Study on the Performance and Optimization of a Scroll Expander Driven by Compressed Air

The scroll expander has been widely studied in various energy systems for power generation and refrigeration. An experimental study of a scroll expander is carried out to examine its performance. Meanwhile, a quasi-dimensional numerical modelling is presented for simulating the working process of a scroll expander, which is verified by the experimental results. The numerical model is then used to simulate the internal flow parameters to get a full understanding of working characteristics of the expander. An optimization analysis is further conducted to examine the effect of major parameters, such as working pressure ratio, air inlet temperature, clearance size and scroll vane height to pitch ratio. The results indicate that there is an optimal pressure ratio for a scroll expander, which is between 3 and 4 for the studied expander. The change of the air inlet temperature does not affect the power generation. However, the expander volumetric and isentropic efficiencies decrease along with the increment of the inlet temperature. The clearance and vane height to scroll pitch ratio also have significant impacts on the expander working performance. The efficiency and power output of the expander should be both considered when determining expander parameters of working pressure ratio, clearance size and scroll vane height to pitch ratio for designing a scroll expander.