Numerical Simulation of Fluid Flow and Solid Structure in Screw Compressors

Abstract

Screw compressor performance is usually predicted by thermodynamic and fluid flow calculations based on a dimensionless flow model. However factors, which affect the power consumption, delivery and reliability of these machines, such as dynamic flow losses, leakage and oil flow drag, are not estimated accurately by such procedures. By the use of 3-D numerical modelling of the compressor fluid flow and structure deformation, these factors can be predicted more precisely and hence losses within the machine can be minimized at the design stage. The authors have developed a CAD-CCM (Computer Aided Design to Computational Continuum Mechanics) interface program to transfer the screw compressor geometry directly into a commercial numerical solver, which simultaneously solves the compressor fluid flow and structural deformation of its parts. All necessary initial and boundary conditions, a procedure for moving of the mesh and additional functional features of the commercial solver are introduced through the user functions automatically generated by the interface program. Results have been obtained for an oil-flooded screw compressor and some of them are presented in this paper. They are presented as overall compressor parameters in the form of power and volume flow. Additionally, pressure-time diagrams of the compression process, flow and pressure patterns in the compressor chambers and rotor deformation are illustrated.