US Patent 11174790 Gas turbine engine having an air-oil heat exchanger

A gas turbine engine includes: a core engine surrounded by a core fairing; a propulsive fan; a nacelle surrounding the propulsive fan, the core fairing and the core engine; and a fan duct for receiving a bypass air flow accelerated by the propulsive fan, the fan duct being defined between the nacelle and the core fairing. The gas turbine engine further includes an air-oil heat exchanger for cooling engine oil using an air flow diverted from the bypass air flow, the heat exchanger being mounted behind a wall of the fan duct. The gas turbine engine further includes a flow passage which receives the diverted air flow at a first location in the fan duct, delivers the diverted air flow to the heat exchanger, and returns the diverted air flow to the fan duct at a second location which is downstream of the first location.