Realistic Trench Film Cooling With a Thermal Barrier Coating and Deposition

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
David A. Kistenmacher ◽  
F. Todd Davidson ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Barrier Coating ◽  
Turbine Vane ◽  
Thermally Conducting

Thermal barrier coatings (TBC) see extensive use in high-temperature gas turbines. However, little work has been done to experimentally characterize the combination of TBC and film cooling. The purpose of this study is to investigate the cooling performance of a thermally conducting turbine vane with a realistic film-cooling trench geometry embedded in TBC. Additionally, the effect of contaminant deposition on the realistic trench was studied. The trench is termed realistic because it takes into account probable manufacturing limitations. The vane model and TBC used for this study were designed to match the thermal behavior of an actual gas turbine vane with TBC by properly scaling their convective heat-transfer coefficients, thermal conductivities, and characteristic length scales. This study built upon previously published results with various film-cooling geometries consisting of round holes, craters, an ideal trench, and a novel trench. The previous study showed that large changes in blowing ratio resulted in negligible effects on cooling performance. Changes to film-cooling geometry also resulted in minor effects on cooling performance. This study found that the realistic trench and an idealized trench perform similarly. However, the width of the realistic trench left the vane wall more exposed to mainstream temperatures, especially at lower film-coolant flow rates. This study also found that the trench designs helped to mitigate deposition formation better than round holes; however, the realistic trench was more prone to deposition within the trench. The overall cooling effectiveness was similar for both trench designs and relatively unchanged from the predeposition performance, while the overall cooling effectiveness for round holes increased due to the additional thermal insulation offered by the unmitigated deposition.

Realistic Trench Film Cooling With a Thermal Barrier Coating and Deposition

2013 ◽  
Author(s):  
David A. Kistenmacher ◽  
F. Todd Davidson ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Barrier Coating ◽  
Turbine Vane ◽  
Thermally Conducting

Thermal barrier coatings (TBC’s) see extensive use in high temperature gas turbines. However, little work has been done to experimentally characterize the combination of TBC and film cooling. The purpose of this study is to investigate the cooling performance of a thermally conducting turbine vane with a realistic film cooling trench geometry embedded in TBC. Additionally, the effect of contaminant deposition on the realistic trench was studied. The trench is termed realistic because it takes into account probable manufacturing limitations. The vane model and TBC used for this study were designed to match the thermal behavior of an actual gas turbine vane with TBC by properly scaling their convective heat transfer coefficients, thermal conductivities, and characteristic length scales. This study built upon previously published results with various film cooling geometries consisting of round holes, craters, an ideal trench, and a novel trench. The previous study showed that large changes in blowing ratio resulted in negligible effects on cooling performance. Changes to film cooling geometry also resulted in minor effects on cooling performance. This study found that the realistic trench and an idealized trench perform similarly. However, the width of the realistic trench left the vane wall more exposed to mainstream temperatures, especially at lower film coolant flow rates. This study also found that the trench designs helped to mitigate deposition formation better than round holes; however, the realistic trench was more prone to deposition within the trench. The overall cooling effectiveness was similar for both trench designs and relatively unchanged from the pre-deposition performance while the overall cooling effectiveness for round holes increased due to the additional thermal insulation offered by the unmitigated deposition.

A Study of Deposition on a Turbine Vane With a Thermal Barrier Coating and Various Film Cooling Geometries

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
F. Todd Davidson ◽  
David A. Kistenmacher ◽  
David G. Bogard
Keyword(s):  
Thermal Barrier Coating ◽  
Film Cooling ◽  
Stokes Number ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Barrier Coating ◽  
Turbine Vane ◽  
Engine Components

Recent interest has been shown in using synthetic gaseous (syngas) fuels to power gas turbine engines. An important issue concerning these fuels is the potential for increased contaminant deposition that can inhibit cooling designs and expedite the material degradation of vital turbine components. The purpose of this study was to provide a detailed understanding of how contaminants deposit on the surface of a turbine vane with a thermal barrier coating (TBC). The vane model used in this study was designed to match the thermal behavior of real engine components by properly scaling the convective heat transfer coefficients as well as the thermal conductivity of the vane wall. Four different film cooling configurations were studied: round holes, craters, a trench, and a modified trench. The contaminants used in this study were small particles of paraffin wax that were sprayed into the mainstream flow of the wind tunnel. The wax particles modeled both the molten nature of contaminants in an engine as well as the particle trajectory by properly matching the expected range of Stokes number. This study found that the presence of film cooling significantly increased the accumulation of deposits. It was also found that the deposition behavior was strongly affected by the film cooling configuration that was used on the pressure side of the vane. The craters and trench performed the best in mitigating the accumulation of deposits immediately downstream of the film cooling configuration. In general, the presence of deposits reduced the film cooling performance on the surface of the TBC. However, the additional thermal insulation provided by the deposits improved the cooling performance at the interface of the TBC and vane wall.

A Study of Deposition on a Turbine Vane With a Thermal Barrier Coating and Various Film Cooling Geometries

2012 ◽  
Author(s):  
F. Todd Davidson ◽  
David A. Kistenmacher ◽  
David G. Bogard
Keyword(s):  
Thermal Barrier Coating ◽  
Film Cooling ◽  
Stokes Number ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Barrier Coating ◽  
Turbine Vane ◽  
Engine Components

Recent interest has been shown in using synthetic gaseous (syngas) fuels to power gas turbine engines. An important issue concerning these fuels is the potential for increased contaminate deposition that can inhibit cooling designs and expedite the material degradation of vital turbine components. The purpose of this study was to provide a detailed understanding of how contaminates deposit on the surface of a turbine vane with a thermal barrier coating (TBC). The vane model used in this study was designed to match the thermal behavior of real engine components by properly scaling the convective heat transfer coefficients as well as the thermal conductivity of the vane wall. Four different film cooling configurations were studied: round holes, craters, a trench and a modified trench. The contaminates used in this study were small particles of paraffin wax that were sprayed into the mainstream flow of the wind tunnel. The wax particles modeled both the molten nature of contaminates in an engine as well as the particle trajectory by properly matching the expected range of Stokes number. This study found that the presence of film cooling significantly increased the accumulation of deposits. It was also found that the deposition behavior was strongly affected by the film cooling configuration that was used on the pressure side of the vane. The craters and trench performed the best in mitigating the accumulation of deposits immediately downstream of the film cooling configuration. In general, the presence of deposits reduced the film cooling performance on the surface of the TBC. However, the additional thermal insulation provided by the deposits improved the cooling performance at the interface of the TBC and vane wall.

Film Cooling With a Thermal Barrier Coating: Round Holes, Craters, and Trenches

2013 ◽  
Vol 136 (4) ◽  
Author(s):  
F. Todd Davidson ◽  
David A. KistenMacher ◽  
David G. Bogard
Keyword(s):  
Thermal Behavior ◽  
Film Cooling ◽  
Thermal Protection ◽  
Engine Performance ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Barrier Coating ◽  
Internally Cooled ◽  
Thermally Conducting

Little work has been done to understand the interconnected nature of film cooling and thermal barrier coatings (TBCs) on protecting high temperature turbine components. With increasing demands for improved engine performance it is vital that a greater understanding of the thermal behavior of turbine components is achieved. The purpose of this study was to investigate how various film cooling geometries affect the cooling performance of a thermally conducting turbine vane with a TBC. The vane model used in this study was designed to match the thermal behavior of real engine components by properly scaling the convective heat transfer coefficients along with the thermal conductivity of the vane wall. This allowed for the measurement of temperatures at the interface of the TBC and vane wall which, when nondimensionalized, are representative of the temperatures present for actual engine vanes. This study found that the addition of a TBC on the surface of an internally cooled vane produced a near constant cooling performance despite significant changes in the blowing ratio. The craters, trench, and modified trench of this study were found to provide much better film cooling coverage than round holes; however, the improved film cooling coverage led to only slight improvements in temperature at the interface of the TBC and vane wall. These results suggest that there is minimal advantage in using more complicated cooling configurations, particularly since they may be more susceptible to TBC spallation. However, the improved film coverage from the trench and crater designs may increase the life of the TBC, which would be greatly beneficial to the long-term thermal protection of the vane.

Film Cooling With a Thermal Barrier Coating: Round Holes, Craters and Trenches

2012 ◽  
Author(s):  
F. Todd Davidson ◽  
David A. Kistenmacher ◽  
David G. Bogard
Keyword(s):  
Thermal Behavior ◽  
Film Cooling ◽  
Thermal Protection ◽  
Engine Performance ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Barrier Coating ◽  
Internally Cooled ◽  
Thermally Conducting

Little work has been done to understand the interconnected nature of film cooling and thermal barrier coatings (TBC’s) on protecting high temperature turbine components. With increasing demands for improved engine performance it is vital that a greater understanding of the thermal behavior of turbine components is achieved. The purpose of this study was to investigate how various film cooling geometries affect the cooling performance of a thermally conducting turbine vane with a TBC. The vane model used in this study was designed to match the thermal behavior of real engine components by properly scaling the convective heat transfer coefficients as well as the thermal conductivity of the vane wall. This allowed for the measurement of temperatures at the interface of the TBC and vane wall which, when non-dimensionalized, are representative of the temperatures present for actual engine vanes. This study found that the addition of TBC on the surface of an internally cooled vane produced a near constant cooling performance despite significant changes in the blowing ratio. The craters, trench and modified trench of this study were found to provide much better film cooling coverage than round holes; however, the improved film cooling coverage led to only slight improvements in temperature at the interface of the TBC and vane wall. These results suggest that there is minimal advantage in using more complicated cooling configurations, particularly since they may be more susceptible to TBC spallation. However, the improved film coverage from the trench and crater designs may increase the life of the TBC which would be greatly beneficial to the long-term thermal protection of the vane.

Effects of Surface Deposition, Hole Blockage, and Thermal Barrier Coating Spallation on Vane Endwall Film Cooling

2006 ◽  
Vol 129 (3) ◽  
pp. 599-607 ◽  
Author(s):  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Thermal Barrier Coating ◽  
Film Cooling ◽  
Gas Turbines ◽  
Large Scale ◽  
Leading Edge ◽  
Thermal Barrier ◽  
Cooling Effectiveness ◽  
Barrier Coating ◽  
Cooling Hole ◽  
Alternate Fuels

With the increase in usage of gas turbines for power generation and given that natural gas resources continue to be depleted, it has become increasingly important to search for alternate fuels. One source of alternate fuels is coal derived synthetic fuels. Coal derived fuels, however, contain traces of ash and other contaminants that can deposit on vane and turbine surfaces affecting their heat transfer through reduced film cooling. The endwall of a first stage vane is one such region that can be susceptible to depositions from these contaminants. This study uses a large-scale turbine vane cascade in which the following effects on film cooling adiabatic effectiveness were investigated in the endwall region: the effect of near-hole deposition, the effect of partial film cooling hole blockage, and the effect of spallation of a thermal barrier coating. The results indicated that deposits near the hole exit can sometimes improve the cooling effectiveness at the leading edge, but with increased deposition heights the cooling deteriorates. Partial hole blockage studies revealed that the cooling effectiveness deteriorates with increases in the number of blocked holes. Spallation studies showed that for a spalled endwall surface downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio.

Film Cooling From a Row of Holes With Both Ends Embedded in Transverse Slots

2008 ◽  
Author(s):  
D. H. Zhang ◽  
L. Sun ◽  
Q. Y. Chen ◽  
M. Lin ◽  
M. Zeng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Aerodynamic Performance ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Discharge Coefficients ◽  
Cylindrical Holes

Embedding a row of typical cylindrical holes in a transverse slot can improve the cooling performance. Rectangular slots can increase the cooling effectiveness but is at the cost of decreasing of discharge coefficients. An experiment is conducted to examine the effects of an overlying transverse inclined trench on the film cooling performance of axial holes. Four different trench configurations are tested including the baseline inclined cylindrical holes. The influence of the geometry of the upstream lip of the exit trench and the geometry of the inlet trench on cooling performance is examined. Detailed film cooling effectiveness and heat transfer coefficients are obtained separately using the steady state IR thermography technique. The discharge coefficients are also acquired to evaluate the aerodynamic performance of different hole configurations. The results show that the film cooling holes with both ends embedded in slots can provide higher film cooling effectiveness and lower heat transfer coefficients; it also can provide higher discharge coefficients whilst retaining the mechanical strength of a row of discrete holes. The cooling performance and the aerodynamic performance of the holes with both ends embedded in inclined slots are superior to the holes with only exit trenched. To a certain extent, the configuration of the upstream lip of the exit trench affects the cooling performance of the downstream of the trench. The filleting for the film hole inlet avail the improvement of the cooling effect, but not for the film hole outlet. Comparing film cooling with embedded holes to unembedded holes, the overall heat flux ratio shows that the film holes with both ends embedded in slots and filleting for the film hole inlet can produce the highest heat flux reduction.

A Novel Method for Designing Fan-Shaped Holes With Short Length-to-Diameter Ratio in Producing High Film Cooling Performance for Thin-Wall Turbine Airfoil

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Weihong Li ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Diameter Ratio ◽  
Short Length ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Shaped Hole ◽  
Length To Diameter Ratio

An experimental investigation of the geometrical parameter effects on the film cooling performance of a fan-shaped hole was conducted on a low speed flat-plate facility. The pressure sensitive paint (PSP) technique and steady liquid crystal (SLC) technique were employed to determine the adiabatic film cooling effectiveness and heat transfer coefficients, respectively, for a blowing ratio ranging from 0.3 to 3 and a density ratio of DR = 1.5. Several geometrical parameters were investigated, including lateral expansion angle, length-to-diameter ratio, and hole entrance shape. Local, laterally averaged, and area-averaged adiabatic film cooling effectiveness, heat transfer coefficients, and net heat flux reduction (NHFR) were shown to provide a comprehensive understanding on the geometrical parameter effects on the thermal performance. A novel method was proposed for designing a fan-shaped hole with short length-to-diameter ratio to design to achieve high film cooling performance. The original and optimized fan-shaped holes were compared in terms of adiabatic film cooling effectiveness, heat transfer coefficients, and NHFR. Results showed that the optimized fan-shaped hole with short length-to-diameter ratio, large lateral diffusion angle, and slot hole entrance shape obtained highest overall thermal performance. It demonstrated the feasibility of adopting the proposed design method to design fan-shaped holes applied in thin wall gas turbine blades.

Degradation of Film Cooling Performance on a Turbine Vane Suction Side due to Surface Roughness

2005 ◽  
Vol 128 (3) ◽  
pp. 547-554 ◽  
Author(s):  
James L. Rutledge ◽  
David Robertson ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Extended Period ◽  
Suction Side ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

After an extended period of operation, the surfaces of turbine airfoils become extremely rough due to deposition, spallation, and erosion. The rough airfoil surfaces will cause film cooling performance degradation due to effects on adiabatic effectiveness and heat transfer coefficients. In this study, the individual and combined effects of roughness upstream and downstream of a row of film cooling holes on the suction side of a turbine vane have been determined. Adiabatic effectiveness and heat transfer coefficients were measured for a range of mainstream turbulence levels and with and without showerhead blowing. Using these parameters, the ultimate film cooling performance was quantified in terms of net heat flux reduction. The dominant effect of roughness was a doubling of the heat transfer coefficients. Maximum adiabatic effectiveness levels were also decreased significantly. Relative to a film cooled smooth surface, a film cooled rough surface was found to increase the heat flux to the surface by 30%–70%.

Separate and Combined Effects of Surface Roughness and Thermal Barrier Coating on Vane Cooling Performance

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Prasert Prapamonthon ◽  
Bo Yin ◽  
Guowei Yang ◽  
Mohan Zhang
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Suction Side ◽  
Local Heat ◽  
Roughness Height ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Barrier Coating

Abstract This work investigates separate and combined effects of the vane surface roughness and thermal barrier coating (TBC) on the cooling performance of a film-cooled high-pressure turbine vane using computational fluid dynamics (CFD) with conjugate heat transfer (CHT) analysis. The cooling effectiveness and heat transfer coefficient, where are predicted within an investigated range of the roughness height from 5 to 20 µm, are compared with those of the smooth vane. Results show that the roughness height increases local heat transfer coefficients in general in the suction side (SS) and the rear-half portion of the pressure side (PS), thereby reducing the cooling effectiveness. The results are different from those in the suction-side vicinity of the leading edge (LE) to further downstream of the pressure side due to uncertain local heat transfer coefficients. In addition, thermal sensitivity to the roughness height and TBC is investigated based on the volume basis in the roughness height range which is extended to 120 µm. Results show that without TBC, a 120 µm increase in the roughness height causes 24 K and 20 K rises of the average and maximum vane temperatures, respectively. With TBC, the average and maximum vane temperatures are reduced as much as 18 K and 27.8 K, respectively.

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