16 April 2016 An ultrasonic horn atomizer with closed loop driving circuit
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Abstract
A novel ultrasonic horn atomizer is developed for the purpose of obtaining small size droplets at a large flow rate. The ultrasonic horn has a non-monotonically decreasing cross sectional area to provide a large atomizing surface. Consisting of two horns and one actuator section, the 301 kHz atomizer nozzle is made of {100} silicon wafer with its axis aligned in the <100> direction to minimize the length. Two PZT plates are adhered to each side of the actuator section to provide driving power. This device atomizes the liquid film on its nozzle tip to generate droplets. It is capable of atomizing more than 350 μl/min water into droplet. The mean diameter of droplet is 9.61 μm and the size distribution is quite narrow. The atomizing mechanism is based on the capillary wave on liquid surface. Once the wave amplitude exceeds the critical value, the motion of surface liquid becomes unstable and releases droplets. Therefore, driving at resonant frequency is the most effective way for atomizing. Dimension deviation combined with different kind of liquid to be atomized causes resonant frequencies of nozzles changed from time to time. Due to the high Q nature of nozzles, atomizing performance will drop drastically once the driving frequency is different from its resonant frequency by very little amount. Therefore, a feedback circuit is designed to tracking resonant frequency automatically instead of adjusting driving frequency manually. Comparing the atomizing performance between the open loop system and the closed loop system, significant improvement is obtained.
Conference Presentation
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Yuan-Fang Chou, Yuan-Fang Chou, Kai-Jhong Chen, Kai-Jhong Chen, Jui-Mei Hsu, Jui-Mei Hsu, Pei-En Chou, Pei-En Chou, "An ultrasonic horn atomizer with closed loop driving circuit", Proc. SPIE 9801, Industrial and Commercial Applications of Smart Structures Technologies 2016, 98010C (16 April 2016); doi: 10.1117/12.2219549; https://doi.org/10.1117/12.2219549
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