Design optimization of wide-operating-range, high-efficiency turbine blade profiles for compressed air energy storage systems

Bypass flow control is an important approach to enhance the discharge-stage performance of compressed air energy storage (CAES) systems, and wide-operating-range, high-efficiency turbines are the key enabling components. This study proposes a multi-disciplinary, multi-condition, and multi-objective optimization design methodology for two dimensional blade profiles, and establishes an optimization platform for the high-pressure radial-inflow turbine of a representative CAES system. The leading-edge radius ratio, the maximum camber and its location, and the maximum thickness and its location are selected as design variables, the mass flow rate is imposed as a constraint, and the drag characteristics and transition locations at representative bypass-controlled operating points are adopted as optimization objectives. An archive-based multi-objective genetic algorithm is employed, enabling rapid screening and quantitative assessment of blade profiles. The results show that the total-to-total isentropic efficiency of the optimized turbine is improved across the entire operating range, increasing by 0.31% at the rated condition and by 0.96% at the minimum load. While the total pressure drop of the first-stage stator is significantly reduced and the total pressure loss coefficient decreases by 5.22% at the rated condition and by 51.21% at the minimum load. In addition, the flow structure in the mid-to-downstream suction-side region of the stator is effectively improved, resulting in the lower profile loss, weakened flow separation, and enhanced flow stability in the blade passages. These findings demonstrate the feasibility and effectiveness of the proposed optimization methodology.