小型撬装式天然气液化流程模拟与分析

基于中国绝大多数天然气田储量不大,而且分布较分散,离天然气管道较远,因此小型撬装式天然气装置在中国具有广阔的应用前景。小型撬装式天然气装置要求设备少、结构紧凑、操作简单、可靠性高、适应性强、操作弹性大。这对于净化与液化流程提出了更高的要求。采用化工流程软件HYSYS,对单阶混合制冷剂流程,氮气膨胀流程和带丙烷预冷氮气膨胀流程三种工艺流程进行了模拟分析,并以单位能耗为指标对上述三种流程进行了优化。结果发现带丙烷预冷氮气膨胀流程换热平均温差较小,而且能耗较低、流程简单、启动快、操作与维护方便,是比较适合于小型撬装式液化天然气装置的流程。     

LNG储运装置的小型BOG回收再液化方法的对比分析北大核心

首先简要介绍了目前LNG储运装置BOG产生的现状,以及目前回收BOG再液化的一些方法。接着分别针对低温制冷机和液氮作为冷源的两种回收再液化方法从设备投资(两者相当)、运营成本(前者比后者低约40%)、投资回收周期(两者相当)等方面进行综合分析比较,最终得出用低温制冷机作为冷源再液化BOG成为LNG是经济的(液化1kg的BOG仅需花费1.35元)。     

撬装式LNG汽车加气站结构设计

介绍了撬装式LNG汽车加气站的基本结构设计及工作原理,着重对LNG加气站的3个主要系统包括储存系统、管路系统、控制系统进行了说明,并给出主要技术参数。分析了LNG加气站设备潜在的安全隐患,提出相关防范措施。实际运行表明,该加气站加气稳定、计量准确,各项指标符合设计要求。     

LNG储罐内BOG再液化工艺研究

LNG储罐是各类LNG工厂和LNG站必不可少的重要设备,由于LNG温度远低于环境温度,尽管对储罐采取绝热措施,但蒸发仍是不可避免的,LNG蒸发使储罐内压力和温度升高,对储罐产生不利影响。为了减少LNG储罐内低温蒸发气(BOG)直接放空或燃烧造成的污染与浪费,在以往BOG再液化工艺基础上进行优化,设计出适用于LNG站储罐内BOG再液化工艺。该工艺利用LNG站对外供气过程中输出的LNG自身冷能,在压缩机、冷凝器等设备的作用下将LNG储罐内BOG再液化,并以60方LNG储罐为例,用Aspen Plus软件对工艺参数进行优化。研究结果表明:该工艺利用对外供气过程中输出的LNG自身冷能不仅可提高BOG的回收率,使BOG在LNG储罐中循环利用,同时可有效减少LNG冷能浪费;60方LNG储罐,输出LNG流量达到110kg/h即可满足BOG冷凝要求;具有设备少、投资小、能耗低、操作简单的优点,为各类LNG站储罐内BOG再液化处理均有应用价值。     

LNG船BOG再液化工艺影响因素分析

BOG是液化天然气(LNG)在运输过程中蒸发出的气体,采用HYSYS对LNG船氮气制冷BOG再液化工艺进行了模拟。以BOG再液化率及制冷系数为流程性能评价指标,分析了制冷剂流量、BOG压缩机出口压力PS1、BOG换热后N2温度TS12对其影响,得到优化的操作条件为:制冷剂流量为4.3kg.s-1,PS1为0.45MPa,TS12为-136℃,此时,BOG再液化率为82.44%,BOG再液化循环制冷系数εBOG为3.13,N2循环制冷系数εN2为1.36。在以上参数确定的情况下,借助拉格朗日-拟牛顿法,以功耗为目标函数,对N2制冷循环三级压缩机组进行优化,得到最小功耗为821.47kW。     

LNG船用BOG再液化装置工艺流程模拟

文中运用工程模拟计算软件ASPEN PLUS对LNG船用蒸发气体(BOG)再液化装置工艺流程进行了较全面和深入的模拟计算.通过对模拟计算结果进行分析,得到用丙烯预冷的再液化工艺流程中的主要工艺设备运行参数:海水冷凝器冷凝温度、BOG压缩机出口压力、丙烯压缩机出口压力以及混合制冷剂压缩机出口压力对再液化效率和能耗有着不同...     

容积式制冷机组性能测试的一种改进实验装置

针对容积式压缩机组测试设备的初始投资高,能耗高的问题,介绍了一种改进的实验装置.其制冷量测量采用制冷剂液体流量计法。研究测试结果表明:(1)改进实验装置控制精度较高;(2)改进的实验装置的相对误差为1.5%。与房间量热计相比,该实验装置节能72.2%且初始投资节省60%。     

链传动式风能转换装置的结构及性能研究

本文针对传统风力机的特点及研究现状,设计了一种全新的链传动式风能转换装置,并对其结构及工作原理进行了较为全面的介绍与深入分析。通过相应的风洞实验,找到了叶片偏角与叶片柔性变化对装置性能影响的规律。其结果表明该装置具有良好的动力性能和进一步开发利用价值,也为今后装置的进一步结构优化奠定了基础。     

Electrostatic hand pressure knapsack spray system with enhanced performance for small scale farms

Electrostatic force fields have been employed and enhanced in the design of an electrostatic knapsack spray system for increasing the deposition efficiency and reducing the drift of pesticides. The designed induction charge based electrostatic sprayer offers optimum electrode position and electrical conductivity of liquid. The experiments were conducted in ambient conditions for liquid feed rate 340 ml/min at hand pressure of 30 psi. The charge-to-mass ratio was found to be 0.419 mC/kg at 3.25 kV by a spray liquid of conductivity 10.25 mS/cm. There has been 2–3 fold increase of chemical deposition with better uniformity on the target (potted plant).     

Application of reduced scale tests to improve the thermal performance of high-voltage substation connectors

The thermal behavior of high-voltage substation connectors is a critical aspect that must be considered during the design stage. Most research about the thermal performance of substation connector devices is based on full-scale models. This paper proposes a downscaling method to evaluate the thermal performance of reduced scale substation connectors. The theoretical results attained in this paper were validated by means of FEM simulations and experimental tests. Reduced scale simulation and testing will be an essential tool for assessing the thermal performance of substation connectors and other electrical equipment during the design and validation stages.     

活塞式压气机性能测试实验台的研制与应用

基于数据采集与处理技术设计了低成本活塞式压气机性能测试实验台,重点讨论了系统硬件和软件的组成特点,分析了实测的p-α图、p-V图和多变指数.实际应用表明,该实验台可以真实再现压气机的热力过程,既可以用于压气机热力学分析的本科实验,又可以用于压气机运行故障的诊断分析.     

Electrostatic precipitation in a small scale wood combustion furnace

Wood combustion generates a high concentration of particulate matter emission, but most of the particulates in the exhaust gas can be filtered through an electrostatic precipitator. The objective of this paper is to model the trajectory of particulates in the exhaust chimney of a small scale wood combustion furnace with an electrostatic precipitator. The precipitator consists of a central electrode subjected to a maximum high voltage of 50 kV and an outer electrode of 180 mm diameter, ground potential. The parameters including particle size, ambient temperature, pressure, gas flow rate and the applied voltage have been varied while computing the trajectories of the particles in the chimney. The trajectories of particulates have been analyzed for different sizes of a typical wood combusting stove by taking different forces into account on particulates. The critical conditions give the trajectory of particles as a function of particulate size and applied voltage together with the function of efficiency.     

嵌入电介质小球的金属薄片的电磁波透射特性

研究了金属板上下两个表面内侧都周期性地嵌入电介质小球体系的透射和吸收性质.结果显示：对于嵌入深度很小的电介质小球,电磁波可通过隧穿效应进入到电介质小球内,并以腔体本征模式的形式存在.当嵌入深度很小时,周期排列的电介质小球会对金属表面做有效的周期性调制,使体系在特定的频率出现金属表面等离子激元.当腔体本征模式与金属表面等离子激元模式的频率相近时,它们之间的耦合将使两种电磁模式大幅度地增强,从而使上层的电介质小球内具有非常强的电磁场.这些高强度的电磁场有相当一部分可通过隧穿效应进入到下层的电介质小球内,并通过 关键词： 腔体模式 表面等离子激元 透射     

Finite element model updating of a small scale bridge

Although considerable experience has been gained in model updating, the critical issues that remain are the choice of parameters and how to deal with ill-conditioning. Although a number of theoretical tools exist to help with both of these tasks, the techniques are advancing by gaining experience with a diverse range of structures. This paper adds to this debate by updating an experimental bridge model with a geometric scale of 1:50 that represents a typical multi-span continuous-deck motorway bridge. The bridge has four identical straight spans and an irregular distribution of piers, and the central pier is shorter than the others. Four configurations corresponding to different pier stiffnesses and the inclusion of an isolation-dissipation device were considered. An initial test without the piers present was also performed. The measurement of data in these different configurations allows the model updating to be performed sequentially, where parameters identified in earlier configurations maintain their estimated values in subsequent configurations. This approach means that each configuration has a small number of uncertain parameters to be identified, leading to a set of well-conditioned estimation problems based on predicting four natural frequencies of the structure. The procedure was successful, and all of the measured natural frequencies were estimated accurately with a maximum error of under 2.5%.     

Further performance tests of a picosecond X-ray and laser induced streak camera system with fast scintillation materials

A further performance test of a fluorescence lifetime spectroscopy system with 2D-photon counting based on a streak camera was carried out. This system offers three different excitation light sources. It includes a pulsable X-ray tube with 40 kV and a laser. A pulsed UV-LED has been installed for sample excitation. The table top measurement device has a temporal resolution down to 20 ps after deconvolution and fluorescence/scintillation decay times can be evaluated in a wavelength selectable range between 200 and 850 nm. Cesium fluoride, cesium chloride and cesium bromide as fast core-valence luminescence emitters with a relatively low light yield were used in the presented performance test. The easily manageable system is able to detect low light levels and to determine the decay times in agreement with literature in most instances. Beside mentioned scintillators PbCO₃, SrI₂ and Lu₂SiO₅:Ce as a high light yield material were also measured.     

Small signal gain measurements in a small scale HF overtone laser

The overtone gain medium of a small-scale HF overtone laser was probed using a sub-Doppler tunable diode laser. Two-dimensional spatially resolved small signal gain and temperature maps were generated for several ro-vibrational transitions in the HF (v=2→v=0) overtone band. Our results compare well with previous measurements of the overtone gain in a similar HF laser device. Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +1-505/846-4807, E-mail: kevin.hewett@kirtland.af.mil     

超导磁体测试用固氮低温系统开发

为简便地实现超导磁体在15～20 K温度区间下的性能测试,项目组成功设计、装配了一套利用固氮作为辅助制冷剂的低温测试系统,并使用二硼化镁材料绕制的小型线圈进行了磁体测试实验。测试表明,该低温测试系统能在约48 h内达到目标温度,且在磁体通流测试过程中保持系统的温度稳定,足以满足超导磁体测试的需求。