Twin screw compressors for air compression and refrigeration have been used since late 1950’s. The efforts of designers in all these years focused on optimization of rotor profiles keeping the uniform rotor lead mostly due to manufacturing constraints. However it is well known that by varying the pitch and/or cross section profile the performance of a compressor could be improved. Variable lead rotors have been extensively used in vacuum pumps and more recently in multiphase pumps and have proven beneficial although difficult to make.
With advancements in manufacturing and measurement technology and with the new manufacturing methods there are signs that screw machines with variable rotor profiles and variable rotor lead might be used more often in future.
The prerequisite for design of such machines is ability to design them, analyse their performance and optimise the. SCORGTM is today the only grid generator for screw machines which can produce numerical mesh for performance analysis of such machines.
This example shows use of SCORGTM to generate numerical mesh for three different screw compressors:
The main advantages of varying the lead on screw rotors are:
More information about grid generation of variable geometry rotors could be found in the following publications:
The capability of SCORGTM to generate numerical grid for rotors with constant and variable lead as well as variable profile is demonstrated in the following video
Watch Video: Variable lead rotors