| 摘要 |
A centrifugal fan comprises a casing 10 with an inlet 11 and an outlet 14, an impeller 13 and a plate 22 mounted adjacent a cut-off point between the outlet 14 and the casing 10. The plate 22 extends away from the outlet 14 in a direction opposite to a direction of rotation 16 of the impeller 13. The width of the plate 22 decreases as it extends away from the outlet 14 (see figure 4) such that, in use, noise generated by the release of a pressure wave, as a blade of the impeller 13 passes the outlet 14, is reduced. The plate 22 may be fixed in position or attached to a pivot 23 such that its position may be adjusted. Adjustment of the position of the plate 22 may be automatically controlled. |
