Abstract
Unstable flow occurs at low flow rate in a centrifugal blower with radial blades and inducers. In order to clarify the cause of the unstable flow such as surge, the authors have visualized the behavior of separation ring formed on the shroud casing wall by means of the oil film technique. The obtained results are as follows; (1) Separation ring is located at the inlet of inducer before the inception of unstable flow, however, the separation ring can exist steadily without unstable flow. (2) Surge is induced by the flow separation due to the excessive deceleration rate of relative velocity in the inducer. (3) By increasing the tip clearance, surge is suppressed by the reduced deceleration rate due to the increased back-flow through the clearance.
