Discreetly defined porous wall structure for transpirational cooling
A wall structure ( 32, 42, 68, 70, 80 ) with layers (A, B, C, D, E) of non-random voids ( 26 A, 26 B, 28 B, 30 B) that interconnect to form discretely defined tortuous passages between an interior ( 21 ) and an exterior surface ( 23 ) of the wall for transpiration cooling of the wall. A coolant flow ( 38 ) through the wall may be metered by restrictions in coolant outlets ( 31 ) and/or within the passages to minimize the coolant requirement. Pockets ( 44 ) may be formed on the exterior surface of the wall for thermal Insulation ( 46 ). The layers may be formed by lamination, additive manufacturing, or casting. Layer geometries include alternating layers (A, B, C) with different overlapping void patterns ( 42 ), 3-D lattice structures ( 70 ), and offset waffle structures ( 80 ).
1. A porous structure comprising:
a wall comprising an interior and an exterior surface;
a pattern of discretely defined voids in the wall forming a plurality of serpentine passages effective to provide transpiration cooling between the interior and exterior surfaces;
wherein the serpentine passages are formed by partially overlapping voids in alternating layers of the wall;
and wherein the layers are non-parallel to a plane of the interior or exterior surface.
2. The porous structure of claim 1 , wherein the layers are substantially normal to the plane of the interior or exterior surface.
3. The porous structure of claim 1 , wherein some of the voids in at least some of the layers are open to the interior wall surface, forming inlets to the serpentine passages, and others of the voids in at least some of the layers are open to the exterior wall surface, forming outlets of the serpentine passages.
4. The porous structure of claim 3 , wherein said some of the voids are not open to the exterior wall surface, and said others of the voids are not open to the interior wall surface, and each serpentine passage goes through at least two of the layers to communicate between the interior and exterior wall surfaces.
5. The porous structure of claim 3 , wherein at least some of said others of the voids comprise a constricted outlet at the exterior surface of the wall to meter a coolant fluid passing through the serpentine passages.
6. The porous structure of claim 3 , wherein a degree of overlap between at least some overlapping voids is restricted to meter a coolant fluid passing through the serpentine passages.
7. The porous structure of claim 1 formed as a lattice of nodes and links comprising interconnected planes of interconnected unit cells on a scale of 0.1 to 5.0 mm unit cell spacing, wherein the lattice allows particles at least up to 10 microns in diameter to pass through the porous structure.
8. The porous structure of claim 1 formed by layers of waffle structures with open-ended cells.
9. The porous structure of claim 8 , wherein adjacent layers are offset by up to half a diagonal spacing of the open-ended cells.
10. The porous structure of claim 9 , wherein each open-ended cell has a bottom wall with a pass-through hole.
11. A porous structure comprising:
a wall comprising layers of voids that are determinate and non-random;
wherein the voids interconnect between layers to form a plurality of tortuous passages between an interior and an exterior surface of the wall; and
wherein the layers are non-parallel to a plane of the interior or exterior surface;
and wherein the tortuous passages are formed by partially overlapping voids in alternating layers of the wall.
12. The porous structure of claim 11 wherein some of the voids in at least some of the layers are open to the interior wall surface, forming inlets to the tortuous passages, and others of the voids in said at least some of the layers or in others of the layers are open to the exterior wall surface, forming outlets of the tortuous passages.
13. The porous structure of claim 3 , wherein the alternating layers comprise a first layer and a second layer, wherein voids in the second layer are open to the interior wall surface and the exterior wall surface to form the respective inlets and the outlets, and wherein the voids in the first layer are closed to the interior wall surface and the exterior wall surface.
14. The porous structure of claim 13 , wherein the second layer includes a greater number of voids than the first layer.
15. A porous structure comprising:
a wall comprising layers of voids that are determinate and non-random;
wherein the voids interconnect between layers to form a plurality of tortuous passages between an interior and an exterior surface of the wall; and
a thermal insulation material disposed within at least some of the voids at the exterior surface of the wall;
wherein the layers are non-parallel to a plane of the interior or exterior surface
wherein said thermal insulation is configured to induce a lateral flow from the at least some of the voids into other of the voids at the exterior surface of the wall.