| 摘要 |
A rotary bladed impeller (1) is disposed at the transition between an entrance passageway (3) to an enlarged diameter diffusion duct (11) surrounding the impeller (1). An annular structure (5) is arranged upstream of the blade tips and projecting inwardly of the duct (11) to define the entrance passageway to guide fluid flowing therethrough within the rotary path of the blade tips. The duct (11) and structure (5) partly define an annular space (7) extending past the blade tips within the duct (11) within which is formed a blade tip driven annular vortex (6) turning so as to diffuse the flow passing through the impeller (1). The annular structure (5) may on its upstream surface be formed to serve as an inlet duct to the impeller without the need for extended inlet ducting, and the diffuser duct may be of other than circular cross-section, and also may be of short length e.g. between 20 and 50 % of the swept diameter of the impeller. |
