Scroll expander for power generation from a low-grade steam source

Abstract

This paper addresses the development of a scroll expander for power generation from a relatively low-temperature steam source. It has a double-sided orbiting scroll member so that no thrust bearing is needed to support the base plate of the orbiting scroll. Three power transmission shafts are placed at the periphery of the orbiting scroll base plate, and these shafts can also function as antirotation devices. Power output is obtained from the main central shaft engaged with the three power transmission shafts through gear assembly. From the measurement of the mass flowrate and shaft power output for the scroll expander prototype with the scroll clearance of ɛ ≈ 64 μm, it was observed that the volumetric efficiency was ηv = 42.3–52.1 per centage and total expander efficiency was nearly constant at ηt ≈ 34 per cent over the shaft speed of 1000–1400 r/min. According to the computer simulation, the volumetric and total efficiencies could be improved to 83 and 65 per cent, respectively, by reducing the clearance by half.