Fuel cell exhaust condensation with turbomachinery water augmentation using cryogenic bottoming cycle

A gas turbine engine assembly comprising:

• a core engine comprising a main compressor where an inlet airflow is compressed and communicated to a combustor to generate an exhaust gas flow that is expanded through a main turbine section to generate shaft power used to drive the main compressor;
• a fuel cell generating electric power from a flow of fuel and oxygen and emitting a fuel cell exhaust flow containing water;
• a bottoming cycle where a working fluid is heated and expanded through a bottoming turbine to generate shaft power;
• a first heat exchanger providing thermal communication between the fuel cell exhaust flow and the working fluid of the bottoming cycle;
• a cryogenic fuel system comprising a cryogenic fuel storage tank, a fuel flow path for routing a cryogenic fuel flow to the combustor of the core engine;
• a fuel/working fluid heat exchanger for cooling the working fluid with the cryogenic fuel flow;
• and
• an evaporator where water within the fuel cell exhaust flow is transformed into a steam flow for injection into the combustor of the core engine;
• and
• a second heat exchanger where the cryogenic fuel flow is heated by the exhaust gas flow from the core engine prior to being injected into the combustor, wherein a portion of the cryogenic fuel heated in the second heat exchanger is communicated to the fuel cell.

A method of operating an aircraft propulsion system comprising:

• generating an exhaust gas flow in a combustor of a core engine by igniting a mixture of compressed air and a cryogenic fuel;
• generating electric power in a fuel cell from a flow of the cryogenic fuel and oxygen and emitting a fuel cell exhaust containing water;
• communicating thermal energy from the fuel cell exhaust into a working fluid within a bottoming cycle where a working fluid is heated and expanded through a bottoming turbine to generate shaft power;
• cooling the working fluid exhausted from the bottoming turbine in a fuel/working fluid heat exchanger where a cryogenic fuel accepts heat from the working fluid;
• heating the cryogenic fuel flow with a portion of the exhaust gas flow generated by the combustor and communicating the heated cryogenic fuel flow to the combustor and to the fuel cell;
• and
• heating a portion of water contained in the fuel cell exhaust to generate a steam flow for injection into the combustor.