Y型过滤器流动与阻力特性数值模拟分析

文中利用CFD软件,结合多孔介质模型对Y型过滤器进行了数值模拟研究,并与实验结果做了对比分析。得到了过滤器流动特性及不同部位压降情况,分析了滤网堵塞率对压降的影响规律,并提出了减小过滤器压力损失的建议方法。研究表明,Y型过滤器压降主要发生在入口滤座区、滤网区和滤芯环形间隙区,其中滤网区压降最大。滤网堵塞程度对压降影响很大,超过50%时压降快速增大。     

公路隧道竖井送排式通风排风口角度优化模型试验研究

文章应用模型试验于公路隧道竖井送排式纵向通风中,并对排风口与隧道轴向夹角对排风段隧道平均风速的影响进行了测试,研究不同排风口角度和不同风速下的变化规律.结果表明,排风口与隧道轴向夹角对排风动力有较大影响,且随着排风段隧道平均风速增大,排风口角度的影响越大.因此排风口与隧道轴向夹角宜取隧道结构和安全性允许条件下的最小值.     

风载作用下悬索桥大跨度油气管道应力分析

中缅油气管道澜沧江跨越段峡谷年平均风速12.4 m/s,最大风速可达30.7 m/s。澜沧江跨越桥在风载作用下非线性振动特性较突出,跨越段管道易产生横纵向位移,从而产生变形及应力增大问题,对管道安全造成影响。文中采用有限元分析方法,对大跨度管道悬索跨越在风载作用下的变形及应力变化问题进行了分析,建立了有限元模型,模拟了风载作用下悬索桥及管道的应力及变形状况。分析了不同检验风速的影响,得到了管道的应力及变形结果。结果表明:管道的最大应力随风速增加呈线性增大,管道达到许用应力的最大风速为240 m/s,约为其所在位置所受极限风速(60.1 m/s)的4倍,故该段悬索跨越管道在极限风速下处于安全状态。     

高频电子除垢设备在空调水系统中的应用

介绍了空调水系统中水质稳定处理的必要工对几种水质处理的方法进行了比较,指出了高频电除垢在空调水系统听应用效果。     

输油管路网式过滤器压降的实验研究

安装在输油管路上用以保护离心泵、流量计等管路设备的过滤器的滤网引起的管路局部压降损失是不可忽略的。通过量纲分析得到了滤网的局部水头损失系数ξ的影响因素：滤网开孔率β和雷诺数Re.并通过实验确定了β和Re对ξ的具体影响,Re对ξ影响不大,可认为与之无关,而β是影响ξ的主要因素。通过回归得到了ξ的计算公式。另外,还分析了输送介质含泥沙时滤网ξ的变化情况。     

不同压实功下改良废弃土加州承载比试验研究

为了实现资源的集约利用,确定废弃土的强度能否满足路基填筑要求,在土中加入10％粉煤灰进行土的改良,进行同种含水量、不同击实功的下试验试样的室内浸水加州承载比试验,研究分析加入粉煤灰以及不同最大干密度情况下不同击实功对试样加州承载比的影响.结果表明:同种条件下,土的加州承载比随着压实功的增加而增大,并且随着最大干密度的增大,加州承载比的提升幅度越大;试样的加州承载比在同一含水量、同一压实功作用下,随着最大干密度的增大而提升,并且在最大干密度为2到2.5范围内的变化速率最大.     

硫酸盐/氯盐侵蚀下水泥胶砂力学性能研究

盐侵蚀对水泥混凝土的劣化作用主要表现为对水泥胶砂的劣化。采用标准ISO抗折强度和抗压强度试验研究不同浓度复合硫酸盐/氯盐侵蚀条件下,水泥胶砂浸泡不同周期的抗折强度和抗压强度;进一步分析水泥胶砂在不同浓度复合硫酸盐/氯盐侵蚀下力学性能的变化规律,并探讨盐蚀条件下水泥胶砂性能劣化机理。结果表明:在复合硫酸盐/氯盐侵蚀下,水泥胶砂力学性能发生不同程度劣化;随着硫酸盐浓度增加,劣化效果越明显,随着氯盐浓度增加,劣化效果有所减弱;盐溶液渗入水泥胶砂孔隙中发生化学侵蚀是导致水泥砂浆性能劣化的主要原因,而氯盐能一定程度上抑制硫酸盐的侵蚀。研究成果可为复合盐侵蚀地区抗侵蚀提供一定的基础。     

水泥改良土加固填筑边坡效果数值分析

文章以某边坡填筑为例,采用Midas/GTS软件进行建模分析,重点分析了采用素土回填、5%水泥土回填、7%水泥土回填和9%水泥土回填时的边坡水平位移、塑性区变化规律,并对不同坡率时的水泥土回填加固效果进行了分析。结果表明:采用一定掺比的水泥土回填可有效地减小边坡水平位移,但加固效果不会随水泥掺比的增大而成倍增加;采用5%、7%和9%水泥土回填改良原有填筑边坡时,使得边坡安全系数分别达到1.24、1.37和1.52,说明水泥土回填起到了良好的加固效果;当采用水泥土回填时,塑性区体积减小,且随着水泥掺比的增大,塑性区范围逐渐减小;不同坡率下,采用水泥土回填加固边坡均能起到较好的效果。     

轨道交通地下车站通风空调系统节能环保技术应用

轨道交通地下车站内部空间广、发热量大,为维持其热环境,通风空调系统的风机、冷水机组、空调机组的装机容量较大。根据上海轨道交通运营线路的能耗统计数据分析,地下车站通风空调系统能耗约占车站总用电量的50%～60%,占整个轨道交通能耗的25%～30%,系统用电成本占运营成本约30%,对轨道交通运营经济性影响较大。因此,降低通风空调系统能耗对轨道交通车站的节能具有十分重要的意义。     

不同通风口参数下自然通风隧道试验研究

为了对比不同通风口参数下的隧道通风效率及通风口风速,文章通过比例模型试验,使用亚克力板搭建比例尺为1∶15的模型隧道。试验设置4个工况来比较不同通风口数量、长度和高度下隧道通风情况。试验结果表明,不同通风口数量、长度和高度下隧道内风速变化分布以及通风效率发生显著变化。基于试验结果 ,文章建议了最佳通风口的设置形式。     

Investigation on lowering commuters’ in-cabin exposure to ultrafine particles

To determine ways to reduce commuters’ ultrafine particle exposure, factors such as ventilation condition, mechanical airflow rate, driving speed, cabin air filter quality, and cabin air filter use are examined. The results show that the in-cabin to on-roadway ratio is reduced by 20% when the fan is set to recirculation-on versus when set to recirculation-off because fewer ultrafine particles are exchanged between the inside and outside of the cabin. Also, when the fan is set to recirculation-off, the ratio is reduced by 40% at lower mechanical airflow rates. The thickest cabin air filter resulted in a 30% in-cabin to on-roadway ratio decrease compared with the thinnest. Thus, driving conditions with the least UFP in-cabin to on-roadway ratio is when a vehicle is operating with a high efficiency cabin filter, the ventilation set to fan-on and recycling is recirculation on, and at a high ventilation airflow rate. Furthermore, recirculating in-cabin air through a high efficiency particulate air filter was found to significantly reduce in-cabin UFP exposure.     

Impact of Visible-Solar-Light-Driven photocatalytic pavement on air quality improvement

Photocatalytic pavement has attracted significant interest in the past decades by both the academia and industry for its ability of spontaneous cleaning of air pollutants, such as motor vehicle exhaust gas. Titanium dioxide (TiO₂) is used as the photocatalyst that is mixed into pavement materials or coated on the pavement to remove motor vehicle exhaust gases, e.g., carbon monoxide (CO), nitrogen oxides (NO_x), under the irradiation of the solar light. However, the pure TiO₂ additive only absorbs the light within the ultraviolet region due to its large bandgap. One approach to increase the ability of TiO₂ to the utilization of the full spectrum of the solar light is doping TiO₂. Therefore, this visible-solar-light-driven photocatalytic pavement embedded with doped-TiO₂ will exhibits a better cleaning efficiency of exhaust gas. This work conducted computational simulations of the cleaning efficiency on reducing exhaust gas NO₂ by photocatalytic pavement with doped-TiO₂, and its subsequent influence on the air quality in the surrounding environment. A three-dimensional model was developed for a section of pavement and its vicinal region. Effects of weather conditions, doped-TiO₂ coverages, road widths and traffic flow conditions on the removal of NO₂ and its influence to the adjacent environment were studied. Results indicate that visible-solar-light-driven photocatalytic pavement with doped-TiO₂ features a significantly higher removal efficiency of exhaust gas compared with the normal photocatalytic pavement. Moreover, the doped-TiO₂ embedded pavement is effective to remove NO₂ with different traffic densities and wind conditions, and consequently improve the air quality of the surrounding environment.     

地铁设备管理用房变频多联体空调通风模式研究

通过对全空气系统及变频多联体复合空调系统的分析和比较,以上海某地铁车站为例,对两种空调方式在初期投资及运行维护费用方面作了分析和研究。为地铁设备管理用房最佳空调通风模式的选择提供参考。     

密闭空间空气净化用滤材检测设备设计研究

随着机动车辆的普及,人们呆在密闭空间即驾乘室以及室内的时间会逐渐拉长,如何有效的控制密闭空间的PM2.5浓度值值得我们去探讨和研究。通过对密闭空间空气净化原理的分析,采用激光粒子计数方法,设计了密闭空间空气净化检验流程及相配套的检测设备,将密闭空间(含室内及驾乘室)大气中的PM2.5含量控制在标准要求的浓度值以内。     

近距离公路隧道污染空气窜流数值模拟分析

文章以水涧山隧道为工程背景,利用FLUENT软件对不同进、排风速及不同间距的隧道左、右洞污染空气的扩散和窜流情况进行了数值模拟分析,并提出了错开隧道口出口、修筑中隔墙及修筑通风横洞等减少近距离隧道污染空气窜流的工程技术措施。     

用气室提高脉冲水射流强度的模拟研究

采用特征线法对用导管-气室水力共振系统提高脉冲水射流的强度进行了模拟研究,表明水力共振系统在合适的系统结构参数和流体参数情况下,可以提高导管出口处的压力振幅。气室容积太大会吸收导管起点压力的振幅,使压力脉动减小,太小则不起作用;喷嘴的出口直径越小,越能提高导管出口压力的振幅。     

乌鲁木齐市疫情期间交通流量对空气质量影响的分析

选取环境空气中PM2.5、PM10、CO、NO₂、O₃污染物及空气质量指数(AQI)分析乌鲁木齐市疫情期间交通流量对空气质量的影响。结果表明,在乌鲁木齐市两次疫情交通管制期间,交通流量显著降低,环境空气中PM2.5、PM10、CO、NO₂、O₃污染物浓度及AQI随之降低,尤其是PM10、CO和NO₂浓度下降较为显著。自乌鲁木齐市解除交通管制,车辆恢复正常通行后,PM10、CO及NO2浓度逐渐增加甚至反超同期。鉴于PM、CO及NO₂是汽车尾气的主要污染物,因此可推测交通流量增加或降低,环境空气质量也会随之发生变化,尤其是空气中PM10、CO及NO₂污染物浓度呈正相关变化。     

A dynamic shortest path algorithm using multi‐step ahead link travel time prediction

In this paper, a multi‐step ahead prediction algorithm of link travel speeds has been developed using a Kalman filtering technique in order to calculate a dynamic shortest path. The one‐step and the multi‐step ahead link travel time prediction models for the calculation of the dynamic shortest path have been applied to the directed test network that is composed of 16 nodes: 3 entrance nodes, 2 exit nodes and 11 internal nodes. Time‐varying traffic conditions such as flows and travel time data for the test network have been generated using the CORSIM model. The results show that the multi‐step ahead algorithm is compared more favorably for searching the dynamic shortest time path than the other algorithm.     

Economic effects of air transport market liberalization in Africa

Although the aviation industry is increasingly becoming important for Africa’s economic development and integration, the ability of airlines to access foreign markets remains hindered by restrictive regulatory policies. Attempts have been made to fully liberalize the intra-African air transport market. Except for general assertions about the merits/demerits of liberalization, our empirical understanding of the welfare effects of such polices in Africa remains rudimentary. This study empirically measures the economic effects of air transport liberalization, mainly on two supply side variables: fare and service quality, measured as departure frequency. The empirical models evaluate how air fares and departure frequency respond to measures of openness in air services agreements, while controlling for other determinants. The results show up to 40% increase in departure frequency in routes that experienced some type of liberalization compared to those governed by restrictive bilateral air service agreements. Furthermore, there is a relatively larger increase in departure frequency in routes which experienced partial liberalization compared to fully liberalized ones. This can be explained by the diminishing marginal effect of progressive liberalization on departure frequency. While the effect of liberalization is substantial in improving service quality, there is no evidence of its fare reducing effect.     

Impacts of traffic-flows on vehicular-exhaust emissions at traffic junctions

This paper examines the impact of traffic-flow on CO, NO₂ and PM emissions at two distinct traffic junctions and evaluates the use of emission factors. The study includes three scenarios regarding pollutant emissions, which combine a field, experimental and semi-empirically estimated traffic parameters for free, interrupted and congested traffic-flow conditions. It evaluates the emission patterns for heterogeneity in traffic characteristics of both junctions. The results suggest the corrections to be made to emission factors at traffic junctions for better forecast of air quality.