Abstract: The external wall of a hollow airfoil for a gas turbine engine has a plurality of longitudinally aligned diffusing coolant passages having their outlets at the outer surface over which a hot gas is intended to flow. The airfoil external wall also includes a longitudinally extending slot formed in the inner surface thereof. Each of the coolant passages intersect such longitudinally extending slot to define metering inlets to each passage for receiving coolant fluid from the slot at a controlled rate. The coolant diffuses as it passes through each passage and exits as a thin film on the external surface of the airfoil. The slot is cast in the inner surface of the wall at the time of forming the airfoil; and the passages are machined into the wall from outside the airfoil. Very small, accurate metering areas for each passage can thereby be formed in single-piece hollow airfoils without access to the interior of the airfoil.

Abstract: Six rows of radial blades, arranged to extend in a spiral (in the direction of axial rotation) covering 55 degrees of arc about a hollow support section, constitute an optimum blade arrangement for maximum efficiency in low velocity airflows. Each blade in the rows is contoured to receive both direct flow pressure as well as airfoil lift in order to provide maximum energy transfers from low velocity airflows.