| The deepening of industrialization and the development of transportation technology all over the world had exacerbated pollution emissions.Countries all over the world regard environmental protection as a problem that must be solved in social progress.Compared with traditional power plants using fossil energy,fuel cells mostly use renewable and pollution-free material such as hydrogen and oxygen for reaction.They are not only environmentally friendly,but also regarded as a powerful tool to deal with the current energy crisis.As the latest achievement in the miniaturization of fuel cell,microfluidic fuel cell meets the demand of portable and wearable electronic devices for small volume power supply,and avoids the problems of traditional fuel cell in structure.Therefore,it is considered to have broad application prospects in the digital era with the rapid development of information technology.Although the research on fuel cells had been in-depth,most of the research on microfluidic fuel cells was limited to theoretical analysis or simple model test.In order to get large-scale market-oriented application of microfluidic fuel cell,its working environment and external interference factors must be comprehensively analyzed from the perspective of practical application.For example,the impact of vibration,drop and other impacts encountered by microfluidic fuel cells in wearable devices.In addition,for the passive microfluidic fuel cell based on paper fiber material,the influence of bending on its operation stability can’t be ignored.These problems must be solved in the development of the above types of microfluidic fuel cells.Only by comprehensively analyzing,deeply studying and then revealing the influence mechanism behind the performance of the cell,can microfluidic fuel cells have the possibility of practical application.In order to find an effective way to solve the above problems and deficiencies,this paper employs numerical simulation software to assist the research.By establishing multi physical field coupling numerical models based on the experimental results of active and passive microfluidic fuel cells,the models with different material supply modes are established,and the material transmission mechanism in microfluidic fuel cells under the influence of multiple factors are analyzed.The main research work includes the following aspects:（1）A three-dimensional numerical model of active vapor-feed microfluidic fuel cell is constructed,the effects of structural parameters such as novel tower-type vapor chamber and electrode shape on cell performance are studied,and the energy efficiency of the model under different parameters is comprehensively evaluated;（2）The numerical model of vibration coupling research based on vapor-feed microfluidic fuel cell is constructed to simulate the cell performance when encountering different types of vibration effects,analyzing the cell performance fluctuation law when changing the vibration parameters;（3）A numerical model of passive microfluidic fuel cell with paper fiber as the structural substrate is constructed.The wicking process driven by capillary pressure inside the paper fiber and the influence of structural parameters on the energy efficiency are studied;（4）Based on the numerical model of paper-based passive microfluidic fuel cell,the deformation of various geometric structures is constructed to explore the influence mechanism of bending and folding on the cell.The main conclusions of this paper are summarized as follows:（1）The vapor-feed microfluidic fuel cell can obtain high power output when the reaction evaporation area ratio of 1:11.1.With tower-type vapor chamber,the cell can obtain 31.86m W/cm2 peak power density and 210.16m A/cm2 current density.The maximum power density of the cell can reach 33.45mw/cm2 when the electrode height is 3mm.By integrating various optimization strategies,the peak power density of the cell can reach 47.43m W/cm2,and the maximum current density can be increased to 344.38m A/cm2.（2）The vibration disturbs the stable fuel gradient distribution in the vapor chamber of vapor-feed microfluidic fuel cell,promotes more fuel to gather in the reaction area,and significantly affects the cell performance.In various vibration parameters,the increase of vibration intensity and frequency can slightly increase the cell output power.When the vibration intensity increased from3.28m·s-2 to 6.56m·s-2,the peak power density of the in-plane and through-plane vibration models increased by 4.85m W/cm2 and 4.03m W/cm2,respectively.In general,the effect of in-plane vibration on cell performance is more obvious than that of through-plane vibration,but the performance fluctuation of the cell is smaller when affected by through-plane vibration,especially in the field of vibration phase changes.（3）The electrode spacing,length and distance from the inlet have some effects on the performance of paper-based passive microfluidic fuel cell.When the channel thickness increases to 570μM,the maximum current density reaches40.85m A/cm2,with the corresponding peak power density of 2.46m W/cm2.In terms of material parameters,the output power is more significantly affected by the change of electrolyte concentration than fuel concentration.（4）Based on the structural characteristics of paper fiber materials,paper-based passive microfluidic fuel cells have certain flexibility,even it is folded at a large angle,the output power can be maintained at 1.71m W/cm2.This characteristic makes the paper-based microfluidic fuel cell have a broad prospect on wearable devices,but it is necessary to avoid extrusion and tearing of the fiber pore structure in practical application.（5）Fiber materials with higher absorption capacity can increase the cell power output by 4.37m W/cm2,increasing the volume of the absorption pad has a similar effect.Meanwhile,properly increasing the operating temperature can increase the cell power and current output by 0.27m W/cm2 and 1.25m A/cm2respectively,but the risk of carbonization of fiber materials at high temperature should be considered. |
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