Performance and Internal Flow Measurement of Low Specific Speed Diagonal Flow Fan (Effect of Tip Clearance)

Abstract

In order to clarify the flow fields with the effect of tip clearance, the experimental investigations were carried out. The test fan is radial-outflow type diagonal flow fan similar to centrifugal fan and its specific-speed is 670 (min^-1, m³/min, m). The velocity fields at rotor outlet were measured using a single slanted hotwire probe. And, the pressures on outer casing wall were measured using a highly responded pressure transducer. With regard to the difference of tip clearance, the performance was not obviously different at high and low flowrate, but was much different near design flowrate. Near design flowrate, the tip leakage vortex was occurred. At high flowrate, the separation on blade pressure surface was occurred.