Oil distribution system for gas turbine engine

1. An oil supply system for supplying oil to a lubricating cavity of a gas turbine engine from a source of oil, the oil supply system comprising: a de-oiler having a de-oiler air-oil inlet, a de-oiler oil outlet hydraulically connected to the lubricating cavity, and a de-oiler air outlet in fluid flow communication with an environment outside of the oil supply system; and a closed-loop oil circuit including a main pump having a main pump inlet and a main pump outlet, the main pump outlet hydraulically connected to the lubricating cavity, a de-aerator having a de-aerator inlet hydraulically connected to a scavenge outlet of the lubricating cavity, a de-aerator air-oil outlet in fluid flow communication with the de-oiler inlet, and a de-aerator oil outlet hydraulically connected to the main pump inlet, the de-aerator oil outlet being hydraulically connected to the lubricating cavity via the main pump and bypasses the source of oil.

2. The oil supply system of claim 1 , wherein the de-aerator is an active de-aerator.

3. The oil supply system of claim 1 , wherein the closed-loop oil circuit is hydraulically connected to a source of oil for supplementing oil into the closed-loop oil circuit.

4. The oil supply system of claim 3 , wherein the source of oil is hydraulically connected to the closed-loop oil circuit upstream of the lubricating cavity and downstream of the de-aerator oil outlet and upstream of the main pump.

5. The oil supply system of claim 3 , wherein a scavenge pump is hydraulically connected to the closed-loop oil circuit downstream of the lubricating cavity and upstream of the de-aerator inlet, the source of oil hydraulically connected to the closed-loop oil circuit either upstream or downstream of the scavenge pump and between the lubricating cavity and the de-aerator.

6. The oil supply system of claim 3 , wherein the lubricating cavity is part of a first group of lubricating cavities, the source of oil is hydraulically connected to the closed-loop oil circuit via one or more lubricating cavities of a second group of lubricating cavities.

7. The oil supply system of claim 6 , wherein the one or more lubricating cavities of the second group of lubricating cavities have a scavenge oil outlet hydraulically connected to the closed-loop oil circuit between the de-aerator and the lubricating cavity of the first group of lubricating cavities.

8. The oil supply system of claim 1 , wherein the lubricating cavity includes a cavity of an accessory gearbox and a bearing cavity, the de-oiler located in the cavity of the accessory gearbox.

9. The oil supply system of claim 3 , wherein the closed-loop oil circuit is hydraulically connected to the source of oil via a make-up flow line, the oil supply system further comprising a warm-up flow line hydraulically connecting the source of oil to the closed-loop oil circuit for drawing a flow of oil from the closed-loop oil circuit to the source of oil.

10. The oil supply system of claim 2 , wherein the de-aerator is a centrifugal de-aerator.

11. The oil supply system of claim 3 , wherein the source of oil is an oil tank, the de-aerator air-oil outlet in communication with the de-oiler inlet via the oil tank.

12. An oil supply system for supplying oil to a lubricating cavity of a gas turbine engine, the oil supply system comprising: a de-oiler having a de-oiler air-oil inlet, a de-oiler oil outlet hydraulically connected to the lubricating cavity, and a de-oiler air outlet in fluid flow communication with an environment outside of the oil supply system; and a closed-loop oil circuit including a de-aerator having a de-aerator inlet hydraulically connected to a scavenge outlet of the lubricating cavity via a scavenge line, an oil outlet hydraulically connected to the lubricating cavity via a main line, and a de-aerator air-oil outlet in fluid flow communication with the de-oiler air-oil inlet, the lubricating cavity includes a cavity of an accessory gearbox and a bearing cavity, the de-oiler located in the cavity of the accessory gearbox.

13. The oil supply system of claim 12 , wherein the de-aerator is a centrifugal de-aerator.

14. The oil supply system of claim 12 , wherein the source of oil is hydraulically connected to the closed-loop oil circuit upstream of the lubricating cavity and downstream of the de-aerator oil outlet.

15. The oil supply system of claim 12 wherein the closed-loop oil circuit is hydraulically connected to a source of oil for supplementing oil into the closed-loop oil circuit.

16. The oil supply system of claim 15 , wherein the source of oil is an oil tank, the de-aerator air outlet in communication with the de-oiler inlet via the oil tank.

17. The oil supply system of claim 15 , wherein the de-aerator oil outlet is hydraulically connected to the lubricating cavity and bypasses the source of oil.

18. A method of removing air from the oil in an oil supply system of a gas turbine engine, comprising:

feeding oil to a lubricating cavity;

scavenging the oil from the lubricating cavity and removing air from the scavenged oil by centrifugation;

removing oil from a flow of air resulting from the centrifugation and expelling the removed air to an environment outside the oil supply system; and

returning the centrifuged oil back to the lubricating cavity while bypassing a source of oil.

19. The method of claim 18 , further comprising adding oil from the source of oil either upstream of a location where the air is removed from the scavenged oil or downstream of the location.