CFD, lubrication, screw compressor, oil-injection
Computational fluid dynamics and mesh generation tools have been well developed, and could be used to calculate the performance of an oil-injected screw compressor. Designers could now effectively obtain reliable results of efficiency, temperature, force and torque. Some physical phenomena inside a screw compressor are not easy to be observed through experiments, such as the oil distribution and the oil film thickness on the rotor surface. Under the ideal lubrication condition, the oil film of proper thickness should be maintained on the local surfaces which are going to contact with each other. This could be numerically explored by computational fluid dynamics. The first case in this study showed the effect of centrifugal force on a thin free surface flow on the rotor surface. Designers could graphically understand how the oil film flows on the rotor surface when rotors separately rotate without meshing with each other and doing the compression work. The second case in this study was the rotor lubrication. The clearance distribution between rotors in the actual contact area was designed by the minimum film thickness and was 1 μm. The pressure gradient on the rotor surface was used to see if the hydrodynamic pressure appeared. Designers could optimize the design of oil injection not only by considering efficiencies, but also by analyzing the pressure gradient and the oil film distribution on rotor surfaces.