oil-free compressors, contactless seals, dry-running, screw compressors
Screw compressors are currently the most frequently used compressor type in the field of industrial compressed air production. Because end products are only allowed to come into contact with absolutely clean compressed air in many fields of industry, there is a considerable demand on the market for the production of compressed air that is entirely oil-free. The high acquisition costs of dry-running compressor systems and the disadvantages in energy terms compared to oil-injected designs need to be offset by a long useful life and guaranteed reliability. The compressor's integrated sealing system makes an important contribution here. High peripheral speeds and pressure differences largely rule out the use of simple, contacting seal systems and drive forward continuous optimization in relation to function and production costs. Based on the calculation of compressible outflows at annular gaps and experimental studies, the sealing performance of various gas choke seals for use in screw compressors will be analyzed and evaluated. Here, the main criteria of pressure reduction and barrier effectiveness, as well as the size and geometric complexity of the seal will be considered. This paper shows that the flows simulated with the help of a chamber model, using pressure-dependent flow coefficients and overflow factors, allow a good comparison in qualitative terms with the real, measured permeability curve for designing sealing systems for dry-running screw compressors.