A Study on the Influence of the Suction Arrangement on the Performance of Twin Screw Compressors

Abstract

Screw compressors are complex flow systems, but operate upon simple considerations: they are positive displacement machines consisting of meshing rotors contained in a casing to form a working chamber, whose volume depends only on the angle of rotation. Their performance is highly affected by leakages, which is dependent on various clearances and the pressure differences across these clearances. Nowadays, the manufacturing and profiling techniques have matured so much, that rotors of even the most complex shapes can be manufactured to tolerances in the order of few microns, resulting in high efficiencies. With manufacturing tolerances this tight, there is only small amount of improvement expected from further exploration of this venue, and a rather different direction for analysis may be more rewarding, i.e. other components of the screw compressor, like the suction and discharge areas. While the available literature includes several references on improvements of the compressor performance based on the analysis of the discharge port and discharge chamber, the investigation of the suction arrangement and inlet port remains fairly unexplored. This is the area of concern for the present paper, where the influence of the port shape and suction arrangement on the overall compressor performance is investigated. Two suction models were investigated for a standard screw compressor by means of CFD, which allowed in-depth analyses and flow visualizations, confirmed by the experimental investigation carried out on the actual compressor.

Turbulent flow development within the discharge cavity of a screw compressor

“…2 A clear understanding of the flow processes is essential as it would greatly help the machine performance and, in fact, their characteristics should be an integrated part of the design and optimisation process of screw compressors. 3,[11][12][13] The flow within the screw compressor can be divided into four sections, from suction to the exhaust. The first is the suction flow that feeds into the second section of five rotors' working chambers through which the gas is pressurised as it is convicted towards the third section of discharge port, where the flow exits into the last section of the discharge cavity.…”

“…13 The simulation by12 has shown that the suction port shape and the inflow trajectory into the rotors’ chambers would influence the flow within the rotors. The investigations of Stosic 2 and Pascu et al 12 have shown that the use of new techniques for rotors profiling helped to manufacture rotors of complex shapes with tolerances of the order of few microns, which improved efficiencies. Also, a limited number of the previous investigations have been carried out 19,20 to characterise flow leakages using experiments and CFD simulations.…”

Isogeometric simulation of thermal expansion for twin screw compressors

“…One of the most common approaches, 0D chamber-model simulations, is described in the work by Kauder [5]. For a systematic introduction to 3D CFD simulations we refer to Kovacevic et al [6], while advanced CFD simulations including leakage flows are presented in [7,8]. A novel efficient tool for fluid domain meshing is proposed by Hesse [9].…”