Engine component wall with a cooling circuit

1. An airfoil for a turbine engine, the airfoil comprising:

an outer wall having an outer surface and an inner surface bounding an interior, the outer wall defining a pressure side and a suction side extending axially between a leading edge and a trailing edge and extending radially between a root and a tip;

a first porous layer provided on the outer surface;

a skin layer provided on an exterior of the first porous layer with at least one channel formed in the skin layer and spaced from the first porous layer, with at least one channel conduit fluidly coupling the first porous layer to the at least one channel;

at least one cooling air supply circuit located within the interior;

a second porous layer provided on the skin layer, opposite the first porous layer;

an exterior coating provided on the second porous layer, opposite the skin layer; and

at least one film hole provided in the exterior coating, fluidly coupling the at least one channel to an exterior of the airfoil through the second porous layer and the exterior coating, and configured to provide a cooling film along the skin layer;

wherein the at least one cooling air supply circuit is fluidly coupled to the at least one porous layer, which is fluidly coupled to the at least one channel via the at least one channel conduit to define a serial cooling air flow path via the at least one cooling air supply circuit, the first porous layer and the second porous layer, and the skin layer.

2. The airfoil of claim 1 further comprising at least one hole in the outer wall fluidly coupling the at least one cooling air supply circuit to the first porous layer.

3. The airfoil of claim 1 wherein the at least one channel is fluidly coupled to both the first porous layer and the second porous layer.

4. The airfoil of claim 3 wherein the at least one channel has an open top fluidly coupled to the second porous layer and an open bottom fluidly coupled to the first porous layer.

5. The airfoil of claim 4 further comprising at least one hole in the outer wall fluidly coupling the at least one cooling air supply circuit to the first porous layer.

6. An engine component for a turbine engine, which generates a hot fluid flow, and provides a cooling fluid flow, comprising:

a wall bounding an interior and separating the hot fluid flow from the cooling fluid flow and having a first surface facing the hot fluid flow in a hot flow path and a second surface facing the cooling fluid flow;

at least one porous layer provided exterior of the first surface;

a skin layer provided on an exterior of the at least one porous layer;

a skin cooling circuit formed in the skin layer including a cooling channel, spaced from the at least one porous layer and having at least one channel conduit fluidly coupling the cooling channel to the at least one porous layer; and

an exterior coating provided exterior of the at least one porous layer, and including a film hole extending through the exterior coating fluidly coupling the skin cooling circuit to an exterior of the engine component;

wherein the cooling fluid flow is fluidly coupled from the interior to the skin layer through the at least one porous layer,

wherein the at least one porous layer comprises first and second porous layers, with the first porous layer provided on the first surface and the second porous layer provided on an outer surface of the skin layer.

7. The engine component of claim 6 further comprising at least one hole in the wall fluidly coupling the interior to the at least one porous layer.

8. The engine component of claim 6 wherein the at least one channel is fluidly coupled to both the first porous layer and the second porous layer.

9. The engine component of claim 8 wherein the at least one channel has an open top fluidly coupled to the second porous layer and an open bottom fluidly coupled to the first porous layer.

10. The engine component of claim 8 further comprising at least one hole in the wall fluidly coupling the interior to the first porous layer.

11. A method of cooling an engine component comprising:

passing a cooling airflow from an interior of the engine component to a first porous layer on an exterior of an outer wall of the engine component defining the interior;

passing the cooling airflow to a channel in a skin layer overlying the first porous layer with the channel spaced from the first porous layer by a first channel conduit;

passing the cooling airflow from the channel through a second channel conduit in the skin layer to a second porous layer on an exterior of the skin layer, such that the channel in the skin layer is spaced from the second porous layer; and

passing the cooling airflow through a film hole in an exterior coating, the film hole connecting the channel to an exterior of the engine component.

12. The method of claim 11 wherein passing the cooling airflow through the film hole comprises passing the cooling airflow from the channel to multiple film holes.