Tip seal and anti-contamination for turbine blades

For an internally cooled airfoil of a blade of a turbine rotor of a gas turbine engine,

• said airfoil subjected to the fluid working medium of said gas turbine engine and including a tip surface, a leading edge, a trailing edge and a pressure side,
• an annular shroud concentrically supported around said airfoil and defining with said tip surface a gap,
• said airfoil having wall means for defining an internal passageway leading cooling air to a discharge port formed adjacent the tip of the airfoil in proximity to the pressure surface for creating a jet of cooling air egressing into said gap at a given angle for creating a blockage in said gap to seal the gap and prevent leakage of said fluid working medium from entering into said gap,
• means for guarding against the clogging of said discharge port including a cavity formed adjacent said discharge port and extending from said pressure surface to the portion of said wall means defining said discharge port that is furthest away from said pressure surface and extending substantially the width of said discharge port.