Session: 30-06 Compressors

Paper Number: 153622

CFD Study on S-CO2 Compressor Boundary Layer Separation During Surge and Stall 

The supercritical carbon dioxide (S-CO₂) Brayton cycle represents a variant of the Brayton cycle that utilizes supercritical carbon dioxide as the working fluid. In this system, the compressor operates at inlet conditions close to the critical point of 7.38 MPa and 304 K for carbon dioxide. Near the critical point, S-CO₂ has a large density and specific heat capacity and a small compression coefficient, which minimizes compression work. Accordingly, from the perspective of system size and efficiency, the S-CO₂ cycle represents a promising candidate, and its adaptable applications are currently under investigation.

One of the fundamental components of the S-CO₂ cycle that differs significantly from the traditional air or gas Brayton cycle is the compressor. In the S-CO₂ cycle, the compressor operates near critical point, which means that the compressor spins at high speeds under high pressure and high-density conditions, and the properties of the fluid passing through the compressor change rapidly. This is a key consideration in the part-load operation of the S-CO₂ cycle, as the operational characteristics of the compressor play a significant factor in the analysis of instability caused by boundary layer separation at the compressor blades due to the flow drop that occurs in low-level operation.

The Korea Advanced Institute of Science and Technology (KAIST) has conducted a study on surge and stall conditions by testing a radial compressor in an Autonomous Brayton Cycle (ABC) test loop. In this study, CFD was analyzed based on the experimental results to investigate the boundary layer separation of the compressor under surge and stall conditions. The rotor used in the CFD analysis was built based on a CAD model of a centrifugal compressor from the Korea Advanced Institute of Science and Technology (KAIST). The simulations were performed using Ansys CFX with S-CO₂ properties taken directly from the NIST REFPROP database to ensure accuracy in terms of physical properties.

Presenting Author: Gihyeon Kim Korea Advanced Institute of Science and Technology

Presenting Author Biography: Presenting author bio
Presenting Author: Gihyeon Kim
Email: orca2005@kaist.ac.kr
Short CV of Presenting Author:
Affiliation: Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST)

Research Area
1. S-CO2 turbomachinery
2. Control system for S-CO2 cycle
3. S-CO2 power cycle for nuclear fission energy

Education
1. Korea Advanced Institute of Science and Technology, Daejeon, Korea
Candidate for Ph.D of Science in Engineering: Nuclear and Quantum Engineering
M.S. degree of Science in Engineering: Nuclear and Quantum Engineering, August 2023
2. Bachelor of Engineering: Korea Advanced Institute of Science and Technology, Daejeon, Korea
Majors : Nuclear and Quantum Engineering and Mechanical Engineering, February 2022

Authors:

Gihyeon Kim Korea Advanced Institute of Science and Technology
Seungkyu Lee Korea Advanced Institute of Science and Technology
Jeong Ik Lee Korea Advanced Institute of Science and Technology