Turbine blade trailing edge with low flow framing channel

1. A core structure for casting a gas turbine engine airfoil, the core structure comprising a trailing edge section for defining a trailing edge of the gas turbine engine airfoil, wherein an axial direction is defined between a leading edge and the trailing edge of the gas turbine engine airfoil, at least a portion of the trailing edge section comprising:

a plurality of rib-forming apertures defined by a plurality of radially-extending channel elements and axially-extending passage elements, wherein the rib-forming apertures are arranged in radially-aligned columns, the rib-forming apertures of alternating radially-aligned columns forming axially-aligned rows; and

a radially outer framing channel element located adjacent to a radially outer edge of the trailing edge section, wherein the radially outer framing channel element comprises a plurality of notches extending radially inwardly from the radially outer edge;

wherein the rib-forming apertures comprising a first axially-aligned outer row are elongated in a radial direction such that a distal portion of the notches overlaps in the axial direction with a proximal portion of the rib-forming apertures comprising the first axially-aligned outer row;

wherein the rib-forming apertures comprise a second axially-aligned outer row located radially inward of the first axially-aligned outer row, wherein the notches are radially aligned with the rib-forming apertures of the second axially-aligned outer row;

wherein the rib-forming apertures comprise a third axially-aligned outer row located radially inward of the second axially-aligned outer row,

wherein the rib-forming apertures comprise a remaining axially-aligned outer row located radially inward of the third axially-aligned outer row,

wherein the rib-forming apertures comprising the first axially-aligned outer row, the third axially-aligned outer row and the remaining axially-aligned outer row form the alternating radially-aligned columns,

wherein a radial height of a first axially-extending passage element and a radial height of a second axially-extending passage element are greater than a minimal radial height of the axially-extending passage elements within the core structure,

wherein the radial height of the first axially-extending passage element is defined between the radially outer edge and a proximal end of the rib-forming apertures comprising the first axially-aligned outer row,

wherein the radial height of the second axially-extending passage element is defined between a distal end of the rib-forming apertures comprising the first axially-aligned outer row and a proximal end of the rib-forming apertures comprising the third axially-aligned outer row, and

wherein the minimal radial height of the axially-extending passage elements is defined between a distal end of the rib-forming apertures comprising the third axially-aligned outer row and a proximal end of the rib-forming apertures comprising the remaining axially-aligned outer row.

2. The core structure of claim 1 , wherein the rib-forming apertures comprising the third axially-aligned outer row are elongated in the radial direction such that the rib-forming apertures comprising the second axially-aligned outer row overlap in the axial direction with the rib-forming apertures comprising the third axially-aligned outer row.

3. The core structure of claim 1 , wherein a portion of the radially outer edge between the notches comprises a substantially planar area.

4. The core structure of claim 1 , wherein the trailing edge section further comprises a radially inner framing channel element located adjacent to a radially inner edge of the trailing edge section, wherein the radially inner framing channel element comprises a further plurality of notches extending radially outwardly from the radially inner edge;

wherein a first axially-aligned inner row of the rib-forming apertures is elongated in the radial direction such that a distal portion of the further plurality of notches overlaps in the axial direction with the rib-forming apertures comprising the first axially-aligned inner row; and

wherein the further plurality of notches are radially aligned with the rib-forming apertures of a second axially-aligned inner row of the rib-forming apertures.

5. The core structure of claim 4 , wherein a portion of the radially inner edge between the further plurality of notches comprises a substantially planar area.

6. An airfoil in a gas turbine engine comprising:

an outer wall defining a leading edge, a trailing edge, a pressure side, a suction side, a radially inner end, and a radially outer tip comprising a tip cap, wherein an axial direction is defined between the leading edge and the trailing edge;

a trailing edge cooling circuit defined in a portion of the outer wall adjacent to the trailing edge and receiving cooling fluid for cooling the outer wall, the trailing edge cooling circuit comprising:

a plurality of axially-extending passages and a plurality of radially-extending channels defined by a plurality of rib structures, wherein the rib structures are arranged in radially-aligned columns that are substantially transverse to a flow axis of the cooling fluid, the rib structures of alternating radially-aligned columns forming axially-aligned rows; and

a radially outer framing channel located adjacent to the tip cap and comprising a plurality of protrusions extending radially inwardly from the tip cap;

wherein the rib structures comprising a first axially-aligned outer row are elongated in a radial direction such that a distal portion of the protrusions overlaps in the axial direction with a proximal portion of the rib structures comprising the first axially-aligned outer row;

wherein the rib structures comprise a second axially-aligned outer row located radially inward of the first axially-aligned outer row, wherein the protrusions are radially aligned with the rib structures of the second axially-aligned outer row;

wherein the rib structures comprise a third axially-aligned outer row located radially inward of the second axially-aligned outer row,

wherein the rib structures comprise a remaining axially-aligned outer row located radially inward of the third axially-aligned outer row,

wherein the rib structures comprising the first axially-aligned outer row, the third axially-aligned outer row, and the remaining axially-aligned outer row form the alternating radially-aligned columns,

wherein the protrusions are substantially transverse to a flow axis of the cooling fluid;

wherein a radial height of a first axially-extending passage and a radial height of a second axially-extending passage are greater than a minimal radial height of the axially-extending passages in the trailing edge cooling circuit,

wherein the radial height of the first axially-extending passage is defined between the tip cap and a proximal end of the rib structures comprising the first axially-aligned outer row,

wherein the radial height of the second axially-extending passage is defined between a distal end of the rib structures comprising the first axially-aligned outer row and a proximal end of the rib structures comprising the third axially-aligned outer row, and

wherein the minimal radial height of the axially-extending passages is defined between a distal end of the rib structures comprising the third axially-aligned outer row and a proximal end of the rib structures comprising the remaining axially-aligned outer row.

7. The airfoil of claim 6 , wherein the rib structures comprising the third axially-aligned outer row are elongated in the radial direction such that the rib structures comprising the second axially-aligned outer row overlap in the axial direction with the rib structures comprising the third axially-aligned outer row.

8. The airfoil of claim 6 , wherein the plurality of rib structures and the plurality of protrusions define a flowpath in the axial direction through the radially outer framing channel that requires the cooling fluid to make a plurality of 90 degree turns.

9. The airfoil of claim 6 , wherein the trailing edge cooling circuit further comprises a radially inner framing channel located adjacent to the radially inner end and comprising a further plurality of protrusions extending radially outwardly from the radially inner edge;

wherein the rib structures comprising a first axially-aligned inner row are elongated in the radial direction such that a distal portion of the further plurality of protrusions overlaps in the axial direction with the rib structures comprising the first axially-aligned inner row;

wherein the rib structures comprising a third axially-aligned inner row are elongated in the radial direction such that the rib structures comprising a second axially-aligned inner row overlap in the axial direction with the rib structures comprising the third axially-aligned inner row;

wherein the further plurality of protrusions are radially aligned with the rib structures comprising the second axially-aligned inner row; and

wherein the further plurality of protrusions are substantially transverse to the flow axis of the cooling fluid.

10. The airfoil of claim 9 , wherein the plurality of rib structures and the further plurality of protrusions define a flowpath in the axial direction through the radially inner framing channel that requires the cooling fluid to make a plurality of 90 degree turns.