Rotor isolation for vibration and noise reduction

A technique for reducing the vibration and noise from marine propulsors is examined theoretically and demonstrated experimentally. A single layer of elastomer is incorporated into a rotor to form a rotating vibration isolation mount. The mount isolates the rotor hub and shaft from the unsteady forces generated on the blades due to their interaction with circumferentially non-uniform, time-averaged inflow and turbulence. This results in reduced vibration and noise. Nonrotating isolated rotor transmissibility is well predicted with a simple lumped parameter rotor model for frequencies below the first bending mode of the blades. Tests performed under operational (i.e., rotating) conditions have shown that rotor isolation provides a reduction of up to 15 dB in transmissibility compared to an identical rotor without isolation.