Performance and Flow Condition of Contra-rotating Small-sized Axial Fan at Partial Flow Rate

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. Therefore, higher rotational speed design is conducted, although, it causes the deterioration of efficiency and the increase of noise. Then the adoption of contrarotating rotors for the small-sized axial fan is proposed for the improvement of performance. In the present paper, the performance curves of the contra-rotating small-sized axial fan with 100mm diameter are shown and the velocity distributions at a partial flow rate at the inlet and the outlet of each front and rear rotor are clarified with experimental results. Furthermore, the flow conditions between front and rear rotors of the contra-rotating small-sized axial fan are investigated by numerical analysis results and causes of the performance deterioration of the contra-rotating small-sized axial fan at the partial flow rate is discussed.

Unsteady flow condition of contra-rotating small-sized axial fan

“…Therefore, there is a strong demand to establish the design method for smallsized axial fans. The performance and the circumferential averaged flow conditions at the designed flow rate and the partial flow rate were clarified by the previous research [8,9]. In the present paper, the performance curves of the contra-rotating small-sized axial fan with 100mm diameter are compared with the unsteady numerical analysis results to verify the validity of the unsteady numerical analysis results.…”

Internal Flow Condition between Front and Rear Rotor of Contra-Rotating Small-Sized Axial Fan at Low Flow Rate

“…On the other hand, the internal flow condition of the contra-rotating axial flow fan at off-design flow rate point is not known well. Then, the internal flow condition at partial flow rate was investigated by a pitot-tube and numerical analysis, and it was clarified that the back flow associated with the tip leakage flow occurred at the inlet tip of both front and rear rotors [12]. It is difficult to measure the internal flow condition at low flow rate and there is no literature related to the internal flow condition of the contra-rotating small sized axial fan at low flow rate.…”

Numerical study on aerodynamic noise performances of axial spacing in a contra-rotating axial fan

“…With development of computer technologies and CFD technologies, the CFD method has already possessed high accuracy and manages to provide abundant flow field information. In turbomachinery researches, the numerical simulation method has been widely applied [7][8][9]. Mohammadi et al [10] performed CFD simulation of a CRF, wherein the hub-tip ratio was 0.598.…”