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In a gas turbine engine having a rim cavity formed between a rotor disk and a stator, and a brush seal or other seal member providing an airflow seal between the stator and a side plate of the rotor disk, a thermally responsive valve device is located in the bypass passage of the stator to form a pa

In a gas turbine engine having a rim cavity formed between a rotor disk and a stator, and a brush seal or other seal member providing an airflow seal between the stator and a side plate of the rotor disk, a thermally responsive valve device is located in the bypass passage of the stator to form a parallel air flow path with the brush seal. As the brush seal wears and the leakage airflow around the worn brush seal increases, the air flow temperature in the rim cavity would decrease. The thermally responsive valve device would detect the decreasing airflow temperature, and reduce the airflow passing through the bypass passage in order to prevent the temperature of the rim cavity from decreasing. The temperature responsive valve device makes use of a bimetallic valve member that regulates airflow based upon temperature.

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We claim the following: 1. In a gas turbine engine having a rotor and a stator adjacent to the rotor, a rim cavity with a brush seal forming a seal leading into the rim cavity, and a bypass air passage passing through the stator and into the rim cavity such that airflow through the brush seal and t

We claim the following: 1. In a gas turbine engine having a rotor and a stator adjacent to the rotor, a rim cavity with a brush seal forming a seal leading into the rim cavity, and a bypass air passage passing through the stator and into the rim cavity such that airflow through the brush seal and through the bypass passage forms a parallel air flow into the rim cavity, the improvement comprising: a thermally responsive air flow device associated with the bypass air passage and responsive to the air temperature in the rim cavity, the thermally responsive air flow device decreasing the airflow through the bypass air passage as the brush seal wears. 2. The gas turbine engine of claim 1, and further comprising: the thermally responsive air flow device comprising: a chamber box member forming the bypass passage; a valve head member forming a variable restriction and having a surface exposed to the rim cavity; a valve stem member connected to the valve head member; and, a thermally responsive spring member connected to the valve stem member; the spring member and the valve stem member being confined within the box cavity. 3. The gas turbine engine of claim 2, and further comprising: a ratcheting member to limit the oscillation of the bypass valve head as a result of a thermally cyclic environment. 4. The gas turbine engine of claim 1, and further comprising: the thermally responsive air flow device comprising: a bimetallic member extending from the stator and in the bypass passage, the bimetallic member having a first metallic sheet exposed to the airflow temperature in the rim cavity and a second metallic sheet secured to the first sheet on an opposite side; and, an airflow passage forming member extending from the stator and in the bypass passage, and forming a flow restriction with the tip of the bimetallic member; whereby a change in temperature exposed to the bimetallic member changes the flow restriction. 5. The gas turbine engine of claim 1, and further comprising: the thermally responsive air flow device further comprises: a valve assembly inserted within the bypass passage, the valve assembly including an outer cylinder member, a valve head movable within the cylinder member and forming a flow restrictor with an inlet of the outer cylinder member, radial holes in the cylinder member to provide an airflow communication from the inlet to the rim cavity, and a thermally responsive spring member connected to move the valve head. 6. The gas turbine engine of claim 5, and further comprising: an inner cylinder member closing an end of the outer cylinder member and forming an abutting surface for the spring member. 7. The gas turbine engine of claim 6, and further comprising: a ratcheting assembly connected between the inner cylinder and the movable members of the valve head. 8. The gas turbine engine of claim 1, and further comprising: The thermally responsive air flow device further comprises: a valve assembly inserted within the bypass passage, the valve assembly including: an inner cylinder member having a central axial passage open at one end and a plurality of radial holes; an outer cylinder member concentric to the inner cylinder member and having a plurality of radial holes; the radial holes of the inner cylinder member being aligned with the radial holes of the outer cylinder member; an outer passage formed between an inner wall of the bypass passage and the outer surface of the outer cylinder member; and, the two cylinder members being made of materials having different thermal expansion coefficients such that a change in temperature will move the radial holes out of alignment. 9. The gas turbine engine of claim 8, and further comprising: an outer annular groove formed on the outer edge of the bypass hole; an inner annular groove formed on the inner edge of the bypass hole; and, the cylinder members each having annular portions that are mounted within the annular grooves of the bypass hole. 10. The gas turbine engine of claim 8, and further comprising: the outer cylinder member includes a plurality of axial holes that communicate the outer passage to the rim cavity. 11. The gas turbine engine of claim 1, and further comprising: The thermally responsive air flow device further comprises: a valve assembly inserted within the bypass passage, the valve assembly including: an inner cylinder member having an end with a plurality of axial holes therein and a stem member forming a central passage open at an opposite end; an outer cylinder member having a plurality of radial holes therein aligned with the holes in the inner cylinder member; an outer passage formed between the inner wall of the bypass passage and the outer cylinder member; a plug having an axial hole, the plug closing the central passage while the hole provides a fluid communication between the central passage and the rim cavity; and the two cylinder members being made of materials having different thermal expansion coefficients such that a change in temperature will move the radial holes out of alignment. 12. The gas turbine engine of claim 11, and further comprising: the thermally responsive air flow device further comprises: a valve assembly inserted within the bypass passage, the valve assembly including: the outer cylinder member having an end that closes the outer passage to the rim cavity such that airflow into the outer passage is forced through the radial holes and into the central passage. 13. The gas turbine engine of claim 1, and further comprising: the thermally responsive air flow device further comprises: a valve assembly inserted within the bypass passage, the valve assembly including: an outer passage formed in the stator wall; an outer cylinder member forming a central passage and having an inlet end with a flow restrictor forming surface thereon, an opposite end that is open, and a plurality of radial holes communicating the central passage with the outer passage; an end cap member having a stem member extending therefrom in the central passage; a valve head member extending from the stem member and forming a flow restrictor with the flow restrictor forming surface on the outer member; and, The outer cylinder member and the end cap member being made of materials having different thermal expansion coefficients such that a change in temperature will move the valve head with respect to the flow restrictor forming surface. 14. The gas turbine engine of claim 13, and further comprising: the end cap member is exposed to the airflow temperature of the rim cavity and the valve head is located on the inlet end of the valve assembly. 15. A process of purging a rim cavity of a gas turbine engine, the gas turbine engine having a rotor and a stator adjacent to the rotor, a side plate over the rotor, the rim cavity formed between the stator and the side plate, the process comprising the steps of: providing for a seal member between the stator and a rotating part of the side plate; providing for a bypass passage in the stator; and, inserting a thermally responsive valve member within the bypass passage, where the thermally responsive valve member reduces airflow through the bypass passage as the airflow temperature in the rim cavity decreases. 16. The process of purging a rim cavity of a gas turbine engine of claim 15, and further comprising the step of: providing for the seal member to be a brush seal. 17. The process of purging a rim cavity of a gas turbine engine of claim 15, and further comprising the step of: providing for the thermally responsive valve member to be a bimetallic valve member. 18. The process of purging a rim cavity of a gas turbine engine of claim 15, and further comprising the step of: providing for a ratcheting member associated with the thermally responsive valve member to limit the oscillation of the bypass valve head as a result of a thermally cyclic environment. 19. In a gas turbine engine having a rotor and a stator adjacent to the rotor, a rim cavity with a brush seal forming a seal leading into the rim cavity, and a bypass air passage passing through the stator and into the rim cavity such that airflow through the brush seal and through the bypass passage forms a parallel air flow into the rim cavity, the improvement comprising: thermally responsive valve means associated with the bypass passage to decrease the airflow through the bypass passage as the brush seal wears. 20. The gas turbine engine of claim 19, and further comprising: a ratcheting member associated with the thermally responsive valve means to limit the oscillation of the bypass valve head as a result of a thermally cyclic environment.