Water cooled exhaust duct

1 . A turbine engine assembly comprising:

a compressor section where an inlet airflow is compressed;

a combustor section where the compressed inlet airflow is mixed with fuel and ignited to generate an exhaust gas flow that is communicated through a core flow path;

a turbine section through which the exhaust gas flow expands to generate a mechanical power output;

a condenser where water is extracted from the exhaust gas flow;

an evaporator system where thermal energy from the exhaust gas flow is utilized to generate a steam flow from at least a portion of water extracted by the condenser for injection into the core flow path; and

a duct system including a duct defining a pathway for the exhaust gas flow between the turbine section and the evaporator system and a cooling passage for a flow of water that accepts heat from the exhaust gas flow to cool the duct, wherein the evaporator system is disposed within the duct system;

a control valve configured to control the flow of water into the cooling passage;

a temperature sensor configured to monitor a temperature of the duct; and

a controller programmed to control a temperature of the duct between the turbine section and the evaporator system by transferring heat from the exhaust gas flow into the flow of water through the cooling passage by operating the control valve to maintain the duct within a predefined temperature range based on information from the temperature sensor.

2 . The turbine engine assembly as recited in claim 1 , wherein the passage includes an inlet that receives the flow of water from a water source and an outlet for communicating a heated water flow from the passage to the evaporator system.

3 . The turbine engine assembly as recited in claim 2 , wherein the inlet and the outlet of the cooling passage is arranged such that the flow of water flows counter to the exhaust gas flow between the turbine section and the evaporator system.

4 . The turbine engine assembly as recited in claim 1 , wherein the duct includes an inner wall spaced radially apart from an outer wall and the cooling passage is at least partially defined within a radial space between the inner wall and the outer wall.

5 . The turbine engine assembly as recited in claim 1 , wherein the passage comprises at least one conduit in thermal contact with the duct.

6 . The turbine engine assembly as recited in claim 1 , wherein the pathway defined by the duct extends between the turbine section and the evaporator system.

7 . The turbine engine assembly as recited in claim 1 , further including a fuel system configured to provide a non-carbon-based fuel to the combustor section.

8 . The turbine engine assembly as recited in claim 1 , further including an intercooling system where a flow of water is utilized for cooling a portion of the compressed inlet flow.

9 . An aircraft propulsion system comprising:

a core engine section defining a core flow path where an inlet airflow is compressed, mixed with fuel, and ignited to generate an exhaust gas flow that is communicated through the core flow path;

a condenser where water is extracted from the exhaust gas flow;

an evaporator system where thermal energy from the exhaust gas flow is utilized to generate a steam flow for injection into the core flow path;

a duct system including a duct defining a pathway for the exhaust gas flow between the core engine section and the evaporator system and a cooling passage for a flow of water that accepts heat from the exhaust gas flow to cool the duct, wherein the cooling passage includes an inlet that receives the flow of water from a water source and an outlet for communicating a heated water flow to the evaporator system, wherein both the evaporator system is disposed within the duct system;

a control valve configured to control the flow of water into the cooling passage; and

a temperature sensor configured to monitor a temperature of the duct between a turbine section of the core engine section and the evaporator system; and

a controller programmed to control a temperature of the duct between the core engine section and the evaporator system by transferring heat from the exhaust gas flow into the flow of water through the cooling passage by operating the control valve to maintain the duct within a predefined temperature range based on information from the temperature sensor.

10 . The aircraft propulsion system as recited in claim 9 , wherein the duct includes an inner wall spaced radially apart from an outer wall and the cooling passage is at least partially defined within a radial space between the inner wall and the outer wall.

11 . The aircraft propulsion system as recited in claim 9 , wherein the cooling passage comprises at least one conduit in thermal contact with the duct.

12 . The aircraft propulsion system as recited in claim 9 , wherein the inlet and the outlet of the cooling passage is arranged such that the flow of water flows counter to the exhaust gas flow between the core engine section and the evaporator system.

13 . The aircraft propulsion system as recited in claim 9 , further including a fuel system configured to provide a non-carbon-based fuel to the core engine section.

14 . A method of operating a gas turbine engine, the method comprising:

generating an exhaust gas flow that is communicated through a core flow path;

expanding the gas flow through a turbine section to generate a mechanical power output;

routing the exhaust gas flow through a duct defining a pathway for the exhaust gas flow between the turbine section and an evaporator system;

extracting water from the exhaust gas flow in a condenser;

monitoring a temperature of the duct;

controlling a temperature of the duct between the turbine section and the evaporator system by transferring heat from the exhaust gas flow into a flow of water in thermal communication with the duct to generate a heated flow of water, wherein controlling the temperature comprises controlling the flow of water through a cooling passage in thermal communication with the duct to maintain the duct within a predefined temperature range; and

generating a steam flow by vaporizing the heating flow of water with heat from the exhaust gas flow in the evaporator system.

15 . The method as recited in claim 14 , further comprising directing the flow of water through the cooling passage in a direction that is counter to a direction of the exhaust gas flow.