Tip Clearance Effects in Radial Flow Impeller Fans Under High Temperature Working Conditions

Three industrial-type centrifugal fans were designed, fabricated and tested in order to investigate the effects of axial (tip) clearance between an unshrouded impeller and stationary casing, so that the flow field behavior may differ considerable from that of a shrouded centrifugal fan impeller. Tests were conducted under high temperatures of gas up to 1000 °C at six different values of tip clearance each. Test results showed that the tip leakage flow due to the tip clearance is an unavoidable factor, which deteriorates the fan performance, and therefore the impeller geometry should be designed considering the tip clearance losses.