地铁双线隧道内流动特性的数值模拟

列车运行时的活塞效应对隧道内空气的流动特性有显著的影响。采用CFD数值模拟的方法,着重对地铁双向隧道内列车运动对隧道内空气流动特性的影响作了初步的讨论。模拟结果显示,在双线隧道中,流场的分布是两列车所引起的活塞效应共同作用的结果;两列车相向行驶时,各自的活塞效应会减弱甚至相互抵消,不利于区间隧道内的自然通风。     

铁路隧道竖井设置对隧道活塞风的影响

隧道活塞风对于隧道内通风环境起到极其大的作用,竖井直接影响隧道内运营通风环境。基于Fluent软件,选用RNG k-ε湍流模型,利用软件二次开发UDF和动网格技术,模拟分析列车通过竖井时隧道活塞风分布规律。研究表明:列车头部形成增压区域,车尾部形成数个尾涡区;列车环隙空间近列车壁面气流速度较大,近隧道壁面气流速度较小,纵向环隙气流的速度从车头到车尾逐渐减小;竖井内流体的速度场受活塞风影响较大,对环隙空间流场的后段作用显著,分流作用使得剪切力的增压减小。     

用于地铁空调系统节能的全工况智能通风窗——“会呼吸”的屏蔽门

针对设置屏蔽门的地铁空调系统无法利用列车活塞风对车站进行自然通风及冷却的问题,开发出一种能够适应全年不同工况的新型智能通风窗。该通风窗根据屏蔽门两侧压力以及站内外空气焓值等参数,自动控制窗户的实时开闭状态,最大限度地利用活塞风降低地铁空调系统运行能耗。通过理论分析和计算论证了该设备在实际运用中的可行性并对其节能效果进行了定量评估。     

列车经过某单线无竖井隧道时的活塞风速计算

采用非恒定流活塞风计算理论,按列车行驶在隧道中的不同位置分四种情况计算活塞风风速,并通过MATLAB软件进行数值求解,得到列车经过某区间隧道时的活塞风速度,为地铁环控系统设计中计算活塞风引起的空调能耗以及降低地铁能耗提供一定的参考。     

柴油机缩口四角ω燃烧室活塞温度场试验研究

针对改进的ZH1105W型柴油机缩口四角ω燃烧系统的热负荷问题,利用热电偶法实测了活塞顶面、侧面和内腔共16个特征点的温度值,并用Ansys软件计算模拟了活塞在标定工况下的温度场。结果表明,活塞顶面工作温度随柴油机转速的升高而升高,在标定工况下活塞顶面工作温度最高达311℃,活塞顶部因位置的不同,温度分布差异较大,排气侧和燃烧室喉口处温度较高,距燃烧室中心越远其温度越低。     

某船用柴油机活塞件疲劳寿命预测及损伤演化分析

针对船用柴油机活塞在运行实际工况下出现活塞烧顶、活塞顶开裂等问题，本文运用有限元软件对船用柴油机活塞进行热机耦合仿真，模拟在周期性爆发压力、惯性力、热应力耦合作用下的活塞受力情况。利用Miner准则对其进行疲劳寿命预测，采用Aeran理论对活塞机械负荷、热负荷以及热机耦合三种边界条件下进行损伤演化分析，建立了活塞不同载荷条件下的加速寿命模型，确定了活塞循环次数与其损伤演化之间的关系。     

柴油机活塞热负荷研究

实测了标定功率工况下活塞表面特征测点的温度值,利用有限元分析软件,并结合活塞传热稳态边界条件,计算了该活塞的稳态温度场。结果表明：标定功率工况下,该柴油机活塞头部表面最高工作温度达354℃,一环槽和一环岸的温度在260～30℃之间,不利于活塞环正常工作。     

过渡工况下柴油机活塞三维温度场的求解

本文利用有限元法计算了柴油机过渡工况下活塞的三维温度场,讨论了有限元法求解非稳态温度场中的一些问题。结合实测活塞温度历程提出了过渡工况下活塞温度及其边界参数的变化模式。文中还利用了有限元前后处理技术,使有限元计算中的单元剖分、编码、数据输入、结果分析、图形输出等方面实现了自动化。为深入进行柴油机零件的计算机辅助分析提供了方便。     

青岛地铁地下站厅层工作区冬季热环境研究

我国北方城市冬季地铁站内厅层工作区热环境特性对工作人员热舒适感非常重要。以青岛城市地铁有代表性的两个地下站的站厅层工作区热环境为研究对象,实验跟踪测试了站台层屏蔽门上部溢流活塞风扩散至站厅层的风量及气流温度变化规律;继而对厅层进出口自然流通的新风进行了风量和温度测试。实验研究发现,站厅层工作区的风速和气温受溢流活塞风和新风的耦合作用,呈现的周期性频率近似于溢流活塞风,而温度接近于新风,则站厅层热环境明显偏离常规热舒适性。面向站厅工作人员热环境及热舒适性进行研究,获取了青岛地铁地下站厅层工作区冬季热环境的特性。     

增压中冷柴油机活塞温度场试验研究

为了解4100QBZL型废气涡轮增压中冷柴油机热负荷问题,实测了最大扭矩工况点和标定功率工况点下活塞顶面21个特征点,燃烧室5个特征点,火力岸、环岸和群部10个特征点的温度,并应用Matlab软件对活塞顶部测点的温度值计算模拟得到了活塞顶部的温度场分布和等温线图。结果表明,增压中冷柴油机活塞顶部不同位置的温度分布差异较大,排气侧和燃烧室喉口处温度较高,离燃烧室中心越远其温度越低。     

Numerical simulation of flow characteristics in a subway station

Transient simulation on the process of subway trains pulling in and out of a station was carried out to investigate the air flow characteristics in a subway station in various situations by utilizing computational fluid dynamics (CFD) methods. The influence of the piston effect on the flow field in the station and its role in natural ventilation are discussed. The results indicate that the piston effect has significant influence on the flow field in the station and it plays an important role in natural ventilation. The ventilation shafts established at both ends of the station can effectively enhance natural ventilation while reducing the velocity of airflow in the station. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20239     

风电机舱细颗粒物运动沉积研究

风电机舱通过加装聚风罩装置,可通过引入外部空气对机舱内发热设备进行通风冷却,降低机舱内的平均温度.但与此同时当冷却空气中夹杂灰尘颗粒时,则会在风电机舱内部发电设备上进行沉积.通过对风电机舱进行简化后建立模型,对风电机舱内含有粉尘颗粒的运动沉积特征进行三维仿真模拟计算,得到风电机舱内部颗粒浓度、温度、运动速度的三维特征变...     

Experimental investigation of new designs of wind towers

Two new designs of wind towers were tested side by side with a conventional wind tower in the city of Yazd, Iran. All the towers were of identical dimensions. The two new designs were one with wetted column, consisting of wetted curtains hung in the tower column, and the other one with wetted surfaces, consisting of wetted evaporative cooling pads mounted at its entrance. The air temperature leaving the wind towers with evaporative cooling provisions were much lower than the air temperature leaving the conventional design, and its relative humidity much higher. The air-flow rate was reduced slightly in these new towers. It was found that the wind tower with wetted column performs better with high wind speeds whereas the tower with wetted surfaces performs better with low wind speeds. It is recommended that these new designs of wind towers should be manufactured in different sizes and incorporated in the designs of new buildings. They can replace the evaporative coolers currently employed in Iran, and other hot arid regions, with considerable saving in electrical energy consumption.     

地铁站台系统的热环境及废热回收

本文对哈尔滨地铁站台环境温度变化、热负荷产生的原因进行了分析预测,分析得出列车运行和新风负荷所占比例最大。选择地铁站台空气调节计算参数后,计算了地铁站台的逐时热负荷,定量描述吸气、排气和站台壁面温度变化,其结果显示：站台排气温度和站台壁面温度逐年上升。地铁可回收废热量的计算结果可为废热回收系统提供依据。     

导流格栅对冷藏陈列柜性能影响的试验研究

在M3工况下对敞开立式食品冷藏陈列柜安装导流格栅前后的冷藏性能进行试验研究,分析了开式食品冷藏陈列柜加装导流格栅前后陈列柜内温度及能耗的变化规律。试验结果表明:在搁架前端加装导流格栅能够显著改善风幕性能,达到节能的效果。在陈列柜搁架安装导流格栅后的后排食品包平均温度都在不同程度上高于安装之前的食品包平均温度。且搁架末端设置空气导流格栅比未设置导流格栅的陈列柜的电能消耗节省约23%。     

活塞膨胀对配气机构的影响

针对发动机运行过程中气门碰活塞的问题，要进行尺寸链的计算。由于活塞的工作温度变化很大，运动速度又很高，在计算中要考虑活塞膨胀对尺寸链的影响。为分析、计算和改进配气机构提供了指导。     

Early development of a shaftless horizontal axis wind turbine for generating electricity from air discharged from ventilation systems

The air discharged from ventilation systems is a high potential wind resource for generating electricity in countries where wind speed is unreliable or weak, such as in Thailand. The air discharged from ventilation systems produces consistent and high-speed wind when benchmarked against natural wind. However, the limitations of conventional wind turbines are that they have negative impacts on the ventilation system and are inconvenient to install in many areas. The innovative shaftless horizontal axis wind turbine (SHWT) introduced in this article has been designed to close the gap between the wind source and the conventional wind turbines in this process. The concept design shows how it could be mounted next to sources of waste wind, requiring only a small space for installation. An open hole is provided to enable airflow to be discharged into the environment. This SHWT has high market potential for utilizing man-made wind to generate electricity from an alternative source which supports sustainable energy development. The purpose of this study is to demonstrate the concept design of a prototype SHWT used for energy recovery from the discharged air of a ventilation system. How the rotor and stator design of the SHWT optimize wind turbine performance and minimize the negative effects on the ventilation system efficiency are also addressed in this study. The performance of the SHWT is demonstrated in a lab-scale test using the type of propeller fan that is generally applied in many sectors in Thailand. The results showed that the SHWT was successful in generating electricity and produced minimal negative effects on the ventilation system's performance. The maximum power output of the prototype SHWT is 7.4 W at a rotational speed of 1644 rpm using eight sets of magnets and 5.1 m/s wind speed. The maximum wind turbine efficiency is 51%. However, it still requires further optimization to enhance the SHWT performance.     

A Clothing Ventilation and Heat Loss Electric Circuit Model with Natural Convection for a Clothed Swinging Arm of a Walking Human

This work aims to develop a computationally effective electric circuit model to estimate the ventilation and heat transfer for walking human in the presence of natural convection. The ventilation circuit includes flow resistance, inductance, and electromotive force elements. It is coupled to an electric resistance circuit of heat flows to adjust the temperature difference inducing natural convection flow. The coupled ventilation and heat circuit models predicted both the segmental ventilation rate and heat loss from the arm at different walking and wind speeds. The developed model of the segmental ventilation and heat transfer from the clothed human segment was validated by performing experiments on a walking thermal manikin using tracer gas method. Good agreement was observed between the model predictions and the experiment at a maximum relative error of 10% lying within the standard deviation range. Results showed that the simplified ventilation-heat circuit models succeeded in estimating the natural convection effect at low computational cost. Moreover, it was shown that the effect of natural convection is more significant in walking at no wind than in windy condition. Accounting for natural convection effect increases the segmental ventilation and heat loss at low air permeability (0.02 m/s) by 68% and 20%, respectively.