Design of S-CO₂ TAC Test Rig for High Back sweep Angle Impeller Validation

While designing a turbomachinery, the complexity of analysis and practical machinability have to be considered, which leads to fixing the design parameters from experience of each vendor. However, an S-CO₂ Brayton cycle is not yet mature power generation technology. The previous study proposed that an S-CO₂ compressor has higher isentropic efficiency as the back sweep angle increases using one dimensional mean stream-line method. This paper will cover a design of TAC (Turbine-Alternator-Compressor) test rig to confirm the effect of high back sweep angle on S-CO₂ radial compressor. S-CO₂ phase change during compression, the bearing technology and blade height were considered to design cycle operation conditions of S-CO₂ TAC test rig. Its main feature compared to existing S-CO₂ compressors is to select the low DN number and the low specific speed for the ball bearing adoption instead of gas bearing or magnetic bearing. Also, impellers with back sweep angle of -30 .deg. C, -50 .deg. C and -70 .deg. C were selected for experimental validation. The high pressure operating conditions causes large axial thrust force on turbomachinery. Thus, the turbine design that minimizes the axial thrust force based on the compressor design will be carried out.