02. Industrial Aerodynamics

In recent years, axial fans have been used under space constraints as electronic equipment has become smaller and denser inside machines. It has been reported that components that act as obstacles to fan intake and exhaust can affect fan performance. In a previous study, the effect on the perforance of an axial flow fan was investigated when a circular plate, simulating an obstruction, was placed downstream of the fan. The results showed that when the distance between the fan and the circular plate was brought closer to a certain distance, fan performance was improved compared to when the circular plate was not placed. However, it has been reported that although fan performance is improved, unstable flow due to swirling flow is generated downstream of the fan in the low flow rate region. An unstable flow is a flow in which an unstable cell consisting of a high pressure region and a low pressure region propagating in the circumferential direction is generated in the space created between the fan and the circular flat plate. In this study, as a method to suppress the unstable flow, we attempted to suppress the unstable flow while maintaining the performance improvement by changing the material of the circular plate downstream of the fan to a porous material. The effects of the distance from the fan to the porous material disk (distance between the disks) and the porosity of the porous material on the suppression of unstable flow and fan performance were experimentally investigated. Specifically, performance curves were drawn and the pressure fluctuation characteristics of the circumferentially propagating unstable flow were measured as parameters of the distance between the disks and porosity. As a result, we succeeded in improving the fan performance and suppressing the unstable flow compared to the open condition without the disks.