| 摘要 |
<p>Disclosed is a centrifugal fan equipped with a fan casing of a scroll structure, wherein noise characteristics are improved more reliably by reducing re-inflow of a backflow from the end of a vane of an impeller, the end being opened to the main shroud side of the vane, to the inner surface side of the vane while maintaining the control effect of a boundary layer by a backflow on the main shroud side. On the inside of a backplate of a fan casing, a recess opened to the main shroud side of a centrifugal impeller and surrounding the outer circumference of an annular member is provided. With this constitution, a part of a main flow leaks to the back side of the annular member as a backflow, and the backflow is subjected to deflection action from an inner circumferential wall surface forming a gap on the outer circumference of the annular member so as to flow along the profile of the outer surface of the annular member. Subsequently, the backflow produces a flow circulating around the annular member through synergistic action of Coanda effect and deflection action and since flow rate of the backflow is reduced by the recess, the backflow is controlled not to disturb the main flow by interfering with the same.</p> |
