Characterization of 0.5 MHz Silicon-Based Ultrasonic Nozzles Using Multiple Fourier Horns
- PDF / 175,412 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 217 Views
A3.5.1
Characterization of 0.5 MHz Silicon-Based Ultrasonic Nozzles Using Multiple Fourier Horns Shirley C. Tsai1, Yu L. Song2, Yuan F. Chou3, Terry K. Tseng, W.J. Chen, J.H. Yang4, J.W. Chen2 and Chen S. Tsai5 Center for Applied Science and Eng. Research, Academia Sinica, Taipei, Taiwan 1 Dept. of Chemical Engineering, California State Univ., Long Beach, CA, USA 2 Dept of Physics, National Taiwan University, Taipei, Taiwan 3 Dept of Mechanical Engineering, National Taiwan University, Taipei, Taiwan 4 Dept of Mechanical Engineering, Chang Gung University, Taipei, Taiwan 5 Dept. of Electrical Eng. and Computer Science, Univ. of California, Irvine, CA, USA ABSTARCT This paper presents the experimental results of impedance analysis and longitudinal vibration measurement of micro-fabricated 0.5 MHz silicon-based ultrasonic nozzles. Each nozzle is made of a piezoelectric drive section and a silicon-resonator consisting of multiple Fourier horns each with half wavelength design and twice amplitude magnification. The experimental results verified the simulation prediction of one pure longitudinal vibration mode at the resonant frequency in excellent agreement with the design value. Furthermore, at the resonant frequency, the measured longitudinal vibration amplitude gain at the nozzle tip increases as the number of Fourier horns (n) increases in good agreement with the theoretical value of 2n. Using this design, very high vibration amplitude at the nozzle tip can be achieved with no reduction in the tip cross sectional area. Therefore, the required electric drive power should be drastically reduced, decreasing the likelihood of transducer failure in ultrasonic atomization. INTRODUCTION Silicon-based ultrasonic nozzles, previously fabricated at 72kHz [1], have a number of advantages over conventional metal-based bulk-type ultrasonic nozzles. Silicon possesses a relatively large electro-mechanical coupling coefficient, a high acoustic velocity, and a high potential for mass production of any resonator profile by MEMS-based fabrication technology. These advantages enable Si-based ultrasonic nozzles to overcome the 120 kHz frequency limitation of metal-based bulk-type ultrasonic nozzles [2]. Together with ultrasound-modulated twin-fluid (UMTF) atomization (spray) technique [3] that utilizes air to assist ultrasonic atomization, further advantages can be realized. For example, UMTF atomization has been demonstrated to produce much smaller and more uniform drops than the conventional ultrasonic atomization at the same fundamental frequency [3,4]. In fact, the peak drop diameter (the diameter where the peak of a drop-size distribution occurs) obtained by UMTF atomization was found equal to the wavelength of the capillary waves generated by the third harmonic frequency [3,4]. In other words, an UMTF atomizer operating at 0.8 MHz fundamental should produce uniform drops the same size as those produced by a conventional ultrasonic nozzle at 2.5 MHz. An ultrasonic nebulizer is made of a transducer disk, commercially available at fre
Data Loading...
