Abstract

Interstage shaft leakage in sCO2 turbomachinery is challenged by high differential pressure, high speed and relatively small shaft diameters where secondary seal leakage flow of conventional seals can adversely impact performance. With several programs now focused on sCO2 power conversion cycles, sealing solutions need to be advanced in their TRL to facilitate commercial applications. To this end, Sandia National Laboratories is working with industry partners to identify and test solutions. Pressure actuated leaf seals is one of the technologies identified with significant application potential. They are well suited to meet these challenges with designs capable of high differential pressure, high speed and favorable rotor dynamics owing to their short axial length without cross-coupled stiffness hazard. Thin sheet metal seal leaves passively close with system differential pressure after transition through shaft modes that can damage fixed seals. These seals have been applied in one sCO2 development application to date. To evaluate their use in sCO2 power conversion cycles with advanced nuclear reactors now under development two seal configurations were designed and fabricated for test in the Sandia Brayton Energy Laboratory at differential pressure of up to 3,000 psid (207bar) and maximum shaft speed of 40,000 RPM. Features of both configurations are discussed. Prior to dynamic testing at Sandia National Laboratories, a static test of each seal configuration was conducted at CMG Tech using high pressure water to confirm pressure actuated seal closure and assess interleaf seal leakage. Test results of measured seal leakage is discussed. Successful demonstration of pressure actuated leaf seal function and low leakage flow in static testing provides a confident starting point for dynamic testing in the Sandia sCO2 test facility. Demonstration of Pressure Actuated Leaf Seals technology readiness for extreme sCO2 conditions advances their consideration for use in a broad range of turbomachinery including gas and steam turbine shaft sealing, compressor interstage sealing, and pump wear rings.

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