Performance improvement of transonic centrifugal compressors by optimization of complex three-dimensional features

Abstract

Transonic centrifugal compressors with high efficiency and wide stable flow range are required in modern gas turbine engines. Blade design with complex three-dimensional features is one of the promising methods to further improve the performance of such cases. Aiming to increase the efficiency while maintaining similar level of the stable flow range, this article investigates aerodynamic potentials of complex three-dimensional features in a transonic centrifugal compressor by multi-point and multi-objective optimizations, in which the camber curves, the sweep feature, and the lean feature have been optimized. During the first round of optimizations, the aforementioned three groups of variables are optimized individually, and their sensitivities to the performance have been analyzed. When optimizing the camber curves, the best result shows an end-bend feature at the front of the hub section, and the efficiency is improved by 1.0% due to the lowered shock strength. When optimizing the sweep feature, the best result presents an S-shape leading edge and a forward sweep feature. The efficiency is increased by 0.5% because of the reduced wake region. The optimized lean feature only improves the efficiency by 0.2%, which shows its relatively low potential. The final round of optimizations couples both the camber curves and the sweep feature, and the best geometry combines both the end-bend and S-shape leading edge patterns. The peak efficiency and the choke mass flow rate have been increased by 2.2% and 8.1%, respectively, which is owing to the combination of the lowered shock strength by optimized camber curves and the reduced wake region by optimized sweep feature. The result indicates significant potential of complex three-dimensional features to improve the performance of transonic centrifugal compressors.