Development of a Solid-Oxide Fuel Cell/Gas Turbine Hybrid System Model for Aerospace Applications

ABSTRACT Recent interest in fuel cell-gas turbine hybrid applications for the aerospace industry has led to the need for accurate computer simulation models to aid in system design and performance evaluation. To meet this requirement, solid oxide fuel cell (SOFC) and fuel processor models have been developed and incorporated into the Numerical Propulsion Systems Simulation (NPSS) software package. The SOFC and reformer models solve systems of equations governing steady-state performance using common theoretical and semi-empirical terms. An example hybrid configuration is presented that demonstrates the new capability as well as the interaction with pre-existing gas turbine and heat exchanger models. Finally, a comparison of calculated SOFC performance with experimental data is presented to demonstrate model validity. Keywords: Solid Oxide Fuel Cell, Reformer, System Model, Aerospace, Hybrid System, NPSS INTRODUCTION Fuel cell technology continues to mature due to innovations from industry, government, and academia. Electric drive-trains for automotive applications are evolving from early pure battery-powered vehicles to commercially viable combustion engine/battery hybrids, with pure fuel cell buses and automobiles undergoing on-road demonstrations. Stationary power fuel cell systems continue to be installed, proving environmental sensitivity and becoming more capable with regard to reliability, availability and user friendliness. New types of fuel cells, such as the direct methanol fuel cell, are potentially creating new market applications for fuel cells including portable power for laptop computers and other compact electronics. This continued progress towards more reliable and cost-effective fuel cells establishes a basis to consider fuel cells in aerospace applications. These applications include electrical power units for commercial aircraft and uninhabited aerial vehicles (UAVs) and also propulsion power for UAVs and other small aircraft. NASA has been using fuel cells for the manned space program since its inception and is currently assessing the feasibility of proton exchange membrane (PEM) fuel cells for its next-generation space launch vehicle. Other space applications for fuel cells such as electrical power for satellites and even planetary in-situ-based electrical power units are also being examined. As in other applications, aerospace fuel cells may offer reduced criteria pollutant (e.g., NO