Instability Study of Magnetic Journal Bearing under S-CO2 Condition

Dokyu Kim,Seungjoon Baik,Jeongik Lee

doi:10.3390/app11083491

Abstract

A supercritical CO2 (S-CO2)-cooled Brayton cycle is under development for distributed power applications for remote regions. In order to successfully develop it, issues of controlling shaft levitation with bearings have to be solved. From several studies, magnetic bearings have been suggested for reliable levitation performance with reduced cost and complexity. However, several studies on magnetic bearing show that instability issues under high-pressure fluid and high-speed operating conditions may exist. The purpose of this research is to provide background for understanding the instability of magnetic bearings under S-CO2 conditions and propose functional requirements of the magnetic bearing. Thus, the rotating shaft with magnetic bearings operating under high pressure fluid was first analyzed. To test the theory, a magnetic bearing test rig was constructed. By comparing experimental data to the analysis results, the analysis results were verified. Therefore, the analysis results can be used for predicting instability in the future and can contribute to the development of better magnetic bearing controllers.

Highlights

A supercritical CO2 (S-CO2 )-cooled Brayton cycle is under development for distributed power applications for remote regions
The analysis results can be used for predicting instability in the future and can contribute to the development of better magnetic bearing controllers
From the and co to air comparison, it was shown that the bearing rotating under pared with air conditions to investigate the instability of bearings underconditions

Summary

Introduction

A supercritical CO2 (S-CO2 )-cooled Brayton cycle is under development for distributed power applications for remote regions. Several studies on magnetic bearing show that instability issues under high-pressure fluid and high-speed operating conditions may exist. This leads to small footprints of the power system. In order to stay competitive with the S-CO2 power cycle in the distributed power generation market, developing a bearing technology appropriate for the power cycle has been proven to be a major technical challenge [3]. The gas foil bearing technology is very challenging to levitate a shaft for power systems above 3 MWe. For wide applications of S-CO2 power systems, enhancing bearing performance is necessary. Magnetic bearing technology can be a favorable option for an S-CO2 cycle with distributed generation with a long maintenance span

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Conclusion