Patent Description:
The high pressure turbine drives the high pressure compressor through an outer shaft to form a high spool, and the low pressure turbine drives the low pressure compressor through an inner shaft to form a low spool. The fan section may also be driven by the low inner shaft. A direct drive gas turbine engine includes a fan section driven by the low spool such that the low pressure compressor, low pressure turbine and fan section rotate at a common speed in a common direction.

<CIT> describes a turbine component that includes a root, a tip, and an airfoil portion having a leading and a trailing edge, an external suction side and pressure side wall between the leading and trailing edge. The walls enclose a central cavity for the passage of cooling air.

<CIT> describes a gas turbine engine hollow airfoil including an airfoil outer wall having width wise spaced aparted pressure and suction side walls joined together at chordally spaced apart leading and trailing edges of the airfoil and extending longitudinally from a root to a tip.

According to an aspect of the present disclosure, there is provided an airfoil as recited in claim <NUM>.

In a further embodiment of any of the foregoing embodiments, the third unbranched arm connects at the node.

In a further embodiment of any of the foregoing embodiments, the third unbranched arm connects at one of the first or second unbranched arms.

In a further embodiment of any of the foregoing embodiments, with the second side wall as a base, the triangular passage defines a height (h) and a width (w) that have a ratio of h/w of less than <NUM>.

In a further embodiment of any of the foregoing embodiments, the ratio is less than <NUM>.

In a further embodiment of any of the foregoing embodiments, the first and second arms are of substantially equal length.

In a further embodiment of any of the foregoing embodiments, the pentagonal passage has a longest side defined by the first side wall.

In a further embodiment of any of the foregoing embodiments, the second side wall is a suction side.

In a further embodiment of any of the foregoing embodiments, the pentagonal passage is part of a serpentine cooling air circuit.

In a further embodiment of any of the foregoing embodiments, the pentagonal passage excludes any cooling apertures through the first and second side walls.

According to an aspect of the present disclosure, there is provided a gas turbine engine as recited in claim <NUM>.

<FIG> shows a representation of a sectioned airfoil <NUM> used in the turbine engine <NUM> (see also <FIG>), and <FIG> illustrates a view of the region identified in <FIG>. The airfoil <NUM> is a turbine blade; however, it is to be understood that this disclosure is also applicable to cooled blades or vanes.

The airfoil <NUM> includes an (outer) airfoil wall <NUM> that spans in a radial direction and delimits the aerodynamic profile of the airfoil <NUM>. In this regard, the wall <NUM> defines a leading end 62a, a trailing end 62b, and first and second side walls 62c/62d that join the leading end 62a and the trailing end 62b. In this example, the first side wall 62c is a pressure side and the second side wall 62d is a suction side. The terminology "first" and "second" as used herein is to differentiate that there are two architecturally distinct components or features. It is to be understood that the terms "first" and "second" are interchangeable in the embodiments herein such that a first component or feature could alternatively be termed as a second component or feature, and vice versa.

The airfoil <NUM> further includes one or more ribs <NUM>. In the illustrated example, the airfoil has two such ribs <NUM>, although in modified examples the airfoil <NUM> can include a single rib <NUM> or more than two ribs <NUM>. And although a single rib <NUM> is described in some instances herein, it is to be understood that each such rib <NUM> has the described attributes of the single rib <NUM>. The ribs <NUM> and a rib <NUM> partition the interior cavity of the airfoil <NUM> into several passages, which in this example include a forward-most passage 66a, an aft-most passage 66d, a forward intermediate passage 66b, and an aft intermediate passage 66c.

Each rib <NUM> connects the first and second side walls 62c/62d and is generally longitudinally elongated between an inner diameter and outer diameter of the airfoil <NUM>. Except for connection through the airfoil wall <NUM>, the ribs <NUM> are disjoined from each other. As used herein, the term "disjoined" refers to the ribs <NUM> excluding any structural attachments to each other. Such an attachment configuration permits each rib <NUM> to reinforce the side walls 62c/62d and facilitate reduction in bulging from internal pressure, while still permitting the ribs <NUM> to move and thermally expand and contract at a different rate than the side walls 62c/62d during thermal cycling and without interference from adjacent ribs <NUM>.

Each rib <NUM> includes first and second unbranched arms <NUM>/<NUM> that initiate at the second side wall 62d and extend there from to meet at a node, identified at N. A third unbranched arm <NUM> initiates at the first side wall 62c and extends perpendicularly (locally) there from. The third unbranched side arm <NUM> connects to the first and second unbranched arms <NUM>/<NUM> at the node (N) in this example. The perpendicular orientation provides the shortest distance to the node (N), thereby facilitating reductions in airfoil mass. The term "unbranched" refers to an arm that has no other arms extending off of it between its initiation point and the node to which it connects. It is to be further understood that the term "perpendicular" or variations thereof encompass deviations from <NUM>° due to manufacturing tolerances or other variances, such as deviations of <NUM>° +/- <NUM>%.

The first and second unbranched arms <NUM>/<NUM> together with the second side wall 62d define a triangular passage <NUM> (triangular in cross-sectional shape, taken in a plane perpendicular to the radial direction). The two ribs <NUM> in the airfoil <NUM> in this example also define the aft-intermediate passage 66c there between. In the illustrated example, the aft-intermediate passage 66c is a pentagonal passage (pentagonal in cross-sectional shape) that is bound by the third unbranched arms <NUM>, the first unbranched arm <NUM> of one of the aft one of the ribs <NUM>, the second unbranched arm <NUM> of the forward one of the ribs <NUM>, and the first side wall 62c.

Cooling air, such as bleed air from the compressor section <NUM>, is fed into and through the passages 66a/66b/66c/66d/<NUM>. For example, the triangular passages <NUM> are radial flow passages and the passages 66a/66b/66c/66d are a part of a serpentine cooling air circuit, generally denoted at <NUM>. In this regard, the triangular passages <NUM> are fed from a radially inner location of the airfoil <NUM> (and/or radially outer location if the airfoil <NUM> is a vane) and the cooling air flows radially outwards. The cooling air is then discharged through the tip of the airfoil and/or through one or more cooling apertures <NUM>. The triangular passages <NUM> serve to cool the second side wall 62d.

Cooling air for the passages 66a/66b/66c/66d is also fed from a radially inner location to either the passage 66a (for a forward-to-aft flow strategy) or passage 66d (for an aft-to-forward flow strategy). The cooling air then flow sequentially through the passages 66a/66b/66c/66d, turning in a platform or tip to flow from one passage to the next. The passages 66a/66b/66c/66d serve to cool the first side wall 62c. As will be appreciated, alternate cooling air feed schemes may alternatively be used, such as but not limited to, separately fed serpentine passage groups.

The passages <NUM> are flow isolated from the passages 66a/66b/66c/66d. As used herein, the phrase "flow isolated" or variations thereof refers to passages, channels, or both that are not fluidly connected to each other within the airfoil <NUM> such that air cannot flow within the airfoil <NUM> from one passage or channel to the other passage or channel. For instance, the cooling of the first side wall 62c is in essence segregated from the cooling of the second side wall 62d. This enables the cooling to be controlled and optimized for each side wall 62c/62d. As an example, different cooling air pressures are utilized in the triangular passages <NUM> versus the passages 66a/66b/66c/66d. Such pressures can be controlled, for example, by metering orifices or the like at or near the inlets of the cooling air into the passages 66a/66b/66c/66d/<NUM>.

Additionally, Coriolis effects cause relatively high heat transfer on the first side wall 62c and relatively low heat transfer on the second side wall 62d in radially outward cooling air flow schemes, facilitating reduction in thermal stresses between the relatively hot side walls 62c/62d and the relatively cool ribs <NUM>. This is further facilitated by the geometry of the pentagonal passage 66c. For example, the passage 66c has a longest side defined by the first side wall 62c and a shortest side defined by one or both of the unbranched arms <NUM>/<NUM>.

In additional examples, to facilitate additional cooling and performance enhancement, the triangular passages <NUM> have low aspect ratio geometries. For instance, referring to the triangular passage <NUM> in <FIG>, the second side wall 62d serves as the base of the triangle and defines a width (w). The arms <NUM>/<NUM> serve as the sides of the triangle and define a height (h). Such a width and height are defined by straight-line distances with respect to mid-line axes of the walls and intersections of such axes. In one example, the triangular passage <NUM> has an aspect ratio h/w of less than <NUM>. A low aspect ratio enables fewer of the triangular passages <NUM> to cool the second side wall 62d, thereby reducing the number of ribs and in turn reducing airfoil mass. In a further example, the triangular passage <NUM> has an aspect ratio h/w of less than <NUM>, which may facilitate further weight reduction as well as minimize reduction in heat transfer due to Coriolis effects.

In an additional example, the unbranched arms <NUM>/<NUM> are of substantially equal length. For example, the lengths are taken as straight line distances with respect to mid-line axes of the walls and intersections of such axes. The term "substantially equal" or variations thereof encompass deviations due to manufacturing tolerances or other variances, such as deviations of <NUM>% between the lengths of the unbranched arms <NUM>/<NUM>. The configuration in which the unbranched arms <NUM>/<NUM> are of substantially equal length facilitates balancing heat transfer and thermal stresses. Additionally, as the unbranched arms <NUM>/<NUM> are non-parallel with the second side wall 62d, the triangular passage <NUM> permits flexibility for the second side wall 62d to thermally expand/contract. For example, differences in thermal growth between the second side wall 62d and the rib <NUM> are taken up by the height of the triangle such that in a relatively cold state the triangle elongates in height and in a relatively hot state the triangle compresses in height.

The configuration of the rib or ribs <NUM> provides additional cooling configurations. For instance, as shown in the airfoil <NUM> in <FIG>, the third unbranched arm <NUM> connects to the second unbranched arm <NUM> at the node (N1) in this example rather than a node that is at the apex of the triangle as in the example in <FIG>. As will be appreciated, the third unbranched arm <NUM> may alternatively connect to the first unbranched arm <NUM>. In either case, the unbranched arm <NUM> is longer than in the example in <FIG> and thus adds mass in comparison. However, changing the location of the node facilitates changing the size of the passages 66b/66c/66d/<NUM> to further tailor cooling effects.

<FIG> illustrates a further example airfoil <NUM> that is the same as the airfoil <NUM> except that the orientation of the ribs <NUM> is flipped such that the triangular passages <NUM> border the first side wall 62c and the passages 66b/66c/66d border the second side wall 62d. For example, such a configuration facilitates reducing the amount of cooling air flow for high heat transfer on the pressure side. Additionally, the passages 66b/66c/66d may be part of a serpentine circuit as discussed above. The passages 66c/66d may exclude any film cooling apertures and the passage 66b may have film cooling apertures such that the cooling air is discharged forward of the gauge point of the airfoil <NUM>. The gauge point is the axial location on the suction side of an airfoil where the gaspath Mach number is maximum and gaspath flow changes from accelerating to decelerating. Injecting the cooling air into the accelerating flow forward of the gauge point facilitates less loss than injecting into the decelerating flow.

In additional examples, the airfoils <NUM>/<NUM>/<NUM> include cooling apertures <NUM>. Flow arrows of the cooling air are shown and a depiction of a flow arrow that extends through a wall indicates that there is a cooling hole or aperture <NUM> at that location (not all of which are numbered).

The cooling apertures <NUM> provide additional cooling schemes to further enhance cooling. For instance, some of the cooling apertures <NUM> may serve as impingement holes to concentrate flow onto the inside surface of the adjacent portion of the wall <NUM>. Other of the cooling apertures that are on the wall <NUM> serve as film cooling holes for the exterior surfaces of the airfoil wall <NUM>. Other of the cooling apertures <NUM> that are on the long portions of the second and third arms <NUM>/<NUM> serve as feed holes to feed cooling air from the serpentine cooling air circuit <NUM> into the passage <NUM>. Therefore, various configurations of the cooling apertures <NUM> can be used to control cooling air flow in the respective airfoils. In these examples, although cooling air may flow radially, the cooling apertures <NUM> provide for impingement cooling and axial flow of the cooling air.

Claim 1:
An airfoil (<NUM>) comprising:
an airfoil wall (<NUM>) defining a leading end (62a), a trailing end (62b), a first side wall (62c), and a second side wall (62d); and
a rib (<NUM>) connecting the first and second side walls (62c, 62d) of the airfoil wall (<NUM>), the rib (<NUM>) including
first and second unbranched arms (<NUM>, <NUM>) initiating at the second side wall (62d) and extending there from to meet at a node (N), and
a third unbranched arm (<NUM>) initiating at the first side wall (62c), the third unbranched arm (<NUM>) extending perpendicularly there from and connecting at either the node (N), the first unbranched arm (<NUM>), or the unbranched second arm (<NUM>),
wherein the first and second unbranched arms (<NUM>, <NUM>) together with the second side wall (62d) define a triangular passage (<NUM>), and
characterised in that the third unbranched arm (<NUM>) and the first side wall (62c) border a passage that is flow isolated from the triangular passage (<NUM>).