| Summary: | 碩士 === 元智大學 === 機械工程學系 === 93 === The aerodynamic noise accounted about ninety percent of the cooling fan noise for a typical electronic system such as those on the personal computers. Therefore, axial fans are designed with stators that could help increase the fan performance and also reduce the fan noise. However, different designs on the stator will influence both the noise level and fan’s performance. The study will then focus how various stator designs on the noise level of a cooling fan.
The characteristics of the axial fan depend on the types of fan blade, the ratio of the hub and the tip diameter, the blade pitch and the blade number. It is found that the noise level is also close related to those parameters. For the investigation, only one parameter is varied each time while keeping other parameters unchanged when testing the fan noise. The stators with different arc length and vane numbers are also tested so as to find the best fit arc length and vane number of the stator.
The noise test is done in a semi-anechoic chamber and suitable arc length and vane numbers of the stator are obtained experimentally. Other than reducing the noise, it is also expected that air-flow rate of the fan will not get worse. The fan is later tested with a wind tunnel following “Air Movement and Control Association 210-85” standard for the best combination of the lowest noise level and the maximum air-flow rate. The results show that the noise level is the lowest when both the leading edge and trailing edge of the stator are cut off for 8.5mm on the original fans tested. If compared with the original stator with nine vanes, the stator of five vanes have better flow rate. Finally, under the condition of integrating noise reduction and demanding the flow rate, it shows that for the proposed fan design, the noise level has dropped 3dB while the maximum flow rate increased 1.17CFM when comparing with those of the original fan. The method presented in the study is believed to be very helpful for the application of fan design.
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