Tip structure for cooled turbine rotor blade

Claim 1

A turbine rotor blade, comprising: a root portion for securing the blade in a rotor disc; an airfoil portion having walls contoured to define concave and convex sides for intercepting a flow of hot motive gases; air channels within the root and airfoil portions for supporting the flow of cooling air therethrough; and a tip portion structured to provide an exhaust path for cooling air from the airfoil portion, said tip portion having: a tip sidewall extending radially outward from said airfoil portion substantially to bound a radially outward facing tip cavity, said tip sidewall generally having an edge portion extending about the airfoil trailing edge and respective portions generally extending from said sidewall edge portion along said airfoil concave and convex sides toward the airfoil leading edge, and a closing sidewall portion located short of the airfoil leading edge and extending across said airfoil portion between said convex and concave sidewall portions, the base of said tip cavity formed by a blade tip surface having therein apertures for venting cooling air from the airfoil portion into said cavity; and a leading edge tip surface located radially inward from the outermost extent of said tip cavity sidewall and extending from said closing sidewall portion to the airfoil leading edge, said leading edge tip surface having aperture means for venting at least one blade cooling channel near the airfoil leading edge, said leading edge tip surface being too narrow to provide for a sidewall enclosed tip venting cavity without obstructing coolant flow near the airfoil leading edge.