Damage Analysis of Thermal Barrier Coatings Subjected to a High-Velocity Impingement of a Solid Sphere

2019 ◽  
Vol 827 ◽  
pp. 349-354
Author(s):  
Kiyohiro Ito ◽  
Fei Gao ◽  
Masayuki Arai
Keyword(s):  
Gas Turbine ◽  
Impact Velocity ◽  
Thermal Barrier Coatings ◽  
High Velocity ◽  
Turbine Blades ◽  
Interfacial Crack ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Wide Range ◽  
The Impact

A delamination of thermal barrier coatings (TBC) applied to turbine blades in gas turbine could be caused by a high-velocity impingement of various foreign objects. It is important to accurately predict the size of interfacial crack for safety operation of gas turbine. In this study, in order to establish a practical equation for prediction of the length of interfacial crack, a high velocity impingement test and a finite element analysis (FEA) based on a cohesive model were conducted. As the result, the length of interfacial crack is linearly increased with the impact velocity. In addition, it was confirmed that it was accurately estimated by the FEA. The equation for prediction of the length of interfacial crack was formulated based on these results and the energy conservation before and after impingement. Finally, the applicability of the equation was demonstrated in a wide range of impact velocity through a comparison with the experimental results.

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 Impact of Cooling with Thermal Barrier Coatings on Flow Passage in a Gas Turbine

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 85
Author(s):  
Yuanzhe Zhang ◽  
Pei Liu ◽  
Zheng Li
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Power Sources ◽  
Barrier Coatings ◽  
Flow Passage ◽  
Blade Cooling ◽  
The Impact

Inlet temperature is vital to the thermal efficiency of gas turbines, which is becoming increasingly important in the context of structural changes in power supplies with more intermittent renewable power sources. Blade cooling is a key method for gas turbines to maintain high inlet temperatures whilst also meeting material temperature limits. However, the implementation of blade cooling within a gas turbine—for instance, thermal barrier coatings (TBCs)—might also change its heat transfer characteristics and lead to challenges in calculating its internal temperature and thermal efficiency. Existing studies have mainly focused on the materials and mechanisms of TBCs and the impact of TBCs on turbine blades. However, these analyses are insufficient for measuring the overall impact of TBCs on turbines. In this study, the impact of TBC thickness on the performance of gas turbines is analyzed. An improved mathematical model for turbine flow passage is proposed, considering the impact of cooling with TBCs. This model has the function of analyzing the impact of TBCs on turbine geometry. By changing the TBCs’ thickness from 0.0005 m to 0.0013 m, its effects on turbine flow passage are quantitatively analyzed using the proposed model. The variation rules of the cooling air ratio, turbine inlet mass flow rate, and turbine flow passage structure within the range of 0.0005 m to 0.0013 m of TBC thicknesses are given.

Thermal Barrier Coating Validation Testing for Industrial Gas Turbine Combustion Hardware

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Jeffery Smith ◽  
John Scheibel ◽  
Daniel Classen ◽  
Scott Paschke ◽  
Shane Elbel ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Turbine Blades ◽  
Current Status ◽  
Thermal Barrier ◽  
Engine Fuel ◽  
Coating System ◽  
Barrier Coatings ◽  
Sintering Resistance

As gas turbine (GT) temperatures have increased, thermal barrier coatings (TBCs) have become a critically important element in hot section component durability. Ceramic TBCs permit significantly increased gas temperatures, reduced cooling requirements, and improve engine fuel efficiency and reliability. TBCs are in use throughout the GT hot section with turbine blades, vanes, and combustion hardware, now being designed with TBCs or upgraded with TBCs during component refurbishment (Miller, 1987, “Current Status of Thermal Barrier Coatings,” Surf. Coat. Technol., 30(1), pp. 1–11; Clarke et al., 2012, “Thermal-Barrier Coatings for More Efficient Gas-Turbine Engines,” MRS Bull., 37(10), pp. 891–898). While the industry standard 6–9 wt. % yttria stabilized zirconia (7YSZ) has been the preferred ceramic composition for the past 30+ yr, efforts have been underway to develop improved TBCs (Stecura, 1986, “Optimization of the Ni–Cr–Al–Y/ZrO2–Y2O3 Thermal Barrier System,” Adv. Ceram. Mater., 1(1), pp. 68–76; Stecura, 1986, “Optimization of the Ni–Cr–Al–Y/ZrO2–Y2O3 Thermal Barrier System,” NASA Technical Memorandum No. 86905). The principal development goals have been to lower thermal conductivity, increase the sintering resistance, and have a more stable crystalline phase structure allowing to use above 1200 °C (2192 °F) (Levi, 2004, “Emerging Materials and Processes for Thermal Barrier Systems,” Curr. Opin. Solid State Mater. Sci., 8(1), pp. 77–91; Clarke, 2003, “Materials Selection Guidelines for Low Thermal Conductivity Thermal Barrier Coatings,” Surf. Coat. Technol., 163–164, pp. 67–74). National Aeronautics and Space Administration (NASA) has developed a series of advanced low conductivity, phase stable and sinter resistant TBC coatings utilizing multiple rare earth dopant oxides (Zhu and Miller, 2004, “Low Conductivity and Sintering-Resistant Thermal Barrier Coatings,” U.S. Patent No. 6,812,176 B1). One of the coating systems NASA developed is based on Ytterbia, Gadolinia, and Yttria additions to ZrO2 (YbGd-YSZ). This advanced low conductivity (low k) TBC is designed specifically for combustion hardware applications. In addition to lower thermal conductivity than 7YSZ, it has demonstrated thermal stability and sintering resistance to 1650 °C (3000 °F). The Electric Power Research Institute (EPRI) and cincinnati thermal spray (CTS) have teamed together in a joint program to commercialize the YbGd-YSZ TBC coating system for GT combustion hardware. The program consists of validation of coating properties, establishment of production coating specifications, and demonstration of coating performance through component engine testing of the YbGd-YSZ TBC coating system. Among the critical to quality coating characteristics that have been established are (a) coating microstructure, (b) TBC tensile bond strength, (c) erosion resistance, (d) thermal conductivity and sintering resistance, and (e) thermal cycle performance. This paper will discuss the coating property validation results comparing the YbGd-YSZ TBC to baseline production combustor coatings and the status of coating commercialization efforts currently underway.

Development of Nondestructive Testing Method for Examining Thermal Resistance of Thermal Barrier Coatings on Gas Turbine Blades

2013 ◽  
Author(s):  
Takayuki Ozeki ◽  
Tomoharu Fujii ◽  
Eiji Sakai ◽  
Tetsuo Fukuchi ◽  
Norikazu Fuse
Keyword(s):  
Thermal Resistance ◽  
Surface Temperature ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Laser Heating ◽  
Turbine Blades ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Gas Turbine Blades ◽  
Hot Gas

In order to improve the efficiency of electric power generation with gas turbines, the turbine inlet gas temperature needs to be increased. Hence, it is necessary to apply thermal barrier coatings (TBCs) to various hot gas path components. Although TBCs protect the substrate of hot gas path components from high-temperature gas, their thermal resistance degrades over time because of erosion and sintering of the topcoat. When the thermal resistance of TBCs degrades, the surface temperature of the substrate becomes higher, and this temperature increase affects the durability of the hot gas path components. Therefore, to understand the performance of serviced TBCs, the thermal resistance of TBCs needs to be examined by the nondestructive testing (NDT) method. This method has already been reported for TBCs applied to a combustion liner. However, recently, TBCs have been applied to gas turbine blades that have complex three-dimensional shapes, and therefore, an NDT method for examining the thermal resistance of TBCs on blades was developed. This method is based on active thermography using carbon dioxide laser heating and surface temperature measurement of the topcoat by using an infrared camera. The thermal resistance of TBCs is calculated from the topcoat surface temperature when the laser beam heats the surface. In this study, the developed method was applied to a cylindrical TBC sample that simulated curvature on the suction side of a blade, and the results showed the appropriate laser heating condition for this method. Under the appropriate condition, this method could also examine the thermal resistance of TBCs present at 70% of the height of the blade. With these results, this method could determine the thermal resistance within an error range of 4%, as compared to destructive testing.

scholarly journals Deposition and Testing of Thermal Barrier Coatings on Gas Turbine Vanes

1999 ◽  
Author(s):  
M. Tului ◽  
G. C. Gualco ◽  
R. Scarpellini
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Gas Flow ◽  
Turbine Blades ◽  
Thick Layer ◽  
Optical Pyrometer ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Gas Turbine Blades ◽  
Innovative Methodology

An innovative methodology to deposit, by plasma spraying, ceramic thermal barrier coatings on gas turbine blades and vanes was developed. Such a methodology produces a pattern of microcracks in the coating, thus improving its thermal shock resistance. After a laboratory campaign of process optimization and coating characterization, real components were coated with a 150 μm thick layer of NiCoCrAlY as a bond coat and a 300 μm thick layer of ZrO2, partially stabilised with 8%of Y2O3, as a top coat. In particular, four vanes, taken from the first stage of a land based gas turbine (V64.3, produced by Ansaldo), were coated on the whole airfoil. The four vanes were submitted to a cyclic oxidation test in a burner rig simulating the operative conditions of a gas turbine. In particular, they were exposed to a gas flow with the same composition, temperature and speed of the inlet gas of a real gas turbine; moreover, they were cooled by an internal stream of compressed air for obtaining the same temperature profile of a vane in operation. The surface temperature of the vanes was monitored during the test by an optical pyrometer and the internal temperature by a thermocouple. After 550 hours of test, corresponding to 550 cycles, the four vanes did not show any sign of damage.

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