High-dimensional multi-objective aerodynamic optimization of a centrifugal air pump through improved impeller–diffuser matching via blade recambering and three-dimensional stacking

This work presents a surrogate-assisted multi-objective aerodynamic optimization of a centrifugal air pump through joint reshaping of the impeller blade and diffuser vane. A 22-dimensional design space is constructed using Bézier-based recambering, leading-edge lean, and independently varied hub and shroud stagger angles. The objective is to improve the stage pressure rise and efficiency while controlling the axial force through enhanced impeller–diffuser matching. Single-objective, bi-objective, and tri-objective optimizations are performed. The Pareto fronts reveal clear tradeoffs in that the total pressure rise and efficiency are positively correlated at moderate loading but become conflicting at high loading, and higher pressure rise is accompanied by increased axial force. The selected optimized model achieves simultaneous improvements in both the stage total pressure rise and efficiency relative to the baseline model, with the axial force coefficient remaining comparable to the baseline. Sobol sensitivity analysis identifies the diffuser vane camberline parameters as the dominant group for stage-level performance, the shroud stagger angle and hub blade camberline as co-dominant for the impeller work input, and reveals pervasive nonlinear cross-component coupling that provides statistical justification for the joint impeller–diffuser optimization strategy. SHapley Additive Explanations analysis corroborates these findings and further quantifies that the combined diffuser vane camberline contribution to stage efficiency exceeds 44%, while the axial force coefficient is governed nearly uniformly by all geometric groups. Analysis on the internal flow mechanisms demonstrates that the streamwise allocation of blade lean is the key for stage performance improvement. Negative lean near the impeller inlet enhances work input, while positive lean downstream suppresses low-energy fluid accumulation in the suction surface–shroud corner and weakens the jet–wake structure. In the diffuser, positive vane lean alleviates total pressure losses in the pressure-side–hub corner by establishing a favorable spanwise pressure gradient. These findings provide design guidelines for low-speed centrifugal turbomachinery aerodynamic optimization through coordinated blade stacking and recambering.