Pressure distribution analysis in a centrifugal compressor volute by CFD

This study aims to develop a Computational Fluid Dynamics (CFD) configuration for the analysis of pressure fluctuations within the volute of a centrifugal compressor. The initial phase of the CFD analysis involved the concurrent use of Ansys® CFX and TRACE, followed by exclusive employment of CFX for the final computations. The reference compressor utilized for this investigation is the Demag® KG3.32, and all comparative assessments were conducted based on measurements acquired in the laboratory of the University of Duisburg-Essen. The numerical model underwent development in three primary stages, commencing with the simplified geometry of the single-passage impeller and culminating in the full 360°domain encompassing the complete impeller and the volute. Initially, a comparative evaluation was performed between the performance characteristics of the CFD model and the experimental data. Discrepancies observed in this comparison were predominantly attributed to uncertainties stemming from the geometric representation within the CFD model. Subsequently, an unsteady time-resolved simulation was executed across the entire domain to detect pressure fluctuations occurring within the volute. Numerous monitoring points were strategically positioned within the volute to analyze the pressure distribution. Following this, analogous monitoring was conducted within the impeller to explore the interactions between the two components. The recorded pressure signals were subjected to analysis in both the time and frequency domains, and a comprehensive process of identifying predominant frequencies was undertaken. Successively, the frequency spectrum obtained was compared against experimental measurements obtained using an accelerometer positioned at the inlet section of the compressor. A concordance between CFD and experimental outcomes was observed within a specific region of the impeller characterized by pronounced flow instabilities. Lastly, an examination of the flow field was undertaken, with particular attention to the impeller domain, in order to elucidate a plausible physical interpretation for the observed pressure non-uniformities within the compressor.