During the tests in similitude conditions at low pressure and low load, a centrifugal compressor exhibited, at low flow rate, unusual very low frequency vibrations. An acoustic study of the piping system of the test loop was performed by TECHNICATOME/SMVI with the LACTUS software (a computer-aided design tool for noise-free and reliable piping networks). It was found that the acoustic resonances were in accordance with the vibration frequencies measured on the compressor, and that the levels of the vibration peaks were proportional to the acoustic transfer function amplitudes. The absence of vibrations during the full load tests confirmed the assumption of the acoustic coupling between the compressor and the piping system of the test loop whose acoustic resonance amplified the pressure pulsations and forced the low frequency vibration of the rotor.
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