Optimized rotor pitch distributions for screw spindle vacuum pumps

Screw spindle vacuum pumps are characterised by a high suction performance and the ability to achieve high pressure ratios. Screw spindle vacuum pumps have varying progressions for the rotor pitch gradient, depending on the manufacturer. From a scientific point of view, the question arises which rotor gradient along the rotors has to be preferred for a particular set of operating conditions with reference to the machine characteristics. To answer this question a simulation of the compression process in the screw spindle vacuum pump is performed. The simulation program is used to calculate an energy-specific optimal rotor pitch applying an evolutionary optimization approach. It turns out that – in contrast to actually available rotor geometries – a continuous increase in rotor pitch from the pressure to the suction side is not ideal. An optimized rotor pitch curve is presented and the underlying physical dependencies are clarified by means of pressure and mass flow diagrams.

► Energetic optimal rotor pitch curve for screw spindle vacuum pumps which is different from the actual state of art.
► Using a simulation program for screw spindle vacuum pumps which is predominantly based on principle of mass conservation.
► Using evolutionary algorithms for the calculation of an energetic optimal pitch distribution for screw spindle vacuum pumps.
► Model selection based of a two-dimensional pareto front with the parameter internal power and suction mass flow.