Abstract
Three dimensional steady and unsteady velocity distributions in the axial flow fan were measured using a hot wire probe for various operational conditions, various rotational speeds and various measuring positions. For measuring the velocity distributions in the blade passage, a specially designed and manufactured hot wire traversing apparatus was used. Steady velocity distributions, turning angles, effects of incident to the cascade, flow leakage through the tip clearance and effects of the flow separation show the flow phenomena through the blade passages. Unsteady velocity distributions show time dependent procedures of the wake flowing through the moving blade passage. Considering these results of measurements, the effects of the upstream stationary blade and the effects of Reynolds number on the flow were considered.
Highlights
In the turbomachinery, there are stationary and moving blade rows making relative movements in the confined area
The moving and stationary blades are made of duralmin and machined by numerically controlled milling machine precisely. It can be operated in a wide range of rotational speeds from 300 to 3000rpm
The value of m is m-0.73 for Re3x 105 where Reynolds number is defined by Re- ut. lt/v and ut and It denote velocity and chord length at the blade tip
Summary
There are stationary and moving blade rows making relative movements in the confined area. The flows in these machinery are surrounded by the blade, casing and hub. Along these surfaces there arise boundary layers. If the operational conditions of these machinery are changed, the flow angles are changed. The viscous wake arising from blade upstream flows in the downstream blade row passages. If the rotational speeds are changed for the same operational conditions, effects of the Reynolds number accompany a change in flow phenomena. Secondary flows accompanying with the change of operational conditions and Reynolds number are shown. Unsteady behaviour arising from the upstream wake are traced and discussed
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