Modelling of Multiphase Twin Screw Machines

Twin screw compressors used in refrigeration, gas and air compression represent approximately 80% of the millions of industrial positive displacement compressors produced globally each year. More than 95% of these are oil injected. Oil injected twin screw compressor is just one type of multiphase screw machines. Other include twin screw expanders, multiphase pumps and motors. Multiphase twin screw machines are traditionally analysed and designed by use of chamber thermodynamic models. However for further improvement of efficiency and reliability it is necessary to use more advanced modelling techniques such as 3D Computational Fluid Dynamics (CFD). In order to obtain fast and accurate solution of multiphase screw machines using CFD, it is important that a numerical grid of the highest quality is generated quickly and reliably. For that purpose, a deforming grid of a twin screw machine is generated using algebraic transfinite interpolation upon which an elliptic partial differential equations (PDE) of the Poisson’s form are solved numerically to produce smooth final computational mesh. This paper gives a review of the current state of art in the application of CFD in modelling of multiphase twin screw machines including compressors, expanders and pumps. Future challenges and development trends in application of CFD for multiphase twin screw machines are also shown in the paper.