Actively controlled contacting seal

1. A contacting seal for a gas turbine engine, comprising:

a seal seat configured to rotate circumferentially about an axis of rotation;

a seal element configured to contact the seal seat at an interface surface, the seal element rotationally fixed relative to the axis of rotation; and

an actively-controlled actuation system operably connected to the seal element to control a contact force between the seal element and the seal seat at the interface surface based on a level of lubricant flow to the interface surface;

wherein the actuation system includes:

a rotationally-stationary ramp including a plurality of ramp teeth;

a rotationally-movable ramp follower including a plurality of complimentary follower teeth meshed with the plurality of ramp teeth;

wherein circumferential movement of the ramp follower in a first direction relative to the ramp urges the seal element toward the seal seat thereby increasing the contact force; and

wherein circumferential movement of the ramp follower in a second direction opposite the first direction reduces the contact force.

2. The contacting seal of claim 1 , further comprising a wave spring disposed between the ramp follower and the seal element.

3. The contacting seal of claim 1 , further comprising an actuator operably connected to the ramp follower configured to urge circumferential movement of the ramp follower relative to the ramp.

4. The contacting seal of claim 3 , wherein the actuator is a hydraulic actuator.

5. The contacting seal of claim 1 , further comprising one or more oil sensors operably connected to the actuation system, wherein the contact force is reduced when the level of lubricant flow is below a threshold.

6. The contacting seal of claim 1 , wherein the seal element is a carbon seal element.

7. A gas turbine engine, comprising:

a rotating shaft;

one or more bearing arrangements supportive of the rotating shaft; and

a contacting seal configured to seal a bearing arrangement of the one or more bearing arrangements, the contacting seal including:

a seal seat configured to rotate circumferentially about an axis of rotation;

a seal element configured to contact the seal seat at an interface surface, the seal element rotationally fixed relative to the axis of rotation; and

an actively-controlled actuation system operably connected to the seal element to control a contact force between the seal element and the seal seat at the interface surface based on a level of lubricant flow to the interface surface;

wherein the actuation system includes:

a rotationally-stationary ramp including a plurality of ramp teeth;

a rotationally-movable ramp follower including a plurality of complimentary follower teeth meshed with the plurality of ramp teeth;

wherein circumferential movement of the ramp follower in a first direction relative to the ramp urges the seal element toward the seal seat thereby increasing the contact force; and

wherein circumferential movement of the ramp follower in a second direction opposite the first direction reduces the contact force.

8. The gas turbine engine of claim 7 , further comprising a wave spring disposed between the ramp follower and the seal element.

9. The gas turbine engine of claim 7 , further comprising an actuator operably connected to the ramp follower configured to urge circumferential movement of the ramp follower relative to the ramp.

10. The gas turbine engine of claim 9 , wherein the actuator is a hydraulic actuator.

11. The gas turbine engine of claim 7 , further comprising one or more oil sensors operably connected to the actuation system, wherein the contact force is reduced when the level of lubricant flow is below a threshold.

12. The gas turbine engine of claim 7 , wherein the seal element is a carbon seal element.

13. A method of operating a contacting seal of a gas turbine engine, comprising:

positioning a rotationally fixed seal element in contact with a rotating seal seat at an interface surface between the seal seat and the seal element; and

actively-controlling a contact pressure between the seal seat and the seal element at the interface surface utilizing an actuation system, the contact pressure based on a level of lubricant flow to the interface surface;

meshing a plurality of ramp teeth of a rotationally stationary ramp with a plurality of follower teeth of a rotationally movable ramp follower; and

moving the ramp follower in a circumferential direction relative to the ramp to adjust the contact pressure at the interface surface;

wherein circumferential movement of the ramp follower in a first direction relative to the ramp urges the seal element toward the seal seat thereby increasing the contact force; and

wherein circumferential movement of the ramp follower in a second direction opposite the first direction reduces the contact force.

14. The method of claim 13 , further comprising biasing the seal element toward the seal seat via a wave spring disposed between the seal element and the ramp follower.

15. The method of claim 13 , further comprising detecting the level of lubricant flow to the interface surface via one or more oil sensors.

16. The method of claim 15 , further comprising reducing the contact force when the detected level of lubricant flow is below a preselected threshold.

17. The method of claim 16 , further comprising increasing the contact force when the detected level of lubricant flow is above the preselected threshold.