Abstract
To enhance the adjusting action and performance of the inlet guide vane (IGV) of a centrifugal fan, this study has proposed a new definition for the prerotation coefficient, and suggested that the prerotation coefficient and the resistance coefficient be used as the main indexes for assessing the IGV performance. The flow fields upstream and downstream of the IGV have been measured with a five-hole probe. Experimental measurements of the flow at the inlet and the outlet of a plate vane IGV of the centrifugal fan have shown that: the IGV has little impact on the distribution of the flow upstream of the IGV; the flow downstream of the IGV is relatively uniform in the circumferential direction but very non-uniform in the radial direction; and the flow prerotation generated by the IGV is very small in the central region of the through-flow cross section behind the IGV. Both the resistance coefficient and the prerotation coefficient of the IGV increase with the increase of the IGV vane angle. The resistance coefficient increases more rapidly than the prerotation coefficient when the vane angle is >50°. Based on analysis of the experimental data, the IGV of the test fan is to improve its performance. The profile of the vane cross section is changed from the original single straightline to two straightline segments. The vane chord length at the inner radius of the IGV is increased to enhance the cascade solidity. It is deduced from the experiments of the improved IGV vane that compared with the original vane, the improved vane is able to reduce the resistance coefficient of the IGV in a wider flowrate-adjusting range and the increase in the cascade solidity can augment the prerotation coefficient with the resistance coefficient kept almost unchanged. By applying all the above measures to decrease the resistance coefficient and increase the prerotation coefficient, the adjustment curve of the test fan has been clearly improved. Compared with the original adjustment curve of the test fan obtained under the same operating conditions, the flowrate adjusting range is extended by ∼9 per cent and the flowrate region with energy-saving effects accounts for ∼71 per cent of the entire flowrate adjusting range. Corresponding to different flowrates in the energy-saving adjusting region, the energy-saving ratio of the fan reaches 1.1∼13.5 per cent.
Published Version
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