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Investigation of the Flow Mechanism of Swept and Bowed Blades with Considera-tion of the Circumferential Fluctuation Source Term before Blade Leading Edge

  

  • Received:2022-05-05 Revised:2022-06-24 Online:2022-06-27 Published:2022-06-27

Abstract: Swept and bowed blades have been widely used in the transonic fan/compressor of aircraft engines to harmonize the conflicts between high loading, high through-flow, high efficiency, and acceptable stall/surge margin. However, these blades can also induce stress, vibration, and stability problems. Therefore, to better apply the advantages of swept blades to fans/compressors and reduce the complexity of their spatial structure, we need a deeper mechanis-tic understanding of swept and bowed aerodynamics. In this paper, the circumferential averaging method is used to derive a quantitatively describable circumferential fluctuation source term, which reveals that the circumferential fluctuation induces a re-equilibrium of the fan/compressor inlet flow field different from that of a straight blade and which in turn affects the design incidence angle of each base element of the swept blade and produces changes in the flow field and performance characteristics of the fan/compressor. This mechanism of the curved blade is verified by numerical simulation and SPIV experiments. The results show that the circumferential fluctuation source term in the curved blade can break the radial equilibrium of the original inlet field, leading to the radial migration of the inlet field, generating the spanwise differences of the key parameters of the inlet field, changing the spanwise distribution of the incidence angle, and thus affecting the overall flow field performance. Meanwhile, an analytical model and a machine learning model are constructed for the circumferential fluctuation source terms affecting the inlet flow field to release the traditional assumption of a uniform flow field of inlet air, to facilitate the aerodynamic design and anal-ysis of the 3D swept and bowed blade.

Key words: turbomachinery, fans/compressors, bow and sweep, quasi-3D method, circumferential fluctuation, incidence

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