In this CFD simulation, a double flow / two-sided SRM screw compressor (in German: zweiflutiger Schraubenverdichter) has been setup with air at inlet pressure 1 bar, outlet pressure 6 bar and rotational speed of 12,333 rpm. The compressor is designed for a volume ratio of 3, i.e. it works in under-compression range here. When compression chamber opens towards pressure port, the chamber pressure is still below outlet pressure and it is filled with air from outlet region, i.e. backflow occurs. With further rotation, the gas is pushed towards the outlet.
The main advantages of a two-sided compressor are balanced axial forces, i.e. no axial forces on the bearings, and that both bearings are at atmospheric pressure. The animation on the top left shows the pressure distribution with straight rotors. Due to the high pressure in the upper mid of the rotors, they are bent downwards and outwards, see (exaggerated) results from Ansys Mechanical down left: Male rotor is bent 5.1 µm outwards and 4.5 µm downwards, female rotor 7.2 µm outwards and 7.1 µm downwards (radial gap size between straight rotors and housing is 50 µm).
With TwinMesh, these bending lines can be considered in the mesh generation. The animation on top right shows the (quite similar) pressure distribution for the simulation with bent rotors, the plot down right compares mass flow rates for both cases. Due to increased gap sizes on pressure side and between the rotors, gap losses are higher and mass flow rates lower for the bent profiles. The average mass flow rate drops by 4%.
