US Patent 7625169 Variable displacement turbine liner

A turbine stage of a gas turbine engine is surrounded by a ring of liner segments. The liner segments can be moved radially in unison towards and away from the tips or fins of blades, by rotation of a connected unison ring, so as to avoid blade fin rub. Alternatively, the segments can be moved in a common direction by bodily movement of the connected unison ring so as to avoid blade fin rub during off axis rotation of the turbine stage.