Experiments on a small-scale axial turbine expander used in CO2 transcritical power cycle

Abstract

As a result of the miniaturization and better temperature matching advantage of CO2-based Transcritical Power Cycle (CTPC) as well as good thermodynamic properties and natural property of CO2, the CTPC system is an appropriate engine waste heat recovery (E-WHR) technology. In the research, a kW-scale partial admission axial turbine expander with conventional carbon ring mechanical seal and angular contact ceramic ball bearings is manufactured specifically and experimental tests of the turbine expander are conducted on the CTPC test bench to investigate the turbine operational characteristics and performance. Based on the experimental data, the rotational speed of turbine ranges from 10,554 rpm to 14,684 rpm with the adjustments of resistance load, and the power generation of the turbine reaches the maximum 692 W at 14,022 rpm. The isentropic efficiency of turbine expander increases with the increase of rotational speed and maximum efficiency 53.43% is achieved at 13,366 rpm, then decreased. The variation of voltage and electric current generated by the turbine expander with rotational speed is also investigated. Test results show that the reason for the low power generation of the turbine expander is the leakage caused by the failure of the dynamic seal.