Numerical investigation of the lean effects in centrifugal compressors

The continuous need of performance improvements in the centrifugal compressor technology for industrial and aeronautical applications, as well as the modern CAD techniques allow and ask for new impeller designs. In this paper a numerical analysis of opposite lean angles on the rotor blades is carried out. These methodologies are widely applied to axial turbomachines, but few papers in the open literature can be found on centrifugal compressors. Blade lean effects on the rotor outlet flow and the vaneless diffuser performances are discussed. Some of the blades have been tested for 3 tip clearances and 3 flow rates to get a deeper understanding of the involved phenomena. Results show a slight dependence of the rotor efficiency on rotor blade lean; notwithstanding, the local flow field at the rotor outlet presents different patterns that affect the flow evolution in the vaneless diffuser and its performances.