PIV量測技術之開發與應用：細水霧噴頭之粒徑分析

Abstract

在本研究中以噴灑壓力(10~50 Kg/cm2)，添加劑體積濃度(0%，3%，6%，10%)以及噴頭種類(Fp-25，Syu)三種不同之實驗參數，討論對SMD以及細水霧密度分佈造成之變動。透過使用PIV系統拍攝垂直噴頭下方1m處，水平距離離噴頭中心23cm，40 cm及52 cm等三個不同量測點所有的實驗照片，照片經由影像軟體後處理可得到細水霧粒子的直徑。 研究結果發現當噴灑壓力上昇時，細水霧的SMD值會隨之減少。當壓力從10 Kg/cm2上升至50 Kg/cm2，相對應的SMD差值甚至高達350μm。對不同種類的噴頭來說，在各測量點上的SMD分佈呈現出不同趨勢。對FP-25噴頭來說，特定噴灑壓力下SMD值會隨著測量位置逐漸向外而降低，而對徐博士設計的噴頭則是相反。因不同濃度的添加劑造成SMD分佈呈現W形狀的曲線，此一現象給予先前的論文中關於火焰撲滅時間的結果適當的解釋。研究結果發現對於含有添加劑的細水霧，其滅火效能主要取決於 SMD之值，其次則是添加劑的化學反應。當噴灑壓力增加時，儘管噴灑角度幾乎不變，距離噴頭下方一公尺的噴灑覆蓋範圍會縮減，且水霧密度增加。一旦噴灑範圍不足以覆蓋火焰整體，火焰將變的難以撲滅。

In this study, SMD and water mist density distribution were investigated with three parameters, discharge pressure (10~50 Kg/cm2), volumetric additive concentration (0%, 3%, 6%, 10%) and nozzle type (FP-25 and Syu). By using PIV, all experimental pictures were caught in three acquisition locations 1m under the nozzle and away from the center axis for 23 cm, 40cm and 52cm respectively. These pictures were processed by image post-processing software to calculate the diameters of water mist droplets. The study indicated that SMD decreased as discharged pressure increased. The difference between SMDs even reached 350μm when discharged pressure varied from 10 Kg/cm2 to Kg/cm2. For different nozzles, the SMD distributions in each acquisition location showed different trend. Under fixed discharged pressure with FP-25 nozzle, the SMDs decreased when the acquisition location is away from the central axis of the nozzle, and the trend of SMD variation was inverse for Syu’s nozzle. With different concentration of additive, the “W” shape curve for SMD variation gave explanations for the extinction time mentioned in the previous thesis. The result showed that the major factor for the performance of fire extinguishing was SMD and the minor one was chemical reaction by organic metal compound. When the discharged pressure increased, despite the spray angle from the nozzle was rarely changed, the spray coverage measured 1m under the nozzle shrunk gradually, and the water mist density increased. Once the coverage was not enough to cover the flame, the fire became hard to extinguish.