Valveless piezoelectric micropump for fuel delivery in direct methanol fuel cell (DMFC) devices

Abstract

Presented in this dissertation is the study of a novel fuel delivery system combined with miniaturized direct methanol fuel cell (DMFC). The core component of this system is a valveless micropump driven by ring-type piezoelectric bending actuator. By applying an alternating electrical field across the actuator, the resultant reciprocating movement of the pump diaphragm can be converted into pumping effect. Nozzle/diffuser elements are used to direct the flow. To make the power system applicable for portable electronic devices, the micropump needs to meet some specific requirements: low power consumption but sufficient fuel flow rate. In this study, both theoretical and experimental methods have been used to investigate the effects of materials properties, actuator dimensions, driving voltage, driving frequency, nozzle/diffuser dimension, and other factors on the performance of the whole system. As a result, a viable design of micropump system for fuel delivery in DMFC devices has been achieved and some further improvements are suggested.In the beginning of this dissertation, the history, working principle, types, and current research status of both fuel cell and micropump are reviewed. Following this comprehensive introduction, the research objective to develop a novel portable power system that combines fuel cell technology and micropump technology is presented. To help design such a system, a series of analytical models are established to estimate the deflection, volume change, flow rate, and power iv consumption of the micropump. Both finite element method (FEM) and experimental method are applied to verify the models. Based on the analytical analysis, material properties and dimensions of the micropump actuator are optimized to obtain maximum flow rate and minimum power consumption. Later a separated micropump prototype has been fabricated and tested. It is observed that the performance of a DMFC device is improved by using this micropump to supply fuel. In addition, the electrochemical impedance analysis of this fuel cell device is conducted to try to understand the reasons for the performance improvement. Finally, the accomplishments of this study are summarized and future perspective is provided.v

Recent advances in microscale pumping technologies: a review and evaluation

“…Micropumps for this application are specifically required to have low energy consumption, while maintaining sufficient flow rates for fuel delivery (Zhang and Wang 2005). …”

Free Volume of PVA/SSA Proton Exchange Membrane Studied by Positron Annihilation Lifetime Spectroscopy

“…The simple physical structure of a fuel cell consists of three main parts: cathode, anode, and electrolyte. Direct methanol fuel cells (DMFCs), which use methanol as a fuel, are used in many portable devices [1]. The electrolyte, also referred to as proton exchange membrane (PEM), should be a polymer material with stringent requirements: the membrane should exhibit high ion exchange capacity, high proton conductivity, and low methanol crossover.…”

Analytical Deflection Model and Parametric Optimization of a Circular Diaphragm-type Piezoactuator

“…Maxwell 静电场电位移 D Z 不变的条件。 ZHANG 等 [10] 在文献 [9]模型基础上，分析恒定气体压力对压电驱 动器位移的影响。相比电压引起位移量，1 kPa 压力 引起的位移量和容积变化量较小。RIHAN [11] 对该模 型进行模拟和试验，发现理论结果与试验结果趋势 相一致，并分析腔体内压升和流量随压电振膜横向 位移变化关系。HUANG 等 [12] 将压电层内各方向弯 矩等效转化为径向剪力 Q r ，分析压电层横向位移以 及压电层等效刚度和压电层振动频率； KHORSHIDI 等 [13] 给出双层压电附合圆形平板各层力矩的表示 法，并分析不同阶频率下的压电位移响应。但压电 内场强为正弦函数，并不满足电位移为常量。文献…”