Thermal Performance Characterization Of Dry Gas Seals In a sCO₂ Compressor Available to Purchase

Commercially available dry gas seals (DGS) are the seal-of-choice for shaft-end sealing locations in compressors used in the oil and gas industry, and supercritical CO₂ power cycles. DGS reliability is tied to how well the 2 to 7 micron gas/supercritical fluid film is sustained under varying pressure, thermal, and speed conditions. Recent sCO₂ turbomachinery development efforts have experienced a couple of catastrophic DGS failures at the compressor shaft-end locations. A suspected root cause of these DGS failures is thermal deformations caused by the excessive windage heating expected with the supercritical CO₂ working fluid when the compressor operates at high pressures and high rotational speeds. In this paper, we investigate the thermal behavior of the DGS operating in a typical sCO₂ compressor. Specifically, we present test data on a specially instrumented, commercially available DGS operating in the GE-SwRI sCO₂ compressor operating under various mission points. Test data shows higher than expected temperatures (about 190 deg C) in the cavities surrounding the DGS, which provides useful insights to turbomachinery designers for designing seal cavities. Furthermore, we compare the measured temperatures with the predictions of a steady-state thermal model of the GE-SwRI sCO₂ compressor. The thermal model uses a 1D flow advection network with cavity swirl solvers, windage and heat transfer coefficients for sCO₂ flow exchanging heat with the surrounding structure. The predictions of the thermal model match reasonably well with the measured temperature data, thereby providing validation to the novel sCO₂ thermal modeling assumptions.