Qualitative investigation on effects of manifold shape on methanol steam reforming for hydrogen production

Fluid velocity distribution among microchannels plays important role on the reaction performances. In this work, the velocity distribution among microchannels with two different manifold structures is compared by a three-dimensional CFD model under two situations respectively, no reaction and methanol steam reforming occurs. Then the performances of methanol steam reforming in both plates are experimentally investigated, and the effect of manifold shape on the hydrogen production performances is qualitatively analyzed by the combination of simulation results of velocity distribution. It is found that the microchannel plate with right-angle manifold enables narrow velocity distributions under different entrance velocities and reaction temperatures, whether no reaction occurs or methanol steam reforming is progressing, which can be the critical element results in better conversion rate and selectivity of process than that of the microchannel plate with oblique-angle manifold. Optimizing the structural parameters to facilitate a relatively uniform velocity distribution to increase the hydrogen production performances may be a key factor to be considered.     

Effects of structural aspects on the performance of a passive air-breathing direct methanol fuel cell

This study systematically investigates the effects of structural aspects on the performance of a passive air-breathing direct methanol fuel cell (DMFC). Three factors are selected in this study: (1) two different open ratios of the current collector; (2) two different assembly methods of the diffusion layer; and (3) three membrane types with different thicknesses. The interrelations and interactions among these factors have been taken into account. The results demonstrate that these structural factors combine to significantly affect the cell performance of DMFCs. The higher open ratio not only provides a larger area for mass transfer passage and facilitates removal of the products, but also promotes higher methanol crossover. The hot-pressed diffusion layer (DL) can mitigate methanol permeation while the non-bonded variant is able to enhance product removal. The increase of membrane thickness helps obtain a lower methanol crossover rate and higher methanol utilisation efficiency, but also depresses cell performance under certain conditions. In this research, the maximum power density of 10.7 mW cm⁻² is obtained by selecting the current collector with a lower open ratio, the non-bonded DL, and the Nafion 117 membrane. The effect of methanol concentration on the performance of DMFCs is also explored.     

Oriented linear cutting fiber sintered felt as an innovative catalyst support for methanol steam reforming

A kind of oriented linear cutting fiber sintered felt as an innovative catalyst support for methanol steam reforming was proposed. Multiple long copper fibers fabricated by cutting method were arranged in parallel and then sintered together in a mold pressing equipment under the condition of high temperature and protective gas atmosphere. The characteristics of oriented linear cutting fiber sintered felt coated with Cu/Zn/Al/Zr catalyst for methanol steam reforming were experimental investigated under different GHSVs and reaction temperatures. Results indicated that the structure of sintered felt was the key influencing factor for the reaction performances on the condition of low GHSV or reaction temperature whereas the structure of sintered felt showed little influences with high GHSV or reaction temperature. By the analysis of SEM image and ultrasonic vibration testing method, it was found that the coarse surface pattern of cutting fiber could effectively enhance the adhesion intensity between the catalyst and the copper fibers, as well as present relatively large specific surface area in the microchannels. And hence the oriented linear cutting fiber sintered felt present better performances of methanol steam reforming than the oriented linear copper wire sintered felt on the condition of low GHSV or reaction temperature.     

回转支承在浓缩机上的应用

浓缩机是选矿厂精选和尾矿脱水处理的主要设备。对传统结构和安装有回转支承的浓缩机进行了结构分析比较,并着重介绍了回转支承的结构特点、选型方法和工作原理。工程实践应用表明,采用回转支承的浓缩机,可使整机结构简单,缩短运动链,且体积小、质量轻、造价低、机械效率高,节省能源。     

孤岛模式下基于快速储能投退机制的微电网多源协调控制

针对小型微电网,提出了单刀双掷开关和快速储能等集成安装在微电网公共连接点处的方案.在此基础上,提出微源综合并网控制模型和基于本地信息的自我决策模型(快速储能模型、后备电源模型),实现了响应速度快但容量较小的快速储能与容量较大但响应速度较慢(或需要一定启动时间)的后备电源之间不依赖于通信的多源协调控制.利用PSCAD/EMTDC软件建立了仿真系统,以超级电容(作为快速储能)和微型燃气轮机(作为后备电源)为例对所提控制策略进行了验证,实现了微源在微电网进入孤岛过程中的主动控制及在孤岛运行模式下的自治运行.     

Preparation and Properties of a Thermal Insulating Layer and a Buffer Layer for Multilayer Pyroelectric Film Infrared Detector

A thermal insulating layer and a buffer layer play a key role in the multilayer pyroelectric thin film infrared detector. In this work, a porous SiO 2 film serving as thermal insulating layer and a dense SiO 2 film serving as buffer layer were prepared by sol-gel method. The porosities of the porous film and the dense film are about 50% and 6%, respectively. Maximum thickness values of a single layer porous film and that of a single layer dense film all come up to 1.5 w m. Rms (root-mean-square) surface roughness of the porous film is about 40 nm and that of the dense film is about 1.5 nm. Experimental result shows 0.4 w m dense SiO 2 film can flatten rough surface of the porous SiO 2 film, and the rms surface roughness is less than 5 nm. The composite SiO 2 film can effectively block thermal diffusion.     

The non-invasive identification of heroin covered by simulation skin based on coherence function algorithm and wavelet

As body-packing is a well-known means of illicit drug carriage across international borders, the goal of our study is to provide a new method for the detection of body-packing (ingested drug packets) based on energy dispersive X-ray diffraction (EDXRD) and algorithms. Packets containing heroin (purity > 90%) were introduced into the experimental body in which pork was used as simulation body. The samples were repeatedly scanned by energy dispersive X-ray diffraction spectrometer, and then, threshold wavelet and coherence function were used to analyze the obtained EDXRD spectra. In our investigation, two criteria were used for the identification of heroin in pork. One was that matching the diffraction profile of unknown material and samples via coherence function which was on the basis of setting-up samples database of heroin in pork. The other was that matching the positions and shapes of heroin diffraction peaks. On the basis of the experimental tests and data analysis, it is indicated that the presented methods are effective and reasonable for the detection of heroin in body.     

塑料挤出机节能高效螺杆设计

在详细分析屏障螺杆的结构特点、工作原理和加工要求的基础上,选择最优设计参数,并使用流体力学软件,数值仿真动态模拟螺杆的挤出过程,达到节能、高效和高质量生产塑料农膜的目的。     

中国DSM发展趋向研讨（下）

需求侧管理(DsM)是一项涉及社会各方的系统工程。该文分析了需求侧管理的工作重点,定义了决策支持系统的主要功能,提出了利用Intemet传输信息构筑决策支持系统的设计思想。