EXPERIMENTAL DEMONSTRATION OF A NOVEL ELASTOHYDRODYNAMIC SEAL CONCEPT FOR sCO₂ TURBOMACHINERY

To unlock the maximum ability of supercritical carbon dioxide (sCO₂) power cycles, technological readiness must be established on the scale of 10 – 600 MWe and at the sCO₂ temperatures and pressures of 350 – 700 °C and 20 –35 MPa for nuclear industries. One of the major challenges at the component level is the lack of suitable shaft seals in sCO₂ operating conditions. So far, all conventional seals are incapable of handling sCO₂ pressures and temperatures in one way or another. Hence, we propose an elastohydrodynamic (EHD) high-pressure, high-temperature, and scalable shaft seal for sCO₂ cycles. The distinctive mechanism of such an EHD seal provides a self-regulated constriction effect to restrict the flow without significant material contact, thereby minimizing leakage and wear. In this study, we conducted an experimental study to prove the EHD seal concept on a 2” static shaft. The shaft was made from stainless steel, whereas the test seal was made from PTFE. The experiments were performed for 121.25 μm initial clearance, and the operating pressure was increased up to 1.50 MPa. It was observed that the EHD seal throttled the leakage rate successfully. The leakage rate increased to a maximum of 7.33 g/s at around 0.64 MPa before it started to decay to 2.72 g/s at the maximum operating pressure of 1.50 MPa. This unique behavior of the EHD seal could become advantageous for sCO2 turbomachinery, where lower leakage rates are required at high pressure and temperature values.