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The Design and Research of Bladeless Fan and Its Internal Mini-fan

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Tutor: WuDaZhuan
School: Zhejiang University
Course: Chemical Process Equipment
Keywords: bladeless fan,noise,non-uniform blade,numerical modeling,FW-H
CLC: TM925.11
Type: Master's thesis
Year:  2014
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Abstract:
Bladeless fan is composed of blowing ring and mini-fan which is internally installed in the bladeless fan, so bladeless fan is safer and more environmental. Now its problems are wind strength and noise. Firstly, bladeless fan lacks structural diversity, which its inner surface of ring commonly is expanding surface, and has little wind strength, so the design and research of new kind of inner surface have high instruction value for continued innovation. In the meantime, the highly running mini-fan is the big noise source, so designing a fan with low noise makes sense for noise reduction of bladeless fan.The paper proposed a new design method for bladeless fan with inner shrinking surface. Basing on this design concept, two kinds of bladeless fan were designed. The first kind of bladeless fan with small gap had been found to testify that inner shrinking surface can zoom in air volume well. The study of the influence of shrinking angle and inlet velocity circulation on the performance of bladeless fan provided the basis for bladeless fan and inner mini-fan¡¯design.In order to lower the noise, a matched two-stage fan, whose blades were distributed non-uniformly, was designed to replace the original high speed fan. The acoustic characteristics with different blade distribution were analyzed by the united RANS and FW-H method. The study found that non-uniform blade can lower the amplitude of pressure fluctuation and sound pressure level (SPL) of blade passing frequency (BPF) within certain limits, but will increases SPL with frequency under BPF beyond the limit. There is an optimal range in blade uniformity.The experimental study found that the new designed bladeless fan has a big improvement in performance and noise reduction. And compared the experiment and calculation result of the new bladeless fan and inner fan, the research method was proved right.In order to solve the steady jet flow problem of bladeless fan with big gap, grids were set in outlet of bladeless fan. Research showed that bladeless fan with small gap needs little grids. A further research about the influence of shrinking angle on fan¡¯s performance and wind direction found that a bigger or smaller angle will lead the wind direction deviating from axis. These results provided a reference for the design of bladeless fan with big gap.This paper provides the design methods of bladeless fan and inner mini-fan, and the structure of bladeless fan with shrinking inner face, specialized two-stage fan with un-uniform blade and bladeless fan with grids in air outlet with big gap, and shows the influence of the key parameter on performance and noise level. The designed bladeless fan reached the design goal, and the analytical results are of great significance for the further innovation and product development of bladeless fan.
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