Development Of An Axial Flow Fan For High Performance And Low Noise

This thesis presents an enhanced method to investigate aerodynamic noise produced by rotating machinery,which it’s now an essential requirement and a critical design drive in order to comply with existing and future noise regulation.The fan is a component that converts the energy of the motor into the pressure of the fluid to make the fluid move.The high aerodynamic efficiency and low noise are one of the important technical specifications of fan design.Numerical models using computational fluid dynamic(CFD)to predict the leafs blower device noise were developed by using Solid Works software to design the geometries and Ansys Fluent software to achieve the aerodynamic & aeroacoustics performance produced by the axial fan.The noise emissions were obtained using Ffowcs Williams and Hawkings(FW-H)model towards an observation points in the far-field.The finite element model of the original axial flow fan was established,convergence results were achieved between the original axial fan model and experiment,showing that it is assured that the numerical model is valid and reliable.The original fan was optimized using different airfoil types parameter,where orthogonal optimization method was used to improve the aerodynamic performance.The influence of the guide vane structural on the aerodynamic performance was investigated and the results show a significant reduction on the flow rate when the guide vane was removed.Furthermore,nine models are evaluated and compared with experimental fan data to investigate the effectiveness of applying the treatment of serration trailing edge method,at different serration ratios and different rang of amplitude(h)and spanwise(λ)wavelength values.The results indicated that a large reverse flow vortex obtained in the original model compared to serrated models.Remarkably,the serration edges showed an efficient noise reduction achieved by models λ/h=0.25 and λ/h=1,which reduced the noise by 14 d B and 4.2 d B,respectively.Besides a noise reduction up to 11.4 d B was achieved using different values of λ and h at the same serration ratio.