Integrated Study on Aerodynamic and Acoustic Characteristics of the Vaneaxial Fan

• Main Authors: Wen-Chi - Yen, 嚴文祺
• Other Authors: Lin, Sheam-Chyun
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/4q76qq

碩士 === 國立臺灣科技大學 === 機械工程系 === 105 === This research intends to enhance the performance of a vaneaxial fan under the limit of the motor specifications. With the aids of numerical simulation and experimental test, a systematic design scheme is established by considering the concerns on both of aerodynamic and acoustic aspects. Based on customer’s requirement, the goal of aerodynamic performances for this axial fan, with a 60cm-in-diameter impeller and operating under 1,425 rpm, is set to be capable to deliver at least 11,500 CFM with air speeds above 11, 8, and 5 m/s at 5, 10, and 15 meters from its outlet, respectively. Besides the concerns on flow rate and air speed, this work also plans to improve the acoustic characteristics of fan by using Helmholtz resonator to reduce the noise, especially on the harmonic frequencies. At first, a commercial fan with the same size is selected as the reference fan for executing the flow optimization. Also, CFD codes Fluent is used to simulate and calculate numerically on this reference fan for providing information of flow field and to estimate torque needed under the limit of motor specification to be 11 N-m. Later, a comprehensive parametric study is performed over impeller, housing, guiding van, and motor tail body in sequence along the flow path. As a result of this optimization procedure, the appropriate design fan, which consists of a impeller with NACA airfoil blade and proper setting angle, a streamlined housing, a well-designed guide vane, and an effective Helmholtz resonator, is attained successfully to deliver a satisfactory aerodynamic performance at 11,682 CFM (a 34.7% increase) and a minor 1~1.5 dBA decrease on the overall acoustic output with a significant 28 dB reduction on its second harmonic frequency. For validating this performance improvement and the numerical model used here, the mockups of appropriate fan and Helmholtz resonator are manufactured and assembled for testing its air speed and acoustic performances for confirming the actual noise-reduction effect. It is found that a rough 35% increase on air velocity at all the measuring locations is observed. Also, the acoustic measurements indicate that a similar noise reduction trend is attained while the deviation between numerical and test results is near 5 dBA, which is reasonable and expected due to the ignorance of motor operating and structure-induced noises in CFD prediction. Consequently, the design and analysis tool established here offers a rigorous and systematic scheme for a complete set of vaneaxial fan.