Blockage Effects From Simulated Thermal Barrier Coatings for Cylindrical and Shaped Cooling Holes

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Christopher A. Whitfield ◽  
Robert P. Schroeder ◽  
Karen A. Thole ◽  
Scott D. Lewis
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Flux Ratio ◽  
Thermal Barrier ◽  
Flow Area ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Cooling Hole

Film cooling and sprayed thermal barrier coatings (TBCs) protect gas turbine components from the hot combustion gas temperatures. As gas turbine designers pursue higher turbine inlet temperatures, film cooling and TBCs are critical in protecting the durability of turbomachinery hardware. One obstacle to the synergy of these technologies is that TBC coatings can block cooling holes when applied to the components, causing a decrease in the film cooling flow area thereby reducing coolant flow for a given pressure ratio (PR). In this study, the effect of TBC blockages was simulated on film cooling holes for widely spaced cylindrical and shaped holes. At low blowing ratios for shaped holes, the blockages were found to have very little effect on adiabatic effectiveness. At high blowing ratios, the area-averaged effectiveness of shaped and cylindrical holes decreased as much as 75% from blockage. The decrease in area-averaged effectiveness was found to scale best with the effective momentum flux ratio of the jet exiting the film cooling hole for the shaped holes.

Blockage Effects From Simulated Thermal Barrier Coatings for Cylindrical and Shaped Cooling Holes

2014 ◽  
Author(s):  
Christopher A. Whitfield ◽  
Robert P. Schroeder ◽  
Karen A. Thole ◽  
Scott D. Lewis
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Flux Ratio ◽  
Thermal Barrier ◽  
Flow Area ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Cooling Hole

Film cooling and sprayed thermal barrier coatings (TBCs) protect gas turbine components from the hot combustion gas temperatures. As gas turbine designers pursue higher turbine inlet temperatures, film cooling and thermal barrier coatings are critical in protecting the durability of turbomachinery hardware. One obstacle to the synergy of these technologies is that TBC coatings can block cooling holes when applied to the components, causing a decrease in the film cooling flow area thereby reducing coolant flow for a given pressure ratio. In this study the effect of TBC blockages was simulated on film cooling holes for widely spaced cylindrical and shaped holes. At low blowing ratios for shaped holes the blockages were found to have very little effect on adiabatic effectiveness. At high blowing ratios, the area-averaged effectiveness of shaped and cylindrical holes decreased as much as 75% from blockage. The decrease in area-averaged effectiveness was found to scale best with the effective momentum flux ratio of the jet exiting the film cooling hole for the shaped holes.

Finite Element Analysis of Thermal-Mechanical Behavior in the Thermal Barrier Coatings With Cooling Hole Structure

2017 ◽  
Author(s):  
Jishen Jiang ◽  
Zhenwei Cai ◽  
Weizhe Wang ◽  
Yingzheng Liu
Keyword(s):  
Mechanical Behavior ◽  
Thermal Barrier Coatings ◽  
Film Cooling ◽  
Operating Conditions ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Adiabatic Wall ◽  
Element Analysis ◽  
Barrier Coatings ◽  
Cooling Hole

The present work aims to investigate the thermal-mechanical behavior in thermal barrier coatings (TBCs) with a round film cooling hole under gas turbine operating conditions. The adiabatic wall temperatures and surface heat transfer coefficients are firstly calculated for thermal boundary conditions. Subsequently, stress analyses during both thermal exposure and cooling down period are presented. The results show that: although the cooling hole has lower temperature, large stress concentration still appears because of the geometry of cooling holes and thermal mismatch between TBCs and substrate. The huge thermal stress may lead to pre-mature failure of TBCs, which should be carefully considered in the design of film cooling-TBC system.

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.

Effect of Pre-Oxidation Treatment on the Thermal Shock Resistance of Thermal Barrier Coatings in a Combustion Gas Environment

2010 ◽  
Vol 654-656 ◽  
pp. 1924-1927 ◽  
Author(s):  
Hui Mei ◽  
Lai Fei Cheng ◽  
Ya Nan Liu ◽  
Li Tong Zhang
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Thermal Shock Resistance ◽  
High Speed ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Oxidation Treatment ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Shock Resistance

Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The TBC coating comprised of 92 wt.% ZrO2 and 8 wt.% Y2O3 (YSZ), CoNiCrAlY bond coat, and MarM247 nickel base super alloy. After APS of YSZ two batches of TBC specimens were tested, one batch of which was pre-oxidised in air for 10h at 1080 oC. Both types of the specimens were directly pushed into a combustion gas at 1150 oC for 25 min and then out to the natural air for quenching. The combustion gas was produced by burning jet fuel with high speed air in a high temperature wind tunnel, which simulates the real service conditions in an aeroengine. Results show that TBCs prepared by the APS had good thermal shock resistance in the combustion gas. The pre-oxidation treatment of the TBC had a significant effect on its thermal shock life. The as-oxidised TBCs always had worse thermal shock resistance than the as-sprayed ones after thermal shock cycles.

Field Evaluation of 2CaO-SiO2-CaO-ZrO2 Thermal Barrier Coating on Gas Turbine Vanes

1997 ◽  
Author(s):  
N. Mifune ◽  
Y. Harada ◽  
H. Taira ◽  
S. Mishima
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coating ◽  
Thermal Barrier Coatings ◽  
Field Evaluation ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Thermal Change ◽  
Barrier Coating ◽  
Turbine Vanes ◽  
Higher Temperature

Abstract Higher-temperature operation in a gas turbine has urged development of heat-resistant coatings and thermal barrier coatings. We have developed a 2CaO-SiO2-CaO-ZrO2 based thermal barrier coating. This coating should effectively prevent separation of the coating by relieving the shear stress generated due to thermal change of environment between layers with dissimilar properties. The coating was applied to stationary vanes of an actual gas turbine in a 25,000-hour test. This paper describes the results of the field test.

Determination of the Structure and Chemistry of Thermally Grown Oxides in Thermal Barrier Coatings

1999 ◽  
Vol 5 (S2) ◽  
pp. 854-855
Author(s):  
M.R. Brickey ◽  
J.L. Lee
Keyword(s):  
Thermal Barrier Coatings ◽  
Nickel Aluminide ◽  
Physical Vapor Deposition ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Engine Operation ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Thermally Grown

Thermal barrier coatings (TBCs) insulate gas turbine hot section components from the hot (∽1200 - 1450°C) combustion gas exhaust stream. An airline company can save millions of dollars per year by using TBCs to protect vital engine components and to improve fuel efficiency. TBCs typically consist of an 8 wt.% yttria-partially-stabilized zirconia (YPSZ) ceramic topcoat deposited on a platinum-nickel-aluminide (Pt-Ni-Al) bondcoat covering a nickel-based superalloy substrate. Thermal exposure during YPSZ electron beam-physical vapor deposition (EB-PVD) and engine operation promotes the formation of a thermally grown oxide (TGO) between the Pt-Ni-Al and the YPSZ layers. Stresses can develop at the Pt-Ni-Al/TGO and TGO/YPSZ interfaces due to TGO growth and thermal expansion coefficient mismatch. These stresses eventually cause spallation of the YPSZ, leaving the metallic substrate vulnerable to high temperature degradation since exhaust temperatures are often higher than the melting temperature of most nickel-based superalloys (∽1200 - 1450°C).

scholarly journals Thermal-barrier coatings for more efficient gas-turbine engines

MRS Bulletin ◽  
2012 ◽  
Vol 37 (10) ◽  
pp. 891-898 ◽  
Author(s):  
David R. Clarke ◽  
Matthias Oechsner ◽  
Nitin P. Padture
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Turbine Engines ◽  
Thermal Barrier ◽  
Gas Turbine Engines ◽  
Barrier Coatings ◽  
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