面向超声雾化供给的直接甲醇燃料电池结构设计理论与方法研究

Direct methanol fuel cell (DMFC) is one of the cells with the highest energy density. However, the bottleneck problem in terms of methanol crossover restricts its application and popularization, which is drawing extensive attentions from researchers. The vapor supply is considered to be one of the most effective methods to relieve methanol crossover at present, but it degrades the cell performance and causes instability, moreover, it can hardly be promoted for its long startup time and uncontrollable vaporizable ratio. In this research, a novel supply method based on ultrasonic atomization is proposed to relieve the methanol crossover through integrating the miniaturised ultrasonic atomizer with anodic flow field plate. The primary advantages of this method are that it can not only relieve methanol crossover but precisely control the feed rate, hence improving fuel efficiency. This research aims to experimentally reveal the mechanism of ultrasonic atomization feed method in relieving methanol crossover, establish a set of design theories and implement the method of ultrasonic atomization feed DMFC by focusing on the design theory of low energy consumption and high-performance ultrasonic atomizer, two-phase flow between methanol droplets and carbon dioxide under the effect of ultrasound, as well as corresponding fuel supply strategy. Thus, the theoretical basis and the experimental foundation are offered for the application of ultrasonic atomization supply in relieving methanol crossover and improving cell performance.

直接甲醇燃料电池是能量密度最高的电池之一，而甲醇渗透这一瓶颈问题制约着它的推广，这引起学术界的广泛关注。汽化供给是目前解决甲醇渗透最有效的方法之一，但它会降低电池性能、造成电池性能不稳定，且存在系统启动时间长和汽化速率不可控等问题而难以应用。本项目提出一种采用超声雾化燃料供给来解决甲醇渗透的新方法，拟将小型化后的超声雾化器与阳极流场板进行一体化设计来实现。该方法的优点在于它既可以缓解甲醇渗透又能对燃料的供给进行精确控制来提升燃料的使用效率。本项目通过实验揭示超声雾化燃料供给方式在缓解甲醇渗透中的作用机理，重点研究低能耗高性能超声雾化器的设计理论、超声作用下甲醇雾滴与二氧化碳气体间的二相流现象及相应的燃料雾化供给策略等问题，建立一套基于超声雾化进行燃料供给的直接甲醇燃料电池的设计理论和实现方法，为应用超声雾化燃料供给来缓解甲醇渗透和提高电池性能提供理论依据和实验基础。

燃料电池以其高效率、低污染、高比能量等优点而被认为是一种理想的能源装置，但燃料渗透、CO2气塞等问题一直制约着DMFC的应用和推广。针对以上问题，本项目创新性地提出了一种基于超声雾化的燃料供给新方法，并设计一种超声场与燃料供给通道、阳极流场板一体化的新型燃料电池结构。项目还通过实验研究了超声雾化供给方式下电池的传质传热特性，揭示了超声雾化燃料供给在缓解甲醇渗透中的作用机理，探明了阳极雾化腔及流场内的气、液二相流动对电池性能的影响。实验结果表明超声雾化供给方式的两极温差值比常规液态供给方式普遍高出了5℃~10℃；在供给甲醇溶液浓度为12M时，雾化供给相比液态供给性能提升高达31.8%；超声雾化供给方式的当量甲醇消耗率远高于液态供给，从而降低了电池阴阳两极甲醇浓度梯度，进而有效缓解了甲醇渗透；当CO2气泡的半径为1.2mm时，电池性能最大下降了45.37%。此外，本项目还对雾化片、流场板等重要部件的结构参数进行了研究，取得了一定的成果。本项目的研究成果为解决燃料电池甲醇渗透的难题提供了一种新思路，对于指导超声雾化燃料电池的设计制作方面具有非常重要的价值。