Wet-face/dry-face seal and methods of operation

1. A seal system comprising:

a first member;

a seal carried by the first member and having a seal face; and

a second member rotatable relative to the first member about an axis and having:

a seat, the seat having a seat face in sliding sealing engagement with the seal face; and

a circumferential array of passageway legs open to the seat face; and

an oil pump for delivering oil via one or more first outlets to the passageway legs in at least a first mode of operation,

wherein the seal system further comprises:

one or more second outlets, the oil pump coupled to the one or more second outlets to deliver oil to a backside of the seat in at least a second mode of operation.

2. The seal system of claim 1 wherein:

the seal is a carbon seal.

3. The seal system of claim 1 wherein:

the seat is steel.

4. The seal system of claim 1 wherein:

the seal and seat are full annular.

5. The seal system of claim 1 further comprising:

a spring biasing the seal into engagement with the seat.

6. The seal system of claim 1 further comprising:

one or more valves for switching between the first mode and the second mode.

7. The seal system of claim 6 wherein:

the one or more valves comprises a first valve positioned along a flowpath from the pump to the one or more first outlets downstream of a branching to the one or more second outlets.

8. The seal system of claim 6 wherein:

the one or more valves consists of a single valve;

the one or more first outlets consists of a single first outlet; and

the one or more second outlets consists of a single second outlet.

9. The seal system of claim 6 wherein:

the one or more valves are positioned to allow flow through the second outlets in the first mode and the second mode and block flow through the first outlets in the second mode.

10. The seal system of claim 1 further comprising a nozzle body wherein:

one of the first outlets is in a first insert in the nozzle body; and

one of the second outlets is in a second insert in the nozzle body.

11. The seal system of claim 10 further comprising a valve in the nozzle body positioned to selectively block flow through the first insert.

12. A gas turbine engine including the seal system of claim 1 wherein:

the second member is a shaft.

13. The gas turbine engine of claim 12 further comprising:

a speed sensor; and

a controller configured to switch between the first mode and the second mode responsive to output from the speed sensor.

14. A method for using the seal system of claim 1 , the method comprising:

shifting between the first mode and the second mode.

15. The method of claim 14 wherein:

in the first mode, oil is not delivered via the second outlets; and

in the second mode, oil is not delivered via the first outlets.

16. The method of claim 14 wherein:

in the first mode, oil is also delivered via the second outlets; and

in the second mode, oil is not delivered via the first outlets.

17. The method of claim 16 wherein:

in the first mode, the relative rotation is at a first speed; and

in the second mode, the relative rotation is at a second speed, less than the first speed.

18. The method of claim 14 wherein:

in the first mode, the relative rotation is at a first speed; and

in the second mode, the relative rotation is at a second speed, less than the first speed.

19. The seal system of claim 1 wherein:

the second member has a radially inwardly open collection channel; and

the passageways extend from the collection channel.

20. The seal system of claim 19 wherein:

the one or more second outlets are positioned to spray said oil against said backside of the seat.

21. The seal system of claim 1 wherein:

in the second mode, oil is not delivered via the first outlets.