THE USE OF ACOUSTIC COMB FILTERS TO AVOID CENTRIFUGAL COMPRESSOR DISCHARGE BLADE-PASS PULSATION INDUCED PIPING VIBRATIONS

Abstract

Centrifugal compressor blade-pass interaction periodic pulsation can cause acoustic resonance conditions and pipe vibrations in the suction and discharge lines of the compressor. A series of two or more progressively placed quarter wave resonators, called a quarter wave comb filter, can be designed to attenuate these pulsations and eliminate the risk of acoustically induced pipe vibrations. Comb filters have been used and demonstrated for over 50 years for a wide range of acoustic attenuation applications and their physics is well understood. This paper discusses the practical design of such a comb filter, its installation in the downstream piping near the discharge of the compressor, basic comb filter design rules, a step-by-step design process for comb filters, and provides a basic case study which quantifies its attenuation effectiveness. A number of parametric studies for key design variables, such as the number of circumferentially located comb filters, stub diameters, and number of filter stages versus pulsation attenuation effectiveness, are also presented. Results showed that two to three-stage comb filters can be effectively used to eliminate centrifugal compressor blade-pass excitation induced pipe radial resonances and associated vibrations.