Patent Application
20230141827
This disclosure relates generally to airfoils with dual-wall cooling and more particularly to a pedestal arrangement for dual-wall cooling of an airfoil.
Gas turbine engines include a compressor, combustor and turbine in flow series along a common shaft. Compressed air from the compressor is mixed with fuel in the combustor to generate hot combustion gases that rotate the turbine blades and drive the compressor. Improvements in the thrust and efficiency of gas turbine engines are linked to increasing turbine entry temperatures, which places a heavy burden on turbine blades. Consequently, there is significant interest in developing improved cooling techniques for airfoils in gas turbine engines. Dual-wall or double-wall cooling configurations are promising advancements for the cooling of turbine blades.
The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views.
A dual-wall or double-wall airfoil for a gas turbine engine may include a hollow spar that is partially or completely surrounded by suction side and pressure side coversheets (or “skins”) and spaced apart from the coversheets by raised features on the outer surface of the spar. These raised features may include pedestals and/or rails arranged to define flow pathways for coolant (e.g., air) between the outer surface of the spar and the respective coversheet. The coolant may provide heat transfer and cooling as it traverses the flow pathways before exiting, typically through exit holes in the respective coversheet or through exit slots. After exit, the coolant may flow in a layer over a hot external surface of the airfoil, providing film cooling. The coolant is delivered into the flow pathways from one or more coolant cavities in the spar. Traditional square pedestal arrays can provide high heat transfer, but may also generate a large pressure drop that is generally not desirable for long flow pathways. Smooth, straight rails tend to be associated with a lower pressure drop, but they may be unable to provide sufficient heat transfer and may be susceptible to being blocked with particulate debris. It is also important to manage the temperature of the coolant, since, as the coolant absorbs heat and increases in temperature, it may become less effective at cooling the airfoil.
The raised features 118 on the outer surface 104a of the pressure side wall 104 and/or the suction side wall 106 may include an arrangement 130 of pedestals 120 having different aspect ratios, where each pedestal 120 has an aspect ratio in the range from about 1:1 to about 5:1. The aspect ratio is equivalent to the length L (long axis) divided by the width W (short axis) of the pedestal, as illustrated in
The pedestals 120 in the arrangement 130 and the raised features 118 in general may have a height that corresponds to the spacing between the outer surface 104a,106a of the side wall 104,106 and the respective coversheet 114,116. The pedestals 120 may have a cross-sectional shape that is described as hexangular, or as a stretched hexagon, when the aspect ratio is greater than 1:1. An aspect ratio of greater than 1:1 may alternatively be achieved with a cross-sectional shape described as an elongated diamond, where the elongated diamond comprises two (opposing) included angles of greater than 90 degrees and two (opposing) included angles of less than 90 degrees. If the aspect ratio is 1:1 or about 1:1, the cross-sectional shape may be a hexagonal or diamond shape.
The aspect ratio may be varied along a predetermined direction, such as along the chordal direction 132 or along the radial direction 134, or along a direction having both chordal and radial components. In one example, it may be beneficial for the aspect ratio of the pedestals 120 to increase toward the trailing edge 110 and/or the leading edge 108 of the airfoil 100. Also or alternatively, the aspect ratio may decrease toward a midspan 136 of the airfoil 100, where heat may be concentrated. Some adjacent pedestals 120 may have the same aspect ratio along the direction of variation; i.e., there may be some local regions where the aspect ratio remains unchanged as part of an overall increasing or decreasing trend. Preferably, the long axes of the pedestals 120 are aligned with the direction of coolant flow, which may be the chordal direction 132, as illustrated, the radial direction 134, or a direction having both chordal and radial components.
As shown in
The arrangement 130 of pedestals 120 may be on the outer surface 104a of the pressure side wall 104 and/or on the outer surface 106a of the suction side wall 106. In one example, as shown in
In other examples, the arrangement 130 of pedestals 120 of varying aspect ratio may extend over an entirety of the midspan cooling circuit 138 in one or both of the chordal and radial directions 132,134. It is also contemplated that the arrangement 130 of pedestals 120 may extend over an entirety of the suction side wall 106 and/or the pressure side wall 104 of the airfoil 100. In one such example, a first cooling circuit configured to deliver coolant to the leading edge 108 may include a first part of the arrangement 130 and a second cooling circuit configured to deliver coolant to the trailing edge 110 of the airfoil 100 may include a second part of the arrangement 130, where the aspect ratio of the pedestals 120 in each of the first and second parts of the arrangement 130 may be varied to control heat transfer and pressure drop as needed.
The dual-wall airfoil 100 described herein may be fabricated using investment casting and diffusion bonding methods known in the art, such as described in U.S. Pat. No. 6,003,754, entitled “Airfoil for a Gas Turbine Engine and Method of Manufacture,” which is hereby incorporated by reference in its entirety. The airfoil 100, including the spar 102 and the pressure and suction side coversheets 114,116, may be formed from one or more materials that have high melting points, good oxidation/corrosion resistance and high-temperature strength. For example, a nickel-base alloy, a titanium-base alloy, and/or an iron-base alloy may be suitable. The alloy may have an equiaxed, directionally solidified, or single-crystal microstructure. The raised features 118 may be integrally formed with the spar 102, or, more specifically, may be integrally formed on the respective suction or pressure side wall 106,104. The raised features 118 may be bonded to or integrally formed with the respective suction or pressure side coversheet 114,116. The airfoil 100 may have a single-piece or a multi-piece construction.
A gas turbine engine 300, such as that shown in
To clarify the use of and to hereby provide notice to the public, the phrases “at least one of <A>, <B>, . . . and <N>” or “at least one of <A>, <B>, . . . or <N>” or “at least one of <A>, <B>, <N>, or combinations thereof” or “<A>, <B>, . . . and/or <N>” are defined by the Applicant in the broadest sense, superseding any other implied definitions hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, . . . and N. In other words, the phrases mean any combination of one or more of the elements A, B, . . . or N including any one element alone or the one element in combination with one or more of the other elements which may also include, in combination, additional elements not listed. Unless otherwise indicated or the context suggests otherwise, as used herein, “a” or “an” means “at least one” or “one or more.”
While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible. Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations.
The subject-matter of the disclosure may also relate, among others, to the following aspects:
A first aspect relates to an airfoil including an arrangement of pedestals of varying aspect ratio for dual-wall cooling, the airfoil comprising: a spar having a pressure side wall and a suction side wall meeting at a leading edge and a trailing edge of the airfoil, each of the pressure side wall and the suction side wall including raised features on an outer surface thereof, an interior of the spar including one or more coolant cavities; and a pressure side coversheet overlying the pressure side wall, an inner surface of the pressure side coversheet being in contact with the raised features on the outer surface of the pressure side wall, thereby defining pressure side flow pathways between the pressure side wall and the pressure side coversheet, the pressure side flow pathways being in fluid communication with the one or more coolant cavities; a suction side coversheet overlying the suction side wall, an inner surface of the suction side coversheet being in contact with the raised features on the outer surface of the suction side wall, thereby defining suction side flow pathways between the suction side wall and the suction side coversheet, the suction side flow pathways being in fluid communication with the one or more coolant cavities, wherein the raised features on the outer surface of the pressure side wall and/or the suction side wall include an arrangement of pedestals, each pedestal comprising an aspect ratio in a range from about 1:1 to about 5:1, and wherein the aspect ratio of the pedestals is varied within the arrangement.
A second aspect relates to the airfoil of the first aspect, wherein the pedestals in the arrangement have a cross-sectional shape selected from the group consisting of diamond, elongated diamond, hexagonal, and hexangular.
A third aspect relates to the airfoil of the first or second aspect, wherein the arrangement of pedestals is on the outer surface of the pressure side wall.
A fourth aspect relates to the airfoil of any preceding aspect, wherein the arrangement of pedestals is on the outer surface of the suction side wall.
A fifth aspect relates to the airfoil of any preceding aspect, wherein the aspect ratio increases and/or decreases across the arrangement.
A sixth aspect relates to the airfoil of any preceding aspect, wherein the aspect ratio is varied along a chordal direction.
A seventh aspect relates to the airfoil of any preceding aspect, wherein the aspect ratio is varied along a radial direction.
An eighth aspect relates to the airfoil of any preceding aspect, wherein the aspect ratio is varied along a direction having a chordal component and a radial component.
A ninth aspect relates to the airfoil of any preceding aspect, wherein the aspect ratio decreases toward a midspan of the airfoil.
A tenth aspect relates to the airfoil of any preceding aspect, wherein the aspect ratio increases toward a trailing edge and/or a leading edge of the airfoil.
An eleventh aspect relates to the airfoil of any preceding aspect, wherein long axes of the pedestals are aligned with a direction of coolant flow over the respective outer surface.
A twelfth aspect relates to the airfoil of any preceding aspect, wherein long axes of the pedestals are aligned with a chordal direction.
A thirteenth aspect relates to the airfoil of any preceding aspect, wherein long axes of the pedestals are aligned with a radial direction.
A fourteenth aspect relates to the airfoil of any preceding aspect, wherein long axes of the pedestals are aligned with a direction having a chordal component and a radial component.
A fifteenth aspect relates to the airfoil of any preceding aspect, wherein a midspan cooling circuit configured to deliver coolant to the leading edge of the airfoil includes the arrangement of pedestals.
A sixteenth aspect relates to the airfoil of the fifteenth aspect, wherein the arrangement of pedestals extends over an entirety of the midspan cooling circuit.
A seventeenth aspect relates to the airfoil of the fifteenth aspect, wherein the arrangement of pedestals extends over just part of the midspan cooling circuit and is separated from a section of raised features positioned nearer to the leading edge by a radial spacing on the respective outer wall.
An eighteenth aspect relates to the airfoil of the fifteenth aspect, wherein the arrangement of pedestals is adjacent to a trailing edge cooling circuit configured to deliver coolant to the trailing edge of the airfoil, wherein the raised features of the trailing edge cooling circuit comprise rails.
A nineteenth aspect relates a gas turbine engine including the airfoil of any preceding aspect.
In addition to the features mentioned in each of the independent aspects enumerated above, some examples may show, alone or in combination, the optional features mentioned in the dependent aspects and/or as disclosed in the description above and shown in the figures.
