Patent Publication Number: US-11661852-B2

Title: Turbine blade trailing edge cooling feed

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Benefit is claimed of U.S. Patent Application No. 62/802,987, filed Feb. 8, 2019, and entitled “Turbine Blade Trailing Edge Cooling Feed”, the disclosure of which is incorporated by reference herein in its entirety as if set forth at length. 
    
    
     BACKGROUND 
     The disclosure relates to cooled blades for gas turbine engines. More particularly, the disclosure relates to construction of feed passageways for trailing edge cooling cavities. 
     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). 
     SUMMARY 
     One aspect of the disclosure involves a turbine blade comprising: an attachment root and an airfoil. The root has: an inner diameter end; a first axial end; a second axial end, 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. The airfoil has: a pressure side; a suction side; a leading edge; and a trailing edge. A cooling passageway system comprises: a plurality of trunks extending from respective inlets along the root inner diameter end from a leading trunk near the first axial end to a trailing trunk near the second axial end; and a plurality of outlets along the airfoil including trailing edge outlets fed by the trailing trunk. Viewed normal to the end-to-end centerplane, the trailing trunk has a turn passing forward and then rearward. 
     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 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, the outside of the turn forming a first bump and the inside of the turn forming a second bump. 
     A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include, a forward extreme of the second bump being radially outboard of a forward extreme of the first bump. 
     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 10% 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 30° to 120°. 
     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 inwardly concave portion, the leading side turning by an angle of 30° to 55°. 
     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 25° to 50° 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 5  between a stacking line and a tangent at the inflection point where the leading side begins to turn back forward being at least 15°. 
     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. 
     A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include a method for using the turbine blade, the method comprising: passing air in through the inlets and out the outlets, wherein: air passing along the turn avoids separation. 
     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 15° to 60. 
     Another aspect of the disclosure involves a turbine blade comprising an attachment root and an airfoil. The root has: an inner diameter end; a first axial end; a second axial end, 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. The airfoil has: a pressure side; a suction side; a leading edge; and a trailing edge. A cooling passageway system comprises: a plurality of trunks extending from respective inlets along the root inner diameter end from a leading trunk near the first axial end to a trailing trunk near the second axial end; and a plurality of outlets along the airfoil including trailing edge outlets fed by the trailing trunk. The trailing trunk has means for limiting flow separation at a turn. 
     A further embodiment of any of the foregoing embodiments may additionally and/or alternatively include the means being means for turning a flow forward and then rearward. 
     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 10% of a span of the adjacent portion. 
     Another aspect of the disclosure involves a turbine blade comprising: an attachment root and an airfoil. The root has: an inner diameter end; a first axial end; a second axial end, 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. The airfoil has: a pressure side; a suction side; a leading edge; and a trailing edge. A cooling passageway system comprises: a plurality of trunks extending from respective inlets along the root inner diameter end from a leading trunk near the first axial end to a trailing trunk near the second axial end; and a plurality of outlets along the airfoil including trailing edge outlets fed by the trailing trunk. Viewed normal to the end-to-end centerplane: the trailing trunk has a turn passing forward and then rearward; an outside of the turn protrudes forward the outside of the turn forms a first bump; the inside of the turn forms a second bump; and a forward extreme of the second bump is radially outboard of a forward extreme of the first bump. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a view of a turbine blade. 
         FIG.  2    is an X-ray pressure side view of the blade of  FIG.  1   . 
         FIG.  2 A  is an enlarged view of a root portion of the blade of  FIG.  2   . 
         FIG.  2 B  is an enlarged view of a passageway turn in the blade of  FIG.  2 A . 
         FIG.  3    is an X-ray pressure side view of a root portion of the blade of  FIG.  1    viewed circumferentially relative to an installed condition. 
         FIG.  4    is an X-ray suction side view of a root portion of the blade of  FIG.  1    viewed circumferentially relative to an installed condition. 
         FIG.  5    is a transverse sectional view of an airfoil of the blade taken along line  5 - 5  of  FIG.  2   . 
         FIG.  6    is an underside or inner diameter (ID) view of the blade of  FIG.  1   . 
         FIG.  7    is a schematicized view of a cooling passageway system of a first alternate blade. 
         FIG.  7 A  is an enlarged view of a passageway turn in the blade of  FIG.  7   . 
         FIG.  8    is a schematicized view of a cooling passageway system of a second alternate blade. 
         FIG.  8 A  is an enlarged view of a passageway turn in the blade of  FIG.  8   . 
         FIG.  9    is a schematicized view of a cooling passageway system of a third alternate blade. 
         FIG.  10    is a schematic plan view of a prior art trailing passageway. 
         FIG.  11    is a schematic plan view of a trailing passageway modified from that of  FIG.  10   . 
         FIG.  11 A  is an enlarged view of a turn in the passageway of  FIG.  11   . 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     In  FIG.  1   , an engine turbine element  20  is illustrated as a blade having an airfoil  22  which extends between an inboard end  24 , and an opposing outboard end  26  (e.g., at a free tip), a distance therebetween extending substantially in the engine radial direction. The airfoil also includes a leading edge  28  and an opposing trailing edge  30 . A pressure side  32  and an opposing suction side  34  extend between the leading edge  28  and trailing edge  30 . 
     The airfoil inboard end  24  is disposed at the outboard surface  40  of a platform  42 . An attachment root  44  extends radially inward from the underside  46  of the platform. 
     The root  44  has an inner diameter (ID) end or face  48 , an upstream axial end  50 , a downstream axial end  52 , and first and second lateral sides  54  and  56 , respectively. The root  44  is complementary to a disk slot (not shown). When fully seated in the disk slot, the faces  50  and  52  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.  6   )) 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 1484, 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.  FIGS.  2 - 6    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.  5    schematically shows spanwise passageway legs  80 ,  81 ,  82 ,  83 ,  84 , and  85  from the leading edge to the trailing edge. The first leg  80  is a leading edge impingement cavity/passageway  80  having separate segments  80 - 1  and  80 - 2  ( FIG.  2   ). The second leg  81  is an up-pass leg forming a radial feed passageway that feeds the impingement cavity  80  and a tip flag passageway  87 . The third leg  82  is an up-pass leg of a second feed passageway. The fourth leg  83  is a down-pass leg of the second feed passageway. The fifth leg  84  is a second up-pass leg of the second feed passageway. The sixth leg  85  is a trailing radial feed passageway feeding a trailing edge discharge slot  88 . The discharge slot extends from the trailing radial feed passageway  85  to an outlet  90  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  100 ,  102 ,  104 , and  106  extending from respective inlets  110 ,  112 ,  114 , and  116  at the inner diameter (ID) face  48  of the root. The trunks  100  and  102  merge outboard in the root to feed the leading feed passageway  81 , tip flag  87 , and impingement passageway  80 . The trunk  104  feeds the second feed passageway. The trunk  106  feeds the passageway  85 . 
     Spanwise arrays of impingement holes extend along impingement walls respectively separating the feed passageway leg  81  from the impingement passageway  80 . Additionally, as noted above, various surface enhancements such as posts/pedestals and standoffs may be provided along the passageways to facilitate heat transfer. 
       FIG.  10    is a schematic plan view of a prior art trailing passageway  800  extending from an inlet  802  along a root ID end to outlets  804  along an airfoil trailing edge. The drawing shows various pedestals  806  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  800  effectively includes a trunk section  810  extending to a trailing edge cavity section  812  which in turn extends radially outward. A trailing edge/slot  814  extends streamwise (airfoil streamwise) downstream. A cooling flow  820  passes along a flowpath defined by the passageway  800 . At the downstream end of the trunk  810  (downstream along the path of the flow  820 ) the flow  820  begins to make turns into the slot  814 . Near the inboard (radially/spanwise) end  830  of the slot  814 , the flow makes a tight turn at a turn  832  from the aft/downstream end of the cross-section of the trunk  810 . This tight turn causes a recirculation or separation bubble/flow  820 - 1  at the turn which locally reduces cooling and reduces flow rate. 
       FIG.  11    shows a modified/improved passageway  900  wherein like features to the passageway  800  are numbered with like numbers. The relevant difference in this example is the addition of a dog leg turn  902  in the trunk  910  at an entrance to the cavity  912 . The dog leg turn shifts the flow  920  relative to the flow  820  and better aims the flow  920  to avoid the separation. This creates a flow  920  with an added component streamwise downstream along the airfoil. Thus, at the inner diameter of the turn to the slot  814 , there is a less abrupt turning of the flow  920  and less chance of separation. However, at the outer diameter of the turn, some of the flow  920  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  814 . 
     Alternatively, the dog leg turn can be viewed as a series of sub turns, first turning to the left in  FIG.  11    (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  902  ends up locally shifting portions of the forward and aft side/edges of the trunk to create respective bumps  930 ,  932 . As is discussed further below, the bump  930  at the forward extreme may interfit with a feature of the adjacent passageway upstream. The forward extreme of the bump  932  may be radially outboard of the forward extreme of the bump  930 . This may promote the turning of flow from purely radial in trunk  910  to purely axial/circumferential as the flow enters the trailing edge cooling slot  814 . 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.  11 A , at the front/leading side, the turn (and thus the adjacent forward flowline/streamline) initially turns forward (turns left in  FIG.  11 A ) by an angle θ 1  of at least 15°, then turns back rearward (turns right in  FIG.  11 A ) by an angle θ 2  of at least 30°, then back forward by an angle θ 3  of at least 15°. 
     Exemplary θ 1  is 15° to 60°, more particularly 25° to 60° or 30° to 55°. Exemplary θ 2  is 30° to 120°, more particularly, 60° to 100° or 75° to 100°. Exemplary θ 3  is 15° to 60°, more particularly 25° to 60° or 30° to 55°. 
     At the rear/trailing side, the turn initially turns forward by an angle θ 4  of at least 15°, before turning back to form the discharge slot. Exemplary θ 4  is 15° to 60°, more particularly, 25° to 50° or 25° to 40°. 
       FIG.  11 A  also shows an angle θ 5  between a stacking line  530  and a tangent at the inflection point where the front/leading side begins to turn back forward (turns left in  FIG.  11 A ) (e.g., between concave portion  226  and convex portion  227  ( FIG.  2 B ) discussed below). Exemplary θ 5  is at least 15° more particularly, 15° to 60° or 25° to 60° or 30° to 55°. 
     Returning to the specific example blade of  FIGS.  2 - 6   ,  FIG.  2    is a view orthogonal to a centerplane  520  ( FIG.  6   ) of the root between the lateral sides  54  and  56  which also forms a centerplane of the associated disk slot.  FIGS.  3  and  4    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.  2    shows the trailing trunk  106  having a turn  200  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  202  ( FIG.  2 A ) of the trunk extends generally radially both along a forward side or edge  210  and a rear side or edge  212 . The turn  200  has an upstream first portion  220  turning forward and a downstream second portion  222  turning rearward (not merely rearward relative to the first portion but rearward absolutely so that, at an apex  224  of the turn, the forward surface protrudes forward from both the turn upstream portion  220  and turn downstream portion  222 ). From the turn downstream portion  222 , the flowpath and forward edge  210  may turn partially back forward (relatively) so that the forward edge  210  is more radial in a downstream cavity than along the turn downstream portion  222 . Thus, inwardly, the forward side or edge along the turn  200  has a convex upstream portion  225  ( FIG.  2 B ) transitioning to a convcave portion  226  along the turn apex  224  and to a downstream convex portion  227   
     A forward extreme of the forward edge  210  along the turn  200  is shown as  230  falling within the inwardly concave (outwardly convex) portion  226 . 
     Along the rear edge  212  of the passageway, the surface also dog legs to have a forward extreme or apex  240 . As with the bumps  930  and  932 , the extremes  230  and  240  are of respective bumps with the rear bump&#39;s extreme  240  radially outboard of the forward bump&#39;s extreme  230 .  FIG.  2 B  also shows a radius of curvature R 1  at the forward edge apex  230  and R 2  at the rear edge apex  240 . As is discussed further below, counterintuitively R 1  may be made tighter (smaller) than R 2  (normally the outside of a turn would be expected to have a greater radius of curvature). 
       FIG.  2    also shows a nesting of the turn  200  with the adjacent passageway immediately forward, with the adjacent passageway also having a turn  260  (at least along its rear edge/side  262 ) to accommodate the forward edge/side along the turn  200 . In the example, the accommodation is between an upstream trunk portion  104  of the adjacent passageway and an ID turn  264  from the downpass  83  to the uppass  84 . 
       FIG.  2 A  shows radial lines through various features including the leading side of the upstream portion  202  (line  550 ), trailing side of the upstream portion  202  (line  552 ), apex  230  (line  554 ), etc. An exemplary shift of the apex  230  is by an amount D 10  which is at least 10% of the local span D 12  of the passageway, or at least 20% or 10% to 100% or 20% to 100%. The shift may be great enough so that the apex  230  is forward of the upstream portion of the trailing edge/side  262  of the adjacent passageway (e.g., forward of trailing edge/side  262  along an upstream potion of trunk  104 ). The apex  230  may similarly be forward of an outboard portion of the adjacent passageway (in this case trailing edge/side  262  along the downstream uppass  84 ). 
       FIG.  7    shows a more extreme shift.  FIG.  7    is a more schematized view of an alternative blade passageway system showing blade outer contour in broken lines. In addition to  550 ,  552 , and  554 ,  FIG.  7 A  labels radial lines for the apex  240  (line  556 ), trailing edge/side  262  along an upstream potion of trunk  104  (line  560 ), and trailing edge/side  262  along the downstream uppass  84  (line  562 ). An exemplary shift of the apex  240  is by an amount D 11  which is at least 5% of the local span D 12  of the passageway. Also the apex  230  is shown forward of line  560  by a distance D 14  and of line  562  by a distance D 16 . Thus, exemplary D 10  is larger than D 11 . 
       FIG.  8    shows an alternative blade wherein the adjacent passageway is, like  FIG.  2    and  FIG.  7   , an uppass-downpass-uppass but wherein the progression is streamwise from downstream to upstream within the airfoil. 
       FIG.  9    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. 
     The use of “first”, “second”, and the like in the following claims is for differentiation within the claim only and does not necessarily indicate relative or absolute importance or temporal order. Similarly, the identification in a claim of one element as “first” (or the like) does not preclude such “first” element from identifying an element that is referred to as “second” (or the like) in another claim or in the description. 
     One or more embodiments have been described. Nevertheless, it will be understood that various modifications may be made. For example, when applied to an existing baseline configuration, details of such baseline may influence details of particular implementations. Accordingly, other embodiments are within the scope of the following claims.