Experimental Analysis of an Elastohydrodynamic Seal for Supercritical Carbon Dioxide Turbomachinery

To unlock the potential of sCO₂ power cycles, technology readiness must be demonstrated 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. The lack of suitable shaft seals in sCO₂ operating conditions is one of the main challenges at the component level. So far, conventional seals all suffer from the incapability of handling sCO₂ pressure and temperature in one way or another. To this end, we propose an elastohydrodynamic (EHD) high-pressure, high-temperature, and scalable shaft seal for sCO₂ cycles. The unique mechanism of such an EHD seal provides a self-regulated constriction effect to restrict the flow without substantial 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 PEEK. The experiments were performed for 12.7 μm initial clearance, and the operating pressure was increased up to 5 MPa. It was observed that the EHD seal throttled the leakage rate successfully. The leakage rate increased to a maximum of 2 g/s at around 4MPa before it started to decay to 1.75 g/s at the maximum operating pressure of 5 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.