Air riding seal with purge cavity

Abstract

An air riding seal for a turbine in a gas turbine engine, where an annular piston is axial moveable within an annular piston chamber formed in a stator of the turbine and forms a seal with a surface on the rotor using pressurized air that forms a cushion in a pocket of the annular piston. A purge cavity is formed on the annular piston and is connected to a purge hole that extends through the annular piston to a lower pressure region around the annular piston or through the rotor to an opposite side. The annular piston is sealed also with inner and outer seals that can be a labyrinth seal to form an additional seal than the cushion of air in the pocket to prevent the face of the air riding seal from overheating.

Claims

1. A gas turbine engine with a turbine having a rotor and a stator exposed to a hot gas flow, the turbine comprising: a rotor blade extending from the rotor; a stator vane extending from the stator; an annular piston axially moveable within an annular piston chamber formed within the stator; the annular piston having a pocket connected to a source of compressed air to form a cushion of air with a surface of the rotor; an outer seal in contact with an outer surface of the annular piston; an inner seal in contact with an inner surface of the annular piston; a purge cavity formed on the annular piston and facing the surface of the rotor; the purge cavity connected to a purge hole that discharges compressed air collected within the purge cavity; and, the purge hole is formed in the rotor.

2. The gas turbine engine of claim 1, and further comprising: the outer seal is a ring seal; and, the inner seal is a labyrinth seal.

3. The gas turbine engine of claim 2, and further comprising: a labyrinth seal extending from the rotor and forming a seal with the stator radial outward of the annular piston.

4. The gas turbine engine of claim 1, and further comprising: a labyrinth seal extending from the rotor and forming a seal with the stator radial inward of the annular piston.

5. A gas turbine engine with a turbine having a rotor and a stator exposed to a hot gas flow, the turbine comprising: a rotor blade extending from the rotor; a stator vane extending from the stator; an annular piston axially moveable within an annular piston chamber formed within the stator; the annular piston having a pocket connected to a source of compressed air to form a cushion of air with a surface of the rotor; a purge cavity formed on the annular piston and facing the surface of the rotor; the purge cavity connected to a purge hole that discharges compressed air collected within the purge cavity; and, the purge hole is formed in the rotor.

6. The gas turbine engine of claim 5, and further comprising: a labyrinth seal extending from the rotor and forming a seal with the stator radial outward of the annular piston.

7. The gas turbine engine of claim 5, and further comprising: a labyrinth seal extending from the rotor and forming a seal with the stator radial inward of the annular piston.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 shows a cross section view of a first embodiment of the air riding seal of the present invention.

(2) FIG. 2 shows a cross section view of a second embodiment of the air riding seal of the present invention.

(3) FIG. 3 shows a cross section view of a third embodiment of the air riding seal of the present invention.

(4) FIG. 4 shows a cross section view of a fourth embodiment of the air riding seal of the present invention.

(5) FIG. 5 shows a cross section view of a fifth embodiment of the air riding seal of the present invention.

(6) FIG. 6 shows a cross section view with flow paths for the FIG. 3 embodiment of the air riding seal of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) The present invention is an air riding seal with a purge cavity used in a turbine of a gas turbine engine, especially for an industrial gas turbine engine. FIG. 1 shows a first embodiment of the present invention of the air riding seal with a purge cavity. An annular piston 13 floats within an annular chamber 15 formed within a stator 12 and rides over a surface of a rotor 11. The annular piston 13 includes a pocket or cushion chamber 21 that floats over the rotor surface due to pressurized air supplied from a supply passage 14 in the stator 12 that is connected to an annular arrangement of pressurized air supply passages 20 formed in the annular piston 13. A purge cavity 23 is formed on the air riding side of the annular piston 13 as in connected to an annular arrangement of purge holes 22 formed within the rotor 11. Inner and outer piston ring seals 17 supported in ring seal grooves formed in the stator provide for a seal against inner and outer surfaces of the annular piston 13. An inner labyrinth seal 18 and an outer labyrinth seal 19 forms another seal between the rotor 11 and the stator 12.

(8) Pressurized air flows through the supply passage 14 an into the annular piston chamber 15, and then through the annular arrangement of supply holes 20 and into the pocket 21 to form a cushion of air for the air riding seal to float over the rotor 11 surface. Leakage of the air either flows radially outward over the upper seal land or flows radially inward where it collects in the purge cavity 23 and flows out through the purge holes 22 formed in the rotor 11.

(9) FIG. 2 shows a second embodiment of the air riding seal similar to the FIG. 1 embodiment except the inner piston ring seal 17 is not used. the inner labyrinth seal 18 is used to form a seal with the inner surface of the annular piston 13.

(10) FIG. 3 shows a third embodiment of the air riding seal in which an annular arrangement of bypass holes 24 formed in the annular piston 13 is used to purge the purge cavity 23. Thus, the pressurized air that flows into the pocket 21 and leaks into the purge cavity 23 will flow into the outer chamber radially outward of the annular piston 13.

(11) FIG. 4 shows a fourth embodiment of the air riding seal where the purge holes 22 are formed in the rotor 11 and not in the annular piston 13.

(12) FIG. 5 shows a fifth embodiment of the air riding seal where the purge holes 24 are formed in the annular piston 13 and the inner piston ring seal 17 is replaced with an inner labyrinth seal that forms a seal with the inner surface of the annular piston 13.

(13) FIG. 6 shows the FIG. 3 embodiment of the air riding seal with the flow paths for the pressurized air. The pressurized air from the supply passage flows into the pocket to form a cushion of air between the annular piston and the rotor surface. The pressurized air within the pocket flows out and into the purge cavity. Some of the pressurized air that leaks past the inner labyrinth seal also flows into the purge cavity. The pressurized air that collects within the purge cavity 23 then flows through the purge holes and into the space radially outward of the annular piston. The pressurized air within the purge cavity and from the lower pressure region 16 around the air riding seal is thus discharged into the higher pressure region around the air riding seal to prevent hot gas flowing through the turbine from entering the inner region of the air riding seal or the pocket.