A 3D Time-Accurate CFD Simulation of the Flow Field Inside a Vaneless Diffuser During Rotating Stall Conditions

TitleA 3D Time-Accurate CFD Simulation of the Flow Field Inside a Vaneless Diffuser During Rotating Stall Conditions
Publication TypeConference Paper
Year of Publication2016
AuthorsMarconcini M, Bianchini A, Checcucci M, Ferrara G, Arnone A, Ferrari L, Biliotti D, Rubino D T
Conference NameASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition
Volume2D: Turbomachinery
PaginationV02DT42A029; 11 pages
Conference LocationSeoul, South Korea, June 13–17, 2016
ISBN Number978-0-7918-4972-9
Accession NumberWOS:000384850500029
Other NumbersScopus 2-s2.0-84991671502
KeywordsComputational fluid dynamics, rotating stall, Vaneless diffusers
An accurate characterization of rotating stall in terms of inception modality, flow structures, and stabilizing force is one of the key goals for high-pressure centrifugal compressors. The unbalanced pressure field that is generated within the diffuser can be in fact connected to a non-negligible aerodynamic force and then to the onset of detrimental sub-synchronous vibrations which can prevent the machine from operating beyond this limit.
An inner comprehension on how the induced flow pattern in these conditions affects the performance of the impeller and its mechanical stability can therefore lead to the development of a more effective regulation system able to mitigate the effects of the phenomenon and extend the left-side margin of the operating curve.
In the present study, a 3D-unsteady CFD approach was applied to the simulation of a radial stage model including the impeller, the vaneless diffuser and the return channel. Simulations were carried out with the TRAF code of the University of Florence. The tested rotor was an industrial impeller operating at high peripheral Mach number, for which unique experimental pressure measurements, including the spatial reconstruction of the pressure field at the diffuser inlet, were available. The comparison between experiments and simulations showed a good matching and corroborated the CFD capabilities in correctly describing also some of the complex unsteady phenomena taking place in proximity of the left margin of the operating curve.


Refereed DesignationRefereed