Single Axial Fan Research Articles

Aerodynamic performances and efficiency of axial flow fan placed in cooling system

Abstract One way to reduce the aerodynamic noise generated by the cooling system of construction machinery is to improve the fan efficiency and then drive the cooling fan at a lower speed. Computational Fluid Dynamics (CFD) is effective for clarifying the mechanisms of the fan efficiency, but there are few reports that capture the flow field around the axial fan blades installed in the cooling system of construction machinery, that is, in a high static pressure environment. Moreover, from the viewpoint of the three-dimensional flow field, the fan efficiency has not been sufficiently studied. In this study, the flow field of the entire cooling system including an axial cooling fan was visualized by numerical simulation using ANSYS-CFX17.0, and the effect of the flow field formed around the blades on the fan efficiency was investigated. In case of a single axial fan, increase or decrease in pressure caused by airflow collision or separation is higher than the entire cooling system. As a result, the loss becomes large. In addition, the increase in loss due to collision or separation occurs regardless of the blade span length, and its magnitude is proportional to the circumferential velocity at each point of the blade except for the blade tip.

Axial Fan Performance under the Influence of a Uniform Ambient Flow Field

In their application to air-cooled condensers, axial fans are often subject to the detrimental influence of ambient flow fields at their inlet or outlet. While effects have been investigated mostly under perpendicular cross-flow conditions on fans operating as part of an array in their target design point, this study aims at examining the integral influence of uniform ambient flow fields on a single axial fan over a wide operating range. For this purpose, a wind tunnel fan test rig has been designed and assessed. Multiple angles between uniform ambient flow field and fan axis are examined in their integral influence on the characteristic curve of two distinct industrial axial fans with varying inlet modifications. Increasingly with the fan flow rate, perpendicular inlet cross-flow was found to always have a detrimental influence on fan performance. The straight bladed fan reacted less sensitively than the forward skewed fan, and the adverse cross-flow influence could be reduced with an inlet guard grille and with short conical shroud extensions. Cross-flow at the fan outlet showed potential static fan pressure increases at low flow rates.

J051033 二重反転形小型軸流ファンの羽根車内の非定常内部流動について

Small-sized axial fan is used as air cooler for electric equipments. But there is demand for higher power of fan according to the increase of quantity of heat from electric device. Therefore, higher rotational speed design is necessary but it causes the deterioration of efficiency and increases the noise. Contra-rotating axial fan is smaller than single axial fan under the same rotational speed, and is effective for lower rotational speed design under the same diameter. In addition, contra-rotating small-sized axial fan is higher efficiency compared with single small-sized axial fan. Then, the adoption of contra-rotating rotor for small-sized fan was proposed for the improvement of performance. In the present paper, the internal flow of contra-rotating small-sized axial fan with 100mm diameter obtained by the numerical analysis is shown. Furthermore, flow condition at inlet of rear rotor influenced by the wake of front rotor which is characteristic unsteady flow condition of contra-rotating rotors and flow condition at outlet of rear rotor is mentioned by the results.

J051033 形状変更が高出力空冷ファンの性能特性に及ぼす影響([J05102]流体機械の研究開発におけるEFD/CFD(3))

Data center has been built with spread of cloud computing. Further, electric power consumption of it is growing rapidly. High power cooling fans are used for servers in the data center and there is a strong demand to increase power of it because of increase of quantity of heat from the servers. Contra-rotating rotors have been adopted for some of the high power cooling fans.Contra-rotating axial fan is smaller than single axial fan under the same rotational speed, and is higher efficiency compared with single small-sized axial fan. It is important to clarify complicated internal flow condition and influence of a geometric shape of the cooling fans on performance and internal flow condition to achieve the high performance cooling fans. Numerical analysis of a cooling fan with 40mm square was conducted and influences of inlet of casing,tip clearance,maximum turning angle position and shape between front and rear rotors on performance were investigated experimentally in this research.

J051031 二重反転形小型軸流ファンにおける前後段翼列間が内部流れに及ぼす影響([J05102]流体機械の研究開発におけるEFD/CFD(3))

Small-sized axial fan is used as air cooler for electric equipments. But there is demand for higher power of fan according to the increase of quantity of heat from electric device. Therefore, higher rotational speed design is necessary but it causes the deterioration of efficiency and increases the noise. Contra-rotating axial fan is smaller than single axial fan under the same rotational speed, and is effective against lower rotational speed design under the same diameter. In addition, contra-rotating small-sized axial fan is higher efficiency compared with single small-sized axial fan. Then the adoption of contra-rotating rotor for small-sized fan was proposed for the improvement of performance. In the present paper, experiment was conducted to investigate the effect on performance by changing the axial distance between front and rear rotors of contra-rotating small-sized axial fan. And the relationship between the performance and axial distance between front and rear rotors was clarified with the experimental results.