Impeller Failure in Centrifugal Compressor Caused by Acoustoelastic Resonance

Over the past five years, repeated failures of the 5th-stage impeller in the CO2 centrifugal compressor of an Integrally Geared Compressor system at Shiraz Petrochemical Company have been reported. These failures consistently exhibited identical fracture patterns, despite multiple investigations and hypotheses proposed by the rotary equipment department proving inconclusive. This study aimed to uncover the root cause of these recurring failures. Detailed analysis identified acoustoelastic resonance as the likely culprit, resulting from the interaction of closely aligned acoustic and structural natural frequencies with similar mode shapes. This interaction induced high-cycle fatigue, ultimately leading to impeller failure. To address the issue, design modifications were proposed, including scalloping and adjustments to the shroud's thickness profile. The redesigned impeller was subsequently analyzed to achieve a 25% separation margin between acoustic and structural natural frequencies, as recommended in the literature, to mitigate the risk of resonance.