Vibrations of Lobed Mixer of Aeroengines: Isogeometric Analysis and Experiment

A lobed mixer is the key component of aeroengines. Its complex curved surfaces can enhance the mixing efficiency between bypass and core flows and carry external forces in working environments. The vibration mechanism of the lobed mixer has not been revealed until now. This work aims to establish an efficient mechanical model of the lobed mixer and investigate its free vibration characteristics. To achieve this goal, a modified multipatch isogeometric analysis method of linear three-dimensional Kirchhoff–Love shells is proposed. Nonuniform rational B-splines are employed to describe the geometric configuration and displacement fields of the lobed mixer, allowing an efficient parametric analysis to be performed without remeshing. Penalty approaches are developed for coupling patch interfaces of arbitrary angles and establishing the mechanical model of bolt flange connections. A modal experiment is employed to verify the model’s validity, yielding a good agreement. Finally, the mode shapes and natural frequencies of the lobed mixer are investigated, taking into account the influences of the geometric parameters of the lobed mixer and bolted flange connections. Vibration mode interchange, natural frequency split, and natural frequency intersection phenomena are discovered. The obtained conclusions can guide the structural design of lobed mixers.