طراحي و ساخت ميكروپمپ پيزوالكتريك با بكارگيري ميكرووالوهاي تسلاي اصلاح شده

چكيده انگليسي :

Design and fabrication of a piezoelectrically actuated micropump using modified Tesla type microvalves Mohammad Ebrahim Kolahdouz me kolahdouz@me iut ac ir March 2010 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Professor Ebrahim Shirani Abstract Using No Moving Part NMP valves in microfluidic systems has been one of the most effective methods for transport and delivery of unidirectional flow Instead of external mechanism fluid flow behavior is responsible for the variation in pressure drop between forward and reverse flow in NMP valves Such microvalves have been widely used as check valves in the construction of diaphragm micropumps In this study two important types of NMP valves including nozzle diffuser microvalve and Tesla microvalve have been investigated and a new designed shape is proposed for the Tesla valve based on numerical analysis of fluid flow inside the valve The main criterion used for evaluation of valve performance was Diodicity which can be defined as the ratio of pressure loss in the reverse flow direction to loss in forward direction at identical volume flow rate Comparison with previous types proved the superiority and novelty of proposed valves Besides a three dimensional modeling of a diaphragm micropump together with the proposed valves was carried out Piezoelectric device was chosen as the actuator of the micropump Tri Electro mechanical fluid coupling effects have been taken into account on the interfaces and boundaries The simulation showed that the new system is more efficient than conventional nozzle diffuser micropump considering both maximum pressure head and flow rate In the next step the efficiency and performance of piezoelectrically actuated micropump was investigated based on driving voltage wave shapes Square shape excitation with the sharpest instantaneous slope had the most notable flow rate compared to the other types in the examined range of frequencies However the power requirement of sawtooth wave shape was much lower than square excitation The second approach used for design and analysis of the diaphragm micropump with piezoelectric actuation was equivalent circuit modeling This model predicts the frequency response of the complete system given the characteristic of the pump components and pump loads Regarding the complexity of the micropump system utilization of such straightforward method leads to quick and acceptably accurate responses In the proposed model the new designed valve was modeled by introduction of a nonlinear resistance to the circuit In this way one can easily model a diaphragm micropump no matter how complex the geometry of valves are As a practical application the possibility of using the proposed micropump for fuel delivery in a Direct Methanol Fuel Cell DMFC was also investigated both qualitatively and quantitatively Finally the numerical models were experimentally validated by real prototype fabrication of the new micropump There were a good agreement between three dimensional simulation and electrical modeling of the micropump The general trend was also the same for both numerics and experiment However some deviations were observed These deviations can be explained considering fabrication limitations and some simplification in computer modeling Key words Tesla microvalves Diodicity Micropump Multi Physics Equivalent circuit modeling Direct Methanol Fuel Cell

كلاهدوز، محمد ابراهيم

طراحي و ساخت ميكروپمپ پيزوالكتريك با بكارگيري ميكرووالوهاي تسلاي اصلاح شده

ميكرووالوتسلا , مدل چند فيزيكي , مدل سازي معادل الكتريكي , پيل سوختي با تزريق مستقيم متانول