Active clearance control

Claim 1

An active clearance control for a gas turbine engine powering aircraft over and operating envelope including high powered and low powered conditions, said engine having a compressor section comprising a plurality of stages of axial compressors rotatably supported in the bore area of the compressor section, each of said stages including a plurality of blades supported in a disc and each blade having a tip, an air seal circumscribing the tips of said blades and defining a gap between said tips and said air seal, and a row of stator vanes mounted ahead of the blades, means for selectively bleeding compressed air from one of said stages substantially at the middle of said stages and at another of said stages downstream therefrom relative to the air flow through said stages, means for feeding said bled air into the bore area adjacent the rotating axis of said plurality of stages of axial compressors, said feeding means including at least one hollow stator vane in one of said rows of stator vanes, and an anti-vortex tube extending from the inner diameter of the hollow stator vane radially inward toward said rotating axis, and control means for modulating said selective bleeding means for admitting compressed air to said bore by said feeding means to heat said discs so that said discs expand toward the air seal and close said gap between said air seal and the tips of said blades during the lower powered condition of said engine.