地铁水平活塞风阀速度场特性实测研究

通过对不同工况下车站两端水平活塞风阀速度场的实测研究,得到进站端和出站端水平活塞风阀风速值分别呈现3个和2个典型变化阶段,定量分析了各阶段风速持续时间和换气体积特点.对比分析得到出站端水平活塞风阀的风速持续时间和速度特征值均高于进站端水平活塞风阀,双风井同时开启工况风阀处换气体积最大,区间通风效果最佳,其次为单独开启出站端活塞风井的工况.     

地铁活塞风道风速及变化规律试验研究

列车在隧道内运行产生的活塞风随列车运行呈现有规律的周期性变化,由于目前列车运行速度高且行车密度高,活塞风对隧道内设备及活塞风道内的设备产生长期的作用,可带来不可忽视的安全问题。以广州地铁某站及某中间风井为研究对象,对地铁风道内的风速进行了现场测试,得到了地铁站及区间风井风道内的风速变化规律。结果表明:该站出站端活塞风道内的正、负风速最大幅值均低于进站端;相比于车站进出站端活塞风井,中间风井内风道的风速更高,最大正风速为5.7m/s,最大负风速为7m/s;区间左右线中间风井活塞风道内风速变化周期和变化规律一致,但风速幅值差别较大。     

地铁列车活塞效应对车站排热风量的影响

为排除列车与铁轨的部分摩擦热和列车空调冷凝热,从而保证隧道内部空气温度和隧道土壤温度维持在正常水平,在地铁车站中往往装有排热装置和活塞风井有效进行通风换气。受隧道壁的限制作用,列车运动会产生活塞效应,活塞效应引起的隧道内部空气速度场和压力场的变化对车站机械排风和自然排风影响很大。本文以某车站为研究对象,运用CFD动网格技术,模拟列车减速进站-靠站-加速离站三个连续工况,分析列车活塞效应对活塞风井通风量和车站机械排风的影响,希望对地铁隧道排热系统的设计提供理论依据。     

风阀对地铁隧道压力的影响研究

随着地铁列车速度的提高,列车运行引起的空气动力学效应对站台屏蔽门、各类风井内风道等的安全影响越来越大。针对广州地铁多条线路,采用现场试验方法,对地铁风道不同位置的壁面压力进行了现场测试,得到了地铁车站站端及区间中间风井不同风阀前后测点的动态压力变化,并通过对比分析,研究了风阀对地铁风道内压力幅值的影响。现场测试结果表明:当列车速度为80km/h时,每道风阀的阻力作用会将风道内最大正压降低10～40Pa,最大负压降低10～60Pa;联通风阀开启会将轨行区和活塞风道内的最大正压降低10～30Pa,最大负压降低30～40Pa。     

列车通过铁路隧道时的数值模拟分析

采用Gambit软件建立隧道列车模型,并利用Flunetl7.0软件设置了相应的活塞风二维动网格模型,模拟了列车在不同车速下经过铁路隧道时,隧道内部速度场和压力场的动态变化规律.研究结果表明:随着列车经过隧道时速度的增大,所产生的活塞风的风速也就越大;当列车经过监测点的速度越大时,活塞风的风速突降的程度也就越大;列车头...     

高铁地下站内气流流动对空调系统的影响研究

高铁地下车站埋深较深,站内空调系统受持续作用的热压风和列车经过时的活塞风影响。采用三维CFD数值模拟计算方法,研究了京张高铁八达岭长城地下站在冬夏季仅热压风、热压风和活塞风共同作用下车站热环境和空调系统负荷的变化。结果表明：在夏季,仅热压风作用时,热压风从室外流入车站,对进站厅热环境和空调系统影响大,每小时进站厅和候车厅空调系统负荷分别增加13.4%和3.7%;热压风和活塞风共同作用下,进站厅和候车厅空调系统负荷分别增加12.0%和3.3%。在冬季,仅热压风作用时,热压风从隧道流入车站,对候车厅热环境和空调系统影响大,进站厅和候车厅空调系统负荷分别增加4.4%和14.3%;热压风和活塞风共同作用下,进站厅和候车厅空调系统负荷分别增加4.0%和12.8%。研究成果可为高铁地下车站空调系统设计和控制提供技术参考。     

地铁可调通风型站台门过渡季节自然通风性能测试

可调通风型站台门是一种区别于传统结构的新型的屏蔽门,门上装有可开启和调节角度的风阀,空调季运行时关闭风阀,车站和隧道空气不相通,过渡季节时开启风阀利用活塞风对车站进行自然通风。目前针对该新型屏蔽门实际的通风性能数据缺乏,因此对设置可调通风型站台门的地铁车站在过渡季节的通风性能进行了测试,测试参数包括对通过可调通风型站台门的风量、地铁车站出入口风量以及车站的CO2浓度和温度。测试分析表明,依靠列车活塞效应引起的通风量能够满足过渡季节车站风量的设计要求,因此过渡季节可以关闭车站风机,减少风机能耗。     

隧道内列车活塞风效应数值模拟分析

随着长及特长单线铁路隧道的大量修建,利用列车活塞风改善隧道内空气质量,降低隧道通风能耗已成为可能。采用数值模拟方法以英国Patchway隧道作为物理模型,利用Flunet17.0软件建立相应动网格模型。模拟计算获得的活塞风速平均值与实测值吻合度较好,表明该模拟方法准确性较高。在此基础上,改变行车速度,对隧道内列车活塞风效应做系列模拟计算。研究结果表明:以patchway隧道和列车数据为基本参数,列车行车速度每增加5m/s,平均活塞风速约以19.48%递增,平均增压约以50%左右递增,表明列车行车车速与活塞风速、风压存在正相关关系。该研究可为工程上列车活塞风效应估算提供借鉴。     

地铁列车进出站振动实测与分析

为了研究列车进出站的环境振动特征,验证理论研究结果,利用实测的地铁进、出站振动数据,并结合列车进、出站的加速度变化模型,在时域上统计列车振动波形的峰值、幅值变化和持续时间特征,在频域上分析列车振动波形的频率分布和加速度振级特征.结果表明:列车出站振动峰值有大于进站振动峰值的趋势;轨道减振措施使竖向高频振动分量受到衰减,...     

换气扇两种换气方式对室内气流影响的数值模拟

通风就是室内外空气互换。有效的机械通风和合理的气流组织对于改善室内空气质量、控制室内空气污染物浓度、保证实现健康建筑有着重要意义。针对某房间安装换气扇的两种换气方式—压入式送风和抽出式排风,建立物理模型和数学模型,并用CFD软件进行了数值模拟,从而得到两种换气方式下的速度矢量图和速度云图,并分析了不同换气方式对室内气流的影响。通过比较,压入式送风方式换气效果更好。     

Research on Angular Output Velocity of a Drive Shaft with Double Cross Universal Joints

The study object is the angular output velocity of the drive shaft which is made up of two series-wound cross universal joints.We have deduced the function relation between the angular output velocity and initiative input angle of the drive shaft with double cross universal joints that is based on the calculation formula of the angular output velocity of a single cross universal joint,and by analyzing the relation between the two input angles.By using this function relation,the constant velocity condition o...     

A prognostic method for fault detection in wind turbine drivetrains

In this paper, a prognostic method is presented for fault detection in gears and bearings in wind turbine drivetrains. This method is based on angular velocity measurements from the gearbox input shaft and the output to the generator, using two additional angular velocity sensors on the intermediate shafts inside the gearbox. An angular velocity error function is defined and compared in the faulty and fault-free conditions in frequency domain. Faults can be detected from the change in the energy level of the frequency spectrum of an error function. The method is demonstrated by detecting bearing faults in three locations: the high-speed shaft stage, the planetary stage and the intermediate-speed shaft stage. Simulations of the faulty and fault-free cases are performed on a gearbox model implemented in multibody dynamic simulation software. The global loads on the gearbox are obtained from a dynamometer test bench and applied to the numerical gearbox model. The method is exemplified using a 750 kW wind turbine gearbox. The case study results show that defects in the high- and intermediate-speed bearings can be detected using this method. It is shown that this procedure is relatively simple, yet accurate enough for early fault detection in wind turbine gearboxes.     

基于MEMS技术的微型固态拖动力式测风传感器

为了获得风速风向的信息,制作了一种拖动力式微型固态测风传感器.它包括两个正交封装的单元,每个单元用来独立地测量风速,含有一个薄平板和两个用来连接平板和硅衬底的短悬梁.由于当风从不同角度吹过传感器时悬梁上的应变不同,因此通过测量单个单元悬梁上的应变值可获得风速值,同时通过正交组装两个测风速单元获得风向值.该传感器在ANSYS软件中进行了模拟,用流体力学进行了分析,并在小型风洞中进行了测试.结果表明在输入电源电压为0.5V时传感器最大灵敏度高达60μV/（m·s^-1）,风向测量的线性度小于6%.     

An investigation on the impact fatigue characteristics of valve leaves for small hermetic reciprocating compressors in a new automated test system

This paper presents an investigation on the impact fatigue characteristics of valve leaves that are prevalently used in hermetic reciprocating compressors especially for the household type refrigerators. A unique automated impact fatigue test system has been designed and produced, which enables to carry out impact fatigue tests of the compressor valve leaves under the desired impact velocities. The test system incorporates a noncontact actuation, a data acquisition system and an acoustic‐based damage detection technique, which continuously monitors the health of the structure. The damage detection system allows parametrical investigation on the impact fatigue life by detecting any possible damage and automatically terminating the test. The investigation relates the impact fatigue lifetime of the valve leaves with the impact velocity, asymmetrical impact, operation temperature, material type (carbon strip steel, stainless strip steel and new stainless strip steel grade) and tumbling operation duration. The observations show that the cracks have initiated from the edges of the valve leaf where is in contact with the valve plate. Subsequently, the cracks initially have propagated in the radial direction inwards the center of the impact area. Various failure cases have been resulted in by either a single crack or inter‐related multiple cracks. Microscopic and metallographic observations have been performed on the specimens to enhance the understanding of the damage mechanisms. The investigation and introduced test system guide the design optimization of the valve leaves in terms of compressor performance due to the energy consumption and lifetime of the valve leaf.     

单轴雷达天线机械系统的动力响应

应用Ｌａｇｒａｎｇｅ方程和有限元法建立了由二个弹性体组成的有高精度要求的单轴雷达天线机械系统动力学方程并结合工程实际给出了天线匀速旋转时的方程和算法，利用它们得到了某型雷达天线机械系统在２０ｍ／ｓ风速下的驱动力矩和位移响应     

超大型冷却塔风荷载特性风洞试验研究

对某超大型冷却塔进行同步测压风洞试验获得内、外表面的脉动风压分布。在外压测试中,改变外表面粗糙度和调整风速等措施,较好地实现了冷却塔大缩尺比模型对表面绕流高雷诺数效应的模拟;采用热线风速仪对冷却塔尾流进行测试,验证了由冷却塔整体气动力时程频谱函数确定涡脱频率方法的合理性;分析了环向断面阻力系数沿塔高的分布规律,在考虑相关性的基础上建议了冷却塔环向外表面的风压极值分布拟合曲线。在内压测试中,比较多种填料层透风率对于内压影响的基础上,采用相关性分析方法确定了内压极值分布规律。     

单、双径向轴承安装时三叉式万向联轴器的附加弯矩分析

为找出三叉式万向联轴器在安装和使用过程中出现振动、噪声的原因,分析采用单、双径向轴承安装三叉式万向联轴器输出轴时联轴器附加弯矩随输入轴转角及偏转角的分布规律。首先建立2种安装方式下联轴器的运动简图,应用空间机构坐标变换技术建立输入轴与输出轴的关系方程,推导出系统存在偏转角时输出轴的运动方程,表明输出轴采用单径向轴承安装时三叉式万向联轴器为准等角速传动,采用双径向轴承安装时其具有等角速传动特性。其次分析这2种安装方式下作用在输入轴和输出轴上的附加弯矩分量,根据虚位移原理确定三叉式万向联轴器输出轴在2种安装方式下系统均出现附加弯矩。通过分析发现:采用单径向轴承安装时,存在偏转弯矩,且一个运动周期内附加弯矩的波动频率是输入轴的3倍,呈正弦曲线变化,且附加弯矩的变化趋势为随偏转角的增大呈直线上升;双径向轴承安装时,偏转弯矩为零,附加弯矩随偏转角的增大而逐渐增大,未出现波动。结果表明:2种安装方式下三叉式万向联轴器上均产生附加弯矩,从而使系统产生振动效应。该结果对研究系统产生振动的原因、确定系统非线性动力学行为具有重要的意义。     

Additional bending moment analysis of the trigeminal universal joint installed by single or twin radial bearing北大核心CSCD

To find out the causes of vibration and noise of the trigeminal universal joint which appeared in the installation and use process, the additional moment distribution with the varies of the input shaft angular and the deflection angle was analyzed. Kinematics diagrams of the trigeminal universal joint when the output shaft installed by single radial bearing or twin radial bearing were established. The system coordinates were established under the two installation ways, and the motion equations were established by the direction cosine matrix tools. It indicated that the trigeminal universal joint installed by the single radial bearing was an approximately isometric speed transmission, and was a constant velocity transmission with twin radial bearing installed. Furthermore, the additional moment component on the input shaft and the output shaft was analyzed under the two installation ways. According to the virtual displacement principle, the additional moment on the tripod universal joint when the output shaft installed by twin radial bearing and single radial bearing were determined. When installed by single radial bearing, the deflection moment exists and the vibration frequency of additional moment was three times of the input shaft as a sine curve. The variation trend of the additional moment was straight up with the increase of deflection angle. When installed by twin radial bearing, the deflection moment was zero and the additional moment increased gradually with the increase of deflection angle but did not fluctuate. The analysis revealed that additional moment existed in the trigeminal universal joint system under both installation ways would produce bending vibration. This study is of great significance to study the causes of vibration and determine the nonlinear dynamics of the system.     

考虑弹性边界曲梁模型的覆冰输电线舞动分析

采用解析法求解覆冰输电线考虑弹性边界的曲梁舞动模型有助于深入理解舞动发生机理。根据扭转向频率特性将三自由度舞动模型简化成更加适用于解析法求解的两自由度舞动模型,然后利用多尺度法分别推导出了1∶1和2∶1内共振情况下的简化幅值方程。接着考察了自由度缩减方法差异引起的轴向模态函数变化和弹性边界对舞动分岔和稳定、舞动幅值和临界风速的影响。结果显示,轴向模态函数的变化对1∶1内共振情况下分岔和稳定、舞动幅值和临界风速的影响较小,对2∶1内共振情况下相应值影响较大。当考虑截面偏心时,1∶1内共振条件下,弹性边界使发生不稳定舞动的风速范围减小。覆冰导线在弹性边界条件下的位移幅值相应减小,下临界风速增大,上临界风速相应减小,舞动风速范围减小。     

竖井爆破最佳延时时间的减振控制研究

为了深入研究在竖井爆破扩挖施工中不同延时时间对爆破效果的影响,总结分析现有相关研究后,综合考虑研究需要,相对全面地将延时时间设定为0、2、5、10、20、25、35 ms,通过控制变量法只考虑不同延时时间对于研究主体的影响规律。利用动力有限元分析软件LS-DYNA建立通风竖井延时爆破扩挖数值模拟模型,计算得出不同延时时间以及不同间隔距离对应的振速时程曲线、峰值振速以及结构失效情况,通过对计算结果的综合分析,从多个角度确定了针对所模拟的工况最佳的延时时间为25 ms,且得出了延时爆破不同延时时间对减振效果的一些实用性规律,对于类似工程延时爆破技术设计及参数优化具有一定的借鉴意义。