Gas Turbine/Solid Oxide Fuel Cell Hybrids for Aircraft Propulsion and Power

The impact on range and endurance of increasing electrical loads on aircraft and burgeoning interest in all-electric aircraft are driving a need for more efficient replacements for engine-driven mechanical generators. This Paper presents a model of a synergistic gas turbine/solid oxide fuel cell system for combined propulsion and electrical power on aircraft. It is developed using Numerical Propulsion System Simulation and features realistic representations of the engine, reformer (a catalytic partial oxidation reactor), solid oxide fuel cell, and external aerodynamic losses. The results show that incorporating the reformer and fuel cell directly into the engine's flowpath reduces vehicle-level fuel consumption of a high-altitude long-endurance aircraft at cruise by at least 8% when the engine is mounted inside the fuselage and at least 4% when the engine is installed within a nacelle. It also increases electrical generation capability by factors of 2 or more versus engine-driven mechanical generators in several aircraft applications. The main limitation in nacelle-mounted applications is increased external aerodynamic drag associated with the protrusion of the fuel cell into the flow around the engine, but it is shown that this can be mitigated through tight integration with high-pressure-ratio engines and careful flowpath design.