Balance piston and seal for gas turbine engine

Claim 1

In a gas turbine engine defining an annular motive gas path, an annular row of stationary vanes having an air foil portion in the motive gas path and a rotatable disc supporting an annular row of rotating blades adjacent said vanes and also having an air foil portion in the motive gas path, a rotor member attached to and driven by said disc, rotating means attached to said rotor member and enclosing an axial portion of said rotor member in spaced relation and terminating in a radially extending face abutting said disc adjacent the blades mounted thereon to define an air flow path for delivering cooling air to said blades, and stationary means attached to said row of vanes and generally enclosing an axial portion of said rotating means in spaced relation to define a sealing air flow path into a disc cavity therebetween with relatively high pressure air flowing therethrough to prevent said hot motive gas from entering said cavity; a first sealing means positioned generally radially inwardly the air foil portions of said vanes and blades, respectively, to obstruct hot motive gas entering the cavity; and a second sealing means positioned downstream of the disc cavity but upstream and radially inwardly of said first sealing means to generally closely seal the sealing air within said cavity and thereby pressurize said cavity with said high pressure air providing a force on said radially extending face of said rotating means in opposition to the normal net thrust on said rotor.