Patent ID: 7775764

Claim:
A rotor assembly for a gas turbine engine, the rotor assembly comprising: first and second rotors defining a first cavity therebetween, wherein each rotor comprises a disc carrying an annular array of radially extending blades; the first rotor defining a cooling air inlet in a radially inward portion of the first rotor; the second rotor defining a cooling air outlet in a radially outward portion of the second rotor, such that cooling air passes radially outwardly through said first cavity during operation of the engine; a third rotor having a bore and defining a second cavity with said second rotor, wherein during operation of the engine said cooling air passes through said outlet then passing into and radially inwardly through said second cavity to pass through said bore; and a fourth rotor defining a third cavity with the third rotor, during operation of the engine the cooling air that passes through the bore of the third rotor then passes into and radially outwardly through the third cavity to pass through a second cooling air outlet defined in a radially outward portion of the fourth rotor, the fourth rotor having a second bore sealed by a seal so that cooling air cannot flow through the second bore, wherein the seal comprises a small clearance between the bore of the rotor and a shaft such that the airflow into the respective cavity preferentially passes through the cooling air outlet.