Design and performance experiment of radial inflow turbine expander for organic Rankine cycle system

Abstract

Expander is the core component of organic Rankine cycle (ORC) system. Taking R245fa as the organic working fluid, the miniaturization design of radial inflow turbine expander with theoretical maximum output power 20 kW and rotational speed of 30 000 r/min is carried out. The deflector and the moving impeller are simulated and designed. The ORC system with preheater and superheater is built for performance analysis of the designed turbine expander. The effects of temperature, pressure and rotational speed on the output power, temperature drop and efficiency of turbine expander are studied experimentally. The experimental results show that with the increase of the inlet temperature, the efficiency of the turbine expander has a minimum value, but the output power keeps increasing gradually. The analysis shows that the lowest efficiency is caused by the deterioration of expansion due to the rapid increase of flow rate. The turbine expander has the maximum efficiency of 0.886 at the inlet temperature 393.15 K and the inlet pressure 1.2 MPa. When the rotational speed increases from 12 000 r/min to 28 000 r/min, the temperature drop increases from 17.2 K to 32.7 K, and the output power increases from 7.04 kW to 17.3 kW. With the increase of rotational speed, the thermal power conversion capacity and temperature drop increase, so the output power increases. The system efficiency increases with the increase of turbine expander efficiency and has the same change rule.