1 Copyright © 2013 by ASME Proceedings of the ASME 2013 International Mechanical Engineering Congress and Exposition IMECE2013 November 15-21, 2013, San Diego, California, USA IMECE2013-62391 A STUDY ON THE INFLUENCE OF THE SUCTION ARRANGEMENT ON THE PERFORMANCE OF TWIN SCREW COMPRESSORS Maria Pascu Howden Compressors Ltd Glasgow, UK Manoj Heiyanthuduwage Howden Compressors Ltd Glasgow, UK Sebastien Mounoury Howden Compressors Ltd Glasgow, UK Graeme Cook Howden Compressors Ltd Glasgow, UK Ahmed Kovacevic City University London, UK 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. Various 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. Keywords: screw compressors, optimum suction, CFD INTRODUCTION Although the basic operation of twin screw compressors is well known and the analytical methods for their performance prediction are well established, only few attempts of investigating the flow in screw compressors by means of CFD can be identified in the available literature. Nevertheless, there are many advantages in considering CFD as integrated part of the design and optimization process of screw compressors (SC). This is mostly because CFD complements the experimental and analytical efforts by providing an alternative cost-effective mean of simulating real fluid flows and substantially reduces lead times and costs of designs and production compared with an experimental based approach, Tiu and Liu [1]. Probably the most noticeable efforts in the field of numerical analysis of SC were made by Kovacevic et. al. [2] and [3], where in addition to establishing a mesh procedure specific to such flow machines, the author also explains adequate boundary calculations to encourage good convergence and minimal numerical errors. Similar efforts were made by Sauls and Branch [4], where the commercial code ANSYS-CFX was used for the detailed analysis of a refrigeration SC designed for use with R134a in air- and water-cooled chillers. Also benefiting from the mesh technique documented in [2], Steinmann [5] reported results from the modeling of a helical-lobed pump and a SC using ANSYS-CFX. While the available literature includes several references on improvements of the compressor performance based on the analysis of the discharge port and discharge