Abstract
Small-sized axial fans are used as air cooler for electric equipments. But there is a strong demand for higher power of fans according to the increase of quantity of heat from electric devices. Contra-rotating rotors were proposed for the improvement of the performance of small-sized axial fans and the advantages of it on the point of view of the performance were confirmed. On the other hand, the contra-rotating small-sized axial fan is operated at off design flow rates and the performance deteriorates at off design flow rates. Therefore, rotational speed control of each front and rear rotor is proposed for the improvement of the performance at off design flow rates in this research. In the present paper, the performance of the contra-rotating small-sized axial fan under the rotational speed control is shown and the internal flow conditions of each rotational speed control method are clarified by the numerical analysis results.
