壓電風扇之流場分析研究

Experimental Investigation of the Flow Field of Piezoelectric Fans

張斯祈(HASH(0x1a8b7550))

指導教授 ： 許文震

國立清華大學/工學院/動力機械工程學系/碩士(2008年)

摘要

本論文以恆溫式熱線測速儀( hot-wire anemometer )量測壓電風扇的各點速度，發現在壓電風扇葉片尖端前1 mm處的平面各點風速，上下區塊和左右區塊皆為對稱的流場型態，故估計風量時，為了省時可只量測一個區塊，並以此區塊代替其他三個區塊。此外，研究中發現在開放空間中，水平擺放與垂直擺放的壓電風扇總風量相同。在尖端位移同樣為4 mm，而寬度不同時，寬度較大的風扇風量亦較大，並發現欲估計4 mm以下尖端位移的壓電風扇流量，只需估計葉片寬度內的流量，即可達90%的精確度。
此外，本論文亦探討了固定頻率下，壓電風扇的尖端位移分別與風量、RA、RQ、RU、R 　之間的關係。其中RA為葉片振動掃過的截面積與風量總影響面積之比，RQ為葉片振動掃過的截面積內之風量與總風量之比，RU為葉片尖端的最大瞬時風速與葉片尖端振動的速度之比，R 　則為葉片尖端的平均風速與葉片尖端振動的速度之比。研究中發現尖端位移越大其風量越大，且為正比的直線關係，而尖端位移越大，RA、RQ、RU、R 皆會衰退，其中又以RA、RQ的趨勢較為接近，而RU、R 的趨勢較為接近。

關鍵字

壓電風扇 ； 流場

並列摘要

In the present study, the wind velocity of piezoelectric fans is measured by using a hot-wire anemometer. The distance between the fan and the probe of the hot-wire anemometer is maintained at 1 mm for all measurements. It is found that the wind velocity of up and down or left and right areas are symmetrical. It is therefore convenient to just measure the velocity distribution of one area for simplicity. In addition, the fan is tested in both vertical and horizontal orientations. The flow rates are the same for both orientations. For the same tip displacement, a wider blade can generate the larger flow rate. When the tip displacement is below 4 mm, 90 percent of total flow rate can be evaluated by solely calculating the flow rate within the blade width. Moreover, the relationship between the tip displacement and flow rate, RA, RQ, RU, and R is studied. RA represents the sweep area of the blade relative to the total area subject to flow field influence. RQ represents flow rates in the sweep area of the blade relative to the total flow rate generation. RU represents the maximum wind velocity on the blade tip over the blade tip velocity. R represents the average wind velocity on the blade tip over the blade tip velocity. It is found that the flow rate is linearly proportional to the tip displacement. However, RA、RQ、RU and R decrease with the increase in the tip displacement. The trend of decline between RA and RQ is similar while that between RU and R is similar.

並列關鍵字

piezoelectric fan ； flow field

參考文獻

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