Patent ID: 6116852
Filing Date: 2000-09-12
Classification: F01D

Abstract:
A gas turbine engine blade tip clearance control system comprising an annular housing, said housing formed about an engine casing to which an annular shroud segment assembly is secured and closely spaced about the blade tips of a stage of blades; said annular housing forming an air passage communicating with said casing for directing a cooling air stream to said engine casing, said engine casing being provided with an annular impingement passage formed therein in a wall surface opposite said annular shroud segment assembly, said impingement passage being defined between opposed spaced annular side walls of said casing, and a thermally operable passive ring valve; said ring valve being formed by two overlapped metal ring segments having a dissimilar coefficient of thermal expansion selected whereby to produce a radial gap between said ring segments when the temperature of said ring segments reaches a predetermined value, said radial gap admitting a cooling air flow into said housing for cooling said casing to control radial growth, said annular housing being formed by a ring valve support structure secured above said casing opposite said annular shroud segment assembly, said two overlapped metal rings being integrated in said support structure and being in facial contact, said radial gap being formed by a space between said metal rings when said rings separate from one another due to said dissimilar coefficient of thermal expansion, said radial gap being a variable radial gap the size of which is affected by the temperature of said metal rings to admit a metered cooling air flow to said casing.