如今，人們開始更加注意環境中懸浮微粒(Particulate Matter, PM)的數量。懸浮微粒對人體的健康風險已被許多研究所證實，因此去除懸浮微粒的技術成為許多研究的目標。靜電集塵器（Electrostatic Precipitator, ESP）是其中一種高效率微粒收集系統。環境中的懸浮微粒是由各種懸浮於空氣中的固體與液體微粒所組成，每一種微粒在靜電集塵器內的表現都不一樣。在本研究中建構了一個二階(two-stage)靜電集塵器，並以微粒影像測速(Particle Image Velocimetry, PIV)技術來研究不同充電微粒之運動軌跡，以比較出靜電集塵器收集不同微粒時之表現。本研究分別使用四種不同的微粒:氧化鋁（Al2O3）、油滴、氯化鈉（NaCl）以及氧化鈦（TiO2）進行研究。實驗中主流速度變化範圍自2.36 m/s~4.18 m/s、冠狀電極電壓變化範圍自8kV~12kV，收集電極則固定為16kV。本研究亦以觀察不同平面之流場來研究ESP流道內三維流動之型態。研究結果顯示在主流速度為2.36 m/s的情形下施予電壓從8kV增加至12kV，Al2O3微粒、油滴微粒、NaCl微粒、TiO2微粒之y分量速度各別增加50.6%、76.0%、33.5% 以及51.9%；同樣施加電壓從8kV至12kV，當主流流速為4.18 m/s 時，Al2O3微粒、油滴微粒、NaCl微粒、TiO2微粒之v分量各別增加 52.7%、59.2%、59.4%以及65.9%。PIV結果顯示油滴微粒的實驗結果有較慢的y分量速度，應為油滴微粒較低的阿基米德數(Archimedes number,3.12E-06)以及較大的遷移係數(mobility number>3)所造成。在低主流速度與低電壓的情況下，TiO2與其他微粒相比有較慢的y分量速度，而在高主流速度與高電壓下，能獲得與其他微粒差不多的y分量速度。流場中央平面之PIV結果顯示y分量速度從-2.6 m/s至-0.5 m/s；相反地，近壁端觀測面之y分量速度僅有-1.0 m/s至多1.0 m/s。此觀察結果與電場強度數值模擬之分布結果相符。電場模擬之結果顯示測試區的中段以及近壁區域之電場強度分布不同。實際流場中只有一半的籠形電場分佈仍可被觀察到，後半部則被主流流場影像移動至更下游之區域。根據實驗結果，油滴微粒適合用來當作PIV的循跡微粒。這是因為油滴微粒的移動參數大於3，代表微粒移動受流動影響大於電場影響，更容易跟隨流場因此較適合用於流場可視化用途。

Nowadays people have been paying more attention to the amount of particulate matter (PM) in the environment. The corresponding health risks of PM on the human body has been confirmed in many studies. Therefore, the technology of removing suspended particles has become the research goal of many researchers. Electrostatic precipitator (ESP) is one of the high-efficiency particle collection technologies. All solid and liquid particles suspended in air are considered PM, and the collection performances of ESP varies for different kinds of particle. In this study, A two-stage ESP is built and the charged particle trajectories are investigated by particle image velocimetry (PIV) to investigate the collection performances of different particles by ESP. Four different seeding particles, aluminum oxide (Al2O3) particle, oil droplet particle, sodium chloride (NaCl) particle, and titanium dioxide (TiO2) particle, are tested in the current study. The velocity of primary flows vary from 2.36 m/s to 4.18 m/s. The corona electrode voltages varies from positive polarity 8 kV to 12 kV, and the voltage of the collector electrode is fixed to 16 kV. The 3D flow patterns inside the channel were also visualized at different planes in this study. The results show that by increasing charge voltage from 8 kV to 12 kV at the 2.36 m/s primary flow velocity, the y-component velocity for Al2O3 particle, oil droplet particle, NaCl particle and TiO2 particle increased by 50.6%, 76.0%, 33.5% and 51.9%, respectively. Moreover, for the case of the 4.18 m/s primary flow, the y-component velocity for Al2O3 particle, oil droplet particle, NaCl particle and TiO2 particle increase by 52.7%, 59.2%, 59.4% and 65.9% after the voltages increase from 8 kV to 12 kV. PIV results for oil droplet particle shows slower y-component velocities of oil droplet particle, which can be caused by the lower Archimedes number of 3.12E-06 and the mobility number that is larger than 3. TiO2 particle has slower y-component velocity than the other particles at the cases of low primary flow velocity and low voltage. On the contrary, the cases with higher primary flow velocity and higher voltage have comparable y-component velocities with the other particles. The PIV results of the middle plane shows the y-component of velocity from -2.6 m/s to -0.5 m/s, in contrast to -1.0 m/s to 1.0 m/s from the near wall observation plane. These results are consistent to the simulation results of the electric field distribution, which shows unequal electric field strengths between the middle and near wall regions of the test section and only half of the cage shape distribution can be observed because primary flow influences the ionic wind to move to the downstream area. According to these results, the oil droplet is suitable as the tracer particle for PIV in ESP studies because its mobility number higher than 3. This means that the charged particle is driven by fluid flow rather than the electric field and is preferred for flow visualization purposes.

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