Patent ID: 8161726

Claim:
A method for cooling lubricating oil, provided in a turbofan engine lubrication system for lubricating moving components, at selectively variable rates in airstreams provided by the fan of the turbofan engine occurring during operation of the turbofan engine by using a heat exchanger, located in a cooling duct extending through at least a portion of a stream structure that is positioned adjacent an engine fan duct wall in the airstreams occurring on the stream side of the engine fan duct wall, for providing air and lubricating oil heat exchanges to so provide air cooling of the lubricating oil, the cooling duct having a duct entrance opening to the fan airstreams of the turbofan engine on the opening of a moveable entrance flap from the duct entrance to result in portions of the airstreams being forced into the duct entrance during at least some of the operations of the turbofan engine, and further comprising a moveable exit flap to at least in part cover a portion of an exit opening of the cooling duct having an end located about at or outside the end of the fan duct nozzle the cooling duct, the method comprising: forcing lubricating oil to lubricate moving parts and to also pass through the heat exchanger having a core with a plurality of passageway structures therein about which air can flow with the passageway structures being connected to an input conduit at one end thereof and connected to an output conduit at an opposite end thereof to enable providing the lubricating oil to, and removal from, interiors of the passageway structures through interiors of the input and output conduits, and opening the entrance flap to uncover a portion of the entrance opening to thereby admit a portion of the fan airstream to the cooling duct and opening the exit flap to uncover a portion of the exit opening that is smaller than the uncovered portion of the entrance opening.