摘要：
An aircraft engine lubricant circulation system comprises a conduit 11 arranged to communicate a lubricant to or from one or more bearings of an engine. The conduit is double walled and defines a space 14, between inner 12 and outer 13 walls, which comprises a phase change material (PCM) that is selected to change phase at a predetermined temperature, to limit the maximum internal temperature that will be reached in transient conditions, e.g. following shutdown, or when taxiing at high ambient temperature. Limiting the maximum temperature may prevent coking.
权利要求：
CLAIMS
1. An aircraft engine circulation system comprising a conduit arranged in use to communicate a lubricant to and from one or more bearings, said conduit comprising a central tube defining a passage for communicating lubricant and a peripheral tube surrounding the central tube and defining a space between the outer surface of the central tube and the inner surface of the peripheral tube wherein the space contains a thermally induced phase changing material arranged in use to change phase when heated.
2. A system as claimed in claim 1, wherein the phase changing material is selected so as to change phase from a solid above a predetermined engine temperature.
3. A system as claimed in claim 1 to 2, wherein the phase changing material is selected so as to change phase from a solid phase towards a liquid phase at a predetermined engine temperature.
4. A system as claimed in and of claims 2 or 3 wherein the phase changing material is selected to return to a solid phase below a predetermined engine temperature.
oS. A system as claimed in any of claims 2 to 4, wherein the phase changing material is arranged to change or begin to change phase between 180 degrees C and 250 degrees C.
6. A system as claimed in any of claims 1 to 5, wherein the phase changing material is arranged to change phase between 200 degrees C and 250 degrees C.
7. A system as claimed in any of claims 1 to 6, wherein the phase changing material is arranged to change phase at approximately 225 degrees C.
8. A system as claimed in any preceding claim, wherein the phase changing material is a salt selected from the group of organic or inorganic salts.
9. A system as claimed in claim 8, wherein the phase changing material is typically an H220 molten salt or an H105 salt.
10. A system as claimed in any of claims 1 to 7, wherein the phase changing material is a metal.
11. A system as claimed in claim 10, wherein the phase changing material is selected from one of lithium, zinc, lead, or an alloy thereof.
12. A system as claimed in claim 10, wherein the phase changing material is an iron or iron containing alloy.
13. A system as claimed in any preceding claim, wherein the radial separation defined between the outer surface of the central tube and the inner surface of the peripheral tube is approximately constant.
14. A system as claimed in claim 13, wherein the radial separation of the outer surface of the central tube and the inner surface of the peripheral tube is between 0.5mm and 1.5mm.
15. A system as claimed in claim 13 or 14, wherein the radial separation of the outer surface of the central tube and the inner surface of the peripheral tube is approximately 1mm.
16. A system as claimed in any of claims 1 to 12, wherein the radial separation of the outer surface of the central tube and the inner surface of the peripheral tube along the length of the conduit is non-uniform.
17. A system as claimed in claim 16, wherein the radial separation along the length of the conduit is selected according to a predetermined/predicted heating of the local region of the conduit.
18. A system as claimed in claim 16 or 17, wherein some regions of the conduit have a radial separation of zero mm.
19. A system as claimed in any of claims 16 to 18, wherein changes in radial separation are either tapered or stepped.
20. A system as claimed in any preceding claim, wherein the tubes are concentric.
21. A system as claimed in any preceding claim, wherein the tubes have the same cross- sectional shape.
22. A system as claimed in any preceding claim, wherein the cross-sectional shape of the tubes is circular or oval.
23. A system as claimed in any preceding claim, wherein the cross-sectional shape of the tubes is non-uniform along the length of the conduit.
24. A system as claimed in any preceding claim, wherein the radial spacing and/or concentricity of the central and peripheral tubes is selected according to the predicted and/or predetermined temperature of the tube in use along a specific length or the conduit during use.
25. A system as claimed in any preceding claim, further comprising a heat exchanger arranged to receive lubricant to and from the central tube.
26. A method of lubricating one or more bearings of an aircraft engine, the method comprising the step of causing a lubricant to be communicated through a heat exchanger and to one or more bearings in an aircraft engine through a lubricating circuit, wherein the lubricating circuit comprises a conduit arranged in use to communicate a lubricant to and from one or more of said bearings, said conduit comprising a central tube defining a passage for communicating lubricant and a peripheral tube surrounding the central tube and defining a space between the outer surface of the central tube and the inner surface of the peripheral tube wherein the space contains a thermally induced phase changing material arranged in use to change phase when heated.
27. A method as claimed in claim 26, wherein the circuit is configured to return the lubricant from the one or more bearings to the heat exchanger to create a continuous circuit.
28. A method of manufacturing a lubrication system for an aircraft engine comprising the steps of forming a conduit arranged in use to communicate a lubricant to and from one or more bearings wherein the conduit comprises a central tube defining a passage for communicating lubricant and a peripheral tube surrounding the central tube and defining a space between the outer surface of the central tube and the inner surface of the peripheral tube wherein the space is provided with a thermally induced phase changing material arranged in use to change phase when heated.
29. A method of manufacturing as claimed in claim 28, wherein the system is formed using an additive manufacturing process.
30. A lubrication arrangement for an aircraft engine comprising a multi-walled lubricant circuit arranged in use to convey lubricant to and from one or more bearings of an aircraft engine, wherein the lubricant circuit comprises an inner-wall defining a central conduit arranged in use to convey a lubricant and an outer-wall defining an outer surface of the circuit, wherein a radial space defined between the inner and out walls comprises a material dissimilar to the inner and outer wall materials.
31. A lubrication arrangement as claimed in claim 30, wherein the dissimilar material is a phase changing material which changes phase in response to a predetermined temperature.
32. An aircraft engine comprising a circulation system according to any of claims 1 to 25.
33. A gas turbine comprising a circulation system as claimed in any of claims 1 to 25