Influence des étanchéités sur le comportement vibratoire des compresseurs centrifuges

Sealing influence on the vibratory behaviour of centrifugal compressors

Thermodyn, Division de Framatome

Abstract

The multi-stage process centrifugal compressors are operated over their first lateral natural frequency, and their behaviour must be free of any subsynchronous frequency. The shaft end sealing devices tighten the flamable and sometimes toxic gas inside the casing: the internal seals limit the recirculations between stages. These devices are considered in the rotordynamic analyses, because they have a significant effect on the damping of the first natural mode, overall at high pressure levels (over 100 bar). Full load and full pressure tests are frequently carried out to check the vibratory behaviour of the most sensitive units. Several very useful models have been developped for ten years in order to characterize the gas seals; nevertheless, the development of more accurate models is yet necessary, which is made very difficult by the nature of the gaseous flows themselves.