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101.
Junhyun Cho Hwanyeong Oh Jaeman Park Kyoungdoug Min Eunsook Lee Jy-Young Jyoung 《International Journal of Hydrogen Energy》2014
The mass transport characteristics of a gas diffusion layer (GDL) predominantly affect the performance of a proton exchange membrane (PEM) fuel cell. However, studies examining the transient response related to the GDL are insufficient, although the dynamic behavior of a PEM fuel cell is an important issue. In this study, the effects of the design of a micro porous layer (MPL) on the transient response of a PEM fuel cell are investigated. The MPL slurry density and multiple functional layers are treated as the variable design parameter. The results show that the transient response is determined by the capillary pressure gradient through the GDL. The trade-off relation for the PEM fuel cell performance under low and high humidity conditions due to the hydrophobic GDL is mitigated by designing a reverse capillary pressure gradient in the MPL. 相似文献
102.
The selective catalytic reduction of NO by H2 under strongly oxidizing conditions (H2-SCR) in the low-temperature range of 100–200 °C has been studied over Pt supported on a series of metal oxides (e.g., La2O3, MgO, Y2O3, CaO, CeO2, TiO2, SiO2 and MgO-CeO2). The Pt/MgO and Pt/CeO2 solids showed the best catalytic behavior with respect to N2 yield and the widest temperature window of operation compared with the other single metal oxide-supported Pt solids. An optimum 50 wt% MgO-50wt% CeO2 support composition and 0.3 wt% Pt loading (in the 0.1–2.0 wt% range) were found in terms of specific reaction rate of N2 production (mols N2/gcat s). High NO conversions (70–95%) and N2 selectivities (80–85%) were also obtained in the 100–200 °C range at a GHSV of 80,000 h−1 with the lowest 0.1 wt% Pt loading and using a feed stream of 0.25 vol% NO, 1 vol% H2, 5 vol% O2 and He as balance gas. Addition of 5 vol% H2O in the latter feed stream had a positive influence on the catalytic performance and practically no effect on the stability of the 0.1 wt% Pt/MgO-CeO2 during 24 h on reaction stream. Moreover, the latter catalytic system exhibited a high stability in the presence of 25–40 ppm SO2 in the feed stream following a given support pretreatment. N2 selectivity values in the 80–85% range were obtained over the 0.1 wt% Pt/MgO-CeO2 catalyst in the 100–200 °C range in the presence of water and SO2 in the feed stream. The above-mentioned results led to the obtainment of patents for the commercial exploitation of Pt/MgO-CeO2 catalyst towards a new NOx control technology in the low-temperature range of 100–200 °C using H2 as reducing agent. Temperature-programmed desorption (TPD) of NO, and transient titration of the adsorbed surface intermediate NOx species with H2 experiments, following reaction, have revealed important information towards the understanding of basic mechanistic issues of the present catalytic system (e.g., surface coverage, number and location of active NOx intermediate species, NOx spillover). 相似文献
103.
Low and negative pressure events in drinking water distribution systems have the potential to result in intrusion of pathogenic microorganisms if an external source of contamination is present (e.g., nearby leaking sewer main) and there is a pathway for contaminant entry (e.g., leaks in drinking water main). While the public health risk associated with such events is not well understood, quantitative microbial risk assessment can be used to estimate such risk. A conceptual model is provided and the state of knowledge, current assumptions, and challenges associated with the conceptual model parameters are presented. This review provides a characterization of the causes, magnitudes, durations and frequencies of low/negative pressure events; pathways for pathogen entry; pathogen occurrence in external sources of contamination; volumes of water that may enter through the different pathways; fate and transport of pathogens from the pathways of entry to customer taps; pathogen exposure to populations consuming the drinking water; and risk associated with pathogen exposure. 相似文献
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以某一内燃机连杆为研究对象,基于瞬态响应特性分析理论,运用APDL语言建立连杆的几何模型及有限元模型,利用有限元分析软件ANSYS 10.0进行瞬态响应分析,得出特定工况下连杆等效动应力的分布区域和变化规律.分析过程中,借助于数据表进行包括惯性载荷在内的动载荷施加,使得仿真程度更高,结果更精确.研究结果表明,最大等效动应力发生在正面小头与杆身过度处,此处是动强度最薄弱的地方. 相似文献
108.
Young-joon Kim Koji Miyazaki Hiroshi Tsukamoto 《Journal of Mechanical Science and Technology》2008,22(10):1930-1936
An inverse transient method with genetic algorithm (GA) was applied to leak detection in pipeline. Transient flow caused by
valve operation was calculated using the characteristics method. The location and discharge of leak were determined so that
the difference of the calculated pressure may be minimized from the reference pressure calculated under a given leak condition.
Calculations were done for the leak at one and two locations in pipeline. Furthermore, the effect of noise in pressure data
was discussed, and the leak locations and leak discharges can be predicted precisely even in the case of noisy data.
This paper was presented at the 9th Asian International Conference on Fluid Machinery (AICFM9), Jeju Korea, October 16–19, 2007. 相似文献
109.
重载列车车轮踏面制动是一个复杂的动态接触热-机耦合问题,介绍了热-机耦合问题的求解方法,并利用有限元分析软件ANSYS对提速货车的单闸瓦踏面制动过程进行了紧急制动工况的数值仿真,定量地给出了车轮踏面温度和应力随时间的变化规律,为研究车轮踏面热疲劳提供了理论依据. 相似文献
110.
在还原性气氛流场瞬变温度测量中,过去一般采用全铠装式或接壳式热电偶,很难实现毫秒级的时间常数,新研制的大温变率流场中特种变送器,由镍铬-镍硅的偶丝裸露式极微细热电偶,及放大电路、冷端补偿电路和超量程限幅电路等组成的仪表放大器2部分构成,首次应用在还原性气氛流场温度测量中,获得了满足试验要求的毫秒级时间常数,其中,以精密电压基准LM385为核心器件的热电偶冷端补偿电路,在0℃-40℃环境温度范围内补偿,温度附加误差为0.2%,提高了系统测量精度。 相似文献