Design and performance analysis of a radial inflow turbogenerator with the aerostatic bearings for organic Rankine cycle system

Abstract The expander is the key equipment of organic Rankine cycle (ORC) system, so it is significant to improve the performance. In this paper, a radial inflow turbogenerator with aerostatic bearings for ORC system is developed. In comparison with previous equipments, the leakage of working fluid and the mechanical transmission losses are reduced in this design. Moreover, no additional lubricant or coolant is required for the turbogenerator. Compressed carbon dioxide as the working fluid, its performance is tested by changing three variables: rotational speed (10000–26000 r/min), turbine inlet temperature (20–100 °C) and generator load (21–49 kW). The experimental results show that the isentropic efficiency and the electromechanical efficiency increase with the increase of the rotational speed. With the increase of turbine inlet temperature, the isentropic efficiency increases, while the electromechanical efficiency decreases. There are no obvious variations between them and the generator load. The pressure ratio increases with the increase of the rotational speed and the generator load. When the rotational speed of the turbogenerator is the rated speed 26,000 r/min, the isentropic efficiency, expansion work and electromechanical efficiency reach the maximum values, 80.6%, 20.47 kW, and 91.1%, respectively.