钛基μDMFC流场板极端润湿微结构及其气液分相效能研究
发布时间：2018-12-18 15:48
【摘要】：微型直接甲醇燃料电池(Micro Direct Methanol Fuel Cell)是一种具有广阔前景的电源,具有能量转换效率高、环境友好、室温工作、快速加燃料以及低噪声等显著优点。气液两相混流是影响μDMFC性能的关键因素之一,表现为阳极CO2气泡占据流场和阴极易发生水淹等阻塞反应物传输的问题。本文围绕这一重要问题,在钛基底上设计、制备了具有极端润湿(超亲水/超疏水)特性的微结构辅助通道以实现气液分流,研究了新型流场中气液分相输运特性及其对电池性能的影响。通过一步阳极氧化法在钛基底上产生微纳分级结构表面,获得了接触角为0°的超亲水特性的钛基板表面。研究了不同工艺参数对超亲水特性的影响,发现氧化电压越高,超亲水性越强；电解液温度对超亲水性的影响在不同电压区间有不同表现,氧化电压为20-40V时,钛表面的超亲水性随着电解液的温度升高而增强,但是这种趋势在60-80V的电压区间发生逆转。经氟硅烷修饰后,超亲水的氧化钛表面变成超疏水,结果表明,本实验获得的超疏水钛表面接触角、滚动角以及接触滞后角分别为160°、2°和1.7°。本文制备的极端润湿表面在酸性、中性、碱性水溶液以及大气环境下均具有良好的稳定性。分别设计了带超疏水排气微通道的新型阳极流场和带超亲水排液微通道的新型阴极流场,利用ANSYS软件计算了微通道的合理深度,结合流场开孔率等要素确定流场沟道宽度及其它结构参数。试验确定了具有极端润湿微结构的钛基流场板微细加工工艺流程,结合光刻与湿法蚀刻技术,通过阳极氧化法获得超亲水辅助沟道,再经氟化可得到超疏水排气通道。最后,通过二次光刻与湿法刻蚀工艺形成燃料或氧气进给的主通道,制备出新型流场板。设计制作包含亲水燃料沟道和超疏水气体通道嵌套排布的聚碳酸酯模拟流场板,以双氧水溶液的分解反应模拟气液两相流过程,流场压降测试结果表明,新流场中的平均压降比参比流场减小了37%,可视化观察表明辅助气体通道加速了气泡的释放。将具有超疏水通道的新型阳极流场组装成电池并研究其阳极流场气液输运特性,结果表明,在相同的电流密度下,压降特性与可视化观察的变化趋势与模拟流场实验吻合。再者,采用具有40和80μm深排气通道两种新阳极,其峰值功率密度分别比采用参考阳极流场的电池提高了33.3%和41.4%。新型阴极流场对μDMFC的影响测试发现,经长期放电后,普通点阵流场的最大功率密度减小幅度约是排液通道深度为80μm新阴极流场的2.3倍,说明新型阴极流场提高了μDMF C阴极的水管理能力。
[Abstract]:Micro direct methanol fuel cell (Micro Direct Methanol Fuel Cell) is a promising power supply with many advantages such as high energy conversion efficiency, environmental friendliness, room temperature operation, fast fueling and low noise. The gas-liquid two-phase mixing is one of the key factors affecting the performance of 渭 DMFC, which is characterized by the flow field occupied by anodic CO2 bubbles and the problems of blocking reactants such as water flooding. Around this important problem, microstructural auxiliary channels with extremely wetting (super hydrophilic / super hydrophobic) properties have been designed on titanium substrate to realize gas-liquid separation. The gas-liquid phase transport characteristics in a new flow field and their effects on the performance of the battery were studied. The surface of titanium substrate with super hydrophilic property with contact angle of 0 掳was obtained by one-step anodizing method. The influence of different process parameters on superhydrophilicity was studied. It was found that the higher the oxidation voltage, the stronger the super hydrophilicity. The effect of electrolyte temperature on superhydrophilicity is different in different voltage ranges. When the oxidation voltage is 20-40 V, the superhydrophilicity of titanium surface increases with the increase of electrolyte temperature. But this trend is reversed in the 60-80 V voltage range. After modification with fluorosilane, the surface of superhydrophilic titanium oxide becomes superhydrophobic. The results show that the contact angle, rolling angle and contact lag angle of superhydrophobic titanium surface are 160 掳, 2 掳and 1.7 掳, respectively. The extremely wetted surface prepared in this paper has good stability in acidic, neutral, alkaline aqueous solution and atmospheric environment. The new anode flow field with super hydrophobic exhaust microchannel and the new cathode flow field with super hydrophilic drain microchannel are designed respectively. The reasonable depth of microchannel is calculated by ANSYS software. The channel width and other structural parameters of the flow field are determined by combining the flow field opening rate and other factors. The micromachining process of titanium substrate flow field plate with extremely wetting microstructure was determined. The super-hydrophilic auxiliary channel was obtained by anodic oxidation combined with lithography and wet etching, and the superhydrophobic exhaust channel was obtained by fluorination. Finally, a new type of flow field plate was prepared by secondary lithography and wet etching to form the main channel of fuel or oxygen feed. A polycarbonate simulated flow field plate consisting of hydrophilic fuel channel and superhydrophobic gas channel was designed and fabricated. The decomposition reaction of hydrogen peroxide solution was used to simulate the gas-liquid two-phase flow process. The average pressure drop in the new flow field is 37% smaller than that in the reference flow field. Visual observation shows that the auxiliary gas channel accelerates the bubble release. The new anode flow field with superhydrophobic channel is assembled into a cell and the gas-liquid transport characteristics of the anode flow field are studied. The results show that the pressure drop characteristics are consistent with the simulated flow field experiments at the same current density. Furthermore, the peak power density of the new anode with 40 渭 m and 80 渭 m deep exhaust channels is increased by 33.3% and 41.4% than that of the cell with reference anode flow field, respectively. The effect of the new cathode flow field on 渭 DMFC is measured. It is found that the maximum power density of the common lattice flow field decreases by about 2.3 times than that of the new cathode flow field with 80 渭 m discharge channel depth after long-term discharge. The new cathode flow field improves the water management ability of 渭 DMF C cathode.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM911.4
本文编号：2386069
[Abstract]:Micro direct methanol fuel cell (Micro Direct Methanol Fuel Cell) is a promising power supply with many advantages such as high energy conversion efficiency, environmental friendliness, room temperature operation, fast fueling and low noise. The gas-liquid two-phase mixing is one of the key factors affecting the performance of 渭 DMFC, which is characterized by the flow field occupied by anodic CO2 bubbles and the problems of blocking reactants such as water flooding. Around this important problem, microstructural auxiliary channels with extremely wetting (super hydrophilic / super hydrophobic) properties have been designed on titanium substrate to realize gas-liquid separation. The gas-liquid phase transport characteristics in a new flow field and their effects on the performance of the battery were studied. The surface of titanium substrate with super hydrophilic property with contact angle of 0 掳was obtained by one-step anodizing method. The influence of different process parameters on superhydrophilicity was studied. It was found that the higher the oxidation voltage, the stronger the super hydrophilicity. The effect of electrolyte temperature on superhydrophilicity is different in different voltage ranges. When the oxidation voltage is 20-40 V, the superhydrophilicity of titanium surface increases with the increase of electrolyte temperature. But this trend is reversed in the 60-80 V voltage range. After modification with fluorosilane, the surface of superhydrophilic titanium oxide becomes superhydrophobic. The results show that the contact angle, rolling angle and contact lag angle of superhydrophobic titanium surface are 160 掳, 2 掳and 1.7 掳, respectively. The extremely wetted surface prepared in this paper has good stability in acidic, neutral, alkaline aqueous solution and atmospheric environment. The new anode flow field with super hydrophobic exhaust microchannel and the new cathode flow field with super hydrophilic drain microchannel are designed respectively. The reasonable depth of microchannel is calculated by ANSYS software. The channel width and other structural parameters of the flow field are determined by combining the flow field opening rate and other factors. The micromachining process of titanium substrate flow field plate with extremely wetting microstructure was determined. The super-hydrophilic auxiliary channel was obtained by anodic oxidation combined with lithography and wet etching, and the superhydrophobic exhaust channel was obtained by fluorination. Finally, a new type of flow field plate was prepared by secondary lithography and wet etching to form the main channel of fuel or oxygen feed. A polycarbonate simulated flow field plate consisting of hydrophilic fuel channel and superhydrophobic gas channel was designed and fabricated. The decomposition reaction of hydrogen peroxide solution was used to simulate the gas-liquid two-phase flow process. The average pressure drop in the new flow field is 37% smaller than that in the reference flow field. Visual observation shows that the auxiliary gas channel accelerates the bubble release. The new anode flow field with superhydrophobic channel is assembled into a cell and the gas-liquid transport characteristics of the anode flow field are studied. The results show that the pressure drop characteristics are consistent with the simulated flow field experiments at the same current density. Furthermore, the peak power density of the new anode with 40 渭 m and 80 渭 m deep exhaust channels is increased by 33.3% and 41.4% than that of the cell with reference anode flow field, respectively. The effect of the new cathode flow field on 渭 DMFC is measured. It is found that the maximum power density of the common lattice flow field decreases by about 2.3 times than that of the new cathode flow field with 80 渭 m discharge channel depth after long-term discharge. The new cathode flow field improves the water management ability of 渭 DMF C cathode.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM911.4
【参考文献】
相关期刊论文 前1条
1 柯新;姚克俭;王良华;;壁面亲水性对DMFC阳极通道内气液两相流影响的数值模拟[J];化工进展;2008年02期
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