本研究探討氣助式多孔噴嘴之霧化特性，並探討旁通氣流與漩渦長度對霧化特性之影響。噴嘴孔數分為十二孔、十四孔及十六孔等三種，旁通氣流之位置分別離噴口L=5mm及L=9.6mm。漩渦長度分別為10mm、20mm及30mm等三種。多孔噴嘴之孔口直徑為0.4~0.8mm，採用漸縮式奇點結構設計，孔距為3.5~5.0mm。本實驗以Malvern RT-sizer粒徑分析儀量測噴霧粒徑。
　　研究結果顯示，多孔噴嘴之孔數為噴霧產生量之控制參數。在霧化氣體壓力6.0bar，水壓5.2bar條件下，噴嘴孔數為十二孔、十四孔及十六孔時，其噴霧產生量分別為34.80kg/hr、36.60kg/hr及43.20kg/hr，相當於每一孔之平均噴霧產生量為2.7kg/hr，而且其噴霧粒徑並未隨孔數增加有太大之變化，故知此型噴嘴具有控制噴霧產生量之優越機制。研究結果亦顯示，噴嘴若配置旁通氣流時，會促使氣液兩相在噴嘴內產生充分之混合現象，故在相同之霧化氣體流量下，其噴霧平均粒徑有顯著之改善，代表以旁通氣流輔助霧化，具有比主氣流更佳之效果。若漩渦長度由10mm增加至30mm時，其噴霧錐角由18度減少至8度，故知漩渦長度具有控制噴霧錐角之機制。此外，改變多孔噴頭之孔徑及孔距，亦具有控制噴霧粒徑及錐角，例如，當霧化氣體壓力為6.0bar時，若多孔噴頭未做改變時孔徑為Φ0.8mm時，十四孔噴霧所產生之噴霧平均粒徑為6.13μm，若孔徑為Φ0.4mm時，其噴霧平均粒徑進一步降低為4.15μm。多孔噴頭孔距之改變亦影響噴霧之特性，例如，當孔距為3.5mm時，十四孔之噴霧錐角為12度，若多孔噴頭孔距增加至5.0mm時，其噴霧錐角則增加為15度，故多孔噴頭亦可以改變孔徑及孔距來控制其噴霧之特性。

　The atomization performance of an air-assist atomizer with multiple orifices is investigated in this research program. There are 12 ,14 and 16 orifices at the nozzle outlet. The orifices of the nozzle are designed as the singularity configuration with 0.4~0.8 mm in diameter. The separation distances of the orifices were 3.5~5.0mm, respectively. The swirlers inside the atomizer have the length of 10mm , 20mm and 30mm. The atomizer was also designed with the bypass flow configuration. The inlet of the bypass flow located at 5mm and 9.6mm from the nozzle outlet. The particle size of the spray is measured by Malvern RT-sizer.
　Results show that the production rate of the spray can be adjusted by changing the number of the orifices because the liquid flow rate is proportional to the umber of orifices. For example, under test condition of (Pa, Pw)=(6.0, 5.2), the liquid flow rates are 34.80kg/hr, 36.60kg/hr and 43.20kg/hr when the numbers of orifices are 12 , 14 and 16, respectively. It turns out that the average liquid flow rate of each orifice is around 2.70kg/hr. What is more important is that the particle size of the sprays does not vary with the change in orifice number. Results also show that the atomizer with bypass flow configuration performed better. The mean particle size of the spray is reduced because of the enhanced mixing processes between the gas and liquid phases in the nozzle. Furthermore, the cone angle of the spray reduced from 18° to 8° when the length of the swirler was increased from 10mm to 30mm. The diameter of the orifice and the pitch between orifices also influence the particle size and cone angle of the spray. In a test of Pa=6.0, the cn14-nozzle produces spray of mean particle size of 6.13μm and 4.15μm as the orifices were designed with diameters of Φ0.4mm and Φ0.8mm, respectively. The cone angles of the spray changed from 12° to 15° when the pitch between the orifices changed from 3.5mm to 5.0mm. Hence the atomization performance of the multiple-orifice nozzle can be adjusted by changing the configuration of the orifices.

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