A COMPARATIVE ANALYSIS OF SLIP FACTOR ON IMPELLERS OF CENTRIFUGAL BLOWER

摘要

The Slip phenomenon strongly influences the working conditions and performance of turbomachines. It is of interest to know accurately the parameters influencing the slip factor and its effect on the turbomachines. The present work incorporates an experimental analysis of the slip factor for different types of impellers. The main purpose is to provide an insight into the effect of different blade exit angle on the slip factor. Therefore, a single stage centrifugal blower with three types of impellers viz. backward curved, backward curved with radial tipped and forward curved was developed for experimentation. A total of 12 test locations, at an interval of 30°, were selected near the impeller outlet regions. The volute of the blower was kept the same for all types of impellers. To analyze a 3-dimensional flow near the impeller region, a five hole probe is used. Pressure measured by a 5-hole probe was recorded with the help of pressure transducers. Experimental results indicate that, the slip factor was not constant at a whole impeller width as well as the impeller outlet radial periphery. The value and nature of the curve for the slip factor was different at all angular positions, along the width of the impeller. This may be due to the effect of rotor-stator interaction. The effect of rotor-stator interaction increases as we move from the tongue to the exit of the volute. This affects the impeller outlet flow at different angular positions. From the experimental results, it was observed that, the impeller outlet blade angle also has a significant effect on the slip factor. For the present case the value of the slip factor was the highest with the backward curved impeller and the lowest with the forward curved impeller.