Review and update on the geometry modeling of single-screw machines with emphasis on expanders

Single-screw type of machines has been widely used in the vapor compression industry for decades. More recently, such machines have been proposed as volumetric expanders in organic Rankine cycle (ORC) for low-grade waste heat recovery applications because of a number of advantages compared to other volumetric machines, e.g., twin-screw, scroll, rotary, reciprocating, such as balanced loading of the main screw, long working life, high volumetric efficiency, low leakages, low noise, low vibration, and a simplified configuration. In this paper, a thorough literature review is proposed to cover the available single-screw geometry models, which are mainly applied to single-screw compressors (SSC). Thus, the geometry model is extended to single-screw expanders (SSE). The validity of the analytic and numerical solutions for the calculation of the volume curves is discussed. The geometry model is applied to a 11 kW single-screw expander and both the profile generation and geometry calculations are validated.