Research On Pressure Loss Distribution Along Radial Direction In An Impeller For Axial Fan

Pressure loss plays a decisive role on impeller efficiency in axial fan design. The designers often just consider its change along axial direction while neglect its difference along radial direction, which is not favorable for designing high efficient and energy-saving fans. Many experiments have shown that the impeller losses are non-uniformly distributed in radial direction and that axial fans will have better performance and higher efficiency if we consider its radial direction distribution. So, this article mainly focuses on researching pressure loss distribution along radial direction in an impeller of axial fan.According to previous research, on the condition that neglecting the tip clearance loss on impeller efficiency, the impeller losses can be divided into three parts:the profile loss, secondary flow loss, and annulus wall friction loss. The three parts losses are calculated respectively in this paper. For the profile loss, equivalent diffusion ratio is used in calculation. Refer to the relationship curve between wake momentum loss thickness and the equivalent diffusion ratio of the cascades, their correlation is fitted by a new correlation, and then the correlation is used in profile loss equation. In the calculation of the secondary flow loss, the total pressure loss is calculated by a new foreign empirical formula firstly. Then according to the secondary loss distribution curve and the empirical formula of secondary flow vortex height in cascades, the universal secondary flow loss distribution in impeller is fitted by cubic polynomial. As to the annulus wall friction loss, after calculating the thickness of the outlet boundary layer of the cascades, boundary layer momentum loss thickness is used to calculate it. And then the annulus wall friction loss distribution is considered to obey exponential distribution according to predecessors’ experience. Finally, the three parts losses models are added together and a new impeller pressure loss model is found.At last, using existing axial fan’s geometric and aerodynamic parameters, the three kind of pressure losses distribution at the outlet of the impeller are calculated by this new loss model, and the total pressure loss coefficient curve along radial direction is drawn. It is compared with the predecessors’ experimental result, and they are perfectly in accordance with each other. The loss model is proved to be valid.