APPLICATION OF CASING TREATMENT TO AN INDUSTRIAL AXIAL-FLOW FAN

This paper deals with an experimental investigation into the influence of a vaned recess casing treatment on the performance of an industria l-type axial-flow fan with a hub-tip ratio of 0.4. The treatment has b een tested in a variety of configurations relative to the fan, with an emphasis on the amount of fan blade tip exposure to the treatment. Tw o sets of blading, one of which is of the fully reversible type, have been investigated. Detailed flow measurements have been carried out wi th a slanted hot wire probe to provide an insight into the operation o f the device and into the nature of the rotating stall in the solid ca sing configuration. Strain gauges have been employed to enable blade s tresses to be recorded and an in-duct microphone to enable comparative tests on fan noise has also been used.