本研究主要在探討液態金屬在內混式霧化方式下噴嘴出口長寬比較低時之霧化特性。內混式霧化器有別於外混式霧化器在於其霧化氣體能量可以在封閉的空間內有效地傳遞於待霧化之液態金屬，因此可以使用少一個數量級之霧化氣體得到更細小之噴霧。本研究所探討的噴嘴出口長寬比分別為1.0、1.5、2.0及3.0，噴嘴出口面積為6mm2及12mm2，同時探討噴嘴邊角效應對霧化特性之影響。實驗方法為將固態之鉛錫合金(錫63%，鉛37%)經由高溫熔解爐熔成液態金屬，接著透過液態金屬霧化器將液態金屬霧化成液滴並利用液態氮將其冷卻成金屬粉末，最再後利用INSITEC RT-sizer粒徑分析儀量測金屬粉末粒徑。實驗結果顯示，當噴嘴出口長寬比固定時，噴嘴出口面積較大之噴嘴因具有較高之氣液質量比，所以其噴霧特性皆優於出口面積較小者。當液態金屬噴射壓力從2.0X105N/m2增加至5.0X105N/m2時，噴嘴出口面積為6mm2及12mm2時之金屬粉末平均粒徑分別從53.85μm降至34.17μm以及從35.42μm降至23.98μm。當固定氣液壓差，增加液態金屬噴射壓力時，液態金屬流量隨之增加，但霧化氣體之流量則變化不大。當液態金屬噴射壓力從2.0X105N/m2增加到5.0X105N/m2時，金屬粉末平均粒徑皆可減小至0.25~0.46倍之範圍，並提高微細金屬粉末粒徑體積百分比V15-25的比例，至於較粗的金屬粉末粒徑體積百分比V25-45則無明改變。當液態金屬噴射壓力為4.0X105N/m2，氣液壓差從0.3X105N/m2增加到1.2X105N/m2時，金屬粉末平均粒徑隨液壓差之增加而減小至0.33~0.45倍之範圍，金屬粉末粒徑體積百分比V15-25、V25-45等亦隨之增加。研究結果亦顯示，當隨著液態金屬噴射壓力從2.0X105N/m2增加至5.0X105N/m2時，圓角及方角噴嘴之平均粒徑分別從26.30μm降至19.70μm以及從34.93μm降至28.00μm，故圓角噴嘴具有較佳之霧化特性。

This research program mainly investigates the characteristics of atomization of melt under lower aspect ratios of internal mixing atomizer. The aspect ratios of the atomizer are 1.0~3.0 with the cross section area of the orifice 6mm2 and 12mm2. The corner effect of the orifice on the atomization performances is also characterized. The eutectic metal (Sn63%, Pb37%) is firstly melted in the crucible. The melt is then introduced through atomizer and injected into the liquid nitrogen pool. Finally the particle size of the metal powders is measured with RT-sizer. Results show the atomizer with the larger cross section area has better atomization performance of its higher gas-to-melt ratio. The particle size with cross section area 6mm2 and 12mm2 decreases from 53.85μm to 34.17μm and 35.42μm to 23.98μm, respectively, as the melt pressure increases from 2.0X105 N/m2 to 5.0X105 N/m2. Keeping the pressure different between gas and melt, the mass flow rate of melt increases as the injection pressure of melt increases, while the mass flow rate of atomization gas remains constant. It results in a significant reduction of particle size. Hence the percentage of smaller particles V15-25 increases, but the percentage of larger particles V25-45 changes slightly as the injection pressure of the melt increases from 2.0X105 N/m2 to 5.0X105 N/m2. The pressure difference between gas and melt also controls the particles. When injection pressure of the melt remains at 4.0X105 N/m2, the particle size reduces to 33%~45%. The percentage of particles in V15-25 and V25-45 increase as well. Results also show that the particle size associated of round and square corner of the atomizer decreases from 26.30μm to 19.70μm and 34.93μm to 28.00μm, respectively, as the melt pressure increases from 2.0X105 N/m2 to 5.0X105 N/m2. Hence the atomizer with round corner has better performances than the square one.

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