Abstract
Axial flow fans used in air-cooled condensers are typically analysed with smooth rounded hubs as they offer superior performance when compared to other hub configurations. However, such a hub configuration is impractical and may increase the manufacturing and installation costs of air-cooled condensers. As such, it is desirable to use a simpler, yet effective, hub configuration in order to reduce the installation cost.
This paper assesses the impact that a simpler hub configuration may have on the performance of an axial flow fan. This is done through a comparison of three hub configurations: a cylindrical hub with a flat nose, a cylindrical hub with a hemispherical nose, and a disk hub, installed on the B2a-fan. Computational fluid dynamics modelling, utilising OpenFOAM, is used to simulate each hub configuration.
It is found that the impact on performance due to hub configuration is dependent on the volumetric flow rate through the fan. A thin disk hub exhibits superior performance at low flow rates, resulting in a 8.4% improvement in total-to-static pressure rise and a 5.7% point improvement in total-to-static efficiency. As volumetric flow rate increases, the effectiveness of the disk hub configuration reduces while the hemispherical and flat nosed cylindrical hub configurations result in similar performance metrics at the design point flow rate. At above design point flow rate, the flat nosed cylindrical hub configuration shows an improvement in performance over the hemispherical nose cylindrical hub configuration, with a 9.5% increase in total-to-static pressure rise and a 5.1% point improvement in total-to-static efficiency.
