視覺法在液滴量測應用及修正因子

Visual of The Droplet Volume Measurement Applications And The Correction Factor

呂俊霖(Jun-Lin Lu)

指導教授 ： 蔡榮鋒

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2012年)

https://doi.org/10.6827/NFU.2012.00202

摘要

本論文，分析對焦（on focus, S）與失焦（off focus, S）之影像，探討失焦量（S），對液滴原始等效直徑（Dx）、液滴內部雷射亮點直徑（d1），原始液滴中心（CDx）至雷射亮點中心（Cd1）之距離（b），雷射亮點中心至液滴左側輪廓距離（L1）、與其至液滴右側輪廓距離（L2）等各幾何參數，發現：
1. 液滴原始等效直徑（Dx）、雷射亮點直徑（d1）、雷射亮點中心至液滴左側輪廓距離（L1）、與其至液滴右側輪廓距離（L2）隨失焦量增加而增加（失焦量增加50%，則其Dx約增加20.5%、d1約增加420%、L1約增加12%、L2約增加67%）；
2. 液滴中心與雷射亮點中心距離（b），不論Dx因失焦量增加而放大多少，（b）值幾乎不變（約增加±2%），顯示（b）值幾乎與失焦量（S）無關；
3. 兩中心之距離（b），可用於計算液滴之真實粒徑（D）【陳建方2011】。

因此，本論文定義液滴失焦度L1/ b之比值α，並探討失焦量（S）對失焦度α與液滴真實直徑（D）之可能影響。

實驗顯示：
(1) 失焦度α值隨失焦量（S）線性增加，每1mm，α值約放大1.7%；
(2) α值在正失焦量與負失焦量，相當對稱，幾無差異；
(3) 失焦量（S）=[(αn－α0)/ α0]/0.017。
本研究之單液滴實驗結果，顯示失焦量（S）可正確分辨液滴垂直降落，因空氣阻力所造成之飄移量（Ldn）= [(αn－α0)/ α0]/0.017及液滴之起始偏移量（S2）。
其中：αn是任意失焦液滴影像之L1n/ bn
α0是基準點±0mm之L1/ b，其值為2.46

本研究最後以商用噴霧器，進行實用性測試。結果顯示，本關係式對直徑大於200μm、失焦量（S）小於±10mm以內之液滴，可根據原始直徑（Dx）、兩中心距離（b）、亮點至左側距離（L1）、失焦度α等，正確計算液滴之真實直徑（D）及失焦量（S）。實務上，量測直徑200μm液滴之鏡頭，焦距很短，景深（depth of focus），通常小於±5mm。本發現在具有相當應用價值。

關鍵字

視覺量測 ； 粒徑 ； 液滴 ； 影像處理

並列摘要

The thesis analyze the on-focus and off-focus images to examine the influence of the gradations of off focus (S) on the original equivalent diameter (Dx), the diameter of the interior spot (d1), the distance (b) between the center of the droplet (CDx) and the center of the interior spot (Cd1), and the distance (L1) between the left edge of the droplet image and Cd1, and the distance (L2) between the right edge of the droplet image and Cd1. The most important findings are summarized as follows:

1. The original equivalent diameter (Dx), the spot diameter of (d1), the distances L1 and L2 increase with the the gradations of off focus (S) (ex. 50 % increases in S leading to increases of Dx, d1, L1, and L2 by 20.5%, 420%, 12% and 67%, respectively.
2. The distance (b) between CDx and Cd1 remains alomost constant (< ±2%) and seems to be independent of the increase of the gradations of off focus (S) up to 100 %.

The distance (b) was used to estimate the real droplet diameter (Chen 2011). The thesis, therefore, suggests the ratio α (L1/ b) as an index of off focus and examine the influence of the gradation of off focus (S) on the ratio α and the real droplet diameter (D).
The experimental results suggest :
(1) the gradation S linearly increases with the ratio α by 1.7% per mm, and is defined as
S =[(αn－α0)/ α0]/0.017.
(2) the ratio α is symmetrical in positive and negative values of the gradation S.

The experimental results confirm that the gradation S the drifting distance (Ldn) due to air drag, which is defined as
Ldn = [(αn－α0)/ α0]/0.017 and the initial droplet shift S2.
where：αn is L1n/ bn of an arbitrary image;
α0 (L1o/ b) is 2.46, the base value obtained at the on-focus positions.

The thesis finally carried out an series of experiments to test the practicability of above findings. The results confirm that the above relationships can correctly estimate real droplet diameter and the gradation of off focus (S) according to the original diameter (Dx), the distances b, L1 and the ratio α for droplet diameter larger than 200 μm, and gradation (S)less than ±10mm. As a result, the above findings are of practicability since a camera lens used to shot images of 200 μm droplets is usually associated with a short focal length with a narrow depth of focus less than ±5mm.

並列關鍵字

Visual measurement ； particle size ； droplet ； image processing

參考文獻

[3] 李正國，「奈米粉末幾何特性影像量測系統之建立」，國立虎尾科技大學，碩士論文，民國94年。

[5] AS. Ramadhas. S. Jayaraj. C. Muraleedharan. 2004. b.cllaracterizatioll and Effect of Using Rubber Seed Oil as Fuel in The Compression Ignition Engines.” Renewable Energy.

[7] Beyler C. L., “The interaction of fire and sprinklers” , Department of Fire Protection Engineering, University of Maryland, 1977.

[8] 夏維泰，賴婉容，「粒徑分析與病媒防治」，台灣昆蟲，第二十九卷第一期，民國98年。

[12] 陳建方，「影響視覺法量測液滴之可能參數」，國立虎尾科技大學，碩士論文，民國100年。