Research on the performance characteristics of an oil-free scroll expander that is applied to a micro-scale compressed air energy storage system
Jian Sun, Bin Peng, Bingguo Zhu, Yaohong Li
Abstract
The oil-free scroll expander, which is the power component of the micro-scale compressed air energy storage (CAES) system, exhibits a satisfactory application prospect. The expander's performance directly influences the efficiency of the expansion power generation system. To enhance the work efficiency of the power generation system, we built a thermodynamic model that facilitates the oil-free scroll expansion mechanism by considering heat transfer and leakage; furthermore, for the micro-scale CAES, we constructed an experiment bench that utilizes air as the working fluid. Based on computational fluid dynamics (CFD), we conducted a three-dimensional unsteady numerical simulation of the fluid flow that occurs in the working chamber of the scroll expander. We observed that the suction pressure loss that occurs during the suction process, which is initiated by the scroll expander, leads to inlet pressure drop, and we noted that the suction pressure directly influences the work efficiency of the power generation system. When the setup is subjected to rotational speeds of 1200–3200 r/min, the difference between the theoretical and measured values of volumetric flow decreases from 0.0226 to 0.000527 m3/min. The pressure, velocity, and temperature distribution of the fluid that exists in the working chamber of the expander are not uniform, and the mass exchange that occurs between adjacent working chambers considerably impacts the distribution of velocity and temperature. As gas flows from the back-pressure chamber to the outlet pipe, most of it flows through the non-deforming domain before flowing into the outlet pipe. The fluid flow in the deforming domain is highly complicated, and even secondary flow can occur.