Development of 180 kW Organic Rankine Cycle (ORC) with a High-Efficiency Two-Stage Axial Turbine

The design of turbines used to convert thermal energy into electrical energy in an organic Rankine cycle (ORC) is crucial. A high-speed turbine requires high-performance bearings, which increases turbine manufacturing costs. In this study, a high-efficiency two-stage axial turbine at a low rotational speed was developed, and the ORC performance was presented. We designed a 180-kW axial turbine of 12,000 rpm. To increase turbine efficiency, the number of turbine stages was set to two, and turbine blades were designed to reduce pressure losses. One-dimensional design parameters of blades that minimized the total pressure loss were selected using an in-house code based on a generalized reduced gradient (GRG) nonlinear algorithm. Three-dimensional turbine blade modeling and numerical analysis were performed using commercial software. The total-to-static isentropic efficiency and output of the two-stage axial turbine were predicted to be 85.1% and 176 kW, respectively. ORC performance was assessed using the predicted turbine performance results. Assuming the temperature of the condenser outlet working fluid to be 25 °C, the ORC thermal efficiency and exergy efficiency were found to be 7.40% and 34.49%, respectively. Our findings highlight the applicability of various rotational speeds and number of stages for an axial turbine in an ORC.