Objective To address the challenge of suppressing low-frequency longitudinal vibration in rotating mechanical equipment and explore a vibration reduction technology with simple structure, no external energy supply and excellent broadband adaptability, this study applied a particle-fluid composite damper to the longitudinal vibration suppression of rotating mechanical equipment.

Methods A dedicated test device for damper performance was constructed to simulate the coupled working conditions of rotation and longitudinal vibration. Comparative tests were conducted to investigate the differences in vibration reduction performance among particle damping, fluid damping and particle-fluid composite damping. The control variable method was adopted to systematically examine the effects of key parameters including particle size, mass filling ratio, shaft speed, excitation frequency, particle/fluid mass ratio, fluid viscosity, cavity axial length and excitation amplitude on the vibration reduction ratio of the composite damper. Moreover, the synergistic vibration suppression mechanism was analyzed from the perspectives of particle dynamics and fluid mechanics.

Results The composite damper exhibited significant vibration reduction effects near the main excitation frequency in the low-frequency forced vibration range of 3 −10 Hz, with a vibration reduction ratio of 8% −20%, which was markedly superior to that of single particle or fluid damping. Fluid viscosity, rotational speed and mass filling ratio had a significant impact on the vibration reduction ratio, while the influence of excitation amplitude was relatively minor. The optimal vibration reduction effect was achieved under the configuration of particle/fluid mass ratio of 3∶1, small particle size, low-viscosity fluid, high mass filling ratio and appropriate cavity axial length.

Conclusions The vibration reduction performance of particle-fluid composite damping is better than that of single damping forms, and it has excellent broadband adaptability in the low-frequency range of 3 −10 Hz. Its performance is significantly regulated by parameters such as fluid viscosity, rotational speed and mass filling ratio. This technology provides new insights into the vibration control of rotating mechanical equipment, and the optimized configuration scheme with particle-dominated filling strategy shows promising engineering application prospects in marine engineering and other related fields. Meanwhile, it is necessary to solve the engineering challenges such as dynamic sealing and dynamic balance for its practical application.