NETL Research Efforts on Development and Integration of Advanced Material Systems and Airfoil Cooling Configurations for Future Land-Based Gas Turbine Engines
Abstract:As future land-based gas turbine engines are being designed to operate with inlet temperatures exceeding 1300°C (2370°F), efforts at NETL have been focused on developing advanced materials systems that are integrated with novel airfoil cooling architectures. Recent achievements in the areas of low cost diffusion bond coat systems applied to single- and poly-crystalline nickel-based superalloys, as well as development of thin nickel-based oxide dispersion strengthened layers are presented in this paper. Integra… Show more
“…These temperatures are at or exceeding current material (melting temperature) limits which require higher heat removal using novel blade designs to allow a more significant cooling of the substrate. 1 While the state-of-the-art internal cooling techniques generally provide a cooling enhancement about two to three times higher than baseline configurations, they would be more effective in lowering the airfoil substrate temperature if the internal channel was located closer to the airfoil external surface. 1 Collective durability data and analyses suggest that such a near-surface arrangement can not only substantially reduce the required coolant flow rate, thus directly increasing turbine system efficiency, but also significantly lengthen component life.…”
Section: Introductionmentioning
confidence: 99%
“…1, is designed to further enhance heat transfer by moving the internal gas passage channels closer to the airfoil surface, providing more coolant closer to the hot gas path surface, thereby increasing heat removal capability on the order of 50–70% over that of advanced internal cooling technologies. 1 If the cooling channels can be incorporated within the actual surface layer and even more uniformly distributed throughout, as in a micro-porous surface layer structure, the cooling will be even further enhanced. 1 Sample geometry of the NSEMC cooling concept with a porous surface layer in a general airfoil cross-section (adapted from Alvin et al .…”
Section: Introductionmentioning
confidence: 99%
“… 1 Sample geometry of the NSEMC cooling concept with a porous surface layer in a general airfoil cross-section (adapted from Alvin et al . 1 )…”
Section: Introductionmentioning
confidence: 99%
“…1. 1 For the outer structural layer to retain strength at ultra-high operating temperatures (above the dissolution limit of most precipitation-strengthened alloys), a Ni-base superalloy material was selected since previous Ni alloys have demonstrated significant strength retention up to about 0.9 T m (in °K). The bulk of the stresses on the airfoil will be accommodated by current high temperature Ni-base alloys that would remain in their conventional (substrate or blade body) role, while the porous coating would act as a thermal protection shield by using the associated cooling air curtain to mitigate exposure to the ultra-high gas flow temperatures.…”
Extreme high temperature conditions demand novel solutions for hot gas filters and coolant access architectures, i.e., porous layers on exposed components. These high temperatures, for example in current turbine engines, are at or exceeding current material limits for high temperature oxidation/ corrosion, creep resistance, and, even, melting temperature. Thus novel blade designs allowing greater heat removal are required to maintain airfoil temperatures below melting and/or rapid creep deformation limits. Gas atomised Ni-base superalloy powders were partially sintered into porous layers to allow full-surface, transpirational cooling of the surface of airfoils. These powder-processed porous layers were fully characterised for surface, morphology, crosssectional microstructure, and mechanical strength characteristics. A sintering model based on pure Ni surface diffusion correlated well with the experimental results and allowed reasonable control over the partial sintering process to obtain a specified level of porosity within the porous layer.
“…These temperatures are at or exceeding current material (melting temperature) limits which require higher heat removal using novel blade designs to allow a more significant cooling of the substrate. 1 While the state-of-the-art internal cooling techniques generally provide a cooling enhancement about two to three times higher than baseline configurations, they would be more effective in lowering the airfoil substrate temperature if the internal channel was located closer to the airfoil external surface. 1 Collective durability data and analyses suggest that such a near-surface arrangement can not only substantially reduce the required coolant flow rate, thus directly increasing turbine system efficiency, but also significantly lengthen component life.…”
Section: Introductionmentioning
confidence: 99%
“…1, is designed to further enhance heat transfer by moving the internal gas passage channels closer to the airfoil surface, providing more coolant closer to the hot gas path surface, thereby increasing heat removal capability on the order of 50–70% over that of advanced internal cooling technologies. 1 If the cooling channels can be incorporated within the actual surface layer and even more uniformly distributed throughout, as in a micro-porous surface layer structure, the cooling will be even further enhanced. 1 Sample geometry of the NSEMC cooling concept with a porous surface layer in a general airfoil cross-section (adapted from Alvin et al .…”
Section: Introductionmentioning
confidence: 99%
“… 1 Sample geometry of the NSEMC cooling concept with a porous surface layer in a general airfoil cross-section (adapted from Alvin et al . 1 )…”
Section: Introductionmentioning
confidence: 99%
“…1. 1 For the outer structural layer to retain strength at ultra-high operating temperatures (above the dissolution limit of most precipitation-strengthened alloys), a Ni-base superalloy material was selected since previous Ni alloys have demonstrated significant strength retention up to about 0.9 T m (in °K). The bulk of the stresses on the airfoil will be accommodated by current high temperature Ni-base alloys that would remain in their conventional (substrate or blade body) role, while the porous coating would act as a thermal protection shield by using the associated cooling air curtain to mitigate exposure to the ultra-high gas flow temperatures.…”
Extreme high temperature conditions demand novel solutions for hot gas filters and coolant access architectures, i.e., porous layers on exposed components. These high temperatures, for example in current turbine engines, are at or exceeding current material limits for high temperature oxidation/ corrosion, creep resistance, and, even, melting temperature. Thus novel blade designs allowing greater heat removal are required to maintain airfoil temperatures below melting and/or rapid creep deformation limits. Gas atomised Ni-base superalloy powders were partially sintered into porous layers to allow full-surface, transpirational cooling of the surface of airfoils. These powder-processed porous layers were fully characterised for surface, morphology, crosssectional microstructure, and mechanical strength characteristics. A sintering model based on pure Ni surface diffusion correlated well with the experimental results and allowed reasonable control over the partial sintering process to obtain a specified level of porosity within the porous layer.
“…Additional efforts were also addressed to establish the basis for enhanced stiffness response with extended high temperature cyclic testing of MCB plus ball milled ODS alloy systems in comparison to current/previously developed HVOF ODS alloy coating [154] and thermal barrier coating (TBC) systems [120] as a possible means of implementing these MCB plus ball milled ODS alloys as a structural high temperature coating on turbine blades by implementing microchannel cooling system beneath or within the coating [155]. In a similar test condition of this study, TBC systems [120] showed spallation failure after 400 thermal cycles, whereas oxide scales on MCB plus ball milled ODS alloy specimens were very adherent to the metal matrix without any spallation up to longer thermal cycles, more than 700 cycles.…”
Section: Temperature Distribution In the Model And Substratementioning
Mechanical and Microstructure Study of Nickel-Based ODS Alloys Processed by Mechano-Chemical Bonding and Ball Milling Belachew N. Amare Due to the need to increase the efficiency of modern power plants, land-based gas turbines are designed to operate at high temperature creating harsh environments for structural materials. The elevated turbine inlet temperature directly affects the materials at the hottest sections, which includes combustion chamber, blades, and vanes. Therefore, the hottest sections should satisfy a number of material requirements such as high creep strength, ductility at low temperature, high temperature oxidation and corrosion resistance. Such requirements are nowadays satisfied by implementing superalloys coated by high temperature thermal barrier coating (TBC) systems to protect from high operating temperature required to obtain an increased efficiency. Oxide dispersive strengthened (ODS) alloys are being considered due to their high temperature creep strength, good oxidation and corrosion resistance for high temperature applications in advanced power plants. These alloys operating at high temperature are subjected to different loading systems such as thermal, mechanical, and thermo-mechanical combined loads at operation. Thus, it is critical to study the high temperature mechanical and microstructure properties of such alloys for their structural integrity. The primary objective of this research work is to investigate the mechanical and microstructure properties of nickel-based ODS alloys produced by combined mechano-chemical bonding (MCB) and ball milling subjected to high temperature oxidation, which are expected to be applied for high temperature turbine coating with micro-channel cooling system. Stiffness response and microstructure evaluation of such alloy systems was studied along with their oxidation mechanism and structural integrity through thermal cyclic exposure. Another objective is to analyze the heat transfer of ODS alloy coatings with micro-channel cooling system using finite element analysis (FEA) to determine their feasibility as a stand-alone structural coating. During this project it was found that stiffness response to increase and remain stable to a certain level and reduce at latter stages of thermal cyclic exposure. The predominant growth and adherent Ni-rich outer oxide scale was found on top of the alumina scale throughout the oxidation cycles. The FEA analysis revealed that ODS alloys could be potential high temperature turbine coating materials if micro-channel cooling system is implemented.
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