Thermal management in the fuel cell component was a critical issue in the operation of a solid oxide fuel cell gas turbine (SOFC/GT) hybrid system. The effective management of fuel cell cathode air mass flow was thought to be a potential method to improve the thermal management during transients.

The U.S. Department of Energy, National Energy Technology Laboratory (NETL) designed and built a hybrid performance (HyPer) facility by interfacing a real time solid oxide fuel cell system numerical model through hardware with a physical gas turbine system. Perturbations were accomplished by diverting part of the compressor discharge directly to atmosphere through the manipulation of a bleed-air bypass valve in open loop experiments using the HyPer facility. Two tests were performed: the fuel cell numerical simulation model was both decoupled and fully coupled with the gas turbine hardware component.

The responses of both physical subsystem and virtual subsystem to the disturbances were evaluated in this paper. Distributed temperatures and current densities along the fuel cell were evaluated. Turbine speed and system pressures were analyzed. The application of bleed-air bypass valve was shown to have a minimal impact on cathode airflow, but a significant effect on turbine speed. Thus, the manipulation of compressor bleed was expected to be an effective means to mitigate the impact of a sudden increase in turbine speed, such as fuel cell load reductions or load trips.

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