US Patent 11286881 Gas turbine engine with reversible heat exchanger

A gas turbine engine system includes a gas turbine engine having a fan bypass duct, a heat exchanger system, and a flow transfer unit configured to selectively allow or preclude flow between the fan bypass duct and the heat exchanger system. A controller is coupled to and configured to vary the state of one or more of a fan exit nozzle, a heat exchanger exit nozzle, and a flow control valve controlling flow between the fan bypass duct and the heat exchanger system.