大功率晶闸管、整流管性能参数微机检测

大功率晶闸管、整流管性能参数是变流装置生产检修的重要依据,其参数的变化将直接影响系统的正常运行.在实用环境下,用微机检测元件的性能参数,可以获得准确的数据,为元件配对选择提供依据.     

高压旋流喷雾特性的三维数值模拟

基于高压旋流喷嘴内部流动对喷雾过程进行数值模拟,并定性研究了喷油压力和环境压力对喷雾特性的影响。研究结果表明：在高的喷油压力下,喷雾贯穿距离增大,液滴索特平均直径减小,但喷雾锥角基本不受影响;在高的环境压力下,喷雾呈现出实心圆锥状,喷雾锥角和贯穿距离都减小,液滴索特平均直径增大。     

客运专线新建线路轨道不平顺功率谱分析

通过对新建铁路轨道不平顺谱密度的分析,可以了解轨道平顺状态,有利于指导轨道施工和线路养护等作业。以秦沈客运专线轨检车实测轨道不平顺数据为统计样本,基于样本平稳性检验,采用FFT方法进行样本空间谱的估计,并由MATLAB编程得到轨道不平顺谱密度。基于轨道高低不平顺样本的总体平均,对所得到的谱密度进行频率平滑,并与我国一级铁路干线的谱密度曲线进行了对比分析：在此基础上,对秦沈客运专线的轨道状态进行了评估。     

滑行艇喷溅区面积及驻点位置变化的模型试验研究

以棱柱型滑行艇为研究对象,开展了滑行艇在高速滑行状态下喷溅区面积及驻点位置变化特征的模型试验研究.模型纵倾角为1.5°,2.2°,3.0°,5.0°,每个纵倾角对应两种尾吃水,分别为37.3,27.3,58.0,38.0,58.0,48.0,73.0,53.0mm,航速为1~5 m/s.艇体喷溅区的流场变化采用高速摄像机拍摄,确定了喷溅区面积和驻点位置的变化规律.结果表明:喷溅区面积与滑行艇纵倾角、吃水及航速密切相关,高速滑行状态下,喷溅区面积随航速的增加而增加,喷溅区面积占滑行面面积的比值为30%~45%;驻点位置随航速的增加向船尾移动,移动距离占船长之比为7.14%~14.28%.     

基于功率键合图的液压节流调速动态性能仿真研究

节流调速回路在小功率液压系统中得到广泛应用，但其速度稳定性不好。文中利用功率键合图法建立了3种节流调速回路的动态特性数学模型，并用Matlab数学软件对其速度进行动态特性仿真，从而讨论了在不同参数（管道直径）下3种节流调速回路的速度稳定性，并进行了分析比较，为今后设计相关液压系统和优化系统参数奠定了基础。     

The visual effects of port redevelopment alternatives

Abstract

In the early 1970s, Seattle Piers 90/91 were declared surplus federal property by the GSA. These obsolescent half‐mile‐long piers and their adjacent uplands were purchased by the Port of Seattle for redevelopment. This urban waterfront site of almost 200 acres presents the Port of Seattle with a number of severe planning problems. While it is the last large deep‐water site on Elliott Bay, it is also in a very sensitive location, since it is overlooked on two sides by vocal residential communities with a history of active intervention in development projects on visual and other environmental grounds.

At Piers 90/91, public concerns over the visual effects of port redevelopment include:

1. nuisance effects of night‐operations lighting on adjacent hillside residences;

2. nighttime obstruction of distant views due to increased foreground illumination;

3. day and night view obstruction by tall structures such as container‐handling cranes;

4. alteration of the character of both day and nighttime views by new port facilities.

As part of a program to study the effects of alternative redevelopment strategies for Piers 90/91, the Port has undertaken a through examination of the visual effects of different uses, their visual appropriateness, and the ways by which adverse visual effects can be mitigated. The results were incorporated into an environmental impact statement which documented compliance with the Seattle Shoreline Master Program and with view protection and glare provisions of the City's S.E.P.A. guidelines.

A systematic Visual Resource Management (VRM) approach was successfully employed on this coastal zone project. Major elements included visibility mapping, key view selection, analysis of existing visual character, simulation of alternatives, assessment of relative visual compatibility, and determination of effective mitigation measures. Community involvement has also been a critical element in this approach to assessing and managing the visual effects of redevelopment in a major urban port.     

船用SCR系统的设计与数值优化

针对某型船用柴油机满足IMO Tier III标准的要求,设计了两型16种SCR反应器,采用数值模拟的方法研究了结构参数对反应器内气体流动的影响。结果表明在30°~45°区间较小的过渡角及较长的过渡段有利于气流的均匀分布;长径比在0.3~3之间变化时,随长径比增加,入口截面的均匀性指数先减小后增加,而中间截面则持续增加后趋于平缓。选取过渡角30°,长径比2.43的圆型SCR反应器研究了喷射参数对于尿素溶液喷射效果的影响,结果表明喷孔与轴线的角度在30°~60°时液滴平均行程随角度的减小而增加,有利于溶液的蒸发,同时喷射点应尽量远离壁面。     

相继增压对某型柴油机性能影响及喷油参数再优化

对某采用相继增压与可控进气涡流复合系统的柴油机建立了缸内仿真模型,分别对可控进气涡流系统和相继增压与可控进气涡流复合系统的燃烧过程进行仿真计算,结果表明,在低工况下后者排气中NOX、Soot的质量分数分别降低了54%和86.1%。并对相继增压与可控进气涡流复合系统柴油机喷油提前角、喷雾锥角进行了再优化仿真计算,结果表明,优化后喷油提前角为20°CA,喷雾锥角为155°。     

乙醇汽油喷雾特性研究及低压直喷喷嘴优化

通过闪光灯喷雾测试试验和乙醇汽油物性的测量、计算,对乙醇汽油喷雾特性进行了研究,最后使用AVL Fire软件完成低压喷嘴结构参数修改,并对不同喷嘴的雾化效果进行了对比.试验结果表明;混合燃料中乙醇比例增大导致乙醇汽油密度、黏度增大,乙醇比例与表面张力关系不大;喷雾贯穿距随着乙醇汽油密度和黏度的升高而降低,而喷雾角与表面...     

矿石码头防尘系统优化改造

分析影响矿石码头洒水防尘系统正常工作的原因,针对主要原因采取相应的对策,大大提高了防尘系统的使用可靠性.