Pressure Rise & Thrust Modeling of the Supercritical CO2 Hardware

by Milton Vernon, Wright, Pickard, & Fuller
Sandia National Laboratories

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Sandia National Laboratories is investigating supercritical CO2 (S-CO2) Brayton cycles as a potentially more efficient and compact power conversion system. Sandia has operated the supercritical CO2 compression loop to verify the models of compressor pressure rise and thrust loads. This report provides a brief summary of the models used for compressor pressure rise and thrust observed in recent operating experience. The compression loop was fabricated during FY2007/FY2008, and the compression loop testing began in late 2008. The tests were performed at Barber-Nichols Inc. in Arvada, Colorado under contract to Sandia. Initial examinations of the measured compression data indicates that the compression is well modeled by centripetal acceleration minus the pressure drop required to accelerate the CO2 through a slight flow area reduction that is built into the existing compressor. Initial examination of the measured thrust data indicates that the thrust is well modeled by the simple integration of the pressures across the front and back faces of the compressor and shaft, with the pressures distribution being impacted by centripetal acceleration of the CO2 as well as the flow through the compressor and shaft seals.