Session: 30-15 Thermal Component Performance

Paper Number: 128872

128872 - Thermal Performance Characterization of Dry Gas Seals in a sCO2 Compressor 

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. Typically, a DGS operates with a very thin gas/supercritical fluid film (typically 2 to 7 microns thin). DGS reliability is tied to how well this ultra-thin 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.  We present test data for the temperature measured on the seal stationary ring and DGS housing locations using several embedded metal thermocouples to monitor the thermal behavior of the DGS during typical sCO₂ compressor missions. We describe how an existing GE-SwRI sCO₂ compressor housing was modified to accommodate and route temperature sensors to the instrumented DGS. Test data shows higher than expected temperatures (about 180 to 190 ^oC) in the cavities surrounding the DGS, which provides useful insights to turbomachinery designers for designing seal cavities. The main reason for these high temperatures is the low sCO₂ flow purging the seal cavity. 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 (accounting for cavity swirl, windage and heat transfer coefficients for sCO₂ flow, air flow and bearing oil flow) exchanging heat with the surrounding structure, along with heat transfer through the structure. The thermal model uses CFD-based flows to account for the sCO₂ flow past the DGS. The predictions of the thermal model match reasonably well with the measured temperature data, thereby providing validation to the modeling assumptions. The high structural temperatures in the regions around the DGS that are predicted by the model as well as measured during the tests point to the importance of devising cooling strategies for reliable operation of the DGS.

Presenting Author: Rahul Bidkar GE Research

Presenting Author Biography: Rahul Bidkar is a Principal Engineer at GE Research working in the field of turbomachinery seals

Authors:

Rahul A. Bidkar GE Research
Uttara Kumar GE Research
Xiaohua Zhang GE Research
Nora Molino GE Research
Joshua Neveu SwRI
John Klaerner Southwest Research Institute
Jeremy Johnson SwRI
J. Jeffrey Moore Southwest Research Institute