Influence of number and thickness of blades on the performance of centrifugal fans

Abstract

The article deals with the research of the influence of the number of blades on the performance curve of small high-pressure centrifugal fans. The classical Euler equation for fans predicts that as the number of blades increases, the so-called loss due to inter-blade circulation will decrease. However, this is in direct contrast to experiments performed on a series of small fan wheels with backward curved blades, as the performance of the fans is only negligibly affected by the number of blades. The analysis performed in the article shows that the circulation between the blades does not cause a loss in terms of energy dissipation, but a change in the velocity diagram. A modified Euler equation is presented, which includes not only the effect of the number of blades, but also the effect of non-zero blade thickness. It is explained how the additional blades adversely affect the resulting fan characteristic. The resulting analytical model shows better agreement with the results of experiments and numerical calculations.