]

Although the five-axis machine tool presents excellent advantages of high-speed, -efficiency, and -precision machining of complex curved surface parts (impeller and blade), its actual motion demonstrates nonlinear principle error due to the participation of the rotating axis. Traditional methods, such as linear interpolation, rotation tool center point (RTCP), and tool point optimization, can effectively control nonlinear errors despite their limitations. A regional compensation optimization method is proposed in this study to solve nonlinear error problems effectively in five-axis machining of complex curved surface parts. First, feature points of the complex free-form surface are identified, and regions are divided to distinguish the compensation optimization algorithm of each interval. Second, JAVA language is applied to develop a special postprocessor with nonlinear error partition compensation module. Finally, the BV100 machine tool is used as the experimental platform, and a turbine blade is utilized as the specimen for simulation and cutting experiments. Results showed that the surface quality and contour accuracy of machined parts improved when the nonlinear error regional compensation optimization algorithm is used. [ABSTRACT FROM AUTHOR]

Recently, airplane travel has become more affordable and thus more common. This has required engineers and scientists to spend thousands of hours on the development of new material and production technologies. High-pressure turbine (HPT) components are the most heavily loaded parts from the thermal, mechanical, and corrosion points of view. Therefore, both the material from which blades and vanes are cast as well as protective coatings are being constantly developed. Better material translates into longer and safer engine operation. Coatings maintain material structures within aggressive environments. However, despite the wide scope of development, there are areas that have not been investigated, one of which is electro-discharge drilling (EDD) machined cooling holes surface and its influence on environmental coating durability. In this paper, the EDD process impact on coating durability is shown. Process residuals, such as redeposited material and recast layers, result in coating inclusions. Oxidation testing also shows the relationship between the cooling hole diameter and coating durability. [ABSTRACT FROM AUTHOR]

Aluminum powder, cellulose acetate, and acetone were used to have the desired coating microstructure, suitable viscosity, and good wettability. The as‐cast IN‐738 was used as the substrate. Different holes with a diameter of 1 mm were drilled. The results of scanning electron microscopy and X‐ray diffraction analyses show that a uniform aluminide coating with a thickness of about 100–120 μm covers the entire inner surface of the hole and the desired β‐NiAl phase is formed. An artificial neural network was used in MATLAB software, and according to surface drawn obtained from mathematical modeling, it was concluded that with slurry viscosity in the range of 200–250 cp and the amount of applied slurry with a value of 20–30 mg cm−2 a suitable coating can be obtained. The oxidation test at 1000°C was performed by the thermogravimetric method for 150 h and the Kp constant for aluminide coatings and uncoated superalloy are successfully calculated to be 0.0034 and 0.0086 mg2 cm−4 h, respectively. [ABSTRACT FROM AUTHOR]

The roughness of thermal barrier coatings (TBCs) prepared on the surface of aero-engine turbine blades affects the lifetime of the coating and the life cycle and aerodynamic performance of the blades. To reduce the TBC surface roughness, this study proposes a robot polishing trajectory planning method that combines reverse engineering and finite element mesh technology. First, a 3D model of the blade was reconstructed in reverse engineering by using the fast surface modeling method. Then, a dense mesh with controlled spacing was obtained by mapping the finite element mesh arbitrary quadrilateral elements on the surface of the blade model. Finally, a robot polishing path of the blade was generated by sorting the index of mesh nodes. Using this approach, polishing experiments of aero-engine turbine blades were systematically carried out, and the coordinate system conversion method from the robot off-line programming simulation environment to the actual work station was used to map the robot trajectory. Meanwhile, the point cloud registration method was introduced to improve the system calibration accuracy. The experiments showed that the technical solution proposed in this paper could reduce the overall surface roughness of the thermal barrier coating from above Ra 8 μm to about Ra 0.5 μm, which contributes to the performance improvement for the TBCs of aero-engine blades. [ABSTRACT FROM AUTHOR]

Horizontal axis wind turbines are used for energy generation at domestic as well as industrial levels. In the wind turbines, a reduction in drag force and an increase in lift force are desired to increase the energy efficiency. In this research work, computational fluid dynamics (CFD) analysis has been performed on a turbine blade's frontal section with an NACA S814 profile. The drag force has been reduced by introducing an array of dimpled structures at the blade surface. The dimpled structures generate a turbulent boundary layer flow on its surface that reduces the drag force and modifies the lift force because it has greater momentum than the laminar flow. The simulation results are verified by the experimental results performed in a wind tunnel and are in close harmony with the simulated results. For accurate results, CFD is performed on the blade's frontal section at the angle of attack (AOA) with a domain of 0° to 80° and at multiple Reynolds numbers. The local attributes, lift force, drag force and pressure coefficient are numerically computed by using the three models on Ansys fluent: the Spalart-Allmaras, the k-epsilon (RNG) and the k-omega shear stress transport (SST). [ABSTRACT FROM AUTHOR]

A technique is proposed to estimate the residual life of a high-pressure turbine blade, and it is based on taking into account the morphological state of a precipitation-hardened material. The calculation results are shown to agree well with the experimental data. [ABSTRACT FROM AUTHOR]

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Background: Using dry friction damper is a very common solution to avoid resonance in turbine blade. Dry friction dampers insert non-linearity to the vibration analysis of the blade disk. To predict nonlinear frequency response of turbine blade, accurate contact simulation is necessary. Purpose: To accurately simulation of contact force in this work, coupling between normal force and tangential displacement in nonlinear interface forces is considered. Method: For this purpose using a model that consider lift-up phenomena (coupling effect) and using experimental set-up, effect of tangential displacement on normal force variation on response of turbine blade is investigated. To solve nonlinear equation, multi-harmonic balance method along with continuation method is used. To transfer nonlinear equation, alternative time–frequency domain is used. Parameters of contact model are identified by experimental set-up that investigated coupling effect between two aluminum surfaces. With these identified parameters of the contact model, frequency response of turbine blade of two previous models of blade is investigated. Results: It is shown that considering coupling effect to predict amplitude and frequency of resonance is necessary and ignore this effect in contact force calculation which cause an error in determining parameters of dry friction damper and also its efficiency. Conclusion: Effect of lift-up phenomena that is physical properties of contact surface on frequency response function of turbine blade is investigated and is shown its effect on vibration response of turbine blade. [ABSTRACT FROM AUTHOR]

The investigation about the degradation behavior of turbine blades exposed to complex and extreme environments for long-term service is of great importance to assess the remaining life of the blades. In our work, the microstructure at different positions of the service-exposed turbine blade was characterized from the micron scale to the nanoscale. The results showed that there are noticeable differences in the microstructure at different positions of the blade and the blade has a complex service history. These conclusions suggest that the most severely damaged part of the blade should be responsible for assessing the remaining life of the blade, moreover, the mechanical properties of materials should not be limited to life at constant temperature and stress, rather non-isothermal and variable stress tests are more instructive in assessing the performance or life of aircraft engine blade materials.

This study focuses on the effects of three groove tip structures (full rib groove tip, partial rib tip on the suction side, and partial rib tip on the pressure side) on tip leakage flow, aerodynamic characteristics of a cascade, and heat transfer in a gas turbine blade. The groove’s width B = 1.6 mm, while the tip clearance is τ = 1.2 mm. Results of the flow parameters, fluid flow, and heat transfer in the recessed channel are discussed. The results show that all ribbed tips obtain more uniform outlet flow angle distribution and higher aerodynamic performance than the plane tips. The total aerodynamic pressure loss of the ribbed tips on the pressure side is the same as that of complete ribbed tips. The evolution mechanisms are different, although both can improve the turbine efficiency. Although the partial rib tip on the pressure side weakens the mixing of the channel vortex and leakage vortex near the trailing edge and has the best control effect on the leakage vortex, the lack of the suction side rib will make it easier for the low-energy fluid to flow into the gap from the front of the suction side, which is not conducive to reducing the leakage flow inside the gap; the full rib tip not only minimizes the tip relative leakage flow and leakage loss but also increases the channel vortex loss. With the complex vortex system in the groove and the rib blocking effect at the leakage outlet, the suction-side rib tip becomes the tip structure with the best leakage flow control effect under the same clearance, but the leakage vortex loss is the highest.

Multi-scale morphology observations and fatigue performance tests were carried out to study the damage evolution mechanism and fatigue performance attenuation behavior of K403 turbine blades in service. During service in field, the dendrite separation and breakage, γ' phase polymerization and rafting, MC carbide decomposition, harmful phase precipitation and grain boundary weakening are having adverse effects on the fatigue performance of turbine blades. Meanwhile, the loss of alloying elements in matrix causes the alloy matrix to soften. In addition, a large number of pores and microcracks formed in the process of service further deteriorate the service performance of turbine blades. Therefore, after long-term operations, the solid solution strengthening, precipitation strengthening, dispersion strengthening and grain boundary strengthening effects of K403 turbine blades are all weakened, which led to serious degradation of the fatigue performance of these turbine blades with the fatigue life reduced. Besides, the crack initiation source of turbine blade is gradually transformed from subsurface metallic pore initiation to carbide initiation.