磁场强化水电解中多重微磁对流对氢/氧气泡的协同影响

Water electrolysis is an irreplaceable medium of energy conversion in the system of clean energy utilization, and is also the key technology of the environmental control and life support system (ECLSS) in manned space flight and submarine. The gaseous product can be expelled effectively from electrolyzer and the potential drop between electrodes can be reduced with the influence of magnetohydrodynamics convection induced by the external static magnetic field. This proposal means to make the process of gas evolution in water electrolysis as the research object, and focus on the influence of the multiple micro magnetohydrodynamics convections on the hydrogen or oxygen gas bubbles evolution. By the method of controlled bubble nucleation and VOF (volume of fluid) simulation of bubble growth, combining visualization experiments and numerical calculation, this proposal means to give the analysis of the influence mechanism of micro magnetohydrodynamics convections on the hydrogen or oxygen gas bubbles induce by the local Lorentz force, paramagnetic gradient force and Kelvin force. First, it means to analyse the exactly mechanism of the micro magnetohydrodynamics convection influence on the bubble evolution from the view of neighbouring bubble interaction induced by the local Lorentz force. Second, it means to give clear analysis of the form of the combined effect of the paramagnetic gradient force and local Lorentz force on the oxygen bubble at the non-ferromagnetic anode surface. The last, it means to analyse the exactly driving mechanism and effect of the multiple micro convections induced by the local Lorentz force, paramagnetic gradient force and Kelvin force on the the oxygen bubble at the ferromagnetic anode surface. The view and focus above in this proposal have not yet been published in the field of bubble dynamics research of magnetic field intensifying water electrolysis for hydrogen/oxygen production.

水电解是清洁能源利用不可或缺的能量转换媒介，也是载人航天和潜艇舱内环控生保系统的关键技术。外加静磁场在电解液中形成磁对流有效驱除气相产物，降低电极间电势差。本项目以磁场强化水电解析气过程为研究对象，关注于多重微观磁对流对电极表面氢/氧气泡演化的影响。通过电极表面气泡可控成核和VOF（volume of fluid）模拟气泡演化过程，结合可视化实验与数值计算，分析局部洛伦兹力、顺磁梯度力和开尔文力引起的微磁对流对于电极表面氢/氧气泡演化的影响机制。其一，从局部洛伦兹力引起临近气泡相互作用角度分析微观磁对流对于氢气泡演化的确切作用机制；其二，明确顺磁梯度力和局部洛伦兹力对非铁磁性阳极表面氧气泡共同作用形式；其三，局部洛伦兹力、顺磁梯度力和开尔文力共同形成的多重微磁对流对铁磁性阳极表面氧气泡的确切驱动机制及作用效果。本项目研究思路与关注重点，在磁场强化水电解制氢/氧气泡动力学研究中未见相关报道。

本项目关注于磁场强化水电解中的气相产物相变演化过程，创新性的从微观磁对流影响下气泡相互作用角度入手，并着眼于多重微磁对流对气泡的协同作用，通过可控气泡生长演化实验和数值模拟方法，1)已揭示了微观磁对流促进电极表面单气泡和多气泡以较小尺寸提前脱离的机制，即对于单个气泡，micro-MHDC在气泡顶部形成低压区将气泡抽离电极表面；对于相邻气泡，作用于个体气泡周围的micro-MHDC彼此干扰引起气泡周围静压不均而产生横向作用力，促使气泡脱离原始生长锚点而提前脱离。2)明晰了气泡尺度内多重磁对流对电极表面氢、氧气泡的驱散机理及作用效果，即在气泡尺度内梯度磁场可以同样产生明显的微磁对流驱散氢气泡；开尔文力和顺磁梯度力作用于氧气泡周围的流体上，在氧气泡底部周围产生额外的挤压力，使氧气泡提前从电极表面释放；结合利用多孔结构电极内产生的微磁对流更有利于气泡排出。3)发现了基于磁化丝状电极实现磁场强化水电解过程的新方法并对其降低水电解能耗效果给出了量化结果，即实现剩磁0.12 T的丝状电极，保持265 T2/m磁场梯度，最大实现阳极电势降低5.4%。更重要的是，此研究革新了原有对于磁场强化水电解过程必须配置体重量大的外部永磁体的认识，可通过低强度高梯度磁化电极的应用实现在紧凑工业电解槽内磁场强化水电解技术的工程应用，具有重要理论意义和实用价值。