基于AMESIM泵控液压机性能优化研究

以AMESIM软件为工具,对泵控液压机系统的位移控制性能进行优化,为进一步的系统优化工作奠定了重要基础。     

Studies of the combined effects of some important factors on the likelihood of flashover

Among those factors that affect the likelihood of flashover in enclosure fires, the thermal inertia of lining materials, ventilation factor of door openings, heat release rate of fuel, and internal dimensions of the enclosure are the most important. The effects of the four factors are related, so it is very necessary to study their combined effects. In the present study, based on analyzing the approximate heat balance on the control volume similar to that in the MQH method, a dimensional relationship was derived that facilitates the estimation of pre‐flashover temperatures, which is used in the popular guidance literature as the key parameters for practical methods of predicting flashover. By correlating a vast amount of data gained in both small‐scale and large‐scale enclosure fire experiments, an important equation was obtained, which can embody explicitly and quantitatively the combined effects of the four important factors on the likelihood of flashover. According to the temperature criteria of 600°C identifying flashover, a new ‘combined method of predicting flashover’ was put forward. The validity of the method was verified in small‐scale experiments, and the results showed that it could be applied to predict well whether flashover occurs in enclosure fires or not. Copyright © 2010 John Wiley & Sons, Ltd.     

Degradation behavior of Ni-YSZ anode-supported solid oxide fuel cell (SOFC) as a function of H2S concentration

This study investigated the effect of H₂S concentration (5, 10 and 50 ppm) on the degradation and performance of Ni-YSZ anode supported solid oxide fuel cells. When supplied with hydrogen fuel containing H₂S, the cell voltage dropped rapidly, and with increasing H₂S concentration, voltage drop % increased (due to higher sulfur coverage on the Ni surface) and saturated more rapidly. A high concentration (50 ppm) of H₂S led to an additional, slow rate voltage loss. In all cases, cell performance did not completely recover even after being supplied with H₂S-free hydrogen fuel, because of the incomplete desorption of sulfur from the Ni surface. After the performance tests, nickel sulfides were detected on the Ni surface by Raman spectra, which were produced by the reaction of the remaining adsorbed sulfur with Ni during the cooling process. This indicates that the formation of nickel sulfides was not responsible for the secondary voltage drop. SEM/EDS analyses combined with FIB revealed that the reason for the additional 2^nd drop was Ni oxidation; at a high sulfur coverage ratio (50 ppm), the outer layer of the Ni particle was oxidized by oxygen ions transported from the electrolyte. This indicates that H₂S concentration as well as current density is a critical factor for Ni oxidation, and gives rise to the second voltage drop (irreversible cell degradation). The present work showed that the degradation behavior and phenomenon can differ significantly depending on the concentration of H₂S, i.e., permanent changes may or may not occur on the anode (such as Ni oxidation) depending upon H₂S concentration.     

Innovative electrodes for direct methanol fuel cells based on carbon nanofibers and bimetallic PtAu nanocatalysts

Direct methanol fuel cells are very promising power sources, but the easy poisoning of the platinum anode electrocatalyst by CO-like reaction intermediates, restricts their industrial application and commercialization. The development of Pt-based alloys or bimetallic catalysts, in which the second metal acts as Pt poisoning inhibitor, is one of the main promising solutions to this problem. In this work we have combined the use of unconventional methods to deposit the catalyst nanoparticles with unconventional carbon supports. Innovative electrodes made of platelet carbon nanofibers, directly grown on graphite paper, as substrate for electrodeposited platinum and gold bimetallic nanoparticles, have been developed. These electrodes allow having a single layer with both the diffusive and catalytic function, and a considerable decrease of noble metals amount (about five times), with consequent large cost reduction. Moreover, the replacement of the conventional ink deposition methods with electrodeposition for platinum and gold dispersion, considerably increases the catalytic activity. The electrocatalytic performance results were encouraging. Gold allows increasing the catalyst poisoning tolerance and then the electrode long term stability. The innovative electrodes show a performance improvement up to three times compared to a commercial carbon substrate electrode (Vulcan XC-72R) with ink-spray deposited PtRu nanoparticles as catalyst.     

采煤机调高泵替换技术研究

MG2×125/560采煤机适用于薄煤层开采,近年来随着机组过度的服役,以及产品的更新换代,因齿轮泵全局短缺,配件无法得到保证。为了解决调高系统的事故频发问题,决定对其进行改造,把MG250/591采煤机调高泵更换在MG2×125/560采煤机机组。通过实验模拟与现场使用,证明改造技术切实可行,能够很好地进行摇臂升降。同时,改造后的调高系统能够节省设备费、增加煤炭产值、减少停工损失等费用共计约843 250元,具有良好的社会效应和明显的经济效益。     

浅谈地源热泵在医院建筑中的应用

随着人们保健意识的日益提高,人们自然对医疗环境的要求也相应提高,对于现代化医疗建筑建设者来讲,营造生态保健型绿色医院就成为我们的努力方向,在现代医院建筑中引入绿色节能的地源热泵技术,使医院真正成为人类和谐舒适,环境优美,绿色生态的现代化疗养场所。因此,地源热泵系统在现代医院建筑中具有很大的应用价值,它将成为我国医院建筑节能领域重点推广的技术之一。     

秸秆固化技术现状及发展趋势分析

从开发利用秸秆固化成型燃料的意义入手,结合国内外应用生物质固化成型技术的现状,分析了当前技术的主要原理及存在的问题,进而提出了技术发展的主要方向及相关两项具有发展潜力的新技术,为今后秸秆固化成型产业的发展提供建议。     

Storage devices for heat exchangers with phase change

Heat exchangers with phase-change achieve minimal dissipation when there is only a small temperature difference between the inlet and the outlet on the side of the sensible heat transfer medium. However, this does not usually occur in applications where these heat exchangers are typically used. In order to overcome this issue, an innovative prototype heat pump was realised. The heat pump was equipped with switchable storage devices to adapt the high temperature difference of the application to small temperature differences in the condenser. This way, the dissipation in the condenser was minimised, which led to COP increases by reducing the required mean pressure in the condenser. The use of storage devices resulted in measured efficiency improvements of 10%–50% in the prototype. With the described set-up, it is possible to approach the maximal thermodynamically possible COP, which makes an adaptation of the theoretical assessment of heat pumps necessary.     

Crosslinking of polybenzimidazole membranes by divinylsulfone post‐treatment for high‐temperature proton exchange membrane fuel cell applications

Phosphoric acid‐doped polybenzimidazole (PBI) has been suggested as a promising electrolyte for proton exchange membrane fuel cells operating at temperatures up to 200 °C. This paper describes the development of a crosslinking procedure for PBI membranes by post‐treatment with divinylsulfone. The crosslinking chemistry was studied and optimized on a low‐molecular‐weight model system and the results were used to optimize the crosslinking conditions of PBI membranes. The crosslinked membranes were characterized with respect to chemical and physiochemical properties, showing improved mechanical strength and oxidative stability compared with their linear analogues. Fuel cell tests were further conducted in order to demonstrate the feasibility of the crosslinked membranes. Copyright © 2011 Society of Chemical Industry     

Enhanced performance of counter flow SOFC with partial internal reformation

We study a counter-flow solid oxide fuel cell system and consider the challenges faced in minimizing thermal variations from the nominal operating conditions for a reasonable range of power tracking. Blower dynamics, reformer transport delays, spatial distribution of the heat generated and the resulting thermal response are among the issues considered. A novel approach, relying on partial internal reformation of the feedstock is proposed as a remedy to maintain a strong level of power tracking with minimal thermal stress to the fuel cell.