Patent Application
20120148383
The present invention is directed generally to turbine vanes, and more particularly to turbine vanes having cooling channels for conducting a cooling fluid through the vane.
In a turbomachine, such as a gas turbine engine, air is pressurized in a compressor section then mixed with fuel and burned in a combustor section to generate hot combustion gases. The hot combustion gases are expanded within a turbine section of the engine where energy is extracted to power the compressor section and to produce useful work, such as turning a generator to produce electricity. The hot combustion gases travel through a series of turbine stages within the turbine section. A turbine stage may include a row of stationary airfoils, i.e., vanes, followed by a row of rotating airfoils, i.e., turbine blades, where the turbine blades extract energy from the hot combustion gases for powering the compressor section and providing output power. Since the airfoils, i.e., vanes and turbine blades, are directly exposed to the hot combustion gases, they are typically provided with an internal cooling passage that conducts a cooling fluid, such as compressor bleed air, through the airfoil.
One type of airfoil extends from a radially inner platform at a root end to a radially outer portion of the airfoil, and includes opposite pressure and suction sidewalls extending axially from leading to trailing edges of the airfoil. The cooling channel extends inside the airfoil between the pressure and suction sidewalls and conducts the cooling fluid in alternating radial directions through the airfoil.
In accordance with an aspect of the invention, a vane structure is provided for a gas turbine engine. The vane structure comprises a radially outer platform and a radially inner platform. An airfoil is provided including an airfoil outer wall extending radially between the outer platform and the inner platform, and the outer wall includes chordally spaced leading and trailing edges. A cooling passage is defined within the outer wall and has a plurality of radially extending channels. An outer end turn structure is located at the outer platform to conduct cooling fluid in a chordal direction between at least two of the channels. The outer end turn structure includes an enlarged portion wherein the enlarged portion is defined by an enlarged dimension, in a direction transverse to the chordal direction, between the at least two channels.
In accordance with another aspect of the invention, a vane structure is provided for a gas turbine engine. The vane structure comprises a radially outer platform including an inner surface defining a portion of a hot gas path through the gas turbine engine and an opposing outer surface in communication with a cooling fluid source. A radially inner platform is provided including an outer surface defining a portion of the hot gas path and an opposing inner surface. An airfoil is provided including an airfoil outer wall extending radially between the outer platform and the inner platform, and the outer wall includes chordally spaced leading and trailing edges. A cooling passage is defined within the outer wall and has a plurality of radially extending channels including an upstream channel, a downstream channel and a medial channel between the upstream channel and the downstream channel. An outer end turn structure extends radially outwardly from the outer surface of the outer platform to conduct cooling fluid in a chordal direction between the medial channel and the downstream channel. The vane structure additionally includes a cooling fluid inlet for providing cooling fluid from the cooling fluid supply to the upstream channel. The cooling fluid inlet extends through the outer end turn structure from a location radially outwardly from the outer surface to the upstream channel.
In accordance with a further aspect of the invention, a vane structure is provided for a gas turbine engine. The vane structure comprises a radially outer platform and a radially inner platform. An airfoil is provided including an airfoil outer wall extending radially between the outer platform and the inner platform, and the outer wall includes chordally spaced leading and trailing edges. A cooling passage is defined within the outer wall and has a plurality of radially extending channels. An end turn structure extends radially from a side of at least one of the inner and outer platforms opposite from the airfoil to conduct cooling fluid in a chordal direction between at least two of the channels. The vane structure additionally includes upstream and downstream rail structures extending radially from the at least one platform, and the end turn structure has an upstream end adjoining an intersection of the upstream rail structure with the at least one platform and a downstream end adjoining an intersection of the downstream rail structure with the at least one platform.
In accordance with additional aspects of the invention: the enlarged dimension may be greater than a dimension of each of at least two of the channels, in the direction transverse to the chordal direction, at a location of the channels adjacent to the enlarged portion; the enlarged portion may extend from a location radially outwardly from the outer surface of the outer platform to a location radially inwardly from the outer surface of the outer platform; upstream and downstream inner rail structures may be provided extending radially inwardly from an inner surface of the inner platform, and including an inner end turn structure having an upstream end adjoining an intersection of the upstream inner rail structure with the inner surface of the inner platform and a downstream end adjoining an intersection of the downstream inner rail structure with the inner surface of the inner platform; the outer wall of the airfoil may include a pressure sidewall and a suction sidewall, and the plurality of channels of the cooling passage may include first, second and medial channels defined by first and second partitions extending between the pressure and suction sidewalls, the second partition may be located between the medial channel and the second channel, and the second partition having an inner end located adjacent the inner platform and having an outer end radially located generally aligned with the inner surface of the outer platform; the cooling fluid inlet may extend to the first or upstream channel and the enlarged portion of the outer end turn structure may provide fluid communication between the medial channel and the downstream channel; the upstream channel may conduct cooling fluid from the cooling fluid inlet in a radially inward direction toward the inner platform, the medial channel may conduct cooling fluid in a radially outward direction toward the outer platform, and the downstream channel may conduct cooling fluid in the radially inward direction; the outer surface of the outer platform may define a substantially planar portion, and a fillet portion may be provided defining a radius from a radially outer portion of the outer end turn structure to the substantially planar surface for effecting a reduction in stress in an area of the radius.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein:
In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.
Referring to
The illustrated vane structure 10 includes a plurality of airfoils 24A, 24B, 24C extending radially between the outer and inner platforms 12, 14 and spaced from each other in a circumferential direction. The airfoils 24A, 24B, 24C may have a substantially identical construction and will be described with reference to the airfoil 24A, it being understood that the other airfoils 24B and 24C may be of substantially similar construction. Further, it should be understood that the vane structure 10 may be formed with a fewer number or a greater number of airfoils than those shown herein.
As seen in
The upstream cooling channel 36A may be defined between the leading edge 32 and a first partition 37 extending between the pressure and suction sidewalls 28, 30. The medial cooling channel 36B is defined between the first partition 37 and a second partition 39 extending between the pressure and suction sidewalls 28, 30. The downstream cooling channel 36C is defined between the second partition 39 and the trailing edge 34. The upstream cooling channel 36A is fluid communication with the medial cooling channel 36B through an inner end turn structure 38, and the medial cooling channel 36B is in fluid communication with the downstream cooling channel 36C through an outer end turn structure 40, as is described further below.
Referring to
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The upstream end 74 of the outer end turn structure 40 is defined at a forward edge of the front outer portion 88, and the downstream end 78 of the outer end structure 40 is defined at a rearward edge of the rear outer portion 90. Further, the first and second end turn walls 82, 90 intersect the outer surface 18 of the outer platform 12 at respective first and second side edges 96, 98. The upstream and downstream ends 74, 78 and the first and second side edges 96, 98 define blended junction locations comprising curved surfaces that form a fillet having predetermined radii between the respective front and rear outer portions 88, 90 and the outer surface 18, and between the first and second end turn walls 82, 90 and the outer surface 18. In particular, blend radii are defined at the intersections of the ends 74, 78 with the outer surface 18, and at the intersections of the side edges 96, 98 with the outer surface 18 to avoid or reduce thermal stress concentrations between the outer end turn structure 40 and the outer platform 12. The blend radii are preferably no less than about 5 mm, and may comprise radii that vary in both the radial direction and around the circumference defined by the intersection of the outer end turn structure 40 with the outer surface 18 of the outer platform 12.
In accordance with the present configuration for an outer end turn structure 40, it has been observed that in prior structures defining turns for cooling channels, increased thermal gradients have been formed between a vane platform and structure forming the cooling channel turns, resulting in increased thermal stress. It has further been observed that thermal stresses have particularly been formed in prior designs at a junction between vane platforms and structure forming cooling channel turns adjacent to a downstream side of an air inlet formed through a radially outer vane platform, at a terminal forward end of the structure forming the cooling channel turns, as well as at other locations where a cooling channel structure meets or joins a vane platform. In accordance with the present configuration for a vane structure 10, the blended junction locations 74, 78, 96, 98 provide junctions where stresses may be more evenly distributed through the junction area.
The thermal stress may be further reduced by the configuration of the outer end turn structure 40 extending to upstream and downstream locations substantially adjacent to the respective upstream and downstream outer rail structures 42, 50. The extended outer end turn structure 40 provides additional thermal mass to distribute the thermal load from the platform 12, while providing additional surface area for convective heat transfer. The extension of the front and rear outer turn portions 88, 90 to locations adjoining the respective upstream and downstream outer rail structures 42, 50 additionally may reduce the stress concentration factor in the area of the outer end turn structure 40 by providing a distribution of loads attributed to thermal stress over a longer portion of the outer end turn structure 40.
A portion of the side walls 82, 84 forming the front outer portion 88 extends on either side of a cooling fluid inlet 100 to locate the cooling fluid inlet radially outwardly from the outer surface 18 of the outer platform 12, as seen in
In accordance with a further aspect of the invention, the outer end turn structure 40 may be formed with a reduced height, i.e., a reduced radial outward extension, as compared to prior structures defining turns for cooling channels. In particular, the outer end turn structure 40 may have a height that is substantially radially inwardly from the hook portions 48, 56, resulting in the entire outer end turn structure 40 being closer to the hot outer platform 12 and having a higher temperature than if it extended further radially outwardly. Hence, a thermal gradient between the outer end turn structure 40 and the outer platform 12 is reduced, with an associated reduction in thermal stress. It may be noted that an impingement plate (not shown) may be located radially outwardly from the outer end turn structure 40 and radially inwardly from the hook portions 48, 56 for providing impingement cooling air from the cooling fluid source CF to the outer end turn structure 40. In accordance with this aspect, and in order to maintain a desired level of heat transfer between the outer end turn structure 40 and cooling fluid supplied by the cooling fluid source CF, a downstream channel passage is formed as a bulb or enlarged portion 102 for conducting cooling fluid between the medial cooling channel 36B and the downstream cooling channel 36C in a chordal direction, i.e., in a generally axial direction extending from the leading edge 32 toward the trailing edge 34.
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Referring to
The inner end turn structure may additionally include opposing first and second turn walls 110, 112 extending in the chordal direction of the airfoil 24A. The first and second end turn walls 110, 112 extend radially inwardly, and each of the end turn walls 110, 112 may be formed with an orientation and curvature, in the chordal direction, that substantially matches the orientation and curvature of a respective one of the pressure and suction sidewalls 28, 30. The inner end turn structure 38 further includes an inner portion 114 extending between the end turn walls 110, 112 and which is generally arched in the chordal direction.
The first and second end turn walls 110, 112 intersect the inner surface 22 of the inner platform 14 at respective side edges (only side edge 116 shown). The upstream and downstream ends 106, 108 and the side edges (as illustrated by side edge 116) define blended junction locations comprising curved surfaces that form a fillet having a predetermined radius between the inner end turn structure 38 and the inner platform 14. The blended junction locations avoid or reduce thermal stress concentrations between the inner end turn structure 38 and the inner platform 14, in a manner similar to that described above with regard to the outer end turn structure 40. The blend radii at the blend junction locations are preferably no less than about 5 mm, and the radii may vary in both the radial direction and around the circumference defined by the intersection of the inner end turn structure 38 with the inner surface 22 of the inner platform 14.
The inner end turn structure 38 may be provided with one or more discharge apertures 118 formed in the end turn walls 110, 112 adjacent an inner end of the upstream cooling channel 36A. Further, a cooling fluid exit aperture 120 may be formed in the arched inner portion 114 of the inner end turn structure 38 adjacent to an inner end of the downstream cooling channel 36C. The discharge apertures 118 and exit aperture 120 may discharge cooling fluid into an inner seal area located in the engine radially inwardly from the inner platform 14. In addition, a plurality of trip strips 122 may be formed along the interior surfaces defining the cooling passage 36 to facilitate heat transfer between the cooling fluid and the surfaces of the cooling passage 36. The trip strips 122 may also be provided to the end turn structures 38, 40. For example, trip strips 122 may be provided to the cooling fluid inlet 100 (
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
