| Small axial flow fan is the important equipment used in heat dissipation. Its ventilationaffects the performance and longevity of products. The noise affects people’s work environment.While the noise produces by fan is the main noise source in many devices. The contra-rotatingdual-rotor small axial flow fan is choosed as the reaserch object in this work. Its air volume andefficiency are better than that of the single rotor small axial flow fans. But its aerodynamic noiseperformance also increases too much. Therefore, to design a dual-rotor small axial flow fan withgood heat dissipation effect and low noise has a strong practical significance.In this paper, the contra-rotating dual-rotor small axial flow fan is selected as the prototypefan. The blades with perforations of dual-rotor small axial flow fans were designed and created.The influence of different stages perforations of blades, perforation diameters of blades andperforation number of blades on aerodynamic performance of the fans are studied by numericalsimulation. Then their static characteristics, the internal flow field and aerodynamic noiseperformance are analyzed. Aslo the interrelation among the static characteristics, the internalflow field and aerodynamic noise performance are studied. Meanwhile, the orthogonaloptimization design of three kinds of blade perforation parameters is developed. The totalpressure efficiency and noise are selected as the optimization objectives. The optimalperformance of fan with perforation blades is obtained. Then the numerical simulation, staticcharacteristics experimental test and aerodynamic noise experimental test are carried out. Themain work and conclusions of this paper are as follows:(1) Three different perforation blades of fans which are the pre-stage perforation, post-stageperforation and pre-stage and post-stage perforation are designed. And their static characteristics,the distribution of static pressure on blade surfaces and aerodynamic noise performance areanalyzed. The results show that: the blades with perforations can reduce the noise of fans. Buttheir static characteristics also decline. The influence of different stages perforations of blades onthe static characteristics and noise of fans are different. Moreover, the whole performance ofpre-stage perforation is the best.(2) Three different perforation blades of fans whose perforation apertures are0.5mm,1mmand1.5mm respectively are simulated. And their static characteristics, the internal flow field andaerodynamic noise performance are analyzed. The results show that: the apertures of blade withperforation should be appropriate. In addition, the apertures of perforations are too small would make the effect of noise reduction is not obvious; certainly, the apertures of perforations are toolarge would make the static characteristics decrease too much. So the whole performance of thefan is the best when the apertures of perforations are1mm.(3) Three different perforation blades of fans whose perforation numbers are4×3,4×4and4×5are simulated and analyzed. The results show that: in a certain range, the noise of the fansdecrease with the increase of the number of perforations. Combined with the staticcharacteristics and aerodynamic noise into account, the number of perforations of4×4perforatedfan is relatively good.(4) The perforation diameters of blades, the number of perforations and the inclined angleof perforations are choosed as the independent variables. The total pressure efficiency and noiseare selected as the dependent variables. The project of orthogonal optimization experiment iscarried out. The multi-objective optimization model is created. Entropy weight method is used tosolve the weight value of optimization goal. Then the range analysis is applied to obtain theoptimal performance of fan with perforation blades. Meanwhile, the experimental test of staticcharacteristics and noise of the prototype fan and optimal fan are advanced. The results showthat: the influence of blade perforation parameters on the performance of fans from big to smallin turn as follows: the perforation diameters, the number of perforations and the inclined angle ofperforations; the static characteristics of optimal fan is slightly worse than that of the prototypefan. And its noise drops by about2.2dB; the results of numerical simulation of staticcharacteristics are consistent with the experimental results. And the trends of them are same. Itindicates that the results of numerical simulation are reliability. While the noise experimental testproves that the blade with perforation can improve the aerodynamic noise performance of fans. |
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