Preliminary experimental study of friction disk type turbine for S-CO2 cycle application

Abstract

The supercritical carbon dioxide (S-CO2) Brayton cycle has been receiving worldwide attention due to the high thermal efficiency and simple system configuration. Because of the incompressible liquid like characteristic of the CO2 near the critical point (30.98℃, 7.38MPa), S-CO2 Brayton cycle can achieve high efficiency by reducing compression work. However, the high pressure operating condition and high density of the fluid caused difficulties in designing appropriate seals and bearings for the turbomachinery. For S-CO2 turbine application, the KAIST research team tested a friction disk type turbine (Tesla turbine) concept for the S-CO2 cycle application. The Tesla turbine is a unique concept of turbomachinery which was designed by Nikola Tesla. Differ to the conventional blade type turbomachine, the Tesla turbine uses only friction forces to turn the rotor and shaft. The KAIST research team tested a lab-scale Tesla turbine in the KAIST S-CO2 experimental facility (S-CO2PE). This paper describes main characteristic of the Tesla turbine with the experimental results and the further optimization study to the S-CO2 cycle application.