Air riding seal with purge cavity
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.
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.