Numerical and Experimental Study of Bladeless Fan

• Main Authors: Ching Yu, 尤清
• Other Authors: Sheam-Chyun Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/296cs6

碩士 === 國立臺灣科技大學 === 機械工程系 === 102 === 　　Appliances are constantly studied and developed with innovative ideas with the intention to furnish a quiet and comfortable living space for people. Recently, the bladeless fan with a simple and modern shape is introduced and becoming popular in the residential fan market. There is no impeller existed in its appearance, so the possible damage caused by the rotating blades is eliminated completely. Besides, this novel design makes the structure simpler and easier to maintain. Obviously, the safety and quiet features are the major reasons for its popularity and acceptance by customers. However, the operating principle and flow characteristics of this bladeless fan are not well understood. Thus this research intends to investigate the physical mechanisms and identify the design parameters of this innovative fan in a systematic manner by a combined effort of numerical and experimental tools. 　　Initially, the Dyson bladeless fan is chosen to analyze its construction and performance measurement for serving as the reference fan. This bladeless fan can be divided into three parts which includes the fan stand, the inducing rim, and the inner fan. Among them the inner fan generates the main airstream to flow through the air path of inducing rim and is the major flow source. The inducing rim provides the appropriate flow passage to create a high-velocity jet for inducing more air stream at the rim exit. Thus, the sum of outlet stream of inner fan and the induced flow around the ring is the total flow rate for this bladeless fan. Clearly, the inner fan and the inducing rim are the key modified portions for enhancing its overall performance and become the investigated topic of this work. 　　At first, several parameters on the geometry of inducing ring, such as the cross-sectional shape, the inclined angle and clearance of air outlet, are studied systematically for enlarging the induced airflow from the rim. Next, an in-line (mixed-flow) fan is selected and designed for serving as the airflow generator (i.e., the inner fan). Note that this new inner fan is an optimized design via a comprehensive parametric analysis on the inlet diameter, the blade number, the twist angle, the central body, and the guide vane. Hence, an adequate design parameter setting of these inducing ring and inner fan is obtained after the aforementioned design procedure and formed the optimized bladeless fan set to yield an improved aerodynamic performance. 　　Furthermore, the prototype of optimized fan design is manufactured by the CNC technique to carry out the corresponding experimental performance verifications. To ensure a reliable outcome, bladeless fan’s performance and noise tests are executed in AMCA and semi-anechoic chambers by following AMCA-210-99, CNS-547 and CNS-8753 codes. Consequently, by comparing the experimental and numerical results, a remarkable agreement between these performance data is observed for verifying the reliability of numerical simulation. Besides, under the same rotating speed, the aerodynamic performance of optimum inner fan is superior to the reference fan by 50.3% and 8.9% enhancements on its maximum flow rate and static pressure, respectively. Also the total overall flow rate of the assembled bladeless fan is improved by a significant 25.4%. In summary, this study successfully establishes a reliable and systematic scheme to design the bladeless fan. Also, the corresponding performance influences caused by those important parameters are analyzed and summed up for serving as the design reference for the bladeless fan.