Applicability of scroll expander and compressor to an external power engine: Conceptual design and performance analysis

Abstract

A scroll expander and scroll compressor for a 10-kW class Ericsson engine utilizing solar energy as heat source has been suggested. Orbiting scroll members of the expander and compressor were designed to have a base plate with double-sided wrap structure for compact size and axial gas force cancellation. For axial compliance of the scroll machines, a back pressure chamber was created on each fixed scroll. In order to compensate for the thermal expansion, flexible coupling between the orbiting scroll base plate and the scroll plate holders and sliding keys between the fixed scroll and the supporting frame were designed. Common shafts were shared by the expander and compressor for direct power transmission. For high- and low-side pressures of 6 and 2.5 MPa, respectively, and expander inlet temperature of 700°C, the proposed engine efficiency was estimated to be 7.3%. The engine efficiency strongly depends on the expander and compressor efficiencies as well as on the regenerator efficiency. The shaft output of the designed scroll expander was calculated to be 38.84 kW, while the input power for the scroll compressor was 27.97 kW, yielding 10.87 kW for the engine output. Copyright © 2011 John Wiley & Sons, Ltd.