Monday 25 April 2011

Aeromechanic Response in High Performance Centrifugal Compressor Stage

Christopher Lusardi
Advisor: Dr. Tan
Impeller blades in centrifugal compressors are exposed to unsteady forces that can increase stress levels in the part, leading to premature structural failure. These unsteady forces may arise from different sources, a significant one of which is the unsteady pressure field from the impeller interaction with the downstream diffuser. The resulting time-varying loads can induce vibratory stresses in the blades that could be significantly higher than the steady-state stresses. There have been experimental/test/field observations of impeller blades breaking at trailing edge as well as leading edge that are traceable to unsteadiness associated with impeller-diffuser interactions. Furthermore, test data shows that not only does the unsteady impeller-diffuser interaction impact the impeller forced response characteristic but that it is also highly sensitive to impeller-diffuser gap variation; the situation with impeller blade leading edge exhibiting high response that is linked to impeller-diffuser interactions constitutes an upstream manifestation of a downstream stimulus. The overall goal is to characterize and identify the unsteady flow process in impeller-diffuser interaction on the observed impeller aeromechanic difficulty such as those described above.

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