| 摘要 |
ROTARY THROAT CUTOFF DEVICE AND METHOD FOR REDUCING CENTRIFUGAL FAN NOISE A rotary cutoff device for reducing noise generated by the impeller blading of rotating centrifugal fans. The rotary device includes a casing partially enclosing a rotor mounted near the centrifugal fan discharge opening. The rotor containing a plurality of resonator cavities consisting either of quarter wave length resonators or of Helmholtz type resonators, each cavity being oriented preferably transverse to the rotor axis and having a length/diameter ratio in the range of 8/1-16/1. The rotor can be rotatably adjustable relative to the fan impeller, or it can be driven by a motor at a surface speed 30-100% that of the fan impeller surface speed, so that the rotor resonator cavities act as either quarter wave length or Helmholtz resonators to absorb effectively the acoustic pulsations generated by the centrifugal fan blade pass frequency of the fan and its harmonics, and reduce substantially the noise generated by centrifugal fans.
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