CFD in rotary positive displacement screw machines

Positive displacement screw machines are classified as compressors, expanders, extruders, blowers, vacuum pumps, liquid and multiphase pumps. They are commonly used in industrial refrigeration, air conditioning, process gas compression and variety of liquid, multiphase and vacuum pumping applications. It is estimated that almost 20% of world energy consumption is used for various means of gas compression and pumping. Therefore, reliability and efficiency of such machines has large impact on economy and ecology important for every manufacturer of such machines.
Screw machines are normally designed with the aid of analytical tools, based often on one-dimensional flow models solved by numerical methods and validated by experiments. Continuing demands for improvements in accuracy when designing such machines for existing or new applications have generated a need to use advanced means of assessment of fluid flow and solid fluid interaction within these machines such as 3D Computational Fluid Dynamics and Computational Continuum Mechanics. The first use of CFD for analysis of screw machines was reported in late 1990’s. Since then, significant developments have been made to allow use of CFD in the design process of such machines. The most significant development which enabled such calculation methods was in representing the flow domains with the numerical grids capable of accurate and fast CFD calculation. This paper reviews the state of the art in application of CFD in modelling of positive displacement screw machines and outlines benefits which the use of such techniques may bring. The paper also identifies challenges and future development trends in application of CFD for rotary positive displacement screw machines.