复合材料雷击放电效应三维数值模拟

建立长空气间隙及复合材料层合板三维有限元模型,采用棒-板长间隙正极性流注生长概率模型为基于经典流注理论的随机放电模型。计算空气间隙区域内各网格点电位,列出电极周围所有流注待发展路径,计算每条流注待发展路径的生长时间,确定具有最小生长时间路径为优先选择路径。流注到达复合材料层合板后选流注与板交叉点作为雷击附着点进行复合材料层合板雷击直接效应分析,获得复合材料层合板在雷电压作用下电势、温度及热应力分布。计算结果表明,流注瞬间产生的高电势、温度及热应力主要沿顶层电导率最大方向对称扩展,所研究的初步结果可作为定性描述;为准确模拟复合材料的雷击放电效应过程,需进一步考虑复合材料的雷击烧蚀及热力学等破坏机理。     

径向不耦合条件下导爆索起爆性能的研究

针对径向不耦合装药条件下导爆索起爆炸药拒爆现象,提出导爆索与炸药之间可能存在的空气间隙是影响导爆索起爆性能的关键因素,从而进行了一系列在不同外径钢管内径向不耦合装药条件下,导爆索起爆乳化炸药简化模型的爆炸试验,并且运用有限元软件ANSYS/LS-DYNA对试验模型进行数值建模分析.结果表明:不耦合装药条件下,导爆索起爆乳化炸药的临界空气间隙尺寸约为25 mm;以乳化炸药冲击波感度为判据,模拟计算出的空气间隙尺寸范围与爆炸试验结果比较吻合.     

管道断面外形对亚音速真空管道磁浮系统气动特性的影响

亚音速真空管道磁浮系统内部流场复杂,研究管道断面外形对气动效应的影响至关重要.基于计算流体力学,考虑流体粘性与列车悬浮间隙建立了三维亚音速真空管道列车空气动力学模型,数值模拟并对比分析了四种不同断面外形管道内的气动力、流场和气动热效应.4种典型的管道外形为圆形、马蹄形、矩形和拱形.研究结果表明:当阻塞比一定时,列车在拱...     

用油膜来调整两平晶空气间隙的方法

根据检定规程,文章阐述了用油膜来调整两平晶空气间隙的方法,达到调整干涉条纹的目的。     

大跨多塔悬索桥纵向地震碰撞反应参数研究

针对大跨桥梁在地震作用下伸缩缝处的碰撞现象,以一座大跨三塔悬索桥为工程背景,建立了考虑墩柱弹塑性的空间非线性碰撞模型,采用非线性时程法详细分析了碰撞刚度、碰撞初始间隙等因素对碰撞效应的影响.分析结果表明:碰撞刚度在可能范围内取值,碰撞效应的变化不明显,碰撞刚度不是敏感参数;碰撞初始间隙是一个敏感参数,其大小对于碰撞效应有一定的影响,初始间隙比的变化对主引桥相对位移和引桥梁端位移影响比较明显.     

空预器密封间隙自动控制系统在大型火电厂中的应用

对燃煤电厂600MW锅炉回转式空气预热器间隙控制系统的应用进行分析。介绍间隙控制控制系统控制结构,叙述安装间隙测量探头注意事项。也介绍PLC编程控制的原理。对电厂运行、热控点检、维护具有一定的指导意义和参考价值。     

不偶合装药管道效应的理论研究

前言在深孔爆破中,由于硝铵类炸药卷与炮孔壁间存在径向间隙,当其装药长度大于一定值时,就会出现管道效应现象。由于这种效应的存在,常使炸药传爆到一定距离后爆轰中止,或爆轰不稳定,致使不能充分利用炸药爆炸能量来破碎岩石,直接影响了深孔爆破效果和井巷掘进速度。而未爆的残药还可能带来其它危害。为了解决这些问题,国內外不少学者进行了大量的实验研究。从对现象的观察和测试结果中提出了管道空气隙内存在有超前于爆轰波     

带排液结构的涡流管的性能实验

设计了带排液结构的涡流管的基本结构并搭建了性能研究实验平台,以空气为介质,研究长径比、排液口位置、排液间隙、可凝组分浓度对涡流管性能的影响。实验结果表明:在实验所进行的冷流率范围内,制热效应随着冷流率的增加而逐渐增大,制冷效应则存在极大值;随着长径比的增加,温度效率的极值有所增大,但是当长径比达到一定的数值后,温度效率和制冷效率增加的幅度显著减小;排液口位置的改变对于涡流管温度效率和湿气脱除率的影响不大;排液间隙的存在对涡流管的冷热分离性能有影响,间隙为1 mm时湿气脱除率最小;随着可凝组分浓度的增加,湿气脱除率逐渐增大,但增大的趋势逐渐趋于平缓。     

底部空气柱装药爆破效果试验研究

本文通过分析了底部空气柱长度变化对爆破作用的影响,结果表明,底部空气柱长度与装药深度之比为0.4～0.8时,爆破效果最佳,爆破体积比传统的装药结构增大45％～55％,显著提高了炸药能量有效利用率。文中提出了底部空气柱效应新概念,探讨了底部空气柱效应的作用机理。     

雷达发射机高原工作可行性分析

本文简述了雷达发射机高原打火的原理，分析了空气间隙与高压打火的关系，提出了几项预防打火的方法。     

Using perforated ventilation ducts to enhance the cooling effect of crushed-rock interlayer on embankments in permafrost regions

A previous laboratory test carried out by the authors proved that the addition of ventilation ducts can efficiently enhance the cooling effect of crushed-rock interlayer. The mechanism revealed by the laboratory test was that, the ventilation ducts intensified natural convection and thus enhanced cooling effect of the crushed-rock interlayer by decreasing its upper boundary temperature. In this study, to further enhance the cooling effect of the crushed-rock interlayer, the ventilation ducts were perforated and then positioned at the upper boundary of the crushed-rock interlayer. Two crushed-rock interlayer embankments with perforated and imperforated (ordinary) ventilation ducts were tested under the same test conditions. The analysis of the temperature characteristics of the two test crushed-rock interlayer embankments with perforated and imperforated ventilation ducts showed that the crushed-rock interlayer embankment performed a more efficient cooling effect when the ventilation ducts were perforated. The effect was straightforward: the addition of the perforation on the ventilation duct wall let the air that was flowing through ventilation ducts partially penetrated into the crushed-rock interlayer. The result was that, during negative air temperature period, the upper boundary temperature of crushed-rock interlayer was decreased to a great extent, and consequently natural convection in the crushed-rock interlayer was intensified. The cooling effect during negative air temperature was efficient enough to restrict the heat injected into the embankment during positive air temperature period. On the whole, the crushed-rock interlayer embankment with perforated ventilation ducts has a good cooling effect to the underlying permafrost. Based on these, the new type of embankment is recommended in the construction of large-width highways in permafrost regions in the future.     

住宅通风竖井烟囱效应对排风的影响和利用

本文从住宅通风竖井的水力工况入手,分析竖井自生通风力引起的烟囱效应在不同时间对通风效果的影响,并就如何利用竖井烟囱效应提高排风效果提出了的全新观念.     

The effect of vacuum on fatigue crack growth

The paper reviews the modern concepts of the vacuum effect on fatigue crack growth under cyclic loading. It reports and discusses experimental data (obtained by the author and others) on the crack growth rate at separate stages of the process, the size and structural characteristics of the plastic zone and the fracture micromechanisms for different metals and alloys in air and in vacuum. The relationship between the macroscopic and microscopic characteristics of crack growth in both environments is considered. The idea is developed that the vacuum effect on the kinetics of crack propagation is associated with changes in the process of dislocation motion in the plastic zone (in contrast to atmospheric conditions) and the mechanism of the effect is sensitive to the fatigue mechanism of metals and alloys.     

气流粉碎机动态参数对粉碎效果影响的研究

超微气流粉碎在现代材料深加工中起着重要作用。本文中通过实验研究了在扁平式气流粉碎机工作过程中粉碎工质压力、进料压力、加料量等动态参数对产品粉碎效果的影响,研究了这些参数与产品粉碎效果之间的关系,从而选定最优参数使气流粉碎机达到最佳粉碎效果。     

Influence of particle size on the exit effect of a full-scale rolling circulating fluidized bed

This paper investigated the influence of particle size on the exit effect of a full-scale rolling circulating fluidized bed (CFB) by using the Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) method. The gas–solid two-phase flow of the full-scale rolling CFB was compared with that of a simplified rolling CFB. Thus, the exit effect of the full-scale rolling CFB was clarified. In the air phase, a peak of air axial velocity v_ya was observed when the full-scale rolling CFB reached the maximum angular displacement. The particle phase possessed back mixing and radial exchange phenomena at the top and bottom of the full-scale rolling CFB, respectively. However, those phenomena were not obvious at the top and bottom of the simplified rolling CFB. The mechanism of the above-mentioned exit effect was then clarified by analyzing the forces acting on the particles under different particle sizes. Finally, the increases in particle size lead to the intensification of the peak of v_ya, particle back mixing, and radial exchange phenomena. Therefore, the intensity of the exit effect of the gas–solid two-phase flow increased as the particle size increased_. The results suggested that the small particles had the potential to promote the purification rate of the full-scale rolling CFB on account of its small exit effect.     

一种节能型家用空调器季节能效比SEER测试与计算

根据ARI标准,对一种节能型家用空调器季节能效比进行了SEER的测试.并按照我国的几个典型城市的温度分布统计,进行了SEER的计算.计算结果表明,该空调器具有很高的季节能效比,在部分负荷时有显著的节能作用.     

浅析人防地下商场空调效果欠佳的原因与对策

从人防地下商场空调系统的设计、施工、维护管理方面提出了一些影响空调效果欠佳的原因,加以详细分析,并给出相应的改进对策,以供参考.     

空压机运行效率下降的原因分析及处理

简介新钢25000m~3/h空分设备空压机运行效率下降时的运行参数,详细分析了空压机运行效率下降的原因,叙述中间冷却器堵塞物清理和酸洗过程以及取得的效果,并提出了保证空压机正常运行的相关注意事项。     

交叉式露点间接蒸发冷却空调机组性能测试研究

为了研究高湿度地区夏季交叉式露点间接蒸发冷却空调机组的性能,2013年7月1-12日在福建省福州市某公司对该空调机组进行了研究,通过测试和计算分析的得出：二一次最佳风量比为1.08,对应湿球效率为91％;最佳风量比下最佳淋水密度625kg/（m·h）;间歇供水时间是制冷15s、通风约为5～6min;最佳风量比和最佳淋水密度下的耗水指标为10.8L/h;制冷量为7.6kW、能效比为15.3.结果表明：交叉式露点间接蒸发冷却空调机组湿球效率接近100％,达到单独使用直接蒸发冷却的效果,而且还不增加空气的合湿量,同时,该机组不仅适合在高湿度地区,在中等湿度地区和干燥地区应用其制冷效果将会更好.