Compressor Surge Frequencies Modeled by the Concept of Emptying and Filling Actions

Abstract

Surge frequencies in compressors can vary much in dependence of many factors, such as compressor conditions, such as sizes, speeds, number of stages, and flowpath geometries, relative compressor locations, etc. The present investigation shows the basic behaviors of surge frequencies in multi-stage axial flow compressors, governed by a small number of essential parameters, which are obtained by physical insight to the phenomena and examinations in a trial-and-error manner on a number of numerical-experimental data. One of the essential parameters is a flowpath-average reduced resonance frequency, implying the number of excitations by the resonance frequency on the fluid particle in passing through the flowpath. Another one is also a reduced frequency formulated by modelling the emptying and filling actions in surge. A generalized basic framework of surge frequencies against resonance frequencies has been constructed by applying the numerical-experimental data on a wide range of conditions of the compressors and the flowpaths in terms of both parameters. The framework thus prepared can be useful for practical purposes, such as for estimation of surge frequencies and surge degeneration (stall stagnation) boundaries, and also for understanding the effects of various related factors. It can provide a rule of thumb for estimation of surge frequency in the condition of sufficiently large values of the reduced resonance frequency parameter. It could serve also as a clue to further study on the details.