A Simplified Model for Stator Asymmetry Design Considering Low-Engine-Order Forced Response

The 2-segment even-split layout in various stator asymmetry layouts effectively mitigates the amplitude of the high-engine-order (HEO) forced response induced by the vane passing frequency (VPF). However, it may increase the level of the low-engine-order (LEO) forced response. A 2-segment non-even-split layout has been proposed in a previous study to reduce the amplitude of LEO aerodynamic excitation arising from the 2-segment even-split layout. This paper presents a full-annular unsteady forced response analysis of a single-stage turbine conducted using an in-house code to compare the aerodynamic excitations on the rotor blades across different 2-segment non-even-split layouts. The analysis reveals that an inappropriate circumferential angle assignment of the 2-segment non-even-split layout is ineffective in simultaneously suppressing the high amplitudes of both HEO and LEO aerodynamic excitations. Determining the optimal layout by calculating various circumferential angle assignments individually incurs significantly high computational costs. To address this issue, a fast and accurate simplified model for stator asymmetry is proposed in this study. The accuracy of the simplified model is validated by comparing its results with the suppression effects of aerodynamic excitation obtained from numerical simulations. The optimal stator asymmetry layout for a single-stage turbine is identified through this simplified model. The results indicate that the selected optimal layout can reduce VPF aerodynamic excitation of the symmetric layout by 45.14% and the 3-engine-order (3EO) aerodynamic excitation introduced by the 2-segment even-split layout by 43.56%, while the negative impact on the aerodynamic performance is significantly smaller than that of the 2-segment even-split layout. This study provides a robust theoretical foundation for enhancing the application of stator asymmetry in engineering, which demonstrates its practical engineering value.