Influence of inlet guide vane on the performance of axial fan for livestock and poultry farming

Higher capacity of negative pressure suction has been required in the traditional agricultural axial fan, particularly with the increase of filtration and deodorization devices in livestock and poultry farming. This study aims to improve the aerodynamic performance of agricultural axial fans, and then to expand their working range. A common type-550 axial fan was taken as the research object. The inlet guide vanes were added under the experiments and numerical simulations. The single factor and response surface analysis were selected to investigate the effects of guide vane installation angle (α), axial distance (L), and number of guide vane (n) on the fan performance and flow field. The influence of each factor on the performance of the fan was then obtained, according to the response surface analysis. The best combination of installation parameters was achieved for the better performance of the axial fan. A series of 3D-printed fan and tunnel experiments were carried out to verify the best combination of installation parameters of inlet guide vanes. Numerical simulation results showed the improved performance was represented by four perspectives after the addition of the inlet guide vane. Firstly, the inlet guide vane was adjusted to a suitable installation angle. After that, the meridian plane axial velocity increased significantly to black the leakage vortex extension to the inlet. As such, the static pressure efficiency was improved, due to the weak internal vortex, and the reduced flow loss. Secondly, the inlet guide vane was adjusted to a suitable installation distance. The fully pre-rotating was found in the inlet flow of the high span, leading to a more uniform flow in the axial flow fan. Thirdly, a suitable number of blades was set in the inlet guide vane. There was a decrease in the intensity of flow change in the inner channel of the axial flow fan, indicating a more stable flow field. Finally, there was an increase in the static pressure difference at the limit position of the blade pressure surface and suction surface, particularly with the higher working capacity of the fan blade. The better performance was achieved with an guide vane mounting angle of −25° to −15°, axial distance of 57 to 81mm, and a number of guide vane of 4 to 6. Specifically, the installation parameters were obtained with the guide vane mounting angle α=−21°, the axial distance L=57 mm, and the number of guide vane n=4. These optimal parameters were used for the installation of the 3D-printed inlet guide vane on the fan. Tunnel experiments showed that the ventilation volume and energy efficiency ratio of the modified fan were significantly improved after adding the inlet guide vane, where the ventilation volume increased from 5.7% to 10.39%, and the energy efficiency ratio increased from 6.62% to 10.89% in the fan performance test. Furthermore, the ventilation volume and energy efficiency ratio increased by 6.76% and 7.75%, respectively, under the working condition of 50 Pa. Consequently, the addition of inlet guide vanes can be expected to enhance the negative pressure suction capacity of agricultural axial flow fans.