Computational study of effects of traffic force on the ventilation in highway curved tunnels

A computational study using dynamic mesh method was carried out to investigate the effects of traffic force caused by a moving vehicle on ventilation in a straight road tunnel and several curved road tunnels with various radii. It has been found that the effect of the radius of the curved tunnel on the traffic force is significant, especially in a curved tunnel with a smaller radius. The traffic force induced by a moving vehicle and the effective drag coefficient increase with the decrease of the radius of the tunnel. The difference between the traffic force in curved tunnels and that in a straight tunnel is negligible when the radius is greater than 2000 m. The static pressure around the vehicle is significantly lower than it is away from vehicle due to the combination of the boundary layer separation and the airflow retardation. And the lowest value occurs at the front of the vehicle. With the decrease of the radius of curved tunnels, the suction around and behind the vehicle is obviously subjected to the limited space due to a bigger vortex approximately approaching the right concave wall and this consequently causes a lower static pressure and a lower dynamic pressure.     

沥青拌和设备用袋式除尘器内部流场分析

介绍沥青拌和设备用袋式除尘器的结构和工作过程,在三维建模软件Pro/E尼中建立J3000型和GLB-3000型袋式除尘器的实体模型,运用流体力学仿真软件Fluent对两类袋式除尘器内部流场进行分析对比.结果表明:两类袋式除尘器内部的流场分布不均,进口方向沿导流板存在射流带,下箱体均存在涡旋,布袋受力不均,使用寿命较短,...     

Water-Circulating Aerator: Optimizing Structure and Predicting Water Flow Rate and Oxygen Transfer

Thermal stratification is a common phenomenon in deep lakes and reservoirs, which often results in water-quality deterioration, including such problems as hypolimnetic anoxia, the release of pollutants from sediments, and algal blooms. Hypolimnetic oxygenation and destratification are the two commonly used methods for resolving these water-quality problems. A new water-quality improvement device, the water-circulating aerator, was designed to destratify lakes and reservoirs, by circulation and oxygenation of upper and lower layers of water. The design of the structure of the water-circulating aerator is detailed. Three mathematical models were built to optimize this structure, estimate the rate of water flow in the aerator, and calculate the rate of oxygen transfer from air bubbles to water in the aerator. These models were verified by experiments. The water-circulating aerator system has been successfully applied in a stratified reservoir to increase dissolved oxygen to reduce the releasing of ammonia-nitrogen from sediments under anoxic conditions.     

Study on the transport of suspended sediment in an open channel flow with permeable spur dikes

The transport of suspended sediment in rivers with spur dikes is an important issue for bank protection and environmental management. Laboratory experiments were performed to study the characteristics of the flow and the transport of suspended sediment in an open channel with permeable dikes. Firstly, the essentials of these characteristics were studied by comparing results of flume experiments on permeable and impermeable dikes. The influence of the aspect ratio (d/l) of the interval between dikes (d) to the length of dikes (l) on these characteristics was then investigated. In these experiments, the properties of horizontal eddies, turbulence structures, and suspended sediment concentrations were studied. The results show that the development of large-scale horizontal eddies requires some distance in a shear layer for permeable dikes, although they are periodically generated from the first dike in the case of impermeable dikes. The basic structures of horizontal eddies are independent of the aspect ratio in the equilibrium region for permeable dikes. The suspended sediment concentrations for cases of permeable dikes gradually decrease between the several upstream dikes and they approach a uniform distribution in the downstream region, although those in the case of the impermeable dikes are relatively uniform in the downstream direction.     

钻具旋转对岩屑运移的影响规律研究

本文通过岩屑运移的启动条件及悬浮条件分别建立考虑钻具旋转影响的岩屑颗粒翻滚、上升的临界启动速度模型,分析钻具旋转对岩屑临界启动速度的影响规律,通过计算发现：在150RPM下,宽间隙处最大影响率为38%,窄间隙处最大影响率为47%;最后根据岩屑临界启动速度模型,考虑钻具旋转作用对偏心环空不同间隙处岩屑启动与运移规律的影响,真实的描述了岩屑在环空中不同位置处的运动状态,提出了评价井眼清洗效果的新方法。     

基于切点跟踪磨削法凸轮运动模型的研究

凸轮加工采用的是一种非圆磨削策略,根据凸轮切点跟踪磨削原理给出了凸轮磨削数学模型和恒线速度磨削条件下凸轮转速数学模型。重点分析了在恒转速和恒线速度磨削两种情况下凸轮转速规律的变化,通过仿真分析,找出影响凸轮加工精度的原因,并依此寻求恰当的加工方法。     

基于ADAMS的复摆颚式破碎机动颚速度和加速度的分析

利用运动学仿真设计软件ADAMS对复摆颚式破碎机动颚进行运动仿真分析;主要分析破碎机破碎腔的给、排料口水平方向速度和加速度的变化规律,看其是否符合破碎理论的要求,并根据分析结果判断破碎机动颚的设计是否合理,这对新型颚式破碎机动颚的设计具有重要意义。     

海上风力发电的风速和风轮机的输出转矩

通过观测的风速数据拟合出风速的威布尔分布曲线,了解风资源的分布情况.并根据风的随机性建立风速变化模型,应用Matlab软件对风速波形进行仿真,进而建立变桨距风机转子的仿真模型.了解在最大风能下,对应的风轮机输出转矩的变化特性以及随着风速的变化所对应的功率变化曲线.仿真结果表明所建立的风力机模型能较好的跟踪风速的变化,实...     

高铬铸铁组织与超声声速关系的测定

文章通过不同热处理手段获得高铬铸铁的不同组织,利用超声声速法、频谱分析和能谱分析对试样的组织进行超声评价研究,建立高铬铸铁组织与超声信号的关系。试验结果表明：相同淬火温度下,冷却速度不同时,空冷时试样中的马氏体最多,因此其声速也最小,炉冷时马氏体量最少,声速最大;不同的淬火温度下,随着淬火温度的不断升高,马氏体的量先增多后减少,因此声速也是先减小后增大;回火后试样中的声速比未回火的声速小,弹性模量的变化是造成声速变化的主要原因。     

制备工艺对消失模涂料性能的影响

选用已成功使用的消失模铸铝涂料为研究对象,对加料顺序、搅拌时间、搅拌速度对涂料性能的影响进行了研究。最后选择最合适的加料顺序为粘结剂→悬浮剂→耐火骨料,最佳的搅拌时间为60min,制备出理想的涂料,并进行了浇注试验。