scholarly journals Strain Localizations in Notches for a Coarse-Grained Ni-Based Superalloy: Simulations and Experiments

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 564
Author(s):  
Francesco Sausto ◽  
Luca Patriarca ◽  
Stefano Foletti ◽  
Stefano Beretta ◽  
Erica Vacchieri
Keyword(s):  
Turbine Blades ◽  
Temperature Gradients ◽  
Coarse Grained ◽  
Fatigue Properties ◽  
Large Scatter ◽  
Strain Measurements ◽  
Crystal Plasticity Finite Element ◽  
Component Design ◽  
Concentration Factors ◽  
Cooling Air

Alloys used for turbine blades have to safely sustain severe thermomechanical loadings during service such as, for example, centrifugal loadings, creep and high temperature gradients. For these applications, cast Ni-based superalloys characterized by a coarse-grained microstructure are widely adopted. This microstructure dictates a strong anisotropic mechanical behaviour and, concurrently, a large scatter in the fatigue properties is observed. In this work, Crystal Plasticity Finite Element (CPFE) simulations and strain measurements performed by means of Digital Image Correlations (DIC) were adopted to study the variability introduced by the coarse-grained microstructure. In particular, the CPFE simulations were calibrated and used to simulate the effect of the grain cluster orientations in proximity to notches, which reproduce the cooling air ducts of the turbine blades. The numerical simulations were experimentally validated by the DIC measurements. This study aims to predict the statistical variability of the strain concentration factors and support component design.

scholarly journals Analysis of the energetic/environmental performances of gas turbine plant: Effect of thermal barrier coatings and mass of cooling air

2009 ◽  
Vol 13 (1) ◽  
pp. 147-164 ◽  
Author(s):  
Ion Ion ◽  
Anibal Portinha ◽  
Jorge Martins ◽  
Vasco Teixeira ◽  
Joaquim Carneiro
Keyword(s):  
Thermal Conductivity ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Turbine Blades ◽  
Heat Transfer Analysis ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Barrier Coatings ◽  
Cooling Air Flow ◽  
Cooling Air

Zirconia stabilized with 8 wt.% Y2O3 is the most common material to be applied in thermal barrier coatings owing to its excellent properties: low thermal conductivity, high toughness and thermal expansion coefficient as ceramic material. Calculation has been made to evaluate the gains of thermal barrier coatings applied on gas turbine blades. The study considers a top ceramic coating Zirconia stabilized with 8 wt.% Y2O3 on a NiCoCrAlY bond coat and Inconel 738LC as substrate. For different thickness and different cooling air flow rates, a thermodynamic analysis has been performed and pollutants emissions (CO, NOx) have been estimated to analyze the effect of rising the gas inlet temperature. The effect of thickness and thermal conductivity of top coating and the mass flow rate of cooling air have been analyzed. The model for heat transfer analysis gives the temperature reduction through the wall blade for the considered conditions and the results presented in this contribution are restricted to a two considered limits: (1) maximum allowable temperature for top layer (1200?C) and (2) for blade material (1000?C). The model can be used to analyze other materials that support higher temperatures helping in the development of new materials for thermal barrier coatings.

scholarly journals Effect of machine hammer peening on the surface integrity of a ZnAl-based corrosion protective coating

2020 ◽  
Vol 318 ◽  
pp. 01008
Author(s):  
Alina Timmermann ◽  
Mohamed Abdulgader ◽  
Leif Hagen ◽  
Alexander Koch ◽  
Philipp Wittke ◽  
...  
Keyword(s):  
Corrosion Fatigue ◽  
Surface Integrity ◽  
Protective Coatings ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Fatigue Properties ◽  
Machine Hammer Peening ◽  
Coated Surfaces ◽  
Thermally Sprayed ◽  
Hammer Peening

Thermally sprayed protective coatings are applied onto many mechanically stressed components such as support structures, shafts, turbine blades or heat exchangers. In addition to the static or cyclic load, a superimposition with corrosion processes occurs in many cases. Thermal sprayed ZnAl coatings are known for their performant corrosion protection properties. Within this context, the potential of ZnAl-based layer systems was analyzed regarding corrosion fatigue behavior. Therefore, a timeand cost-efficient testing strategy based on a corrosion-superimposed load increase procedure was used to estimate the effects of a corrosive attack during cyclic loading. The investigated coating systems were thermally sprayed and partially post-processed with a Machine Hammer Peening (MHP) operation. This treatment was identified as an appropriate technique for compressing and smoothing coated surfaces. The inter-relationships between the parametrization of the MHP process, the resulting surface integrity, and the estimated corrosion fatigue properties were analyzed. The investigations indicate a positive effect of MHP post-processing operations on the surface properties of the ZnAl-based coating system.

Pulsed Impingement Turbine Cooling and its Effect on the Efficiency of Gas Turbines With Pressure Gain Combustion

2020 ◽  
Author(s):  
Nicolai Neumann ◽  
Dieter Peitsch ◽  
Arne Berthold ◽  
Frank Haucke ◽  
Panagiotis Stathopoulos
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Impingement Cooling ◽  
Turbine Cooling ◽  
Pressure Gain Combustion ◽  
Cooling Air ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Abstract Performance improvements of conventional gas turbines are becoming increasingly difficult and costly to achieve. Pressure Gain Combustion (PGC) has emerged as a promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine cycle. Previous cycle analyses considering turbine cooling methods have shown that the application of pressure gain combustion may require more turbine cooling air. This has a direct impact on the cycle efficiency and reduces the possible efficiency gain that can potentially be harvested from the new combustion technology. Novel cooling techniques could unlock an existing potential for a further increase in efficiency. Such a novel turbine cooling approach is the application of pulsed impingement jets inside the turbine blades. In the first part of this paper, results of pulsed impingement cooling experiments on a curved plate are presented. The potential of this novel cooling approach to increase the convective heat transfer in the inner side of turbine blades is quantified. The second part of this paper presents a gas turbine cycle analysis where the improved cooling approach is incorporated in the cooling air calculation. The effect of pulsed impingement cooling on the overall cycle efficiency is shown for both Joule and PGC cycles. In contrast to the authors’ anticipation, the results suggest that for relevant thermodynamic cycles pulsed impingement cooling increases the thermal efficiency of Joule cycles more significantly than it does in the case of PGC cycles. Thermal efficiency improvements of 1.0 p.p. for pure convective cooling and 0.5 p.p. for combined convective and film with TBC are observed for Joule cycles. But just up to 0.5 p.p. for pure convective cooling and 0.3 p.p. for combined convective and film cooling with TBC are recorded for PGC cycles.

scholarly journals Three-dimensional optimal design of a cooled turbine considering the coolant-requirement change

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 768-778
Author(s):  
Wei Ba ◽  
Ziyuan Wang ◽  
Xuesong Li ◽  
Chunwei Gu
Keyword(s):  
Optimal Design ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Pressure Surface ◽  
Component Efficiency ◽  
Requirement Change ◽  
Cooling Air ◽  
Gas Turbine Cycle

Abstract Cooling technology is widely applied in modern turbines to protect the turbine blades, and extracting high-pressure cooling air from a compressor exerts a remarkable influence on the gas-turbine performance. However, the three-dimensional optimal design of a turbine in modern industrial practice is usually carried out by pursuing high component efficiency without considering possible changes in coolant requirement; hence, it may not exactly lead to improvement in the gas-turbine cycle efficiency. In this study, the turbine stator was twisted and leaned to achieve higher comprehensive efficiency, which is the cycle-based efficiency definition for a cooled turbine that considers both turbine aerodynamic performance and coolant requirement. First, the influence of twist and compound lean on turbine aerodynamic performance, considering stator-hub leakage, was investigated. Then, a method to predict the coolant requirement for turbines with different stator designs was applied, to evaluate coolant-requirement change at the design condition. The optimized turbines were finally compared to demonstrate the necessity of considering the coolant-requirement change in the optimal design. This indicated that proper twisting to open the throat area in the stator hub and compound lean to the pressure surface side could help improve the cooled-turbine comprehensive efficiency.

Part II. Research on the Performance of a Type of Internally Air-cooled Turbine Blade

1953 ◽  
Vol 167 (1) ◽  
pp. 351-370 ◽  
Author(s):  
D. G. Ainley
Keyword(s):  
Gas Flow ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Small Diameter ◽  
Rotor Blades ◽  
Air Cooling ◽  
Gas Temperature ◽  
Flow Through ◽  
Cooling Air ◽  
Practical Feasibility

A comprehensive series of tests have been made on an experimental single-stage turbine to determine the cooling characteristics and the overall stage performance of a set of air-cooled turbine blades. These blades, which are described fully in Part I of this paper had, internally, a multiplicity of passages of small diameter along which cool air was passed through the whole length of the blade. Analysis of the, test data indicated that, when a quantity of cooling air amounting to 2 per cent, by weight, of the total gas-flow through the turbine is fed to the row of rotor blades, an increase in gas temperature of about 270 deg. C. (518 deg. F.) should be permissible above the maximum allowable value for a row of uncooled blades made from the same material. The degree of cooling achieved throughout each blade was far from uniform and large thermal stresses must result. It appears, however, that the consequences of this are not highly detrimental to the performance of the present type of blading, it being demonstrated that the main effect of the induced thermal stress is apparently to transfer the major tensile stresses to the cooler (and hence stronger) regions of the blade. The results obtained from the present investigations do not represent a limit to the potentialities of internal air-cooling, but form merely a first exploratory step. At the same time the practical feasibility of air cooling is made apparent, and advances up to the present are undoubtedly encouraging.

Fatigue properties of a glass-fibre-reinforced polyester material used in wind turbine blades

1998 ◽  
Vol 33 (3) ◽  
pp. 183-193
Author(s):  
J Vázquez ◽  
A Silvera ◽  
F Arias ◽  
E Soria
Keyword(s):  
Wind Turbine ◽  
Fatigue Limit ◽  
Glass Fibre ◽  
Moisture Absorption ◽  
Turbine Blades ◽  
Fatigue Properties ◽  
Dynamic Tests ◽  
Wind Turbine Blades ◽  
Static Tests ◽  
Glass Fibre Reinforced

Glass-fibre-reinforced polyester (GFRP) is a composite commonly used in the manufacture of wind turbine blades. In the present work, one such material has been subject to static and dynamic tests in order to obtain data that can be applied to the design of wind turbine blades and other machine elements. The results of the static tests established a basis for the determination of a set of tension-tension (constant amplitude and sinusoidal load) dynamic tests with the aim of establishing a mathematical model in order to predict life as a function of the load state and calculate the fatigue limit. The multiplicative model (y = axb) for y = log of life and x = transformed stress (a and b are characteristic parameters of the material obtained from data) matches the data quite well. The conclusion is that the GFRP studied has no fatigue limit. The possible decrease of fatigue strength of the material with solar radiation and moisture absorption was also investigated, with a negative result.

Magnetron Sputtered Intermetallic Al2Au and Al-Zr-Y Coatings for the Oxidation Protection of γ-TiAl

2006 ◽  
Vol 980 ◽  
Author(s):  
Martin Moser ◽  
Paul Heinz Mayrhofer ◽  
Reinhold Braun
Keyword(s):  
Elevated Temperatures ◽  
Turbine Blades ◽  
Mass Gain ◽  
Coarse Grained ◽  
Dual Phase ◽  
Scanning Calorimetry ◽  
Protective Oxide ◽  
Oxidation Protection ◽  
Good Oxidation Resistance ◽  
Phase Intermetallic

AbstractAl-based intermetallic coatings are widely used as bond coats and for oxidation protection of turbine blades and engine components. Here we present and discuss the structural and thermal properties of novel unbalanced-magnetron sputtered Al-based coatings (single-phase intermetallic Al2Au, binary Al-Zr, and nano-structured Al-Zr-Y) developed to protect gamma-TiAl from environmental attack at elevated temperatures. Al-Zr films exhibit a coarse-grained dual-phase Al3Zr2-Al2Zr structure and are nano-structured by alloying with ~5, 10, and 14 at% Y.Combined dynamic differential-scanning calorimetry and thermogravimetric analyses up to a temperature of 1150 °C reveal that the Al2Au film is very stable with only marginal mass gain from oxidation found between 800 and 1000 °C. High temperature X-ray diffraction shows that this coating retains its (311) texture up to 900 °C where Al2O3 formation leads to the depletion of Al in Al2Au and subsequently the precipitation of intermetallic AlAu. When gamma-TiAl is coated with Al2Au and exposed to cyclic oxidation tests at 750 and 850 °C good oxidation resistance is obtained as a protective oxide layer is formed.Dual-phase Al3Zr2-Al2Zr coatings form ZrO2 and Al2O3 in oxidizing atmosphere. However, the phase transition from monoclinic (m-)ZrO2 to tetragonal (t-)ZrO2 with the accompanying volume change causes flaking of the oxide. Yttrium addition to the Al-Zr films stabilizes the cubic (c-) and t-ZrO2 and hence avoids the fatal tetragonal-monocline transformation. The thermally grown c-ZrO2 based oxides allow good adhesion to thermal barrier coatings which are themselves based on c-ZrO2.

Effect of Film-Cooling Hole Location on Turbulator Heat Transfer Enhancement in Turbine Blade Internal Air-Cooling Circuits

1999 ◽  
Author(s):  
J. M. McDonough ◽  
V. E. Garzón ◽  
D. E. Schulte
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
High Performance ◽  
Turbulence Modeling ◽  
Pressure Coefficient ◽  
Turbine Blades ◽  
Air Cooling ◽  
Eddy Simulation ◽  
Cooling Hole ◽  
Cooling Air

Numerical results demonstrating the effect of film-cooling hole placement on turbulator heat transfer effectiveness in internal convective cooling air circuits of turbine blades in high-performance gas turbine engines is presented for a two-dimensional model problem. Of particular interest will be the performance of a new turbulence modeling formalism similar to large-eddy simulation (LES) but employing subgrid-scale models constructed from nonlinear discrete dynamical systems, and not requiring filtering of the resolved-scale governing equations. Computed results for temperature distribution, flow streamlines, pressure coefficient and heat transfer Stanton number are compared for three different cooling hole/turbulator configurations, and turbulence kinetic energy is compared with results from a standard k-ε model.

Adiabatic Effectiveness Measurements and Predictions of Leakage Flows Along a Blade Endwall

2005 ◽  
Vol 127 (3) ◽  
pp. 609-618 ◽  
Author(s):  
W. W. Ranson ◽  
K. A. Thole ◽  
F. J. Cunha
Keyword(s):  
High Pressure ◽  
Turbine Blades ◽  
Leakage Flow ◽  
Leakage Flows ◽  
High Pressure Compressor ◽  
Flow Through ◽  
Cooling Air ◽  
Low Speed Wind Tunnel ◽  
Paper Address ◽  
Good Agreement

Traditional cooling schemes have been developed to cool turbine blades using high-pressure compressor air that bypasses the combustor. This high-pressure forces cooling air into the hot main gas path through seal slots. While parasitic leakages can provide a cooling benefit, they also represent aerodynamic losses. The results from the combined experimental and computational studies reported in this paper address the cooling benefit from leakage flows that occur along the platform of a first stage turbine blade. A scaled-up, blade geometry with an upstream slot, a mid-passage slot, and a downstream slot was tested in a linear cascade placed in a low-speed wind tunnel. Results show that the leakage flow through the mid-passage gap provides only a small cooling benefit to the platform. There is little to no benefit to the blade platform that results by increasing the coolant flow through the mid-passage gap. Unlike the mid-passage gap, leakage flow from the upstream slot provides good cooling to the platform surface, particularly in certain regions of the platform. Relatively good agreement was observed between the computational and experimental results, although computations overpredicted the cooling.

Low Cycle Fatigue and Fracture Behavior of Nickel-Base Superalloy CM247LC at 760°C

2004 ◽  
Vol 449-452 ◽  
pp. 561-564 ◽  
Author(s):  
Seong Moon Seo ◽  
In Sup Kim ◽  
Chang Yong Jo
Keyword(s):  
Fatigue Crack ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Strain Range ◽  
Initiation Site ◽  
Coarse Grained ◽  
Fatigue Properties ◽  
Nickel Base Superalloy ◽  
Cycle Fatigue ◽  
Fine Grained

Low cycle fatigue (LCF) behavior of coarse and fine grained superalloy CM247LC at 760°C has been investigated. Both coarse and fine grained CM247LC showed similar cyclic stress response, however, the fine grained CM247LC specimen exhibited relatively uniform and superior fatigue properties to the coarse grained one. It was found that fatigue crack initiation of the alloy was keen to the applied strain range. Fatigue crack initiated at the surface of the specimen with high strain range (∆εt≥( 0.7%) while the initiation site moved to the internal defects at low strain range (∆εt≤0.6%).

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