Heat exchanger
A gas turbine engine has a fan, a compressor section, a combustor, and a turbine section. The fan delivers a portion of air into the compressor, and into a duct, as bypass air. A bleed air system bleeds a quantity of air from the compressor into a chamber at least at low power conditions of the engine. The bleed air system has an opening which may be selectively closed to block bleed air, or opened to allow bleed flow from the compressor into the chamber. A heat exchanger is positioned such that a first surface of the heat exchanger is contacted by bypass air in the duct, and a second surface of the heat exchanger is contacted by bleed air when the bleed air system directs air from the compressor into the chamber.
1. A gas turbine engine comprising:
a fan, a compressor section, a combustor, and a turbine section, said fan delivering a portion of air into said compressor, and said fan delivering a portion of air into a duct, as bypass air;
a bleed air system for bleeding a quantity of air from the compressor into a chamber at least low power conditions of the gas turbine engine, said bleed air system having an opening which may be selectively closed to block bleed air, or opened to allow bleed air from the compressor to the chamber;
a heat exchanger having fluid containing passages to be cooled and a heat exchanger wall, said heat exchanger positioned such that a radially outer surface of said heat exchanger wall is contacted by bypass air in the duct, and a radially inner surface of said heat exchanger wall is contacted by bleed air when said bleed air system is directing air from the compressor into the chamber, wherein said heat exchanger wall separates the bypass air from the bleed air;
and said heat exchanger fluid containing passages communicating with a lubricating fluid from an accessory on said gas turbine engine.
2. The gas turbine engine as set forth in claim 1 , wherein fins are formed on said radially outer surface of said heat exchanger wall extending into the bypass air.
3. The gas turbine engine as set forth in claim 2 , wherein fins are also formed on said radially inner surface of said heat exchanger wall and extend toward the bleed air.
4. The gas turbine engine as set forth in claim 3 , wherein said fins on said radially inner surface extend for a greater height away from the fluid containing passages than do said fins on said radially outer surface.
5. The gas turbine engine as set forth in claim 4 , wherein said fins on said radially outer surface extend for a greater length along a flow path of the bypass air than do the fins on said radially inner surface.
6. The gas turbine engine of claim 1 , wherein said accessory is a generator, and said lubricating fluid is oil from said generator.
7. A gas turbine engine comprising:
a fan duct having a bypass air flow;
a bleed air system for bleeding a bleed air flow from a compressor section into a bleed air chamber, wherein the bleed air flow is selectively bled from the compressor section into the bleed air chamber;
a heat exchanger having a first convective cooling feature and a second convective cooling feature on a heat exchanger wall, wherein the first convective cooling feature is disposed on a radially outer side of the heat exchanger wall and at least partially in fluid communication with the bypass air flow of the gas turbine engine, wherein the second convective cooling feature is disposed on a radially inner side of the heat exchanger wall and at least partially in the bleed air chamber of the gas turbine engine and at least partially in fluid communication with the bleed air flow, wherein said heat exchanger wall separates the bypass air flow from the bleed air flow;
and said heat exchanger selectively cooling a lubricating fluid associated with a generator.
8. The gas turbine engine of claim 7 , further comprising a selectively controllable valve that controls the bleed air flow from the compressor section of the gas turbine engine to the bleed air chamber.