| Small axial fans as the cooling equipment are widely used in many electric applications, which is important for the running condition of the electronic equipment. Small axial fans are selected as the research objects, and numerical simulation is applied in the paper in order to find out how the structural parameters affect static performance and noise and internal flow characteristics of the small axial fans such as shape, numbers, slant angle and diameter of the struts. The response surface method is designed with the static pressure and noise as the optimized target, the best small axial fan is obtained. The static characteristic experiment and the hotwire experiment are performed. The main contents and results are shown as follows:(1) Small axial fans are selected as the research objects. The fan models are built by the reverse engineering of the software UG. The measurement of the struts of the fans is performed. The struts are designed, and then the designed struts are assembled with the fan model. The simulation method is briefly present here.(2) The fan models with the square struts and the cylindrical struts are designed. Their static performance, noise and internal flow characteristics are analyzed by the numerical simulation. The research results turn out that: compared with the fan without struts, the struts downstream the fan have the evident blockage effect on the flow, leading to the decrease of the static pressure and efficiency of the fan. But the unsteady interaction between the struts and the blades makes the noise decreased. Compared with the fan with square struts, the air around the cylindrical struts can flow more smoothly, and the interaction between the cylindrical struts and the blades is lower, and the tip leakage flow is less, and the loss is decreased, and the static pressure and efficiency is increased.(3) The small axial fans with different numbers and different slant angles of the struts are design, and static performance and noise and internal flow characteristics are analyzed. The research results turn out that: the fan noise is lowest when the strut numbers and blade numbers is equal; the noise of the fan with slant struts is lower that of the fan with radical struts, and the fan with slant struts whose slant direction is reversed rotation direction and slant angle is 60 degree gets the best noise performance.(4) The number and the diameter and the slant angle are selected as optimized variables, and the static pressure and the noise are set as the optimized objects. Entropy method is adopted to determine the weight of the optimized objects. The response surface model is designed and the most optimized fan is obtained. Numerical simulation is applied to compare the static performances, noises and internal flow characteristics of the organized fan model and the optimized fan model. The static characteristic experiment and the hotwire experiment are performed. The research results turn out that: the optimized model gets the better static performances, noises and internal flow characteristics. The result of static characteristic experiment is in good coincidence with that of simulation, which demonstrates the accuracy of the numerical simulation. The velocity and turbulent intensity distributions are obtained through the hotwire experiment. |
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