Airfoil cooling circuit

摘要

A turbine airfoil (12) includes a plurality of internal ribs (34) defining at least two independent serpentine cooling circuits (36, 38) having outer and inner serpentine portions (36a, 38a), respectively, in different longitudinal tiers with the outer serpentine position being disposed longitudinally above the inner tier serpentine position for differentially longitudinally cooling the airfoil. The outer and inner serpentine portions include outer and inner exits (36c, 38c) and entrances (36b, 38b) wherein the outer and inner exits (36c, 38c) are positioned aft of the outer and inner entrances (36b, 38b), respectively, so as to have a chordal flow direction aftwards from the leading edge to the trailing edge within the serpentine portions.