广州地铁3号线列车牵引系统线路接触器故障分析及改进

简要介绍了广州地铁3号线牵引系统的组成和功能,以系统实际故障为例,分析3号线在运营2年后出现的一些硬件故障现象,并提出了改进措施,经实际装车试验情况良好。     

Effect of carbon nanotube concentration on cooling behaviors of oil-based nanofluids during the immersion quenching

Oil-based nanofluids including 0.75%—1.75%(mass fraction) carbon nanotubes(CNTs) without any surfactants have been synthesized by a two-step process. The probes machined from 45~# steel with 22 mm diameter and 50 mm length are quenched in the as-synthesized CNT nanofluids for testing the cooling behaviors of the nanofluids. The laser diffraction particle size analyzer, scanning electronic microscope(SEM), X-ray diffractometer and transmission electron microscope(TEM) are used to characterize the quality and distribution of CNTs in the nanofluids. The wettability and viscosity of 30~# oil and oil-based CNT nanofluids are measured by a goniometer at 15℃ and a rotational type viscometer at 40℃, respectively. The results show that the cooling efficiency of the oil-based CNT nanofluids is better than that of 30~# oil. Moreover, the cooling rate of the naonofluids increases with the further increase of the CNT concentration. When the mass fraction of CNTs increases to 1.75%, the cooling rate of the naonofluids reaches a maximum at 760℃ and it is increased by 77.8% as compared to that of base oil. The improved cooling rate of oil by CNTs is mainly due to the uniform distribution and excellent thermal conductivity of CNTs.     

多区域地铁车厢火灾烟气蔓延特性的数值仿真研究

提出火灾时人员疏散评价指标-可用安全疏散时间,利用火灾动态模拟器(FDS)软件建立广州地铁3号线B型车前3节车厢全尺寸比例火灾仿真模型,对仿真结果进行烟气蔓延特性分析。根据实验单一变量原则,在车厢不同区域设置3类典型火源,对比其烟气蔓延特性,求解可用安全疏散时间。仿真结果表明,不同区域的火源燃烧对于静止地铁车厢的烟气蔓延特性有一定影响,相同火源功率条件下地铁车厢中部发生火灾的危险性比车厢端部发生火灾的危险性大。