现代控制技术在工程机械上应用的探讨

以摊铺机控制系统为例，阐述了CAN总线在工程机械现代控制系统中的应用，并对工程机械远程监控系统作了初步探讨。     

圆柱体表面缺陷检测的ANSYS仿真

采用交变磁场测量的圆柱体表面缺陷的ANSYS仿真,以各向同性铝圆柱体为试件,采用柱坐标系及矩形激励线圈,电流流向为圆柱体轴向.将圆柱体体划分后再对各分体局部网格划分.划分较密的缺陷部分向周围划分较疏部分过渡时,采用四面体自由划分衔接.对带有表面周向缺陷的圆柱体网格划分后,产生的单元类型为四面体与六面体的混合.其仿真采用波前求解器.仿真路径为激励线圈沿缺陷长度方向、经过缺陷中心点进行周向移动.     

不同温度下磁场对PEMFC的工作性能影响

在质子交换膜燃料电池(PEMFC)阳极侧垂直加载410 mT磁场,考察不同气体温度下磁场对PEMFC工作性能的影响。结果发现:PEMFC在加载磁场后的工作性能优于不加载磁场的电池性能,当工作温度为45℃时,磁场提升PEMFC功率密度最大,达到14.4%。当PEMFC阳极侧和阴极侧采用不同温度条件时,加载磁场后PEMFC的工作性能提升幅度有很大不同,不加磁场时,氢气侧65℃、氧气侧45℃时的极化曲线斜率比氢气侧45℃、氧气侧65℃时的大很多,但加载磁场后,两者之间的斜率差缩小,表明磁场对电池内部氧气传质影响大于对氢气的影响。     

Quantitative study of the effect of electromagnetic field on scale deposition on nanofiltration membranes via UTDR

Ultrasonic time-domain reflectometry (UTDR) as an in situ, non-invasive real-time technique has been successfully utilized to quantify membrane fouling and cleaning. This study describes an existing ultrasonic technique for quantitative study of the effect of magnetic fields on CaCO₃ scale deposition on the membrane surface during crossflow nanofiltration (NF). The fouling experiments were conducted with CaCO₃ solution containing Ca²⁺ of 1.8 and 3 mmol/L. The experimental electromagnetic field (EMF) was 0.02 T. A commercial NF membrane and a highly sensitive ultrasonic sensor were used in all the experiments. Results show a good relationship between the ultrasonic measurements and the development of CaCO₃ scale on the NF membrane surface. An increase in the amplitude of differential signal with operation time results from the deposition of the CaCO₃ scale layer. In addition, the movement of the differential signal in the time domain observed is associated with an increase in the thickness of the fouling layer. The UTDR technique is capable of measuring the rate of fouling layer formation under different treatment conditions, i.e. with non-magnetic field (NMF) and EMF. Scale layer of deposited CaCO₃ obtained in the experiment with NMF is denser and thicker than that with EMF. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses imply that the magnetic treatment suppresses the formation of calcite crystals and prefers vaterite and aragonite. Furthermore, the ultrasonic technique is sensitive to the different fouling rate between experiments carried out with 1.8 and 3 mmol/L CaCO₃ solutions. The thickness of the fouling layer measured by weight measurement is consistent with that obtained by UTDR in real time. The thinner and less dense scale layer is the main reason for the slower flux decline. Overall, independent measurements such as the flux-decline data, SEM analysis and weight measurement corroborate the ultrasonic measurements.     

Effect of the Inside Placement of Electrically Conductive Beads on Electric Field Uniformity in a Microwave Applicator

Non-uniform heating is a major issue in microwave applications, mainly due to inherently uneven distribution of electromagnetic energy in the microwave applicator. In this work, our aim is to improve electric field distribution uniformity by utilizing microwave reflection from electrically conductive beads placed in the microwave oven. The effects of position, size, and number of electrically conductive beads on the electric field distribution were numerically investigated, and validated through water-load experiments in the cavity. It is found that uniform electric field distribution was realized to some extent by appropriate placement of electrically conductive beads; meanwhile, average electric field intensity in the microwave oven was increased.     

分析南京沙洲停保场改建工程设计变更的监理

为了满足市民公交出行的需求,南京市不断加强扩大城市停车场地的改建。本文主要分析了南京沙洲停保场在改建过程中,如何加强设计变更的监理控制方法及提高设计变更监理效率,以促进南京公交场站改建工程的发展。     

新型续流增磁直流电动机驱动控制系统

为消除传统型直流电动机驱动控制系统在电动汽车应用时存在的缺陷,依据弱磁调速的控制思想,研制出新型的续流增磁电动机及其驱动控制系统。依据该电动机控制系统原理图和试验数据,分析系统弱磁调速原理和工作特性。与传统型串励直流电动机相比,该系统在控制思想、控制结构和再生制动性能方面均具有极大的优越性。热量考核试验表明高频工作中的IGBT开关损耗对控制系统温升影响显著。试验结果和装车试验显示,该系统抗干扰能力强、调节速度快、平稳性好,低速增磁增扭和高速弱磁增速的特性能很好地满足电动公交大客车的动力特性要求。     

地下车库诱导式通风与风管式通风系统的数值模拟分析

诱导式通风和风管式通风作为2种常用的通风系统,在地下车库通风设计中得到了广泛的应用.本文以某地下车库为载体,首先对诱导式通风系统和风管式通风系统进行了数值模拟计算.而后从气流组织、污染物浓度分布和经济性方面对2种通风方式进行分析评价,得出诱导式通风系统在气流分布方面虽不如风管式通风系统均匀,扰动较大,但有利于污染物的排放;同时,该系统运行经济,节省费用可观,综合考虑可知诱导式通风系统拥有较大的优势,具有很好的推广前景.     

在线液面连续监测在油水井动态分析中的应用

塔河油田主力油藏为碳酸盐岩缝洞型油藏,辖区油井分布广且井间距离大,前期主要是依靠人工井口测试获取液面数据;受到人员及监测仪器设备数量及运行情况的影响,测试工作量大、监测数据存在滞后,人工监测不能实时全面反映油井能量变化、机采井异常等情况。针对油田生产中动液面无法连续测量的问题,开展了液面远程在线监测,实现液面的连续监测和远程采集。通过液面远程在线连续监测,为油水井动态分析提供完整液面数据,可及时判断油井生产状况、调整优化机采工作制度,保证油井处于高效、安全的生产状态,达到节能降耗和油井效益最大化的目的。