In some gas turbine engines, an outer shroud is added to an airfoil in order to reduce tip leakage loss. The addition of the outer shroud may increase the centrifugal load on the turbine, thereby causing higher stresses in the airfoil. Also, the tangential extension from the airfoil supporting such an outer shroud may generate a bending stress at the intersection of the airfoil and of the shroud. In order to reduce the stress concentration at the airfoil at the shroud intersection, fillets of variable radius have been used. However, such fillets may result in a reduction of the flow area. Accordingly, there is a need to provide an improved outer shroud configuration.
The manufacturing process to produce a blade is typically a casting process. A casting is a manufacturing process by which a liquid material—in this case a metal in liquid phase—is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. If the pouring happened from the shroud extremity, then the shroud external shape as presented into the U.S. Pat. No. 7,527,477 B2 could require an expensive machining.