Powerplant fuel system utilizing ammonia

A powerplant, comprising:

• a turbine engine including a flowpath, a compressor section, a combustor section and a turbine section, the flowpath extending through the compressor section, the combustor section and the turbine section from an inlet into the flowpath to an exhaust from the flowpath, and the combustor section comprising a combustor with a combustion chamber;
• and
• a fuel system including a reservoir, a heat exchanger, a heating device, a cracker and a fuel injector, the heat exchanger configured to vaporize a first flow of liquid ammonia received from the reservoir into ammonia gas using heat energy, the heat exchanger configured to receive the heat energy from the heating device during a first operating mode, the heat exchanger configured to receive the heat energy from the turbine engine during a second operating mode, the cracker configured to at least partially crack the ammonia gas into hydrogen gas and nitrogen gas, and the fuel system configured to deliver the hydrogen gas or a combination of the hydrogen gas and the nitrogen gas to the fuel injector for injection into the combustion chamber;
• wherein the first operating mode is associated with initial startup operation of the turbine engine;
• wherein the second operating mode is associated with post-startup operation of the turbine engine;
• and
• wherein the turbine engine is thermally coupled to the heat exchanger through a first heat transfer fluid, and further comprising a control valve configured to:
• close to prevent a flow of the first heat transfer fluid from the turbine engine to the heat exchanger in the first operating mode;
• and
• open to permit the flow of the first heat transfer fluid from the turbine engine to the heat exchanger in the second operating mode;
• wherein the heating device is thermally coupled to the heat exchanger through a second heat transfer fluid, and the second heat transfer fluid comprises a heat transfer liquid.