Gas turbine engine with reversible heat exchanger

1. A gas turbine engine system comprising:

a gas turbine engine configured to provide thrust for propelling an aircraft, the gas turbine engine system including an engine core, a fan bypass duct, a first propulsor in the form of a fan, and a fan exit nozzle, the engine core including a compressor, a combustor, and a turbine arranged along an axis, the fan bypass duct arranged annularly around the engine core and having an inlet and a first outlet, the fan coupled to the turbine for rotation therewith and configured to propel air from atmosphere through the fan bypass duct to provide the thrust in a first direction extending from the inlet of the fan bypass duct toward the first outlet of the fan bypass duct, the fan exit nozzle located at the first outlet of the fan bypass duct, and the fan exit nozzle reconfigurable between a first configuration wherein the fan exit nozzle diffuses airflow through the fan exit nozzle to reduce the thrust in the first direction and a second configuration wherein the fan exit nozzle concentrates airflow through the fan exit nozzle to increase the thrust in the first direction;

a heat exchanger system configured to provide cooling for the gas turbine engine, the heat exchanger system including a heat exchanger duct, a heat exchanger exit nozzle, and a heat exchanger, the heat exchanger duct being radially outwardly spaced from the fan bypass duct relative to the axis and having a first inlet receiving a first flow of cooling air and a first outlet discharging the first flow of cooling air, the heat exchanger disposed within the heat exchanger duct between the first inlet of the heat exchanger duct and the first outlet of the heat exchanger duct, and the heat exchanger exit nozzle located at the first outlet of the heat exchanger duct and reconfigurable between a first configuration and a second configuration, wherein the heat exchanger exit nozzle allows greater airflow therethrough when the heat exchanger exit nozzle is in the first configuration and lesser airflow therethrough when the heat exchanger exit nozzle is in the second configuration; and

a flow transfer unit configured to selectively provide fluid communication between the heat exchanger duct and the fan bypass duct, the flow transfer unit including a transfer duct connected between the fan bypass duct and the heat exchanger duct, wherein the transfer duct cooperates with the fan bypass duct to define a second outlet of the fan bypass duct discharging a second flow of cooling air and wherein the transfer duct cooperates with the heat exchanger duct to define a second inlet of the heat exchanger duct receiving the second flow of cooling air between the heat exchanger and the first outlet of the heat exchanger duct, and a flow control valve coupled with the transfer duct and configured to selectively allow or restrict airflow from the fan bypass duct to the heat exchanger duct; and

wherein the first inlet of the heat exchanger duct is reversed to be a second outlet of the heat exchanger duct discharging the second flow of cooling air when the heat exchanger exit nozzle is in the second configuration and the flow control valve allows airflow from the fan bypass duct to the heat exchanger duct.

2. The gas turbine engine system of claim 1 , further comprising a controller connected to the fan exit nozzle, the heat exchanger exit nozzle, and the flow control valve, the controller configured to operate the gas turbine engine in one of a thrust mode and a reverse thrust mode.

3. The gas turbine engine system of claim 2 , wherein the fan exit nozzle is in the second configuration, the heat exchanger exit nozzle is in the first configuration, and the flow control valve is open to allow airflow between the fan bypass duct and the heat exchanger duct in response to the controller operating the gas turbine engine in the reverse thrust mode.

4. The gas turbine engine system of claim 2 , wherein the fan exit nozzle is in the first configuration, the heat exchanger exit nozzle is in the second configuration, and the flow control valve is closed to restrict airflow between the fan bypass duct and the heat exchanger duct in response to the controller operating the gas turbine engine in the thrust mode.

5. The gas turbine engine system of claim 2 , wherein the first flow of cooing air flows into the heat exchanger duct through the first inlet of the heat exchanger duct and exits the heat exchanger duct through the first outlet of the heat exchanger duct in response to the controller operating the gas turbine engine in the thrust mode.

6. The gas turbine engine system of claim 5 , wherein the first flow of cooling air exits the first outlet of the heat exchanger duct in a direction substantially the same as the first direction.

7. The gas turbine engine system of claim 2 , wherein the second flow of cooling air flows into the heat exchanger duct through the second inlet of the heat exchanger duct and exits the heat exchanger duct through the first inlet of the heat exchanger duct in response to the controller operating the gas turbine engine in the reverse thrust mode.

8. The gas turbine engine system of claim 7 , wherein the second flow of cooling air exits the first inlet of the at exchanger duct in a direction substantially opposite the first direction.

9. A gas turbine engine system comprising:

a gas turbine engine that includes an engine core, a fan bypass duct, a fan, and a fan exit nozzle, the fan bypass duct arranged annularly around the engine core, the fan configured to propel air through the fan bypass duct, and the fan exit nozzle located at a first outlet of the fan bypass duct and configured to move between a first thrust position and a second thrust position;

a heat exchanger system that includes a heat exchanger duct radially outwardly spaced from the fan bypass duct relative to the axis, a heat exchanger disposed within the heat exchanger duct between a first inlet of the heat exchanger duct and a first outlet of the heat exchanger duct, and a heat exchanger exit nozzle at the first outlet of the heat exchanger duct, wherein the first inlet of the heat exchanger duct receives a first flow of cooling air and the first outlet of the heat exchanger duct discharges the first flow of cooling air, and wherein the heat exchanger exit nozzie is reconfigurable between a first configuration that allows greater airflow therethrough and a second configuration that allows lesser airflow therethrough; and

a flow transfer unit that includes a transfer duct fluidly connected between the fan bypass duct and the heat exchanger duct and a flow control valve configured to selectively allow or block fluid communication between the fan bypass duct and the heat exchanger duct, wherein the transfer duct cooperates with the fan bypass duct to define a second outlet of the fan bypass duct discharging a second flow of cooling air, wherein the transfer duct cooperates with the heat exchanger duct to define a second inlet of the heat exchanger duct receiving the second flow of cooling air, and wherein the second inlet of the heat exchanger duct is located between the heat exchanger and the first outlet of the heat exchanger duct; and

wherein the first inlet of the heat exchanger duct is reversed to be a second outlet of the heat exchanger duct discharging the second flow of cooling air when the heat exchanger exit nozzle is in the second configuration and the flow control vive allows airflow from the fan bypass duct to the heat exchanger duct.

10. The gas turbine engine system of claim 9 , further comprising a controller connected to the fan exit nozzle and the flow control valve, the controller configured to operate the gas turbine engine in one of a thrust mode and a reverse thrust mode.

11. The gas turbine engine system of claim 10 , wherein the first flow of cooling air flows into the heat exchanger duct through the first inlet of the heat exchanger duct and exits the heat exchanger duct through the first outlet of the heat exchanger duct in response to the controller operating the gas turbine engine in the thrust mode, and wherein the second flow of cooling air flows into the heat exchanger duct through the second inlet of the heat exchanger duct and exits the heat exchanger duct through the first inlet of the heat exchanger duct, which becomes the second outlet of the heat exchanger duct in response to the controller operating the gas turbine engine in the reverse thrust mode.

12. The gas turbine engine system of claim 11 , wherein the fan exit nozzle is in the first thrust position in response to the controller operating the gas turbine engine in the thrust mode, and wherein the fan exit nozzle is in the second thrust position in response to the controller operating the gas turbine engine in the reverse thrust mode.

13. The gas turbine engine system of claim 12 , wherein the gas turbine engine produces greater thrust in a first direction when the fan exit nozzle is in the first thrust position, and wherein the gas turbine engine produces lesser thrust in the first direction when the fan exit nozzle is in the second thrust position.

14. The gas turbine engine system of claim 10 , wherein the heat exchanger exit nozzle is configured to allow airflow through the first outlet of the heat exchanger duct in response to the controller operating the gas turbine engine in the thrust mode, and wherein the heat exchanger exit nozzle further is configured to block airflow through the first outlet of the heat exchanger duct in response to the controller operating the gas turbine engine in the reverse thrust mode.