Study on mass transfer enhancement of locally improved structures and the application in serpentine and parallel flow fields of PEM fuel cells

Oxygen transport and water management within proton exchange membrane (PEM) fuel cells can be enhanced by locally improved structures in the flow field. Structures such as the new variable diameter structure and the block structure can significantly improve the PEM performance. In this paper, a three-dimensional numerical model is established to compare different types of locally improved structures. The structures, which employed the same compression volume, consist of a block structure, long block structure, and the new variable diameter structure. The mass transfer characteristics and the optimal layout of the locally improved structures are studied. Then, the new variable diameter structure and the block structure are incorporated into the serpentine flow field (SFF) and the parallel flow field (PFF) to form new flow fields, and their effects on the SFF and PFF are analyzed. The new variable diameter structure improves the uniformity of oxygen, and the block structure enhances the local mass transfer. The presence of the locally improved structure in the middle of the FF gives the best performance. In addition, the improved SFF has very limited performance and poor water management, but the oxygen distribution in the variable diameter PFF (PFF@VD) was significantly improved, and the peak power was increased by 26%. The energy consumption caused by pressure drop (ECP) is adopted to evaluate the performance of the flow field with locally improved structures; the PFF@VD has a higher proportion of net output power compared to the unmodified PFF.     

Formation of Dense Inclusion Buildup on Submerged Entry Nozzle by Electric Current Pulse

In this work, low-density electric current pulse(ECP) has been applied to submerged entry nozzle(SEN) and its effect on the morphology of the inclusion buildup and the distribution of the inclusions in slab has been explored. The results reveal that under the unique effects of ECP, part of small inclusions less than 10 lm is expelled through the boundary layer along the current direction to form dense inclusion buildup. This method is of great potential to prolong the service life of SEN and improve the quality of the steel product.     

电脉冲处理对亚共晶铁碳合金珠光体组织的影响

研究了电脉冲（ECP）处理对亚共晶铁碳合金珠光体组织的影响。结果表明,亚共晶铁碳合金经ECP处理后,促进了石墨的生成,增加了铁素体的形核率,最终导致组织中铁素体相对含量增加,珠光体相对含量相应降低;ECP处理同样增加了共析转变的有效驱动力,且随着输出电压的升高,珠光体内的渗碳体层片逐渐变短、变薄,珠光体的显微硬度逐渐增加。     

蜗杆制造误差检测中的一种新型数据通讯方法

环面蜗杆制造误差的检测 (CAE)是一项创新性的研究。本文研究了上下位机分布式测试系统的数据通讯方法 ,上位PC机负责系统发送命令和处理数据 ,下位单片机负责完成实时数据采集任务。该方法具有测量误差小、检测精度高、高速并行通讯、采样数据实时传输且模式的灵活性更大、传输速度可自动调整、方便好用等优点     

铸型冷却强度对脉冲电流细化纯铝凝固组织的影响

通过改变脉冲电流参数和铸锭的冷却速度,研究了脉冲电流细化纯铝的规律.试验结果表明:在较快的冷却速度下脉冲电流峰值对组织细化程度的影响明显强于脉冲频率的作用.当频率超过200Hz后电流的热效应导致细化效果反而变差,同时电流的作用存在一个极限值,当电流峰值达到125A之后细化效果明显增强,但是继续提高参数,细化效果并没有随之提高.在较慢的冷却速率下,由于增加了脉冲电流的有效作用时间以及晶核迁移的时间,易于获得等轴晶组织.     

ECP系统车辆控制设备仿真平台设计

针对ECP系统地面联调试验的需求,通过建立制动缸压力模型,利用PL－LonWorks模块,设计开发了适用于电力线载波LonWorks通信且具备列车排序能力的ECP车辆控制设备的仿真平台。测试表明该仿真平台满足ECP系统地面联调试验需求。     

基于移动AGENT系统的网络分布式数据访问

给出了一个访问网络数据库的移动Agent的系统,该系统建立在ECP协议和移动Agent基础上,用纯JAVA代码实现,利用ECP在提高通信效率的情况下访问网络分布式数据库。     

碳载体预处理对燃料电池Co-N/C非铂催化剂氧还原性能的影响EI北大核心CSCD

钴(Co)基氧还原催化剂以价格低、储量高、易获得等优势成为代替铂基氧还原催化剂重要选择之一。本工作先对科琴黑进行硝酸酸化预处理,与四水合乙酸钴混合后在氨气气氛下800℃热解制备出Co-N/C氧还原催化剂。由红外光谱测试、联碱中和滴定与比表面积测定可知,经硝酸酸化预处理后,科琴黑表面含氧官能团数量增多,科琴黑孔径不变,中孔比例增加。XRD和TEM测试表明科琴黑和四水合乙酸钴经氨气热处理后,生成了分散均匀无团聚的Co_(5.47)-N/C催化剂。电化学测试表明载体经预处理后,制备的Co-N/C催化剂的氧还原反应(ORR)的电催化性能更好,在碱性条件下电流密度达到了预处理前的4.2倍,在催化动力学中属于四电子转移。     

NGN技术及其应用

NGN是一种以软交换技术为核心的新兴技术。文章介绍了NGN的关键技术,指出其主要功能和应用范围。     

高温高压电化学测量系统在核电厂中的应用研究进展

针对压水堆核电厂一、二回路水化学及腐蚀的监测情况,综述了高温高压电化学测量系统的模拟研究现状,探讨了在线电化学测量的三种研究方案,并以实时电化学腐蚀电位(ECP)的测量为例说明了其在核电厂评价及运行工况优化过程中的作用,指出在线电化学测量技术在核电厂具有很大应用潜力.