The Challenge of Using the Single-Screw Compressor with Steam

Tests are reported on a small (110 mm diameter main rotor) singlescrew air compressor adapted for use with steam. A novel gaterotor design was employed with sliding pads to take up tooth flank clearances. There was also water atomisation into the suction. The test rig allowed preliminary runs to be made on nitrogen at 2990 and 5600 RPM. The best volumetric efficiency was only 57% and this was due to excessive clearances in certain locations. Runs -on steam gave maximum volumetric efficiences of 30%. The additional losses were due to heat transfer effects, both steady-state and transient. Based on the understanding gained detailed recommendations are given on ways to achieve high performance in steam compression with the single-screw machine.