Brahim ABED, CheikhLEROUX, Arthur2026-03-042024-07-2520242024-05-102024978844722745710.12795/9788447227457_142https://pepa.une.es/handle/123456789/70317Counter-rotating turbomachines offer more design and control options than conventional machines. While axial counter-rotating turbomachines have been widely studied, few studies have focused on centrifugal ones. This paper presents a detailed numerical study on the benefits of counter-rotating impellers for centrifugal compressors, specifically the impact of speed ratio on performance gain. The study used 0D/1D models and optimization methods to meet design criteria. The aerodynamic performance of the new designs was compared to a baseline configuration consisting of a centrifugal impeller and a vaned wedge diffuser. The new design features a first impeller with perfect axial inlet and mixed flow or a purely radial blade at the impeller exit, and a parametrically designed counterrotating bladed diffuser with radial or mixed flow inlet and radial outlet. Optimized solutions were determined using validated 0D/1D loss models and analyzed using a 3D CFD solver. The results show that this new configuration can increase efficiency on a wide range compared to the baseline using speed ratio modulation.Libro digitalpp. 761-771Creative Commons Attribution 4.0 International (CC BY 4.0)Creative Commons Attribution 4.0 International (CC BY 4.0)http://creativecommons.org/licenses/by/4.0/openAccess