本研究探討微型噴嘴之噴霧特性，並探討微噴霧受側吹氣流影響下噴霧流場粒子之分布。實驗在常溫常壓下進行，以水為工作流體，霧化壓力在5至11atm 之範圍內，三組微型噴嘴出口長寬比AR為2.0、5.0和10.0，孔口水力直徑ｄH分別為53.33μm、66.67μm、72.73μm，側吹氣流位於噴嘴出口下方Z＝10mm處，噴霧液滴粒徑和體積分布是以Insitec-RTSizer粒徑分析儀來量測。微型噴嘴流量在出口AR=2.0時，可控制至約0.003 g/sec-atm之流量範圍，適用於微流量控制器之應用。若出口AR=10,0，當噴射壓力由5atm提高至11atm時，動壓對全壓的比率由32.8 %增加至36.44 %，壓損對全壓的比率則是由67.2 %降至63.56 %，故知當霧化壓力提高，將增加工作流體有效動量之比率。在同一噴射壓力下，噴嘴出口於低長寬比時會有較大的壓力損失，例如在噴霧壓力為5atm時，出口AR=2.0的動壓對全壓的百分比僅為出口AR=10的36%。微型噴嘴之霧化SMD隨著噴射壓力增加，噴霧平均粒徑皆有變小的現象，而增加噴嘴出口長寬比時，在噴嘴出口中長和寬方向上的應變率不同，流體不穩定性增加，故有較好的霧化效果。在微型噴嘴出口AR=10下，霧化壓力為9atm，出口下游Z=10mm處，側吹氣流距軸心位置C=10mm處，沒有側吹時，小於100μm的小液滴佔噴霧流體積分布的5.19%，加上Vb ＝5m/s之側吹氣流後，小於100μm的小液滴體積剩下0.44%，此值比沒有側吹氣流時大幅減少91.52%，粒子體積分布標準差為124.17μm，僅較沒有側吹時小0.3%，顯示側吹氣流Vb=5m/s時，能在不影響噴霧流的情況下，可以有效減少較小液滴數目。在增大側吹速度至Vb＝20m/s下，其粒子間碰撞相對韋伯數大於20，粒子間碰撞以拉伸分離和反射分離產生小粒子之機會較大，因此小粒子體積分布增加。而雖有部分小粒子被吹離軸心位置，但噴霧流粒子碰撞又產生新的小液滴及較大液滴，使得大粒子體積分布增加，所以其噴霧粒子分布範圍變寬。在噴霧流徑向位置上，亦可以發現被側吹氣流吹離軸心而帶至較遠位置的小粒子。噴霧流在受側吹後，沿軸向往下游SMD有遞增的現象，此乃因小液滴因側吹相互追撞結合而減少，其值仍較無側吹時為大。增加噴嘴出口長寬比時，噴霧粒子的體積分布範圍增加，因此噴霧流在受到側吹後，粒子間碰撞產生拉伸分離或者反射分離的粒子二次霧化機率為提高，故此時噴霧在側吹下小粒子增多。噴霧流氣動力分析的結果顯示，噴霧流外圍粒子速度較慢，粒子碰撞間主要以碰撞結合成大粒子為主，而在噴霧流中心處，因其粒子速度較快，St遠大1，粒子受側吹氣流加速效應較小，粒子間碰撞主要以拉伸分離和反射分離產生小粒子為主。

This research is to investigate the atomization performance of micro-nozzle and the effects of side blow on the droplet distribution of a single stream spray from micro-nozzle. All experiments are performed under room temperature and atmosphere pressure. Working pressure is 5atm to 11atm. The orifice aspect ratios of the micro nozzles are 2.0 , 5.0 and 10.0 with hydraulic diameter 53.33μm、66.67μm and 72.73μm respectively. The side blow is located at Z=10mm below the nozzle exit. The particle size distribution of the spray is measured by INSITEC RT-Sizer particle analyzer. Results show that the mass flow rate as low as 0.003g/sec-atm is achieved with this micro nozzle with aspect ratio 1:2. Results show that better atomization performance is achieved as the orifice aspect ratio increases. It seems that the different strain rate in the length and width directions, enhances the instability of the fluid and hence its atomization performance. Using the nozzle with orifice AR=10.0, Pt=9atm, Z=10mm and side blow at C=10mm, the volume of the smaller droplets (<100μm) is 5.19% of the spray without side blow. When the side blow increases to Vb =5m/s, the volume of the smaller droplets (<100μm) reduces to 0.44% of the spray, a value which is only 8.48% of the case without side blow. However, the standard deviation of the particle distribution remains unchanged. When the side blow velocity further increases to Vb =20m/s, the relative Weber number (Weij) associated with the particle collision is higher than 20, hence the volume of the smaller droplets increases because more small droplets are produced through the mechanisms of stretching separation and reflexive separation. The smaller droplets can be found at the radial away from r=0 due to side blow. Hence the SMD of the spray with side blow tends to increase in the downstream as comparing to the case without side blow. The distribution of spray particles becomes wider as the orifice aspect ratio increases. The particle collisions are mainly related to stretching separation and reflexive separation process in the core region because the particle velocities are high enough and St >> 1. This in turn results in the production of small particles. However, the particle collisions are mainly related to the collision coalescence process in the outer region because of the lower particle velocity. Hence the bigger particles due to coalescence are measured.

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