Transient Thermal Analysis of Screw Compressors, Part Ⅱ Transient Thermal Analysis of a Screw Compressor to Determine Rotor-to-Housing Clearances

摘要

This paper is the second of a three part report on the transient thermal analysis of screw compressors. As noted in Part I, clearances between rotating and stationary parts of a screw compressor directly influence compressor performance and reliability. While tight clearances lead to higher performance, catastrophic failure can result if clearances are too tight and rotors contact the housing. The design goal is to select clearances tight enough for high performance but not so tight that "rotor rubs" occur and product reliability becomes an issue. The analytical tool described here gives insight into how the various clearances change during compressor operation. Armed with this knowledge, the designer can explore different concepts that ultimately lead to a more reliable, robust, and energy efficient compressor. In this part of the report, an analytical method is described that uses the calculated heat transfer coefficients and bulk temperatures from Part Ⅰ. After applying these thermal boundary conditions, transient metal temperatures are predicted throughout the compressor. Next, the predicted metal temperatures are compared to experiment. Finally, changes in rotor-to-housing clearances caused by thermal transients are quantified and discussed.