Thermal protection for seals

1 . A flammable fluid containment assembly for an aircraft engine, comprising:

an aircraft engine component having an internal cavity containing a flammable fluid;

a transfer tube having a central axis, the transfer tube fluidly connected to the internal cavity of the aircraft engine component;

a sealing ring at a radial interface between the aircraft engine component and the transfer tube; and

a first thermal barrier between the sealing ring and the aircraft engine component, the first thermal barrier including a first sleeve mounted to an inner diameter surface of the aircraft engine component around the sealing ring, the first sleeve having an outer diameter surface and an inner diameter surface, the outer diameter surface of the first sleeve and the inner diameter surface of the aircraft engine component defining a first annular cavity therebetween, the first annular cavity filled with a first thermal insulation medium and axially spanning the sealing ring; and

a second thermal barrier between the sealing ring and the flammable fluid inside the transfer tube, the second thermal barrier including a second sleeve mounted inside the transfer tube, the second sleeve having an inner diameter surface and an outer diameter surface, the outer diameter surface of the second sleeve and an inner diameter surface of the transfer tube defining a second annular cavity therebetween, the second annular cavity filled with a second thermal insulation medium and axially spanning the sealing ring, the inner diameter surface of the second sleeve forming a flow boundary surface for the flammable fluid flowing through the transfer tube.

2 . The flammable fluid containment assembly according to claim 1 , wherein the sealing ring is disposed radially between the first and second thermal barriers.

3 . The flammable fluid containment assembly according to claim 2 , wherein the first annular cavity and the second annular cavity are at least partly filled with air to form first and second annular air gaps on opposed inner and outer radial sides of the sealing ring.

4 . The flammable fluid containment assembly according to claim 1 , wherein the first thermal insulation medium is air, and wherein the first annular cavity forms an air gap between the aircraft engine component and the sealing ring.

5 . The flammable fluid containment assembly according to claim 1 , wherein the aircraft engine component includes a case having a transfer tube receiving bore in fluid communication with the internal cavity, the transfer tube receiving bore circumscribed the inner diameter surface of the aircraft engine component, the transfer tube having a first end axially slidably received in the transfer tube receiving bore, and wherein the sealing ring is in sealing engagement with an outer diameter surface of the transfer tube and the inner diameter surface of the first sleeve.

6 . The flammable fluid containment assembly according to claim 5 , wherein the first annular cavity is a dead air cavity radially between the inner diameter surface of the transfer tube receiving bore and an outer diameter surface of the first sleeve.

7 . The flammable fluid containment assembly according to claim 5 , wherein the first sleeve has a pair of circumferential rails projecting radially outwardly from opposed axial ends thereof, and wherein the circumferential rails are welded or brazed to the inner diameter surface circumscribing the transfer tube receiving bore of the case, and wherein the first annular gap is defined axially between the circumferential rails.

8 . The flammable fluid containment assembly according to claim 1 , wherein an inner diameter of the second sleeve varies along the central axis of the transfer tube, wherein the second thermal barrier is provided on an inner diameter surface of the transfer tube.

9 . The flammable fluid containment assembly according to claim 1 , wherein the second sleeve has a first end brazed to the inner diameter surface of the transfer tube and a second end brazed or welded to an axially facing end surface of the transfer tube.