Patent ID: 8240980

Claim:
In a gas turbine engine having an outer shroud segment secured to an isolation ring forming a gap with a tip of a rotor blade, and a stator vane with an outer endwall located adjacent to the outer shroud segment and forming an axial inter-stage gap, an improvement comprising: the isolation ring having a circumferential rail extending into the axial inter-stage gap; the vane outer endwall having a circumferential rail extending into the axial inter-stage gap; the outer shroud segment having a circumferential rail extending in an aft direction; the outer shroud segment having a cooling hole connecting the impingement cavity of the outer shroud segment to the axial inter-stage gap to discharge cooling air into the axial inter-stage gap; and, the rails on the isolation ring, the endwall and the shroud segment form a serpentine flow passage in the axial inter-stage gap.