Performance Evaluation of Two-Stage Turbine for the Organic Rankine Cycle System

An experimental performance test was conducted to evaluate the performance of 200 kW ORC (Organic rankine cycle) turbine. To satisfy the expansion ratio, a two-stage turbine was designed. The turbine rotors were positioned as back to back to compensate the thrust force, and the target speed was designed as 15000 rpm. The working fluid was R-245fa organic fluid, and a set of ball bearing was adopted. To guarantee the stable operation of the ORC turbine at the design speed, several procedures were conducted. This paper introduces the procedures carried out before the main test to satisfy the design speed operation. Rotor dynamic analysis, rotor balancing, spin test, and ball bearing stabilization were performed to ensure stable ORC turbine operation. In addition, the ball bearing grease for the high-temperature operation condition was adopted, and the bearing cooling device was also installed. During the test, vibration level and bearing temperature were monitored in real time. The ORC turbine loop was constructed to evaluate the performance of the ORC turbine. With the progress for stable operation, the developed ORC turbine could maintain its stability and get the target performance at the loop test. These introduced procedures could be used as reference to develop a modified ORC turbine.