Design and development of MEMs rotary fans
Date of Issue2010
School of Mechanical and Aerospace Engineering
As miniaturization technologies improve, electronic devices are becoming smaller and, hence, smaller devices are needed for heat removal. Micro fans are very crucial in compact cooling technologies. Among them, axial fans have unique properties that make them very useful in different applications. Previous studies concentrate mainly on centrifugal micro turbomachines because micro fabrication limitations do not allow making efficient 3-D axial fans. In the present project, a mini-axial fan was designed and fabricated. A conventional fan design method was adopted to obtain the preliminary design. 2-D numerical modelling was carried out to modify the design. During the design procedure, fabrication limitations were considered. Hence, the modelled geometries were influenced by UV photolithography which is selected as the fabrication method in this project. Being a planar technique, only layer-bylayer 3-D devices can be produced using UV lithography. SU-8, because of its special properties, was selected as the photoresist. A comparison was made between modified and non-modified geometries. It was concluded that the obtained results did not violate the assumptions made. Nonetheless, some modifications are necessary to improve the fan efficiency. Some prototypes were fabricated and we succeeded in fabricating some fans with oblique walls using UV lithography. The relationship between the product quality and some of the parameters were determined. The fabricated fans where tested. The pressure generated by the fans was measured. The results show that the 2-D numerical analysis can predict the best angle of attack approximately according to lift/drag ratio criteria. The fabricated fans were tested and the results were compared to 2-D numerical analyses at the same angle of attack. It is concluded that the 2-D simulations and the lift/drag ratio criteria can give us an acceptable estimation of the best angle of attack. In general, the best angle of attack based on static pressure generation is 20°. The flow rates generated by the fans with the angle of attacks of 15° and 20° are almost the same.