Patent Application
20170356294
The present invention relates to improved cooling passageways formed in airfoils of a gas turbine engine and a method of manufacturing the improved cooling passageways.
In a typical operation of a gas turbine engine, the combustor generates high temperature combustion gases that pass through a turbine having a plurality of airfoils. In order to protect these airfoils from the extreme temperatures of the combustion gases, a variety of cooling techniques have been developed. For instance, a plurality of cooling holes may be formed in an outer surface of the turbine airfoil. These cooling holes are adapted to communicate a cooling fluid (e.g., air or steam) from an inner reservoir within the turbine airfoil to the exterior surface of the turbine airfoil. The high velocity of the high temperature combustion gases causes the emitted cooling fluid to wrap over the outer surface of the turbine airfoil and create a thin, protective film layer of cooling fluid between the airfoil outer surface and the high temperature combustion gases. Surface coverage and uniformity of this protective film is essential in improving long term durability and structural integrity of the turbine airfoil.
Referring to
A high-level overview of various aspects of the invention is provided here for that reason, to provide an overview of the disclosure and to introduce a selection of concepts that are further described below in the detailed description section below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in isolation to determine the scope of the claimed subject matter.
One aspect of the present invention is directed to an airfoil for a gas turbine engine. The airfoil includes a wall having a first surface and a second surface and a passageway extending through the wall, in a longitudinal direction, from a first opening in the first surface to a second opening in the second surface. The passageway includes a plurality of sections between the first opening and the second opening. The plurality of sections are in fluid communication with each other and adapted to communicate a cooling fluid from within the airfoil out through the second opening where it may form the layer of protective film. The plurality of sections includes a first diffuser section providing a first change in cross-sectional area within the passageway, and second diffuser section providing a second change in cross-sectional area within the passageway, a flow conditioning section located between the first diffuser section and the second diffuser section and having a constant cross-sectional area across its length within the passageway, and an edge section located adjacent to the second opening having two edge surfaces set opposite each other across the passageway and extending along the passageway substantially in parallel alignment to one another. In some aspects, the plurality of sections further includes a flow controlling section beginning at the first opening and extending within the passageway to the first diffuser section. A longitudinal axis represents, in general, the longitudinal direction of passageway extension. In some embodiments, the passageway is formed through the wall in the longitudinal direction such that the longitudinal axis extends through the wall at an angle not normal to the outer surface of the wall. In other embodiments, the angle between the second surface of the wall and the longitudinal axis is small enough that the perimeter of the second opening includes a portion of the second diffuser section and the edge section. In embodiments where the passageway is formed at severe angles, a portion of the edge section forms a channel in the wall of the airfoil.
Another aspect of the present invention is directed to a method of manufacturing an airfoil for a gas turbine engine having improved cooling passageways. The method includes the step of providing an airfoil having a wall extending from a first surface to a second surface. The method further includes the step of forming one or more passageways through the wall. The one or more passageways extend from a respective first opening in the first surface to a respective second opening in the second surface. Each of the one or more passageways includes a plurality of sections between the respective first openings and the respective second openings. The plurality of sections comprise a first diffuser section providing a first change in cross-sectional area within the respective passageway, a second diffuser section providing a second change in cross-sectional area within the respective passageway, a flow conditioning section located between the first and second diffuser sections, the flow conditioning section having a constant cross-sectional area across its length, and an edge section positioned adjacent to the second opening and having two surfaces opposite each other across the passageway, the two surfaces extending along the passageway substantially in parallel to one another. In some aspects the method further includes the step of providing an electrode having one or more shaped electrode teeth. The one or more shaped electrode teeth each has a plurality of tooth sections. The plurality of tooth sections includes a tip section, a constant area section, a first expansion section, and a constant width section. In this respect, the step of forming at least one passageway through the wall is performed by plunging the electrode through the wall (e.g., using an EDM plunge process). In other embodiments of the present invention, the tip section may include a leading tip section, a second constant area section, and a second expansion section. In some embodiments where there are at least three shaped electrode teeth, the at least three shaped electrode teeth are aligned in a row on the electrode.
In yet another aspect of the present invention, an improved cooling hole formed in the wall of a turbine airfoil of a gas turbine engine is provided. The improved cooling hole includes a first opening formed on an inner surface of a turbine airfoil wall and adapted to communicate a cooling fluid from within the airfoil, through a plurality of cavities, and out of a second opening formed on an outer surface of the airfoil wall. The plurality of cavities includes a flow controlling cavity, a first diffusing cavity, a flow conditioning cavity, a second diffusing cavity, and an edge cavity. The flow controlling cavity is formed between flow controlling surfaces that extend from the first opening to the first diffusing cavity. The flow controlling cavity may have a constant cross-sectional area across its length. The first diffusing cavity is formed between first diffusing surfaces that extend from the flow controlling cavity to the flow conditioning cavity. The first diffusing cavity has a first end located proximate to a flow controlling cavity and a second end located proximate to the flow conditioning cavity. The first end of the first diffusing cavity has a first cross-sectional area and the second end of the first diffusing cavity has a second cross-sectional area. The first cross-sectional area is smaller than the second cross-sectional area. The flow conditioning cavity extends from the first diffusing cavity to the second diffusing cavity. The flow conditioning cavity may have a constant cross-sectional area across its length and decreases the turbulence in the cooling fluid that flows through such cavity. The second diffusing cavity extends from the flow conditioning cavity to an edge cavity. The second diffusing cavity has a first end and a second end. In one embodiment, the first end has a cross-sectional area equal to the second cross-sectional area and the second end has a third cross-sectional area. The second cross-sectional area is smaller than the third cross-sectional area. The edge cavity extends from the second diffusing cavity to the second opening in the airfoil wall. The edge cavity has edge surfaces located opposite each other across the edge cavity. The opposing surfaces extend along the edge cavity in parallel to one another from the second diffusing cavity to the second opening and increase coverage and uniformity of the cooling fluid's protective film while allowing positioning of cooling passageways closer to each other with reduced tolerance stack associated with the minimum distance between one cooling passageway to the adjacent one.
Examples of the present invention are described in detail below with reference to the attached drawing figures, wherein:
The subject matter of the present invention is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the terms “step” and/or “block” might be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly stated.
Referring initially to
Turning now to
Referring to
The exemplary passageway 30a is formed in, and extends through, the wall 20 in a longitudinal direction. A longitudinal axis A is shown extending through the exemplary passageway 30a in the longitudinal direction. The longitudinal axis A intersects the plane of the second surface 24 at an angle α. In some embodiments, the angle α may be normal to the plane of the second surface 24. In the illustrated embodiment, the angle α is not normal to the plane of the second surface 24. The exemplary passageway 30a extends generally straight in the longitudinal direction.
The exemplary passageway 30a may include a plurality of sections. The plurality of sections are formed between the first opening 32 and the second opening 34. The plurality of sections are characterized by different cross-sectional areas along the length of each section in the longitudinal direction. In general, the plurality of sections includes at least a first diffuser section 40 providing a first change in cross-sectional area, a second diffuser section 44 providing a second change in cross-sectional area, a flow conditioning section 42 positioned between the first diffuser section 40 and the second diffuser section 44 and having a constant cross-sectional area across its length that reduces the turbulence (relative to prior art) in the cooling fluid passing therethrough, and an edge section 46 having two edge surfaces. The two edge surfaces include a first edge surface 50 and a second edge surface 52 and are positioned across the exemplary passageway 30a from one another. In some embodiments, the first edge surface 50 and the second edge surface 52 extend in parallel alignment with the longitudinal axis A. The edge section 46 is located adjacent to the second opening 34 and is adapted for reducing turbulence in the cooling fluid as it is emitted from the exemplary passageway 30a, for allowing tighter tolerances when forming the exemplary passageway 30a, and for increasing coverage and uniformity associated with a portion of the cooling fluid protective film emitted from the second opening 34. The edge section 46 creates velocity boundary condition on the edges of the emitted flow which prevents intersection of the cooling flow from adjacent cooling passageways and is overall favorable in increasing circumferentially averaged film effectiveness of the cooling fluid, or at least a portion thereof, as it flows between the first edge surface 50 and the second edge surface 52.
The edge section 46 also allows tighter tolerances to be used when manufacturing the airfoil 10 because the first edge surface 50 and second edge surface 52 extend in parallel to one another. Hence, when the one or more passageways 30 are formed in the wall 20, variations in casting surface profile and plunge depth will not cause two adjacent passageways to intersect within, or at the surface of, the wall. This is an improvement over the prior art cooling holes 30A (shown in
The edge section 46 also increases film coverage and uniformity associated with the flow of the cooling fluid when it is emitted between the first edge surface 50 and the second edge surface 52 of the exemplary passageway 30a, where an adjacent passageway 30b (shown in
In some embodiments, a flow controlling section 48 is positioned between the first opening 32 and the first diffuser section 40 and is adapted for metering the flow of cooling fluid through the exemplary passageway 30a. The flow controlling section 48 may have a constant cross-sectional area across its length. In some embodiments, the cross-sectional area of the flow conditioning section 42 is 1.8 to 3.6 times larger than the cross-sectional area of the flow controlling section 48.
In some aspects of the present invention, a plurality of other sections may be formed between the above described sections. In other aspects, no other sections are formed between the above described sections.
Referring to
The cross-sectional area of the first diffuser section 40 and the second diffuser section 44 may increase in a number of manners. In one aspect, the cross-sectional area may increase by the height dimension increasing along the length of the diffusing section, as is illustrated between reference point B and reference point B′ along a portion of the first diffuser section 40 (best seen in
In some aspects, a surface angle β of the first diffuser section 40 may be between 5° and 15°. In other aspects, a surface angle γ of the second diffuser section 44 may be between 5° and 15°. In one aspect, the surface angle β and the surface angle γ are equal.
The illustrated first diffuser section 40 has a first cross-sectional area at reference point B and has a second cross-sectional area at reference point C. The first cross-sectional area is smaller than the second cross-sectional area. The cross-sectional area of the second diffuser section 44 at its smaller end (marked by reference point C′) may be the same as the second cross-sectional area at reference point C, as illustrated in
An effective cross-sectional area may be determined for the portion of the exemplary passageway 30a that comprises the channel 36 by taking a cross-sectional area normal to the longitudinal axis A and providing an effective segment to close the channel 36 (best seen in
Referring to
The one or more passageways 30 may be configured in a row, as illustrated in
Referring to
In some aspects, the method 600 further includes the step of providing an electrode 70 (shown in
In some aspects, the step of forming one or more passageways 30 through the wall 20, as depicted in block 620, may comprise plunging the one or more shaped electrode teeth 72 through the wall 20 of the airfoil 10 to form the one or more passageways 30. For example, the one or more passageways 30 may be formed through an EDM plunge process.
Referring to
The flow controlling cavity 90 may be formed within one or more flow controlling surfaces that extend between the first opening 32 and the first diffusing cavity 92. The flow controlling cavity 90 may have a constant cross-sectional area along the length of the one or more flow controlling surfaces. The flow controlling cavity 90 may be adapted for metering the amount of cooling fluid passing through the improved cooling hole 130.
The first diffusing cavity 92 may be formed within one or more first diffusing surfaces that extend between a first end associated with the flow controlling cavity 90 and a second end associated with the flow conditioning cavity 94. The cross-sectional area of the first diffusing cavity 92 increases between the first end and second end of the one or more first diffusing surfaces. The first diffusing cavity 92 expands the stream of cooling fluid passing through the improved cooling hole 130 to promote formation of a more effective layer of protective film on the second surface 24.
The flow conditioning cavity 94 may be formed within one or more flow conditioning surfaces that extend between a first end associated with the first diffusing cavity 92 and a second end associated with the second diffusing cavity 96. The flow conditioning cavity 94 may have a constant cross-sectional area along the length of the one or more flow conditioning surfaces to promote less turbulent flow of the cooling fluid passing through the improved cooling hole 130.
The second diffusing cavity 96 may be formed within one or more second diffusing surfaces that extend between a first end associated with the flow conditioning cavity 94 and a second end associated with the edge cavity 98. The cross-sectional area of the second diffusing cavity 96 increases between the first end and second end of the one or more second diffusing surfaces. The second diffusing cavity 96 expands the stream of cooling fluid passing through the improved cooling hole 130 to promote formation of a more effective layer of protective film on the second surface 24.
The edge cavity 98 may be formed within one or more edge surfaces that extend between the second diffusing cavity 96 and the second opening 34 and includes at least two opposing surfaces set across the edge cavity 98 from one another and that extend in parallel from the second diffusing cavity 96 to the second opening 34. The edge cavity 98 may have a constant cross-sectional area along the length of the one or more edge surfaces. In another aspect, the edge cavity 98 may have a constant width along the length of the at least two opposing surfaces. The edge cavity 98 may be adapted for emitting the cooling fluid in a manner that increases film coverage and uniformity in the stream of cooling fluid passing through the improved cooling hole 130 and emitting in a direction that results in less turbulence causing interference from an adjacent stream of cooling fluid emitted from an adjacent improved cooling hole 130.
From the foregoing, it will be seen that aspects described herein are well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. Since many possible aspects described herein may be made without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.
