Systems and methods for operating an aircraft engine using multiple fuel types

An aircraft propulsion system comprising:

• a compressor section forming a first portion of a core flow path through the aircraft propulsion system, the compressor section includes an inlet guide vane assembly, the inlet guide vane assembly includes a plurality of inlet guide vanes, an inlet guide vane actuator (IGVA), and an IGVA servo, the plurality of inlet guide vanes are positionable to control an air flow direction of an air flow at the first portion of the core flow path, the IGVA is operably coupled with the plurality of inlet guide vanes, the IGVA servo is connected in fluid communication with the IGVA;
• a combustor section including a combustor forming a second portion of the core flow path;
• an engine oil system including a fuel-oil heat exchanger;
• and
• a fuel system assembly including a jet fuel system, a hydrogen fuel system and a switching valve,
• the jet fuel system connected in fluid communication with the combustor and the IGVA servo, the jet fuel system configured to selectively direct a jet fuel to the combustor, the jet fuel system further selectively connected in fluid communication with the fuel-oil heat exchanger by the switching valve,
• the hydrogen fuel system connected in fluid communication with the combustor, the hydrogen fuel system including a liquid hydrogen source, the hydrogen fuel system configured to selectively direct a hydrogen fuel to the combustor from the liquid hydrogen source, the hydrogen fuel system further selectively connected in fluid communication with the fuel-oil heat exchanger by the switching valve, and
• the switching valve configurable to direct one of the jet fuel or the hydrogen fuel through the fuel-oil heat exchanger.

A method for operating a fuel system assembly of an aircraft propulsion system, the fuel system assembly including a jet fuel system and a hydrogen fuel system, the method comprising:

• directing an engine oil along an oil flow path to one or more engine oil loads of the aircraft propulsion system with an engine oil system, the engine oil system including a fuel-oil heat exchanger forming a portion of the oil flow path;
• directing,
• in a first fuel mode, a jet fuel from the jet fuel system to a combustor of the aircraft propulsion system, and
• in a second fuel mode, a hydrogen fuel from the hydrogen fuel system to the combustor;
• and
• cooling the engine oil at the fuel-oil heat exchanger with the jet fuel in the first fuel mode and with the hydrogen fuel in the second fuel mode, cooling the engine oil at the fuel-oil heat exchanger in the second fuel mode including effecting a phase transformation of the hydrogen fuel from a liquid hydrogen fuel to a gaseous hydrogen fuel prior to directing the hydrogen fuel to the combustor.