RANS structural uncertainty quantification of transonic centrifugal compressors aerodynamics using eigenvalue perturbation

Faced with the challenges in aerodynamic performance prediction of transonic centrifugal compressors caused by RANS turbulence model structural uncertainty, this study focuses on the aerodynamic uncertainty quantification of centrifugal compressors based on the eigenspace perturbation framework and conducts a comparative analysis of uniform and non-uniform eigenvalue perturbation strategies. Taking the classic Krain centrifugal impeller as the research object, the influence of RANS turbulence model structural uncertainty is quantified via controlled perturbations. The results show non-uniform perturbation is significantly superior to uniform perturbation in prediction accuracy and operating condition adaptability, with its predicted pressure ratio and efficiency uncertainty intervals basically covering experimental data over the entire flow range and the maximum efficiency deviation within 2.5%. Under non-uniform perturbation, the 1C mode predicts an average 4.5% increase in total pressure ratio and a 24.9% entropy reduction in the tip region, reflecting lower flow losses and enhanced work capacity. In contrast, the 2Cmin mode predicts an average 2.8% decrease in total pressure ratio and a 2.4% higher entropy than the baseline, indicating higher expected flow losses and more conservative performance predictions. Flow field analysis reveals perturbations modulate local turbulent structures, notably affecting tip leakage flow and downstream regions, thus altering secondary flow development and flow loss spatial distribution patterns. Results of other perturbation modes fall between these two extremes, collectively forming an aerodynamic uncertainty envelope.