This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/cphg.98.

During fluid mixing in stirred reactor, energy, which spreads among the fluid with the impeller, is used for fluid rotation and internal transfer. Meanwhile, a part of the energy is consumed by fluid mixing noise. The premises of effective mixing are to improve utilization rate of energy. The energy-saving and noise reduction behavior of rigid-flexible combination impeller in fluid mixing were studied by adopting the combination of numerical simulation and experimental analysis. Comparative experiments were carried out to study the noise variation between rigid-flexible combination impeller and rigid impeller at 210 rpm. The results showed that the energy was mainly concentrated at the tip of rigid impeller (the maximum speed of fluid was 2.85 m/s, while turbulent kinetic energy was 0.32 m 2 /s 2 ). Meanwhile, the energy at the tip of rigid-flexible combination impeller was thoroughly dissipated (the maximum speed of fluid was 2.31 m/s, while turbulent kinetic energy was 0.26 m 2 /s 2 ), which evenly distributed the energy at the flow field, thereby contributing to good mixing performance. The sound pressure level of the rigidflexible combination impeller was 7% lower than that of rigid impeller at the same location, whereas the measured value at the surface and the simulated values were identical.