Model Fidelity Requirements for Closed-Brayton-Cycle Space Power Systems

Abstract

C LOSED-BRAYTON-CYCLE (CBC) power conversion is one technology that can be used in space power systems for spacecraft, surface bases, and planetary rovers.More than 270works on Brayton space power system topics appear in the literature over the last 30 years. Brayton system conceptual designs for milliwatt to megawatt power converters have been developed [1–9]. When optimizing a CBC power conversion system (PCS), numerous factors affect overall system performance; a partial list includes turbomachinery efficiency, heat exchanger effectiveness, workingfluid composition, and cycle temperatures and pressures. The present work also addresses the significance of compressor bleed flows and different internal loss mechanisms. Unfortunately, in much of the literature, CBC modeling fidelity is unclear. If items such as the aforementioned factors are not specifically addressed, a reader cannot confidently rely on the results. Effecting CBC model improvements, the present work has two objectives: to demonstrate system-level impacts of fidelity differences in CBC models and to recommend a minimum CBC modeling fidelity for conceptual design studies.