ORC, Scroll expander, Unsteady flow, Mass flow, Performance analysis
As a key component of organic Rankine cycle system(ORC), the performance analysis of the scroll expander is critical for the whole system, and the force analysis of the orbiting scroll plays an important role in the output performance of the expander. In this study, CFD based 3D unsteady flow numerical simulation is performed on scroll expander, the flow characteristics, mechanical properties, output torque and power of the R134a scroll expander under different speed are analyzed in detail with dynamic mesh technology. The analysis shows that the inlet mass flow rate increases with the raise of shaft speed, the output torque of expander decreases with the raise of shaft speed, and the output power increases gradually. When the expander speed and outlet pressure is constant, the output torque and output power increase with the increase of inlet pressure. An experimental rig for scroll expander is set up. From the comparison of the simulated and measured data, it can be seen that the expander model predicts the output power very well (within 5%). The proposed numerical simulation modeling can accurately describe all the suction, expansion and discharge processes for scroll expander. The results supply the theoretical support for performance optimization of scroll expander.