| 摘要 |
<p>The duct 3, comprises an outer annular element 10 which extends in the vicinity of the periphery of the blades 5 of the impeller, at least one inner annular element 11 coaxial with the outer annular element 10 and with the impeller, and a plurality of interconnection elements 13 which extend, spaced apart angularly, between the inner and outer annular elements 11, 10; the interconnection elements 13 are shaped in a manner such that they can deflect the flow towards the axial direction, reducing the tangential component of the velocity of the air-flow between the annular elements 10, 11 when the impeller is in operation. The impeller blades may be curved forwardly and the interconnection elements may be curved rearwardly relative to the direction of rotation of the impeller. The interconnection elements may have a constant set angle or a radially outwardly decreasing angle of inclination (fig. 4).</p> |
