Patent Description:
The disclosure relates to cooled blades for gas turbine engines. More particularly, the invention relates to construction of feed passageways for trailing edge cooling cavities. Such turbine blade constructions are for example disclosed in <CIT> or <CIT>.

In exemplary gas turbine engine cooled blades (e.g., of turbine sections) the blades are cooled by cooling air introduced to a cooling passageway system through inlets in the inner diameter (ID) end of a blade attachment root (e.g., a firtree or dovetail profile). Outlets are typically along the gaspath-contacting surface of the blade including along the airfoil and optionally along the outer diameter (OD) surface of the platform. Along the airfoil, cooling outlet locations include along the leading edge, along the pressure and/or suction sides, and along the trailing edge. A typical cooling passageway configuration has a trailing edge slot fed from a trailing edge cavity.

Exemplary feeding of the trailing edge cavity is from the rearmost or downstreammost cooling inlet in the root. A trunk passes radially outward from the inlet to the trailing edge cavity. Depending upon implementation, the trunk may pass directly to the cavity or may feed an uppass which, in turn, feeds the trailing edge cavity as a downpass.

Exemplary blade manufacturing techniques are investment casting techniques using ceramic cores to form the entirety or bulk of the cooling passageway system. Various methods use hybrid ceramic and refractory metal cores. An example of such a hybrid core involves a refractory metal sheet mated to a main ceramic feedcore with the refractory metal sheet ultimately casting the trailing edge discharge slot and a mating leg of the feedcore casting the trailing edge passageway/cavity that feeds the discharge slot. Additional refractory metal cores may be used at other locations along the airfoil. Furthermore, some cooling outlets may be drilled or machined (e.g., mechanically drilled or electrodischarge machined (EDM)).

In one exemplary baseline group of blades, the trailing edge passageway proceeds radially outward through a trunk section and then turns toward the trailing edge in the trailing edge cavity to feed the trailing edge outlets (e.g., via the discharge slot).

One aspect of the disclosure involves a turbine blade as set forth in claim <NUM>.

A further embodiment may additionally include, viewed normal to the end-to-end centerplane, an outside of the turn protruding forward.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, viewed normal to the end-to-end centerplane, the outside of the turn having a tighter curvature than an inside of the turn.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, viewed normal to the end-to-end centerplane, the outside of the turn protruding forward of an adjacent portion of the trunk by at least <NUM>% of a span of the adjacent portion.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, viewed normal to the end-to-end centerplane, a leading side of the turn including the outside of the turn having a transition from inwardly convex to inwardly concave to inwardly convex.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, along the inwardly concave portion of the leading side of the turn, the leading side turning by an angle of <NUM>° to <NUM>°.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, along the inwardly convex portion of the leading side of the turn radially outboard of the of the inwardly concave portion, the leading side turning by an angle of <NUM>° to <NUM>°.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, a trailing side of the turn having an inwardly concave portion turning by an angle of <NUM>° to <NUM>° before an inwardly convex transition to a discharge slot.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, an angle θ<NUM> between a stacking line and a tangent at the inflection point where the leading side begins to turn back forward being at least <NUM>°.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, viewed normal to the end-to-end centerplane, an outside of the turn having a tighter curvature than an inside of the turn.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, viewed normal to the end-to-end centerplane, the trailing trunk turning radially nests with a next forward one of the trunks.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the next forward trunk feeding an uppass-downpass-uppass.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, viewed normal to the end-to-end centerplane, the trailing trunk turn radially nesting between the next forward one of the trunks and a turn from the downpass to the downstream uppass.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the next forward trunk feeding an uppass with which the turn nests.

Another aspect of the invention includes a method for using the turbine blade, as set forth in claim <NUM>.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include at a downstream end of the turn, the air fanning out.

A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, at a downstream end of the turn, the air fanning out with a forward flowline turning by an angle of <NUM>° to <NUM>.

In <FIG>, an engine turbine element <NUM> is illustrated as a blade having an airfoil <NUM> which extends between an inboard end <NUM>, and an opposing outboard end <NUM> (e.g., at a free tip), a distance therebetween extending substantially in the engine radial direction. The airfoil also includes a leading edge <NUM> and an opposing trailing edge <NUM>. A pressure side <NUM> and an opposing suction side <NUM> extend between the leading edge <NUM> and trailing edge <NUM>.

The airfoil inboard end <NUM> is disposed at the outboard surface <NUM> of a platform <NUM>. An attachment root <NUM> extends radially inward from the underside <NUM> of the platform.

The root <NUM> has an inner diameter (ID) end or face <NUM>, an upstream axial end <NUM>, a downstream axial end <NUM>, and first and second lateral sides <NUM> and <NUM>, respectively. The root <NUM> is complementary to a disk slot (not shown). When fully seated in the disk slot, the faces <NUM> and <NUM> may face exactly forward/upstream and rearward/downstream in the engine frame of reference. Depending on disk configuration (slot orientation), the sides may extend parallel to the engine centerline between the axial ends (root having a rectangular footprint/section) or may extend skew (root having a non-right parallelogram footprint (<FIG>)) such as in the illustrated example.

The turbine blade is cast of a high temperature alloy, such as a Ni-based superalloy, for example, PWA <NUM>, which is a nickel base single crystal alloy.

The blade may also have a thermal barrier coating (TBC, e.g., one or more layer ceramic atop of one or more layer bondcoat) system along at least a portion of the airfoil. <FIG> show further details of the blade.

The blade has an internal cooling passageway system extending from one or more inlets along a root to a plurality of outlets (along or mostly along the airfoil and platform surfaces). <FIG> schematically shows spanwise passageway legs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> from the leading edge to the trailing edge. The first leg <NUM> is a leading edge impingement cavity/passageway <NUM> having separate segments <NUM>-<NUM> and <NUM>-<NUM> (<FIG>). The second leg <NUM> is an up-pass leg forming a radial feed passageway that feeds the impingement cavity <NUM> and a tip flag passageway <NUM>. The third leg <NUM> is an up-pass leg of a second feed passageway. The fourth leg <NUM> is a down-pass leg of the second feed passageway. The fifth leg <NUM> is a second up-pass leg of the second feed passageway. The sixth leg <NUM> is a trailing radial feed passageway feeding a trailing edge discharge slot <NUM>. The discharge slot extends from the trailing radial feed passageway <NUM> to an outlet <NUM> at, or near, the actual trailing edge of the blade with posts/pedestals of varying shape and distribution spanning between suction and pressure sides of the slot.

Additional outlets (e.g., cast or drilled holes, slots or other cooling features) are not shown but may be present.

The blade also includes a plurality of feed trunks <NUM>, <NUM>, <NUM>, and <NUM> extending from respective inlets <NUM>, <NUM>, <NUM>, and <NUM> at the inner diameter (ID) face <NUM> of the root. The trunks <NUM> and <NUM> merge outboard in the root to feed the leading feed passageway <NUM>, tip flag <NUM>, and impingement passageway <NUM>. The trunk <NUM> feeds the second feed passageway. The trunk <NUM> feeds the passageway <NUM>.

Spanwise arrays of impingement holes extend along impingement walls respectively separating the feed passageway leg <NUM> from the impingement passageway <NUM>. Additionally, as noted above, various surface enhancements such as posts/pedestals and standoffs may be provided along the passageways to facilitate heat transfer.

<FIG> is a schematic plan view of a prior art trailing passageway <NUM> extending from an inlet <NUM> along a root ID end to outlets <NUM> along an airfoil trailing edge. The drawing shows various pedestals <NUM> in the passageway spanning between respective sides of the passageway being a suction side and a pressure side, respectively, near the airfoil suction side and pressure side. The passageway <NUM> effectively includes a trunk section <NUM> extending to a trailing edge cavity section <NUM> which in turn extends radially outward. A trailing edge/slot <NUM> extends streamwise (airfoil streamwise) downstream. A cooling flow <NUM> passes along a flowpath defined by the passageway <NUM>. At the downstream end of the trunk <NUM> (downstream along the path of the flow <NUM>) the flow <NUM> begins to make turns into the slot <NUM>. Near the inboard (radially/spanwise) end <NUM> of the slot <NUM>, the flow makes a tight turn at a turn <NUM> from the aft/downstream end of the cross-section of the trunk <NUM>. This tight turn causes a recirculation or separation bubble/flow <NUM>-<NUM> at the turn which locally reduces cooling and reduces flow rate.

<FIG> shows a modified/improved passageway <NUM> wherein like features to the passageway <NUM> are numbered with like numbers. The relevant difference in this example is the addition of a dog leg turn <NUM> in the trunk <NUM> at an entrance to the cavity <NUM>. The dog leg turn shifts the flow <NUM> relative to the flow <NUM> and better aims the flow <NUM> to avoid the separation. This creates a flow <NUM> with an added component streamwise downstream along the airfoil. Thus, at the inner diameter of the turn to the slot <NUM>, there is a less abrupt turning of the flow <NUM> and less chance of separation. However, at the outer diameter of the turn, some of the flow <NUM> may turn slightly back forward but only relatively. This creates an outward fanning of flow between a portion turning toward the trailing edge near the ID end of the discharge slot to feed a rootward portion of the slot and a portion turning back spanwise/radially outward to feed a tipward portion of the slot <NUM>.

Alternatively, the dog leg turn can be viewed as a series of sub turns, first turning to the left in <FIG> (both leading side and trailing side tuning left), then turning right along the apex (both leading side and trailing side turning right), then fanning out (trailing side continuing to turn right into the discharge slot for feeding the onboard portion of the discharge slot and leading side turning left to flow more radially for feeding outboard portions of the discharge slot).

In effect, there is a maximum diffusion angle for which flow can adequately fill the turns as the root passage expands into the main body of the trailing passageway and discharge slot. The reduction of this abrupt angle along the trailing side reduces or eliminates flow separation from the wall. At the outer diameter of the turn this concept also applies. The diffusion angle at the outer diameter of the turn is designed to be sufficiently small as to not introduce a separation zone here instead.

The turn <NUM> ends up locally shifting portions of the forward and aft side/edges of the trunk to create respective bumps <NUM>, <NUM>. As is discussed further below, the bump <NUM> at the forward extreme may interfit with a feature of the adjacent passageway upstream. The forward extreme of the bump <NUM> may be radially outboard of the forward extreme of the bump <NUM>. This may promote the turning of flow from purely radial in trunk <NUM> to purely axial/circumferential as the flow enters the trailing edge cooling slot <NUM>. For example, this relative positioning allows the flow to expand as it approaches the apexes. This slows the flow and promotes turning without separation/recirculation along the aft side/edge.

In <FIG>, at the front/leading side, the turn (and thus the adjacent forward flowline/streamline) initially turns forward (turns left in <FIG>) by an angle θ<NUM> of at least <NUM>°, then turns back rearward (turns right in <FIG>) by an angle θ<NUM> of at least <NUM>°, then back forward by an angle θ<NUM> of at least <NUM>°.

Exemplary θ<NUM> is <NUM>° to <NUM>°, more particularly <NUM>° to <NUM>° or <NUM>° to <NUM>°. Exemplary θ<NUM> is <NUM>° to <NUM>°, more particularly, <NUM>° to <NUM>° or <NUM>° to <NUM>°. Exemplary θ<NUM> is <NUM>° to <NUM>°, more particularly <NUM>° to <NUM>° or <NUM>° to <NUM>°.

At the rear/trailing side, the turn initially turns forward by an angle θ<NUM> of at least <NUM>°, before turning back to form the discharge slot. Exemplary θ<NUM> is <NUM>° to <NUM>°, more particularly, <NUM>° to <NUM>° or <NUM>° to <NUM>°.

<FIG> also shows an angle θ<NUM> between a stacking line <NUM> and a tangent at the inflection point where the front/leading side begins to turn back forward (turns left in <FIG>) (e.g., between concave portion <NUM> and convex portion <NUM> (<FIG>) discussed below). Exemplary θ<NUM> is at least <NUM>° more particularly, <NUM>° to <NUM>° or <NUM>° to <NUM>° or <NUM>° to <NUM>°.

Returning to the specific example blade of <FIG>, <FIG> is a view orthogonal to a centerplane <NUM> (<FIG>) of the root between the lateral sides <NUM> and <NUM> which also forms a centerplane of the associated disk slot. <FIG> and <FIG> are views of the two lateral sides taken parallel to the ends. These illustrate how perspective can change the appearance of position. Thus, one may distinguish relative position between absolute front-to-back position and front-to-back viewed normal to the root/slot end-to-end centerplane.

<FIG> shows the trailing trunk <NUM> having a turn <NUM> formed as a dog leg or zigzag turn. An upstream (along the air flowpath through the blade rather than upstream along the core flowpath through the engine) portion <NUM> (<FIG>) of the trunk extends generally radially both along a forward side or edge <NUM> and a rear side or edge <NUM>. The turn <NUM> has an upstream first portion <NUM> turning forward and a downstream second portion <NUM> turning rearward (not merely rearward relative to the first portion but rearward absolutely so that, at an apex <NUM> of the turn, the forward surface protrudes forward from both the turn upstream portion <NUM> and turn downstream portion <NUM>). From the turn downstream portion <NUM>, the flowpath and forward edge <NUM> may turn partially back forward (relatively) so that the forward edge <NUM> is more radial in a downstream cavity than along the turn downstream portion <NUM>. Thus, inwardly, the forward side or edge along the turn <NUM> has a convex upstream portion <NUM> (<FIG>) transitioning to a convcave portion <NUM> along the turn apex <NUM> and to a downstream convex portion <NUM>.

A forward extreme of the forward edge <NUM> along the turn <NUM> is shown as <NUM> falling within the inwardly concave (outwardly convex) portion <NUM>.

Along the rear edge <NUM> of the passageway, the surface also dog legs to have a forward extreme or apex <NUM>. As with the bumps <NUM> and <NUM>, the extremes <NUM> and <NUM> are of respective bumps with the rear bump's extreme <NUM> radially outboard of the forward bump's extreme <NUM>. <FIG> also shows a radius of curvature R<NUM> at the forward edge apex <NUM> and R<NUM> at the rear edge apex <NUM>. As is discussed further below, counterintuitively R<NUM> may be made tighter (smaller) than R<NUM> (normally the outside of a turn would be expected to have a greater radius of curvature).

<FIG> also shows a nesting of the turn <NUM> with the adjacent passageway immediately forward, with the adjacent passageway also having a turn <NUM> (at least along its rear edge/side <NUM>) to accommodate the forward edge/side along the turn <NUM>. In the example, the accommodation is between an upstream trunk portion <NUM> of the adjacent passageway and an ID turn <NUM> from the downpass <NUM> to the uppass <NUM>.

<FIG> shows radial lines through various features including the leading side of the upstream portion <NUM> (line <NUM>), trailing side of the upstream portion <NUM> (line <NUM>), apex <NUM> (line <NUM>), etc. An exemplary shift of the apex <NUM> is by an amount D<NUM> which is at least <NUM>% of the local span D<NUM> of the passageway, or at least <NUM>% or <NUM>% to <NUM>% or <NUM>% to <NUM>%. The shift may be great enough so that the apex <NUM> is forward of the upstream portion of the trailing edge/side <NUM> of the adjacent passageway (e.g., forward of trailing edge/side <NUM> along an upstream potion of trunk <NUM>). The apex <NUM> may similarly be forward of an outboard portion of the adjacent passageway (in this case trailing edge/side <NUM> along the downstream uppass <NUM>).

<FIG> shows a more extreme shift. <FIG> is a more schematized view of an alternative blade passageway system showing blade outer contour in broken lines. In addition to <NUM>, <NUM>, and <NUM>, <FIG> labels radial lines for the apex <NUM> (line <NUM>), trailing edge/side <NUM> along an upstream potion of trunk <NUM> (line <NUM>), and trailing edge/side <NUM> along the downstream uppass <NUM> (line <NUM>). An exemplary shift of the apex <NUM> is by an amount D<NUM> which is at least <NUM>% of the local span D<NUM> of the passageway. Also the apex <NUM> is shown forward of line <NUM> by a distance D<NUM> and of line <NUM> by a distance D<NUM>. Thus, exemplary D<NUM> is larger than D<NUM>.

<FIG> shows an alternative blade wherein the adjacent passageway is, like <FIG> and <FIG>, an uppass-downpass-uppass but wherein the progression is streamwise from downstream to upstream within the airfoil.

<FIG> shows a yet alternative passageway system wherein the adjacent passageway is not an uppass-downpass-uppass.

Manufacture may be via conventional casting techniques (discussed above) where ceramic cores cast the trunks and adjacent passageway sections. The ceramic cores or mated metallic cores may cast the discharge slot.

Claim 1:
A turbine blade comprising:
an attachment root (<NUM>) having:
an inner diameter end;
a first axial end (<NUM>);
a second axial end (<NUM>),
a rearward direction defined from the first axial end to the second axial end;
a first lateral side; and
a second lateral side, an end-to-end centerplane between and extending parallel to the first and second lateral sides;
an airfoil (<NUM>) having:
a pressure side;
a suction side;
a leading edge; and
a trailing edge; and
a cooling passageway system comprising:
a plurality of trunks (<NUM>,<NUM>,<NUM>,<NUM>) extending from respective inlets (<NUM>,<NUM>,<NUM>,<NUM>) along the root inner diameter end from a leading trunk : (<NUM>) near the first axial end (<NUM>) to a trailing trunk (<NUM>) near the second axial end (<NUM>); and
a plurality of outlets along the airfoil including trailing edge outlets (<NUM>) fed by the trailing trunk,
characterised in that,
viewed normal to the end-to-end centerplane:
the trailing trunk has a turn (<NUM>) passing forward and then rearward;
an outside of the turn protrudes forward;
the outside of the turn forms a first bump (<NUM>,<NUM>);
the inside of the turn forms a second bump (<NUM>,<NUM>); and
a forward extreme of the second bump is radially outboard of a forward extreme of the first bump.