From September 7th to 9th, 2015, the International Conference on Compressors and their Systems
took place at Mermaid Conference & Events Centre
in London, UK, organised by the City University London. We from CFX Berlin attended this famous conference for the first time having our own exhibition booth. And of course we also got the chance to present some recent work on screw compressor CFD analysis in the shourt course before the conference as well as in the conference itself.
People often ask us for real world simulation examples. Unfortunately, most of our work is “top secret” and we cannot talk about it. Therefore, we thought that this new “TwinMesh – Blog” is a perfect platform to publish some free available and helpful material from the conference preparation. So the first example is the paper on CFD simulation of a screw compressor including leakage flows and rotor heating, some work that was done by my colleagues Andreas Spille-Kohoff and Ahmed El-Shorbagy.
Computational Fluid Dynamics (CFD) simulations have promising potential to become an important part in the development process of positive displacement (PD) machines such like twin screw compressors and expanders. CFD delivers deep insights into the flow and thermodynamic behaviour of PD machines. However, the numerical simulation of such machines is more complex compared to dynamic pumps like turbines or fans. The fluid transport in size-changing chambers with very small clearances between the rotors and between rotors and casing demands complex meshes that change with each time step. Additionally, the losses due to leakage flows and the heat transfer to the rotors need high-quality meshes so that automatic remeshing is almost impossible.
In our conference paper, setup steps and results for the simulation of a dry screw compressor are shown. The rotating parts are meshed with TwinMesh, a special hexahedral meshing program for gear pumps, gerotors, lobe pumps, and screw compressors. In particular, these meshes include axial and radial clearances between housing and rotors and beside the fluid volume the rotor solids are also meshed.
The CFD simulation of the screw compressor accounts for gas flow with compressibility and turbulence effects, heat transfer between gas and rotors, and leakage flows through the clearances. We show time-resolved results for torques, forces, interlobe pressure, mass flow, and heat flow between gas and rotors, as well as time- and space-resolved results for pressure, velocity, temperature etc. for different discharge ports and working points of the screw compressor. These results are also used as thermal loads for deformation simulations of the rotors.
If you would like to read the full paper you can find it via IOP Conference Series.
For all of you who prefer to have a look on the full conference slide show this is available via the following download button here.