Cooling systems for gas turbine engines

1. An air-oil cooler for a gas turbine engine, comprising:

a lubricant channel extending between a lubricant inlet and a lubricant outlet, the lubricant channel being a dual-pass lubricant channel comprising a partition that separates the lubricant channel into a first channel portion and a second channel portion, the first channel portion being in fluid communication with the lubricant inlet at one on one end and is in fluid communication with the second channel portion on an opposite end forming a first pass of lubricant by a coolant air flow, the second channel portion being in fluid communication with the first channel portion on one end and is in fluid communication with the lubricant outlet on an opposite end forming a second pass of lubricant by the coolant air flow;

a lubricant bypass channel radially inward of and extending parallel with the lubricant channel; and

an air cooling structure bounding the lubricant channel and configured to provide the coolant air flow, wherein the air cooling structure has an arcuate shape configured for circumferentially spanning at least a portion of a gas turbine engine core, and wherein the lubricant inlet and lubricant outlet being located on a single end of the air cooling structure.

2. The air-oil cooler as recited in claim 1 , wherein the air cooling structure has an annular shape configured to extend about a circumference of the gas turbine engine.

3. The air-oil cooler as recited in claim 2 , wherein the air cooling structure is a first air cooling structure, and further including a second air cooling structure circumferentially adjacent the first air cooling structure.

4. The air-oil cooler as recited in claim 1 , wherein the air cooling structure is a first air cooling structure, and further including a second air cooling structure circumferentially adjacent the first air cooling structure.

5. The air-oil cooler as recited in claim 1 , wherein the air cooling structure defines a plurality of fins oriented obliquely with respect to the lubricant channel.

6. The air-oil cooler as recited in claim 5 , further including a shroud spanning radially outer ends of the plurality of fins.

7. A lubrication system for a gas turbine engine, comprising:

an air-oil cooler, comprising:

a lubricant channel extending between a lubricant inlet and a lubricant outlet, the lubricant channel being a dual-pass lubricant channel comprising a partition that separates the lubricant channel into a first channel portion and a second channel portion, the first channel portion being in fluid communication with the lubricant inlet at one on one end and is in fluid communication with the second channel portion on an opposite end forming a first pass of lubricant by a coolant air flow, the second channel portion being in fluid communication with the first channel portion on one end and is in fluid communication with the lubricant outlet on an opposite end forming a second pass of lubricant by the coolant air flow;

a bypass channel radially inward of and extending parallel with the lubricant channel, wherein the air-oil cooler is configured to apportion lubricant flow between the lubricant channel and the bypass channel to maintain lubricant in the lubricant channel above a congealing temperature and reduce lubricant pressure drop across the air-oil cooler;

an air cooling structure bounding the lubricant channel, wherein the air cooling structure has an arcuate shape configured for circumferentially spanning at least a portion of a gas turbine engine core, wherein the lubricant inlet and lubricant outlet being located on a single end of the air cooling structure;

an air diverter in selective fluid communication with an external environment to selectively provide airflow to the air-oil cooler, wherein the air diverter varies the airflow to the air-oil cooler based on an operational condition, wherein the operational condition is a lubricant temperature or a temperature of the external environment.

8. The system as recited in claim 7 , further including a fixed orifice or pressure relief valve fluidly coupling the bypass channel and lubricant channel for apportioning lubricant between the bypass channel and the lubricant channel.

9. The system as recited in claim 7 , wherein the lubricant channel includes fins for transferring heat from lubricant traversing the lubricant channel.

10. The system as recited in claim 7 , wherein the bypass channel is a decongeal channel configured for warming oil in the lubricant channel using heat from the gas turbine engine.

11. The system as recited in claim 7 , wherein the air-oil cooler is a first air-oil cooler and further including a second air-oil cooler circumferentially adjacent to the first air-oil cooler.

12. A gas turbine engine, comprising:

a lubricant circuit, including:

a bearing compartment;

a lubricant channel in fluid communication with the bearing compartment, the lubricant channel extending between a lubricant inlet and a lubricant outlet, the lubricant channel being a dual-pass lubricant channel comprising a partition that separates the lubricant channel into a first channel portion and a second channel portion, the first channel portion being in fluid communication with the lubricant inlet at one on one end and is in fluid communication with the second channel portion on an opposite end forming a first pass of lubricant by a coolant air flow, the second channel portion being in fluid communication with the first channel portion on one end and is in fluid communication with the lubricant outlet on an opposite end forming a second pass of lubricant by the coolant air flow; and

a lubricant bypass channel radially inward of and extending parallel with the lubricant channel;

an air cooling structure bounding the lubricant channel, wherein the air cooling structure has an arcuate shape circumferentially spanning a gas turbine engine core, wherein the lubricant inlet and lubricant outlet being located on a single end of the air cooling structure; and

an air diverter in fluid communication with the heat exchanger and configured for reducing drag associated with airflow across the air cooling structure, wherein the air diverter includes a nozzle flap operably connected to a synchronization ring for movement between a first position and a second position, wherein the nozzle flap is configured to provide a greater flow of air to the air cooling structure in the first position than in the second position.

13. The engine as recited in claim 12 , wherein the synchronization ring is coupled to an end of the nozzle flap and the synchronization ring is configured for displacing the nozzle flap radially with respect to an engine axis of the engine by rotating about a core of the gas turbine engine.

14. The engine as recited in claim 12 , further including a link coupling the synchronization ring to an aft end of the nozzle flap.

15. The engine as recited in claim 12 , further including a link coupling the synchronization ring to a forward end of the nozzle flap.

16. The engine as recited in claim 12 , wherein the synchronization ring spans the circumference of the engine core.