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The influence of discharge ports on rotor contact in screw compressors.

Author(s) : STOSIC N., MUJIC E., KOVACEVIC A., et al.

Summary

One means of minimizing interlobe leakage in a screw compressor is to design it so that the pressure distribution across the female rotor causes it to maintain contact with the trailing flank of the male rotor. This is because the sealing length on that side of the rotor is longer than on the more traditionally used leading flank. The disadvantage of this is that it creates torque on the female rotor opposite in sign to that caused by the drag forces. The net torque, which is the result of the small difference between relatively large forces, may then change its sign during the compression cycle and this is the main cause of rotor instability and mechanical noise in screw compressors. Thus, some adjustment of the pressure distribution may be required to avoid rotor flutter or rattling. A well-proven mathematical model was used to calculate the torque on the female rotor and determine the best pressure distribution that would avoid this effect. The improvement resulting from this was confirmed experimentally on a prototype compressor, which had previously generated high levels of contact noise and vibration under some operating conditions. Trial and error changes were made to the discharge port size and shape until the best result was achieved. By this means, the female rotor motion was stabilized. This resulted not only in reduced noise generation but also in improved compressor performance.

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Details

  • Original title: The influence of discharge ports on rotor contact in screw compressors.
  • Record ID : 2007-2024
  • Languages: English
  • Source: 2006 Purdue Conferences. 18th International Compressor Engineering Conference at Purdue & 11th International Refrigeration and Air-Conditioning Conference at Purdue [CD-ROM].
  • Publication date: 2006/07/17

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