Influence of flank clearance on the performance of a scroll expander prototype

Abstract

Scroll expanders are positive displacement machines with great potential for the implementation of organic Rankine cycle (ORC) and compressed air energy storage (CAES) systems, particularly for small scale plants or laboratory research. Despite the widespread use of scroll devices as compressors and vacuum pumps, its use as expanders is comparatively more recent. The current work presents experimental results obtained with an open-drive and oil-free scroll expander constructed for research purposes working with air. The influence of flank clearance over the expander performance is investigated with two configurations: 57 μm and 165 μm. The prototype geometry is described in detail: equations that define the scroll wraps, sealing implementation and inlet cross-section. Maximum isentropic efficiency of 50.5% was obtained with the smaller flank clearance of 57 μm. Friction losses were also measured experimentally. Appropriate correlations for mechanical power, isentropic efficiency and filling factor were obtained from experimental data as a function of pressure ratio.