Multistage centrifugal compressor surge analysis: Part I - Experimental investigation

This paper reports an experimental investigation on centrifugal compressor surge. The compression system consists of a four-stage blower with vaned di ffusers and a large plenum discharging into the atmosphere through a thrott le valve. Measurements of unsteady pressure and flow rate in the plant, and of instantaneous velocity in the diffusers of the first and fourth compres sor stage, are performed during deep surge, at several valve settings and t hree different rotation speeds. Additional rests have been carried out on a different system configuration, i.e., without plenum, in order to obtain t he steady-state compressor characteristics and to collect reference data on stall in surge-free conditions. In this configuration, a fully developed r otating stall was detected in the compressor diffusers, while during surge it affects only a limited part of the surge cycle. The goal of the present experimental work was to get a deeper insight into unstable operating condi tions of multistage centrifugal compressors and to validate a theoretical m odel of the system instability to be used for the design of dynamic control systems.