In this study, a novel design concept for PEMFC （polymer electrolyte membrane fuel cell） stacks is presented with single cells inserted in pockets surrounded by a hydraulic medium. The hydraulic pressure introduces ...In this study, a novel design concept for PEMFC （polymer electrolyte membrane fuel cell） stacks is presented with single cells inserted in pockets surrounded by a hydraulic medium. The hydraulic pressure introduces necessary compression forces to the membrane electrode assembly of each cell within a stack. Moreover, homogeneous cell cooling is achieved by this medium. First, prototypes presented in this work indicate that, upscaling of cells for the novel stack design is possible without significant performance losses. Due to its modularity and scalability, this stack design meets the requirements for large PEMFC units.展开更多
The 3D inverse design method, which methodology is far superior to the conventional design method that based on geometrical description, is gradually applied in pump blade design. However, no complete description abou...The 3D inverse design method, which methodology is far superior to the conventional design method that based on geometrical description, is gradually applied in pump blade design. However, no complete description about the method is outlined. Also, there are no general rules available to set the two important input parameters, blade loading distribution and stacking condition. In this sense, the basic theory and the mechanism why the design method can suppress the formation of secondary flow are summarized. And also, several typical pump design cases with different specific speeds ranging from centrifugal pump to axial pump are surveyed. The results indicates that, for centrifugal pump and mixed pump or turbine, the ratio of blade loading on the hub to that on the shroud is more than unit in the fore part of the blade, whereas in the aft part, the ratio is decreased to satisfy the same wrap angle for hub and shroud. And the choice of blade loading type depends on the balancing of efficiency and cavitation. If the cavitation is more weighted, the better choice is aft-loaded, otherwise, the fore-loaded or mid-loaded is preferable to improve the efficiency. The stacking condition, which is an auxiliary to suppress the secondary flow, can have great effect on the jet-wake outflow and the operation range for pump. Ultimately, how to link the design method to modem optimization techniques is illustrated. With the know-how design methodology and the know-how systematic optimization approach, the application of optimization design is promising for engineering. This paper summarizes the 3D inverse design method systematically.展开更多
探讨“经验法则”(rules of thumb)在高速印制电路板PCB设计中的应用,强调这些基于实践而非理论且易于记忆、大致准确的指南或原则,在缺乏昂贵分析工具时的重要作用。详细介绍在传输线、叠层、返回电流路径、串扰、信号完整性等方面的...探讨“经验法则”(rules of thumb)在高速印制电路板PCB设计中的应用,强调这些基于实践而非理论且易于记忆、大致准确的指南或原则,在缺乏昂贵分析工具时的重要作用。详细介绍在传输线、叠层、返回电流路径、串扰、信号完整性等方面的经验法则,包括阻抗匹配、走线布局、电流密度、电磁场影响等关键因素。同时,指出经验法则具有局限性,即“规则是用来打破的”,每个PCB设计都可能需要打破至少一条法则,以适应特定情况。展开更多
文摘In this study, a novel design concept for PEMFC （polymer electrolyte membrane fuel cell） stacks is presented with single cells inserted in pockets surrounded by a hydraulic medium. The hydraulic pressure introduces necessary compression forces to the membrane electrode assembly of each cell within a stack. Moreover, homogeneous cell cooling is achieved by this medium. First, prototypes presented in this work indicate that, upscaling of cells for the novel stack design is possible without significant performance losses. Due to its modularity and scalability, this stack design meets the requirements for large PEMFC units.
基金Supported by National Basic Research Program of China(973 Program,Grant No.2009CB724302)
文摘The 3D inverse design method, which methodology is far superior to the conventional design method that based on geometrical description, is gradually applied in pump blade design. However, no complete description about the method is outlined. Also, there are no general rules available to set the two important input parameters, blade loading distribution and stacking condition. In this sense, the basic theory and the mechanism why the design method can suppress the formation of secondary flow are summarized. And also, several typical pump design cases with different specific speeds ranging from centrifugal pump to axial pump are surveyed. The results indicates that, for centrifugal pump and mixed pump or turbine, the ratio of blade loading on the hub to that on the shroud is more than unit in the fore part of the blade, whereas in the aft part, the ratio is decreased to satisfy the same wrap angle for hub and shroud. And the choice of blade loading type depends on the balancing of efficiency and cavitation. If the cavitation is more weighted, the better choice is aft-loaded, otherwise, the fore-loaded or mid-loaded is preferable to improve the efficiency. The stacking condition, which is an auxiliary to suppress the secondary flow, can have great effect on the jet-wake outflow and the operation range for pump. Ultimately, how to link the design method to modem optimization techniques is illustrated. With the know-how design methodology and the know-how systematic optimization approach, the application of optimization design is promising for engineering. This paper summarizes the 3D inverse design method systematically.
文摘探讨“经验法则”(rules of thumb)在高速印制电路板PCB设计中的应用,强调这些基于实践而非理论且易于记忆、大致准确的指南或原则,在缺乏昂贵分析工具时的重要作用。详细介绍在传输线、叠层、返回电流路径、串扰、信号完整性等方面的经验法则,包括阻抗匹配、走线布局、电流密度、电磁场影响等关键因素。同时,指出经验法则具有局限性,即“规则是用来打破的”,每个PCB设计都可能需要打破至少一条法则,以适应特定情况。
