Session: 6.1.1 - Student Competition

Paper Number: 108781

108781 - Experimental Analysis of an Elastohydrodynamic Seal for Supercritical Carbon Dioxide Turbomachinery 

Supercritical carbon dioxide (sCO₂) power cycles are superior to traditional water-based, air-breathing, direct-fired, open Brayton cycles, or indirect-fired, closed Rankine cycles in terms of efficiency and equipment footprint. They hold promising potential in nuclear power production, fossil fuel power plants, concentrated solar power, geothermal power, and ship propulsion. 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 at 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. Under the EHD mechanism, the higher the pressures are, the tighter the sealing becomes, while still sustaining a continuous sCO₂ film. For proof-of-concept purposes, a 2” static test rig was designed at Georgia Southern University before the actual dynamic testing at the Sandia National Laboratories. For the sake of simplicity, the working fluid was chosen to be nitrogen, and the tests were conducted at room temperature. The test rig consisted of a 16.5 MPa N₂ tank; a cylindrical chamber, housing the static shaft and the test seal; steel tubing with compression-type fittings; an OMEGA – PX5500C0-2.5KA10E pressure sensor to measure the pressure of the N₂ after the pressure regulator from the tank; and an OMEGA-FMA-1623AI mass flow meter. The static shaft had a diameter of 2" and was made from steel, whereas the test seal was made from PEEK. Pressure, temperature, and mass flow rate data were measured using LabVIEW software and a National Instruments DAQ - Module NI-9205. The experiments were performed for 50 µm initial clearance and inlet pressure increased up to 4 MPa. Initial experiments successfully demonstrated the throttling behavior of the EHD seal. Based on these preliminary results, the proposed EHD seal design could potentially be used in sCO2 turbomachinery.

This project is financially supported by US DOE through STTR Phase I and II grants under grant no: DE-SC0020851.

Presenting Author: Jonah Henry Georgia Southern University

Presenting Author Biography: Mr. Jonah Henry is an Undergraduate Research Assistant in the Department of Mechanical Engineering at Georgia Southern University. Mr. Henry has been leading fabrication efforts for innovative seal designs for supercritical carbon dioxide applications for the past 2 years. He is expected to graduate in Spring 2024.