Small size axial flow fans are used as a cooling component for computers,electronic equipment and other electronic components.With the increasing power of electrical equipment,the demand for lower noise and higher ventilation of cooling fan is also increasing.Traditional methods of improving ventilation by raising the fan's rotation speed causes a decrease in efficiency and an increase in noise.In this paper,different structures of fans were simulated,and as a result,the counter-rotating fan can achieve higher pressure,efficiency and facilitate ventilation in a smaller space.Furthermore,some other conclusions are as follows:(1) Higher pressure rise can be obtained by a counter-rotating fan than by the two-stage rotor fan in the same axial length.Meanwhile,the counter-rotating fan has a broader work scope.(2) The main noise type of the counter-rotating fan is rotating noise;the small peak pulse caused by vortex noise mainly due to the eddy current produced by small eddies.(3) When the distance of counter-rotating fans is smaller than 2 times the chord,the greater distance the greater total pressure of the circum-averages and along the axial direction,the total pressure begin to decline until the distance is three times the chord,so there is an optimal distance between rotors.The simulation results are of important significance to the quantitative analysis and optimization design of the counter-rotating fan.
Based on the gas-liquid two-phase mixture transportation test, the k-c-A; turbulence model was applied to simulate the two-phase turbulent flow in a vortex pump. By comparing the simulation and experiment results, inner flow features were revealed. The bubbles in the channel distribute mainly at the pressure side of the blades, and the aggregation degree of the bubbles is enhanced with an increase in inlet gas volume fraction. Experimental results indicate that the influence of the gas phase on vortex pump performance is small when the gas volume fraction is less than 10%. When the gas volume fraction contiuuously increases to 15%, the characteristic curves abruptly drop due to the gas blocking phenomenon.
Y.Li,Z.C.Zhu,W.Q.He,Y.P.Wang and B.L.Cui The Lab of Multi-phase Fluid Transmission Technology,Zhejiang Sci-Tech University,Hangzhou 310018,China
