Advanced Hydrogen Cycles to Help Decarbonize the Aviation Industry Hydrogen Fuel Cycles for Aero Gas Turbines

Abstract Hydrogen is currently being considered by the aviation industry as a key enabler to decarbonize the future of flight. While presenting numerous challenges, hydrogen also offers unique opportunities for both the airframe and powerplant. This study builds on the previously introduced modeling work of Part 1, which ran as a Conference proceeding [16], and explores various near-term hydrogen-fueled gas turbine cycles to understand their viability and constraints, while identifying opportunities for improved fuel burn. The baseline hydrogen cycle uses air bled off the high-pressure compressor to drive a preheater, increasing the fuel temperature from the fuel pump delivery to the combustor injection temperature requirement. Sensitivities with respect to the location of the compressor interstage bleed port and fuel delivery temperature are discussed. Although combustion stability requirements rather that the pure cycle performance optimum will ultimately dictate the actual bleed extraction point. The study also explores the use of fuel recuperators to recover energy from the high temperature core flow and transfer it back into the engine via the fuel line. The use of both full and partial recuperators of various designs and installation are investigated to determine the associated cycle efficiency benefit and integration challenge. It has been found at cycle level that the core pressure losses introduced by the fuel recuperator are a key design factor in both the selection of the recuperator type as well as the amount of flow split between the core and the recuperator nozzle. Finally, the fuel turbine concept, using high temperature and high-pressure supercritical hydrogen is modeled and studied. This utilizes the high pressure, high temperature supercritical hydrogen out of the fuel recuperator to drive a turbine, which in turn generates sufficient power to run the high-pressure fuel pump with any excess power available to run other engine and aircraft ancillaries. The designs space and mechanical limitations of such a component and the constraints it needs to work with, due to the gas turbine cycle requirements, are explored further. A direct comparison against the equivalent kerosene engine is provided, showing how gas turbine cycles with various levels of hydrogen fuel conditioning and integration technologies differ from the current kerosene cycles.