Variable permeability and oxidation-resistant airfoil

Claim 1

A transpiration-cooled turbine blade having a hollow strut member having a supply of air under pressure to the interior thereof, the external surface of the strut having a plurality of longitudinal and transverSe raised lands thereon defining a plurality of discrete recesses, a porous skin surrounding the strut and attached to the lands to define with the recesses a plurality of plenum chambers, the porous skin having capillary passages therethrough for flow of cooling air, each of the recesses having an aperture through the strut wall communicating with the hollow interior thereof and transmitting a jet of cooling air to the plenum chamber impinging on the inner surface of the skin, the porous skin having its capillary passages blocked over each strut aperture by an impervious spot approximately twice the diameter of its associated aperture to divert the air jet and distribute the cooling air throughout the respective plenum chamber before bleeding through the skin, the spots being formed by filling the capillary passages of the skin with aluminum particles cemented in place by a ceramic binder composition to leave the skin with a smooth external aerodynamic surface.